Abnormal-paper sensing apparatus in a printing machine.

摘要

An abnormal-paper sensing apparatus in a printing machine which senses the presence of a front folded corner of a sheet of printing paper. The sheet of paper (7) hits against front lays (5) provided at a front end of an insertion guide plate (1) and stops. The insertion guide plate has a pair of recesses (8) provided in a front end portion thereof so as to extend thereacross at positions where the recesses can face the front corners of the sheet of paper which passes over the recesses. The recesses have a triangular cross section with a longer side (8a) positioned on the side of the front end of the insertion guide plate and with a shorter side (8b) positioned on the side of the rear end of the insertion guide plate. When the sheet of paper hits against front lays and stops, and if the sheet of paper has a folded angle at its front end, the corresponding recess is exposed and reflects the projected light diffusively, so that the sensors do not receive a quantity of reflected light enough to continue paper feeding.