Patent GB-1033726-A (GB)
Title: Screen printing machines
IPC: B41F15/08
Filed: 1962-12-28
Abstract: 1,033,726. Stencilling apparatus; feeding sheets. GENERAL RESEARCH Inc. Dec. 28, 1962 [Jan. 5, 1962], No. 48882/62. Headings B6B and B6C. In a screen-stencilling machine of the kind having a reciprocable screen-stencil carriage arranged to co-operate with an oscillatable stock-supporting cylinder, Fig. 3, and take-off means which convey the printed stock from the cylinder, the take-off means comprises a delivery board 119 (Figs. 1 and 3) having means for applying differential air pressures arranged so as to draw the printed stock away from a screen stencil in the carriage and hold the stock during the delivery conveyance thereof. The take-off means comprise endlessbands 315 having suction openings 331 which pass over suction openings 332, Fig. 35 (not shown), in the delivery board from a point adjacent the cylinder. Sheet feed.-The machine also comprises a feed board 118 along which the sheets to be printed are advanced to the cylinder. Associated with this board are a stationary preset stock-sheet side stop 245, Fig. 12 (not shown), and two discrete, alternatively-operable, slidable members 237, 260 in the form of reciprocable slides arranged to grip the undersurfaces of the sheets of suction and to be moved along their respective reciprocation paths, which lie transversely of the sheet advance path, to effect side registration of the sheets, the slide 237 being disposed to effect .such registration by drawing the sheets against the stationary side stop 245 whilst the other slide 260 is disposed to push the sheets into side registration by means of a pushing stop 259 which it carries. The stationary side stop and the pushing stop are each carried by a block the position of which is adjustable across the feed board transversely of the direction of sheet feed and each stop is correspondingly adjustable relatively to the associated block so as to provide coarse and fine adjustments in the presetting of the stop. Each of the slides is adapted for the mounting of a pushing stop thereon whilst the feed board is adapted for the mounting of a stationary side stop to coact with either side. Each slide is tubular and elongated in its direction of reciprocation and is mounted on the underside of the feed board such that a slide portion, such as 240, Fig. 14 (not shown), in the case of 237, projects upwardly through an elongated slot in the board the portion having along its upper surface a row of spaced-apart suction orifices 241, 262, Fig. 12 (not shown), for gripping the sheets. The slides, which are spring-biased into extreme positions of their travel paths, are driven via a rotary drive cam. The feed board also has two different types of releasable stocksheet advance stops, operative for halting the advance of each sheet at the delivery end of the board, namely, pivotably mounted stops 264, Fig. 20 (not shown), for paper stock, which are cam-rocked and slidably mounted stops 285, Figs. 15 and 19 (not shown), for cardboard stock, which are operated by an air motor. The feed board delivery end also incorporates finger extensions on which the stock sheets are pressed down by means of bifurcated pivotallymounted arms 280 (Fig. 12) which are camrocked to release the sheets in synchronism with the release and application of the pivotably-mounted stops 264. The sheets are advanced along the board by endless-band conveyer tapes 208, Fig. 12, engaging their under-surfaces, the sheets being weighed into contact with the tapes by balls 232 which are loosely mounted in a carrier 229 overlying the tapes bear on the upper faces of the sheets. Operation.-Stock sheets are fed into the machine over the feed board 118 and conveyer tapes 231. During such travel each sheet is moved laterally into correctly registering position by one of the suction " pull-over " or " push-over " devices located in the board near the cylinder 117. Before being released to the oscillating cylinder 117 for printing each sheet is halted by the movable stops 264 or 285, the movement of which is co-ordinated with the movement of the cylinder 117 and the stencil 77. Whether of paper or cardboard the sheets are pressed downwardly against fingers 283, Fig. 12, to ensure their entry into slots 130, Fig. 21 (not shown), of the grippers 129 on the cylinder 117. The surface of the cylinder 117 is perforated and a vacuum is applied to the interior thereof to hold the sheet thereon (see Specification 704,726). At the precise moment when the cylinder 117 reaches the end of its non-printing oscillation in a counter-clockwise direction, the stops 264 or 285 release a sheet to the grippers 129, the squeegee 80 is lowered on to the stencil 77, and the machine operates through its printing stroke with the cylinder 117 oscillating clockwise to support and carry the stock, and with the stencil 77 moving to the right while the squeegee 80 forces printing ink through the stencil 77 on to the stock 120. After printing the stencil is moved to the left and returned to its starting position, the cylinder 117 is rotated counter-clockwise to its starting position, the squeegee 80 is elevated off the stencil 77, and the printed sheet is delivered over the vacuumized delivery board 119.