FIELD

The present disclosure relates to an apparatus for cyclically releasing an axial load.

BACKGROUND

Many industries, such as in the oil and gas exploration and production industry, utilise tools which permit cyclical releasing, or dumping, of an axial load. For example, repeated dumping of a load may be desirable in jarring tools used in wellbores, for example during drilling operations, running operations, retrieval operations and the like.

SUMMARY

An aspect of the present disclosure relates to an apparatus for cyclically releasing axial load, the apparatus comprising: a control mechanism comprising a control member radially moveable between a load retaining position in which the control mechanism provides an axial support to a load member to allow the load member to be axially loaded against the control mechanism, and a load release position in which the control mechanism removes the axial support to the load member to allow axial load applied on the load member to be at least partially released; a mandrel, wherein the mandrel and the control mechanism are rotatable relative to each other; and a control cam mounted on the mandrel, wherein the control cam cooperates with the control member during relative rotation between the mandrel and the control mechanism to cause the control member to cyclically move radially between its load retaining position and load release position.

In use, applied axial load on or in the load member may be cyclically released, or dumped, in accordance with relative rotation between the mandrel and the control mechanism. In this respect, continuous relative rotation between the mandrel and the control mechanism may result in continuous cycles of load releasing. Such ability to provide a repeated release of axial load in response to a rotational input may be advantageous in many applications. For example, where space is restricted, such as in through bore applications, rotation may be a desirable means of driving the apparatus. In this respect, although the apparatus may be used in any environment, in some examples the apparatus may define a through bore apparatus. Such a through bore apparatus may be of use in any bore, such as might be provided within a wellbore, tubing string, tool string, pipeline and/or the like. In some examples the apparatus may be a downhole apparatus.

The frequency of load release may be a function of the relative rotational speed between the mandrel and the control mechanism. Thus, the frequency of load release may be readily, and infinitely, varied based on controlling the speed of relative rotation.

In some examples residual load may remain within the load member when the control member is moved towards its load release position. In this respect releasing load may be considered to also encompass reducing load.

Furthermore, removing the axial support from the load member may also comprise moving the position of the axial support in a direction which allows load to be released (e.g., reduced). As such, the load member may be continuously supported by the control mechanism, albeit with the position of the axial support shifted in accordance with operation of the control member.

The apparatus may also be defined as or considered to be for use in cyclically retaining and releasing a load. That is, the apparatus may function to initially retain load within the load member, and subsequently release this. As described in further detail below, the apparatus may also function to apply or generate load within the load member.

Cyclical load retention and release may provide a useful function in a related or integrated apparatus or system. For example, the apparatus may be used in or in combination with a jarring system or apparatus, wherein the control mechanism causes the load member to cyclically retain (or generate) and release potential energy within the jarring system to create repeated jarring forces. For example, when the control member is in its load retaining position the load member may function to hold or lift a jarring mass against a bias force, wherein movement of the control member towards its load release position permits the load member to dump load and allow the jarring mass to be accelerated by the bias force to generate a jarring force. In some examples the jarring mass may be arrested to generate a jarring force, for example by an arresting mechanism such as a spring mechanism, by impact with an anvil surface and/or the like. In some examples the jarring mass may define a hammer.

In another example, the cyclical retention and release of the load member may be used in a hydraulic system such as a piston pump and/or the like. For example, stroking of a piston in one direction may result in the load member being loaded, and releasing the load in the load member may facilitate a reverse stroke of the piston. Such a piston pump may be used to provide high pressure to a target location, for example to provide high pressure fluid for use in setting a tool, such as an anchor, packer, bridge plug and/or the like. A piston pump may be used in injection operations, for example to inject a fluid, such as a treatment chemical, tracer element and/or the like into a target location, such as a production flow from a wellbore. Further details concerning example applications of the apparatus will be provided below.

The cyclical retention and release of the load member may be used in other mechanical systems, such as in setting tools and the like. For example, the cyclical retention and release of the load member may facilitate incremental axial movement of an actuator member in a direction which operates, sets or actuates a tool, apparatus, system and/or the like. In such an example incremental movement may be facilitated by a ratchet assembly and/or the like.

Both the control mechanism and the mandrel may be rotatable to facilitate relative rotation therebetween. The control mechanism may be rotatable while the mandrel is held against rotation. In one example the mandrel may be rotatable while the control mechanism is held against rotation.

The apparatus may comprise a housing, wherein the control mechanism and mandrel are located within the housing, for example wholly or partly. The load member may be wholly or partly located within the housing. The housing may be provided by a single component or a number of components interconnected together. The housing may be generally tubular in form. In some examples the housing may define an outermost surface of the apparatus. The housing may form part of a housing of a related system or apparatus, such as a downhole tool, jarring apparatus, pump system, chemical injection or dosing system and/or the like. The housing may comprise one or more further components or elements to facilitate use. For example, in downhole applications the housing may comprise an anchor assembly for anchoring the apparatus within a bore.

In some examples, when the control member is in its load retaining position and the load member axially loaded, the axial load may be transmitted through the control member and into the housing. In this respect, when the control member is in its load retaining position load within the load member may be reacted into the housing.

The control mechanism may be rotatably fixed relative to the housing. In this respect, relative rotation between the mandrel and the housing may establish relative rotation between the mandrel and the control mechanism. The control mechanism may be rotatably fixed to the housing via a connection mechanism, such as via castellations, pinned connection, threaded connection and/or the like.

The mandrel may be positioned radially inwardly of the control mechanism. In this example the control cam may cooperate with the control member such that the control member moves radially outwardly to be positioned in its load retaining position, and moves radially inwardly to be positioned in its load release position.

The control cam by being associated with the mandrel may also or alternatively be defined as a mandrel cam.

The control cam may be integral with the mandrel. For example, the control cam may be defined by an outer profile of the mandrel. The control cam may be separately provided and mounted on the mandrel. In some examples the control cam may be rigidly mounted on or provided with the mandrel. Alternatively, the control cam may be provided with at least one degree of freedom relative to the mandrel. In one example the control cam may be permitted to move axially relative to the mandrel. Such an axial degree of freedom may be beneficial in some examples to accommodate any relative axial movement between the control member and the mandrel.

The control cam may extend axially relative to the mandrel. In one example the control cam may be generally elongate. Such an elongate arrangement may permit an increased cam contact area which may provide increased load capacity. Furthermore, arranging the control to extend axially may more readily allow an increased cam load surface to be provided by utilising axially longer cams. This may therefore permit greater load capacity to be readily provided. This may contrast with axially facing cams where load surface area is be more quickly limited by the diameter of the apparatus, especially within through bore applications.

The control cam may define a leading side and a trailing side with respect to the relative rotation between the mandrel and the control mechanism. In this respect, the leading side of the control cam may be considered to be that side which initially engages the control member during relative rotation between the mandrel and the control mechanism, wherein the trailing side may be construed accordingly.

The leading side of the control cam may define a lifting cam profile configured to engage and displace (i.e., lift) the control member radially in a first radial direction towards its load retaining position. The lifting cam profile may be formed to permit a desired rate of radial displacement of the control member during relative rotation between the mandrel and the control mechanism. For example, a steep lifting cam profile may provide a more rapid rate of radial displacement of the control member than a shallower cam profile. In this respect the lifting cam profile may be selected or provided in accordance with a desired application.

The trailing side of the control cam may define a dropping cam profile configured to permit the control member to move radially in a reverse second radial direction towards its load release position. In some examples the dropping cam profile may comprise an abrupt or stepped profile which facilitates rapid radial movement of the control member in the second radial direction. Such an arrangement may permit a rapid release of the load within the load member.

The lifting cam profile may extend to merge with the dropping cam profile. In this example the control cam may function to continuously radially displace or lift the control member until the dropping cam profile is positioned to allow the control member to drop. Alternatively, the control cam may define a retaining profile intermediate the lifting and dropping cam profiles. The retaining profile may be configured to hold the control member at a fixed radial displacement until the dropping cam profile is positioned to allow the control member to drop. The control member may define corresponding cam follower profiles configured to cooperate with one or more cam profiles of the control cam.

One or more cam profiles on the control cam and/or control member may be such that the control cam and/or control member must be assembled within the apparatus in a specific orientation to ensure proper operation. In this respect the control cam and/or control member may comprise at least one assembly aid to ensure assembly in the correct orientation. At least one assembly aid may comprise specific dimensional compliance between components only when assembled in the correct orientation. That is, an attempt to assemble a component in an incorrect orientation will not be permitted due to dimensional non-compliance or incompatibility of features.

The control member may be biased towards its load release position. Such bias may be provided by virtue of load applied in the load member acting against the control mechanism. In this example the control cam may function to displace the control member radially towards its load retaining position against this bias, thus assisting to retain load within the load member, wherein when the radial support provided by the control cam is removed the control member may be permitted to be moved under the effect of the bias towards its load release position.

As noted above, in some examples axial load within the load member may function to bias the control member radially towards its load release position. As such, the control cam may be subject to stresses applied by the axial load via the control member. However, as the control cam effectively supports loads in a radial direction then the full axial load will not be transferred to the control cam, but rather only a radial force component. As such, the control cam may be subject to lower stresses than might be the case in axial cam assemblies which would be exposed to the entire axial load.

In one example a single control cam may be provided. As such, a single cycle of retaining a releasing axial load applied on the load member may be provided for one full 360 degrees of relative rotation between the mandrel and the control mechanism.

In an alternative example a plurality of control cams may be provided circumferentially distributed around the mandrel, for example evenly distributed. As such, multiple cycles of retaining a releasing axial load applied on the load member may be provided for one full 360 degrees of relative rotation between the mandrel and the control mechanism. In some examples 2, 3, 4, 5, 6 etc. control cams may be provided.

The load member may form part of a separate apparatus or system. Alternatively, the apparatus may comprise the load member. The load member may comprise a unitary component. In alternative examples the load member may be formed from multiple components interconnected or arranged together. In this example the load member may define a load assembly. The load member may be provided by a sleeve or sleeve assembly. The load member may circumscribe the mandrel. In one example an end region of the load member may engage the control mechanism, and an opposite end region of the load member may engage a system (e.g., jarring system, pumping system, setting system etc.) requiring cyclical releasing of axial load.

In some examples at least a portion of the load member may be located radially relative to the control member. For example, at least a portion of the load member may circumscribe the control member. In other examples the load member may be positioned axially relative to the control member.

A single control member may be provided. Alternatively a plurality of control members may be provided. The plurality of control members may be circumferentially distributed relative to each other, for example evenly circumferentially distributed relative to each other. Providing a plurality of control members may allow load sharing within the control mechanism. The number of control members may correspond to the number of control cams (or vice versa). In this example the circumferential spacing between the control members may correspond to the circumferential spacing of the control cams. This may permit the control members to be moved simultaneously.

In some examples multiple control members may be associated with a common load member. In this respect the control members may share the load applied by or against the common load member. In other examples at least two control members may be associated with separate load members. Such separate load members may be coaxially arranged, circumferentially arranged and/or the like. In this case the individual load members may be operated in phase or out of phase with each other. This arrangement may have multiple applications, such as in some pumping applications. The control member may be configured to directly engage and disengage the load member to provide for cyclical retention and release of axial load within the load member. In alternative examples the control member may be configured to indirectly engage the load member.

When the control member is in its load retaining position to provide the axial support to the load member, the load member may be prevented from movement in a first axial direction. When the control member is moved towards its load release position the previously supported load member may become free to move in the first axial direction. This axial release of the load member in the first axial direction permits load carried within the load member, previously held against the control mechanism, to be relieved. Upon axial release the load member may be caused to move in the first direction, for example as a result of the applied and previously retained load (i.e., release of potential energy). Such movement may facilitate or permit a desired function, such as the dropping of a jarring mass, providing a reverse stroke of a piston, and/or the like.

The control mechanism may be configured to move the load member in a second axial direction which is opposite the first axial direction. The control mechanism may be configured to move the load member in the second axial direction subsequent to a load release event and movement of the load member in the first axial direction. In this respect the control mechanism may effectively reset the load member following a load release event. Such resetting of the load member may permit the control member to be subsequently positioned within its load retaining position. Alternatively, or additionally, such resetting of the load member may cause the load member to provide a desired operation, such as lifting a jarring mass, providing a forward stroke of a piston or setting mechanism, resetting an axial lifting assembly, and/or the like. Resetting of the load member may result in the load member being loaded against the control mechanism. In this respect, the control mechanism may also be defined as a loading mechanism.

In one example the control mechanism may move the load member in the second axial direction prior to the control member being configured within its load retaining position. Such an arrangement may be beneficial where a desired relative alignment between the load member and the control member is required to permit the control member to be positioned within its load retaining position, for example to ensure alignment between cooperating engagement profiles in the load member and the control member. In such an example the load member may be moved in the second axial direction over a required distance prior to the control member being radially moved or positioned within its load retaining position.

The control mechanism may move the load member in the second axial direction during movement of the control member towards its load retaining position. In some examples, radial movement of the control member towards its load retaining position may be converted to axial movement of the load member in the second axial direction, as will be described in further detail below.

The control mechanism may comprise a biasing arrangement, such as a spring arrangement, which functions to bias the load member in the second axial direction subsequent to a load release event.

The control mechanism may be configured to move the load member in the second axial direction in response to relative rotation between the mandrel and at least a portion of the control mechanism.

The control mechanism may comprise an axial reset cam assembly which functions in response to relative rotation between the mandrel and the control mechanism to move the load member in the second axial direction subsequent to a load release event. In one example the control mechanism may comprise first and second reset cams comprising cooperating axial cam profiles, wherein rotating sliding engagement of the axial cam profiles causes axial extension of the cam assembly, thus establishing the desired movement of the load member in the second axial direction. The first reset cam may be rotatably secured relative to the mandrel and the second reset cam may be rotatably secured relative to the load member. In such an example, the mandrel may provide a rotary drive input to the reset cam assembly.

When the control member radially moves towards its load retaining position said control member may be brought into engagement with the load member, wherein such engagement may permit the control member to provide the axial support to the load member. The control member may thus directly resist axial movement of the load member in the first axial direction. When the control member moves towards its load release position said control member may disengage the load member to thus remove the axial support and permit load within the load member previously applied against the control member to be released. In this example the control member may function as a latch member. The control member may be in the form of a radial dog.

The load member may define a profile configured to be engaged by the control member. The profile may comprise an axial load shoulder configured to axially engage the control member. The profile may comprise one or more recesses, shoulders, lips, teeth and/or the like. The control member may define a corresponding profile to engage a profile of the load member. For example, the control member may comprise a corresponding axial load shoulder. The control member may comprise one or more recesses, shoulders, lips, teeth and/or the like.

In some examples a cooperating engagement profile between the control member and the load member may be such that radial engagement of the control member with the load member may apply or establish an axial load within the load member. For example, a cooperating profile may define axially oriented tapers or wedge surfaces which cooperate to convert radial movement of the control member, established by the control cams, to axial load within the load member.

The control mechanism may axially engage the load member, directly or indirectly.

The control mechanism may be axially extendable between an axially collapsed configuration and an axially extended configuration. Movement of the control mechanism towards its axially extended configuration may facilitate retention of load within the load member. Movement of the control mechanism towards its axially collapsed configuration may facilitate release of axial load from the load member.

The control mechanism may be reconfigured in accordance with radial movement of the control member between its load retaining and load release positions. In this respect, the control mechanism may be operated between its axially collapsed and extended configurations in response to relative rotation between the mandrel and the control mechanism. The control mechanism may be axially extended in response to radial movement of the control member towards its load retaining position. As such, the control mechanism may function to retain axial load within the load member when in this axially extended position.

The control mechanism may comprise a bias arrangement which biases the control mechanism towards its axially extended configuration. Such an arrangement may provide a boost force to reduce the force applied on the control cam when operating to move the control member radially towards its load retaining position.

The control mechanism may be axially collapsed when the control member is in its load release position. As such, the control mechanism may function to allow axial load applied on the load member to be at least partially released when in this axially collapsed position.

In some examples axial extension of the control mechanism may cause axial movement of the load member. Based on previous examples axial extension of the control mechanism may cause movement of the load member in the second axial direction. Such axial movement of the load member may cause the load member to provide a desired operation, such as lifting a jarring mass, providing a forward stroke of a piston, operating a setting mechanism, resetting an axial lifting assembly, and/or the like. Axial movement of the load member may result in the load member being loaded against the control mechanism. In this respect, and as also noted above, the control mechanism may also be defined as a loading mechanism.

Thus, the control mechanism may provide a dual function, of firstly providing and removing an axial support to a load member to thus allow load to be cyclically retained and released, and secondly in generating load within the load member against the axial support.

The control mechanism may comprise first and second axial ends, wherein the first axial end is fixed, for example relative to a housing of the apparatus, and the second axial end is axially moveable. In this example any axial extension within the control mechanism may be applied in a single direction. This may maximise the axial movement transferred to the load member, which may provide benefits in applications requiring a greater stroke length. The second axial end of the control mechanism may be engaged with the load member, such that axial movement of the second axial end facilitates or permits corresponding axial movement of the load member. In one example the second axial end of the control mechanism may be provided separately from the load member. Alternatively, the second axial end of the control mechanism may be integrally formed with the load member.

The control mechanism may comprise a first end member provided on one axial side of the control member, wherein a first interface arrangement is provided between the first end member and the control member, said first interface arrangement being configured to convert radial movement of the control member to relative axial movement between the first end member and the control member. This relative axial movement between the control member and the first end member may thus facilitate axial extension and collapse of the control mechanism.

In some examples the first end member may be axially fixed such that the control member is caused to be moved axially by virtue of the first interface arrangement. Alternatively, the control member may be axially fixed such that the first end member is caused to be moved axially by virtue of the first interface arrangement.

The first interface arrangement may comprise a wedge profile between the control member and the first end member. This wedge profile may be configured to convert relative radial movement of the control member to relative axial movement between the control member and the first end member. In this example the first end member may define a first wedge member. The wedge profile may be defined by a first wedge or tapered surface on the control member and a second corresponding wedge or tapered surface on the first end member. Cooperation between the first and second wedge surfaces may convert radial movement of the control member to relative axial movement between the control member and the first end member.

The first interface arrangement may comprise a toggle assembly between the control member and the first end member. The toggle assembly may comprise a toggle arm pivotally connected at one end to the control member via a first pivot joint, and pivotally connected at an opposite end to the first end member via a second pivot joint. In this example radial movement of the control member varies the incline of the toggle arm which thus provides relative axial movement between the control member and the first end member. The first end member may also be defined as a pivot plate.

In one example the radial travel of the control member may be limited, for example by engagement with a housing of the apparatus, such that the relative positions of the first and second pivot joints is such that any axial force applied between the control member and the first end member resolves to a radial force which acts to bias the control member towards its load release position. As such, the toggle assembly is arranged to prevent inverted movement of the control member.

The control mechanism may comprise a second end member provided on an opposite axial side of the control member, wherein a second interface arrangement is provided between the control member and the second end member, said second interface arrangement being configured to convert radial movement of the control member to relative axial movement between the second end member and the control member. As such, the relative axial movement established by the first and second interface arrangements may be additive, thus providing an increased axial displacement between the axially extended and collapsed configurations of the control mechanism.

In one example the first end member may be axially fixed and the control member and second end member may be axially moveable to facilitate axial extension and collapse of the control mechanism.

In one example the second interface arrangement may comprise a wedge profile between the control member and the second end member. In this example the second end member may define a wedge member.

The second interface arrangement may comprise a toggle assembly between the control member and the second end member. The toggle assembly may comprise a toggle arm pivotally connected at one end to the control member via a first pivot joint, and pivotally connected at an opposite end to the second end member via a second pivot joint. In this example radial movement of the control member varies the incline of the toggle arm which thus provides relative axial movement between the control member and the end member. The second interface arrangement may be configured similarly to the first interface arrangement. Alternatively, the first and second interface arrangements may be of differing form. For example the first interface arrangement may comprise a wedge profile between the control member and the first end member, and the second interface arrangement may comprise a toggle assembly between the control member and the second end member, or vice versa.

The apparatus may comprise a control cage, wherein the control member is mounted with or within the control cage. In some examples the control cage may form part of the control mechanism. The control cage may be rotatably fixed relative to a housing of the apparatus. In some examples the control cage may facilitate rotary connection of the control mechanism relative to the housing. The control cage may define a radial pocket, wherein the control member is radially moveable within said radial pocket in accordance with cooperation with the control cam. The radial pocket may be positioned intermediate opposing ends of the control cage. In some examples the radial pocket may also accommodate one or both first and second end members. The radial pocket may define a sufficient axial length to accommodate extension and contraction of the control mechanism.

The control cage may be axially moveable within the apparatus. Such axial movement of the control cage may permit the control mechanism to be configured between axially extended and axially collapsed configurations. In one example the control member may be axially secured with the control cage, such that axial movement of the control cage is associated with axial movement of the control member, and vice versa. The control cage may thus function as an axial carriage for the control member. In this example the control cage may function to ensure the control member is robustly supported within the apparatus during movement in multiple directions, specifically axially and radially. For example, the control cage may interface with the control member to ensure that the control member may move entirely radially relative to the control cage, whereas any axial movement of the control member may be provided by axial movement of the control cage. Such an arrangement may assist to prevent the control member binding within the apparatus.

The control cage and the control member may comprise cooperating engagement profiles which permit the control member to move radially relative to the control cage. The cooperating profiles may define a radial bearing arrangement. The cooperating engagement profiles may function to axially secure the control member to the control cage while permitting relative radial movement therebetween. For example, the control member may comprise one or more protrusions, such as wings, which are engaged within respective corresponding slots within the control cage. The cooperating engagement profiles may minimise the risk of the control members being subject to any pitching movement. That is, the cooperating engagement profiles may seek to direct the control member to move purely radially, which may provide advantages in terms avoiding binding of the control member and/or the like.

In one example the cooperating engagement profiles may ensure that the control member may be mounted within the control cage in only one orientation, to ensure correct operation of the apparatus. For example, a first protrusion on the control member may be configured to engage a corresponding first slot within the control cage, and a second protrusion on the control member may be configured to engage a corresponding second slot within the control cage, wherein the first protrusion and slot define a different geometry, such a dimension, than the second protrusion and slot.

The control cage may define an axially split cage assembly, having a first cage portion and a second cage portion. The first and second cage portions may be axially moveable relative to each other. Such an arrangement may permit the control mechanism to be configured between axially extended and axially collapsed configurations.

One of the first and second cage portions may be secured to a housing of the apparatus, and the other of the first and second cage portions may be engaged with, for example integrally formed with, the load member.

In one example the control mechanism may comprise a first end member axially secured to the first cage portion and a second end member axially secured to the second cage portion, wherein the control member is interconnected between the first and second end members such that the control member spans an interface between the first and second cage portions. In this respect radial movement of the control member may cause relative axial movement between the first and second end members, wherein such relative axial movement is permitted by the split cage assembly.

In one example the first and second end members may define different geometries, for example widths, to ensure correct assembly with the associated cage portion. Such an arrangement may ensure appropriate orientation of the control member with respect to the control cam.

The first and second cage portions may be rotatably connected together via a rotary connection. Such an arrangement may permit any torque to be transmitted across the control cage. The rotary connection may be provided by cooperating castellations, splines and/or the like. In some examples the rotary connection may define a tighter dimensional tolerance (or closer interference) than that provided between the control member and the cage portions. Such an arrangement may prevent or minimise the risk of torque applied between the first and second cage portions from binding the control member.

The control mechanism may comprise a bias arrangements configured to bias the first and second cage portions in a desired direction relative to each other. In one example the bias arrangement may be configured to bias the first and second cage portions apart, which may provide a boost force to reduce the force applied on the control cam when operating to move the control member radially towards its load retaining position.

The control mechanism may comprise a dampening arrangement between the first and second cage portions. Such a dampening arrangement may function to dampen movement between the cage portions, for example to prevent or minimise the risk of impact therebetween. Such dampening may be provided or engaged when load is released from the load member.

In one example the control cage may be radially interposed between the mandrel and the load member, wherein the control member extends radially through the control cage, for example a radial pocket in the control cage. As such, the control member may be radially moved, according to the control cam, into and out of engagement with the load member. The control cage may be axially secured or fixed within the apparatus, for example axially secured relative to a housing of the apparatus. Such an arrangement may limit or prevent axial movement of the control member.

Multiple apparatuses disclosed herein may be used in combination. For example, multiple apparatuses may be arranged in series which may facilitate a greater collective lift capability being provided. For example, in examples where the control mechanism is capable of axial extension, such axial extension may be additive in apparatuses arranged in series.

In some examples operation of the control mechanism may function to move the control member to provide an operation within an associated system, such as a jarring system. For example, the load member may be used to lift a jarring mass, to engage a lifting structure which is used to lift a jarring mass and/or the like. In this example the apparatus may be configured to provide adjustment of the available lift provided by the load member. For example, the load member may comprise a telescoping arrangement which may function to axially extend and/or contract the length of the load member. This arrangement may shift the point at which lifting is initiated.

An aspect of the present disclosure relates to an apparatus for cyclically releasing axial load, the apparatus comprising: first and second assemblies rotatable relative to each other a control mechanism rotatably secured to the first assembly and comprising a control member radially moveable between a load retaining position in which the control mechanism provides an axial support to a load member to allow the load member to be axially loaded against the control mechanism, and a load release position in which the control mechanism removes the axial support to the load member to allow axial load applied on the load member to be at least partially released; a control cam mounted on the second assembly, wherein the control cam cooperates with the control member during relative rotation between the first and second assemblies to cause the control member to cyclically move radially between its load retaining position and load release position.

An aspect of the present disclosure relates to a method for cyclically releasing axial load, comprising: establishing relative rotation between a mandrel comprising a control cam and a control mechanism, wherein the control cam cyclically operates a control member of the control mechanism to move radially between a load retaining position in which the control mechanism provides an axial support to a load member to allow the load member to be axially loaded against the control mechanism, and a load release position in which the control mechanism removes the axial support to the load member to allow axial load applied on the load member to be at least partially released.

The method may comprise use or operation of the apparatus of any other aspect.

As noted above, the apparatus disclosed herein may be used in numerous applications where load is to be cyclically released from a load member. In one specific example, referred to above, the apparatus may be used as part of or in combination with a jarring apparatus, such as might be used in a downhole environment, although non-downhole jarring applications are envisaged by the present disclosure.

In this respect, an aspect of the present disclosure relates to a jarring apparatus, comprising: a jarring mass axially moveable in reverse first and second axial directions; a force arrangement configured to bias the jarring mass in the first axial direction; a load member; a control mechanism comprising a control member radially moveable between a load retaining position in which the control mechanism provides an axial support to the load member to allow the load member to hold the jarring mass against the bias acting in the first axial direction, and a load release position in which the control mechanism removes the axial support to the load member to allow the jarring mass to be accelerated by the force arrangement and create a jarring force; a mandrel, wherein the mandrel and the control mechanism are rotatable relative to each other; and a control cam mounted on the mandrel, wherein the control cam cooperates with the control member during relative rotation between the mandrel and the control mechanism to cause the control member to cyclically move radially between its load retaining position and load release position. Thus, in response to relative rotation between the mandrel and the control mechanism the jarring mass may be repeatedly held and released thus causing repeated jarring events.

The jarring apparatus may comprise an arresting mechanism configured to arrest movement of the jarring mass in the first direction to thus generate a jarring force. The arresting mechanism may comprise an anvil surface, wherein the jarring mass impacts the anvil surface in the first axial direction to generate an impact based jarring force. The arresting mechanism may comprise a damping arrangement configured to rapidly decelerate movement of the jarring mass in the first direction and thus generate a jarring force.

The jarring apparatus may comprise an apparatus (e.g., a cyclical load retaining and releasing apparatus) according to any other aspect.

The force arrangement may comprise a power spring, for example. Alternatively, or additionally, the force arrangement may be provided by tensile properties of the apparatus and/or an associated work string. For example, displacement of the jarring mass in the second direction may generate tension within the apparatus and/or an associated work string. Release of this tension by operation of the control mechanism may function to bias or move the jarring mass in the first direction.

The control mechanism may be configured to axially move the load member to displace the jarring mass against the bias of the force mechanism. Such displacement, or lifting, of the jarring mass may generate potential energy within the force arrangement. In this example lifting of the jarring mass and generating potential energy may cause the load member to become loaded against the control mechanism. When the control member is moved to its load release position by virtue of interaction with the control cam, the load member may no longer support the load within the energised jarring system, such that the potential energy converts to kinetic energy with the jarring mass accelerating in the first direction to generate a jarring force, for example by impact against an anvil surface, by engagement with a damping mechanism and/or the like.

It should be understood that the term “lift” or “lifting” with reference to the jarring mass is not intended to be limited to an increase in vertical height, but is instead used to define any displacement of the jarring mass against a bias force which generates potential energy. In a similar manner, the release and movement of the jarring mass under action of the bias force may be defined as dropping motion of the jarring mass.

The load member may be engaged at one end with the control mechanism and at an opposite end with the jarring mass. In this example the load member may directly lift and drop the jarring mass in accordance with operation of the control mechanism.

In some examples a lifting mechanism may be interposed between the load member and the jarring mass, wherein the lifting mechanism functions to lift the jarring mass, and the control mechanism functions to cyclically load and unload the lifting mechanism. For example, when the control member is in its load retaining position the load member axially supports the lifting mechanism to permit said lifting mechanism to displace or lift the jarring mass against the bias of the force mechanism, and when the control member is in its load release position the load member releases load from within the lifting mechanism to thus release, or drop, the jarring mass.

The lifting mechanism may comprise a first lifting structure engaged with the load member and a second lifting structure engaged with a jarring mass. Relative rotation between the first and second lifting structures may cause cyclical relative displacement in one axial direction to define a lifting phase and relative displacement in a reverse axial direction to define a dropping phase. In one example the apparatus may be configured such that the control member is moved to its load release position prior to initiation of the dropping phase of the lifting mechanism. In this respect the effective release of the jarring mass is initiated by the control mechanism, and not by transition of the lifting mechanism to its dropping phase. This may function to minimise loading applied through the lifting mechanism.

The first and second lifting structures may comprise inter-engaging profiles which cooperate during relative rotation of the lifting structures to cause the cyclical lifting and dropping phases. The inter-engaging profiles may be configured such that a surface area of contact therebetween reduces as the lifting phase progresses. When exposed to load such a reducing surface area of contact results in increasing stresses applied between the inter-engaging profiles of the first and second lifting structures. As such, axially releasing the load member via the control mechanism prior to completion of the lifting phase may prevent excessive loading being applied over the reducing surface area of contact, reducing stresses applied and minimising wear and risk of damage or failure.

In some examples the timing of the axial release of the second lifting structure may be adjustable. Such adjustment may be achieved prior to deployment and use of the jarring apparatus. In some examples, such adjustment may be achieved while the jarring apparatus is deployed and/or in use.

The inter-engaging profiles may permit at least one cycle of lifting and dropping phases for a single 360 degrees of relative rotation between the first and second lifting structures. In one example the inter-engaging profiles may permit multiple cycles (such as 2, 3, 4 etc.) of lifting and dropping phases for a single 360 degrees of relative rotation.

The inter-engaging profiles may be configured for rotating sliding engagement therebetween. The inter-engaging profiles may be defined by circumferential ramp structures. In one example the inter-engaging profiles may comprise rotary cam surfaces. In such examples the first and second lifting structures may define respective first and second lifting cams. The number of individual cam profiles provided on each lifting structure may dictate the number of lifting and dropping phases provided for a single 360 degrees of relative rotation between the lifting structures.

In one example the first lifting structure may be rotatably fixed relative to the control mechanism, and the second lifting structure may be rotatably fixed relative to the mandrel. In this example the lifting structure may be operated by relative rotation between the mandrel and the control mechanism.

An aspect of the present disclosure relates to a method for generating a jarring force using a jarring apparatus according to any other aspect.

An aspect of the present disclosure relates to a pressurising apparatus, comprising: a piston member and an apparatus for cyclically releasing axial load against the piston member. The apparatus for cyclically releasing axial load against the piston member may be provided in accordance with an apparatus according to any other aspect. In this respect, a load member of an apparatus may engage the piston member, wherein a control mechanism may cyclically reconfigure the load mechanism between load retaining and load releasing configurations to accommodate appropriate movement of the piston member to act on a fluid.

An aspect of the present disclosure relates to a jarring apparatus, comprising: first and second assemblies being rotatable relative to each other; a jarring mass axially moveable relative to at least one of the first and second assemblies; a first lifting structure axially engaged with the jarring mass and being rotatably fixed relative to the first assembly; a second lifting structure axially engaged with a load member and being rotatably fixed relative to the second assembly, the first and second lifting structures being configured to cooperate during relative rotation therebetween to cause cyclical relative displacement in one axial direction to define a lifting phase and relative displacement in a reverse axial direction to define a dropping phase, a control mechanism rotatably fixed relative to the second assembly and comprising a control member radially moveable between: a load retaining position in which the control mechanism axially supports the second lifting structure during the lifting phase to provide axial lifting of the jarring mass against a bias force; and a load release position in which the control mechanism axially releases the second lifting structure prior to initiation of the dropping phase to permit release of the jarring mass to be driven axially by the bias force and generate a jarring force within the apparatus; and a control cam mounted on the first assembly, wherein the control cam cooperates with the control member during relative rotation between the first and second assemblies to cause the control member to cyclically move radially between its load retaining position and load release position.

In one example the first assembly may comprise a mandrel or mandrel assembly. As such, the control cam may also be defined as a mandrel cam. The second assembly may comprise a housing or housing assembly. A load member may be provided between the control mechanism and the second lifting structure.

It should be understood that the features defined in relation to one aspect may be applied in any other aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal cross-sectional view of an apparatus for cyclically retaining and releasing axial load;

Figure 2 is a lateral cross-sectional view of the apparatus of Figure 1 taken along line 2-2;

Figure 3 is an isometric view of a control mechanism of the apparatus of Figure 1;

Figure 4 is an exploded isometric view of the control mechanism of Figure 3;

Figures 5 to 8 illustrate a sequence of operation of the apparatus of Figure 1;

Figures 9 to 12 diagrammatically illustrate the effect of varying a control cam profile within the apparatus of Figure 1 ;

Figures 13 to 18 illustrate a sequence of operation of a jarring apparatus which incorporates the apparatus of Figure 1 ;

Figure 19 is a longitudinal cross sectional view of an alternative jarring apparatus which incorporates the apparatus of Figure 1.

Figures 20 is an elevation view a lifting mechanism of the jarring apparatus of Figure 19. Figures 21 to 26 illustrate a sequence of operation of the jarring apparatus of Figure 19;

Figure 27 is an exploded isometric view of a control mechanism and lift adjusting assembly of the apparatus of Figure 19;

Figures 28 and 29 diagrammatically illustrate the effect of adjusting the lift within the apparatus of Figure 19;

Figure 30 is a longitudinal cross sectional view illustrating alternative examples of an apparatus for cyclically retaining and releasing axial load;

Figure 31 is a longitudinal cross sectional view of a portion of an alternative apparatus for cyclically retaining and releasing axial load;

Figure 32 is a lateral cross-sectional view of the apparatus of Figure 31 taken along line 32-32;

Figure 33 is an exploded view of a toggle assembly of the control mechanism of Figure 32;

Figure 34 is an isometric view of a control mechanism of the apparatus of Figure 31 ;

Figure 35 is an isometric partial sectional view of the control mechanism of Figure 34;

Figure 36 is an enlarged view of the toggle assembly of the apparatus of Figure 31 ;

Figures 37 and 38 illustrate a stage of operation of the apparatus of Figure 31 ;

Figure 39 provides a broken longitudinal cross sectional view of an example jarring apparatus which incorporates the apparatus of Figure 31 ;

Figure 40 is a broken longitudinal cross section on alternative example of a jarring apparatus which incorporates the apparatus of Figure 31 ; Figure 41 is a longitudinal cross sectional view of a portion of an alternative example of an apparatus for cyclically retaining and releasing axial load;

Figure 42 is a lateral cross-sectional view of the apparatus of Figure 41 taken along line 42-42;

Figure 43 is an elevation view of a reset cam assembly of the apparatus of Figure 41 ;

Figure 44 is an isometric cut away view of a control mechanism of the apparatus of Figure 41;

Figures 45 to 53 illustrate a sequence of operation of the apparatus of Figure 41 ;

Figure 54 is a broken longitudinal cross section of a jarring apparatus which incorporates the apparatus of Figure 41 ;

Figure 55 is a diagrammatic broken longitudinal cross section of an alternative jarring apparatus which incorporates the apparatus of Figure 41 ;

Figure 56 is a longitudinal cross sectional view of a packer apparatus which incorporates an apparatus, such as apparatus shown in Figure 1, for cyclically retaining and releasing axial load, wherein the packer apparatus is illustrated in an unset configuration; and

Figure 57 is a longitudinal cross sectional view of the packer apparatus of Figure 56 in a set configuration.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 is a longitudinal cross sectional view of an apparatus, generally identified by reference numeral 10, for cyclically releasing axial load. The apparatus 10 may be used in any application where such repeated release of an axial load is required. While some specific example applications will be provided herein, these are not intended to be limiting. As such, Figure 1 generally illustrates a system 12 which is operated or is affected by the apparatus 10. The apparatus 10 comprises a housing 14 which accommodates the system 12. However, in other examples the system 12 may be located externally of the housing 14.

The apparatus 10 comprises a load member 16 in the form of an axial sleeve which extends to engage the system 12. The apparatus 10 further comprises a control mechanism 18 which is rotatably secured relative to the housing 14 via a rotary connector 20, for example a castellated connector. A mandrel 22 is rotatably mounted within the housing 14 and is thus rotatable relative to the control mechanism 18. As will be described in further detail below, the control mechanism 18 is operated in response to rotation of the mandrel 22 to cyclically retain and release axial loading transmitted between the system 12 and the control mechanism 18 via the load member 16. That is, the control mechanism 18 may be considered to function to allow the load member 16 to be cyclically loaded and unloaded relative to the control mechanism 18, thus providing a cyclical load dumping effect within the system 12.

The control mechanism 18 comprises a plurality of radially moveable control members 24 which are evenly circumferentially distributed relative to each other. Each control member 24 is associated with respective first and second end members 26, 28, wherein the first end members 26 are axially and rotatably secured to the rotary connector 20 via hook connectors 30, and the second end members 28 are axially and rotatably secured to the load member 16 via hook connectors 32. In this respect the load member 16 may be rotatably secured to the housing 14 via the control mechanism 18, and a control cage described later.

A first interface arrangement 34 in the form of cooperating wedge profiles is provided between the respective control members 24 and first end members 26, and a second interface arrangement 36 also in the form of cooperating wedge profiles is provided between the respective control members 24 and second end members 28. The first and second end members 26, 28 may thus also or alternatively be defined as wedge members or plates.

The first and second interface arrangements 34, 36 are configured such that radial movement of the control members 24 affects the axial length between the first and second end members 26, 28. As such, the radial position of the control members 24 can cause or permit axial extension and collapse of the control mechanism 18, which may thus affect the load within the load member 16. More specifically, the control mechanism 18 may be axially extended to retain load within the load member 16 when the control members 24 are located radially outwardly. In this respect an outward radial position of the control members 24 may be defined as a load retaining position. Conversely, the control mechanism 18 may be axially collapsed to release or dump load from the load member 16 when the control members 24 are located radially inwardly. In this respect an inward radial position of the control members 24 may be defined as a load release position.

Reference is additionally made to Figure 2 which is a lateral cross sectional view through line 2-2 of Figure 1. The mandrel 22 comprises a plurality of circumferentially distributed and axially extending mandrel or control cams 38 which are configured such that during rotation of the mandrel 22 in the direction of arrow 40 the cams 38 cyclically engage and radially lift and drop the control members 24. The control members 24 each comprise a follower profile or surface 41 configured to be engaged by the control cams 38 during rotation of the mandrel 22. Further, each control cam 38 defines a leading lifting cam profile 42 and a trailing dropping profile 44 which control the rate of radial displacement of the control members 24 in reverse directions. In the present example the leading lifting cam profiles 42 provide for a gradual lifting or outward radial displacement of the control members 24, whereas the trailing dropping profiles 44 provide for rapid dropping or inward radial displacement of the control members 24. Such a rapid dropping of the control members 24 may facilitate rapid load release from the load member 16. As will be described in more detail below, the profile of the control cam members 38 may be varied in accordance with the desired application.

When axial load is applied to the control mechanism 18 this may function to bias the control member radially towards its load release position, by operation of the interface arrangements 34, 36. As such, the control cams 38 may be subject to stresses applied by the axial load via the control members 24. However, as the control cams 38 effectively support load in a radial direction then the full axial load will not be transferred to the control cams 38, but rather only a radial force component. As such, the control cams 38 may be subject to lower stresses than might be the case in axial cam assemblies which would be exposed to the entire axial load. The magnitude of the radial force component may also be dictated by the form of the interface arrangements 34, 36, which may be provided accordingly. Furthermore, as the control cams 38 extend axially along the outer surface of the mandrel 22 this may permit a greater length of cam to be utilised, which may permit a greater cam surface contact area and thus load capacity to be achieved.

Reference is additionally made to Figure 3 which is an isometric view of the control mechanism 18, and to Figure 4 which is a corresponding exploded isometric view of the control mechanism 18. The control mechanism 18 further comprises a control cage 48 which is permitted to move axially within the control mechanism 18, at least by a limited distance. The control cage 48 defines a plurality of circumferentially arranged radial slots 50 which each accommodate respective sets of a control member 24 and first and second end members 26, 28. The slots 50 have an axial length which can accommodate the full axial extension of a control member 24 and associated first and second end members 26, 28.

Each control member 24 comprises first and second pairs of wings 52, 54 which are received within cooperating first and second pairs of radial bearing slots 56, 58 formed within the control cage 48, specifically in each radial slot 50. Engagement between the pairs of wings 52, 54 and respective bearing slots 52, 54 provides an axial connection between the control members 24 and the control cage 48, while permitting the control members 24 to be radially moved relative to the cage 48. In this respect, any required axial movement of the control members 24 during operation may be accommodated by axial movement of the control cage 48. As such, the control cage 48 may define a carriage member, which facilitates any required axial movement of the control members 24 while providing a robust support thereto during radial movement thereof. This arrangement may minimise the risk of the control members 24 binding within the apparatus 10. In particular, the axial arrangement of the wings 52, 54 and slots 56, 58 seeks to prevent any pitching movement of the control members 24, thus assisting to limit movement only in the radial direction, and contributing to preventing binding of the control members 24.

In the present example the first and second pairs of wing members 52, 54 and corresponding bearing slots 56, 58 define different widths. Such an arrangement prevents the control members 24 from being assembled within the control mechanism 18 in an incorrect orientation which might otherwise prevent the apparatus 10 from operating, for example by incorrect alignment of the follower surface 41 of the control member 24.

Still referring to Figures 1 to 4, the apparatus 10 further comprises an optional control biasing arrangement in the form of a spring 60 which functions to bias the control mechanism 18 towards an axially extended configuration. The force of the spring 60 may thus provide a boost force to assist the control cams 38 in radially displacing the control members 24 outwardly. That is, the spring 60 may act in a direction to seek to provide axial separation within the first and second interface arrangements 34, 36. In the example illustrated the spring 60 operates between first and second spring collars 62, 64. The first spring collar 62 is secured, for example by a threaded connection, to the load member 16. The second spring collar 64 is axially supported by a number of strut rods 66 which effectively bypass the control cage 48 and engage the connector 20. As such, one side of the spring 60 is effectively reacted into the housing 14, and an opposite end reacts against the load member 16, thus providing a bias force in a desired direction.

The apparatus further comprises a pair of control cam retaining rings 68, 70 (Figures 1 and 4), which function to radially constrain the control cams 38 against the mandrel 22. The cam retraining rings 68, 70 may be define different geometric features, such as dimensions to ensure they can only be mounted in a specific orientation within the apparatus 10. Further, the control cams may define specific geometric features which only engage with a specific one of the control cam retaining rings 68, 70 which ensure the control cams 38 are correctly installed.

The cam retaining rings 68, 70 also axially secure the control cams 38 relative to the control cage 48. Such arrangement ensures that the control cams 38 remain in a fixed axial position relative to the control members 24, which as noted above are also axially fixed relative to the control cage 48.

During use, the apparatus 10 may be initially configured as illustrated in Figure 1 , with the control members 24 fully radially retracted, which may correspond to their load release position. In this configuration load within the load member 16 may be at a minimum. However, some load may be applied on the control mechanism 18 by the load member 16 which retains the control mechanism 18 in the illustrated axially collapsed configuration.

Subsequent rotation of the mandrel 22 in the direction of arrow 40 is illustrated in Figures 5 and 6, wherein Figure 5 is a longitudinal cross sectional view of the apparatus 10 and Figure 6 is a lateral cross sectional view take through line 6-6 in Figure 5. In this configuration the control cams 38 have initiated displacement of the control members 24 radially outwardly, which results in axial extension of the control mechanism 18 via the first and second interface arrangements 34, 36. Specifically, radial movement of the control members 24 results in axial displacement of the control members 24 and second end members 28 in the direction of arrow 70 (which may be defined as a second axial direction), to thus extend the control mechanism 18. Axial movement of the control members 24 also provides axial movement of the control cage 48. Further, by virtue of the connection of the second end members 28 to the load member 16 the load member 16 is displaced in the same second axial direction 70. Such displacement of the load member 16 may provide a useful function within the system 12. For example, the load member 16 may drive a fluid piston, for example which is part of a fluid pump, injection system and/or the like. Alternatively, the load member 16 may directly or indirectly lift a jarring mass in preparation to generate a jarring force within the system 12. As a further example the load member 16 may provide a resetting function to a separate lifting mechanism used to lift a jarring mass.

In some examples such movement of the load member 16 in the second axial direction may cause load to be generated within the load member 16 and held against the control mechanism 18. As such, the control mechanism 18 may also be defined as a loading mechanism. However, in alternative examples movement of the load member 16 may not necessarily be associated with an increase or significant increase in load within the load member 16. Instead, any load generated within the load member 16 may be established within the system 12, and retained within the load member 16 against the control mechanism 18. As such, the control mechanism 18 may accommodate load generation within the load member 16, irrespective of whether this load is derived from movement of the load member 16 in the second direction, or from an alternative load source. Subsequent rotation of the mandrel 22 in the direction of arrow 40 is illustrated in Figures 7 and 8, wherein Figure 7 is a longitudinal cross sectional view of the apparatus 10 and Figure 8 is a lateral cross sectional view taken through line 8-8 in Figure 7. In this configuration the control cams 38 have peaked (i.e., immediately prior to the dropping profile 44 of the control cams 38 being appropriately aligned with the control members 24), such that the control members 24 are radially displaced to their maximum radial extension, and thus the control mechanism 18 configured in its maximum axial extension.

Subsequent rotation of the mandrel 22 causes the apparatus 10 to return to the initial configuration of Figures 1 and 2. In this respect the control cams 38 rotate past the control members 24, permitting the control members to rapidly drop or radially retract, and the control mechanism 18 to be axially collapsed. In this respect, load within the load member 16 previously held against the control mechanism 18 may be rapidly relieved or dumped, which may be associated with corresponding axial movement of the load member 16 in a first axial direction, illustrated by arrow 69. Such load dumping and possible axial movement of the load member 16 may provide a desired function within associated system 12, such as permitting a reverse stroke of a piston, allowing a jarring mass to drop, and/or the like. In this respect, once the support of the control cams 38 is removed load within the load member 16 may effectively cause the control mechanism 18 to axially retract, driving the control members 24 radially inwardly by virtue of the first and second interface arrangements 34, 36.

As noted above, the rate of radial displacement of the control members 24 may be affected by the cam profile provided between the control cams 38 and the control members 24. Figure 9 illustrates the cam profile of the apparatus 10 of Figure 1, which includes a continuous leading lifting cam profile 42 which terminates at an abrupt trailing dropping profile 44. The progression of radial displacement of the control member 24 with respect to mandrel rotation is graphically illustrated in Figure 10. In this respect a continuous radial displacement of the control member 24 is provided in a lifting phase 72 followed by rapid dropping of the control member 24 in a dropping phase 74, with the cycle repeated during continuous rotation of the mandrel 22.

Figure 11 illustrates a modified cam profile, in which control cams 38 define a steeper leading lifting cam profile, a retaining profile 45 and an abrupt trailing dropping profile 44. The progression of radial displacement of an associated control member 24 with respect to mandrel rotation is graphically illustrated in Figure 12. In this respect a rapid radial displacement of the control member 24 is provided in a lifting phase 72a, followed by the control member 24 being held in its radially extended position for a period in a retaining phase 75, an then followed by rapid dropping of the control member 24 in a dropping phase 74a, with the cycle repeated during continuous rotation of the mandrel 22. In this example the retaining phase 75 may provide a period in which load may be generated within the load member, for example via the associated system, with this load thus held against the control mechanism 18.

It should be recognised that any suitable form of cam profile may thus be selected in accordance with desired operation.

In the description above the apparatus 10 is shown operatively associated with a system 12. The system 12 may be any system which requires load within the load member 16 to be cyclically retained and released. A specific example of a jarring system will now be described, initially with reference to Figures 13 and 14, wherein Figure 13 is a longitudinal cross sectional view of the apparatus 10 in combination with a jarring system 80, and Figure 14 is a lateral cross section taken along line 14-14 of Figure 13. In this example the entire apparatus 10 may be defined as a jarring apparatus which includes the jarring system 80.

The jarring system 80 comprises an anvil 82 secured to the housing 14 and a jarring mass 84. The jarring mass 84 is biased in the first axial direction 69 towards engagement with the anvil 82. Such biasing may be provided by a spring arrangement (not shown), by tension applied within the apparatus, for example through the mandrel and/or the like. The jarring system 80 includes a pusher sleeve 86 which is engaged with the load member 16 of apparatus 10. In some examples the pusher sleeve may be integral or considered to be part of the load sleeve. In the configuration illustrated in Figure 13 the pusher sleeve 86 is initially axially separated from the jarring mass by a gap 88 and the control members 24 are radially retracted (i.e., in their load release position) such that the control mechanism 18 is axially collapsed. The corresponding relative position of the control cams 38 and control members 24 is shown in Figure 14. Upon rotation of the mandrel 22 the control cams 38 engage and radially displace the control members 24, as illustrated in Figure 15 and 16. Such radial displacement of the control members 24 causes the control mechanism 18 to axially extend and shift the load member 16 axially, which in turn axially moves the pusher sleeve 86 into engagement with the jarring mass 84 and closes gap 88.

Further rotation of the mandrel 22 further displaces the control members 24 to their full radial displacement, as illustrated in Figures 17 and 18, which provides full axial extension of the control mechanism 18. This full extension causes the load member 16 to further shift the pusher sleeve 86 and now lift the jarring mass 84 against the bias of the spring arrangement (not shown), creating an axial gap 88 between the jarring mass 84 and the anvil 82.

Further rotation of the mandrel 22 reverts the apparatus to the configuration illustrated in Figures 13 and 14. In this respect the control cams 38 rotate past the control members 24, permitting the control members 24 to rapidly drop or radially retract, and the control mechanism 18 to be axially collapsed. This causes the load member 16 to lose its support and therefore allows the bias force acting on the jarring mass 84 to accelerate the mass 84 to impact against the anvil 82 and generate an impact or jarring force. Continuous rotation of the mandrel 22 may permit repeated impacts and jarring forces to be generated.

As noted above, a degree of lost motion is required to close the initial gap 88 between the pusher sleeve 86 and the jarring mass 84 before the jarring mass 84 is lifted. That is, a proportion of the available axial movement of the control mechanism 18 is required to close the gap 88 prior to the jarring mass 84 being lifted. As such, the extent by which the jarring mass 84 may be lifted is a function of the remaining available axial extension within the control mechanism 18. This arrangement may permit adjustability of the axial lift of the jarring mass 84 to be provided. In this respect, and with reference again to Figure 13, an adjustment cap 92 is threadedly secured to the end of the pusher sleeve 86 adjacent the load member 16. In the illustrated example the cap 92 is fully threaded onto the pusher sleeve 86, which results in a maximum initial gap 88 between the pusher sleeve 86 and the jarring mass 84. However, the cap 92 may be adjusted by backing this off relative to the pusher sleeve 86 which provides a telescoping effect, ultimately increasing the length of the pusher sleeve 86. This therefore has the effect of reducing the initial gap 88, such that a smaller proportion of the axial range of the control mechanism 18 is utilised in closing the gap 88, and thus a larger proportion of the axial range is utilised to lift the jarring mass 84. In this respect a larger lift of the jarring mass 84 may result in a larger jarring force being generated. In some examples the cap 92 may be adjusted to eliminate any initial gap 88. The cap 92 may alternatively, or additionally, be secured to the load member 16. In fact, a telescoping type adjustment may be provided at any location in a load transmission path between the control mechanism 18 and the jarring mass 84.

In the example provided above the jarring mass 84 is provided as a separate structure. However, in some examples the jarring mass may be integrally formed with or provided by the mandrel 22. For example, the mandrel 22 may comprise an impact surface configured to engage the anvil 82, wherein displacement of the impact surface to provide a separation gap between the anvil and the impact surface generates tension within the mandrel 22 (and/or any connected work or running string). Such tension may act to bias the impact surface towards the anvil, such that when the control mechanism 18 dumps the supporting axial load the impact surface is driven to impact the anvil. As such, an reference herein to a jarring mass, within any described aspect or example, may equally refer to any component which may be capable of being energised and released to create a jarring force. In some examples an impact force may not be necessary, and instead a damping mechanism may alternatively be used to rapidly arrest the jarring mass or equivalent structure.

In the example presented above axial extension and collapse of the control mechanism provides corresponding reverse axial movement of the load member, which provides direct lifting and release/dropping of a jarring mass. However in other examples a separate lifting mechanism may be interposed between the load member and the jarring mass. Such an example will now be described with reference to Figure 19 which is a broken cross sectional view of the apparatus 10 including a modified jarring system 100. In this example the jarring system 100 again includes an anvil 102 secured to the housing 14 and a jarring mass 104 (or impact surface secured to the mandrel 22). The jarring mass 104 is biased in the first axial direction 69 towards engagement with the anvil 102. Such biasing may be provided by a spring arrangement (not shown), tension within the mandrel 22 and/or the like. The jarring system 100 includes a lifting mechanism 106 which includes first and second lifting structures provided in the form of respective first and second lifting cams 108, 110 which each comprise complimentary rotary cam profiles 112, 114 which interengage and cooperate upon relative rotation therebetween to cyclically cause the lifting cams 108, 110 to be displaced in one axial direction in a lifting phase, and to be displaced in a reverse axial direction in a dropping phase. Figure 20 provides an elevation view of the lifting mechanism 106 which more clearly illustrates the form and interaction of the cam profiles 112, 114.

In the present example the first lifting cam 108 is rotatably secured to the load member 16, and as described previously the load member 16 is rotatably secured to the housing 14 via the control mechanism 18. The second lifting cam 110 is rotatably secured to the mandrel 22, such that relative rotation between the mandrel 22 and housing 14 causes relative rotation and operation of the lifting mechanism 106. The second lifting cam 110 is also axially engaged with a pusher sleeve 116 which extends to engage the jarring mass 104.

Operation of the apparatus 10 and jarring system 100 will now be described initially with reference to Figures 21(a)-(c) and 22, wherein Figure 21(a) provides an illustration in the region of the control mechanism 18, Figure 21(b) provides an elevation view of the lifting mechanism 106, Figure 21(c) provides an illustration in the region of the anvil 102 and jarring mass 104, and Figure 22 is a lateral cross sectional view taken through line 22-22 of Figure 21(a).

In the initial illustrated configuration the control members 24 have been fully radially extended which fully axially extends the control mechanism 18. The form or profile of the control cams 38 is such that the control mechanism 18 may be held in this extended configuration for a period of rotation of the mandrel 22. When the control mechanism 18 is in this fully extended configuration the load member 16 may axially support the first lifting cam 108 of the lifting mechanism 18. The rotational position of the mandrel 22 is such that the cam profiles 112, 114 of the respective first and second lifting cams 108, 110 are in initial engagement without any lifting therebetween yet performed, such that the jarring mass 104 remains engaged against the anvil 102. Subsequent rotation of the mandrel 22 is illustrated in the similar drawing sequence of Figures 23(a)-(c) and 24. In this respect the mandrel 22 has been rotated such that the control members 24 remain radially supported such that the control mechanism 18 remains in its fully extended position, thus continuing to axially support the first lifting cam 108 via the load member. With the first lifting cam 108 supported in this way the second lifting cam 110 is axially displaced by virtue of the cooperating cam profiles 112, 114, thus causing he jarring mass 104 to be lifted relative to the anvil 102 via the pusher sleeve 116.

Further rotation of the mandrel 22 is illustrated in the similar drawing sequence of Figures 25(a)-(c) and 26, in which the control cams 38 have rotated past the control members 24, permitting the control members 24 to be moved radially inwardly and the control mechanism 18 to axially collapse. Such axial collapse of the control mechanism 18 may effectively cause the load retained within the load member 16, which is holding the jarring mass 114 in its lifted position, to be released or dumped, resulting in the bias force applied on or within the jarring mass 114 to drive this to impact the anvil 102 and thus generate a jarring force.

It should be noted that in the present example the load is released or dumped while the cam profiles 112, 114 of the first and second lifting cams 108, 110 are still engaged in a lifting phase. In this respect the cam profiles 112, 114 may complete their lifting phase while under significantly reduced axial load, thus providing a degree of protection to the first and second lifting cams 108, 110. In particular, as the cam profiles 112, 114 progress during the lifting phase the area of contact therebetween reduces, which can result in significant stresses being applied when under load. The ability to dump the axial load to generate a jarring force prior to the cam profiles reaching their peak position may thus contribute to minimising exposure to significant stresses.

In a similar manner to previous examples, the apparatus 10 and jarring system 100 may accommodate adjustment of the permitted extent of lifting of the jarring mass 104, which may permit adjustment in the jarring force generated. Such adjustment capability will now be described initially with reference to Figure 27 which is an exploded view of the control mechanism 18 of the apparatus 10, showing the mounting arrangement of the first lifting cam 108 to the load member 16. In this respect, the apparatus comprises an adjustment collar 120 which may be screwed onto the end of the load member 16 to a required axial position or setting, with the first lifting cam 108 then secured over the adjustment collar 120. As such, the axial position of the adjustment collar 120 on the load member 16 may establish an axial setting of the first lifting cam 108, which as described below may provide for adjustment in the maximum lift of the jarring mass 104.

The load member 16 includes a circumferential array of radial slots 122 in an end region thereof. Similarly, both the adjustment collar 120 and the first lifting cam 108 include corresponding arrays of slots 124, 126, wherein all radial slots 122, 124, 126 are provided with the same circumferential spacing such that alignment therebetween may be achieved. When the adjustment collar 120 is threaded onto the load member 16 to the desired location, the adjustment collar 120 may then be finely adjusted to ensure alignment between respective slots 122, 124. The first lifting cam 108 may then be mounted over the adjustment collar 120 and the slots 126 brought into alignment with slots 122, 124. Radial locking keys (not shown) may then be located within the aligned slots 122, 124, 126 to this secure the assembly together.

Figure 28(a) illustrates the adjustment collar 120 set at its minimum setting, fully threaded onto the end of the load member 16. Figure 28(b) shows the corresponding relative alignment between the first and second lifting cams 108, 110 at the point of initial engagement of the respective cam profiles 112, 114 and without yet having lifted the jarring mass 104, as illustrated in Figure 28(c). In this respect the lifting profiles are brought into engagement late in the rotation cycle and as such the available lift is minimal before the load member 16 is released.

Figure 29(a) illustrates the adjustment collar 120 set at its maximum setting, which results in the adjustment collar 120 and first lifting cam effectively being telescoped from the end of the load member 16. Figure 29(b) shows the corresponding relative alignment between the first and second lifting cams 108, 110 at the point of initial engagement of the respective cam profiles 112, 114 and without yet having lifted the jarring mass 104 as illustrated in Figure 28(c). In this respect the lifting profiles are brought into engagement early in a rotation cycle and as such the available lift is maximal before the load member 16 is released. In the examples provided above each control member 24 is associated with first and second end members and first and second interface arrangements therebetween, such that axial extension and collapse of the control mechanism may be provided by both interface arrangements. However, in alternative examples a single interface arrangement may be provided on one side of the control member 24 only, such as illustrated in the alternative examples of Figures 30(a) and 30(b), which for brevity are illustrated together in upper and lower halves of an apparatus. Specifically, in the example of Figure 30(a) an interface arrangement 136a is provided only between control member 124a and end member 128b on one side of the control member 124a. In the alternative example of Figure 30(b) an interface arrangement 134b is provided only between control member 124b and end member 126b. These examples may be provided where a lower magnitude of axial extension and collapse of a control mechanism is required.

Figure 31 is a longitudinal cross sectional view of an alternative apparatus, generally identified by reference numeral 210, for cyclically retaining and releasing axial load. The apparatus 210 is similar in many respects to the apparatus 10 described above, and as such like features share like reference numerals, incremented by 200.

The apparatus 210 may be used in any application where repeated retaining and releasing of an axial load is required. While some specific example applications will be provided herein, these are not intended to be limiting. As such, Figure 31 generally illustrates a system 212 which is operated or is affected by the apparatus 210.

The apparatus 210 comprises a housing 214 which accommodates the system 212. However, in other examples the system 212 may be located externally of the housing 214.

The apparatus 210 comprises a load member 216 in the form of an axial sleeve which extends to engage the system 212. The apparatus 210 further comprises a control mechanism 218 which is rotatably secured relative to the housing 214. A mandrel 222 is rotatably mounted within the housing 214 and is thus rotatable relative to the control mechanism 218. As will be described in further detail below, the control mechanism 218 is operated in response to rotation of the mandrel 222 to cyclically retain and release axial loading transmitted between the system 212 and the control mechanism 218 via the load member 216. That is, the control mechanism 218 may be considered to function to allow the load member 216 to be cyclically loaded and unloaded relative to the control mechanism 218, thus providing a cyclical load dumping effect within the system 212.

The control mechanism 218 comprises a plurality of radially moveable control members 224 which are evenly circumferentially distributed relative to each other. Each control member 224 is associated with respective first and second end members 226, 228, wherein the second end members 228 are axially and rotatably secured to the load member 216 via hook connectors 232.

A first interface arrangement 234 in the form of a toggle assembly is provided between the respective control members 224 and first end members 226, and a second interface arrangement 236 also in the form of a toggle assembly is provided between the respective control members 224 and second end members 228.

Reference is additionally made to Figure 33, which is an exploded view of a control member 224 and associated first and second end members 226, 228 and interface arrangements or toggle assemblies 234, 236. The first toggle assembly 234 comprises a toggle arm 150 pivotally connected at one end to the control member 224 via a first pivot joint or pin 152, and pivotally connected at an opposite end to the first end member 226 via a second pivot joint or pin 154. Similarly, the second toggle assembly 236 comprises a toggle arm 156 pivotally connected at one end to the control member 224 via a first pivot joint or pin 158, and pivotally connected at an opposite end to the second end member 228 via a second pivot joint or pin 160. In this example radial movement of the control member 224 varies the incline of the toggle arms 150, 156 which thus provides relative axial movement between the first and second end members 226, 228. As such radial movement of the control members 224 can cause or permit axial extension and collapse of the control mechanism 218, which may thus affect the load within the load member 216. More specifically, the control mechanism 218 may be axially extended to retain load within the load member 216 when the control members 224 are located radially outwardly. In this respect an outward radial position of the control members 224 may be defined as a load retaining position. Conversely, the control mechanism 218 may be axially collapsed to release or dump load from the load member 216 when the control members 224 are located radially inwardly. In this respect an inward radial position of the control members 224 may be defined as a load release position.

Reference is additionally made to Figure 32 which is a lateral cross sectional view through line 32-32 of Figure 31. The mandrel 222 comprises a plurality of circumferentially distributed control cams 238 which are configured such that during rotation of the mandrel 222 in the direction of arrow 240 the cams 238 cyclically engage and radially lift and drop the control members 224.

Reference is additionally made to Figure 34 which is an isometric view of the control mechanism 218. The control mechanism 218 further comprises a control cage 248 which is axially split and includes first and second cage portions 162, 164 which are permitted to move axially relative to each other to accommodate axial extension and collapse of the control mechanism 218. In this example the first cage portion 162 is secured to the housing 214, and the second cage portion is secured to (e.g., integrally formed with) the load member 216. With brief additional reference to Figure 35, the first and second cage portions 162, 164 are biased apart via a plurality of circumferentially arranged biasing assemblies 166. Each biasing assembly 166 comprises a spring 168 and piston member 170 mounted within a spring bore 172 formed in the first cage portion 162 (although the second cage portion 164 could equally include a spring bore 172). The piston member 170 extends from the spring bore 172 to engage an end face of the adjacent second cage portion 164, thus providing a biasing force thereagainst. Such a biasing arrangement may provide a boost force to assist in moving the control mechanism 218 towards its extended configuration, springs also impact dampener upon load release to prevent cage portions hammering together

Referring again to Figure 34, the first and second cage portions 162, 164 collectively define circumferentially arranged radial slots 250 which each accommodate respective sets of a control member 224 and first and second end members 226, 228. In this example the first end member 226 defines a first width 174 which closely corresponds to the width of the portion of the slot 250 formed in the first cage portion 162 and the second end member 228 defines a second width 176 which closely corresponds to the width of the portion of the slot 250 formed in the second cage portion 164. In this example the first and second widths 174, 176 are different such that the end members 226, 228 and interconnected control member 224 can only be inserted within the control cage 248 in the correct orientation. Furthermore, the arrangement of the first and second toggle assemblies 234, 236 may be such that the control member 224 may be secured between the first and second end members 226, 228 only in a defined orientation, again contributing to preventing incorrect assembly of the apparatus 210.

The first and second cage portions 162, 164 comprise a rotatable connection arrangement therebetween, specifically in the form of inter-engaging castellations 201, 202. These castellations 201, 202 may permit torque to be transmitted across the control cage 248, for example to ensure the load member 216 may be rotatably secured to the housing 214. In some examples the castellations 201 , 202 may define a closer inter-engagement, interference or tolerance than the slots 250 relative to the control members 224. This arrangement may ensure that any torque applied across the control cage 248 will be accommodated by the castellations 201, 202, thus avoiding binding of the control members 224.

In one example as illustrated in Figure 36 the radial travel of the control members 224 may be limited, for example by engagement with the housing 214 of the apparatus 210. When in the illustrated limit of radial extension the respective pairs of first and second pivot joints 152, 154 and 158, 160 of the first and second toggle assemblies 234, 236 may be inclined at an angle a, such that any applied axial force between the end members 226, 228 will resolve to a radial force which acts radially inwardly to bias the control member 224 towards its load release position. As such, the toggle assemblies 234, 236 are arranged to prevent inverted movement of the control member 224.

In the configuration of Figure 31 the control members 224 are held radially outwardly by the control cams 238, such that the load member 216 may be loaded against the control mechanism 218. Upon rotation of the mandrel 222 in the direction of arrow 240 the control cams 238 may move past the control members 224 as illustrated in Figures 37 and 38, permitting the control members 224 to be displaced radially inwardly and the control mechanism 218 to become axially collapsed and thus release or dump load from the load member 216.

In the description above the apparatus 210 is shown operatively associated with a system 212. The system 212 may be any system which requires load within the load member 216 to be cyclically retained and released. A specific example of a jarring system will now be described with reference to Figure 39 which shows apparatus 210 in combination with a jarring system 280. In this example the entire apparatus 210 may be defined as a jarring apparatus which includes the jarring system 280. This arrangement is similar to that disclosed with reference to Figures 13, in that the load member 216 in combination with the control mechanism 218 operates a jarring mass 284 to be lifted and dropped relative to an anvil 282. The same principles described above thus apply and for brevity no further description will be given.

In an alternative example, as illustrated in Figure 40, the jarring system may further incorporate a lifting mechanism 306 which is interposed between the control mechanism 218 and the jarring mass 284. This arrangement is similar to that described initially with reference to Figure 19 and for brevity no further detailed description will be provided.

In the example provided above each control member 224 is associated with first and second end members and first and second toggle interface arrangements therebetween. However, in alternative examples a single toggle interface arrangement may be provided on one side of the control member 224 similar to the wedge profile examples of Figures 30(a) and 30(b).

Figure 41 is a longitudinal cross sectional view of an alternative apparatus, generally identified by reference numeral 410, for cyclically retaining and releasing axial load. The apparatus 410 is similar in many respects to the apparatus 10 described above, and as such like features share like reference numerals, incremented by 400.

The apparatus 410 may be used in any application where repeated retaining and releasing of an axial load is required. While some specific example applications will be provided herein, these are not intended to be limiting.

The apparatus 410 comprises a housing 414 and a load member 416 in the form of an axial sleeve mounted within the housing 414. The apparatus 410 further comprises a control mechanism 418 which is rotatably secured relative to the housing 414. A mandrel 422 is rotatably mounted within the housing 414 and is thus rotatable relative to the control mechanism 418. As will be described in further detail below, the control mechanism 418 is operated in response to rotation of the mandrel 422 to cyclically retain and release axial loading within the load member 416. That is, the control mechanism 418 may be considered to function to allow the load member 416 to be cyclically loaded and unloaded relative to the control mechanism 418, thus providing a cyclical load dumping effect within an associated system.

The control mechanism 418 comprises a plurality of radially moveable control members 424 which are evenly circumferentially distributed relative to each other. The control members 424 are mounted within respective radial slots 450 provided within a control cage 448 which is secured to the housing 414. In the present example the control members 424 are provided in the form of radial dogs.

Reference is additionally made to Figure 42 which is a lateral cross sectional view through line 42-42 of Figure 41. The mandrel 422 comprises a plurality of circumferentially distributed control cams 438 which are configured such that during rotation of the mandrel 422 in the direction of arrow 440 the cams 438 cyclically engage and radially lift and drop the control members 424.

One end of the load member 416 circumscribes the control mechanism 418 and comprises a first locking profile 175, wherein the control members 424 comprise corresponding second locking profiles 176. When the load member 416 is appropriately aligned with the control mechanism 418 the control members 424 may be radially extended, by the control cams 438, to effectively axially lock the load member 416 by inter-engagement of the locking profiles 175, 176.

The apparatus 410 further comprises a reset mechanism 177 which acts axially between an end face of the control cage 448 and a load shoulder 184 provided on the load member 416. With additional reference to Figures 43 and 44, the reset mechanism 177 comprises a reset cam 178 which is rotationally fixed to the mandrel 422 via keys 179, and a cam insert 180 which is rotationally fixed to the load member 416 via pins 181 (Figure 44). The reset cam 178 comprises a first cam profile 182 and the cam inset 180 comprises a cooperating second cam profile 183, wherein the cam profiles 182, 183 inter-engage and cooperate upon relative rotation therebetween to cyclically cause the reset cam 178 and cam insert 180 to be displaced in one axial direction in a lifting phase, and to be displaced in a reverse axial direction in a dropping phase. In this respect, the reset mechanism 177 may be configured to displace the load member 416 in the direction of arrow 185 relative to the control cage 448.

A sequence of operation of the apparatus 410 will now be described, starting in the configuration presented in Figure 41. In this initial configuration the control cams 438 support the control members 424 in a radially extended position to engage and lock the load member 416. In this configuration the load member 416 may support a desired operation in a related system or apparatus.

A subsequent phase of operation is illustrated in Figures 45 to 47, wherein Figure 45 is a longitudinal sectional view of the apparatus 410, Figure 46 is a sectional view taken along line 46-46 of Figure 45, and Figure 47 is an elevation view of the reset mechanism 177. In this example the mandrel 422 has further rotated in the direction of arrow 440 such that the control cams 438 move past the control members 424, thus removing the locking effect on the load member 416. As such, load held within the load member 416 against the control mechanism 418 is released, which in the present example causes the load member to be translated a distance in the direction of arrow 186. When in this initial load dump configuration the first and second cam profiles 182, 183 within the reset mechanism 177 remain disengaged, and the respective profiles 175, 176 of the load member 416 and the control members 424 are axially misaligned.

Further rotation of the mandrel 422 reconfigures the apparatus 410 into the configuration illustrated in the corresponding drawing sequence in Figures 48 to 50, reference to which is now made. In this example the mandrel 422 has rotated such that the first and second cam profiles 182, 183 of the reset mechanism cooperate to cause the load member 416 to move in the direction of arrow 185. Such movement of the load member 416 may align the respective profiles 175, 176 of the load member 416 and control members 424. Furthermore, this movement of the load member 416 may optionally provide a useful function in an associated system or apparatus, such as to lift a jarring mass, reset a lifting mechanism, drive a piston in a forward stroke and/or the like. In the illustrated configuration of Figures 48 to 50 the control cams 438 are not yet aligned with the control members 424.

Subsequent rotation of the mandrel 422 may reconfigure the apparatus 410 into the configuration illustrated in the corresponding drawing sequence in Figures 51 to 53, reference to which is now made. In this phase the control cams 438 again displace the control members 424 radially outwardly to provide cooperation between profiles 175,

176, thus once again locking the load member 416 against movement such that load within the load member may be held against the control mechanism 418. In the present example the profiles 175, 176 define slightly tapered axial shoulders, such that during this phase of operation the load member 416 is slightly moved or biased in direction 185 (se Figure 41). Such an arrangement may unload the reset mechanism

177, thus avoiding said mechanism 177 from possibly holding load as the load member 416 becomes loaded.

The apparatus 410 may be operatively associated with any system which requires load to be retained and released or dumped via the load member 416. A specific example of a jarring system will now be described with reference to Figure 54 which shows the apparatus 410 in combination with a jarring system 480. In this example the entire apparatus 410 may be defined as a jarring apparatus which includes the jarring system 480. This arrangement is similar to that disclosed with reference to Figures 13, in that the load member 416 in combination with the control mechanism 418 operates a jarring mass 484 to be lifted and dropped relative to an anvil 482. The same principles described above thus apply and for brevity no further description will be given.

In an alternative example, as illustrated in Figure 55, the jarring system may further incorporate a lifting mechanism 506 which is interposed between the control mechanism 418 and the jarring mass 484. This arrangement is similar to that described initially with reference to Figure 19 and for brevity no further detailed description will be provided.

It has been made clear that the described apparatuses may be used in combination with any system which requires repeated load retention and dumping. Some example uses in jarring applications have been described. However, to provide a further example reference is now made to Figure 56. In this respect apparatus 10 first illustrated in Figure 1 is provided, and as such no further detail will be provided. The load member 16 is connected with (e.g., integrated with) a piston 500 which seals one end of a hydraulic chamber 502. A packer assembly 504 is mounted on the housing 14 and includes a setting piston 506 which seals an opposite end of the hydraulic chamber 502. The packer assembly 504 further comprises an axially compressible packer element 508 which is positioned between the setting piston 506 and a retaining body 510. Although not illustrated, a ratchet assembly is provided between the setting piston and the mandrel 22, wherein the ratchet assembly retains any setting force applied on the packer element 508 from the setting piston 506. During a loading cycle within the apparatus 10 the load member 16 drives the piston 500 in the direction of arrow 70 which pressurises the hydraulic chamber 502 and provides corresponding axial movement of the setting piston 506, which thus applies a compressive force to the packer element 508, with this force being locked in by the ratchet assembly. During a load release cycle within the apparatus 10 the load being held by the load member 16 against the control mechanism 18 is relieved or dumped, with the piston 500 and load member 16 being moved in the direction of arrow 69 by virtue of a power spring 512 within the hydraulic chamber 502. This movement of the piston 500 increases the volume of the hydraulic chamber 502, wherein hydraulic locking of the chamber is prevented by receiving hydraulic fluid from a central bore 514 of the mandrel 22 via a check valve 516. This cycle may thus be repeated to incrementally cause the packer element 508 to be pressure set, as illustrated in Figure 57, by continuous rotation of the mandrel 22.

In a modified example the hydraulic chamber may be eliminated and a rigid transmission member (e.g., a load member or assembly) may be provided between the control mechanism 18 and setting piston 506 (which thus does not necessarily need to be a piston). As such, the apparatus 10 may function to incrementally shift the setting piston 506, with a ratchet assembly locking in each incremental movement step, and the spring 512 effectively resetting the control mechanism in preparation for a subsequent cycle.