Flow formed gear

Abstract

A method of forming a ring gear from a ring blank includes providing a mandrel having a central axis and an outer annular forming surface. The outer annular forming surface defines a plurality of forming elements having a forming element axis offset from the central axis of the mandrel. The ring blank has a ring axis and is placed over the mandrel generally aligning the central axis of the mandrel with the ring axis of the ring blank. A roll is provided having a roll axis that is generally parallel with the element axis. The roll is forced radially inwardly while circumscribing the central axis. The roll pivots around the roll axis deforming the ring blank radially inwardly forming teeth on an inner surface of the ring blank that coaxial with the element axis and offset from the mandrel axis.

1 - 10 . (canceled) 
     
     
         11 . A method of forming a ring gear from a ring blank having a wall defining radially-spaced inner and outer annular surfaces, comprising the steps of:
 providing a mandrel having a central axis and an outer forming surface defining a plurality of forming elements, each forming element having a forming element axis angularly offset from the central axis of the mandrel;   disposing the ring blank in surrounding relationship with the outer forming surface of the mandrel;   providing a roll having a direction of rolling travel along which the roll and the mandrel move relative to each other that is substantially perpendicular to the forming element axis of the forming element interposed between the roll and the mandrel central axis;   applying a force on the ring blank radially inwardly relative to the mandrel central axis with the roll as the roll moves in its direction of rolling travel on the outer annular surface of the ring blank, thereby deforming the wall of the ring blank radially inwardly and forming a plurality of teeth with each tooth being spaced from the adjacent tooth on the inner annular surface of the ring blank, the formed tooth being substantially parallel with the forming element axis and angularly offset from the mandrel central axis.   
     
     
         12 . The method of  claim 11 , further comprising moving the roll and the mandrel relative to each other in a direction generally parallel with the mandrel central axis. 
     
     
         13 . The method of  claim 11 , wherein the step of providing a roll includes providing a roll having a roll axis about which the roll rotates that is substantially parallel with the forming element axis of the forming element interposed between the roll and the mandrel central axis. 
     
     
         14 . The method of  claim 11 , wherein said step of disposing the ring blank in surrounding relationship with the outer forming surface of the mandrel includes placing the inner annular surface of the ring blank in abutting relationship with a radially outermost portion of the outer forming surface of the mandrel. 
     
     
         15 . The method of  claim 11 , further comprising securing the ring blank upon the mandrel with an interference fit prior to applying a force on the ring blank with the roll. 
     
     
         16 . The method of  claim 11 , further comprising moving the roll and the mandrel relative to each other about and generally parallel with the mandrel central axis. 
     
     
         17 . The method of  claim 11 , wherein said step of deforming includes moving the roll and the mandrel outer forming surface relative to each other at a nonincreasing radial distance between the roll and the mandrel central axis. 
     
     
         18 . The method of  claim 11 , further comprising moving the roll and the mandrel relative to each other by rotating at least one of the roll and the mandrel while deforming the ring blank. 
     
     
         19 . The method of  claim 11 , further comprising moving the roll and the mandrel relative to each other in a direction generally parallel with the mandrel central axis and along the full extent of the ring blank. 
     
     
         20 . The method of  claim 11 , wherein said step of providing a roll is further defined by providing a plurality of rolls circumferentially spaced around the mandrel, each roll having a direction of rolling travel along which the respective roll and the mandrel move relative to each other that is substantially perpendicular to the forming element axis of the forming element interposed between that respective roll and the mandrel central axis, and further comprising moving the plurality of rolls and the mandrel relative to each other. 
     
     
         21 . The method of  claim 20 , wherein said step of deforming includes moving the plurality of rolls and the mandrel outer forming surface relative to each other at nonincreasing radial distances between the respective rolls and the mandrel central axis. 
     
     
         22 . A method of forming a ring gear from a ring blank having a central axis and inner and outer annular surfaces, comprising the steps of:
 providing a mandrel having a central axis and a generally cylindrical outer forming surface defining a plurality of circumferentially distributed forming elements located between radially inner and outer diameters of the mandrel, each forming element having a forming element axis angularly offset from the central axis of the mandrel;   disposing the ring blank about the mandrel and placing the inner annular surface of the ring blank in abutting relationship with the outer diameter of the mandrel, thereby defining a plurality of circumferentially distributed spaces radially inward of the inner annular surface of the ring blank;   providing a roll having a roll axis that is substantially parallel with the forming element axis of the forming element forming element interposed between the roll and the mandrel central axis;   forcing the ring blank radially inwardly relative to the mandrel central axis with the roll as the roll and the ring blank move relative to each other in a direction substantially perpendicular to the roll axis, thereby deforming the inner annular surface over and between the forming elements and forming gear teeth in the plurality of circumferentially distributed spaces, with each gear tooth being spaced from the adjacent tooth on the inner annular surface of the ring blank, the formed tooth being angularly offset from the ring blank central axis.   
     
     
         23 . The method of  claim 22 , wherein the ring blank and mandrel central axes are coaxial when the inner annular surface of the ring blank is in abutting relationship with the outer diameter of the mandrel. 
     
     
         24 . The method of  claim 22 , further comprising securing the ring blank to the mandrel with an interference fit prior to forcing the ring blank radially inwardly. 
     
     
         25 . The method of  claim 22 , further comprising moving the roll and the mandrel relative to each other in a direction generally parallel with the mandrel central axis. 
     
     
         26 . The method of  claim 22 , wherein the step of providing a roll includes providing a roll having a direction of rolling travel that is substantially perpendicular to the forming element axis of the forming element interposed between the roll and the mandrel central axis. 
     
     
         27 . The method of  claim 22 , wherein said step of deforming includes moving the roll and the mandrel outer forming surface relative to each other at a nonincreasing radial distance between the roll and the mandrel central axis. 
     
     
         28 . The method of  claim 22 , further comprising moving the roll and the mandrel relative to each other by rotating at least one of the roll and the mandrel while deforming the ring blank. 
     
     
         29 . The method of  claim 22 , further comprising the step of forming a substantially uniform outer annular surface on the ring blank with the roll while the roll and the mandrel move relative to each other. 
     
     
         30 . The method of  claim 22 , wherein said step of providing a roll is further defined by providing a plurality of rolls circumferentially spaced around the mandrel, each roll having a roll axis that is substantially parallel with the forming element axis of the forming element interposed between that respective roll and the mandrel central axis, and further comprising moving the plurality of rolls and the mandrel relative to each other.