ES421300A1 - Methods of and apparatus for reproducing images by transferring electrostatic charges - Google Patents

Abstract

Documents are reproduced on a continuous strip of paper by transferring from a photoconductive belt to the paper an array of electrostatic charges, configured to conform to images on the documents. Both the paper and the photoconductive belt are trained around metallic drums which have identical peripheral speeds. The drums are juxtaposed so that they essentially bring the paper and photoconductive belt into contact along a line lying in a plane whiich is tangent to both drums. When the electrostatic charges on the belt arrive at this line, they are transferred to the paper because there is a potential difference existing between the drums due to corona charging of the drum carrying the photoconductive belt and grounding of the drum carrying the paper. The charges, of course, retain the line configuration of the image as they are transferred from the belt to the paper. The capacitance existing between the drums with the photoconductive belt and paper varies due to environmental conditions, such as temperature and humidity, and varies due to lack of compatibility between the photoconductive layer and the paper. This variation in capacitance causes imperfections in images transferred to the paper. In order to compensate for variations caused by this capacitance, the two drums are connected through a circuit which contains an auxiliary capacitor that has a capacitance at least 100 times greater than the capacitance existing between the drums. Since the capacitance of this auxiliary capacitor is so high, it renders the capacitance existing between the two drums insignificant in relation to the total capacitance thereby, in essence, rendering the capacitance independent of both environmental conditions and incompatibility between the paper and photoconductive belt.