GB668914A - Arrangement for comparing two periodically recurring cycles of events for measuring or regulating purposes - Google Patents

Abstract

668,914. Photo-electric control systems. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. April 12, 1950 [April 25, 1949], No. 8990/50. Class 40 (iii). [Also in Group XXXV] To measure or control the phase relation between two mechanical or electrical cycles, two photo-cells receive light beams from one cycle and act as gates for electrical pulses generated from the other cycle to produce pulses corresponding to the phase relation. As applied to a multi-colour printing process, the paper web 2, Fig. 1, is fed from one colour printing roller 1 beneath photo-electric cell 8 which is affected by marks 26, Fig. 2, on the paper; the paper passes over rollers 3, 4, 5 to a second printing cylinder 7 which carries a disc 10 having juxtaposed apertures 12 and mirrors 13, Fig. 2, for transmitting light from a source 11 alternately to two cells 16, 17. The cells 16, 17 act as gates, being conductive for the periods of their illumination a1, b1, Fig. 3, so that each cell passes part of the pulse c1 developed by cell 8 (cell 21 in Fig. 2). If the cells 16, 17 pass equal portions of pulse c1, no resulting signal occurs, but if the pulse c1 is not precisely bisected, a signal results which can be applied over amplifier 28, Fig. 1, to control a motor 6 to adjust jockey wheel 4 and thus the length of web between printing cylinders 1, 7, to obtain exact registration.