Patent GB-513524-A (GB)
Title: Improvements in photographic printing machines
IPC: G03B27/46
Filed: 1938-03-10
Abstract: 513,524. Photographic projection printing apparatus. CHILD, A. J., HALL, J. C., SMITH, W., and STOBART, J. W. March 10, 1938, No. 7462. [Class 98 (i)] In a photographic printing- machine in which light is reflected from a strip bearing pictures &c. and having a step-by-step motion through a lens system on to a sensitized strip moving in synchronism with, but in the opposite direction to, the picture strip, the movement of the strips is effected by dogs engaging perforations in the strips and carried by plates reciprocated in guides by pins mounted on rotary discs driven through axially displaceable countershafts from a main shaft, means being provided to disengage the dogs from the strips and re-engage them without interrupting the driving mechanism. As shown, the picture strip 1 passes from a drum 3 through the narrow space between an end wall of the machine casing and a hinged cover 8 and is exposed through an aperture 9 in the wall to the light from electric lamps 10, the light reflected from the strip being projected by a lens 12 to form images of the pictures on a sensitized film 2 passing from a drum 5 through the space between the end wall and hinged cover 15 at the opposite end of the casing. The step-by-step motion of the strip 1 is effected by dogs 37, Fig. 6, mounted on a plate 35 reciprocated in guides 36. Fig. 4, on the inside of an end wall of the casing by a pin 33 located between guide strips 34 on the plate and carried by a disc 30 on the end of a countershaft 31 having a cam 41 secured to its opposite end. The shaft 31 is in driving connection with a sleeve 27 rotated through toothed-gearing from a main shaft 19 driven by an electric motor 17. The shaft 31 is urged to the left to disengage the dogs from the strip by a spring 32, but is periodically displaced to the right to engage the dogs by a roller 39 carried by the toothed-wheel 22 and coacting with the cam 41. The strip 1 is held in position during the time the dogs. are disengaged by a stop 46, Fig. 5, formed on the end of a pivoted lever 42 coacting with a leaf-spring 44 which forces the stop away from strip when the dogs are disengaged. Similar mechanism is provided for effecting synchronous motion of the sensitized strip 2. A punch 68 is provided on the hinged cover 15 of the easing to make a mark on the sensitized strip, and reflective masks bearing lettering may be provided on one or more sides of the aperture 9 so that such lettering is photographed on the sensitized strip. The lamps 10 may be extinguished during movement of the strips by a cam 54 mounted on the wheel 22 and coacting with a pivoted lever 55 carrying a tilting mercury switch 57, Fig. 1, in the lamp circuit, including a rheostat 58 adjustable by a finger 59 movable over a scale 60 so that the brightness of the lamps may be regulated. Switches 61 may be provided on the hinged cover plates of the casing to cut off the supply of current to the motor and the lamps whenever the plates are opened, and a further switch 62 is provided to permit supply to the lamps when the motor is inoperative.