GB1348611A - Lockable self-cleaning electric ovens - Google Patents

Abstract

1348611 Locks JEGA FRIEDRICHSTHALER EISENWERK JENEWEIN & GAPP GmbH 11 Feb 1972 [11 Aug 1971] 6568/72 Heading E2A [Also in Division F4] A self-cleaning electric oven 1 comprises heating elements 2, 3 which are selectively set by a manually actuated switch 28 either to a selected operating temperature or to a temperature at which a self cleaning operation takes place, a door switch 10 which allows the self cleaning operation only when the door is closed, a door fastening mechanism with a locking member and a temperature responsive device which comprises a heat expandable agent and an actuator and which is operative when the switch 28 has been set for the self cleaning operation and the oven has attained a safe limit temperature of 300‹C wherein operation of the device causes the actuator to secure the door fastening mechanism in the locking condition and to set a control switch 22 to close an auxiliary current circuit to effect further energisation of the heating elements to heat the oven to the self cleaning temperature the auxiliary current circuit being independent of the current circuit for the heating elements. The door fastening mechanism comprises a pair of levers 13 pivoting on a support strip 15 on the oven, the levers being urged by springs 17 so that inwardly bent ends secure a pin 5 on the door between them, the levers being locked by a head member 20b at one end of a piston rod 20a of a hydraulic cylinder actuator 20 the member being insertable between the levers to lock them in position. A slide 6 slidable on the oven is moved against the pressure of a spring 7 when the door is closed to operate the switch 10 in a circuit for a heating element 26b surrounding a vessel 26a containing fluid and which is connected by a tube 26c to the cylinder. At about 300‹C a temperature sensor 34 in the oven completes the circuit for the heating element 26b. As the fluid is heated the rod 20a moves and inserts the head member 20b between the levers to lock the door and a stop 20c on the rod 20a closes the switch 22 for the heating circuit for the oven to be heated to the self cleaning temperature. If the sensor controlled circuit fails and the door pin is not locked by the head member 20b it is locked by the deformation of bimetallic elements between the head member and a stop 15a on the support strip 15. Alternatively the rod 20a may pass through a U-shaped metallic spring which deforms when heated to engage behind the head member and move it to locking position.