Apparatus for film treating

Claim 1

A solid state pulse waveform generator for corona discharge treatment, at a predetermined constant voltage, of plastic bodies comprising: a source of dc power; at least two sequentiallyconductive thyristor devices connected in parallel circuit relationship with each other and arranged in series circuit relationship with the load circuit and said source of dc power; reverse-conduction diode means, connected in parallel across each of said thyristor devices and inductive and capacitive elements arranged in series circuit relationship with each other and in series circuit relationship with each parallel combination of said thyristor devices and diode means and capable of oscillating at a frequency higher than the frequency of timing circuit means to effect independent turnoff of said thyristor devices; timing circuit means for sequentially rendering conductive said thyristor devices at a variable frequency; and load circuit means including a step-up, high voltage transformer having inductively coupled primary and secondary windings with a turns ratio capable of developing a voltage in the range of 5,000 to 50,000 volts in said secondary winding; said generator operating in conjunction with corona treating means comprising at least two spaced electrodes, one of which is insulated with a dielectric barrier, connected across said high voltage secondary winding; and wherein the value of said variable frequency of said timing circuit means is adjustable to control the output pulse rate in the sonic frequency range to optimize the power delivered at said predetermined constant voltage to said treating means.