GB818754A - Improvements in electrical heating apparatus - Google Patents

Abstract

818,754. Control systems for heating resistors. METROPOLITAN-VICKERS ELECTRICAL CO. Ltd. Jan. 18, 1957 [Oct. 19, 1955], No. 29891/55. Class 38 (4). [Also in Group XXXVII] Electric heating apparatus having two heating elements comprises in addition to the normal energy regulator a further switching member controlled by an operation separate from that which controls the energy regulator such that one or more of the heating elements may be energized at will with the elements always under the control of the energy regulator. The energy regulator is generally of the type disclosed in Specification 587,947, [Group XXXVII], modified by the addition of a snapaction switch of the type disclosed in Specification 419,917, [Group. XXXVII]. Rotation of a shaft 34 causes a cam 36, which co-operates with a member 37<SP>1</SP>, to alter the setting of a bimetal energy regulator 19 to control the amount of energy supplied to the heating elements 60, 61 over the contacts 5, 6. Axial movement of the shaft 34 causes operation of the contacts 101, 106 of the additional snap-action switch through the medium of a spigot 111 which cooperates with a strip 108 of the trifurcated snapaction switch such that the heating element 61 can be switched at will into or out of circuit without destroying the setting of the energy regulator 19 whilst the energy regulator 19 remains the controlling means of either heating element 60 alone or elements 60, 61 in parallel. The axial movement of the shaft 34 is located by a spring-loaded ball 113 and grooves 115, 116. In a further embodiment the snap-action switch is controlled by the rotation of a shaft coaxial with the shaft 34. Specifications 517,538, [Group XXXVII], and 731,770, [Group XI], also are referred to.