GB1593495A - Thermally actuated gas flow control valve assemblies - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THERMALLY ACTUATED GAS FLOW CONTROL VALVE ASSEMBLIES (71) We, T.I. DOMESTIC AP PLIANCES LIMITED, a British Company, of Radiation House, North Circular Road, London, NW10 0JP do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to thermallyactuated gas flow control valve assemblies and has particular reference to such assemblies for controlling the flow of an inflammable gas, for example natural gas or town gas.

According to the present invention, a thermally-actuated gas flow control valve assembly includes a housing with a gas flow path comprising a gas inlet, a gas outlet and a gas flow control valve for controlling the flow of gas from the inlet to the outlet, a bimetal strip and an electric heater for heating the bimetal strip, the bimetal strip and the electric heater being isolated from the gas flow path in gas-tight manner by means including flexible sealing means impervious to the gas, the gas flow control valve having a stem which passes through and is secured in gas tight manner to the flexible sealing means, the bimetal strip being operatively connected to the stem for actuating the gas flow control valve.

The electric heater may be in the form of an electrically-energised heating coil wound round the strip or otherwise arranged in heat conductive relationship therewith.

In one embodiment of the invention, the bimetal strip and electric heater are located in a further housing.

By way of example only, embodiments of the invention suitable for use with a gasfired appliance will now be described in greater detail with reference to the accompanying drawings of which: Fig. 1 is a cross-section in diagrammatic form only of a first embodiment, Fig. 2 is a cross-section similar to that of Fig. 1 showing moving parts in a different position, and Fig. 3 is a cross-section in diagrammatic form only of a second embodiment.

In the embodiment shown in Fig. 1, a gas flow path 1 has an inlet 2 and an exit 3 and is contained in a housing 4. Intermediate the inlet 2 and outlet 3 the flow path is formed with a seating 5 for a valve 6 carried by a flexible sealing means 7. The seating 5 is formed in a recess 8 in the housing 4. The periphery of the means 7 is gripped in gas-tight manner between a ledge round the recess 8 and the lower face of a second housing 9. The flexible sealing means is of a flexible material impervious to gas.

The valve 6 is mounted upon an operating member 10 which passes through the sealing means in an upward direction as seen in Fig. 1 and rthough an aperture 11 in the lower wall of the housing 9. The member 10 has a head 12 which is in mechanical contact with but isolated electrically from the free end of a bimetal strip 13 whose other end is mounted upon and secured to a ledge 14 of the housing 9 by means of a fixing screw 15. An electrically-energisable heating coil 16 is wound round the bimetal strip 13, one end of the coil being electrically secured to a terminal tag 17 also held in position by the screw 15. The other end of the coil is secured to a second terminal tag 18 fixed to another ledge 19 of the housing 9 by screw 20.

The member 10 also extends downwardly, as viewed in Fig. 1, from valve 6 and its lower end engages a guide recess 21 in the housing 4.

Housing 9 has a removable lid 22 through which the terminal tags 17 and 18 project as shown.

At normal room temperature, with coil 16 de-energised, bimetal strip 13 adopts the position shown in Fig. 1 in which the free end presses downwardly on the member 10 and maintains the valve 6 on the seating 5 thereby preventing gas flow from inlet 2 to outlet 3. In that position, the sealing means 7 is flexed downwardly as shown.

On energisation of the heating coil 16 by a control circuit not shown, the bimetal strip 13 commences to flex upwardly, because of the larger coefficient of thermal expansion of the lower component of the strip. That flexing allows the sealing means 7 to move upwardly carrying with it the operating member l() and lifting the valve 6 from the seating 5 permitting gas flow from inlet 2 to outlet 3. If desired, the action of the diaphragm can be assisted by a return spring.

Fig. 3 shows an alternative arrangement of the flow control valve, the other components of the embodiment shown in Fig. 3 being the same as those shown in Fig. 1. The valve 23 of the Fig. 3 embodiment is so arranged that, at normal room temperature and with coil 16 de-energised, valve 23 is held off its seating 24 by the bimetal strip against the action of a return spring 25 acting on an enlarged part 26 of the valve 23. The part 26 also guides the valve during its movement. In the position of the parts as shown in Fig. 3, gas flows from inlet 2 to outlet 3. When the coil 16 is energised, the bimetal flexes upwardly in a manner similar to that described above and allows the spring 25 to urge the valve 23 towards and then into contact with its seating 24.

The orientation of the bimetal strip in the coil de-energised condition may be that shown in Fig. 2. In this case energisation of the coil causes the bimetal strip to flex downwardly and close the valve.

It will be appreciated that the bimetal strip and the heating coil are fully isolated from the gas flow path through housing 4 and there is thus no risk of ignition or overheating of the gas.

Although the bimetal strip and its heating coil have been described above as being located in a second housing this is not essential because isolation is achieved by the location of the gas flow path in its own housing and by the operation of the gas valve by the bimetal strip through the flexible sealing means which is impervious to gas.

Embodiments of the invention can be used to control gas flow to the gas burner of a gas fired appliance. The embodiments may also form part of a flame failure device.

Embodiments may also be incorporated in other forms of safety device for gas-fired appliances, for example over-heat devices.

WHAT WE CLAIM IS:- 1. A thermally-actuated gas flow control valve assembly including a housing with a gas flow path comprising a gas inlet, a gas outlet and a gas flow control valve for controlling the flow of gas from the inlet to the outlet, a bimetal strip and an electric heater for heating the bimetal strip, the bimetal strip and the electric heater being isolated from the gas flow path in gastight manner by means including flexible sealing means impervious to the gas, the gas flow control valve having a stem which passes through and is secured in gas tight manner to the flexible sealing means, the bimetal strip being operatively connected to the stem for actuating the gas flow control valve.

2. An assembly as claimed in claim 1 in which the bimetal strip and electric heater are located in a further housing.

3. An assembly as claimed in claim 1 or 2 in which the electric heater is in the form of a heating coil wound round the bimetal strip.

4. A flame failure device incorporating an assembly as claimed in any one of claims 1-3.

5. A gas-fired appliance incorporating an assembly as claimed in any one of claims 1-3.

6. A thermally-actuated gas flow control valve assembly substantially as herein described with reference to and as illustrated by Fig.

1 and Fig. 2 or Fig. 3 of the accompanying drawings.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. thereby preventing gas flow from inlet 2 to outlet 3. In that position, the sealing means 7 is flexed downwardly as shown. On energisation of the heating coil 16 by a control circuit not shown, the bimetal strip 13 commences to flex upwardly, because of the larger coefficient of thermal expansion of the lower component of the strip. That flexing allows the sealing means 7 to move upwardly carrying with it the operating member l() and lifting the valve 6 from the seating 5 permitting gas flow from inlet 2 to outlet 3. If desired, the action of the diaphragm can be assisted by a return spring. Fig. 3 shows an alternative arrangement of the flow control valve, the other components of the embodiment shown in Fig. 3 being the same as those shown in Fig. 1. The valve 23 of the Fig. 3 embodiment is so arranged that, at normal room temperature and with coil 16 de-energised, valve 23 is held off its seating 24 by the bimetal strip against the action of a return spring 25 acting on an enlarged part 26 of the valve 23. The part 26 also guides the valve during its movement. In the position of the parts as shown in Fig. 3, gas flows from inlet 2 to outlet 3. When the coil 16 is energised, the bimetal flexes upwardly in a manner similar to that described above and allows the spring 25 to urge the valve 23 towards and then into contact with its seating 24. The orientation of the bimetal strip in the coil de-energised condition may be that shown in Fig. 2. In this case energisation of the coil causes the bimetal strip to flex downwardly and close the valve. It will be appreciated that the bimetal strip and the heating coil are fully isolated from the gas flow path through housing 4 and there is thus no risk of ignition or overheating of the gas. Although the bimetal strip and its heating coil have been described above as being located in a second housing this is not essential because isolation is achieved by the location of the gas flow path in its own housing and by the operation of the gas valve by the bimetal strip through the flexible sealing means which is impervious to gas. Embodiments of the invention can be used to control gas flow to the gas burner of a gas fired appliance. The embodiments may also form part of a flame failure device. Embodiments may also be incorporated in other forms of safety device for gas-fired appliances, for example over-heat devices. WHAT WE CLAIM IS:-

1. A thermally-actuated gas flow control valve assembly including a housing with a gas flow path comprising a gas inlet, a gas outlet and a gas flow control valve for controlling the flow of gas from the inlet to the outlet, a bimetal strip and an electric heater for heating the bimetal strip, the bimetal strip and the electric heater being isolated from the gas flow path in gastight manner by means including flexible sealing means impervious to the gas, the gas flow control valve having a stem which passes through and is secured in gas tight manner to the flexible sealing means, the bimetal strip being operatively connected to the stem for actuating the gas flow control valve.

2. An assembly as claimed in claim 1 in which the bimetal strip and electric heater are located in a further housing.

3. An assembly as claimed in claim 1 or 2 in which the electric heater is in the form of a heating coil wound round the bimetal strip.

4. A flame failure device incorporating an assembly as claimed in any one of claims 1-3.

5. A gas-fired appliance incorporating an assembly as claimed in any one of claims 1-3.

6. A thermally-actuated gas flow control valve assembly substantially as herein described with reference to and as illustrated by Fig.

1 and Fig. 2 or Fig. 3 of the accompanying drawings.