| 摘要 |
A frame (2) supports the printed roll (30) as it unwinds passed the transparent surface between the rollers (12,14). The rollers are connected by a first large diameter pulley wheel (36) freely mounted on the first roller (12) and a second small diameter pulley (38) on the second roller (14). They are connected by a belt (42) to drive the rollers differentially in one direction. A similar inverse set of pulleys and belt (34,40,44) drives the rollers in reverse. The first large pulley has a sprung strip in a cavity which engages a circumferential rib in one direction of rotation and slips over it in the reverse rotation. The first small pulley (34) responds in the reverse way.
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