Patent EA-000657-B1 (EA)
Title: Hydroforming die assembly and method for pinch-free tube forming
Inventor: HORTON FRANK A
IPC: B21D26/02
Filed: 1997-08-21
Abstract: 1. A hydroforming die assembly comprising: a first moveable die structure; a second moveable die structure; a fixed die structure; said first moveable die structure, said second moveable die structure, and said fixed die structure being cooperable to define a die cavity into which a metallic tube can be disposed; wherein relative movement between said first and second moveable die structures seals said die cavity; and wherein, after said die cavity is sealed, movement of said first moveable die structure with respect to said fixed die structure progressively reduces the cross-sectional area of said die cavity to deform said metallic tube within said die cavity. 2. The hydroforming die assembly according to Claim 1, further comprising: hydroforming port members constructed and arranged to provide pressurized fluid to an interior of said metallic tube so as to expand said metallic tube outwardly into conformity with surfaces defining said cavity. 3. The hydroforming die assembly according to Claim 2, wherein said hydroforming port members arc capable of relative movement therebetween to enable said hydroforming port members to longitudinally compresses said metallic tube therebetween so as to flow metal material of said metallic tube in a longitudinal direction to replenish the wall thickness of the tube as it is being expanded. 4. The hydroformng die assembly according to Claim 1, wherein said fixed die structure is received within an opening in said second moveable die structure, and wherein said first die structure moves into engagement with said second die structure to seal said die cavity. 5. The hydroforming die assembly according to Claim 4, wherein said second moveable die structure is mounted on a plurality of compressible spring members, wherein said first moveable die structure is moved downwardly into engagement with said second die structure to seal said die cavity, and wherein continued downward movement of said first moveable die structure after said engagement moves said second moveable die structure downwardly therewith against a bias of said spring members, and wherein said continued downward movement of said first moveable die structure and downward movement of said second moveable die structure reduces the cross-sectional area of said die cavity to deform said metallic tube. 6. A hydroforming die assembly according to Claim 5, wherein said compressible spring members comprise nitrogen spring cylinders. 7. A hydroforming die assembly according to Claim 5, further comprising a pair of opposing lower clamp structures mounted on said second moveable die structure and constructed and arranged to engage an underside of said metallic tube at opposite longitudinal ends thereof, and wherein said lower clamp structures suspend said metallic tube in overlying relation to said fixed die structure prior to said first moveable die structure moving downwardly into engagement with said second moveable die structure. 8. A hydroforming die assembly according to Claim 7, wherein said lower clamp structures are mounted on said second moveable die structure by spring cylinders to enable relative movement between said lower clamp structures and said second moveable die structure. 9. A hydroforming die assembly according to Claim 7, wherein said lower clamp structures form an interference fit with opposite longitudinal ends of said metallic tube. 10. A hydroforming die assembly according to Claim 8, further comprising a pair of opposing clamp structures mounted on said first moveable die structure and constructed and arranged to engage an upper surface of said metallic tube at opposite longitudinal ends when said first moveable die structure moves into engagement with said second die structure, said opposing clamp structures mounted on said first moveable die structure cooperating with said lower clamp structures mounted on said second moveable die structure to capture the exterior surface of said metallic tube at opposite ends. 11. A hydroforming die assembly comprising: a first die structure; a second die structure; a third die structure; said first die structure, said second die structure, and said third die structure being cooperable to define a die cavity into which a metallic tube can be disposed; said first die structure being moveable to seal said die cavity; and wherein after said die cavity is sealed, said first and second die structures are moveable to reduce a cross-sectional area of said die cavity to deform said metallic tube within said die cavity. 12. A hydroforming die assembly according to Claim 11 wherein said second die structure remains stationary as said first die structure is moved to seal said die cavity. 13. A hydroforming die assembly according to Claim 12, wherein said third die structure remains fixed as said first and second die structures move to progressively reduce the cross-sectional area of said die cavity. 14. The hydroforming die assembly according to Claim 11, further comprising: hydroforming port members constructed and arranged to provide pressurized fluid to an interior of said metallic tube so as to expand said metallic tube outwardly into conformity with surfaces defining said cavity. 15. The hydroforming die assembly according to Claim 14, wherein relative movement between said hydrofonning port members longitudinally compresses said metallic tube therebetween so as to flow metal material of said metallic tube in a longitudinal direction to replenish the wall thickness of the tube as it is being expanded. 16. The hydroforming die assembly according to Claim 11, wherein said die structure is received within an opening in said second moveable die structure, and wherein said first die structure moves into engagement with said second die structure to seal said die cavity. 17. The hydroforming die assembly according to Claim 16, wherein said second die structure is mounted on a plurality of compressible spring members, wherein said first die structure is moved downwardly into engagement with said second die structure so that continued downward movement of said first moveable die structure after said engagement moves said second die structure downwardly therewith against a bias of said spring members, and wherein said continued downward movement of said first die structure and downward movement of said second moveable die structure reduces the cross-sectional area of said die cavity. 18. A hydroforming die assembly according to Claim 17, wherein said compressible spring members comprise nitrogen spring cylinders. 19. A method of hydroforming a metallic tube comprising: placing the metallic tube in a hydroforming die assembly having three separate d ie structures, said three die structures being cooperable to define a die cavity; moving a first one of said die structures to seal said die cavity; then moving said first one of said die structures and a second one of said die.structures to reduce a cross-sectional area of said die cavity; and deforming said metallic tube as a result of reducing the cross-sectional area of said die cavity. 20. The method according to Claim 19, further comprising: providing fluid pressure to an interior of said metallic tube prior to deforming of said metallic tube prior to deforming said metallic tube so as to provide internal support to said metallic tube as it is deformed. 21. A hydroforming die assembly comprising: a lower die assembly defining a lower die cavity portion into which a metallic tube can be placed, said lower die assembly providing side walls defining opposite sides of said lower die cavity portion, and a lower wall defining a lower surface of said lower die cavity portion; an upper movable die structure having sealing surfaces which are movable to engage said lower die assembly on opposite sides of said lower die cavity portion to se al said lower die cavity portion and thereby provide a sealed die cavity; said lower die assembly and said upper die structure being cooperable to reduce a size of said sealed die cavity to deform said metallic tube after said die cavity is sealed.