Patent Description:
A kitchen appliance may be used with various different tools for performing different processing tasks of a food item which is placed within the receptacle, in particular within the bowl, of the appliance. Example tools are a knife, a shredder, a dough hook, etc..

The kitchen appliance may be configured to provide a guided cooking function to guide a user of the appliance through different processing steps of a recipe for preparing a processed food item. In this context, the kitchen appliance may be configured to automatically operate the motor for driving a tool which is attached to the kitchen appliance.

<CIT> describes a coffee maker with a cycle timer. <CIT> describes a circuit for driving a relay. <CIT> describes a camera with a relay for controlling the rewinding motor of the camera. <CIT> describes an appliance with a locking function.

The present document addresses the technical problem of increasing the safety of an appliance which is configured to automatically operate a tool. The technical problem is solved by the independent claim. Preferred examples are described in the dependent claims.

According to the invention a control circuit configured to control a relay for activating an electric motor, of a household appliance, is described. The appliance may comprise a receptacle with a rotatable tool, such as a knife, a dough hook, a shredder or a mixing tool. The motor may be configured to drive the rotatable tool. The appliance may be a kitchen appliance, in particular a kitchen machine or a kitchen robot appliance. Alternatively, or in addition, the kitchen appliance may be a guided cooking appliance and/or a cook processor. In other words, the appliance may be configured to provide a guided cooking functionality. In this context, the appliance, notably a control unit of the appliance, may be configured to initiate the operation of the motor for driving the rotatable tool.

The control unit, e.g., a microcontroller, of the appliance is configured to generate a control signal for controlling the relay, in particular for closing the relay. The control signal may be an alternating signal which alternates between HIGH and LOW. In particular, the control signal may be a pulse width modulated (PWM) signal. The alternating control signal may be used to cause the relay to close, thereby activating the motor.

Furthermore, the appliance comprises a manual control element (such as a "Start" button or switch) which is configured to generate an edge within an actuation signal subject to actuation of the manual control element. The manual control element is part of a user interface of the appliance. The manual control element can be actuated by a user of the appliance to cause the motor to start operation.

The manual control element is configured to generate an actuation signal. The actuation signal may e.g., have the state LOW or HIGH. By way of example, the state of the actuation signal may be LOW, if the manual control element is in the state "OFF" (for preventing operation of the motor). On the other hand, the state of the actuation signal may be HIGH, if the manual control element is in the state "ON" (for causing the motor to operate). Actuation of the manual control element generates an edge within the actuation signal, e.g., a rising edge from LOW to HIGH (when the user changes the state of the manual control element from "OFF" to "ON"). On the other hand, actuation of the manual control element may generate a falling edge from HIGH to LOW (if the user changes the state of the manual control element from "ON" to "OFF").

The control circuit may be implemented on one or more printed circuit boards. The control circuit comprises an AND gate which is configured to forward the control signal at an input port of the AND gate to an output port of the AND gate, in dependence of the state of a safety signal. The AND gate comprises (at least or exactly) two input ports. The first input port may be configured is coupled to the control unit of the appliance for receiving the control signal that is generated by the control unit. In other words, the first input port of the AND gate is configured to receive the control signal from the control unit of the appliance. The second input port is used for receiving the safety signal.

The safety signal is generated by a latch of the control circuit. Hence, the second input port of the AND gate may be coupled to the output port of the latch of the control circuit. Furthermore, the output port of the AND gate is configured to be coupled to the relay for controlling the state of the relay.

Hence, an AND gate may be used for ensuring that the control signal for controlling the relay is only passed to the relay, if the state of the safety signal is HIGH. If the state of the safety signal at the second input port of the AND gate is HIGH, the signal at the output port of the AND gate may be equal to the (control) signal at the first input port of the AND gate. On the other hand, if the state of the safety signal at the second input port of the AND gate is LOW, the output port of the AND gate may be a constant LOW, which may cause the relay to be open, thereby preventing the motor to operate.

The control circuit further comprises the latch which is configured to set the state of the safety signal at the output port of the latch. In particular, the latch may be configured to set the state of the safety signal in dependence of the presence of an edge within the actuation signal at an input port of the latch. In a preferred example, the latch comprises or is a D-Flip-Flop.

Hence, a latch may be used to set the state of the safety signal to HIGH if, in particular only if, an edge is detected within the actuation signal (which indicates that the manual control element has been actuated by a user of the appliance).

Overall, a control circuit is provided which is configured to prevent the control signal of the control unit to be provided to the relay, as long as no actuation of the manual control element of the appliance has been detected. As a result of this, an unattended start of the motor of the appliance (e.g., due to a software update within the control unit of the appliance) can be prevented in a reliable manner.

The actuation signal may be applied to a clock input port of the latch (notably when using a D-Flip-Flop). Furthermore, a data input port of the latch may be constantly set to HIGH. As a result of this, the state of the safety signal at the output port of the latch may be controlled in a particularly reliable manner.

The latch may be configured to set the safety signal to HIGH, if, in particular only if, the actuation signal comprises a rising edge from LOW to HIGH. As indicated above, the rising edge of the actuation signal may correspond to an actuation of the manual control element when changing the manual control element from the "OFF" state to the "ON" state. As a result of this, a particularly safe operation of the motor may be achieved.

The latch may comprise a reset input port for receiving a reset signal. The reset signal may be generated by the control unit of the appliance. The reset input port of the latch may be configured to be coupled to the control unit for receiving the reset signal.

The latch may be configured to set the state of the safety signal at the output port of the latch in dependence of the presence of an edge within the actuation signal at the input port (in particular at the clock input port) of the latch if, in particular only if, the reset signal is HIGH. In particular, the latch may be configured to set the safety signal to HIGH if, in particular only if, the reset signal at the reset input port is HIGH. On the other hand, the safety signal may be LOW (thereby preventing the AND gate to forward the control signal to the output port of the AND gate), if the reset signal at the reset input port is LOW.

Hence, an additional reset signal may be used to ensure that (a possibly erroneous) control signal is blocked by the control circuit from being passed to the relay. The control unit of the appliance may be configured to set the reset signal to LOW (e.g., during a SW update), in order to prevent an unattended start of the motor in a particularly reliable manner. On the other hand, the control unit may be configured to set the reset signal to HIGH (e.g., during normal operation of the appliance), in order to enable the activation of the motor.

The latch may be configured to set the safety signal to LOW regardless the presence of an edge within the actuation signal at the input port, in particular at the clock input port, of the latch if the reset signal is LOW. As a result of this, unattended actuation of the motor of the appliance may be prevented in a particularly reliable manner.

As indicated above, the control signal may be an alternating signal which alternates between LOW and HIGH periodically, e.g., with a frequency of <NUM> or higher. The control circuit may comprise a driving element which is coupled to the output port of the AND gate and which is configured to generate an alternating current through a control coil of the relay, based on the alternating control signal. The driving element may comprise a transistor which is opened and closed in dependence of the control signal at the output port of the AND gate for generating the alternating current through the control coil of the relay. By making use of a driving element for driving the relay, the relay may be opened or closed in a particularly reliable manner, thereby controlling operation of the motor in a reliable manner.

The control signal may be an electric signal which alternates between a reference voltage and a logic voltage. The reference voltage may correspond to the LOW state and the logic voltage may correspond to the HIGH voltage. The alternating current may be an electric signal which alternates between the reference voltage and a drive voltage, wherein the drive voltage is typically higher than the logic voltage. By way of example, the logic voltage is at 5V and the drive voltage is at 12V. By making use of a drive voltage which is higher than the logic voltage, the relay may be controlled in a particularly reliable manner.

According to the present invention, a household appliance, in particular a kitchen and/or a cooking appliance, is described. The appliance comprises a motor for driving a tool of the appliance, wherein the tool may be located within a receptacle of the appliance. Furthermore, the appliance comprises a relay which is configured to couple the motor with a power supply (e.g., with the mains supply) for activating the motor. In addition, the appliance comprises a control unit which is configured to generate a control signal for controlling the relay Furthermore, the appliance comprises a manual control element which is configured to generate an edge within an actuation signal, subject to actuation of the manual control element by a user of the appliance. The appliance further comprises the control circuit described herein, which is configured to control the relay.

The control unit is configured to determine that the motor is to be activated. As indicated above, the appliance may be configured to provide a guided cooking functionality based on recipe data regarding a recipe for a food item which is to be cooked using the appliance. The control unit is configured to determine that the motor is to be activated based on the recipe data. Furthermore, the control unit is configured to generate a control signal for closing the relay, if it has been determined that the motor is to be activated. The control signal may be an alternating electrical signal.

In addition, the control unit is configured to cause an instruction to the user to be output via a user interface of the appliance, in reaction to determining that the motor is to be activated. The instruction may be directed at causing the user to actuate the manual control element for activating the motor. By way of example, a text instruction may be output on a display of the appliance. Alternatively, or in addition, a speech instruction may be output via a loudspeaker of the appliance.

Hence, the user of the appliance may be instructed to actuate the manual control element (e.g., for changing the manual control element from the state "OFF" to the state "ON"). By doing this, an unattended start of the motor of the appliance may be prevented in a reliable manner.

As indicated above, the control circuit is configured to forward the control signal to the driving element for controlling the relay if, in particular only if, a reset signal is set (in particular, is set to HIGH). The control unit is configured to set the reset signal (to HIGH) in reaction to determining that the motor is to be activated. Hence, for operating the motor, it may be required that the (alternating) control signal is generated and that the reset signal is set (to HIGH). By doing this, the safety of the appliance may be further increased.

The control unit is configured to determine that the motor is to be deactivated or is to be inactive. In reaction to this, generation of the control signal may be suspended and/or prevented. Furthermore, the reset signal may be set to LOW. As a result of this, unattended operation of the motor may be prevented in a particularly reliable manner.

As outlined above, the present document is directed at increasing the safety of a kitchen appliance which comprises a motor for driving a tool or attachment of the appliance. In this context, <FIG> shows a block diagram of an example appliance <NUM> which comprises a base unit <NUM> onto which a receptacle <NUM>, in particular a bowl, is placed. The receptacle <NUM> may be configured to be covered by a lid <NUM>. The base unit <NUM> comprises a motor <NUM> which is configured to drive a tool <NUM> which is located within the receptable <NUM>. The tool <NUM> may be detachable and/or exchangeable.

The appliance <NUM> may comprise a heating unit <NUM> (which may alternatively, or in addition, be integrated into the receptacle <NUM>) for heating the receptacle <NUM>, e.g., for allowing a food item to be cooked within the receptacle <NUM>. Furthermore, the appliance <NUM> may comprise a weighing unit <NUM> which is configured to measure the weight of the one or more food items which are placed within the receptacle <NUM> or onto the appliance <NUM> (since the weighting unit <NUM> may be integrated at the bottom of the appliance <NUM>). In addition, the appliance <NUM> may comprise a user interface <NUM>, <NUM> which allows a user to interact with the appliance <NUM>, e.g., for activating or for deactivating the motor <NUM>. The user interface <NUM>, <NUM> may comprise a manual control element <NUM>, e.g., a knob, which allows a user to turn on the motor <NUM> of the appliance <NUM>. In addition, the appliance <NUM> may be connected to the internet, to another appliance and/or to a (smart) device via a (wireless) communication interface such as WLAN. A control unit <NUM> of the appliance <NUM> may be configured to operate the appliance <NUM>, in particular the motor <NUM> and/or the heating unit <NUM>, in dependence of a user input received via the user interface <NUM>, <NUM> (of the appliance <NUM> or of a remote device).

<FIG> shows a perspective view of an exemplary appliance <NUM>.

The control unit <NUM> of the appliance <NUM> may be configured to control the motor <NUM> in dependence of recipe data regarding a recipe for a food item. For turning on the motor <NUM>, the control unit <NUM> may cause a relay of the appliance <NUM> to couple the motor <NUM> with a power supply, e.g., with the mains supply circuit, of the appliance <NUM>.

The software (SW) which is running on the control unit <NUM> of the appliance <NUM> may be updated, e.g., via the communication interface of the appliance <NUM>. The SW update may lead, e.g., during a transition period of the SW update procedure, to an undefined state of the control unit <NUM>, which may cause the motor <NUM> of the appliance <NUM> to operate in an unsupervised manner.

<FIG> illustrates a control circuit <NUM> for controlling the relay <NUM> of an appliance <NUM> in a particular secure manner. The control circuit <NUM> comprises an AND gate <NUM> which is configured to provide the control signal <NUM> for controlling the driver element <NUM> to close the relay <NUM>. The control signal <NUM> may be PWM (pulse width modulated) signal which is configured to open and close the transistor of the driver element <NUM> in a periodic manner, thereby generating an alternating current through the coil of the relay <NUM>, which generates the magnetic field for closing the relay <NUM>.

The control signal <NUM> may be generated by the control unit <NUM>, as indicated by the input control signal <NUM> entering the input port "<NUM>" of the AND gate <NUM>. The input control signal <NUM> may be passed to the output port "<NUM>" of the AND gate <NUM> (thereby providing the control signal <NUM> for controlling the driver element <NUM>), if, in particular only if, the safety signal <NUM> on the input port "<NUM>" of the AND gate <NUM> is HIGH.

The safety signal <NUM> may be dependent on an actuation of a manual control element <NUM> of the appliance <NUM>. In particular, the control circuit <NUM> may be configured to generate the safety signal <NUM> such that the safety signal <NUM> is HIGH, if (possibly only if) the manual control element <NUM>, e.g., the knob for turning ON or OFF the motor <NUM>, has been actuated by a user. The control circuit <NUM> may comprise a Flip-Flop or latch <NUM>, in particular a D-Flip-Flop, which is configured to generate the safety signal <NUM> in dependence of an actuation signal <NUM> which indicates an actuation of the manual control element <NUM> of the appliance <NUM>. The actuation signal <NUM> may be coupled to the clock input "CK" of the latch <NUM>. The data input "D" (port number "<NUM>") may be constantly set to HIGH. As a result of this, the latch <NUM> causes the output port Q, i.e., the safety signal <NUM>, to go HIGH at the rising edge of the actuation signal <NUM>. Hence, it can be ensured in combination with the AND gate <NUM> that the input control signal <NUM> is only passed to the driving element <NUM> subject to an actuation of the manual control element <NUM> (from OFF to ON).

The latch <NUM> may further comprise a reset input port (port number "<NUM>") which receives a reset signal <NUM>. The reset signal <NUM> may be provided by the control unit <NUM>. The reset signal <NUM> may be set to LOW during a SW updated of the control unit <NUM> and/or subsequent to finishing a guided cooking operation step. On the other hand, the reset signal <NUM> may be set to HIGH at the beginning and during a guided cooking operation step. If the reset signal <NUM> is LOW, then the safety signal <NUM> at the output port of the latch <NUM> is also LOW, regardless the state of the actuation signal <NUM>. On the other hand, if the reset signal <NUM> is HIGH, then the safety signal <NUM> is set to HIGH, subject to a rising edge of the actuation signal <NUM>, i.e., subject to actuation of the manual control element <NUM>. By making use of the reset input port of the latch <NUM>, the safety of the appliance <NUM> may be increased further.

The control unit <NUM> of the appliance <NUM> may be configured to cause the reset signal <NUM> to be LOW, whenever the operation of the motor <NUM> should be avoided, e.g., during a SW update or at the end of a guided cooking step which involved operation of the motor <NUM>. Furthermore, the control unit <NUM> may be configured to cause the input control signal <NUM> to be constant (e.g., constantly LOW or constantly HIGH), whenever the operation of the motor <NUM> should be avoided. As a result of this, unattended operation of the motor <NUM> can be avoided in a particularly reliable manner.

On the other hand, if operation of the motor <NUM> is to be allowed, the reset signal <NUM> may be set to HIGH and a PWM input control signal <NUM> may be generated. Furthermore, a user indication may be output via the user interface <NUM>, indicating to the user that the manual control element <NUM> should be actuated to start operation of the motor <NUM>. The actuation of the manual control element <NUM> causes the actuation signal <NUM> to go from LOW to HIGH, and the rising edge of the actuation signal <NUM> causes the safety signal <NUM> at the output port of the latch <NUM> to go HIGH, thereby allowing the input control signal <NUM> to pass through the AND gate <NUM>.

An erroneous operation of the control unit <NUM> during a SW update may lead to a situation where a PWM input control signal <NUM> is generated and/or where the reset signal <NUM> is set HIGH. This, however, does not lead to an unattended operation of the motor <NUM>, because the safety signal <NUM> is only set HIGH in reaction to a rising edge of the actuation signal <NUM>, i.e., in reaction to the user actuating the manual control element <NUM>. Hence, an unattended and/or unintended operation of the motor <NUM> can be avoided in a reliable manner.

Claim 1:
A household appliance (<NUM>) which comprises,
- a motor (<NUM>) for driving a tool (<NUM>) of the appliance (<NUM>);
- a relay (<NUM>) configured to couple the motor (<NUM>) with a power supply for activating the motor (<NUM>);
- a control unit (<NUM>) configured to generate a control signal (<NUM>) for controlling the relay (<NUM>);
- a manual control element (<NUM>) configured to generate an edge within an actuation signal (<NUM>) subject to actuation of the manual control element (<NUM>) by a user of the appliance (<NUM>); wherein the control unit (<NUM>) is configured to
- determine that the motor (<NUM>) is to be activated;
- in reaction to this, generate the control signal (<NUM>) for closing the relay (<NUM>);
- cause an instruction to the user to be output via a user interface (<NUM>) of the appliance (<NUM>), in reaction to determining that the motor (<NUM>) is to be activated; wherein the instruction is directed at causing the user to actuate the manual control element (<NUM>) for activating the motor (<NUM>); and
- a control circuit (<NUM>) configured to control the relay (<NUM>) for activating the motor (<NUM>) of the appliance (<NUM>); wherein the control circuit (<NUM>) comprises,
- an AND gate (<NUM>) configured to forward the control signal (<NUM>) at an input port of the AND gate (<NUM>) to an output port of the AND gate (<NUM>) in dependence of a state of a safety signal (<NUM>); wherein the output port of the AND gate (<NUM>) is coupled to the relay (<NUM>); and
- a latch (<NUM>) configured to set the state of the safety signal (<NUM>) at an output port of the latch (<NUM>) in dependence of the presence of an edge within the actuation signal (<NUM>) at an input port of the latch (<NUM>).