GB747006A - Improvements in or relating to offset rotary printing machines - Google Patents

Abstract

747,006. Rotary offset printing-machines. GESTETNER, Ltd. Aug. 4, 1954 [Sept. 2, 1953], No. 22679/54. Class 100 (2). In an offset rotary printing-machine having a plate cylinder, ink and water supply systems for the plate cylinder, an eccentrically-mounted offset-cylinder and an eccentrically-mounted impression-cylinder, means are provided for detecting the presence of sheets fed to the machine and mechanism under the control of the sheet detector operative in the absence of a sheet to trip the offset cylinder out of contact with the plate and impression cylinders and to simultaneously interrupt the supply of ink to the plate cylinder; theie is also provided a manual control for moving 'the impression cylinder towards and away from the offset cylinder, and mechanical interconnection between the manual control and the control mechanism whereby when the impression cylinder is withdrawn by the manual control the control mechanism is automatically adjusted to move the offset cylinder against the plate cylinder and to establish the flow of ink to the plate cylinder so that an inked image may be established on the offset cylinder before printing starts. Fig. 2 shows pait of the control means of the printing machine, the plate cylinder 113 being supplied with ink and water as described in Specification 747,003. The eccentricallymounted shaft of the offset cylinder 112 is rotatable to move the cylinder into and out of engagement with the plate and impression cylinders by an arm 425. The impression cylinder shaft is also eccentrically mounted so that it can be rotated by handle 483 to move the cylinder away from the offset cylinder to prevent it being inked during the process of building up an inked image on the offset cylinder before sheets are fed to the machine. Normal control mechanism.-The normal control mechanism, governed by the sheet detector serves to trip the offset cylinder when no sheet is fed. The sheet detector is as described in Specification 747,005 and is mounted on a spindle 381. An arm 382a on this spindle is connected to a swinging arm 388 carrying spaced parallel guides 390 between which slides a pin 391 on a pawl 392 reciprocated on a bell-crank lever 394 actuated by a cam 397. When no sheet is fed the detector is unsupported and falls, allowing the guides 390 and pawl 392 to swing down to the lower position so that in the next movement of the lever 394 the pawl engages a shoulder 433 on a lever 434 pivoted at 435 which is displaced thereby. A link 436 connected to lever 434 is likewise displaced to the right, and causes rotation of a lever 438 and through link 440 upward pivotal displacement of a pusher 402. The pusher is connected to a lever 399 reciprocated by a cam 405 and is adapted, in the upper position, to engage and rotate a rocker 413 in a clockwise direction. The rocker is connected by link 420 to arm 425 on the shaft of the offset cylinder. In normal operation when no sheet is fed to the machine the detector, through the mechanism described, causes rotation of rocker 413 to the position shown in full lines in Fig. 2. This allows arm 425 to move under spring pressure to trip the offset cylinder out of contact with plate cylinder 113 and impression cylinder 66. Rotation of rocker 413 also lifts an arm 415 and a link 374 connected thereto which is adapted to interrupt the feed of ink from the ink reservoir to the plate cylinder as desciibed in Specification 747,007. When a sheet is fed the pawl is lifted out of engagement with lever 434 so that pusher 402 reciprocating in the lower position returns rocker 413 to the dotted line position causing the offset cylinder to re-engage the plate and impression cylinders. Mounting impression cylinder.-As shown in Fig. 4, the impression cylinder 66 is mourted by bearings 183 on a shaft 182 which is keyed in an eccentric sleeve 185 rotatable in a bush 186 secured to the frame member 40. A disc 450 (see also Fig. 6) is adjustably attached to frame member 40 surrounding bush 186. A block 451 rotatably mounted on shaft 182 bears against the end of bush 186 on one side and against an arm 468 on the other which is non- rotatably secured to the shaft 182 and held by a nut 477. A bolt 471 screwing into block 451 passes through an annular slot 473 in arm 468 so that by tightening bolt 471 the arm 468 is clamped to the block. A bracket 463 on block 451 carries a screw 464 and adjustment nut 465, the screw being, connected to a spring 466, the other end of which is attached to arm 468. The block is normally secured against rotation by a pawl 454 engaging a notch 455 as described below so that the spring 466 tends to rotate the arm 468 and shaft 182 in a clockwise direction. When sheets of different thicknesses are passed through the machine the impression cylinder is capable of movement towards and away from the offset cylinder by rotation of the eccentric shaft 182, arm 468 moving relative to block 451. The pressure applied is adjustable by nut 465. When sheets of constant thickness are being printed this resilient mounting may be put out of action by tightening bolt 471. Manual'control.-Clamped to the end of shaft 182 are a handle 483, Fig. 4, and a sleeve 480 carrying an arm 484 at the inner end. The pawl 454 is pivoted to disc 450 at 453 and spring- loaded to engage notch 455. A pin 459 projecting from the pawl is engaged by arm 484 so that rotation of handle 483 first causes the pawl to release block 451. Rotation of the handle also causes rotation of shaft 182 and tripping of the impression cylinder. An arm 490 depending from arm 484 carries a pin 491 engageable in a notch 496 in a finger 492 spring-loaded in a clockwise direction and connected by link 497 to lever 434, Fig. 2. A lever 461 pivoted at 435 has an upstanding arm adapted to engage a pin on arm 382a and rotate it so as to lift the sheet detector and pawl 392, thereby rendering the detector inoperative. When the handle 483 is rotated anticlockwise from the vertical position shown in Fig. 2, arm 484 engages pin 459 so that the pawl 454 is disengaged from notch 455 and the pin also bears against surface 460 of lever 461 so that it is rotated into engagement with pin 383 rendering the sheet detector ineffective to cause tripping of the offset cylinder and interruption of the supply of ink to the plate cylinder. In the normal vertical position of the handle (Fig. 2) pin 491 rests on a horizontal surface of finger 492 but when it is rotated the pin is received in notch 496. When the handle is released, a spring 398 tends to return it to the initial position but the engagement of pin 491 in the notch prevents full return movement. The finger is displaced to release the handle when the lever 434 is next displaced by pawl 392. Since the notch 496 is wider than pin 491 a partial return movement may be effected by spring 398 sufficient to allow the lever 461 to release the arm 382a. Since no sheets are yet being fed the detector falls so that the pawl 392 engages lever 434 and displaces it, thereby freeing finger 492 and allowing full return of the control lever to the vertical position and return of the impression cylinder to its normal operative position. By this means the return of the mechanism to the normal control is synchronised with the operation of the machine. Specifications 747,002 and 747,008 also are referred to.