GB899302A - Improvements relating to the electrophoretic coating of articles - Google Patents

Abstract

899,302. Electro-phoretic coating apparatus. BAILEY, J. W. (Sylvania Electric Products Inc.). Nov. 23, 1959, No. 39734/59. Class 41. In an apparatus for coating articles electrophoretically, e.g. tungsten filaments coated with a refractory oxide deposited from a suspension thereof in nitrocellulose lacquer, the articles are passed automatically by an indexing carrier through a plurality of work stations including, a first and second coating bath, a rinsing station and a drying station, the last two of which may be in several stages. The double coating is stated to provide a crack-free coating of the filament when heated, the final coating being of lower density. A coating station, Fig. 7, consists of a glass cup member 209 mounted in a housing 201 and is adjustable for height so that the required length of uncoated filament is predetermined. The cup has an overflow 211 and liquid suspension supply line 216, to keep the coating liquid at the desired level, and is provided with a magnetic stirrer 221, rotated by a magnet 205 mounted below it. An electrode of wire mesh 225 has an insulated bottom member 227, and is supported by the lead-in strap 231. The coiled tungsten filament is supplied from a transfer turret machine (not shown), and is gripped between spring-loaded jaws by one leg of the filament only. The jaw carrier descends a predetermined amount to immerse the filament in the coating medium 215 and deposition proceeds for a standard time, e.g. ¢ to 2 seconds at 1000 to 1500 v. The insulating bottom element 227 provides a calm surface to the stirred suspension. The energy is then cut off and the coated filament raised out of the bath. A second similar coating operation follows, and in succeeding stations the filament is washed with a solvent (twice) and heated in four air drying stages. The filaments are finally fired at 1670‹ C. for seven minutes. The washing solvent is preferably petroleum ether and amyl acetate followed by petroleum ether alone. The movements of the filaments into and out of the work stations, which are arranged on a rotary frame, and movement from one station to the next are rendered automatic by Geneva mechanism with associated gear providing the required movements at predetermined intervals of time. U.S.A. Specifications 2,442,863 and 2,442,864 are referred to.