GB716957A - Method of and apparatus for the deposition of atomized liquid coating material - Google Patents

Abstract

<PICT:0716957/III/1> <PICT:0716957/III/2> A method of coating a moving surface comprises directing at the moving surface a plurality of annular sprays of liquid coating material each capable of producing on the surface a band of coating material varying in thickness in predetermined pattern from edge to edge of the band, the thickness-patterns of the several bands being generally similar and including areas of different width and the sprays being so disposed transversely of the path of surface movement that a relatively thick portion of one band coincides with a relatively thin portion of another, the several bands complementing each other to create on the moving surface a coating of substantially uniform thickness. Three annular sprays may be used to give spray patterns on a stationary surface, as in Fig. 3, where the diameters of the circles of maximum thickness of the smaller patterns 32 and 33 lie between 60 per cent, and 90 per cent. of the corresponding diameter of the larger pattern 31, and the patterns 32 and 33 are offset from each other by a distance between 30 per cent. and 70 per cent. of their aforesaid diameters either side of the pattern 31. When the surface is moved in the direction indicated by the arrow the band of coating obtained is as shown exaggerated in Fig. 4, where the p band from each spray is shown as well as the aggregate coating of all three sprays which is comparatively even. Electrostatic sprays may be used, and the sprays may be offset longitudinally of the direction of surface movement as in Fig. 3. For coating wide surfaces several groups of three sprays may be used arranged so that the side portions of the Fig. 4 aggregate pattern overlap to complement each other. In a modification a single annular sprayhead may be moved successively and repeatedly through three positions, one being further from the surface than the other two to give a broader pattern, the total effect being equivalent to having a spray in each of the three positions. Specification 710,852 is referred to.