Patent GB-1416260-A (GB)
Title: Pattern copying and reproducing apparatus
IPC: G03F7/12
Filed: 1973-10-08
Abstract: 1416260 Local copying P ZIMMER 8 Oct 1973 [6 Oct 1972] 46867/73 Heading H4F A pattern carried by a rotating drum 15 (Fig. 1) is scanned photo-electrically to produce signals which are employed to expose a photosensitive layer on a matrix 1 carried by a second rotating drum such that a plurality of copies of the pattern are produced along the axis of the latter drum (e.g. in spaces 21) and if desired, circumferentially around the drum. Instead of photographic reproduction, mechanical, electron or laser beam perforation may be employed. The invention is stated to be particularly suitable for the manufacture of stencils for textile printing. As shown in Fig. 1, the pattern is scanned successively and repetitively by two heads 13, 14 the driving arrangement being such that, when head 13 has completed one complete traverse of the full width 42 of the pattern, head 14 commences to scan whilst head 13 is rapidly returned and then accurately positioned to commence a further scan during which head 14 is rapidly returned as depicted in Fig. 5. The signals generated by the heads are employed to control the application of " screen " pulses from a selected one of photo-electric cells 9 (responsive to a stroke pattern such as 10, 11 depending on the fineness of the screen pattern required) to a flash tube 5 producing on the matrix 1 an image of a slit 4 which moves over the lengths 21 synchronously with the movement of the heads 13, 14 over the pattern length 42. However, if more than one pattern is to be reproduced, circumferentially, on the matrix 1, the rotational speed of the latter is increased, relative to the rotational speed of drum 15 by the same number factor by means of a gear-box 16. The driving arrangement is controlled by a motor 18 operating via a magnetic-clutch gear-box 27 which drives the traversing screw 26 for the " writing " head 2 and via a shaft 30, a pair of planet gears 35 coupled to traversing screws 32, 33 for the heads 13, 14 respectively and adjustable between the scan and the rapid retrace modes by means of two further magnetic-clutch gear-boxes 40 having inputs from respective servomotors 41. In practice the scanning heads 13, 14 are arranged at diametrically opposite positions of the drum 15 as shown in Fig. 2, each head having an objective lens 44 and radial position adjusting screws 49 to allow accurate focusing on the pattern's surface such focusing being observed via eye-pieces 47 which receive light reflected from semi-reflecting mirrors 45 through which light is transmitted to the photo-cells 43. Because of the 180 degree displacement of the heads 13, 14 the signals from the photocells 43 are stored on a magnetic store 23 (Fig. 1) comprising, as shown in Fig. 3 a magnetizable disc 52 rotating at one-half the speed of drum 15. The signals from scanning head 13 are recorded via recording head 53 and those from scanning head 14 via recording head 54 both trains of signals being " read " out for controlling the selection of the photocells 9 (Fig. 1) by means of heads 56 or 57. An embodiment employing a single scanning 13 is described with reference to Fig. 6 (not shown).