Patent GB-903238-A (GB)
Title: Improvements in or relating to printing presses
Inventor: UDALL HUMFREY NICHOLAS
IPC: B41F3/02
Filed: 1959-10-06
Abstract: 903,238. Printing presses. LINOTYPE & MACHINERY Ltd. Sept. 29, 1960 [Oct. 6, 1959; March 11, 1960], Nos. 33781/59 and 8602/60. Class 100 (2). A sheet fed printing press of the kind in which a type bed makes reciprocatory movements relatively to an impression cylinder (or cylinders) which cylinder makes cyclic on-off impression movements, moving into contact with the bed to effect printing during one stroke of the bed, and moving away from the bed to allow a free return stroke of the bed, comprises means operated in synchronism with the press drive, preventing movement of the cylinder into operative contact with the bed until the correct time for such a movement in a complete printing cycle of the press obtains. In the embodiment shown in Figs. 1 and 2, which uses a combination of hydraulic, mechanical and electrical means, the impression cylinder is moved hydraulically a valve 9 functioning to control the pressure fluid supply. This valve embodies a slidable spindle 16 which is actuated in dependence upon the press drive through a cam 10 and followers 13 and 18. The spindle is biased by the pressure fluid such that during uninterrupted operation of the press the follower 13 constantly engages the cam 10. When the portion 12 of the cam moves the spindle to the right the impression cylinder is moved from and kept off the bed whilst during engagement of the follower 13 with the cam portion 11 the impression cylinder is moved into printing operation. This cyclic reciprocation of the spindle continues until an " off " button is actuated which causes an energized solenoid 30 to become de-energized and drop a spring- loaded pivoted latch 20 such that the latch seeks to engage behind a head 23 formed on the outer extremity of the valve spindle to prevent the spindle, and hence the cam follower 13, from tracking the cam portion 11 when this portion should next contact the follower. If the " off " button is pushed during a printing movement of the impression cylinder the latch drops on the head 23 and is unable to engage behind it until the valve spindle is moved by the cam portion 12 on completion of the printing. When the " on " button of the press is actuated the solenoid is energized but if the cam portion 11 is opposite the locked or held spindle, although the spring 27 is tensioned, the latch will not move up to release the head 23 because of the contact pressure between the engaged head and latch. Release of the spindle only ensues when the cam portion 12 once again contacts the follower 13. Electrical means are provided to effect " one cycle " only operation of the printing press. In this case the solenoid is deenergized immediately after lifting the latch and releasing the valve spindle in its correct time relative to the printing cycle. When the control system is to be applied to a twoimpression cylinder printing press the second cylinder has its on-off impression mechanism initiated at the same time as that of the first cylinder mechanism. Whereas the first cylinder must commence its cyclic operations at the beginning of the cycle immediately following initiation, the second cylinder operation has to be delayed so that it commences its cyclic operation during the printing press cycle following that of the commencement of the operation of the first cylinder since any sheet printed during one cycle on the first cylinder is printed during the following cycle on the second cylinder; A similar delay is provided when the impression cylinders are taken off impression. When the first cylinder contact mechanism is isolated the second cylinder mechanism must continue to operate in the same time sequence as when the first cylinder mechanism is operative. Likewise, when the second cylinder mechanism is rendered inoperative the first cylinder mechanism will continue to operate in the same timed sequence as when the second cylinder mechanism is operative. Mechanism for effecting the above-mentioned control, which is also hydraulic, mechanical and electrical, comprises a cam-shaft 1, Fig. 4, which mounts the cam 10 for controlling the first cylinder and a cam 2 for controlling the second cylinder through an hydraulic valve 108, latch 111 for engaging behind the valve spindle head 110 and a solenoid S2. The camshaft, which makes one rotation per complete printing cycle, also mounts a rotary switch 5 which through brush contacts S, L and C, switches the cylinders "on" and "off"  impression in correct timed sequence. Buttons are provided in the electrical circuit for " one cycle " operation. A rotary plug-type valve 113, Fig. 9 (not shown), may be used instead of the valve 108 which is of the piston-type. In such a case the valve head 110 and latch 111 are replaced by a step on a triangular plate and a plunger, respectively. In a further embodiment of a two impression cylinder press-control mechanism a cam 121, Fig. 10, rotating at a speed directly proportional to the printing speed of the press, is used to operate, through a trip linkage, a master cylinder 122. Rotation of the cam effects oscillation for lever 123, pivotally mounted at one end on a pin 124, secured to the press frame, not shown. The cam has a high portion 125 which swings the lever 123 clockwise so that when an interposer 126 is in the position shown, swinging of the lever 123 will swing a lever 127, pivotally mounted on the pin 124 and force the pistonrod 122<SP>1</SP> of the master cylinder into the cylinder. The hydraulic fluid therefrom is pumped through a pressure relief valve 128 into the impression cylinder pull-down vanes 129. Continued rotation of the cam allows the lever 123 to swing back to position shown, the pressure in the system forcing the piston-rod from the master cylinder, thereby retracting the vanes 129. The electrical circuit controlling the operation of this two cylinder impression mechanism is the same as that used in the control mechanism described above with reference to Figs. 1, 2 and 4. The two impression cylinder presses may be used to print in two colours.