WO2008149158A1

WO2008149158A1 - Remote drive mechanism

Info

Publication number: WO2008149158A1
Application number: PCT/GB2008/050417
Authority: WO
Inventors: Adrian Richard Brown
Original assignee: Smith Flow Control Limited
Priority date: 2007-06-07
Filing date: 2008-06-06
Publication date: 2008-12-11
Also published as: GB0710939D0

Abstract

A remote drive mechanism has a flexible cable (26) extending around a drive pulley and a remote driven pulley (30), contained within respective housings (14,23). The two ends of the flexible cable (26) are joined by a substantially rigid crimped connector (46). Motion of the connector (46) around the pulleys 30 is accommodated by providing each pulley with a plurality of jaws (36) each radially movable inwardly and spring-urged outwardly such that as the connector (46) engages and moves around a pulley, the jaws (36) engaged by the connector move radially inwardly against the force provided by springs (42).

Description

REMOTE DRIVE MECHANISM

This invention relates to a remote drive mechanism including a flexible cable extending around first and second pulleys. In particular, but not exclusively, this invention relates to a remote drive mechanism intended for use with a fluid flow control valve, to allow the remote actuation of that valve. Drive mechanisms for fluid flow control valves which may be operated remotely are well known. Typically, an electric or hydraulic actuator is mounted on the valve, a control arrangement being disposed remotely from that valve and connected to the actuator, to allow operation of the valve. Such an arrangement may be advantageous where the valve is located in an inaccessible position, or where it is located in a hazardous environment, such as in a nuclear installation or in a petrochemical processing plant. Particularly in the case of the latter, the remote control mechanism must be very reliable, in order to allow the operation of the valve even under emergency conditions.

A particular disadvantage of the known forms of remote drive mechanisms as described above is that they require the use of an external source of power, and usually electricity, either to power the actuator or to drive an hydraulic pump. Under emergency conditions, the electricity supply may fail so preventing operation of the electric actuator mounted on the valve or the operation of the hydraulic pump in the case of an actuator requiring a source of hydraulic fluid under pressure. Generally, a purely mechanical remote control drive mechanism may be more reliable, but there are difficulties associated with such mechanisms if the drive cannot follow a simple linear path, from an operating member to an actuator mounted on the valve, especially in the case of a valve requiring many turns to drive it from fully closed to fully open or vice versa.

A known system for the remote actuation of a multi-turn valve is described in WO 2004/048830. The operating member is connected to a first pulley and a second pulley is mounted on, or associated with, the valve. An endless flexible cable extends around the pulleys, the cable passing through guides as required, between the two pulleys. The ends of the cable are joined together by a special form of articulated coupler to allow the joined ends to pass smoothly around either pulley without significantly affecting the effective length of the endless loop of cable. However, such a system is difficult to implement and the length of the coupler must be maintained very short, in order that it might freely pass around the pulleys. With a very short coupler, a less than totally reliable connection may be achieved between the two ends of the cable joined thereby.

This invention aims at providing a remote drive mechanism of the same general kind as that described in WO 2004/048830 but which allows the use of a conventional crimped tubular connector, for joining together the two ends of a flexible cable extending around drive and driven pulleys in a remote drive mechanism.

According to this invention, there is provided a remote drive mechanism comprising a flexible cable extending around first and second pulleys one of which is arranged for connection to an operating device and the other of which is arranged for connection to a driven device, the two ends of the cable being joined together by a substantially rigid connector, at least one of the first and second pulleys having a plurality of jaws each having a peripheral surface for engaging the flexible cable and being mounted for movement so that the peripheral surface thereof may move generally in the radial direction, and spring means arranged to urge each jaw to move the peripheral surface thereof generally radially outwardly.

It will be appreciated that with the remote drive mechanism of this invention, a substantially rigid connector is used to join together the two ends of the drive cable. The connector should be tubular so that the two end portions of the cable are received in the opposed ends of the connector, which typically is then crimped on to the cable. The connector should have a sufficient length to enable a reliable connection to the two ends of the cable to be achieved.

The connector may thus be essentially conventional, using known technology.

So long as the connector is on a run of the cable between the two pulleys, the effective length of the endless loop will remain substantially constant, as the drive mechanism is operated. However, when the connector passes around the relatively small radius of curvature of a pulley, the length of the connector may become significant, shortening the effective length of the cable loop. By providing the pulley with movable jaws as described above, the change in the effective length of the cable loop can be accommodated so as to prevent binding of the remote drive mechanism. Preferably, the flexible cable of the remote drive mechanism comprises an elongate core member and a helical drive member wound tightly around the core member, at a substantially constant pitch, so as to be attached thereto. Such a cable emulates a screw-thread with rounded flanks and the peripheral surface of each jaw should be suitably profiled for interengagement with that emulated screw-thread, in order to prevent slippage between the cable and the pulley. Thus, the peripheral surface of each jaw should be formed with a plurality of grooves spaced therealong and disposed at an appropriate angle for interengagement with the helical drive member of the cable. Further, that surface may have a peripherally-extending groove of arcuate cross-section for receiving the flexible cable.

In the preferred form of this invention as discussed above, when the connector passes around the pulley, the connector cannot be received in the grooves of each jaw in the same manner as is the flexible cable and this also serves to reduce the effective length of the endless loop passing around the two pulleys. This reduction is also accommodated by the movable jaws sliding radially inwardly of the pulley and so operation of the remote drive mechanism can continue, without binding.

Though the jaws of the pulley could be pivoted to a carrier, it is preferred for those jaws to be guided for radial sliding movement, so allowing the peripheral surfaces of the jaws to move radially inwardly and outwardly as required. Each jaw may have at least one compression spring associated therewith, arranged to act between an abutment provided on the jaw and an opposed surface on the carrier, to urge the jaw radially outwardly. Such an abutment may be defined by the bottom of a blind bore formed in the jaw, the associated spring extending into the bore to engage the abutment. Conveniently, each jaw has three compression springs associated therewith, all of the springs for all of the jaws being arranged in a common plane parallel to the plane in which all of the jaws slide, and so normal to the rotational axis of the pulley.

Depending upon the number of turns of the driven pulley required to effect actuation of a valve with which the mechanism is associated and also the mechanical advantage of the drive mechanism, it may be necessary for the connector to pass around both pulleys, and possibly more than once around each pulley, to effect complete actuation of a valve from fully closed to fully open, or vice versa. In such a case, both pulleys should have a similar construction with movable jaws, to allow the connector to pass around those pulleys, as often as is required.

It will be appreciated that the remote drive mechanism of this invention may be used to operate a valve disposed some distance from an operating member for the mechanism, and which need not be in the same plane as the pulley associated with the valve. In such a case, the flexible cable may pass along tubular guides constraining the cable to follow a predefined path, which may be curved both in a plane containing a run of the cable and also out of that plane. The tubular guides could be metallic and plastically deformable, but a preferred form of guide comprises a composite duct having a hard plastics material liner within which the flexible cable runs, a plurality of steel wires extending lengthwise of the guide and an outer sheath covering the steel wires.

Depending upon the intended use of the remote drive mechanism, at least one of the first and second pulleys, but quite possibly both, may be accommodated in a housing to which tubular guides for the flexible cable are attached. The housings may be substantially waterproof, for example by providing suitable gaskets between separable parts thereof and also sealing elements through which the guides and flexible cable pass. At least one, if not both, housings may then be submerged, should the need arise.

A particular advantage of the drive mechanism of this invention is that it is purely mechanical and so does not rely upon any external source of power. As a consequence, even in emergency conditions when an electricity supply may suffer an outage, the mechanism may still be used to operate a valve in a reliable manner. By way of example only, one specific embodiment of remote drive mechanism of this invention will now be described in detail, reference being made to the accompanying drawings in which :-

Figure 1 illustrates the drive mechanism arranged for operating a rising stem gate valve;

Figure 2 is a detail view on an enlarged scale of an operating part of the mechanism and including a handwheel;

Figure 3 is a detail view on an enlarged scale of the driven part of the mechanism; Figure 4 is an under-plan view on the driven part of the mechanism, on a further enlarged scale and with the housing bottom wall and lower carrier plate removed to show the internal arrangement; and

Figure 5 is a vertical section through the driven part of the mechanism.

Referring initially to Figures 1 to 3, there is shown an embodiment of the remote drive mechanism intended for the remote actuation of a gate valve 10

(shown only in part) and including top works 1 1 from which projects a rising stem 12 connected to the gate of the valve. A nut (not shown) is engaged with the rising stem 12 and is rotatably mounted on the top works 1 1 and, in this embodiment, is arranged for rotation by the driven part 13 of the remote drive mechanism. The driven part includes a housing 14 for a driven pulley (not shown in Figures 1 to 3 but to be described in more detail below) connected to an adaptor 15 engaged with the nut of the valve. The adaptor includes internal jaws (not shown) operable by screws 16 so as to permit the adaptor to be clamped to various sizes of nut, as may be found with different valves. The housing 14 is provided with downwardly projecting legs 17 by means of which the housing may be secured to the top works 1 1 , with a two-part clamp

18 engaged with the legs 17. The configuration of the legs and clamp is such that the housing 14 may be secured to many different designs of valve top works - and if appropriate, the legs 17 may be changed for others, such as of different lengths or having a different crank from that shown in the drawings, to permit the attachment of the housing 14 to a particular valve. The housing 14 also is provided with a plurality of feet 19 permitting the mounting of the housing on a flat surface, such as may be required in the case of a gearbox valve.

The valve may be operated remotely by an operating part 21 including a rotatable handwheel 22 connected to a drive pulley (not shown in Figures 1 and 2 but to be described in more detail below) disposed within a housing 23. The housings 14 and 23, respectively of the driven and operating parts 13,21 , are essentially the same and are interconnected by a pair of tubular guides 24,25 within which extends an endless flexible cable 26 (Figure 4) passing around said pulleys disposed within the housings. In this way, rotation of the handwheel 22 turns the pulley within housing 23, so causing translation of the flexible cable which thus transfers drive to the pulley within the housing 14 of the driven part 13. In turn, this rotates the adaptor 15 and so also the nut, to effect operation of the valve 10.

The endless flexible cable 26 is shown in Figure 4 and comprises a core 27 around which a wire 28 is helically wound at a constant pitch. The core may be multi-stranded or solid, and typically is of steel or other flexible metal. The wire 28 should be wound sufficiently tightly to bind to the core, without the need for any other bonding agent or welding.

Figures 4 and 5 show the arrangement of the pulley 30 within the housing 14 of the driven part 13. The pulley within the housing 23 of the operating part 21 is essentially the same and so will not be described separately. The pulley 30 includes a hub 31 rotatably mounted in the top and bottom walls 32,33 of the housing 14, the adaptor 15 being coupled to the hub 31 , below the bottom wall 33. Within the housing, the hub supports upper and lower carrier plates 34,35 between which is mounted a plurality of jaws 36. Each jaw 36 is slidable in the radial direction between a respective pair of posts 37, each jaw also including a key 38 slidably received in a slot 39 in the upper carrier plate 35. The outer periphery of the upper carrier plate 34 is toothed and the housing 23 includes a bore 40 in which may be rotatably mounted a shaft (not shown) carrying a pinion (also not shown) for engaging the teeth of the upper carrier plate 34. In this case, the handwheel may be connected to the shaft in order to give a reduction drive to the pulley, so reducing the required manual effort in rotating the handwheel.

Each jaw has an outer peripheral surface 41 adapted for co-operation with the drive cable 26 extending through the guides 24,25 and around both pulleys. Three helical compression springs 42 are associated with each jaw 36, each spring being located in a respective bore 43 in the jaw and engaging a wall 44 provided between the upper and lower carrier plates 34,35. In this way, each jaw is spring-urged radially outwardly but may move radially inwardly against the force provided by the three springs 42 , as shown with jaw 36A in Figure 4.

The outer peripheral surface 41 of each jaw is of arcuate form in cross- section, and is provided with grooves to receive successive turns of the wire 28 wound around core 27 of the cable 26. In this way, a positive non-slip drive may be obtained between the cable 26 and the pulley. The ends of the cable 26 are joined together by a connector in the form of a sleeve 46 crimped on to the end portions of the core 27. Before the bore of the sleeve can receive those end portions, the wire 28 is removed therefrom. Then the cores are inserted into the sleeve and the sleeve is crimped on to the core end portions. The inner diameter of the sleeve before crimping is thus slightly greater than the diameter of the core 27 of the cable 26 and the outer diameter of the sleeve is slightly smaller than the overall diameter of the cable 26, including wire 28. In this way, the connector may pass freely and along the tubular guides 24,25.

A particular problem arises when the connector sleeve 46 must pass around a pulley. As the outer diameter of the sleeve 46 cannot be received in the grooves of the outer peripheral surface 41 of each jaw 36, the connector sleeve will ride outwardly of the peripheral surface, as shown in Figure 4. This reduces the effective length of the endless loop of the flexible cable 26 and so would normally cause binding, but with this embodiment of the invention the spring loading of each jaw 36 allows the connector sleeve freely to pass around the pulley. Each jaw 36 engaging the connector sleeve 46 slides radially inwardly against the spring bias provided by springs 42, as shown in Figure 4, where jaw 36A is shown as having slid inwardly, in this way.

In Figure 1 each guide 24,25 is shown as extending linearly between the housing 14 of the driven part 13 and the housing 23 of the operating part 21 . In a practical installation, the guides may be relatively long (perhaps several metres) and may include bends both in the plane containing a housing (as shown in Figure 1 ) and also out of that plane (not shown). Since the cable 26 is symmetrical about all axial planes, it may bend freely in any lateral direction, but with the cable constrained by the guides. In this way, remote operation of a valve may be achieved, even if the axis of the operating handwheel 22 and that of the rising stem 12 of the valve 10 are not parallel and are spaced some considerable distance apart. Further, valves requiring multi-turns to effect operation from one extreme setting to the other may be remotely operated by the mechanism of this invention. Should either housing 14,23 be located externally or even where it is likely to be submerged, it may be made substantially waterproof by furnishing a gasket between the top and bottom walls 32,33 and closing off the aperture in the top wall through which carrier plate 34 can be seen in Figure 2. Further, sealing glands may be provided around the valve stem and rotatable nut supporting the handwheel 22, as well as at the unions where the guides 24,25 connect to the housings.

Claims

1 . A remote drive mechanism comprising a flexible cable extending around first and second pulleys one of which is arranged for connection to an operating device and the other of which is arranged for connection to a driven devices, the two ends of the cable being joined together by a substantially rigid connector, at least one of the first and second pulleys having a plurality of jaws each having a peripheral surface for engaging the flexible cable and being mounted for movement so that the peripheral surface thereof may move generally in the radial direction, and spring means arranged to urge each jaw to move the peripheral surface thereof generally radially outwardly.

2. A remote drive mechanism as claimed in claim 1 , wherein the connector is tubular and the two ends of the cable are received respectively in opposed ends of the connector.

3. A remote drive mechanism as claimed in claim 1 or claim 2, wherein the cable comprises an elongate core member and a helical drive member wound tightly around the core member at a constant pitch, the peripheral surface of each jaw being profiled for interengagement with the drive member to prevent slippage between the cable and the pulley.

4. A remote drive mechanism as claimed in claim 3, wherein the peripheral surface of each jaw is formed with a plurality of grooves spaced therealong to receive successive turns of the helical drive member.

5. A remote drive mechanism as claimed in claim 3 or claim 4, wherein the peripheral surface of each jaw is of arcuate cross-section, to accommodate the flexible cable.

6. A remote drive mechanism as claimed in any of the preceding claims, wherein each jaw is slidably mounted on a carrier for sliding movement in the radial direction.

7. A remote drive mechanism as claimed in claim 6, wherein each jaw has at least one compression spring associated therewith, which spring is arranged to act between an abutment provided on the jaw and an opposed surface of the carrier.

8. A remote drive mechanism as claimed in claim 7, wherein the abutment is defined by the bottom of a blind bore formed in the jaw, the associated spring extending into the bore to engage the abutment.

9. A remote drive mechanism as claimed in claim 7 or claim 8, wherein each jaw has three compression springs associated therewith arranged in a common plane parallel to the plane in which the jaws slide.

10. A remote drive mechanism as claimed in any of claims 6 to 9, wherein each jaw is provided with a key received in a radially-extending slot formed in the carrier.

1 1 . A remote drive mechanism as claimed in any of the preceding claims, wherein the first and second pulleys are similarly configured each with a plurality of jaws each of which is mounted for movement so that the peripheral surface thereof may move generally in the radial direction.

12. A remote drive mechanism as claimed in claim 1 1 , wherein each pulley has a hub rotatably mounted within a housing, the hub having a radially extending carrier on which each of the associated jaws is slidably mounted.

13. A remote drive mechanism as claimed in claim 12, wherein the hub has a pair of opposed spaced carriers, each jaw being slidably mounted between said carriers.

14. A remote drive mechanism as claimed in claim 12 or claim 13, wherein the hub of one pulley is provided with a manually operable handwheel, to permit rotation of the pulley.

15. A remote drive mechanism as claimed in claim 14, wherein the hub of the other pulley is adapted for connection to the rotatable operating member of a fluid flow control valve.

16. A remote drive mechanism as claimed in claim 15, wherein said rotatable operating member comprises the nut of a rising stem valve.

17. A remote drive mechanism as claimed in any of claims 12 to 16, wherein tubular guides for the flexible cable extend between the respective housings for the two pulleys.

18. A remote drive mechanism as claimed in claim 14 or claim 15, wherein the hub of the other pulley is provided with an adjustable adaptor for clamping on to a nut of a rising stem valve.

19. A remote drive mechanism as claimed in any of claims 12 to 18, wherein the housing is provided with a clamp arrangement to permit the attachment of the housing to a valve top works, without modification of the top works or valve.

20. A remote drive mechanism as claimed in claim 19, wherein the tubular guides are non-linear whereby the flexible cable follows a curved path, between the first and second pulleys.

21 . A remote drive mechanism as claimed in any of claims 12 to 20, wherein the housings are substantially sealed to prevent the ingress of water or other contaminants thereinto.