PROCEDIMIENTO Y DISPOSITIVO PARA EVITAR EL SOBRECALENTAMIEN-TO DE LA RESISTENCIA ELECTRICA DE CALENTAMIENTO DE UN CATA- LIZADOR DE HUMOS EN UN HORNO DE LIMPIEZA POR PIROLISIS.

摘要

1520908 Supply circuits for heat cleanable ovens COMPAGNIE EUROPEENNE POUR L'EQUIPMENT MENAGER 23 Oct 1975 [29 Oct 1974] 43672/75 Heading H2H A cooker having a heat cleanable oven comprises a catalyzer which includes a heating resistor whereby the temperature of the catalyzer is increased, energization of the heating resistor being terminated when the oven temperature reaches a value at which the catalyzer becomes effective but lower than the cleaning temperature. An oven comprises four heating resistors A, B, V, S, suitably situated in the oven which resistors a,re used in the cleaning and cooking operations of the oven, a heating resistor G used for a grilling operation and a heating resistor C associated with a smoke catalyzer (not shown) preferably containing palladium oxide which becomes effective above 350‹ C. A selector switch Co (shown in Fig. 1 in the oven cleaning position) connects resistors A, B across an A.C. source u, v in series with a cooking thermostat Tc and switch contact P2-3 and resistors V, S in parallel across the A.C. source by way of an oven door switch Lp, the 500‹ C. contact of a cleaning thermostat Tn and contacts a, b, c of the switch Co. The resistor C which accelerates the heating of the smoke catalyzer is energized from the A.C. supply by way of the door switch Lp, the 350‹ C. contact of the cleaning thermostat Tn and the contact a of switch Co. Initially the four heaters A, B, V, S are energized during cleaning together with the resistor C. As the oven temperature increases the thermostat Tc opens at a maximum cooking temperature below 350‹ C. thus de-energizing heaters A, B. When the oven temperature reaches 350‹ C. at which the smoke catalyzer becomes effective the 350‹ C. contact of the thermostat Tn opens to de-energize the catalyzer heating resistor C. Thereafter the heaters V, S remain energized to complete the cleaning operation with the oven temperature being cycled about 500‹ C. by the 500‹ contact of the thermostat Tn. When the switch Co is in the cooking position (Fig. 2, not shown) the heaters A, B are permanently energized with the heaters V, S, cyclically energized by way of the cooking thermostat Tc at the desired oven temperature. During cooking the heater resistor C is also permanently energized by way of the 350‹ contact of the thermostat Tn and a contact of the switch Co in the P4-5 position.