| 摘要 |
<p>PURPOSE:To maintain the tension of a band constant at all times by interchanging a member, which is operative to coact with or to release a back tension arm, with the use of a change-over device for changing the speed of the band in response to the speed thereof. CONSTITUTION:When in a fast-forward condition, a coactive releasing member 20 is pushed in the direction of arrow 43 by a coil spring 42 so that a step 39 is stopped in a position having abutment contact with a stopper 38 and so that an end face 44 abuts against a projection 31 to push a coactive member 27 in the direction of the arrow 43. In this instance, since the spring 42 has a stronger than a tension spring 32, it fixes the member 27 to block the coaction with a back tension arm 14. At the same time, a downward projection 30 is released from the abutment engagement with a downward projection 24 so that it is set free. As a result, the arm 14 is biased by another tension spring 34 in the directon of arrow 45 so that it is forced into contact under a preset force with a tape 10 through a tension pin 15. As a result, if the tension of the tape 10 is increased, the pin 15 is pushed in the direction of arrow 46 to loosen a brake band 35 thereby to weaken the tension. Thus, it is possible to maintain the tape tension constant at all times.</p> |
