Patent GB-712862-A (GB)
Title: Photographic contact-printing apparatus
Inventor: KENNEDY WALTER DAVID
IPC: G03B27/22
Filed: 1952-03-07
Abstract: 712,862. Photographic contact-printing. KENNEDY INSTRUMENTS, Ltd. March 3, 1953 [March 7, 1952], No. 6058/52. Class 98(2) Photographic contact-printing apparatus comprises a light-transmitting curved plate in the form of a complete cylinder or the major part of a cylinder, wheels on the end of the cylinder, guide rails along which the wheels may be rolled to and fro, a source of electric light mounted within the cylinder and supported between the wheels by bearings whereby the wheels are free to rotate without transmitting rotational movement to the source of light or its mounting, a flexible apron adapted to be laid close to the cylinder and to sandwich between itself and the cylinder a sheet of light-sensitive material and an original sheet to be copied, the apron extending in a flat plane tangential to the cylinder and terminating in that plane in a thin flat edge parallel to the axis of the cylinder, means for rolling the cylinder by its wheels along the rails to wrap the apron round the cylinder so that the terminal edge lies close to the cylinder, and means holding the apron under tension in a direction perpendicular to the axis of the cylinder. As shown, a box-like structure 11 of sheet metal has channel-sectioned members 17 at the sides near its upper surface, which is sloping. An electric transformer 22 housed in the back of the structure is connected to an electric supply cable 28 housed at the side of structure 11. A bar 23 is bent to pivot at its ends in the structure 11, and a band 50 passes over this bar and another bar (not shown) connected by adjustable springs to the back of structure 11, so that bar 23 is urged against one or the other of pairs of stops 29, 30. An electric lamp 14, a glass cylinder 32, and a glass part cylinder 31 are carried between wheels 15 running on the upper surfaces of rails 17. Wheels 15 are connected by tie-rods 33 and support the part cylinder 31 so that it is at almost the same radius from the centre of rotation as the rims of wheels 15. A metal cylinder 35 is supported by three ball races 34 in each wheel 15. A cylinder 36 (not shown) fits over cylinder 32 and the ends of cylinders 35, and is apertured to allow passage of light from the lamp. Blocks 39 fixed to cylinders 35 carry the lamp 14, and also carry end-plates 40 fitted with cooling fins and carrying guide rollers 42 which travel in channels 17, so that when the wheels 15 roll over their tracks, the cylinders 35 and the part carried thereby are not rotated, the lamp being fed by cable 28. An apron 16 fastened to the wheels 15 at 43 turns over the end of the top surface of structure 11 and is tensioned by springs (not shown) within the structure. The apron preferably comprises juxtaposed strips separately tensioned, and is kept taut by ribbons 53 attached to wheels 15 at 52 and anchored within the structure 11. A metal hood 45 fixed to the end plates 40 prevents egress of light from the apparatus, and has a handle 46 by which the wheels 15 may be drawn forward. During this movement, apron 16 is wrapped upon the partcylinder 31, and if a photographic paper and an original to be copied are first laid on the apron, they are sandwiched between the apron and the part cylinder for exposure to lamp 14. The forward movement of the wheels 15 is limited by a stop 51 carried by one of the end plates 40 engaging a starting lever 48 on a timing unit 20, mounted at the side of the structure 11. This timer is of the kind described in Specification 712,863. The wheels 15 are held in forward position by a sear 49 projecting from the timer and engaging stop 51, while the photographic paper is exposed to light from lamp 14. At the end of the exposure the sear is retracted and the wheels roll back down the slope by gravity. The backward movement is limited by wedge-shaped rubber stops 47 in the channels 17. To ensure even distribution of light, the inside of cylinder 36 has a highly reflecting and diffusing surface, which is blackened near the brightest part of the lamp 14. Specifications 687,240, 687,368 and 687,369 also are referred to.