Patent GB-710871-A (GB)
Title: Improvements in offset rotary lithographic printing machines
Inventor: GULLIXSON HAROLD RANDOLPH
IPC: B41L19/00
Filed: 1951-04-25
Abstract: 710,871. Lithographic printing-machines. DITTO, Inc. April 25, 1951, No. 9653/51. Classes 100 (1) and 100 (2) An offset lithographic machine having a cylinder 14, Fig. 2, provided with plate and impression surfaces 15, 16 and rotatably mounted on a frame, a table 7 for sheets to be fed to the cylinder, a blanket roll 18 in operative association with the plate and impression surfaces 15, 16 and a tray 26 for receiving printed sheets from the cylinder, is characterized in that the feed table 7 and receiving tray 26 are both located in front of the cylinder 14 adjacent the bottom and top thereof respectively while the blanket roll 18 is to the rear of the cylinder 14, which latter is rotated in a direction to move a sheet fed to the bottom of the cylinder upwardly between the blanket roll and the cylinder and to deliver it to the receiving tray with its surfaces reversed in relation to its position on the feed table, the printed surface of the sheet being uppermost in the receiving tray. Rotary machines (Fig. 2).-Sheets are fed from the table 7 via an air separator by means of a sheet feeding device 9 both as described in Specification 699,704. The sheet is positioned against stop fingers 12 mounted on a camoperated shaft which when the sheet is to be fed forward operates to lower the fingers in recesses between constantly driven rollers 11. In timed relation with the operation of the stop fingers, idler rollers 10 are lowered by cam mechanism to co-operate with the driven rollers 11 and feed the sheet forward to the cylinder 14. A sheet detector 13 is also cam operated in timed relationship with the stop fingers and rollers 10. (Figs. 8 to 15 not shown). The sheet is then taken by grippers on the impression surface 16 of the cylinder and carried past the blanket roll 18 as described in Specification 710,873 where it is printed upon. After passing a series of hold-down rollers 22 the sheet is taken by a stripper 23 and fed into the receiving table 26. During the printing of the sheet on the impression surface 16 of the cylinder the printing surface 15 of the cylinder co-operates with a damping apparatus 28 as described in Specification 710,875, and inking apparatus 29 as described in Specification 710,874. The cylinders are driven by an electric motor which also drives a vacuum and compression pump 34 which supplies air for operating the table 7 by bellows 305, the air separator 8, the sheet feeder 9, and the damping apparatus 28, as described in the above Specifications. The surfaces 15, 16 may be circumferentially adjusted as described in Specification 710,872. Gripper mechanism (Figs. 30, 37).-The grippers 17 for taking the sheet from the feeding mechanism comprise a plurality of tabs 200 secured around a shaft 192 rotatably mounted in bearing blocks 191 secured to the leading end face of the impression segment of the cylinder 14. Secured to the tab 200 are a set of wide and short gripper fingers 201 and a set of longer and narrower ejector fingers 202. The ejector fingers 202 are of a width such that they may pass into recesses 203 in the cylinder 14 on rotation of the shaft 192 whereas the gripper fingers rest on the surfaces 204 their width being too great to allow passage into the recesses 203. Rotation of the shaft 192 is effected by a cam follower 194 which runs on cam surfaces 206, 207, 209 to rotate the shaft 192 anti-clockwise against the action of a spring 198. Printing surfaces (Figs. 16, 17, 27).-The plate clamp for the leading edge of the plate comprises a jaw member 12'6 secured by bolts 122 which pass through a spacer block 129 to the printing surface 15 of the cylinder 14. The bolts 122, however, pass through slots in the jaw member 126 so as to allow vertical movement of the jaw 126 against the action of a spring 136. Vertical movement of the jaw member 126 allows the plate to be positioned between the jaws and leaves 133 of a hinge 131 the other leaf 130 of which is secured by the bolts 122 to the surface 15. Release of the jaw member clamps the plate in position. The trailing edge clamp is of similar construction but two sets of bolts 140, 144 are provided together with a second hinge 138 so that the spring 136a causes the jaw member to swing outwardly, thereby straining the plate. In a modification, Figs. 24 to 26 (not shown), the leaves 133 are provided with protuberances to assist in gripping the plate. In a further modification (Fig. 27) a hinge 176 is movable with the jaw member 175, a spring 180 holding the leaves 177 of the hinge on the distance piece 166 when the jaw member is lifted for insertion of the plate. Delivery apparatus (Figs. 33, 34, 35, 42, 43).- The stripper 23 comprises an arcuate plate 210 having upwardly extruding hangers 211 at opposite ends pivoted on stubs 212 and stub shaft 213. One of the stub shafts extends through the machine frame and is connected by linkage 214, 215 ... 220, to a piston 221 of a cylinder 223. Also operatively connected to the piston 221 is a bracket 229 carrying the hold down roller 22. During operation of the machine the parts are in the position shown in full lines in Fig. 33, air being supplied from the pump 34 to the cylinder 223, but when the machine is not working and no air is supplied to the cylinder the parts assume the position shown in broken lines to allow access to the cylinder 14. The plate 210 is provided with stripper fingers 238 which enter the spaces between the gripper fingers 201 and assist the ejector fingers 202 in stripping the sheet from the cylinder 14. The sheets then pass into the receiving tray 26 which comprises a plate 245 having an upwardly inclined wall 247 riveted to a pair of supporting arms 250. The arms 250 are secured to a shaft 253 having flattened ends 254 disposed in recesses in plates 255, secured to the inner faces of the machine side frame so that the table 26 may be removed by upward lifting. The front end of the tray rests upon supporting posts 276. The table is provided with movable side guides 260 and a forward stop 270 formed of a resilient strip of metal 271, which by means of rivet 274 and slot 272 and rivet 275 and hole 273 may be placed in two positions, the rivet 275 taking the position of rivet 274 in the other position to that shown. Driving arrangements; faulty. feed control devices (Fig. 45).-Closure of motor control switch M energizes the motor 33 which drives the pump for supplying air to the various air operated mechanisms and also serves to make power available via a rectifier R for the electric control circuits. Electromagnetic coils 309', 315, 316 ... 320 respectively control when energized an air valve 309 leading to the damper mechanism, the inking mechanism 29 by placing a ductor roll into contact with the ink fountain roll, the moisture forme roll by placing it in contact with the cylinder 14, and the coils 318, 319, 320 when energized cause operative association of the blanket roll with the cylinder 14. Initially a mercury switch 323 is open, the switch being also operatively associated with a valve controlling the sheet feeder 9 so that until the switch is closed no sheets are fed to the machine and the detector finger 110 makes contact with plate 41 thereby energizing a relay 321 which on closing its contacts 332, 353 energizes a relay 322. Relay 322 completes a holding circuit for itself over contact 336 and relay 321 is maintained energized over contacts 115 even after the detector finger 110 breaks contact with the plate 41. Each of the control coils may now be energized by manually depressing their associated control buttons M.F., I.F., M.C., I.C., B.C. the return circuits being completed over their lower contacts, lines 343, 344, 399, contact 338, and lines 331, 327 When it is desired to start printing the switch 323 is closed, a sheet is fed, relay 321 is de-energized and all the coils are thereupon energized, return circuits being provided over their upper fixed contacts, line 367, directly in the case of buttons I.F. and B.C., and via switch 323 in the case of buttons M.F., M.C., I.C., then from lines 367 to lines 351', 352, relay contact 353, lines 333, 337, relay contact 336, and lines 335, 327. During the normal running of the machine, any one of the coils may be deenergized by depressing its associated control button, there being no return circuit over the lower fixed contacts after the relay 321 is deenergized. Prior to stopping the machine by opening the switch M, the mercury switch 323 may be operated an extent sufficient to break electrical contact but maintain the air supply to the sheet feeder, thus rendering the moisture feed inoperative, and removing the moisture and ink forme rollers from operative association with the cylinder 14, but leaving the blanket roll in operative position until opening of the main switch M.