GB2351341A

GB2351341A - Valve assembly for use in controlling the ignition of a gas burner

Info

Publication number: GB2351341A
Application number: GB0007487A
Authority: GB
Inventors: Peter Evans
Original assignee: Concentric Controls Ltd
Current assignee: Concentric Controls Ltd
Priority date: 1999-03-29
Filing date: 2000-03-29
Publication date: 2000-12-27
Also published as: GB9907071D0; GB0007487D0

Abstract

A control valve assembly for controlling a gas burner or appliance, comprises a control knob spindle (4) which can be depressed or moved to an ignition position against the force of a spring. The arrangement is such that the gas burner or appliance can be ignited by moving the control knob to the ignition position and holding the knob in said position only for a short period of time (less than 20 seconds, possibly as low as 2 seconds) before release. Preferably a microswitch provided on the spindle (4) is actuated upon appropriate depression of the spindle (4). The spindle can then be released almost immediately. An auxiliary power supply (2) provides the required voltage to hold valve (7) open allowing gas flow through the burner. The gas is automatically ignited by a piezoelectric spark ignitor (8). The auxiliary power supply (2) is electrically connected to the magnet (6) of the valve (7). The supply is disabled by a detector (3), once the detector detects a sufficiently strong signal from a thermocouple (9).

Description

2351341 Valve Assembly This invention relates to a valve assembly and more

particularly to a control valve assembly for regulating the supply of gas to a gas burner or other appliance, for example, a domestic gas fire.

In such gas burners or appliances it is known to incorporate a manually operated thermoelectric flame safety shut-off valve assembly or system (FSD). In operation, the user has first to move a control knob from an "off'" position to an ignition position and depress the knob spindle for a period of about 20 seconds, after which the knob can be released and moved to a particular setting in order to give the comfort level or heat output required.

An initial time period of about 20 seconds is necessary for depressing the knob in order to ensure that a tip of a thermocouple of the shut off valve is heated sufficiently to generate a "hold-in" current required for an electromagnetic unit to hold a valve member'of the FSD open after the knob is released, allowing gas to flow through to the burner or appliance.

An object of the present invention is to at least alleviate the aforementioned, or other, problern associated with control valve assemblies.

According to the present invention there is provided a valve assembly for controlling the flow of gas to a gas bumer or appliance comprising a start member movable by a user against biasing means to an ignition position in which gas is allowed to flow through the valve; restraining means which provides a force which operably opposes the biasing means for a pre-selected time period commencing shortly after the user moves the start member to the ignition position thereby 2 Preferably, the restraining means is initially activated by electrical means triggered by, movement of the start member and comprises an electromagnet.

Preferably, the electromagnet is energised by an auxiliary power supply which ceases to energise the electromagnet once a sensing means detects that the gas burner or appliance has ignited correctly Preferably, the pre-selected time period is less than 20 seconds, more preferably less than 5 seconds and most preferably less than 2 seconds.

Normally, the restraining means is maintained after the pre-selected time period if sensing means detect that the gas burner or appliance has ignited correctly.

The sensing means may comprise a thermocouple that detects that the gas burner or appliance has ignited correctly and activates a main power supply that energises the electromagnet so that the valve remains open after the auxiliary power supply ceases to energise the electromagnet Preferably the valve assembly comprises a valve member that moves relative to a v,alve seat in order to allow gas to flow or prevent gas from flowing. Preferably, the biasing means comprises at least one spring and the valve member is also biased, in a closed position, against the valve seat by a spring. Preferably, the biasing action of the spring is opposed by the restraining means.

By embodiments of the present invention a gas burner or appliance could be ignited by pushing in the control knob to an ignition position at which point, advantageously, the control knob can be substantially immediately released rather than having to hold the knob depressed for example for a period of 20 seconds or so as in the prior art.

3 Preferably, the knob need only be depressed or held in the ignition position for a time period of less than 15, 10, 5, 3 or 2 seconds.

In one embodiment of the present invention an auxiliary power supply is provided to hold the knob in said ignition position. The arrangement may be such that the auxiliary power supply is arranged to energise an electromagnet of the control valve assembly (which is preferably the same electromagnet which is normally energised by a thermocouple of the control valve assembly) in order to open a valve of the control valve assembly allowing gas through to the burner or appliance whilst said burner or appliance is ignited preferably by a piezoelectric spark, ignitor. The auxiliary power supply may be activated by means of a switch (preferably a microswitch) on the control spindle. It is envisaged that usually, a detector will be provided arranged to detect when a signal from the thermocouple (where provided) has reached a predetermined level (usually slightly in excess of the electromagnetic valve holding voltage/current) in order to enable the auxiliary power supply holding said electromagnetic valve open to be cut off. Thus the electromagnetic valve can then be maintained open by said thermocouple current/voltage generated from a burner flame in contact with the thermocouple.

Further according to the present invention there is provided a control valve assembly having any feature or combination of features derivable from this patent specification and/or a method of controlling gas flow to a gas burner or appliance ",herein a control knob can be moved or depressed to an ignition position and held there only momentarily or for a period of less than 20 seconds before release in order to ignite the burner.

Many other advantageous features of the present invention will be evident from the following description and drawings.

4 An embodiment of a control valve assembly for a gas burner or appliance in accordance with the present invention will now be described, by way of example only, with reference to the accompanying simplified diagrammatic drawings in which:- FIGURE I shows a longitudinal sectional vie,", of a known control valve assembly for a gas burner appliance; FIGURE 2 shows an exploded view of the control valve assembly shown in FIGURE 1, and FIGURE 3 shows a schematic arrangement of a control valve assembly in accordance with the present invention.

FIGURES I and 2 of the drawings show a known form of manually operated then-noelectric flame safety shut-off valve control assembly or device 100 (FSD). The control valve assembly 100 is very well known and thus will not be described in great detail. The various parts of the device are marked clearly on FIGURE 2 of the drawings.

In operation of the known device 100, the control knob spindle 101 is depressed against the spring force provided by spring 102 and the inner end 101a of the spindle 101 lifts valve member 103 away from its seat 104 allowing gas to flow through the valve control assembly 100 to the valve 103, 104 and out burner port 105 to a burner.

Substantially at the same time a piezoelectric device 106 is activated by the control spindle 10 1 to generate a spark to ignite a pilot flame. A thermocouple (not shown in FIGURES I or 2) is arranged in proximity to a burner flame, which thermocouple is connected to the electromagnet 107 such that, after a certain temperature has been detected by the thermocouple, the electromagnet 107 is actuated sufficiently to hold the valve member 103 in an open position away from the valve seat 104 on release of the spindle 101 (which is returned to its start position by the spring 102 in a manner which should be self-evident from the drawings).

In practice, usually, the knob spindle 101 has to be depressed for a period of about 20 seconds for the thermocouple to provide the necessary holding current to energise the electromagnet 107 to retain the valve member 103 from its seat 104 against the spring biasing force providing by spring 108. Should the burner flame go out for any reason this would be detected by the thermocouple which would be unable to continue to provide the required holding force for the electromagnet so that the valve member 103 would return to its seat 104 thereby shutting off the valve and gas supply to the burner.

The arrangement as shown in FIGURE 3 of the dra-wings operates in a similar overall manner to the arrangement shown in FIGURES 1 & 2 except it substantially eliminates the 20 second or so holding period of the control spindle. FIGURE 3 of the drawings shows a control valve assembly 1 of substantially similar form to the control valve assembly 100 save for the addition of an auxiliary power supply 2 and a detector unit 3 arranged to detect when a signal in the form of a voltage/current has reached a predetermined level (slightly in excess of the magnetic valve holding voltage/current) which will enable the auxially power supply holding the magnetic valve open to be cut off, said magnetic valve being maintained open by the thermocouple current/voltage generated from the burner flame.

As shown in FIGURE 3 of the drawings, in a particular arrangement in accordance with the present invention a micro-switch arrangement is provided on the control spindle 4, which micro-switch 5 is actuated on appropriate depression of the control spindle 4 to energise an auxiliary power supply 2 connected directly to the electromagnet 6 of the electromagnetically controlled valve 7 comparable with the valve 103, 104 of FIGURE 1. Thus, once the control spindle 4 has been pushed to such an ignition position activating micro-switch 5 it can be released almost 6 immediatels, and the auxiliary power supply 2 will still provide the required value of current/voltage to hold the valve 7 open allowing gas flow through to the burner, which gas is automatically ignited by the piezoelectric spark ignitor indicated generally by, the reference numeral 8 in FIGURE 3. As should be evident from the drawing the auxiliary power supply 2 is electrically coupled to the magnet 6 of the valve 7 and said supply is disabled after a period of 20 seconds or so by the detector 3, once the detector 3 detects a sufficiently strong signal from the thermocouple 9 shown diagrammatically in FIGURE 3 adjacent to a flame of the burner.B.

If the currentivoltage generated by the thermocouple 9 should not reach the predetermined valve of the holding currentlvoltage within a predetermined time interval (say 20 seconds), the auxiliary power supply 2 is still automatically disabled and the FSD returns to the closed position, the current/voltage being generated by the thermocouple 9 being insufficient to retain the valve 7 open.

Once the valve 7 has been held open by the thermocouple current, the main flame can be established and the FSD will work in the usual manner.

To summarise the embodiment described:- The thermocouple circuit is split in the usual way. The magnetic valve side of the circuit is connected to an auxiliary power supply which is operated immediately, the knob of the FSD is pressed, and the valve makes contact with the magnet faces, (this can be by means of a micro-switch attached to the spindle or other means). This auxiliary power is sufficient to retain the FSD valve open, when the spindle depression is released.

Spark ignition can be operated from micro-switch.

7 The thermocouple tip, or heated side of the then-nocouple circuit is connected to a detector which interacts with the auxiliary power module in the following way:- a) When a voltage/circuit is detected coming generally from the heated junction of the thermocouple and which reaches a predetermined level (slightly in excess of the magnetic valve hold current), the instant that this is reached the auxiliary power is removed and the FSD is held open by the current enerated by the thermocouple 9 alone.

b) If the current generated by the then-nocouple fails to reach the holdin and current valve within a predetermined time interval the auxiliary power supply is removed and the FSD returns to the closed position, the current generated by the then-nocouple insufficient to retain the valve open.

Once the main flame has been established the FSD works in the normal way.

It is to be understood that the scope of the present invention is not to be unduly limited by the particular choice of terminology and that a specific term may be replaced by any equivalent or generic term. For example, the term "burner" could be replaced by "gas fire". "Microswitch" could be replaced by "switch". "Valve" may be replaced by "closure". Further it is to be understood that individual features, method or functions related to the valve assembly might be individually patentably inventive. In particular, any disclosure in this specification for a range for a variable or parameter shall be taken to include a disclosure of an), selectable or derivable sub-range without that range and shall be taken to include a disclosure of any value for the variable or parameter lying within or at an end of the range.

Claims

8 Claims

1. A valve assembly for controlling the flow of gas to a gas burner or appliance comprising a start member movable by a user against biasing means to an ignition position in which gas is allowed to flow through the valve; restraining means which provides a force which operably opposes the biasing means for a pre-selected time period commencing shortly after the user moves the start member to the ignition position thereby allowing the start member to remain in the ignition position without user intervention.

2. A valve assembly according to Claim 1 wherein the restraining means is initially activated by electrical means triggered by movement of the start member.

3. A valve assembly according to Claim 1 or 2 wherein the restraining means comprises an electromagnet.

4. A valve assembly according to Claim 3 wherein the electromagnet is energised by an auxiliary power supply.

5. A valve assembly according to any preceding claim wherein the preselected time period is less than 20 seconds, preferably less than 5 seconds.

6. A valve assembly according to any preceding claim wherein the restraining means is maintained after the pre-selected time period if sensing means detect that the gas burner or appliance has ignited correctly.

7. A valve assembly according to Claim 6 wherein the sensing means is a thermocouple.

8. A valve assembly according to Claim 4,5 or 6 wherein when a thermocouple detects that the gas burner or-appliance has ignited correctly and activates a main power supply that energises the electromagnet so that the valve remains open after the auxiliary power supply ceases to energise the electromagnet

9 9, A valve assembly according to Claim 8 wherein the auxiliary power supply ceases to energise the electromagnet once the thermocouple detects that the gas burner or appliance has ignited correctly.

10. A valve assembly according to any preceding claim wherein the biasing means comprises at least one spring.

11. A valve assembly according to any preceding claim wherein a valve member i-noves relative to a valve seat in order to allow gas to flow or prevent gas from flowing.

12. A gas valve according to Claim 11 wherein the valve member is biased, in a closed position, against the valve seat by a spring.

13. A gas valve according to Claim 12 wherein the biasing action of the spring is opposed by the restraining means.

14. A valve assembly for controlling the flow of gas to a gas burner or appliance, the assembly having a control knob which can be depressed or moved to an ignition position, the arrangement being such that the gas burner or appliance can be ignited by moving the control knob to the ignition position and holding the knob in said position momentarily (or for a period of at least less than 20 seconds) before release.

15. A control valve assembly, for controlling a gas burner or appliance as described above with reference to Figures 1 to 3.