GB2146411A

GB2146411A - Thermally-actuated gas glow control valve assemblies

Info

Publication number: GB2146411A
Application number: GB08320563A
Authority: GB
Inventors: Hugh Vernon Barnes
Original assignee: TI Domestic Appliances Ltd
Current assignee: TI Domestic Appliances Ltd
Priority date: 1983-07-29
Filing date: 1983-07-29
Publication date: 1985-04-17
Also published as: GB8320563D0; GB2146411B

Abstract

A thermally-actuated gas flow control valve assembly has a gas valve (15, 16, 17) carried by a flexible diaphragm (23) that isolates a gas flow path in which the valve is located from an actuating rod (34), whose linear expansion operates the valve through a movement magnifying lever (30). The rod (34) is heated by an electric heating coil (41). <IMAGE>

Description

SPECIFICATION Improvements in or relating to thermally-actuated gas flow control valve assemblies This invention relates to thermally-actuated 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.

It is an object of the present invention, to provide a control valve assembly that is quick acting and of simple construction.

According to the present invention, a thermallyactuated gas flow control valve assembly includes a housing with a gas flow path with a gas inlet, a gas outlet and a gas flow control valve for controlling gas flow from the inlet to the outlet, a thermally responsive elongate member, an electric heating coil for heating the rod and a linkage operatively interconnecting the member and the gas valve to operate the latter, and in which the operative connection includes flexible sealing means impervious to gas and so arranged as to isolate the gas path from the member and heater coil.

The linkage may operate to magnify the increase that occurs in length of the member when the latter is heated.

The linkage may comprise a pivotally-mounted lever.

Means may be provided for adjusting the axial position of the member and where the linkage comprises a pivotally-mounted lever, the relationship between the latter and the gas flow control valve is variable by adjustment of the axial position of the member.

The electric heating coil may be wound on a former supported on and in good thermal contact with the member.

Preferably, the member is of a material having a high coefficient of linear expansion and of good thermal conductivity.

By way of example only, an embodiment of the invention suitable for use with a gas-fired appliance will now be described in greater detail with reference to the accompanying drawings of which: Figure 1 is a cross section of the embodiment, and, Figure 2 is a section on the line Il-Il of Fig. 1.

The base portion 1 of a housing 2 has an inlet 3 leading to a central internal chamber 4 upwardlyopen as can be seen in Fig. 1 and having an exit 5.

The floor 6 of the chamber 4 has a central boss 7 while the chamber itself has an internal shoulder 8 which divides the chamber 4 into lower and upper portions 9 and 10 respectively. Lower portion 9 communicates with inlet 1 via an intermediate passage 11 of smaller diameter than ihlet 1. Similarly, upper portion 10 communicates with outlet 5 via an intermediate passage 12 similar to passage 11.

Seated on shoulder 8 is a valve seating 13.

Seating 13 is of sheet metal formed into a shallow cup and is entered into chamber 4 from the open end thereof and is pressed into engagement with shoulder 8. The seating has a downwardlyturned lip 14 for engagement with a sealing washer 15 seated on a flange 16 of a valve member 17. The valve member 17 has a blind bore 18 into which extends a vertical guide rod 19 fixed in a central recess 20 in the boss 7.

Positioned at its lower end by the boss 7 and at its upper end by a boss 21 on the lower face of the flange 16 of the valve member 17 is a helical spring 22.

The guide rod 19 forms a guide for the valve member 17 whose upper end passes through and is secured to a flexible diaphragm 23 whose periphery seats on a second internal shoulder 24 in the chamber and adjacent the upper open end thereof. The flexible diaphragm 23 is of rubber or some other gas impervious material. The diaphragm 23 is held in position on the shoulder 24 by a sheet metal pressing 25 apertured pressed into position in body 1. The upper end of the valve member 17 extends upwardly into contact with the longer arm 27 of a right angle lever 28 pivotally mounted at 29 between extensions 30 of the base portion 1 of the housing 21.

The shorter arm 31 of lever 28 has a conical recess 32 against the inner end of which bears the pointed end 33 of an elongate member in the form of a rod 34 of a material having a high coefficient of linear expansion and of good thermal conductivity, for example an aluminium alloy. The other end of rod 34 is supported against a ball 35 in the bore 36 of a plug 37 screwed into a threaded passageway 38 in a second extension 39 of the base portion 1 of the housing 2. Rotation of the plug 37 moves the rod 34 axially. Such movement of the rod enables manufacturing tolerances to be accommodated. If it is necessary to vary the angular position of the lever and hence the position of the longer arm 27 relatively to the valve member 17, this can also be done by adjustment of the axial position of the rod.

In good thermal contact with rod 34 is a former 40 on which is wound a heating coil 41 whose ends are electrically connected to terminals 42 supported on a strip 43 of electrically insulating material supported between the extensions 30 and 39.

The mass of the rod 34 is kept small to ensure rapid response on heating and this means that the diameter of the rod must be kept small. The former 40 is of a size sufficient to accommodate a heating coil of the required thermal output and it can be seen from Fig. 2 that the former is a frame whose width greatly exceeds the diameter of the rod 34.

Fitted over the extensions 30 and 39 is a cover 44 having apertures 45 through which project the terminals 42. The cover 44 is secured to the base portion 1 by screws (not shown).

With the movable components in the positions shown in the drawings, the heating coil 41 being de-energised, and the rod 34 is cold, sealing washer 15 is urged against lip 14 by spring 22. Inlet 3 is thus isolated from outlet 5.

If now, heating coil 41 is energised from a source of electrical power (not shown), rod 34 is heated and rapidly expands so causing lever 28 to pivot in an anti-clckwise direction about pivot 29, the longer arm 27 of the lever depressing the valve member 17 downwardly against the action of spring 22. Sealing washer 15 moves away from lip 14 and communication is established between inlet 3 and outlet 5. When the coil 41 is de-energised, rod 34 cools and valve member 17 moves upwardly under restoring of spring 22 so causing lever 28 to pivot in a clockwise direction. Sealing washer 15 seats on rim 14 thereby isolating inlet 3 from outlet 5.

The use of an elongate member, for example a rod, as the heat responsive member considerably reduces the response time of the assembly and it is found that communication between inlet 3 and outlet 5 can be established in times as short as 5 seconds compared with a response time of about 20 seconds for a conventional thermally actuated valve in which the thermally responsive member is a bimetal strip.

Lever 28 acts to magnify the increase in length of the rod 34 as the latter heats up in order to produce the necessary movement of the valve member 17. It will be appreciated that other forms of magnifying linkage can be used instead of the lever 28. The lever 28 also provides a degree of thermal isolation of the rod 34 from thevalvemember 17.

It will be appreciated that the diaphragm 23 isolates the gas path (inlet 3, passage 11, chamber 4, passage 12, outlet 5) from the heating coil 41 and the electrical contacts associated therewith. Thus, the risk of ignition or overheating of gas flow along the gas path is negligible.

Embodiments of the invention can be used to control gas flow to the gas burner of a gas-fired appliance. The embodiment may also form part of flame failure devices and may also be incorporated in other forms of safety device for gas-fired appliances, for example over-heat devices.

Claims

1. A thermally-actuated gas flow control valve assembly including a housing with a gas flow path with a gas inlet, a gas outlet and a gas flow control valve for controlling gas flow from the inlet to the outlet, a thermally-responsive elongate member, an electric heating coil for heating the member and a linkage operatively interconnecting the member and the gas valve to operate the latter, and in which the operative connection includes flexible sealing means impervious to gas so arranged as to isolate the gas path from the member and heater coil.

2. An assembly as claimed in claim 1 in which, in use, the linkage magnifies the changes in length of the member that occurs when the member heats and cools.

3. An assembly as claimed in claim 2 in which the linkage comprises a pivotally-mounted lever.

4. An assembly as claimed in any one of the preceding claims in which means are provided for adjusting the axial position of the member.

5. An assembly as claimed in claim 4 when appended to claim 3 in which the relationship between the lever and the control valve is variable by adjustment of the axial position of the member.

6. An assembly as claimed in any one of the preceding claims in which the heating coil is wound on a former mounted upon the member and in thermal contact therewith.

7. An assembly as claimed in any one of the preceding claims in which the elongate member is of a material having a high coefficient of linear expansion and of good thermal conductivity.

8. A thermally-actuated gas flow control valve assembly substantially as described herein with reference to and as illustrated by the accompanying drawings.

9. A gas-fired appliance incorporating an assembly as claimed in any one of the preceding claims.