International Business Machines Corporation

James L Bacon

Larry Mason Ernst

Gerald L Smith

Jesse Wayne Spears

William G Hauptman

In an electrophotographic copying device having charging, imaging, developing, transferring, precleaning and cleaning facilities, the arrangement being in the conventional sense, but incorporates a combined charging and precleaning unit that is operable to perform either a charging function or a precleaning function at the proper time during a copying/cleaning cycle. A combined precharging/transferring unit is also incorporated to facilitate precharging or transferring at a predetermined time during the copying process.

Photoconductor charging technique

An apparatus and method for improving the print quality of a coarse scan/fine print image processing device. The apparatus includes an encoder which assigns a code to a coarsely scanned picture element (PEL). The assigned code is representative of the reflectance characteristic of the PEL. For fine reproduction of coarsely scanned data, the coarsely scanned PEL is summed with at least four adjacent horizontal and vertical PELs to reproduce a fine PEL comprising of at least four subelements.

Coarse scan/fine print algorithm

A digitally regulated power supply for the corona charging unit of an electrostatic copying machine in which a sample of the ionic current of the corona unit is utilized in conjunction with a digital regulator to regulate the power supply establishing the charge of the corona. The digital regulator in conjunction with at least one pulse width modulated power supply permits very fast rise and fall times of the power supply current. Further, between duty cycles of the machine, the digital regulator stores a representation of the correct operating point of the corona charging unit determined in the immediately prior duty cycle. In the next duty cycle, the representation is utilized by the digital regulator to initially regulate the power supply.

Digitally regulated power supply for use in electrostatic  transfer

A corona and associated electrical drive as shown herein, neutralize the static charges on non-conductive sheets or webs. The neutralization of static charge is accomplished by passing the material to be neutralized under a double wire corona. Both wires in the corona are connected to an AC signal. The AC signal drives both wires with a signal that alternates in polarity at frequency f. The wires are spaced apart a predetermined distance calculated from a function dependent upon the frequency of the AC signal and the speed of the paper moving under the corona wires. The predetermined distance is such that a given area of the paper will pass under one wire at a first polarity and under the second wire at the opposite polarity. Further enhancement of neutralization can be accomplished by using a second double wire corona out of phase with the first double wire corona. In addition the sheet or web as it passes under the corona wires is supported to prevent static charge on the support from balancing a static charge on the sheet or web. Accordingly, the only static charge present as the sheet or web moves under the corona is that charge carried by the sheet or web. The corona wires will neutralize that charge either by discharging it with oppositely charged ions or depositing oppositely charged ions to balance the charge already on the sheet or web. Thus as the sheet or web moves away from the neutralizing station the sheet or web has a net charge which is substantially zero.

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Boulder, CO, United States of America

James L Bacon