Coating processes – Spray coating utilizing flame or plasma heat
Reexamination Certificate
2000-03-29
2001-11-20
Bareford, Katherine A. (Department: 1762)
Coating processes
Spray coating utilizing flame or plasma heat
C427S422000, C118S302000, C118S323000, C239S079000, C239S085000
Reexamination Certificate
active
06319560
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for coating the outer surface of a workpiece.
Thermal spraying, also known as flame spraying, involves the heat softening of a heat fusible material, such as a metal or ceramic, and propelling the softened material in particulate form against the surface which is to be coated. In many instances where a three dimensional object is to be coated, the thermal spray gun is held in a fixed position and the object is moved relative to the gun in order to coat the entire outer surface.
The ability to move the workpiece while the gun is stationary is possible in many situations, however, it is impractical where the workpiece is large in size or where it is desired to recoat a workpiece while it is still mounted in place, for example, the landing gears for an aircraft. The difficulty of moving the landing gears of an aircraft while connected to the aircraft is evident.
There is therefore a need for an apparatus and method for coating the outer surface of a workpiece while the workpiece is held stationary.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide an apparatus and method for coating the outer surface of a workpiece wherein a thermal spray gun is rotated around a workpiece disposed at the axis of rotation of the thermal spray gun.
Another object of the present invention is to provide a convenient and simple method and apparatus for supplying the oxygen, fuel and powder to the thermal spray gun while it is rotating.
These and other objects of the present invention are achieved in accordance with the present invention by an apparatus having a support mounted for rotation about an axis and having a fixture mounting a thermal spray gun with a coating spray thereof directed towards the axis, whereby a workpiece disposed at the axis will be coated thereby. The thermal spray gun has inputs for powder, fuel and oxygen and a supply line for each of the powder, fuel and oxygen is rotatable with the support for supplying the powder, fuel and oxygen to the thermal spray gun. At least one coupling having a first portion rotatable with the support and a second portion having ports for receiving the powder, fuel and oxygen communicates the powder, fuel and oxygen to the corresponding supply lines. A motor rotates the support.
In order to coat the outer surface of a workpiece, such as a landing gear which is of substantial length, the apparatus further comprises a mechanism for moving the support, supply lines, coupling and motor parallel to the axis to effect a coating of an outer surface along a length of the workpiece.
In accordance with the invention, in a particularly advantageous commercial embodiment of the invention, the thermal spray gun is a high velocity oxy fuel spray gun. Such a gun is disclosed in U.S. Pat. No. 4,865,252, the disclosure of which is incorporated herein by reference.
In accordance with the method of the present invention, a workpiece is disposed in a fixed position along an axis and a thermal spray gun is rotated around the axis on a support with the thermal spray thereof directed towards the axis. Powder, fuel and oxygen are rotatably coupled to the gun and the thermal spray gun and the support are moved along the axis while rotating.
Another object of the present invention is to provide an apparatus and a method for the rotation of a thermal spray gun with powder injection for the purpose of applying a coating on to a stationary part outer diameter.
In accordance with the present invention, a rotary coupling with five channels, including water in, water out, fuel gas, oxygen and air cooling and with an additional center feed-through for powder flow, has a center shaft rotating within a stationary housing. The shaft assembly is driven via a belt drive by an electric motor to create a constant speed rotation. A manifold block attaches to the center shaft to provide a convenient hose connection point. The process gun is fixtured to the device in an arrangement that causes the gun to be aimed towards the center of rotation. The fixturing scheme allows the adjustment of the gun distance from the center line to optimize the spray distance based on a part diameter.
A counterbalance is fixtured opposite the gun for dynamic balance while rotating. Powder is delivered through the center of the rotating shaft and a separate stainless steel tube is attached to the manifold connection block. The tube rotates with the device and extends beyond the rotary coupling. The rotary powder feedthrough consists of a two part stationary housing. An O-ring provides a positive gas tight seal and a set of compressed felt packings protect the O-ring from abrasive powders. A port is provided to create a positive gas flow through the felt packings. The end cap includes the hose connection and provides compression and retention for the felt packing.
In accordance with the method of the present invention, the device is mounted onto a robot or other device that provides a linear motion along the center of rotation. The device is positioned above the workpiece, for example a shaft, to be coated and the gun is lit. The device is then rotated with the gun lit and powder is introduced and the entire rotating device is advanced slowly over the shaft creating a desired coating.
The present invention allows for the thermal spray coating of outer diameters that cannot practicably be rotated. The apparatus and method eliminate the requirement for large complex part handling equipment and related room and exhaust.
REFERENCES:
patent: 4358471 (1982-11-01), Derkacs et al.
patent: 33 01 548 A1 (1984-07-01), None
Hawley David
Nestler Montia
Varley Kevin
Bareford Katherine A.
Clifford Chance Rogers & Wells LLP
Schaefer, Esq. Ira J.
Sulzer Metco (US) Inc.
LandOfFree
Apparatus and method for coating the outer surface of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for coating the outer surface of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for coating the outer surface of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2616979