The present invention relates to an improved electrostatic copying machine for copying two original documents on the opposite sides of a copy sheet in superposition in such a manner that the centers of the two copies imaged on the opposite sides of the copy sheet are coincident with each other.
Electrostatic copying machines have been proposed heretofore which copy two different original documents on the opposite sides of a copy sheet in such a manner that the two copied images are superposed and centered on the copy sheet. However, it is often desired to copy in such a manner that the centers of the copied images on the opposite sides of the copy sheet are coincident with each other and that the copied images are offset from the center of the copy sheet, leaving a blank space at an edge of the copy sheet which can be used as a binding area for binding a number of copy sheets together in book form. An electrostatic copying machine capable of copying on both sides of a copy sheet and which is further capable of copying in such a manner that the two copied images are thus superposed but offset from the center of the copy sheet has not heretofore been invented.
It is further desirable to provide copy sheets of two different sizes in suitable cassettes in such a manner that the desired size can be selected merely by changing over a switch or lever. Such copy machines are known in the art. However, a copying process on both sides of a copy sheet requires that an intermediate sheet holder be provided to temporarily hold the copy sheet between the first and second copy operations. Where it is desired to change the sheet size, the sheet holders must be readjusted in conjunction with each other to accommodate the new size. This operation is time consuming and relatively difficult, and furthermore increases the chances of a sheet jam and due to improper adjustment. A copying machine which copies on both sides of a copy sheet and which furthermore allows changeover from one copy sheet size to another by a simple switching operation has not been available heretofore.