Metal deforming – By application of fluent medium – or energy field – With actuated tool engaging work
Reexamination Certificate
2000-05-23
2001-01-23
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With actuated tool engaging work
C072S062000, C029S421100
Reexamination Certificate
active
06176114
ABSTRACT:
TECHNICAL FIELD
This invention relates to hydroforming and more particularly to sequential hydroforming a series of expansions in a tubular component.
BACKGROUND OF THE INVENTION
With the current method and apparatus a tube member is inserted into a die and the ends of the tube are engaged by sealing units. Fluid is introduced into the tube through the sealing units and pressurized to enforce stretching of the tube diameter to fill the die cavity which has the desired final shape of the expansion. Frequently in addition to and simultaneously with the pressurized fluid, an axial force is applied to one or both tube ends to assist in feeding material to the areas of expansion. This will reduce the tendency of the tube wall thickness to decrease as the diameter expands.
The currently employed technique has some serious disadvantages. The process is limited to expanding material into two adjacent cavities in the die when axial assist is employed. If the die has additional cavities, the material will be forced into the end cavities if conventional axial feed techniques are employed. The high pressure within the tube creates a large normal force between the tube and the die which results in large frictional forces when the tube diameter expands to abut the die surface. This is particularly true when the tube is attempting to expand into the center expansion cavities of the die. Another disadvantage is that the die must have at least the same length as the die. A further disadvantage is found in components having the expansion nodules formed at a distance from one end of the tube. This is related to the frictional forces that are created between the die and the tube as the fluid pressure therein is increased.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved method and apparatus for sequentially hydroforming a series of expanded areas on a tubular member.
In one aspect of the present invention, the expanded areas are formed singularly in sequential progression in a die cavity. In another aspect of the present invention, the tube material is fed into the die cavity from only one end. In yet another aspect of the present invention, the tube is fed axially into the die cavity independently of the pressure supply mechanism. In still another aspect of the present invention, the pressure supply mechanism comprises a seal component that sealingly engages the inner surface of the die. In still another aspect of the present invention, the tube is fed by a mechanism from a position external to the die cavity.
In yet still another aspect of the present invention, an axially moveable mandrel is disposed in the interior of the tube. In a further aspect of the present invention, the an axial feed mechanism is provided to move the mandrel and the tube in one axial direction during hydroforming and the mandrel in the opposite axial direction between forming steps. In a yet further aspect of the present invention, an axial movement mechanism is provided to move a portion of the pressure supply mechanism axially during the forming of an expansion area. In a still further aspect of the present invention, a pusher mechanism is provided to move the tube axially relative to the die during the hydroforming process. In a yet still further aspect of the present invention, a tube feed mechanism is provided at both ends of the tube and oppositely moveable mandrels are disposed for axial movement along the interior of the tube to position; and an interior pressure is supplied to sequentially form pairs of expanded areas.
Four embodiments of the invention are shown and described in the following description and drawings. In each of the embodiments, a die is provided with a plurality of recesses formed therein. A tubular member is positioned in a central longitudinal opening of the die and the die is closed. A sealing mandrel is disposed in the tube with one end thereof near the recess to be formed. Pressure is admitted to the interior of the tube to cause expansion thereof into the recess and the tube is simultaneously fed into the die by a pusher mechanism. The tube feed prevents the thinning of tube wall during expansion.
In one of the embodiments the tube feed is independent of the mandrel position control. In another embodiment the tube feed and mandrel move simultaneously during expansion of the tube and the mandrel is positioned independently of the tube feed between expansion operations. In yet another embodiment the tube feed mechanism operates on one end of the tube and the mandrel is positioned from the other end of the tube. With this embodiment the tube positioned at the mandrel end of the die and the die is moved relative to the mandrel to effectively cause the tube feed movement. In a further embodiment a tube feed mechanism and mandrel positioning control are disposed at both ends of the tube to permit the simultaneous expansion of two locations on the tube.
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General Motors Corporation
Jones David
Leahy Charles E.
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