Patent GB-733404-A (GB)
Title: Dampening mechanism for lithographic offset presses and the like
IPC: B41F7/26
Filed: 1953-10-26
Abstract: 733,404. Printing-machines. SCHULTZ, J. Oct. 26, 1953, No. 29542/53. Class 100 (2). Damping mechanism for lithographic printing presses.-Mechanism for moistening damping rollers of lithographic presses includes a rotary member adapted to receive and dispense moisture, which member is mounted on a pivoted bracket for alternative movement into contact with a water-supply roller or with a damping roller, counterbalance means being provided on the other side of the bracket so that movement of the member is automatically controlled by its moisture content. The printing press, Fig. 1, comprises a lithographic cylinder B, an offset cylinder H and impression cylinder J. Ink is applied to the cylinder B by an ink fountain A. Moisture is applied to the cylinder B by a cylinder D, Fig. 3, having an absorbent surface 61, which is supplied with water by a brass roller G adapted to receive it from the moisture receiving and dispensing member. Roller G may be manually reciprocable to assist spreading the moisture axially. Water is supplied to member L by roller K engaging a roller 5 running in a reservoir C. Another absorbent surfaced roller M co-operates with roller G to help distribute the moisture along the length of roller G. As shown in Fig. 2, roller K comprises a number of separate discs k and member L is composed of a series of independent wheels l each mounted on a yoke or bracket 18 adapted to be rockingly supported on the sharp edge of a cross bar N mounted between side plates E, F. A screwed extension 24 carries a counterweight 25 which may be displaced to vary the amount of water contained in the absorbent covering of the wheel l. When the water content is low the counterweight causes the yoke 18. to tilt so that the wheel l engages the supply roller K. When the water content is sufficient the yoke tilts so that the 'wheel engages the roller G and transfers water to it. The wheel l is held in one position or the other by a depending spring blade 27 engaged by a rotatable disc 28 carried by a bracket 29 and repeatedly raised and lowered by levers R pivoted at 36 and having followers 37 engaging cams P on a shaft p. As cams P rotate the disc 28 rises and falls. In the risen position it displaces the wheel l to one position or the other, preventing a neutral, inoperative position. The water content of the wheels l may also be controlled by rollers 42, Fig. 9, each bearing on a bracket 18 and adapted to be moved from a position on the wheel side of the bar N to a position on the counterweight side. Each roller is connected by a link 43 with a crank 44 extending the full width of the machine. The crank is rotated to displace all the rollers by a lever 47 co-operating with a scale 45. By this means an " overall " control of the amount of water is provided to govern the water supplied to the whole surface of the cylinder B. This may need to be varied for different types of paper. The control of individual wheels l by counterweights 25 governs the water supplied to the corresponding zone of the cylinder B. This may need to be varied for the particular design on the lithographic cylinder. The reservoir C, Fig. 1, rollers 5 and K and wheels l are mounted between the side plates E, F pivoted at 36 to brackets O. A slotted tie bar 85 pivoted to a lug 99 on a bracket O engages a pin 106 on mounting plate E to limit the angle of swing of the assembly. The brackets O on each side are secured by cross shafts 67, 78 to runners 91, slidably mounted on guide rods S projecting from the machine frame. A handle 89, when raised to rotate the shaft 78, causes the runners 91 and all the damping mechanism carried thereby to move away from the lithographic cylinder. A lever 101 is effective to latch the handle 89 in the raised position to maintain the parts in the dotted line position of Fig. 1. In addition the mounting plates E, F may be tilted as already described to the second dotted line position. The rollers D, G and M may be readily removed from their mountings on frame members 48 when the damping mechanism is displaced away from the cylinder B. Each roller spindle d, g and m is retained in slotted bearings 54, 53 and 92. Bearings 54 and 53 may be closed by swinging plates 55 and 63 actuated by wing members. The cylinder D is constructed as shown in Fig. 12. End caps 57 are formed with bosses 58 fitting into the ends of an internal cylinder 56, e.g. of aluminium. Stub-shafts d fit into sockets in the caps and are retained by screws. An elastic sleeve 70 fits over the flanges 65 of the caps and is retained by wires 64 tightly engaging the grooves 66. Surrounding sleeve 70 is a sleeve 72 of a non-stretchable material, e.g. rubber and fabric. The outside absorbent sleeve 61, e.g. of molleton, surrounding sleeve 72 is retained by cords 62. The inner sleeve is inflatable by means of an air valve 73 passing through the cap, a pressure of about 2 lb./square inch being suitable. In a modification the sleeves 72 and 71 may be replaced by a single sleeve which is both inelastic, to maintain the cylindrical form, and absorbent, to retain moisture.