MXPA98005596A - Method for reinforcing members structure - Google Patents

Abstract

The present invention relates to a member for structural reinforcement comprising a flexible member, which bends as pressure is applied so that it can be fed into a hollow structural part having a cavity of linear geometry not straight, and it passes at least one bend or bending, having a length greater than its diameter or width, characterized in that at least a part of the outer surface of the length of the flexible member is covered with a layer or coating of an expandable resin, which is bend with the flexible member as pressure is applied aés

Description

"METHOD FOR REINFORCING STRUCTURAL MEMBERS" REFERENCE TO THE RELATED APPLICATION This request is based on provisional application Serial Number 60 / 053,264, filed on July 21, 1997.

FIELD OF THE INVENTION The present invention relates generally to the reinforcement of hollow structural members and more specifically relates to the reinforcement of structures having closed regions that present special access problems.

BACKGROUND OF THE INVENTION In recent years, a number of factors have required fundamental changes in the approach to automotive structural design. These include the need to fill the ever increasing standards of impact resistance and fuel economy and the need to produce a competitively priced vehicle in a global market. Sometimes, these requirements are seemingly unequal to each other. For example, impact resistance can be achieved in most cases simply by increasing the thickness of the steel or through the use of high strength steels. These approaches, however, greatly increase the weight and / or cost of the vehicle. While lightweight resins are available that can be used to fill all the hollow cavities of the structural members in order to provide greater strength, these materials are expensive and therefore their use in large quantities undesirably increases the cost of the vehicle. The present inventor has studied a novel approach to reinforcement of the structural part through localized reinforcement of critical regions using thermally expandable resins filled with microspheres, such as: a composite door beam having a resin-based core that occupies no more than of a third part of the perforation of the metal tube; a hollow laminated beam characterized by a high ratio of stiffness to mass and having an outer portion that is separated from the inner tube by a thin layer of structural foam, a carrier insert reinforcement in the form of a "W" carrying a body of foam to be used to reinforce a hollow beam; a dividing wall using a thermally expandable foam to provide localized reinforcement of a rail for fixing a motor cradle or the like. Although these techniques are well suited for a number of applications, there is a need for localized reinforcement of regions that have special access problems. More specifically, in a number of hollow structural parts, the member has a region or enclosed space that is placed at a certain distance from the opening of the space and which is difficult to reach due to a bending or bending in the member. In some cases, the member and the channel it defines have an irregular geometry that makes it difficult to access a specific internal region. Of course in some cases, it may be possible to simply fill the entire structure with a liquid resin which is then cured, but as stated above, this approach can be prohively expensive in a number of applications. Accordingly, there is a need for an alternative method in order to provide localized reinforcement of these parts. The present invention provides a solution to this problem. It is an object of the present invention to provide a method for providing a local reinforcement in a region of a hollow structural part that is difficult to fill using conventional techniques.

A further object of the present invention is to provide a method for introducing a resin reinforcement located on a structural part wherein the region to be reinforced lies beyond a curvature in a channel. A still further object of the present invention is to provide a method for centralizing a resin reinforcement in a hollow structural part in a region that is difficult to access.

COMPENDIUM OF THE INVENTION In one aspect, the present invention provides a one piece reinforcement method in a localized region. The method includes the steps of providing a flexible member that has a length considerably greater than its width; covering at least a portion of the flexible member with a thermally expandable resin; and inserting the flexible member into the cavity of a hollow structural part. The insertion step includes the step of flexing the flexible member to accommodate the geometry of the part cavity. The resin is then thermally expanded in such a way that the resin is bound to the structural part. In this way, localized reinforcement can be achieved for any number of pieces whose internal geometry would make it difficult or impossible to be able to be reinforced using conventional techniques. In one aspect, the flexible member is a tube around which the resin is applied with a layer or coating. The resin-coated tube is then inserted into the structural part and flexed as it is applied under pressure so that it can be fed into the part cavity, i.e., conforms to the desired configuration as it is inserted into the piece. the piece. In one aspect, the resin includes a swelling agent and glass microspheres. After the flexible member is in place in the part, the part is heated, for example, after installation in a motor vehicle, to a temperature sufficient to activate the swelling agent and thermally expand the resin. As the resin expands, it attaches to the internal walls of the piece, forming a pipe-type structure in a tube with high strength characteristics. In one aspect, the thermally expandable resin includes, in parts by weight, from about 40 percent to about 80 percent resin, from about 10 percent to about 50 percent microspheres, from about 0.5 percent to about 5 percent. percent of the swelling agent, from about 1 percent to about 15 percent of the filler or filler, from about 0.5 percent to about 2 percent of the accelerator and from about 1 percent to about 8 percent of the curing agent. In still another aspect, the flexible member includes one or more spacers separating them from the internal walls of the structural part. These and other aspects, features and objects of the invention will be described more fully in the following detailed description of the preferred embodiments of the invention, with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a resin support tube used in the method of the present invention. Figure 2 illustrates a side elevational view partially in section showing the position of the unexpanded resin in the resin support tube. Figure 3 illustrates another resin support tube with a non-expanded resin coating. Figure 4 illustrates a structural member curved in cross section to reveal the resin support tube in position prior to resin expansion. Figure 5 illustrates the curved structural member of Figure 4 in cross section, revealing the expanded resin that forms an internal reinforcement. Figure 6 is a front view of the resin support tube having radial spacers for use in the present invention. Figure 7 is an end view of the support tube of Figure 6, in the direction of arrow 7--7. Figure 8 illustrates a structural member curved in cross section, revealing the unexpanded resin and placement of the spacers.

DETAILED DESCRIPTION OF THE MODALITIES PREFERRED OF THE INVENTION Referring to Figures 1 and 2 of the drawings, the flexible member or tube 20 is shown which serves as a support for a non-expanded resin liner 22. the flexible member 20 is especially preferably a hollow tube similar to that used as a conduit for electrical installation 23. The various flexible conduits will be known to those skilled in the art. A specific preferred flexible conduit is a metal spiral tube that can be flexed without deformation of the metal due to its spiral construction. Of course, it may not be necessary for the tube 20 to be round in cross section and other configurations such as square or oval may be appropriate. When the flexible member 20 is a hollow metal tube, it will typically be formed of aluminum and preferably have a wall thickness of about .5 to about 1.2 millimeters. The diameter of the tube 20 will vary depending on the application, but will typically be from about 8 to about 40 millimeters, and typically will be from about 50 to about 800, and preferably from 200 millimeters in most automotive applications. In some applications, the tube 20 will deform beyond its elastic limit during placement in the structure to be reinforced. In addition, in some applications, a more elastic tube or a rod that is essentially spring biased in its position in the structural cavity can be used. Although hollow tube 20 is especially preferred, particularly since it provides a light weight structure, solid rods can also be used. It may be desirable to use plastic rods or tubes instead of metal, such as tube 20 in some applications.

The length of the tube 20 is a function of the distance to the site to be reinforced from the opening of the cavity. The length of the tube 20 is greater than its diameter or width and in many applications the tube 20 will preferably be at least five times or it may be 20 times and often more than 100 times longer than its diameter in cross section. In many applications, the tube 20 will have a length of 50 to about 200 millimeters. Also, in some applications, it may be desirable to cover essentially all of the tube 20a, shown as a spiral conduit in Figure 3, with the resin lining 22a. The resin liner 22 in most applications will be a layer that extends around the entire outer surface of the tube 20, and will usually be of relatively uniform thickness, e.g., about 2 about 6 millimeters, in the unexpanded state. . The resin liner 22 can be prepared by cutting with a matrix the resin sheet to the required geometry and wrapping the pre-cut sheet around the tube 20. Alternatively, the coating can be molded into the carrier, although it may be possible to use other forms of coating, such as by spraying or the like.

The polymer used to form the resin liner 22 is a resin-based material that is preferably thermally expandable. A number of resin-based compositions can be used to form the resin liner 22 in the present invention. Preferred compositions impart excellent strength and stiffness characteristics while being added only marginally to weight. With specific reference now to the composition of the liner 22, the density of the material should preferably be from about 320 grams per cubic meter to about 800 grams per cubic meter to minimize the weight. The melting temperature, the temperature of thermal distortion and the temperature at which chemical disintegration occurs must also be sufficiently high such that the liner 22 maintains its structure at high temperatures typically encountered in paint ovens and the like. Therefore, the liner 22 must be able to withstand temperatures in excess of 160 ° C and preferably 177 ° C for short periods of time. Also, the liner 22 should be able to withstand heats of about 32 ° C to 93 ° C for extended periods, without exhibiting considerable heat distortion or distortion. In more detail, in a particularly preferred embodiment, the thermally expanded structural foam of the liner 22 includes a synthetic resin, a cell-forming agent and a filler or filler, a synthetic resin comprises from about 40 percent to about 80 percent by weight, preferably from about 45 percent to about 75 percent by weight, and more preferably from about 50 percent to about 70 percent by weight of the liner 22. Most preferably, a portion of the resin includes a Epoxy flexible. As used herein, the term "cell-forming agent" generally refers to the agents that produce bubbles, pores or cavities in the liner 22. That is, the liner 22 has a cellular structure having numerous cells placed through it. its mass. This cellular structure provides a high strength, low density material that provides a tough structure, but nevertheless of light weight. Cell forming agents that are compatible with the present invention include "hollow" reinforcing microspheres or microbubbles that can be formed from either glass or plastic. The glass microspheres are particularly preferred. Also, the cell forming agent may comprise a swelling agent which can be either a chemical swelling agent or a physical swelling agent. When the cell forming agent comprises microspheres or macrospheresis from about 10 percent to about 50 percent by weight, preferably from about 15 percent to about 45 percent by weight, and especially preferably from 20 percent to about 40 percent by weight of the material that forms the liner 22. When the cell forming agent comprises a swelling agent, it is from about 0.5 percent to about 5.0 percent by weight, preferably from about 1 percent to about 4.0 percent by weight, and most preferably from about 1 percent to about 2 weight percent of liner 22. Suitable fillers or fillers include glass or plastic microspheres, fuming silica, calcium carbonate, ground glass fiber and crushed glass. A thixotropic filler or filler material is particularly preferred. Other materials may be appropriate. A filler or filler comprises from about 1 percent to about 15 percent by weight, preferably from about 2 percent to about 10 percent by weight, and especially preferably from about 3 percent to about 8 percent by weight of liner 22. Preferred synthetic resins for use in the present invention include thermosetting resins such as epoxy resins, vinyl ester resins, thermosetting polyester resins and urethane resins. It is not intended that the scope of the present invention be limited by the molecular weight of the resin and the appropriate weights will be understood by those skilled in the art based on the present disclosure. When the resin component of the liquid filler or filler is a thermosetting resin, various accelerators such as imidazoles and curing agents, preferably dicyandiamide can also be included to improve the cure rate. A functional amount of the accelerator is typically from about 0.5 percent to about 2.0 percent of the resin weight, with the corresponding reduction in one of the three components, the resin, the cell-forming agent or the filler or filler. Similarly, the amount of the curing agent used is typically from about 1 percent to about 8 percent of the resin weight, with a corresponding reduction in one of the three components, the resin, the cell-forming agent or the material filling or loading. Effective amounts of processing aids, stabilizers, colorants, ultraviolet light absorbing agents and the like can also be included in the layer. Thermoplastic materials may also be appropriate.

In the following table, a preferred formulation is indicated for liner 22. It has been found that this formulation provides a material that is fully expanded and cured at a temperature of about 160 ° C and provides excellent structural properties. All percentages in the present expulsion are percentage by weight unless specifically designated otherwise.

INGREDIENT PERCENTAGE IN WEIGHT EPON 828 (epoxy resin) 37.0 DER 331 (flexible epoxy resin) 18.0 DI-CY (dicyandiamide curing agent) 4.0 IMIDAZOLE (accelerator) 0.8 SMOKING SILICA (filler or thixotropic filler) 1.1 CELOGEN AZ199 (azodicarbonamide blowing agent) 1.2 B38 MICROS (glass microspheres) 37.0 WINNOFIL CALCIUM CARBONATE (CaC? 3 filler or filler?> 0.9 Referring now to Figure 4 of the drawings, the structural part 24 is seen in cross section and defines the cavity 26. For purposes of illustration only, the structural part 24 is shown here as a portion of an automotive roll bar. Other preferred applications are for use to strengthen the upper joints of the A pillar and the seat frames. The structural part 24 has an arched or curved portion 28 defining an arcuate portion 30 of the cavity 26. Cavity-like cavities 26, ie, those which are difficult to access, are the focus of the present invention. The flexible tube 20 is shown in position in the cavity 26 before the thermal expansion of the resin. The tube 20 is bent to conform to the configuration of the cavity 26. This configuration operation is preferably carried out at the site. In other words, the flexible tube 20 having the resin liner 22 placed at a preselected location relative to the ends of the tube 20 is inserted into the cavity 26. As force is applied to the tube 20, it moves further to through the passage. As it encounters resistance from the internal walls 32, the flexible tube 20 is flexed "in" in this way through the cavity 26, including beyond the arcuate portion 30. Alternatively, it may be possible in some applications to flex the tube 20 to a shaping geometry before inserting it into the cavity 26. The flexible tube 20 is inserted at a distance - In ¬ sufficient to place the resin liner 22 in position in the arched portion 28. Once in position, the outer end 34 or tube 20 is clamped in position relative to the tube 20 with a clamp (not shown) or is fixed in position otherwise if required. The cavity 26 is the non-straight linear geometry that could be more complicated than that which is simply flexed with its arcuate portion in such a manner as illustrated in Figure 4. When there are multiple bends or irregularities, a resin liner 22 could be provided. for some or all of the irregularities and this could be done by providing individual separated resin sections or by providing one or more continuous resin sections that are placed in two or more bends or bends. Referring now to Figure 5 of the drawings, the resin 22 is shown in the expanded state. That is, once the tube 20 and the resin 22 are in position in the structural part 24, the resin is expanded by heating the entire assembly to a temperature that activates the swelling agent to expand and cure the resin liner 22. . In automotive applications, this is typically achieved as the vehicle moves through the paint furnace. The resin 22 expands up to several times its original volume, preferably at least twice its original volume. The expanded resin is contacted and firmly bonded to the surrounding walls 32 of the structural part 24. It also heals to form a rigid reinforcement in piece 24. In this way, a minimum amount of resin is used at the precise location where reinforcement is required. Referring now to Figures 6 and 7 of the drawings, the tube 20 is provided with a radical separation assembly 36 having legs 38, typically two to four in number. As seen in Figure 8, the separation assembly 33 serves for the function of generally centering the tube 20 on the structural part 24. It may be preferable that the legs 38 be somewhat resilient, ie, it may be desirable to allow the legs 38 to flex inwardly as the tube 20 is inserted into the cavity 26. Even though the invention has been described primarily in relation to With automotive or vehicle parts, it will be understood that the invention can be implemented as part of other products, such as airplanes, ships, bicycles or virtually anything that requires energy for movement. Similarly, the invention can be used with stationary or static structures such as buildings to provide a rigid support when subjected to vibration such as from an earth or earthquake movement, or simply to provide a lightweight support for structures subject to loads . Further, even when the invention has been described primarily with respect to thermally expandable foams and with respect to metal parts such as the structural part and the flexible member, other materials may be used. For example, the foam could be any suitable known expandable foam that is chemically activated to expand and forms a rigid structural foam, the flexible member could be made of non-metal materials, for example, various plastics or polymeric materials or various fibrous materials of wood type that have enough stiffness to function as a support or backing for the foam. When a thermally expandable foam is used, the flexible member must be able to withstand the heat encountered during thermal curing. When other types of foam materials are used, however, it is not necessary that the flexible member be able to withstand high temperatures. Instead, the basic requirement for the flexible member is that it has sufficient rigidity to function as intended. It is also possible, for example, to use as the flexible member, materials that in themselves become rigid during healing or additional treatment. The invention can also be carried out when the structural part is made of materials other than metal. However, it is preferred that the materials be selected for the structural part and the flexible member as well as the foam so that the thin foam not expanded during the expansion forms an intense bond with the structural part and the flexible member, so that will result in a structural composition. Although specific embodiments of this invention are shown and described herein, it will be understood, of course, that the invention is not limited thereto, since many modifications can be made particularly by those skilled in the art in view of this disclosure. It is therefore proposed, by means of the appended claims, to cover any of those modifications that fall within the true spirit and scope of this invention.

Claims (32)

R E I V I N D I C A C I O N E S:

1. A method for reinforcing a piece comprising the steps of: providing a flexible member having a length greater than its width; covering at least a portion of the flexible member with an expandable resin; inserting the flexible member into a cavity of a hollow part, the insertion step includes the step of terminating the flexible member to accommodate the geometry of the cavity; and expanding the expandable resin in such a way that the resin is bound to the piece.

The method for reinforcing a piece according to claim 1, wherein the flexible means is a hollow tube.

3. The method for reinforcing a piece according to claim 1, wherein the flexible member is a solid or solid rod.

4. The method for reinforcing a piece according to claim 1, wherein the resin is thermally expandable and contains hollow microspheres.

The method for reinforcing a part according to claim 1, wherein the part is selected from the group consisting of a pillar joint A and a seat frame and a bearing bar for a motor vehicle.

The method for reinforcing a part according to claim 1, wherein the flexible member has a spacer attached to separate the flexible member from the internal walls of the part before the expansion step.

The method for reinforcing a piece according to claim 1, wherein the length of the flexible tube is at least five times its diameter.

The method for reinforcing a piece according to claim 1, wherein the diameter of the flexible tube is between about 8 and about 40 millimeters and its length is about 50 to about 200 millimeters.

The method for reinforcing a piece according to claim 1, wherein the expandable resin forms a layer that surrounds and envelops at least a portion of the flexible member.

The method for reinforcing a piece according to claim 1, wherein the layer has a uniform thickness of about 2 to about 8 millimeters.

11. The method for reinforcing a piece according to claim 1, wherein the flexible member is hollow and has a wall thickness of about .5 to about 1.2 millimeters.

The method for reinforcing a piece according to claim 1, wherein the flexible tube is formed of metal.

The method for reinforcing a piece according to claim 12, wherein the metal is aluminum.

The method for reinforcing a piece according to claim 1, wherein the flexible member is elastically deformed before the insertion step, the deformation being such that the flexible member conforms to the geometry of the cavity.

The method for reinforcing a piece according to claim 1, wherein the flexible member is configured during the insertion step by contact with the piece.

16. The method for reinforcing a part according to claim 1, wherein the flexible member is secured in the part before the expansion step.

17. The method for reinforcing a piece according to claim 1, wherein the length of the flexible member is at least five times its width.

18. The method for reinforcing a piece according to claim 1, wherein essentially the entire flexible tube is covered by an expandable resin.

The method for reinforcing a piece according to claim 1, wherein the resin is thermally expandable and includes, in parts by weight, from about 40 percent to about 80 percent resin, from about 10 percent to about 50 percent of microspheres, from about 0.5 percent to about 5 percent of the swelling agent, from about 1 percent to about 15 percent of the filler or filler, from about 0.5 percent to about 2 percent of an accelerator, and from about 1 percent to about 8 percent of a healing agent.

The method for reinforcing a piece according to claim 1, wherein the resin is thermally expandable, and includes in parts by weight, 55 percent epoxy resin, 4 percent dicyandiamide curing agent, .8 per 100 percent of the imidazole accelerator, 1.1 percent fumed silica, 1.2 percent of the azodicarbonamide blooming agent, 37 percent of glass microspheres, and .9 percent of a filler or calcium carbonate filler.

21. The method for reinforcing a piece according to claim 1, wherein the flexible member is a hollow tube with an electrical installation extending longitudinally therein.

The method for reinforcing a piece according to claim 1, wherein the cavity is of non-linear linear geometry having at least one bend or flexure, and introducing the flexible member through the cavity until the resin is placed in the flex or bend.

23. The method for reinforcing a piece according to claim 1, wherein there is a plurality of bends or bends and placing the resin in more than one of the bends or bends.

24. The method for reinforcing a piece according to claim 1, wherein the resin is a sheet cut with matrix that is wound around the flexible member or is a coating molded into the flexible member.

25. The method for reinforcing a piece according to claim 1, wherein the flexible member is a spiral wound tube.

26. The method for reinforcing a part according to claim 1, wherein the part is a piece of vehicle, the thermally expandable rhein being and expanding the resin in a vehicle paint furnace during a step to carry out the painting. .

27. A reinforcement part made by the method of claim 1.

28. A method for reinforcing a structural part having a space whose access is difficult due to the geometry of the part, comprising the steps of: providing a flexible member hollow that has a length at least five times its width; coating at least a portion of the flexible member with an expandable resin; inserting the flexible member into the cavity of a hollow structural part, including the step of inserting the step of bending or flexing the flexible member to accommodate the geometry of the cavity; securing the flexible member in the structural part; and expanding the expandable resin in such a way that the expandable resin is bound to the structural part.

29. A reinforced structural part comprising a rigid part having an elongated cavity of linear geometry not straight with at least one bend or flex, a flexible member longitudinally placed in the cavity, including through bending or bending a layer of resin in the Flexible member placed in the bend or flexure, the resin layer is made of structural foam that expands when activated, and the resin layer expands in intimate contact with and remains bound to the piece in bending or bending.

30. The part of claim 29, wherein the part is a vehicle part that is selected from the group consisting of a bearing bar and an articulation of the A pillar and a frame of the seat.

31. The piece of claim 29, wherein the flexible member is hollow, an electrical installation extending longitudinally through the flexible member.

32. The piece of claim 29, which includes at least one spacer assembly mounted around the flexible member at an outward site of the resin layer and the spacer assembly has a plurality of legs extending outwardly in the body. cavity in resilient contact with the internal surface of the piece.