GB1604036A

GB1604036A - Controls for liquid heating appliances

Info

Publication number: GB1604036A
Application number: GB5015077A
Authority: GB
Original assignee: TI Russell Hobbs Ltd
Current assignee: TI Russell Hobbs Ltd
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-12-02

Description

(54) CONTROLS FOR LIQUID HEATING APPLIANCES (71) We, T I RUSSELL HOBBS LIMITED, a British Company of Grindley Lane Blythe Bridge, Stoke-on-Trent, Staffordshire ST11 9LN, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to controls for liquid heating appliances and, in particu lar, to a temperature-controlled switch that operates to interrupt the supply of electric current to a heater element when a tempera ture responsive element of the switch senses a critical temperature.

One form of such a switch is a vapour controlled switch in a kettle which, in one known form, comprises a strip of tempera ture-responsive bimetallic material that is secured at one of its ends and has its other end free to cooperate with a rockable dolly which, when rocked from an ON to an OFF position by distortion of the bimetal strip, opens a pair of contacts in the electric circuitry of the kettle to interrupt the supply of electricity to the heating element of the kettle.

In this form of switch, an adjustment of the operating temperature is made possible by the provision of a screw that acts on the bimetal strip at a position adjacent its fixed end and can be advanced or retreated so as to move the bimetal strip.

This arrangement has the disadvantage that a relatively small movement of the screw produces a large change in the position and condition of the bimetal strip, so that accu rate adjustment is difficult. Moreover, the bimetal can be strained past its elastic limit by overturning of the screw.

According to the present invention there is provided a temperature controlled switch for an electric liquid heating appliance compris ing a housing which carries a bimetal ele ment and a manually operable switch-actu ating member which is operatively associated with the bimetal element by a push rod and which is movable from an ON to an OFF position by deformation of the bimetal ele ment upon temperature change thereof to interrupt, in use, the supply of electricity to a heater element of the appliance, the switchactuating member including an adjustable part which can be adjusted to vary the effective distance between the push-rod and the member so that the temperature at which the member is moved by deformation of the bimetal element to actuate the switch can be varied.

The adjustable part may be a screw accommodated in an internally screwthreaded insert which is in turn accommodated in a passage in the movable member, which passage extends between two sides of the member. The end of the passage closest to the push-rod may be closed by a flexible free end of a strip, against one side of which the screw is arranged to act to vary the position of the free end of the strip, and against the other side of which the push-rod acts.

The bimetal element may be in the form of a strip bent into the shape of a U and having one of the arms thereof apertured to allow the push-rod to pass through it to be acted on by the other arm of the U.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a vertical sectional view of a first control embodying the invention, and Fig. 2 is a vertical sectional view of a second control embodying the invention.

Fig. I shows a plastic housing 11 which is mounted, in use, on the rear of a kettle (not shown). The housing 11 accommodates contacts (not shown) of a vapour controlled switch which are so arranged in the electrical circuitry of the kettle that the supply of electricity to a heating element (not shown) of the kettle is interrupted when the switch is open. The switch is operated by a dolly 12 rockably mounted on the housing 11 by means of brackets (not shown) that are engaged by knife-edge pivots 10 of the dolly.

The dolly 12 is movable with an over-centre action between an ON and an OFF position.

In use, the rear side of the housing is closed by a cover (not shown) and the dolly 12 extends through a slot in the cover so as to be accessible to the user of the kettle. The dolly 12 carries a laterally extending arm 13 which cooperates with a movable contact of the switch and separates the movable contact from a fixed contact when the dolly is rocked from its ON to its OFF poisition.

Movement tFf the dolly 12 in response to boiling of liquid in the kettle is effected by a bimetal strip 14 secured by a nut and bolt fastening 15 to the side of the housing remote from the dolly 12 within a steam chamber defined between the rear wall of the kettle body and a front-face the the housing 11. I steam pipe 16, pait only of which is shown Fig. 1, extends between the liquid-containing interior of the kettle and a position adjacent the, bimetal strip 14. The end of the strip 14 remote from the fastening 15 co-operates with one end of a push-rod 17 that extends through a passage 8 in the housing 11 and has its other end positioned to co-operate with the dolly 12.

The dolly 12 has a passage 19 extending through it in which is fixedly mounted an internally screw-threaded hollow insert 21.

Extending through the insert 21 is an'" adjust- ing screw 22 one end of which is slotted and is within the passage 19 and the other end of which extends slightly beyond a face of the dolly 12 which is adjacent to push-rod 17.

The screw 22 may contain B nylon insert, to produce some friction and prevent accide"nta'l backing off. The opening the said face of the dolly 12 through which the screw 22 extends is covered by a free end of a flexible adjusting strip 23 secured towards its other end by a fastening 24 to a lower part of the said face. When the screw 22 is turned in the insert 21, the screw 42 is is advanced or retracted moving the free end of the adjust- ing strip 23 towards or away from the push- rod 17. Thus, variation of the position of the screw 22 adjusts the, amount of movement of the push rod necessary to rock the dolly r2 from its ON to Eis OFF position and thus adjusts the sensitivity of the vapour-controlled switch.

Fig. 2 shows an alternative embodiment that differs from the one shown in Fig. 1 in the form of the bimetal element and corresponding parts have been given the same reference numerals in Fig. 2 as, they have in Fig. 1.

In Fig. 2, the bimetal element is a strip 31 bent into the shape of an inverted U, the arms of which are of unequal length. The longer arm is secured, near, its free end, by a fastening 32, to the front face of the housing 11 and is held in its U-shape by a nut and bolt connector 33 that extends between the two arms of the U at a position adjacent the bottom of the U. The longer arm of the U is apertured to allow the push-rod 17 to pass through it to a position adjacent the shorter arm of the U. When steam enters the steam chamber via the pipe 16, the free, shorter, arm of the U flexes and moves the push-rod The advantages of the embodiments de scribed are, inter alia, that adjustment of the vapour controlled switch can be carried out bv a user of the kettle. by means of,a small screw driver. that no parts need to be removed to gain access to the adjusting screw, that the adjustment is not sensitive to small movements of the,. screw and that the adjustment screw is well away from the steam area and is. therefore. not so liable to become locked by c'oridsion :and deposits.

Claims

WHAT WE CLAIM IS: ' 1 A temperature-controlled switch for an electric liquid heating appliance compris ing a housing which carries a bimetal ele ment and a manually operable switch-actu ating member which is operatively associated with the bimetal element by a push rod and which is movable from an ON to an OFF position by deformation of the bimetal ele ment upon temperature change thereof to interrupt, in use, the supply of electricity to a heater element of the appliance, the switch actuating member including an adjustable part which can be adjusted to vary the effective distance between the push-rod and the member so ,that the temperature at which :the member is moved by deformation of the bimetal element to actuate the switch can be varied.
2. A temperature-controlled switch ac cording to Claim 1 wherein the said adjusta ble part is a screw accommodated in an internally screw-threaded insert accommo dated in a passage in the switch actuating member, which passage extends between the sides of the member.
3. A temperature-controlled switch ac cording to Claim 2 wherein the end of the passge closes to the push-rod may be closed by a flexible free end of a strip against one side of which the screw is arranged to act to vary the position of the free end of the strip and against the other side of which the push rod acts.
4. A temperature-controlled switch ac cording to any of Claims 1 to 3 wherein the bimetal element is in the form of a strip bent into the shape of a U and having one of the arms thereof apertured to allow the push-rod to pass through it to be acted on by the other arm of the U.
5. A temperature-controlled switch for an electric liquid heating appliance substantially as hereinbefore described with refer ence to and as illustrated in the accompany ing drawings.
6. An electric liquid heating appliance a' te' tymperature controlled switch according to any of Claims 1 to 5.
7. An electric liquid heating appliance according to Claim 6 wherein the said adjustable part is accessible to a user of the appliance while the appliance is assembled.