Composite gear having carburized teeth and method of making same

A method of making a composite gear comprising the steps of:

• providing a circular gear ring having an inner surface and an outer surface comprised of a plurality of gear teeth and a circular gear hub having a pair of axially facing sides and an outer surface, said inner and outer surfaces each having midportions and axially adjacent portions;
• positioning said hub within said gear ring so that midportions of said hub outer and ring inner surfaces are in pressure abutment;
• welding said ring to said hub at a line axially spaced from each axial edge of said abutting midportion, and
• cooling said welded gear and hub whereby upon cooling, said welded portions are placed in radial tension and said midportions are in pressure abutment.

A method of assembly of a gear wherein said gear comprises an annular gear ring having teeth formed in the outer surface thereof and an cylindrical inner surface, and a gear hub having first and second parallel sides and an outer cylindrical surface extending therebetween, said hub outer surface having an interference fit with said ring inner surface, said hub also having first and second annular flanges extending both radially and axially outwardly from an area on said first and second sides respectively inwardly of said hub outer surface, said method comprising the steps of:

• carburizing at least said teeth of said gear ring;
• locating said hub coaxially within said ring;
• welding said first annular flange to said inner surface of said ring and
• welding said second annular flange to said inner surface of said ring whereby upon the cooling of said welds, any distortion of said teeth or said gear ring caused by the step of carburizing is removed.

In the assembly of a large diameter bull gear comprising a gear ring having a toothed outer surface and an inner surface comprised of a cylindrical abutment area having an inner diameter and axially adjacent first and second cylindrical welding portions having unequal first and second diameters respectively both of which are less than said inner diameter and a hub portion having a coaxial interference fit with said inner diameter;

• said hub portion having a pair of axially facing circular sides and an outer surface extending therebetween and a pair of annular flanges extending both radially and axially outwardly from opposite sides of said hub at a point inwardly of said outer surface, a method comprising the steps of:
• carburizing said gear ring;
• removing a portion of said inner surface at said first diameter so that a first cylindrical welding surface having a diameter greater than said first diameter but less than said inner diameter remains thereby creating a stepped shoulder between said first welding surface and said mating portion;
• removing said second inner portion so that a second welding surface is created having a diameter equal to said inner diameter;
• positioning said gear hub within said gear ring adjacent said shoulder;
• welding said first annular flange to said first welding surface and,
• welding said second annular flange to said second welding surface.