GB1595365A

GB1595365A - Valves

Info

Publication number: GB1595365A
Application number: GB1320578A
Authority: GB
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1978-04-04
Filing date: 1978-04-04
Publication date: 1981-08-12

Description

(54) VALVES (71) We, NORTHERN ENGINEERING IN DUSTRIES LIMITED, a British company, of NEl House, Regent Centre, Newcastle on Tyne NE3 3SB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to valves.

According to the present invention there is provided a valve assembly comprising a housing containing a normally-open main valve and a normally-closed pilot sensing valve, the main valve comprising a stem having a valve member engageable with an annular seat providing a fluid path between an inlet and an outlet of the housing, the stem being in sealed sliding relationship with the housing at opposite sides of the valve member at equal diameters so that the main valve is balanced when open the pilot valve being arranged between a pilot inlet to the housing and a chamber to one side of a flexible diaphragm mounted in the housing, the valve stem being pushed by a compression spring towards the other side of the diaphragm and the pilot valve being openable at a predetermined pilot inlet pressure to cause fluid pressure to act on said one side of the diaphragm to move the valve stem so as to close the main valve, the main valve being re-openable by operation of a re-set member which is supported by the housing so as to be manually movable to cause movement of the stem to unseat the valve member.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 is a schematic mainly sectional side view of a valve assembly, Figure 2 is a schematic mainly sectional side view of a detail, in an alternative form, of a valve assembly that is otherwise the same as the valve assembly of Fig. 1, and Figure 3 is a detail view of components that can be provided in a valve assembly that is otherwise substantially the same as the valve assembly of Fig. 1.

The valve assembly shown in Figure 1 has a body 1 having a fluid flow path therethrough from an inlet port 2 via a bore 3, an annular valve seat 4 terminating the bore 3 and a chamber 5 to an outlet port 6. The annular valve seat 4 can be contacted by a resilient seating ring 7 carried by a valve member 8 within a shoulder 8C of the valve member 8 that is disposed in the chamber 5.

The valve member 8 has a first cylindrical part 8A slidably disposed in the bore 3 and sealed thereto by an O-ring seal 9; and a second cylindrical part 8B slidably mounted in a bore 10 between the chamber 5 and a diaphragm chamber 11. The valve member part 8B is sealed to the bore 10 by an O-ring seal 12. The inlet port 2 communicates with the bore 3 between the valve member part 8A and the valve seat 4.

The diaphragm chamber 11 is divided into first and second parts 1 IA, 1 lB by a flexible diaphragm 13 to which the valve member 8 is secured. The bore 10 opens into the first diaphragm chamber part 11 A, this part being vented to atmosphere by a vent passage 14.

The second diaphragm chamber part 11 B is a pressure chamber part and the components so far described constitute a flexible-diaphragm operated on/off valve of the assembly. The pressure chamber part 1 lB is connected via a port 15 to a pilot sensing valve of the assembly that controls this flexible-diaphragm operated on/off valve.

In the form of assembly shown in Fig. 1 the pilot sensing valve has an inlet port 16 that is connected to contain fluid at the same pressure as fluid in the on/off valve inlet port 2. Between the inlet port 16 and the port 15 there is a valve seat 18 onto which a ball 19 is urged to seat by the bias of a spring 20 acting on a piston 21. The ball 19 is disposed in a chamber 22 (into which the port 15 opens) that is vented to atmosphere via a fine bleed duct 23. The force exerted by the spring 20 can be adjusted by rotating a screw threaded plug 24 on which the spring bears.

The flexible-diaphragm operated on/off valve has a manual reset button 25 a stem of which carries a head 26 that is disposed in the bore 3 on the side of the valve member cylindrical part 8k remote from the valve seat 4. The part of the bore 3 that contains the head 26 is vented to atmosphere via a vent 27. The head 26 is spring-biassed away from the valve member cylindrical part 8A.

In the flexible-diaphragm operated on/off valve the diameters a and b of the valve member parts 8A and 8B respectively arc equal so that the valve member is unbalanced in operation when the valve is open. The bore c of the valve seat may be: (i) identical in size to diameters a and b giving a valve member that is totally ba!anced in operation whether the valve is open or closed: (ii) larger than diameters a and h, in which case the valve member is unbalanced towards the open condition when closed; or (iii) smaller than diameters a and b (as illustrated in Fig. 1), in which case the valve member is unbalanced towards the closed condition when closed.

In the case (illustrated) of (iii) above, a spring 28 is provided to bias the valve member 8 towards the open condition. This spring is unncessary in the case of (i) and (ii).

In the pilot sensing valve the diameter dof the bore of the valve seat 18 is smaller than the diameter e of the piston 21 so that in operation once the pressure in the inlet port 16 has become sufficiently high to open the sensing valve this pressure acts on the larger area of the piston 20 to hold the sensing valve open until the pressure falls to a value much lower than the original opening pressure.

In operation and assuming the flexiblediaphragm operated valve is open, and that the pilot sensing valve is shut, a pressurised flow of fluid (gases and/or liquids) flows through the flexible-diaphragm operated valve via the path 2/3/4/5/6 for as long as the fluid pressure is below a predetermined value set by the pilot sensing valve. Should the pressure in the path 2/3/4/5/6 build up to this predetermined value the pilot sensing valve opens passing fluid flow into the pressure chamber part 1 1B of the diaphragm chamber 11 so that the valve member 8 is actuated to shut rapidly. The various diameters discussed above are such that the flexible-diaphragm operated valve remains shut until reset by manual operation of the reset button 25.

Fig. 2 shows an alternative form of the pilot sensing valve in which this valve is a three port closed centre spool valve, communication between the inlet port 16 (one of the three ports of the valve) of the pilot sensing valve and the port 15 of the flexible-diaphragm operated valve (constituting a second of the three ports of the pilot sensing valve) being controlled by a spool valve member 28. The third port of this three port spool valve is a port 29 to atmosphere. In the closed condition of the sensing valve illustrated in Figure 2 the spool 28A of the valve member 28 closes the inlet port 16, an O-ring se31 29 in a groove in the wall of the port 16 sealing on the spool 28A. The pressure chamber part 1 lB is vented to atmosphere via the port 15 and the port 29.Pressure rise above a predetermined level in the port 16 moves the valve member 28 first to seal off the port 29 from the port 15, when an O-ring seal 30 carried by the spool 28 moves into a bore 31 via which the ports 15 and 29 are in communication, and then progressively to open a path between the port 16 and the port 15 as the spool 28 moves clear of the O-ring seal 29.

When the pilot sensing valve of Fig. 2 is incorporated in the assembly in place of the pilot sensing valve of Fig. 1, the fine bleed duct 23 required in the form of Fig. 1 to be permanently in communication with the pressure chamber part 11B (to enable the assembly to be reset in the open condition after closing of the diaphragm operated valve) is not necessary. Another way of avoiding this continuous leak is illustrated in Figure 3. In a valve assembly otherwise as illustrated in Figure 1 the fine bleed duct 23 in the pilot sensing valve is omitted and instead a manually operable, normallyclosed, pressure release valve 32 is provided which, when opened, vents the pressure chamber part 1 lB to atmosphere via a port 33. The pressure release valve 32 consists of a ball 34 spring-urged normally to seat on a valve seat 35.A stem 36 on the ball 34 projects through the seat 35 for co-operation with a head 37 carried by a stem 38 of a push button 39 spring-urged to a position in which the ball 34 seats on the seat 35. Depression of the push button 39 overcomes the spring action to lift the ball 34 off the seat 35.

It will be appreciated that in each of the valve assemblies described there is a normally-open flexible-diaphragm operated valve (components 215) and a normallyclosed pilot sensing valve (components 16 24 or 16 and 28-31) connected to sense the pressure of fluid in the inlet port (2) of the flexible-diaphragm operated valve; the pilot sensing valve being arranged to open, in use of the assembly, if the sensed pressure reaches a predetermined value set by the pilot sensing valve, thereafter to pass fluid at this pressure to act on the diaphragm (13) of the flexible-diaphragm operated valve to close this valve as soon as the pilot sensing valves has opened. The construction is such that the flexible-diaphragm operated valve closes rapidly, that is it "slams" shut, so that the effect is that a pressure build up in the flow path (2/3/4/5/6) through the flexiblediaphragm operated valve sufficient to open the sensing valve results in rapid shutting-off of the flow through the flexible-diaphragm operated valve.

In the above the pilot sensing valve has in each case been described as connected to sense the pressure of fluid in the inlet port of the flexible-diaphragm operated valve. The pilot sensing valve can, however, be connected to sense instead the fluid pressure prevailing elsewhere in a fluid flow line in which the flow path through the flexiblediaphragm operated valve is connected. A preferred example of such an alternative connection is with the assembly connected upstream of a pressure reducing valve so that the port 2 of the flexible-diaphragm operated valve is at the inlet pressure of the fluid flow line and the port 6 is connected to the inlet of the reducing valve.In this case the port 16 of the pilot sensing valve is connected to sense the pressure downstream of the pressure reducing valve so that if this downstream pressure rises to the predetermined value set by the pilot sensing valve the flexiblediaphragm operated valve slams shut.

WHAT WE CLAIM IS: 1. A valve assembly comprising a housing containing a normally-open main valve and a normally-closed pilot sensing valve, the main valve comprising a stem having a valve member engageable with an annular seat providing a fluid path between an inlet and an outlet of the housing, the stem being in sealed sliding relationship with the housing at opposite sides of the valve member at equal diameters so that the main valve is balanced when open the pilot valve being arranged between a pilot inlet to the housing and a chamber to one side of a flexible diaphragm mounted in the housing, the valve stem being pushed by a compression spring towards the other side of the diaphragm and the pilot valve being openable at a predetermined pilot inlet pressure to cause fluid pressure to act on said one side of the diaphragm to move the valve stem so as to close the main valve, the main valve being re-openable by operation of a re-set member which is supported by the housing so as to be manually movable to cause movement of the stem to unseat the valve member.

2. A valve assembly as claimed in claim 1, wherein a valve member of the flexiblediaphragm operated valve includes a seating that can seal to close the valve on a valve seat that is in said fluid flow path through this valve, the valve member having first and second parts between which the seating is disposed and which are slidable each in fluid-tight manner in first and second bores respectively; said first bore being included, between said first valve member part and said valve seat, in said fluid flow path on one side of the valve seat, and said second bore communicating at one end with said fluid flow path on the other side of the valve seat and at the other end with a first part of a diaphragm chamber of the flexible-diaphragm operated valve, this first diaphragm chamber part being divided from a second part of the chamber by the flexible diaphragm of the valve; the second diaphragm chamber part being a pressure chamber part connected to the outlet of the pilot sensing valve.

3. A valve assembly as claimed in claim 2, wherein the pilot sensing valve includes a valve seat, between the inlet and outlet ports of this valve, onto which a valve member is biassed by resilient means.

4. A valve assembly as claimed in claim 3, wherein the biassing force exerted by said resilient means is adjustable.

5. A valve assembly as claimed in claim 3 or 4, wherein the effective surface areas of the first and second valve parts exposed to said fluid flow path through the flexiblediaphragm operated valve are equal, and wherein the area of the bore through the valve seat of the pilot sensing valve is equal to the effective surface area of each of the first and second valve member parts.

6. A valve assembly as claimed in claim 3 or 4, wherein the effective surface areas of the first and second valve member parts exposed to said fluid flow path through the flexible-diaphragm operated valve are equal, and wherein the area of the bore through the valve seat of the pilot sensing valve is larger than the effective surface area of each of the first and second valve member parts.

7. A valve assembly as claimed in claim 3 or 4, wherein the effective surface areas of the first and second valve member parts exposed to said fluid flow path through the flexible-diaphragm operated valve are equal, wherein the area of the bore through the valve seat of the pilot sensing valve is smaller than the effective surface area of each of the first and second valve member parts, and wherein the valve member of the flexiblediaphragm operated valve is biassed towards its valve open condition by resilient means.

8. A valve assembly as claimed in any one of claims 3 to 7, wherein said resilient means of the pilot sensing valve acts, in the sense to close this valve, on a piston of larger effective surface area than the area of the bore through the valve seat of this valve.

9. A valve assembly as claimed in any one of claims 3 to 8, wherein a chamber between the valve seat of the pilot sensing valve and the outlet port of this valve is vented to atmosphere via a fine bleed duct.

10. A valve assembly as claimed in any one of claims 3 to 8, wherein a manually operable, normally-closed pressure release valve is provided which, when opened, vents said pressure chamber part of the flexiblediaphragm operated valve to atmosphere.

11. A valve assembly as claimed in claim

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. operated valve. In the above the pilot sensing valve has in each case been described as connected to sense the pressure of fluid in the inlet port of the flexible-diaphragm operated valve. The pilot sensing valve can, however, be connected to sense instead the fluid pressure prevailing elsewhere in a fluid flow line in which the flow path through the flexiblediaphragm operated valve is connected. A preferred example of such an alternative connection is with the assembly connected upstream of a pressure reducing valve so that the port 2 of the flexible-diaphragm operated valve is at the inlet pressure of the fluid flow line and the port 6 is connected to the inlet of the reducing valve.In this case the port 16 of the pilot sensing valve is connected to sense the pressure downstream of the pressure reducing valve so that if this downstream pressure rises to the predetermined value set by the pilot sensing valve the flexiblediaphragm operated valve slams shut. WHAT WE CLAIM IS:

1. A valve assembly comprising a housing containing a normally-open main valve and a normally-closed pilot sensing valve, the main valve comprising a stem having a valve member engageable with an annular seat providing a fluid path between an inlet and an outlet of the housing, the stem being in sealed sliding relationship with the housing at opposite sides of the valve member at equal diameters so that the main valve is balanced when open the pilot valve being arranged between a pilot inlet to the housing and a chamber to one side of a flexible diaphragm mounted in the housing, the valve stem being pushed by a compression spring towards the other side of the diaphragm and the pilot valve being openable at a predetermined pilot inlet pressure to cause fluid pressure to act on said one side of the diaphragm to move the valve stem so as to close the main valve, the main valve being re-openable by operation of a re-set member which is supported by the housing so as to be manually movable to cause movement of the stem to unseat the valve member.

11. A valve assembly as claimed in claim

2, wherein the pilot sensing valve is a three port closed centre spool valve, the third port of which is open to atmosphere so that said pressure chamber part of the flexible-diaphragm operated valve is vented to atmosphere via the outlet port and the third port of the pilot sensing valve when the pilot sensing valve is closed, and is sealed from the atmosphere and open to the inlet port of the pilot sensing valve when the pilot sensing valve is open.

12. A valve assembly as claimed in any one of claims 2 to 11, wherein manuallyoperable means is provided for re-setting the valve member of the flexible-diaphragm operated valve in its valve-open condition after valve closure has occurred.

13. A valve assembly as claimed in any one of the preceding claims, wherein the pilot sensing valve of the assembly is connected to sense the pressure of fluid at the inlet of the flexible-diaphragm operated valve of the assembly.

14. A valve assembly substantially as hereinbefore described with reference to Figure 1 or Figure 2 or Figure 3 of the accompanying drawing.

15. A valve assembly as claimed in any one of the preceding claims in combination with a pressure reducing valve, the pressure reducing valve being connected to the outlet of the flexible-diaphragm operated valve of the assembly, and the pilot sensing valve of the assembly being connected to sense the pressure of fluid downstream of the pressure reducing valve.