GB2280944A

GB2280944A - Gas valve

Info

Publication number: GB2280944A
Application number: GB9414499A
Authority: GB
Inventors: Alan Thomas Wright
Original assignee: Carver and Co Engineers Ltd
Current assignee: Carver and Co Engineers Ltd
Priority date: 1993-08-10
Filing date: 1994-07-18
Publication date: 1995-02-15
Also published as: GB9414499D0

Abstract

A gas valve in which a valve member 30 and/or a valve seat 33 are carried by bimetallic members 27, 28 which can be heated by a heating element 26 to open the valve. The valve may be the second modulating stage of a compound valve in which the first stage is a solenoid actuated valve 61. When the element 26 is heated the bimetallic members bow towards each other so that the valve member is moved away from the seat 33. The degree of opening and thus the gas flow rate is dependent on the degree of heating. If there is excessive gas pressure or excessive temperature, the valve member is pressed against seat 37 to close the valve. There may be two of the gas valves in series. The biassing force of a spring 66 in the solenoid actuated valve 61 may be replaced or augmented by a permanent magnet (71) Fig 6. <IMAGE>

Description

This invention concerns fluid flow control valves.

There are known gas valves of a kind comprising (a) a body having an interior chamber, an inlet to chamber and an outlet from chamber; (b) a valve member and a valve seat which are disposed within the chamber and are relatively movable between an open position permitting fluid from the inlet to the outlet and a closed position preventing flow from the inlet to the outlet; and (c) an actuator responsive to heat to cause said movement.

A valve of this kind is known in which the actuator is bimetallic member connected to the valve member, and is located externally of the body for heating by a pilot light flame produced by burning of gas so as to hold the valve open for supplying gas to a main burner only when the pilot light is burning.

In another known valve of said kind of miniature form the bimetallic actuator forms one wall of the chamber and carries the valve member on its inside face.

An electrical resistance heating element is formed integrally in the outside face of the bimetallic actuator for heating the actuator to move the valve member from the closed position to the open position.

For various reasons such known valves of said kind are not suitable for modulating the supply of fuel gas to a main burner in respect of which there are problems of ensuring adequate safety in the event of malfunction of the control of the voltage of the electrical supply or of the control of the pressure of the gas supply.

According to the present invention there is provided a gas valve of said kind and characterised in that one of the valve member and the valve seat of the valve is carried by a flexible diaphragm in the chamber between the inlet and the outlet so that increase in inlet pressure tends to restrict the valve opening or hold the valve closed.

The valve of the invention greatly reduces the safety risk which could arise upon malfunction of the control of the pressure of the gas supply.

The actuator preferably comprises bimetallic device, which device preferably constitutes the flexible diaphragm.

According to the present invention there is provided a gas valve of said kind and characterised in that the actuator is a bimetallic device which is disposed in the chamber so as to be exposed on both sides to flow of gas through the chamber.

The valve of the invention thus utilises gas flow cooling of the bimetallic device to improve thermal protection of the bimetal and thus reduce said risks.

According to the present invention there is provided a gas valve of said kind and characterised in that an electrical resistance heating element, for heating the actuator device, is disposed in the chamber so as to be directly exposed to the flow of gas through the chamber.

The valve of the invention provides improved response to control inputs and offers gas cooling protection against thermal overload of the element in the event of malfunction of the control of the voltage of the electrical supply.

According to the present invention there is provided a gas valve of said kind and characterised in that two of the actuators are disposed in the chamber between the inlet and the outlet, one actuator carrying the valve member and the other actuator carrying either the valve seat for that valve member or a second valve member or valve seat.

At least one of the actuators is preferably a bimetallic device.

The duplex valve of the invention enables said risks to be reduced substantially, at reasonable cost and minimal additional bulk.

In some embodiments the bimetallic device or one of the bimetallic devices carries the valve member and gas flows through or around the bimetallic device; and the valve seat may be carried so as to be movable on the or a pressure responsive diaphragm or on the or a second bimetallic device, or may be disposed on the body or a partition in the chamber so as to be static.

In other embodiments the bimetallic device or one of the bimetallic devices carries the valve seat and gas flows through or around the bimetallic device; and the valve member may be carried so as to be movable on the or a pressure responsive diaphragm or on the or a second bimetallic device, or may be disposed on the body or a partition in the chamber so as to be static.

In some embodiments wherein two bimetallic devices are employed, the first thereof carries the valve member and the second carries the valve seat; and the bimetallic devices may be arranged to deflect in the same direction in response to applied heat, whereby to provide compensation for variation in ambient or gas supply temperatures, or in opposite directions to compound the valve opening in response to applied heat.

In other embodiments wherein two or more bimetallic devices are employed, the first bimetallic device carries the valve member or its respective seat, and the second bimetallic device carries a second valve member or its respective seat.

The first and second bimetallic devices may be heated in common by a single heat source; or may be heated independently by respective heat sources, and a partition or thermal shield may be interposed in the chamber between the heat sources.

The or each bimetallic device is preferably of disc form. Each bimetallic device is preferably apertured to allow gas to flow through the device and is preferably located by a seal engaging the body.

The heating means is preferably an electrical resistance heating element. The element is preferably carried by an electrical and thermal insulating support in the chamber, or upon one or both of the bimetallic devices.

The support may extend out of the chamber and may carry external cold tails of the element. The cold tails are preferably secured to a circuit board of electrical control means.

The bimetallic device or devices, the heating element or elements, and the support are preferably located in parallel proximity to each other between parallel end walls of the body to provide a layered barrier in which the valve member or members and valve seat or seats are disposed between the inlet and the outlet.

The inlet and outlet are preferably provided with filters and are preferably threaded to receive pipe fittings.

The body is preferably formed from an insulating material, preferably a material having high electrical resistance and low thermal conductivity, such as a ceramic material, such as steatite porcelain. The mean thickness of the walls of the body is preferably at least 2mm, e.g. 3 to 5 mm.

The valve of the invention may be incorporated in a valve assembly in which the flow to the valve is controlled by a fast acting solenoid actuated stop valve.

According to the present invention there is further provided a compound valve assembly comprising a first stage incorporating a solenoid actuated stop valve in series with a second stage incorporating a thermally controlled flow modulating valve, wherein an outlet orifice of the first stage serves as the inlet orifice of the second stage.

The stop valve preferably comprises a movable valve member biased to close the stop valve by a bias arrangement which is adjustable to vary the bias force, and is preferably also adjustable to vary the working stroke, between a valve fully open position and a valve closed position, of the valve member.

According to the present invention there is provided a stop valve comprising an armature movable electromagnetically, by a force produced by a fixed solenoid from a valve closed position in which the armature causes a valve member to close a valve orifice to a valve open position to which the armature moves the valve member to open the valve orifice, wherein the stop valve further comprises a permanent magnet located, preferably adjacent one end of the solenoid, to provide a magnetic bias which has greatest effect on the armature in the valve closed position.

A spring may provide a supplementary bias to supplement the magnetic bias.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings wherein FIGURES 1,2 and 3 are all cross-sectional diagrams showing the general arrangement of respective embodiments of valves of the invention; FIGURE 4 shows an end view of a valve arranged as shown in FIGURE 3, and FIGURES 5 and 6 are further cross-sectional diagrams showing further embodiments of the invention.

In the first embodiment, the valve comprises a body 10, defining a thermally insulated chamber 11 and two fluid flow passages 12 and 13 heading to the chamber; and comprises within the chamber, a valve mechanism 14 disposed to form a partition between the flow passages 12 and 13.

The body 10 comprises two parts 20 and 21 formed from steatite ceramic so as to have relatively thick, e.g. 3 mm thick approximately, thermally insulating walls, which parts are clamped to opposite sides of a printed circuit board 15 by means of fasteners 19 (which parts are shown partially unclamped in the drawings).

The peripheral wall of each part provides a socket 16 to receive a pipe fitting (not shown). A seal 17 and filter 18 may be located in the socket 16. Each part is stepped to provide an annular recess in the chamber 11 to receive sealing rings 22 and 23 or 24 and 25. The board 15 serves as a separator between the recesses and is sealingly engaged by the rings 23 and 24. The sealing rings 22 to 25 further serve as resilient mountings for the bimetals to permit limited axial and radial movement of the peripheries of the bimetals.

The mechanism 14 comprises an electrical resistance heating element 26, mounted on the board 15 which carries conductors for the supply of electricity to the element, for heating an actuator which in this embodiment comprises two disc bimetals 27 and 28. The element 26 occupies an aperture in the board 15 as to extend between and heat both bimetals 27 and 28. The first bimetal 27 provides a central mounting 29 for a valve member 30 and has gas flow apertures 31 therein. The second bimetal 28 has a central aperture 32 therein, and a portion around the aperture 32 which serves as a valve seat 33. The peripheral margin of each bimetal is clamped between a respective pair of the sealing rings 22 and 23 or 24 and 25.

The valve member 30 has a threaded shank 34 engaged in an internal thread in the mounting 29, and a head 35 which carries an 0-ring seal 36 to engage the valve seat 33. The shank 34 extends through both bimetals 27 and 28, so that opposite ends of the valve member confront the flow passages 12 and 13.

In the arrangement shown, the flow passage 12 is employed as an inlet and the passage 13 as an outlet, and the valve is shown in a closed condition. The bimetals are arranged so as to deflect progressively with increasing temperature so that each becomes more convex towards the element 26, whereby to move the valve member towards the outlet and the valve seat towards the inlet to open the valve progressively. The resultant flow rate, given a constant supply pressure, will therefore vary with the heat output of the element and can be controlled electrically. Gas cooling of the bimetals and the element greatly reduces the closing or flow-reducing response time of the valve when the heating supply current is switched off or reduced.

Calibration of the valve is effected by insertion of a tool via the outlet to engage the head 35 for rotating the valve member to adjust its axial position relative to the mounting.

An emergency valve seat 37 with a seal 38 may be provided around the outlet, for engagement by the head 35 in the event of an excessive deflection of the actuator occasioned by application of excessive heating or excessive pressure to the actuator.

The valve of FIGURE 1 is capable of considerable variation and development, some of which variations and developments are illustrated in FIGURE 2, in which a duplex valve having two valve mechanisms 14A and 40 is shown. The body 10A includes an intermediate part 41 which provides a pair of further annular recesses to receive further sealing rings 22 to 25 for locating and sealing the valve components in the manner previously described.

The valve mechanism 14A is similar to the mechanism 14 except in that the element 26 lies on one side of the board 15A which has a small central aperture therein through which the shank 34 passes, so that only the bimetal 28 is heated. The bimetal 27 is thus primarily responsive to the temperature of the incoming gas, to decrease the valve opening with decreasing supply temperature. The end of the shank provides a tool engagement slot for adjustment of the valve member via the inlet. A second, possibly independently controlled, element 26 (not shown) could be disposed on the board 15A to confront and heat the bimetal 27.

In the valve mechanism 40, a further element 26 lies on the other side of a further board 15A, and the bimetal 28 is omitted and replaced by a spring disc 42 which provides the valve seat 33 for the valve member 30.

The disc 42 is pressure sensitive, and serves to restrict the valve opening with increasing differential between the supply pressure and outlet pressure. The outlet part of the body also provides a valve abutment 43 which serves as a stop to prevent excessive displacement of the valve member (and disc 42) in the event of an excessive increase in supply pressure. The mechanism 40 can be simplified by omitting the disc 42 and adjusting the valve member 30 (upwards in FIGURE 2) to bring the seal 36 into proximity with a part of the board ISA which serves as a valve seat 33 as indicated in broken lines.

The embodiment shown in FIGURES 3 and 4 is a duplex development of the first embodiment arranged for simplicity of manufacture. The body lOB includes an insert 50 housed within the two main parts 20B and 21B to provide therewith the recesses for the sealing rings 22 to 25. In this embodiment, the boards 15B are of disc form and are contained within the chamber. The main parts 20B and 21B are clamped directly together by through bolts (not shown) in bores 51, and provide further bores 52 for the cold tails 53 of the elements 26 to extend out of the valve from parts of the chamber sealed off from the remainder of the rings 22 to 25.

The inlet and outlet fittings and sockets are omitted from FIGURES 2 to 4.

The valves are intended to give controlled modulation of a flow of gas, and in duplex form to utilise one of the two mechanisms for flow modulation and the other as a safety valve for on/off switching of the flow, with or without inherent compensation or partial compensation for temperature and/or pressure of the gas supply. Such compensation is preferably provided, at least partially, by negative feedback in an electronic control system, e.g. a burner control system, which controls the electrical energisation of the elements or other actuators, for controlling the flow of fuel gas to a burner.

The valve may be incorporated as the second stage in a compound valve having a rapid acting first stage which preferably serves as a stop valve.

For example, referring to FIGURES 5 and 6, the first embodiment of valve may be modified so that the inlet flow passage 12 leads to a valve orifice in a valve seat 60 of a first stage solenoid actuated stop valve 61.

The valve 61 comprises a solenoid 62 in a case 73 secured to the part 20, an armature 63 slidable within the solenoid 62 between a valve closed position (shown) in which it holds a valve member 64 against the seat 60 to close the valve, and a valve open position in which the armature is raised from the position shown to lift the valve member 64 from the seat. The valve member may have an elastomeric head 65, and otherwise be integral with the armature. The valve 61 includes bias means, to urge the armature to the valve closing position, which includes a bias spring 66 reacting against a keeper plug 67, which serves as a stop to limit the upwards stroke of the armature. The position of the plug 67 is manually variable, by means of a threaded shank 68 which engages an end closure 69 of the valve, for adjustment of the spring bias force and of the armature stroke.The plug 67 carries a gas tight seal 70.

In the modified embodiment shown in FIGURE 6, the spring is optional and merely supplements a magnetic bias provided by a permanent magnet 71 located between the valve seat and the end of the armature proximal to the valve seat, so as to be located in a position slightly spaced apart, e.g. less than 2mm, preferably about lmm, from said proximal end when the armature is in the valve closing position. This magnetic bias, or combination of weak spring and magnetic biases, provides considerable advantages.For example, for a given force holding the valve in the closed position, the required spring strength rating is reduced or possibly obviated by the amount of the magnetic force, allowing a weaker or no spring to be employed, thus in turn reducing the electrical energisation wattage of the solenoid required to hold the armature at the other end of its stroke (where the magnetic force on the armature is weakest); and in the event of spring failure, the magnet alone ensures that the valve will be held closed when the solenoid is de-energised. The magnetic bias used without a spring has offered a reduction of holding wattage greater than 102 in comparison with a spring biased valve of otherwise similar construction.

The invention is not confined to details of the foregoing examples, and many modifications and variations thereof are possible within the scope of the invention.

For example, the actuator may be of any suitable shape, form or material, such as a memory metal coil, to move the valve member or seat in response to heat. The configuration of the valve member and seat and the mounting thereof for relative movement may be varied as required, e.g. the valve member may be fixed and the valve seat moved by the actuator. The inlet and outlet may be disposed in any suitable positions, e.g. offset from the centre-line of the valve.

The scope of the invention includes a valve having any novel part, feature or functional arrangement disclosed herein or in the accompanying drawings, and any combination thereof with known matter whether disclosed herein or not. For instance, the present invention further provides a valve of said kind wherein the actuator comprises a bimetallic disc located at its periphery by seals arranged to permit radial movement of the disc. The present invention further provides a valve of said kind wherein the actuator is located in the chamber so as to be separate from the body, and wherein parts of the body defining the chamber are formed from an electrically and thermally insulating ceramic material, such as a ceramic material.

In the stop valve, the permanent magnet 71 may be distanced from the solenoid further towards the valve seat or located around the valve seat 60 so as to act on an extension of the armature, e.g. on the valve member 64.

Claims

1. A gas valve comprising (a) a body having an interior chamber, an inlet to chamber and an outlet from chamber; (b) a valve member and a valve seat which are disposed within the chamber and are relatively movable between an open position permitting fluid from the inlet to the outlet and a closed position preventing flow from the inlet to the outlet; and (c) an actuator responsive to heat to cause said movement, characterised in that one of the valve member and the valve seat of the valve is carried by a flexible diaphragm in the chamber between the inlet and the outlet so that increase in inlet pressure tends to restrict the valve opening or hold the valve closed.

2. A gas valve comprising (a) a body having an interior chamber, an inlet to chamber and an outlet from chamber; (b) a valve member and a valve seat which are disposed within the chamber and are relatively movable between an open position permitting fluid from the inlet to the outlet and a closed position preventing flow from the inlet to the outlet; and (c) an actuator responsive to heat to cause said movement, characterised in that the actuator is a bimetallic device which is disposed in the chamber so as to be exposed on both sides to flow of gas through the chamber.

3. A gas valve comprising (a) a body having an interior chamber, an inlet to chamber and an outlet from chamber; (b) a valve member and a valve seat which are disposed within the chamber and are relatively movable between an open position permitting fluid from the inlet to the outlet and a closed position preventing flow from the inlet to the outlet; and (c) an actuator responsive to heat to cause said movement, characterised in that an electrical resistance heating element, for heating the actuator device, is disposed in the chamber so as to be directly exposed to the flow of gas through the chamber.

4. A gas valve comprising (a) a body having an interior chamber, an inlet to chamber and an outlet from chamber; (b) a valve member and a valve seat which are disposed within the chamber and are relatively movable between an open position permitting fluid from the inlet to the outlet and a closed position preventing flow from the inlet to the outlet; and (c) an actuator responsive to heat to cause said movement, characterised in that two of the actuators are disposed in the chamber between the inlet and the outlet, one actuator carrying the valve member and the other actuator carrying either the valve seat for that valve member or a second valve member or valve seat.

5. A gas valve as claimed in Claim 1, 2 or 4 wherein an electrical resistance heating element is disposed in said chamber.

6. A gas valve as claimed in Claim 2, 3 or 4 wherein a flexible diaphragm carries one of the valve seat or valve member.

7. A gas valve as claimed in Claim 1, 3 or 4 wherein the actuator is a bimetallic device.

8. A gas valve as claimed in any preceding claim wherein the body is formed from an electrically and thermally insulating material.

9. A gas valve as claimed in Claim 8 wherein said material is a ceramic material.

10. A gas valve as claimed in Claim 9 wherein the average wall thickness of the body around the chamber is at least 2mm.

11. A gas valve as claimed in any preceding claim wherein the actuator is resiliently mounted in said chamber by sealing members engaging the periphery of the actuator.

12. A gas valve as claimed in any preceding claim wherein a further valve seat or a valve abutment is provided in said chamber adjacent the outlet, which is engageable by the valve member in the event of excessive heat being applied to the actuator.

13. A gas valve as claimed in Claim 12 wherein the actuator is movable by application of excessive pressure at the inlet to engage said further seat or valve abutment.

14. A gas valve as claimed in any preceding claim wherein the valve seat is carried by the or a bimetallic device which serves also as a flexible diaphragm in the chamber between the inlet and the outlet.

15. A gas valve as claimed in Claim 14 wherein the actuator is carried by a or one bimetallic device which is apertured to permit flow of gas and is interposed between the flexible diaphragm and the inlet.

16. A gas valve as claimed in any preceding claim wherein two of the actuators are disposed in the chamber between the inlet and the outlet, one actuator carrying the valve member and the other actuator carrying either the valve seat for that valve member or a second valve member or valve seat.

17. A compound valve assembly comprising a first stage incorporating a solenoid actuated stop valve in series with a second stage incorporating a thermally controlled flow modulating valve, wherein an outlet orifice of the first stage serves as the inlet orifice of the second stage.

18. An assembly as claimed in Claim 17 wherein the modulating valve is a gas valve as claimed in any one of Claims 1 to 16.

19. A stop valve comprising an armature movable electromagnetically, by a force produced by a fixed solenoid from a valve closed position, in which the armature causes a valve member to close a valve orifice, to a valve open position to which the armature moves the valve member to open the valve orifice, wherein the stop valve further comprises a permanent magnet located to provide a magnetic bias which has greatest effect on the armature or valve member in the valve closed position.

20. A stop valve as claimed in Claim 19 wherein the permanent magnet is located adjacent to one and of the solenoid.

21. A stop valve as claimed in Claim 19 wherein the permanent magnet is located between the solenoid and the valve seat.

22. A stop valve as claimed in Claim 19 wherein the permanent magnet is located around the valve seat.

23. A stop valve as claimed in Claim 19, 20, 21 or 22 wherein the permanent magnet is located so as to be spaced apart from one end of the armature or valve member when the valve is closed.

24. A stop valve as claimed in Claim 23 wherein said spacing is less than 2mm.

25. A valve substantially as hereinbefore described with reference to any FIGURE of the accompanying drawings.

26. A valve having any novel part, functional feature or combination of parts and/or functional features described hereinbefore or in the accompanying drawings.