Coating processes – Spray coating utilizing flame or plasma heat – Nonuniform or patterned coating
Patent
1997-05-30
1999-01-05
Bareford, Katherine A.
Coating processes
Spray coating utilizing flame or plasma heat
Nonuniform or patterned coating
427453, 427455, 427456, C23C 412
Patent
active
058559639
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/AT96/00182, filed Oct. 3, 1996.
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a process for producing a coating on the surface of plasticizing screws for injection molding machines, in which a metal, carbide-metal or ceramic material is applied with a low degree of distortion to a screw main body consisting of steel, by means of at least one spray jet using the high-speed flame spray process.
In order to improve the wear resistance of plasticizing screws, the conventional state of the art provides that the plasticizing screws are hardened or coated by means of flame spraying with subsequent heat treatment. Both can result in deformation of the screw, while in the case of flame spraying, cracks can occur in the coating in the subsequent operation of straightening the plasticizing screw. A plasticizing screw of that kind is therefore not resistant to corrosion.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved process for coating plasticizing screws, by means of which it is possible to produce a wear-resistant and corrosion-resistant coating, which is operative to produce a conveyor effect, on the surface of the plasticizing screw.
The object in accordance with the invention is attained in that in the coating operation the spray jet acts on the various surface regions of the screw main body, namely the flight top side, the flight flanks and the screw bottom, partially independently of each other, a mechanical bond being made between the screw main body and the coating.
Therefore a fused bond is not made between the screw main body and the coating.
If a plasticizing screw is coated with the process according to the invention, there is no need for a subsequent heat treatment which could result in distortion of the plasticizing screw.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the invention are described hereinafter with reference to the Figures of the accompanying drawings.
FIG. 1a is a partial side elevational view showing the main body of the screw and spray jet with jet nozzle according to the present invention;
FIG. 1b is a view similar to FIG. 1a with the spray nozzle in a different position;
FIG. 1c is a view similar to FIG. 1a with the spray nozzle in a still further position;
FIG. 2a is a view similar to FIG. 1 with the spray nozzle in a still further position;
FIG. 2b is a view similar to FIG. 1a with the spray nozzle again in a different position;
FIG. 2c is a view similar to FIG. 1a with the spray nozzle in a still further different position;
FIG. 3 is a view similar to FIG. 1a with the spray nozzle in a further position;
FIG. 4 is a view similar to FIG. 3 with the spray nozzle in a different position;
FIG. 5 is an enlarged partial side elevational view showing the main body of the screw with spray jet and spray nozzle with a shield system;
FIG. 5a is a sectional view through a spray jet taken along line 5a--5a of FIG. 5;
FIG. 6 is a view similar to FIG. 5 showing a different embodiment for the shield system; and
FIG. 7 is a view similar to FIG. 1a showing the main body of the screw with cover means according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The screw main body 1 which is made of steel has a screw flight 2. The screw flight 2 extends in a helical configuration around the screw main body 1. It has a flight top side 3 and two flight flanks 4. Disposed in the free space between the screw flight 2 is the screw bottom 5.
The pitch and/or configuration of the screw flight 2 varies over the length of the screw main body 1. This configuration of the plasticizing screw however is independent of the invention.
Coating of the entire screw surface 1 and the screw flight 2 is effected by means of a burner or torch nozzle 6 by means of which a spray jet of metal, hard-metal or carbide-metal, or ceramic material is applied to the screw main body 1 and the screw flight 2, using the high-speed flame spray process.
In that procedure the burner nozzle 6 is moved a
REFERENCES:
patent: 4233072 (1980-11-01), Watanabe
patent: 4766042 (1988-08-01), Otani
patent: 5135378 (1992-08-01), Catton
patent: 5198268 (1993-03-01), Grossman
Baldinger Peter
Urbanek Otto
Bareford Katherine A.
Engel Machinenbau Gesellschaft M.B.H.
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