Patent GB-727229-A (GB)
Title: Improvements in or relating to printing machines
IPC: B41F33/16
Filed: 1953-11-30
Abstract: 727,229. Printing machines. DAVIDSON CORPORATION. Nov. 30, 1953 [Nov. 28, 1952], No. 33271/53. Classes 100 (1) and 100 (2). A rotary printing machine having a lithographic printing plate and inking and damping means (K, J, Fig. 1) to apply ink and damping solution to the plate is provided with means to render the inking means inoperative for a pre-set number of revolutions to effect preliminary damping of the plate and with automatic release means for rendering the inking means operative after the completion of these revolutions. The machine shown has a plate cylinder 2, Fig. 1, and an offset cylinder 1 of half the diameter. The offset cylinder receives an inked image from the plate on cylinder 2 in one revolution and in the following revolution it transfers the image to a copy sheet, the other half of the plate cylinder then acting as impression surface. Sheets are fed to the printing couple by a suction separator C, mounted on a pile table 3. Sheets are separated in succession from the pile and fed to the printing machine by a conveyer D. The machine may be used for direct printing. Inking mechanism.-The inking mechanism comprises a roller 25, Fig. 3A, receiving ink from a reservoir and conveying it to a pair of rollers 26 for application to the printing plate. The rollers 26 are carried on arms 27 pivoted about the axis of roller 25 and are cyclically displaced by cam means, not shown, into and out of contact with the plate cylinder in order to ink the plate thereon. The rollers are also displaceable by a cam 30 bearing on adjustable screw members 29 mounted on the arms and thus serving to render the inking mechanism inoperative. Once during each revolution of cylinder 2 the cam 30 is rotated to lift the rollers, by a link 56 connected at one end to a lever 55 on the cam-shaft 31 and at its other end to a lever 57, Fig. 1, displaced by a cam 46 acting through another cam follower roller 47 controlling the tripping mechanism for the offset cylinder 1 as described below. The lever 55 is adapted to co-operate with an arm 54 which may when in the position shown in Fig. 3A, prevent clockwise movement of the lever 55 under the action of spring 59 and thus prevent the inking rollers moving into contact with theplate cylinder. The arm 54 is displaced to the inoperative position (shown dotted) by the weight of the armature 52a of a solenoid 52 when the solenoid is de-energized. This allows clockwise rotation of cam 30 under the action of spring 59. The solenoid is controlled by the circuit shown in Fig. 5 which includes a switch 71 adapted after the predetermined number of preliminary damping operations to be opened to de-energize the solenoid. Counting mechanism for preliminary damping.-As shown in Figs. 1 and 2B a counting mechanism mounted on the machine on a base 60, comprises a pair of aligned shafts 66, 68 adapted to be coupled together by a clutch 53 the parts 53b, 53c of which are biased to uncoupling position by a spring. A two-armed lever has one arm 63, Fig. 1, bearing against the clutch part 53c and the other arm 65 engaged by the armature 52a of the solenoid 52. The arrangement is such that when the solenoid is energized the armature is lifted and moves the clutch to coupled position. The shaft 68 is driven from the printing cylinder. shaft through a reduction gear and the shaft 66 carries a finger 73 adapted to trip a switch 71 by contact with an arm 71a. The shaft 66 is biased to the zero position by a torsion spring 69. A setting knob 62 has a pointer co-operating with a scale 61 and carries a finger 72 adapted to engage finger 73 and rotate shaft 66 away from a zero position the clutch being disconnected for this operation. When the machine is started, the solenoid 52 being energized to couple the clutch, the rotation of shaft 68 is transmitted to shaft 66 and slowly turns the finger 73 from its set position to the position where it engages arm 71a and opens switch 71. This causes de-energization of solenoid 52 as described below. The falling of the armature 52a renders the arm 54, Fig. 3a inoperative so that the inking rollers can on the next cycle move into inking contact with the plate cylinder. Also the armature allows the clutch to move to the disengaged position so that the shaft 66 is free to turn back to the pro-set position under the influence of spring 69. Sheet-feeding mechanism.-The sheets are separated from a pile by a suction separator 4, Fig. 4A, which is lifted to separate the top sheet and swing in an anticlockwise direction to forward the sheet to a conveyer for presentation to the machine. The separator 4 is carried on a lever 13 oscillated through a link 16 by a lever 15 carrying a roller 15b spring urged against a cam surface 14a of a reciprocating lever 14. The suction is applied to the separator through a pipe 18 connected to a housing 19 having a vent closable by a flap 21. When the flap is opened the suction is destroyed and the separator head 4 is made inoperative. The flap is opened cyclically to release the separated sheets by an arm 22 connected by a link 23 to the rocking lever 14. The flap may also be opened to prevent feed of sheets by a solenoid 80 the armature of which is connected to the flap. The solenoid 80 is connected in parallel with the solenoid 52 (see Fig. 5), so that on de-energization of the latter to cause the inking means to become operative, the former is also de-energized to cause the feed of sheets to commence. Detecting faulty sheet feed.-The sheets pass to the printing couple 'over a table 5, Fig. 1, having a slot registering with the end of a lever 35 mounted on a rocking lever 34. In the absence of a sheet, the end of the lever 35 is adapted to fall through the slot and engage a shoulder on the. end of a lever 36 below the table. The next oscillation of lever 34 will then cause the lever 36 to be displaced about the axle 37. A radial pin 38 mounted to move with lever 36 is connected by a spring 39 to an arm 40. Displacement of the lever 36 therefore tends to displace arm 40 in an anticlockwise direction. This is prevented by the engagement of the end of arm 40 with a shoulder 43 on a disc 44 fixed to the end of a shaft carrying the cylinder 1. This shaft has eccentric bearing end portions so that on rotation, the cylinder 1 is moved into and out of engagement with the cylinder 2. The disc 44 is biased in an anticlockwise direction by a spring 45 connected to a pin 41 and this prevents the arm 40 moving out of engagement with the shoulder 43 until the disc is displaced slightly in a clockwise direction by lever 48 having the roller 47 engaging cam 46 on the shaft of cylinder 2. If there is not sheet presented at the table 5 the arm 40 is displaced at the end of the current printing cycle and releases the disc 44 to rotate under the influence of spring 45 thereby tripping the cylinder 1 out of contact with the cylinder 2 for any printing cycle for which no sheet is supplied.. The disc 44 is reset by the engagement between the rise part of the cam 46 and the follower roller 47. The sheets are forwarded from the table 5 by a pair of rollers 6, 7 the upper one of which is movably mounted on an arm 11 and operated by an arm 9 engaging a cam 8. A link 42 connects arm 9 with lever 34 to rock the faulty feed detector 35. Counting printing operations.-The number of sheets to be printed is predetermined and the machine is automatically stopped when that number is reached. A counter 83 is set to the number required by a handle 83a and counts the sheets printed by means of a lever 88 rocked by a cam 90 on the cylinder 2 and adapted to-operate a finger on the counter. The lever is biased downwardly by a spring 8 8a. In the absence of a sheet fed to the printing couple the movement of the tripping arm 40 is used to prevent the counter registering the printing operation. To this end the arm 40 carries a lever 99 normally aligned with a slot 88b in a flange on the lever 88. Displacement of the arm 40 causes the lever 99 to move out of alignment with the slot and so that it supports the lever 88 against downward movement. When the set number is reached the counter closes a switch 85 adapted to stop the machine as described below. Control circuit and operation.-As shown in Fig. 5, the mains supply is connected through a switch 51 to a transformer T the secondary of which is adapted to energize solenoids 52, 80 and the pick-up coil 103 of a main switch M. This switch is held in the "on" position by a latch 108 controlled by a coil 109 adapted to be energized through "stop" switches 110 and 85 and through switch contacts 106. The motors 86, 87 of the printing machine and sheetfeeding machine are supplied through switch contacts 107 in the switch M. Before starting the machine it is necessary to adjust.the setting knob 62 (Fig. 2B), to the required number of preliminary damping operations, to set the counter 83 to the required number of copies and close the switches 71, 100, 101. When the switch 51 is then closed the solenoids 52, 80 are energized, rendering the inking mechanism and the sheet feed inoperative. The "start" switch 102 is then closed and all subsequent operations are automatic. Closing of switch 102 energizes pick-up coil 103 of switch M so that contacts 107 are closed to start the driving motors 86, 87 contacts 106 are closed so that any subsequent operation of emergency stop button 110 or counter switch 85 causes energization of release coil 109 and tripping of switch M, and contacts 105 are opened so that solenoids 52 and 80 come under the control of switch 71. On completion of the preliminary damping operations switch 71 is opened as described above and the solenoids de-energized. This makes the inking mechanism become effective and closes the flap valve 20 (Fig. 4A), so that the sheet feeding mechanism becomes operative. After the required number of copies have been printed the switch 85 is closed by