GB406348A - Improvements in or relating to the coating of surfaces of articles with liquid material - Google Patents

Abstract

In a process for coating surfaces with liquid materials for example applying a coloured coating to leather, the liquid material is nebulized and distributed in a controllable body of air, which is then moved towards the surface to be coated. A suitable apparatus consists of a chamber 10, Fig. 1, having a spray gun 28 mounted thereon and containing an inner wall 160 of an adsorbent material such as cellulose wall board covered with blotting paper provided with an opening 26 through which the spray enters. The chamber 10 is provided with an upper inlet 12 below which is mounted a fan 20 generating a downward current of air p which passes through an opening 164 in a baffle 162 to a lower outlet 14. A horizontal work table 16 is rotatably mounted below the outlet 14 in a lower chamber into which the current of air passes and is drawn off through a blower 22. Air is supplied to the top of the chamber through a conduit 124, and is regulated by valves 130, 134. The air <PICT:0406348/III/1> <PICT:0406348/III/2> may be brought to any desired humidity and temperature and led through a conduit 128 to the apparatus. The spray gun is provided with a reservoir 92 which is connected at its base to a cup adapted to receive the neck of an inverted bottle containing the liquid dye. The reservoir may be drained through a tap when it is desired to change the dye. The imperfectly nebulized liquid, first formed when the spray gun is started, is prevented from reaching the chamber 10 by a moveable shutter 174, which is actuated by a time-release mechanism operated by the gun. The shutter 174, Fig. 6, is connected through a pivoted arm 170 to a piston 190, moving in a cylinder 192. An air compressor 68 is connected through a pipe 210 provided with a choke valve 212 to the cylinder 192, and through pressure reducing valve 72 to the spray gun. The air compressor 68 is operated by a motor 54-which also actuates the work table, fan and blower. In operation, a piece of leather is placed centrally on the work table through a door 166, and the motor is started by a switch, generating a downward current of air over the rotating table, the shutter 174 closing the spray orifice. The compressor 68 builds up a pressure of about 6 lbs. in the spray gun, and the liquid ejected from the gun against the shutter falls through a tube 182 into the reservoir. Meanwhile a restricted stream of air passes through the valve 212 into the cylinder 192, in which the pressure slowly rises until sufficient to overcome the resistance of an adjustably tensioned spring 200, when the piston moves to the left and retracts the shutter. The nebulized liquid then passes through the opening 26 and is projected at right angles to the stream of air in which it is finally distributed and is drawn downwards over the leather passing over the outer edge thereof into the lower chamber. When the motor is switched off, air escapes from the cylinder 192 through a release valve 220, and the shutter is moved by the spring 200, whereby the spray opening is closed when pressure is falling in the spray gun. Specifications 101,775 and 229,351, [both in Class 95], are referred to.