EP2495498A1 - Gas cooker and method for operating same - Google Patents

Abstract

The gas cooking appliance has a cooking plate (109a) with a gas burner (127a) and a switching unit is arranged in a cooking plate. A switching unit has a switch and an elongate pushing rod (135) for switching operation. The pushing rod is arranged in an area of the gas burner of the cooking plate and has a pushing rod lower side and pushing rod upper side. The pushing rod is moved by placing a cooking vessel (147) on the cooking plate around a moving magnitude (Hmech) along an actuating path. An independent claim is also included for a method for operating a gas cooking appliance.

Description

Field of application and state of the art

The invention relates to a gas cooking appliance with at least one gas hob with a gas burner and a method for operating such a gas cooking appliance.

From the JP 2006-097973 A is a generic gas cooking appliance known with several gas hobs, each having a gas burner and which is also associated with a switching device. Depending on a switching state of the switching device, a gas supply to the associated gas burner can be blocked or opened and the ignition can be released to the gas burner. The switching state of the switching device is dependent on whether a cooking vessel is placed on the associated gas hob or not. If there is no cooking vessel on the gas hob, the gas supply to the gas burner is blocked and the ignition of the gas burner is not possible. If, however, a cooking vessel is set up, the gas supply can be released and the gas burner can be ignited. To change the switching state, a plunger mechanism is provided with a plunger, which can be moved by placing the cooking vessel on the gas hob along a Betätigungsweges down. If the pestle is in a lower position along the actuation path when the cooking vessel is set up, a switch is actuated and the gas supply to the gas burner of the cooking place, on which the cooking vessel is arranged, is released. If the cooking vessel is removed from the gas hob, the plunger moves back up to a rest position in which a plunger top is located above a cooking vessel footprint.

Task and solution

The object underlying the invention is to provide an aforementioned gas cooking appliance and a method for operating such a gas cooking appliance with which problems of the prior art can be eliminated and in particular a required amount of movement of the plunger along the actuating path for changing the switching state can be reduced ,

This object is achieved by a gas cooking appliance with the features of claim 1 and by a method having the features of claim 13. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. Some of the following features and properties apply to both the sensor element device and the method. They are described in part only once, but apply independently for both the gas cooker and the process. The wording of the claims is incorporated herein by express reference.

An inventive gas cooking appliance has at least one gas hob with a gas burner and at least one switching device associated with the gas hob. In this case, the switching device has a switch and an elongate plunger for switch operation. The straight plunger is arranged in the region of the gas burner of the associated gas hob and has a plunger bottom and a plunger top. It is movable in its longitudinal direction along a Betätigungsweges. The plunger is further configured to actuate the switch when the plunger bottom is in a switch actuation position along the actuation path, and operatively connected to the switch.

A position of the plunger bottom along the actuation path can be achieved by moving the entire plunger along this actuation path and / or by changing a plunger length while the position is unchanged the plunger top are changed. The ram length is determined by the distance between the plunger bottom and the plunger top. The plunger can be moved by placing a cooking vessel on the gas hob by a first amount of movement along the actuation path. In this case, the plunger is moved starting from a rest position by a mechanically generated amount. In this case, the plunger is in the rest position when its plunger top is located above a cooking vessel footprint when the plunger thus protrudes with its plunger top to a supernatant above the cooking vessel footprint. The plunger is thus moved mechanically around this supernatant.

As a result of heating the plunger from a quiescent temperature to a predefined switching temperature, the plunger bottom is moved by a length increase by a second amount of movement along the actuation path. If the plunger is arranged in the region of the gas burner and thus in its heat zone, preferably at a distance of less than 10 cm from the gas burner, it can be heated to the predefined switching temperature by the operation of the gas burner. The quiescent temperature is exhibited by the plunger when not heated by the operation of the gas burner, and is usually at room temperature. In a gas cooking appliance according to the invention, the switch operating position is present when the plunger bottom has been moved together from the rest position by the first amount of movement and the second amount of movement together. This means that the switch is not already triggered by the erection of the cooking vessel, which mechanically causes a movement of the plunger along the actuation path, but additionally a thermally generated increase in length of the plunger is required by the second amount of movement. Likewise, the thermally generated increase in length of the plunger alone is advantageously not enough for the switch operation.

In a further development of the invention, the gas cooking appliance has a control device and a gas valve, which can be controlled by the control device, wherein the control device is designed to control the gas valve in response to a switching state of the switch. In such a gas cooking appliance, it is possible to open or block a gas supply to the gas burner by means of the gas valve as a function of the switching state. It is alternatively or additionally possible, depending on the switching state of the switch to control a control valve and to change the gas supply to the gas burner, preferably to reduce. If there is no cooking vessel on the gas hob, the plunger bottom is not in the switch actuation position and the switch is in an idle state, so that the gas supply to the gas burner of this hotplate can be blocked or reduced. However, to enable the operation of the switch at all, it is necessary to ignite and operate the gas burner at least for a predefined, limited time after setting up the cooking vessel once, for example, for five to ten seconds. If the required predefined increase in length is not effected within this predefined limited time as a result of the heating of the plunger in order to reach the switch operating position with the plunger underside, the gas supply can be reduced or blocked. Preferably, this predefined time is dimensioned so that the plunger without setting up a cooking vessel on the gas hob within this time can not heat to the switching temperature and thus does not reach the required length increase. But if a cooking vessel placed on the gas hob, a radiation of the gas burner outgoing heat is prevented upwards through the bottom of the pot or cooking vessel by a heat zone or bubble forms, so that the plunger can reach the required switching temperature.

In a preferred embodiment of the invention, the plunger has a shape-memory metal or a thermo-bimetallic spring, in particular in the region of the plunger bottom. The plunger can also be a thermo-bimetallic spring have on its plunger bottom and in another area a shape memory metal.

For the purposes of this application, thermal bimetals are understood as meaning layer composite materials which have at least two components with different coefficients of expansion. A heating of the bimetallic strip leads to the fact that one component expands more than the other, so that a temperature-dependent curvature of the bimetallic strip is formed.

In a preferred embodiment, the first mechanical movement amount is a maximum of 3 mm to 5 mm. By dividing the total amount of movement into a mechanical component and a thermal component of the mechanical proportion of the total amount of movement can be significantly reduced. This is particularly advantageous when moving the cooking vessel over different gas hobs or cooking zones away. A plunger, which requires a much larger amount of mechanical movement to operate the switch, would hinder such movement of the cooking vessel.

In a further development of the invention, the switch actuating device for transmitting the amount of movement of the plunger bottom to the switch on a lever with two free lever ends. The lever between the two lever ends is rotatably mounted. One of the two lever ends facing the plunger so that the lever can be actuated by moving the plunger and / or the plunger bottom along the actuation path. In this case, the plunger facing the first lever end is movable in the same direction as the plunger and consequently the second lever end in the opposite direction.

In a further development of the invention, in a region of the second lever end, that is, the lever end remote from the plunger, at least attached a puller wire which is connected to the switch to transmit the movement of the plunger or the plunger bottom via the lever to the switch and to actuate this, when the plunger bottom is in the switch operating position. By means of the lever and the pull wire, a pressure movement of the plunger can be converted into a pulling movement. By means of the pull wire, the pulling movement can then be easily transmitted over a greater distance within the gas cooking appliance to the switch. This allows the arrangement of the switch outside the heat zone of the gas burner, which brings significant benefits. Also, a translation or a reduction is possible by respective design of the lever or the arrangement of its rotatable mounting.

In an advantageous embodiment, the pull wire consists at least in sections of a shape memory metal. Preferably, the pull wire is completely made of a shape memory metal. It can also be advantageously a so-called super-elastic pull wire. In the context of this application, shape-memory metals, which are also referred to as shape memory alloys, are alloys which have a temperature-dependent stress-strain characteristic. Usually, shape-memory metals have a martensitic structure at lower temperatures and, at higher temperatures, above a transition temperature, an austenitic structure. Both phases differ very strongly in their properties. In the austenitic state, these alloys generally have stress-strain characteristics similar to those of conventional alloys. In the martensitic state, a change in shape or an elongation initially takes place only by a displacement of the highly mobile twin boundaries and not as usual by dislocation movements, so that high strains can already be achieved for small stresses. This means that even with low tensile forces a relatively large change in length can be effected. This effect is also called a superelastic effect. Known shape memory alloys include NiTi, CuZnAl and CuAlNi.

The use of a pull wire made of a shape-memory metal as a transmission means or actuator for transmitting a movement of the lever to the switch has the advantage that even with small forces or deflections a sufficient change in length or sufficient pulling action can be achieved for switch operation , This can also be transmitted over a certain distance to the remote switch. Furthermore, the friction, in particular at deflections, can be reduced.

In an advantageous embodiment, the switch is arranged in an area outside the heat zone of the gas burner, preferably with at least 10 cm to 15 cm distance to the gas burner.

In a further development of the invention, the plunger top is formed by a rotatably mounted rolling elements, preferably by a ball. In particular, the plunger has a ball rotatably mounted in all three directions in space on its plunger top. As a result, the movement of the cooking vessel over several cooking zones away from one gas hob to the next can be improved.

In a further development of the invention, the plunger has a temperature sensor for detecting a cooking vessel bottom temperature of the cooking vessel erected on the gas hob. In this case, the temperature sensor is preferably arranged on the plunger upper side and contacts a cooking vessel bottom of a cooking vessel erected on the gas hob.

In one development of the invention, the gas cooking appliance has a sinking device by means of which the plunger and / or the entire switching device is at least partially, preferably completely, retractable. So it can be stowed almost completely, for example, optical Reasons or for easier cleanability. In this case, the sinking device is in particular designed so that the plunger experiences no movement along the actuation path when sinking. Advantageously, a lock can be triggered by the sinking of the plunger to block the gas supply to the gas burner.

• Aufstellen eines Kochgefäßes auf die Gaskochstelle,
• Zünden des Gasbrenners der Gaskochstelle und Öffnen des Gasventils zum Gasbrenner für eine vordefinierte begrenzte Zeit,
• Prüfen, ob innerhalb der vordefinierten Zeit der Schalter betätigt worden ist und
• Öffnen des Gasventils für die dauerhafte Gaszufuhr zum Gasbrenner, falls der Schalter innerhalb der vordefinierten Zeit betätigt worden ist, andernfalls Sperren der Gaszufuhr zum Gasbrenner.

An inventive method for operating such a gas cooking appliance with a control device and a gas valve for controlling a gas supply to the gas burner comprises the following steps:

• Placing a cooking vessel on the gas hob,
• Igniting the gas burner of the gas hob and opening the gas valve to the gas burner for a predefined limited time,
• Check if the switch has been operated within the predefined time and
• Opening the gas valve for permanent gas supply to the gas burner, if the switch has been operated within the predefined time, otherwise blocking the gas supply to the gas burner.

In an advantageous embodiment, the gas supply can be disabled after the limited predefined time, when the cooking vessel is removed from the gas hob or has been removed, so that the plunger has moved back to the rest position by the first amount of movement.

In one embodiment of the invention, a lighting of a control element is turned on to indicate to an operator, for which gas hob, the gas supply is permanently enabled when the switch is actuated. For this purpose, the gas cooking appliance has at least one illuminated control element assigned to the gas hob. This lighting of the control element can be activated in dependence on the position of the plunger bottom along the actuating path.

In one embodiment of the invention, the lighting of the control element is turned on when the plunger bottom is in a position along the actuation path in which a current total amount of movement of the plunger bottom is equal to or greater than the rest position by setting up a cooking vessel can be generated on the gas hob first movement amount.

In a further development of the invention, the gas burner is turned off only when the plunger bottom is longer than a predefined Wiederzündzeit in the position along the actuating travel, in which the current total amount of movement of the plunger bottom relative to the rest position less than the total amount of movement of Switch actuation position is and within this Wiederzündzeit no confirmation input of the operator has been made. This reignition time can be about 20 to 30 seconds.

In an advantageous embodiment, the cooking vessel bottom temperature is detected and the gas supply to the gas burner blocked when the cooking vessel bottom temperature has reached a critical temperature and / or a characteristic for a selected cooking process predefined temperature.

These and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

ein Ausführungsbeispiel eines erfindungsgemäßen Gaskochgerätes in Draufsicht,

Fig. 2

einen Schnitt entlang der Schnittebene A-A' ohne ein auf der Gaskochstelle angeordnetes Kochgefäß,

Fig. 3

einen Schnitt durch das Gaskochgerät entlang der Schnittebene A-A' wie in Fig. 2 mit einem auf die Gaskochstelle aufgestellten Kochgefäß und

Fig. 4

eine Schnittdarstellung entlang der Schnittebene A-A' mit versenktem Stößel.

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. The embodiments shown in the individual figures have some features that do not have the other illustrated embodiments of the invention, however, which can be combined with each other without departing from the scope of the invention. In the drawings show:

Fig. 1

An embodiment of a gas cooking appliance according to the invention in plan view,

Fig. 2

a section along the sectional plane AA 'without a cooking vessel arranged on the gas hob,

Fig. 3

a section through the gas cooking appliance along the sectional plane AA 'as in Fig. 2 with a cooking vessel set up on the gas hob and

Fig. 4

a sectional view along the cutting plane AA 'with recessed plunger.

Detailed description of the embodiments

Fig. 1 shows an embodiment of a gas cooking appliance 100 according to the invention with a plurality of gas wells 109a-c, each gas hob 109a-c having a gas burner, not shown here. The gas supply to the respective gas burners via corresponding gas supply lines and can each be controlled or regulated by means of a control valve as a gas valve for the respective gas burner for adjusting a discharged burner power. Exemplary is in Fig. 1 the gas supply line 103a to the gas hob 109a shown with a check valve 105a and a control valve 107a. Accordingly, the gas supply of the other gas hobs 109b and 109c. Furthermore, each gas hob 109a-c is associated with a switching device only partially shown here, which, inter alia, a plunger 135 and for each gas hob 109a-c has a switch 114a-c, see Fig. 2 ,

By means of cable pulls 111a-c, a movement of the plunger 135 can be transmitted to the associated switch 114a-c for each gas hob. The switches 114a-c are advantageously microswitches and connected to the control device of the gas cooking appliance. The switches 114a-c are preferably located outside a heating zone of the respective gas burners of the gas cooking zones 109a-c or within the control device. The gas cooking appliance further comprises a controller 113 to control the shut-off and control valves of the individual gas hobs 109a-c to set a desired gas flow rate to the gas burner or to shut off the gas supply to the gas burner.

The gas cooking appliance 100 also has operating elements 115 for setting a desired burner output of the respectively associated gas cooking points 109a-c.

Fig. 2 shows by way of example a section along the sectional plane AA 'in the region of the gas hob 109a. The same applies to the other gas hobs 109b and 109c. The gas hob 109a has a pot carrier 125 for setting up a cooking vessel on the gas hob 109a. In the center of the gas hob 109a is a gas burner 127a, in the center of which in turn a plunger mechanism 131 with the plunger 135 is arranged. However, the plunger mechanism 131 can also be arranged laterally on the gas burner or in another position in the region of the gas burner. The pot carrier 125 and the gas burner 127a and a part of the plunger mechanism 131 are located above a hob surface 123, while the other part of the plunger mechanism 131 and the cable 111 ac are 111 in the area below the hob surface 123.

Here, the plunger 135 is shown in a rest position in which it protrudes with its plunger top up on the cooking vessel footprint 129 by a first _{amount of} movement H _mech or a mechanically generated stroke. The plunger 135 is vertically displaceable within a cylindrical housing 133 along a Betätigungsweges. If a cooking vessel is placed on the gas hob 109, then the plunger moves downwards by the first amount of movement H _mech or the mechanically producible stroke. However, this first _{amount of} movement H _mech is not sufficient to move a lever 137 sufficiently far, which serves to transmit a plunger movement to the switch 114 a, not shown here. The lever 137 has a first free end of the lever 137a and a second free end of the lever 137b and is rotatably mounted about an axis of rotation 139 perpendicular to the plane of the drawing. In order to move the lever 137 sufficiently far, in addition to said first amount of movement H _mech, a second amount of movement H is _thermally required of a plunger bottom along the actuation path, see Fig. 3 , A position of the plunger bottom can be changed not only by moving the entire plunger 135 along the actuating path, but also by an increase in length of the plunger in the fixed position of the plunger top.

In the rest position or in a quiescent temperature, which corresponds to the ambient temperature, the plunger has a plunger length L ₀ , which is determined by the distance of the plunger top to plunger bottom. If the plunger 135 is heated from a quiescent temperature to a predefined switching temperature, the length of the plunger 135 increases starting from the length L ₀ . In this case, the plunger on the plunger length L ₁ , if he has the predefined switching temperature, see Fig. 3 , The heating of the plunger 135 takes place during operation of the gas burner 127a. If the plunger 135, as shown in this exemplary embodiment, is arranged in the region of a heat zone of the gas burner 127a, ie closer than 10 cm to the gas burner 127a, then it heats up very rapidly. So in a short time starting from a rest temperature reaches the predefined switching temperature and thus the required increase in length to achieve a switch operating position of the plunger bottom. Then, the switch 114a is actuated due to the sufficient overall movement of the plunger bottom, as will be explained below.

Fig. 3 shows a section through the gas cooking appliance along the sectional plane AA 'in the region of the gas hob 109a according to Fig. 2 but with a cooking vessel 147 set up on the gas hob 109a. The cooking vessel 147 moves the plunger 135 vertically down the actuating travel within the cylindrical housing 133 by the first _{amount of} movement H _mech . If the gas burner 127a is then ignited, heating of the plunger 135 occurs as a result of the heat released by the burner and stowed under the cooking vessel 147, so that the aforementioned increase in length of the plunger 135 is effected by the plunger length L ₀ on the plunger length L ₁ . Has the plunger 135 reaches the predefined switching temperature, it has a length L ₁ and the plunger bottom was moved by the increase in length additionally by a second amount of movement H _thermally along the actuation path downwards. Thus, the plunger bottom has been _thermally moved a total of the first mechanically generated amount of movement H _mech plus the second thermally generated amount of movement H and is thus in the switch operating position.

This total amount of movement results in movement of the lever 137 such that the lever end 137b facing the plunger 135 is pushed down by the plunger 135 and the other free end of the lever 137a is moved upwardly accordingly. At the free end of the lever 137a of the cable 111a is attached, which is connected to the micro-switch 114a. In the illustrated embodiment, the cable 111a comprises a pull wire 112a, which consists of a shape memory alloy or a shape memory metal and is guided in a shell. Preferably, the sheath and this super-elastic pull wire 112a coordinated so that the friction of the two parts is minimized to each other. By the lever 137 so the plunger movement is transmitted to the switch 114a. When the plunger bottom is in the switch operating position, the pulling force applied to the puller wire 112a and the movement are sufficient to actuate the microswitch 114a.

When the cooking vessel 147 is removed from the gas hob 109a, a restoring force of a return spring 141 causes the plunger 135 to be moved upward again by the first _{amount of} movement H _mech . When the plunger 135 cools again or cools down to the quiescent temperature, its also decreases again to the initial length or the quiescent length L ₀ . The plunger bottom is then no longer in the switch operating position. The lever 137 has moved back to its original position and thus the switch 114a is no longer actuated. Depending on the dimensions of the return spring 141 and selection of the plunger material, the movement amounts H _mech and H are _thermally adjustable to different powers of the gas burner and allow an adjustment.

In Fig. 4 is also a section through the gas hob 109 a along the sectional plane AA 'shown, however, the plunger mechanism is sunk in this representation or lowered below the cooking vessel footprint 129. For this purpose, the gas cooking appliance 100 on a sinking device, which makes it possible to lower the plunger mechanism at least below the cooking vessel footprint 129. In the illustrated embodiment, the plunger mechanism may be lowered even further below the gas burner 127a. The sinking device is designed so that the plunger 135 is not moved along the actuation path when sinking, so that the lever 137 is also not moved and no switch actuation of the switch 114a is triggered via the puller wire 112a.

In a method according to the invention for operating the gas cooking appliance 100, first a cooking vessel 147 is placed on the gas hob 109a. As a result, the plunger 135 is moved downward along the actuation path by the first _{amount of} movement H _mech . By means of a control device 113, the gas burner 127a of the gas hob 109a can be ignited and the gas supply to the gas burner 127a can be released for a limited, predefined time, for example five seconds to fifteen seconds. When the gas burner 127a is in operation, the plunger 135 heats up and its plunger length increases. Reaches the plunger within the predefined, limited time the predefined switching temperature, and thus the predefined length L _1, the tappet bottom is thermally conditioned moved by the second moving amount H _thermally along the actuating path downwardly and then is located in the switch operating position. Thus, if the switch 114a is operated within the predefined limited time, the gas supply to the gas burner 127a may be permanently opened and left open. Otherwise, by means of the shut-off valve 103a, which is preferably a solenoid valve, or the control valve 107a, the gas supply to the gas burner 127a can be reduced or completely blocked.

When the cooking vessel 147 is removed from the gas hob 109a, the plunger 135 moves upward again by the first mechanically generated amount of movement H _mech , which is sufficient to change the switching state of the switch 114a. Then, by means of the control device 113, the gas supply to the gas burner 127a can be correspondingly reduced or blocked, so that the burner output is reduced and the gas burner 127a is operated only with a small flame. Is the plunger bottom longer than a predefined Wiederzündzeit at the position along the Betätigungsweges in which the current total amount of movement of the plunger bottom relative to the rest position is less than the total _{amount of} movement H _mech + H _{thermal of} the switch operating position, and is carried out within this Reignition no confirming input from the operator, the gas supply to the gas burner 127a may be completely disabled.

Depending on the switching state of the switch 114a, an illumination of an associated operating element 115 of the gas hob 109a can be switched on, for example if the gas supply to the gas hob 109a is permanently enabled to indicate to an operator for which gas hob the gas supply is permanently enabled. It is also possible that the illumination of the control element 115 of the associated gas hob 109 a is already turned on when the plunger bottom is in a position along the actuation path whose current total amount of movement from the rest position is equal to or greater than by setting up a Cooking vessel on the hob producible first movement _amount H _mech .

In the in the Fig. 2 to 4 illustrated embodiment, the plunger 135 at its plunger top in a rotationally mounted in all three directions in space ball 135a as rolling elements, so that a displacement of the cooking vessel on the gas hob 109a or between multiple gas wells 109a-c or cooking zones is easily possible ,

The illustrated ram also has areas 135b, 135c of different material. In the embodiment shown, the lower portion 135c of the plunger 135 consists of a shape-memory metal or a shape memory alloy. The plunger 135 can also consist entirely of a shape-memory metal or only in its upper region 135b or 135b and 135a. In an alternative embodiment not shown here, the plunger 135 has a thermo-bimetallic spring in its lower region 135c.

In addition to the plunger 135, the plunger mechanism 131 also has a thermocouple 143 as a temperature sensor to a cooking pot bottom temperature capture. The gas supply to the gas burner 127a may be disabled when the cooking vessel bottom temperature has reached a critical temperature and / or a predefined temperature characteristic of a selected cooking process. In this way it is possible, with appropriate choice of the predefined temperature to avoid oil fires or to significantly reduce the risk of oil fires. By the voltage applied to the underside of the cooking vessel plunger 135, an advantageous attachment of a temperature sensor can be achieved.

With the gas cooking appliance 100 according to the invention also cooking vessels 147 can be easily moved in the gas hob 109a or over several gas hobs 109a-c or cooking zones and yet the safety of a conventional gas cooking appliance without a plunger mechanism for pot detection can be significantly increased. Compared with generic gas cooking appliances with a plunger mechanism for pot detection or as a switching device gas cooking appliance according to the invention has the advantage that the required amount of mechanical movement is significantly reduced, which makes it possible to move cooking vessels 147 in the first place. The reduction of the mechanical amount of movement takes place in that the missing mechanical amount of movement or stroke is generated thermally. In particular, by the use of a thermo-bimetallic spring or a shape-memory metal in the region of the plunger bottom can be achieved in a simple manner a thermally generated amount of movement.

Claims (15)

Gas cooking appliance (100) having at least one gas hob (109a-c) with a gas burner (127a) and at least one switching device associated with the gas hob (109a-c), - wherein the switching means comprises a switch (114a-c) and an elongate plunger (135) for switch operation, wherein the plunger (135) in the region of the gas burner (127a) of the associated gas hob (109a-c) is arranged, a plunger bottom and has a plunger top and is movable in its longitudinal direction along a Betätigungsweges, wherein a position of the plunger bottom along the actuating path is variable by moving the entire plunger (135) along the actuating path and / or by changing a plunger length with unchanged position of the plunger top, - wherein the plunger by setting up a cooking vessel (147) on the gas hob (109a-c) by a first amount of movement (H _mech ) along the actuation path is movable, and - wherein the plunger bottom is movable due to heating of the plunger to a predefined switching temperature, starting from a rest temperature by an increase in length by a second amount of movement (H _thermally ) along the actuation path, - The plunger bottom is in a switch operating position when it has been moved together from the rest position by the first _{amount of} movement (H _mech ) and the second _{amount of} movement (H _thermally ) together. Gas cooking appliance (100) according to claim 1, characterized in that the gas cooking appliance (100) comprises a control device (113) and a gas valve (105a, 107a), wherein the gas valve (105a, 107a) is controllable by the control device (113) and the control device (113) is adapted to control the gas valve (105a, 107a) in response to a switching state of the switch (114a-c). Gas cooking appliance (100) according to claim 1 or 2, characterized in that the plunger (135) has a shape-memory metal or a bimetallic spring, in particular in the region (135c) of the plunger bottom. Gas cooking appliance (100) according to one of the preceding claims, characterized in that the first amount of movement (H _mech ) is a maximum of 5 mm, preferably a maximum of 3 mm. Gas cooking apparatus (100) according to any one of the preceding claims, characterized in that the switch actuating means for transmitting the amount of movement of the plunger bottom to the switch (114a) has a lever (137) with two free lever ends (137a, 137b), wherein he is rotatably mounted between the two lever ends (137a, 137b) and a lever end (137b) facing the plunger (135) is such that the lever (137) by moving the plunger (135) and / or the plunger -Unterseite is operable along the Betätigungsweges, wherein the plunger (135) facing the lever end (137b) is movable in the same direction as the plunger (135) and consequently the second lever end (137a) is movable in the opposite direction , Gas cooking appliance (100) according to claim 5, characterized in that in a region of the second lever end (137a) a puller wire (112a) is attached, which is connected to the switch (114a-c) to control the movement of the plunger (135 ) or the plunger bottom via the lever (137) to the switch and to actuate it when the plunger bottom is in the switch operating position, in particular the puller wire (112 a) at least partially made of a shape-memory metal, preferably completely. Gas cooking appliance (100) according to one of the preceding claims, characterized in that the switch (114a-c) is arranged in a region outside the heat zone of the gas burner (127a), preferably at least 10 cm to 15 cm distance therefrom. Gas cooking apparatus (100) according to any one of the preceding claims, characterized in that the plunger top is formed by a rotatably mounted rolling elements (135a), preferably by a ball (135a), in particular by a three-axis in space rotatably mounted ball ( 135a). Gas cooking appliance (100) according to any one of the preceding claims, characterized in that the plunger (135) has a temperature sensor for detecting a cooking vessel bottom temperature of a cooking vessel (147) mounted on the gas hob (109a-c), wherein preferably the temperature sensor on the plunger top is arranged. Gas cooking appliance (100) according to one of the preceding claims, characterized by a sinking device by means of which the plunger (135) at least partially, in particular completely, retractable, wherein preferably the sinking device is formed so that the plunger (135) during the sinking no movement along the actuation path, wherein in particular the sinking of the plunger (135) triggers a lock for blocking the gas supply to the gas burner (127a). Gas cooking appliance (100) according to one of the preceding claims, characterized in that the gas cooking appliance (100) one of the gas hob (109a-c) associated, illuminable control element (115), wherein an illumination of the operating element (115) is activatable in dependence on the position of the plunger bottom along the actuating path. A method of operating a gas cooking apparatus (100) according to any one of claims 1 to 11, comprising control means (113) and gas valve (105a; 107a) for controlling gas supply to the gas burner (127a), the gas valve (105a; 107a) being controlled by the control means (113) is controllable and the control device (113) is adapted to control the gas valve (105a, 107a) in dependence on a switching state of the switch (114a-c), characterized by the following steps: Setting up a cooking vessel (147) on the gas hob (109a-c), Igniting the gas burner (127a) of the gas hob (1 09a-c) and opening the gas valve (105a; 107a) and thereby opening the gas supply to the gas burner (127a) for a limited, predefined time; Checking whether the switch (114a-c) has been actuated within the course of the predefined time, and - Opening the gas valve (105a, 107a) for the permanent gas supply to the gas burner (127a), if the switch (114a-c) has been actuated in time, otherwise blocking the gas supply to the gas burner (127a). A method according to claim 12, characterized in that illumination of a control element (115) is turned on to indicate to an operator for which gas hob (109a-c) the gas supply is permanently enabled when the switch (114a-c) is actuated, the gas cooking appliance (100) for this purpose has at least one illuminable operating element (115) associated with the gas cooking location (109a-c), wherein preferably the lighting of the operating element (115) of the associated gas cooking location (109a-c) is switched on is when the plunger bottom is in a position along the Betätigungsweges in which a current total movement amount of the plunger bottom is equal to or greater than the rest position by setting the cooking vessel (147) on the gas hob (109a-c ) producible first amount of movement (H _mech ). A method according to claim 12 or 13, characterized in that a burner power of the gas burner (127a) is reduced or the gas burner (127a) is switched off by blocking the gas supply when the plunger bottom is in a position along the actuation path, in which actual total amount of movement of the plunger bottom relative to the rest position is less than the total _{amount of} movement (H _mech + H _thermal ) of the plunger bottom in the switch operating position. A method according to claim 14, characterized in that the gas burner (127a) is turned off only when the plunger bottom is longer than a predefined Wiederzündzeit in the position along the actuation path in which the current total amount of movement of the plunger bottom relative to the Rest position is less than the total _{amount of} movement (H _mech + H _thermal ) of the switch operating position and within this Wiederzündzeit no confirmation input of the operator has taken place.

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