US 4,132,090 A · Crowned involute splines and method of making

Abstract

An improved drive shaft is disclosed of the type used in a rotary fluid pressure device including an input-output shaft and a gerotor gear set having an externally toothed member which orbits and rotates within an internally toothed member. Both the input-output shaft and the externally toothed member define straight internal splines, and the drive shaft includes a set of crowned, involute external splines at each end thereof, in engagement with the respective straight internal splines. The crowned external splines are hobbed with a hob on which the cutter teeth have a pressure angle .phi..sub.H greater than the primary pressure angle .phi..sub.S of the crowned splines. The increased pressure angle .phi..sub.H of the cutter teeth makes it possible to reduce the crown angle on the splines, while still maintaining the necessary clearance X between each external spline and the adjacent internal spline at any given axial distance Y along the external spline from the central plane. Reducing the crown angle makes it possible either to increase the length of the external splines for a given shank diameter, or to increase the shank diameter for a given spline length. In either case, the result is an increase in the torque carrying capacity of the shaft by a factor F, wherein F equals the ratio of sin .phi..sub.H /sin .phi..sub.S.

Claims12

Dependent claims

A method of making an improved drive shaft of the type having first and second sets of axially-disposed external crowned splines for transmitting torque between first and second sets of internal straight splines;

the sets of internal straight splines defining an eccentricity E;
each of the sets of external crowned splines defining a central plane oriented generally perpendicular to the axis of said shaft;
said shaft defining an axial length L between said first and second central planes and a running angle A wherein A = arcsin E/L;
each of said external splines having a primary pressure angle .phi..sub.S and being crowned an amount sufficient to provide a clearance X between the external spline and the adjacent internal spline at any given axial distance Y along the external spline from the central plane, the clearance X and distance Y being related by the equation X = Y tan A, the method comprising:
providing a hob cutter having cutter teeth with a pressure angle .phi..sub.H, wherein .phi..sub.H is greater than .phi..sub.S ;
rotating said hob cutter to effect hobbing of said splines;
simultaneously with the preceding step feeding said hob cutter along the length of said external splines, the axis of said hob cutter following a path defined by a variable dimension Z, Z being the radially inward movement of the hob cutter axis from a reference line toward the axis of said shaft and conforming to the following equation:
Z = Y tan A/sin .phi..sub.H .

5 more elements

A method of making a drive shaft having its torque carrying capacity increased by a factor F, the drive shaft having a set of external crowned splines and an axially-disposed universal connection for transmitting torque between a set of internal straight splines and means adapted to receive said universal connection;

the set of straight splines and the receiving means defining an eccentricity E;
said set of crowned splines defining a central plane oriented generally perpendicular to the axis of said shaft;
said shaft defining an axial length L between said central plane and the pivot point of the universal connection and further defining a running angle A wherein A = arcsin E/L;
each of said external splines having a spline length T and a primary pressure angle .phi..sub.S and having a crown angle sufficient to provide a clearance X between the external spline and the adjacent internal spline at any given axial distance Y from the central plane, the clearance X and distance Y being related by the equation X = Y tan A, the method comprising:
providing a hob cutter having cutter teeth defining a pressure angle .phi..sub.H, wherein .phi..sub.H is greater than .phi..sub.S ;
rotating said hob cutter in a manner to effect hobbing of said splines;
and simultaneously with the preceding step feeding said hob cutter along the portion of said shaft adapted to include said external crowned splines, the axis of said hob cutter following a path defined by the equation:
Z = Y tan A/sin .phi..sub.H
for Y equal to or greater than 0 and equal to or less than T/2, wherein Z is the radially inward displacement of the hob cutter axis from a reference line on which Z = 0 when Y = 0,
whereby the torque increase factor F equals sin .phi..sub.H /sin .phi..sub.S.

7 more elements

Dependencies are inferred from the claim text.

Crowned involute splines and method of making

Life of this patent

Crowned involute splines and method of making

Life of this patent

Abstract

Claims12