GB1008769A - Apparatus for checking the pitch of uniformly spaced visible effects in the course of being formed in a travelling strip or web - Google Patents

Abstract

1,008,769. Optical stroboscopic apparatus. E. A. TIMSON. July 30, 1963 [July 31, 1962], No. 29286/62. Heading G2J. Spaced holes h, printed spots or other visible effects in or on a strip or web W are checked as to uniformity of spacing whilst the strip or web is moving. As shown a source l 1 of red light is spaced a distance from a source l 2 , emitting green light, equal to the pitch p, or a multiple thereof, of the holes h, the sources l 1 , l 2 being flashed on and off,electrically or by mechanical shutters, synchronously with the passage of successive holes h past the sources l 1 l 2 . The images I of the holes are reflected by mirrors m 1 -m 4 and focussed by lens L on a ground glass screen GS so that when the holes h are correctly spaced the images exactly overlap and a yellow spot is seen, but when the spacing is incorrect the yellow spot has side edges of red and green the extent and disposition of such colouration showing the magnitude of the inaccuracy and whether the spacing is greater or less than desired. The tensioning of the web W, as it passes through a machine in which the holes are punched, may be varied to bring the spacing p back to the required value. The mirrors m 1 -m 4 may be in the form of prisms, the visible effects sensed by the apparatus may be ones, e.g. holes, specially positioned on the web for the purpose and associated with the visible effects whose pitch is to be checked and photo-electric means may be used to detect any lack of coincidence of the images I.