Patent GB-686770-A (GB)
Title: Improvements in and relating to photographic contact printing
IPC: G03B27/08
Filed: 1949-12-15
Abstract: 686,770. Photographic contact printing apparatus. KODAK, Ltd. Dec. 15, 1949 [Dec. 15, 1948], No. 32156/49. Class 98 (ii).j A photographic contact printing machine for use with continuously moving strips of film having perforations along at least one edge thereof, comprises a printing sprocket 10 for simultaneously advancing a plurality of negative or positive films as 13, 14, 15 and a lightsensitive film 16; a plurality of printing stations disposed around the periphery of the sprocket for successively printing each of the plurality of films upon the light-sensitive film; means such as rollers 28 for guiding one of said plurality of films and the light-sensitive film into superposed engagement upon the sprocket at each printing station, and a film stripper such as rollers 29 and a wedge-shaped deflector adjacent the sprocket (Fig. 2, not shown) just beyond each printing station for removing the films from the sprocket, said guide means and film stripper being so positioned relative to each other and to the sprocket that each pair of superposed films engages with the sprocket only at the printing station; a shutter and a source of light for illuminating intermittently the superposed films at the several printing stations; said printing sprocket 10 having a row of teeth along one margin of a width substantially equal to the width of the film perforations and of a thickness less than the height of the perforations and being so synchronized with the shutter of the illuminating means that the leading edge of only one tooth in said row contacts the leading edges of the perforations of the superposed films during the exposure interval at each printing station. Preferably there are also provided a plurality of auxiliary sprockets 17, each synchronized with the printing sprocket and adapted to lead one of the plurality of films from its supply reel 18 and to lead a second one of said films from the printing sprocket to its take-up reel 19 and to drive the light-sensitive film between the printing stations. The light-sensitive film may be fed from its supply reel 37 and returned to its take-up reel 38 by one of these auxiliary sprockets. Film tensioning means such as spring-biased rollers 26, 27 may be arranged between each auxiliary sprocket and the printing sprocket. The row of teeth on the printing sprocket 10 which fill the sprocket laterally may be arranged so that every fourth tooth is larger than the others or is displaced forwardly of its normal position as described in Specification 649,190 to which reference is made. The spacing of the sprocket teeth is arranged to be slightly greater than that of the film perforations so that movement of the superposed films relative to each other and to the sprocket is ensured so as to permit exact registration prior to the printing interval. The printing sprocket may be provided with a second row of teeth smaller both in width and height than the film perforations, each of the teeth in line with the film-driving teeth of the first row having its front face in line with that of the tooth in the first row. To avoid lack of registration between the several component prints due to irregularities in the positioning of the film driving sprocket teeth, the same tooth may be caused to drive any one frame of the light-sensitive film and the corresponding frames of the component films by making the length of the light-sensitive film loop between successive printing stations equal to one and one-third times the circumference of the printing sprocket. Each of the printing stations may be provided with a gate having a printing aperture of a height equal to one frame, together with one inter-frame space, the gate having means for pressing the margins of the films on to the printing sprocket, printing being effected for the period occupied by the film travelling one inter-frame space. Either a single light source and shutter with prisms for directing the printing beams to each printing station may be used or separate sources 39 and shutters 35 may be used at each station and reflectors and condensers for said sources may be employed. As applied to printing lenticular colour films from colour separation records, the colour filters are disposed at a distance from the lenticular film equal to the distance of the virtual image of the multicolour projection filter as seen from the film by means of the projection objective. If condensers are used between the light source and the filters, the distance of the virtual image of the filter as seen from the film by means of the condenser is made equal to the film-virtual image of projection filter distance. As shown, the projection filter comprises a central red band flanked successively by green and blue bands and red, green and blue printing filters 40, 41, 42 are placed in front of the printing gates so as to print the component records on to a horizontally lenticulated film. Specifications 392,987 and 532,826 also are referred to.