Patent GB-675498-A (GB)
IPC: B65H29/56
Abstract: 675,498. Damping-apparatus for lithographic machines. DAVIDSON CORPORATION. April 11, 1950 [April 29, 1949], No. 8901/50. Class 100 (ii). In a dampening fountain means for an offset printing press having a rotatable printing cylinder 10 which carries form roll cam means 77, the cam means 77 are adapted to engage a form roll 115 to dispose it out of engagement with the cylinder 10, the cylinder also carrying means 145 to move the form roll 115 into engagement with a rotatable roll 100 of a fountain. General features.-A cylinder 10, Fig. 1, is mounted in a frame for rotation through gears 23, 25 and comprises a plate segment 14 and a platen segment 15 each of a circumferential extent slightly less than half that -of the cylinder. A cylinder 16 carrying a rubber or like transfer blanket 18 is mounted above the cylinder 10 and is rotated at twice the speed of the cylinder 10 and is of half its diameter. Dampening means 20 and inking means 22 are disposed below the cylinder 10 and means 50 are provided above the cylinder for pressing a sheet on to the platen. The means 20, 22 and 50 are automatically operated by rotation of the cylinder 10 and automatically operated sheet gripping and ejecting means 30 are mounted on the leading edge of the platen. Sheet gripping and ejecting means.-A plurality of spring loaded gripping fingers 33, Fig. 7, are attached to a rotatable shaft 32 so as to hold the leading edge of a sheet against a grip bar 34. The shaft 32 carries a crank 37, Fig. 1, at its end and a rotatable follower 38 on the end of this crank can engage a cam 39 on the frame of the machine to open all the grippers so that a sheet can be hand fed into them from a feed board 40. A U-section stripper 43 embraces each gripper and engages the underside of the sheet to raise it when the shaft 32 is rotated by engagement of the follower 38 with a second cam 45 on the frame of the machine so that the sheet engages a transversely mounted stripper blade 49. Sheet pressure roll means.-The sheet is held in engagement with the cylinder 10 prior to stripping by a pair of discs 62, Fig. 1, which are adjustably mounted on a shaft which is mounted on adjustable eccentric pins in a spring loaded frame 52. The frame 52 is pivoted to the machine frame at points 53. A rotatable follower 70 is attached to the frame 52 by a pivoted arm 66 and a coil spring 68 is positioned between the frame 52 and an extension on the arm 66. This permits the discs 62 to yield if the thickness of the sheet is varied. The follower 70 engages a cam 77 carried by the cylinder 10 which urges the discs 62 into engagement with the sheet during the stripping action. Dampening fountain means.-A liquid containing tray 80, Fig. 1, is swingably supported by a pair of links 82 and its position is adjustable by means of a spring loaded threaded rod 87 engaging a nut on one of the links. A roller 100 is rotatably mounted in the tray and this is provided with spring-urged brake blocks on its shaft. Liquid is conveyed to the cylinder 10 from the roller 100 by a dampening form roller 115 which is mounted in forks carried by a pivoted bracket 118. The roller 115 is held in the forks by spring loaded C-shaped members 122, which also serve to hold the roller 115 against the cylinder 10. The roller 115 may be manually moved away from the cylinder 10 by means of a rotatable shaft 134 having a flat which engages an adjustable screw 132 on its bracket. The dampening roller shaft 117 carries cam followers'which engage the cams 77 carried by the cylinder 10 to keep the roller 115 away from the platen segment of the cylinder. The roller shaft 117 also carries cam followers which engage cams 145 to press the roller 115 into engagement with the fountain roller 100. The period of engagement may be varied by means of the tray positioning rod 87 to alter the amount of dampening if required. Inking means.-A main ink roller 150 to which ink is applied manually is driven from the cylinder 10 and engages an ink form roller 158 which is mounted in forks in the ends of pivoted brackets 153. The roller 158 is held in the forks by spring loaded C-shaped members 160 which also urge the roller against the cylinder 10. Cam followers on the roller shaft engage the cams 77 to keep the roller 158 away from the platen. The roller 158 may be moved to an inoperative position by means of a rotatable shaft 163'.