GB2355276A

GB2355276A - Trenching machine with vibrating share point

Info

Publication number: GB2355276A
Application number: GB0024899A
Authority: GB
Inventors: Timothy William Grinsted
Original assignee: Engineering Business Ltd
Current assignee: Engineering Business Ltd
Priority date: 1999-10-11
Filing date: 2000-10-11
Publication date: 2001-04-18
Anticipated expiration: 2020-10-11
Also published as: GB0024899D0; GB2355276B; GB9923964D0; GB0024790D0

Abstract

A trenching machine for use in the burial of cables or pipelines in the sea bed includes a share point [16] which is made to vibrate relative to the rest of the machine by a hammering device [17]. In one embodiment, the hammering device [17] consists of an oscillating hydraulic hammer, which repeatedly hits an anvil connected to the share point [16] by a shaft. The action of the hammering device [17] may be monitored and controlled.

Description

2355276 Trenching Machines The invention relates to trenching machines

such as ploughs, particularly but not exclusively, those for burial of cables and pipelines in the seabed or in a bed of 5 water.

Introduction

A substantial part of the world's international telecommunication is transmitted by means of fibre optic cables laid on.the sea bed. A cable can carry a large number of simultaneous telephone calls and damage to the cable can result in considerable financial loss and disruption. Therefore means to efficiently bury such cable or pipes have been developed in recent years.

It is becoming common to bury sub-marine cables or pipes (eg telecommunication cables) beneath the sea floor to protect them from damage by fishing equipment or anchors. Trenching machines such as cable or pipelaying ploughs are known to excavate the sea bed, cable laying ploughs also simultaneously lay and cover the cable. Typically, sub-marine ploughs are towed via a tow rope by a vessel on the surface of the water. The plough may also be towed by an underwater tractor. Such ploughs are fitted with a soil engaging share that is shaped to dig into the sea bed under the action of the towing force and produce a trench that the cable or pipe is placed into.

The sea bed is typically of variable composition including sand, mud and rock. The last of these can result in ineffective ploughing due to the plough being unable to traverse areas of rock or hard sea bed. Under these circumstances the plough may not move forward or rides. up over the rock or hard sea bed and so fails to bury the cable or pipe to the required depth to protect it. This can be a serious' disadvantage resulting in a higher risk of damage to the cable or pipe. Also t66 operation of the plough under these circumstances can be very erratic, with the plough stopping and then accelerating uncontrollably. This is particularly so in deeper water where longer tow ropes are necessary, such ropes having more stored energy from elastic stTetch and the catenary characteristics.

Impact devices are known for use on land in rock ripping machines, and result in a reduced average cutting force and more even progress.

The invention applies not only to machines which lay pipeline or cable but also those which only excavate a trench. The term "cable"' should be interpreted to include cable, pipeline, wire or any other elongate item to be buried.

It is an object of the invention to alleviate the above problems.

Statements of Invention 15

According to the invention there is provided a trenching machine comprising a share, the share comprising a share point, capable of reciprocating relative to the machine.

Preferably, the share point reciprocates in a direction substantially in line with the direction of action of the share point.

Preferably, the share comprises guide means for guiding movement of the share point.

Preferably, the share point forms or is connected to an anvil; the share further comprising an oscillating part for engaging the anvil whereby oscillating movement of the oscillating part causes it to hit the anvil, and hence the share point repeatedly.

In this way when trenching, energy is imparted to the material to be trenchea or ploughed aiding the break up of this material.

2 Preferably, the oscillating part reciprocates relative to the machine.

Preferably, the oscillating part reciprocates in a direction substantially in line 5 with the direction of action of the share point.

Preferably, the anvil is located within the share.

Preferably, the oscillating part is located within the share.

Preferably, the anvil and oscillating part are substantially in line with one another Preferably, the oscillating part comprises a hydraulic hammer.

Preferably, the share point and anvil are connected by a shaft. Preferably the shaft is elongate. Preferably the shaft has a substantially square or rectangular crosssectional shape.

Preferably, the share is provided with guide means for engaging and guiding a shaft connecting the anvil and share point. Preferably, the guide means are mounted about the shaft. Preferably, the shaft and/or guide means are shaped to co-operate with one another.

Preferably, the oscillating part is provided with sealing means to prevent or reduce the ingress of the material to be ploughed. Preferably, the oscillating part comprises a casing. Preferably, the casing is partially or wholly filled with liquid.

In a yet ftu-ther preferred embodiment of the invention the plough is provided with monitoring means which allow the progress of the plough to be assessed and/err in response to which the share point can be activated.

3 0 I I Preferably, the share comprises means to monitor the motion of the oscillating part and/or pressure within the part during operation.

Specific Embodiment of the Invention An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings wherein:

Figure I illustrates a side view of a plough according to the invention; and Figure 2 illustrates a side view of the share shown in Figure 1.

Figure I illustrates a sea bed cable plough is made up of a chassis 1, a share 3, and support skids 2. The front skids 2 support the plough on the sea bed 6 and the share 3 penetrates the sea bed as the plough is towed by a ship (not shown) via tow rope 5. The front skids 2 are adjustable hydraulically to set the trenching depth of the plough. Cable 7 enters the plough at the bellmouth 12 and exits underground at the back of the plough 8. The plough may be fitted with a control and monitoring system and a hydraulic power pack 13, allowing the operators on the ship to operate it via umbilical 14. The plough is shown fitted with two share points 15, 16. The lower part of the share contains a hammering device 17 that can act on point 16.

Figure 2 illustrates an enlarged area outlined with a circle in figure 1. Share point 21 is mounted on shaft 22, which is supported in guides 23. The shaft 22 extends back towards hydraulic hammer assembly 24 mounted within share 25.

Hydraulic hammer 24 contains a mass 26 that can slide axially to and fto on guides between extended and retracted positions, one contacting an anvil 27 connected to shaft 22 and one away from it. In this case the casing 31 acts to guide mass 26. The position of mass 26 is controlled by hydraulic cylinder 28. A hydraulic power pack.

with appropriate valves powers the cylinder 28 to reciprocate the mass 26 so that it 4 strikes the anvil 27. The anvil 27 contacts shaft 22 and thus transmits the impact to the point 21 where the energy may break an obstructing rock 29.

The oscillating hammer 24 may act directly on the share point (the share point fimctioning as its own anvil) or it may act on anvil 27 connected to share point 21 directly or to a shaft 22 which connects to share point 2 1. The hammer acts typically substantially in line with the direction of action of the share point 21.

The position of mass 26 or the extension of cylinder 28 may be monitored and used to control the reciprocation of the mass 26. The momentum of the mass imparted to the anvil 27 ( and hence to share point. 2 1) may be varied by varying the oscillating frequency and/or the distance of travel of the mass. Whilst it is preferable for the hammer 24 and anvil 27 to be located within the share, this need not be the case. For example the anvil could be connected, directly or indirectly to an external part of share point 21. The shaft 22 may be of any cross-sectional shape, but a rectangular shape is preferred as it provides rotational control of point 2 1.

The hydraulic hammer 24 is sealed to prevent ingress of soil and rock particles and fluid filled, typically with oil, and pressure compensated for operation under water. Anvil 27 passes through seals in support plate 30 so that the fluid is retained.

Thus the invention provides in one embodiment a sub-marine plough which advantageously incorporates an impact device into a share, the activity of which facilitates the formation of trenches in which cables or pipes can be laid uniformly and efficiently.

Under normal circumstances the share point 21 engages the material to be ploughed and the reaction from this material cause share point 21 to be retracted prior to it being extended by the impact from the hydraulic hammer. Alternatively, or in,- addition, means for actively retracting the share point may be provided such as a hydraulic rain, resilient means (such as spring) or the like.

P715400B

Claims

1. A trenching machine comprising a share, the share comprising a share point, capable of reciprocating relative to the machine.

2. A trenching machine according to Claim 1 in which the share point reciprocates in a direction substantially in line with the direction of action of the 10 share point.

3. A trenching machine according to any preceding claim in which the share is provided with guide means for guiding the movement of the share point.

4. A trenching machine according to Claim I in which the share point forms or is connected to an anvil; the share further comprising an oscillating part for engaging the anvil whereby oscillating movement of the oscillating part causes it to hit the anvil, and hence the share point repeatedly.

5. A trenching machine according to Claim 4 in which the oscillating part reciprocates relative to the machine.

6. A trenching machine according to Claim 5, in which the oscillating part reciprocates in a direction substantially in line with the direction of action of the 25 share point.

7. A trenching machine according to any of Claims 4-6 in which the anvil is located within the share.

8. A trenching machine according to any of Claims 4-7 in which the oscillating' part is located within the share.

6

9. A trenching machine according to any of Claims 4-7 in which the oscillating part comprises a hydraulic hammer.

10. A trenching machine according to any of claims 4-7 in which the share point and anvil are connected by a shaft.

11. A trenching machine according to Claim 10 in which the shaft has a substantially square or rectangular cross-sectional shape.

12. A trenching machine according to any of Claims 4-11 in which the share comprises guide means for engaging and guiding a shaft connecting the anvil and share point to guide the movement of the share point.

13. A trenching machine according to Claim 12, in which the shaft and/or guide means are shaped to co-operate with one another.

14. A trenching machine according to any of Claims 3-14 in which the oscillating part is partially or wholly filled with a liquid.

15. A trenching machine according to any preceding claim in which sealing means are provided in the share to prevent or reduce the ingress of material to be ploughed.

16. A trenching machine according to any preceding claim in which the trenching machine is provided with monitoring means in response to which the share point can be activated.

17. A trenching device substantially as hereinbefore described with reference to 30 and/or as illustrated in figures I and 2.

P7154OGB 7