| 摘要 |
Apparatus for feeding sheet material past a printing station. A cylindrical platen is included having circumferentially arranged guide pins which cooperate with corresponding perforations along the edges of the sheet material to provide positive feeding and accurate alignment of the sheet material. The printing station is disposed immediately adjacent the platen and serves to imprint the desired information on the sheet material. The guide pins, which would otherwise interfere with the operation of the printing station, are retracted into the platen when passing the printing station during the rotation of the platen. In a preferred embodiment, this goal is accomplished by rotating the platen about a fixed, coaxially disposed cam. The pins are radially spring biased against the cam so that the amount of radial extension of each of the pins from the outer surface of platen is determined by the surface contour of the cam. The cam is structured to cause the extension of each pin during most of the rotation of the platen, but to allow retraction thereof during the portion of the rotation in which that pin passes the printing station.
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