Improvements in induction heating systems

摘要

875,210. Valve oscillator circuits; R.F. couplings. SOC. DE TRAITEMENTS ELECTROLYTIQUES ET ELECTROTHERMIQUES. Feb. 3, 1959 [Feb. 7, 1958], No. 3789/59. Classes 40(6) and 40(7) [Also in Groups XI and XXXVI] A high-frequency induction heating system which is to be used as an auxiliary heating source for a glass fibre spinner operating at temperature of the order of 1,000‹C. has the heating coil and immediate circuit separate from the valve oscillator supplying the power, which it is necessary to place in a region of lower temperature. The oscillator and heater units are coupled by means of a co-axial cable as indicated in the figure. The oscillator is based on triode valve 2 whose anode is connected to the central conductor 24 of the coaxial line and also to inductance 11 in series with the coupling transformer 12 coupling the anode and grid circuits. A capacitor 10 across inductance 11 is adjusted so that the impedance of the feed-back circuit increases with increase of operating frequency and serves to stabilize the voltage output of the oscillator. The heating coil 18 is tuned by capacitor 19 and operates as a step-up auto-transformer, the input from the co-axial line being connected across tappings 23 and 31. It is preferred to arrange a two-part connector at 20, 21, 22 so that the actual heating coil may be replaced if necessary. Because the impedance of the working circuit is much lower than that of coil 11 the operating frequency of the system is determined by the values of components 18 and 19.