| 摘要 |
PURPOSE:To apply a required back tension according to the running direction of a ribbon to obtain a stable running of the ribbon in a ribbon cassette using the back- face of the ribbon, by a method wherein a tension applying member made of a plate spring, etc. is allowed to act on a pressed portion in a direction offset by a predetermined angle from the vertical direction to the pressed portion. CONSTITUTION:A plate spring 8 is bent inward at a top end thereof 8b to be engaged with a projecting portion 2h. A plate spring 9 is also shaped symmetrical to the plate spring 8. The plate spring 8 has an engaging portion 0 with a projecting portion 2k serving as a fulcrum to press the projecting portion 2h at a pressing portion A by a force P at right angles to OA. In this case, since the projecting portion 2h is not forced at right angles to the acting direction of the plate spring 8 but offset by an angle theta therefrom, a component force P' of the force P vertical to the surface of the projecting portion 2h acts as a force acting on the surface of the projecting portion 2h. As a result, when a ribbon 5 is fed in a direction of Arrow (m), the component force P' comes to assist in the pressing action of the plate spring 8 against the projecting portion 2h at the top end thereof 8b. The reverse running direction of the ribbon 5 makes all the frictional force act in the reverse direction.
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