The invention relates to a gas cooktop with at least one gas burner, a main pipe for supplying gas, a main nozzle on the gas burner and an operator control device influencing the main nozzle to adjust the heating power of the gas burner between a minimum power and a nominal power. The nominal power represents the highest power that can be permanently demanded. In general, the operator control device contains a valve that is arranged in the main gas pipe and provides at least one straight-through position and one closed position. As a rule, the straight-through position can be adjusted in steps or continuously between a minimum throughput and a nominal throughput.
A so-called booster function is known in electric cookers. Here, usually at the start of a cooking process, a particularly high power output is generated in order to reduce the waiting time before the simmering state is reached. The increased power output at the start of the cooking process is used for example to rapidly heat up the still cold cooking pot and the product being cooked that has likewise not yet reached the correct temperature. Other typical applications for this are the heating-up of a large quantity of water or the rapid searing of meat. On expiration of a time interval the power is automatically reduced to a level selected by the operator.
The object of the invention is therefore to provide a device that allows the gas cooktop to be operated for a limited time above the nominal power, that is to say in a so-called booster mode. In this case, the booster mode shall be possible not just at the start of a cooking process.
This object is achieved in a gas cooktop of the type stated in the introduction by a timer switching device that allows the heating power to be increased beyond the nominal power for the duration of a time interval. Consequently, a heating power that is increased by around 20 to 30% can be demanded for a period of 10 to 15 minutes, for example. In gas cooktops it is necessary to limit the time interval of the power overshoot because the nominal power of the gas cooktop is chosen so that it can also be demanded in the continuous operating mode without causing damage. Exceeding the nominal power could, for example, cause parts made from special steel in the area of the gas cooktop to be permanently discolored if heated up above a threshold temperature of around 200° C. In principle, the device for the booster mode can be arranged at any cooking point. For economic reasons however, it is recommended that only one gas burner, namely the heavier-duty or heaviest-duty one be fitted for the booster mode.
An increase in the heating power of the gas burner can be simply controlled via its gas supply. According to an advantageous embodiment of the invention, a shut-off device can be connected in the main pipe via the timer switching device, which shut-off device allows an additional gas flow to the gas burner, that is to say a gas flow that exceeds the maximum power. In a simplest embodiment, the shut-off device has either a straight-through or a closed position. In order to avoid the aforesaid damage due to maloperation, the shut-off device can be activated only via the timer switching device.
In order to increase the power of the gas burner, an increased gas flow is therefore supplied to it. This gas supply can be achieved in different ways. According to a first alternative, an auxiliary gas pipe that opens into an auxiliary nozzle in a gas burner, can be connected via the shut-off device. The increase in the heating power is effected by providing the gas flow with additional access to the gas burner. For its part, this construction offers two performance options:
According to a first embodiment, the auxiliary gas pipe can have a larger cross-section than the main pipe and be operated alternately to the main pipe for the duration of the time interval. The booster operation therefore takes place exclusively via its own pipe system with its own nozzle. This has the advantage that it can be precisely specified via the dimensioning of its own pipe system in order to eliminate damage due to unintentional power overshoot.
On the other hand, a special pipe for booster operation means greater technical outlay. According to a second embodiment, the auxiliary gas pipe can therefore be operated in addition to the main pipe for the duration of the time interval. The gas flow which reaches the gas burner in the booster mode is then determined by the passage through the main pipe and additionally by the passage through the auxiliary pipe. The auxiliary pipe of the second alternative can therefore be of smaller dimensions than those of the first embodiment, which reduces the technical outlay and the costs of the second embodiment. According to a second alternative, a main nozzle that provides the gas passage for the booster mode, and a restrictor connected upstream of it which defines the nominal power of the gas burner, can be arranged in a main line. The choice of restrictor depends, among other things, on the type of burner and on the different calorific values of various types of gases. It should therefore be easily interchangeable—like the main nozzle—or easily adjustable. In a simple case its adjustment can be ensured by means of a screw, for example. According to the invention, the auxiliary gas pipe now forms a bypass around a restrictor in the main pipe. The power of the gas burner in the booster mode is therefore obtained by routing the gas flow unimpeded around the restrictor and as a result the restrictor is made virtually inoperative. A further reduction in the technical outlay for the booster mode can thus be achieved because a second pipe and an auxiliary nozzle in the burner can be dispensed with. Here a further two construction possibilities present themselves. On the one hand, an additional path around the restrictor can be provided for the gas flow, so that the passage through the restrictor and that through the other gas pipe together produce the gas flow for the booster power. On the other hand, an alternate path around the restrictor can be provided for the gas flow, which alone makes the gas passage available for the booster power, whilst the restrictor is completely deactivated. Whereas in the first case a simple shut-off device suffices to open the other pipe just in the booster mode and close it for the rest of the time, for the second option a two-way valve is required to conduct the gas flow either through the restrictor for normal operation or through the other pipe for the booster mode. In both cases it is obvious to combine the restrictor and the shut-off device in a compact component in order to reduce the technical outlay and space requirement for this.
According to a further advantageous embodiment of the invention, the shut-off device can be designed as a solenoid valve. In this form it represents a simple technical construction since its function, however, is reliably fulfilled and can be controlled with low technical outlay via switching currents, for example.
In order to prevent damage to the gas cooktop, the booster mode should therefore be maintained only for a specific time interval. The timer switching device required therefor can be based on a mechanical or an electronic operating principle, or a combination of these. The length of the time interval to be controlled by said operating principle must in any case be set. This can be effected by the operator or in the factory. The latter is to be preferred since damage to the cooktop due to a time interval that is set excessively long cannot be ruled out in the case of operator intervention. According to a further advantageous embodiment of the invention, the gas cooktop can therefore have a control system with a timer switching device that activates the shut-off device for the duration of the preset time interval in accordance with an operator signal. A control system in which a timer switching function can be accommodated is usually provided anyway in modern gas cooktops. In the simplest form, the operator signal can be generated by a switch in the control panel of the gas cooktop. An optical and/or audible indicator can be provided as the check-back signal for the switch-on operation.
According to a further advantageous embodiment of the invention, the control system can additionally activate the shut-off device in accordance with signals generated by the appliance. Preferably, these signals refer to the temperature actually detected in the parts susceptible to damage. On the one hand they can be measured directly by temperature sensors. This is certainly the most precise data acquisition option, but does mean higher technical outlay and correspondingly high costs. On the other hand, the temperature can be determined indirectly via the time that the relevant gas burner is in operation. For example, the control system can therefore activate the booster mode according to whether the relevant gas burner is already in operation and so is already at the minimum operating temperature. If this is the case, then the control system can shorten the time interval for the booster mode in order to prevent the aforesaid heating-up of the gas burner from exceeding a critical temperature and thus causing damage.
By way of an example, the principle of the invention is explained in further detail below with the aid of a drawing. In the drawing:
Two branches 8, between which two gas pipe sections 9 and 10 run in parallel, are arranged in the main gas pipe 2. A restrictor 11 having a diameter of 1.25 cm is arranged in the pipe section 9. A solenoid valve 12, with which the pipe section 10 can be opened or fully closed, is arranged in the pipe section 10 running in parallel. For reasons of space and maintenance, the branches 8, the restrictor 11 and the solenoid valve 12 can be combined in a compact component 13.
At its end, the main gas pipe 2 opens into the main nozzle 5, which has a diameter of 1.3 cm. The main nozzle 5 therefore has a greater diameter than that of the restrictor 11. The purpose of this is, via the restrictor 11, to limit the maximum or nominal power of the cooktop to a value at which the gas cooktop and, in particular, the gas burner 1 sustain no damage during continuous operation, for example due to overheating. This nominal power can be 2.8 KW, for example.
In addition to the twist knob 6 of the operator control device 4, a so-called booster switch 20 is arranged on a control panel, not shown in detail. Said booster switch is connected via an electrical cable connection 21 to a control unit 22. The control unit 22 is connected via an additional electrical cable connection 23 to the solenoid valve 12. The solenoid valve 12 can therefore be activated by means of the booster switch 20 only by the interposition of the control unit 22.
In normal operation the heating power of the gas burner 1 is controlled by means of the operator control device 4. This operator control device allows the power of the gas flow in the main pipe 2 to be set between zero throughput, or minimum power, just before extinction of the gas burner flame, and nominal power. In this case, the gas flow takes the path through the main gas pipe 2, the pipe section 9 and the restrictor 11 to the main nozzle 5. Even when nominal power at the gas burner 1 is chosen, the heating-up period of a cooking pot on the gas burner 1 can be undesirably long.
If the operator wishes to accelerate the initial heating-up process, then he can operate the booster switch 20. The switch 20 then passes a signal to the control unit 22 which thereupon opens the solenoid valve 12. This makes it possible for the gas flow to bypass the restrictor 11 via the pipe section 10. The unrestricted gas flow in the pipe section 10 thus reaches the main nozzle 5, which now has the smallest cross-section within the main pipe 2. With its larger diameter in relation to that of the restrictor 11, the main nozzle 5 provides a higher power at the gas burner 1, of 3.3 KW, for example. However, since during continuous operation this higher power could lead to damage due to overheating at the gas burner 1, for instance, the control unit 22 closes the solenoid valve 12 automatically and time-dependently according to a predetermined, factory-set time interval, for example. Consequently, maloperation on the part of the operator and resulting damage are virtually eliminated.
In normal operation, the gas flow takes the path from the gas source 3 along the main gas pipe 2, past the operator control device 4 to the main nozzle 5. The gas burner 1 is supplied with combustible fuel via this path during a normal cooking process. Here, in contrast to the exemplary embodiment described above, the nominal power of the gas burner 1 is determined by the diameter of the main nozzle 5. When the booster switch 20 is operated the solenoid valve 12 opens the auxiliary pipe 30. The gas flow can then reach the gas burner 1 via the auxiliary pipe 30 and the following auxiliary nozzle 31 as well as via the main pipe 2. This gives rise to an additional gas flow which increases the power of the gas burner 1. The open position of the solenoid valve 12 is also time-limited in this embodiment. At the expiration of a preset time interval that is also stored in the control unit, the control unit 22 automatically closes the solenoid valve 12 in order to turn off the additional gas flow through the auxiliary pipe 30.
In contrast to the previously described exemplary embodiments, gas is admitted to the valve 40, even in the normal operation of the gas burner 1 of
Since the preceding arrangements that have been described in detail involve exemplary embodiments, they can be modified to a great extent by the expert in the usual manner without departing from the scope of the invention. Furthermore, the use of the indefinite article “a” does not preclude the relevant features from also existing in the plural.
Number | Date | Country | Kind |
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05017744 | Aug 2005 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/064934 | 8/2/2006 | WO | 00 | 2/15/2008 |
Publishing Document | Publishing Date | Country | Kind |
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WO2007/020189 | 2/22/2007 | WO | A |
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20080216810 A1 | Sep 2008 | US |