Patent GB-652907-A (GB)
Title: Improvements in or relating to printing presses
IPC: B41F21/05
Filed: 1948-09-14
Abstract: 652,907. Printing-machines. DAVIDSON MANUFACTURING CORPORATION. Sept. 14, 1948, No. 24148. Convention date, Oct. 1, 1947. [Class 100 (ii)] A rotary printing-machine which is especially applicable for obtaining a few copies from each of several plates, and which is described in connection with a machine as described in Specifications 550,413 and 550,523, in which a large cylinder, as 8, Fig. 1, is fitted with a lithographic plate 17 on one half of its periphery and with an impression surface 16 on its other half, and the large cylinder co-operates with a cylinder 11 of half the diameter which is fitted with an offset blanket 15 and first receives an impression from the plate 17 and then transfers it to a sheet on the impression surface 16, is constructed with means for stopping the rotation of the cylinder 8 at the end of a complete revolution, and for automatically opening the grippers 40 in this position so that the sheets can be fed by hand to the grippers prior to re-starting the printing. As applied to machines in which the cylinder 8 is operated by a crank 23 fitted with an operating handle 21, and the cylinder 11 is geared to the cylinder 8 and mounted in eccentric bearings, the rotation of the cylinders is stopped automatically by the engagement of a spring- plunger 29 mounted in the crank-handle with a stop member 39'secured to the machine frame 6. The plunger 29 also moves a pivoted cam arm 55 counterclockwise against the action of a spring 60 and thus acts upon a roller 52 on a crank 50 mounted on the shaft of the grippers 40, and so opens the grippers. The grippers close automatically when the plunger 29 is withdrawn to permit rotation of the cylinder 8. The printed sheets are released from the grippers by means of a cam 66, and are delivered by a roller 67 to a box 69. The plate 17 is treated with a damping-roller 73 and inking-roller 73<SP>1</SP> which are mounted in spring-pressed arms and are tripped by cams 70 when passing the impression surface 16. Supply ducts 82, 82<SP>1</SP> and rollers 83, 831 are provided for the rollers 73, 73<SP>1</SP>, and the pressure of the rollers against the plate 17 is controlled by adjustable screws 78, 78<SP>1</SP> and fixed abutments 79, 79<SP>1</SP>. In a modification, Figs. 3 and 6, the machine may be operated by hand or by a motor 99 operating through a clutch comprising friction discs 113, 114, which are moved by a clutch collar 106 to couple a driving-gear 93 to a shaft 94 connected to the motor 99 by a belt drive and worm gearing, the collar being operated to open the clutch after one complete revolution of the cylinder 8 from the position shown in Fig. 3 in which the grippers 40 are held open to receive a hand-fed sheet as in the first form described above, and the cylinder 8 is held stationary by engagement of the plunger 29 of the crank-handle 25<SP>1</SP> with a recess in a lever 143 which is biassed in a clockwise direction by a spring-pressed rod 147 pivoted to the lever, and mounted on the framing. The lever 143 controls the cam which maintains the grippers 140 open. The printing action is started by depressing a treadle 162, Fig. 3, against the action of a spring 164, thus raising a link 170 by means of a pin-and-slot connection 172, 173, and link 170 rotates a bell-crank 176 secured to a shaft 178, which at one end is fitted with a crank arm 180 connected by a link 185 to an arm 190 of a shaft 192 fitted with an extension 198 adapted to engage a projection 140 on the crank-handle 25<SP>1</SP> and so withdraw the plunger 29 from engagement with the catch lever 143. The depression of the link 170 also releases catch mechanism which permits a clutch-operating rod 116 to be moved to the right in Fig. 6 by the action of a pair of cam members 123, 124, which are moved relatively to one another to cause axial motion of the rod 116 and a shift fork 117 by means of which the clutch members 113, 114 are made to engage so as to drive gears 93, 92, 90 and so to rotate the cylinders 8, 11. The link 170 is held in depressed position against the action of a spring 200 by a catch lever 215, but near the end of a complete revolution of the cylinder 8 a pin 220 on the cylinder releases the lever 215 and the link 170 then rises under spring action, and the cams 123, 124 are operated to throw-out the clutch so as to stop the machine. The lever 143 holds the cylinders in position to receive a new sheet and the grippers are opened. The machine may be modified to print by direct printing instead of offset in known manner.