Patent GB-733643-A (GB)
Title: Improvements in or relating to stencil screen printing apparatus
Inventor: WHEELWRIGHT JOHN SYLVESTER
IPC: B41F15/08
Filed: 1952-07-07
Abstract: 733,643. Stencilling-machines. WHEELWRIGHT & CO., Ltd., J. Oct. 7, 1953 [July 7, 1952], No. 17065/52. Class 100 (2). A stencilling-machine comprises a stencil screen mounted in a frame 2, Figs. 1, 2, hingedly mounted upon a carriage 3 movable on tracks A provided at either side of a printing table B which is adapted to receive a length of textile material, adjustable means on the table for accurately positioning the movable carriage for successive printing operations carried out along the length of the material, and power-operated driving means causing a squeegee to move across the screen. The frame 2 is resiliently connected by spring-loaded plungers 7 to strut members 35 hinged to the carriage 3 at 4 and at their free ends connected to the frame through toggle links 5, and arms 5a mounted on a shaft 6. Rotation of this shaft causes the screen to be lifted out of printing engagement with the material on the table. A chain 30 passing over sprockets 31 mounted on cross members 35a of the frame is driven by a motor 32 and has a pin 9 connected by links 10 to a squeegee carrier 33 slidably mounted on a rod 36. The struts 35 also act as guide rods for the cross member 33a of the squeegee carrier which is caused to move backwards and forwards across the screen by the chain. Two resilient squeegee blades 34 extending across the screen are mounted for alternate operation as shown in Fig. 7. The blades 34 are carried on a central block 37 and supported along their length by adjustable bridles 34a. The block 37 is mounted on a lever 11 swingable about a pivot 11a and having an upper arm connected at 11c to links 41 pivoted-to toggle levers 42, 43 having abutments 45 at their upper ends. A sliding catch 14 is urged downward by spring 46 to engage the head of lever 11 to retain it in operative position. Abutments 13 at each side of the frame have sloping faces 13<SP>1</SP> adapted to engage under rollers 47 at each end of the travel of the squeegee to lift and release the catch. One of the abutments 45 then engages a fixed member 12 and causes the toggle levers to be turned into the alternative position so that the other squeegee blade is presented to the screen for the next printing operation. Stops 20, Fig. 8, are adjustably attached to the tracks to locate the carriage at the correct position for each stencilling operation. 'A spring-loaded control lever 17, Fig. 5, mounted for movement in two directions at right-angles on a bracket 48 (Fig. 1) attached to the carriage 3 co-operates with a gate 19 (see Fig. 9) and has a roller 18 at its inner end adapted to ride up the cam face 21 of each stop and snap into the notch 20a to locate the carriage. This movement of the lever causes a switch 51 to close which controls the motor 32, so that as soon as the carriage is located the squeegee commences its printing stroke. The lever 17 is depressed to stop the motor 32 and free the roller 18 from the notch 20a and may be positioned in one or other of two side notches 52, 53 in the gate 19. Sideways rotation of the lever operates one or other of a pair of switches 15, 16 controlling the forward and reverse circuits of a motor adapted to advance the carriage along the table. When the roller 18 engages the cam face 21 of the stop 20 corresponding to the next printing position, the lever is freed from the side notch of the gate 19 and falls into the central notch thereby closing switch 51 to cause operation of the squeege. Rotation of the shaft 6 to lift the screen may be effected by a motor controlled by switches actuated by the squeegee carrier at either end of its travel, the lifting of the screen may energize the motor for moving the carriage to its next position along the web. Also the movement of the lever 17, caused by engaging a stop 20, may be used to initiate lowering of the screen to printing position. This renders the apparatus entirely automatic.