Patent GB-957818-A (GB)
Title: Improvements in screen printing machines
Inventor: SUGDEN FRANK KAY
IPC: B41F15/08
Filed: 1962-04-27
Abstract: 957,818. Printing apparatus. WALL PAPER MANUFACTURERS Ltd. April 29, 1963 [April 27, 1962], No. 16100/62. Heading B6C. In a screen printing machine of the type in which a screen is mounted in a frame reciprocating above a cylinder over which a web passes to provide line contact with the screen, the printing media being applied to the web through the screen by a blade or squeegee, the cylinder is driven at a surface speed substantially equal to the linear speed of the screen and rack means are provided to superimpose upon or subtract from the motion of the cylinder for any longitudinal dimensional change in register of the web. In the described embodiment a screen frame holder 1 is supported by a carriage 2 carrying a frame 3 reciprocated by hollow piston rods 5 in a cylinder 4 into which oil is pumped through the rods 5. The screen is reciprocated over a cylinder 6 mounted on a shaft 24 and rotated in unison with longitudinal movement of the screen and a web of material 7 is drawn over the cylinder 6 and maintained in contact therewith by a nip roller 8. To change the movement of the cylinder 6 relatively to the screen, a rack 9 is mounted on the carriage 2, the rack being urged in one direction (to the left in the drawings) by a fluid-actuated cylinder 11, Fig. 1, supplied through a hollow piston-rod 12 (Fig. 6, not shown). The opposite end of the rack engages a pinion 13, Fig. 7, mounted on the machine frame and actuated by a vertical rack 14 carrying a roller 15 engaging a pivoted lever 16. When the lever 16 is horizontal the rack is free to move with the carriage, but if the free end of the lever is moved upwards the rack 14 rises and in rotating the pinion 13 causes the rack 9 to move further to the left, thereby moving the carriage and screen relatively to the cylinder so that on the succeeding traverse of the screen the pattern may be brought back into substantial register, a predetermined tolerance in register being permissible. Similarly, by rocking the lever 16 in the opposite direction the rack and carriage may be moved in the reverse direction. The position of the pattern as it passes over the cylinder 6 may be viewed through a window 17 and the necessary correction made before a succeeding traverse of the carriage. Any wandering of the web from a central position on the cylinder may be adjusted by canting the nip roller 8 through a conical adjustment device 18. The reciprocation of the rack 9 drives a pinion 23 mounted on the shaft 24 through a freewheel one-way clutch 26, Fig. 3, a brake 25 being provided to prevent movement of the shaft 24 during return movement of the carriage. The screen returns out of contact with the cylinder 6, the holder 1 being lifted for this purpose by a piston on an hydraulic cylinder 29. The carriage is started from rest by the admission of oil through one of the rods 5 into the cylinder 4, the speed at which the carriage travels being governed by the volume of oil allowed to escape through an exhaust valve arranged in a casing 31. The effective escape area of this valve is controlled by a cam 51 through a cam follower 52 mounted on a rod 53 pivoted on a pin 54 on the casing 31. The cam is rotated through movement of the carriage. The squeegee 32 is lifted at the end of each operative stroke by the piston of an hydraulic cylinder 35, Fig. 5, carried by the machine frame which rocks a shaft 34 to remove the squeegee out of contact with the screen during the return stroke of the carriage. When the carriage is at the commencement of its stroke the squeegee is moved to the right (Fig. 2) beyond the pattern on the screen and lowered on a supply of printing media which has been supplied to the screen from a reservoir 36. Through the actuation of hydraulic cylinders 37 and 38 the squeegee draws the media on to the edge of the patterned portion of the screen for application therethrough as the carriage travels to the opposite end of the stroke. The squeegee is then given a further movement to the left (Fig. 2), through the hydraulic cylinder 38, to remove any surplus media from the rear edge of the screen. This surplus flows down an incline 39 into a container 41 for return to the supply reservoir 36. The pressure of the squeegee on the screen may be adjusted by a screw having a knurled head 45.