Patent GB-666782-A (GB)
Title: Improvements in or relating to rotary offset printing presses
IPC: B41F33/08
Filed: 1949-01-27
Abstract: 666,782. Printing-machines. HOE & CRABTREE, Ltd., R. Jan. 27, 1949 [Jan. 27, 1948], No. 2340/49. Class 100 (ii). Rotary offset machines; tripping-mechanism. -In a sheet-fed multi-unit offset printing- machine, each unit of which comprises a plate cylinder, an inking-mechanism therefor, a blanket cylinder, an impression cylinder, and tripping-mechanism for tripping the cylinders and the inking-mechanism off in a predetermined order and at predetermned times in the operating cycle of the unit, the machine having a sequential trip control operating in dependence on the absence of a sheet to be printed to operate the unit trip control in succession, there is provided also a premature plate cylinder tripping means for tripping on the plate cylinder of a unit in advance of the cycle in which the corresponding impression cylinder is tripped on. The machine described is a multi-colour offset machine generally of the type disclosed in U.S.A. Specification 2,419,403, each unit comprising a plate cylinder 1, Fig. 1, blanket cylinder 2, and impression cylinder 3, Fig. 2, the tripping of the cylinders and inking-apparatus being accomplished, through eccentric bearings, on the rotation of the blanket cylinder. A cam 6, Fig. 2, rotating with the blanket cylinder 2, rocks a pivoted arm 8 which reciprocates a bar 10 provided with abutments 13, 14 adapted to engage studs 15, 16 on a plate on the impression trip shaft 17. If the bar 10 is raised, the shaft 17 will be rocked clockwise to trip the impression cylinder 3 away from the blanket cylinder 2; when the bar 10 is lowered, the cylinder 3 is tripped on to the cylinder 2. Tripping on or off is controlled by a link 20 connected to the bar 10 and one arm of a Y-shaped member 21, pivoted on a shaft 22. One arm of the member 21 is provided with a toe 23, which is shown as engaged by a catch 24 to position the member 21 and bar 10 in the tripping on position; if the catch 24 is released, the member 21 is urged by a spring to swing the bar 10 upwardly, when permitted by a cam 27, into tripping off position. The mechanism for tripping the plate cylinder 1, Fig. 1, is generally similar, and comprises a plate 30, rocked by the cam 6 on the blanket cylinder 2, to reciprocate a bar 34 adapted to rock a trip shaft 39 to trip the cylinder 1. The position of the bar 34 is controlled from the impression trip shaft 17, and is determined by a rod 45 connected to a bell-crank 46, pivoted at 9, which is connected by a link 47 to an arm 48 fixed on the shaft 17. The inking-apparatus (not shown) is also tripped by linkages operated from the impression trip shaft 17. The machine may include a. chain conveyer sheet-feeding mechanism of the type wherein sheets are fed through each unit of the press by gripper bars each provided with a roller 55, Fig. 2, which is settable at a sheet-registry unit, by means of detecting mechanism, into either of two positions. If the sheet is absent, the roller 55 is set in the upper position shown to engage and rock a pivoted shoe 56, whereby the catch 24 is tripped to permit the member 21 to initiate the tripping-off cycle of the cylinders in that unit. Means is provided for temporarily holding the catch 24 down after the shoe 56 has returned to its initial position. The gripper bar and roller 55 then pass to the second unit of the press, and, normally, this unit trips one full cycle later than the first unit. In the present invention, all or selected plate cylinders 1 can be tripped prematurely e.g. the plate cylinder of the second unit of the press may'be tripped on at the same time as that of the first unit and one rotation of the blanket cylinder 2 in advance of normal tripping. In the case of presses having uneven spacing between units, or uneven cylinder diameters, the time of tripping is modified accordingly. To facilitate this premature tripping in each unit, the link 47, Fig. 1, comprises two sections 70, 71, hinged at 72, and arranged to open in one direction only, and the section 71 is formed with aT-head 75, 77, the part 75 for engaging a stop 76, and the part 77 being adapted to engage a pin 78 carried by a sleeve 79. If the sleeve 79 is moved to the left, the hinge 72 of the link 47 will be broken upwardly, and clockwise rotation of the impression cylinder trip shaft 17 will merely bend the link about its hinge, and the plate cylinder tripping means will not be set to trip-off. The sleeve 79 is slidably mounted between spring-pressed rollers on a rod 90 which abuts a second rod 90A extending to the second unit, and so on. All the rods 90, 90A &c. are urged by springs to the left. The bar 90 has pivoted thereto a bar 110 having a notch engaging a pin 113 on an arm 114 secured to the sheet-stripping shaft 115 associated with the sheet-registering unit. When a sheet is accepted, the shaft 115 rocks to force. the rods 90, 90A &c. to the left carrying all the sleeves 79, breaking the links 47, and the plate cylinders in all the units will now trip on under control of cams 6. Therefore, in the first unit the plate cylinder is tripped on one cycle earlier, that in the second unit two cycles earlier, and so on. The premature tripping control can be rendered inoperative from the registering unit by moving a hand-lever 120 to raise the bar 110 clear of the pin 113 on the arm 114. Movement of the sleeve 79 in each unit can be prevented by a spring-urged dog 96 adapted to engage a notch in the sleeve, and this dog can be held up by a hook 102 on a plate fixed to the impression cylinder trip shaft 17 to allow the movement of the sleeve 79. The hook 102 is moved by the shaft 17 to lift the dog 96 when the impression cylinder is tripped off. Once a sheet has been rejected, all the succeeding sheets are rejected until the mechanism is reset. A latch 121 co-operates with a pin on the arm 114 for this purpose, and must be released manually. The operating rods 90, 90A &c. can also be controlled from each printing unit by means comprising a bar 125 which is notched to engage over a pin on the plate fixed to the impression trip shaft 17, when allowed to do so by a handlever 132, so that when the shaft 17 is rotated to the tripping on position, the bar 125 will rock a lever 129 engaging a pin on the rod 90A to force that rod and succeeding ones to'the left. By suitably setting the various hand-levers 132, and the hand-lever 120 of the registering unit, premature tripping of the plate cylinders may be varied. An emergency trip for tripping off all units comprises a rod 140, extending the length of the machine, urged to the left by springs but movable to the right by a hand lever 142, whereby a pin on the rod rocks an arm 60 (not shown) fixed to the trip control catch 24. The catch 24 in each unit is rotated counterclockwise to set the unit to trip off during the same cycle. The premature tripping-mechanism for any unit can be rendered inoperative by means of a hand-lever 153, adapted to rock an arm 150 which has a fork engaging a pin on the sleeve 79, so that the sleeve is held to the right and cannot break the link 47. On reverse rotation of the machine, a pawl 160, Fig. 4 (not shown), on the blanket cylinder 2 of each unit rocks a bell-crank lever which operates through a rod and link means to drop the catch 24 to set the unit for tripping-off. Electric control of tripping-mechanism. Most of the above described mechanical tripping can be effected by electrical means, shown in Figs. 6 and 7. The plate cylinder, impression cylinder, and other mechanism, apart from the tripping controls are as described above. The impression cylinder tripping is controlled by a bell-crank catch 200, operated by a solenoid 210, and like the catch 24 described above, can release the Y- shaped member 21 to co-operate with the cam 27 on the blanket cylinder 2 to cause the impression cylinder to trip off. The plate cylinder trip shaft 39 is operated by a bar 202 which is similar to the bar 34, Fig. 1, except that it is raised and lowered by a cam-controlled Y-shaped member 205 provided with a toe 206 co-operating with a catch 207 controlled by a solenoid 220. Fig. 7 shows the controls for three units I, II, III in a multicolour offset press, the solenoids 210 being controlled by relays A<SP>1</SP>, A<SP>2</SP> &c., and the solenoids 220 by relays B', B<SP>2</SP> &c. Power lines are indicated by L<SP>1</SP>, L'. Switches 231, 232 in the circuits of the relays have upper dead contacts whereby the plate and impression cylinders controlled thereby will remain tripped on, unless tripped off by emergency or reverse tripping circuits. By setting a switch 231 or 232 in its lowermost position, the plate or impression cylinder controlled thereby will trip off and remain tripped off. Switches C, D, Fig. 6, controlled by the abutments on trip shafts 39, 17, are shown as C<SP>2</SP>, C<SP>3</SP>, and D<SP>2</SP>, D' in Fig. 7. A connection from each printing unit is established through the middle contacts of switches 231, 232 to a rotary controller running in synchronism with the press and carrying switch elements 235 co-operating with switches S<SP>1</SP>-S<SP>4</SP>. On rejection of a sheet, the appropriate element 235 will be set outwardly to operate the switches, as described in U.S.A. Specification 2,419,403. Switches E<SP>2</SP>, E<SP>3</SP> &c. can be set for selecting the printing unit which is to control the premature tripping of later units. Assuming the press is out of operation, all the elements 235 are set to close the switches S', S<SP>2</SP> &c., and all plate and impression cylinders are tripped off, then switches D', D' &c. will be open, and switches C<SP>2</SP>, C<SP>3</SP> &c. in their lower positions. Then the relays A', A<SP>2</SP>, A<SP>3</SP> will be controlled by switches S', S<SP>2</SP>, S<SP>3</SP>, and the relays B<SP>1</SP>, B<SP>2</SP>, B<SP>3</SP> by switch S<SP>1</SP>. When a sheet is accepted, an element 235 will not close swi