US 6,442,992 B1 · Hollow rack shaft and method of manufacturing the same

Abstract

In a method of manufacturing a hollow rack shaft, an approximately rectangular plate having a wide rack tooth portion, is bent lengthwise into a gutter-like cross section to provide: at the central portion, a flat bottom portion on which rack teeth are formed later and a pair of mutually facing leg portions, and, in the vicinity of both ends, a semicircular bottom portion and a pair of mutually facing leg portions. The mutually facing leg portions at the central portion have a larger clearance than the clearance of the mutually facing leg portions in the vicinity of both ends. The rack teeth are then formed on the flat bottom portion through the plastic flow of the flat bottom portion and a part of material of the pair of leg portions of this flat bottom portion. The gutter-shaped plate, on which the rack teeth have been formed, is then formed into a tube having a hollow inner surface, by bending the plate and butt joining the edge portions.

Claims14

Dependent claims

A tubular rack shaft having a longitudinal axis, an inner tubular surface, and an outer tubular surface, said tubular rack shaft comprising:

first and second longitudinally extending tubular end portions;
a longitudinally extending tubular intermediate portion connecting said first and second tubular end portions, said intermediate portion having a longitudinally extending rack tooth portion plastically formed therein, said rack tooth portion comprising a rack tooth bottom having rack teeth extending transversely with respect to the longitudinal axis of the rack shaft;
wherein a portion of said inner tubular surface corresponding to the rack teeth has a width perpendicular to the longitudinal axis of the rack shaft which is greater than a width determined by inside radius R of the tubular rack shaft, position X of the inner tubular surface of the rack tooth bottom, and plate thickness t of the rack tooth bottom.

A tubular rack shaft having a longitudinally extending intermediate portion joining first and second longitudinally extending end portions, wherein said longitudinally extending intermediate portion has rack teeth, wherein each of said first and second longitudinally extending end portions is a generally cylindrical tubular portion, and wherein said tubular rack shaft is manufactured through the following processes in order of mention:

a first process comprising bending an approximately rectangular plate, having a longitudinally extending intermediate portion joining longitudinally extending end portions, the longitudinally extending intermediate portion of said plate having a width which is greater than a width of either of said longitudinally extending end portions of said plate, to form a gutter-shaped workpiece having a longitudinally extending intermediate portion joining first and second longitudinally extending end portions, wherein the longitudinally extending intermediate portion of said workpiece has a flat bottom portion and a pair of mutually facing legs, wherein each of said longitudinally extending end portions of said workpiece has a semi-circular bottom portion and a pair of mutually facing legs, and wherein a distance between the mutually facing legs of the intermediate portion of said workpiece is greater than a distance between the mutually facing legs of each of the end portions of said workpiece;
a second process comprising press forming rack teeth extending transversely of said flat bottom portion by inserting a die between the legs of said longitudinally extending intermediate portion of said workpiece and pressing thus inserted die against an inner surface of said flat bottom portion to form an inner side of said rack teeth, and
a third process comprising converting said workpiece, having rack teeth formed therein, into a tubular shape by bending each pair of legs of said workpiece so as to butt together their free longitudinal edges and joining the thus butted edges.

A method of manufacturing a tubular rack shaft having a longitudinally extending intermediate portion joining first and second longitudinally extending end portions, wherein said longitudinally extending intermediate portion has rack teeth, and wherein each of said first and second longitudinally extending end portions is a generally cylindrical tubular portion, said method of manufacturing comprising following processes in order of mention:

a first process comprising bending an approximately rectangular plate, having a longitudinally extending intermediate portion joining longitudinally extending end portions, to form a gutter-shaped workpiece having a longitudinally extending intermediate portion joining first and second longitudinally extending end portions, wherein the longitudinally extending intermediate portion of said workpiece has a flat bottom portion and a pair of mutually facing legs, wherein each of said longitudinally extending end portions of said workpiece has a semi-circular bottom portion and a pair of mutually facing legs, and wherein a distance between the mutually facing legs of the longitudinally extending intermediate portion of said workpiece is greater than a distance between the mutually facing legs of each of the longitudinally extending end portions of said workpiece;
a second process comprising press forming rack teeth extending transversely of said flat bottom portion by inserting a die between the legs of said longitudinally extending intermediate portion of said workpiece and pressing thus inserted die against an inner surface of said flat bottom portion to form an inner side of said rack teeth;
and
a third process comprising converting said workpiece, having rack teeth formed therein, into a tubular shape by bending each pair of legs of said workpiece so as to butt together their free longitudinal edges.

1 more element

Dependencies are inferred from the claim text.

Hollow rack shaft and method of manufacturing the same

Life of this patent

Hollow rack shaft and method of manufacturing the same

Life of this patent

Abstract

Claims14