IE20070541A1 - Stirring device - Google Patents

Abstract

The present invention relates to a stirring device (2) for a vessel (1), such as a cooking vessel. The stirring device comprises a heat-activatable engine (6) and stirring means (11). The stirring means (11) is disposable within the vessel (1) and driveable by the engine (6). When the vessel (1) is heated or cooled, the engine (6) is activated to drive the stirring means (11). <Figure 1>

Description

The present invention relates to stirring devices, and in particular to devices for stirring the contents of cooking vessels.

Background to the Invention While cooking, it is often necessary to stir or mix the contents of a cooking pot for a considerable period of time, in order to achieve a desired level of mixing or a desired texture of the resultant mix. Many populafdishes such as risottos, soups, sauces and porridge require almost constant stirring during the cooking process to avoid sticking, burning or lumpiness in the finished dish. Similarly, when making ice-cream, frequent or continuous stirring is required in order to prevent formation of ice crystals and to ensure that a creamy consistency is achieved.

Stirring by hand with a utensil such as a spoon or whisk requires constant attention and can be tiring. Various electrical and mechanical mixing devices are available to reduce the effort required. Mechanical devices, however, still require operation by hand, and while they represent an improvement over hand mixing, prolonged use of such devices is tiring. Electric mixers may provide good results, but require electrical power from battery or mains. The majority of such devices are mains operated. If a cook wishes to stir the contents of a choking pot while cooking, it may not be convenient or safe to have to plug the device into the mains near the cooker or stove. Furthermore, such devices, while requiring little effort by the cook, must be held in position in the pot to ensure that even mixing or stirring is achieved.

It is therefore desirable to provide a stirring device for a cooking vessel which is powered by the same energy source used for cooking and which does not require constant supervision by the cook during cooking. fc0 7Q Summary of the Invention The present invention relates to a stirring device for a vessel, comprising a heatactivatable engine and stirring means, disposable within the vessel and driveable by the engine, wherein when the vessel is heated or cooled, for example, by arranging the vessel adjacent a heating or cooling element, the engine is activated to drive the stirring means. The vessel may be a cooking vessel, such as a cooking pot or saucepan. Alternatively, the vessel may be a cooling vessel, such as the bucket of an ice-cream maker.

The term heat-activatable engine is used herein to include any apparatus capable of producing mechanical energy upon application of (absolute) heat, as well as apparatus capable of producing mechanical energy when a temperature difference exists between two portions thereof, such as a Stirling engine or a thermoelectric device in conjunction with an electric motor.

An advantage of the present arrangement is that the stirring device is powered by the same energy source used for cooking, that is, the heat source used for cooking (or the cooling element used for freezing). The stirring device is therefore energy efficient and does not require a separate mains connection.

In one embodiment of the invention, the heat-activatable engine is activated when heat is applied thereto. This type of stirring device will only be activated when the vessel is heated, for example, by arranging the vessel adjacent a heating element such as a cooker ring or hotplate.

In another embodiment of the invention, the heat-activatable engine is activated when a temperature difference exists between first and second portions of the engine. The engine may be adapted to be activated when the vessel is either heated or cooled, for example, by positioning the vessel adjacent a heating or cooling element. The heatactivatable engine of the stirring device may be oriented such that when the vessel is heated or cooled, the first portion of the engine is closer to the heating or cooling element than the second portion of the engine, thereby creating a temperature difference between the first and second portions to activate the engine. θ54ί Where the engine is adapted to be activated when the vessel is heated, the stirring device may further comprise a heat sink associated with the second portion of the engine. The heat sink draws heat away from the “cool” side of the engine, thereby ensuring that there is a sufficient temperature difference between the first and second portions to activate the engine.

When the vessel is arranged adjacent a heat source, the temperature difference between the “hot” side of the engine (adjacent the heat source) and the “cool” side of the engine (further away from the heat source) will activate the engine. Similarly, when the vessel is arranged adjacent to a cooling element (for ex-ample, in an ice-cream maker), the temperature gradient between the “cool” side of the engine (adjacent the cooling element) and the “hot” side of the engine (further away from the element) will activate the engine.

The stirring device may further comprise a driver gear coupled to the heat-activatable engine and a driven gear coupled to the stirring means and driveably engageable with the driver gear to drive the stirring means. The gear ratio (between the driver gear and the driven gear) may be selected to drive the stirring means at a different rate than the heat-activatable engine. The stirring device may comprise a plurality of driven gears, each driveably engageable with the driver gear to drive the stirring means and each providing a different gear ratio with the driver gear. The stirring device may further comprise selection means for selecting one of said plurality of driven gears to set or adjust the stirring speed.

The heat-activatable engine may comprise a Stirling engine, for example, a Stirling displacement engine. The Stirling displacement engine is a closed-cycle heatactivatable engine. The working gas, which may be air or another suitable gas, is permanently contained within a cylinder. The Stirling engine operates through the use of an external heat source and an external heat sink, each maintained within a limited temperature range, and having a sufficiently large temperature difference between them. According to one embodiment of the present invention, the temperature gradient between the cooking heat source (for example, the hob or stove plate) and the ambient 1^0 7 0 5 4 1 environment may be used to power the Stirling engine. Similarly, in an ice-cream maker, the temperature gradient between the cooling element in the ice-cream maker and the ambient environment may be used to power the engine.

The engine comprises two pistons, a displacer piston and a power piston, which are 90 degrees out of phase with one another. The power piston provides the output power to turn a flywheel, whereas the function of the displacer piston is to move the working gas between the hot and cold sides of the cylinder. When heat is applied to the engine, the working gas expands and causes the power piston to rise. This in turn causes the displacer piston to lower, moving the gas to the cold side of the cylinder. When the gas cools, it contracts and the power piston is pulled downwards. The displacer piston moves upwards, moving the gas to the hot side of the cylinder, thereby completing the cycle.

In the present invention, the Stirling engine need not be positioned so that it is directly adjacent the heat source when in use; the engine will be activated once it is positioned so that a temperature differential is created between the two sides of the Stirling engine.

In an alternative embodiment, the heat-activatable engine comprises a Peltier device and an electric motor. A Peltier (or Seebeck) device is a thermoelectric solid-state device which functions as a heat pump. According to one embodiment of the present invention, the temperature gradient between the cooking heat source (for example, the hob or stove plate) and the ambient environment may be used to power the / thermoelectric device. Similarly, in an ice-cream maker, the temperature gradient between the cooling element in the ice-cream maker and the ambient environment may be used to power the device.

A Peltier/Seebeck device typically comprises two ceramic plates with an array of small bismuth telluride, lead telluride or silicon germanium couples sandwiched therebetween. Each couple comprises one n-type and one p-type semiconductor pellet. When a temperature difference is provided, the thermoelectric device functions as a power generator. Electrons in the n-type element are driven from the warmer plate towards the cooler plate, thus creating a current through the circuit. The holes in the p-type element «07054) will then flow in the direction of the current. The thermal energy from the heat source (or ambient environment) is thereby converted into electrical energy, which may be used to power a load such as a motor.

According to one embodiment of the invention, the heat-activatable engine is activated when a temperature difference exists between first and second portions of the engine, and the stirring device further comprises an energy absorbing element arranged adjacent the first portion of the engine, for absorbing energy produced by an energy source.

Thus, when energy is applied to the stirring device, for example by heating, energy is absorbed by the absorbing element and converted into heat to create a temperature difference between the first and second portions of the engine, thereby activating the engine to drive the stirring means.

This arrangement may be particularly useful for stirring the contents of a cooking vessel when all portions of the vessel and stirring device are heated substantially equally, such as during microwave cooking. The use of an energy absorbing member allows a “hot” point to be created close to the first portion of the engine, thereby providing the required temperature differential to activate the engine and drive the stirring means. In this embodiment, the heat-activatable engine may be a Stirling engine or a thermoelectric device in combination with an electric motor.

According to another embodiment of the invention, the heat-activatable engine is activated when heat is applied thereto, and the stirring device further comprises an energy absorbing element arranged adjacent the engine, for absorbing energy produced by an energy source. Thus, when energy is applied to the vessel, for example by heating, energy is absorbed by the absorbing element to create a heat source, thereby activating the engine to drive the stirring means.

Brief Description of the Drawings Figure 1 is a cross-sectional view of a cooking pot incorporating a first embodiment of the stirring device of the present invention; Figure 2 is a cross-sectional view of a cooking pot incorporating a second embodiment of the stirring device of the present invention; and £070541 Figure 3 is a cross-sectional view of a cooking pot incorporating a third embodiment of the stirring device of the present invention.

Detailed Description of the Drawings A cooking pot 1 incorporating the stirring device 2 of the present invention is shown in Figure 1. The pot 1 comprises a cooking vessel portion 3 and a handle portion 4. The pot further comprises a lid 5.

The stirring device 2 comprises a beta-type Stirling engine 6, which is arranged at a side portion of the pot 1, between the cooking vessel portion 3 and the handle portion 4. The lower surface 7 of the cylinder of the Stirling engine 6 is adjacent the bottom surface 17 of the pot 1, so that when the pot 1 is arranged on a cooker or stove, heat is applied to the surface 7 of the Stirling engine 6. The upper surface 14 of the cylinder is connected to a heat sink or cooling tower 9. The walls of the cylinder are made from a thermally insulating material to ensure that a temperature difference exists between the “hot” side 7 of the Stirling engine adjacent the base 17 of the pot and the “cool” side 14 of the Stirling engine connected to the heat sink 9. As described above, the Stirling engine converts this temperature difference into mechanical energy.

The stirring device 2 also comprises a paddle 11 rotatably attached to the lid 5 by means of a rotatable shaft 18, so that when the lid 5 is placed on the pot 1, the paddle 11 is disposed within the vessel portion 3 of the pot 1. The stirring device 2 further comprises a driver gear 12 coupled to the flywheel of the Stirling engine 6. The driver gear 12 is connected to a driven gear 13 in the lid 5. The driven gear 13 is coupled to the shaft 18 which is, in turn, connected to the paddle 11. When the lid is placed on the pot, driven gear 13 is driveably engaged with driver gear 12. Driven gear 13 is substantially larger than driver gear 12, such that driven gear 13 rotates at a slower rate than driver gear 12.

When the pot 1 is arranged on the cooking heat source, a temperature gradient is created between the base 17 of the pot 1 and the heat sink 9, and the pistons of the Stirling engine are set in motion. The flywheel of the Stirling engine 6 rotates and drives the gear 12. Driver gear 12 drives driven gear 13, which in turn rotates the shaft 18 and the »070541 paddle 11 within the vessel portion 3 to stir the contents of the pot. The stirring means further comprises a knob 16 coupled to the shaft 18, which may be used to initiate rotation of the paddle if necessary.

Because the paddle 11 is attached to the pot lid 5, it may be easily removed to allow the pot 1 and the paddle 11 to be cleaned.

In an alternative embodiment, the stirring device 2 may comprise a gamma-type Stirling engine.

A cooking pot 21 incorporating a second embodiment of the stirring device 22 is shown in Figure 2. The pot 21 comprises a cooking vessel portion 23 and a handle portion 24. In this arrangement, the driven gear 213 is arranged within the rim of the pot rather than the lid and is directly connected to the shaft 218 and the paddle 211. The paddle 211 is removeable from the pot 21 for cleaning. The driver gear 212 is connected to an alphatype Stirling engine 26. The lower surface 27 of the cylinder of the Stirling engine 26 is adjacent the bottom surface 217 of the pot 21. The upper surface 214 of the cylinder of the Stirling engine is connected to a heat sink 29 arranged in the handle portion 24. The walls of the cylinder are made from a thermally insulating material to ensure that a temperature difference exists between the “hot” side 27 of the Stirling engine adjacent the base 217 of the pot and “cool” side 214 of the Stirling engine connected to the heat sink 29 in the handle. Operation of the stirring device is substantially as described above with reference to Figure 1. i In an alternative embodiment, the driven gear 213 may be provided in the base of the pot 21, and the shaft 218 and paddle 211 rotatably mounted on the base of the pot. The paddle 211 may be detachable from the base of the pot to facilitate cleaning.

A cooking pot 31 incorporating a third embodiment of the stirring device 32 is shown in Figure 3. The pot 31 comprises a cooking vessel portion 33, a handle portion 34 and a lid 35. ΙΕο 7 0 5 4 1 The stirring device 32 comprises a Peltier/Seebeck (or thermoelectric) device 36, which is arranged on a side portion of the pot 31. One side 37 of the thermoelectric device is adjacent the side wall of the pot 31, so that when the pot 31 is arranged on a cooker or stove, heat is applied to the surface 37 of the thermoelectric device 36. The other side 314 of the thermoelectric device 36 is connected to a heat sink 39. Thus, a temperature difference exists between the “hot” side 37 of the thermoelectric device adjacent the side wall of the pot and the “cool” side 314 of the thermoelectric device connected to the heat sink 39. As described above, this temperature difference is converted to electrical energy by the thermoelectric device.

The stirring device 32 also comprises a paddle 311 rotatably attached to the lid 35 by means of a rotatable shaft 318, so that when the lid 35 is placed on the pot 31, the paddle 311 is disposed within the vessel portion 33 of the pot 31. The shaft 318 is coupled to an electric motor 30 arranged within the lid 35 of the pot 31, which is in turn connected to the output of the thermoelectric device.

When the pot 31 is arranged on the cooking heat source, a temperature gradient is created between the two sides of the thermoelectric device 36 and and electric current is generated. The current output from the thermoelectric device 36 is used to power the electric motor 30, thereby rotating the shaft 318 and the paddle 311 to stir the contents of the vessel portion 33.

The words “comprises/comprising” and the words “having/including” when used herein /· with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. »070541

Claims (15)

1. A stirring device for a vessel, comprising: a heat-activatable engine; and stirring means, disposable within the vessel and driveable by the engine; wherein when the vessel is heated or cooled, the engine is activated to drive the stirring means.

2. A stirring device as claimed in claim 1, wherein: the heat-activatable engine is activated when a temperature difference exists between first and second portions of the engine; and wherein when the vessel is heated or cooled, the engine is activated to drive the stirring means.

3. A stirring device as claimed in claim 2, wherein: the heat-activatable engine is oriented such that when the vessel is heated or cooled, the first portion of the engine is closer to a heating or cooling element than the second portion of the engine, thereby creating a temperature difference between the first and second portions to activate the engine.

4. A stirring device as claimed in claim 2 or claim 3, further comprising: a heat sink associated with the second portion of the engine.

5. A stirring device as claimed in claim 1, wherein: the heat-activatable engine is activated when heat is applied thereto; and wherein when the vessel is heated, the engine is activated to drive the stirring means.

6. A stirring device as claimed in any preceding claim, further comprising: a driver gear coupled to the heat-activatable engine; and a driven gear coupled to the stirring means and driveably engageable with the driver gear to drive the stirring means. *070541

7. A stirring device as claimed in claim 6, wherein the gear ratio is selected to drive the stirring means at a different rate to the heat-activatable engine.

8. A stirring device as claimed in claim 6, comprising: a plurality of driven gears coupled to the stirring means, each driveably engageable with the driver gear to drive the stirring means and each providing a different gear ratio with the driver gear; and selection means for selecting one of said plurality of driven gears t,o set the stirring speed.

9. A stirring device as claimed in any preceding claim, wherein the heat-activatable engine is a Stirling engine.

10. A stirring device as claimed in claim 9, wherein the engine is a Stirling displacement engine.

11. .A stirring device as claimed in any of claims 1 to 8, wherein the heat-activatable engine comprises a thermoelectric device and an electric motor.

12. A stirring device as claimed in any preceding claim, wherein: the heat-activatable engine is activated when a temperature difference exists between first and second portions of the engine; the stirring device further comprising: I an energy absorbing element arranged adjacent the first portion of the engine, for absorbing energy produced by an energy source; such that when energy is applied to the cooking vessel, energy is absorbed by the absorbing element and converted into heat to create a temperature difference between the first and second portions of the engine, thereby activating the engine to drive the stirring means.

13. A cooking pot comprising the stirring device of any preceding claim.

14.A lid for a cooking pot comprising the stirring device of any of claims 1 to 12.

15.A stirring device substantially as hereinbefore described with reference to and/or as illustrated in Figure 1, 2 or 3 of the accompanying drawings. TOMKINS & CO f 1/3 Figure 1 too 70 5 2/3 Figure 2 3/3 /Eo 70 5 4 ί Figure 3 spec2004