GB2183010A - Valve actuator - Google Patents

Abstract

In a fluid-controlling valve having a movable valve member and an actuating mechanism comprising a rotatable worm and nut mounted for axial movement along the worm, either said worm or said nut is operatively connected to said movable valve member so that an input movement to the other of the aforesaid components (i.e. the nut or the worm) will result in a desired output movement of the valve member. In one embodiment rotation of a worm 16 by means of a handle 17a results in 90 DEG rotation of a fork 19 attached to a nut 17 so as to actuate a butterfly disc (12 Figs. 1,2). In a second embodiment and nut (27 Fig. 4) forms a piston which is reciprocated in a cylinder (25) by fluid pressure so as to rotate a worm formed on a shaft (24) and thereby actuate a multi-turn valve spindle (26). <IMAGE>

Description

SPECIFICATION Valve actuator This invention relates to a fluid controlling valve which may for example be used in the petrochemical industry or in any other application where it is desired to control the flow of liquids, semiliquids and gases, hereinafter all referred to, for convenience, as fluids. Such valves (which may for example be in the form of globe valves, gate valves, diaphragm valves, ball valves, plug valves or butterfly valves) may require considerable effort to change the position of the movable valve member as may be required and in some cases power-actuated devices are employed to effect the desired movement. In other cases manually operable devices may be provided but it is one object of the present invention to provide a fluid controlling valve having an improved form of actuating mechanism.

In accordance with the invention there is provided a fluid controlling valve having a movable valve member and an actuating mechanism which comprises a rotatable worm on which is mounted a nut for axial movement along the worm, one of said components of the actuating mechanism being operatively connected to said movable valve member so that an input movement of the other component will result in the desired movement of the movable valve member.

Thus the worm and nut mechanism (which may be of the re-circulating ball type) may be manually operable in which case the worm shaft can be provided with a rotatable handwheel which, on rotation, is adapted to move the nut along the worm in one or othe other axial direction, the nut having a projection which extends between the arms of a forked element which is itself connected to the valve stem on which the movable valve member is mounted. Thus anguiar movement of the handwheel will result in axial movement of the nut which in turn is translated into angular movement of the rocker shaft and of the valve member. Such an arrangement can be used where it is required for example to turn the valve member through an angle of approximately 90".

Alternatively, where it is required to turn the valve stem to which the valve member is connected through an angle which comprises one or more complete turns, the nut itself becomes the input member and is moved axially along the worm by means for example of a power-actuated device such as a pneumatic or hydraulic piston and cylinder unit. Such movement will result in rotation of the worm which then becomes the output member of the worm and nut mechanism, said worm being connected to the valve stem and thereby effecting the desired rotation thereof.

The invention will now be more particularly described with reference to the accompanying drawings wherein Figure 1 is a perspective view of one example of a valve and actuator in accordance with the invention, Figure 2 is a part-sectional end view of the assembly seen in Figure 1, Figure 3 is a sectional elevation, of the worm and nut actuating mechanism seen in Figures 1 and 2, and Figure 4 is a sectional elevation of an example of a worm and nut mechanism of the re-circulating ball type which may be used as an actuator with a valve in which it is required to rotate the valve stem through several complete turns between the open and closed positions of the valve.

Referring firstly to Figure 1 of the drawings there is shown therein a valve 10 which is disposed within a pipeline 11 for the purpose of controlling the flow of a fluid therethrough, said valve being of the so-called butterfly type which includes a disc 12 which is mounted for movement about a diameter which in the example shown extends in a generally vertical direction, such movement comprising an angular movement of approximately 90" between the fully closed and the fully open positions of the valve. Thus said disc 12 is connected to a valve stem 13 which projects upwardly through the valve housing into an actuator mechanism generally indicated by reference numeral 14.

The aforesaid actuating mechanism 14 comprises a worm and nut mechanism of the recirculating ball type mounted in a housing 15, the worm shaft 16 projecting through the housing and being provided at its outer end with a rotatable handwheel 17a. On said worm shaft 16 is mounted a nut 1 7 the threads of the co-acting worm shaft 16 and nut 17 being interconnected by a plurality of re-circulating balls in a known manner. Furthermore the nut is provided with an upwardly extending projection 18 which extends between the arms of a forked element 19 which itself projects radially from a hollow rocker shaft 20. The upper end of said projection 18 is provided with a roller 21 which engages in a horizontally extending slot formed in the upper cover 22 of the housing 15.Such engagement between the roller 21 and the co-acting slot guides the nut so that in use it will move in an axial direction without rotation relative to the work shaft 16. The aforesaid rocker shaft 20 is interconnected with the valve stem 13 by means for example of a key 23 which extends partly into a keyway formed in the interior surface of the hollow rocker shaft 20 and partly into a corresponding keyway formed in the exterior surface of the valve stem 13. Thus rotation of the handwheel 17a will effect axial movement of said nut 17 in an axial direction with respect to the worm 16 and this will have the effect of engaging the aforesaid forks of the forked member 19 to turn the rocker shaft 20 and thereby the valve stem 13 and with it the disc 12.

As previously mentioned the angular movement of said valve stem between the fully open and fully closed positions of the disc 12 will amount to an angle of approximately 90" and accordingly suitable adjustable stops are provided in the worm and nut mechanism to define the limiting positions of the movement of such mechanism. For example such stops can be arranged to engage opposite sides of the aforesaid forked member 19.

Furthermore, a friction clutch mechanism (or a similar mechanism) may be provided in the connection between the handwheel 1 7a and the worm 16. Thus in the example shown in Figure 3, the handwheel 17a is connected to an input shaft 40 by means of a pin 41. At its inner end, the input shaft 40 is enlarged to form a hollow portion 42 which receives the adjacent end of the worm 16. The latter is provided with a pin 43 which extends transversely through a cylindrical aperture formed in the worm so as to project at its two opposite ends outwardly of the worm 16 and into a pair of oppositely disposed apertures 8 and 9 formed in said hollow portion 42 of the input shaft, said apertures each having a periphery which is of camshaped configuration.There is also provided a clutch member 44 having a radially extending flange 45 which is engaged on one side- by a spring pack 46 and on the other side by one face of an annular friction plate 47. Said clutch member 44 is itself connected to the worm 16 by means of a key 48 and the other face of the friction plate 47 is engaged by a shoulder of a nonrotatable part 49 of the clutch housing, whereas the aforesaid spring pack 46 is also engaged, on that side opposite to the clutch member 44, by another nonrotatable part 50.

In use, if the handwheel 1 7a is turned in either direction, the pin 43 will be urged (by means of the inter-action of the ends of the pin with the aforesaid cam-shaped aperture 8 and 9 in the hollow portion 42) to the right (as seen in the drawing), the worm 16 being similarly urged towards the right with the pin 43. The adjacent axial ends of the hollow portion 42 and the clutch member 44 will thus be engaged to compress the spring pack 46 and relieve pressure on the friction plate 47.

The worm 1 6 will then be able to turn freely.

On the other hand, if the butterfly valve member attempts to move from a predetermined set position the inter-action of the pin 43 in the cam-shaped apertures 8 and 9 of the hollow portion 42 will relieve the pressure between the adjacent axial ends of the hollow portion 42 and the clutch member 44 and thus permit the spring pack 46 to press the clutch member 44 into tight engagement with the friction plate 47, thereby preventing rotation of the worm 16 and any actual movement of the butterfly valve member. Thus the worm and nut mechanism is effectively nonreversible, which is very desirable in the case where the mechanism is being used to actuate a butterfly valve. Furthermore, it will also be appreciated that by using a worm and nut mechanism, a highly efficient actuator requiring a relatively low input torque will be provided.

Moreover the action of the forked member 19 will be such that a higher mechanical advantage will be established at positions corresponding to the fully open and fully closed positions of the valve where additional effort on the valve actuator may sometimes be required.

In the above described arrangement the movable valve member (i.e. the disc 12) is required to turn through an angle of approximately 90 between its fully open and fully closed positions. However in other kinds of valves (for example a gate valve) the valve stem itself may be required to turn through several complete turns and in this case it is arranged that the aforementioned nut of the worm and nut mechanism becomes the input member whilst the worm becomes the output member. In this case the aforesaid handwheel is dispensed with and the nut is extended to form a piston within a cylinder to which pneumatic or hydraulic pressure can be applied.

Such an arrangement of a worm and nut mechanism is shown in Figure 3 which thus represents an actuator which can be operated by fluid pressure and which is adapted to be connected to a valve having a valve stem which is required to be rotated through several complete turns. As shown the worm shaft 24 projects through a cylinder 25 and at its projecting end 26 forms an output shaft which in use will be connected to the associated valve stem. Mounted on said worm shaft 24 is a nut 27 which is interconnected with the worm shaft by means of recirculating balls 28. The nut is provided at one end with a radially extending flange 29 which thus forms a piston and connections 30 and 3 1 are provided at opposite ends of the cylinder 25 for the admission and return of pressurised fluid or air. Furthermore the nut is formed in its exterior surface with an axially directed groove 32 which engages a projection 33 extending through the wall of the cylinder 25 and which thus forms a guide to prevent said nut from rotating. Adjustable stops 34 and 35 are provided at opposite ends of said cylinder 25 to limit the maximum travel of the nut 29 in either axial direction and a safety valve mechanism generally indicated by reference 36 is provided to relieve pressure at one end or the other of said cylinder 25 when the combined nut/piston 27/29 reaches either end of its stroke.Thus the positions of the stops 34 and 35 can be adjusted by screwing them in or out in order to determine accurately the end positions of the nut/piston assembly 27/29, such end positions corresponding of course to the fully closed and fully open positions of the movable valve member of the valve which is associated with the actuator seen in Figure 3. The safety mechanism 36 incorporates a pair of opposed valve members 37 and 38 which each have a stem arranged so that the two stems project respectively from opposite ends of the nut 27 and the two valve members are normally urged away from each other by a spring 39.When pressure is applied to one end or the other of said cylinder 25 the spring 39 is compressed to permit one of said valve members 37 and 38 to lift off its seat whilst the other remains on its seat but at the end of the stroke of the nut/piston assembly 27/29 in one direction or the other, one of the valve member stems will engage the adjacent stops 34 or 35 and will thus be lifted off its seat and thereby relieve the pressure in the pressurised end of the cylinder 25.

.In the above-described embodiments, the valve which has a movable valve member arranged to turn through an angle of 90" is provided with a manual worm and nut actuator whereas the multi-turn valve has a powerdriven worm and nut actuator. It is however to be understood that a power-driven worm and nut actuator may be applied to a valve having a 90" angle of movement and that a manual worm and nut actuator may be applied to a multi-turn valve.

Claims (8)

1. A fluid controlling valve having a moveable valve member and an actuating mechanism which comprises a rotatable worm on which is mounted a nut for axial movement along the worm, one of said components of the actuating mechanism being operatively connected to said moveable valve member so tnat an input movement of the other component will result in the desired movement of the moveable valve member.

2. A fluid controlling valve as claimed in Claim wherein the worm and nut mechanism is manually operable, the worm shaft being provided with a manually rotatable member which, on rotation, is adapted to move the nut along the worm in one or other axial direction, the nut having a projection which extends between the arms of a forced element which is itself connected to a valve stem on which the moveable valve member is mounted.

3. A fluid controlling valve as claimed in Claim wherein the nut of the worm and nut mechanism comprises the inout member of the mechanism and is arranged to be moved axially along the worm by means of a power actuated device, said worm being connected to the valve stem to effect the desired rotation thereof when said nut is moved axially along the worm.

4. A fluid controlling valve according to any one of the preceding c3aims wherein adjustable stops are provided to define opposed limiting positions of the movement of the worm and nut mechanism.

5. A fluid controlling valve as claimed in Claim or Claim 2 wherein a clutch mechanism is connected to the worm and nut mechanism to ensure that said worm and nut mechanism is non-reversible in use.

6. A fluid controlling valve as claimed in any one of the preceding claims in which said worm and nut mechanism is of the recirculating ball type.

7. A fluid controlling valve substantially as hereinbefore described with reference to and as shown in Figures 1-3 of the accompanying drawings.

8. A fluid controlling valve substantially as hereinbefore described with reference to and as shown in the Figure 4 of the accompanying drawings.