Improvements in and relating to high frequency heating apparatus

Abstract

Abstract 759,038. Automatic frequency control systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Sept. 20, 1954 [Sept. 21, 1953], No. 25997/53. Class 38 (4). In an R.F. heating, e.g. diathermy, apparatus in which the oscillator 11, 12 is coupled to a treatment circuit 16 influencing the frequency of the oscillator the oscillator is coupled also to a frequency discriminator whose output, amplified and applied to a motor 19, controls variable tuning elements, e.g. capacitors 15a, 15b of the treatment circuit to compensate any reactance charges in the load circuit and stabilize the oscillator at the cross-over frequency of the discriminator. A switch 35 may be operated to disconnect one of the push-pull amplifier valves 33, 34 and drive the motor 19 till the discriminator operating range is reached. The capacitors 15a, 15b may be controlled by cams giving the capacitors a continuous increase followed by a quick return to their minimum value, of, if the capacitors are of the alternate increase and decrease type a further switch may be in series with the switch 35 and controlled by a cam on the cam-shaft so that the motor 9 is always driven till a position of stability of the capacitors is obtained. Specification 718,439 is referred to.

Inventors

• 👤 Peter Robert Styles

Bibliographic Details