Copying machine for producing margins of constant width

Claim 1

A copying machine comprising a document table for placing an original thereon, a photoconductive drum, an optical system movable relative to the document table for exposing the original to light to form an electrostatic latent image of the original in variable magnification on the drum at an image forming station, a white color member attached to the table for covering the leading end portion of the original from the exposing light, means for developing the latent image, means for transporting copy paper to a transfer station, means for transferring the developed image from the photoconductive drum to the copy paper brought into contact with the drum at the transfer station, means for fixing the transferred image to the copy paper, detection means for producing an output upon detecting that the boundary between the white color member and the original has been exposed to light by the optical system, timer means for measuring a specified period of time from the time the detection means produces the output and drive means for initiating the paper transporting means into operation in response to an input from the timer means, the distance of transport of the copy paper from the transporting means to the transfer station being smaller than the distance from the image forming station to the transfer station along the periphery of the photoconductive drum and the total period of time (t 1 ), which is the time measured by the timer plus the time to transport the copy paper from the transporting means to the transfer station, being shorter than the period of time for rotating the drum from the image forming station to the transfer station (t 2 ), the difference between t 1 and t 2 resulting in the formation of a margin on the copy paper, whereby a margin of constant width is formed without readjusting the feed timing of the copy paper even if the copy magnification is varied.