Patent GB-846626-A (GB)
Title: Improvements in or relating to stencilling machines
IPC: B41F15/08
Filed: 1958-07-11
Abstract: 846,626. Stencilling-apparatus. BLACK, J. A. July 11, 1958 [July 26, 1957], No. 22332/58. Class 100(2) A stencilling-machine comprises a stock-supporting platen and a stencil mounted for relative movement intc a starting position out of registration, with the platen free to receive a sheet of stock to be printed, and into .a printing position in registration, the platen having stock-supporting arms extending beneath the stencil in the starting position, the stencil having stripper fingers which engage behind a sheet on the platen and transfer it to the arms during movement into the starting position, and the sheet-carrying surface of the platen having perforations to enable suction to be applied to the sheet, the machine having means for applying the suction during the printing operation and relieving the suction thereafter. A sheet of stock to be printed is placed on a platen 49, Fig. 2. A squeegee assembly 76 including a blade 77 is adjusted vertically on rods 78, and the stencil frame 53, Figs. 2 and 5, which is pivoted at one end at 91 to a bar 92 and at the other end has arms 95 which rest on a stencil carriage 54, is adjusted vertically with respect to the carriage according to the thickness of the stock, at the pivoted end by adjusting serrated blocks 103 with respect to serrations 101 on the bar 92, and at the other end by means of screws threaded into the carriage. A motor 25 is then started by a switch 143 for a cycle of operation, causing stock delivery tapes 119 to be driven, and a cam shatt 30 to be rotated. The motor operates a compressor which applies suction to perforations in the surface of the platen to hold the stock thereon. The platen is moved to the right by a crank arm 34 on the cam shaft, a gear 43 engaging a stationary rack and also engaging a movable rack bar carrying a gear 46 engaging a stationary rack and also engaging a further rack on the platen, so that the platen moves through four times the travel of the end of the arm 34. When the platen reaches its right-hand position, spring- latches 57 pivoted thereon engage angle brackets on the carriage 54 to couple the stencil to the platen. A cam 85 on the shaft 30 releases a roller 84 on a bar 83 connecting bars 80 pivoted at 81 to allow springs 86 to lower the rods 78 pivoted to the bars 80 at 79, and lower the squeegee on to the stencil. The arm 34 then moves the platen, stock and stencil together to the left past the squeezee for printing. At the end of the printing stroke, a cam on the shaft 30 acts on a switch to shut off the compressor and release the stock. During the printing stroke, rollers 99 on the stencil carriage ride up stationary ramps 100 to peel the stencil off the stock progressively. At the end of the stroke, the squeegee is carried by its cam, and stationary cams release the latches 57, whereupon the stencil carriage is moved rapidly to the right by means of a compression spring in a cylinder 68, a piston rod 72, gear sector 65, gears 64, 62, and racks 61 on the carriage, the spring having been compressed during the printing stroke. Pivoted stripper fingers on the carriage engage behind the printed stock and move it on to extension arms 115 of the platen, and on the next movement of the platen they are transferred to the tapes 119. At the end of the return stroke, a cam on the shaft 30 actuates a switch to stop the motor for sufficient time to position a new stock sheet, when it is restarted by a timing device. A manual stop switch is also provided. The squeegee can also be raised and lowered by a foot-pedal and a link 88. There is also provided a member, raised at the start of the printing stroke and lowered after the printing stroke, which acts to restore the surplus colour, which collects at the right-hand end of the stencil after the printing stroke, into an even coating over the stencil. When the stock sheets are considerably smaller than the area of the stencil, the cam 85 for the squeegee is replaced by an adjustable cam, both cams being axially movable along the shaft 30 into selective engagement with the roller 84. The slope of the ramps 100 is adjustable by screws 108.