GB912806A - Screen printing apparatus - Google Patents

Abstract

912,806. Screen printing. ARGON SERVICE Ltd. Dec. 24, 1958 [Dec. 28, 1957], No. 41660/58. Class 100 (2). In a screen-printing apparatus a frame 3 carrying the screen is mounted on a shaft 4 rotatable in bearings 5 on the frame 1, the shaft 4 also having arms 6 rigidly mounted thereon and secured together by a bar 20. A spring 45 continuously urges the frame 3 into the raised position shown in Fig. 2. A squeegee 7 in a holder 8 which is mounted on a carriage comprising two telescopic end members 10 and two horizontal bars 9 extending therebetween is reciprocable over the screen by lever devices 14, 15 connected at 13 to the telescopic end members 10. The members 10 carry at their lower ends rollers 11 which run in guides 12 at the sides of the frame 3. The levers 15 are secured at their lower ends to a shaft 17 journalled in the frame 1 and an arm 18 is also secured to the shaft 17. The arm 18 is pivoted to the connecting rod of a piston 22 of a pneumatic ram the cylinder 21 of which is pivoted to an arm 19 rigidly secured to the bar 20. A lever 33, Fig. 3, is pivotally connected to the frame 1 at 42 and to the bar 20 and at its lower end actuates a Bowden cable 43 controlling a band brake 31, the drum 30 of which is secured to the shaft 17. In order to print on stock on the table 2 the operator depresses a pedal 26 controlling a valve 25 whereby, with the parts in the Fig. 2 position, air under pressure is fed through a pipe 24 into the right-hand end of the cylinder 21. As the shaft 17 is restrained against rotation by the band-brake 31 the cylinder 21 moves to the right and causes the frame 3 to swing downwards, against the bias of the spring 45, until it rests flat on the table 2. During this movement the bar 20 has moved to the right, thus causing the lever 33 to oscillate and release the band-brake 31, whereupon the piston 22 is free to move to the left and rotate the shaft 17. Rotation of the shaft 17 causes the squeegee 7 to move across the screen in a printing stroke. Rollers 36 carried by arms 35 pivotally mounted on the lower of the bars 9 run along the tops of the guides 12 and at the end of the printing stroke abut against stops 40 on the frame 3 so that the arms 35 are swung towards the shaft 4, thus slightly raising the bars 9 and squeegee 7 so that the latter applies less pressure to the screen on the return stroke. As the squeegee ends its printing stroke a rod 29 pivoted to one of the links 15 engages an adjustable screw stop 48 on a rod 28 causing the latter rod to oscillate and, through a further rod 27 reverse the valve 25. Air under pressure is thereby fed to the left-hand end of the cylinder 21 through a pipe 23 and the pipe 24 is connected to exhaust, so that the parts are restored to their Fig. 2 positions. At the end of the squeegee return stroke the rollers 36 engage stops 41 and cause the arms 35 to swing away from the shaft 4 and lower the squeegee.