GB1457579A - Pyrolytic self-cleaning cooker ovens - Google Patents

Abstract

1457579 Locks ETABS EUGENE SCHOLTES 16 April 1974 [17 April 1973] 16436/74 Heading E2A [Also in Divisions F3 F4 and H2] An electric cooker oven of the kind which is cleaned by burning off the deposits adhering to the inner walls comprises an electromagnetically operated lock bolt 34 Fig. 1 to lock the door during the cleaning operation, a safety switch 13 in the circuit of the heating resistances being operated by the lock bolt, the lock bolt being controlled inturn by a pair of windings having opposite actions, which are connected via a two-way switch 11, operated by a thermostat preset to the oven-cleaning temperature. The safety switch 13 consists of a two-way switch, the movable contact 37 of which must necessarily change to the other contact to maintain the energisation of the heating resistances of the oven after the switch 11 of the thermostat has changed over. The door latch consists of a hook member 20, Fig. 3 on the door and a spring-loaded pivoted retaining member 19 on the oven housing which moves over-centre as the door opens and closes. As it does so a rod 23 moves down and up again. The bolt 30 in the projected position prevents this movement and thereby prevents the door being opened. For cleaning the oven, (Fig. 2, not shown) the control switch 1, Fig. 1 is turned to connect contacts e-m, which energise the extra heating resistance 5, and contacts d-k, which complete a circuit from lock winding 33 so that when thermostat switch 11 transfers to contact t the winding 33 is energised to shoot the bolt 30. The end of the bolt displaces the control lever 36 of switch 13 which transfers to contact r, by-passing switch 11 and maintaining the energisation of heating resistors 2 and 3. Unless the bolt 30 is properly shot, therefore the heaters 2 and 3 are deenergised and the oven does not reach a high temperature. The cleaning operation is normally brought to an end by a programme motor 17 which opens contacts 9 and 18 after a set time. As the oven cools down the switch 11 reverts to contact r, re-energising winding 32 to withdraw the bolt. The temperature during the cleaning operation is limited to say 500‹C by thermostat switch 10. A safety thermostat 40a opens switch 40 if the outside of the oven gets too hot during the cleaning operation. In another form (Figs. 4, 5 not shown) the door is hinged about its lower edge and has a retaining hook on its upper edge. The locking bolt comprises a vertical plate with an opening to receive the hook are connected by control rods to a winding, one at each end of the oven casing.