Patent GB-710873-A (GB)
Title: Improvements in offset rotary lithographic printing machines
Inventor: BRUNS HERBERT FREDERICK
IPC: B41L19/00
Filed: 1951-04-25
Abstract: 710,873. Lithographic printing-machines. DITTO, Inc. April 25, 1951, No. 9655/51. Class 100 (2) Tripping arrangements.-An offset lithographic duplicating machine comprising a cylinder which has plate and impression surfaces and which is rotatably mounted on a fixed axis on a frame member and adjacent a blanket roll which is movable towards and away from the cylinder is characterized in that the blanket Toll is rotatably supported by a hanger or hangers which is or are pivotally connected to the frame member and which is or are connected to a resilient member for urging the blanket roll towards the cylinder, the position of the blanket roll relative to the cylinder as urged by the resilient member being controlled by a mechanism operatively connected to at least one hanger. As applied to the machine described in Specification 710,871, and as shown in Fig. 6, the blanket roll comprises a cylindrical body part 86 supported on a non-rotatable shaft 94. The blanket roll also carries a gear 60 in mesh with a ring gear 58 on the cylinder 14. The ends of the shaft 94 extend through openings in the side plates 4 of the machine, a stud 96 being located above each opening. Depending from the stud 96 is a pivoted hanger arm 100 adapted to embrace the shaft 94. The lower end of the hanger 100 is connected to a tension spring 110 by a coupling 108. A depending arm 112 is also mounted on each stud 96 which serve to clamp the shaft 94 and which abut pins 114 mounted on arms 116 on a rock shaft 118 so that rotation of shaft 118 in a clockwise direction causes displacement of the blanket roll 86 away from the main cylinder 14 against the action of spring 110. The arms 112 are mounted on eccentric parts of the studs 96, Fig. 8a (not shown) so that by rotation of studs 96 the blanket roll may be brought into exact parallelism with the cylinder 14. Fastened on the shaft 118 is a main lever 120 having parts 128, 130, 132 on which are mounted three auxiliary levers 122, 124, 126. Each lever is provided with a cam 134, 138, 142 co-operating with a cam surface 136, 140, 144 respectively, the cams being secured to one end of the cylinder 14 shaft 74. The lever 122 when operative serves to move the blanket roll away from the main cylinder, the second lever 124 controls the pressure exerted by the blanket roll on the printing plate segment of the cylinder 14, while the third lever 126 controls the pressure exerted by the blanket roll on the impression surface of the cylinder 14. The lever 122 normally is allowed to pivot freely up and down under the action of cam 136, a latch 150 being held out of operative association with the end of the lever 122 by a solenoid 148 normally energized and mounted on the main lever 120, If the solenoid is de-energized the latch 150 moves under action of a spring 158 to bear against the end of lever 122 thereby causing lever 120 to move with lever 122. If at the same time a second electromagnet 172 is de-energized the levers 120, 122 are held by means of a latch 164 and a stop member 163 so that the blanket roll is permanently out of operative association with the main cylinder 14. The arrangement is such that prior to feeding of sheets to be printed the solenoid 172 may be energized manually but solenoid 148 may not, so that the lever 120 is constrained to follow the movements of lever 122 whereby the blanket roll may make contact with the plate segment of the cylinder 14 for inking the blanket roll but is maintained away from the impression surface of the cylinder. When sheets are fed solenoid 148 is energized automatically thus freeing the lever 120 and solenoid 172 is de-energized, the latch 164 having no effect, however, until failure of the sheet feed or stopping of the machine causes solenoid 148 to be de-energized and lever 120 to be raised and latched so as to prevent the blanket roll from touching the main cylinder. The inner end of the lever 124 is provided with an adjustable abutment part 176 the lower end of which abuts the lever 120 so that a slight rocking movement may be imparted to the shaft 118 by the action of the cam 140 so as to reduce the pressure between the blanket roll and the plate segment. The third lever 126 also rocks the lever 120 in a similar manner to lever 124 to control the pressure between the blanket roll and the impression segment of the cylinder the cams 140 and 144 having diametrically opposed rises and dwells. The movement imparted to the shaft 118 by the lever 126 may be adjusted by means of a knob 190 operating a cam 180 which bears against the lever 126. The cam 180 may be mounted on an extension of the shaft 118. A handle 196 is provided on the lever 126 so that the blanket roll may be manually moved away from the main cylinder. In a modification, Fig. 11 (not shown), the main lever carries a roller which engages a cam so that movement is imparted to the blanket roll to control the pressure between both the impression segment and plate segment of the main cylinder, and the main lever also carries two auxiliary levers, each of which may be latched thereto by means of a solenoid to control the moving of the blanket roll away from the cylinder in one case and the moving of it toward the cylinder in the other.