Patent GB-726100-A (GB)
Title: Improvements in or relating to a plate dampening device and a printing press containing the same
IPC: B41F3/30
Filed: 1953-03-13
Abstract: 726,100. Printing- machines. HARRIS-SEYBOLD CO. March 13, 1953 [March 27, 1952], No. 6967/53. Class 100 (2). [Also in Group XXIX] Damping-apparatus for lithographic and like plates.- A plate damping device, for use in a planographic printing press having a rotating cylinder 10, Fig. 3, carrying a planographic plate 9, comprises a straight wire electrode 50 parallel to but spaced from the cylinder, a metallic shell 40 enclosing the electrode and open towards the cylinder a nozzle 87 for creating a fog which is directed into the space between the inner surface of the shell and the cylinder, the wire electrode being connected to a source of direct current high potential and the shell and cylinder being connected to earth so that moisture particles coming within the field of force of the electrode are charged and deposited on the plate 9 or on the shell 40. A tube 14 extending between brackets 13, Fig. 1, across the front of the machine carries collars 20 to each of which is attached a depending strip 22 supporting a housing 25 the front wall of which is formed by the shell 40. The rear wall of the housing is formed by a sheet 29, e.g. of a transparent plastic. The housings are arranged side-by-side so as to cover the operative width of the printing cylinder 10, the ends are substantially closed by cheek-plates 41 supported from the tube 14 on collars 42 and having arcuate edges engaging in grooves cut circumferentially in the ends of the cylinder. The housings are closed at the bottom by a pan 19 extending the full width of the housings and containing a supply of liquid, e.g. water, with or without certain chemicals added. The part 38 of the shell 40 is substantially cylindrical about the electrode 50 as centre and about the same distance away as the electrode is from the cylinder 10. The upper part 35 of the shell forms a narrow throat 36 with the cylinder 10. At the bottom end the shell has a lip 39. The pan forms a throat 46 with the bottom of the shell and a constriction 84 is formed between the lip 39 and a deflector 47 mounted on the pan. The wire electrode 50 is stretched between anchorages 54, 64 in insulating slabs 51, 65 supported from the tube 14. The anchorage 64 is connected through a member 68 to a plug-and-socket connector 73 bringing the high potential to the wire 50. Each nozzle 87 is supplied with air under pressure through a pipe 95 connected to tube 14. Liquid from the pan 19 is drawn up through a syphon 89. The air pressure is also taken to a jet 98 inside the housing directing air against the spray from nozzle 87 so that the fog is rendered substantially stationary inside the housing. The fog is drawn out of the housing by the upward movement of the cylinder past the restriction 84 and fills the space 45 inside the shell. The liquid particles are charged by the field of the wire 50 and migrate towards the earthed cylinder or shell. Liquid falling on the shell is returned to the pan 18 by a small hole 101. Tubular metal shields 76, Fig. 1, mounted on the end-plates 41, prevent condensation on the faces of the insulators 51, 65. The air pressure to the nozzles is regulated by a tap 93 and the liquid supply by a screw 96. The housings and the wire are adjustable, by rotation about the tube 14 without altering the size of the throat 36 substantially.