Abstract: Apparatus for sensing the passage of sheets (48) through a nip (24), comprises a pair of guide surfaces (20,27) defining the nip (24); means (17,20) for passing sheets (48) through the nip (24); and sensing means formed by pairs of light emitting diodes (37) and phototransistors (38) (37,38) for sensing the deflection of one guide surface relatively to the other. Monitoring means (41,42,43) are provided for monitoring the output of the sensing means (37,38) and for storing a guide surface profile corresponding to the sensing means output when no sheet (48) is present. Comparison means (44) compares subsequent test profiles generated by the monitoring means (41,42) with the stored profile; and detection means (42) detects the presence of a sheet in the nip (24) only when there is a substantially uniform difference between the stored and test profiles.

Abstract: Sheet sensing apparatus comprises a shaft (9); two roller assemblies (20) mounted on the shaft (9) by means including a resilient portion (30), the roller assemblies contacting guide surfaces (27) provided by drive rollers (17). Sensing means (37,38) are provided within the shaft (9) for sensing deflection of the resilient portion (30) relatively to the shaft in response to the passage of one or more sheets (44) through the nips (24) between the roller assemblies (20) and the drive rollers (17). Monitoring means (not shown) connected to the sensing means monitors the sensed deflections of the resilient portion (30).