Gear tooth design

Abstract

A new gear design providing increased load-carrying ability while being particularly adaptable to manufacture by lower-cost forming methods with powder metal or plastic materials. The teeth of the gears are unconventional in appearance, having a generally elliptical face outline formed by oppositely curved root and topland lines so that the height of each tooth face is maximum at midpoint and reduces substantially to zero at the length extremeties. The teeth are substantially inclined .Iadd.depthwise .Iaddend.to the pitch .[.line.]. .Iadd.element .Iaddend.and each gear has a large and small end, the tooth slots being invisible when the finished gear is viewed along its axis from the large end. The disclosure includes constructions and calculations for designing conjugate pairs of such unconventionally-shaped gears having preferred running characteristics.

What is claimed is: 
     
       1. A gear of a mating gear pair having engaging tooth profiles, said gear comprising tooth and slot configurations in which: a. the root lines are concave curves,   b. the topland surfaces of the teeth are convex curves, .[.substantially parallel to the root lines of the mating gears.].   c. the maximum tooth height is substantially at mid-length of each tooth,   d. said tooth height reduces substantially to zero at the length extremities, and   e. the working areas of .[.the teeth.]. .Iadd.each tooth .Iaddend.are inclined .Iadd.depthwise .Iaddend.to the pitch .[.line.]. .Iadd.element.Iaddend..   
     
     
       2. A gear according to claim 1 in which the tooth slots are invisible when said gear is viewed axially from one of its ends. 
     
     
       3. A gear according to claim 1 wherein said mating gear pair is a pair of bevel gears whose pitch apex lies on the axis of imaginary generating crown gears and wherein .[.planes tangent to the tooth profiles at the pitch line on.]. .Iadd.plane tooth surfaces of said crown gears which generate .Iaddend.alternate sides of a tooth slot intersect in a line, said line intersecting said crown gear axis at a point remote from the pitch apex of said gear pair. 
     
     
       4. A gear according to claim 3 in which the radius of concavity of the root line of said gear is less than the length of a radial line from the axis of rotation of said gear to the centroid of its working tooth area. 
     
     
       5. A gear according to claim 1 wherein said concave and convex curves are substantially circular arcs. 
     
     
       6. A bevel gear of a mating gear pair having engaging tooth profiles, said bevel gear comprising tooth and slot configurations in which: a. the root lines are concave curves,   b. the topland surfaces of the teeth are convex curves, .[.substantially parallel to the root lines of the mating gear.].   c. the maximum tooth height is substantially at mid-length of each tooth,   d. said tooth height reduces substantially to zero at the length extremities, and   e. the working areas of .[.the teeth.]. .Iadd.each tooth .Iaddend.are inclined .Iadd.depthwise .Iaddend.to the pitch .[.line.]. .Iadd.element.Iaddend. .   
     
     
       7. A bevel gear according to claim 6 in which the tooth slots are invisible when said bevel gear is viewed axially from one of its ends. 
     
     
       8. A bevel gear according to claim 6 wherein said concave and convex curves are substantially circular arcs. 
     
     
       9. A cylindrical gear of a mating cylindrical gear pair having engaging tooth profiles, said cylindrical gear comprising tooth and slot configurations in which: a. the root lines are concave curves,   b. the topland surfaces of the teeth are convex curves, .[.substantially parallel to the root lines of the mating gear.].   c. the maximum tooth height is substantially at mid-length of each tooth,   d. said tooth height reduces substantially to zero at the length extremities, and   e. the working areas of .[.the teeth.]. .Iadd.each tooth .Iaddend.are inclined .Iadd.depthwise .Iaddend.to the pitch .[.line.]. .Iadd.element.Iaddend..   
     
     
       10. A cylindrical gear according to claim 9 in which the tooth slots are invisible when said gear is viewed axially from one of its ends. 
     
     
       11. A cylindrical gear according to claim 9 wherein said concave and convex curves are substantially circular arcs.