Short wave diathermy circuit

Claim 2

A diathermy comprising a pair of vacuum tubes in a push-pull tuned plate, tuned grid oscillator circuit having a coil in the tuned plate circuit for applying short wave signals to a patient undergoing treatment, the tuned plate circuit oscillating at a fundamental short wave frequency, each of said tubes having at least a control grid connected to the tuned grid circuit and a screen grid, a source of screen control potential and means coupled to each screen grid for enabling said fundamental frequency to be fed back from the said plate circuit through each screen grid to the corresponding control grid and comprising an impedance for each screen grid for coupling the corresponding screen grid to said source of screen control potential for controlling the power delivered by the coil to a patient undergoing treatment.

Claim 3

A diathermy according to claim 1 wherein the said tuned plate circuit is tuned to a different frequency than that of said tuned grid circuit.

Claim 4

A diathermy according to claim 2 wherein the frequency at which said tuned plate circuit is tuned is lower than that of said grid circuit.

Claim 5

A diathermy as defined in claim 1 wherein each of said impedances comprises a resistor.

Claim 6

A diathermy as defined in claim 1 wherein said tubes comprise a beam tube.

Claim 7

A diathermy comprising a pair of vacuum tubes in a push-pull tuned plate, tuned grid oscillator circuit having a coil in the tuned plate circuit for applying short wave signals to a patient undergoing treatment, the tuned plate circuit oscillating at a fundamental short wave frequency, each of said tubes having at least a control grid connected to the tuned grid circuit and a screen grid, a source of screen control potential and means coupled to each screen grid for enabling said fundamental frequency to be fed back from said plate circuit through each screen grid to the corresponding control grid and comprising impedance means coupled between said screen grids and said source of control potential for controlling the potential to the screen grids and thereby control tHe power delivered by the coil to a patient undergoing treatment.

Claim 8

A diathermy comprising a pair of vacuum tubes in a push-pull tuned plate, tuned grid oscillator circuit having a coil in the tuned plate circuit for applying short wave signals to a patient undergoing treatment, the tuned plate circuit oscillating at a fundamental short wave frequency, each of said tubes having at least a control grid connected to the tuned grid circuit and a screen grid, a source of screen control potential and means coupled to each screen grid for enabling said fundamental frequency to be fed back from said plate circuit through each screen grid to the corresponding control grid and comprising impedance means coupled between said screen grids and said source of control potential for controlling the potential to the screen grids and thereby control tHe power delivered by the coil to a patient undergoing treatment.

Claim 9

A diathermy as defined in claim 6 wherein said impedance means comprises at least two resistors connected in series between said screen grids and the junction between said resistors being connected to such source of control potential the resistors thereby causing any harmonics to be suppressed.

Claim 10

A diathermy as defined in claim 6 wherein said coil is a helical induction coil.

Claim 11

A diathermy comprising a push-pull tuned plate, tuned grid oscillator circuit having first and second vacuum tubes, each having at least a control grid and a screen grid, a cathode electrode and a plate electrode, a source of negative potential, the cathode electrodes being coupled to the source of negative potential and the plate electrodes being coupled across a tuned plate tank circuit comprising a helical induction coil which coil is for applying short wave signals to a patient undergoing treatment, and at least two capacitors connected together in series and coupled in parallel with said coil, a source of positive potential for the circuit connected to said coil, a reference potential coupled to the junction between said at least two series connected capacitors, a tuned grid circuit comprising a tank circuit having a coil coupled between the two control grids and impedance means for coupling the cathodes of said tubes to the coil in the tuned grid circuit, a resistor for each screen grid, each resistor having one end coupled to the corresponding screen grid and a source of screen control potential coupled to the other end of said resistors for controlling the power applied to the patient.

Claim 12

A diathermy comprising a push-pull tuned plate, tuned grid oscillator circuit having first and second vacuum tubes, each having at least a control grid and a screen grid, a cathode electrode and a plate electrode, a source of negative potential, the cathode electrodes being coupled to the source of negative potential and the plate electrodes being coupled across a tuned plate tank circuit comprising a helical induction coil which coil is for applying short wave signals to a patient undergoing treatment, and at least two capacitors connected together in series and coupled in parallel with said coil, a source of positive potential for the circuit connected to said coil, a reference potential coupled to the junction between said at least two series connected capacitors, a tuned grid circuit comprising a tank circuit having a coil coupled between the two control grids and impedance means for coupling the cathodes of said tubes to the coil in the tuned grid circuit, a resistor for each screen grid, each resistor having one end coupled to the corresponding screen grid and a source of screen control potential coupled to the other end of said resistors for controlling the power applied to the patient.

Claim 13

A diathermy comprising at least one vacuum tube in a tuned plate, tuned grid oscillator circuit having a coil in the tuned plate circuit for applying short wave signals to a patient undergoing treatment, the tuned plate circuit oscillating at a fundamental short wave frequency, said tube having at least a control grid connected to the tuned grid circuit and a screen grid, a source of screen control potential and means coupled to said screen grid for enabling said fundamental frequency to be fed back from said plate circuit through said screen grid to said control grid and comprising an impedance for coupling the screen grid to said source of control potential for controlling the power delivered by the coil to a patient undergoing treatment.

Claim 14

A diathermy comprising at least one vacuum tube in a tuned plate, tuned grid oscillator circuit having a coil in the tuned plate circuit for applying short wave signals to a patient undergoing treatment, the tuned plate circuit oscillating at a fundamental short wave frequency, said tube having at least a control grid connected to the tuned grid circuit and a screen grid, a source of screen control potential and means coupled to said screen grid for enabling said fundamental frequency to be fed back from said plate circuit through said screen grid to said control grid and comprising an impedance for coupling the screen grid to said source of control potential for controlling the power delivered by the coil to a patient undergoing treatment.

Claim 15

A diathermy according to claim 10 wherein said tube comprises a beam tube.