Metal deforming – Tool and/or tool holder – Tool comprising closed periphery deforming passageway
Reexamination Certificate
2000-02-23
2002-04-16
Larson, Lowell A. (Department: 3725)
Metal deforming
Tool and/or tool holder
Tool comprising closed periphery deforming passageway
C072S357000, C072S478000
Reexamination Certificate
active
06370933
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to dies and methods for forming parts, and more particularly, to dies and methods for reducing or controlling the formation of flash on parts.
Horizontal split dies typically include a lower die half and an upper die half which together define an inlet, a cavity corresponding to the shape of the desired part, and an outlet. In addition, matingly-engaging portions of the lower die half and the upper die half form a parting-line therebetween.
To form a part, a workpiece is placed in the inlet and pushed through the cavity of the dies by, for example, a forge press. During this extrusion process, large pressures are developed. When the pressure becomes too high, portions of the workpiece are forced between the lower and upper die halves along the parting line.
The resulting thin slab of material formed along the parting line, which remains in contact with the workpiece, is referred to as flash. Flash is undesirable, and therefore, is generally removed via manual grinding operations, which are labor intensive and add to the production cost of the part.
There is a need for dies and methods for reducing, eliminating, or controlling the formation of flash on parts.
SUMMARY OF THE INVENTION
The present invention in one aspect, provides a die for forming a part in which the die includes a first die section and a second die section defining a cavity therein for forming the part. The first die section and the second die section have a first surface and a second surface, respectively, which together define a parting line. The first die section includes a land defining a first surface portion of the first surface. The land is sized and configured so that a stress on the first surface portion is substantially equal to and less than an elastic limit of the land when the first surface portion is engaged with the second surface and the first die section and the second die section are held together with a predetermined force during the forming of the part.
In another aspect of the present invention, the first surface includes a second surface portion offset from the first surface portion so that when the first die section and the second die section are held together with the predetermined force during the forming of the part, the second surface portion engages the second surface and the stress on the first surface portion is substantially equal to and less than an elastic limit of the land.
In another aspect of the present invention, a die for forming a part includes a first die section and a second die section defining a cavity therein for forming the part. The first die section and the second die section each have a first surface and a second surface, respectively, which together define a parting line having at least one bend for controlling the formation of flash when forming the part.
Still other aspects of the present invention include methods for forming such dies and methods for forming a part and reducing or controlling the formation of flash.
REFERENCES:
patent: 3089591 (1963-05-01), Groos
patent: 3679345 (1972-07-01), Malutich
patent: 4359443 (1982-11-01), Michaels
patent: 5956993 (1999-09-01), Akamatsu
patent: 747558 (1980-07-01), None
Girard Alain
Karafillis Apostolos Pavlos
Majorell Arne Ronald
Mika David Peter
Clarke Penney
Ingraham Donald S.
Larson Lowell A.
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