GB494446A - Improvements in machines for photographic contact printing on to sensitised cylinders - Google Patents

Abstract

494,446. Photographic contact-printing apparatus. PAPER PATENTS CO. Sept. 14, 1937, No. 24979. Convention date, March 13. [Class 98 (ii)] A machine for photographic contact-printing on to the sensitized surface of a cylinder from a flat transparency which is moved in tangential contact with it as it is rotated, is provided with means to allow a slight slippage at the point of contact when the length of the transparency differs slightly from the circumference of the cylinder. In the form shown a base 1 supports uprights 3 which carry clamp members 39 supporting the lighting apparatus and printing roller and guides 29 for the framework 27 which carries an intermediate framework 31 to which is attached the transparent original 26. The framework 29 is moved vertically by threaded rods 7 engaging it at 33, and rotatable through gearing 23, 24 by a shaft 17 belt driven from an electric motor. One of two belts, giving different speeds is selected by the clutch 20. The sensitized cylinder 35 is carried in bearings 41 mounted with adjustments 43 on the beam 37 clamped to the uprights 3 by the members 39. These members 39 also carry cross beams 59, Fig. 3, with horizontal and vertical adjustments (not shown) which carry members 53 (shown in detail in Fig. 6), to define a slit 66 through which light from the arc 81 is directed by the water-cooled reflector system 83, and to press the transparency into good contact with the cylinder. Each is attached to a number of levers 54 pivoted on spindles 57 and acted on by springs 55. When the eccentrically mounted rods 63 are rotated they act on the levers 54 to remove the pressure from the transparency. The gear 89, Fig. 1, mounted on the printing cylinder spindle is equal in diameter to the cylinder and engages a helically cut rack 91 mounted on the framework 27. The rack is pivoted at its middle point, Fig. 11, and is adjustable by screws 93 giving an effective change in length to produce the slippage of the transparency on the surface of the cylinder. For measuring purposes, a scale 95 is provided, Fig. 1, to move with the transparency and co-operate with a crosshair 97 carried by the member 39. The other member 39 carries a cross-hair which is used in co-operation with another carried by a radial arm 45 to ascertain precisely when the cylinder has made a complete revolution.