Patent GB-529255-A (GB)
Title: Improvement in dry spray for preventing offset
IPC: B41F23/06
Filed: 1939-05-24
Abstract: 529,255. Printing machines; sheet delivery apparatus. COLE, H. May 24, 1939, No. 15470. Convention date, Aug. 9, 1938. [Classes 100 (i) and 100 (ii)] In means for preventing set-off by spraying the printed sheets or webs by blowing blasts of air carrying finely comminuted powder such as wax of high melting point across the sheets or webs after printing, when the powder is retained by the wet ink, a refillable powder container has a compressed-air inlet at the bottom, a discharge valve at the top, and at least one pipe connection to the spray nozzle. Air filtered in a unit 14. Fig. 2, is blown through powder in the chamber R, Fig. 3, by jets comprising the ends of helical grooves 37 in a plug 38, the jets being moved after each blast to avoid the formation of a permanent tunnel through the powder. The compressed air passes through a valve 25, pipe 13, pressure regulator 15, and filter 14 to the nozzle 33, held in a seating 32 in a valve seat member 31 by a cap 34 screwed thereon. The member 31 is rotatably mounted in a bush 30 screwed into the base 29 of the chamber R, adjacent an emptying plug 72 therefor. A master-lever 21, pivoted to the chamber R at 22,. engages a slotted lever 42, the eye 43 of which encircles the member 31. A spring-urged pawl 41 on the lever 42 engages a ratchet wheel 40 affixed to the member 31. Oscillation of the lever 21 is produced by achain 23 attached to a suitable part of the press and oscillates the lever 42, thereby rotating the member 31 and all parts affixed thereto. A ball valve 35 rests in the upper end of member 31, which is closed by a tight-fitting plug 38 having helical grooves 37 to allow of air-passage, and preferably drilled centrally to allow air to pass up a pipe 45 coaxially affixed to the member 38 and having a pin-hole nozzle 46 at its upper end, and a scraper arm 47 for cleaning the walls of the chamber R screwed to its lower end. A plug 7.1 permits  of powder being placed in chamber R, to the top of which an outlet chamber O is affixed by screws. Finely atomized powder passes through a nozzle 66 on a pipe 65, placed opposite the nozzle 46, and enters a narrow bore 63. A cylinder valve 54 with bore 62 and air retaining rings 64 is mounted between washers 57, 55a by screws 58, 56 and is.rockable by the lever 60 keyed to the squared end 59 of the valve 54. This lever 60 is connected by a pitman link 61 to the other end of the master lever 21. After passing the valve 54, the air and powder enter an enlarged chamber 50 and pass therefrom by narrow bores 69 to enlargements 70 in control valves 17. From the valves the spring passes via tubes 18 to the nozzle equipment, the narrow bores always being followed by enlargements in the tubing to ensure the preservation of the suspension of the powder. Undivided spray heads may be used, or pipes 80, Fig. 8, perforated at 81, with breather cans at the ends to avoid obstructive packing of powder there. Sleeves may be moved on the tube 80 to close desired perforations. Normally the lever 21 oscillates the valve 54 to admit a blast of air, while it also rotates the member 31 and assembly fixed thereto. The Specification as open to inspection under Sect. 91 describes also an alternative nozzle with a fish-tail 75, Fig. 11 (Canceled), and a pressure gauge 79; this nozzle can straddle a number of sheets if desired and blow between them thus causing leviation with less chance of set-off. In this case, clear air devoid of powder is blown through the nozzle. This subject-matter does not appear in the Specification as accepted.