GB2489970A - Driving a portable kitchen appliance with an enhanced storage capacitive device - Google Patents

Abstract

An electric driving arrangement for a portable kitchen appliance includes a re-chargeable enhanced storage capacitive device (ESC) 42. The ESC device can be a hybrid capacitor employing battery and capacitor technology; a super capacitor; an ultra capacitor or a double layer capacitor. Two ESC devices can be of different types and connected in parallel and/or series. An electronic controller 40 can connect the ESC device to, and drive, a motor 44 of the kitchen appliance. The electronic controller can compensate for a variation in voltage of the ESC device over time and cause the motor to operate with a desired selectable operating regime such as its operational speed. The appliance can be a cordless hand mixer or blender and dock with a charging device which can comprise a linear regulating device (fig 1) or a switched mode power supply (fig 2).

Description

I

PORTABLE KITCHEN APPLiANCES AND ELECTRICAL DRiViNG

ARRANGEMENTS THEREFOR

[0001] The present invention relates to portable kitchen appliances and electrical driving arrangements therefor, and it relates more particularly, though not exclusively, to such arrangements for hand held appliances, such as hand mixers and hand blenders.

[0002] Such appliances typically comprise a main driver unit that contains a prime mover, such as a motor, together with one or more attachments that can be releasably secured to the driver unit to adapt the appliance for a particular task or tasks. In the case of a hand blender, for example, these attachments are typically wand-like, tubular devices fitted at one end with mechanisms for latching to the driver unit and for picking is up the motor drive, and carrying a shrouded cutting or processing tool at the other end. The tool is driven in rotation by means including a shaft running axially through the attachment.

[0003] Most kitchen appliances, even hand held ones, are mains operated and thus are constrained in use by attachment to a mains lead running to an electrical outlet socket mounted on a wall or a worktop for instance. The mains lead has to be dragged around as an appliance is used, and this can be both a hindrance and a potential danger, particularly if it should become snagged with another appliance or a vessel containing hot ingredients or hot water, or is draped across a hot surface, for

example.

[0004] The ability to move freely around the kitchen and, for example, blend food stuffs in a pan on a stove would thus be an advantage, implying the use of a truly portable appliance having a power source that does not require a permanent mains connection. Such portable appliances are often referred to as being "cordless" appliances.

[0005] A common problem with known cordless electrical appliances, however, is that they typically utilise rechargeable batteries which may be left in a discharged state after a previous use, or may become discharged during use, making it necessary to wait a considerable period of time, whilst recharging tkkes place, before they can again be used. In this respect, whilst conventional rechargeable batteries can deliver in the region of thirty minutes of useful work from a fully charged state, the recharging process, even with advanced battery technology such as Lithium-ion, takes considerably longer. Thus, if the battery is not always maintained in a fully charged state, and/or if it becomes discharged in use, before the process for which the appliance is being used is complete, the food preparation process can be delayed or interrupted for a considerable time whilst the battery is recharged.

[0006] Rechargeable batteries and their associated control circuitry are, moreover, intrinsically costly and are subject to environmental disposal requirements, which introduce significant on-cost.

[0007] It is an object of the invention to address the above-described difficulties.

[0008] According to the invention from one aspect, there is provided an electrical driving arrangement for a kitchen appliance; the arrangement including one or more rechargeable enhanced-storage capacitive devices, by which is meant devices such as hybrid capacitors, which employ a blend of capacitor and battery technologies, and/or devices of the kind known variously as "supercapacitors", "ultracapacitors" or "double-layer capacitors".

[0009] Preferably, the kitchen appliance comprises a "cordless" hand held appliance such as a hand blender or a hand mixer and includes a motor driven by said arrangement. In any event, the invention encompasses a kitchen appliance powered by said arrangement.

[0010] Enhanced-storage capacitive devices will hereinafter be referred to, individually and collectively, as "ESC devices" for ease of reference, but it is to be understood that such reference is intended to include such devices of all the aforesaid descriptions, as well as combinations of such devices and equivalent or similar devices called by other names.

[0011] Arrangements according to some preferred examples of the invention comprise a plurality of ESC devices connected in series and/or parallel; moreover at least two of said ESC devices may, in some preferred embodiments, be devices of different type.

[0012] ESC devices advantageously can be recharged much more rapidly than can batteries. However, at present they typically offer a significantly shorter working time and moreover their discharge characteristics can tend to impact adversely on the operational performance of the appliance, since the voltage of an ESC device typically starts to immediately diminish once a working cycle commences.

[0013] ft is thus another object of the present invention to provide a system and method of power management to allow energy stored by an ESC device to be applied to the prime mover (usually a motor) of a cordless appliance in a more controlled manner, such that the prime mover is supplied with power in accordance with a desired and predetermined power transmission regime.

[0014] According to a second aspect of the invention, therefore, there is provided, in or for a kitchen appliance, an electrical driving arrangement including one or more rechargeable ESC devices (as defined herein) and further comprising an electric motor and an electronic controller connected between said arrangement and the motor; the ESC device having a voltage output exhibiting a characteristic variation with time and the electronic controller being configured to modify the said voltage with time in a predetermined manner, thereby to impose a desired operating regime upon the motor, rather than that associated with the said output voltage characteristic of the ESC device.

[0015] Tn addition to the ability to be recharged in a matter of seconds (compared to minutes or even hours for conventional batteries) ESC devices have additional advantages, including simpler charging methods, using simpler electronics. Additionally, ESC devices can typically be recharged many thousands of times, whilst exhibiting little or no memory effect, and some such devices can be recharged in excess of 100,000 times, compared to a few hundred times for batteries. Moreover, Lithium-ion and Lithium-polymer batteries can explode if discharged too fast, and thus require costly protective electronics to prevent this happening. It is not necessary to provide such protection for ESC devices, allowing them to have a very high power density.

[0016] Furtheimore, EU regulations require batteries in electrical products to be removable by the user at the end of the product's life, and manufacturers are taxed for the disposal of the batteries. These regulations do not currently apply to appliances powered by ESC devices.

[0017] In order that the invention may be cleatly understood and readily carried into effect, one embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: [0018] Figure 1 shows, in block-diagrammatic form, one example of a charging circuit suitable for use with a driving arrangement incoiporating an ESC device; [0019] Figure 2 shows another example of a charging circuit suitable for use in this context [0020] Figure 3 shows, in block diagrammatic form, part of an electrical driving arrangement, in accordance with one exemplary embodiment of the invention, for a kitchen appliance such as a hand blender; [0021] Figure 4 shows graphs indicative of one way of operating an arrangement of the kind shown in Figure 3; and [0022] Figure 5 shows graphs indicative of another way of operating an arrangement of the kind shown in Figure 3.

[0023] It is preferred that a charger is provided with the appliance and specially configured for use therewith; such a charger typically comprising a m2ins-powered unit having a receptacle shaped and sized so that the "cordless" kitchen appliance, or at least the driver unit thereof, can be snugly fitted therein for storage and charging. The charger needs of course to be capable of supplying appropriate current and voltage to charge the ESC device(s) in the appliance. The charger, when powered, is preferably designed to consume energy only when the appliance (or its driver unit) is inserted into the receptacle and, typically, the operational status of the charger is indicated by means of one or more visual displays located on the charger unit and/or the appliance itself. In addition, the charger unit may conveniently provide storage niches or protrusions to house or support one or more attachments provided with the appliance.

[0024] The charger unit typically contains an isolating transformer, a bridge rectifier and a suitable device to reduce surge current when the appliance (or its driver unit) is inserted into its receptacle.

[0025] Figure 1 shows, in simplified and block diagrammatic form, one example of a circuit that may be included in a typical charger unit suitable for the present purposes and configured as a linearly regulated power supply unit, or PSU, 10.

[0026] The PSU 10 comprises a transformer 112. a bridge rectifier 14, a linear regulator circuit 16 and capacitors 18 and 20 used for smoothing as is well known.

[0027] AC voltage is applied to the primary I 2a of the transformer and the output of the transformer is rectified by the bridge 14. The transformer 12 is chosen according to the mains input voltage and the required voltage for the input to the regulator 16. The regulator 16 is used to provide the correct voltage to charge the capacitor(s) in an ESC device (not shown in Figure 1) connected to the output terminals 22 of the PSU 10, The power rating of the transformer 12 is of course chosen so the current required is not exceeded. When the power supply 10 is first connected to the ESC device, it operates in constant current mode with the voltage folding back to match the capacitor voltage. When the capacitor voltage matches the regulator output voltage the power supply operates in constant voltage mode and the current will decrease over time.

[0028] Figure 2 shows a switched mode PSU (SMPSU) 24, usable in place of the PSU 10, which incorporates a flyback converter, allowing electrical isolation between the mains input 26 and the DC output 28. The high frequency switching employed in such supply units allows the transformer 30 to be much smaller than the transformer 12 utilised in the linear PSU 10.

[0029] In any event, and however the ESC device or devices in the electrical driving arrangement of a kitchen appliance in accordance with the invention are charged, it is desirable to compensate for certain characteristic operational features associated with the use of ESC devices.

[0030] in this respect, a typical ESC device has a voltage output characteristic exhibiting a fairly rapid decrease with time. Accordingly, and depending upon the type of motor used and its operational voltage requirements, connection of one or more ESC device(s) directly to the motor of the kitchen appliance, may cause the motor speed to rapidly fall below a useable limit. To counter this tendency, the present embodiment provides an electronic controller 40 connected between a power supply 42, comprising one or more USC devices, and a motor 44 as shown in Figure 3. The controller 40 provides a control signal 46 to control the application of power to the motor 44. The control signal 46is preferably, and in this example, frequency based, using a variable duty cycle.

Effectively, the arrangement shown in Figure 3 causes the motor to run in accordance with a desired operating regime, rather than accepting the performance provided by the intrinsic voltage output characteristics of the USC device, if desired, the arrangement can be configured to store control si_s capable of causing the motor to nm in accordance with any of several alternative operating regimes, each regime being appropriate for a different task, or range of tasks, for which the appliance may be used, and a selector device is provided allowing a user to select a chosen operation which, in turn, selects the control signals for the appropriate operating regime and utilises them to compensate appropriately for the voltage output characteristics of the ESC device.

[00311 In operation of the arrangement of Figure 3, the control may be imposed "open loop", in the sense that the control is asserted simply in accordance with a predetermined algorithm or other control function which operates with fixed timing in response to actuation of the appliance by a user. This open loop control is preferably supplemented with, a "closed loop" control, wherein an optional sensing element 48, powered by the ESC device 42, is used to measure a parameter indicative of the motor speed which is fed to the controller 40. Monitoring the parameter permits the control signal 46 to be varied, thereby allowing the voltage across the motor 44 to be adjusted if necessary to maintain a prescribed operational speed. Moreover, when the monitored parameter drops below a predetermined limit, the controller 40 can be configured to automatically remove power from the motor 44 and provide an indication to the user that the appliance should be placed in the charger and charged.

[0032] Figure 4 shows graphs indicative of the operation of an arrangement in accordance with one example of the invention, utilising an open loop control system. In Figure 4, the linearly falling solid line marked 50 represents the output voltage characteristic of a typical ESC device 42. The dashed line marked 52 represents a linearly increasing variable duty cycle imposed by the controller 44 in accordance with a predetermined, or pre-programmed, function that progressively changes during an operating period of the driver unit to provide a constant power input, shown by the chain-dotted line 54, to the prime mover (e.g. motor) of the cordless appliance. It will be appreciated that, by using the controller 40 to effectively multiply repeated samples of the falling ESC output voltage characteristic 50 by respective samples of the rising duty cycle characteristic 52, the substantially flat power input characteristic 54 can be achieved. It will also be appreciated that ESC devices having non-linear output voltage characteristics can be used, and further (whatever the voltage output characteristics of the ESC device(s)), that the use of differing duty cycle characteristics can achieve power input characteristics that differ from the flat characteristic 54.

[0033] Graphs indicative of such a different profile are shown in Figure 5, wherein the falling solid line marked 60 represents the output voltage characteristic of an ESC device 42; the dashed line marked 62 represents is a fluctuating duty cycle imposed by the controller 44 in accordance with a predetermined, or pre-programmed, function that progressively changes during an operating period of the driver unit to provide a predetermined, variable power input, shown by the chain-dotted line 64, to the prime mover (e.g. motor) of the cordless appliance. At switch-on, the duty cycle imposed by the controller 40 is, as shown by the line 62, 100%, thereby providing the full ESC initial voltage to the motor and allowing large or tough ingredients to be processed. The duty cycle is then reduced to approximately 50% to provide a gentler blending. As the ESC device 42 discharges, the duty cycle is increased to compensate for the reducing capacitor voltage. The actual durations of the various duty cycle phases can be adjusted to suit the application.

II

[0034] As previously mentioned, an arrangement in accordance with the invention may include a facility for selecting any of two or more pre-determined duty cycle functions in order to power the prime mover differently for different tasks. In connection with such a facility, the processor 40 may comprise, or may itself be controlled by, a microprocessor capable of storing the algorithms and/or other data necessary to implement the various duty cycle functions, and a selector means allowing the user to select a setting assigned to a particular task and thereby automatically apply the appropriate duty cycle function to the controller 40.

[0035] It is envisaged that arrangements in accordance with various examples of the invention may include individual USC devices; plural, similar ESC devices connected in series and/or parallel, or combinational set-ups including different kinds of ESC device. For example, it may be advantageous in some circumstances to utilise a combination of hybrid devices and supercapacitors, coupled together in a configuration selected to provide a combined operational characteristic selected for a particular operation or range of operations.

Claims (12)

1. Claims: 1. An electrical driving arrangement for a kitchen appliance; the arrangement including at least one rechargeable enhanced-storage capacitive device ("ESC device") as defined herein.
2. 2. An arrangement according to claim ii, wherein said at least one ESC device comprises one or more hybrid capacitor devices.
3. 3. An arrangement according to claim 1 or claim 2, wherein said at least one ESC device comprises one or more devices of the kind known variously as "supercapacitors", "ultracapacitors" or "double-layer capacitors".
4. 4. An arrangement according to any preceding claim comprising a plurality of ESC devices connected in series and/or parallel.
5. 5. An arrangement according to claim 4, wherein at least two of said ESC devices are devices of different type.
6. 6. A kitchen appliance comprising a motor and an arrangement according to any preceding claim connected to drive said motor.
7. 7. An appliance according to claim 6, further comprising an electronic controller connected between said arrangement and the motor; the ESC device having a voltage output exhibiting a characteristic variation with time and the electronic controller being configured to modify the said voltage with time in a predetermined manner, thereby to impose a desired operating regime upon the motor, rather than that associated with the said output voltage characteristic of the ESC device.
8. 8. An appliance according to claim 6 or claim 7, configured as a portable hand mixer or hand blender.
9. 9. An appliance according to any of claims 6 to 8 associated with a charging device for charging said at least one ESC device; said charging device and said appliance being configured to dock together such that said appliance is supported by said charging device for storage and charging.
10. 10. In or for a cordless kitchen appliance including an electric motor, an electrical driving arrangement for said motor including one or more rechargeable ESC devices (as defined herein) and further comprising an electronic controller connected between said arrangement and the motor; the ESC device having a voltage output exhibiting a characteristic variation with time and the electronic controller being configured to modify the said voltage with time in a predetermined manner, thereby to impose a desired operating regime upon the motor, rather than that associated with the said output voltage characteristic of the ESC device.
11. 11. An arrangement according to claim 10, further including means for storing control data for implementing a plurality of different predetermined operating regimes for said appliance and user-operable selection means enabling a user to select the most appropriate of said regimes for a task in hand.
12. 12. An electrical driving arrangement for a cordless kitchen appliance substantially as described herein andfor as shown in the accompanying drawings.