Extruder and method of extrusion

Abstract

An extruder includes a container having a main bore for receiving billets, a die and a piston. The container is formed with at least one gas release vent opening into the main bore at a position intermediate between the extruding end of the bore and a midpoint of the bore's length. Each gas release vent has a valve for allowing selective release of trapped gas. This structure allows venting of gases in such a manner as to allow sequential loading of billets without removal of scrap between them.

What is claimed is:  
     
         1 . An extruder comprising: 
 (a) a container having a main bore for receiving billets, said main bore having a loading end and an extruding end separated by a length;    (b) at least one die associated with said extruding end of said main bore; and    (c) a piston deployed for forcing a billet along said main bore towards said extruding end, wherein said container is formed with at least one gas release vent opening into said main bore at a position intermediate between said extruding end and a midpoint of said length, each of said gas release vents being provided with a valve deployable between an open state for allowing release of trapped gas and a closed state for preventing penetration of material from the billets into said at least one gas release vent.    
     
     
         2 . The extruder of  claim 1 , wherein said at least one gas release vent is implemented as a plurality of gas release vents spaced along at least one line between said extruding end and said midpoint of said length.  
     
     
         3 . The extruder of  claim 1 , wherein said at least one gas release vent includes a plurality of gas release vents opening into said main bore substantially along the top of said main bore.  
     
     
         4 . The extruder of  claim 1 , wherein said at least one gas release vent includes a plurality of gas release vents opening into said main bore at a plurality of different angular positions around the surface of the main bore.  
     
     
         5 . The extruder of  claim 1 , wherein said main bore has a first internal diameter adjacent to said loading end and a second internal diameter adjacent to said extruding end, said second internal diameter being larger than said first internal diameter.  
     
     
         6 . The extruder of  claim 5 , wherein said main bore has a first portion extending substantially from said loading end along at least to said midpoint, said first portion being substantially cylindrical with said first internal diameter, and wherein said main bore has a second portion extending substantially from said first portion to said extruding end, said second portion having a gradually increasing internal diameter.  
     
     
         7 . The extruder of  claim 6 , wherein said second portion has a substantially conical internal surface.  
     
     
         8 . The extruder of  claim 7 , wherein said substantially conical internal surface has a conical angle of between about 1° and about 10°.  
     
     
         9 . A method of producing an extruded profile using an extruder including a container with a main bore, the main bore having a loading end and an extruding end separated by a length, the container being formed with at least one selectively openable gas release vent opening into the main bore at a position intermediate between the extruding end and a midpoint of the length, the method comprising: 
 (a) introducing into the main bore a first billet;    (b) forcing the first billet towards the extruding end so as to force material from the billet through a die associated with the extruding end of the bore;    (c) while material from the first billet remains within the main bore, introducing a second billet into the main bore;    (d) pressing the second billet towards the material from the first billet so as to cause joining of the material from the first billet and the second billet;    (e) opening the at least one gas release vent so as to release gas trapped within the main bore; and    (f) forcing the second billet towards the extruding end so as to force material from both the first and second billets through the die.    
     
     
         10 . The method of  claim 9 , wherein said opening is performed using a plurality of gas release vents spaced along at least one line between the extruding end and the midpoint of the length.  
     
     
         11 . The method of  claim 9 , wherein said opening is performed using a plurality of gas release vents opening into said main bore substantially along the top of said main bore.  
     
     
         12 . The method of  claim 9 , wherein said opening is performed using a plurality of gas release vents opening into said main bore at a plurality of different angular positions around the surface of the main bore.  
     
     
         13 . The method of  claim 9 , wherein the main bore has a larger internal diameter adjacent to the extruding end than adjacent to the loading end.  
     
     
         14 . The method of  claim 13 , wherein the main bore has a portion of gradually increasing internal diameter from a location between the midpoint and the extruding end extending substantially to the extruding end.  
     
     
         15 . The method of  claim 14 , wherein said second portion has a substantially conical internal surface.  
     
     
         16 . The method of  claim 15 , wherein said substantially conical internal surface has a conical angle of between about 1° and about 10°.  
     
     
         17 . The method of  claim 9 , further comprising preparing each billet prior to introduction into the main bore by removing material from at least a portion of an outer surface of the billet so as to increase smoothness of the billet.  
     
     
         18 . The method of  claim 9 , wherein the billets are aluminum billets.