Patent GB-866259-A (GB)
Title: Improvements relating to printing machines
IPC: B41F15/08
Filed: 1956-06-18
Abstract: 866,259. Stencilling apparatus. McCORMICK, W. P. Sept. 18, 1957 [June 18, 1956], No. 18729/56. Class 100(2) A printing machine of the type comprising a reciprocable silk screen 18 patterned for use as a stencil for printing the pattern upon sheets fed in succession between the screen and a cylindrically arcuate impression surface 24 movable underneath, and in unison with the screen, has bearing surfaces around which are flexed unstretchable members 37 with grippers 44 for gripping the leading edge of each sheet to be printed, guides 34 for the members 37 extending from the side surfaces, a pair of power-driven gearwheels 29 associated respectively with the side surface and with the impression surface, and a pair of toothed racks 16 on the screen carrier meshing with the gearwheels 29. The members 37 are anchored in relation to the bearing surfaces and are reciprocated in paths defined by the bearing surfaces and guides 34. The members 37, when flared around the side surfaces, are coaxial with the gearwheels 29 and have the same radius as the pitch circles of their teeth. The machine comprises side frame members 10, 11 on a bar 12. The members 10, 11 are provided along their tops with members 14 within which slides 15 connected to the racks 16 are fitted. The racks are interconnected by ties to form a carrier for the screen 18. The screen is adjustably mounted on the carrier by fitments 19. The impression surface comprises a semicylindrical sheet 24 mounted on coaxial discs 25 on a shaft 26, the discs being rebated at 25a to allow access of the gripper mechanism. Coaxial with the discs 25 are mounted pulleys 28 and gears 29. The flexible members 37 comprise steel bands flexed around the pulleys 28 and fixed thereto by screws 38. The bands 37 also pass over pulleys 30 carried by an axle 31 in slidably adjustable bearings 32 fitted to brackets 33 provided on the guide rails 34. The rails 34 extend from the impression surface and are formed with arms 35 having bearings 36 embracing the shaft 26. The inclination of the rails 34 may be varied by a screw-jacking mechanism 40. Between the rails 34 a delivery mechanism comprising endless tapes 92 is provided. The bands 37 carry a gripper carriage 42 mounted on wheels 43 which run on the rails 34. A series of grippers 44 is spaced along a spindle 45 and is spring-urged against the edge of a top plate 46 on the carriage. Fixed rail sections 47 on brackets 48 are horizontally arranged in line with the rails 34, arcuate rail sections 49 being provided between the rails 34 and 47 which are tangential thereto. The gripper carriage is connected to the bands 37 by brackets provided with pins which engage slots formed in attachments 52 on the carriage. The grippers are operated by a lever 53 on the carriage which co-operates at each end of the carriage travel with cams 55 and 58, the cam 55 being pivoted so that it operates the lever 53 only when the carriage is travelling towardsTthe impression surface. The machine is driven by a motor 62 which drives, through a variable speed gear unit 63, speed reduction gear 64 and quick-return mechanism comprising eccentric or elliptic gears 65, 66, a crank shaft 60. The shaft 60 is provided with a crank 69 which, through a rod 73 and lost-motion connection 74, oscillates a lever 70 connected by a link 76 to a bracket 77 on one of the racks 16. A known type of squeegee 78 is provided which is fixed in a spindle 79 and is operated by a cam 83 which engages a cam follower on the spindle 79. A sprocket wheel 87 is attached coaxially to the cam 83 and is driven by a chain 90 which passes over a sprocket wheel on the shaft 60. A feed table 91 is provided. As the gripper carriage is driven by the impression-surface which in turn is driven by the screen rack 16, there is no relative motion between the sheet to be printed and the screen and impression surface. The inclination of the guide 34 is adjusted in dependence on the stiffness and heaviness of the sheets to be printed.