GB619211A - Improvements relating to high frequency heating processes - Google Patents

Abstract

619,211. Dielectric heating. LUDLOW, J. H., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Nov. 27, 1946, No. 35182. [Class 39 (iii)] A timing device, for use with a dielectric heating process which is followed by a curing period in a press, comprises two valve timing circuits adapted to switch off the dielectric heating at the end of a first predetermined period and simultaneously start the second timing circuit which at the end of a second predetermined period provides a warning signal that the curing period is completed. Closing switch S to complete the circuit to the dielectric heating apparatus H also closes the mechanically coupled switch S, which makes V, conductive, resulting in a fall of anode potential until the anode current is transferred to the screen grid resulting in a heavy current which operates the relay A. This will open the normally closed contacts A; in the heater circuit. At the same time the normally open contacts A2 in the screen grid circuit of V2 will be closed causing V2 to become conductive. A second timing operation similar to the first ensues at the end of which relay B will operate to close the contacts B, and operate an audible or visible signal. The operation of relay B may also be employed to open the press. Specification 602,642, [Group XL (c)], is referred to.