Patent EA-001686-B1 (EA)
Title: Method and apparatus for forming an elongated tubular metal member
Inventor: HORTON FRANK A
IPC: B21D26/02
Filed: 1998-07-13
Abstract: 1. A method of forming an elongated tubular metal member having a cross-sectional configuration such that it includes a first cross-sectional dimension which is greater than a second cross-sectional dimension orthogonal to said first cross-sectional dimension along an extent thereof, said method utilizing a die assembly having first and second die structures having surfaces cooperable to define a die cavity having a first cross-sectional dimension which is greater than a second cross-sectional dimension generally orthogonal to said first cross-sectional dimension, said method comprising: roll-forming sheet metal to form a tubular metal blank having an oval cross-section, said oval cross-section including a major axis along a greater diameter thereof and a minor axis along a smaller diameter thereof, said major and minor axes being generally orthogonal to one another; placing the tubular metal blank into said second die structure, said second die structure being constructed and arranged to receive the tubular metal blank having said oval cross-section without distorting said tubular metal blank from its oval cross-section, said tubular metal blank being placed into said second die structure such that said major axis of said oval cross-section thereof extends in generally the same direction as said first cross-sectional dimension when said first and second die structures cooperate to form said die cavity and such that said minor axis of said oval cross-section thereof extends in generally the same direction as said second crosssectional dimension of said die cavity when said first and second die structures cooperate to form said die cavity; engaging opposite ends of the tubular metal blank with tube-end engaging structures so as to substantially seal opposite ends of the tubular metal blank; an injecting fluid under pressure into the tubular metal blank placed in the die cavity to expand the tubular metal blank into conformity with the surfaces defining the die cavity. 2. The method of claim 1, wherein said elongated tubular metal member and said die cavity each have a substantially similar box-shaped cross sectional configuration, and wherein said placing of said tubular metal blank comprises: orienting said tubular metal blank within said die cavity such that said major axis of the cross-section thereof extends in generally the same direction as a longer cross-sectional dimension of said box-shaped cross sectional configuration of said die cavity, and said minor axis of the cross-section thereof extends generally in the same direction as a shorter crosssectional dimension of said box-shaped cross sectional configuration of said die cavity. 3. The method of claim 1, further comprising effecting relative movement between said first die structure and said second die structure to close said die cavity without distorting the oval cross-sectional configuration of said tubular metal blank disposed therein. 4. The method of claim 3, said method further comprising progressively reducing the cross-sectional area of said die cavity after said die cavity is closed to thereby deform the oval cross section of said tubular metal blank within said die cavity after said die cavity is closed. 5. The method of claim 2, wherein said longer cross-sectional dimension of said boxshaped cross sectional configuration of said die cavity extends in a generally vertical direction, wherein said shorter cross-sectional dimension of said box-shaped cross sectional configuration of said die cavity extends in a generally horizontal direction, and wherein said shorter crosssectional dimension of said box-shaped cross sectional configuration of said die cavity is greater than an outer diameter of said tubular metal blank taken along said minor axis, and wherein said placing step further comprises: orienting said tubular metal blank within said die cavity such that said major axis of the cross-section thereof extends generally vertically, and such that said minor axis of the cross-section thereof extends generally horizontally. 6. The method of claim 1, wherein the surfaces defining said die cavity cooperate to provide said die cavity with a substantially rectangular cross-sectional configuration, and wherein said injecting causes said tubular metal blank to expand outwardly into conformity with said surfaces so as to provide the formed elongated tubular metal member with a substantially rectangular cross-section. 7. The method of claim 1, further comprising clamping spaced-apart portions of the tubular metal blank with clamping structures positioned on opposite ends of said die cavity, the clamping structures presenting clamping surfaces defining substantially oval surface configurations conforming to an oval outer peripheral surface of the tubular metal blank. 8. The method of claim 1, further comprising: longitudinally compressing said tubular metal blank so as to replenish a wall thickness of said tubular metal blank as it is expanded. 9. The method of claim 3, wherein said first die structure comprises a movable upper die structure, said method further comprising moving said movable upper die structure so as to close said die cavity. 10. The method of claim 9, wherein said second die structure comprises a fixed die structure, and wherein said method further comprises: moving said upper movable die structure relative to said fixed die structure after said die cavity is closed so as to progressively reduce the cross-sectional area of said die cavity after said die cavity is closed and thereby deform the oval cross section of said tubular metal blank within said die cavity after said die cavity is closed. 11. The method of claim 10, wherein said second die structure further comprises a movable lower die structure, and wherein said method further comprises engaging said movable upper structure with said movable lower die structure to close said die cavity, and moving said movable lower die structure and said movable upper die structure relative to said fixed die structure so as to progressively reduce the cross-sectional area of said die cavity after said die cavity is closed and thereby deform the oval cross section of said tubular metal blank within said die cavity after said die cavity is closed. 12. An apparatus for forming a tubular metal blank into an elongated tubular metal member having a substantially box-shaped transverse cross-section along an extent thereof, said apparatus comprising: a die assembly having an internal die surface defining a die cavity, said die cavity having a substantially box-shaped surface configuration and being constructed and arranged to receive the tubular metal blank having a generally oval cross-section; clamping structures positioned on opposite ends of said die cavity and constructed and arranged to securely clamp spaced-apart portions of the tubular metal blank, said clamping structures presenting clamping surfaces defining a generally oval surface configuration generally conforming to a generally oval outer peripheral surface of the tubular metal blank; and tube-end engaging structure constructed and arranged to engage and substantially seal opposite ends of the tubular metal blank, said tube-end engaging structure presenting a generally oval outer surface configuration conforming to a generally oval inner peripheral surface of the tubular metal blank. 13. The apparatus of claim 12, wherein said die assembly comprises: a moveable upper die structure; a second die structure which includes a fixed die structure; said moveable upper die structure, and said second die structure being cooperable to define said die cavity; wherein relative movement between said moveable upper die structure and said second die structure closes said die cavity, and after said die cavity is closed, movement of said moveable upper die structure with respect to said fixed die structure progressively reduces the cross-sectional area of said die cavity to deform the tubular metal blank within said die cavity. 14. The apparatus of claim 13, wherein said second die structure further comprises a moveable lower die structure, wherein said fixed die structure is received within an opening in said moveable lower die structure, and wherein said moveable upper die structure moves into engagement with said moveable lower die structure to close said die cavity. 15. The apparatus of claim 14, wherein said moveable lower die structure is mounted on a plurality of compressible spring members, wherein said moveable upper die structure is moved downwardly into engagement with said moveable lower die structure to close said die cavity, and wherein continued downward movement of said moveable upper die structure after said engagement moves said moveable lower die structure downwardly therewith against a bias of said spring members, and wherein said moveable upper and lower die structures are constructed and arranged so that said continued downward movement of said moveable upper die structure and downward movement of said moveable lower die structure reduces the cross-sectional area of said die cavity to deform the tubular metal blank. 16. The apparatus of claim 12, wherein said clamping surfaces defining said generally oval surface configuration each transition into a box U-shaped surface configuration as said clamping surfaces extend inwardly toward said die cavity. 17. The apparatus of claim 12, wherein said die cavity has a generally rectangular surface configuration. 18. A method of forming an elongated tubular metal member, said elongated tubular member being formed in a die cavity having surfaces constructed and arranged to provide said die cavity with a shape generally corresponding to a shape of said of said elongated tubular member, said cross-section of said elongated tubular member and hence of said die cavity having a relatively larger dimension thereof transverse to a relatively smaller dimension thereof, said method comprising: placi