Patent GB-704726-A (GB)
Title: Improvements in or relating to silk screen stencilling machines
IPC: B41F15/08
Filed: 1952-05-12
Abstract: 704,726. Stencilling-apparatus; feeding sheets. BLACK, J. A. May 12, 1952, No. 11957/52. Classes 100 (1) and 100 (2) In a silk screen stencilling- machine the sheets &c. are carried and supported for stencilling by a drum 87 which is oscillated about a fixed horizontal axis by the engagement of gears 86 thereon with racks 85 on a reciprocating stencil-carriage frame 72, the outer shell of the drum being perforated and communicating with a suction pump 40 whereby the sheets are gripped to the drum during stencilling. All the parts, including the pump 40, are driven by a motor 23 through a variable-speed gear 31 which is regulated by a hand-wheel 32. Apart from the gear-wheel drive to cranks which reciprocate the stencil frame 1 the driving means consists of a series of belts and pulleys. The carriage 72 is of angle iron having a rectangular wooden frame 80 removably mounted therein to which is affixed a silk screen 79. Pairs of rollers 73 on the carriage engage runways 74 on rails 75. Stub shafts on the carriage engage blocks, such as 66, adapted to slide in the slotted upper ends of rocker arms 56 which are pivoted at 58 ana rocked by adjustable connecting-rods 53 from cranks 46. The cranks 46 are connected to a .transmission mechanism 45 geared to the speed gear 31 whereby the carriage 72 is reciprocated, and, through the racks 85 and gears 86, the drum 87 is oscillated. A rubber &c. squeegee 93 is adjustaby clamped between bars and removably secured by hand-screws 96 to a bar 97 having its ends attached to blocks 100 which are vertically-slidable in slots in bearings 102 secured to the rails 75. The squeegee is verticallyreciprocated by adjustable rods 108, connected at their upper ends to the blocks 100 and at their lower ends to pivoted links 114 which are engaged by cams 118. A spreader 244 for the coating material is attached to the squeegee, and a splash shield 106 is secured to the carriage 72. One of the cams 118 actuates a valve 122 in the suction pipe line 125, 126 leading from the pump 40 to a channelled block 127. This block communicates with an arcuate chambered member 132 secured on one side of the drum 87, so that oscillation of the drum brings chambers 135, 136 and 137 into successive registry with the channel in the block 127. The drum 87 has a wooden core with passages therein to connect the chambers 135-137 each to a set of perforations in the outer shell of the drum. As the drum oscillates, the three sets of perforations are successively connected to the suction pump, and a sheet is thus gripped to the drum during the stencilling operation. Grippers 156 mounted on the drum 87, as described below, take sheets from a feed table and release them on to a delivery conveyer after the stencilling operation. Sheet-registering and feeding.-Sheets 105 are fed by an operator on to moving tapes 188 arranged on rollers carried by an inclined table 181, the sheets being held against the tapes by steel balls 201 disposed in bars 203 carried by a frame 204 secured to the table. The tapes are inclined to the direction of travel of the sheets and so urge them against an adjustable side register plate 205 (not shown). The leading edge of each sheet engages a front stop comprising the hooked end of an arm 212 secured to a rock-shaft 209 which is rocked to release the sheet when an arm 215 secured to the shaft is struck by a pin on the drum 87. The registered sheet is then seized by grippers 156 on the drum, and is held to the drum by suction, as described above, and by the weight of flexible fingers loosely mounted on the rock-shaft 209. Prior to release by the front stop 212, finger 219 on an arm 217 bears against the sheet, this arm being pivoted on a shaft 218 which is rocked when a sliding bar 221 is engaged by a pin on the drum 87. The grippers 156 are secured to a shaft 155 mounted in bearings in a longitudinal recess in the drum 87, a coil spring 158 (not shown) urging the shaft and grippers into sheetgripping position. The shaft 155 is rocked to open and close the grippers to receive and release a sheet by cam means. To open and then close the grippers to receive a sheet, a crank arm secured to the shaft 155 is engaged by a rockable cam 161, Fig. 1, and a second crank arm 178 engages a fixed cam plate 174 to open the grippers to release a sheet on to delivery tapes 229. Strippers 226 bear constantly against the drum to peel the stencilled sheets therefrom.