GB2265968A

GB2265968A - Pressure reducing devices

Info

Publication number: GB2265968A
Application number: GB9206977A
Authority: GB
Inventors: Edward Grant Needham
Original assignee: Spirax Sarco Ltd
Current assignee: Spirax Sarco Ltd
Priority date: 1992-03-31
Filing date: 1992-03-31
Publication date: 1993-10-13
Anticipated expiration: 2012-03-31
Also published as: JPH05289753A; GB2265968B; GB9206977D0

Abstract

A pressure reducing device comprises an inlet 6, an outlet 8 and a valve 12 which controls flow between the inlet 6 and the outlet 8. The valve 12 comprises a ball 22 which cooperates with a seat 20 formed on a valve body 18. The valve body 18 has a guide passage 36 for an operating rod 38. The valve is operated through the operating rod 38 by actuating means 16. The actuating means 16 comprises a spring 56 and a bellows 50 which act on the operating rod 38 by means of a movable plate 54. The plate 54 has a conical recess 74 which accommodates one end of the rod 38, the protrusion 72 defined by the formation of the recess serving to locate one end of the spring 56. <IMAGE>

Description

PRESSURE REDUCING DEVICES This invention relates to pressure reducing devices.

According to one aspect of the present invention there is provided a pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve comprising a valve element and a valve seat, opening and closing of the valve being controlled by actuating means which is responsive to the pressure at the outlet and which acts upon the valve member through an operating rod, the valve seat being formed on a valve seat body which is secured to the casing and is provided with a guide passage receiving the valve operating rod.

By forming the guide passage in the valve seat body, it is possible to ensure that the guide passage is accurately aligned with the valve seat, and consequently the operating rod will be accurately aligned with the valve member.

In a preferred embodiment in accordance with the present invention, the valve seat is situated between the actuating means and the valve member, and the operating rod extends through the valve seat to operate the valve member. The valve member may be a ball which the operating rod abuts to displace it from the valve seat.

The valve seat body is preferably removable from the casing in the direction towards the actuating means. With this construction, a single cover can be provided on the casing, and removal of this cover provides access both to the actuating means and the valve seat body. The valve seat body may be mounted in an opening formed in the casing, for example in a partition which separates the inlet from the outlet.

The valve seat body may be part of a sub-assembly comprising a valve member and other associated components which are formed so that they can be passed through the aperture during removal or insertion of the valve seat body.

The operating rod may have a reduced diameter portion at the end region which passes through the valve seat body for engagement with the valve member.

This minimizes obstruction of the flow passage through the valve seat when the valve is open.

In a preferred embodiment, the actuating means comprises an axially extensible bellows having support means at one end fixed with respect to the casing and having a movable wall at the other end, disposed between the support means and the valve member. The movable wall is acted upon in the valve-opening direction by resilient means, and is acted upon in the opposite direction by pressure in a chamber which communicates with the outlet.

With such a construction, the resilient means may be accommodated partially within the bellows, so reducing the overall height of the device.

The movable wall may act on the valve member through an operating rod. The operating rod may abut the movable wall in a manner permitting universal pivoting of the operating rod relatively to the movable wall. In a preferred embodiment, the movable wall has a recess which receives the operating rod. The recess may have a conical shape.

Preferably, the movable wall comprises a plate which is formed to provide the recess on one side and a complementary projection on the other side. Such a construction has advantages if the resilient means is a spring, since the spring may directly abut the movable wall on the side opposite the operating rod, in which case the projection provides location for the end of the spring.

The support means may be a supporting ring clamped between the casing and a cover.

According to another aspect of the present invention there is provided a pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve, in which opening and closing of the valve is controlled by actuating means which is responsive to the pressure at the outlet, the actuating means comprising an axially extensive bellows which operates the valve by means of an operating rod, the bellows carrying a movable plate which is formed to provide a conical recess on one side of the plate, in which the end of the operating rod is received, the movable plate being acted upon in the valve-opening direction by a spring which is located on a projection, corresponding to the recess, on the side of the movable plate opposite the operating rod.

The resilient means, particularly if it is a spring, may react at the end away from the movable wall against an adjustable abutment. This abutment may comprise a nut mounted on a rotatable screwthreaded spindle, so that rotation of the spindle causes axial displacement of the nut, thereby adjusting the loading on the resilient means. The screwthreaded spindle may be provided with a knob for rotating it, and this knob may have a "click" mechanism for retaining the knob in a set position and for assisting an operator in determining how far the knob has been turned. This mechanism may, for example, comprise at least one resilient blade formed on the knob, which engages serrated formations on the cover.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawing which is a sectional view of a pressure reducing device.

The device shown in the drawing comprises a casing 2 provided with a cover 4. The casing 2 has an inlet 6 and an outlet 8 which are separated from each other by a partition 10 provided with a valve 12. The casing 2 and the cover 4 define a housing 14 which accommodates actuating means 16 for the valve 12.

The valve 12 comprises a valve seat body 18 having a valve seat 20 with which a valve member in the form of a ball 22 cooperates. The ball 22 is biased towards the valve seat 20 by a spring 24. The spring 24 is seated in a cup 26 provided at the lower end of a generally cylindrical strainer 28. The strainer 28 is secured at its upper end in a groove 30 formed in the valve seat body 18. The strainer 28 has a series of formations 32 which serve to centre the ball 22.

The valve seat body 18 has an external screw thread 19 which engages a corresponding screw threaded aperture 21 formed in the partition 10. The upper end of the valve seat member 18 has a hexagonal head 44 which retains a bulkhead plate 46 in position. The bulkhead plate 46 has a small hole 48 which provides communication between the outlet 8 and the space 14.

The valve seat body 18 has a bush 34, for example of graphite-filled plastics material, inserted in it.

This bush 34 has a guide passage 36 within which an operating rod 38 is slidable. At its lower end, the operating rod 38 has a portion 40 of reduced diameter, the extremity of which abuts the ball 22. The reduced diameter portion 40 passes through a bore 42 in the valve seat member 18, which bore terminates at the valve seat 20.

A bellows 50 is supported in the space 14 by a supporting ring 52 which is clamped between the casing 2 and the cover 4. At its lower end, the bellows 50 is provided with a movable wall in the form of a pressed plate 54, which abuts the upper end of the operating rod 38. The plate 54 has a conical region 72 which defines a recess 74 on the side facing the operating rod 38. A regulating spring 56 acts between the plate 54 and an adjustment nut 58. The spring 56 is located on the plate 54 by the conical region 72, which has approximately the same diameter as the inner diameter of the spring 56.

The nut 58 cooperates with ribs 60 formed on the interior of the cover 4, to prevent the nut 58 from turning. The nut 58 is mounted on a screwthreaded spindle 62 which is provided, at its upper end, with a knob 64. The knob 64 is a plastics moulding, and has several (for example five) flexible blades 66 which cooperate with a circular serrated formation 68 on the upper end of the cover 4. The upper wall of the cover 4 has a circular array of holes 70, centred on the lengthwise axis of the spindle 62, and the knob 64 is provided with a single hole (not shown) at the same distance from that axis as the holes 70.

For use, the device shown in the drawing is mounted in pipework between a supply of fluid (for example steam) under pressure, and equipment which is to be supplied with steam at a pressure lower than that of the source. Steam from the source enters the device from the inlet 6 and, when the valve 12 is open, passes to the consuming equipment through the outlet 8.

The regulating spring 56 acts through the plate 54 on the operating rod 38, and tends to displace the ball 22 from the valve seat 20 against the restoring action of the spring 24 and against the force applied to the ball 22 by the pressure at the inlet 6. However, the pressure at the outlet 8 is communicated to the part of the space 14 below the bellows 50, and so acts on the plate 54 to oppose the action of the spring 56. When the pressure at the outlet 8 reaches a predetermined value, the upward force applied to the plate 54 will overcome the action of the spring 56, and the ball 22 will return to the seat 20, closing the valve 12. Thus the pressure at the outlet 8 can be maintained at a substantially constant value.

The pressure at which the valve 12 will change from open to closed, and vice versa, can be adjusted by turning the knob 64 by hand. This rotates the spindle 62, adjusting the position of the nut 58 and consequently the pre-load applied to the spring 56. As the knob 64 is rotated, the blades 66 give audible "clicks" as they snap over the formations 68 on the cover 4. This assists the operator in determining how far the knob has been turned, and consequently how the pressure at the outlet 8 has been altered. The blades 66 also serve to retain the knob 64 in a set position, although additional security can be provided by inserting a pin through the hole in the knob 64 into one of the holes 70 in the cover 4.

Because the bush 34 is fitted within the valve seat member 18, the guide passage 36 can be aligned accurately with the valve seat 20. Consequently, the operating rod 38 will move accurately along a line passing through the centre of the ball 22 (when the ball 22 is seated on the valve seat 20), so that reliable contact between the ball 22 and the seat 20 can be assured. Also, since the operating rod 38 merely abuts the plate 54, any variation in the orientation of the plate 54, for example as a result of the end of the spring 56 not being accurately perpendicular to the lengthwise axis of the operating rod 38, will not cause lateral forces to be applied to the operating rod 38 As a result, there is no tendency for the operating rod 38 to tilt in the guide passage 36, and the operating rod 38 will therefore move smoothly in the passage 36.

As a result of the configuration of the bellows 50, with the movable plate 54 disposed below the supporting ring 52 (i.e. nearer to the valve 12), the bellows is able to accommodate the lower region of spring 56, with the result that the total height of the device can be minimized.

For servicing, the cover 4 is removed from the casing 2, for example by releasing securing bolts (not shown). This provides access to the space 14, allowing the spring 56 to be removed, followed by the bellows 50 and the plate 54. The operating rod 38 can then be withdrawn from the guide passage 36, after which the valve 12 can be removed as a unit by unscrewing the valve seat body 18 from the aperture 21. It will be appreciated from the drawing that the strainer 28 and the components fitted within it can all be removed upwardly through the aperture 21, so avoiding the need for separate access to be provided at the lower region of the casing 2. If necessary, a different valve assembly 12 can be fitted, for example with a bore 42 of different diameter, to provide a device with different flow characteristics.

In the embodiment described above, the operating rod 40 merely abuts the ball 22 with the result that the ball 22 is free to rotate relatively to the rod.

If any wear of the ball 22 occurs where it contacts the seat, subsequent rotation of the ball 22 may allow leakage at the points where the old seat contact line on the ball meets the seat. To avoid this problem, it may be desirable to fix the ball 22 to the rod 40, for example by welding. If this is done, the ball 22 can rotate relatively to the seat 20 only about the axis of the rod 40, and this will not alter the position of the line of contact on the ball 22.

Claims

1. A pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve comprising a valve element and a valve seat, opening and closing of the valve being controlled by actuating means which is responsive to the pressure at the outlet and which acts upon the valve member through an operating rod, the valve seat being formed on a valve seat body which is secured to the casing and is provided with a guide passage receiving the valve operating rod.

2. A pressure reducing device as claimed in claim 1, in which the valve seat is situated between the actuating means and the valve member, the operating rod extending through the valve seat to operate the valve member.

3. A pressure reducing device as claimed in claim 1 or 2, in which the valve member is a ball which the operating rod abuts to displace it from the valve seat.

4. A pressure reducing device as claimed in any one of the preceding claims, in which the valve seat body is removable from the casing in the direction towards the actuating means.

5. A pressure reducing device as claimed in any one of the preceding claims, in which the valve seat body is mounted in an aperture formed in a partition which separates the inlet from the outlet.

60 A pressure reducing device as claimed in claim 5, in which the valve seat body is part of a subassembly which is able to pass through the aperture.

7. A pressure reducing device as claimed in any one of the preceding claims, in which the operating rod has a reduced diameter portion at the end region which passes through the valve seat body for engagement with the valve member.

8. A pressure reducing device as claimed in any one of the preceding claims, in which the actuating means comprises an axially extensible bellows having support means at one end fixed with respect to the casing and having a movable wall at the other end.

9. A pressure reducing device as claimed in claim 8, in which the movable wall is disposed between the support means and the valve member.

10. A pressure reducing device as claimed in claim 8 or 9, in which the movable wall is acted upon in the valve-opening direction by resilient means, and acted upon in the opposite direction by pressure in a chamber which communicates with the outlet.

11. A pressure reducing device as claimed in claim 10, in which the resilient means is accommodated partially within the bellows.

12. A pressure reducing device substantially as described herein with reference to, and as shown in, the accompanying drawing.

12. A pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve, in which opening and closing of the valve is controlled by actuating means which is responsive to the pressure at the outlet, the actuating means comprising an axially extensible bellows which operates the valve by means of an operating rod, the bellows carrying a movable plate which is formed to provide a conical recess on one side of the plate, in which the end of the operating rod is received, the movable plate being acted upon in the valve-opening direction by a spring which is located on a projection corresponding to the recess on the side of the movable plate opposite the operating rod.

11. A pressure reducing device substantially as described herein with reference to, and as shown in, the accompanying drawing.

Amendments to the claims have been filed as follows

1. A pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve assembly comprising a valve seat body and a valve element which is held captive with respect to the valve seat body, opening and closing of the valve assembly being controlled by actuating means which is responsive to the pressure at the outlet and which acts upon the valve element through an operating rod, the valve seat body comprising a valve seat and a guide passage receiving the valve operating rod, and being secured to the casing for removal in a direction towards the actuating means.

2. A pressure reducing device as claimed in claim 1, in which the valve seat is situated between the actuating means and the valve element, the operating rod extending through the valve seat to operate the valve element.

3. A pressure reducing device as claimed in claim 1 or 2, in which the valve element is a ball which the operating rod abuts to displace it from the valve seat.

4. A pressure reducing device as claimed in any one of the preceding claims, in which the valve seat body is mounted in an aperture formed in a partition which separates the inlet from the outlet.

5. A pressure reducing device as claimed in claim 4, in which the valve assembly is able to pass through the aperture.

6. A pressure reducing device as claimed in any one of the preceding claims1 in which the operating rod has a reduced diameter portion at the end region which passes through the valve seat body for engagement with the valve element.

7. A pressure reducing device as claimed in any one of the preceding claims, in which the actuating means comprises an axially extensible bellows having support means at one end fixed with respect to the casing and having a movable wall at the other end.

8. A pressure reducing device as claimed in claim 7, in which the movable wall is disposed between the support means and the valve element.

9. A pressure reducing device as claimed in claim 7 or 8, in which the movable wall is acted upon in the valve-opening direction by resilient means, and acted upon in the opposite direction by pressure in a chamber which communicates with the outlet.

10. A pressure reducing device as claimed in claim 9, in which the resilient means is accommodated partially within the bellows.

11. A pressure reducing device comprising a casing having an inlet and an outlet which communicate with each other through a valve, in which opening and closing of the valve is controlled by actuating means which is responsive to the pressure at the outlet, the actuating means comprising an axially extensible bellows which operates the valve by means of an operating rod, the bellows carrying a movable plate which is formed to provide a conical recess on one side of the plate, in which the end of the operating rod is received, the movable plate being acted upon in the valve-opening direction by a spring which is located on a projection corresponding to the recess on the side of the movable plate opposite the operating rod.