GB2131943A - Gas burner start mechanism - Google Patents

Abstract

A domestic water heater connected to several taps has a venturi flow sensor to operate the main valve. The main valve 1 has a chamber 2 with a gas inlet 3 and outlets 4 and 5 to the pilot burner and the main burner respectively. Before gas in the chamber 2 reaches either outlet, it must pass though a valve channel 6. Valve plates 7 and 8 can be moved over an entrance and an exit respectively of the valve channel. A starter button 11 can be pushed inwardly to seal off the main burner outlet while the ignition sequence for the pilot burner occurs; a latch ensures that the button remains in a position to maintain the main burner outlet closed, unless an operator takes positive action to release the latch. <IMAGE>

Description

SPECIFICATION Gas burner start mechanism The present invention relates to a gas burner starter mechanism, particularly (but not solely) for a water heater with a venturi flow sensor.

A known domestic water heater, capable of supplying hot water to several remote taps, has an automatic valve for supplying gas to the main burner, the valve being operable by a water flow sensing system using a venturi.

Thus when a tap is turned on, the water flow causes the valve to supply gas to the main burner, which is then ignited by a pilot burner.

If a person attempts to light, or re-light, the pilot burner when a tap is on, the full flow of the main burner will be immediately ignited; this can result in an accident, especially if the casing has been taken off during servicing of the heater.

British Patent Specification No. 1 279594 describes (on page 3 with reference to its Fig.

4) a gas flow control valve with a push-button control and rotary cock valve. In order to ignite the burners, the push button is depressed to open up the gas inlet and then turned to rotate the cock until the outlet to the pilot burner is open while the outlet to the main burner remains closed. Only once the pilot burner is alight can the cock be further turned in order to open up the main burner and release the push-button.

The present invention provides a gas burner starter mechanism comprising: a chamber having an inlet for the entry of gas, an outlet for the exit of gas to a pilot burner and an outlet for the exit of gas to a main burner; valve means, manually operable in a single direction to close off the main burner outlet from communication with the inlet; and means to selectively maintain the valve means in a position in which the main burner output is closed off.

Thus, when igniting the pilot burner, the main burner output can be closed off so that even if there is a tap on, the flow of gas is interrupted.

In a heater incorporating the starter mechanism of the present invention, the operator is required to make a separate and quite deliberate action to permit gas to flow to the main burner.

In a heater incorporating the starter mechanism of the present invention, gas is permitted to flow to the main burner only when the operator releases elements of the maintenance means whose sole function is to hold the valve means at a position in which the main burner output is closed off.

In one form of the invention the closure means includes an elongate member movable along the length of its axis, and the maintenance means comprise co-operable parts on the elongate member and on another section of the mechanism. The co-operable parts may be a latch, fixed at one end to the chamber, and a flange extending laterally from a section of the elongate member along its length; alternatively, they may be formed by a latch, fixed at one end to the chamber, for engagement with the free end of the elongate member.

Preferably the flange has a cut-away region to receive the latch, thereby ensuring that the mechanism is compact.

Preferably, the latch is movable laterally of the axis of the elongate member for disengagement of the co-operable parts.

in the starter mechanism of the present invention, a single manual action (namely a depression) on the valve means ensures that the mechanism is in a state permitting the flow of gas to the pilot burner but not to the main burner. However in the prior apparatus mentioned in British Patent Specification No.

1279594, it is necessary firstly to depress the push-button and then, while it remains depressed, to rotate it before the apparatus is in a state suitable for ignition of the pilot burner.

The mechanism of the present invention is easier to operate and simpler in construction than the stated prior art.

In order that the invention may more readily be understood, a description is now given, by way of example only, reference being made to the accompanying drawings, in which: Figures 1 to 3 shows a cross-section of a main valve for a heater embodying the present invention in various stages of the ignition sequence; Figure 4 illustrates a modification of a part of the valve of Figs. 1 to 3; and Figure 5 is a view in the direction of arrows 5-5 of Fig. 4.

A domestic water heater connected to several taps has a venturi flow sensor to operate the main valve. The main valve 1 (shown in Fig. 1 when in the "off" position) has a chamber 2 with a gas inlet 3 and outlets 4 and 5 to the pilot burner and the main burner respectively. Before gas in the chamber reaches either outlet, it must pass through a valve channel 6. Valve plates 7 and 8 can be moved over an entrance and an exit respectively of the valve channel 6. In the "off" position, valve plate 7 is held against the entrance of channel 6 by a spring 9 so that gas is unable to flow into channel 6; valve plate 8 is held away from an exit of channel 6 by a spring 10.

In the first stage of igniting the pilot burner, a starter button 11 is pushed inwardly by the operator against the action of spring 10, thereby urging valve plate 8 towards an exit of channel 6. Fig. 2 shows the situation when plate 8 has just reached that exit of channel 6 and is now closing it off. A strip of spring steel fixed at one end to the exterior of valve 1 forms a latch 1 2. When button 11 is in the position shown in Fig. 2, latch 1 2 moves laterally of the rod axis from the position shown in Fig. 1 to its rest position in which its flange 1 3 abuts the free end of button 11.

Thus latch 1 2 acts as a stop to prevent spring 10 returning the button 11 and the plate 8 towards their positions shown in Fig. 1, and so maintains the main burner outlet 5 closed off.

In the next ignition stage, the operator further depresses button 11 in order to slide rod 14 through the centre of plate 8 until its end pushes valve plate 7 away from the entrance to channel 6. Thus gas can flow to the pilot burner outlet 4 while the button 11 remains depressed; by operating an ignition device a pilot flame can be lit. Once the pilot flame is alight, a thermocouple positioned in the flame generates sufficient current to energise an electromagnet unit 1 5 which maintains the entrance to channel 6 open by attracting an armature 1 6 connected to plate 7.

When button 11 is released, it returns to the position in which its free end abuts flange 1 3 (see Fig. 2). In order to ignite the main burner, the latch 1 2 must be pushed by the operator laterally away from button 11 to disengage it from flame 13, thereby returning latch 1 2 and button 11 to their original position. Thus plate 6 is removed from that exit of channel 6 enabling gas to pass to main burner outlet 5.

The position of all the components during full operation of the burner is shown in Fig. 3.

To turn the burner off, stop button 1 7 is depressed thereby actuating a lever 1 8 which moves armature 1 6 out of contact with electromagnet unit 1 5. Thus valve plate 7 is urged by spring 9 against the exit of channel 6 thereby stopping the flow of gas to the main burner outlet 5.

Figs. 4 and 5 show a different arrangement of co-operable parts between the button 11 and a latch, the operation of the valve being otherwise identical to that of Fig. 1. This latch 1 7 has an elongate base 1 8 of plastics material, one end of which is attached to the exterior of valve 1 and the other is arcuate to form a handle extending beyond button 11 even when in its fully extended position. Button 11 has been omitted from Figs. 4 and 5 for clarity. At opposite edges of base 18 and about halfway along its length, latch 1 7 has two walls 1 9 each having a tooth 20 which is co-operable with an engagement edge 21 on a flange 22 fixed to rod 14 by a circlip. Each tooth 20 has a profile substantially identical (but inverted) to that of the corresponding engagement edge 21, thereby facilitating the sliding of flange 22 over the teeth 20 when button 11 is first depressed inwardly. Flange 22 can be released from engagement with latch 1 7 by pushing the handle downwardly as seen in Fig. 4.

This arrangement of co-operable parts provides a compact cheap construction with secure engagement and easy release.

Claims (8)

1. A gas burner starter mechanism comprising: a chamber having an inlet for the entry of gas, an outlet for the exit of gas to a plot burner and an outlet for the exit of gas to a main burner; valve means, manually operable in a single direction to close off the main burner outlet from communication with the inlet; and means to selectively maintain the valve means in a position in which the main burner output is closed off.

2. A mechanism according to Claim 1, wherein the closure means includes an elongate member movable along the length of its axis, and the maintenance means comprise co-operable parts on the elongate member and on another section of the mechanism.

3. A mechanism according to Claim 2, wherein the co-operable parts include a latch, fixed at one end to the chamber, and a flange extending laterally from a section of the elongate member along its length.

4. A mechanism according to Claim 3 wherein the flange has a cut-away region to receive the latch.

5. A mechanism according to Claim 2, wherein the co-operable parts include a latch, fixed at one end to the chamber, for engagement with the free end of the elongate member.

6. A mechanism according to any one of Claims 3 to 5, wherein the latch is movable laterally of the axis of the elongate member for disengagement of the co-operable parts.

7. A gas burner starter mechanism substantially as hereinbefore described with reference to Figs. 1 to 3, or to Figs. 1 to 3 when modified by Figs. 4 and 5, of the accompanying drawings.

8. A gas burner having a starter mechanism according to any one of Claims 1 to 8.