GB814096A - Improvements in or relating to method and apparatus for dip coating - Google Patents

Abstract

<PICT:0814096/III/1> An article is lacquered by withdrawing it from a dip tank at a speed sufficiently fast to pick up a substantial excess of mobile lacquer, preventing immediate solidification of the lacquer, swinging the article about a horizontal axis at a speed sufficiently slow so as initially to provide maximum flow of the excess mobile lacquer from end to end of the article but at a speed sufficiently fast to prevent drip, and continuing such rotation for at least one hundred revolutions, the solidification of the lacquer being delayed to prevent complete solidification thereof until substantial completion of the hundred revolutions. As shown, Fig. 1, a machine for lacquering a number of articles consists of a frame fitted with pairs of sprockets 11, 13, 15, 17, 19 around which pass two endless chains 7 between which are fixed rods 21 bearing spikes 23 on which the articles are impaled, the rods being fitted with driving wheels 25 engaging in a track 27 so that the movement of the chains causes the rods to revolve. The track 27 may be constituted by vee-belts. A container 9 of the coating material, molten or in solution, is so placed that each spike passes through the material. The speed of the continued rotation of the rods after the dipping process is completed is such that the coating material flows back and forth on the surface of each object until hardened but is neither flung off nor allowed to drip off. The coating material may be for example a nitrocellulose solution which may be hot or cold, or ethyl cellulose or cellulose acetate butyrate, which may be used as a hot melt. The coated articles may be passed through an enclosed space which may be heated to control the rate of evaporation of solvents and/or cooling of the coating. Thick coatings may be built up by re-cycling articles through the machine more than once. Specification 276,864, [Class 95], is referred to.