| 摘要 |
1,246,405. Automatic tension control. A. MONFORTS. Jan. 9, 1969 [Jan. 20, 1968], No. 1394/69. Heading G3R. Tension in a web of elastic material supplied to a measuring device is automatically controlled by varying the speed of a feedroller in dependence on the size of a shallow loop in the web which is detected without contact at least at its upper limit. In the inspection/measuring machine shown, textile web supplied by a driven feedroll 2 to a driven measuring roll 1 with its associated measuring head 1A, is finally taken up by a driven draw-off roll 3. A photo-electric or ultrasonic head 4, which produces signals corresponding to the amount of slight sag in the web, causes operation of switches to increase or decrease the speed of feedroll 2 whenever the amount of sag reaches upper or lower limits so that the sag is maintained between these limits. A head 5 may control the speed of roll 3 in a similar manner especially if the web is fed in the reverse direction. Delicate materials may be partly supported by air jets 10 and 11 and time delay devices may be incorporated to prevent too frequent operation of the switches. A modification in which the speed of feed is adjusted for preset time periods at the upper limit of sag only, is referred to.
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