GB639393A - Radiation thermostat control for toaster - Google Patents

Abstract

639,393. Electric toasters. DEHN, S. G. (Sunbeam Corporation). June 6, 1946, No. 17233. [Class 39 (iii)] [Also in Groups VI, XIII, XXXV and XXXVII] Heat supply in a toaster is cut off when the bread surface reaches a predetermined temperature by a thermostat 78 spaced from the bread slice and operated by radiant energy emitted from a large area of the bread surface ; and the thermostat comprises a bimetallic strip 78 in a housing 73 open at the front only so that the strip is subjected to heat only from the bread and is shielded from direct radiation from the heating elements when the bread is being toasted. The strip 78 actuates a switch 87 to cut off current when the bread surface reaches a certain temperature, but as the toast then cools, the switch continues the heating in a cyclic manner. When the bread is removed, radiation from an opposite heating element 65 impinges on the strip 78 and current is again supplied cyclically. The bread 43 is supported between tensioned wires 48 in a metal casing with wire-wound heating rods 65 on opposite sides of the bread. Reflectors 54 shaped so that the toast is heated evenly are held in transverse end walls and in a central transverse partition 59. The toaster has a slidably removable bottom plate 69 carrying a crumb tray 72. A lamp 93 indicates when the heaters are on. The bimetallic strip 78 is constructed in accordance with Specification 564,991, [Group XXXVII], and its ends, which are of reduced width, are held against angular movement on expansion by bolts 83. The high expansion side of the strip faces the bread so that the strip on rise of temperature moves outwardly to open contacts 87, 88 to cut off current supply. Outward movement of the strip is limited by an adjustable stop 97. The strip is mounted in a housing 73 in a reflector 54 so that its mid-portion only, which is coated with carbon, is exposed to heat from the bread surface. The housing 73 has a polished interior and focuses heat from the bread on to the strip. The strip moves by snap-action and its ends are polished, one end being slotted so that it is held adjustably by bolt 83 to vary the stress of the strip. The ends of the strip compensate for the temperature of the housing. A control knob 34 moves through links a baffle 102 pivoted on a rod 103 whereby the strip may be adjustably shielded by the baffle from radiation from the bread. A silver strip 86 connects contact 87 to a bolt 83.