Method and apparatus for forging gear teeth

Abstract

A forged gear and a method of manufacture thereof. The forged gear comprises a bevel gear with a plurality of teeth, each tooth having a tip disposed between two faces and two ends, the two faces extending in a substantially longitudinal direction of the tooth, wherein the tip of each tooth has at least one substantially crowned portion between the two ends along the longitudinal direction. The method of manufacture comprises forging the gear from a blank such that during the forging operation a substantial portion of the length of each forged tooth tip does not contact the die cavity.

1 . A forged bevel gear having a plurality of teeth, each tooth having a tip disposed between two faces and two ends, said two faces extending in a substantially longitudinal direction of said tooth, characterised in that said tip has at least one substantially crowned portion between said two ends along said longitudinal direction.  
   
   
       2 . A forged gear as claimed in  claim 1 , wherein said crowned portion is forged as a smooth continuous surface.  
   
   
       3 . A forged gear as claimed in  claim 1 , wherein said substantially longitudinal direction of said tooth lies along a substantially radial direction.  
   
   
       4 . A forged gear as claimed in  claim 3 , wherein said radial direction is curvilinear.  
   
   
       5 . A forged gear as claimed in  claim 3 , wherein said radial direction is straight.  
   
   
       6 . A forged gear as claimed in  claim 2 , wherein said at least one crowned portion is two crowned portions.  
   
   
       7 . A forged gear as claimed in  claim 6 , wherein a central portion is located between said two crowned portions, and said central portion is any one of a substantially flat portion, a slightly rounded portion or a rounded portion.  
   
   
       8 . A forged gear as claimed in  claim 6 , wherein a substantially concave portion is centrally located between said two crowned portions.  
   
   
       9 . A forged gear as claimed in  claim 1 , wherein at least one flat is machined onto said gear between said at least one substantially crowned portion and one of said ends.  
   
   
       10 . A forged gear as claimed in  claim 1 , wherein at least 25% of the length of said tip is crowned.  
   
   
       11 . A forged gear as claimed in  claim 1 , wherein at least 50% of the length of said tip is crowned.  
   
   
       12 . A method of forging a gear from a blank, said gear having a plurality of teeth, each said tooth having a tip disposed between two faces and two ends, said two faces extending in a substantially longitudinal direction of said tooth, said method comprising the steps of: 
 i) placing said blank within a die means comprising a cavity having a shape that is the near obverse of said teeth; and    ii) forging said blank within said cavity to form said teeth thereon;    characterised in that during said forging, a substantial portion of the length of each said tip does not contact said cavity.    
   
   
       13 . A method of forging a gear as claimed in  claim 12 , wherein said substantial portion is at least fifty percent of the length of said tip.  
   
   
       14 . A method of forging a gear as claimed in  claim 12 , wherein said substantial portion is at least sixty percent of the length of said tip.  
   
   
       15 . A method of forging a gear as claimed in  claim 12 , wherein said substantial portion is at least seventy-five percent of the length of said tip.  
   
   
       16 . A method of forging a gear as claimed in  claim 12 , wherein said tip has at least one substantially crowned portion between said two ends along said longitudinal direction.  
   
   
       17 . A method of forging a gear as claimed in  claim 12  wherein said gear is a bevel gear.  
   
   
       18 . A forged gear manufactured by the method of  claim 12 .  
   
   
       19 . A forged bevel gear having a hypoid configuration for use in a vehicle power transmission, said gear comprising a plurality of teeth, each tooth having a tip disposed between two faces and two ends, said two faces extending in a substantially radial direction, characterised in that said tip has at least one substantially crowned portion between said two ends along said radial direction.  
   
   
       20 . A forged gear manufactured by the method of  claim 13.