GB2284648A - Gas control valves - Google Patents

Abstract

A gas control valve (Figure 1) has a first flow control valve provided by plug 26 turned by spindle 30, and a second valve 16 which is a flame failure device control valve including a magnet arrangement 22. In the normal established flame position, valve 16 is held off its seat against spring 20 by the magnet, and locking collar 50 is driven by spring 52 to engage the radial pin 38. Figure 1 shows valve 16 closed and the locking collar before it is so driven. If the flame fails, the stem 30 cannot be turned to reactivate the igniter until the FFD has closed and pin 60 has returned the collar to the illustrated position. This allows any build up of gas to be dissipated by the ordinary flue of the gas appliance and prevents the possibility of explosion when the igniter is again used. <IMAGE>

Description

GAS CONTROL VALVES This invention relates to gas control valves comprising an igniter and including or associated with a magnetic flame failure device (FFD). Effectively there are two valves in series in the gas supply line, one of which is the FFD which includes an electromagnetic device. When there is an established flame at a burner fed by the valves, the heat affects a thermo-couple which energises the magnet to hold the FFD valve open, whilst the other of the two valves is used to control the flow rate.

One problem with valves of this kind is that if the flame fails, gas continues to flow until the thermocouple has cooled and the magnet de-energises and a spring closes the valve. This is not thought to be significant in open spaces, since usually flame failure occurs when the gas is first lit, and the arrangement is (preferably) such that gas is only applied at a low rate until the flame is established. So the possibility of any build up of much gas is remote. However, there are certain gas appliances where there is what might be called a semi-open space (or a semi-confined space) for example the kind of domestic gas fire where the flame and radiant panels are located behind a glass screen. Even then, the unburnt gas will dissipate via the flue unless the fire is relit before it has dissipated.It is found possible with such an appliance for a rare situation to occur where even the low rate flow of gas can build up to a large volume and if an attempt is then made to relight the flame, an explosion can occur. This can shatter the glass screen with potentially serious results. The object of the invention is to avoid this risk even though it is a very remote one.

According to the invention there is an interlock between the igniter and the FFD valve which allows the FFD to be normally overridden to allow gas flow whilst the igniter is operated, but which prevents the igniter being operated when the FFD is held open by its normal magnetic means.

Conveniently the interlock works by lost motion between different parts. The igniter may be operated by lost motion between a first and second spindle, and there may be a relatively displaceable locking collar which is ineffective until the FFD has magnetically latched, but is then operative until the FFD has disengaged.

One embodiment of the invention is now more particularly described with reference to the accompanying drawings wherein : Figures 1 and 2 are elevations of a valve in the Off position; in Figure 1 the magnetic FFD valve is closed and in Figure 2 it is open.

Figure 3 is a detail as explained hereinafter.

Turning to Figure 1, the valve comprises a body 10 formed with an inlet 12 and an outlet 14. A seat 16 is closeable by valve element 18 which is urged closed by spring 20.

Magnetic FFD valve 22 is coupled to the valve closure element by a spindle 24. When the magnet is engaged it holds the valve 18 in the Figure 2 position in which gas can flow from inlet to outlet via the plug valve. In the Figure 1 position, no such flow is possible.

The flow rate is controlled by the plug 26 which is angularly moveable in the body to change the alignment of one or more flow control ports (not shown in the plug) with the passage 28 leading to the outlet 14.

The igniter, not shown, is a piezo-electric device which is cam and spring operated and is driven by angular movement of the control stem 30. The same stem 30 is used to both control flow rate by turning the plug and temporarily hold the FFD valve in the Figure 2 position by axial displacement. The arrangement is such that the movement necessary for igniter operation turns the plug to a low rate gas flow position and continued movement in the same direction when possible (see below) increases the flow rate to a maximum. The igniter is unidirectionally operated, so that if the gas does not light, the spindle has to be turned back to the zero rate flow (Off) position before it can be operated again.

This is a safety system which is adequate and sufficient for most purposes, albeit not for the special case of the semi-confined space explained hereinbefore.

In more detail stem 30 has diametrically aligned slots 32 containing drive pin 60 which extends diametrically of the push rod 36. The end of the push rod is received in a blind bore 34 in the stem 30. There may be angular lost motion between pin 60 and the slot and the arrangement allows for axial displacement of the stem 30 relative to the push rod 36 to operate the socalled niting device as explained below.

Radially extending pin 38 is fast with the stem 30 and engages in the niting device. This comprises formations on the adjacent faces of the valve body and the cap 40 which is fixed to body 10. Figure 3 is a development generally peripherally extending as a cross section of the parts showing the niting recesses and faces. The stem 30 is driven to the Figure 1 position by the spring 42 which is effective between the plug and the stem.

To operate the igniter, stem 30 is displaced in the direction of arrow A Figure 1 in order to open the magnetic valve, that is to say take the closure 16 from the Figure 1 position to the Figure 2 position. This requires movement of the niting pin from the 381 position of Figure 3 so as to take the pin out of the recess in the cap before the angular movement can take place. The angular movement is limited when the niting pin 38, held in the axial displaced position, reaches the position 382 in Figure 3. This angular movement has turned the plug to the low-rate flow position, whilst the axial movement has opened the magnetic valve. The same angular movement has operated the igniter.If the flame is lit, the stem 30 is held in the axially displaced position whilst the flame is established and until the heating causes the magnetic operation of the FFD device 22 so as to hold the parts in the Figure 2 position even when the stem is released (Figure 2 shows the released position).

However, if the stem is released to be spring-driven back its starting position too soon, and the magnetic valve is not magnetically latched, the parts will return to the Figure 1 position, and the operation has to be repeated.

In order to increase the gas flow rate, it is necessary to allow that axial return of the stem, so as to take the niting pin from the 382 position to the 383 position in Figure 3 and then move it on towards or to the 384 position. That movement from the 383 to 384 position increases the flow rate of gas, but in this specific embodiment, two parking positions 44 46 are provided for the niting pin to provide controlled simmering positions. 384 represents the full flow position.

At anytime the gas may be turned Off by effectively displacing the niting pin from wherever it is back to the 381 position and this will turn the plug valve to the zero flow position, and whilst the magnetic valve will remain open for a short time until a cooling effect deenergises the magnet, no gas flow is possible because the plug valve is closed when turned Off. The problem arises when the FFD valve has been magnetically energised and held in the open position, but the flame has failed and then an attempt is made to re-ignite it. There may be a build up of gas in a somewhat confined space as mentioned earlier herein, and the ignition may cause an explosion.

To prevent this using the present invention, it is necessary to prevent the igniter being operated until the magnetic valve has re-closed.

According to the invention then, a sliding locking collar 50 is provided having longitudinally extending ribs 54 engaged in complementary grooves in the cap so as to make the collar non-rotatable. The collar is provided with a groove similar to the niting grooves and arranged to engage the niting pin in the same way. The collar is urged towards the magnetic valve by a weak spring 52.

In the Figure 1 position, the spring 42 acting on the stem 30 and hence on the niting pin 38 displaces the collar 50 against a spring 52 so that it is held effectively inoperative. When the stem 30 is manually displaced to lift the niting pin out of the 381 position and turn it, this action is completed before the spring 52 can displace the locking plate and it is effectively held in position by the engagement of the niting pin with the collar at an angular position different from that of the locking recess in the collar.

It will be noted that in Figure 1 the locking collar is urged in the arrow A position by the spring 52 but urged in the opposite direction by the stronger spring 20 acting via the push rod 36 and the pin 60, which projects across the face of the collar 50. Spring 42 does not act upon the collar 50 but only upon the stem 30 and niting pin 38.

In the Figure 2 position, the spring 20 is held in a compressed condition by the magnet and so the pin 60 is held in an axially displaced position allowing spring 52 to displace the locking collar to engage with the niting pin. The stem may be turned back to the 381 position from which a repeat igniter operation is at times possible, but due to the displacement of pin 60, the locking collar can then be spring 52 urged to lock the pin 38 so as to prevent re-ignition unless and until the valve 22 re-closes. When that occurs, the pin 60 displaces the collar 50 back to the Figure 1 position, freeing the pin 38 for the repeat operation. The shape of the locking collar is such that it does not prevent the niting pin being turned from the 383 position to the 384 position so as to turn up the gas if the flame has been properly established.

In a modification, the piezo-electric device is separate from the gas valve but associated therewith. In this case it is necessary for the interlock to couple the two together, using the principles of the invention.

Claims (7)

1. A gas control valve comprising an igniter and including or associated with a flane failure device (FFD) which provides a magnetically operated second control valve in series with a first control valve, characterised by the provision of an interlock between the two control valves which allows the FFD to be overridden and the second valve held open to allow gas flow whilst the igniter is operated, but which prevents the igniter being operated when the second valve is held open Dy the FFD magnetic neans.

2. A. valve as claimed in Claim 1 wherein the interlock comprises a locking collar which is axially movable but angularly fast relative to a spindle which has to be turned to actuate the igniter.

3. A valve as claimed in Claim 2 wherein said spindle is also arranged to be aiall displaced with lost otion relative to a second spindle to hold the second valve open before its magnetic action.

4. A valve as claimed in Claim 3 wherein the first spindle is arranged to turn the said first valve to vary te rate of possible flow through that valve.

5. A valve as claimed in Claim 4 wherein the first spindle carries a radially extending pin associated with a control (niting) slot and the second spindle carries a like radial pin for co-operation with a face of the locking collar.

6. A valve as claimed in Claim 5 wherein the first spindle is spring urged in a direction which closes the second valve an the first spring is suc as to be overcome by the magnet when energised, and the locking collar is spring urged in the opposite direction b weaker spring.

7. A gas control valve substantially as described with reference to the accompanying drawing.