Method and apparatus for applying coatings onto articles of manufacture

Powdered coating material is projected simultaneously towards opposite ends of slots or passageways in a heated article which is rotated at a given speed relative to the powder projecting devices in order to coat the walls and edges of the slots or passageways and the end faces of the article. A preheated stator core (10), (Fig. 5, not shown), having windings slots (13a, 13b) is mounted on a rotatable holder (20) and is rotated thereon around the axis (R) so that the ends of the slots (13a, 13b) pass in turn between pairs of powder projecting nozzles (A, B and C, D). The nozzles (A, B and C, D) are disposed substantially opposite to each other though they may be slightly offset, the oppositely directed impinging streams of powder causing turbulence in the slots which aids the formation of a uniform thickness of coating material. Each nozzle includes an injector (18) supplied with air under pressure through a line (80) while powder material is supplied e.g. from a fluidised bed via line (83) to the nozzle. Each nozzle is pivotally mounted and thereby movable to a position which allows for the removal of the coated core. For this purpose also the holder 20 is provided with a deformable outer surface such that when the holder is connected to a source of compressed air the outer surface is expanded sufficiently to grip the bore of the stator core. When the holder is disconnected from the pressure source the surface becomes deflated and the core may be removed. The surface parts of the holder (20) which make contact with the stator core serve to mask these portions from the coating materials. The rotational speed of the core is such as to give a linear velocity relative to the nozzles in the range 0.5 to 3.0 inches/second. Reference is made to the use of thermosetting epoxy resins and to a synthetic polyester resin which requires post-curing to harden the coated material. The apparatus may be mounted within a closed casing having suction means for extracting surplus powder material (Fig. 1 not shown).