Metal deforming – By application of fluent medium – or energy field – With cutting
Reexamination Certificate
2001-11-30
2002-06-11
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With cutting
C072S056000, C029S421100, C083S053000
Reexamination Certificate
active
06401507
ABSTRACT:
TECHNICAL FIELD
This invention relates to method and apparatus for hydroforming, indie hydropiercing and slug ejecting and more particularly to the manner of hydroforming, in-die hydropiercing and slug ejecting using a die button, backup plunger and slug ejector all mounted in one of two dies that form the hydroforming cavity in which a part is both formed and pierced.
BACKGROUND OF THE INVENTION
Prior to the present invention, it was known to provide in-die hydropiercing and slug-ejecting apparatus as disclosed in U.S. Pat. No. 5,398,533 assigned to the assignee of this invention. In that apparatus, the hydroforming fluid pressure forming the part is also utilized to blowout and thereby pierce a hole in the part with the aid of a die button mounted in the lower one of the two dies forming the hydroforming cavity. And this is accomplished without jeopardizing the hydroforming process and without incurring significant hydroforming fluid leakage. Such apparatus also has provision for ejecting the slug produced from forming the hole.
In the above U.S. Patent, the die button is mounted in the lower die with an outer end flush with the cavity surface of the lower die at the location where the hole is desired in the part. The desired hole shape is circular and for that purpose the die button has a round, centrally located cylindrical piercing hole with a sharp cutting edge at its outer end. The die button is further provided with a cylindrical bore of larger diameter than the piercing hole and immediately below the latter. And a backup plunger is received in the die button bore having an outer end that is initially positioned in a flush position in the piercing hole with respect to the cutting edge of the latter and then in a retracted or piercing position in the bore below the piercing hole by mechanical means in the form of a cam operated mechanism. And an elastomeric seal received on the plunger below its outer end remains in sealing contact with the die button bore during plunger movement to prevent hydroforming fluid leakage past the plunger during piercing.
The lower die is further provided with an ejection chute that is open at one end to the die button bore and at an opposite end exits this die. And the plunger is further retractable to an ejecting position where the above mentioned plunger seal moves past and the outer end of the plunger is located immediately below the opening to the ejection chute.
In the operation of the above apparatus, the dies are closed about the part to be formed and while the upper end of the plunger is held in its flush position in the die button, hydroforming fluid at a high pressure is supplied to the interior of the part forcing it to expand outwardly and conform to the die cavity and the outer end of the plunger. The plunger is then retracted to the piercing position allowing the hydroforming pressure to blow out a slug through and past the cutting edge of the die button and onto the outer end of the plunger where it then rests free of the larger diameter die button bore.
Following the piercing of the slug, the hydroforming fluid is then exhausted from the part and while the dies remain closed about the part, the plunger is then further retracted to its ejecting position where the slug which is resting thereon is ejected by an ejector mechanism onto the ejection chute and slides down by the force of gravity to exit the lower die.
Since the die button has only one cutting edge it must be replaced with wear. Furthermore, the piercing is performed with the hydroforming pressure used to form the part and thus imposes a significant sealing burden on the plunger to prevent leakage there past. Moreover, since the plunger seal must pass over the opening to the ejection chute, such action can cause excessive wear of the seal forcing its early replacement.
SUMMARY OF THE INVENTION
The method and apparatus according to the present invention is a significant improvement over such prior method and apparatus. And in describing the invention, it will be understood that the terms “prepiercing” and “hydroprepiercing” are used herein interchangeably to describe an operation wherein the hydroforming fluid pressure forming the part is utilized to stretch the region in the part to be pierced only partially into a die button without actually piercing or penetrating this region of the part. With the actual piercing then following this operation at a reduced hydroforming fluid pressure to significantly reduce the sealing requirements of the plunger to prevent leakage there past.
With that understanding, the present invention is directed to an in-die hydroprepiercing, hydropiercing and slug-ejecting method wherein a quick change reversible die button insert is fastened to a cylinder fixed in the lower one of two dies that form the die cavity. And a backup plunger is mounted in the fixed cylinder for effecting hydroprepiercing a region of the part, hydropiercing a hole in this thus weakened region, and finally ejecting the slug produced from the piercing. For such purposes, the plunger has a small diameter end portion closely received in the die button, a large diameter end portion located below the lower end of the fixed cylinder and closely received in a moveable cylinder, and an intermediate portion of intermediate diameter closely received in the fixed cylinder. The small diameter end portion of the plunger has an end face that is flush with the die button when the plunger is in a hydroforming/slug-ejecting position determined by the large diameter end portion of the plunger abutting with an adjusting collar that is fastened to and axially adjustable with respect to the moveable cylinder and is abuttable with an inner end of the fixed cylinder. In the plunger hydroforming/slug-ejecting position, the plunger end face together with the outer side of the die button and outer annular edge of the fixed cylinder form an uninterrupted continuation of the die cavity surface in the lower die.
The cylinder in which the large diameter plunger end portion is received is moveable between a hydroforming/prepiercing/slug-ejecting conditioning position and a piercing conditioning position by a hydraulically operated actuator operated with the hydroforming fluid rather than a separate hydraulic power supply. The plunger is moved to and held in its hydroforming/slug-ejecting position during the hydroforming of the part by supplying the hydroforming fluid to the moveable cylinder actuator to extend the moveable cylinder to and hold it in its hydroforming/prepiercing/slug-ejecting conditioning position and also supplying the hydroforming fluid to act on the large diameter plunger end portion to extend and hold the plunger in its hydroforming/slug-ejecting position. While the moveable cylinder remains in its hydroforming/prepiercing/slug-ejecting conditioning position, the pressure in the moveable cylinder is released allowing the plunger to retract to a prepiercing position in the die button by the force of the hydroforming pressure in the part pressing a region of the part outward against the plunger end face and as a result stretching this region of the part partially into the die button and thus weakening this region but not piercing same.
The hydroforming pressure in the part is then reduced to a pressure just sufficient to pierce the weakened region when left unsupported by the plunger. And the plunger is then allowed to further retract to its piercing position in the die button when the moveable cylinder is retracted to its piercing conditioning position by releasing the hydroforming pressure in its actuator. This allows the plunger to again be retracted but now by the force of the reduced hydroforming pressure in the part pressing outward against the plunger end at the previously weakened region and as a result then piercing a slug cleanly from the part and onto the plunger end face to form the desired hole. And because the hydroforming pressure in the part has been significantly reduced for the piercing operation, the hydroforming fluid is less prone to leak past the plunger
Ghiran Mircea M
Gmurowski Romuald
Krcek Glenn Mark
Shimanovski Bruce Steven
General Motors Corporation
Jones David
Leahy Charles E.
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