GB1565682A - Control of gas flame heating means - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO CONTROL OF GAS FLAME HEATING MEANS (71) 1, THE SECRETARY OF STATE FOR THE ENVIRONMENT, LONDON, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the control of gas flame heating means and more particularly, but not exclusively, is concerned with the control of gas flame heating means on cooking appliances for catering establishments.

In catering establishments, it is commonplace for gas burners on cooking hobs to be left burning gas for much or all of the time that staff are present in the establishment.

However, the heat from the burners is required only when a cooking vessel is placed over the flame. Large volumes of gas could be saved if the burners were to be used only while a cooking vessel requires to be heated.

According to the present invention there is provided a control device for a gas burner comprising a gas supply valve through which gas can be supplied to the gas burner and sensing means which includes a temperature-sensitive element, which sensing means can respond by a change in temperature of the temperature-sensitive element to the presence of an article placed over the gas burner in a position for heating thereby, the response of the sensing means being effective to maintain the gas supply valve in an open position against a bias towards a closed position.

Preferably, the control device includes a sensor which responds to the placing of an article to be heated in an operative position relative to the gas burner and a pilot flame controller, operable by the sensor to extinguish the pilot flame when the article to be heated is withdrawn from the operating position. The sensor and pilot flame controller thus serve to ensure that the pilot flame can act on the sensing means only when the article is in an operating position.

The pilot a me controller is preferably a gas valve, actuated by the sensor. The gas valve controls the supply of gas to the pilot jet in such a way that the valve is opened when an article is to be heated is placed over the burner. Opening of the valve permits the burning of gas at the pilot jet with consequent action thereof on the sensing means.

It is intended that the device according to the present invention should be used for control of gas burners on cooking hobs in catering establishments. However, it is recognised that the device may have other applications for example wherever gas flames are used intermittently for heating or surface treating solid articles placed within the area of influence of the flame. The remainder of the description in this specification will relate to the application of the invention to gas cooking hobs.

The sensor can comprise a vertically disposed rod, arranged to be slidable up and down in the burner. Its lower end is preferably adapted to co-operate with the gas valve controlling the pilot flame to open the valve against resilient loading when the rod is depressed. The upper end of the rod normally projects above the top surface of the gas hob above the burner, so that when a cooking vessel is placed on the hob above the burner, the rod is displaced downwardly to open the gas valve. Preferably the upper end of the rod carries a domed head and incorporates some means of adjusting the length of the rod for best operation of the valve.

The gas valve is conveniently situated beneath the hob and beneath a support channel under the gas burner. It can have a housing which includes a seating onto which a ball is urged by a spring to substantially interrupt flow of gas through the valve. The ball can however be displaced from its seating by downward displacement of the rod, whose lower end contacts a button which projects through a hole in the housing to contact the ball. Preferably, the gas valve includes means for adjusting the force with which the ball is urged onto its seating by the spring.

The sensing means preferably comprises a temperature-sensitive element constituting a heat sensing means. The heat sensing means and the gas supply valve are preferably provided by a thermocouple and flame failure valve respectively (together constituting a thermoelectric flame failure device). However, the thermoelectric flame failure device can be replaced by, for example a gas supply valve operated by a mechanical signal from such sensing means as a bimetallic strip or expansion chamber. In either case, the gas supply valve is biased towards a closed position. A thermoelectric flame failure supply valve comprises a gas valve which can be held open by flow of electrical current through the turns of a coil. It is arranged that if the current is interrupted the valve closes.Electrical current to the coil is provided as long as the thermocouple or other sensing means continues to generate a potential difference and pass it to the flame failure valve. If the potential difference dies away the current to the coil will cease and the valve will close, preferably after a short delay. Flame failure valves are generally provided with a means for manual operation of the valve, such as a button. The button is depressed to hold the valve open for as long as it takes to establish the signal from the sensing means. Thereafter, the pressure on the button can be released as the current in the coil acts to keep the valve open. It is preferable that the supply of gas to the pilot flame controller is controlled by the gas supply valve of the flame failure device.

For a better understanding of the invention, and to show more clearly how the same may be carried into effect, reference will now be made by way of example, to the drawing filed with the provisional specification, which is a schematic vertical section of a control device according to the present invention.

In the drawing a gas burner, represented generally by reference 2, is fed with gas through a pipe 4. Gas flows into the pipe 4 from a supply conduit 6 a flame failure valve 8 (constituting a gas supply valve) and a gas cock 10. The flame failure valve 8 and gas cock 10 are linked by a pipe 12 and from the valve 8 a small bore branch pipe 14 passes to a gas valve, represented generally by 16. The valve 16 controls flow of gas along a further small bore pipe 18 to a pilot jet 20 and thus serves as a pilot flame controller.

The gas burner 2 is situated above a support channel 22 and beneath the hob 24 of a gas cooking appliance. The pilot jet 20 is situated close to the burner 2 so that when the burner is in use, gas flowing from the pilot jet 20 will be ignited by the flame at the gas burner. The gas at both the pilot jet 20 and the gas burner can be ignited by a spark ignition device (not shown) situated close to the pilot jet.

A thermocouple 25 constituting a sensing means is situated adjacent the pilot jet and is arranged so that it is heated by a flame at the pilot jet but not to any significant extent by a flame at the gas burner in the absence of a flame at the pilot jet. The thermocouple 25 is connected to the flame failure gas supply valve 8 by conductive paths 26.

The valve 16 comprises a hollow body 28 containing a ball 30 and spring 32. The spring urges the ball onto a seating 34 to close the valve. The body 28 has a hole 36 which accommodates the lower end of a button 39.

A rod 38 is arranged so that its lower end contacts the button 39. When it moves downwardly it pushes the button 39 which displaces the ball 30 from its seating 34 to allow flow of gas through the valve 16 to the pipe 18 from the pipe 14. The valve 16 is situated under the support channel 22 beneath the gas burner 2. The valve 16 includes means (not shown) to adjust the force with which the spring 32 urges the ball towards the seating 34.

The gas burner 2 comprises a cast iron base 40 and a removable top 42. The base is jig drilled through its centre and a sleeve 44 is pressed into the bore so-formed. The top 42 is a sliding fit on the sleeve 44. The rod 38 is carried within the sleeve 44 and projects from the top of the sleeve 44.

The upper end of the rod 38 carries and is received within a domed head 46 which projects above the hob 24 except when depressed by the presence of an article on the hob above the burner 2. Not shown in the drawing is a means to adjust the distance between the lower end of the rod 38 and the top surface of the domed head 46. The rod 38 carrying the domed head 46 can be removed upwardly from the sleeve 44.

The flame failure gas supply valve 8 is shown purely schematically. It comprises a coil 48 within which is slidably mounted a movable valve member 50 biased towards a closed position. The thermocouple leads 26 are connected to the coil so that when the thermocouple 25 is heated by the pilot flame, current flows through the coil and can maintain the moveable valve member in an "open" position, although such current is not sufficient to move the valve member from the closed to the open position. Such rnovement is effected by a push rod 52 carrying a button 54 connected to the moveable valve member 50. Pressing the button 54 opens the valve allowing gas to pass to both conduit 12 and pipe 14 from the gas supply.

The device operates as follows: An article to be heated, eg a saucepan is placed on the hob 24 above the burner 2.

This depresses the rod 38, opening the valve 16. Button 54 is depressed, opening valve 8 and allowing gas to flow to the pilot jet 20 and to the gas cock 10. A pilot flame is ignited at the pilot jet 20 by a means not shown (preferably a spark igniter) and the flame heats the thermocouple 25. Such heating causes current to flow in the coil 48 and the valve 8 will thereafter stay open without the assistance of the rod 52. When the cock 10 is opened gas flows to the burner 2 where it is ignited by the pilot jet or by the spark ignition device. Alternatively, if the gas cock is open when the button 54 is depressed, flames at the pilot jet and gas burner can be ignited simultaneously.

When the saucepan is removed from the hob 24, the rod 38 is urged upwardly by the action of the spring 32 and the valve 16 closes. The pilot flame is extinguished and the thermocouple 25 cools. The current in the coil 48 falls to zero and the valve 8 closes after a short delay (typically of about 45 seconds from removing the saucepan from the hob). The burner is consequently extinguished and must be relit according to the above procedure. However, if an article is placed on the hob 24 before the valve 8 closes, the valve 16 will be opened and the pilot flame re-ignited from the flame of the burner 2. The thermocouple 25 will therefore be heated and can prevent closure of the valve 8 if its rise in temperature is sufficiently rapid.

WHAT I CLAIM IS: 1. A control device for a gas burner comprising a gas supply valve through which gas can be supplied to the gas burner and a sensing means which includes a temperature-sensitive element which sensing means can respond by a change in temperature of the temperature-sensitive element to the presence of an article placed over the gas burner in a position for heating thereby, the response of the sensing means being effective to maintain the gas supply valve in an open position against a bias towards a closed position.

2. A control device as claimed in claim 1 wherein the temperature-sensitive element is a thermocouple.

3. A control device as claimed in claim 1 or claim 2, wherein the change in temperature of the temperature-sensitive element is produced by the action of a flame thereupon.

4. A control device as claimed in claim 3 including a pilot jet for supporting a pilot flame to act upon the temperature-sensitive element, means to supply gas to the pilot jet and a pilot flame controller for providing a supply of gas sufficient to support a pilot flame, to the pilot jet upon placement of an article to be heated over the gas burner.

5. A control device as claimed in claim 4 including a sensor which is moveable by the article to be heated to actuate the pilot flame controller.

6. A control device as claimed in claim 5 wherein the sensor comprises a rod for location within a bore in the gas burner.

7. A control device substantially as hereinbefore described with reference to the drawing filed with the provisional specification.

8. A hob for heating cooking utensils, including at least one gas burner provided with a control device as claimed in any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. This depresses the rod 38, opening the valve 16. Button 54 is depressed, opening valve 8 and allowing gas to flow to the pilot jet 20 and to the gas cock 10. A pilot flame is ignited at the pilot jet 20 by a means not shown (preferably a spark igniter) and the flame heats the thermocouple 25. Such heating causes current to flow in the coil 48 and the valve 8 will thereafter stay open without the assistance of the rod 52. When the cock 10 is opened gas flows to the burner 2 where it is ignited by the pilot jet or by the spark ignition device. Alternatively, if the gas cock is open when the button 54 is depressed, flames at the pilot jet and gas burner can be ignited simultaneously. When the saucepan is removed from the hob 24, the rod 38 is urged upwardly by the action of the spring 32 and the valve 16 closes. The pilot flame is extinguished and the thermocouple 25 cools. The current in the coil 48 falls to zero and the valve 8 closes after a short delay (typically of about 45 seconds from removing the saucepan from the hob). The burner is consequently extinguished and must be relit according to the above procedure. However, if an article is placed on the hob 24 before the valve 8 closes, the valve 16 will be opened and the pilot flame re-ignited from the flame of the burner 2. The thermocouple 25 will therefore be heated and can prevent closure of the valve 8 if its rise in temperature is sufficiently rapid. WHAT I CLAIM IS:

1. A control device for a gas burner comprising a gas supply valve through which gas can be supplied to the gas burner and a sensing means which includes a temperature-sensitive element which sensing means can respond by a change in temperature of the temperature-sensitive element to the presence of an article placed over the gas burner in a position for heating thereby, the response of the sensing means being effective to maintain the gas supply valve in an open position against a bias towards a closed position.

2. A control device as claimed in claim 1 wherein the temperature-sensitive element is a thermocouple.

3. A control device as claimed in claim 1 or claim 2, wherein the change in temperature of the temperature-sensitive element is produced by the action of a flame thereupon.

4. A control device as claimed in claim 3 including a pilot jet for supporting a pilot flame to act upon the temperature-sensitive element, means to supply gas to the pilot jet and a pilot flame controller for providing a supply of gas sufficient to support a pilot flame, to the pilot jet upon placement of an article to be heated over the gas burner.

5. A control device as claimed in claim 4 including a sensor which is moveable by the article to be heated to actuate the pilot flame controller.

6. A control device as claimed in claim 5 wherein the sensor comprises a rod for location within a bore in the gas burner.

7. A control device substantially as hereinbefore described with reference to the drawing filed with the provisional specification.

8. A hob for heating cooking utensils, including at least one gas burner provided with a control device as claimed in any one of the preceding claims.