GB2138557A - Valve assembly for gas burner - Google Patents

Abstract

A valve assembly suitable for controlling the gas supply to a gas burning appliance has a body structure with a gas inlet 5, followed by a normally closed valve 33B and then two gas outlets 7 and 8. A passageway 11 connects the second outlet to a further outlet 12 and there is a valve 20 in the passageway which is capable of closing off the passageway. A solenoid assembly 41B is displaceable within the body structure between an unenergised position in which the second valve is held open and the first valve is closed and a second energised position in which the first valve is held open and the gas pressure in the passageway closes the second valve. The solenoid 41B is initially energised to open valve 33B and supply gas to both outlet 7 (pilot burner) and outlet 8 (main burner). Gas pressure in passageway 11 closes valve 20. A latch 48 holds the valve 33B open after the pilot burner has heated a thermocouple. The solenoid is then de-energised and gas can flow to the main burner upon opening of valve 20. <IMAGE>

Description

SPECIFICATION Valve assembly This invention relates to a valve assembly which is suitable for controlling the gas supply to a domestic gas-burning appliance.

A particlar application is to a valve assembly for a flame-failure device fitted to a domestic gas fire or central heating burner. A flame-failure device detects the presence of a flame on a pilot burner and, in the absence of a flame, shuts off the gas supply to the pilot burner and to the main burner of the appliance.

According to the present invention, a valve assembly comprises a body structure having a gas inlet into the structure and first and second gas outlets from the structure, a normally closed first valve in the structure separating the gas inlet from the first and second outlets, a passageway providing a gas path from the second outlet of the structure to a further outlet of the assembly, a second valve in said passageway capable of closing off said passageway, a solenoid assembly including a core displaceable within the body structure between a first, de-energised, position in which the core causes the second valve to be open, and a second, energised, positioned in which the core causes the first valve to open and allows pressure of gas in said passageway to close the second valve, and an electromagnetic latching device for holding the first valve in the open position.

In use, the valve assembly is connected in the gas supply to the appliance with the first outlet connected to the pilot burner and the further outlet of the assembly connected to the main burner. The electromagnetic latching device is energised by electrical energy generated by a thermocouple heated by the flame of the pilot burner.

The solenoid is energised from an electrical supply by closing a switch and the movement of the solenoid core, from its first position to its second position, causes the first valve to be opened thereby allowing gas to flow to the pilot burner via the first outlet, and gas also to flow along the passageway towards the further outlet.

The pressure of the gas in the passageway causes the second valve to close, thereby closing off the passageway. Whilst the thermocouple is being heated, the solenoid retains the core in this position. After a short time interval, 10 to 30 seconds, the thermocouple is adequately heated and produces an emf which energises the latching device to hold open the first valve. The solenoid is then de-energised by opening the switch. The displacement of the core to its first, de-energised, position causes the second valve to be opened and the gas to flow to the further outlet and thence to the main burner.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawing which is a sectional side elevation of a valve assembly according to the present invention.

A valve assembly for controlling the flow of gas to a central heating burner has a body structure 1 made up of two tubular bodies connected in endto-end relation. The body 3 has a gas inlet 5, a first gas outlet 7 and a second gas outlet 8. A second body 9 is screw-threaded atone end on to the lower end of the body 3 and, at its opposite end, is screw-threaded on to a casting 10 which has a passageway 11 extending through it. One end of the passageway 11 is connected by a pipe (not shown) to the second outlet 8 and the opposite end 12 of the passageway serves as a further outlet of the assembly. Thus, there is a gas path from the second outlet 8 to the further outlet 12.

The casting 10 defines a central, generally cylindrical, portion 1 5 having an opening 1 6 at its upper end which leads into the lower end of the body 9, and there is a valve seating 1 7 extending around the periphery of this opening. There is a further opening 1 8 in the casting leading from the lower end of the body 9 to the further outlet 12. A resilient gasket 1 9 is clamped around its edges between the lower end of the body 9 and the casting 10 and this resilient gasket has a metal stud 20 located centrally of it. The stud extends through the gasket and the lower end of the stud is in the form of a valve member which, when brought into engagement with the valve seat 17, serves to close off the opening 1 6.The stud 20 and the valve seat 1 7 constitute a second valve which is in the passageway 11 and which is capable of closing off the passageway. A screw 21 is positioned in a threaded lower portion of the cylindrical portion 1 5 and, on rotating the screw, a peg on the screw can be brought into engagement with the underside of the stud 20 in order to limit its downward movement.

A first valve 33 is located in the first body between the inlet 5 and the outlets 7 and 8 and comprises a valve seat 33A and a displaceable valve plunger 33B. The plunger is normally biased into the closed position with the valve seat 33A by a spring 34.

A solenoid assembly 41 has a coil 41A surrounding part of the body 3 and a core 41 B displaceable within the body. In the non-energised condition of the coil 41 A, the core is supported on an apertured plate 42 which is located within the body 9. The plate is screw-threaded and, by rotating it, it can be moved up and down within the body. The underside of the core carries a rod 43 which has a head 44 at its lower end. A spring 45 acts between the head and the upper side of the stud 20. By moving the plate 42 towards and away from the stud 20, the pressure applied on the stud by the spring is varied. This regulates the pressure at which valve opening 1 6 is closed. The upper side of the core carries a further rod 46 which passes through a gas seal 47 in the body 3, below the first and second outlets 7 and 8.The seal is formed by a resilient ring surrounding the rod 46 and urged against the underside of an apertured plate by a spring bearing against the top of the core 41 B.

At the upper end of the body 3, there is an electromagnetic latching device 48 and the upper end of the body carries a cap 49 into which a thermocouple is screwed to supply electrical energy to the latching device 48.

In use, the gas supply is connected to the inlet 5, the main burner of the central heating burner is connected to the outlet 12 and the pilot burner is connected to the outlet 7. The thermocouple (not shown) is associated with the pilot burner and electrical power, generated when the thermocouple is in use, is supplied to the electromagnetic latching device 48.

The solenoid coil 41A is connected to an electrical source, such as a battery via a normally open switch, which may be operated automatically or manually.

The solenoid core resting on the plate 42 holds the valve 20 in its open position. The valve 33 is closed. Thus, no gas can leave the assembly through any of the outlets. On closing the solenoid switch and holding it closed, the core 41 B is attracted by the energised coil and takes up a position where the valve plunger 33B is lifted off its seat by the rod 46. This permits the gas to flow through the first valve and out of the outlets 7 and 8. From the outlet 7, the gas flows to the pilot burner, and, from the outlet 8, it flows through the passage to the second valve 20. The pressure of the gas in the passageway 11, acting on the underside of the valve 20, causes it to be lifted sufficiently to close off the valve opening 1 6. Thus, no gas is supplied to the further gas outlet 12.The gas flowing to the pilot burner is ignited by an igniter (not shown) and this raises the temperature of the thermocouple and energises the latching device 48. This, in turn, latches the valve plunger 33B in the open position. The solenoid is now deenergised by closing the switch, allowing the core to fall on to the plate 42. The rod 43 and the spring 45 apply a force to the stud at the centre of the diaphragm. This causes the valve 20 to be pushed away from its seating and for the valve to abut against the screw 21. In this position, the valve is open and the gas in the passageway 11 can flow through the valve beneath the gasket 1 9 and out of the further outlet 1 2 to the main burner.The position of the screw 21 determines the size of the opening between the valve 20 and the seat 1 7 and, thus, controls the amount of gas which flows through to the main burner.

To switch off the gas supply to the burners, a switch in the circuit of the thermocouple is open, causing the latching device to disengage the valve plunger 33B and the valve 33 is closed. As soon as the gas is cut off from the burners, and the flames are extinguished, the thermocouple cools and, even if the switch is re-closed, the latching device is not energised and valve 33 remains closed. In the event of a failure in the gas flow, the thermocouple cools and the latching device releases plunger 33B to close the valve 33.

It will be appreciated that, with a valve assembly according to the present invention, a considerable saving in the running costs of a central heating burner can be made because the pilot burner is only suppled with gas and ignited a short time before the main burner is supplied with gas. When the main burner is extinguished, the pilot burner is extinguished also. Thus, the supply of gas to the pilot burner for long periods when the main burner is not in use is avoided.

A central heating burner is necessarily connected to a flue and, when the burner has been in use, the hot flue pulls cold air through the burner to the flue. This necessarily causes the burner to be unnecessarily cooled. It has been proposed to install a damper in the flue which cuts off the flue when the burner is not in use and the valve assembly of the present invention may be used to bring about the opening of the damper immediately before the burner is brought into use and to close the damper when the burner is extinguished.

Claims (8)

1. A valve assembly comprising a body structure having a gas inlet into the structure and first and second gas outlets, a normally closed first valve in the structure separating the gas inlet from the first and second outlets, a passageway providing a gas path from the second outlet to an outlet of the assembly, a second valve in said passageway capable of closing off said passageway, a solenoid assembly including a core displaceable within the body structure between a first, de-energised, position in which the core causes the second valve to be open, and a second, energised, positioned in which the core causes the first valve to be open and allows pressure of gas in said passageway to close the second valve, and an electromagnetic latching device for holding the first valve in the open positino.

2. A valve assembly as claimed in claim 1, in which the body structure comprises two tubular bodies connected in end-to-end relation with the gas inlet, the first valve and the first and second oulets in the first tubular body, and the second valve in the second tubular body.

3. A valve assembly as claimed in claim 1 or 2, in which the second valve comprises an opening forming part of said passageway, and a stud having a valve member urgeable by gas pressure in the passageway against the wall of the opening to close off the opening.

4. A valve assembly as claimed in claim 3, wherein said stud is mounted in a resilient gasket which closes off the adjacent end of the body structure.

51 A valve assembly as claimed in claim 4, in which said core, in said first position, applies a force to said stud to move the stud in the direction to open the second valve.

6. A valve assembly as claimed in claim 5, in which the movement of the stud in the direction to open said second valve is limited by an adjustable stop member.

7. A valve assembly as claimed in claim 5 or 6, in which said force applied to the stud is adjustable.

8. A valve assembly substantially as hereinbefore described with reference to the accompanying drawing.