| 摘要 |
<p>PURPOSE:To prevent winding-up of a tape from going to tight by switching a sliding part by a back tension spring from a flange surface of a large diameter of a spring sleeve to a thrust receiving part of a small diameter by a function of a shape memory spring and controlling the brake torque. CONSTITUTION:The title device is constituted so that one of back tension springs 8 is received by a spring sleeve 9, and the spring sleeve 9 is fitted to the outside of a bearing housing 4, and varies its inside by following up a variation caused by a temperature of a shape memory spring 10 which is wound to the outside of the spring sleeve 9. Accordingly, when an ambient temperature goes to a set temperature of a low temperature, force by which the shape memory spring 10 winds and tightens the spring sleeve 9 ceases to exist, frictional force by back tension spring force works on a thrust receiving part of a small diameter of the spring sleeve 9 and a thrust receiving surface of a bearing housing 4, and the brake torque decreases. Also, when the ambient temperature exceeds the set temperature, the shape memory spring 10 winds and tightens the spring sleeve 9, and the back tension spring 8 slides by the flange surface of a large diameter of the spring sleeve 9. In such a way, it is prevented that winding-up of a tape becomes tight.</p> |
