Machine and process for forming longitudinally curved tooth gears

A method of forming longitudinally curved tooth gears comprising the steps of:

• mounting a work gear on a work support;
• mounting a dish-shaped tool on a tool support;
• rotating said dish-shaped tool about an axis passing substantially through the center of said tool;
• relatively oscillating said tool with respect to said work support about a cradle axis which extends substantially perpendicular to the lengthwise direction of a tooth to be formed in said work gear;
• relatively reciprocating said work support with respect to said tool in a direction substantially along said cradle axis in a timed relationship with said step of oscillating said tool for defining a working path of said tool and
• controlling said timed relationship to effect a relative withdrawal of said cradle axis for reducing longitudinal mismatch between mating tooth surfaces of longitudinally curved tooth gears.

A bevel or hypoid gear having longitudinally curved teeth formed according to a method comprising the steps of:

• mounting a work gear on a work support;
• mounting a dish-shaped tool on a tool support;
• rotating said dish-shaped tool about an axis passing substantially through the center of said tool;
• relatively oscillating said tool with respect to said work support about a cradle axis which extends substantially perpendicular to the lengthwise direction of a tooth to be formed in said work gear;
• relatively reciprocating said work support with respect to said tool in a direction substantially along said cradle axis in a timed relationship with said step of oscillating said tool for defining a working path of said tool;
• controlling said timed relationship to effect a relative withdrawal of said work support along said cradle axis with respect to the relative angular displacement of said tool about said cradle axis for reducing longitudinal mismatch between mating tooth surfaces of longitudinally curved tooth gears;
• said working path being further defined by a center and two end positions corresponding to relative angular displacement of said tool about said cradle axis;
• and
• said timed relationship being further controlled to effect an increase in the rate of relative withdrawal of said work support as a function of the relative angular displacement of said tool along first portions of said working path defined between said center and each of said end positions followed by a decrease in the rate of relative withdrawal of said work support along second portions of said working path between said first portions and each of said end positions.