Patent ID: 7892609

Claim:
A plasma spraying method for coating a surface of a substrate with a coating material in a spray procedure comprising providing a spray pistol with a plasma burner heating device for heating the coating material in a heating zone, where the coating material passes from the heating zone to the substrate to provide a coating, providing first and second conduits containing the coating material through which the coating material is introduced into the heating zone, the first and second conduits being attached in a fixed position to a holder that is movable relative to the heating zone between two different first and second positions, so that in the first position the first conduit directs coating material from the first conduit into the heating zone to provide a first coating layer on the substrate surface and the second conduit is sufficiently away from the heating zone to prevent a vacuum in the heating zone from sucking coating material in the second conduit into the heating zone and to prevent coating material from the second conduit from entering the heating zone, and in the second position the second conduit directs coating material from the second conduit into the heating zone to provide a second coating layer on the substrate surface and the first conduit is sufficiently away from the heating zone to prevent a vacuum in the heating zone from sucking material in the first conduit into the heating zone and to prevent coating material from the first conduit from entering the heating zone, and moving the holder to the first position, and while the holder is in the first position, flowing coating material through the first conduit into the heating zone, and passing this coating material from the heating zone onto the substrate to form a first coating layer on the surface of the substrate, and simultaneously preventing material in the second conduit from entering the heating zone, and then moving the holder to the second position and, while the holder is in the second position, flowing coating material through the second conduit into the heating zone, and passing this coating material from the heating zone onto the substrate to form a second coating layer on the surface of the substrate, and simultaneously preventing material in the first conduit from entering the heating zone, so that the first and second coating layers are applied to the substrate surface without interrupting the spraying procedure and without causing cross-contamination of coating materials from the respective conduits in the heating zone.