GB2255493A - Heating apparatus with sound actuable switch - Google Patents

Abstract

An apparatus for boiling water, comprising a sound detector 25 responsive to emission of sound by the sound emitter 11 to produce a signal, a switch 22 to control the supply of energy for heating a vessel, for example a kettle, and an actuator 26 responsive to the maintenance of said signal for a predetermined period to actuate the switch to halt the supply of energy to the kettle. Heating may be by gas, electric or electromagnetic induction. <IMAGE>

Description

HEATING APPARATUS This invention concerns heating apparatus, and controls for heating apparatus, for boiling water.

It is customary to boil water in utensils (such as kettles, jugs and pots) upon stoves, and to control the stove manually to regulate the rate at which heat is applied and to stop the heating when the water has boiled.

Such manual control is tedious, and to avoid such tedium, various forms of vessels have been developed over the years to include thermal sensors which actuate heating controls when specific temperature conditions are established. For example, "automatic" electric kettles incorporating bimetallic or other thermal sensors which respond to being subjected to steam to switch off the electric heater of the kettle.

However, problems of cost, electrical safety and complexity arise when such heat responsive sensors are employed. For instance, each sensor device has to be designed or integrated into a specific form of utensil, e.g. electric kettle, because of the need to provide a good (e.g. low flow resistance vapour path or a low thermal inertia path) thermal input the sensor device for effective control of the heating.

An object of the invention is to enable such problems to be reduced or avoided.

In general, the present invention provides apparatus for boiling water having a control system for controlling the heating of the water, which control system comprises a sound detector to detect a sound signal characteristically produced by a sound generating device actuable by a flow of steam; and wherein the control system is responsive to said signal to cause said heating to cease only after said signal has been maintained for a predetermined period.

The sound generating device may comprise a whistle, a reed or a clacker actuated by the pressure created by the production of steam forcing a flow of steam through the sound generating device.

The sound detector is preferably mounted on a base or stand upon which a vessel holding the water may be placed.

The base or stand may be of a form which provides electrical contacts for supplying electricity to a heating device incorporated in the vessel; or may be of a form, such as a gas burner or stove hotplate, which supplies heat direct to the vessel placed over or on the burner or hotplate; or may be of a form which supplies electromagnetic energy to heat inductively a metal part in or of the vessel.

In an embodiment of the present invention there is provided kettle apparatus comprising a whistling kettle having a metal or part-metal body and a whistle device; together with a stand assembly comprising an induction heater, control means to control the power supply to the induction heater, and a sound detector responsive to the noise of the whistle; wherein the switch means is responsive to the sound detector to switch off the power supply to the induction heater when the whistle has sounded for a predetermined time.

The apparatus is preferably provided with a switch to prevent operation of the heater unless a kettle is in position to be heated by the heater, and a manually operable control switch.

The present invention further provides electric kettle apparatus comprising a kettle and a stand, wherein the kettle comprises a steam driven sound emitter; and wherein the stand comprises a sound detector responsive to emission of sound by the sound emitter to produce a signal, a switch to control the supply of energy for heating the kettle, and an actuator responsive to the maintenance of said signal for a predetermined period to actuate the switch to halt the supply of energy to the kettle.

Said predetermined period is preferably at least two seconds but may be any period within the range of 3 to 10 seconds.

The signal or whistle is preferably audible to normal persons.

The signal or whistle may be of dual frequency form, of which one frequency may be ultrasonic.

The vessel or kettle may be provided with a vent to allow a proportion of the steam to by-pass the sound generating device. Said vent may be closable or restrictable to reduce said proportion.

Preferably, the impedance provided by the sound generating device to the flow of steam therethrough is presettable or adjustable.

The control system is preferably arranged so that the intensity of said signal has to be maintained above a predetermined minimum intensity for said predetermined period. Also, the sensitivity of the sound detector may be adjustable or settable to vary the level of said minimum intensity.

The invention further provides a base or stand, for a kettle having a sound generating device, comprising a sound detector responsive to emission of sound by the sound generating device to produce a signal, a switch to control the supply of energy for heating the kettle, and an actuator responsive to the maintenance of said signal for a predetermined period to actuate the switch to halt the supply of energy to the kettle.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein FIGURE 1 shows a first embodiment of apparatus of the invention, FIGURE 2 shows the schematic arrangement of a control system and a heating circuit of a second embodiment apparatus of the invention.

The apparatus comprises a simple whistling kettle having a metal body 10 and a whistle 11 removably located in a spout opening of the kettle. The apparatus further includes a stand 20 providing a recess for location of the kettle under which or in which recess is situated an electro-magnetic induction heater 21 which receives power from a control device 22. The control device receives control inputs from a manual on/off switch 23, a load or position sensing switch 24 and a whistle detector 25, which together constitute a control system for the apparatus.

The apparatus functions so that the water in the kettle is heated by electro-magnetic induction heating of the metal base of the kettle when the switches 23 and 24 are closed, until a predetermined time has elapsed after the whistle detector has been triggered by the water in the kettle boiling to actuate the whistle 11. The whistle detector is a frequency selective microphone device the output of which is fed to a timer 26 which starts counting a predetermined period when the detector 25 is actuated and continues counting whilst the output is maintained until the end of said period is reached, whereupon the timer actuates the control device 22 to switch off the power input to the induction heater 21. In the event of the whistle 11 ceasing to whistle, e.g. due to the switch 23 being actuated manually, the timer is automatically reset. The timer 26 may be integrated into the control device 22.

The control device 22 may be automatically reset by removing and replacing the kettle, but is preferably resettable only by the switch 23 being switched on again (or off and on again).

Referring to FIGURE 2, the apparatus comprises an electric kettle 40 and a base 41. The kettle has a heating element 42, thermally protected by a two stage thermal cut-out switch arrangement 43, to which terminal pins 44 in the bottom of the kettle are electrically connected.

The base 41 provides sockets 45 to receive the pins and a switch 46 closed by insertion of the pins in the sockets in known manner.

A heating control system 30 is interposed between the switch 44 and mains electrical input terminals 47. A lamp L1 is connected across the live and neutral terminals.

The system 30 comprises a step-down transformer and rectifier unit 31 giving a DC supply to a sensor, relays R1 and R2, manually actuable "start" and "stop" switches 33 and 34 and to a lamp L2. The system is arranged to function so that when the start switch 33 is closed momentarily relay R2 is energised to close normally open contacts R2A,B,C and D. The closing of contacts R2C and D energises the lines to the base switch 46 for heating the element. The closing of contacts R2B enables but does not energise relay R1, and the closing of contacts R2A latches in relay R2 to hold all R2 contacts closed when the start switch is released. Lamp L2 parallels relay R2 and is energised therewith during heating.

Relay R2 can be de-energised to open all the R2 contacts and terminate heating, by energising relay R1 to open normally closed contacts RlA, which can be achieved either by closing momentarily the stop switch or by actuation of the sensor 32.

In this embodiment the sensor 32 is a sound sensor which is responsive to the simultaneous creation of two specific sound frequencies by means of a sound generator 33, comprising a reeds each tuned to create a specific note when subjected to a pressure generated flow of steam, which generator is suitably provided in the kettle 40 so as to be actuated when the water therein is boiled. The sensor 32 incorporates the previously described timer 26 the output of which controls relay R1 via contacts R2B.

The invention is not confined to details of the examples disclosed and many variations are possible within the scope of the invention as defined by the appended claims.

For example, the control unit or system may comprise a microprocessor, a solid state or other electronic unit or other arrangement which is arranged to cause the heating of the water to be terminated when the unit has sensed the presence of the sound or vibration signal over a predetermined period of time.

The heater 21 may be replaced by an electric resistance heating element or other hot plate.

The control system can be employed to control an electrically actuated gas valve for use in embodiments in which the vessel is heated by a gas burner instead of, for example, an electrically powered hotplate, so that the gas valve is caused to close, when the water in the vessel has boiled, to shut off the gas supply to the burner.

Said predetermined period is preferably set at a value between five and eight seconds, an optimum setting being six or seven seconds.

The value may be set constructionally or in another fixed manner in the control unit or system, or may be adjustably pre-settable.

The sound intensity of the signal necessary to effect a response from the control system may be set or varied by presetting or adjustment of the control system e.g. by setting or varying the sensitivity of the detector 25 or sensor 32 or by use of a signal threshold gate in the output from the detector or sensor. The sound intensity, for a given rate of boiling, emitted by the sound generator may be preset, or may be made adjustable by paralleling the sound generator with a variable steam escape vent and/or by adjustment of the sound generator.

The invention also provides and includes within its scope any heating apparatus or control unit or system comprising any novel part, feature or function disclosed herein or the drawings, and any novel combination of parts, features of functions so disclosed.

Claims (20)

1. Apparatus for boiling water having a control system for controlling the heating of the water, which control system comprises a sound detector to detect a sound signal characteristically produced by a sound generating device actuable by a flow or steam; and wherein the control system is responsive to said signal to cause said heating to cease only after said signal has been maintained for a predetermined period.

2. Apparatus as claimed in Claim 1 comprising a vessel and a base or stand, wherein the sound generating device is provided on the vessel; and wherein the base or stand is provided with the control system.

3. Apparatus as claimed in Claim 2 wherein the base or stand is of a form which provides electrical contacts for supplying electricity to a heating device incorporated in the vessel.

4. Apparatus as claimed in Claim 2 wherein the base or stand is of a form, such as a gas burner or stove hotplate, which supplies heat direct to the vessel placed over or on the burner or hotplate.

5. Apparatus as claimed in Claim 2 wherein the base or stand is of a form which supplies electromagnetic energy to heat inductively a metal part in or of the vessel.

6. Apparatus as claimed in Claim 1 comprising a kettle, having a metal or part-metal body, and a stand or base comprising an induction heater; wherein the control system is arranged to control the power supply to the induction heater.

7. Apparatus as claimed in any one of Claims 2 to 6 further comprising a switch to prevent said heating unless the vessel or kettle is in position to be heated, and comprising a manually operable control switch.

8. Apparatus as claimed in any one of Claims 2 to 7 wherein the vessel or kettle is provided with a vent to allow a proportion of the steam to by-pass the sound generating device, and wherein said vent is closable or is restrictable to reduce said proportion.

9. Apparatus as claimed in any preceding claim wherein said period is at least two seconds.

10. Apparatus as claimed in any preceding claim wherein said period is within the range of 3 to 10 seconds.

11. Apparatus as claimed in any preceding claim wherein said period is within the range of 5 to 9 seconds.

12. Apparatus as claimed in any preceding claim wherein said period is preset.

13. Apparatus as claimed in any preceding claim wherein said period is adjustably presettable.

14. Apparatus as claimed in any preceding claim wherein the sound generating device comprises a whistle, a reed or a clacker, actuated by the pressure created by the production of steam forcing a flow of steam through the sound generating device.

15. Apparatus as claimed in any preceding claim wherein the signal or whistle is audible, or includes at least one audible frequency.

16. Apparatus as claimed in any preceding claim wherein the impedance provided by the sound generating device to the flow of steam therethrough is presettable or adjustable.

17. Apparatus as claimed in any preceding claim wherein the control system is arranged so that the intensity of said signal has to be maintained above a predetermined minimum intensity for said predetermined period.

18. Apparatus as claimed in Claim 17 wherein the sensitivity of the sound detector is adjustable or settable to vary the level of said minimum intensity.

19. A base or stand, for a kettle having a sound generating device, comprising a sound detector responsive to emission of sound by the sound generating device to produce a signal, a switch to control the supply of energy for heating the kettle, and an actuator responsive to the maintenance of said signal for a predetermined period to actuate the switch to halt the supply of energy to the kettle.

20. Apparatus or a base or stand substantially as hereinbefore described with reference to the accompanying drawings.