927,505. Automatic speed and tension control. FERNSEH G.m.b.H. Feb. 24, 1961 [Feb. 27, 1960], No. 6861/61. Class 38 (4). [Also in Group XX] When a film 3 is initially drawn through gate 1 by sprocket 2, sprocket 5 is not rotated, so that the output shaft 19 of differential 9 moves slider 13 to increase the effective resistance of controller 14. This increases the torque exerted by motor 10 on spool 4, the speed of the film moving over sprocket 5 increasing from zero whereby the speed of the shaft 19 is reduced. This in turn reduces the torque transmitted by coupling 11, and thus the slider 13 is returned towards centre tap 24 until the speeds of the film moving into and out of the loop formed by roll 6 are equal. During the period in which these speeds are unequal, a lever 7 is moved to turn the resistance element of controller 14 so increasing the torque exerted by motor 10 until the reduced size of the loop returns the resistance element to its initial position. Since the control signal so obtained is proportional to the loop-length it is also proportional to the time-integral of of the difference between the entry and exit speeds. In another arrangement, the differential 19 is dispensed with, and the speeddifference is detected by measuring the angular velocity of the lever 7. This lever is geared to shaft 19 controlling the movement of slider 13 in accordance with the torque transmitted by fluid coupling 11 and acting against spring 12, Fig. 2 (not shown).
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