ELECTRIC LIQUID BOILING APPARATUS HAVING AN ELECTRONIC TEMPERATURE SENSOR CONTROL

• US 3,784,788 A
• Filed: 05/04/1972
• Issued: 01/08/1974
• Est. Priority Date: 05/04/1971
• Status: Expired due to Term

• Current Assignee: HARVEY, PAUL ALWYN, 78 SOUTH TERRACE, SURBITON, SURREY,
• Original Assignee: Denise Gisele Josette Fourny
• Inventors: Fourny, Denise Gisele Josette
• Primary Examiner(s): Mayewsky, Volodymyr Y.
• Application Number:
  US05/250,349
• Time in Patent Office: 614 Days
• Field of Search: 219/328,330,441,442,449,494,504,516,522 99/280,281 317/98 338/22R,22SD
• US Class Current: 219/441
• CPC Class Codes: A47J 27/21091 of electronic type
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H05B 1/0269 For heating of fluids
• CPC Class Codes: H05B 2213/07 Heating plates with temperature control means

Abstract

An electric liquid boiling apparatus, particularly an electric kettle, having an automatic cut-out operated by an electronic temperature sensor, e.g. a thermistor which is subjected to vapour when the liquid boils.

Claims

1. In an apparatus for boiling liquid comprising a container for the liquid, said container having an opening therein through which hot liquid vapor is ejected when the liquid boils, an electric heating element in the container for heating the liquid therein and means for carrying electric current to said heating element, the improvement comprising a current-controlled switch device in series with said current carrying means;

a control circuit having an input and an output, said output being connected to the current controlled switch device; and

an electronic temperature sensor means having a high temperature coefficient positioned so as to be subjected to said ejected hot liquid vapor when the liquid in the container boils and being electrically connected to said input of said control circuit, whereby when the liquid boils, the electronic temperature sensor is heated and the control circuit operates the current-controlled switch device to cut off the heating current for the heating element.

2. Apparatus as claimed in claim 1 wherein the temperature sensor means is a thermistor.

3. Apparatus as claimed in claim 1 wherein the temperature sensor means is situated outside said opening adjacent thereto.

4. Apparatus as claimed in claim 1 including a thermally conductive metal strip in thermal contact with said heating element and said electronic temperature sensor means, whereby said switch device is operative to break the current supply to the heating element both when the liquid boils and when the heating element overheats.

5. Apparatus as claimed in claim 1 including a second electronic temperature sensor means, said second sensor means being in thermal contact with said heating element, the two temperature sensor means being electrically connected in parallel so that heating of either operates the switch device, whereby said switch device is operative to break the current supply to the heating element both when the liquid boils and when the heating element overheats.

6. Apparatus as claimed in claim 1 wherein the switch device is an electromechanical relay which is manually resettable.

7. Apparatus as claimed in claim 6 wherein the control circuit comprises a transistor having an emitter-collector path connected to control the energization of the relay and a base emitter path connected to the said input to be controlled by said temperature sensor means.

8. Apparatus as claimed in claim 1 wherein said container is a kettle for boiling water, said kettle including a handle, the control circuit and switch deviCe being included in said handle, a duct in the handle communicating with said opening and with the air-space above the water, said duct having the temperature sensor means positioned therein.