The present disclosure relates to an apparatus for inserting an elongate object into a trench, and relates particularly, but not exclusively, apparatus for inserting a cable into a trench in a floor of a body of water, such as the seabed.

Lowering a cable into a trench formed by a trenching vehicle is achieved either passively (by means of reliance on the self-weight of the cable) or actively, i.e. by positively inserting the cable into the trench by means of a mechanical arm, known as a depressor, attached to the trenching vehicle.

Self-weight lowering has advantages over use of an active depressor in that there is no physical contact between a cable and a depressor, which therefore reduces the risk of damage to the cable. In particular, in self-weight lowering, the cable is subjected to reduced bending compared with passage around a depressor, where it can be forced into an 's’ bend, which can damage the cable.

Another advantage of self-weight lowering is the elimination of radial loading on the cable, which can cause significant risk of damage to the cable. For example, some power cables are sensitive to radial loading, i.e. forces acting perpendicularly to the axis of the cable. Cable manufacturers often specify a loading limit which must not be exceeded during the laying and burial process. For this reason, the amount of downforce applied by a depressor onto a cable must be quantified and limited. In some instances, the depressor acts only as a sensor in order to determine cable position, i.e. burial depth.

Conversely, the use of a depressor provides one or more advantages over selfweight lowering. In particular, self-weight lowering can involve an increase in the number of trenching passes necessary to lower the cable to the required depth. Each pass lowers the cable a distance dependent upon cable weight, cable diameter, soil strength and composition, how effectively the trench is jetted (to fluidise debris in the trench), cable tension and trenching speed. In the absence of a depressor contacting the cable, the depth of burial is more difficult to measure. Cable depth could be measured using onboard survey equipment, typically using cable sensors or sonar. However, post-lay survey is often carried out to confirm the actual burial depth.

The total force acting on a conventional depressor is normally measured by means of a shear-pin load cell typically fitted in-line with a raise/lower actuator (a hydraulic cylinder) for raising and lowering the depressor. The force acting on the depressor is the combined cable force and soil forces, which are generated by friction and soil surcharge, i.e. the interaction between the depressor and the cut soil generated during the trenching process.

The load cell measures force in the direction of its shear planes, which are set in a single orientation. These shear planes tend to suit a narrow range of depressor heights, as a result of which measuring the full range of height is more difficult as it would rely on the load cell rotating in line with the actuator.

In addition, the use of conventional depressors has the disadvantage that operators often see high loads, which they may attribute to high cable tension. In these circumstances, trenching speed may be reduced, as well as burial depth, or both, but it is possible that these high forces result from soil forces and not from cable tension, as a result of which the reduction in trenching speed and/or burial depth may be unnecessary.

Preferred embodiments seek to overcome this disadvantage. The present invention seek to address at least one of the known problems of the prior art.

According to an aspect of the disclosure, there is provided an object engaging apparatus for engaging an elongate object being inserted into a trench, the apparatus comprising: object engaging means adapted to be mounted to a support and to engage an elongate object being inserted into a trench; restraining means for substantially preventing movement of said object engaging means relative to the support in a first direction as a result of movement of the object engaging means relative to the elongate object in an axial direction of the elongate object; and force measuring means for providing an output dependent on a force applied to the object engaging means in a second direction transverse to said first direction.

According to an aspect of the present invention, there is provided an object engaging apparatus for engaging an elongate object being inserted into a trench, the object engaging apparatus comprising: object engaging means adapted to be mounted to a support and to engage an elongate object being inserted into a trench; restraining means for substantially preventing movement of said object engaging means relative to the support in a first direction as a result of movement of the object engaging means relative to the elongate object in an axial direction of the elongate object; and force measuring means for providing an output dependent on a force applied to the object engaging means in a second direction perpendicular to said first direction.

According to an aspect of the present invention there is provided, an object engaging apparatus for engaging an elongate object being inserted into a trench, the object engaging apparatus comprising:

-object engaging means configured to be mountable to a support and configured to be engageable to an elongate object being inserted into a trench;

-restraining means for preventing movement of said object engaging means relative to a support in a first direction relative to an axial direction of an engaged elongate object, when in use; and force measuring means for measuring a force applied to the object engaging means in a second direction, perpendicular to said first direction. According to an aspect of the present invention, there is provided an object engaging apparatus for engaging an elongate object being inserted into a trench, the object engaging apparatus comprising:

- an object engager configured to be mountable to a support, and configured to be engageable with an elongate object;

- a restrainer for preventing movement of the object engager relative to a support, when in use, in a first direction; and

-a force sensor for providing an output dependent on a force applied to the object engager in a second direction perpendicular to said first direction.

According to another aspect of the present invention there is provided an object engaging apparatus for engaging an elongate object being inserted into a trench, the object engaging apparatus comprising:

-object engaging means configured to be mountable to a support and configured to be engageable to an elongate object being inserted into a trench;

-restraining means for preventing movement of said object engaging means relative to a support in a first direction; and force measuring means for measuring a force applied to the object engaging means in a second direction, perpendicular to said first direction.

In some embodiments wherein the output from the sensor or the force measuring means is a measurement of the force exerted on it.

In some embodiments the object engaging means or object engager is a cable shoe.

In some embodiments there comprises a plurality of object engaging means, object engagers or cable shoes. Advantageously having a plurality of object engaging means, object engagers or cable shoes may enable a plurality of force measurements along a length of the elongated object being lowered to the seabed, and thus assist in more effective detection of the force exerted on the elongated object, for example a cable, to detect stress before the stress reaches a critical point but also if the process of lowering can be speeded up without causing stress.

In preferred embodiments the object engaging means or object engager or cable shoe is configured to be releasably attachable, or releasably mounted to a support. In preferred embodiments the object engaging means or object engager or cable shoe is configured to be releasably attachable, or releasably mounted to a support, when in use. In preferred embodiments the object engager, or cable shoe, is configured to be releasably engageable with an elongated cable. In some embodiments the object engager is configured that when in use, the object engager will be releasably mounted to a support at the top portion of the object engager, and releasably engaged with a elongate object, for example a cable, at the lower portion of the object engager.

It is when in use that the object engaging means may be attached or mounted on a support.

In some embodiments the object engager, or object engaging means, comprises a through bore, or bore hole, configured to receive a force sensor. In some embodiments the force measuring means or force sensor is configured to be receivable in a through bore of the engaging means or object engager

In some embodiments the object engager comprises a through bore configured to correspond with two corresponding through holes of the support when in use. In some embodiments the through bore of the object engager is configured to be at a top portion of the object engager when in use. In some embodiments the through bore of the object engager is positioned at an opposite portion of the object engager to the object engaging portion of the object engager. In some embodiments the though bore is configured that in use the axis of the through bore is across the direction of travel or across the axis of the engaged elongate object when in use. In some embodiments the through bore is configured that in use the axis of the through bore is on a horizontal plane perpendicular to the direction of travel when in use or axis of an engaged longitudinal object when in use.

In some embodiments the object engager may be configured that the through bore of the object engager is configured that the axis of the through bore is in a horizontal plane with two holes in a support, when in use. In some embodiments the force sensor is configured to be received by the though bore of the object engager and two corresponding holes of a support. In some embodiments the force sensor is configured to attach the object engager to a support. In some embodiments the force sensor is configured to be able to comprise a pivot point of attachment, between the object engager and a support.

In some embodiments the through bore of the object engager is configure to receive the force sensor.

In some embodiments the force measuring means or force sensor is configured to be positionable the through bore of the object engager or cable shoe.

In some embodiments the force measuring means or force sensor is configured to be receivable through the through bore of the object engager.

In some embodiments the force measuring means or force sensor or load cell, is configured to be receivable through two corresponding holes of a support. When in use with a support.

In some embodiments the force sensor is configured to act as the releasably attaching means or attacher to releasably join the engaging means to a support when in use.

In some embodiments the force sensor is configure to act as a securing pivot for attaching the object engaging means, or object engager, to a support. In some embodiments the force sensor comprises a load cell. Advantageously this may enable a force exerted on the load cell or force sensor to be measured. Advantageously as the load cell or force sensor may act as the joining point or pivot for releasably attaching the engager to the support when in use the force sensor or load cell will receive all or very nearly all the vertical force exerted on the load cell.

The advantage that the force sensor can act as the securing means to releasably attach the object engager to a support when in use is that there are fewer parts and the force sensor is able to give accurate measurements of the force exerted.

The use of the load cell or force measuring means, or force sensor in this way and / or position and orientation is that the sensor can accurately measure the load force on it and thus this corresponds directed with the force exerted on the elongated object, for example a cable. The load cell or force measuring means or force sensor may more accurately measure the downward force exerted on the elongated object, for example a cable, as the measurement on the load cell is equivalent to or directly proportional to the downward force on the elongated object, for example the cable.

In some embodiment there comprises a controller or other means to convey to a user, or an alarm signal, or computer and/or record the measurements from the force sensor, or load cell, force measuring means. The person skilled in the art would understand how these parts may be connected and used to convey the measurement to a user or computer or alarm system.

In some embodiments the restraining means or restrainer comprises at least one projection from a side of the object engager, that is configured to be receivable to a corresponding slot of a corresponding support. In some embodiments there comprises at least two projections from the object engager. Aptly in some embodiments there are two projections from opposite sides of the object engager, and that these projections are configured to be receivable within a slot of a corresponding support when in use. In some embodiments the restraining means or restrainer comprises at least one pin configured to be releasably attachable to the object engager. In some embodiments the at least one pin configured to be releasably attachable to the object engager is configured to be receivable within a corresponding slot of a corresponding support, when in use. Aptly in some embodiments there are two pins, and that these pins are configured to be attachable to opposite sides of the object engager, and configured to be receivable in corresponding slots of a support when in use.

Advantageously the projections or pins of the restrainer, are configured to be receivable in corresponding slots of a support, when in use, such that vertical motion, including up and down, or including upward or downward or both at different times, of the object engager is possible but within the slot but other directions of motion are restrained. Therefore when in use, the force sensor acts like pivot enabling backward and forward motion along the direction of travel, or backward and forward along the axis of an engaged elongated object, but not a motion substantially horizontal to the axis of an engaged elongated object of the direction of travel when in use. The restrainer restrains the backward and forward motion, along the direction of travel, or along the axis of an engaged elongated object, thus the only motion still possible is vertically up or down, when orientated in use. Thus advantageously the present invention can more accurately determine that the vertical force is measured, with less interference from other forces from other direction.

In some embodiments there comprises at least two restraining means or restrainers.

In some embodiments the restrainer restrains the movement of the object engaging means or object engager, relative to the support in a first direction. Advantageously this restrains the movement of the object engager, or object engaging means in the backward and forward direction along the axis of an engaged (when in use) elongated object or retrains backward and forward along the direction of travel when in use.

In some embodiments the said first direction comprises a backward and forward direction along the axis of an engaged elongated object.

In some embodiments the restrainer prevents the movement of the object engaging means or object engager, relative to the support in a first direction. In some embodiments the said first direction is a backward on forward direction along the axis of an engaged elongated object. Advantageously this prevents the movement of the object engager, or object engaging means in the backward and forward direction along the axis of an engaged elongated object or prevents backward and forward along the direction of travel when in use.

By providing restraining means for substantially preventing movement of the object engaging means relative to the support in a first direction as a result of movement of the object engaging means relative to the elongate object in an axial direction of the elongate object, and force measuring means for providing an output dependent on a force applied to the object engaging means in a second direction transverse, or perpendicular, to the first direction, this provides the advantage of more accurately measuring radial forces applied to the object, while largely ignoring forces applied to the object engaging means not caused by radial forces between the object engaging means and the elongate object. This in turn enables the risk of damage to the elongate object to be reduced.

In some embodiments the second direction comprises a vertical upward or downward direction.

In some embodiments the second direction may include both vertical, upward and downward direction. The skilled person would understand that may be at different times or instances. By gravity, the elongated object will fall to the seabed, or floor of the body of water, and a downward force exerted onto the elongated object will assist this motion and may increase the speed of the downward motion of the elongated cable.

The object engaging means may comprise an object engaging surface, wherein the restraining means is located adjacent said object engaging surface.

This provides the advantage of more effectively reacting forces applied to the object engaging means in an axial direction of the elongate object so that movement of the object engaging means relative to the support is substantially caused by forces between the object engaging means and the elongate object transverse, or perpendicular, to the axial direction. This in turn enables a simple determination of transverse, or perpendicular, forces applied to the elongate object.

The restraining means may comprise at least one protrusion adapted to be located on one of the object engaging means and the support and adapted to engage the other of the object engaging means and the support.

The force measuring means may comprise at least one load cell. In some embodiment the force measuring means, of force senor comprises a load cell.

The apparatus may further comprise proximity detection means for detecting proximity of the elongate object.

This provides the advantage of enabling the trajectory of the object to be determined, thereby reducing the risk of its minimal bend radius being exceeded, and enables the absence of an elongate object in the trench to be determined. This is especially so when a number of proximity detectors as used along a length of the elongate object when engaged to a number of engaging means, of object engager, or cable shoes. This provides the advantage of enabling the trajectory of the object to be determined, thereby reducing the risk of its minimal bend radius being exceeded, and enables the absence of an elongate object in the trench to be determined.

In some embodiments there comprises a proximity detection means or proximity detector. In some embodiments the proximity detection means or the proximity detector comprises a metal detector. In some embodiments the proximity detection means or the proximity detector comprises a magnet. In some embodiments the proximity detection means or the proximity detector comprises a magnet, wherein the magnet is configured to detect metal at the lower surface of the object engaging means or object engager.

Advantageously the proximity detector may be able to distinguish between the proximity of an elongate object for example a cable and other objects for example soil, or a fish.

In practice the elongated object to be lowered to the floor of the body of water may be a cable that comprises metal. Therefore in embodiments where the proximity detector (or proximity detection means) comprises a metal detector or magnet the proximity detector can distinguish between whether a cable, is engaged with the object engager (or object engagement means), and other non-metal objects like fish, or soil. This assists that the user will know if the force measurements detected are the force exerted on the elongated object, for example a metal containing cable, or are a false reading due to some other object.

In some embodiments the apparatus of the present invention comprises plastic. In some embodiments the object engagement means or object engager comprises plastic. In some embodiments the restraining means or restrainer comprises plastic. In some embodiments the pins comprise plastic. In some embodiments the force sensor comprises plastic. It is helpful to accurately detect the metal containing elongate object, for example a cable comprising metal, when the object engager is free of metal, especially at the contact engaging portion of the object engager, or object engaging means.

According to another aspect of the disclosure, there is provided an object inserting apparatus for inserting an elongate object into a trench, the apparatus comprising: a support adapted to be mounted to a vehicle body of a vehicle and to be moveable relative to the vehicle to insert an elongate object into a trench; and at least one object engaging apparatus as defined above.

The object inserting apparatus may comprise a plurality of said object engaging apparatus.

This provides the advantage of distributing the forces applied to the elongate object over a larger area, thereby minimising the risk of damage to the elongate object, and enabling the trajectory of the elongate object to be determined.

The object inserting apparatus may further comprise actuator means for moving the support relative to the vehicle body.

This provides the advantage of enabling the contact force between the object engaging means and the elongate object, caused by the weight of the object inserting apparatus, to be reduced by means of actuation of the actuator means, therefore further reducing the risk of damage to the elongate object.

The support may be adapted to be pivotably mounted to the vehicle body.

According to a further aspect of the disclosure, there is provided a vehicle comprising a vehicle body and an object inserting apparatus as defined above.

The vehicle may further comprise trench forming means. The vehicle may further comprise movement means for moving the vehicle relative to a trench.

According to another aspect of the invention there is provided a system for assisting the lowering of an elongate object to the seabed, wherein the system comprises: an apparatus as herein described.

According to another aspect of the invention there is provided a system for assisting the lowering of an elongate object to the seabed, wherein the system comprises: -an object engaging apparatus that comprising a cable shoe wherein the cable shoe comprises a through bore configured to receive a force sensor, and comprises an elongate object engagement surface, configured to receive an elongate object;

- at least one pin, that is configured to be releasably attachable to a side of the cable shoe;

- a support configured to be releasably attachable to a vehicle, wherein the support comprises at least one slot wherein the at least one slot is configured to receive the at least one said pin, and the slot is configured to allow vertical motion, of the said pin within the confinements of the slot but restrain other directions of motion, the support further comprising at least two holes;

-a force sensor, configure to be receivable within the through bore of the engaging apparatus and to be receivable through two holes of the support, such that the force sensor releasably joins the engagement apparatus to the support.

As the pin may be, in use, attached to the cable shoe, or object engaging apparatus the slot also allows the cable shoe, or object engagement apparatus to move up and down but prevents other directions of motion in use with the configuration of the object engagement apparatus joined to the support by the force sensor comprising the pivot join between the object engagement apparatus and the support.

In some embodiments the object engagement surface is positioned at a lower portion of the engaging apparatus, or object engaging means, or object engager. In some embodiments the object engagement surface of the engaging apparatus, or object engaging means, or object engager, comprises a smooth surface. This helps reduce friction and stress on the elongated object as it is lowered towards the floor of the body of water.

In some embodiments of the system the slot of the support is longer in the vertical direction than wider in the horizontal direction. This enables vertical motion of the pin or projection within the confinement of the slot, when in use, and therefore enables vertical motion of the engagement apparatus when in use, while restraining other motions form other directions. Advantageously this may assist in a more accurate measurement of the vertical force of the elongate object on the force sensor.

In some embodiments of the system the width of the slot in the horizontal direction is only a little wider than the wides diameter of the corresponding pin that the slot is configured to receive. This may enable easy up and down vertical motion of the pin within the slot but prevent horizontal directed motion.

In some embodiments of the system, the system further comprises a vehicle configured to be attachable to the support.

In specific embodiments of the system the vehicle comprising a plough configured to be able to form a trench if dragged along the seabed.

In some embodiments of the system the support is configured to be moveable up or down, or up and down, within the water body to assist in lowering the elongate object to the seabed. In some embodiments of the system the support is configured to have a changeable weight in order to control the force exerted on the elongate object. This may be achieved by buoyancy, counteracting forces or other means to in effect have more or less downward force being applied by the support.

In some embodiments of the system the support comprises a depressor. In some embodiment of the system the support is configured to comprise two holes in a horizontal plane with the axis of the through bore of the cable shoe when in use.

In some embodiment of the system the support may comprise at least one slot. In some embodiments of the system the clot of the support may be an open slot.

In some embodiments of the system the support comprises at least one flange, that projects downwardly. In some embodiments of the system the support comprises at least one flange, that projects downwardly. In some embodiments of the system the support comprises at least one flange, that projects downwardly, wherein the at least two flanges are configured to receive the object engaging apparatus or object engager or object engaging means, between the at least two said flanges.

In some embodiments of the system the at least two flanges are oriented opposite each other.

In some embodiments of the system the at least two, preferably two, flanges each flange comprise a hole that corresponds in position with the corresponding hole of the opposite flange. In some embodiments of the system the at least two, preferably two, flanges each flange comprise a hole that corresponds in position with the corresponding hole of the opposite flange, configured that the axis of the two said corresponding holes are on a horizontal plane and configured to be able to receive a force sensor through the two said corresponding holes. In preferred embodiments the horizontal axis of the corresponding said holes of the support will be configured to be in the same horizontal plane substantially as the trough bore of the object engager when in use.

In some embodiments of the system the flanges of the support each comprise a, or the slot. In some embodiments of the system each slot on the flange is an open slot. In some embodiments of the system the slot of a flange is configured to receive a pin, wherein the pin is configured to be attachable to an object engager when the object engager is positioned between two flanges of the support.

In some embodiments of the system the flanges of the support comprise plastic. This may aid the detection of cables comprising metal if these are engaged to the object engager or cable shoe, when a proximity detector comprising a metal detector is used.

In another aspect of the present invention there is provided a method of measuring the vertical force exerted on an elongated object when lowering to the floor of a body of water, for example a seabed, wherein the method comprises using an apparatus or system as herein described.

In another aspect of the present invention there is provided a method of measuring the vertical force exerted on an elongated object when lowering to the floor of a body of water for example a seabed, wherein the method comprises the step of: -positioning an elongated object to be lowered to the seabed, under an engagement apparatus, or system, as herein described.

In another aspect of the present invention there is provided a method of measuring the vertical force exerted on an elongated object when lowering to the floor of a body of water, for example a seabed, wherein the method comprises the step of: -positioning elongated object to be lowered to the seabed, under an engagement apparatus, or object engagement means, or object engager or system, as herein described.

To aid understanding of the present invention one general non-limiting example of the invention will be described: the lowering of an elongated object may be assisted by the present invention and the force exerted on the elongated object may be measured, in order to prevent too much stress on the elongated object as it is being lowered. In some embodiments, an object engager may be used wherein the object engager may comprise a through bore, and at least one, preferably at least two corresponding protrusions projecting from at least one side of the object engager. In some preferred embodiments the projections are replaced by one or more pins so as to make fitting the object engager easier. In embodiments with pins ideally the pins may be releasably attachable to at least one side of the object engager. In some embodiments the pins or protrusions are configured to be received in corresponding slots of a support when in use. In some embodiments the object engagement apparatus or system further comprises a force sensor, which may be a load cell, and this force sensor or load cell may be configured to be received in the through bore of the object engagement means or object engager. The object engager may be configured that the through bore may correspond in a horizontal plane with two holes in the support, such that the force sensor that is configured to be received by the though bore of the object engager and the two corresponding holes of the support may attach the object engager to the support comprising the pivot point of the attachment. This type of pivot point attachment of the object engager and the support may if not restrained allow backward and forward motion. Aptly in some embodiments the object engager or engagement apparatus and the support may be configured that the back and for the motion would be in an axial direction to any elongated object engaged to the object engager. In some embodiment there is a restrainer. In some embodiments the restrainer may comprise in full or in part a pin and slot type arrangement or be configured to enable a pin and slot type arrangement. In some embodiments the object engager comprises the at least one protrusions or pin configured to be received by a corresponding slot on a corresponding support. Thus in some embodiments with the arrangement of both the force sensor comprising the pivot joint attaching the object engager to the support, and the restrainer preventing the backward and forward motion of the object engager, along the axial direction of an elongated object when engaged to the object engager, substantially the only motion therefore left is an up and down vertical motion the pitch of which is limited by the internal vertical length of the slot. This may enable a more accurate measurement of the force sensor to the downward force exerted on an elongated object when engaged to the present invention or as used with the present invention. In alternative embodiments the protrusion or pin to slot arrangement may be the other way around. In some alternative embodiments the object engager comprises slots configured to receive a pin, or to receive a protrusion on a support. Having a separate pin and the slots on a support may aid fitting the object engager to the support. If the protrusions of the restraining means or restrainer are fixed these could still be positioned in place by a friction fit, especially in embodiments wherein the engagement apparatus or object engager comprises plastic.

Any one or more features of any example, aspect or embodiment of the present invention as described herein can be combined with any other one or more features of any other example, aspect or embodiment of the present invention as described herein.

By the term "engaged” as used herein with regard to the engaged elongated object or engaged cable, this means engaged when in use, when the elongated object or cable is engaged to the engagements means, or engager or cable shoe.

By the term "first direction” as used herein with regard to the motion of engaging means or object engager or the like, this is used to mean backward and forward motion, or including a backward motion and/or including a forward motion, or backward and forward along the axis of an elongated object when the elongated object is engaged to the apparatus, system or engager or engaging means, when in use. This would also be backward and/ or forward motion along the direction of travel when the invention is in use.

By the terms "force measuring means” and "force sensor” as used herein these terms are used interchangeably having the same meaning, am example of which is a load cell. By the terms "object engaging means” and "object engager” these terms are used interchangeably and means the same. An example of an "object engaging means” and/ or " an object engager” is a cable shoe.

By the term "restraining means” and "restrainer” as used herein these terms are used interchangeably having the same meaning. The restrainer for example may comprise in part or in whole a pin and slot arrangement, one part maybe on, or attached to, the object attachment apparatus, or object engager and the other part on a support to be attached to in use.

By the term "second direction transverse or perpendicular to the first” when used with regard to the motion of the engager, or engaging means or apparatus or the like, means a vertical direction, including up and including down, or up and down, or up or down vertically, for example when in use, and when orientated for use.

By the terms "top” and "lower” and the like terms, as used herein this is used to refer to the orientation of the object engager, the apparatus and system of the present invention when in use, when orientated for use. These terms are used to help explain the invention and not necessarily limiting.

A preferred embodiment will now be described, by way of example only and not in any limitative sense, with reference to the following drawings, in which: -

Figure 1 is a schematic side cross sectional view of a cable burying vehicle of an embodiment;

Figure 2 is a side cross sectional view of a depressor of the vehicle of Figure 1;

Figure 3 is a view along the line X-X in Figure 2; and

Figure 4 is a cross sectional view along the line Y-Y in Figure 3. Figure 5 is a view of an example of cable shoe embodiment and attachment features according to the present invention.

Figure 6 is a cross sectional side view of an example of a cable shoe and attachment features according to the present invention.

Referring to the figures, a cable burying vehicle 2 for burying a cable 4 in a trench 6 in the sea bed 8 (Figure 2) has a vehicle body 10, trench forming means in the form of jetter swords 12 mounted to the vehicle body 10, and moving means in the form of tracks 14 for moving the vehicle 2 relative to the trench 6. An object inserting apparatus in the form of a depressor 16 for inserting the cable 4 into the trench 6 comprises a support 18 pivotably mounted to the vehicle body 10 and which is raised or lowered relative to the vehicle body 10 by means of actuator means in the form of a hydraulic actuator 20.

The depressor 16 includes object engaging apparatus in the form of a plurality of cable shoes 22 mounted at a lower part of the support 18. The cable shoes 22 have object engaging means in the form of cable shoe contact surfaces 24 and are positioned such that the cable shoe contact surfaces form an arc, the radius of which is equal to or greater than the minimum allowable bend radius of the cable 4. Each cable shoe contact surface 24 may also be profiled to the minimum bend radius of the cable 4. The cable shoes 22 can be provided with proximity detection means in the form of proximity sensors 26 (Figure 3) for detecting the presence of the cable 4. In this case, the cable shoes 22 are manufactured from a material which is not detected by the proximity sensors 26.

Each cable shoe 22 is mounted on the support 18 by means of force measuring means in the form of a shear pin load cell 28, and rotation of each cable shoe 22 about the corresponding load cell 28 (equivalent to movement of the cable shoe 22 relative to the support 18 in an axial direction of the cable 4) is limited by restraining means in the form of one or more locating pins 30 located approximately in line with the corresponding cable shoe contact surface 24. Clearance between locating pin 30 and cable shoe 22 or support 18, allows limited movement of cable shoe 22 in a second direction transverse, or perpendicular, to the first direction. As a result, cable friction is reacted by the locating pins 30 only, and not the load cells 28, as a result of which the load cells 28 experience substantially only load in the direction of their respective shear planes, and therefore measure true contact force between the cable 4 and the cable shoes 22, i.e. radial load applied to the cable 4 in a direction transverse, or perpendicular, to its axis.

The proximity sensors 26, where fitted, detect and validate the presence of the cable 4, to ensure that the load pin readings of the load cells 28 refer to cable contact and not to purely soil contact forces. The shoe proximity sensors 26 and the load cells 28 are monitored separately, and therefore contact locations are defined and load pin forces measured at specific locations. This gives an indication of the shape of the cable catenary through the lay process.

Cable radial loading can be reduced by applying hydraulic pressure to the actuator 20 (typically on an annulus side of a lift cylinder of the actuator 20) to reduce the submerged weight of the depressor 16, and therefore reduce the cable contact force, thereby reducing the risk of damage to the cable 4. Although the depressor 16 will then give only a limited downward force on the cable 4, the cable burial depth can still be measured.

Figure 5 and Figure 6 show another embodiment of the cable shoe 22 embodiment of the present invention. As can be seen in this embodiment the cable shoe 22 is positioned between two flanges 18a of a support 18. The flanges 18a of the support 18 comprises through holes 32 able to receive the force sensors, in this embodiment a load cell 28. The flanges 18a of a support 18 also comprise slots 33 configured to receive pin 30. The pin 30 is configured to be received by the slots 33 and to releasably attach to the object engager/ cable shoe 22 In this example, the cable shoe 22 comprises plastic material. In this example the flanges 18a of a support 18 comprise plastic. Also shown is a proximity sensor 26 which is able to validate the presence, or absence, of a cable 4, to ensure that the load /force readings of the load cell 28 are to the cable 4 contact and not anything else, for example soil. In this example the proximity sensor 26 is able to detect the presence of metal in the area of the contact surface 24 of the cable shoe 22, thus able to detect any metal containing cable 4. Therefore the proximity sensor 26 can differentiate between the presence of a cable 4, containing metal, and the presence of other non-metallic items like soil. The cable shoe 22 embodiment of figure 5 and 6 can also be releasably attached, or mounted to, a support 18 by a force measuring means, and in this example this is by a shear pin load cell 28. The shear pin load cell 28 is received within a through bore 34 of the cable shoe 22. As can be seen by a dashed line, the axis of the through bore 34 of the cable shoe 22 is in a horizontal plane with corresponding holes in the flanges 18a of the support 18, such that the load cell 28 is received by the two corresponding holes of the support 18 and the through bore 34 of the cable shoe 22. The shear pin load cell 28 functions to attach to the cable shoe 22 to a support 18 via flanges 18a of a support 18. The support 18 is largely above the cable shoe and cable when in use, with the flanges 18a to the upper sides of the cable shoe . In this embodiment the load cell 28 acts as a pivot joint to attach the cable shoe 22 to a support 18. By this attachment alone the cable shoe 22 may pivot backwards and forwards along the axis of the engaged cable 4, or direction of travel. However this is prevented by the pin 30 and it corresponding slot 33 seen around the pin 30 in Figure 6. The slot 33 is an opening in a support 18 or a flange 18a of a support 18, in this embodiment. The locating pin 30 prevents axial movement of the cable shoe 22, in other words prevents the cable shoe 22 pivoting in the backwards and forwards directions of the direction of the vehicle when in use. The locating pin 30 is able to move within a slot 33 upwards or downwards in a vertical direction. This enables the cable shoe 22 to only move in a vertical, upwards or downwards motion, when in use, and thus the shear pin load cell 28 only measures the vertical load pressure on it. The shear pin load cell 28 is able to monitor and measure the force exerted on it. This is equivalent to or directly proportional to the force exerted on the elongated object or cable when engaged to the cable shoe. The support 18 in this embodiment is configured to comprise two holes 32 in a horizontal plane with the axis of the through bore 34 of the cable shoe 22. The invention will be described by way of the following non-exhaustive list of examples, this does not exclude or limit other examples and embodiments of the invention.

Examples

1. An object engaging apparatus for engaging an elongate object being inserted into a trench, the apparatus comprising: object engaging means adapted to be mounted to a support and to engage an elongate object being inserted into a trench; restraining means for substantially preventing movement of said object engaging means relative to the support in a first direction as a result of movement of the object engaging means relative to the elongate object in an axial direction of the elongate object; and force measuring means for providing an output dependent on a force applied to the object engaging means in a second direction transverse, or perpendicular, to said first direction.

2. An apparatus according to example 1, wherein the object engaging means comprises an object engaging surface, wherein the restraining means is located adjacent said object engaging surface.

3. An apparatus according to example 1 or 2, wherein the restraining means comprises at least one protrusion adapted to be located on one of the object engaging means and the support and adapted to engage the other of the object engaging means and the support.

4. An apparatus according to any one of the preceding examples, wherein the force measuring means comprises at least one load cell.

5. An apparatus according to any one of the preceding examples, further comprising proximity detection means for detecting proximity of the elongate object. 6. An object inserting apparatus for inserting an elongate object into a trench, the apparatus comprising: a support adapted to be mounted to a vehicle body of a vehicle and to be moveable relative to the vehicle to insert an elongate object into a trench; and at least one object engaging apparatus according to any one of the preceding numbered examples.

7. An apparatus according to example 6, comprising a plurality of said object engaging apparatus.

8. An apparatus according to example 6 or 7, further comprising actuator means for moving the support relative to the vehicle body.

9. An apparatus according to any one of examples 6 to 8, wherein the support is adapted to be pivotably mounted to the vehicle body.

10. A vehicle comprising a vehicle body and an object inserting apparatus according to any one of examples 6 to 9.

11. A vehicle according to example 10, further comprising trench forming means.

12. A vehicle according to example 10 or 11, further comprising movement means for moving the vehicle relative to a trench.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the disclosure as defined by the appended claims.