GB578709A - Improvements in or relating to control-units for electric cookers - Google Patents

Abstract

578,709. Control systems for heating resistances. McAULEY, G. May 8, 1944, No. 8645. [Class 38 (iv)] An electromagnetic contactor supplying power to a cooker, may be closed and opened automatically at desired times and is manually controllable at will. The contactor may control at the same time auxiliary circuits, for example for an electric fire or audible alarm device. The time switch shown in the Figure, comprises a motor M, driving at a slow speed, two independently adjustable cams CN and CF, which close and open respectively, in their zero positions, a mercury switch MS. Operation of the "auto" push-button switch, energises a relay A through normally closed contacts of the "on" push-button switch, normally open contacts of the " auto " pushbutton switch and normally closed contacts of the " off push-button switch. The relay locks in over its contact A3 and contacts A1 and A2 operate respectively to light an indicating lamp L1 and start the motor M. Relay contact A4 operates to transfer the energising circuit for the contactor coil C from the " on " push-button switch to the mercury switch MS, which closes and latches in to energise the contactor after an interval determined by the cam CN. The closure of the contactor lights an indicating lamp L2. The latch is released after a further interval determined by the cam CF. Operation of the " off " pushbutton switch at any time, will de-energise the relay and the contactor. Operation of the " on " push-button switch at any time, will de-energise the relay and energise the contactor through normally closed contacts of the "auto" and "off" push-button switches in series, relay contact A4 and normally open contacts of the " on " push-button switch. Closure of the contactor effects a locking circuit for coil C through the contactor blade C3, relay contact A4 and normally closed contacts of the "off" and " auto push-button switches in series. P1 and P2 are sockets for connecting auxiliary apparatus in parallel with the cooker. Audible warning of the operation of the contactor to closed or open positions, may be obtained by connection of a transformer BT through a selector switch ALS as shown, so that the time switch may operate to give alarm clock service.