Patent GB-713279-A (GB)
Title: Improvements in and relating to photographic contact printing
IPC: G03B27/08
Filed: 1952-03-28
Abstract: 713,279. Kinematograph printing. KODAK, Ltd. April 28, 1952 [April 28, 1951], No. 10592/52. Class 98(2) A photographic contact printing machine for use with continuously moving, superposed strips of film having perforations along at least one edge thereof comprises a sprocket for advancing the films. means for guiding the films into engagement with the sprocket and stripping means for removing the films from the sprocket. the guide means and stripping means being so positioned relative to the sprocket that the films engage with the sprocket over only a small part of its circumference, an illumination system including shutter means for intermittently producing a moving printing beam, the shutter means including a movable apertured element, the movement of the apertured element being synchronized with the rotation of the sprocket whereby the printing beam is caused to travel in synchronization with the films upon the sprocket whereby a substantially complete picture frame is continuously exposed during the exposure interval while the films are in motion upon the sprocket, the sprocket having a row of teeth, the teeth being of a width equal to the width of the film perforation and being so dimensioned and spaced, on the sprocket that the leading edge of a single tooth in the row is in contact with the aligned edges of the perforations of the superposed films during each exposure interval. As shown, light from a lamp 12 passes through a condenser in a mounting 15, a slit 11 in a cylindrical shutter 10, a teat absorbing or reflecting filter 20, and a second condenser 17, to a film gate 23. This gate is formed in a frame mounted on an arm 24 and connected by bellows 33 to a lens tube 39 in which condenser 17 is slidably mounted. The negative and positive films 36, 37 are fed over a sprocket 38, over rollers 41, 42 on spring-urged pivoted arms 43, and under a guide roller 49, to a sprocket 26. Sprocket 26 has either one or two sets of teeth engaging the marginal perforations of the film, the teeth being so spaced that only one tooth, or one tooth on each side, engages the perforations at one time, the films slipping on change-over from one tooth to the next until the leading edges of the engaged perforations of the two films are in exact register. Further to this end, roller 49, and rollers 54, 55 which 'strip the films from the sprocket 26, are placed near the film gate, the rollers having peripheral grooves in registry with the sprocket teeth. The films then form face loops before being fed out over a sprocket 40. A bowed spring 31 engages a pin 27 on arm 24 to press the arm against a stop 35, so adjusted that the films are not pressed too closely to the sprocket. The curvature of spring 31 holds the arm when it is drawn back to allow threading of the film. Similar spring arrangements hold in place the pivoted levers 50, 52 on which rollers 49, 54, 55 are mounted. A motor 62 drives, through a coupling 63, a shaft 61, which is geared to the drum 10 and to sprockets 26, 38, 40. The slit 11 slopes on the drum wall so that the beam of light passing through it moves down, the ratio of the gearing being such that the beam moves at the same speed as the film. The width of the slit is the height of a frame, and the drum axis is tilted to compensate for the slope of the slit, so that one frame of the film is exposed as it moves past the film gate, which is higher than the frame but of the same width. Thus as long as the slit 11 is illuminated, a frame area passing through the gate is exposed. When the end of the slit is reached, the light is cut off while the exposed frame moves out of the gate and the next frame moves in. Specification 649,190 is referred to.