Patent GB-499835-A (GB)
Title: Improvements in decoration of surfaces of articles by printing
IPC: B41F17/00
Filed: 1937-07-29
Abstract: 499,835. Printing-machines. OXVAR, Ltd. (Oxford Varnish Corporation) July 29, 1937, No. 21066. [Class 100 (ii)] Printing on curved surfaces ; rotary offset machines ; offset cylinders and blankets.-A support for a printing-unit is pivotally mounted so as to overhang the work and to move in a plane perpendicular to that of a work support and is movable in substantially any direction in a plane parallel with that of the work support. The machine shown is for printing on a frame, such as a sheet-metal automobile windowframe W of generally rectangular shape as shown in Fig. 7 and having a cross-section as shown in Fig. 8. The frame W is placed on a work-holder 21 which supports the frame throughout the whole of its length by means of a vertical rib 23 ; a flange W<3> on the frame engages loosely with the inner surface of the rib 23 to permit the frame to float slightly. The work-holder W is moved about over a flat table 11 by a rotary pinion 31 engaging a rack in the form of a roller chain fitted inside the work-holder, and is guided by a roller 38 engaging the inside wall and an adjustablymounted roller 41 engaging the outer wall. To prevent the work-holder from rising off the table, a belt 65 attached to a post 43 and to a spring 68 frictionally engages the holder on two sides. Alternatively, the work-holder 21 may be held down by devices each comprising an horizontal roller engaging the rim of the work-holder and a vertical roller engaging an horizontal flange on the work-holder. A wood block 70, which is pivoted at 71, bears against a rubber cushion 72 and is spring-pressed inwardly, provides a guide for the workholder when moving parallel to the front edge of the table 11. A printing-unit 20, Figs. 1 and 3, is mounted on a carriage 90 angularly adjustable about a supporting-shaft 100 which can slide in and out of a bracket 101 adapted to swivel on a column 14 and to be clamped in adjusted position. The unit 20 is slidable on the carriage and is counterbalanced by weights ; it is moved towards and from the work by turning a hand wheel 128 to rotate a pinion 126 engaging a rack 125 on the unit. Rotation of the hand wheel throws in a clutch 55 through which the pinion 31 is driven from a motor M. The decorating-device consists of an endless offset blanket 142, Fig. 5, which picks up an impresstion from an etched plate on a rotary roller 140 and is supported by rollers 74, 75 carried by brackets 76, 79 respectively, the tension being regulated by angular adjustment of the bracket 79 and the upper part of the bracket 76 being formed as a guide engaging a guideway to provide for impression adjustment of the blanket. The roller 74 is driven by gearing capable of adjustment to suit the adjusted position of the belt, and has a peripheral groove 95 similar to the curvature of work, ribs at each side of the groove to prevent axial slip of the blanket, and bevelled ends to retard the flow of ink along the roller. The blanket 142 comprises a foundation of latex and a glue-glycerine covering, a narrow elastic band being disposed between the base and the covering ; the band may be shorter in length than the blanket to prevent separation of the covering from the base. The work-holder is placed approximately in the position W<5>, Fig. 7, and a crank 176 is turned, whereby a chain 207 advances the holder until an adjustable stop 210 is engaged, thus positioning the work always in the same initial position. In operation, the blanket is brought down on to the work, a pivoted shield 212, Figs. 7 and 8, shaped to the curvature of the work is then swung down on to it and the blanket is moved to contact with the shield until the required pressure is attained and leaves the shield as the work progresses. The shield 212 is then raised, and a second shield 213 is moved down on to the decorated work so that the blanket rides up on to it at the end of printing, thus preventing overlapping and smudging of the impression. The shields are geared together and are actuated from a cam 219 on the bar 70. An automatic machine is described in which a rotary cam acts through a spring to move the printing-unit up to the work and withdraws the unit positively when the decoration is completed, and the unit in its downward movement throws in a clutch whereby the pinion 31 is driven. The cam is adjustable angularly to vary the portion of the design applied first. Inking apparatus ; set-off, preventing.-The plate on the roller 140 is inked by a tube 180, Figs. 3 and 5, dipping in a container 174. Ink is drawn up the tube by a rotary screw 181 and is discharged through an aperture 184 on to the roller. Scraper blades 185, 186 pivoted at 187 to a bracket adjustable about an axis 187a are pressed against the blanket 142 and the roller 140 by a spring 190 connecting the ends of the blades. A cam 192 is provided for turning the blades simultaneously into inoperative positions. The scrapers are reciprocated longitudinally by a rotary cam 202. Ink removed drips into a pan 194 from which it is returned to the reservoir by a pump 175. This comprises a tube 115, Fig. 13, which has at its lower end an aperture closed by a spring- pressed ball 135 and is reciprocated vertically by the cam 202, anda stationary tube 114 closed by a spring-pressed ball 119 and arranged inside the tube 115. Ink trapped in the space between the balls is forced into the tube 114 on the up-stroke of the tube 115. On the down. stroke, the ball 119 closes the aperture causing a partial vacuum in the tube 115 whereby ink is sucked thereinto when the ball 135 engages the bottom wall of the pan 194. Specification 463,590 is referred to.