| 摘要 |
<p>PURPOSE:To simplify a tape tension control mechanism with accurate control by controlling the damping degree of a reel drive disk so that the load of the reel drive disk is in inverse proportion to the rotational frequency of the reel drive disk after detecting said rotational frequency. CONSTITUTION:A reflecting plate 12 having black and white patterns printed successively in a radial form is attached to the lower side of a pulley 3 of a reel ?drive disk. A photoreflector 14 is set on a substrate 13 opposed to the plate 12. Then the rotary pulse obtained by a reflector 14 is converted into a direct current by an integration circuit 15 and inverted by an inverter 16 to obtain a signal which is in inverse proportion to the revolving speed of the reel drive disk. The output of this signal is amplified by an amplifier 17 and applied to a coil 6 in the form of the DC voltage. As a result, the attracting power by an iron core 5 acts on a magnetic plate 9, and the load torque obtained in this case is proportion to said attracting power. Thus it is possible to control the load torque in inverse proportion to the revolving speed of a supply reel. This keeps a fixed level of tape tension. Thus the accurate control is possible for the tape tension in such a simple mechanism.</p> |
