Patent GB-1030617-A (GB)
Title: Photographic projection printing apparatus
IPC: G03B27/36
Filed: 1963-07-05
Abstract: 1,030,617. Projection printing apparatus. AGFA A.G. July 5, 1963 [July 7, 1962], No. 26804/63. Heading G2A. In projection printing apparatus having automatic focusing by means of a cam on an axis fixed with respect to the objective carrier, said cam being capable of varying the distance between objective plane and negative plane by means of a follower lever, the arrangement is such that the axis of the lever pivot, the axis of the follower roller of the lever on the cam, and the axis of a supporter roller on the lever are all parallel in a common plane, the supporter roller being adjustable along the lever, and movable on a supporting surface fixed relative to the negative plane. Fig. 2a shows the cam 3 mounted on a spindle 2 of the objective carrier II. On a further fixed spindle 6 is pivoted a lever 7 carrying a follower roller 8 bearing against the cam surface, and, at the other end of the lever, another roller 9 supported by a surface 10 in fixed relation to the negative carrier I. Roller 9, on a separate portion 7a of lever 7 (Fig. 5), can be adjusted along the latter by screws 38. In Fig. 2a the full lines show one focusing position at a particular reproduction ratio with an objective of standard focal length, and the broken lines show another focusing position with the same reproduction ratio but a smaller focal length objective. A spindle 53 carries a worm wheel 54, meshing with another worm wheel 52 mounted on the same spindle 2 as the cam disc 3. The upper end of spindle b3 is threaded, and engages in a nut 56 fixed to the positive carrier III In the practical embodiment of Figs. 3-6, the positive carrier I<SP>1</SP> is in the form of a table on wheels 11. Fixed to this table are two columns 12 connected at their upper ends by a bridge piece I<SP>11</SP>. On one column is guided an objective carrier II<SP>1</SP>, to which is fixed a driving carriage II<SP>11</SP>, guided on the bridge piece I<SP>11</SP>. A positive carriage III<SP>1</SP> carries a feed cassette 13 and take-up cassette 14, the film passing along a positive stage 17. The negative stage 18 is provided on the carrier table I<SP>1</SP> An electric motor 27 fixed with respect to the driving carriage II<SP>11</SP> drives a spindle 30 which threads through a nut 31 secured to the positive carriage III<SP>1</SP>, so moving the latter. The spindle 30 also has a worm section 34 which meshes with a worm 35 fixed to the cam disc 3, so turning the latter, and varying the position of the lever 7, whose roller 9 is supported by surface 10; in this case surface 10 is located on a bracket 39 extending down from bridge piece I<SP>1l</SP>. At the lower end of spindle 30 the objective carriage II<SP>1</SP> is suspended by means of an axial bearing 33. Thus on rotation of spindle 30, the distance between the driving carriage II<SP>11</SP> and the carriage II<SP>1</SP> is maintained constant, while the distance between the driving carriage and the positive carriage, and thus the distance between the objective carriage and the positive carriage, is varied in a linear ratio with respect to the number of revolutions. The cam is connected by Bowden cables 40, 41 to setting devices on the table I<SP>1</SP> for controlling the reproduction ratio, and also for photoelectric control of exposure.