GB2152986A

GB2152986A - Equipment for use on uneven or inclined surfaces

Info

Publication number: GB2152986A
Application number: GB08333322A
Authority: GB
Inventors: Robert George Martin
Original assignee: QMC Indusrial Research Ltd
Current assignee: QMC Indusrial Research Ltd
Priority date: 1983-12-14
Filing date: 1983-12-14
Publication date: 1985-08-14
Also published as: GB8333322D0

Abstract

A piling rig (1) for use on the sea bed for embedding an anchor has a central frame (2) and four legs (3). Each leg (3) comprises an inner leg member (20) telescopically mounted within an outer leg member (29), and a hydraulic cylinder and displacement member. The cylinders are connected by way of respective non-return valves to a common hydraulic accumulator having a piston the movement of which is limited by an internal constriction in the cylinder. As the piling rig is lowered onto the sea bed, the weight of the rig forces fluid from the cylinders into the accumulator until the piston is displaced sufficiently to encounter the constriction (17), the legs then being locked in position as no further fluid can be displaced and no fluid can return through the non-return valves. The non-return valves are by-passed by further, oppositely arranged, non-return valves in series with an ON/OFF valve to allow fluid to return to the legs when the rig is lifted from the sea bed. <IMAGE>

Description

SPECIFICATION Equipment for use on uneven or inclined surfaces This invention relates to equipment for use on uneven or inclined surfaces.

Equipment which has a small base and a high centre of gravity such as pile-driving equipment needs to be carefully positioned in order to prevent it from toppling over. If, however, the equipment is to be used on the bed of the sea in deep water it is not an easy undertaking to ensure that the equipment remains steady and upright, particularly if the sea bed is uneven or inclined. Nor is it easy for divers to make adjustments to equipment under water and it is in any case expensive and time-consuming to employ divers.

The present invention provides equipment for use on an uneven or inclined surface, the equipment having a plurality of legs on which, in use the equipment stands, each leg being capable, in response to the weight of the equipment acting on the legs, from a fully-extended length, wherein means are provided to limit the total contraction of the legs, that is to say the sum of the individual contractions, to a predetermined value significantly less than the sum of the maximum individual contractions the legs could have if the total contraction were not so limited.

If such equipment is lowered onto a surface with the legs initially fully extended, contraction of the legs will take place as the weight of the equipment is taken on the legs. When, however, the predetermined value is attained no further contraction can take place. The lengths of the legs are thus adapted to the unevenness or incline of the surface and the equipment stands in the orientation in which it was set down.

Preferably, the predetermined value is not greater than two thirds the sum of the said maximum individual contractions and preferably the predetermined value is at least one third the sum of the said maximum individual contractions. The predetermined value may be approximately one half the sum of the said maximum individual contractions. By this means adaption of the lengths to a good range of inclined or uneven surfaces can be achieved.

Preferably, each leg has a respective hydraulic cylinder assembly operative to define the length of that leg, each cylinder assembly is connected by way of respective non-return valve means to a hydraulic fluid reservoir common to the hydraulic piston and cylinder assemblies and the means to limit the total contraction is arranged to allow only a predetermined amount of hydraulic fluid, corresponding to the said predetermined value, to be displaced between the cylinder and the reservoir in response to the weight of the equipment acting on the legs.

Preferably, the arrangement is such that, in use, the weight of the equipment displaces fluid from the cylinder assemblies into the reservoir.

Each leg may comprise a first leg member telescopically mounted within a second leg member.

Preferably, the hydraulic cylinder assemblies are displacement cylinders.

The hydraulic fluid reservoir may comprise a piston and a cylinder, the arrangement being such that the diameter and stroke of the piston limits the amount of fluid displaceable between the reservoir and the individual hydraulic cylinder assemblies.

Advantageously, means are provided to by-pass the non-return value means at will and means are provided to bias the legs to an extended condition.

When the non-return valve means are by-passed the displaced hydraulic fluid can return whilst the legs regain their extended condition under the bias. By this means, the initial condition of the equipment can be regained when the weight of the equipment is taken off the legs. Preferably, the means to bias the legs to an extended condition comprises means to apply pressure to the displaced hydraulic fluid. The means to apply pressure to the displaced hydraulic fluid may comprise gas which, in use, is compressed when the hydraulic fluid is displaced in response to the weight of the equipment acting on the legs.

Preferably, a stop is provided to prevent movement of the piston of the hydraulic fluid reservoir beyond a position part way along the length of the associated cylinder and the said piston is arranged to compress gas in the remaining length of the cylinder. The stop may be an internal constriction in the associated cylinder.

Advantageously, the means provided to by-pass the non-return valve means at will comprise second respective non-return value means, arranged oppositely to the first-mentioned non-return value means, connected between each of the hydraulic cylinder assemblies and a common ON/OFF valve means connected to the hydraulic fluid reservoir.

By this means, the equipment can be returned to its initial condition by taking the weight of the leg and opening the ON/OFF valve means. Instead, however, the means provided to by-pass the nonreturn valve means at will may comprise respec tive ON/OFF valve means connected between each of the hydraulic cylinder assemblies, and the hydraulic fluid reservoir.

Preferably, the number of legs is four.

The equipment may be pile-driving equipment.

A piling rig constructed in accordance with the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of the filing rig, Figure 2 shows a section through a leg of the rig, Figure 3 is a cross-section taken on the line Ill-Ill marked in Figure 2, and Figure 4 shows diagrammatically a hydraulic circuit employed in the piling rig.

Referring to the drawings, a piling rig 1 for use on the sea bed in deep water is shown. The rig has a central frame 2 and four legs 3. The central frame 2 consists of four columns 4 arranged, as seen in plan, in a square configuration, and a number of cross-members 5 secured to the columns.

Two of the legs 3 are arranged behind and left and right of the central frame 2 and are secured to respective mounting columns 6 which are in turn secured to the central frame and to each other. The remaining two legs are arranged in front and left and right of the central frame 2 and are secured to it by supporting struts 7.

The rig 1 has a piling weight 8 and an associated mechanism of known type (not shown).

Each leg 3 comprises a respective outer member 29 of square section, an inner member 20 also of square section telescopically mounted within the outer member, and a foot 11 in the form of a square metal plate. Each leg 3 also includes a respective hydraulic cylinder assembly in the form of a displacement cylinder of which the cylinder proper is shown as reference 9 (Figure 2) and the displacement member is shown as reference 10.

Bearing members 21 mounted on the inner member 20 serve to mount it for axial movement within the outer member 19.

A mounting structure 22 is provided within the outer member 29 at the top end thereof and the cylinder 9 (not shown in Figure 3) is attached to the mounting structure by means of a pin 23. Similarly, the displacement member 10 is secured to a mounting structure 24 within the inner member 20.

As shown in Figure 4, one end of each cylinder 9 is connected by way of a respective first non-return valve 12 to a common hydraulic reservoir and pressure storage vessel 13, the first non-return valves 12 being so arranged as to permit flow from the cylinders to the pressure storage vessel. The same end of each cylinder 9 is also connected by way of a respective second non-return valve 14 to one side of a valve 15 common to all the cylinders, the second non-return valves 14 being arranged oppositely to the first non-return valves 12. The other side of the valve 15 is connected to the reservoir and pressure storage vessel 13.

The reservoir and pressure storage vessel 13 consists of a closed cylinder in which a piston 16 is provided and which has an internal constriction 17 near the middle of the cylinder. The connection of the first non-return valves 12 and the valve 15 to the reservoir and pressure storage vessel 13 is made at one end of the cylinder and the piston 16 lies between that end and the constriction 17. The space between the piston 16 and the other end of the cylinder contains air whereas the space between the piston and the one end of the cylinder is filled with hydraulic fluid in communication with hydraulic fluid in the circuit constituted by cylinders 9, non-return valves 12 and 14, and valve 15.

Each displacement member 10 consists of a respective rod 18 having a bearing member 19 at the end within the associated cylinder 9. The ends of the cylinders 9 remote from the connection to the non-return valves 12 and 14 provide a sealed bearing surface for the rods 18 passing through them.

The reservoir and pressure storage vessel 13, the non-return valves 12 and 14, and the valve 15 are mounted in the central frame 2 although they are not shown in Figure 1.

The displacement members 10 have a one metre stroke and the internal volume of the pressure storage vessel 13 between the end connected to the non-return valves and the piston 16, when the piston is adjacent the constriction 17 is equivalent to the total fluid displaced by all four displacement members 10 moving 0.5 metres.

The operation and use of the piling rig 1 will now be described. It is to be assumed that, initially, the piston 16 is remote from the constriction 17 and adjacent the end of the reservoir and pressure storage vessel 13, the displacement members 10 are fully projecting from their associated cylinders 9 (as shown in broken outline in Figure 2), and the valve 15 is closed.

The piling rig, in the initial condition just described, is gently lowered to the sea bed by means of a vessel equipped with a crane. The rig descends in the vertical orientation shown in Figure 1 (or at a slight angle to the vertical if a steady current is flowing underwater) and in due course one or more of the feet 11 touch the sea bed. Some of the weight of the rig is now taken by the leg or legs, the feet of which have touched the sea bed, and the associated displacement member or members 10 move into their associated cylinders 9. Hydraulic fluid is thus displaced, passes through the one or more associated first non-return valves 12 and enters the reservoir and pressure storage vessel 13, the piston 16 being displaced towards the constriction 17 and the air in the vessel being compressed.If the sea bed happens to be level at the location where the piling rig lands, all four feet will touch the sea bed virtually simultaneously. On the other hand, if the sea bed is inclined or uneven, not all the feet will touch the sea bed at once. The displacement members 10 of those feet 11 which first touch the sea bed move upwardly into their associated cylinders 9 and then the remaining feet subsequently make contact with the sea bed as the rig settles into position (assuming that the sea bed is not excessively uneven or inclined).

As the piling rig settles on the sea bed, all four displacement members 10 move into their associated cylinders 9 until sufficient hydraulic fluid has been displaced to bring the piston 16 into engagement with the constriction 17 which acts as a stop.

Once the piston 16 has reached the constriction 17, further displacement of hydraulic fluid by the displacement members 10 is impossible. Moreover, the first non-return valves 12 prevent fluid returning from the pressure storage vessel 13 to the cylinders 9 and the second non-return valves 14 prevent flow of hydraulic fluid from one cylinder 9 to another. Thus, the displacement members 10 are effectively locked in position in their associated cylinders 9 and the piling rig now stands on the sea bed in that same orientation with its legs adapted to the surface of the sea bed at that location. Any tendency of the equipment to topple over on one leg is prevented by the associated one of the second non-return valves 14 stopping flow of hydraulic fluid from that leg to the other legs. If the prevailing underwater current has resulted in the piling rig being set down at some small angle to the vertical, that will be an advantage because the rig will then face into the current.

One use for the piling rig 1 is to embed an anchor of the type described in British patent specification 2,043,141B. In that case, the anchor is mounted on the rig beneath the piling weight 8 and lowered with the rig to the sea bed. Care is, of course, taken to arrange the anchor so that it does not interfere with the operation of the legs of the rig.

When the piling rig has been used for embedding the anchor or other purpose, it is hauled back to the surface of the sea.

The valve 15 is now opened and the air compressed in pressure vessel 13 drives the piston 16 upwardly and displaces hydraulic fluid by way of the second non-return valves 14 back into the cylinders 9. By this means, the displacement members 10 are returned to their initial fully extended position. The valve 15 is now closed once again and the piling rig is ready for use in a further piling operation.

Instead of the use of a single valve 15 connected to the four non-return valves 14, the valve 15 can be replaced by a direct connection and the non-return valves 14 by individual ON/OFF valves.

The inner and outer telescopic leg members serve to provide lateral rigidity but may be omitted for applications in which hydraulic cylinder assemblies used alone would provide sufficient lateral rigidity. If, however, separate leg members are provided, the hydraulic cylinder assemblies may be located externally of them and connected to them by means of a linkage. The linkage may be such that the weight of the equipment acting on the legs draws fluid into the piston and cylinder arrangements although an arrangement in which fluid is displaced from the hydraulic cylinder assemblies is preferred.

Instead of displacement cylinders, the hydraulic cylinder assemblies may take the form of hydraulic piston and cylinder arrangements.

Instead of using gas compressed during setting down of the rig to restore the legs to their fully-extended condition a connection may be provided for applying pressure to the hydraulic system from an external source for re-setting the legs. It is also possible to reset the legs by simply suspending the rig and allowing the weight of the legs to act as a restoring force without the need for pressurising the hydraulic system.

Claims

1. Equipment for use on an uneven or inclined surface, the equipment having a plurality of legs on which, in use, the equipment stands, each leg being capable, in response to the weight of the equipment acting on the legs, of contracting in length, independently of the other legs, from a fully-extended length, wherein means are provided to limit the total contraction of the legs, that is to say the sum of the individual contractions, to a predetermined value significantly less than the sum of the maximum individual contractions the legs could have if the total contraction were not so limited.

2. Equipment as claimed in claim 1, wherein the predetermined value is not greater than two thirds the sum of the said maximum individual contractions.

3. Equipment as claimed in claim 1 or claim 2, wherein the predetermined value is at least one third the sum of the said maximum individual contractions.

4. Equipment as claimed in claim 1, wherein the predetermined value is approximately one half the sum of the said maximum individual contractions.

5. Equipment as claimed in any preceding claim, wherein each leg has a respective hydraulic cylinder assembly operative to define the length of that leg, each cylinder assembly is connected by way of respective non-return valve means to a hydraulic fluid reservoir common to the hydraulic cylinder assemblies and the means to limit the total contraction is arranged to allow only a predetermined amount of hydraulic fluid, corresponding to the said predetermined value, to be displaced between the cylinder assemblies and the reservoir in response to the weight of the equipment acting on the legs.

6. Equipment as claimed in claim 5, wherein the arrangement is such that, in use, the weight of the equipment displaces fluid from the cylinder assemblies into the reservoir.

7. Equipment as claimed in any preceding claim, wherein each leg comprises a first leg member telescopically mounted within a second leg member.

8. Equipment as claimed in claim 5, 6 or 7, wherein the hydraulic cylinder assemblies are displacement cylinders.

9. Equipment as claimed in any of claims 5 to 8, wherein the hydraulic fluid reservoir comprises a piston and cylinder, the arrangement being such that the diameter and stroke of the piston limits the amount of fluid displaceable between the reservoir and the individual hydraulic cylinder assemblies.

10. Equipment as claimed in any of claims 5 to 9, wherein means are provided to by-pass the nonreturn valve means at will and means are provided to bias the legs to an extended condition.

11. Equipment as claimed in claim 10, wherein the means to bias the legs to an extended condition comprises means to apply pressure to the displaced hydraulic fluid.

12. Equipment as claimed in claim 11, wherein the means to apply pressure to the displaced hydraulic fluid comprises gas which, in use, is compressed when the hydraulic fluid is displaced in response to the weight of the equipment acting on the legs.

13. Equipment as claimed in both claim 9 and claim 12 when dependent on claim 6, wherein a stop is provided to prevent movement of the piston of the hydraulic fluid reservoir beyond a position part way along the length of the associated cylinder and the said piston is arranged to compress gas in the remaining length of the cylinder.

14. Equipment as claimed in claim 13, wherein the stop is an internal constriction in the associated cylinder.

15. Equipment as claimed in any of claims 10 to 14, wherein the means provided to by-pass the non-return valve means at will comprise second respective non-return valve means, arranged oppositely to the first-mentioned non-return valve means, connected between each of the hydraulic cylinder assemblies and a common ON/OFF valve means connected to the hydraulic fluid reservoir.

16. Equipment as claimed in any of claims 10 to 14, wherein the means provided to by-pass the non-return valve means at will comprise respective ON/OFF valve means connected between each of the hydraulic cylinder assemblies and the hydraulic fluid reservoir

17. Equipment as claimed in any preceding claim, wherein the numer of legs is four.

18. Equipment as claimed in any preceding claim, wherein the equipment is pile-driving equipment.

19. Equipment for use on an uneven or inclined surface, the equipment being substantially as herein described with reference to, and as illustrated by, the accompanying drawings.

New claims or amendments to claims filed on 5.6.84 Superseded claims 1 New or amended claims: CLAIMS

1. Equipment for use on an uneven or inclined surface, the equipment having a plurality of legs on which, in use, the equipment stands, each leg being capable, in response to the weight of the equipment acting on the legs, of contracting in length, independently of the other legs, from a fully-extended length, wherein means are provided which, when the equipment is used on diverse uneven or inclined surfaces, allow the legs to contract until the total contraction of the legs, that is to say the sum of the individual contractions, has reached a fixed predetermined value significantly less than the sum of the maximum individual contractions the legs could have if the total contraction were not so limited.