Field

The present invention relates to attachment recognition for a food processing appliance. Background

Food processing appliances such as, for example, hand blenders (also known as stick blenders) typically carry out food processing tasks using attachments configured for the specific task to be undertaken. For example, a hand blender may be provided with a whisk attachment for carrying out whisking, and a blending attachment for carrying out blending. Different attachments require different configurations of the appliance to which they attach, for example the speed or range of speeds that are suitable for whisking may not be the same as that which are suitable for blending, yet the motor of the food processing appliance must be capable of adapting to both.

To allow adaptation of food processing appliances to the tools that are attached to them it has been proposed that food processing appliances be made capable of recognising the attachments that are attached to them electronically. Kenwood’s patent publication no. WO2018104743A2 (WO’743) shows a particular example of this.

Flowever, the attachment recognitions of the prior art suffer from excessive complexity and cost. For example, the solution of the aforementioned WO’743 requires an RFID tag with an integrated circuit/processing component. Such tags typically have a memory in the range from 32 bits to more than 64K, which is excessive for tool recognition where, for example, 16 tools may potentially be distinguished between using only 4 bits of data. A cheaper, more simple solution is desired. The present invention aims to at least partially ameliorate the above-described problems of the prior art.

Summary of the Invention

Aspects and embodiments of the present invention are set out in the appended claims. These and other aspects and embodiments of the invention are also described herein.

According to an aspect of the invention described herein, there may be provided an appliance having a base unit, the appliance comprising: an attachment formation configured to removably receive differing attachments; wherein the base unit comprises: an inductive sensor configured to detect, by inductive coupling, at least one characteristic of a circuit, preferably an identity circuit, of the attachment with the attachment received at the base unit, the circuit being an analogue and/or discrete circuit; and wherein the base unit is configured to operate differently in dependence on the detected at least one characteristic. This advantageously may provide an appliance which may distinguish between differing attachments and operate the appliance in a manner appropriate to that attachment. The appliance may be relatively simple and easily manufacturable. Advantageously, no digital electronic information need be exchanged between appliance and attachment, reducing the complexity of the attachment and appliance. Preferably, the at least one characteristic comprises an analogue (i.e. continuously valued) characteristic of the circuit, for example, a Q factor and/or a resonant frequency. Preferably, the inductive sensor is configured to detect and/or sense an analogue or continuously valued signal, preferably thereby to detect the at least one characteristic without receiving digital data from the circuit. The circuit may be a simple and/or passive circuit. Preferably, the at least one characteristic of the circuit does not comprise or relate to digital data. Preferably, the circuit does not comprise an RFID tag. Preferably, the circuit does not transmit digital data to the appliance. Optionally, the at least one characteristic varies and/or is configured to vary in dependence on one or more environmental and/or operating conditions. The performance of the appliance may be improved by varying its operation in dependence on environmental or operating conditions sensed by the attachment. Preferably, the base unit is configured to operate differently by operating according to different active modes, for example, by switching from operating according to a first active mode of a plurality of active modes to operating according to a second active mode of the plurality of active modes. In general, an active mode corresponds to a mode of operation of the appliance for performing a particular function of the appliance. For example, an active mode may comprise one or more of: transmitting drive impetus, heating, cooling or otherwise delivering energy to or doing work on or with an attachment and/or a medium being processed by the appliance. Preferably, the circuit comprises an inductor, preferably for coupling to the inductive sensor.

Preferably, the base unit is configured to operate according to a first active mode for a first attachment and a second active mode for a second attachment. This may permit the base unit to perform differently for different attachments which may have different operation requirements.

Optionally, the base unit is configured to operate according to a first active mode for a first environmental and/or operating condition sensed by the attachment and a second active mode for a second environmental and/or operating condition sensed by the attachment. This may permit the base unit to perform differently when used with the same attachment under different environmental and/or operating conditions.

Preferably, the at least one characteristic is associated with a natural response of the circuit. This may permit the circuit of the attachment to function without a power source in the attachment and for detection of the characteristic to be independent of an applied external bias or power source. Preferably, the circuit comprises at least one of: a resistor, an inductor and a capacitor. Preferably these may be discrete components. This may provide for a simple method of altering the distinguishing circuit characteristics between differing attachments by use of different circuit components for differing attachments.

Optionally, the circuit is a resonant circuit. This may allow the characteristic properties of resonant circuits to be used to distinguish between differing attachments by relatively simple methods.

Optionally, the resonant circuit is an LC circuit. This is advantageous in allowing simple and cheaply manufacturable resonant circuits with differing characteristics to be provided for differing attachments.

Optionally, the resonant circuit is an RLC circuit. This is advantageous as the characteristics of the RLC circuit may be tuned or varied by selecting or varying the resistor which is typically a cheap and easily manufacturable component.

Preferably, the at least one characteristic comprises a Q factor of the resonant circuit and/or a resonant frequency of the resonant circuit. The Q factor may be advantageously used as it permits a simple technique, for example, a ring down method, to be used to estimate the characteristic of the circuit. The resonant frequency may be an advantageous characteristic as it also permits a simple technique for detecting the characteristic, for example, by scanning frequencies and detecting the peak voltage response. Use of the Q factor may only need a single frequency to be scanned, providing an even simpler approach to tool recognition.

Preferably, the base unit comprises a memory and a processor, wherein the processor is configured to compare the detected at least one characteristic to at least two values for the at least one characteristic stored in the memory to identify the attachment, and to operate the base unit based on the identification. This is advantageous as it may allow the characteristic of the attachment circuit to be compared to pre-defined identifying characteristics of the attachment which may allow for simple attachment recognition with low memory requirements.

Optionally, the inductive sensor is configured to alternate between a transmission mode during a first time period (TE) and a reception mode during a second time period (TD), and preferably wherein TD is at least 5ps long and, more preferably, at least 10ps long. Advantageously, this may allow sufficient oscillations to occur for more accurate estimates of the Q factor.

Optionally, the inductive sensor is configured to scan multiple frequencies, preferably wherein the inductive sensor scans frequencies within the range 30kHz to 130kHz. Advantageously, this may permit a number of differing attachments to be identified based on differing characteristic resonant frequencies, in particular, a range of 30kHz to 130kHz may permit around 16 tools to be distinguished.

Preferably, the inductive sensor comprises a coil, preferably wherein the coil is located concentrically with the attachment formation. This may allow improved inductive coupling of the inductive sensor and the circuit.

Optionally, the appliance comprises an interlock configured to prevent operation of the inductive sensor when the attachment is not attached to the appliance. This may help prevent detection of attachments close to, but not attached to, the appliance.

Optionally, the base unit comprises a user interface and is configured, when no circuit is detected by the inductive detector, to indicate via the user interface that an attachment should be attached. This may promptly alert the user to an incorrectly attached or missing attachment.

Optionally, the base unit comprises: a motor configured to transmit drive impetus to the attachment, and operating the base unit differently in dependence on the detected at least one characteristic comprises operating the motor at a first motor speed or range of speeds of operation, or at a second motor speed or range of speeds of operation, in dependence on the detected at least one characteristic; and/or a heating and/or cooling element configured to heat and/or cool the attachment, and operating the base unit differently in dependence on the detected at least one characteristic comprises operating the heater and/or cooling element at a first output temperature or range of temperatures, or at a second output temperature or range of temperatures, in dependence on the detected at least one characteristic; and/or a combination of a heating and/or cooling element and a motor, and operating the base unit differently in dependence on the detected at least one characteristic comprises one of the heating and/or cooling element and motor being active, or the other of the heating and/or cooling element and motor being active, in dependence on the detected at least one characteristic. This may allow safe and appropriate drive and/or heating and/or cooling to be automatically applied to a number of different tools.

Preferably, the appliance is a hand-blender. Hand-blenders typically may have a number of differing attachments, each of which require different operation or active modes for optimal performance so this disclosure may provide for an improved hand- blender.

According to an aspect described herein, there is provided an attachment for an appliance comprising: an attachment formation by which the attachment is configured to be removably attachable to the appliance; and a circuit, preferably an identity circuit, configured to inductively couple to an inductive sensor of the appliance when the attachment is attached to the appliance; wherein the circuit is an analogue and/or discrete circuit; and optionally wherein at least one characteristic of the circuit distinguishes the attachment from a differing attachment and/or at least one characteristic of the circuit varies and/or is configured to vary in dependence on one or more environmental and/or operating conditions. Advantageously, the attachment may be identified by an appliance by a characteristic of its circuit without exchanging digital electronic information with the appliance. The appliance may then vary its operation in dependence on the identified tool. Preferably, the at least one characteristic comprises an analogue (i.e. continuously valued) characteristic of the circuit, for example, a Q factor and/or a resonant frequency. Preferably, the inductive sensor is configured to detect and/or sense an analogue (i.e. continuously valued) signal, preferably thereby to detect the at least one characteristic without receiving digital data from the circuit. Preferably, the at least one characteristic of the circuit does not comprise or relate to digital data. Preferably, the circuit does not comprise an RFID tag. Preferably, the circuit does not transmit digital data to appliance. Optionally, the at least one characteristic varies and/or is configured to vary in dependence on one or more environmental and/or operating conditions. The performance of the appliance may be improved by varying its operation in dependence on environmental or operating conditions sensed by the attachment. Preferably, the circuit comprises an inductor, preferably for coupling to the inductive sensor.

Preferably, the circuit comprises at least one of: a resistor, an inductor and a capacitor. This may provide for a simple method of altering the distinguishing circuit characteristics between differing attachments by use of different circuit components.

Preferably, the circuit is a resonant circuit, preferably wherein the resonant circuit is an LC circuit or an RLC circuit. This is advantageous in allowing simple and cheaply manufacturable resonant circuits with differing characteristics to be provided for differing attachments. The circuits may be simple and/or passive circuits. The characteristics of an LC or RLC circuit may be tuned or varied by selecting or varying a resistor which is typically a cheap and easily manufacturable component. Preferably, the at least one characteristic comprises a Q factor of the resonant circuit and/or a resonant frequency of the resonant circuit. The Q factor may be advantageously used as it permits a simple technique, for example, a ring down method, to be used to estimate the characteristic of the circuit. The resonant frequency may be an advantageous characteristic as it also permits a simple technique for detecting the characteristic, for example, by scanning frequencies and detecting the peak voltage response. Use of the Q factor may only need a single frequency to be scanned, providing an even simpler approach to tool recognition.

Optionally, the circuit comprises a variable resistor, variable inductor, variable capacitor or other such discrete component, preferably wherein the component is at least one of: a temperature-variable component having a predetermined temperature relationship; a component configured to vary a characteristic with a pressure within the attachment; a component configured to vary a characteristic with a speed of a moving part of the attachment; and a component with a user-variable characteristic. This may be advantageous in permitting the operation of the appliance to be varied in dependence on environmental or working conditions of the attachment for optimal performance.

Optionally, the circuit comprises a variable resistor, variable inductor, variable capacitor or other such discrete component, preferably wherein the component is a variable resistor, the variable resistor being at least one of: a temperature-variable resistor having a predetermined temperature/resistance relationship; a resistor configured to vary its resistance with a pressure within the attachment; a resistor configured to vary its resistance with a speed of a moving part of the attachment; and a resistor with user-variable resistance. This may be advantageous in permitting the operation of the appliance to be varied in dependence on environmental or working conditions of the attachment for optimal performance. Optionally, the circuit comprises a switch configured to prevent operation of the circuit unless the switch is actuated, preferably wherein the switch is configured to be actuated by attachment of a further attachment to the attachment. This may be advantageous in providing additional safety for the user, for example, by preventing operation of the appliance if a lid of an attachment is not attached.

Preferably, the circuit comprises a coil, preferably wherein the coil is concentric with the attachment formation. This may allow improved inductive coupling of the inductive sensor and the circuit.

Preferably, the attachment has a food-safe and/or dishwasher-safe construction. This may be advantageous for processing ingredients which are to be consumed and for simple cleaning of the attachment. This may also prevent damage to the attachment circuit.

According to an aspect described herein, there may be provided a kit of parts comprising a plurality of attachments, each attachment being according to any aspect described herein, preferably wherein each such attachment is different and/or has a differing characteristic. This may permit a range of attachments to be provided for use whose identity or mode of operation can be determined automatically. Optionally, each of the plurality of attachments may be different and a subset of the plurality of attachments may have similar or the same characteristics. This may be advantageous where two different attachments are to be operated in the same manner, for example, at a similar speed and as such an appliance may not need to distinguish between them.

According to an aspect described herein, there may be provided a kit of parts comprising an appliance according to any aspect described herein, and at least one attachment according to any aspect described herein attachable thereto. Optionally, the kit may comprise a plurality of attachments, each attachment being according to any aspect described herein, preferably wherein each such attachment is different and/or has a differing characteristic. This may provide a kit which permits the one or more attachments or tools to be automatically operated in a correct or preferred manner by a single appliance. This may reduce the need for multiple appliances and improve performance of the appliance, for example, in food processing.

Preferably, the kit comprises at least two attachments, and the appliance is configured to identify the attachment attached to it based on at least one detected characteristic of a circuit of the attached attachment and to operate the base unit of the appliance based on the identification. This may allow swift and simple interchange of attachments to the appliance for the user.

Preferably, the kit is configured such that, when an attachment is attached to the appliance, the coil of the attachment is substantially aligned with the coil of the appliance. Advantageously, this may allow for improved inductive coupling of the inductive sensor and the circuit.

Preferably, the inductive sensor and the circuit of the attachment are configured such that the circuit of the attachment can only be sensed by the inductive sensor within 20cm or less of each other, more preferably within 5cm or less of each other, and more preferably still within 3cm or less of each other. This may advantageously prevent false detections of nearby attachments not currently in use.

Optionally, the circuits of the at least two attachments have each a capacitor having a differing capacitance. This allows for simple approach using typically cheap mass- produced electronic parts to provide a characteristic of the circuit of each attachment, for example, the Q factor or the resonant frequency, which is distinguishable between attachments. Optionally, the circuits of the at least two attachments of any kit described herein may have each have a capacitor having a differing capacitance, and/or an inductor having a differing inductance, and/or a resistor having a differing resistance.

According to an aspect described herein, a method of operating an appliance may be provided comprising: detecting, by an inductive sensor, a characteristic of a circuit of an attachment attached to the appliance, the circuit being an analogue and/or a discrete circuit; and operating the appliance differently in dependence on the detected at least one characteristic. Preferably, the at least one characteristic comprises an analogue (i.e. continuously valued) characteristic of the circuit, for example, a Q factor and/or a resonant frequency. Preferably, the inductive sensor is configured to detect and/or sense an analogue (i.e. continuously valued) signal, preferably thereby to detect the at least one characteristic without receiving digital data from the circuit. Preferably, the at least one characteristic of the circuit does not comprise or relate to digital data. Preferably, the circuit does not comprise an RFID tag. Preferably, the circuit does not transmit digital data to the appliance. Optionally, the at least one characteristic is configured to vary in dependence on one or more environmental and/or operating conditions. This may allow for an improved tool recognition of the appliance, not requiring the exchange of digital electronic data.

According to an aspect described herein, there may be provided an appliance comprising a base unit comprising an attachment point configured to removably receive differing attachments, wherein the base unit comprises an inductive sensor configured to detect: a Q factor of an LC circuit associated with an attachment attached to the base unit, where Q = 2p x - energy stored. - and/or a resonant energy dissipated per cycle frequency f ₀ of an LC circuit associated with an attachment attached to the base unit, and wherein the base unit is configured to vary the operation of a component of the base unit between a first active mode and a second active mode responsive to the detected Q and/or f ₀ value. This may allow for an improved tool recognition of the appliance. Preferably, the base unit comprises a memory and a processor, where the processor is configured to compare the detected Q factor and/or f ₀ of the LC circuit to two or more stored Q and/or f ₀ values stored in the memory to identify the attachment, and control the component based on the identification. Advantageously, this permits minimal processing and memory requirements.

Optionally, the inductive sensor is configured to alternate between a transmission mode during a first time period (TE) and a reception mode during a second time period (TD), and preferably wherein TD is at least 5ps long and more preferably at least 10ps long. Advantageously, this may allow for a more accurate determination of the circuit characteristic(s).

Optionally, the inductive sensor is configured to scan multiple frequencies. This may allow an appliance to distinguish between attachments in a simple manner by detecting resonant frequencies.

Preferably, the inductive sensor scans frequencies within the range 30kHz to 130kHz. This may permit around 16 tools to be distinguished by resonant frequency.

Preferably, the inductive sensor comprises a coil. This may simplify manufacture of the appliance and permit disposal near the attachment point for improved coupling to the attachment.

Preferably, the coil is located concentrically with the attachment point. This may allow for improved inductive coupling to the attachment.

Optionally, the appliance comprises an interlock configured to prevent operation of the inductive sensor when the attachment is not attached to the appliance. This may prevent false detections of attachments close to but not connected to the appliance. Optionally, the base unit comprises a user interface and is configured, when no attachment LC circuit is detected by the inductive detector, to indicate that an attachment should be attached via the user interface. This may promptly indicate to a user when an attachment is missing or incorrectly attached.

Optionally, the component may comprise: a motor configured to transmit drive impetus to the attachment, for which the first active mode is a first motor speed or range of speeds of operation, and the second active mode is a second motor speed or range of speeds of operation, and/or a heating and/or cooling element configured to heat and/or cool the attachment, where the first active mode is a first output temperature or range of temperatures, and/or a combination of a heating and/or cooling element and a motor, where the first active mode is one or both of the of heating and/or cooling element and motor being active, and the second active mode is the other of the heating and/or cooling element and motor being active. This may allow safe and appropriate drive and/or heating and/or cooling to be automatically applied to a number of different tools without user input.

Preferably, the appliance is a hand blender. Hand-blenders typically may have a number of differing attachments, each of which may require different active modes for optimal performance so this disclosure may provide for an improved hand- blender.

According to an aspect described herein, there may be provided an attachment for an appliance, wherein the attachment has an attachment location configured to be removably attachable to the appliance, and where the attachment comprises an LC circuit having a Q factor where Q = 2p x - energy stored. - and/or a resonant energy dissipated per cycle frequency f ₀ , wherein the Q factor and/or resonant frequency f ₀ relates to a characteristic of the attachment configured to be detectable by an inductive sensor of the appliance when attached to the appliance. Advantageously, the attachment may by identified by an appliance by the characteristic of its circuit without exchanging digital electronic information with the appliance. The appliance may then vary its operation in dependence on the identified tool.

Optionally, the LC circuit is an RLC circuit. The is advantageous as the characteristics of the RLC circuit may be tuned or varied by selecting or varying a resistor, which is typically a cheap and easily manufacturable component.

Optionally, the resistor of the RLC circuit is a variable resistor. Optionally, the resistor is one of: a temperature-variable resistor having a predetermined temperature/resistance relationship; a resistor configured to vary its resistance with a pressure within the attachment; a resistor configured to vary its resistance with a speed of a moving part of the attachment; a resistor with user-variable resistance. This may be advantageous in permitting the operation of the appliance to be varied in dependence on environmental or working conditions of the attachment for optimal performance. Optionally, the LC circuit comprises a switch configured to prevent operation of the LC circuit unless it is actuated. This may help to provide a safer appliance and/or prevent detection of attachments which are not attached to the appliance.

Optionally, the switch is configured to be actuated by attachment of a further attachment to the attachment. This may be advantageous in providing additional safety for the user, for example, preventing operation if a lid is not attached.

Preferably, the LC circuit comprises a coil. Preferably, the coil is concentric with the attachment location. This may allow improved inductive coupling of the inductive sensor and the circuit. Preferably, the attachment has a food-safe and/or dishwasher-safe construction. This may be advantageous for processing ingredients to be consumed and simple cleaning of the attachment, while also preventing damage to the circuit.

According to an aspect of the invention described herein, there may be provided a kit of parts comprising an appliance according to any aspect described herein, and at least one attachment according to any aspect attachable thereto.

Preferably, the one or more attachment comprises at least two attachments, and wherein the appliance is configured to identify the attachment attached to it based on the Q-factor and/or resonant frequency and vary an operation of the component based on the identification. This may allow swift and simple interchange of attachments to the appliance for the user.

Preferably, the kit is configured such that, where the at least one attachment is attached to the appliance, the coil of the attachment is substantially aligned with the coil of the appliance. Advantageously, this may allow for improved inductive coupling of the inductive sensor and the circuit.

Preferably, the inductive sensor and the LC circuit are configured such that the LC circuit can only be sensed by the inductive circuit within 20cm or less of each other, more preferably 5cm or less of each other, and more preferably still within 3cm or less of each other. This may advantageously prevent false detections of nearby attachments not currently in use.

Optionally, the circuits of the at least two attachments have each a capacitor having a differing capacitance

It will be appreciated that a kit may be provided comprising an appliance according to any aspect described herein, and at least one attachment according to any aspect described herein. In general, an appliance may be configured to operate with any of the attachments described herein. In general, an attachment or plurality of attachments may be configured to operate with any appliance described herein.

In general, there may be provided an appliance, attachments for an appliance, kits of parts and a method for recognising different attachments attached to an appliance by an inductive sensor and operating the appliance based on that recognition.

Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. Furthermore, any, some and/or all features in one aspect can be applied to any, some and/or all features in any other aspect, in any appropriate combination.

It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and/or supplied and/or used independently.

In this specification the word 'or' can be interpreted in the exclusive or inclusive sense unless stated otherwise.

Furthermore, features implemented in hardware may generally be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly. Whilst the invention has been described in the field of domestic food processing and preparation machines, it can also be implemented in any field of use where efficient, effective and convenient preparation and/or processing of material is desired, either on an industrial scale and/or in small amounts. The field of use includes the preparation and/or processing of: chemicals; paints; building materials; clothing materials; agricultural and/or veterinary feeds and/or treatments, including fertilisers, grain and other agricultural and/or veterinary products; oils; fuels; dyes; cosmetics; plastics; tars; finishes; waxes; varnishes; beverages; solders; alloys; effluent; and/or other substances, and any reference to “food” herein may be replaced by such working mediums.

The invention described herein may be used in any kitchen appliance and/or as a stand-alone device. This includes any domestic food-processing and/or preparation machine, including both top-driven machines ( e.g . stand-mixers) and bottom-driven machines {e.g. blenders). It may be implemented in heated and/or cooled machines. It may be used in a machine that is built-in to a work-top or work surface, or in a stand-alone device. The invention can also be provided as a stand-alone device.

“Food processing” as described herein should be taken to encompass chopping, whisking, stirring, kneading, mincing, grinding, shaping, shredding, grating, cooking, freezing, making ice-cream, juicing (centrifugally or with a scroll), or other food processing activities involving the physical and/or chemical transformation of food and/or beverage material by mechanical, chemical, and/or thermal means. “Food processing attachment” encompasses any attachable component configured, for example on rotation and/or energising, to carry out any of the previously described food processing tasks.

The term “discrete circuit” as used herein preferably connotes a circuit in which one or more components of the circuit are manufactured separately, more preferably wherein each component of the circuit is manufactured separately. A “discrete circuit” may preferably connote that a circuit is not an integrated circuit.

The term “analogue circuit” as used herein preferably connotes a circuit composed of analogue electronic components. An “analogue circuit” may preferably connote a circuit operating on continuously valued signals. An “analogue circuit” may preferably connote a circuit not comprising digital electronic components.

As used herein, a “natural response” of a circuit may preferably connote the behaviour of a circuit when no external bias or power source is applied to the circuit.

As used herein, “operating” in the context of the appliance preferably connotes operating so as to perform a function of the appliance (i.e. operating according to an active mode). As used herein, “operating differently” preferably connotes operating according to different active modes.

Brief Description of Drawings

One or more aspects will now be described, by way of example only and with reference to the accompanying drawings having like-reference numerals, in which:

Fig. 1a is a schematic flow-chart showing the operation of an attachment identification system according to an embodiment of the invention;

Fig. 1 b is a circuit diagram of a first attachment circuit;

Fig. 1c is a circuit diagram of a second attachment circuit; Fig. 2a is a side-on cut-away partial diagram of an appliance and an attachment incorporating the identification system of Fig.1 ; Fig. 2b is a side-on, schematic, not-to-scale, simplified diagram of the appliance and attachment of Fig. 2a;

Fig. 3a is a side-on cut-away diagram of the identification system of Fig. 1 with a first attachment attached; Fig. 3b is a graph depicting a frequency response of the attachment of Fig. 3a;

Fig. 4a is a side-on cut-away diagram of the identification system of Fig. 1 with a second attachment attached; and,

Fig. 4b is a graph depicting a frequency response of the attachment of Fig. 4a.

Specific Description Fig. 1 depicts the operation of an identification system 100 according to an aspect of the present invention. At step 110 a tank drive circuit 111 (which may be a half-bridge or full-bridge inverter) converts an input voltage Vo (preferably from a DC source) into an output wave 112 (which may be a saw-tooth wave as depicted). The output wave 112 is then transmitted via a transmitter coil 210 (see Fig. 2) to the attachment circuit, preferably an identity circuit which allows the appliance to identify the attachment, in this case an LC (or “tank”) circuit 121, where it in step 120 it induces a current in the inductor L of the circuit 121.

The attachment circuit may be an LC circuit 121 which is so-called because it comprises an inductor such as an inductance coil (depicted by the “L”) and a capacitor (depicted by the “C”) connected in series. LC (or indeed other resonant circuits) are also known as “tank” circuits as, once the capacitor is charged or the inductor has a magnetic field, the induced current within then tends to flow back-and- forth from one side of the capacitor C charging it, through the inductor L creating a magnetic field that induces current, to the other side of the capacitor C charging it with an opposite polarity. This oscillation is supposedly similar to water sloshing back-and-forth within a water-tank that has been shaken.

Two possible identity circuit designs are shown in Figs. 1b and 1c. Fig. 1c depicts a classic LC circuit design. Fig. 1b depicts a simpler design where the capacitor is omitted and only an inductor is used. In a further alternative, the circuit 121 can be an RLC circuit, that is a circuit comprising a resistor R, an inductor L, and a capacitor C. In an RLC circuit, the resistor R can be connected either in parallel or in series with the inductor L and the capacitor C. An RLC circuit differs from an LC circuit (which in reality will also have a degree of electrical resistance) in that the resistor is an additional discrete resistive component of known, predetermined/controllable resistance. LC and RLC circuits are examples of resonant circuits.

One characteristic of a resonant circuit is a factor known as the “Q” (or “Quality”) factor. The Q factor is dimensionless measure of the ratio between the energy in the system of the resonant circuit 121, and the energy lost from the system with each oscillation, and may be calculated according to the equation (the skilled person will understand that a Q factor may be calculated according to different formulae):

A simple way of estimating this is the so-called “ring-down method” where the number of cycles needed for the amplitude in volts of the oscillations to half is multiplied by 4.53 to give the value of Q. As the energy dissipated per cycle is directly proportionate to the resistance of the circuit in a RLC circuit with the resistor connected in series, meaning that Q decreases as the resistance increases, the Q factor can be selected in such a circuit by selecting the resistance of the resistor R. In a circuit where the resistor R is connected in parallel with the inductor L and the capacitor C, the energy stored in the circuit is proportionate to the resistance of the resistor R and hence Q is directly proportionate to R. As resistors are mass-produced and cheap components, it is preferable that, where an RLC circuit is used as the circuit 121, the resistors are varied between circuits 121 associated with attachments 200 whilst the inductors and capacitors of the circuits 121 are common components.

Another characteristic of a resonant circuit is its resonant frequency / ₀ , which is the linear frequency at which the current will oscillate within the circuit if no external bias is applied. In the case of an LC circuit this is determined by the capacitance of the capacitor C and the inductance of the inductor L according to the equation:

Therefore, by varying either the capacitance of the capacitor C or the inductance of the inductor L, or both, a specific resonant frequency of the LC circuit 121 may be selected. Different LC circuits 121 may therefore be provided to different attachments 200 to assign different resonant frequencies to them, allowing different attachments 200 to be detected by detecting the resonant frequency of the LC circuit 121 associated with them. Preferably, the resonant frequency of the LC circuit 121 is varied between attachments 200 by varying the capacitance of the capacitor C, allowing the inductor L (which tends to be larger and harder to make, whilst capacitors are mass-produced electronic components) to potentially be a common part across the attachments 400.

Other circuits, for example the circuit depicted in Figure 1b, may not be resonant circuits, but may, like a resonant circuit, have a so-called ‘natural response’ once a current source or external bias is removed, as will be understood by the person skilled in the art, from which characteristics of the circuit may be derived. For example, the current in the circuit of Figure 1b may decay exponentially once the tank drive circuit stops inducing a current in the circuit. The characteristic time scale of the current decay is dependent on the inductance L of the inductor and may be related to other characteristics of the circuit, for example, any resistance. The current decay may be detected by the inductive sensor in a similar way as in the ring-down method described above. Similarly, an inductor may have a Q factor associated with it, which is typically a ratio of its inductive reactance to its resistance at a given frequency. Such a characteristic may also be detected by the inductive sensor. The coupling of the inductor L of the attachment circuit, when coupled to the inductive sensor, may alter the effective inductance of a circuit of the inductive sensor, which may in turn lead to a detectable change in the inductive sensor from which the inductance of the inductor of the circuit attachment may be inferred. Any one of these characteristics and those described above may be suitable for detecting the identity of an attachment in which the circuit is disposed.

As shown in Fig. 2a, the attachment 400 and the appliance 300 can be removably attached to each other using, for example, a screw-fitting, a bayonet-fitting, spring- loaded tabs extending from one element into recesses in the other, or other similar means. Each of the attachment 400 and the appliance 300 may have an attachment formation suitable for mutually engaging. The transmitter coil 310 is located at a position in the appliance 300 that is located close to, and concentric with the inductor coil 410 of the attachment 400 when the attachment 400 is correctly attached to the appliance 300. For example, when the attachment 400 is correctly attached to the appliance 300, the inductor coil 410 and transmitter coil 310 are preferably within 20cm or less, more preferably 5cm or less of each other, and more preferably still within 3cm or less of each other. The inductor coil 410 and transmitter coil 310 are preferably aligned so as to be substantially concentric and generate magnetic fields that are axially aligned. The inductor coil 410 and the transmitter coil 310 are preferably of substantially similar dimensions - for example they may both have diameters in the range of 3cm-15cm. In this way bi-directional inductive coupling is ensured between the inductor coil 410 and transmitter coil 310 when the appliance 300 and attachment 400 are connected. Whilst the inductor 410 and transmitter 310 are described as coils, other shapes and antenna-types may be used. However, coils are preferred as they are symmetrical and circular.

Preferably substantial inductive coupling won’t occur when the attachment 400 is not connected to the appliance 300. Alternatively or additionally, the appliance 300 may be interlocked (e.g., using a suitable push-rod/microswitch arrangement) such that it will not emit via the transmitter coil 310 unless an attachment 400 is attached to the appliance 300. In this way inductive coupling between the appliance 300 and the attachment 400 can be avoided when they are not attached to each other, such that the appliance 300 will not accidentally recognise attachments 400 that are not attached to it.

To detect the resonant frequency f ₀ of the LC circuit 121, the tank drive circuit 111 scans a range of output frequencies. For example this range may be 30kHz to 130kHz, which, particularly with a capacitor having 5% tolerance, is a range sufficiently broad that 16 distinguishable physical characteristics of the LC circuit 121 can be contained in it, allowing a typical large-sized suite of attachments 200 for a food processing device to be distinguished between. The range may be continually scanned or (more efficiently) it may be scanned only at those values where pre determined resonant frequencies may be expected to be found (e.g., the 16 pre assigned resonant frequencies relating to different attachments). Once an attachment 400 is identified, to limit energy use, the appliance 300 may switch to a mode where it periodically emits at the already-identified resonant frequency of the attached attachment to confirm that it is still attached. Alternatively, the appliance 300 may cease transmitting until e.g., an interlock such as that discussed above indicates that either the attachment 400 has been detached or that a different attachment has been attached. The Q-value may be detected using only excitation of the LC circuit 121 by the transmitter coil 310 at a fixed frequency f _T , and then identifying the Q-value based on sensed oscillation of the LC circuit 121 using e.g., the ring-down method discussed above. As such, detection of Q-value alone is more easily achieved than detection of the resonant frequency f ₀ of the LC circuit 121 as only one frequency is scanned.

The resonant frequency f ₀ and/or Q-value of the LC circuit 121 may detected using a time-gated contactless interrogation technique such as that described in Masud, M., Bau, M., Demori, M., Ferrari, M., & Ferrari, V. (2017). Contactless Interrogation System for Capacitive Sensors with Time-Gated Technique. Proceedings of Eurosensors, 1(4), 395. https://doi.org/10.3390/proceedinqs1040395, the entire disclosure of which is hereby incorporated by reference. That is, a technique where the inductor L of the LC circuit 121 is periodically excited during a first time period (TE) at differing frequencies by the tank drive circuit 111, and this excitation is then removed during another time period (TD) at which point the transmitter coil 210 becomes a detector sensing the voltage induced in it by the current 122 flowing through the inductor L of the LC circuit 121. This has the advantage of being a contactless method and thus avoids the need for a wired connection between the appliance 300 and the attachment 400. The need for a data-processor in the attachment 400 to enable tool recognition is thus also avoided.

Fig. 2b shows a schematic view of the arrangement of Fig. 2a. The appliance 300 houses the tank drive circuit 111 which is in electronic communication with the transmitter coil 310. The tank drive circuit 111 may be part of, or be a function carried out by the components of, a data processor 350 having an integral memory. The peak-detector 131 and micro-controller 141 may similarly be provided in the data processor 350. The data processor 350 controls the motor 320 responsive to the resonant frequency f ₀ and/or Q-value detected, and can vary its output between various stored modes of active operation (e.g., speeds or speed ranges). A user- interface 330 is also provided on the appliance 300 (e.g., a touch-screen interface) which can both receive user input and provide feedback to the user. A control knob or sliding switch 340 for controlling the motor 320 is also provided on the appliance 300. The motor 320 transmits drive impetus to the attachment 400 via a drive-shaft 430. The coil 310 is concentric with the drive-shaft 430.

As is also shown in Fig. 2b, an attachment 400 having a coil 410 is provided removably attached to the appliance 300 by removable-attachment means 460. The removable attachment means 460 may be provided as formations on the appliance 300 or the attachment 400, or shared between them. The attachment 400 has an LC circuit 121 with a coil 410. The drive shaft 430 extends through the attachment 400 to a food processing tool 420 (e.g., a blending or cutting tool) to drive it to rotate. The attachment coil 410 may be concentric both with the drive-shaft 430 and with the coil 310 of the appliance when attached to it to enhance inductive coupling between them. A blending cup or housing 450 may be provided wholly or partially surrounding the tool 420 to contain food being processed. A variable-resistance sensor 440 of any of the types discussed above may also be provided in the attachment 400 in electronic communication with the LC circuit 121.

As shown in Figs. 3a-4b, a range of frequencies F are scanned by the transmitter coil 310 and the voltage V induced in the transmitter coil 310 by the inductor L is then sensed for the frequencies F scanned. The frequency F _Y at which the maximum voltage V _Y is then detected as the peak voltage corresponding to the resonant frequency of the LC circuit 121. F _Y and/or V _Y may differ between LC circuits 121 for different attachments 400. Hence, the LC circuit 121 in attachment A has a V _Y of V _Y A and an F _{Y O} f F _Y A, and that of attachment B has a V _Y of V _Y B and an F _{Y O} f F _Y B, and F _Y A is different to F _Y B and/or V _Y A is different to V _Y B.

At step 130, the peak detector 131 determines the sensed V _Y and/or F _Y and compares these to pre-stored values in a memory of the peak detector 131 corresponding to differing attachments 400. Pre-stored instructions can be associated with the pre stored values, including e.g., maximum safe operating speeds, maximum safe warming temperatures etc. of the attachments 400. Alternatively or additionally, the Q-value may be calculated electronically using the ring-down technique described above and compared to stored Q-values. Particularly where the ring-down technique is used, TD must be long enough for sufficient oscillations to occur within the LC circuit 121 for the desired characteristic to be calculated, and a sampling rate of the peak detector 131 should be sufficiently high to detect the desired characteristic. For example, TD should preferably be at least 5ps long and more preferably at least 10ps long. The sampling frequency of the peak detector 131 may preferably be at least twice the resonant frequency.

At step 140, a micro-controller 141 controls components of the appliance 300 based on the output of the peak detector 131. For example, it may control a motor of the appliance 300 to drive a tool of the attachment 400 to rotate at a predetermined speed or limit it to be driven within a pre-determ ined range of speeds according to specific attachment detected. The output speed of the motor of the appliance 400 may also be varied by, for example, controlling a solenoid-operated gearbox. Additionally or alternatively it may permit activation of a heating and/or cooling element associated with the appliance 300 in order to warm/cool food material within the attachment 400, or vary an output temperature (or range of allowable temperatures) of the heating/cooling element. In a further additional or alternative configuration, the peak detector 131 may recognise a null case where no attachment 400 is attached, and instruct the user to attach the attachment 400 via a suitable user interface (e.g., a touch-screen interface, buzzer, indicator light etc.) as well as potentially preventing activation of a motor and/or heating element of the appliance 300. A switch or switches may be put in series with the LC circuit 121 that is/are actuated by attaching of a further attachment (or further attachments) to the attachment 400. For example, the switch may be a microswitch actuated by a push-rod that is in turn actuated so as to complete the circuit by attaching of the further attachment. In this way, an attachment 400 that requires attaching of a further attachment to operate correctly (for example a whisk attachment that requires the attachment of whisks, or a food processing attachment that has a container having a lid that should be attached) will not complete the LC circuit 121 unless the further attachment is attached to the attachment 400. Where the LC circuit 121 is not completed as the switch is not closed, the peak detector 131 can detect a null case and instruct the user that attachment is required.

In a further alternative a sensor may be included into the LC circuit 121. For example, a temperature-variable resistor Rv may be used that may optionally be connected to the LC circuit by actuating a switch to connect it to the circuit during use. In this case, as the resonant frequency f ₀ of the LC circuit 121 does not vary substantially with the resistance of the variable resistor Rv, but the Q-value does vary, detection of the attachment 400 by the appliance 300 using the value of f ₀ is not impacted. The resistance of the resistor Rv may be calculated based on the Q-value, and hence the temperature calculated based on a known relationship between temperature and resistance of the temperature-variable resistor Rv. Whilst a temperature-variable resistor Rv is used in this example, other sensors the resistance of which vary according to physical conditions such as pressure etc. may also be used. For example, the resistor Rv may be a spring-loaded potentiometer where the potentiometer is pushed against the bias of the spring by e.g., a pressure within the attachment 400, or by the extension of a weighted governor away from a drive-shaft under centrifugal force for sensing a speed of the drive-shaft. Additionally, the variable resistor Rv may be a hand-variable potentiometer such that the user can vary the resistance of the resistor Rvto send instructions to the appliance 300. In this way both attachment recognition, and telemetry/instructions from a sensor within the attachment, is achievable without the need for a data-processor in the attachment 400 or wired connection between the attachment 400 and the appliance 300. It will be appreciated that other circuit components (in particular, discrete components such as variable inductors, variable capacitors and variable resistors) may be configured to provide information about environmental or operating conditions of the attachment. These may act to vary the at least one circuit characteristic in order to provide such information to the appliance.

Preferably the attachment 400 and its components (e.g., the LC circuit 121, the coil 410) are dishwasher-safe. This may be achieved by sealing the LC circuit 121, coil 410, and other electronic components within a dishwasher-safe enclosure made of, for example, HDPE or a similar dishwasher-safe plastic. Making the attachment 400 food-safe may be achieved in a similar fashion by sealing the electronic components in a food-safe enclosure.

As used herein, the term "removable attachment" (and similar terms such as “removably attachable"), as used in relation to an attachment between a first object and a second object, preferably connotes that the first object is attached to the second object and can be detached (and preferably re-attached, detached again, and so on, repetitively), and/or that the first object may be removed from the second object without damaging the first object or the second object; more preferably the term connotes that the first object may be re-attached to the second object without damaging the first object or the second object, and/or that the first object may be removed from (and optionally also re-attached to) the second object by hand and/or without the use of tools (e.g. screwdrivers, spanners, etc.). Mechanisms such as a snap-fit, a bayonet attachment, and a hand-rotatable locking nut may be used in this regard. “Food safe” in this context means any substance that does not shed substances harmful to human health in clinically significant quantities if ingested. For example, it should be BPA-free.

“Dishwasher safe” means that it should be physically and chemically stable during prolonged exposure to the conditions prevailing within a dishwasher machine. For example it should be able to withstand exposure to a mixture of water and a typical dishwasher substance (e.g., washing with Fairy™ or Finish™ dishwasher tablets and water, at temperatures of 82 degrees centigrade for as long as 8 hours without visibly degrading (e.g., cracking)). It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.