Metal deforming – By use of non-deforming work-gripping clamp and relatively... – By individually non-deforming clamps
Reexamination Certificate
2000-02-11
2001-07-17
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
By individually non-deforming clamps
C072S299000
Reexamination Certificate
active
06260398
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a hollow extrusion bending apparatus and method. More particularly, the present invention relates to a hollow extrusion bending apparatus and method wherein the extrusion is bent in two perpendicular planes and twisted.
BACKGROUND OF THE INVENTION
In the metal forming arts, there are known a variety of stretch-forming techniques in which a workpiece, usually an elongated extrusion or a sheet-form member, is formed to the profile of a forming die surface in conjunction with the application to the workpiece of tension exceeding its yield point. The tension is applied along the line coinciding with the bend axis of the workpiece that is deformed during the forming process.
The known stretch-forming processes typically have been applied in the forming of aluminum alloy components such as elongated extrusion sections or thin section panels like those often used for aircraft fuselage skin.
One known stretch-forming process, for example, is often referred to as “stretch wrapping” or “stretch-wrap forming” and involves the application of mechanical tension to a workpiece to thereby stretch it during formation. Subsequently, while the tension is maintained, the workpiece is wrapped about a form die. When a hollow extrusion is bent over a form die without being under tension, the resulting compressive forces on the inner surface of the extrusion cause this inner surface to buckle or deform. The basic goal of stretch-wrap forming is to stretch the extrusion along its bend axis to a point where the inner surface will not deform when subsequently bent over a form die. Stretch-wrap forming may be well suited to forming a workpiece to long sweeping curvatures of liberal radii.
Other stretch-forming techniques include moving die arrangements, in which the gripping heads are stationary and the forming die is moved perpendicular into the workpiece. Another technique is radial draw forming, in which one grouping head and the die are mounted on a table that rotates to slowly draw the part under tension over the rotating die.
An advantage of the various stretch-forming processes may generally include a decrease or elimination of the buckling of the inner surface of the workpiece. Furthermore, the desired results may be achieved with only minimal reduction in workpiece section thickness, typically not exceeding a five percent reduction.
However, the above stretch-forming processes generally require an unacceptable amount of human interaction and may not be suitable for a mass production environment. Also, imparting additional bends or even twists in the extrusion typically requires additional, time-consuming process steps whereby the extrusion may be dismounted from one bending machine, remounted in another, and then bent again. These extra process steps slow down the overall extrusion forming process and can not easily be accomplished by an automated assembly line.
In view of the foregoing, a need has been recognized in connection with the provision of a multiple bend or twist apparatus and method for use in a mass production environment. The apparatus can be used with limited human interaction and is well suited to an automated environment. Generally, the apparatus and method may form more complex extrusions in one process step and in a decreased amount of time compared to current methods. The profiles of the various stretches, bends, and twists may be precisely controlled and need not be constant throughout the forming process.
SUMMARY OF THE INVENTION
The present invention, in accordance with at least one presently preferred embodiment, generally contemplates a method and apparatus for forming hollow extrusions with one or more bends and/or twists. Preferably, the apparatus can impart one or more of the forming operations described above in one process step. Typically, this process step can be largely automated, and the amount of stretch, bend, or twist can be precisely controlled and need not be constant throughout the forming process.
In one presently preferred embodiment, a hollow extrusion can be mounted with gripper mounts and then secured in the bending apparatus. With one mechanical motion, the apparatus may stretch the extrusion along its longitudinal axis and bend the extrusion in a plane that is perpendicular to that axis. The transfer of motion from the applied mechanical force to the stretching and bending process may be accomplished with a cam and follower arrangement.
In another presently preferred embodiment of the present invention, a single mechanical motion applied to the apparatus may be translated into a stretching of a mounted extrusion along its longitudinal axis as well as a twisting of the part around this same axis. This motion translation may be accomplished by any of a variety of commonly known processes in the mechanical or other engineering arts.
In still another presently preferred embodiment of the present invention, the apparatus and method may stretch a mounted extrusion along its longitudinal axis while bending the extrusion in one or more planes while also twisting the extrusion. An almost limitless combination of various bends and twists can be imparted to an extrusion in accordance with the present invention.
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Allison Blair T.
Cisko Larry W.
Graham William A.
Ringbloom Paul E.
Alcoa Inc.
Crane Daniel C.
Kucler Robert D.
Trempus Thomas R.
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