GB2152638A - Pressure regulating valve assembly - Google Patents

Abstract

A pressure regulating valve assembly has a first valve (11, 12) arranged to deliver to an outlet (14) a desired constant delivery pressure from a higher inlet pressure at an inlet (15), and a second valve (33) arranged to relieve pressure downstream of the first valve if this pressure should exceed the said desired delivery pressure by a predetermined amount. The two valves are biassed by a common spring (22). In a second embodiment, Fig. 2, (not shown), the two valves are arranged coaxially and one valve (124) carries the seat (144) for the other valve (138). <IMAGE>

Description

SPECIFICATION Pressure regulating valve assembly This invention relates to pressure regulating valves and particularly but not exclusively to such valves intended to reduce the pressure of compressed gases stored in bottles or cylinders to a conveniently usable pressure.

There is a requirement for the pressure downstream of the pressure regulating valve to be vented if this pressure exceeds the desired regulated pressure by a specified margin. Such a requirement may be met by a burster disc connected to the system at the appropriate point but once the burster disc has operated the system cannot quickly be restored to use. Alternatively a conventional pressure relief valve such as a spring controlled pressure relief valve can be connected to the system but this is expensive, adds weight and occupies space, both lightness and compactness being at a premium in many environments such as those of aircraft or vehicles.

According to the present invention, a pressure regulating valve assembly has a first valve, a spring biassingthe valve to tend to maintain a regulated pressure downstream of the valve, and a second valve biassed by the said spring and arranged to open at a pressure downstream of the first valve which is higher than the said regulated pressure. Thus a single spring is used to bias both valves.

This can be achieved, for example, by arranging for the areas on which the respective pressures operate to be different. In one possible construction, each valve has a closure member, the closure members of the two valves being rigidly connected together. Thus, a valve member may carry two valve disks facing in the same direction and cooperating with two valve seats of different effective areas to afford the first and second valves; in such an arrangement the spring preferably biasses the first valve disk away from and the second towards the respective valve seat.

It will be understood that the term 'valve disk' is used herein in the conventional manner to refer to that part of a valve which cooperates with the valve seat to provide obturation and does not imply that such part has any particular shape.

In a second possible construction, each valve has a closure member, the closure members of'the two valves being axially movable relative to one another. For example, the valve member of the second valve may surround and slide axially relative to (and possibly on) the valve member of the first valve.

The invention may be carried into practice in various ways but two pressure regulating valve assemblies constructed in accordance with the invention will now be described by way of example with reference to the accompanying drawings, the two figures of which are respectively somewhat diagrammatic longitudinal sections of the two valve assemblies.

The valve assembly shown in Figure 1 comprises a valve body 1 having an internal bore 2 with a shoulder 3 against which is retained a flange 4 on a valve guide 5 by a spring retained cup 6 threaded into a larger diameter portion 7 of the valve body. Slidable within the valve guide 5 is a valve member 8 formed at one end with a valve disk 9 having a tapered portion 11 which cooperates with an edge 1 2 which is located at one end of the valve guide 5 and forms a first valve seat. The valve disk 9 and valve seat 1 2 form a first or regulating valve.

The valve body is formed with screw threads 1 3 enabling the valve to be screwed into a bulkhead or connected to a line to which compressed fluid may be delivered through the valve and out of an exit 14 at one end of the valve body. The valve body is provided with radial inlet passages 1 5 through which compressed gas at a higher pressure can enter an annular gallery 1 6 formed by a groove surrounding the valve guide 5 from which the gas passes through radial passages 1 7 to a groove 1 8 formed around the circumference of the valve member 8. Compressed gas can then travel via a longitudinal groove 1 9 and a further annular groove 21 to the valve formed by the valve seat 1 2 and the valve disk 9.

The valve formed by the valve seat 1 2 and the valve disk 9 is biassed to the open position by a compression coil spring 22 located between a shim 23 abutting the end wall 24 of the spring retainer 6 and a flange 25 on a first spring force transfer member 26. The transfer member 26 has an inwardly directed flange 27 at the end opposite to the outwardly directed flange 25 and the inner surface 28 of this flange is conical. Interposed between the end of the valve member 8 remote from the valve disk 9 and the transfer member 26 is a second transfer member 29 which is generally of test-tube shape and has a rounded surface 31 at its closed end engaging the conical surface 28 on the first transfer member to provide a self-alignment feature.

The open end of the second transfer member 29 is formed with a second valve seat 32 which engages a facing conical surface 33 on the valve member 8. It will be understood that the spring 22 biasses the valve seat 32 into engagement with the surface 33 which in effect forms the second valve disk of a second or relief valve. The part of the valve member 8 to the left of the surface 33 is guided within the second transfer member 29 and an O-ring 40 provides a degree of mechanical damping.

The valve guide 5 is sealed against the bore 2 of the valve body by two O-rings 41 and 42 while the valve member 8 is sealed in the bore of the valve guide member 5 by an O ring 43. A bore 44 extends along the full length of the valve member 8 so that the pressure in the outlet 1 4 is communicated to the space 45 between the opposite end of the valve member 8 and the closed end of the second transfer member 29 while cross ports 46 connect the longitudinal passage 44 to a circumferential groove 47 on one end face of which the conical valve seat 33 is formed.

It will be noted that the internal diameter of the second transfer member 29 and hence the effective diameter of the valve formed between the valve seat 32 and the valve disk 33 is smaller than the internal diameter of the bore in the valve guide 5 and hence the effective diameter of the valve formed between the valve seat 1 2 and the valve disk 11.

Operation of the valve is as follows. Pressure normally at a level of 700 bar is supplied to the passages 1 5 and is transmitted through the ports 1 7 and the grooves 18, 1 9 and 21 to the first valve which in the absence of substantial pressure in the outlet 1 4 will be open, thus permitting flow to the outlet.

When pressure builds up in the outlet 14 to a level determined by the spring 22, the force provided by the pressure in the outlet 14 on the valve disk 9 will exceed the counter-force provided by ambient pressure acting on the valve member 8 in the opposite direction and the force of the spring 22 so that the pressure regulating valve will close. pressure in the outlet 1 4 will thus be maintained at the required pressure which, in the example being described, is 83 bar. If for any reason the pressure in the outlet 14 should exceed a predetermined higher pressure, in this particular case 1 20 bar, the pressure acting in the chamber 45 against the force of the spring 22 (and the substantially negligible atmospheric pressure) will cause the second transfer member 29 to move to the left as seen in the drawing.The valve member 8 cannot follow because of the engagement of the valve disk 9 on the valve seat 1 2 and consequently the valve seat 32 will separate from the valve disk 33 to allow flow through the axial passage 44, the cross ports 46 and the groove 47 through the second valve and out of a central opening 48 in the spring retainer 6.

The valve assembly shown in Figure 2 comprises a valve body 101 having at the left hand end, as seen in Figure 2, screw threads 102 to enable the valve body to be secured in a socket 103 in a mounting member 104 indicated by chain dotted lines. The mounting member provides an inlet duct 105 leading to an inlet chamber 106 opening to an inlet passage 107 in the valve body 101. The inlet passage 107 contains a filter 108 mounted in a first counterbore and a guide member 109 screwed into a second counterbore and retaining an O-ring 111 in a third counterbore in the inlet passage 107.

The valve body 101 forms a chamber 112 which is closed by an end cap 11 3 containing apertures 114 so that the major part of the chamber 11 2 is maintained at ambient pressure. A central screw threaded aperture 11 5 in the end cap 11 3 contains a locating stud 11 6 whose position can be adjusted by means of a screwdriver slot 11 7 and can be fixed by means of a lock nut 118.A valve mounting spindle 119 has a first portion 121 of lesser diameter which extends through the O-ring 111 and is radially located by the guide member 109 and the spindle 11 9 has a portion of larger diameter 1 22 having a rounded end 1 23 which engages the inner end of the locating stud 116. A communication passage 1 20 connects the left hand end of the spindle 11 9 to a point on the circumference of the larger diameter portion 122.

Slidable on the larger diameter portion 1 22 of the spindle 11 9 is a first valve member 1 24 having a sleeve portion 1 25 which slides on the spindle 11 9 and is sealed thereagainst by an O-ring 1 26 and a valve disk portion 1 27 having a central bore 1 28 which is of slightly larger diameter than the lesser diameter portion 121 of the spindle 119. The rear face of the valve disk 1 27 is bevelled to form a valve surface 1 29 which engages the corner 131 formed at one end of the larger diameter portion 1 22 of the spindle 11 9 to provide a first valve.The left hand face of the valve disk 1 27 is relieved at 1 32 to provide communication between the first valve and an outlet passage 1 33 in the valve body 101.

The outlet passage 1 33 is constituted by an axial drilling 1 34 and a radial passage 1 35 which leads into an annular space 1 36 between the mounting member 104 and the valve body 101, this space communicating with an outlet duct 1 37 in the mounting member.

A second valve member 1 38 has a sleeve portion 139 and a disk portion 141 and is axially slidable on the sleeve portion 1 25 of the first valve member 1 24. The outer periphery of the second valve member 1 38 is sealed against the interior surface of the chamber 11 2 by a lip seal 142. The left hand end of the valve disk 141 as seen in Figure 2 is formed with an axially-directed circumferential ridge 143 the inner surface of which is chamfered to form a valve surface 1 44 which cooperates with the outer circumferential corner of the valve disk 1 27 of the first valve member 1 24 and to provide a second valve.

A generally axially directed passage 1 45 extends through the valve disk 141 of the second valve member from a position radially within the second valve to the part of the chamber 11 2 which is at ambient pressure.

A compression coil spring 146 extends between the valve disk 141 of the second valve member 1 38 and an annular washer 147 abutting the end cap 11 3 to bias the first and second valve members to the left as seen in Figure 2.

Operation of the valve assembly as shown in Figure 2 is as follows. Pressure at for example 10,000 pounds per square inch (6.9 X 104 kPa) is admitted through the inlet passage 105 and this pressure, acting on the mounting spindle 119, maintains the right hand end 1 23 of the spindle against the locating stud 11 6 and hence maintains the corner 131 forming part of the first valve in the required position. Pressure passes through the passage 1 20 in the spindle 11 9 to the first valve 129, 131 which will initially be in the open position due to the biassing operation of the spring 146.Flow then passes through the first valve, the clearance between the bore 1 28 and the spindle 119, the relief 1 32 in the face of the valve disk 1 27 and the outlet passage 133 to the outlet duct 1 37.

The outlet pressure will act on the left hand surface of the combined assembly constituted by the first valve member 1 24 and the second valve member 1 38 and if the pressure is sufficient to overcome the bias of the spring 1 46 this assembly will be moved to the right to close the first valve 129, 131. In this way a substantially constant regulated pressure wjll be maintained in the outlet duct 137; the value of this pressure can be adjusted by movement of the locating stud 11 6 but may.

for example, be 425 psi (2.93 x 10:i kPa).

If the pressure in the outlet passage 1 33 exceeds a predetermined pressure which is higher than the regulated outlet pressure and which may. for example. be 750 psi (5.1 7 x 10i kPa), the first valve will first be closed and then the second valve disk 1 38 will be moved to the right against the bias of the spring 1 46 to open the second valve, thus allowing pressure to be relieved through the second valve. the passage 145, the chamber 112 and the apertures 114.

Claims (11)

1. A pressure regulating valve assembly having a first valve. a spring biassing the valve to tend to maintain a regulated pressure downstream of the valve. and a second valve biassed by the said spring and arranged to open at a pressure downstream of the first valve which is higher than the said regulated pressure.

2. A valve assembly as claimed in Claim 1 in which the areas on which the respective pressures operate are different.

3. A valve assembly as claimed in Claim 1 or Claim 2 in which each valve has a closure member, the closure members of the two valves being rigidly connected together.

4. A valve assembly as claimed in Claim 1 or Claim 2 which includes a valve member carrying two valve disks facing in the same direction and cooperating with two valve seats of different effective areas to afford the first and second valves.

5. A valve assembly as claimed in Claim 4 in which the spring biasses the first valve disk away from and the second valve disk towards the respective valve seat.

6. A valve assembly as claimed in Claim 5 in which the valve member extends away from the first valve disk beyond the second valve disk and the second valve seat is formed on a closed spring transfer member on which the spring acts.

7. A valve assembly as claimed in Claim 6 in which the spring transfer member has a convex surface engaged by a concave surface on a second spring transfer member on which the spring acts to provide selfalignment between the two transfer members.

8. A valve assembly as claimed in Claim 1 or Claim 2 in which each valve has a closure member, the closure members of the two valves being axially movable relative to one another.

9. A valve assembly as claimed in Claim 8 in which the valve member of the second valve surrounds and slides axially relative to the valve member of the first valve and engages a portion of the first valve member to afford the second valve.

1 0. A valve assembly as claimed in Claim 9 in which the valve member of the second valve slides axially on the valve member of the first valve.

11. A pressure regulating valve assembly substantially as described herein with reference to Figure 1 or Figure 2 of the accompanying drawings.