Apparatus for Inserting an Elongate Object into a Trench

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 self-weight 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:

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:

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:

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:

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:

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.