Patent GB-694767-A (GB)
Title: Improvements in or relating to apparatus for photographically reproducing printing surfaces
IPC: G03B27/66
Filed: 1951-12-18
Abstract: 694,767. Photographic production of printing surfaces. HUEBNER, W. C. Dec. 18, 1951 [Feb. 24, 1951], No. 29575/51. Class 98 (ii). Apparatus for positioning combined mask and screen member relative to a photographic light-sensitive surface which is supported by a frame having a central opening, comprises a plate-like member which is rotatably mounted on the frame and has a central opening in line with the opening in the frame, a pair of superposed members movably supported on the plate-like member and having central openings in line with the openings in the circular member and the frame, means for moving each pair of members between two predetermined positions in mutually perpendicular directions, and means on the outer member to carry the mask and screen member over the opening, so that the mask and screen member can be moved sequentially into four positions in rectangular arrangement, and may also be rotated relative to the frame. As shown, Fig. 1, a frame 10 has a circular opening 11, and a disc 15 is rotatably supported on the frame by rollers 12, a rectangular opening in the disc 15 being in line with opening 11. A pair of members 17, 18 are mounted on disc 15 and have rectangular openings substantially in line with that in disc 15. A combined screen and mask member 20 is supported on member 18 over the opening thereof, and may comprise a glass plate with a series of lines 28 ruled thereon at right-angles and spaced apart by the thickness of the lines, which may be, e.g., 0.004 inch. Member 17 is guided by rollers 30, 31 and blocks 32 to move in a direction parallel to frame 10. Similarly, member 18 is guided by rollers 33 and blocks 34 to move on member 17 in a direction perpendicu. lar to the direction of movement of member 17 and parallel to frame 10. A lever 35 has a hub disc eccentrically pivoted on a stud 35b mounted on member 17. The hub is journaled in a block 36, bearing, by means of an intermediate block 37, against member 18, which is thus moved on member 17 against spring means 39 when lever 35 is rocked. A lever 47 is similarly mounted to move member 17 on frame 10. Levers 35, 47 have studs which spring into holes arranged in pairs on arcuate members 44, 51, and so positioned that the movement of member 20 resultant on movement of either lever from one hole to the other is equal to the thickness of one of the lines. Arcuate members 44, 51 are exchangeable to fit different members 20. By this means four contiguous areas can be successively exposed by each opening in member 20. By bringing member 20 successively into its four positions, four exposures of different durations can be made on a single sensitized surface, which is brought into contact with member 20 as by vacuum means. Member 20 may also be used as a half-tone screen, and when colour separation negatives are prepared, it is desirable to turn member 20 between the exposures by turning disc 15 on rollers 12. The angle of rotation is indicated on a scale 59 by an index 58 on a block 56, which may be caused to clamp the edge of disc 15 by a screw 57. The member 20 may also be moved linearly as described above, between exposures. In halftone work the photographic material is mounted on a carrier 59, Fig. 3, the distance of which from the member 20 is variable by means of a graduated disc 63. This disc is mounted on a shaft 60. journaled in frame 10 and in a reinforcing member 61 fixed thereto, and carrying an elongated pinion 64 meshing with a rack 65 fixed to a bar 66. slidable in brackets 67 on carrier 59. Bar 66 has racks at each end engaging pinions 70 meshing with racks 72 on members 73 fixed to frame 10. Rotation of disc 63 thus causes carrier 59 to move towards and away from frame 10, a similar bar 66 being arranged at the other side of the frame.