Method of and apparatus for continuous coating of elongated articles

摘要

Elongated objects are conveyed into a coating tank by conveying screws having axes spaced apart along the length of the objects and threads of varying diameter which co-operate with skids below the screws and extend into the tank, the skids being also spaced apart along the length of the objects being coated. As shown (Figs. 1) and 2), pipes P are passed through rotating purge chamber 3 into entry chamber 16 of furnace F and deposited singly on to parallel conveyer chains 7 which carry them through heating chamber 17 to bring them to the coating temperature. They are removed from this conveyer by screw conveyers S, S1 which lower them into coating kettle 19, the end of the pipe controlled by conveyer S being lower than that controlled by conveyer S1, as is shown clearly in Figs. 7 and 9 by the corresponding positions of pipes L to Q respectively. The pipe is thus lowered into the coating bath in a tilted position so that gas inside is completely purged therefrom. Beyond the last thread of screw S1 is a slot 45 into which the end of the pipe falls and acquires an opposite inclination, in which attitude it is brought out of the bath by magnets attached to grooves 40 and 42 on screws S and S1. Surplus coating material is removed from the outside of the pipe by passing it through a ring of jets of steam or air under pressure, while the interior is smoothed by the attachment of a bell supplied with a source of high pressure air or steam to one end of the pipe, surplus coating material being blown out of the other end (Fig. 4, not shown). In a modification (Fig. 11) a screw conveyer S11 with a double inclined portion 83 moves the pipes into flux bath 80 and then lifts them out again. In a further modification (Fig. 12) a double thread 86, 87 is shown suitable for passing smaller tubes through the bath for the same duration of immersion but with doubled throughput.