| 摘要 |
A method and apparatus for controlling the tension in a tape (16, 18) along a feed path between a reel (84, 112) and a processing station (20) is disclosed. A motor (146, 162) having a controllable torque is coupled to the reel. An advancement mechanism (22, 142) advances the tape through the processing station. Sensors (190, 192) produce signals proportional to the advancement of the tape through the processing station as well as the advance of the reel. These signals are compared to produce an indicia of the present operating radius of the tape on the reel, which is dependent upon the amount of tape wound upon the reel. With this indicia determined, empirically derived data can be consulted to determined the energization of the motor necessary to produce a torque that will compensate for the changing tape diameter on the reel, maintaining the tension in the tape substantially constant independent of the transfer of tape with respect to the reel. In a preferred embodiment, this arrangement is employed to control the tension in thermal transfer ribbon (16) and receiving paper (18) between a print roller (22) and their respective reels (146, 162) in a thermal transfer printer (10).
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