Extruder screw with long wearing surfaces

Abstract

A method of extending the life of an extruder screw by affixing tiles of wear-resistant material along the crest of the extruder screw flighting threads, and optionally grinding the hardened material to remove any sharp edges. In another configuration of the present invention, plates of wear-resistant material are secured to the leading edges of the extruder screw threads to further prolong the life of the extruder screw.

The invention claimed is: 
     
       1. An extruder screw, comprising:
 a generally cylindrical shaft; 
 at least one thread extending from the periphery of the shaft, the thread having a leading face, a trailing face, and a fighting flighting crest, and the fighting flighting crest being generally parallel to the periphery of the shaft; 
 a plurality of rows of wear-resistant tiles, each tile having a wear surface and an opposite binding surface, and each tile having a plurality of edges, wherein the binding surface of each tile is adapted to be bonded to the thread; 
 a first row of tiles that are secured to the leading face of the thread, wherein at least one edge of each tile in the first row is generally aligned with the fighting flighting crest of the thread; and 
 a second row of tiles that are secured to the fighting flighting crest of the thread, wherein at least one edge of each tile in the second row is generally aligned with the wear surface of at least one tile in the first row. 
 
     
     
       2. The extruder screw of  claim 1  wherein the tiles are brazed to the thread. 
     
     
       3. The extruder screw of  claim 1  wherein the tiles are made of tungsten-carbide. 
     
     
       4. The extruder screw of  claim 1  wherein the first set of wear-resistant tiles is arranged with the tiles substantially flush to one another so as to form a substantially continuous wear-resistant surface. 
     
     
       5. The extruder screw of  claim 1  wherein the second set of tiles is arranged with the tiles substantially flush to one another so as to form a substantially continuous wear-resistant surface. 
     
     
       6. The extruder screw of  claim 1  further comprising a plurality of spacers secured to the thread, between the tiles. 
     
     
       7. The extruder screw of  claim 6  wherein the spacers are brazed to the thread. 
     
     
       8. The extruder screw of  claim 6  wherein the tiles are made of tungsten-carbide. 
     
     
       9. An extruder screw, comprising:
 a screw shaft; 
 at least one thread extending radially from and perpendicular to the periphery of the screw shaft, the thread having a leading face, a trailing face, and a fighting flighting crest, and the fighting flighting crest being generally parallel to the periphery of the screw shaft and the fighting flighting crest having a plurality of edges; 
 a plurality of wear-resistant tiles, each tile having a wear surface and an opposite binding surface, and each tile having a plurality of edges, wherein the binding surface is bonded to the thread; 
 a first plurality of tiles secured to the leading face of the thread, wherein at least one edge of the tiles is generally coextensive with the edge of the fighting flighting crest of the thread and is generally aligned with the edge of the fighting flighting crest of the thread; and 
 a second plurality of tiles secured to the fighting flighting crest of the thread, wherein at least one edge of each tile in the second plurality of tiles is generally coextensive with the wear surface of at least one tile in the first plurality of tiles. 
 
     
     
       10. The extruder screw of  claim 9  wherein the tiles are brazed to the thread. 
     
     
       11. The extruder screw of  claim 9  wherein the tiles are made of tungsten-carbide. 
     
     
       12. The extruder screw of  claim 9  wherein the first set of tiles is arranged with the tiles substantially flush to one another so as to form a substantially continuous wear-resistant surface. 
     
     
       13. The extruder screw of  claim 9  wherein the second set of tiles is arranged with the tiles substantially flush to one another so as to form a substantially continuous wear-resistant surface. 
     
     
       14. The extruder screw of  claim 9  flirt her comprising a plurality of spacers secured to the thread, between the tiles. 
     
     
       15. The extruder screw of  claim 14  wherein the spacers are brazed to the thread. 
     
     
       16. The extruder screw of  claim 14  wherein the tiles are made of tungsten-carbide. 
     
     
       17. An extruder screw comprising:
 a shaft;   a flight extending helically about the shaft, the flight having a crest; and   a plurality of generally rectangular hard metal tiles secured to the crest of the flight, each tile having a first pair of edge surfaces generally orthogonal to the crest and a second pair of edge surfaces generally aligned with the crest, the first pair of edge surfaces of each tile being adjacent and spaced-apart from the first edge surface of another tile, wherein the crest of the flight is provided with a wear-resistant surface.    
     
     
       18. The extruder screw of claim 17 wherein the tiles are brazed to the flight.  
     
     
       19. The extruder screw of claim 17 wherein the tiles are made of tungsten carbide.  
     
     
       20. The extruder screw of claim 17 wherein the tiles are ground to form a substantially continuous wear-resistant surface.  
     
     
       21. The extruder screw of claim 17, wherein each of the tiles has a generally flat top face and a generally flat bottom face, the bottom face being brazed to the crest of the flight.  
     
     
       22. An extruder screw comprising:
 a shaft;   a flight extending helically about the shaft, the flight having a crest; and   a plurality of generally flat, rectangular hard metal tiles brazed to the crest of the flight, each tile having a top face, a bottom face, a first pair of surfaces disposed generally orthogonal to the crest, and a second pair of surfaces disposed generally aligned with the crest, the first pair of surfaces of each tile being adjacent and spaced-apart from the first surface of another tile, wherein the crest of the flight is provided with a wear-resistant surface.    
     
     
       23. The extruder screw of claim 22 wherein the tiles are made of tungsten-carbide.  
     
     
       24. The extruder screw of claim 22 wherein the crest is ground to form a substantially continuous wear-resistant surface.