GB2198520A - Gas oven - Google Patents

Abstract

A gas oven comprises an oven burner (12), which is associated with an ionisation monitoring device (3), a grill burner (9) which is provided with a thermo-electric ignition protection device (11), and an electromagnetic inlet valve (4) between a gas entry (5) and the oven burner (12). The inlet valve is openable by way of an electric thermostat (2) for temperature regulation of the oven. A gas thermostat (6) is provided between the gas entry (5) and the grill burner (9), while arranged in the gas duct between the gas thermostat (6) and the grill burner (9) is a gas-deflecting cock (8) by way of which a connection between the gas thermostat and the oven burner is producible through an emergency duct (7). The oven burner is thus able to operate in the event of a current failure, and the grill burner can be regulated without needing to open the oven door. <IMAGE>

Description

GAS OVEN The present invention relates to a gas oven, in particular a household gas baking oven.

Domestic gas ovens are usually equipped with capillary thermostats, which regulate the oven temperature within a range of 150 to 2700C.

Regulation to lower temperatures, for example to about 500C, is not possible in known ovens with only one burner and capillary thermostats.

Oven burners are firmly tied to a certain regulating behaviour, so that the spread of the oven temperature is confined by means of capillary thermostat regulation. Automatic switching on and off by means of a programmer (time switch) is not possible, since the switching pulses emanating from the programmer cannot be utilised by capillary thermostats. Protection or monitoring of the oven burner usually takes place by way of thermo-electric protection means.

Also known is the use of electro-magnetic valves, which can be opened and closed by means of an electrical thermostat associated with the oven switch, whereby oven temperatures between 50 and 2700C can be controlled. In this case, protection or monitoring of the oven burner takes place by means of an ionisation monitoring system which operates on the basis of the conductivity of the burner flames.

When the burner flame is present, current continues to be supplied by means of a control element to the electro-magnetic valve so that the valve remains open. On extinction of the burner flame, current supply to the valve is interrupted so that it is closed. Through the use of electro-magnetic valves, control of ovens is possible for the purpose of switching on and off by way of a programmer. However, utilisation of the oven burner in the event of current failure is not possible, since the valve can be opened only in the presence of current.

The additional gas grills provided in such ovens are operated at a fixed power and are not capable of regulation. This has the consequence that the grilling operation is possible only with the oven door open.

There is thus a need for a gas oven in which the operation thereof is programmable and possible even in the case of current failure, with the grilling operation being able to take place with the oven door closed.

According to the present invention there is provided a gas oven comprising an oven burner, ionisation detecting means to monitor operation of the oven burner, a grill burner provided with thermoelectric ignition protection means, gas inlet means connected by a first duct to the oven burner and by a second duct to the grill burner, an electromagnetic valve arranged in the first duct, an electric thermostat to control the eleccromagnetic valve, a gas thermostat arranged in the second duct between the inlet means and the grill burner, and a deflecting valve arranged in the second duct between the gas thermostat and the grill burner and operable to open a gas supply cdnnection between the gas thermostat and the oven burner.

In a preferred embodiment, the gas thermostat is provided with an actuating knob and arranged in the gas duct between the gas inlet valve or entry and the grill burner. A gas-deflecting cock is arranged in the same duct, but between the gas thermostat and the grill burner, for switching-over to gas conduction by way of a pipe provided between the gas cock and oven burner. There is thus the possibility of regulating the grill burner by way of the gas thermostat with the oven door closed. Through the arrangement of the gas thermostat and the gas-deflecting cock, a switch over can be undertaken in the event of failure of the electric current so that gas for the oven burner can be conducted, with thermal regulation, by way of the gas thermostat, the deflecting cock and the additional emergency connecting duct to the oven burner.Thus operation of the oven burner is possible even in the case of current failure. In order to provide reliable and optimum operation of both burners of the oven, the burners are equipped with respective thermo-electric ignition protection means, preferably with a respective thermal element as sensor. The ignition protection means are each arranged between the gas thermostat and the respective burner. In addition, the thermal elements of the ignition protection means are connected in parallel in advantageous manner. This has the advantage that the grill burner can, with the oven door closed, be set and monitored in accordance with the desired temperature.

The oven burner, too, can be monitored and secured appropriately through the thermal element in emergency operation in the event of current failure. Thus, an optimum manner of operation of the gas burners is ensured without the food in the oven being destroyed when current failure occurs; this food is able to be heated in emergency burner operation in temperature-regulated manner. During grilling operation, the temperature can be so regulated that the food to be grilled is cooked without the oven door having to remain open, whereby energy saving and a reduction in the air pollution may be achieved. Moreover, fat-enriched fumes from the oven can no longer pollute the oven portion above the door to the same extent.

It is of advantage if actuating knobs at an oven switch for the oven burner and at the gas thermostat for the grill burner are mutually interlockable mechanically by way of a device. This ensures that only one of the burners can be activated at a time, so that unintended overheating of the oven will not occur.

Preferably, the gas-deflecting cock is constructed as a two-way cock. In normal operation, the grill burner is supplied with gas by way of the thermostat. On switching over to the second path, emergency operation of the oven burner is permitted and gas for the oven burner is conducted by way of the gas thermostat.

It is also of advantage if the gas-deflecting cock is associated with a switch which is electrically connected with the oven switch and serves for the interruption of the current supply by way of the ionisation equipment to the electromagnetic valve. Consequently, the electromagnetic valve cannot switch on during emergency operation on return of the current. If normal operation is desired again on renewed presence of current, then the deflecting cock can be brought back to the normal setting, whereby the electromagnetic valve is again freed. By this means it is prevented that disturbances can occur through possible more frequent jumping-over from normal operation to emergency operation.

It is furthermore of advantage if a programmer or time switch of the oven is connected with the oven switch by way of an emergency switch of the gas-deflecting cock. As a result, the time switch can address the oven switch only in normal operation.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, the single figure of which is a schematic circuit diagram of a gas oven embodying the invention.

Referring now to the drawing, there is shown a gas oven in which a gas connecting pipe 22 leads directly from a gas entry 5 to an electromagnetic inlet valve 4. A further connecting pipe 14 leads from this to an oven burner 12.

In addition, a gas connecting pipe 16 leads from the gas entry 5 to a gas thermostat 6. This stands in communication by way of a connecting pipe 15, a gas-deflecting cock 8, which can be a two-way cock, and a connecting pipe 10 with a grill burner 9.

An emergency feed duct 17 leads from the cock 8 to the pipe 14 of the burner 12.

The oven includes an oven switch 1, which is associated with an electrical thermostat 2. The switch 1 serves for placing the burner 12 in operation, which is monitored by an ionisation device 3. The device 3 is connected on the one hand by way of sensors with the oven burner and on the other hand with the valve 4, the switch 1, the thermostat 2 and with two indicators 23 and 24, which indicate normal operation or disturbance of the oven burner. Also present is a connection to an air-circulating motor 25 and a cooling blower 26, which are connected with the oven switch 1 or the thermostat 2.

The gas thermostat 6 is connected by way of a thermo-electric ignition protection device with a thermal element 11, which may expediently comprise a thermocouple, to the grill burner 9. A similar connection, namely by way of a thermo-electric ignition protection device with a thermal element 13, is provided between the thermostat 6 and the burner 12. The devices 11 and 13 are connected in parallel.

In order to ensure that only one burner, either the grill burner 9 or the oven burner 12, can be put into operation at a time, actuating knobs 18 and 19 respectively of the oven switch 1 and the thermostat 6 are mutually interlockable by way of a mechanical latch 20. The thermostat 6 is. also associated with a switch 31, which is connected by way of an electrical line 32 with the baking switch 1, the thermostat 2 and the motor 25 as well as the cooling housing 24 in order, when the grill burner 9 is put into operation through depression of the knob 19, to activate these components until the thermal element current holds the thermo-electric ignition protection device.

The cock 8 is associated with an emergency switch 7, by way of which the current supply to the valve 4 through the line 30 is interrupted in the setting "emergency operation" of the cock 8. On restoration of the current supply, the valve 4 thus cannot switch on normal operation when emergency operation is switched on. The cock 8 must be brought back to its normal setting for switching on normal operation in the presence of current.

Also provided is a programmer in the form of a time switch 21 which is connected by way of a line 29 with the emergency switch 7 and from this by way of the line 30 with the switch 1. When the switch 7 is open, this prevents the clock 21 in emergency operation from switching on the normal operation at the same time.

The oven burner 12 is associated with two sensors 27 and 28, wherein the sensor 27 stands in operative connection with the thermostat 2 and the sensor 28 with the thermostat 6.

In use of the oven, when normal operation is switched on, gas flows out of the gas entry 5 by way of the pipe 22, the valve 4 and the pipe 14 to the burner 12. This is switched on and ignited by way of the switch 1, whereby an actuation of the knob 19 for switching on of the burner 9 is blocked by way of the latch 20. The operation of the oven burner 12 is monitored by way of the ionisation protection device 3. When the baking oven is switched on, the temperature is regulated selectably between about 50 to 2700C by way of the thermostat 2.

If the grill burner 9 is to be switched on in place of the oven burner 12, then the gas thermostat 6 is actuated. For this purpose, the knob 19 must be depressed in usual operation during the ignition process until the thermal element current holds the thermo-electric ignition protection device. The burner 9 can then be regulated steplessly by way of the gas thermostat 6. Through depression of the knob 19, actuation of the knob 18 for the switching on of the switch 1 is blocked by way of the latch 20, so that switching on of the burner 12 is prevented.

In the event of current failure, the oven burner 12 can no longer be fed and monitored normally, since the valve 4 and the electrical monitoring elements fail at the same time. Now the possibility exists, through actuation of the cock 8, of maintaining emergency operation of the burner 12. For this purpose, the cock 8 is reset from normal operation to emergency operation, whereby the gas from the gas entry 5 passing through the thermostat 6 is conducted through the cock 8 and the duct 17 to the feed duct 14 of the burner 12. It is thus possible to regulate the baking burner 12 with the aid of the thermostat 6 in emergency operation. The ignition protection of the burner 12 in this case takes place thermo-electrically by way of the thermal element 13, which is connected in parallel with the grill thermal element 11. At the same time, in the setting "emergency operation" of the cock 8 and in dependence on the switch 7, the current supply to the valve 4 and to the ionisation device 3 as well as the connection from the timer switch 21 to the switch 1 are interrupted so that if the current is restored during emergency operation the valve 4 cannot be switched on. When normal operation is desired again, the cock 8 must be brought again to normal setting.

The failure of the oven burner 12 in the event of current supply interruption is signalled optically by the indicators 23 and 24 so that the operator can at once undertake switching over from normal operation to emergency operation. Indication of current supply interruption can also be provided additionally or exclusively by acoustic means.

Claims (8)

1. A gas oven comprising an oven burner, ionisation detecting means to monitor operation of the oven burner, a grill burner provided with thermo-electric ignition protection means, gas inlet means connected by a first duct to the oven burner and by a second duct to the grill burner, an electromagnetic valve arranged in the first duct, an electric thermostat to control the electromagnetic valve, a gas thermostat arranged in the second duct between the inlet means and the grill burner, and a deflecting valve arranged in the second duct between the gas thermostat and the grill burner and operable to open a gas supply connection between the gas thermostat and the oven burner.

2. An oven as claimed in claim 1, the protection means comprising a thermal element for control of the gas thermostat.

3. An oven as claimed in claim 2, wherein the oven burner is provided with thermo-electric ignition protection means comprising a thermal element for control of the gas thermostat separately of the control provided by the thermal element of the protection means of the grill burner.

4. An oven as claimed in any one of the preceding claims, comprising switching means for controlling the oven burner, first actuating means for actuating the switch means, second actuating means for actuating the gas thermostat, and mechanical interlocking means so interlocking the first and second actuating means that actuation of one precludes actuation of the other.

5. An oven as claimed in any one of the preceding claims, wherein the deflecting valve is a two-way gas cock.

6. An oven as claimed in any one of the preceding claims, comprising an emergency switch associated with the deflecting valve and operable to interrupt operating current supply to the electromagnetic valve.

7. An oven as claimed in any one of claims 1 to 3, comprising switching means for controlling the oven burner, timing means to control operation of the oven by way of the switching means, and an emergency switch associated with the deflecting valve and arranged in an electrical connection between the timing means and the switching means.

8. A gas oven substantially as hereinbefore described with reference to the accompanying drawing.