Plasma spraying method and apparatus

Claim 2

Plasma spraying apparatus comprising a plasma gun including a pair of spaced electrodes connected to a source of voltage and operable to generate a plasma in response to current flow between said electrodes, a transformer haVing a first winding electrically connected in series between one of said electrodes and said voltage source, said transformer also including a second winding, and a control circuit for maintaining a uniform power level between said electrodes regardless of variance in voltage and current flow which can occur between said electrodes in the absence of said control circuit, said control circuit including said second winding.

Claim 3

Plasma spraying apparatus in accordance with claim 1 wherein said control circuit comprises means for introducing a reference power level signal, means for generating a power level signal proportional to the power level between said electrodes, means for combining the reference power level signal and the power level signal to generate a power level differential signal, and means for applying said power level differential signal to said current flow controlling means to vary the current flow between said electrodes so as to maintain a uniform power level.

Claim 4

Plasma spraying apparatus in accordance with claim 2 wherein said means for generating said power level signal comprises means for generating a voltage signal proportional to the voltage applied to said electrodes, means for generating a current signal proportional to the current flow between said electrodes, and means for multiplying said voltage signal and said current signal to generate said power level signals.

Claim 5

Apparatus in accordance with claim 2 wherein said control circuit further includes means for introducing a manual power level signal, and said means for applying said power level differential signal to said current flow controlling means includes means for combining said power level differential signal and said manual power level signal to generate a power level control signal which is applied to said current flow controlling means.

Claim 6

Plasma spraying apparatus in accordance with claim 4 wherein said control circuit includes a switch operable between an automatic position and a manual position disconnecting said power level differential signal from said means for combining said power level differential signal and said manual power level signal, whereby said power level control signal is regulated solely by said manual power level signal.

Claim 7

Plasma spraying apparatus in accordance with claim 4 wherein said circuit further includes an amplifier connected between said power level differential signal generating means and said power level control signal generating means, an integrator connected between said power level differential signal generating means and said power level control signal generating means in parallel with said amplifier, and means for shunting said integrator in the event said power level differential signal is above a predetermined level.

Claim 8

Plasma spraying apparatus in accordance with claim 6 wherein said circuit further includes means connected to said integrator for passing to ground current above a predetermined potential.

Claim 9

Plasma spraying apparatus comprising a plasma gun including a pair of spaced electrodes connected to a source of voltage and operable to generate a plasma in response to current flow between said electrodes, means electrically connected in series between one of said electrodes and said voltage source for controlling current flow between said electrodes, a first control circuit means connected to said current controlling means for maintaining a uniform power level between said electrodes regardless of variance in voltage and current flow which can occur between said electrodes in the absence of said first control circuit means, a second circuit means for suppressing current between said electrodes during initiation of plasma generation, and switch means for detachably connecting said second circuit means to said first circuit means for effecting current suppression during initiation of plasma generation.

Claim 10

Plasma spraying apparatus comprising a plasma gun including a pair of spaced electrodes connected to a source of voltage and operable to generate a plasma in response to current flow between said electrodes, means electrically connected in series between one of said electrodes and said voltage source for controlling current flow between said electrodes, a first control circuit means connected to said current controlling means for maintaining a uniform power level between said electrodes regardless of variance in voltage and current flow which can occur between said electrodes in the absence of said first control circuit means, a second circuit means for suppressing current between said electrodes during initiation of plasma generation, and switch means for detachably connecting said second circuit means to said first circuit means for effecting current suppression during initiation of plasma generation.

Claim 11

Plasma spraying apparatus in accordance with claim 8 wherein said current suppressing means includes saiD current signal generating means, means for introducing a reference current signal, and means for combining said current signal and said reference current signal to generate a differential current signal.

Claim 12

Plasma spraying apparatus in accordance with claim 8 wherein said current suppressing means includes a time-delay switch operably connecting said current suppressing means in said control circuit for a given time.

Claim 13

Plasma spraying apparatus in accordance with claim 10 wherein said circuit further includes means for switching said circuit between an automatic operating mode and a manual operating mode and wherein said time-delay switch is operable to electrically connect said current suppressing means in said circuit when said circuit is in said automatic operating mode.