Patent GB-412968-A (GB)
Title: Improvements in or relating to high frequency electrical apparatus for use for therapeutic diathermic surgical and like purposes
IPC: A61N1/40
Filed: 1933-01-06
Abstract: 412,968. Electromedical appliances. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, and LAY, A. W., Stanmoss, Mountview Road, Kingsbury, both in London. Jan. 6, 1933, No. 535. [Class 81 (ii).] Electrotherapeutic high frequency apparatus comprises a valve oscillator having a tunable oscillatory circuit to determine the frequency of the oscillations generated, a first output circuit inductively coupled to the oscillator circuit and independently tunable to resonance therewith for the application of diathermy or for surgical treatment and a second output circuit tapped directly on the oscillator circuit for the application of fulgeration, and a switch to connect the patient to either of the output circuits. Fig. 6 shows an arrangement whereby the oscillations are generated by a pair of valves V2 back-coupled in known manner and fed completely from the supply mains via a transformer T, the high tension current being rectified by a pair of diodes V1. Condensers C10 shunt any high frequency potentials in the filament circuits to earth. A voltmeter V is provided to measure the potential applied to the filaments of valves V2 and a meter MA to measure the anode currents of the said valves. The oscillatory circuit is fed through condenser C1 and tuned by condenser C2. The patient is represented by broken lines as a resistance R5 shunted by condenser C5 and may be connected by switch S to the circuit comprising coil CL inductively coupled to the oscillator coil L and tuned by condenser C8, for diathermy or in the case of surgical treatment the patient is connected to one side of the circuit and the surgical instrument to the other. A coupling condenser C6 and ammeter are also inserted in the circuit. When the apparatus is employed for fulgeration, the patient connected to terminals c and d is connected in the other position of the switch S directly, via a variable tapping RA to the oscillator coil L. Protective condensers C6 and C7 are interposed in the leads to the patient. One terminal to which the patient is connected may be earthed to avoid shocks and burning. A foot-operated remote control switch FS may be inserted in the socket SM in one of the primary leads to the transformer, and the socket is automatically shorted when the plug PM is withdrawn. The foot-operated switch is provided with an off position and two on positions connected by a resistance RFS. This resistance enables the operator to practise surgery without an undesirable spark passing between the instrument and the body, the resistance being in circuit when the instrument is first applied. The oscillator coil may consist of an air-spaced helix 1 wound over a frame comprising longitudinal members 11 supported by cruciform end members 2. The tapping is made by a roller contact 8 carried by a radial arm 5 which is rotated by a knob 3 via bars 6 along which the arm 5 can slide, and longitudinal movement is also imparted by a threaded shaft 12 to which the arm is attached and which runs in a threaded sleeve 13 attached to the coil structure. Contact of the tapping can thus be made with any point on the helix. Insulators 4 and 16 are provided, and contact with the arm 5 is made via spring contacts 10.