Metal deforming – By use of closed-die and coacting work-forcer – Forcing work into or within closed die; e.g. – forging
Reexamination Certificate
1999-03-16
2001-01-30
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Forcing work into or within closed die; e.g., forging
C029S893340
Reexamination Certificate
active
06178801
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a forging device for forming a helical gear having crown-shaped teeth with the tooth thicker in the axial direction center of the twisted tooth than at both axial direction ends.
A prior art is disclosed in JP-B-6-98449. That is, a helical gear forging device in which a die having twist forming teeth is fitted for vertical sliding in the axially central part of a die holder through downward diminishing taper surfaces, a cylindrical material is placed on the die, and the device comprises a first and a second punches for pressing the material and the die from above, a counter punch in engagement with the lower end part of the die to restrict the downward movement of the material, and a rotary device for rotating the die holder in the direction opposite the direction in which the material is rotated with the die.
The above-described device of the prior art is the one in which the material is forced into the die, and twist teeth are formed on the outside circumferential surface of the material. Therefore, the thickness of the formed twist tooth is nearly constant over its entire length.
SUMMARY OF THE INVENTION
It is therefore, an object of the invention is to provide a novel forging device for forming a helical gear having crown-shaped teeth with the tooth thicker in the axial direction center of the twist tooth than at both axial direction ends.
This invention is constituted as describe below to accomplish the above-mentioned object. That is, the invention is constituted that, for forging a crown-shaped gear, crown twist forming teeth are formed on the inside circumferential surface of a finishing die with the thickness of each tooth being thinner in the middle part than toward both axial direction ends, the finishing die is fitted for axial sliding in the axial direction in the axially central part of a die holder through taper surfaces diminishing from its one end to the other, a half-finished work with its outside circumferential surface having rough-formed twist teeth is brought into screw engagement with the finishing die, and a first punch for pressing the half-finished work from one axial end toward the other, a second punch for pressing the finishing die from one axial end toward the other, and a rotary device for rotating the die holder in the direction opposite the direction in which the half-finished work is rotated with the finishing die when the first and second punches are working to press.
The invention is further constituted as above wherein the taper angle of the taper surface of the die holder is made slightly smaller than that of the taper surface of the finishing die.
The invention is still further constituted that the taper angle of the taper surface of the die holder is made slightly smaller on the small diameter side with respect to an apex in the approximate center in its axial direction than the taper angle of the taper surface of the finishing die, and is made slightly larger on the larger diameter side than the taper angle of the taper surface of the finishing die.
The invention is yet further constituted that the second punch presses the finishing die in the axial direction from one end to the other when the half-finished work is located in the middle part in the axial direction of the finishing die.
The invention is in addition constituted that the rotary device is provided with the die holder and a punch holder for axially moving together with the first and second punches, with one of them being formed with lead grooves tilted to the direction of twist of the crown twist forming tooth, and with the other of them being provided with guide pins or rollers for fitting into the lead grooves.
The invention is also constituted that a core is fitted to be immovable in the axial direction in the axially central part of the finishing die, a cylindrical half-finished work having rough-formed twist teeth on its outside circumferential surface and an axial hole in its axially central part is provided, the half-finished work is fitted between the finishing die and the core, and the first and second punches are provided to press the half-finished work and the finishing die axially from one end to the other.
The invention is additionally further constituted that a solid cylindrical half-finished work with its outside circumferential surface having rough-formed twist teeth is brought into screw engagement with the finishing die, a first and the second punches are provided to press a half-finished work and the finishing die axially from one end to the other, a counter punch in engagement with the other end part of the finishing die and for restricting the axial movement of the half-finished work is provided, and a rotary device is provided to rotate the die holder in the direction opposite the direction in which the half-finished work is rotated with the finishing die when the first and second punches are working to press.
REFERENCES:
patent: 1338462 (1920-04-01), Rydbeck
patent: 3-8519 (1991-01-01), None
patent: 3-32436 (1991-02-01), None
patent: 4-197547 (1992-07-01), None
Arent Fox Kintner & Plotkin & Kahn, PLLC
Larson Lowell A.
Ohashi Technica, Inc.
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