The present invention relates to a failsafe mechanism for a tool, such as a lifting or separating wedge. Examples of the invention are optionally useful in hydraulic or mechanical tools, and are optionally useful in tools that use high operating loads, to lift heavy objects, or to apply high forces.

Lifting and separating wedges are well known. Failsafe mechanisms used in such tools rely on safety valves in other systems, such as pumps that are used to power the tools. For example, a hydraulic lifting wedge can comprise a piston and cylinder arrangement within the lifting wedge, which can be connected to a separate pump, in order to apply pressurised fluid to the piston rod within the cylinder to operate the tool. The pump may have a safety valve set to relieve the pressure within the pump or the cylinder at a particular limit within which the pump or the tool can safely operate. Also, a safety valve having a similar pressure relief facility can be incorporated within the hydraulic lifting wedge itself. In most cases, this is entirely satisfactory, and in the event that pressurised fluid is delivered to the cylinder above a threshold at which the lifting wedge can safely operate, the pressure relief valve on the pump, or on the lifting wedge, simply opens to relieve the pressure, and this reduces the load to safe operating parameters.

Lifting and separating wedges of known designs can exert extremely high forces in order to lift weights of the order of several tonnes, and or to apply similar loads to separate large items, such as pipeline flanges. While pressure relief valves of the kind discussed above are normally satisfactory, in the event of failure of the valve, or deliberate tampering with the valve to prevent its normal operation, loads can sometimes be applied to the lifting and separating devices that are higher than can safely be accommodated by the tool, and this has occasionally resulted in unpredictable failure of the tool at extremely high loads. This can cause injury to the operator, for example if the tool is ejected from a joint between a pair of opposed pipeline flanges, or if a part of the jaws of the tool snaps and flies off. In accordance with the present invention there is provided a failsafe mechanism for a tool, comprising an actuator rod adapted to change repeatedly between active and inactive configurations to activate and deactivate the tool in response to a control mechanism, and a housing for the actuator rod, wherein the actuator rod has a deformation region, and being adapted to change between an operative

configuration, which allows the actuator rod to change repeatedly between the inactive and active configurations, and an inoperative configuration, which resists or prevents change of the actuator rod between the active and inactive

configurations, and wherein in the event of a load being applied to the actuator rod in excess of a load limit of the deformation region, the actuator rod is configured to deform preferentially at the deformation region, which is adapted to change from the operative configuration to the inoperative configuration, to resist change of the actuator rod between the active and inactive configurations. Optionally the deformation region is adapted to deform in a predictable manner, for example in a predictable direction. Optionally the direction of deformation of the deformation region is controlled by asymmetric structures on the deformation region, permitting deformation of the deformation region at low loads in the desired direction, and resisting deformation in other directions. Optionally the deformation region expands (optionally radially) from the actuator rod under loads being applied in excess of the load limit.

Optionally the portions of the actuator rod apart from the deformation region are adapted to withstand the load limit that is adapted to deform the deformation region, so loads applied just above the load limit which deform the deformation region optionally only deform the deformation region, and the remainder of the actuator rod is unaffected. Thus the deformation region is the least able to resist axial loads applied to the actuator rod, and preferentially deforms before the rest of the actuator rod when loads are applied above the load limit of the deformation region. Optionally the actuator rod translates axially through a collar, which optionally guides the axial movement of the actuator rod between the active and inactive configurations. Optionally the collar is adapted to allow passage of the actuator rod through the collar when the actuator rod is in the operative configuration, but when the actuator rod is in the inoperative configuration, the collar is optionally arranged to resist passage of the actuator rod therethrough.

Optionally, the actuator rod is a close fit within the collar. Optionally the tool can be a hydraulic tool having a piston and a cylinder, wherein the piston is movable within the cylinder in response to pressurised fluid within the cylinder. Optionally the piston is sealed to the cylinder, and the actuator rod comprises a piston rod connected to the piston. Optionally the housing comprises the cylinder. In certain examples of the invention, the failsafe mechanism can be applied to mechanical tools that do not incorporate hydraulic features. In such cases, the actuator rod can be a pushrod that can be housed within the collar.

Optionally the housing guides the movement of the actuator rod between the active and inactive configurations. Optionally the change in the actuator rod between the active and inactive configurations comprises movement of the actuator rod, optionally axial movement through the collar.

Optionally the actuator rod has an axis, and optionally the change in configuration in the actuator rod between active and inactive configurations involves axial translation of the actuator rod along the axis.

Optionally the deformation region is provided in a wall of the actuator rod, optionally radially spaced from a chamber in the rod. Optionally, the deformation region comprises a section of side wall in the actuator rod that has an asymmetric region in the form of a reduced thickness as compared with the remainder of the rod, although the deformation region can also be formed by a different (weaker) material to the remainder of the actuator rod, having optionally the same thickness, but a reduced strength.

Optionally the deformation region is arranged to pass through the collar when the actuator rod changes between the active and the inactive configurations.

Optionally, the actuator rod has a chamber adjacent to the deformation region, and in certain examples, the deformation region can comprise a blind ended chamber within the actuator rod that is provided with a reduced wall thickness in the area of the deformation region.

Optionally the actuator rod can comprise more than one deformation region.

Optionally the deformation region can comprise an annular portion of the actuator rod.

Optionally, the deformation region is adapted to pass through the collar in its operative configuration, but is adapted to resist passage through the collar in its inoperative configuration. Optionally the deformation region changes from the operative configuration to the inoperative configuration by radial expansion. In certain examples, the radial expansion of the deformation region is circumferential around the whole circumference of the actuator rod, but in certain other examples, this is not necessary, and only a portion of the circumference of the actuator rod is deformed, e.g. radially expanded, in order to change the deformation region from the operative configuration to the inoperative configuration.

Optionally, the radial expansion of the deformation region from the operative configuration into the inoperative configuration is achieved by application of hydraulic pressure within the chamber of the actuator rod. Optionally, the chamber of the actuator rod can be in fluid communication with the hydraulic cylinder, in relation to a hydraulic example of a tool according to the invention, so that hydraulic fluid used to move the actuator rod in the form of the piston rod is also used to change the deformation region from the operative configuration to the inoperative configuration.

Optionally, where more than one deformation region is provided in the actuator rod, the deformation regions can be axially spaced along the actuator rod. Optionally the inoperative configuration of the deformation region prevents movement of the actuator rod through the collar, and thereby prevents operation of the tool at the high load above the load limit of the deformation region. Optionally the change in configuration of the deformation region from the operative configuration to the inoperative configuration is irreversible, and after the deformation region has changed into the inoperative configuration, the tool optionally requires intervention, usually to replace or repair the actuator rod, and optionally the housing, and optionally the collar.

Optionally the transition from the operative to the inoperative configuration locks the actuator rod in the housing, resisting axial movement, at least in the direction of movement of the actuator rod toward the operative configuration, optionally in an axial direction of movement of the rod through the collar, and optionally in both axial directions of movement of the rod through the collar.

Optionally the axial position of the deformation region is selected in relation to the axial length of the actuator rod to prevent operation of the tool and to lock the tool at a predictable position, optionally governed by the relative position of the deformation region in relation to the housing, and particularly advantageously in relation to the collar. Thus, in examples of the invention, even when dangerously high loads are applied to the actuator rod, the actuator rod optionally locks in a predictable and safe position, preventing operation of the tool. Optionally, the deformation region can change to the inoperative configuration when the actuator rod is in the active or in the inactive configuration. Accordingly, the tool can be locked in its active or in its inactive configurations, optionally depending on the position of the deformation region in relation to the travel of the actuator rod through the bore of the collar.

In certain examples of the invention, the deformation region can be adapted to engage on an inner surface of the collar. Optionally the mechanism can comprise gripping formations to enhance the resistance to axial translocation of the actuator rod through the collar, when the deformation region has changed to the inoperative configuration, for example, when the deformation region has radially expanded against the inner wall of the collar. The gripping portions can optionally be provided on the actuator rod, e.g. on the outer surface of the actuator rod, or can be provided on the collar, e.g. on the inner surface of the collar. The gripping formations can optionally comprise corrugations or ridges or the like, possibly extending circumferentially, and adapted to present irregularities on the outer surface of the deformation region, or on the inner surface of the collar, in order to bite into the opposing surface, and resist axial translocation of the actuator rod once the deformation region has changed to the inoperative configuration.

Optionally the deformation region has a short axial length along the axis of the actuator rod, so that the location of the deformation of the deformation region in the inoperative configuration can be more accurately predicted.

Optionally the change of the deformation region to the inoperative configuration limits the movement of the actuator rod in only one direction, but optionally can limit the movement of the actuator rod in both directions.

The various aspects of the present invention can be practiced alone or in

combination with one or more of the other aspects, as will be appreciated by those skilled in the relevant arts. The various aspects of the invention can optionally be provided in combination with one or more of the optional features of the other aspects of the invention. Also, optional features described in relation to one embodiment can optionally be combined alone or together with other features in different embodiments of the invention. Various embodiments and aspects of the invention will now be described in detail with reference to the accompanying figures. Still other aspects, features, and advantages of the present invention are readily apparent from the entire description thereof, including the figures, which illustrates a number of exemplary

embodiments and aspects and implementations. The invention is also capable of other and different embodiments and aspects, and its several details can be modified in various respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising,"

"having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention.

In this disclosure, whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition, element or group of elements with transitional phrases "consisting essentially of", "consisting", "selected from the group of consisting of", "including", or "is" preceding the recitation of the composition, element or group of elements and vice versa. All numerical values in this disclosure are understood as being modified by "about". All singular forms of elements, or any other components described herein are understood to include plural forms thereof and vice versa. References to positional descriptions such as "upper" and "lower", and directions such as "up", "down" etc in relation to the invention are to be interpreted by a skilled reader in the context of the examples described and are not to be interpreted as limiting the invention to the literal interpretation of the term, but instead should be as understood by the skilled addressee. In the accompanying drawings,

Fig 1 is a perspective view of a hydraulic piston and cylinder arrangement used in a first example of a failsafe mechanism;

Fig 2 is an end view of the Fig 1 cylinder;

Fig 3 is part section view through line A-A of Fig 2;

Fig 4 is a side view similar to Fig 3, showing the piston rod axially translated within the cylinder in response to normal hydraulic pressure within the cylinder;

Fig 5 is a side view similar to Figs 3 and 4, showing the piston in a locked and inactive configuration by the radial expansion of the deformation region in the piston rod;

Figs 6, 7 and 8 show side sectional views of a second example of a piston and cylinder arrangement incorporating a failsafe mechanism;

Figs 9, 10 and 11 show end views of the arrangements shown in Figs 6, 7 and 8;

Figs 12, 13 and 14 show the different inoperative configurations of the piston and cylinder arrangements shown in Figs 6, 7 and 8, with the piston rod locked in three different positions within the cylinder;

Figs 15, 16 and 17 show corresponding end views of Figs 12, 13 and 14.

Referring now to the drawings, a hydraulic tool incorporating a failsafe mechanism in accordance with the invention optionally comprises a cylinder and piston arrangement 1 as shown in Figs 1 to 5. The arrangement 1 comprises a housing in the form of a hydraulic cylinder 5, having a central bore forming a chamber 6, which houses a piston, having an actuator rod in the form of a piston rod 5 which extends through an axial bore in a collar 8 on the end of the cylinder 5. The piston rod 10 is optionally a close fit within the bore of the collar 8, and the collar 8 is optionally coaxial with the bore of the chamber 6. The piston optionally has a flange which is optionally sealed in the bore of the chamber 6, so that the piston optionally translates axially along its long axis X-X to extend the piston rod 10 out through the collar 8 in response to the delivery of pressurised fluid into the chamber 6 behind the sealed flange of the piston. The extension of the piston rod 10 from the cylinder 5 operates a lifting or separating wedge for example, but the arrangement can be used to operate a range of different tools within the scope of the invention.

The piston rod 10 advantageously incorporates a chamber in the form of an axial bore which has an asymmetric wall portion in the form of an undercut forming the chamber 11 in a central portion of the piston rod 10. The axial bore connects the chamber 11 in the piston rod 10 to the chamber 6 in the housing 5, so fluid pressure is transmitted between the two chambers 6, 11 along the axial bore.

The undercut removes approximately 50% of the wall thickness of the piston rod surrounding the bore, as best shown in Fig 3, to create a weakened deformation region 15 of the piston rod 10, radially outwards of the chamber 11. The deformation region 15 extends axially along the piston rod 10, stopping at a point just before the piston rod 10 enters the bore of the collar 8, so that the deformation region 15 is contained within the bore of the chamber 6 of the cylinder 5 when the piston is in the inactive configuration as shown in Fig 3. In this configuration, the force retracting the piston into the cylinder 5 is greater than the force applied by the pressurised fluid in the chamber 6 behind the sealed area of the piston, so the piston is in a zero stroke position, with the flange in the piston abutting against an end cap at the opposite end of the cylinder 5 to the collar 8. Optionally, the piston can be retracted into the zero stroke configuration by a spring that is held in compression between the housing and the flange. In this zero stroke position, the force applied by the hydraulic pressure behind the flange of the piston in the chamber 6 is less than the load limit (designated X) of the deformation region 15, so that the deformation region 15 essentially behaves in the same way as any other part of the piston rod, and maintains its structural integrity within the load limit. Alternatively, or additionally, a spring (not shown) can be held in tension between the piston rod 10 and the cylinder, within the bore of the piston rod 10, to retract the piston rod 10 back into the cylinder when the extension force reduces below the tension of the spring.

Fig 4 shows the same arrangement with the piston rod 10 fully extended in response to an increased hydraulic pressure in the chamber 6 behind the sealed area of the piston. In the Fig 4 configuration, the force applied by the hydraulic pressure in the chamber 6 is sufficient to overcome the force of any spring or other device tending to retract the piston into the cylinder 5, but it is still below the load limit X of the deformation region 15, and so at these low forces, the deformation region 15 still retains its structural integrity, and does not deform the piston rod 10. Therefore, the piston rod 10 is free to repeatedly cycle axially in both directions through the collar 8 between the active configuration shown in Fig 4 and the inactive configuration shown in Fig 3, provided the force applied by the hydraulic pressure in the chamber 6 remains within the load limit X of the deformation region 15. In the event that the force applied by the hydraulic fluid in the chamber 6 exceeds the load limit X of the deformation region 15, the arrangement of the piston and housing 1 adopts the configuration shown in Fig 5. In this configuration, the high- pressure in the chamber 6 behind the piston is transmitted to the chamber 11 by means of the coaxial bore in the piston rod 10. Because the force transmitted to the chamber 11 exceeds the load limit X of the deformation region 15, the asymmetric thin walls of the deformation region 15 selectively deform by expanding radially outwards from the operative configuration shown in Figs 3 and 4, to the inoperative configuration shown in Fig 5, although the deformation is limited to the deformation region 15, as the load limit of the remainder of the piston rod 10 is above X.

The deformation region 15 expands radially outwards as a result of the fluid pressure differential across the chamber 11. Optionally, the direction of deformation of the deformation region can be controlled by internal ridges in the undercut area, which limit inward deformation, and preferentially allow outward deformation, which can be useful in other examples of the invention, which do not necessarily use internal hydraulic pressure to expand the deformation region.

In the inoperative configuration shown in Fig 5, the radial expansion of the thin- walled deformation region 15 has buckled the side walls of the piston rod 10 outwardly in a radial direction at the deformation region so that the piston rod 10 can no longer pass through the bore of the collar 8, and so despite the high force resulting from the pressure in the chamber 6 behind the piston, the piston cannot translate axially through the cylinder 5, and remains locked in the inoperative configuration shown in Fig 5. This prevents the extension of the piston rod 10 from the cylinder 5, and consequently prevents the operation of the tool. Note that merely a slight ovality of the piston rod can be sufficient deformation to obstruct movement of the piston rod 10 through the collar 8, and deformation does not need to be symmetrical nor does it need to cover the whole circumference of the piston rod 10.

A second example of a piston and cylinder arrangement 21 is shown in Figs 6 to 17, comprising a cylinder 25 and a piston having a piston rod 30. The second example is generally similar to the first example, and equivalent parts are numbered similarly, but reference numbers are increased by 20. In the second example, the cylinder 25 has a bore with a chamber 26, and the piston has a flange sealed in the chamber 26 as previously described. In the modified arrangement of Figs 6 to 17, the piston rod 30 has more than one deformation region 35, each comprising an undercut chamber 31 similar to the chamber 11 described for the first example.

The piston rod 30 has first and second deformation regions 35, which are optionally axially spaced from one another along the axis of the piston rod 30. Optionally the first and second deformation regions 35 are configured to expand radially to deform the deformation regions 35 at approximately the same load limit X, but in certain examples of the invention the separate deformation regions 35 can be configured to deform at different load limits.

As shown in Figs 6, 7 and 8, when the piston rod 30 is operating within its normal parameters, no deformation of the deformation regions 35 takes place, and the piston rod 30 moves freely along its axis in both directions within the collar 28. However, when the hydraulic pressure within the chamber 26 is applying a force to the piston rod 30 that exceeds the load limit X of the deformation regions 35, the deformation regions 35 deform as shown in Figs 12 to 17, thereby arresting the movement of the piston rod 30 within the collar 28, and preventing operation of the tool.

Optionally, the axial distance between the first and second deformation regions 35 can be approximately similar to the axial length of the collar 28, and is shown in Fig 12, the deformation regions 35 can deform on opposite sides of the collar 28, thereby arresting movement of the piston rod 30. Optionally, one or more of the deformation regions 35 can deform while in the bore of the collar 28, as shown in Fig 13, or each of the deformation regions 35 can deform when both of them are outside the cylinder 25.

As can be seen by contrasting the end views of Figs 15 to 17 showing the inoperative configuration with Figs 9 to 11 showing the operative configuration, the deformation region 35 deforms radially around the whole circumference of the piston rod 30.