GB2101272A - Gas valve assemblies - Google Patents

Abstract

A gas valve assembly incorporates two valves in series. One is a modulating valve having a tapered plug (58), rotatable in a tapered bore (55). Ports 68, 57 in the plug and bore overlap through a range of registering positions. The other is an on/off valve inside the plug and with an axially movable valve member (61). Coupling between the valves is such that when the modulating valve is in its range of registering positions the valve can be open only when the modulating valve is in a position such as to permit gas to flow at at least a certain minimum rate. To this end the plug is rotated by a niting pin (75), which also follows a shaped track (77) controlling the axial movement of the pin and consequential operation of the on/off valve. A resilient ring co- operates with the pin to provide a positive action and to prevent the on/off valve remaining only partially open. There may also be a flame- failure valve. <IMAGE>

Description

SPECIFICATION Gas valve assemblies This invention relates to gas valve assemblies and aims to provide an assembly which is particularly suitable for use in controlling the supply of combustible gas to a burner, when the gas concerned is of a kind that burns with a relatively slow flame speed. Natural gas and Ipg (liquid petroleum gas) are typical gases of that kind. A problem that tends to arise with the use of a gas of that kind is that when such a gas is supplied to a relatively extensive burner at a rate of flow considerably lower than the maximum rate of flow for which the burner has been designed, it is difficult to maintain regular combustion, and indeed combustion may cease altogether.

According to the present invention there is provided a gas valve assembly with a gas inlet and a gas outlet and comprising a modulating valve in series with an on/off valve, the modulating valve comprising a body having a tapered bore and a correspondingly tapered plug in the bore, the plug and body being capable of relative rotation through a range of registering positions in each of which complementary ports in the tapered surfaces of the plug and bore overlap, the degree of overlap varying with the relative rotation, the ports in the bore and plug leading to gas-ways in the assembly, the assembly also including control means such that (at least in normal use) on relative rotation of the plug and body through the whole range of registering positions the on/off valve is open only in an operative part or operative parts of the range, that operative part or those operative parts of the range being such as to permit gas to flow through the assembly at a rate no less than a predetermined minimum rate.

The assembly is therefore such that (at least in normal use) if the relative rotational positions of the plug and body are such that the extent to which the ports in the plug and bore overlap is insufficient to enable gas to flow through the assembly at a rate as high as the predetermined minimum rate, then the on/off valve is closed.

The term modulating valve is used to denote a valve which can be set to any of a plurality of different states in each of which it is capable of permitting gas to flow at a different rate.

In a predetermined arrangement the on/off valve is disposed inside the plug, and the on/off valve preferably comprises a valve member within the plug and movable along the rotational axis of the plug to co-operate with a valve seat.

The assembly may include at least one further gas outlet additional to the gas outlet referred to above. The further outlet or each further outlet may communicate with the gas inlet by way of associated ports in the plug and bore. Moreover the further outlet or at least one of the further outlets may also be in series with the on/off valve, the arrangement again being such that (at least in normal use) on relative rotation of the plug and body gas is permitted to flow through that further outlet at a rate no lower than a predetermined minimum rate (which may be the same as or different from the aforementioned predetermined minimum rate).

In a preferred form of assembly relative rotation of the plug and body can be effected to a base position in which the ports in the plug and bore are out of register, whereby the flow of gas from the inlet to the outlet or to each of said outlets is positively prevented. The control means is preferably such that when the plug and body are in the base position the on/off valve is normally open, the arrangement preferably being such, however, that the on/off valve must close or be closed before relative rotation between the plug and body can be effected in a direction such as to bring them into or towards their range or ranges of registering positions.

The arrangement is preferably such that relative rotation of the plug and body from the base position into the operative part or an operative part of the range of registering positions first permits gas to flow at said predetermined minimum rate, and then permits gas to flow at faster rates. This arrangement is not essential, however, and the arrangement may be such that on said relative rotation from the base position gas is permitted to flow at a faster rate before being restricted to said predetermined minimum rate.

The control means preferably comprises a profiled track and a follower which undergoes relative movement lengthwise of the track on relative rotation between the plug and the body, such relative lengthwise movement also giving rise (at least in normal use) to relative transverse movement between the follower and the track, that transverse movement giving rise to the opening and closing of the on/off valve. The on/off valve may be biassed towards an open position, and may close in response to relative transverse movement between the track and the follower.

The arrangement is preferably such that in use the predetermined minimum rate of flow of gas through the assembly is at least 50%, and preferably at least about 60%, of the maximum rate of flow.

Embodiments of the invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a gas valve assembly embodying the present invention, Figure 2 is an end view of the gas valve assembly shown in Figure 1, as viewed from the left of Figure 1, Figure 3 is a longitudinal section, to a larger scale, through a plug constituting part of the gas valve assembly shown in Figures 1 and 2, Figure 4 is a diagrammatic view of niting means constituting part of the gas valve assembly shown in Figures 1 and 2, the view representing a development of portion of a niting track and including circles representing various positions of a niting pin in its movement along the track, Figure 5 is a longitudinal section through a second form of gas valve assembly embodying the present invention, Figure 6 is a diagrammatic view, similar to Figure 4, illustrating niting means of the assembly shown in Figure 5, Figure 7 is a diagrammatic view, similar to Figure 6, illustrating an alternative form of niting means for the assembly shown in Figure 5, Figure 8 is a perspective view of a resilient element for use in niting means for an assembly embodying the present invention, Figure 9 is an elevation of another design of resilient element, Figure 10 is a longitudinal section through another form of valve assembly embodying the present invention, and Figure 11 is a diagrammatic view, similar to Figure 4, illustrating niting means of the assembly shown in Figure 1 0.

The gas valve assembly illustrated in Figures i to 4 is intended for use in controlling the supply of natural gas to the burner of a space-heating appliance. The appliance has two burners each in the form of a rectangular, porous, ceramic plaque. The plaques are disposed side-by-side in a common vertical plane. In use, gas is supplied to the rear of one or both of the plaques, seeps through the plaque or plaques and is burned at the front thereof. Combustion is irregular and uncertain if gas is supplied to a plaque at a rate lower than a certain rate, and the gas valve assembly illustrated is such that in normal use it cannot be set to a state such that gas is supplied to at least a first one of the plaques at a rate lower than a predetermined minimum rate selected to ensure that with gas supplied at that rate combustion is regular.

The gas valve assembly comprises a body 10 formed internally with a tapered bore (not shown) of a generally conventional kind. There are three ports in the tapered surface of the bore. The ports are spaced lengthwise along the bore and are also disposed at different angular positions around the axis of the bore. The port nearest to the narrower end of the tapered bore leads to a pilot outlet 11.

The port nearest the broader end of the tapered bore leads to a first main outlet 12, while the intermediate port leads to a second main outlet 1 3. Beyond the narrower end of the tapered bore the interior of the body 10 is formed with an axially directed valve seat for co-operation with a valve member of a thermo-electric flame-failure device (not shown) of conventional form. Beyond the valve seat the interior of the body is formed with a lateral bore leading to a gas inlet 14, while the adjacent end part of the body, beyond the inlet port, constitutes a housing for a solenoid which forms part of the flame-failure device. The flame-failure device also comprises a thermocouple which, when heated by a gas flame, generates electricity for energising the solenoid. The solenoid co-operates with an axially movable armature connected to the valve member of the flame-failure device.A helical compression spring biasses the valve member axially towards a closed position in which it engages the valve seat. The arrangement is such that when the solenoid is energised it can retain the valve member in an open position in which it is spaced from the valve, but when the solenoid is de-energised the spring acts to close the valve.

On being re-energised the solenoid is insufficiently powerful to re-open the valve, it being necessary to open the valve by mechanical means, as described below.

A plug 1 5 (Figure 3) is rotatably mounted in the tapered bore in the body 10, one end part 16 of the plug being tapered, and the remainder of the plug being cylindrical. The plug is formed with an axial hole which extends through it. That part 1 8 of the hole nearest the narrower end of the tapered part 1 6 of the plug is of a uniform diameter, smaller than that of an adjacent part 19 of the hole which is adjacent to the broader end of the tapered part 1 6 of the plug. That part 20 of the hole which extends inside the cylindrical part 1 7 of the plug is of yet larger diameter.There are three radially extending openings in the plug, a pilot opening 21 which is nearest the narrower end of the tapered part 1 6 and leads from the narrowest part 1 8 of the axial hole to a pilot port in the tapered surface of the plug, a first main opening 22 nearer the broader end of the tapered part 1 6 and a second main opening 23 between the openings 21 and 22, each of the first and second main openings 22 and 23 leading from central part 1 9 of the axial hole to an individually associated port in the tapered surface of the plug.

An operating rod 24 extends axially inside the hole in the plug 1 5. The rod extends through an O-ring 25 which constitutes a valve member and which co-operates with an annular valve seat constituted by part of the shoulder formed where the parts 1 8 and 19 of the axial hole meet each other. The co-operating valve member and valve seat constitute an on/off valve. The valve member is urged towards its seat by a helical compression spring 26 around the rod, one end of the spring bearing on a conical washer 27 abutting the valve member and the other end of the spring abutting a locating sleeve 28 mounted inside the axial hole in the plug. Part of the sleeve is disposed in the central part 1 9 of the hole while a broader part of the sleeve is disposed in the broadest part 20 of the hole, so that the sleeve can pass no further towards the narrower end of the plug. A circumferential groove in the sleeve 28 contains an O-ring seal 29. The rod 24 extends through an axial hole in the sleeve, that end part of the hole adjacent to the end part 1 7 of the plug being opened out and containing another O-ring seal 30 which seals against the sleeve and the rod to prevent gas escaping through the sleeve. The seal 30 is retained in place by a washer 31 which is in turn held in place by a spring 32, one end of which bears against the washer and the other end of which bears against a washer 33 on the rod and abutting the underside of a head 34 on the end of the rod.

The spring 32 is stronger than the spring 26 so that when the rod 24 is otherwise unconstrained the spring 32 acts to move the rod to a position (not as illustrated) in which a washer 35, which is disposed on the rod below the O-ring valve member 25 and is held against axial movement by a circlip 36, engages the valve member 25 and lifts it from its seat.

An axially extending slot 37 is formed in the cylindrical part 1 7 of the plug. A niting pin (not shown) projects radially through the slot, its inner end being anchored in an operating spindle 38 and its outer end entering a profiled niting track 39 extending around the body. The niting track and niting pin constitute a profiled track and follower as referred to above.

In use the gas inlet 14 is connected to a source of natural gas, the pilot outlet 11 is connected to a pilot burner, the first main outlet 12 is connected to a first one of the plaques and the second main outlet 1 3 is connected to a second one of the plaques. The pilot burner is so positioned that when lit it can ignite gas from at least the first plaque. The thermo-couple of the flame-failure device is disposed adjacent to the pilot burner so that it is heated when gas from the pilot burner is lit.

The assembly operates in the following manner. Initially the plug is in a base position in which none of the openings 21,22 and 23 is in register with the port of its associated outlet 11, 12 and 13 respectively; the niting pin is guided by the niting track to a base position, as indicated at 40 in Figure 4, in which it is spaced from the plug as far as possible, while the operating rod 24 is moved by the spring 32 to a position in which the valve member 25 is lifted from its seat.

When it is desired to light the burner of the appliance, the operating spindle 38 is pushed axially inwards until the niting pin abuts the opposite side of the niting track at 41. The operating spindle is then free for rotation, and on rotation causes the niting pin to move along an inclined portion 42, of the niting track, thus closing the on/off valve. The niting pin then reaches a portion 43 of the niting track which extends in an axial direction. By this time the port of the pilot opening 21 is in register with the ports of the pilot outlet 11.

The user then pushes the operating shaft 38 axially as far as possible, that is until the niting pin reaches the position 44. This causes the operating rod 24 to move axially, against the action of the spring 32. When this occurs the washer 35 is moved away from or further away from the valve member 25. The end of the operating rod further from the head 34 pushes open the flame-faiiure valve enabling gas to pass to the pilot burner. The gas issuing from the pilot is lit by any suitable means, and when the thermo-couple is heated to a sufficiently high temperature the operating shaft is released, thus enabling the spring 32 to move the niting pin against the face 45 of the niting track. The flamefailure valve remains open, but the on/off valve remains closed.

When the assembly is in this position the user can readily rotate the operating spindle 38 in one direction, but cannot rotate it back to the base position without first pushing it inwards a short way. Rotation of the spindle in the one direction rotates the plug through the position in which the niting pin is at 46 and continues until the port of the first main opening 22 is partially in register with the port of the first main outlet 14. Release of the spindle then allows the niting pin to move to the position 47, under the influence of the spring 32. This causes the on/off valve to open and allow gas to pass to the first plaque where it is ignited by the flame of the pilot burner. In normal use the user would not prevent the rapid axial movement of the spindle and the consequent rapid opening of the on/off valve to a widely open position.

The arrangement is such that when the on/off valve opens in this way the ports referred to above are sufficiently in register to permit about 60% of the maximum possible rate of flow of gas to the first plaque. If the user were to attempt to reduce that rate of flow by rotating the plug to a position in which the ports were less in register he would first have to push the spindle inwards, thus closing the on/off valve and cutting off the flow of gas to the first plaque, though leaving the supply of gas to the pilot burner unaffected.

If the user, on the other hand, rotates the shaft to bring the ports into full register the niting pin moves over a projection 48 in the niting track, as indicated at 49, before reaching the position indicated at 50 in which the ports are fully in register and the maximum flow of gas to the first plaque is achieved. The presence of the projection 48 does not cause the on/off valve to close but serves to make it difficult for the user to set the valve to a position intermediate the positions in which the niting pin is at the position indicated at 47 and the position indicated at 50.

It will be appreciated from the foregoing description that on rotation of the plug through the whole range of positions in which the ports are partially or wholly in register, the on/off valve is open only in an operative part of that range, the operative part being such as to permit gas to flow through the assembly at a rate no less than about 60% of the maximum possible rate.

Should the user also wish to use the second plaque he must first push the operating spindle 38 inwards, and must then rotate the spindle further. Pushing the spindle inwards closes the on/off valve so that the gas supply to the first plaque is temporarily cut off. As the spindle is then rotated the port of the second main opening 23 comes progressively into register with the port of the second main outlet 13. This continues until the niting pin is able to move transversely of the track again and to take up the position indicated at 51. The on/off valve opens, and gas passes to the second plaque at a flow rate of about 60% of the maximum possible flow rate. Meanwhile gas passes at the maximum possible rate to the first plaque because the port of the first main opening 22 is extended around part of the plug to permit this flow of gas.

To bring the flow of gas to both plaques to the maximum values, the spindle is rotated to bring the niting pin past a projection 52 similar to the projection 48 and to an end portion 53 in which the ports for the gas supply to the second plaque are fully in register. The gas supply to the first plaque remains at the maximum flow rate.

Likewise, as the plug is rotated, so as to carry the niting pin from the axial portion 43 of the track to the end portion 53, the flow of gas to the pilot burner is fully maintained because the port of the pilot opening 21 is extended for an appropriate distance around the plug.

In a modification, not illustrated, that part of the niting track between the positions 47 and 50 is straight so that the niting pin can be set at any desired intermediate position. In addition, or alternatively, that part of track between the positions 51 and 53 may likewise be straight.

In a further modification, also not illustrated, that part of the niting track between positions 50 and 51 of the niting pin is so shaped as not to cause closure of the on/off valve. In consequence, the rate of flow of gas to the second plaque can be made less than the predetermined minimum value for that plaque. In practice, however, this arrangement may be acceptable as combustion of the gas from the second plaque is maintained by the stable and relatively extensive flames of the gas from the first plaque, possibly assisted by the pilot flame. In order to discourage the user from setting the niting pin at a position between positions 50 and 51, the niting track between these positions may be formed with a rounded projection similar to one of the projections 48 and 52.

With either form of assembly, when the user wishes to turn the appliance off, he rotates the spindle to bring the plug back to the base position. As the pilot burner is then out the thermocouple cools and the flame-failure valve closes.

The valve assembly shown in Figures 5 and 6 is similar in general form to that shown in Figures 1 to 4 but differs in detail. The main difference is that it is designed to supply gas to only a single burner, and is not coupled to a flame-failure device or to a pilot burner.

The assembly comprises a body 54 with a bore 55 of which an intermediate part is tapered. There is an axial gas inlet 56 beyond the narrower end of the bore and a lateral gas outlet 57 having a port opening into the tapered surface of the bore.

A tapered plug 58 is mounted for rotation in the tapered part of the bore and is formed with an axial hole 59. Part of the hole near the narrower end of the plug is of smaller diameter than a central part of the hole so that a shoulder is formed between those two parts. An inner portion of the shoulder constitutes a valve seat 60 which forms part of an on/off valve. An O-ring 61 constitutes the valve member of the on/off valve and is mounted on an operating rod 62 extending along the axis of the hole in the plug. The O-ring 61 is maintained on the rod by a washer 63 backed by a circlip 64 which enters a groove in the rod. One end of a spring 65 around the rod bears on a concave washer 66 abutting the 0ring. The other end of the spring bears against a locating sleeve 67 which is disposed in the hole and is in gas-tight, screw-threaded engagement with the plug.A radially directed opening 68 in the plug leads from the axial hole 59 to a port in the tapered surface of the plug which can be aligned with a port at the inner end of the gas outlet 57.

The rod 62 is slidable axially through a hole in the sleeve 67. An O-ring 69 is disposed in an enlarged end portion of that hole seal against the sleeve and the rod to prevent gas escaping through the hole. A washer 70 abuts the O-ring 69 and is held in place by a spring 71 disposed around the operating rod 62. One end of the spring bears on the washer and the other end bears on a head 72 of the operating rod 62. The spring 71 is stronger than the spring 65 so that in the absence of other restraints the on/off valve is open.

A control spindle 73 extends into an axial collar 74 constituting an extension of the plug 58. The head 72 and adjacent part of the operating rod are received in a blind hole in the end of the spindle. A niting pin 75 extends radially from the control spindle 73, through an axially extending slot 76 in the collar 74 and into a niting track 77 in the body 54.

The shape of the niting track 77 is shown in Figure 6. The plug 58 can be rotated to a base position in which the ports of the opening 68 and gas outlet 57 are out of register, and the niting pin 75 is in the position indicated at 78 in Figure 6.

The spring 71 holds the niting pin in this position and holds the on/off valve open.

When it is desired to allow gas to pass through the valve it is first necessary to push the control spindle 73 axially inwards against the action of the spring 71. This closes the on/off valve and brings the niting pin to the position indicated at 79. The spindle is then rotated until the niting pin reaches the position indicated at 80. By this time the ports of the opening 68 and outlet 57 partially overlap each other. When the spindle is then released, the spring 71 rapidly moves the spindle axially, bringing the niting pin to the position indicated at 81. At the same time the on/off valve opens to allow gas to pass through the assembly at a rate equal to approximately 60% of the maximum possible rate. Further rotation of the spindle brings the niting pin to the position indicated at 82.The on/off valve remains open, while the ports are brought fully into register and thus allow gas to flow through the assembly at the maximum possible rate. That part of the niting track between positions 81 and 82 is straight so that the niting pin can take up any intermediate position while the on/off valve remains open. This makes it possible for the user to set the plug to any desired angular position such that the rate of flow of gas is in the range between the maximum and about 60% of the maximum. The plug thus serves as a modulating valve.

It is to be understood that in each of the embodiments of the invention described above a knob (not shown) would normally be secured to the operating spindle for manipulation by the user.

It is possible that the valve assembly illustrated in Figures 5 and 6 could give rise to difficulty. When the assembly in in a position such that the niting pin 75 is in the position 81, allowing gas to pass to the burner, axial pressure applied to the operating knob could cause the pin to move to the position 80, thus cutting off the gas supply. Release of the knob would then allow the spring 71 to return the assembly to its former position thus allowing gas to flow again. Unless means such as pilot burners were provided to ensure re-ignition of the gas, it could happen that unlit gas would leak from the burner.

In order to avoid that difficulty, and corresponding difficulties in other valve assemblies embodying the present invention, it is preferred to provide resilient retaining means operative to prevent the opening of the on/off valve, to permit the passage of gas through the assembly, without manual assistance.

The retaining means preferably comprises an element of resilient material in the shape of an incomplete or broken ring, adjacent end portions of the element normally being too close together to prevent the passage of the niting pin between them, but yielding to allow the niting pin to pass when manually generated force is applied to the pin.

The arrangement is preferably such that if the ports are fully in register and if torque alone is applied to the component carrying the niting pin, in a direction tending to bring the ports out of register, the pin is guided axially so as to enable it to pass between the adjacent end portions of the element, thus bringing about automatic closure of the on/off valve. If a reverse torque alone is then applied to the component carrying the niting pin, the arrangement may either be such that the pin is not guided axially so that the on/off valve remains closed until an axial force is applied to the component, or be such that the pin is guided axially so as to enable it to pass back again between the adjacent end portions of the element, thus bringing about automatic opening of the on/off valve.

The adjacent end portions of the element are preferably shaped in such a manner that when the niting pin is passing between them and urging them resiliently apart there is only a relatively restricted range of positions of the pin in which it is possible to trap the pin between the end portions. Further, the arrangement is preferably such that if the user attempts to misuse the assembly by manipulating it in such a way that the pin is trapped between the end portions of the element, the on/off valve is either closed or is open sufficiently wide to permit gas to flow through the assembly at a rate determined principally by the partially-registering ports and not by the on/off valve. While the former arrangement may sometimes be employed it is envisaged that the latter arrangement will be employed more frequently.

The element is preferably formed from resilient sheet metal. Preferably the element is coaxial or substantially co-axial with the tapered plug.

If an element of the kind outlined above were incorporated in a valve assembly of the kind shown in Figure 5, it could conveniently be accommodated in the annular gap 83 between the collar 74 on the plug 58 and the adjacent part of the body 54 surrounding the collar. In such an arrangement the element would bear axially on an annular end face of the plug 58. As this might cause problems in use, slight modifications would preferably be made to the shapes of the plug and body so as to provide on the body an annular face which is in effect an outward extension of the annular end face of the plug. The element would then bear axially on the annular face on the body rather than on the adjacent annular end face of the plug. The width of the latter face would preferably be reduced, or the face might be eliminated entirely.

One possible niting arrangement is illustrated in Figure 7. Here the positions of the niting pin are almost exactly the same as the correspondingly numbered positions in Figure 6. The niting track itself, however, is no longer defined entirely by an aperture in the body, part of it is defined by a spring steel element 84 which is in the shape of a part-cylindrical collar, or broken ring. Adjacent end portions 85 and 86 of the element are normally too close together, as illustrated, to allow the niting pin to pass to and fro between the positions 80 and 81, but on the application of manual force to the control spindle 73 the end parts can be separated resiliently to allow the pin to pass. At a position diametrically opposite to the gap between the end portions 85 and 86, the element 84 is anchored to the body to prevent bodily rotation of the element relative to the body.

Of course, when the end portions 85 and 86 part to permit passage of the niting pin, those portions move radially outwards and also move around the axis of the body to a very limited extent.

The end portion 85 is shaped to provide a notch for receiving the niting pin in its base position 78 and to provide an edge 87 which is engaged by the pin in its movement from positions 79 to 80. On reaching the position 80 the pin strikes an axially extending edge 88 of the other end portion 86, the arrangement being such that if torque alone is applied to the control spindle 73, the portion 86 yields circumferentially to a slight extent and allows the pin to engage an inclined edge 89 of the niting aperture in the body so that the pin is guided to the position 81. As the pin moves from position 80 to 81 , the end portion 85 of the element is also displaced in the opposite circumferential direction.

In an alternative arrangement (not illustrated) the portion of the body adjacent to the inclined edge 89 is cut away so that the application of torque alone to the spindle 73 does not bring about any axial movement of the pin, the pin remaining substantially in the position 80.

When the niting pin is in either of the positions 81 and 82, or is in some position between those positions, gas can pass through the burner. If it is then desired to cut off the gas supply to the burner, the control spindle 73 is rotated to bring the pin to the position 81 (if it is not already there) and into engagement with an inclined end edge 90 of the end portion 85. Even if torque alone is applied to the spindle, the pin rides along the edge 90, causing the end portions 85 and 86 to part temporarily. The on/off valve is thus closed.

An attempt might be made to misuse the assembly by trying to adjust the niting pin so that it takes up a stable position in which it is trapped between the positions 80 and 81, gripped between the end portions 85 and 86. Owing to the shape of the end portion 86, this would be difficult to achieve, but even if it were achieved, the assembly is so designed that the on/off valve would be open to an extent such as not to impede the flow of gas through the assembly. In a modified construction the arrangement is such that if the niting pin takes up this stable position the on/off valve is closed.

If desired, the assembly may be such that there is no notch or equivalent niting arrangement to retain the plug valve in its base position. Thus, for example, the notch enabling the pin to move from position 79 to position 78 may be omitted.

Figure 8 shows an element 91 made from resilient sheet metal and in the form of an incomplete or broken ring. This element may be used in a valve assembly similar to that shown in Figure 5. Adjacent end portions 92 and 93 of the element define between them a niting track 94.

The shape of the track is slightly different from that of the element 84, but its operation is similar.

The element may be anchored against rotation by integral, outwardly directed tags 95 which engage complementary faces on the body of the assembly.

An alternative form of element is illustrated in Figure 9. Here, the element 96 is formed with symmetrically shaped end portions 97 and 98 defining between them an axially extending track.

A central part of the track is of restricted width such that the niting pin must push the end portions resiliently part as it traverses that central part of the track. Unlike the elements described above, the element 96 is freely rotatable relative to the body of the assembly, its rotational position being determined by the niting pin. The niting track itself is defined by the body or by some other component or components attached to the body. Three positions of the niting pin are illustrated in Figure 9. Position 99 corresponds to an off position of the on/off valve. 00 represents the position of the pin, in which the on/off valve is still off, and the pin is about to cause the end portions to part; and 101 represents the position of the pin when the on/off valve is open.It will be seen that the adjacent edges of the end portions 97 and 98 are so shaped as to afford greater resistance to the opening of the on/off valve than to the closure of that valve.

Figure 10 illustrates a valve assembly generally similar to that shown in Figure 5. The assembly has a body 102 with a tapered plug 103 rotatable in it. The gas ways and ports in the plug are the same as those in the valve of Figure 5 and will therefore not be described here. The plug 103 has an axial bore 104 of which an intermediate portion is of reduced diameter. Part of this intermediate portion constitutes a seating for an on/off valve of which the valve member comprises a generally cylindrical head 105 formed with a peripheral groove containing an O-ring seal 106.

The head is formed at one end of an operating rod 107 which is integrally connected to a control spindle 108. A helical compression spring 109 around the operating rod 107 bears at one end on the spindle 108 and at the other end on a washer 110 which in turn engages an O-ring seal 111 which engages the wall of the bore 104 and operating rod 107 to prevent the passage of gas along the bore towards the spindle 108.

A niting pin 112 projects radially from the spindle 108, and through an axial slot (not shown), similar to the slot 76, in an integral collar 113 on the plug, similar to the collar 74. The pin also extends through a gap between the adjacent end portions of a generally cylindrical element 114 made from resilient sheet steel. The element is housed between the collar 113 and an adjacent part of the body, and its inner end abuts an annular face 115 on the body.

An end plate 11 6 is secured to one end of the body 102 by screws (not shown). Axially extending tags 117 on the element 114 project through slots in the end plate, which thus prevents rotation of the element relative to the body and also prevents the axial movement of the element. Around part of its circumference the end part of the body 102, beneath the end plate 116, is cut back to a uniform axial depth so as to leave an arcuate opening bounded at one side by the end plate and at the other by an arcuate face 118 on the body. At its ends the arcuate opening is bounded by end faces 11 9 which are parallel with the rotational axis of the plug and subtend an angle of rather more than 1800 at the axis. The niting pin 112 projects outwards through this arcuate opening. On rotation of the control spindle 108 the pin can be moved from a base position in which it abuts one of the end faces 11 9 to a fully on position in which it abuts the other of the end faces. When the pin is rotated in this way its axial position is determined by the gap in the element 114. The gap is so shaped that during the initial stages of rotation from the base position the on/off valve remains closed (as illustrated) but when the ports in the plug and body are sufficiently in register to enable about 60% of the maximum rate of flow of gas to occur, the on/off valve can be opened.

A developed view of the niting track is shown in Figure 11. The end portions of the element are shown at 120 and 121. At 122 the niting pin is shown in its base position; at 123 it abuts the end portion 120, the ports in the plug and body now overlapping. At 124 the niting pin is being pushed through the narrowest part of the gap between the end portions 120 and 121, and is urging those parts resiliently apart. When the pin is in this position (or in any position within a very restricted range of adjacent positions) in which it is trapped in a stable manner between the end portions, the on/off valve is sufficiently far open to permit gas to flow through the assembly at a rate determined principally by the partially-registering ports and not by the on/off valve.Alternatively the arrangement could be made such that the on/off valve was closed when the pin was anywhere in this range of stable positions. At 125 the niting pin is in its fully on position. A rigid tag 126 is pressed down from the material of the top plate 116 adjacent to the end portion 120 of the element 114. If a torque is applied to the control spindle 108 to turn the assembly away from its base position the niting pin mov.es from position 122 to position 123 and strikes the edge of the end portion 120. As this edge is parallel with the axis of rotation there is no inherent tendency for the pin to move to the position 124. If the torque is increased, the portion 120 will yield slightly and the pin will strike the edge of the tag 126 which will resist any further movement of the pin and prevent the element being damaged or being pushed bodily out of place.In an alternative arrangement (not illustrated) an edge of the tag 126 is inclined in such a manner that on the application of torque to the control spindle as described above the portion 120 will yield slightly and the pin will engage the inclined edge and be guided axially from position 123, through position 1 24 and to the range of positions in which gas can pass through the assembly.

Numerous other modifications and alterations may be made to the assemblies without departing from the scope of the present invention. In particular it will be appreciated that other assemblies may be provided that incorporate features selected from different ones of the embodiments described above. For example, the assembly shown in Figure 5, in which the on/off valve is opened by an outward movement of the control spindle 73, may be modified so that the on/off valve is opened by an inward movement of the control spindle, as in the valve shown in Figure 10. Likewise, in the valve shown in Figure 10, the control spindle and operating rod are constituted by different parts of a unitary component. A similar arrangement may be adopted in modified versions of the valve shown in Figures 3 and 5, where the control spindles may be integral with or attached to the operating rods. Yet again, the valve shown in Figures 3 and 5 may be modified to incorporate resilient elements of any of the kinds described.

Claims (29)

Claims

1. A gas valve assembly with a gas inlet and a gas outlet and comprising a modulating valve (as herein defined) in series with an on/off valve, the modulating valve comprising a body having a tapered bore and a correspondingly tapered plug in the bore, the plug and body being capable of relative rotation through a range of registering positions in each of which complementary ports in the tapered surfaces of the plug and bore overlap, the degree of overlap varying with the relative rotation, the ports in the bore and plug leading to gas-ways in the assembly, the assembly also including control means such that (at least in normal use) on relative rotation of the plug and body through the whole range of registering positions the on/off valve is open only in an operative part or operative parts of the range, that operative part or those operative parts of the range being such as to permit gas to flow through the assembly at a rate no less than a predetermined minimum rate.

2. A gas valve assembly according to claim 1 in which relative rotation of the plug and body can be effected to a base position in which the ports in the plug and bore are out of register, whereby the flow of gas from the inlet to the outlet is positively prevented by the plug.

3. A gas valve assembly according to claim 2 in which the control means is such that when the plug and body are in the base position the on/off valve is normally open.

4. A gas valve assembly according to claim 3 in which the arrangement is such that the on/off valve must close or be closed before relative rotation between the plug and body can be effected in a direction such as to bring them into or towards their range or ranges of registering positions.

5. A gas valve assembly according to any one of claims 2 to 4 in which the arrangement is such that relative rotation of the plug and body from the base position into the operative part or an operative part of the range of registering positions first permits gas to flow at said predetermined minimum rate, and then permits gas to flow at faster rates.

6. A gas valve assembly according to any one of the preceding claims in which the on/off valve is disposed inside the plug.

7. A gas valve assembly according to claim 6 in which the on/off valve comprises a valve member within the plug and movable along the rotational axis of the plug to co-operate with a valve seat.

8. A gas valve assembly according to claim 7 in which the control means comprises a profiled track and a follower which undergoes relative movement lengthwise of the track on relative rotation between the plug and the body, such relative lengthwise movement also giving rise (at least in normal use) to relative transverse movement between the follower and the track, that transverse movement giving rise to the opening and closing of the on/off valve.

9. A gas valve assembly according to claim 8 in which the on/off valve is biassed towards an open position, and may close in response to relative transverse movement between the track and the follower.

10. A gas valve assembly according to either of claims 8 and 9 in which there is provided resilient retaining means operative to prevent the opening of the on/off valve without manual assistance.

11. A gas valve assembly according to claim 10 in which the retaining means comprises an element of resilient material in the shape of an incomplete or broken ring, adjacent end portions of the element normally being too close together to permit the passage of a niting pin between them, but yielding to allow the niting pin to pass when manually generated force is applied to the pin.

1 2. A gas valve assembly according to claim 11 in which the arrangement is such that if the ports are fully in register and if torque alone is applied to the component carrying the niting pin, in a direction tending to bring the ports out of register, the pin is guided axially so as to enable it to pass between the adjacent end portions of the element, thus bringing about automatic closure of the on/off valve.

13. A gas valve assembly according to either of claims 11 and 12 in which the arrangement is such that if, when the on/off valve is closed and the ports are out of register, a torque alone is applied to the component carrying the niting pin in a direction such as to tend to open the on/off valve and bring the ports into register, the pin is not guided axially so that the on/off valve remains closed until an axial force is applied to the component.

1 4. A gas valve assembly according to either of claims 11 and 12 in which the arrangement is such that if, when the on/off valve is closed and the ports are out of register, a torque alone is applied to the component carrying to the niting pin in a direction such as to tend to open the on/off valve and bring the ports into register, the pin is guided axially so as to enable it to pass between the adjacent end portions of the element, thus bringing about automatic opening of the on/off valve.

1 5. A gas valve assembly according to any one of claims 11 to 14 in which the adjacent end portions of the element are shaped in such a manner that when the niting pin is passing between them and urging them resiliently apart there is only a relatively restricted range of positions of the pin in which it is possible to trap the pin between the end portions.

1 6. A gas valve assembly according to claim 1 5 in which the arrangement is such that if, in use, the user attempts to misuse the assembly by manipulating it in such a way that the pin is trapped between the end portions of the element, the on/off valve is either closed or is open sufficiently wide to permit gas to flow through the assembly at a rate determined principally by the partially-registering ports and not by the on/off valve.

1 7. A gas valve assembly according to any one of claims 11 to 1 6 in which the element is formed from sheet metal.

1 8. A gas valve assembly according to any one of claims 11 to 17 in which the element is coaxial or substantially co-axial with the tapered plug.

1 9. A gas valve assembly according to any one of claims 11 to 17 in which said niting pin also constitutes said follower.

20. A gas valve assembly according to any one of the preceding claims in which the arrangement is such that in use the minimum rate of flow of gas through the outlet is at least 50% of the maximum rate of flow.

21. A gas valve assembly according to any one of claims 1 to 19 in which the arrangement is such that in use the minimum rate of flow of gas through the outlet is about 60% of the maximum rate of flow.

22. A gas valve assembly according to any one of the preceding claims incorporating a flamefailure valve between the gas inlet and the on/off valve, a pilot outlet between the flame-failure valve and the on/off valve, an electromagnet operative, when a thermocouple is heated, to retain the flame-failure valve open against a spring-bias urging the valve closed, the arrangement being such that the control means can be manipulated to open the flame-failure valve and that, when the control means is manipulated thus, gas is prevented from passing to the gas outlet.

23. A gas valve assembly according to any one of the preceding claims, including a further gas outlet communicating with the gas inlet by way of associated ports in the plug and the bore, the further gas outlet being in series with the on/off valve and the arrangement being such that (at least in normal use) on relative rotation of the plug and body gas is permitted to flow through that further outlet at a rate no lower than a predetermined minimum rate.

24. A gas valve assembly according to claim 23 in which the arrangement is such that in use on relative rotation of the plug and body through a range of positions such that the flow of gas through the further gas outlet is modulated, the flow of gas through the first-mentioned gas outlet remains constant.

25. A gas valve assembly substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

26. A gas valve assembly substantially as hereinbefore described with reference to Figures 5 and 6 of the accompanying drawings.

27. A gas valve assembly according to claim 26 but modified substantially as hereinbefore described with reference to Figure 7 of the accompanying drawings.

28. A gas valve assembly substantially as hereinbefore described with reference to Figures 10 and 11 of the accompanying drawings.

29. A gas valve assembly according to any one of the preceding claims and incorporating retaining means substantially as hereinbefore described with reference to either Figure 8 or Figure 9 of the accompanying drawings.