GB2210347A - Linear winch - Google Patents

Abstract

A linear winch for displacing a rope 3 comprises a first wedge assembly 1 including a wedge arrangement 2 and drive means 5 for linearly displacing this wedge arrangement for gripping the rope, a second wedge assembly 26 including a wedge arrangement 27 and drive means 28 for linearly displacing this wedge arrangement for gripping the rope, and drive means for linearly displacing the second wedge assembly 26 relative to the first wedge assembly 1, this drive means comprising a main drive 10 and a slower-acting subsidiary drive 12. The subsidiary drive is used to assist driving the wedges home to locate about the rope before the main drive is actuated. <IMAGE>

Description

LINEAR WINCH This invention relates to a linear winch which may be used for effecting or controlling the longitudinal displacement of a rope, cable or the like element.

Hitherto winches have mainly been of the type comprising a driven rotary drum around which the rope or cable is looped. These winches are considerably bulky. There are also certain types of linear winch, but these are not suited to heavy duty uses.

We have now devised a linear winch suited to heavy duty uses and which may be used for pulling oil pipes along the sea bed in deep water (e.g. in an underwater oil field), or for lowering ropes against their own weight and the weight of any object suspended from them, or for similar heavy duty uses out of water.

In accordance with this invention, there is provided a linear winch comprising a first wedge assembly having a through-passage for receiving a rope and including a wedge arrangement and drive means for linearly displacing this wedge arrangement to cause the first assembly to grip the rope, a second wedge assembly having a through-passage for receiving the rope and including a wedge arrangement and drive means for linearly displacing this wedge arrangement to cause the second assembly to grip the rope, and drive means for linearly displacing the second wedge assembly linearly relative to the first wedge assembly, which drive means comprises a main drive and a slower subsidiary drive.

The relatively slow displacement provided by the subsidiary drive is used to assist in driving the wedges home to locate about the rope, before the main drive executes its displacement.

The linear winch may be constructed and arranged to effect intermittent displacement of the rope, with the first wedge assembly gripping and holding the rope still as the second wedge assembly returns towards the first wedge assembly, whereafter the second wedge assembly takes over the gripping function and then displaces away from the first wedge assembly. Alternatively, the winch may be constructed and arranged to effect continuous displacement of the rope: in this case the first wedge assembly is arranged to grip and displace the rope whilst the second wedge assembly is performing its return movement, and vice versa.

Embodiments of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is partly a side view, partly a longitudinal section of a linear winch of intermittent type; and FIGURE 2 is partly a side view, partly a longitudinal section of a linear winch of continuous type.

Referring to Figure 1 of the drawings, there is shown a linear rope winch for effecting or controlling the linear displacement of a rope or cable 3. The winch comprises a generally elongate cylindrical structure with an axial through-passage for receiving the rope 3, such that the winch occupies relatively little space.

The winch comprises a first or front wedge assembly 1 which is mounted to a fixed base structure la. This wedge assembly 1 comprises a body 4 having a conical inner surface supporting a set of three conically-shaped wedges 2 which can be linearly displaced into or out of gripping contact with the rope 3 by a double-acting drive jack 5.

This jack comprises a tubular cylinder body 8 mounted to the end of wedge assembly body 14, the cylinder body 8 housing a tubular piston 7 which is connected to the wedges 2 by flexible puller bars 6. The piston 7 has an annular rib 7a on its outer surface, defining annular volumes either side of this rib and between the piston and its cylinder, for receiving pressurised hydraulic fluid or oil via ports 9 for displacing the piston in its respective linear directions. The relative hydraulic areas either side of piston rib 7a are such that there is a slight tendency towards wedge-engagement when both ports 9 are pressurised equally, overcoming the bias of a coil spring 11 which tends to retract the wedges 2 when there is no applied hydraulic pressure.

The winch further comprises a second or back wedge assembly 26 which will be described later, and a drive arrangement 10, 12 for displacing the back wedge assembly 26 relative to the front wedge assembly 1. The drive arrangement comprises a main puller jack assembly 10 and a subsidiary puller jack assembly 12. The main puller jack assembly 10 is a double-acting hydraulic jack of relatively long stroke and comprises a tubular piston 13 sliding in a cylindrical socket formed in a cylinder member 14, which is provided with a sealing tube 15 at its centre to provide an axial bore to receive the rope 3.A port 16 is provided for the introduction of pressurised hydraulic fluid to extend the main jack, i.e. to introduce the fluid to the inner end of the cylinder and displace the piston 13 out of the cylinder 14 with the effect of displacing the cylinder 14 and backwedgeassembly 26 away from the front wedge assembly 1. A port 17 and passages 17a, 17b are provided for the introduction of hydraulic fluid to an annular volume defined between the inner surface of the piston 13 and the cylinder for acting on an annulus 18 of the piston to retract the main jack. An annular space 19 between the outer surface of the piston 13 and the cylinder is left nonhydraulic and incorporates an arrangement for preventing relative rotation between the piston 13 and cylinder 14.

This anti-rotation arrangement comprises a key 20 on the cylinder 14 received in a longitudinal groove 2Cta on the outer surface of the piston 13. The cylinder 14 is provided with a proximity switch 40 co-operating with a series of indentations 41 drilled in the outer surface of the piston 13. Thus as the piston 13 is displaced relative to the cylinder 14, a series of electrical pulses are generated by the proximity switch 40 and transmitted over a cable 42 to a monitoring and control system for the winch.

The subsidiary puller jack assembly 12 comprises a tubular piston 21 sliding in a cylindrical socket formed in the free end of the body member 8. A pin 22 is fixed to the body member 8 and projects longitudinally of the cylinder to slide in a bore 23 formed in the piston 21, to prevent rotation between the piston 21 and its cylinder.

The pistons 13 and 21 of the main and subsidiary puller jacks are secured together via an adaptor ring 21a. The subsidiary puller jack assembly is a double-acting jack of smaller stroke than the main puller-jack assembly 10 and is arranged to move at slower speed. Hydraulic fluid is introduced via ports 9, 9a to the opposite sides of the piston 21 for respectively extending or retracting the subsidiary puller jack.

The back wedge assembly 26 comprises a body 26a having a conical inner surface supporting a set of three conically-shaped wedges 27 which can be linearly displaced into or out of gripping contact with the rope 3 by a doubleacting drive jack 28, via flexible puller bars 29. The arrangement corresponds with the front wedge assembly 1 and a tubular piston 30 is coupled to the puller bars 29 and is displaceable within a cylinder body 31 secured to the free end of body 26a. The piston 30 is extended or retracted by introducing hydraulic fluid into a port 38 or a port 39 respectively. A coil spring 40 is provided to bias the piston 30 in the retracting direction for when there is no applied hydraulic pressure.The hydraulic areas of the piston 30 are such that with equal hydraulic pressure on both of its sides, there is a slight tendency towards wedge-engagement, overcoming the bias of spring 140.

The back wedge assembly 26 further comprises an auxiliary wedge jack 32 for applying a pushing force to the wedges 27 to dislodge these should they become stuck and the drive jack 28 be unable to retract them. The auxiliary wedge jack 32 comprises a cylinder body 34 mounted to the cylinder body 14 of the main puller jack 10, the body 26a of the back wedge assembly 26 being mounted to this cylinder body 34. A tubular piston 33 slides in a cylindrical socket formed between the body 34 and a central tube 35 mounted to it and forming a through-bore for the rope 3. Ports 36 and 37 are provided for introducing hydraulic fluid into the cylinder, for displacing the piston 33 respectively for dislodging the wedges 27 or moving out of contact with them.

The winch is provided with inlet ports e.g. 25 leading through respective radial ducts to the longitudinal through-bore which receives the rope 3. When the winch is used under water, filtered sea water is fed into the winch at these ports 25 so that the through-bore for the rope is continuously flushed out, the water leaving the winch through its opposite ends, to prevent silting. Additional side outlets 24 may be provided, for flushing out regions in which silt might otherwise accumulate.

The basic cycle of operation of the linear winch is as follows. The front wedge assembly 1 is used to grip the rope 3 whilst the back wedge assembly 26 is moved towards the front wedge assembly 1 using the main and subsidiary puller jacks 10 and 12. At the end of this movement, the back wedge assembly 26 is used to grip the rope 3 and the front wedge assembly 1 is released, then the back wedge assembly 26 is moved away from the front wedge assembly 1 to displace the rope 3, in the direction from left to right in Figure 1. Then the front wedge assembly 1 is applied to grip the rope 3, so that the back wedge assembly 26 can be released from the rope and moved back towards the front wedge assembly for the cycle to be repeated.

When the front wedge drive jack 5 undergoes its stroke to move the wedges 2 of the front wedge assembly into gripping engagement with the rope, the subsidiary puller jack 12 undergoes its retracting stroke, whilst the back wedge assembly 26 still grips the rope. This has the effect of rendering the rope slack over its portion between the front and back wedges and allowing a slight reverse movement of the rope as the front wedges drive home and locate about the rope. Then the back wedges 27 are retracted by the back wedge drive jack 28 and the main puller jack 10 is retracted. Initially retraction of the main puller jack assists in dislodging the back wedges 27 but further dislodging force may be provided by the auxiliary jack 32 if required as mentioned previously.

Once the main puller jack 10 has completed its retraction stroke, the back wedges 27 are re-engaged with the rope using the back wedge drive jack. At the same time the subsidiary puller jack 12 undergoes its extension stroke (the front wedge assembly still gripping the rope), having the effect of displacing the body 30 of the back wedge assembly 26 towards the right in Figure 1 and so assisting in driving the back wedges home and locating them about the rope 3. Then the front wedges 2 are released from the rope and the main puller jack 10 extended to displace the rope in its required direction.

Because the subsidiary jack 12 moves at relatively slow speed, the engagement of the front or back wedges occurs gently each time and avoids shock.

An hydraulic valving system will be placed adjacent the winch.The control system for controlling the feed of pressurised hydraulic fluid will preferably be arranged above the sea and will include a monitoring system fed with the signals from the proximity switch, enabling the linear position of the main puller jack to be determined at all times. Thus, should the winch stick at any time, then by knowing which ports are pressurised and knowing the linear position of the main puller jack, then deduction can be made as to the reason for the fault.

In the winch shown, the inner surfaces of the wedges 2 and 27 may be profiled to match the profile of the outer surface of the rope 3 to be handled.

The linear winch which has been described with reference to Figure 1 displaces the rope intermittently.

The modified winch shown in Figure 2 serves to displace the rope continuously. Referring to Figure 2, this continuous-type winch comprises a forward assembly 100 and a rearward assembly 102. A fixed support tube 106 surrounds the forward assembly 100 and has the rearward assembly mounted to its free end. The rearward assembly comprises a subsidiary puller jack 112 mounted to the free end of the support tube 106, a main puller jack 110, a wedge assembly 126, a drive jack 128 for wedge assembly 126 and an auxiliary jack or ejector 132, all these being constructed and arranged as the corresponding assemblies 10, 12, 26, 28 and 32 of the winch shown in Figure 1. The forward jack assembly 100 comprises a corresponding structure of subsidiary puller jack 112a mounted to fixed structure, main puller jack 110a, wedge assembly 126a and drive jack 128a. There is no auxiliary jack because the rearward assembly will provide force to dislodge the wedges of assembly 126a should these stick.

In use of the linear winch shown in Figure 2, the forward and rearward assemblies grip and displace the rope alternately with one another to give a continuous displacement of the rope. The relatively slow extending stroke of each subsidiary puller-jack is used, as described above, to assist the wedges of the respective wedge assembly driving home and locating about the rope, before the main puller jack executes its stroke.

Claims (6)

1) A linear winch, comprising a first wedge assembly having a through-passage for receiving a rope and including a wedge arrangement and drive means for linearly displacing the wedge arrangement to cause the first wedge assembly to grip the rope, a second wedge assembly having a throughpassage for receiving the rope and including a wedge arrangement and drive means for linearly displacing this wedge arrangement to cause the second assembly to grip the rope, and drive means for linearly displacing the second wedge assembly linearly relative to the first wedge assembly, which drive means comprises a main drive and a slower subsidiary drive.

2) A linear winch as claimed in claim 1, further comprising a control means arranged to cause operation of the subsidiary drive as the drive means for each wedge arrangement displaces the respective wedge arrangement into gripping relationship with the rope, the displacement caused by the subsidiary drive being in a direction to assist in applying the respective wedge arrangement to the rope.

3) A linear winch as claimed in class 2, in which the control means causes operation of the main drive after said operation of the subsidiary drive.

4) A linear winch as claimed in any preceding claim, arranged to effect intermittent displacement of the rope with the first wedge assembly gripping and holding the rope still as the second wedge assembly executes a return movement, whereafter the second wedge assembly takes over the gripping function before executing a stroke.

5) A linear winch as claimed in any one of claims 1 to 3, arranged to effect continuous displacement of the rope with each wedge assembly in turn gripping and displacing the rope whilst the other wedge assembly executes a return movement.

6) A linear winch substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.