Patent GB-751922-A (GB)
Title: Silk screen printing machines
IPC: B41F15/08
Filed: 1954-08-18
Abstract: 751,922. Stencilling-apparatus. DUBUIT, L. G. Aug. 18, 1954 [Jan. 30, 1954; June 9, 1954], No. 24085/54. Class 100 (2). In a machine for stencilling sheets in register, raising of a bar carrying the squeegee causes first the squeegee to be raised, then after a delay causes the screen to be raised, sheet-locating elements to be moved to an inoperative position, and sheet-holding means to be rendered inoperative, while lowering of the bar causes the reverse procedure. The squeegee 32 is mounted for rocking movement, so as to reverse its inclination when the stroke direction is reversed, on a cradle 27 pivoted at 26 on a sheath 23 which is adjustably mounted on a bar 18 formed with a handle 19 at one end carrying a counterweight 20 at the other end, and secured to a carriage 14 which can run along and pivot about a rail 7 secured to brackets 6 and extending near and parallel to a long side of the printing table 2 The screen frame 44 is held at the centre of two opposite sides by jaws 42 on bar members 35 adjustably secured to bars 11, 11<SP>1</SP> connected tc the hubs of two bell-crank levers 9, to the ends of the upper and lower arms of which are se cured cross-pieces 12 and 13b respectively The jaws 42 are adjustable along the bar mem bers 35. The screen may thus be of any desired size, so that small screens can be used for multi colour printing where each colour represents only a small area. The table 2 is hollow, being formed with upper and lower iron plates 4, 4<SP>1</SP> and cross-pieces connecting the longer sides of the table and having therein passages to allow passage of air between the compartments thus formed, and there are provided apertures in the cross-pieces and in the plates 4, 4<SP>1</SP> to allow the passage of sheet-locating cleats 50. Below each aperture is secured an angle-iron 46 slotted at 46a to receive adjustably a gusset 48 to which is pivoted one of the cleats 50 urged by a spring 52 into vertical sheet-locating position against a stop 51. The cleat is held in retracted positior by an adjustable slider 54 on a rod 55 pivoted to the cross-piece 13b. The plate 4 is provided with holes 67 and the interior of the table com. municates through a throttle 63, conduit 62 and piping 66 with a source of vacuum. The throttle is urged to closed position by a spring 64. When the handle 19 is raised, the squeegee is raised clear of the screen, and after a delay the bar 18 engages the cross-piece 12 to rock the levers 9 and raise the screen frame 44 off the table, the cross-piece 13b acting through the rods 55 to release the cleats 50, which move intc locating position, and through a rod 57 to allow the throttle 63 to close. The sheet is then re. moved and replaced. On lowering the 1 andle 19, the throttle is opened, the cleats retracted; the screen lowered and the squeegee lowered. In another form, the-table comprises only one plate 4 provided with similar cleat apertures, and cross-pieces formed with rectilinear slots. To each cross-piece is thereby adjustably secured a gusset carrying a rod protruding above the table, carrying at its upper end a sheet-clamping plate, and spring-urged downwards into clamping position. The rod 57 acts, at the end of the downward movement of the handle 19, on a bell-crank to raise the clamping rod and release the sheet. The clamping rods may also replace the cleats 50 as locating elements.