Patent GB-350858-A (GB)
Title: Improvements in and relating to machines for printing photographic films
IPC: G03B27/10
Filed: 1930-10-03
Abstract: 350,858. Continuous filmprinting apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Kellogg, E. W.; 1185, Ardsley Road, Schanectady, New York, U.S.A.) Oct. 3, 1930, No. 29656. Convention date, Oct. 4, 1929. [Class 98 (ii).] Printing apparatus, more particularly for kinematograph films bearing sound records, is adapted to compensate for the difference between the negative and positive films due to shrinkage by incorporating in the apparatus means for imparting to the films at the printing zone a curvature which may be adjusted manually or automatically to the desired degree. As shown in Fig. 1, the negative and positive films 1, 2 are drawn from supply spools by sprockets 3, 8, and are fed to take-up spools by sprockets 4, 9. In the machine, they pass over control sprockets 36, 37 to the printing zone of a lamp 14, where they are pressed together at their edges between spaced tyres 20 on a roller 19 driven by a motor 24 and either a fixed curved skid or spaced rings 26 which turn freely on a shaft 27 and may be fitted with tyres. On each side of the printing zone the films pass between rollers 32 mounted on a slide 31 which may be moved along guide-rods 30 to vary the curvature of the films at the printing zones by actuating a reversible motor 33 whose shaft 34 is in screwed engagement with the slide. Control of the curvature is effected from the sprocket holes of the films through the sprockets 36, 37. As the films are drawn over these sprockets, any difference in the pitch of the sprocket holes due to shrinkage causes one sprocket to turn faster than the other, and this differential rotation is communicated through a differential gear 38 to a contact 40 on the planet ring of the gear. The movement of this contact may either serve to indicate to the machine operator the direction in which the slide 31 should be moved, or it may, through a yoke 42, automatically complete the circuit of the motor 33 driving the slide 31, the yoke being carried by a bell-crank lever 41 coupled at 43 to the slide 31 so as to follow its movements and disengage the contact 40 from the yoke when the slide has imparted the desired curvature to the films and the sprockets 36, 37 are rotating in unison. The feed sprockets 3, 4 and 8, 9 are driven by shafts 5, 10 from motors 6, 11 whose speeds are controlled so that there shall always be slack between them and the roller 19 by coupling the shafts 5, 10 to the respective control sprockets 36, 37 through differential gears such as 48, the planet ring 50 of which bears the movable contact 51 of a rheostat 52 in series in the motor circuit. If desired, the films may be backed by a continuous or endless band as of steel as they pass through the machine. In a modification, the slide 31 is absent, and the curvature of the films is controlled by varying the curvature of a pair of bands as of steel of approximately elliptical shape, which pass at one end of the major axis between the tyres 20 of the roller 19 and rings 26 of smaller size than those of Fig. 1. These bands are flexed by a roller which bears on them internally at the other end of the major axis, and is mounted on a lever fast with a wheel driven from a motor controlled in the same manner as the motor 33, said lever carrying the pin 43 engaging the tail of the bell-crank follower lever 41. In another modification, shown in Fig. 3, the rings 26 are replaced by tyred rollers 65 turning freely in bearings 66 mounted on gears 67 driven by a common worm 68 on the shaft of a reversible driving motor 62 which is controlled in the same manner as the motor 33, Fig. 1. The axes of the wheels 67 lie along the common tangents to the tyres 20 and rollers 65, so that as the wheels 67 rotate the curvature of the films 1, 2 is varied by variation of the inclinations of the planes of the rollers 65 to the planes of the tyres 20. The printing light 14, Fig. 1, is enclosed in a housing 15 having a tube 16 fitted with lenses 17 which either concentrate the light into a narrow band transverse to the films, or project light approaching parallelism upon the films. The whole apparatus is enclosed in a light-proof casing.