GB2117484A

GB2117484A - Valve actuating gearing

Info

Publication number: GB2117484A
Application number: GB8206811A
Authority: GB
Inventors: William Gregory Jenkins
Original assignee: Richardsons Westgarth and Co Ltd
Current assignee: Richardsons Westgarth and Co Ltd
Priority date: 1982-03-09
Filing date: 1982-03-09
Publication date: 1983-10-12
Also published as: GB2117484B; WO1983003126A1; EP0102997A1

Abstract

Apparatus for actuating rotary devices such as valves, particularly where a plurality of such valves are located along a pipeline or conduit. According to the invention, apparatus for operating such a device has a main spindle (4) coupled to the device and rotatably mounted in a housing (40). A wheel gear (8) mounted on the spindle(4) has teeth along its periphery and a worm gear (14) meshes therewith. Rotation of the worm gear (14) either manually or from a power source, operates the device. The teeth on the wheel gear (8) are preferably inclined, and the plane of the wheel gear (8) made adjustable with respect to the axis of the worm gear (14) such that the degree of meshing engagement therebetween can be adjusted during the operating life of the apparatus. It is also preferred that the apparatus be made declutchable where a power operated actuator (42) is also installed on the device. This can be achieved by mounting the worm gear (14) on a pivotal support member (22) which enables it to be switched into and out of engagement with the wheel gear (8). In this way a selectively engageable override system can be provided.

Description

SPECIFICATION Gearbox for valve actuator This invention relates to the actuation of rotary devices such as valves. It relates particularly to apparatus for actuating such devices, either directly or as part of an override system for a remotely controlled power actuator coupled to a device.

Override systems are used to provide a safety system in the event of power failure to the actuator In oil pipelines and other fields such as marine, offshore and chemical industries, valves are provided at frequent intervals along the length of the line. Such valves can be actuated manually, but actuators therefor are normally electrically, pneumatically or hydraulically operated, and a variety of designs are available. Some are fail-safe in operation, such as those available from Hytork Actuators of Gloucester, England, but provision is never-the less still normally made for manual operation, such are the risks involved. A simple manual override can give rise to problems in view of the forces involved, and the present invention is directed at a simple worm and wheel apparatus for actuating such valves which is economic to install yet easy and efficient in its operation.The apparatus can be used either coupled direct to a semi-rotary device, or for overriding a power operated actuator installed on the device.

According to the present invention, apparatus for operating a semi-rotary device comprises an housing; a main spindle rotatable in the housing for coupling to a said device; a wheel gear mounted on the spindle for rotation therewith and having teeth along the periphery thereof; and a worm gear meshing with the teeth on the wheel gear, the worm gear being rotatable to rotate the wheel gear and thereby the main spindle to actuate the device. The apparatus can be manual, or power operable. Preferably, the teeth on the wheel gear are inclined to the axis of the spindle. Such incline can be selected to facilitate removal of the wheel gear, with or without the spindle, for maintenance or service. The spindle is normally held in the housing by a removable gear cover to enable the gearbox to be dismantled in this way without difficulty.

The use of inclined teeth on the wheel gear also provides an anti-backlash facility. When the apparatus is assembled the perpendicular spacing between the plane of the wheel gear and the axis of the worm gear can be set to establish the correct degree of meshing engagement. This spacing can be adjusted during the operating life of the apparatus to take up any slack in the meshing due to wear on the teeth or worm. This anti-backlash facility is particularly important where the apparatus is motorized.

The wheel gear is normally only a sector and can be provided with abutment surfaces at its circumferential ends, for engagement with stops in the housing at the chosen limits of rotation of the spindle. One or each stop might include a limit switch actuator for generating a signal indicating the respective extreme positions of the spindle.

In certain circumstances, for example where the operating forces for the semi-rotary device or valve are very large, the wheel gear might be circular and coupled to the device or valve through an epicyclic gear to achieve a large gear reduction. Alternatively, the wheel gear can be part circular, and the worm gear driven through a gear mechanism, epicyclic or other, achieving a similar gear reduction. For power operated apparatus of the invention, this can be particularly beneficial as it reduces the power requirements of the drive means employed. It will be appreciated that, while the wheel gear used is normally a quadrant, the shape and size of the wheel gear can be selected to suit a particular application.

Apparatus according to the invention for use as part of an override system may be made declutcbable where a power operated actuator is installed on a semi-rotary device. This can be achieved by rotatably mounting the worm gear in a support member which is selectively shiftable to take the worm gear out of mesh with the wheel gear.

Conveniently, the support member can be pivotally mounted on the housing. In a preferred embodiment, the support member is a tubular body rotatable in the housing, the worm gear being mounted therein for rotation about an axis parallel to but offset from the axis of the body. Some form of latching mechanism is also normally provided for locking the support member with the worm gear in mesh with the wheel gear. Such a latching mechanism can be adjustable to provide additional flexibility in setting the mesh between the wheel gear and the worm gear as described above.

Declutchable apparatus according to the invention can be fitted either directly to a semi-rotary device, or to an actuator already coupled thereto. An advantage of the former arrangement is that operation of the device by the apparatus does not rely upon the actuator to couple the two together. This means that the device is still operable when the actuator has had to be removed for repair or service.

The apparatus need not extend axially beyond the ends of its main spindle. Thus it can be, and normally is mounted between the actuator and the device, although it might be located on the opposite side of the device from the actuator Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings wherein Figure 1 shows a cross-section of apparatus according to a first embodiment of the invention, the section being taken in a plane transverse to the axis of the output spindle; Figure2 is a section taken on line ll-ll of Figure 1; Figure 3 shows a section similarto that of Figure 1, of a second embodiment of the invention; Figure 4 is a section taken on line IV-IV of Figure 3;; Figures 5A and B are elevation and sectional views showing the latch mechanism for the embodiment of Figures 3 and 4; and Figure 6 is an elevation showing apparatus according to the invention coupled to a valve actuator.

The apparatus shown in Figures 1 and 2 operates as an actuator coupled directly to a semi-rotary device, and comprises a main housing 2 in which a main output spindle 4 is supported with its axis vertical on needle thrust bearings 6 although any suitable bearing mechanism may be used. Bearings may sometimes be required at both ends of the spindle 4. A wheel gear 8 extends partially around the spindle 4 and is secured to a flange on the spindle by means of bolts 10. The wheel gear shown is in the form of a sector having an arc of 90 , but other sizes of an arc can of course be adopted. The spindle 4 is rotatable with the sector 8 in the housing between limits defined by stops in the form of screws 12 threaded in the housing 2. The circumferential or quadrant ends of the sector 8 will abut against the respective stop at either extreme position thereof.

The sector 8 is formed with teeth along its periphery which mesh with a worm gear 14 also mounted for rotation in the housing 2 but about an axis perpendicular to that of the spindle 4. As shown in Figure 2, the teeth are inclined to the axis of the spindle 4. The worm gear 14 is shown supported in tapered roller bearings 16 although once again, any suitable bearing mechanism may be used in a particular application. Oil seals 18, for example synthetic rubber O-ring seals, are inclined on the spindle 4 and worm gear 14, enabling the housing to be operated full of oil if desired.

The worm and gear arrangement employed in the present invention has the advantage that it is self-locking. The gear cannot drive the worm, and this constitutes an additional safety feature, further reducing the risk of unintentional opening or closing of the device to which it is coupled.

The housing 2 can be formed with a removable cover 20 through which the upper end of the spindle 4 passes. This enables the gearbox to be easily inspected, and dismantled if necessary. The incline on the teeth of the wormwheel sector 8 facilitates the upward withdrawal of the spindle 4 bearing the sector 8. It also provides means by which the degree of meshing between the sector8 and worm gear 14 can be adjusted. The position of the sector 8 can be varied using shims 7 or using taper roller bearings in place of bearings 6 with adjustable outer races. By varying the position of the sector 8 along its axis the engagement (horizontal) of the teeth and the worm can be changed. This means that wear can be taken up, larger manufacturing tolerances can be employed, and that an anti-backlash facility is provided.

This lastfeature is particularly important where the rotation of the worm wheel is motorized in some way. Although not shown, it will be appreciated that a motor might easily be coupled to the worm gear 14 to provide high speed rotation thereof if desired.

The apparatus shown in Figures 3 and 4 is suitable for use as a manual override where a power actuator is employed. It is generally similar in construction to that of Figures 1 and 2 and where appropriate the same reference numbers are used. It differs though in the manner of supporting the worm gear 14.

Whereas in the first embodiment it is supported directly in the housing 2, in this case it is rotatably supported, again by bearings 16, in a pivotable support member 22. The member 22 is mounted in the housing 2 and is pivotable therein to take the worm gear 14 out of mesh with the sector 8. The apparatus is thus declutchable. This is accomplished in this embodiment by rotatably mounting the worm gear 14 on an eccentric axis in the member 22 which is itself rotatable in the housing 2. A sophisticated bearing mechanism is not normally required to support the member 22 in the housing 2 and O-rings 18 and flanges 38 at either end can be sufficient. A handle 24 is provided to rotate the member and a latching mechanism is also included to secure the member with the worm gear 14 either in mesh or out of mesh with the sector 8.The handle 24 is in the form of a spring strip of metal bent on itself as shown in Figure 5. One end is secured to the member 22 by bolts 26 and at the other end a latch member 28 is mounted for selective engagement behind a projection 30 formed on the housing 2 to define either extreme position of the member 22.

The latch member 28 has a body 32 into which is screwed a bolt 34 bearing a lock nut 36. The end of the bolt 34 projects from the bodyto define the orientation at which the member 22 holds worm gear 14 in mesh with the sector 8. Rotation of the bolt 34 adjusts the extent of its projection and thereby the centre-to-centre spacing of the worm gear 14 and the sector 8. This provides an additional adjustment mechanism, supplementing the antibacklash facilities discussed above. Similar adjustment is not normally required at the "out of mesh" orientation of the member 22. It will be appreciated that a variety of locating mechanisms may be used, with or without an adjustment facility, such as sprung spigots in openings in the housing 2. Further, spring means can be used to bias the member 22 to one or other of its extreme orientations.

Because the apparatus is declutchable or disengageable, and adjustable when assembled, it will be appreciated that the sector 8 may be mounted in the housing with its teeth inclined in either direction, priorto meshing with the worm gear which may be held in the disengaged position. The embodiment of Figures 3 and 4 also differs from that of Figures 1 and 2 in that the stops 12 each include a limit switch actuator for generating a signal indicative ofthe respective extreme position of the spindle 4.

Due to the modular nature of the assemble many of the components of the gearbox may be made in inexpensive materials. For example, the casing and spindles can be made in a standard gauge iron, while the meshing parts may need to be hardened depending on application. Indeed, the main spindle 4 may be formed integral with the sector 8, with only the teeth on the sector case-hardened if necessary.

The worm gear 14 can be similarly selectively strengthened.

Figure 6 shows a gearbox 40 of the kind shown in Figures 3 and 4 mounted on an actuator 42. In this Figure, the actuator 42 is shown coupled to the male end 44 (Figure 4) of the spindle 4. The valve to be operated by the actuator or gearbox may be coupled either to the male end 46 of the actuator spindle 48 or the female end 50 of the gearbox spindle 4. The worm gear 14 is shown in mesh with the wheel gear sector 8, but the member 22 will be rotated (anticlockwise as shown) to disengage or declutch the sector 8 except when manual override is required.

During normal operation the arrangement illustrated will be operated solely by the actuator 42, the sector 8 following the movement of the actuator spindle 48.

Such an actuator, typically an Hytork actuator as referred to above, operates on a supply of air under pressure to pistons on either side of the actuator spindle or pinion 48. Each piston bears a rack engaging the pinion along one side of the actuator.

Air pressure on the outer ends of the pistons causes inward movement thereof and consequent rotation of the pinion 48 in one direction; air pressure on the inner ends generating the opposite movements.

Claims

1. Apparatus for actuating a semi-rotary device comprising an housing; a main spindle rotatable in the housing for coupling to a said device; a worm wheel sector mounted on the spindle for rotation therewith and having gear teeth along the periphery thereof; and a worm gear meshing with the teeth on the worm wheel sector, the worm gear being rotatable to rotate the worm wheel sector and thereby the main spindle to actuate a said device.

2. Apparatus according to Claim 1 wherein the teeth on the worm wheel sector are inclined to the axis of the spindle.

3. Apparatus according to Claim 1 or Claim 2 wherein the spindle is held in the housing by a removable gear cover, the spindle being removable from the housing with the worm wheel sector when the cover is removed.

4. Apparatus according to any preceding Claim wherein the worm wheel sector is mounted on a flange integral with the spindle.

5. Apparatus according to any preceding Claim wherein the circumferential ends of the worm wheel sector are provided with abutment surfaces, and wherein stops are mounted in the housing for engagement with the abutment surfaces to define the limits of rotation of the spindle.

6. Apparatus according to Claim 5 wherein each stop includes a limit switch actuator for generating a signal indicating the respective extreme positions of the spindle.

7. Apparatus according to any preceding Claim including drive means for rotating the worm gear.

8. Apparatus according to any preceding Claim wherein the main spindle is coupled to a semi-rotary device.

9. Apparatus according to any preceding Claim wherein the worm gear is rotatably mounted in a pivotable support member, the support member being selectively pivotable to take the worm gear out of mesh with the worm wheel sector.

10. Apparatus according to Claim 9 wherein the support member is a tubular body rotatable in the housing, and having the worm gear mounted therein for rotation about an axis parallel to but offset from the axis of the body.

11. Apparatus according to Claim 9 or Claim 10 including a latch mechanism for locking the support member with the worm gear in mesh with the worm wheel sector.

12. The combination of a power operated valve actuator and apparatus according to any of Claims 9 to 11.

13. The combination of Claim 12 coupled to a valve in an oil pipeline.

14. The combination of Claim 13 wherein the gearbox is interposed between the valve and the actuator.

15. Apparatus for actuating a semi-rotary device substantially as described herein with reference to Figures 1 and 2 or Figures 3 to 5 of the accompanying drawings.