GB707071A - Improvements in or relating to high frequency electric induction heating - Google Patents

Abstract

707,071. Induction heating. WICKMAN, Ltd. May 9, 1952 [May 1, 1951], No. 10230/51. Class 39 (3) A work coil comprises two or more component coils connected in parallel and arranged to be coupled respectively to different parts of a workpiece, and one or more inductances connected in series with one or some of the component coils which are arranged to adjust the relative current flow in the component coils, and thereby the heating of the different parts of the workpiece. In Figs. 2 and 3 the work coil includes three single turn coils 16, 17, 18 secured together, and connected electrically in parallel by conducting blocks 23 and bolts 24. The coils have longitudinally extending slots 20 and sets of apertures 22, 19, 21 which embrace various parts of a set of workpieces, not shown. The slots in the coils 16 and 18 are widened at one end to form rectangular apertures 26, and a pair of short circuiting strips 27, 28 with a connecting screw 29 are adjustable along each aperture 26 to vary the coil inductance. The parts of the coils supporting the said strips may be bent away from one another. In Fig. 4 the work coil comprises a central coil 35 of two turns electrically in parallel with, and sandwiched between, two single turn coils 38. The coils are of tubing and are connected together at 41, 42 so that they surround a tubular workpiece 31 having enlarged annular end walls 33. The current through the coil 35 may be varied by a variable inductance 43 electrically in series therewith, and comprising a U-shaped tubing bridging a gap in one of the coil turns, and short circuited by an adjustable pair of plates 46 clamped together by a nut and bolt 47. Specification 673,241 is referred to.