GB808180A - Improvements in anti-set-off devices for printing machines - Google Patents

Abstract

808,180. Set-off preventing. SMYTHHORNE Ltd., and TAYLOR, H. W. Feb. 14, 1957 [Feb. 7, 1956], No. 3781/56. Class 100(2) A device for spraying powder on to printed sheets as they pass through a printing press so as to prevent set-off comprices a container for the powder, means for feeding air under pressure into the bottom of the container below the surface of the powder contained therein to agitate the powder and blow it to the top of the container, means for retaining or supporting a substantially constant quantity of powder at the top of the container, means for continuously circulating powder in the top of the container, and means for conveying powder from the top of the container to nozzles for spraying;the powder on to the printed sheets. The container 4 is closed at its upper end by a closure head 5 and at its lower by a perforated plug 6. An air inlet pipe 8 carried by the head 5 is disposed axially of the container and a reduced threaded portion thereof passes through the hole in the plug 6 and is engaged by a nut 7. The pipe 8 carries a cup-shaped air-deflector 9 which is held in abutment with the plug 6 by a radially slotted nut 10; the radial slot registers with a hole 11 in the pipe 8 and opens into deflector 9. A cylindrical member 12 also carried by the closure head is disposed concentrically with the pipe 8 and forms an annular passage therewith; the bottom of the member is open and a slot 13 is provided at the top of the wall. A frusto conical canopy 14 encircles the cylinder below the slot 13 and is suspended from the closure head by rods 15. A nozzle 16 is arranged eccentrically on the closure head to direct a jet of air at an angle on to the canopy 14 as at 17. The closure head 5 is connected at one end to a source of air under pressure by a pipe 19 and at the other to the powder-spraying nozzles (not shown) by a pipe 20. Conduits convey air under pressure to the inlet pipe 8 and the nozzle 16, while other conduits convey air to a venturi 25 under the action of which air is sucked from the interior of the container 4 through an outlet 26 to convey air and powder in suspension through the pipe 20 to the spraying nozzles. The container 4 is charged with powder to about the level of the dotted lines. In operation air travels down the pipe 8 and out of the hole 11 whence it is deflected up the annular passage formed by the cylinder 12 carrying with it some of the powder from the bottom of the container. The powder emerges from the slot 13 and falls on the canopy 14 whence it is blown about the upper part of the container by air from the nozzle 16 until it is sucked through the outlet 26. In a modification the cylinder 12 is dispensed with and the hole 11 opens directly into the powder which is blown up through an annular opening between the pipe 8 and the canopy 14. In either embodiment a valve may be provided whereby air under pressure is blown intermittently into the container 4.