Patent GB-911830-A (GB)
Title: Improvements in devices for moving the offset cylinder in offset printing machines
Inventor: JURNY JOSEPH
IPC: B41F13/28
Filed: 1960-09-02
Abstract: 911,830. Cylinder - tripping mechanism. ADAMOVSKE STROJIRNY, NARODNI PODNIK. Sept. 2, 1960, No. 30278/60. Class 100 (2). The offset cylinder 1 of an offset printing machine is mounted in eccentric bearings which are controlled through a spring-loaded cam mechanism so that the cylinder may be automatically moved in two stages, first into contact with the plate cylinder and then into contact with both the plate and impression cylinders. The spring-loaded mechanism comprises a roller follower 21 engaging a cam 20 secured to a flange of the cylinder 1. The follower is carried by one arm of a two - armed lever 22 pivotally mounted at 23 to the sidewall of the machine, the other arm of which carries a lever 25 pivotally mounted thereon through a pin 24 and resiliently biased thereto by a spring 29. The lever 25 carries rollers 28, 27 riding on the respective edges of a rocker-arm 6 and a sleeve 5, Fig. 2. The latter, which comprises a bifurcated arm pivotally mounting a lever 12 through a pin 11 and an edge surface having two recesses along which the roller 27 tracks, is keyed to the shaft 2 on which the cylinder 1 is rotatably mounted and rotatably mounts the rockerarm 6 which is biased by a spring 8 to normally lie relative to the sleeve 5 such that a projection on the arm abuts a pin 7 on the sleeve. The arm edge part engaging the roller 28 is spiral relative to the axis of the shaft 2 and includes a recess. The outer end of the lever 12 carries a spring-loaded slidable guiding pin 13 pressed by a spring 14 against the surface of a guide rail 16 which is secured to the sidewall of the machine and embodies two projections behind which the pin 13 is adapted to snap. In operation, and with the parts in the positions shown in Fig. 2, rotation of the cylinder 1 and hence the cam 20 causes the rollers 27 and 28 to idly reciprocate along the edges of the sleeve 5 and the arm 6. On turning the socket arm into the position in which the recesss in the arm and the first recess of the sleeve 5 register, using, e.g. a push-button, link, cable, &c., the roller 28 engages the recess in the arm whilst the roller 27 drops into the first recess in the sleeve 5 such that the subsequent forward thrust of the lever 25 deriving from an anticlockwise movement of the lever arm carrying the follower 21 due to the moving cam 20 turns the arm 6 and sleeve 5, and hence the bearing of the cylinder 1, into the position of Fig. 5. The sleeve is held through the pin 13, snapping into engagement behind the first projection on the rail 16 whilst subsequent cam movement causes the lever 25 to transfer the roller 27 from the first to the second recess of the sleeve. The roller 28 remains in the recess of the arm 6 as the arm is freely rotatable relative to the sleeve. The next forward thrust of the lever 25 causes further rotation of the sleeve, and hence the shaft 2, to the position of Fig. 6, where the sleeve is held by the pin 13 snapping behind the second projection on the rail 16. Due to the spiral nature of the edge surface of the rocker-arm 6 the subsequent withdrawal of the lever 25 causes both rollers 27, 28 to disengage from their respective recesses whereupon the arm 6 springs back to the position of Fig. 2, whilst the sleeve and hence the shaft 2 and cylinder 1 remain in a position in which the cylinder is in operative contact with both the plate and impression cylinders. Whilst printing is in progress the cam 20 rotates continuously, the rollers 27, 28 reciprocating idly along the surfaces of the sleeve and arm with which they are engaged. To trip the cylinder 1 the pin 13 is depressed to disengage from the rail 16 to allow a spring 18 to return the sleeve and shaft to the position of Fig. 2. Such tripping may be effected by a paper-feed mechanism failing to operate.