APPARATUS FOR INSERTING AN ELONGATE OBJECT INTO A TRENCH

Abstract

A depressor (16) for inserting a cable (4) into a trench (6) is disclosed. The depressor (16) comprises a plurality of cable shoes (22) adapted to be mounted to a support (18) and to engage the cable (4). Locating pins substantially prevent movement of the cable shoes (22) relative to the support (18) in a first direction as a result of movement of the cable shoes (22) relative to the cable (4) in an axial direction of the cable (4). A load cell provides an output dependent on a force applied to the cable shoes (22) in a second direction transverse, or perpendicular, to the first direction.

Claims

1. 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.

2. An apparatus according to claim 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 claim 1, wherein the restraining means comprises at least one protrusion configured to be releasably attachable to one side of the object engaging means and is configured to be receivable by a slot of a support.

4. An apparatus according to claim 1, wherein the force measuring means comprises at least one load cell.

5. An apparatus according to claim 1, further comprising a proximity detection means for detecting proximity of the elongate object.

6. An apparatus according to claim 4, wherein the load cell is configured to be receivable in a bore hole of the object engaging means.

7. An apparatus according to claim 4, wherein the load cell is configured to be receivable through two corresponding holes of a support.

8. An apparatus according to claim 5, wherein the proximity detection means comprises a metal detecting sensor.

9. An object inserting system for inserting an elongate object into a trench, the apparatus comprising: a support configured 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 claim 1.

10. An apparatus according to claim 9, comprising a plurality of said object engaging apparatus.

11. An apparatus according to claim 9, further comprising actuator means for moving the support relative to the vehicle body.

12. An apparatus according to claim 9, wherein the support is adapted to be pivotably mounted to the vehicle body.

13. A vehicle comprising a vehicle body and an object inserting apparatus according to claim 9.

14. A vehicle according to claim 13, further comprising trench forming means.

15. A vehicle according to claim 13, further comprising movement means for moving the vehicle relative to a trench.

16. A method of measuring the force exerted on an elongated object being lowered to the seabed, comprising the step of: positioning an elongated object to be lowered to the seabed under an object engaging apparatus comprising: object engaging means configured to be mountable to a support and configured to be engageable to the 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.

17. An apparatus as claimed in claim 1, wherein the first direction is a backward or forward direction along the longitudinal axis of an elongate object when engaged to the engagement apparatus or object engager, or the direction or travel, when in use.

18. An apparatus as claimed in claim 1, wherein the second direction is an upward or downward vertical direction.

Description

[0119] FIG. 1 is a schematic side cross sectional view of a cable burying vehicle of an embodiment;

[0120] FIG. 2 is a side cross sectional view of a depressor of the vehicle of FIG. 1;

[0121] FIG. 3 is a view along the line X-X in FIG. 2; and

[0122] FIG. 4 is a cross sectional view along the line Y-Y in FIG. 3.

[0123] FIG. 5 is a view of an example of cable shoe embodiment and attachment features according to the present invention.

[0124] FIG. 6 is a cross sectional side view of an example of a cable shoe and attachment features according to the present invention.

[0125] Referring to the figures, a cable burying vehicle 2 for burying a cable 4 in a trench 6 in the sea bed 8 (FIG. 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.

[0126] 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 (FIG. 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] FIG. 5 and FIG. 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 FIGS. 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 FIG. 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.

[0131] 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

[0132] 1. An object engaging apparatus for engaging an elongate object being inserted into a trench, the apparatus comprising: [0133] object engaging means adapted to be mounted to a support and to engage an elongate object being inserted into a trench; [0134] 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 [0135] 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. [0136] 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. [0137] 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. [0138] 4. An apparatus according to any one of the preceding examples, wherein the force measuring means comprises at least one load cell. [0139] 5. An apparatus according to any one of the preceding examples, further comprising proximity detection means for detecting proximity of the elongate object. [0140] 6. An object inserting apparatus for inserting an elongate object into a trench, the apparatus comprising: [0141] 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 [0142] at least one object engaging apparatus according to any one of the preceding numbered examples. [0143] 7. An apparatus according to example 6, comprising a plurality of said object engaging apparatus. [0144] 8. An apparatus according to example 6 or 7, further comprising actuator means for moving the support relative to the vehicle body. [0145] 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. [0146] 10. A vehicle comprising a vehicle body and an object inserting apparatus according to any one of examples 6 to 9. [0147] 11. A vehicle according to example 10, further comprising trench forming means. [0148] 12. A vehicle according to example 10 or 11, further comprising movement means for moving the vehicle relative to a trench.

[0149] 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.