Method and apparatus for spray-coating articles

摘要

Articles are coated by moving them in succession along a predetermined path, creating over the surface of the moving articles a high voltage electrostatic field, the lines of force of which are generally normal to such path, and spraying liquid coating material into the field so that the spray-direction possesses a substantial component parallel to the path of article travel and generally normal to said lines of force. Referring to the drawings, cabinet 10 comprises side walls 11, top 12 and floor plates 13 sup ported by posts 14, while conveyer chain 15 travels past loading station 26, below the floor of the cabinet and past unloading station 25, and carries carrier units 28 including a rod 33 extending upwardly through the opening between the two floor plates 13 of the cabinet and carrying at its upper end an electrode 35 serving as a support for article 36 to be coated. Spray guns 44 are carried on horizontal rods 43 clamped to rods 41 slidable along rods 37 and are arranged to direct a spray 46 of coating material in the general direction of the opposite end of the cabinet. A pair of tubular insulating members 47 are mounted on each side wall 11 of the cabinet and carry strung between them a fine wire electrode 48 connected to one terminal of an electrical generating apparatus, the opposite terminal of which is connected by a conductor 51 to a pair of wires 52 extending longitudinally beneath the floor of the cabinet and adapted to engage the vertical rods 33 in their travel through the cabinet and so to complete the electric circuit. The articles may, if desired, be slowly rotated to insure uniform coating. This is done by means of conveyer 64 mounted on plate 67 movable toward and away from conveyer 15 so as to bring chain 64 into and out of mesh with sprockets 31 on conveyer 15. Plate 67 has secured thereto a pin 70 carrying a T-fitting 72 which carries rod 74 passing through fixed brackets 77 to T-fitting 81 comprising stud 83 and handle 82 which can be moved so as to fit inside or outside detent 84 secured to the cabinet wall. Spring 80 acting against washer 78 held by pin 79 normally urges the chain 64 into engagement with sprockets 31 and moving of stud 83 inside detent permits this, while moving it outside the detent breaks the engagement. In a modification (Fig. 7) in which only one side of an article is to be coated, the article 136 is carried by support 133, the discharge electrode is a metallic point 148 mounted on the end of one of the insulators 47 and the collecting electrode is a plate 135 mounted on a similar support on the opposite side of the path of travel of the article 136.