Restack jam detection

Claim 1

In a sheet handling apparatus in which flimsy sheets are stacked on top of a stack thereof in a generally horizontal stack support tray between generally vertically extending spaced apart side guide members by being fed in over the top of said stack from one end thereof and released to normally generally planarly stack on top of said stack, the improvement for detecting mis-stacking comprising: optical sensing means defining a sheet interruptable optical sensing path extending transversely above said stack positioned to be interrupted by mis-stacked non-planar sheets variously extending above said stack; sheet mis-stacking indicator means connected to be actuated by said optical sensing means by interruption of said optical sensing path; and timing means operatively connecting with said optical sensing means and said mis-stacking indicator means to prevent activation of said mis-stacking indicator means by brief interruptions of said optical sensing path from said normal stacking and to allow an activation of said mis-stacking indicator means by an interruption of said optical sensing path continuing for a preset time period indicative of the presence of a mis-stacked sheet; in which one said side guide member is fixed and the other said side guide member is repositionable to adjust to different sheet sizes, and wherein said optical sensing means comprises a fixed light beam emitter and light beam detector means closely associated with said fixed side guide member and a light reflector means on said repositionable side guide member for normally reflecting the light beam from said light beam emitter back to said light beam detector means to form said optical sensing path irrespective of the respositioning of said repositionable side guide member.