GB2206674A

GB2206674A - Gas control valve

Info

Publication number: GB2206674A
Application number: GB08812008A
Authority: GB
Inventors: Thomas Ronald Yates
Original assignee: TANKGAS ENGINEERING Ltd
Current assignee: TANKGAS ENGINEERING Ltd
Priority date: 1987-05-23
Filing date: 1988-05-20
Publication date: 1989-01-11
Also published as: GB8812008D0; GB8712260D0

Abstract

A gas control valve comprises a body 111 having a passage 114 for flow of gas in a direction from an inlet 112 towards an outlet 113, valve means 132 to close said passage under the control of a latch means moveable between a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first open position and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second, closed position the latch means being moved from the retaining position to the release position responsive to the pressure of the gas supply. The latch means may be moveable, by a single gas pressure sensing means, in opposite directions to different release positions depending on whether the pressure rises above or falls below a predetermined pressure range. As shown, the latter is moveable parallel to the direction of valve movement. In a modification, the latch is mounted for movement transversely of the direction of valve movement. <IMAGE>

Description

Gas QonOi Valve" Description of Invention This invention relates to a gas control valve to interrupt the flow of gas from a gas supply in response to variation in the pressure of the gas supply.

Such gas control valves are typically used in installations utilising liquified petroleum gas, for example, propane or butane, so that the gas supply is isolated from the remainder of the installation if the gas supply pressure falls below, or rises above, a predetermined level.

An object of the invention is to provide a new and improved gas control valve to interrupt the flow of gas from a gas supply in response to variation in the pressure of the gas supply.

According to the present invention we provide a gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable between a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, the latch means being moved from the retaining position to the release position responsive to the pressure of the gas supply.

According to a first more specific aspect of the present invention we provide a gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable between a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, the latch means being moved from the retaining position to the release position by means of a single gas pressure sensing means which is responsive to the pressure of the gas supply.

According to a second more specific aspect of the present invention we provide a gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable in a first direction from a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, when the pressure of the gas supply rises above a first predetermined pressure and the latch means being moveable in a second direction from the retaining position to a release position when the pressure of the gas supply falls below a second predetermined pressure.

Preferably, in the second more specific aspect of the invention, the latch means is moved from the retaining position to either of the release positions by means of a single gas pressure sensing means which is responsive to the pressure of the gas supply.

Preferably, in either more specific aspect of the invention, the single gas pressure sensing means comprises a gas pressure responsive member moveable within a chamber and connected to the latch means, one side of the member in the chamber being exposed to the pressure of the gas supply and the member being biased towards one end of its permitted movement by a biasing means which opposes the force imposed upon the member by the gas supply, the member when in a first position in which the force exerted by the gas supply is balanced by the biasing means, maintaining the latch means in the retaining position whilst when the member is displaced from said first position by virtue of the gas supply rising above or falling below the pressure at which the force exerted by the gas supply is balanced by the biasing means the latch member is moved to the or a release position.

The member in the chamber may comprise a diaphragm member having a part fixed relative to the wall of the chamber and the diaphragm being deformable to permit of movement of a part thereof connected to the latch member to cause movement from the retaining position to the release position.

The latch means may be engageable with the valve means through a detent member moveable into retaining engagement between the latch means and the valve means when the latch member is in said retaining position and moveable out of said retaining engagement when the latch means is moved to the or a release position.

The detent means may comprise a detent member disposed between the latch member and a valve means control member and the detent member being moveable into retaining engagement with the valve means control member in a direction transverse to the direction of movement of the valve means control member required to move the valve means between the first and second positions.

The detent member may be restrained from movement relative to the body in said direction of movement of the valve means control member.

The latch means may drive the detent member into retaining engagement with the valve means control member.

The detent member may comprise a spherical ball which may be received in a bore in a member fixed relative to the body and a pert of the ball being engaged by a cam surface on the latch member to maintain the ball in engagement with a socket provided on the valve means control member.

The fixed member may comprise a tubular cylindrical sleeve, the bore may comprise a radial bore and the socket may be provided in and may comprise an annular groove in, a part of the valve means control member which is slidably received within the sleeve.

Two detent members may be provided at diametrically opposite parts of the sleeve and the latch means has diametrically opposed first cam surface parts adiacent the mid point of the sleeve which project inwardly towards the central axis of said part of the valve means control member so that when the inwardly projecting parts of the cam surfaces are aligned with the bores in the sleeve the balls are displaced inwardly to be disposed within the socket such as the annular recess and thus retain the valve means in said first position.

The latch means may have second parts of the cam surface on opposite sides of said inwardly directed part which are spaced radially outwardly so that when either of said second cam parts are aligned with the balls the balls may be displaced outwardly of said socket so that the valve means can move to said second position.

The latch means may be moveable transversly to the direction of movement of the valve means between the first and second positions and the latch means may comprise a yoke which encompasses the sleeve.

Alternatively, the latch means may be moveable porallel to the direction of movement of the valve means between the first and second positions and in this case the latch means may comprise a tube which is telescopically disposed relative to said sleeve.

Resilient biasing means may be provided to act on the valve means control member normally to bias said valve means from said first position towards the second position.

The valve means may comprise a stem which may carry a valve head at one end moveable into sealing engagement with a valve seat disposed in said passage.

The valve means may comprise a valve head moveable in a direction generally transverse to said passage the passage including a valve seat disposed within said passage and the passage being configured to cause flow of gas through an aperture defined within the valve seat so that the aperture is closed when the head is in sealing engagement with the valve seat.

Reset means may be provided to move the valve means from the second position to the first position.

The reset means may comprise a plunger engageable with the valve head to disploce the valve means from the second position to the first position.

The plunger may pass through a wall of the body in a direction generally transverse to the axis of said passage from the entry end towards the exit end.

The biasing means acting upon the pressure responsive member may be adjustable and may comprise a coil compression spring engaged with an abutment which is moveable to permit of adjustment of the force exerted by the coil compression spring.

A secondary biasing means may be provided to act on the pressure responsive member in a direction opposed to said first biasing means and the secondary biasing means may be adjustable and may comprise a coil compression spring.

A retaining means may be provided to retain the latch means in a said release position.

The retaining means may retain the latch means in said release position which the latch means occupies as a result of the pressure of the gas supply rising above a first predetermined pressure.

The retaining means may be manually operable to release the latch means from said retaining position.

Means may be provided to restrict unauthorised access to the retaining means to permit operation of the retaining means to release the latch means from the said release position and the said means may comprise an obturating mens.

Two embodiments of the invention will now be described by way of example with reference to the accompanying drawings wherein FIGURE I is a side elevation of a gas control valve embodying the invention, FIGURE 2 is a section on the line 2-2 of Figure I, FIGURE 3 is a section on the line 3-3 of Figure 2, and FIGURE 4 is a view similar to that of Figure 2 but of an alternative embodiment of the invention.

Referring to the drawings a gas control valve is indicated generally at 10 and comprises a body 11 having an inlet 12 and an outlet 13 interconnected by a passage 14 having a longitudinal axis A-A.

The inlet 1 2 is provided with a conventional screw thread for connection by conventional means to a reservoir, not shown, of liquified petroleum gas such as propane or butane. The outlet 13 is likewise provided with a screw thread for connection by conventional means to an apparatus powered by the liquified petroleum gas, such as a gas fire. If the pressure of the gas supply falls below a predetermined pressure, for example, as a result of the gas supply being exhausted then, for safety reasons, it is necessary for the reservoir to be disconnected from the remainder of the installation so that, for example, if the reservoir is replaced gas is not automatically re instated to the remainder of the installation such as the heater.In addition, for safety reasons, if the pressure in the reservoir increases above a predetermined pressure, for example, as a result of an increase in the temperature so that the pressure rises about a pressure which the remainder of the installation can safety accommodate then it is necessary to interrupt the supply of gas from the reservoir to the remainder of the installation. The valve 10 provides such an interruption of supply.

The body 11 carries an extension part 15 which is attached to the body 11 by screws ló with a sealing O-ring 17 between the body 11 and the extension 15. The extension 15 defines a chamber 18 in which is disposed a flexible diaphragm 19 of generally circular configuration, the periphery 20 of which is trapped in sealing engagement between the extension part 15 and a cap 21 secured to the extension pert 15 by a plurality of screws.

Adjacent its middle the diaphragm 19 is clamped by a screw 22 and disc 23 to one end 24 of a latch member 25. As best shown in Figure 3 the latch member 25 has a yoke part 26 within which is received a cylindrical sleeve 27 housed in the extension part 15. On the opposite side of the yoke part 26 to the end 24 is a hollow boss 28 slidably received within a cylindrical socket 29 provided in the extension part 15. A coil compression spring 30 is received within the boss 28 to bias the latch member 25 to the right in Figure 2. If desired, however, the spring 30 may be omitted or some other form of biasing means may be provided and means to adjust the force exerted by the spring 30 may be provided.

A coil compression spring 31 acts on the disc 23 and is engaged with a screw threaded plug 32 received in a threaded bore 33 provided in a nose part 34 of the cap 21. By rotating the plug 32 its position within the nose part 34 may be adjusted thereby adjusting the force exerted by the spring 3 1 on the disc 23 and hence on the latch member.

An auxiliary passage 35 extends from the passage 14 to the chamber 18 on the opposite side of the diaphragm 19 to the spring 31 so that the force of the gas under the pressure of the gas supply opposes the bias of the spring 31 alone or in combination with the force of the spring 30, when provided. The strength of the spring 31 or springs 30 and 3 1 is arranged so that the latch member 25 occupies the position shown in Figures 1 and 3 when the pressure of the gas in the gas supply is at a predetermined pressure at which the force exerted on the latch member by the gas or by the gas and spring 30 is balanced by the force exerted by the spring 31.

Slidably received within the sleeve 27 is a generally cylindrical stem 40 of a valve means control member 41 which also comprises a head 42 carried at one end of the stem 40 and having an O-ring 43 for sealing engagement with a valve seat 44 which defines an aperture 45 through which gas must flow from the entry end 12 to the exit end 13 of the passage 14. The passage aperture 45 faces transversely of the longitudinal axis A-A of the passage 14 and the valve head 42 is moved radial to the axis of the passage 14 into and out of sealing engagement with the valve seat 44 as hereinafter to be described. A coil compression spring 46 is disposed within a recess 47 of the extension part 15 and normally biases the stem 40 downwardly in Figure 2 so as normally to bias sealing ring 43 into sealing engagement with the valve seat 44.

The stem 40 is provided with a portion 50 of reduced cross-section adjacent to and spaced from one end and the sleeve 27 is provided with a pair of diametrically opposed radial passages 51 in each of which a detent member comprising a spherical ball 52 is a clearance fit. The yoke part 26 of the latch member 25 is provided with a pair of opposed cam surfaces 53a, 53b each of which has an inwardly extending first part 54a, 54b disposed between two outwardly positioned second parts 55a, 55b and 56a, 56b respectively.

When a second cam surface part 55a, 55b or 56a, 56b is aligned with the balls 52 they may move out of the recess 50 and thus permit movement of a stem part 57 past the balls 52 under the influence of the coil spring 46. When the first cam surface parts 54a, 54b are aligned with the balls 52 the balls are prevented from movement out of the recess 50 and thus movement of the stem under the influence of the spring 46 is prevented.

A resetting means 60 is provided which comprises a resetting plunger 61 slidably mounted in a boss 62.provided on the body 11. The plunger 61 has a shoulder 63 and a coil compression spring 64 is engaged between the shoulders 63 and the base 65 of a counter bore 66 provided in the body II. The plunger 61 has a sealing 0 ring 67 for sealing engagement with the passage 68 of the boss 62. The plunger 61 has a nose part 69 for engagement with the head 42.

A cover 70 of clear flexible plastics material is fastened to the exterior of the boss 62 so that the position of the plunger 61 I can be seen and so that the plunger can be moved upwardly by a user by pressing on the base 7 1 of a cover 70 if the plunger is displaced downwardly from the position shown in Figure 2 as a result of downward displacement of the stem 40 under the influence of the spring 46 as hereinafter described.

In use, assuming that the valve member is in the condition shown in Figures I and 2 and that the pressure of the gas in the gas supply is at a predetermined pressure. Under these conditions the gas pressure in the chamber 18 acting on the left hand side of the diaphragm 19 is such as to exactly balance the force acting on the diaphragm 19 by the spring 31. In the case where no spring 30 is provided then the gas force alone exactly balances the force exerted by the spring 31 or where a spring 30 is provided then it is the resultant of the force exerted by the gas and the spring 30 which counterbalances the force exerted by the spring 31.

If the pressure of the gas supply rises or falls below said predetermined pressure then there will be a corresponding movement of the latch member 25 to the right or left respectively in Figure 2 as a result of the differential force acting thereon. Because of the extent of the first cam surfaces 54a, 54b a limited amount of movement of the diaphragm is permitted with the first cam surface parts 54a, 54b remaining in engagement with the balls 52 thus retaining the stem 40 in the position shown in Figure 2. Thus, relatively small variations in pressure will not affect the control valve.If however, the pressure rises above a first predetermined pressure or falls below a second predetermined pressure sufficient in each case to cause the latch member to move in the respective direction sufficiently to move the first cam surface parts 54a, 54b out of alignment with the balls 52 and second cam surface part 55a, 55b, or 56a, 56b into alignment with the balls 52 then the balls 52 are permitted to move out of the recess 50 so that the stem part 57 can move downwardly past the balls 52 under the influence of the spring 46 to bring the seal 43 into sealing engagement with the valve seat 44 thus interrupting the flow of gas through the passage 14. At the same time the plunger 61 I is moved downwardly to give a visual indication, through the transparent cover 70 that the valve has been operated to interrupt the supply of gas.When it is desired to reset the valve the plunger 61 I is moved upwardly by pressing on the bottom 71 of the cover 69 to move the valve stem 40 to the position shown in Figure 2.

Whilst the valve stem is displaced from the position shown in Figure 2 the balls 52 are maintained displaced outwardly by engagement with the part 57 of the stem and the balls 52 engage the shoulders 71 or 72 between the cam surface parts 54a, 54b and 55a, 55b or 5a, 56b respectively and thus maintain the latch member in the position it occupied to cause the valve to interrupt the supply, thereby permitting movement of the valve stem back to the position shown in Figure 2 by the resetting means 60. When the valve stem has been moved to the position shown in Figure 2 the balls 52 can move into the recess 50 thereby permitting the latch member to move to the position shown in Figures 2 and 3 if the gas pressure has been restored to a value lying between the first and second predetermined values.Of course, if the gas pressure has not been restored to a pressure lying within these values then the latch member will remain or move to the other release position where the balls 52 are permitted to move out of the recess 50 so that on release of the plunger 61 the supply of gas will again be interrupted.

Referring now to Figure 4 there is shown a cross-section through an alternative embodyment of the invention which essentially differs from the embodyment previously described in that the direction of movement of the pressure responsive member and the associated latch member is parallel to the direction of movement of the valve member, whereas in the previously described embodyment these directions are perpendicular. In addition the embodyment of Figure 4 is provided with a retaining means to retain the latch member in a release position to which the latch member has moved as a result of the pressure acting on the pressure responsive member being above a predetermined pressure.

Referring now to Figure 4, a gas control valve is indicated generally at 110 and comprises a body Ill having an inlet 112 and an outlet 113 interconnected by a passage 114. The details of the inlet 112 and outlet 113 are as described in connection with the inlet 12 and outlet 1 3 of the first embodyment. The body Ill carries an extension part 115 fastened to the body in the same way as extension part 15 of the first described embodyment.

The extension 115 defines a chamber 118 in which is disposed a flexible diaphram 119 of generally circular configuration, the periphery 120 of which is trapped in sealing engagement between the extension part 115 and a cap 121 secured to the extension part 115 by plurality of screws. Adjacent to its middle the diaphragm 119 is clamped by a nut 122 to a shouldered disc 123 having a threaded stem 124 with which the nut 122 is engaged. A washer 122a and disc 122b are also clamped to the disc 123 by the nut 122. Fastened to the disc 123 is a tubular latch member 125 within which is received a cylindrical sleeve 127 which is threadedly engaged at its lower end with the extension part 115. The sleeve 127 has a counterbore 128 at its lower end in which is received a coil compression spring 1.29 which engages a valve head 131 of a valve means 132. The valve head 131 carries an 0-Ring 133 for sealing engagement with a valve seat 135.

Rigid with the head 131 is a tubular stem 136 provided with a pair of diametrically opposed recesses 137 in which detent members in the form of spherical balls 138 may be engaged to maintain the valve member 131 in a first position, shown in Figure 4, in which the passage 114 is not closed as a result of the balls 138 being maintained in engagement in the recesses 137 by diametrically opposed cam surfaces 139a and b provided on the tubular latch member 125.

A coil compression spring 140 acts between the disc 122b and a mounting member 141, threadedly engaged with the cap 121 so as normally to bias the latch member 125 in a direction shown downwardly in Figure 4. The force exerted by the spring 140 is adjustable by varying the position of the mounting member relative to the cap 121 and hence relative to the disc 122b.

A retaining means 145 is provided within the cap 121 and comprises a lever 146 pivoted to the mounting member 141 as shown at 147 and having a manually engagable arm 148 acted upon by a coil compression spring 149 engaged with the mounting member 141 so as normally to bias the lever 146 in an anti-clockwise direction about the axis of the pivot 147.

The lever 146 has a further arm 150 having a hook part 151 for engagement with the underside of a sleeve 152 threadedly engaged with the stem 124. An obturating member 153 is provided in the end of the cap 121 so as normally to prevent access to the manually engagable arm 148.

A resetting means 160 is provided in a similar manner to the resetting means 60 of the first embodyment.

In use, assuming that the valve member is in the condition shown in Figure 4 and that the pressure of the gas in the gas supply is at a predetermined pressure. Under these conditions the gas pressure in the chamber 118 which is communicated from the passage 114 through radial openings 155 and axial passage 155a in the stem 136, and radial openings 156 in the tubular latch member 125, to act on the underside of the diaphragm 119 is such as to exactly balance the force exerted on the diaphragm 119 by the spring 140. Thus the latch member 125 is maintained in the position shown in Figure 4 so that the balls 138 are maintained in the recesses 137, so that the valve head 131 is maintained out of sealing engagement with the valve seat 135.

If the pressure of the gas supply rises or falls below said predetermined pressure, then there will be a corresponding movement of the latch member 125 up or down respectively in Figure 4 as a result of the differential force acting thereon. Because of the limited extent of the cam surfaces 1 39a and bs a limited amount of movement of the diaphragm is permitted with the first cam surface parts 139a, 139b remaining in engagement with the balls 138, thus retaining the stem 136 in the position shown in Figure 4. Thus, small variations in pressure will not affect the control valve.If, however, the pressure rises above a first predetermined pressure or falls below a second predetermined pressure, sufficient in each case to cause the latch member 125 to move in the respective direction, sufficiently to move the first cam surface parts 139a and 139b out of alignment with the balls 138 and second cam surface ports 139c and d to move into alignment with the balls 138 then the balls 138 are permitted to move out of the recesses 137 so that the stem part 136 can move downwardly under the influence of the spring 129 so that the valve head 131 is moved to sealing engagement with the seat 135. As in the case of the first embodyment the balls 138 are maintained outwardly to permit resetting using the resetting means 160.

If the latch member 125 has been caused to move upwardly by virtue of the pressure exceeding the first predetermined pressure, then the retaining means 145 will retain the latch means in this release position by virtue of the hook part 151 engaging under the sleeve 152. The sleeve 152 can be adjusted longitudinally of the stem 124 so that latching occurs at a predetermined extent of movement of the release means 125. In this case, the valve cannot be reset utilising the resetting means 160 because the cam surfaces 139a, 139b are not aligned with the balls 138 to maintain them in the recesses 137 and thus the valve would immediately reclose on release of the resetting plunger of the resetting means 160. This is so that only an authorised person can reset the valve after the reason for the excessive gas pressure has been investigated.The authorised person is able to remove the obturating member 153 and thus gain access to the lever arm 148 to press it downwardly to release the hook part 151 from the sleeve 152, thereby permitting the sleeve 125 to return to the position shown in Figure 4 under the influence of the spring 140 balanced by the correct gas pressure in the passage 114.

If desired, the control valve of the present invention may be associated with a conventional pressure regulating mechanism disposed downstream of the control valve.

The control valve of the present invention is simple and economicol to produce with a minimum of moving ports.

The features disclosed in the foregoing description, or the accompany ing drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a metal or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable between a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, the latch means being moved from the retaining position to the release position responsive to the pressure of the gas supply.

2. A gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable between a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, the latch means being moved from the retaining position to the release position by means of a single gas pressure sensing means which is responsive to the pressure of the gas supply.

3. A gas control valve comprising a body having a passage for flow of gas in a direction from an inlet end towards an outlet end, valve means to close said passage under the control of a latch means moveable in a first direction from a retaining position in which the latch means is releasably engaged with the valve means to retain the valve means in a first position in which the valve means does not close said passage and a release position in which the latch means is released from engagement with the valve means to permit of movement of the valve means to a second position in which the valve means closes said passage, when the pressure of the gas supply rises above a first predetermined pressure and the latch means being moveable in a second direction from the retaining position to a release position when the pressure of the gas supply falls below a second predetermined pressure.

4. A gas control valve according to Claim 3 wherein the latch means is moved from the retaining position to either of the release positions by means of a single gas pressure sensing means which is responsive to the pressure of the gas supply.

5. A gas control valve according to Claim 2 or Claim 4 wherein the single gas pressure sensing means comprises a gas pressure responsive member moveable within a chamber and connected to the latch means, one side of the member in the chamber being exposed to the pressure of the gas supply and the member being biased towards one end of its permitted movement by a biasing means which opposes the force imposed upon the member by the gas supply, the member when in a first position in which the force exerted by the gas supply is balanced by the biasing means, maintaining the latch means in the retaining position whilst when the member is displaced from said first position by virtue of the gas supply rising above or falling below the pressure at which the force exerted by the gas supply is balanced by the biasing means the latch member is moved to the or a release position.

6. A gas control valve according to Claim 5 wherein the member in the chamber comprises a diaphragm member having a part fixed relative to the wall of the chamber and the diaphragm being deformable to permit of movement of a port thereof connected to the latch member to cause movement from the retaining position to the release position.

7. A gas control valve according to any one of the preceding claims wherein the latch means is engageable with the valve means through a detent member moveable into retaining engagement between the latch means and the valve means when the latch member is in said retaining position and moveable out of said retaining engagement when the latch means is moved to the or a release position.

8. A gas control valve according to Claim 7 wherein the detent means comprises a detent member disposed between the latch member and a valve means control member and the detent member being moveable into retaining engagement with the valve means control member in a direction transverse to the direction of movement of the valve means control member required to move the valve means between the first and second positions.

9. A gas control valve according to Claim 8 wherein the detent member is restrained from movement relative to the body in said direction of movement of the valve means control member.

10. A gas control valve according to Claim 8 or Claim 9 wherein the latch means drives the detent member into retaining engagement with the valve means control member.

II. A gas control valve according to any one of Claims 8 to 10 wherein the detent member comprises a spherical ball which is received in a bore in a member fixed relative to the body and a part of the ball being engaged by a cam surface on the latch member to maintain the ball in engagement with a socket provided on the valve means control member.

12. A gas control valve according to Claim II wherein the fixed member comprises a tubular cylindrical sleeve, the bore comprises a radial bore and the socket is provided in a part of the valve means control member which is slidably received within the sleeve.

13. A gas control valve according to Claim 12 wherein two detent members are provided at diametrically opposite parts of the sleeve and the latch means has diametrically opposed first cam surface parts adjacent the mid point of the sleeve which project inwardly towards the central axis of said part of the valve means control member so that when the inwardly projecting parts of the cam surfaces are aligned with the bores in the sleeve the balls are displaced inwardly to be disposed within the socket and thus retain the valve means in said first position.

14. A gas control valve according to Claim 13 wherein the latch means has second ports of the cam surface on opposite sides of said inwardly directed part which are spaced radially outwardly so that when either of said second cam parts are aligned with the balls the balls may be displaced outwardly of said socket so that the valve means can move to said second position.

15. A gas control valve according to any one of the preceding claims wherein the latch means is moveable transversly to the direction of movement of the valve means between the first and second positions.

16. A gas control valve according to Claim 15 when dependent upon Claim 1 3 or Claim 14 wherein the latch means is a yoke which encompasses the sleeve.

17. A gas control valve according to any one of Claims I to 14 wherein the latch means is moveable parallel to the direction of movement of the valve means between the first and second positions.

18. A gas control valve according to Claim 17 when dependent upon Claim 13 or Claim 14 wherein the latch means is a tube which is telescopically disposed relative to said sleeve.

19. As gas control valve according to any one of the preceding claims wherein resilient biasing means are provided to act on the valve means normally to bias the valve means from said first position towards the second position.

20. A gas control valve according to any one of the preceding claims wherein the valve means comprises a stem carrying a valve head at one end which is moveable into sealing engagement with a valve seat disposed in said passage.

21. A gas control valve according to any one of the preceding claims wherein the valve means comprises a valve head moveable in a direction generally transverse to said passage, the passage including a valve seat disposed within said passage and the passage being configured to cause flow of gas through an aperture defined within the valve seat so that the aperture is closed when the head is in sealing engagement with the valve seat.

22. A gas control valve according to any one of the preceding claims wherein reset means are provided to move the valve means from the second position to the first position.

23. A gas control valve according to Claim 22 when dependent upon Claim 20 or Claim 21 wherein the reset means comprises a plunger engageable with the valve head to displace the valve means from the second position to the first position.

24. A gas control valve according to Claim 23 wherein the plunger passes through a wall of the body in a direction generally transverse to the axis of said passage from the entry end towards the exit end.

25. A gas control valve according to Claim 5 or any one of Claims 6 to 24 when dependent directly or indirectly upon Claim 5 wherein the biasing means acting upon the pressure responsive member is adjustable.

26. A gas control valve according to Claim 25 wherein the biasing means comprises a coil compression spring engaged with an abutment which is moveable to permit of adjustment of the force exerted by the coil compression spring.

27. A gas control valve according to Claim 25 or Claim 26 wherein a secondary biasing means is provided to act on the pressure responsive member in a direction opposed to said biasing means.

28. A gas control valve according to Claim 27 wherein the secondary biasing means is adjustable.

29. A gas control valve according to any one of the preceding claims comprising a retaining means to retain the latch means in a said release position.

30. A gas control valve according to Claim 29 wherein the retaining means retains the latch means in said release position as a result of the pressure of the gas supply rising above a first predetermined pressure.

31. A gas control valve according to Claim 30 wherein the retaining means is manually operable to release the latch means from said release position.

32. A gas control means according to Claim 31 wherein means are provided to restrain unauthorised operation of the retaining means to release the latch - means from said release position.

33. A gas control valve according to Claim 32 wherein said means comprises an obturating means.

34. A gas control valve substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.

35. Any novel feature or novel combination of features disclosed herein andfor shown in the accompanying drawings.