WO2020043437A1

WO2020043437A1 - Microwave appliance and method for securing a microwave appliance against microwave radiation exiting from a treatment space

Info

Publication number: WO2020043437A1
Application number: PCT/EP2019/071069
Authority: WO
Inventors: Max STIEF; Peter Guggenberger; Matthias Vogt
Original assignee: BSH Hausgeräte GmbH
Priority date: 2018-08-27
Filing date: 2019-08-06
Publication date: 2020-03-05
Also published as: DE102018214392A1

Abstract

The invention relates to a microwave appliance (1) having: a treatment space (2) with a loading opening (3), which can be closed by means of a microwave-tight door (4); a microwave device (6, 7) with a microwave generator (6), the microwave device being designed to radiate microwaves generated by the microwave generator into the treatment space; and a first safety switch (11), which is switchable depending on a first, smaller target switch angle (SSW1) of the door; and a second safety switch (13), which is switchable depending on a second, larger target switch angle (SSW2) of the door. The microwave generator can be activated only if the safety switches (11, 13) are switched during the transfer from an open position of the door into a closed position in accordance with the intended order of their target switch angles (SSW2, SSW1). The first safety switch is an openly accessible switch, and the second safety switch is a switch that is hidden from the user. The invention also relates to a method for securing a microwave appliance against microwave radiation exiting from a treatment space. The invention can be particularly advantageously applied to household microwave appliances.

Description

Microwave device and method for securing a microwave device against microwave radiation emerging from a treatment room

The invention relates to a microwave device, comprising a treatment room with a loading opening, which can be closed by means of a microwave-proof door, a microwave device with a microwave generator, which microwave device is set up to radiate microwaves generated by the microwave generator into the treatment room, and a first safety switch , which can be switched as a function of a first, smaller setpoint switching angle of the door and a second safety switch which can be switched as a function of a second, larger setpoint switching angle of the door, the microwave generator being able to be activated only when the safety switch is in transition from an open position of the door be switched to a closed position according to the intended sequence of their desired switching angle. The invention also relates to a method for securing a microwave device against microwave radiation emerging from a treatment room, in which, when a microwave-tight door is closed, a microwave generator is only activated or is ready for operation when first a second safety switch and then a first safety switch ter is switched. The invention is particularly advantageously applicable to household microwave devices.

US 2014197161 A1 discloses a door switch device for a microwave oven which deactivates the microwave system without a plunger being immersed. For this purpose, the microwave oven has several electrical hinge switches that are activated in a specific order. This is achieved in that a first miniature snap switch is equipped with an activation arm, while a second switch has no activation arm. When the door is closed, the first switch equipped with the activation arm is always activated first, followed by the switch without the activation arm. The switches are electrically connected, activation of the first switch activating the second switch, which indicates that the microwave door is closed properly. The disadvantage, however, is the lack of accuracy of the hinge switches, which can lead to high leakage rate values for microwaves. In particular, the accuracy of the hinge switch is highly dependent on a stiffness of the door and door connection system (hinges, lever mechanism in the switching system, etc.). Appropriately robust construction and rigid materials can improve accuracy, but this is expensive, time-consuming and still too imprecise.

EP 2 146 549 A1 discloses a safety device for a cooking device with a microwave function. The safety device comprises at least one electrically actuable closing switch which interrupts the power supply of a microwave source in an open position and can be switched to a closed position by a closing signal. The safety device further comprises a first and a second changeover switch, which are coupled to a door of the cooking appliance in such a way that they are normally in a first switch position when the door is open and in a second switch position when the door is closed. The first and second changeover switches are connected in such a way that they pass the closing signal to the closing switch when they are in the second switching position and the closing signal is not passed to the closing switch when the second changeover switch is in the first switching position. Finally, means are provided which are suitable for permanently interrupting the power supply to the microwave source if the closing switch is still closed after a predetermined delay time after the first switch has been switched to the first position. It is disadvantageous here that if the door is closed slowly, the device fuse can trigger unintentionally or software incorrectly detects a faulty switch.

DE 195 04 574 A1 discloses an oven with a cooking space, which is equipped with radiant heaters and / or a microwave generator for cooking the food. The appliance door is hinged to the appliance housing in a known manner and can be pivoted about a horizontal axis. A locking and locking device consists of two independently operating circuits with several switches, the associated spring-loaded control elements. Two parts designed as keys are located on the door and engage in the slot-like openings in the locking plate. The locking device always allows free access to the cooking space in all conventional operating modes and in the event of a power failure. However, microwave generation only begins after the appliance door has been locked and it is not possible to open the door without interrupting this operating mode. The Ver- Locking device is located on a locking plate, in which an independent circuit is arranged on each side. A circuit can only be activated if the microwave mode is set. This has a specially shaped control element for a switch, which establishes a connection from a plunger armature of a coil to the switch and at the same time locks the device door. A disadvantage of such a locking concept is that an opening button must always be pressed to open the door. In all cooking programs it is not possible to open the door before pressing this button. In addition, there is no protruding door tappet in the present case, but the key system is clearly visible, which can be disadvantageous in terms of visual appearance.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to reliably prevent the escape of microwave radiation from a treatment room of a household microwave device in a structurally particularly simple manner, even if at least At least one openly accessible safety switch should not be switched as intended, in particular if the door has been manipulated specifically and / or if the appliance door is opened abruptly.

This object is achieved in accordance with the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, the description and the drawings.

The object is achieved by a microwave device, comprising

a treatment room with a loading opening, which can be closed by means of a micro-tight door,

a microwave device with a microwave generator, which microwave device is set up to radiate microwaves generated by the microwave generator into the treatment room,

- A first switch (hereinafter referred to as "safety switch" without restriction of generality), which can be switched as a function of a first, smaller target switching angle of the door and a second switch (hereinafter referred to as "safety switch" without restriction of generality), which is switchable depending on a second, larger target switching angle of the door, in which

the microwave generator can only be activated if the safety switches are switched during the transition from an open position of the door to a closed position in accordance with the normal or intended sequence of their desired switching angles,

- The first safety switch is an openly accessible switch and

- The second safety switch is a switch hidden for a user.

This microwave device has the advantage that it is reliably prevented in a particularly cost-effective manner that the microwave generator can be activated when the door is open. In order to be able to activate the microwave generator, the second, hidden safety switch in front of the first, openly accessible safety switch must be actuated when the door closes. A "hidden" safety switch is not accessible to a user and therefore cannot be manipulated by a user or cannot be manipulated without effort, but is typically also considerably more difficult to adjust or adjust to an exact maintenance of a set switching angle when mounting than an openly accessible safety switch. In the present microwave device, use is made of the fact that the second safety switch does not have to meet high requirements for compliance with the second setpoint switching angle, but rather can switch within a relatively wide tolerance range around the second setpoint switching angle, as long as it only switches reliably in front of the first safety switch. The reason for this is that the second safety switch only serves to maintain the switching sequence for the first safety switch, but does not itself monitor any door opening angle of the door that is relevant in terms of safety. Because the second safety switch has to make its set switching angle comparatively imprecise, there is no need for complex adjustment, and the second safety switch can also be designed to be comparatively simple and inexpensive.

In contrast, due to its open accessibility, the safety switch can be precisely adjusted or set particularly easily. It can be used in particular to precisely monitor a safety-related setpoint switching angle of the door, for example whether it is so close to a door flange that no or practically no microwave radiation can escape through a gap between the flange and the door ("non-critical door opening area"), and indeed not when microwaves are radiated into the treatment room. The first safety switch can thus ensure in particular that the microwave generator can only be activated when the door opening angle is in the non-critical door opening area. Since the transition between the non-critical door opening area and a critical door opening area in which microwave radiation can emerge has only a small angular width, it is advantageous that the first safety switch can be precisely adjusted due to its structure to prevent microwaves from escaping to be able to prevent from the treatment room particularly reliably. This also prevents microwave radiation from escaping when the door is opened abruptly. The first safety switch can in particular be a "limit switch", the first setpoint switching angle of which represents the smallest setpoint switching angle of all the safety switches.

The combination of a hidden and openly accessible safety switch makes it possible to provide a particularly safe and reliable safety circuit for a microwave device that can be implemented inexpensively. In contrast, the use of two openly accessible safety switches is considerably more susceptible to manipulation by a user. The use of two hidden safety switches, on the other hand, only allows precise adherence to safety-relevant door opening angles if the installation effort is very high.

There is also the advantage that such a quick switching is possible that if the door is opened very quickly or abruptly, the microwave generator can be deactivated (e.g. switched off or switched off) before microwave radiation can escape from the treatment room.

Another advantage is that this switch concept can also be implemented without software evaluation or electronic switches and therefore does not require expensive PEC software.

Alternatively, the switching concept can also be implemented by using at least one electronic switch. Reaching the switching angle associated with the electronic switch (corresponding to a switching state) is monitored by software and, depending on this, an electrical switching element such as a relay or the like. switched. This has the advantage that the switching element is particularly versatile in the household Microwave device can be positioned and / or combinations and / or sequences of switching states of several electronic switches can be evaluated by software. The evaluation in turn advantageously enables a check and identification of certain malfunctions and / or protection against manipulation. For example, all options can be evaluated that include changing the sequence when the door is closed and / or opened or in the event of a failure or failure of at least one safety switch. These can then be assigned to a real case. In particular, it is advantageous that as many malfunctions and manipulation options as possible lead to a safe state, ie either to trigger a device fuse or at least to a non-operation of the microwave generator. Equally, it is advantageous if a random actuation of openly accessible safety switches does not lead to the triggering of the device fuse, etc.

The fact that the microwave generator can only be activated (eg energized) when the safety switches are switched during the transition from an open position of the door to a closed position in accordance with the intended sequence of their desired switching angles includes, in particular, that if possible only if the Switch the safety switch in accordance with the intended sequence of operations; microwave operation is made possible. The (switching) sequence includes in particular that when the door is closed, safety switches with a larger setpoint switching angle or nominal switching angle are switched in front of safety switches with a smaller setpoint switching angle.

A "switching angle" is understood in particular to mean a door opening angle of the door, upon reaching which a safety switch changes its switching state, e.g. from electrically conductive to electrically blocking, or vice versa. This can also be referred to as the safety switch having this switching angle. The safety switch can be adjusted to the door opening angle.

A safety switch can in particular be understood to be a switch by means of which the microwave generator can be activated or deactivated. The safety switch, in particular an openly accessible safety switch, can be "dominant" or "non-dominant". Under a dominant safety switch, which are understood to be a switch in which, if an error occurs on it, the microwave function or the microwave generator is either permanently or temporarily deactivated. This can happen, for example, by triggering a fuse or by disabling the microwave function in electronics.

It is a further development that the microwave device is a household microwave device. The microwave device can be an independent microwave device or can be a microwave combination device. The microwave combination device can, for example, be an oven with additional microwave functionality, possibly also with additional steam generation functionality, etc.

The fact that the loading opening can be closed by means of the microwave-proof door means in particular that when the door is closed, no microwave radiation can escape through the door or through a gap between the door and an associated door flange. For this, the door flange or the combination of door and door flange e.g. be designed as a lambda / 4 trap.

In addition to the microwave generator, the microwave device can have, for example, a wave guide which guides microwaves generated by the microwave generator in the direction of the treatment room, and / or a rotatable or stationary antenna, wobbler, etc. Microwave devices for household appliances are generally known and are therefore not described in more detail here.

The door opening angle of the door when the doors are closed is assumed to be 0 °. A target switching angle of a safety switch corresponds to a door opening angle of the door at which this safety switch is to switch. The fact that the second setpoint switching angle is larger than the first setpoint switching angle thus includes that the second safety switch switches at a larger door opening angle than the first safety switch. Under target conditions, when the door changes from an open state (in which the door opening angle is greater than the second target switching angle), the first switches the second safety switch and then the first safety switch, that is, according to the sequence or size of their target switching angles . The microwave generator can only be activated if this sequence is adhered to: if, for example, both safety switches are open in their normal state when the door is open, the second safety switch in front of the first safety switch is closed when the door is closed. Only this sequence of closing the safety switches leads to an activation or activation of the microwave generator for its operation. If the openly accessible first safety switch is set to its closed state by user manipulation (e.g. by covering it with adhesive tape or similar) or if it remains inadvertently stuck in its closed state, the first safety switch is already closed when the door is open while the door is open second safety switch is still open. When the door is closed, the switching sequence changes: the first safety switch is closed before the second safety switch. In this case, the microwave generator cannot be activated.

Activating the microwave generator can in particular be understood to mean that

However, the switching states of the safety switches associated with the open or closed door are not limited to an open / conductive or closed / blocking switching state. Thus, the second safety switch can generally switch from a first (open or closed) switching state to a second (closed or open) switching state when the door is closed, and analogously the first safety switch can generally switch from a first (open or closed) switching state when the door is closed change to a second (closed or open) switching state. The corresponding switching states of the two safety switches do not need to be the same: e.g. The first safety switch can be open or conductive when the door is open, while the second safety switch is closed or locking when the door is open.

The type of safety switch is also not restricted and can be mechanical switches (eg buttons, rockers etc.), magnetic switches, electrical switches (eg with a relay as switching element), electronic switches (eg with a transistor as switching element) etc. or Combinations of these include. The safety switches can be of the same or different types. In particular, at least openly accessible safety switches can be one that projects forward, in particular one that protrudes Have door flange guided, actuating element such as a plunger, etc., the movement of which is transferable to a switching element of the safety switch for switching it. Alternatively, at least one of the safety switches, in particular an openly accessible safety switch, can be designed as an electronic switch, the switching state of which is determined by software evaluation. In this case, it is advantageous if the associated software is PEC software.

It is an embodiment that the second, hidden safety switch is a switch that can be switched by the door hinge and the first, openly accessible safety switch is arranged in the region of an edge of a door flange opposite the door hinge. This has the advantage that a particularly compact and precisely switchable switch arrangement is provided. The second safety switch can be switched reliably. The hinge thus serves as an actuator for the second safety switch. The safety switch can e.g. be accommodated in the hinge or be arranged on an outside of the treatment room.

The first safety switch, on the other hand, is located at a position at which the door swings out particularly strongly when its door opening angle changes. As a result, the setpoint switching angle in the area of the first safety switch can be set particularly precisely. So is the door e.g. can be swiveled horizontally around its lower edge, the first safety switch is located on an upper edge of the door flange.

It is an embodiment that

- Between a first power supply line and a second power supply line of a microwave operating device for operating the microwave generator, the first safety switch and an overcurrent protection device are electrically connected in series,

- The second safety switch is electrically connected in parallel to the microwave operating device and electrically in series with the first safety switch and the overcurrent protection device, and

- When the door is closed, the first safety switch is turned on and the second safety switch is turned off. io

This has the advantage that the switch arrangement can be designed as a simple circuit of wired electrical components and e.g. there is no need for an electronic PEC circuit. However, this is not absolutely necessary and at least one electronic switch can also be used.

The microwave operating device can be the microwave generator itself or a component thereof (e.g. an inverter). Alternatively, the microwave operating device can be a circuit for selectively activating and deactivating the microwave generator, e.g. a relay, a main switch or similar

The overcurrent protection device can e.g. a fuse, an electronic fuse, or a circuit breaker.

When energized, the microwave operating device makes it possible to operate the microwave generator. The microwave operating device can e.g. an inverter or a high-voltage transformer of the microwave generator.

It is an embodiment that

the microwave device has a third, openly accessible safety switch and a first and a second relay,

the microwave operating device is arranged in series between the first relay and the second relay,

- The second safety switch is electrically connected in parallel to the microwave operating device, the first relay and the second relay and

- The third safety switch switches the first relay and the second relay so that the two relays are switched on when the door is closed.

Such a third safety switch achieves the advantage of galvanic isolation of the microwave operating device, in particular an inverter, when the door is opened so far that a set switching angle (hereinafter referred to as "third" set switching angle without restriction of the general unit) of the third Safety switch reached or exceeded. This provides additional security against microwaves escaping from the treatment room, since both the first and the second the third safety switch must be switched in order to be able to activate the microwave operating device.

It is an embodiment that a third setpoint switching angle of the third safety switch corresponds to the first setpoint switching angle of the first safety switch. This has the advantage that operation of the microwave generator is blocked independently of one another by the first safety switch and the third safety switch if the door is opened so far that microwaves could escape from the treatment room.

It is an embodiment that the third safety switch is arranged in the area of an edge of a door flange opposite the door hinge and the first safety switch and the third safety switch are arranged on different sides of the door flange when the loading opening is viewed from the front. This has the advantage that operation of the microwave generator can also be reliably blocked if the door is bent open at a corner in the region of the upper edge of the door flange. One of these two safety switches then switches according to the regulations, but the other of these two safety switches is not switched as intended when the door is closed, so that operation of the microwave operating device is also prevented thereby.

It is an embodiment that the microwave device has a fourth safety switch, which is hidden for a user and is connected in series with the microwave operating device. This achieves the advantage of further increased security against microwaves escaping from the treatment room.

It is a development that the fourth safety switch is electrically connected in parallel to the second safety switch.

It is a further development that a setpoint switching angle (hereinafter referred to as "fourth" setpoint switching angle without restricting generality) of the fourth safety switch corresponds to the second setpoint switching angle of the second safety switch. However, the second safety switch and the fourth safety switch can in principle also have different setpoint switching angles. It is a further development that the fourth safety switch is a hinge switch, that is to say that it is switched by an hinge as an actuator and is hidden by the hinge.

It is a further development that the fourth safety switch is hidden and switched by the same door hinge as the second safety switch. This has the advantage that a particularly compact and inexpensive construction is made possible, since only one of the typically two door hinges needs to be designed as an actuator.

It is a further development that the microwave device has at least one further safety switch. The advantage of an even higher safety gain is achieved. The at least one further safety switch can be an openly accessible or a hidden switch.

It is a further development that the at least one further safety switch is an openly accessible fifth safety switch. This can e.g. be arranged on an edge of the door flange opposite the hinges, e.g. on an upper edge. In particular, the fifth safety switch can be arranged in a central region of this edge.

It is an embodiment that the door is designed without a push. The fact that the door is tamper-free or tappet-free includes, in particular, that the inside of the door facing the treatment room does not have any plungers which are required to actuate the safety switches. This has the advantage that a user can no longer get caught on the tappets when he is taking food from the treatment room or introducing it into the treatment room. This significantly reduces the risk of injury. The above combination of openly accessible and hidden safety switch makes it considerably easier to dispense with plungers.

The object is also achieved by a method for securing a microwave device against microwave radiation emerging from a treatment room, in which a microwave function or a microwave generator is activated when a microwave-tight door is closed (for example the microwave generator is supplied with current) when first a hidden second safety switch and then an openly accessible first safety switch is switched.

The method can be designed analogously to the microwave device and has the same advantages.

An error check of the accessible safety switches can also be implemented if the microwave device is connected to voltage, e.g. mains voltage, for example when starting up for the first time. For example, a switch unit wedged on the device transport can be recognized. To check errors, a user can e.g. Open the door once and close it again. The sequence of the switching of the safety switches, in particular electronic switches, is communicated to an evaluation device. The device is only fully functional if the safety switches switch in the correct order.

The above-described properties, features and advantages of this invention and the manner in which they are achieved can be more clearly understood in connection with the following schematic description of an exemplary embodiment, which is explained in more detail in connection with the drawings.

1 shows a front view of a non-scale sketch of a microwave oven with the door fully open;

2 shows a sectional illustration in side view of a non-scale sketch of the microwave device with the door in different door opening angles; and FIG. 3 shows a possible safety circuit for preventing an escape from

Microwaves from the microwave oven with the door open.

1 shows a front view of a household microwave device 1, having a treatment room 2 with a loading opening 3, which can be closed by means of a microwave-proof door 4 (indicated in dashed lines in its fully open state with a door opening angle of approximately 90 °) . The loading opening 3 is surrounded by a door flange 5, on which the door 5 rests in the completely closed state (corresponding to a door opening angle of 0 °) and then forms a lambda / 4 trap for microwave radiation. The household microwave device 1 also has a microwave device 6, 7 with a microwave generator 6, which is set up to be used by the microwave generator 6 to radiate generated microwaves into the treatment room 2 via a microwave guide 7.

The door 4 is shown here purely by way of example as a horizontally opening door 4 which can be pivoted via a left door hinge 8 and a right door hinge 9, which are arranged below the treatment room 2.

On an upper edge 10 of the door flange 5, an actuating element of a first safety switch 11 in the form of a plunger 12 projects outward through the door flange 5, specifically here on a left end section of the upper edge 10.

The household microwave device 1 also has a second safety switch 13 which is arranged and hidden outside the treatment room 2 (that is to say is not accessible to a user) and can be switched here by the left door hinge 8. The second safety switch 13 is consequently a hinge switch.

Optionally, the household microwave device 1 additionally has a third safety switch 14, the actuating element of which, in the form of a plunger 15, projects outwards through the door flange 5 and is openly accessible. The plunger 15 is arranged here, for example, on a right end section of the upper edge 10 of the door flange 5. The first safety switch 11 or its plunger 12 and the third safety switch 14 or its plunger 15 are therefore arranged in a frontal view of the loading opening 3 on different sides (left-hand or right-hand side) of the door flange 10. The

Optionally, the household microwave device 1 additionally has a hidden fourth safety switch 16 which is arranged outside the treatment room 2 and which can likewise be switched by the left door hinge 8. The fourth safety switch 16 is thus also a hinge switch.

Optionally, the household microwave device 1 also has a fifth safety switch 17, the actuating element of which, in the form of a plunger 18, projects outwards through the door flange 5 and is openly accessible. The plunger 18 is here For example, it is arranged on a central section of the upper edge 10 of the door flange 5, but is not limited to this and can also be actuated, for example, by means of the plunger 12 or the plunger 15.

The door 4 is therefore formed without a ram.

2 shows a sectional illustration in side view of a non-scale sketch of the microwave device 1 with the door 4 in different door opening angles W. When the door 4 is closed, the door opening angle is W = 0 °, for example W = 90 when the door 4 is fully open °. When the door 4 is closed from its fully open position, a door opening angle W is first achieved which corresponds to a second setpoint switching angle SSW2. When the second setpoint switching angle SSW2 is reached, actuated by the door hinge 8, both the second safety switch 13 and — if present — the fourth safety switch 16. A fourth setpoint switching angle of the fourth safety switch 16 thus corresponds to the second setpoint switching angle SSW2 of the second safety switch 13. With the second setpoint switching angle SSW 2 there is thus a change in a respective switching state (conducting / blocking) of the safety switches 13 and possibly 16. The two safety switches 13 and 16 do not need to be exactly adjusted to the second setpoint switching angle SSW 2.

If the door 4 is closed further, the door reaches a door opening angle W, which corresponds to a first setpoint switching angle SSW 1, at the upper edge of the door 4 after a predetermined switching path ds2. The switching path ds2 can be 2 mm, for example. The safety switches 11 and 13 are thus adjusted to one another on the switching path ds2.

When the first setpoint switching angle SSW1 is reached, the door 4 presses in the plunger 12 and - if present - the plunger 15 to such an extent that the first safety switch 11 and possibly also the third safety switch 14 switch, that is to say their respective switching state (conductive / blocking ) to change. A third setpoint switching angle of the third safety switch 14 thus corresponds to the first setpoint switching angle SSW1 of the first safety switch 11. The two safety switches 11 and 14 are adjusted comparatively precisely, so that a gap dimension ds1 belonging to the first setpoint switching angle SSW1 between the door 4 and the upper edge 10 of the door flange 5 is reached exactly. The door 4 is so close to the door flange 5 that the gap dimension ds1 is reached or undercut practically no more microwave radiation emerges from the treatment room 2 through a gap between the door flange 5 and the door, even if the door is not completely closed.

The first setpoint switching angle SSW1 is thus smaller than the second setpoint switching angle SSW2.

3 shows a possible safety circuit of the household microwave device 1 for preventing microwaves from escaping from the household microwave device 1 when the door 4 is open with W> SSW2.

The safety circuit has a first power supply line (current-carrying line L) and a second power supply line (neutral line N). An overcurrent protection device 19 is connected to the current-carrying line L, which on the other hand is connected to the first safety switch 11.

The other side of the first safety switch 11 is connected to the second safety switch 13 and, parallel to it, to an inverter 20 of the microwave generator 6. Both the second safety switch 13 and the inverter 20 are connected to the neutral line N on the other hand. The inverter, the first safety switch 11 and the overcurrent protection device 19 are thus electrically connected in series between the current-carrying line L and the neutral line N.

The second safety switch 13 bridges the inverter 20 if it is in its conductive switching state. The second safety switch 13 is consequently electrically connected in parallel to the inverter 20 and electrically in series with the first safety switch 11 and with the overcurrent protection device 19.

When the door 4 is open, the first safety switch 11 is switched open or blocking, while the second safety switch 13 is closed or switched on.

If, in a particularly simple development of the safety circuit, only these two safety switches 11 and 13 are present, no current can flow through the inverter 20 when the door 4 with W> SSW2 is open, since the first safety switch 11 is switched off and thus the Circuit of the inverter 20 breaks. If the door 4 reaches a door opening angle W, which corresponds to the second setpoint switching angle SSW2, the second safety switch 13 opens. However, since the first safety switch 11 is still open, no current can still flow through the inverter 20.

When the first setpoint switching angle SSW1 is reached, the first safety switch 11 closes, so that current can now flow through the first safety switch 11 and through the inverter 20, especially since the bypass provided by the second safety switch 13 is blocked. When the door 4 is closed, the first safety switch 11 is switched on and the second safety switch 13 is switched off.

However, if the first safety switch 11 is closed when the door 4 is open (for example due to deliberate manipulation by a user or due to unwanted sticking or getting caught), when a microwave function of the household microwave appliance 1 is actuated, a short-circuit current is generated for a short time, which is caused by the two Safety circuit 11 and 13 and the overcurrent protection device 19 flows. This short-circuit current is considerably higher than a working current of the inverter 20, and the overcurrent protection device 19 is set such that it triggers when this short-circuit current flows through it. As a result, the electrical connection between the current-carrying line L and the neutral line N is interrupted, and the inverter 20 cannot be operated or cannot be activated. The inverter 20 and thus also the microwave generator 6 as a whole can therefore only be activated if the safety switches 11 and 13 are switched when changing from an open position of the door to a closed position in accordance with the sequence of their desired switching angles, namely first the second safety switch 13 and then the first safety switch 11. The second safety switch 13 opens up the possibility of using it as a monitoring switch for a first safety switch 11 serving as a main switch. In this case, the second safety switch 13 can protect the first safety switch 11 in a dominant manner. A main switch separates the microwave generator 6 on all poles from the electrical supply, here: the live line L.

If the household microwave appliance 1 also has the third, openly accessible safety switch 14, this can switch a first relay 21 and a second relay 22 Taxes. The safety switch 14 is classified as PEC-safe because the switching circuit runs directly via the coil (s) of the first relay 21 and the second relay 22. The first relay 21 is arranged between the inverter 20 and the first safety switch 11, while the second relay 22 is arranged between the inverter 20 and the neutral line N. The inverter 20 is thus arranged in series between the first relay 21 and the second relay 22, while the second safety switch 13 is arranged electrically in parallel with it.

If the door 4 is opened further than the first setpoint switching angle SSW1, the two relays 21 and 22 are open, otherwise they are closed. When the door 4 is closed, the two relays 21 and 22 are thus turned on, so that current can then flow through the inverter 20. If the door 4 is opened further than the first setpoint switching angle SSW 1, the two relays 21 and 22 are switched to block and electrically isolate the inverter 20 from both lines L and N. The safety switch 14 is thus designed as a main switch.

If the third safety switch 14 is closed when the door 4 is open (for example due to deliberate manipulation by a user or due to unwanted sticking or getting caught), the relays 21 and 22 are conductive. However, because of the safety switches 11 and 13, the inverter 20 still cannot be supplied with current or activated.

If the household microwave device 1 has the fourth safety switch 16 hidden for a user, this can e.g. be connected in series to the inverter 20, here e.g. between the first relay 21 and the first safety switch 11. The second safety switch 13 can thus also bridge the fourth safety switch 16. The fourth safety switch 16 is also designed here as a hinge switch and in particular has the same setpoint switching angle as the second safety switch 13. The fourth safety switch 16 can serve in particular to ensure that the overcurrent protection device 19 is not triggered when the door 4 is open. It is a main switch here.

If the household microwave device 1 has the fifth safety switch 17, which is openly accessible to a user, this can be connected between the inverter 20 and the first relay 20. In particular, the fifth safety switch 17 can be First switching position, connect the inverter 20 to the first relay 21 and, in a second switching position, either simply disconnect the inverter 20 from the first relay 21 or, as shown, connect the first relay 21 directly to the neutral conductor N. In particular, the fifth safety switch 17 can be in the second switching position when the door 4 is opened further than the first setpoint switching angle SSW 1, otherwise in the first switching position. The fifth safety switch 17 is designed in particular as a monitoring switch.

In one variant, the second safety switch 13 is designed as a rocker switch with two set switching angles SSW1 and SSW3, SSW1 <SSW2 <SSW3. If the door 4 is e.g. opened further than SSW3 (i.e. that W> SSW3 applies), the second safety switch 13 is opened again. This prevents a short-circuit current from flowing through the overcurrent protection device 19 when the door 4 with W> SSW3 is opened further, if the microwave function is actuated at the same time when the first safety switch 11 is accidentally or deliberately closed. Frequent tripping of the overcurrent protection device 19 is thus particularly reliably prevented.

Due to its special connection and the adjustment of the individual safety switches 11, 13, 14, 16, 17 to one another, the above circuit arrangement fulfills the intended safety function without additional software evaluation.

However, at least one of the safety switches 11, 13, 14, 16, 17 can also be designed as an electronic switch. An electronic switch can be used to detect a switching state in terms of software and, depending on this, a fuse can be triggered, a message can be sent to electronics, which then blocks microwave operation, etc. As an alternative or in addition to preventing microwave operation, a general indication can be given (Warning or error message) are issued to a user, e.g. via a display of the microwave oven.

In order to output a specific error message, a sequence of a switching of the safety switches when the door is closed and / or opened and / or in the event of a failure or fault of at least one safety switch can be checked. This advantageously enables a checking and identification of certain malfunctions and / or protection against manipulation. Of course, the present invention is not limited to the exemplary embodiment shown. In general, "a", "a" etc. can be understood to mean a single number or a plurality, in particular in the sense of "at least one" or "one or more" etc., as long as this is not explicitly excluded, for example by the expression "exactly one" etc.

A number can also include the specified number as well as a customary tolerance range, as long as this is not explicitly excluded.

Reference list

1 household microwave oven

2 treatment rooms

3 loading opening

4 door

5 door flange

6 microwave generator

7 microwave guidance

8 Left door hinge

9 Right door hinge

10 Upper edge of the door flange

1 1 First safety switch

12 pestles

13 Second safety switch

14 Third safety switch

15 pestles

16 Fourth safety switch

17 Fifth safety switch

18 plungers

19 Overcurrent protection device

20 inverters

21 First relay

22 Second relay

ds1 gap dimension

ds2 way

L Live wire

N neutral line

SSW1 First setpoint switching angle

SSW2 Second setpoint switching angle

SSW3 Third setpoint switching angle

W door opening angle

Claims

1. Microwave device (1) having

a treatment room (2) with a loading opening (3) which can be closed by means of a microwave-proof door (4),

a microwave device (6, 7) with a microwave generator (6), which microwave device (6, 7) is set up to irradiate microwaves generated by the microwave generator (6) into the treatment room (2), and a first safety switch (1 1 ), which can be switched depending on a first, smaller setpoint switching angle (SSW1) of the door (4) and a second safety switch (13), which can be set depending on a second, larger setpoint switching angle (SSW2) of the door (4) is

in which

the microwave generator (6) can only be activated when the safety switches (11, 13) change from an open position of the door (4) to a closed position in accordance with the intended sequence of their operation

Set switching angle (SSW2, SSW1) are switched,

the first safety switch (1 1) is an openly accessible switch and the second safety switch (13) is a switch hidden for a user.

2. Microwave device (1) according to claim 1, wherein the second, hidden safety switch (13) is a switch that can be switched by a door hinge (8, 9) and the first, openly accessible safety switch (1 1) in the area of a Door hinge (8, 9) opposite edge (10) of a door flange (5) is arranged.

3. Microwave device (1) according to one of the preceding claims, wherein

between a first power supply line (L) and a second power supply line (N) a microwave operating device (20) for operating the microwave generator (6), the first safety switch (11) and an overcurrent protection device (19) electrically in series are switched, the second safety switch (13) is electrically connected in parallel to the microwave operating device (20) and electrically in series with the first safety switch (11) and the overcurrent protection device (19), and when the door (4) is closed, the first safety switch (1 1) is switched on and the second safety switch (13) is switched off.

4. Microwave device (1) according to claim 3, wherein

the microwave device (1) has a third, openly accessible safety switch

(14) and a first relay (21) and a second relay (22), the microwave operating device (20) in series between the first relay

(21) and the second relay (22) is arranged,

the second safety switch (13) is electrically connected in parallel to the microwave operating device (20), the first relay (21) and the second relay (22) and

the third safety switch (14), the first relay (21) and the second relay

(22) switches so that when the door (4) is closed, the two relays (21, 22) are switched on.

5. Microwave device (1) according to claim 4, wherein a third setpoint switching angle of the third safety switch (14) corresponds to the first setpoint switching angle (SSW1) of the first safety switch (11).

6. Microwave device (1) according to claim 4, wherein the third safety switch (14) is arranged in the region of an edge (10) of a door flange (5) opposite the door hinge (8, 9) and the first safety switch (11) and the third safety switch (14) is arranged in a frontal view of the loading opening (3) on different sides of the door flange (5).

7. Microwave device (1) according to one of the preceding claims, wherein the microwave device (1) has a fourth, hidden for a user safety switch (16) which is connected in series to the microwave operating device (20).

8. Microwave device (1) according to one of the preceding claims, wherein the door (4) is formed without a push.

9. A method for securing a microwave device (1) against microwave radiation emerging from a treatment room (2), in which when a microwave-tight door (4) is closed, a microwave generator (6) is only activated when a hidden one is first arranged second safety switch (13) and then an openly accessible first safety switch (1 1) is switched.