Charge control system for xerographic machines

Claim 1

In an electrostatic type reproduction machine for producing copies of an original, the machine having a photoreceptor, charging means for placing a charge on the photoreceptor in preparation for imaging, exposure means for exposing the charged photoreceptor to the original whereby to create a latent electrostatic image of the original on the photoreceptor, developing means for developing the latent electrostatic image on the photoreceptor, and transfer means for transferring the developed image to a sheet of copy material, the combination comprising: light means for illuminating said photoreceptor to reduce the charge level of said photoreceptor; supplemental charging means for increasing the charge on said photoreceptor; a power source for said light means and said supplemental charging means; means for monitoring the charge on said photoreceptor to produce a control signal proportional to the degree of overcharge or undercharge of said photoreceptor; said monitoring means including means for generating a first signal reflecting the optimum charge for said photoreceptor, means for generating a second signal reflecting the existing charge on said photoreceptor, and comparator means for comparing said first and second signals to provide said control signal; and control means for proportionally actuating said light means and said supplemental charging means in response to said control signal, said control means including first control gate means responsive to a control signal of one polarity for regulating power input from said power source to said light means in proportion to the strength of said control signal; and second control gate means responsive to a control signal of the opposite polarity for regulating power input from said power source to said supplemental charging means in proportion to the strength of said control signal.