GB781714A - Method and machine for producing facsimile cliches - Google Patents

Abstract

781,714. Local copying by scanning. RAIBLI, O. May 11, 1955 [May 14, 1954], No. 13655/55. Class 40 (3). In an arrangement for producing a printing- plate by the photo-electric scanning of an original in substantially parallel paths, the plate is produced by cutting generally parallel continuous grooves extending from one edge to another edge of the plate in such a way that the depth and also the width of the groove are controlled by the impulses derived from the scanning of the original, and the printing-plate is constituted by a grid of spaced elongated surface portions of varying widths left between the intervening grooves. In the general arrangement, Fig, 1. a screw 43 on a shaft 19 intermittently traverses the scanning carriage 44 relative to a transmitting drum 27 carried by a stub shaft 24 and connected by a clutch member 23 to a shaft 22. The bearing-member 24 can be moved by a knob 25 so that the drum 27 can be replaced. Members 52 adjustable on a threaded shaft 51 co-operate with projections 53 on the carriage to determine the limits of transverse movement. The electromagnetic cutting-head 40 is mounted in a carriage 33 traversed by a threaded shaft 32 connected to the intermittently rotated shaft 19, and the drum 26 carrying the plate to be engraved is mounted on a stub shaft 24 and connected by a clutch 23 to the shaft 22. As shown, the drums are driven by a pulley 30 attached to the drum 26. In the scanning device, Fig. 4, light from a source 57 is reflected by a mirror 59 to an annular lens 60 and after reflection passes through a lens system 54 and via a lens 56 to a photo-electric cell 55, the incident beam being chopped by a disc 62 driven from a motor 61. The reproducing member, Fig. 5, comprises a permanent magnet 69, the pieces 67, 68, 70 and a moving coil 64 attached to a member 72 mounted for axial movement by means of a rod 71 and springs 73. The member 72 is connected to a hook 74 engaging one end of a rigid member 75 mounted on a member 77 by a spring 76 and engaging the upper end of an operating member comprising a tube 82 carried by springs 79, 80 and provided with a wedge-shaped cutting-tool 81. The spacing of the scanning paths is effected by rotation of the shaft 19 at the end of each revolution of the shaft 22 and the fineness of scanning and reproduction can be adjusted. A cam 90, Fig. 11, on the shaft 22 rocks a pivoted rod 92 connected to a spring 96 by a chain 94 passing over a sprocket 95 freely rotatable on the shaft 19. The sprocket 95 is connected to a disc 97 carrying a pawl 98 engaging a ratchet-wheel 100 secured to the shaft 19. A sprocket 102 rotated by a sprocket 104 driven by gears 105, 107 rotated by an adjustable operating handle 110 carries a projection 116 which co-operates with a stop 115 on the disc 97 to determine the extent of rotation of the sprocket 95 by the spring 96 and consequently the rotational extent of positive drive by wheel 97 carrying the driving pawl 98. The cutter may be operated so that in the reproduction of a white area, the grooves are cut more deeply with the result that the effective surface is locally below the normal level of the engraved surface, as indicated by Fig. 7 (not shown). In a modification, for the production of raised or projecting autotypes, after the plate has been engraved, the cutting-tool is replaced by a milling tool, Fig. 15 (not shown), which is operated by a modified re-scanning of the original of which portions are covered by a black mask. Corresponding to those portions which have not been darkened the milling-tool will enter the grooves and cut away portions of the plate adjoining the grooves so that the portions of the surface to be reproduced are left at a higher level than that of the remaining portions which are not to be printed. The arrangement may be used to produce colour reproductions of an original, the engraved plates resulting from the scanning of patterns corresponding to the colour components of the original being cut so that the longitudinal direction of the grooves extends at different oblique angles for the respective plates. With this arrangement the moire effect is considerably reduced.