ERASE LAMP SHUTTER
Original Publication Date: 1983-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
In photocopying application, a light image of an original document is projected upon the charged surface of a photoreceptor drum or belt forming a latent image of the document. This latent image is subsequently developed. Each latent image is exposed and discharged within a "frame" corresponding, at unity magnification, to the dimension of the original document. The areas on the photoreceptor abutting succeeding "frames" of latent images referred to as "interdocument gaps", are not exposed to light and hence retain the original charge. The charge must be removed (erased) so as not to be developed in the subsequent development step. The main requirement for any erase mechanism is that the erase be accurate so that none of the document area is erased and that the erase energy level be controlled so that the photoreceptor is discharged to within a specific tolerance. An erase mechanism which meets these criteria is shown in Figure 1. In Figure la, erase energy is provided by light from a lamp (not shown) positioned above photoreceptor belt 10. Interposed between the lamp and the photoreceptor is a shutter assembly comprising independent shutter blades 12 and 14. A fixed slit 16 between the shutter blades and the photoreceptor defines the erasure zone. Figure la shows the status of the system just prior to initiation of the erase function. Photoreceptor 10, moving in the indicated direction, carries a latent image frame 18 whose trailing edge 18b has just entered the erase zone defined by slit 16. Shutter blade 14 is positioned so as to completely block light from striking the photoreceptor. In Figure lb, blade 14 begins moving in the same direction as the photoreceptor and at the same speed. This movement is initiated when the image frame edge 18b is aligned with the left edge of blade 14. The interdocument gap 20 begins to be erased as shown. Figure lc shows blade 14 retracted to its oDen position; full erase is taking place through slit 16.