Method and apparatus for the electrostatic powder-coating of objects

摘要

A method of coating an object with electrically insulating powder comprises positioning the object alongside a fluidized bed of the powder, the bed containing ionizing means which are maintained at a high potential difference with respect to the object to be coated. The object to be coated may be conveyed between a plurality of horizontally disposed troughs containing fluidized beds of powder said troughs being spaced to cover substantially the whole surface area of the object (Fig. 1 not shown). Alternatively one or more troughs may be mounted and arranged to reciprocate in a vertical direction to ensure uniform coverage of the surface of the object (Fig. 5 not shown). In one embodiment a bathtub is inverted over a complementarily-shaped member which carries a plurality of horizontal troughs extending in loop form around its surface and coating is effected by fluidizing and electrostatically charing powder in the troughs (Figs. 3 and 4 not shown). The ionizing means may comprise a series of spike members immersed in or protruding from the fluidized bed (Fig. 2 not shown) or may comprise a conducting or semiconducting grid or mesh upon which the fluidized bed is supported and through which fluidizing air is distributed (Fig. 6 not shown). The object being coated is heated or otherwise treated to fuse the powder coating material into a coherent coating layer.