| 摘要 |
<p>PURPOSE:To prevent the damage of a tape and tape driving system by detecting abnormal rotation in reel take-up operation and then by bringing a motor under control so that its speed will not exceed a fixed value. CONSTITUTION:Since detecting method 5 never detects the sag of a tape when the tape is sagging slightly, take-up reel motor 1 increases in rotating speed temporarily in order to absorb the sag. This increase is detected by rotating-speed deciding means 13 and then compared with a reference voltage from potentiometer 18 and in accordance with an increase in the output-side DC voltage of speed modulator 15, the decrease of the output of comparator 20 and the turning-on operation of switch SW2 expressing the take-up operation of motor 1 are detected by rotation- direction detecting means 16 to turn on diode 19. Then, the base potential of transistor 2 is suppressed to the potential of the traveling contact of potentiometer 18, so that the increase of the rotating speed of motor 1 will be suppressed. Then, switch SW2 turns off when the sag is eliminated, releasing the rotating-speed increase suppressing operation of motor 1.</p> |
