To eliminate cutting machining, reduce expenditure required in disposal of cutting chips, and thereby lower the cost required by making equipment common even if each spline part to be applied with nylon coating is different in size, and making the film of nylon coating arbitrary and uniform in thickness.
After a substrate treatment for the inner circumferential tooth surface of the spline sleeve 1 of an universal joint is performed by a shot blast primer coating device 4. The spline sleeve 1 is kept at grounding potential, and concurrently, it is rotated by a rotating device 3 so as to be heated up to a constant temperature by a heating device. Electrically charged nylon powder is injected in a radial form out of the tip end of a spray gun 5 so as to be sprayed over the inner circumferential tooth surface, so that nylon is electrostatically coated. After coating is over, shower is sprayed thereon by a cooling device 8, and coated nylon is thereby to be fixed thereto.
KATO TSUYOSHI
TAIRA HIRONOBU
Next Patent: CONSTANT VELOCITY UNIVERSAL JOINT