GB556499A - Improvements in the control of electric heating elements, particularly in ovens - Google Patents

Abstract

556,499. Automatic control systems for electric heating apparatus; thermal switches. WILCOLATOR CO. June 1, 1942, No. 7402. Convention date, June 20, 1941. [Class 38 (iv)] [Also in Group XXXVII] Temperature.-Heating apparatus, e.g. ovens, having two heating units 38, 39, an adjustable thermostat 42 and a selecting switch 44, is arranged so that in one position of switch 44 both units may be operative for rapid heating. The circuit of unit 38 then passes through two contacts, such as 32, 33, subject to the combined action of two thermal members, one, such as 23, dependent on operation of the heating apparatus, the other, such as 34, dependent on operation of one of the units. Figs. 1 and 4 refer to a construction in which a bimetal member 23 is exposed to oven temperature and a bimetal member 34 is heated by current to the unit 38 to be eliminated as soon as the thermostat operates..According to Fig. 7 the member 23a is in an enclosure heated by a coil 64 in series with the other unit 39 ; this form may be housed with the switch 44 and the thermostat 42. Figs. 11, 13 show contacts 85, 86 in series with unit 38 (not shown) and carried respectively by a bimetal member 81 and the base of a tube 76 apertured at each side and having a reduced extremity 82 to which the member 81 is secured. The lower limb of the tube is exposed to radiant heat from unit 39 but protects the upper limb so that, when unit 39 is on, contacts 85, 86 are pressed together. The oven heat bends member 81 to press an insulating extension 89 against the side of contact 86 so that when unit 39 cools, on operation of the thermostat, the insulator snaps over the contact and prevents further action of unit 38. Specifications 521,556, [Group XXXVII], and 547,625, [Group XXXVIII], are referred to.