A process for the preparation of a coating gleichmaessigen resistor on an insulating surface

摘要

PICT:0954246/C1/1 A method of applying a coating of high uniform electric resistivity to a surface of an insulating element, comprises preheating the element in a tubular enclosure at a strictly uniform temperature for a time sufficient to establish thermal equilibrium throughout the mass of the element, then withdrawing the element and immediately feeding it past a spray of the coating composition, the withdrawal and feed velocity of the element past the spray being so high that the entire spraying operation is completed within a time of substantially one second or less to ensure that said thermal equilibrium and consequently a constant surface temperature of the element are maintained substantially throughout the spraying period. As shown, a glass plate 42 mounted in a clamp 40 secured to bent arm 38 which can be displaced axially by means operated by motor 30, is held in furnace 20 comprising a plurality of separate heating sections defined by windings 26a, 26b and 26c, each section being provided with temperature probes, e.g. thermocouples 28a, 28b and 28c, and with a thermostatic control circuit, e.g. 27a, 27b and 27c, till thermal equilibrium is established and then withdrawn from the furnace and fed past a spray comprising a mixture of tin tetrachloride and antimony trichloride from sprayer 44. The coating solution may be sprayed by compressed air. Specification 876,472 is referred to.