Patent GB-537245-A (GB)
Title: Improvements in or relating to stencil printing machines
IPC: B41F15/08
Filed: 1939-12-13
Abstract: 537,245. Stencilling apparatus. TRIGGS, W. W. (Colorgraphic Process Corporation). Dec. 13, 1939, No. 32146. [Classes 100 (i) and 100 (ii)] In a stencil printing apparatus, the sheets are carried from a feed table 93, Fig. 1, to a table 6 on which they are printed, by gripper bars 25 carried by intermittently actuated endless chains 24, means being provided to retard the chains at the end of each movement and to store energy which initiates the motion at the 'beginning of the next movement. Such means comprises arms 38, 39, Fig. 10, pivoted to a member 37 fast on the continuously rotating shaft 16, Figs. 1 and 10, the arms being connected to the member 37 by springs 42 and being provided with angle bars 40, 41. In Fig. 10, the chains are moving to the right and the arms 38 39 in clockwise direction at a slower speed than that of the chains. Towards the end of a feed movement of the chains, a gripper bar 25 engages the angle bar 40 turning the arm 38 against the action of its spring 42 which thus acts to check the movement of the chain. During the printing period, the arms 38, 39 continue to turn and the angle bar 41 engages the rear of the gripper bar 25 tensioning the spring 42 associated therewith, the spring thus serving to initiate the next feeding movement of the chains. Jerking of the chains is thus avoided. The table 6, which is hollow and connected to a suction pump, is carried by arms pivoted to the frame of the apparatus and raised and lowered by a cam 15 on the shaft 16 acting through linkage 13, 12, 11, 10, 9. The stencil is stretched on an arcuate support secured in a frame 46, Figs. 1 and 3, provided with arcuate racks 45 engaging racks 44 on the machine frame, a bracket 48 secured to the frame 46 being connected by a link 49 to a crank pin on a gear 51, Fig. 1, driven intermittently through mutilated gearing from the shaft 16 so that the stencil receives a rocking movement on the table 6. During each rocking movement of the stencil, colour is forced therethrough by one of a pair of squeegees 53, 54, Fig. 5, fixed to a frame 55 provided with arms 56 carrying studs 57 on which are mounted plates 58 the upper ends of which embrace the arms 56. Arms 59 also secured to the frame 55 are provided with pins 61 engaging cam slots 62 in the plates 58 and with slots 63 receiving the studs 57. A cam 64 on the lower end of one of the arms 59 co-operates with spaced abutments 65 on a slidable bar 66 connected by a link 67 to a sprocket wheel 68 connected by a chain 69 to a sprocket wheel on a shaft 33, Fig. 1, driven intermittently by mutilated gear from the shaft 16. The squeegee frame 55 is reciprocated by links 71, 72, shaft 73, arm 74 and links 75, 50 from the gear 51 and at the end of each stroke, the oar 66 is actuated to cause one of the abutments 65 to engage the cam 64 and reverse the frame 55 and thus bring the previously inactive squeegee into operative position. The plates 58 are secured to arms 80 which by means of link 79, crank 81, pinion 77 and gear segment 76 fixed to shaft 73, are caused to remain substantially horizontal as the squeegee frame is reciprocated. A bar 82 engaging beneath a roller mounted on one of the plates 58 may be raised by means of a pedal 85 to hold the squeegee mechanism out of contact with the stencil when desired. To prevent adherence of the sheet to the stencil, a flexible band extends across the machine frame between the stencil and a part of the sheet outside the area to be printed. Pivoted fingers arranged at the front edge of the table are adapted, as the table is raised to printing position, to engage behind the gripper bar holding the leading end of the sheet to move the bar into contact with the edge of the table to register the sheet.