Patent GB-746128-A (GB)
Title: Improvements relating to rotary printing machines
IPC: B41F31/30
Filed: 1954-02-23
Abstract: 746,128. Rotary printing-machines. DAVIDSON CORPORATION. Feb. 23,1954 [Feb. 24, 1953], No. 5279/54. Classes 100 (1) and 100 (2). A rotary offset printing-machine comprises a main cylinder 53 mounted on a shaft 49, Figs. 1 and 3, and having end plates 48 supporting part cylindrical segments 54, 55 each having automatically operated gripping means 56, 57 to receive the paper to be printed and a printing plate respectively. The printing plate is inked and damped and transfers an image onto an offset cylinder 51 of half the diameter of the main cylinder, the image being transferred to the paper on the platen surface 54 on the next revolution of the offset cylinder. The line between the centres of the cylinders lies at approximately 20 degrees from vertical. Sheets for printing are fed to the main cylinder at a point between 45 degrees above and 20 degrees below the horizontal line through the axis and, as shown, at approximately 26 degrees above this horizontal line. Gripper mechanism.-The grippers 56 for securing the paper on the segment 54 and those 57 for securing the printing plate on segment 55 are identical and the former are shown in Fig. 5. Gripper arms 58 are fixed at spaced intervals along a shaft 64 which has bearings in the end plates 48 and is rotated to lift the grippers by an arm 66 at one end carrying a roller 67 co-operating with cams 72 or 73 (Fig. 3). A spring normally urges the grippers against an anvil 61 formed by cutting away a corner of segment 54. Downwardly projecting pins 63 on the grippers act as stops to register sheets 60 fed to the grippers. Ejector fingers 59 guide the sheets to the correct position in the gripper and later serve to throw them out of the gripped position, the fingers 59 being fixed to a cross-shaft 71 also having bearings in end plates 48. An arm at the end of the shaft 71 has a follower 69 bearing on a cam 68 on shaft 64 so that as this shaft is rotated the ejectors 59 are moved between a raised position for receiving sheets in, or ejecting sheets from the grippers, and a lowered position, as shown in Fig. 6, where they are received in recesses in the anvil and overlaid by a sheet 60 held under the grippers. The rollers 67 actuating  grippers 56 by engagement with fixed cams 72, 73 are of such a length that they engage the cams at each revolution as shown in Fig. 7, but those 67a, Fig. 8, controlling the grippers 57 are shorter so that they normally do not engage cams 72, 73. When it is desired to actuate the grippers 57 to release one printing plate and insert a different one, the cams 72, 73 are displaced towards the main cylinder. For this purpose they are mounted on parallel spring loaded rods 118 sliding in guides 120 in the fixed frame member 119. A lever 123, bearing on a bridge member at the rear end of the rods, is carried on a spindle 124, Fig. 9, rotatable in bearings 125 by an external control. The cam 73 is projected, by operation of a press-button 129, into the position (shown dotted in Fig. 8), where it actuates plate-gripper 57, the pressbutton acting through a bell-crank lever 127 to rotate spindle 124. This causes the printing plate to be discharged. The cam 72 is similarly projected by a lever 143 on spindle 141 rotated by a bell-crank lever 139 actuated through a link 137 by a lever 135 having a handle 136. The lever 135 also acts to change the phase of the feeding mechanism as now described. Sheet feeding mechanism.-Sheets 60, Fig. 5, are fed by hand or automatically over a feed table 116 (Fig. 3) into abutment with registering stops 115 which are normally raised so as to lie in the path of the sheets. A constantly driven feed roller 113 exposed through holes in an extension 114 of the feed table 116 is adapted to forward the sheets when gripped between this roller and a roller 112 displaceable downwardly into gripping position and upwardly into releasing position. The stops 115 are lowered by anti-clockwise rotation of a shaft 107 which also causes a stop 108 on arm 106 to abut a finger 109 on the pivot shaft 110 of arms 111 thereby moving rollers 112 to the gripping position. The shaft 107 is rotated to initiate feed of the sheet by a link 104 connected at the other end to a lever 102, Fig. 9. A rocker 101 pivoted to this lever has slots at each end for engagement alternatively with pins on levers 98, 131. The rocker is spring loaded normally to engage with the lever 98 at 100. This lever is urged in a clockwise direction by spring 99 and the other end has a roller 97 engaging a cam 95 adjustably mounted on the shaft 49 of the main cylinder. As the cylinder rotates the fall part of the cam causes the sheet between the rollers 112, 113 to be gripped and fed to the grippers 56 as shown in Fig. 5. When it is desired to attach a new printing plate to the cylinder, the lever 135 is moved to the dotted line position so that the end 134 engages the rocker 101 and displaces it into engagement with the lever 131 which is actuated from the other side of the cam through roller 130. By this means the phase of the operation of the feeding mechanism may be changed by 180 degrees so that plates fed thereby are received into the grippers 57 associated with the plate segment 55 of the cylinder. Faulty feed detection.-When no sheet is presented on the feed table between feed rollers 112, 113 mechanism is provided for tripping the blanket cylinder out of engagement with the platen surface. The feed roller 113 is formed with a series of grooves in each of which are located levers 164, Fig. 12, mounted on a shaft 166 and shaped to fit round the spindle 37. The extension 114 of the feed table is formed with a shelf 178 against which the ends 165 of levers 164 normally rest below the level of a sheet if one is properly fed. Fingers 173 reciprocate over the ends 165 of the levers 164 riding on the sheet if one is present. The fingers are actuated through arms 175, rocked by a cam 183, Fig. 10, acting through lever 180, link 179 and arm 177. When a sheet is not fed, the fingers drop onto shelf 178 and when next reciprocated they engage and displace levers 164 thereby rotating shaft 166. A spring 172 connecting shaft 166 to a lever 168 mounted on it, is stressed by rotation of the shaft and tends to rotate lever 168 in the same direction. This tends to displace link 169 and to free a latch 160 normally holding the offset cylinder in contact with the main cylinder as described below. Changing printing plate.-When it is necessary to change the printing plate the operator merely has to press button 129 until the old plate appears in the delivery tray as described below and to put lever 135 into the dotted line position. When the new plate is fed to the stop 115 it is gripped at the correct instant (through the operation of cam 95, Fig. 9, lever 131, rocker 101, link 104 and shaft 107) and forwarded to the grippers 57. Delivery apparatus.-At a certain point in the rotation of the main cylinder' the actuating roller 67 of the grippers 56 engages the cam 73, opening the grippers and lifting the leading edge of the sheet away from the anvil. The leading edge is deflected out of the path of the grippers by brackets 78, Fig. 3, so positioned as to enter the sheet between rollers 79, 80 which lift it over a lip 85 so that it falls into a receiving tray 86. A roller 87 on a swinging arm 88 is, at the correct moment, urged against the sheet to prevent whipping of the trailing end or smudging as it leaves the main cylinder. The roller 87 is actuated through a spring 93 by a roller 92 mounted on arm 91 for engagement with a cam 251, Fig. 15, extending round approximately half the circumference of the main cylinder. When the button 129 is depressed to discharge the printing plate it is passed into the receiving tray in the same way where it is visible to the operator. He releases the button when the plate appears. Inking and damping apparatus.- Driven shafts 42, 45, Fig. 15, carry transfer rollers 43, 46 for the inking and damping mechanisms which are substantially identical. A bracket 191 swinging about the axis of roller 43 carries an inking roller 192 urged by a spring 201, into engagement with the main cylinder. The damping roller 197 is similarly mounted and the spring 201 is arranged to urge it against the cylinder in the same way. An adjustable abutment 194 on arm 193 of the bracket 191 bears against a cam surface formed on a spindle 207 rotatable from a handle 204 through arm 202, link 205 and arm 206. Actuation of the handle 204 thereby moves the inking roller into and out of engagement with the main cylinder. A similar handle 209 (Fig. 1) and lever 208 controls the damping roller 197 in the same way. Ink is fed to the transfer roller 43 by a messenger roller 195 swingably mounted on a bracket 242 and rocked by a cam 250 on the shaft of the main cylinder acting through arm 245, link 244 and lever 243. In one position the roller 195 is in contact with a fountain roller 223 and receives ink and in the other position it is in inking contact with transfer roller 43. The damping apparatus has a similar fountain roller 231 and  messenger roller 200. The inking and damping rollers are displaced out of contact with the main cylinder to avoid inking and damping the sheet carried on segment 54 by the cam 251 attached to this segment and adapted to engage the ends of the rollers or discs attached to them. Controlling rate of feed of ink and damping liquid.-The amount of ink or damping liquid picked up is varied by varying the extent of the rotation of the fountain roller during each printing cycle. The fountain roller 231, Fig. 16,  is rotated by a pawl 236 on a swinging arm  actuated by an eccentric on the main cylinder through link 238. The pawl is allowed to engage a ratchet 232 attached to the fountain roller over an arc which is determined by the position of a cam 229 adapted to lift the pawl  away from the ratchet over part of its movement. The cam i