Photographic processing roller having a surface roughened by electric discharge machining

Claim 1

In an improved cylindrical processing roller for use in a motor driven photographic processing apparatus of the type for advancing an integral type self-processable film unit to the exterior of a camera while simultaneously spreading a fluid processing composition between selected layers of the film unit and of the type having a circumferential surface of given length machined to a precision diameter to facilitate spreading the fluid processing composition in a substantially uniform thin layer between the film unit's selected layers, the improvement comprising a plurality of generally spaced apart, substantially uniform sized and shaped microscopic craters formed along a predetermined length of said surface by transferring to said predetermined length of said surface a plurality of high energy pulses each of which contains sufficient energy to locally melt said surface thereby creating individual ones of said craters, said craters covering no more than 50 percent of the area of said predetermined surface length and each being surrounded by a substantially uniform annular lip which extends above said surface by an amount insufficient to mark the film unit's surface and has a volume which generally equals the volume of the depressed portion of the crater which is below said surface, said roller surface being thus configured to provide said roller with a high-friction characteristic for transporting a film unit while being insufficiently rough to leave any visually perceptible marks on a film unit's surface, to minimize pickup of particulate matter from the film unit which would otherwise build up and reduce said high-friction characteristic, and to maintain the effectiveness of said roller's precision diameter so that substantially no change in its fluid spreading performance results from the presence of said craters.