| 摘要 |
<p>An adjustable load tear bar mechanism for a friction feed platen (15) that comprises a tear bar assembly (31) and spring loading mechanisms (33) is disclosed. The tear bar assembly (31) comprises a tear bar (51) mounted between a pair of side arms (41, 43) located on opposite ends of the platen (15). The tear bar (51) is an inverted, generally U-shaped channel. Positioned in the channel is a roller shaft (45) on which a plurality of friction feed rollers (47) are mounted. The downstream ends of the side arms (which overlie the platen) are pivotally attached to walls (11, 13) of the printer chassis. The tear bar (51) and roller shaft (45) extend between the upstream ends of the side arms (41, 43). Mounted on the roller shaft (45) so as to be rotatable therewith are arm hooks (53, 55). One of the arm hooks is part of a detent mechanism that includes teeth (125) that co-act with a spring (59) and plunger (57) housed in one of the side arms (43). The position of the teeth (125) and, thus, the rotational position of the roller shaft (45) is controlled by a detent lever (121). The arm hooks (53, 55) are attached by the spring loading mechanisms (33) to the printer chassis. More specifically, the hook arms are attached by hooks (165) to springs (163) mounted in housings (161) connected to the printer chassis upstream of the tear bar (51). The position of the arm hooks (53, 55), which control the pressure applied by the tear bar (51) and friction rollers (47) to the platen (15), is controlled by the latched position of the detent mechanism.</p> |
