GB2034020A

GB2034020A - Automatic Gas Burning Apparatus

Info

Publication number: GB2034020A
Application number: GB7842223A
Authority: GB
Original assignee: Main Gas Appliances Ltd
Current assignee: Main Gas Appliances Ltd
Priority date: 1978-10-27
Filing date: 1978-10-27
Publication date: 1980-05-29
Also published as: GB2034020B; DE2943333A1; FR2439942A1

Abstract

Automatic domestic cooking ovens are known which have timing equipment which enables the user to preset a starting time and a duration for the cooking operation, a pilot burner within the oven being supplied with gas and ignited electrically at the preset starting time and in turn igniting a principal burner within the oven. To avoid using a mercury vapour flame failure device and a time controlled gas valve in addition to the valve of the flame failure device, a safety valve 11 having a gas inlet port 12 and gas outlet port 13 is used with an electrical air gas mixture igniter 17 and a thermo-electric device 19 arranged to operate in response to combustion of an air gas mixture at the burner 14. A timer device 27 predetermining the onset and duration of an operative state of the igniter 17 causes partial opening of the safety valve 11 initially at the onset of operation of the igniter 17. The safety valve 11 is controlled by the thermo- electric device 19 for a predetermined time starting substantially at or before the onset of partial opening of the safety valve. During control of the safety valve 11 by the thermo-electric device 19 heating of the thermo- electric device 19 by combustion of the air gas mixture enables full opening of the safety valve 11. <IMAGE>

Description

SPECIFICATION Automatic Gas Burning Apparatus The present invention relates to automatic gas burning apparatus and especially, but not exclusively, to automatic gas burning apparatus for domestic cooking ovens. The term "gas" in this specification refers to natural gas, town gas and other gaseous substances which can be burnt in air to produce carbon dioxide and water vapour.

Automatic domestic cooking ovens are known which have timing equipment which enables the user to preset a starting time and a duration for the cooking operation, a pilot burner within the oven being supplied with gas and ignited electrically at the preset starting time and in turn igniting a principal burner within the oven.

Hitherto, the burning of gas supplied to the principal burner has been monitored by a mercury vapour flame failure device such as that described at pages 160--161 of the Principles and Practice of Gas Appliances Controls by V. C. Miles a L. H.

Pinkess, published in 1 970 by Walter King Limited of Holborn Hall, 100, Grays Inn Road, London, WC1. However, such mercury flame failure devices are a potential source of health hazard in cooking ovens. Furthermore, a typical automatic gas burning apparatus which incorporates a mercury vapour flame failure device includes a time controlled gas valve in addition to the valve of the flame failure device.

According to the present invention there is provided automatic gas burning apparatus including a safety valve having a gas inlet port and one or more gas outlet ports, means for permitting combustion of an air gas mixture thereat when supplied with gas from the safety valve, the said means being in communication with the outlet port or ports of the safety valve, electrical means for igniting air gas mixtures at the means permitting combustion, thermoelectric means arranged to operate in response to combustion of an air gas mixture at the means permitting combustion, and timing means for predetermining the onset and duration of an operative state of the ignition means and for causing partial opening of the safety valve for a duration starting at substantially the onset of the operative state of the ignition means and lasting for no more than a predetermined maximum time, the timing means also being such as to establish control of the safety valve by the thermo-electric means for a predetermined time starting substantially at or before the onset of partial opening of the safety valve, and the safety valve and the thermo-electric means being such that during control of the safety valve by the thermoelectric means heating of the thermo-electric means to a condition thereof establishable by combustion of an air gas mixture at the means permitting combustion enables full opening of the safety valve to be effected at the termination of partial opening thereof and to be maintained until whichever of termination of the said control and termination of the said heating occurs first.

The safety valve may be such as to have a mechanical mode of operation and an electrical mode of operation, mechanical operation of the safety valve effecting partial opening of the valve and electrical operation of the valve effecting full opening of the valve when and only when the electrical operation is begun while the valve is partially open as a result of mechanical operation thereof. The timing means may then include electro-mechanical means arranged to effect mechanical operation of the valve.

In a preferred embodiment of the present invention, the safety valve has first and second movable valving members therein, the first being movable between a first position in which it completely closes a path for gas through the safety valve from the inlet port to the outlet port or ports, and a second position in which it allows gas to flow from the inlet port to the or one or more of the outlet ports of the safety valve, the second valving member being movable between a first position in which it does not close the path for gas from the inlet port to the outlet port or ports and a second position in which it partially closes the path for gas from the inlet port to the said means permitting combustion, the safety valve being such that the first and second valving members are biassed to remain in their respective first positions, mechanical actuation of the safety valve moves the first and second valving members from their respective first positions to their respective second positions, and electrical operation of the safety valve is able to retain the first valving member in its second position but not to move the first valving member from its first position to its second position. Preferably, the safety valve is such that mechanical operation thereof requires linear movement of an actuator member thereof. The electro-mechanical means may then include a solenoid with a core member arranged to effect the required linear movement of the actuator member of the safety valve.

Means for establishing the said predetermined maximum time may then include a normally closed thermal switch in a circuit for supplying power to the solenoid, connection of this circuit to a power supply causing electrical heating of a heater arranged to heat the thermal switch whereby the predetermined maximum time is the time starting at the onset of supplying of power to this circuit and ending at opening of the thermal switch in response to the heating thereof by the said heater.

Control of the safety valve by the thermoelectric means in a preferred embodiment is established by closure of a safety switch in an electric circuit which is completed by the said closure and enables thermo-electrically generated current from the thermo-electric means to be supplied to the safety valve.

The invention will now be described in more detail, solely by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of a first embodiment of the invention in a quiescent condition; Fig. 2 is a schematic view of the embodiment of Fig. 1 in a ready condition prior to ignition of an air gas mixture; Fig. 3 is a schematic view of the embodiment of Figs. 1 and 2 at the beginning of ignition of an air gas mixture; Fig. 4 is a schematic view of the embodiment of Figs. 1 to 3 when combustion of an air gas mixture is established; Fig. 5 is a schematic view of another embodiment of the invention at the start of ignition of an air gas mixture; Fig. 6 a, b, and c are three schematic sectional views of a safety valve suitable for use in the embodiment of Figs. 1 to 4; and Figs. 7 a, b and c are schematic sectional view of another safety valve suitable for use in an embodiment of Fig. 5.

In Fig. 1 there is shown schematically an automatic gas burning apparatus for'a domestic cooking oven. This apparatus includes a safety valve 11 having a gas inlet port 12 and a gas outlet port 13. The gas outlet port 13 is in communication with a gas burner 14 for burning an air gas mixture thereat, the outlet port 1 3 being connected by a pipe 1 5 to a gas jet 1 6 disposed to cause entrainment of air with the gas into the burner 14.An igniter electrode 1 7 is suitably arranged for igniting air gas mixtures at the burner and is electrically connected to an ignition unit 18 of the type which causes sparks to be passed between the electrode 1 7 and the burner 14 when power is supplied to the unit 1 8 and an air gas mixture is present in the vicinity of the electrode 1 7.

A thermo-electric device 19, which in this case is a thermo-couple, is arranged to be heated by operation of the burner 14. One element of the thermo-electric device 19 is connected directly to an electric input terminal of the safety valve 11.

The other element of the thermo-electric device 19 is coupled through a switch 20 to another electric input terminal of the safety valve 11.

The inlet port 12 of the safety valve 11 is connected by a pipe 21 to the outlet port of a thermostat valve 22, the inlet port of which is connected to receive gas from a main supply not shown. One of the contacts 23 of the thermostat valve 22 is connected to the live terminal 24 of an alternating current supply. The other one of the contacts 23 of the thermostat valve 22 is connected through a switch 25 to one input terminal of the ignition unit 1 8. The other input terminal of the ignition unit 18 is connected directly to the neutral terminal 26 of the alternating current supply. The two switches 20 and 25 are both controlled by an automatic timing unit 27 of the kind which allows the user to pre-set a starting time and a finishing time for a cooking operation.In Fig. 1, the timing unit 27 is in its manual control state in which both switches 20 and 25 are closed so that the switch 20 completes coupling of the thermo-electric device 1 9 to the safety valve, and the switch 25 completes coupling of the one input terminal of the ignition unit 1 8 to one of the contacts 23 of the thermostat valve. The thermostat valve 22 is shown in Fig. 1 in its closed state, the contacts 23 then being open. Consequently, gas is prevented by the thermostat valve 22 from reaching the safety valve 11, and power is not supplied to the ignition unit 1 8.

Connected in parallel with the ignition unit 1 8 is a thermal switch unit 28 arranged for coupling alternating current power to a full wave rectifier bridge 29 coupled to supply the winding 30 of a solenoid having a linearly moveable core member 31 aligned with a mechanical actuator member 32 of the safety valve 11. When the solenoid winding 30 is not energized, the core member 31 remains in the position shown in Fig. 1 in which it is out of contact with the actuator member 32 of the safety valve 11. A smoothing capacitor 33 is connected in parallel with the winding 30.

The thermal switch unit 28 has two input terminals 34 and 35 between which a heating resistor 36 is connected. The input terminal 34 is connected directly to an output terminal 37, and the input terminal 35 is connected through the bimetallic switch 38 of the thermal unit 28 to an output terminal 39. The switch 38 is closed when the heating resistor 36 receives no power.

Fig. 2 shows the embodiment of Fig. 1 in the state in which the thermostat valve 22 is set to a suitable cooking temperature and, since it is assumed that this temperature is not exceeded, is fully open and allows gas to pass through the pipe 21 to the inlet port 12 of the safety valve. The contacts 23 of the thermostat valve are closed thereby connecting one contact of the switch 25 to the live terminal 24 of the alternating current supply. The timing unit 27 is set to initiate a cooking operation at a future time and to maintain the cooking operation for a chosen length of time.

Accordingly, both switches 20 and 22 are open.

The open state of the switch 25 ensures that neither the ignition unit 1 8 nor the thermal switch unit 28 receives electric power.

Fig. 3 shows the state of the apparatus of Fig.

2 shortly after the timing unit 27 has reached a predetermined time for starting the cooking operation. The timing unit 27 has closed the switches 20 and 25 thereby allowing power to be supplied to the thermal switch unit 28 and then to the winding 30 of the solenoid, and to the ignition unit 1 8. Energization of the winding 30 causes the core member 31 to be moved in the direction of an arrow 40 shown in Fig. 3 whereby the core member 31 pushes the actuator member 32 of the safety valve 11 linearly inwards in relation to the valve 11. Such mechanical operation of the valve 11 causes partial opening of the valve 11 allowing a less than full flow of gas to pass through the pipe 1 5 from the outlet port 11 to the jet 1 6 and hence to the burner 14 with entrained air. Closure of the switch 25 completes the circuit for the igniter unit 1 8, the switch 23 already being closed. The igniter unit 1 8 generates sparks at its electrode 17 as soon as the switch 25 is closed if there is no flame to provide a conductive path from the electrode 1 7 to the burner 14. The sparking ceases when the air gas mixture at the burner 14 ignites. Since there is a less than full flow of gas to the burner 14 at ignition, the ignition is quiet. Furthermore, if there is a malfunction of ignition and the air gas mixture does not ignite, the escape of gas is small.

The supplying of power to the thermal switch unit 28 causes the heating resistor 36 to warm up and in turn to heat the bimetallic switch 38. After a predetermined length of time from the closure of the switch 25 the temperature of the switch 38 is such that the switch 38 breaks the connection between the input terminal 35 and the output terminal 39 of the unit 28. Consequently, power is no longer supplied to the winding 30 and the solenoid is de-energized whereupon the core member 31 returns to the position shown in Figs.

1 and 2. The actuator member of the valve 11 automatically returns to the position shown in Figs. 1 and 2. However, the switch 20 is in its closed state and the thermo-electric device 1 9 is heated by the combustion of the air gas mixture and the burner 14. The state of the apparatus is then as shown in Fig. 4 in which the safety valve 11 is fully opened, combustion of the air gas mixture is taking place at the burner 14, thermoelectric current generated by the thermo-electric device 1 9 is passing through the switch 20 to the safety valve 11 to maintain it in its fully opened condition, the actuator member 32 of the valve 11 is in its initial position and the solenoid winding 30 is in a de-energized condition, the bimetallic switch 38 being open, and the ignition unit 1 8 is supplied with power through the closed switches 23 and 25 so that temporary extinction of the burner 14 is corrected by the response of the ignition unit 1 8. If combustion of the air gas mixture at the burner 14 ceases for sufficient length of time for the thermo-electric device 1 9 to cool down and correspondingly cease to generate sufficient current to maintain the fully opened state of the valve 11, the valve 11 closes completely thereby preventing the escape of unburnt gas from the jet 16. In the absence of such safety action by the valve 11, a cooking operation is terminated by the timing unit 27 opening the two switches 20 and 25 at the predetermined time.The opening of these two switches 20 and 25 immediately results in complete closure of the valve 11 and deenergization of the ignition unit 18.

Fig. 5 shows an alternative embodiment in which parts corresponding to parts of the embodiment of Figs. 1 to 4 are given the same reference numerals, the state of the apparatus represented in Fig. 5 corresponding to that of Fig.

3. The apparatus of Fig. 5 differs from that of Figs.

1 to 4 in having a different safety valve 11' which has two outlet ports 13' and 13". The outlet port 13' is connected to the jet 1 6 by the pipe 1 5 as in Figs. 1 to 4. The outlet port 13" is connected to a pilot burner 41 by a pipe 1 5'. When the safety valve is completely closed, gas supplied to its inlet port 12 cannot reach either of the two outlet ports 13' and 13". When the valve 11' is partially open as a result of movement of the actuator member 32 by the solenoid core member 31 as shown in Fig. 5, gas supplied to the inlet port 1 2 is allowed to pass only to the outlet port 1 3" and thus to the pilot burner only. The air gas mixture is therefore ignited initially at the pilot burner 41.

The pilot burner 41 is arranged to heat the thermo-electric device 1 9 so that on release of the actuator member 32, the valve 11' is held fully opened by the supply of thermo-electric current from the device 1 9 to the valve 11'. When the valve 11' is fully opened, gas supplied to the inlet port 12 is allowed to pass to both outlet ports 13' and 13" and thus reaches the principal burner 14 as well as the pilot burner 41. The air gas mixture at the principal burner 14 is ignited by the flame at the pilot burner 41. When the supply of thermo-electric current from the device 1 9 to the valve 11' ceases for any reason, the valve 11' completely closes.

Figs. 6(a), (b) and (c) show a safety valve suitable for use in the embodiment of Figs. 1 to 4, the same reference numerals being used in Figs. 6 (a), (b) and (c) as are used in Figs. 1 to 4 for corresponding parts. The safety valve of Figs. 6 (a), (b) and (c) has an inlet chamber 51, an outlet chamber 52 and an interconnecting tube 53 mounted in a wall 54 which separates the inlet and outlet chambers 51 and 52. A first disc-like valving member 55 is fixed to an actuating rod 56 which extends through a gas tight bearing in a bottom wall 57 of the inlet chamber 51 and has a soft iron armature 58 secured to its end outside the inlet chamber 51.Mounted within the safety valve 11 below the wall 57 is an electro-magnet 59 which becomes magnetized only when supplied with thermo-electric current from the thermo-electric device 1 9. The switch 20 of Figs.

1 to 4 is not shown in Figs. 6 (a), (b) and (c) the thermo-electric device 1 9 being shown connected directly to the windings of the electromagnet 59. A helical spring 60 is trapped between the first valving member 55 and the wall 57 and biases the valving member 55 into contact with the bottom rim of the tube 53.

The actuator member 32 is in the form of a hollow cylindrical cap which has fixably and coaxially mounted therein an actuator rod 61 which extends through a gas tight bearing in an upper wall 62 of the outlet chamber 52. A helical spring 63 trapped between the top of the actuator member 32 and the wall 62 biases the actuator member 32 upwards. A second disc-like valving member 64 is mounted so as to be slideable in the axial direction on the actuator rods 61 below the wall 62. A further helical spring surrounding the portion of the rod 61 between the wall 62 and the second valving member 64 determines a rest position for the valving member 64 in the unactuated position shown in Figs. 6 (a) and (c).

In this unactuated position, the second valving member is well spaced from the upper rim of the tube 53 as shown. A small hole 66 extends through the second valving member so that when the actuator member 32 is pressed down to the position shown in Fig. 6 (b), although the rod 61 pushes the rod 56 down and thereby unseats the first valving member from the bottom rim of the tube 53 and allows gas to pass from the inlet port 12 into the tube 53, the closing of the upper end of the tube 53 by the second valving member 64 is not a complete closure since gas can pass through the hole 66 into the outlet chamber 52 and thence through the outlet port 13, and through the tube 1 5 and to the burner 14. The burner 14 is shown in a simplified manner in Figs.

6 (a), (b) and (c). It will be seen from Fig. 6 (b) that in the state of the safety valve 11 shown there, the second valving member 64 has moved from a first position shown in Fig. 6 (a) in which it does not close the path for gas from the inlet port 12 to the outlet port 13 to a second position in which it partially closes the path for gas from the inlet port 12 to the burner 14, and that the first valving member has moved from a first position shown in Fig. 6 (a) in which it completely closes the path for gas from the inlet port 12 to a position in which it allows gas to flow from the inlet port 12 to the outlet port 13. It will also be seen from Fig.

6 (b) that in the second position of the valving member 55, the armature 58 is in contact with the poles of the electro-magnet 59.

Consequently, if there is thermo-electric current flowing through the windings of the electromagnet 59, the armature 58 will be retained in this position even when the actuator member 32 is allowed to move back to its rest position as shown in Fig. 6 (a) and Fig. 6 (c). If the arrangement is working normally, the small flow of gas to the burner 14 in Fig. 6 (b) will mix with air and the air gas mixture will be ignited by the electrode 1 7 as indicated in Fig. 6 (c). The thermo-electric device 1 9 will therefore be heated and thermo-electric current will flow to the electro-magnet 59 which will therefore retain the armature 58. The armature 58 is rigidly connected to the first valving member 55 which is therefore held away from the lower rim of the tube 53 as shown in Fig. 6 (c).Release of the actuator member 32 allows the spring 63 to return the actuator member 32 to its rest position, thereby carrying the second valving member 64 well clear of the upper rim of the tube 53. It will be realized that if the thermo-electric device 1 9 ceases to supply current to the electro magnet 59 in the condition shown in Fig. 6 (c), then the armature 58 will be released, and the spring 60 will push the first valving member 55 back into gas tight sealing contact with the low rim of the tube 53 thereby completely closing a path for gas from the inlet port 12 to the outlet port 13, the valve 11 being again in the state shown in Fig. 6 (a).

Figs. 7 (a), (b) and (c) are similar to Figs. 6 (a), (b) and (c) and show a safety valve 11' suitable for use in the embodiment of Fig. 5. Those parts in Figs. 7 (a), (b) and (c) which are identical to parts in Figs. 6 (a), (b) and (c) are given the same reference numerals and those parts which are similar but not identical are given primed reference numerals.

Fig. 7 (a) corresponds to Fig. 6 (a) in showing the completely closed state of the valve 11'. It will be seen that the second valving member 64' does not in this case have a hole 66 extending therethrough. Furthermore, the valve 11' has two outlet ports, a principal outlet port 13' and a secondary outlet port 1 3". The principal outlet port 13' is in communication with the burner 14 which is the principal burner through a pipe 1 5 as in Fig. 6 (a). The secondary outlet port 13" is in communication with the pilot burner 41 of Fig. 5 through a pipe 15'. The secondary outlet port 13 is in communication with the interior of the tube 53' which otherwise is the same as the tube 53 of Fig. 6 (a).The electrode 1 7 is arranged to ignite air gas mixtures at the pilot burner 41 as shown in Fig. 7 (a) from which it can be seen that when the actuator member 32 is depressed, the second valving member 64' completely closes the upper end ofthe tube 53' while the rod 61 depresses the first valving member 55 thereby unseating the first valving member 55 from the lower rim of the tube 53' and bring the armature 58 into contact with the poles of the electro-magnet 59. Thus, in Fig. 7 (b) the inlet port 12 is in communication with the secondary outlet port 13" through the tube 53', whereas there is no path for gas between the inlet port 12 and the principal outlet port 13'.Provided that the air gas mixture at the pilot burner 41 is now ignited, the electro-magnet 59 is energized and holds the second valving member 55 in its second position as shown in Figs. 7 (b) and 7 (c). Release of the actuator member 32 in this condition allows the spring 63 to raise the actuator member 32 and therefore the second valving member 64', thereby opening the path for gas between the inlet port 12 and the principal outlet port 13 through the tube 53'. The flame of the pilot burner 41 can then ignite the air gas mixture at the principal burner 14.

The safety valve 11' of Figs. 7 (a), (b) and (c) may be a type TM2 valve as manufactured by Evered s Company (Control) Limited of Mafeking Road, Wallasey, West Midlands B66 2BW, and marketed by Concentric Controls Limited of Aston, Birmingham.

The solenoid having the winding 30 used in the embodiments of Figs. 1 to 4 and 5 may be an Oliver Pell solenoid, which is operated as a D C solenoid. However, the solenoid need not be operated as a D C solenoid although if A C operated, preferably the solenoid circuitry should be very quiet.

An advantage of the embodiments of Figs. 1 to 4 and Fig. 5 is that the apparatus can be used for cooking during an electrical power supply failure.

The timing unit 27 can be set to manual operation, the thermostat valve 22 can be opened manually, and the safety valve 11 or 11' can be operated manually by depressing the core member 31, which, as shown, is provided with a button. The burner 14 can then be lit with a match, the core member 31 being held down manually until thermo-electric current from the thermo-electric device 1 9 energises the electromagnet 59 to hold the valve open. It will be understood that the timing unit 27 is such that when set to manual operation, the switch 20 is held closed.

A further advantage of these embodiments is that if there is an electrical power supply failure while the apparatus is in the cooking phase, e.g.

as illustrated by Fig. 4, the cooking continues undisturbed and the valve 11 or 11' is still effective as a safety valve since the timing unit 27 does not require electrical power to enable it to keep the switches 20 and 25 closed.

Claims

1. Automatic gas burning apparatus including a safety valve having a gas inlet port and one or more gas outlet ports, means for permitting combustion of an air gas mixture thereat when supplied with gas from the safety valve, the said means being in communication with the outlet port or ports of the safety valve, electrical means for igniting air gas mixtures at the means permitting combustion, thermo-electric means arranged to operate in response to combustion of an air gas mixture at the means permitting combustion, and timing means for predetermining the onset and duration of an operative state of the ignition means and for causing partial opening of the safety valve for a duration starting at substantially the onset of the operative state of the ignition means and lasting for no more than a predetermined maximum time, the timing means also being such as to establish control of the safety valve by the thermo-electric means for a predetermined time starting substantially at or before the onset of the partial opening of the safety valve, and the safety valve and the thermoelectric means being such that during control of the safety valve by the thermo-electric means heating of the thermo-electric means to a condition thereof establishable by combustion of an air gas mixture at the means permitting combustion enables full opening of the safety valve to be effected at the termination of partial opening thereof and to be maintained until whichever of termination of the said control and termination of the said heating occurs first.

2. Automatic gas burning apparatus according to claim 1, wherein the safety valve has a mechanical mode of operation and an electrical mode of operation, mechanical operation of the safety valve effecting partial opening of the valve and electrical operation of the valve effecting full opening of the valve when and only when the electrical operation is begun while the valve is partially open as a result of mechanical operation thereof, the timing means having electromechanical means arranged to effect mechanical operation of the valve.

3. Automatic gas burning apparatus according to claim 1 or 2, wherein the safety valve has first and second movable valving members therein, the first being movable between a first position in which it completely closes a path for gas through the safety valve from the inlet port to the outlet port or ports, and a second position in which it allows gas to flow from the inlet port to the or one or more of the outlet ports of the safety valve, the second valving member being movable between a first position in which it does not close the path for gas from the inlet port to the outlet port or ports and a second position in which it practically closes the path for gas from the inlet port to the said means permitting combustion, the safety valve being such that the first and second valving members are biassed to remain in their respective first positions, mechanical actuation of the safety valve moves the first and second valving members from their respective first positions to their respective second positions, and electrical operation of the safety valve is able to retain the first valving member in its second position but not to move the first valving member from its first position to its second position.

4. Automatic gas burning apparatus according to claims 2 and 3, wherein the electro-mechanical means includes a solenoid with a core member arranged to effect linear movement of an actuator member of the safety valve.

5. Automatic gas burning apparatus according to claim 4, wherein for establishing the said predetermined maximum time, a normally closed thermal switch is provided in a circuit for supplying power to the solenoid, connection of this circuit to a power supply causing electrical heating of a heater arranged to heat the thermal switch whereby the predetermined maximum time is the time starting at the onset of supplying of power to this circuit and ending at opening of the thermal switch in response to the heating thereof by the said heater.

6. Automatic gas burning apparatus according to any preceding claims wherein control of the safety valve by the thermo-electric means is established by closure of a safety switch in an electric circuit which is completed by the said closure and enables thermo-electrically generated current from the thermo-electric means to be supplied to the safety valve.

7. Automatic gas burning apparatus, substantially as described hereinbefore with reference to Figs. 1, 2, 3, 4 and 6, or to Figs. 5 and 7 of the accompanying drawings.