GB747005A - Improvements in or relating to offset rotary printing machines - Google Patents

Abstract

747,005. Rotary printing- machines. GES-TETNER, Ltd. Aug. 4, 1954 [Sept. 2, 1953], No. 22678/54. Class 100 (2). In a rotary offset printing-machine comprising an offset cylinder 112, Fig. 2, movable towards and away from the plate and impression cylinders and an ink and water supply system, there are provided means for detecting the presence of sheets fed to the machine, means for rendering the ink system inoperative and a mechanism actuated by the detector means when the sheet feed is interrupted for simultaneously withdrawing the offset cylinder and actuating the means for rendering the ink system inoperative. As shown in Fig. 4, the sheet detector comprises one or more fingers 380 mounted on a rotatable shaft 381 and co-operating with one or more openings 383 in a guide plate 58. The sheet 50 passes between plate 58 and a lower guide plate 57 formed with openings 382 corresponding to those in plate 58. The sheet is advanced by carrier bands 52 to a point in contact with a front stop 60 (as described in Specification 747,002). The detector fingers 380 are lifted and allowed to fall in synchronism with the operation of the machine, as described below. When no sheet is present the fingers fall through openings 382 and initiate tripping of the offset cylinder. An arm 382a, Fig. 2, mounted on the end of spindle 381, is connected by link 386 to a swinging arm 388 carrying spaced parallel guides 390 between which slides a pin 391 on a pawl 392. The pawl is reciprocated by being carried on a bell-lever 394, the other arm of which has a follower 396 engaging a cam 397. A peg 446 co-operates with the shaped underside of the pawl, causing the pawl to lift as it moves into its most retracted position (as shown). This lifting movement is transmitted through the guides 390 and arm 388 to the arm 382a and causes the detector fingers to rise during the time a fresh sheet should be fed to the stop 60. As the pawl 392 moves forward again it slides off the peg 446 so that the detector fingers are lowered on to the sheet 50, if one is present. The sheet supports the fingers and maintains the pawl in a raised, inoperative position. In the absence of a sheet the pawl assumes a lower position so that in the next movement of the lever 394 it engages a shoulder 433 on a lever 434 pivoted at 435, whereby the lever is displaced in an anticlockwise direction. A link 436 connected to lever 434 causes a corresponding clockwise rotation of a lever 438 and upward movement of a link 440. The link 440 has a longitudinal slot through which passes a pin 441 on a pusher 402, springs 448 being connected on opposite sides of the pin 441 to pegs 443 on link 440 so that the pusher is resiliently connected to the link. The pusher is reciprocated in time with the operation of the machine by a cam 405 acting through cam follower 406 and a lever 399 connected to the pusher at 401. The follower 406 is carried on a spring-loaded arm 407 movable in one direction relative to lever 399 so that backward rotation of cam 405 merely trips the arm 407 and does not operate the pusher. The pusher moves in a guide 1402 and has shoulders 404 capable of engaging pins 444 on a rocker 413. Rocker 413 is connected by link 420 to an arm 423 secured to the eccentrically mounted offset cylinder shaft 175. When the rocker 413 is in the position shown in full lines, the offset cylinder is withdrawn from the plate and impression cylinders. Resting on rocker 413 is a lever 415 connected to a link 374. When this link is in its uppermost position (as shown) it causes the ink supply to the plate cylinder to be interrupted, as described in Specification 747,007. Rotation of rocker 413 to the dotted line position causes the offset cylinder to engage the plate and impression cylinders and the supply of ink to the plate cylinder to be re-established. When pusher 402 is lifted to the upper position due to the absence of a sheet for printing, the upper shoulder 404 engages the corresponding pin 444,on the next reciprocation of the pusher and rotates the rocker anticlockwise, tripping the offset cylinder and interrupting the ink supply as described. If a sheet is fed for the following cycle the pusher falls to the lower position and returns the parts to their operative positions. Specification 747,003 also is refeired to.