Switch for water boiling appliance such as a kettle

Abstract

A steam-responsive switch for use in an electrical water boiling appliance comprises a main body ( 12 ) from which extends a tubular portion ( 13 ) having at or near its leading end a heat responsive bimetal ( 16 ) extending across the mouth thereof which changes shape above a predetermined temperature defining a chamber behind the member and at the opposite face of the main body ( 12 ) an electrical contact pair, the bimetal ( 16 ) engaging on its rear face a slidable pushrod ( 20 ) which extends through the main body ( 12 ) in a sealed manner to act on the electrical contact pair, the tubular portion having a steam/air vent ( 64 ) at one side thereof adjacent the rear face of the bimetal ( 16 ).

1 . A steam-responsive switch for use in an electrical water boiling appliance comprising a main body from which extends a tubular portion having at or near its leading end a heat responsive member extending across the mouth thereof which changes shape above a predetermined temperature defining a chamber behind the member and at the opposite face of the main body an electrical contact pair, the heat responsive member engaging on its rear face a slidable actuating member which extends through the main body in a sealed manner to act on the electrical contact pair, the tubular portion having a vent at one side thereof adjacent the rear face of the heat responsive member opening into the chamber, for the egress of steam and the ingress of cool air.  
     
     
         2 . A steam-responsive switch according to  claim 1  wherein the heat-responsive member is a bimetallic element of dished shape which inverts above said predetermined temperature.  
     
     
         3 . A steam-responsive switch according to  claim 2  wherein the bimetallic element has a cut-out region therein which defines a tongue-shaped portion which engages said actuating member.  
     
     
         4 . A steam-responsive switch according to  claim 3  wherein the bimetallic element is disposed such that the tongue-shaped portion extends towards said steam vent.  
     
     
         5 . A steam-responsive switch according to  claim 3  wherein the actuating member engages the tongue-shaped portion at a position spaced from the tongue end.  
     
     
         6 . A steam-responsive switch according to  claim 1  wherein said actuating member comprises a pushrod which extends through an opening in said main body and wherein a resilient bellows-type seal is provided between the pushrod and the main body to prevent steam or water from entering said opening.  
     
     
         7 . A steam-responsive switch according to  claim 6  wherein the pushrod engages a bistable over-centre lever having an actuating portion which engages the electrical contact pair.  
     
     
         8 . A steam-responsive switch according to  claim 1  wherein sealing means is provided extending circumferentially about the tubular portion close to the main body portion.  
     
     
         9 . A steam-responsive switch according to  claim 8  wherein the sealing means comprises an O-ring seal.  
     
     
         10 . A steam-responsive switch according to  claim 7  wherein a cover part is provided to fit over the main body enclosing said electrical contacts therein and having openings to allow electrical connection to said contacts and through which a portion of said lever extends, said openings being surrounded by upstanding water-shedding collars.  
     
     
         11 . A steam-responsive switch according to  claim 1  wherein the main body is of short generally cylindrical form and the tubular portion is of circular section.  
     
     
         12 . A steam-responsive switch for a water boiling appliance comprising a forwardly-facing tubular portion of circular section having a heat responsive member arranged to extend across the forwardly-facing open mouth thereof and a rear portion supporting an electrical contact pair having a movable contact, a movable actuating member being provided which extends from the heat responsive member to the rear portion to act on the contact pair, the rear portion being of outer dimension slightly greater than the tubular portion with a shoulder therebetween whereby the switch has a plug-like shape for making a push-fit within a cylindrical opening or recess in an appliance. a rear portion supporting an electrical contact pair having a movable contact, a movable actuating member being provided which extends from the heat responsive member to the rear portion to act on the contact pair.  
     
     
         13 . A steam-responsive switch according to  claim 12  wherein the rear portion comprises a main body portion from which protrudes said tubular portion and a cover which fits over the main body portion defining said shoulder.  
     
     
         14 . A steam-responsive switch according to  claim 13  where the main body portion supports said contact pair on a rear face thereof, the movable actuating member extending through the main body in a sealed manner to act on the contact pair.  
     
     
         15 . A steam-responsive switch for use in an electrical water boiling appliance comprising a main body from which extends a tubular portion having at or near its leading end a heat responsive member extending across the mouth thereof which changes shape above a predetermined temperature defining a chamber behind the member and at the opposite face of the main body an electrical contact pair, the heat responsive member engaging a slidable actuating member which extends through the main body to act on the electrical contact pair, and a flexible bellowstype seal provided between the actuating member and the main body through which the actuating member extends.  
     
     
         16 . A steam-responsive switch according to  claim 15  wherein at the region where the bellows-type seal engages the main body, the main body is provided with a circular groove into which a tubular end of the seal is received.  
     
     
         17 . A steam-responsive switch according to  claim 15  wherein the actuating member is a push rod having an enlarged head portion which the heat-responsive member abuts.  
     
     
         18 . A steam-responsive switch according to  claim 15  wherein the bellows-type seal is formed of a silicone.  
     
     
         19 . An electrical water boiling appliance with a steam-responsive switch, the appliance having a main water carrying body provided with a steam port at an upper region of the body and an opening or recess defined on the body or a housing part joined thereto which communicates with the steam port, the switch having a main switch body from which extends a tubular portion fitted into said opening or recess having at or near its leading end a heat responsive member extending across the mouth thereof which changes shape above a predetermined temperature defining a chamber behind the member, with an electrical contact pair disposed at the opposite face of the main switch body, a slidable actuating member which engages the heat responsive member extending through the main switch body in a sealed manner to act on the electrical contact pair, the tubular portion having a vent at one side thereof adjacent the rear face of the heat responsive member opening into the chamber for the egress of steam and the ingress of cool air.  
     
     
         20 . An electrical water boiling appliance according to  claim 19  wherein the switch vent is disposed at a lower side of the tubular portion.  
     
     
         21 . An electrical water boiling appliance according to  claim 20  wherein the heat-responsive member is a dished bimetallic element with a cut-out region therein which defines a tongue portion which extends towards the switch vent.  
     
     
         22 . An electrical water boiling appliance according to  claim 19  wherein the appliance body or housing part connected thereto is formed with a passageway in communication with the switch vent and with the exterior of the appliance.  
     
     
         23 . An electrical water boiling appliance according to  claim 19  wherein the opening or recess is circular, whilst the tubular portion of the switch is circular whereby the switch can be push-fitted into the opening or recess.