GB838599A - Plate positioning arrangement for a printing plate finishing machine - Google Patents

Abstract

838,599. Printing surfaces. MIEHLE-GOSS-DEXTER Inc. Feb. 17, 1958 [Feb. 20, 1957], No. 5095/58. Class 100(2) A method of aligning a curved stereotype printing plate with respect to a reference image in a milling machine so as to permit precise milling of tension lockup pockets on the plate, comprises the step of supporting the plate entirely by its inner curved surface and thus exposing its entire printing image, superimposing a transparent reference image which is prealigned with respect to the milling machine over the plate image, shifting the plate both axially and peripherally to bring a desired portion of the plate image into precise alignment with the corresponding portion of the reference image and skewing the plate to bring all other portions of the plate image into alignment with the remaining corresponding portions of the reference image. The machine for carrying out the method comprises a saddle 12 on which a plate P may be clamped by axially adjustable clamps as 21, (Fig. 2) slidable on rods 23, 24. The saddle is provided with openings 18, 19 through which travelling cutters 13, 14 may operate. The saddle is angularly and axially adjustable and is provided with trunnions 31, 32 journalled in bearings 33, 34. For angularly adjusting the saddle the trunnion 31 has an extension 33 to which is slidably keyed a rocking arm 36 having a bifurcated end 39 which carries a threaded nut 38. The nut 38 co-operates with a screw 37 which is rotated by a hand wheel. For axially adjusting the saddle the trunnion 32 has an exterior 43 to which is pinned a threaded sleeve 44 which co-operates with a nut 45 captive in a housing 46. A worm gear 47 on a hand operated shaft is provided for rotating nut 45 and thus moving axially the saddle 12. Four plate positioning stops are provided. Each stop, as 63, comprises a finger 65 having an abutment face 66 and pivoted at 68 to a block 69 which slides in grooves in the saddle 12. The finger 65 may be pushed downwardly against the action of a spring 70. The block 69 is attached to a rod 84 by means of a screw 85 which engages the side walls of a groove 86 joined to the rod. The rod is screw threaded in the saddle 12 and provided with a handle 88 by means of which the stop is adjusted. Each stop may be individually adjusted for skewing the plate. To allow the two stops which engage the leading edge of the plate to be retracted when the plate has been milled an additional rod 95 is provided in the blocks 69 of the two leading stops. One end of the rod engages the finger 65 and the other end is clamped by block 96 to the saddle 12. Thus when block 69 is retracted rod 95 remains stationary and bears on the finger 95 to rotate it about the pivot 68. In carrying out the method a first, black and white, plate is positioned and clamped on the saddle 12, milled and an imprint taken therefrom, as by printing ink, on a transparent sheet 110. Each edge of the sheet 110 is provided with bars 111, 1J12. The bar 112 is attached to hook members 113 which are snapped on pivot pins 114 extending inwardly from aligning blocks 116, 117. The bar 111 is fitted between two aligning blocks 121, 122. The aligning blocks 116, 117 and 121, 122 are attached to the machine frame by brackets 118, 123 respectively. After an image has been made on the transparent sheet it is removed together with the black and white plate. The first colour plate is then placed on the saddle and the transparent sheet placed thereover. Register of the plate is attained by adjusting the saddle 12 and the plate adjusting and skewing stops, the procedure being repeated for subsequent colour plates. Specifications 838,597 and 838,598 are referred to.