Helical and spur gear drive with double crowned pinion tooth surfaces and conjugated gear tooth surfaces

Abstract

Helical or spur gear drive comprising a driven gear and driving gear wherein the driving gear has double crowned teeth defined as (i) an envelope to a family of surfaces generated by a skew or straight rack-cutter having a parabolic tooth profile in normal section and then (ii) as an envelope to a family of tool surfaces that are generated while the tool performs a plunging motion with respect to the driving gear in the direction of the shortest distance between the axes of rotation of the tool and the driving gear and tool plunging motion is varied by a parabolic function, whose variable is displacement of the tool in a direction parallel to the rotational axis of the driving gear. The driven gear has a tooth surface defined as the envelope to a family of surfaces generated by a rack-cutter which surface is parabolic cylinder or a plane. The generated pinion/gear tooth surfaces are in theoretical point contact at every instant and they produce a preselected parabolic function of transmission errors in the process of meshing. The pinion/gear exhibit reduced vibration and noise, reduced shift of bearing contact caused by misalignment, and reduced contact stresses due to convex-concave contact of tooth surfaces.