Hydroform structural reinforcement system

Details Hydroform structural reinforcement system Hydroform structural reinforcement system

2002-04-25

2003-02-25

Patel, Kiran (Department: 3612)

Land vehicles: bodies and tops

Bodies

Body shell

C296S187060, C296S901010, C052S749100, C052S309150

Reexamination Certificate

active

06523884

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a structural reinforcement system for use in increasing the stiffness, strength, or durability of different portions of automotive or aerospace vehicles. More particularly, the present invention relates to structurally reinforced closed forms, such as a hydroform structure or hydroform rail, which utilizes an expandable and foamable material to cross-link, structurally adhere, and reinforce the form when the foamable material becomes chemically active and expands upon heating.
BACKGROUND OF THE INVENTION
Traditionally, closed form or hydroforming techniques are used to draw and shape metal tubes. Conventional hydroforming techniques often involve two steps: (1) placing the desired bends in the tube and (2) forming the tube to the desired configuration. Step 2 of this process usually requires placing a tubular member having an open bore in a mold and pinching off the ends of the tube. A pressurized liquid is then injected into the open bore, causing the tube to stretch and expand out against the mold.
The manufacturing advantages of the hydroforming process is that it allows formation of relatively long tubular structures having a seamless perimeter. This process elminates the cost of welding, machining, or fastening operations often used to shape the part in the desired configuration. As a result, a hydroform or closed form structure very often has a high length to diameter ratio. For instance, a hydroform structure may have a length in excess of 15′ and a diameter ranging from approximately ¾″ to more than 12″. To this end, a further manufacturing process advantage of a hydroform structure is that it can exceed the length of other tubular members, such as torsion bars or tubular bars, formed using other processes.
Additionally, hydroforming processing creates complex structural shapes that typically include bends and contour changes. Often the number of bends and contour changes in a hydroformed bar are greater and more complex than those found in torsion bars or other tubular structures formed using different techniques.
Hydroform structures typically have a constant wall thickness prior to forming, and might develop strength differences at the site of bends or changes in contour, as well as at certain locations along a long tubular section. Thus, it is often desirable to reinforce closed form and hydroform sections to improve their structural stiffness, strength, and durability, particularly in automotive vehicle applications.
Traditional ways of reinforcing tubular structures such as hydroforms and other closed forms include sliding a metal sleeve inside the tube and welding the reinforcing member in place. However, because the hydroform often includes one or more bends or one or more changes in contour and/or diameter, it is often difficult to insert the sleeve into the hydroform at the precise location of the weak portion. Other techniques include reinforcing the hydroform from the outside by welding the sleeve onto the outside of the hydroform. However, hydroforms are often used in applications having very close tolerances, resulting in little or no clearance for an externally placed reinforcing member. Accordingly, exterior reinforcements are often not as effective as interior reinforcements.
Additionally, in many operations the weight of the tubular member is critical and must be kept low as possible. Thus, the use of an external sleeve adds unwanted weight to the tubular assembly. Still further, the welding operation tends to be labor intensive, time consuming and inexact, increasing the cost of forming the hydroform member and producing parts that have questionable reliability. Finally, these additional manufacturing steps and operations are often cumbersome and difficult to integrate into a final vehicle manufacturing process in that additional tooling would need to be developed by the manufacturer and assembly plant resources, labor, maintenance, and space would need to be dedicated and expensed by the vehicle manufacturer.
Accordingly, there is a need in industry and manufacturing operations for system, device, and method for reinforcing the weak areas of closed forms and other hydroform tubes without significantly increasing the weight and manufacturing complexity. In particular, there is a need for reinforcing a closed form or hydroform, which utilizes a plurality of members or pieces to achieve integrated reinforcement within the closed form since the contour or shape of typical tubes do not allow for placement of single piece reinforcement members. In this regard, the present invention addresses and overcomes the shortcomings found in the prior art by providing a multi-piece reinforcement system having at least two members capable of being nested together within a hydroform that may then be fixed in location through the use of a third member which serves as a locking and positioning member of the reinforcement system within the hydroform or other closed form. However, design of two nesting member could also create a lock mechanism. Structural reinforcement of the hydroform is achieved through activation by heat of an adhesive material disposed along at least two of the members, such a material would typically expand to contact a substrate surface and in doing so structurally adhere the multiple members to each other and the hydroform.
SUMMARY OF THE INVENTION
The invention relates to methods and systems for reinforcing a closed form or hydroform member. In one embodiment, the hydroform member includes an outer structural member having an open bore; and an expandable material or structural foam supported by the outer structural member. The expandable material extends along at least a portion of the length of the outer structural member, and may fill at least a portion of the length of the bore.
The expandable material is generally and preferably a heat-activated epoxy-based resin having foamable characteristics upon activation through the use of heat typically encountered in an e-coat or other automotive painting operation. As the foam is heated, it expands, cross-links, and structurally adheres to adjacent surfaces. Preferred structural foam materials are commercially available from L&L Products, Inc. of Romeo, Mich. under the designation L5204, L5206, L5207, L5208, or L5209. Generally speaking, these automotive vehicle applications may utilize technology and processes such as those disclosed in U.S. Pat. Nos. 4,922,596, 4,978,562, 5,124,186, and 5,884,960 and commonly owned, co-pending U.S. patent application Ser. No. 09/502,686 filed Feb. 11, 2000, Ser. No. 09/524,961 filed Mar. 14, 2000, and particularly, Ser. No. 09/459,756 filed Dec. 10, 1999, all of which are expressly incorporated by reference.
The system generally employs two or more members adapted for stiffening the structure to be reinforced and helping to redirect applied loads. In use, the members are inserted into a closed form, such as a hydroformed tube, with the heat activated bonding material serving as the load transferring and potentially energy absorbing medium. In a particularly preferred embodiment, at least two of the composite members are composed of an injection molded nylon carrier, an injection molded polymer, or a molded metal (such as aluminum, magnesium, and titanium, an alloy derived from the metals or a metallic foam derived from these metals or other metal foam) and it is at least partially coated with a bonding material on at least one of its sides, and in some instances on four or more sides. A preferred bonding medium is an epoxy-based resin, such as L5204, L5206, L5207, L5208 or L5209 structural foam commercially available from L & L Products, Inc. of Romeo, Mich. However, the third member which serves to lock and position the first two members could also utilize an adhesive material along its outer surface. In addition, it is contemplated that the member could comprise a nylon or other polymeric material as set forth in commonly owned U.S. Pat. No. 6,103,341, expressly incorporate

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