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US 5,352,539 AGranted
Extruder housing for double-screw extruder having an annularly stepped internal bore covered by a hot isostatically-pressed structure, and method of making same
AssigneeFriedrich Theysohn GmbH
InventorWerner G. Psiuk
Life of this patent
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Abstract
An extruder housing is formed for a double-worm or double-screw extruder by providing a steel body with a seamless one-piece structure and hot-isostatically pressing the body and the powder-metallurgical wear-resistant material lining the preferably conical bores of the housing to form a wear-resistant layer which is bonded to the steel body by a diffusion layer.
Claims12
An extruder housing for a double-screw extruder for processing plastics and synthetic resins, said extruder house comprising:
- a seamless elongated body formed with a pair of adjacent longitudinally extending generally conical bores for receiving respective conical extruder screws and together defining a figure-eight cross section cavity, each of said bores being provided with a plurality of axially spaced generally annular steps;
- a wear resistant layer of a hard powder-metallurgical material in a hot isostatic-pressed structure extending along and lining said cavity against said body, said layer filling said steps and having smooth conical walls;
- and
- a diffusion layer formed by said material of said layer and material of said body bonding said wear resistant layer to said body.
1 more element
A method of producing an extruder housing comprising the steps of:
- (a) forming a seamless-elongated body having a pair of adjacent longitudinally-extending bores together defining a figure-eight cross section each of said bores being provided with a plurality of axially spaced generally annular steps;
- (b) lining said bores with a powder of a hard material capable of hot-isostatic pressing into a coherent layer along said bores and filling said steps with said powder;
- (c) confining said powder between a pair of conical cores and the walls of said bores;
- (d) sealing said powder in said body;
- (e) introducing said body with said cores, and said powder into a pressure vessel and subjecting said powder to hot isostatic pressing by applying pressure from the exterior of said body inwardly and plastically deforming said body, therefore bonding said body into a wear-resistant layer along said bores and forming a diffusion layer of material of said powder and material of said body bonding said wear-resistant layer to said body;
- and
- (f) removing said cores to leave smooth conical walls of said layer delimiting smooth cavities for receiving generally conical screws.
4 more elements
Dependencies are inferred from the claim text.