Pin mount for optical writer/image-recording element in a document printer/copier

This invention relates to the field of document printing/copying. More particularly, it relates to improvements in apparatus for precisely and repeatedly positioning an electro-optical printhead or "optical writer," e.g. a linear array of light-emitting diodes, relative to a reusable image-recording drum in a document printer/copier, that is, an electrophotographic printer and/or copier, to enable, for example, removal, servicing and replacement of the optical writer and/or image-recording drum without altering a desired positional relationship between the optical writer and image-recording drum inside the document printer/copier. A photoconductive drum assembly and an optical writer used in an electrophotographic printer/copier share the same mechanical fiducials for positioning these subsystems within the printer/copier frame or housing. Preferably, a pair of mounting pins used to position and support the drum assembly in a printer frame is also used to position the optical writer. As a result of this mounting scheme, a tolerance stacking problem is reduced and each subsystem can be removed from the printer housing without disturbing the position of the other. Further, the need for a mechanism to retract the optical writer from the vicinity of the drum surface to facilitate drum removal is eliminated, thereby lowering cost and increasing reliability.