ELECTROPHOTOGRAPHIC PRINTER

摘要

A printer comprises a photosensitive drum for changing print information to a toner image and a transfer roller for transferring the toner image to a sheet. The transfer roller touching the photosensitive drum can be opened or closed by electric means, or its contact pressure can be controlled. A printing transfer surface position of the photosensitive drum is disposed with a suitable quantity of offset from the conveying surface of an ordinary sheet. The surface of the sheet can be reliably brought into close contact with the photosensitive drum at the timing of printing by closing the transfer roller, and the sheet and the photosensitive drum are separated at times other than printing by opening (releasing) the transfer roller, so that the sheet can be conveyed without touching the drum. Further, a transfer roller which can be opened and closed by electric means by a pitch shorter than the length of the sheet is disposed at each of the front and rear sides of the photosensitive drum. During the period other than the printing processing (such as mere transfer processing, etc.), not only the opened sheet but also the closed sheet can be stably transferred in both normal and reverse directions without bringing it into contact with the photosensitive drum by closing the transfer roller.