GB1349857A - Web advancing mechanism - Google Patents

Abstract

1349857 Cinematography EASTMAN KODAK CO 19 April 1971 [6 Feb 1970] 21018/71 Heading G2E A mechanism particularly for the transport of unperforated film includes a continuous, flexible, transparent belt 21 which carries film 11 through an area illuminated by lamp 12. The film 11 is drawn from a spool 14 and received on spool 24. Roll 17 is driven by motor 18 and rolls 22, 23 rotate due to contact with the belt 21. The belt 21 is of a shallow U-cross section so that the film 11 fits therein and does not project above and is fictionally gripped by its sides. The film may be advanced intermittently or continuously. In the former arrangement a regular pulse from a clock circuit (72), Fig. 3, (not shown), causes an amplified output from a waveform generator (73) to drive the motor 18 long enough to move the film through one frame. The same pulse from the clock (72) is also electronically delayed so that it can actuate an optical detector (74) to determine whether the frame is correctly aligned for projection and, if not, to send a correction signal to the motor 18 to reposition the frame. In an alternative circuit, Fig. 5, (not shown), no correction signal is transmitted to the motor 18 but a differential optical detector (94) checks the position of the frame as before and by combination of its output with a reference signal from a source (102) the net signal modifies the gain of amplifier (93) which amplifies the signal from the waveform generator to the motor 18 to correct subsequent film movements.