This invention relates generally to a method for joining elongated structural components, and more particularly, to such a method which may be utilized to join together such components in the construction and assembly of a vehicle frame or chassis or a subassembly thereof.

It is known that various structural components for automobiles and other vehicles can be made from aluminum and other light metal alloys. Until recently, most automotive uses for such materials have been in hang-on components such as hoods and decklids that are selected to save weight. Considerable developmental work is now underway, however, to utilize aluminum and other light metal alloys in the primary body of the automobile. An automobile chassis or frame comprised of light metal alloys weighs considerably less than a steel frame that is designed to satisfy the same requirements of safety and durability. An automobile utilizing such a light metal alloy frame has improved fuel efficiency without sacrificing performance, and if the alloy utilized is an aluminum alloy, it is more easily recycled than a steel-frame vehicle, and it offers improved corrosion resistance. In addition, it is known that a spaceframe concept may be utilized to distribute and absorb the forces encountered in the normal operation of an automobile, as well as to absorb and dissipate the energy of a crash or rollover and hereby provide

improved safety and protection for the occupants. The spaceframe is a latticed framework of structural beams and columns that are joined together at their ends. These elongated structural components of a spaceframe (sometimes referred to as lineals) are connected together by mechanical means such as bolts, rivets and clinches, by welding and adhesive bonding, and by a combination of these methods. Another method for connecting the lineals of a spaceframe is by use of separate joining components or connecting members

(sometimes referred to as nodes) into which the lineals are designed to fit. The lineals are then attached to the nodes by any of the known connecting methods referred to above. The spaceframe concept is not limited to use in automobiles and other vehicles. Overhead sign structures and roof frames are other examples of a structural use of the spaceframe concept. Futhermore, the spaceframe concept is not limited to use with components made from any particular type of material. A variety of materials, including steel, aluminum, other light metals and various alloys may be utilized in spaceframe construction. However, because of the advantages inherent in the spaceframe concept for automobiles, and because of the advantages inherent in a use of aluminum and other light metal alloys in the construction of automobile and other vehicular frames, the light metal alloy automotive spaceframe has been developed. U.S. Patent No. 4,618,163 of Hasler et al. describes an automobile spaceframe chassis that is made from a plurality of tubular light metal rods that are held together by connecting members also made from light metal. The connecting members of the automotive frame of Hasler et al. can be made by an injection molding, casting or forging process, and they are provided with receiving means for engaging with the

ends of the rods. Some of these rods may be assembled by inserting their end sections into recesses in the connecting members. However, at least some of the rods are provided at their ends with a recess or cut-out for mating with a correspondingly shaped protrusion on a connecting member, by movement in a direction substantially normal to their longitudinal axis. As Hasler et al. report, this is of significant advantage, because if all of the tubular members were assembled by inserting their end sections into recesses in the connecting members, the last member to be mounted in an assembly or subassembly could only be mounted by flexing or bending the structure. The elongated frame members of Hasler et al. are secured to the connecting members by welding, soldering or cementing, or by the use of mechanical fasteners such as bolts, screws and rivets.

Most joints have high localized stresses, such as at the bolt or rivet holes in the lineals and/or at the bolt holes or lineal-engaging protrusions of the nodes. Under repetitive loading, cracks can initiate at these high-stress locations. Residual stresses or annealing effects from welding may also affect fatigue strength and buckling strength. Furthermore, the tensile or co pressive strength of some joints may be reduced in the heat-affected zones adjoining the welds. Adhesively bonded, welded or soldered joints must be carefully and properly made if failure is to be avoided. Furthermore, the joining process introduces several additional manufacturing processes and steps in the assembly of spaceframes. If the lineals are to be joined by means of connecting members or nodes, as is frequently the case (because, among other reasons, it allows the spaceframe to exhibit smooth lines) , the nodes must be cast or otherwise formed in a separate manufacturing operation. If the lineals are to be

mechanically attached to each other or to the nodes by means of bolts or other fasteners, they (and, where necessary, the nodes) must be provided with appropriate holes. In the alternative, or in addition, welding, soldering or adhesive bonding equipment and materials may be required to effect the joining of the components. Furthermore, the tolerances of the various components that are to be assembled together must be exact, in order for holes to align with other holes or with protrusions, or in order for surfaces to fit together for welding, soldering or adhesive bonding. Finally, the spaceframe must be assembled in a series of discrete steps involving the joining of individual lineals to nodes to form subassemblies and the joining of the various subassemblies to form the spaceframe. It would be desirable, therefore, if the elongated structural components of a spaceframe could be joined together without the requirement for close tolerances at the joints or the necessity for additional manufacturing steps and equipment, such as for welding, soldering or adhesive bonding. It would also be desirable if the elongated structural components of a spaceframe could be joined together without the necessity for a separate manufacturing operation to produce the connecting members or nodes. It would also be desirable if the elongated structural components of a space frame or a subassembly thereof could be joined together simultaneously.

Accordingly, it is an object of the invention claimed herein to provide a method for joining elongated structural components to form an integral structure, without requiring that separate connecting members or nodes be produced in another manufacturing operation. It is another object of the invention to provide such a method that may be utilized to form such a structure by joining elongated, extruded, tubular structural components. It is yet another object of the

invention to provide such a method, while avoiding the disadvantages and limitations of previously-known methods which require the close tolerances necessary for welding, bolting, adhesive bonding or otherwise mechanically joining the structural components together or to a connecting member. It is another object of this invention to provide a method for joining elongated structural components to form an integral structure, while avoiding weld-induced distortion in the components.

Another object of this invention is to provide a method for joining a plurality of elongated structural components to form a spaceframe or chassis for an automobile, or a subassembly thereof. Still another object of this invention is to provide such a method that may be utilized to join such components simultaneously.

Additional objects and advantages of this invention will become apparent from an examination of the drawings and the ensuing description.

A method is disclosed for joining elongated structural components to form an integral structure According to this method, a mold means is provided which is adapted to receive therein in a supporting manner a portion of each of a plurality of elongated structural components. A portion of each of such elongated structural components are placed into the mold means in close proximity each to the other, and a fluid molding material is introduced into the mold means. The fluid molding material is allowed to solidify or cure around the elongated structural components in the mold thereby forming an integral structure consisting of a plurality of elongated structural components that are joined together by a molded component.

A method for constructing an assembly or subassembly of a spaceframe structure is also

disclosed, according to which a plurality of molds are arranged in a spaced relationship each to the other so that the molds are located at points of intersection between and among a plurality of elongated structural components when said components are arranged in the configuration of such assembly or subassembly. A portion of each of a plurality of elongated structural components are placed into the molds in close proximity each to the other, and a fluid molding material is introduced into a plurality of the molds and allowed to solidify or cure around the portions of the elongated structural components in the molds, thereby joining the portions of the elongated structural components together. A structural frame formed by such method is also disclosed.

In order to facilitate an understanding of the invention, several embodiments of the invention are illustrated in the drawings, and a detailed description of the preferred embodiments follows. It is not intended however, that the invention be limited to the particular embodiments described or to use in connection with the apparatus shown. Various changes are contemplated such as would ordinarily occur to one skilled in the art to which the invention relates. Figure 1 is a perspective view of a spaceframe for an automobile that is constructed according to a preferred embodiment of the invention.

Figure 1A is an enlarged view of a portion of a mold and two of the structural components of the spaceframe of Figure 1 illustrating the joining of the structural components according to an embodiment of the invention.

Figure IB is an enlarged view of a portion of a mold and two of the structural components of the spaceframe of Figure 1 illustrating the joining of the structural components according to an alternative embodiment of the invention.

Figure 2 is a partial perspective view of the two structural components of Figure 1A joined according to the invention.

Figure 3 is a cross-sectional view of a structural component similar to those shown in Figure IB, illustrating the anchoring feature of an embodiment of the invention.

Figure 4 is a cross-sectional view of a structural component illustrating the anchoring feature of an alternative embodiment of the invention.

Figure 5 is a top view of a portion of a structural component having a plurality of anchoring features, which component may be joined according to the invention. Figure 6 is a cross-sectional view of a portion of a tubular structural component having an anchoring feature, which component may be joined according to the invention.

Figure 7 is a partial perspective view of two structural components having anchoring features that may be joined according to an alternative embodiment of the invention.

Figure 8 is a cross-sectional view of a tubular structural component having an end plug, which component may be joined according to an embodiment of the invention.

Figure 9 is a cross-sectional view of a tubular structural component having an end plug, which component may be joined according to an alternative embodiment of the invention.

Figure 10 is a perspective view of a mold and two structural components illustrating the joining of one such component at an end thereof with another at a location intermediate between the ends of such second component according to the invention.

Figure 11 is a top view of a portion of the mold and the structural components of Figure 10.

Figure 12 is a plan view of a portion of the mold and the structural components of Figure 11. Figure 13 is a perspective view of an assembly or subassembly of structural components that are joined according to the invention.

Figure 14 is a perspective view of a portion of the molding apparatus that may be utilized to construct the assembly or subassembly of Figure 13 according to the invention. The invention is useful for joining structural components made from a variety of materials, including aluminum alloys and other light metal alloys. However, the invention may also be utilized for joining structural components made from steel and other materials. In addition, the molding materials used in accordance with a preferred embodiment of the invention include aluminum and aluminum alloys. However, other light metal casting alloys, thermoplastic resins, fiber-reinforced composites and other known molding materials may also be used. Nevertheless, it is contemplated that a principal use for the invention is in the construction and assembly of spaceframes made from structural components or lineals comprised of aluminum alloys, using molding materials that are also comprised of aluminum alloys.

Aluminum alloys consist primarily of aluminum, with one of more alloying elements. Among the alloying elements commonly utilized is the group consisting of copper, iron, lithium, magnesium, manganese, silicon and zinc. These alloying elements are considered to be "essentially character forming" elements because alloys that contain one or more of such elements derive certain characteristic properties from such elements. Although iron and silicon are included in this group of essentially character forming elements, they may also be considered to be undesirable impurities when present in certain quantities.

Generally, the amounts of such elements which, if present in an alloy, will impart desirable characteristic properties are (expressed as percentage by weight of the total alloy) 0.5-10.0% copper, 0. 3- 2.0% iron, 0.2-3.0% lithium, 0.5-10.0% magnesium, 0.15- 2.0% manganese, 0.3-1.5% silicon, and 0.05-12.0% zinc. Aluminum alloys may contain, either with or without the aforementioned character forming elements, quantities of certain well-known ancillary alloying elements which serve to enhance particular properties. Such ancillary elements include bismuth, boron, cadmium, chromium, iron, lead, lithium, manganese, nickel, silicon, tin, titanium, vanadium and zirconium. Generally, the amounts of such elements which, if present in an alloy, will desirably enhance particular properties are (expressed as percentage by weight of the total alloy) 0.3-0.7% bismuth, 0.05-0.5% cadmium, 0.05-0.4% chromium, 0.3-2.0% iron, 0.3-0.7% lead, 0.2- 3.0% lithium, 0.15-2.0% manganese, 0.05-0.4% nickel, 0.3-1.5% silicon, 0.3-0.7% tin, 0.01-0.25% titanium, 0.05-0.25% vanadium and 0.05-0.25% zirconium.

Aluminum alloy compositions are described herein according to Aluminum Association alloy designations. Wrought alloys (sheet and plate, extrusions and forgings) are generally indicated by the letters "AA" followed by four numerals. Cast alloys are generally indicated by thee letters "AA" followed by four numerals, with a decimal point between the third and fourth numerals. The first numeral defines the major alloying element for both wrought and cast alloys. The major alloying element is usually 5% or less by weight in wrought alloys, and the same or a higher percentage in cast alloys. Most alloys contain two to four other elements, but in much smaller percentages than the major alloying element.

A series of related or similar alloys may be described as the Aluminum Association "5XXX Series",

for example. Such description of a series of alloys is intended to include any wrought alloy which has been designated by the Aluminum Association with a "5" as the first numeral, indicating that its major alloying element is magnesium. Thus, AA5XXX includes an alloy that may be designated "AA5000", as well as an alloy that may be designated "AA5999", as well as any alloy having a numerical designation between "5000" and "5999". In addition, a subgroup of similar or related alloys may be described by a designation such as

"AA5X52", which includes alloys that may be designated as follows: AA5052, AA5152, AA5252, AA5352, AA5452, AA5552, AA5652, AA5752, AA5852 and AA5952. Additional information about these alloy designations may be obtained by consulting the "Registration Record of International Alloy Designations and Chemical Composition Limits For Wrought Aluminum and Wrought Aluminum Alloys" published by the Aluminum Association in Washington, D.C. Temper designations are also specified by the

Aluminum Association. The temper designation tells bow the product was fabricated, and applies to both wrought and cast products. Some temper designations describe alloys and product forms that receive and respond to a thermal treatment after fabrication. These alloys are said to be heat-treatable. Wrought alloys in the 2XXX, 6XXX, and 7XXX series and most of thee cast alloys are generally in this group. Non-heat-treatable alloys gain their strength and other properties by strain hardening, and a different temper designation is specified for such alloys. Included in this group are the 1XXX, 3XXX and 5XXX series of wrought alloys. The invention may be useful in joining structural components of an automotive spaceframe, as has been mentioned. Figure 1 illustrates such a spaceframe that may be assembled according to the invention. As shown therein, spaceframe 20 is

comprised of a plurality of elongated structural components 22 (not all of which are labeled) that are joined together by molded components 24 (not all of which are labeled) according to the method disclosed and claimed herein.

Figure 1A shows the lower portion 26 of a mold that may be utilized to join together structural components 22a and 22b of spaceframe 20 of Figure 1. Similarly, Figure IB illustrates the lower portion 28 of a mold that may be utilized to join together structural components 22c and 22d of spaceframe 20 of Figure 1. Figure 2 shows the two structural components of Figure 1A as joined according to the invention Prior to placement of the elongated components in a mold, the components may be cleaned if necessary. According to a preferred embodiment of the invention, the ends to be joined are roughened by chemical means or mechanically, as by shot-blasting in order to augment the mechanical engagement between the elongated structural components and the' molded components that join them.

According to another preferred embodiment of the invention, the elongated components are also provided with anchoring features, such as extension sections, flanges, simple inaccurate holes, slots, ragged or toothed edges, dents and/or collapsed portions at the ends to be joined. Such anchoring features, which can readily be made by cheap blanking presses, are intended to provide anchoring of the elongated structural components within the molded components of the integral structures made according to the invention. The anchoring will be obtained by the fluid molding material flowing through the holes and slots, and encapsulating the other anchoring features, and subsequently solidifying into anchoring plugs. Figures 3, 4, 5, 6 and 7 illustrate the effects of certain anchoring features that may be

employed in the practice of the invention. None of these figures attempt to show the joining of structural components according to a practice of the invention; however, they are intended to show the usefulness of employing anchoring features in the practice of the invention.

Figure 3 illustrates the encapsulation and anchoring effect that may be obtained in a structural component 30 having two holes therethrough. As shown therein, component 30 has been encapsulated by molded component 32, according to a practice of the invention. A portion of the molded component has also flowed through the holes in component 30 to further anchor molded component 32 thereto. Similarly, Figure 4 shows the encapsulating effect that is obtainable according to a practice of the invention in joining a structural component 34 having a series of dents or indentations 36 therein. As shown therein, component 34 has been encapsulated by molded component 38. Figure 5 illustrates the use of a slot 40, holes 42 and toothed edges 44 that may serve as anchoring features for a structural component such as component 46. Figure 6 illustrates that the end of a hollow extruded lineal 48 may be collapsed, as at pinch points 50 and 52, to provide anchoring features.

Figure 7 shows two tubular extrusions 54 and 56 that have been fastened together by a method such as the punch/joining method that is described in U.S. Patent No. 4,611,381 prior to being joined according to the invention. The result is a hole 58 having interlocking collars 60 and 62 that serve to fasten the extrusions together and provide a hole through which an anchoring plug of molding material (not shown) can be formed. Although Figure 7 illustrates elongated structural components that are fastened together prior to being placed in the mold according to the invention,

it is not necessary that the elongated structural components be fastened together at all prior to placement in the mold. However, according to a preferred embodiment of the invention, such fastening may provide improved results.

Referring again to Figures 1A, 2 and IB, each of components 22a and 22b (of Figures 1A and 2) are extrusions having a rectangular cross section and an anchoring feature comprised of a flat extension section 64a and 64b. Similarly, each of components 22c and 22d (of Figure IB) are extrusions having a rectangular cross section and anchoring holes 66c and 66d. A pair of such holes is shown in each of components 22c and 22d, although any convenient number could be provided. Components 22a and 22b are joined together loosely by threaded fastener 68 prior to being placed in mold portion 26. Use of a threaded fastener is only one of the ways in which such fastening may be accomplished, although as has been mentioned, such fastening is not required. If desired, however, the elongated components may alternatively be fastened together, prior to being joined according to the mold- joining method of the invention, by any other known and convenient fastening method, including welding, clinching and adhesive bonding, as well as the method illustrated in Figure 7. Components 22a and 22b could also be joined together by placing a wire, cotter pin or the like (not shown) through the hole in their extension sections, instead of fastener 68. It is not necessary that the fastening be accomplished with the degree of reliability required of such fastening techniques according to prior practices, because such fastening does not provide the primary means of joining of the elongated components. Instead, the elongated components are fastened together according to this embodiment of the invention in order to facilitate transport of the components to the mold, to facilitate

their placement in the mold in the proper orientation for being joined together and to help to insure that the components remain in the proper orientation and position in the mold during the joining process. In cases where the lineals are tubular extrusions, such as components 22a and 22b of Figures 1A and 2, and 22c and 22d of Figure IB, flow barriers may be incorporated to prevent the flow of fluid molding material into the hollow parts of the lineals. Such barriers may comprise plugs that fit within the extrusions, such as plugs 70a and 70b that are shown within the open ends of components 22a and 22b, respectively, of Figures 1A and 2. Alternatively, they may be incorporated into the molds, such as barriers or dams 72c and 72d of mold portion 28 of Figure IB.

Preferred results have been obtained when such plugs or barriers are comprised of sand, such as molding sand. Other plugs may be formed of metal of another suitable material, such as the cup shaped plug 74 shown in the end of tubular component 76 of Figure 8, or the magneformed plug 78 shown in the end of tubular component 80 of Figure 9.

According to the practice of the invention, a mold means is provided which is adapted to receive therein in a supporting manner a portion of each of a plurality of elongated structural components. Referring again to Figures 1A and IB, lower portions 26 (Figure 1A) and 28 (Figure IB) of such mold means are illustrated. Elongated structural components, such as components 22a and 22b of Figure 1A, are then placed in the lower section of the mold in close proximity to each other in the configuration in which they are to be joined. Flat extension sections 64a and 64b of components 22a and 22b, respectively, are shown overlapping in mold section 26. Similarly, the ends of components 22c and 22d of Figure IB are shown in close proximity in mold section 28. The orientation of

components in the mold will depend on the design of the mold and mold cavity, which will in turn depend on the shape of the structural components and the configuration of the structural assembly or subassembly to be constructed according to the invention. In addition, the mold cavity, such as cavity 82 (Figure 1A) and cavity 84 (Figure IB) will preferably include some space around the ends of the components to be joined together to accommodate the fluid molding material that will effect the joining.

After arrangement of the elongated components in the lower portion of the mold, the upper portion of the mold is lowered into place to mate with the lower portion. Of course, it should be appreciated that the mold can be designed to have left and right sections, or more than two sections, depending on the number of elongated components to be joined and the nature and orientation of the joint to be formed. Several of the joints in an automotive spaceframe such as spaceframe 20 of Figure 1 unite three or four elongated structural components, and the design of the mold means necessary to permit joining of such components according to a practice of the invention will be somewhat more complex than is required to join two components. The structural components that may be joined according to the invention include aluminum alloys and other light metal alloys, steel and other structural materials. However, as has been mentioned, the invention is particularly useful in the construction of spaceframe structure from elongated structural components made from aluminum alloys. Preferred results have been obtained when the invention is utilized to join structural components or lineals comprised of aluminum alloys selected from the group consisting of non-heat-treatable AA5XXX alloys and heat-treatable AA6XXX alloys.

After the mold is assembled with the portions

of the structural components to be joined therein, a fluid molding material is introduced into the mold means. The fluid molding material may be introduced under pressure, by gravity feed, or by inducing a partial vacuum in the mold cavity. As has been mentioned, light metal casting alloys (such as aluminum alloys) , thermoplastic resins, fiber reinforced composites and other known molding materials may be used. Preferred results have been obtained in joining lineals of aluminum alloys by a use of an aluminum casting alloy selected from the group consisting of non-heat-treatable AA5xx.x and heat-treatable AA3xx.x alloys. A preferred non-heat-treatable casting alloy is AA518.0, and a preferred heat-treatable casting alloy is AA356.0.

Of course, when the fluid molding material used is a molten metal suitable for casting, it is preferred that the mold means be of a heat dissipating type. Such molds are typically provided with an internal cooling mechanism, and they dissipate heat from the molten metal by means of water cooling, oil cooling or evaporative cooling.

If the lineals to be joined according to the invention are comprised of non-heat-treatable alloys, a use of non-heat-treatable cast alloys, or at least alloys that do not require solution heat treating, as the molding material will provide preferred results. It would also be preferred that the alloys of which the lineals are comprised do not require artificial aging. However, if aging is required for the lineals, the cast alloy will preferably be matched in aging response with the alloy of the lineals.

It is not believed that a consistent metallurgical bond is always obtained between the cast alloy and the alloy of the lineals. Instead, it is believed that the cast joints behave more like mechanical joints such as bolted joints than like

metallurgical joints such as welded joints. However, by having the cast alloy solidify in close and intimate contact with the lineals ends, especially where anchoring features are provided, it is anticipated that the joint will be as strong as a welded joint and exhibit superior fatigue resistance.

Elimination of welding operations in the construction of spaceframes will significantly reduce weld-induced distortion in the spaceframe components. The gas metal arc welding process requires the administration of an intense, localized heat source to the components to be joined thereby. Welding produces intense residual stresses at the joints. Furthermore, as the welds solidify, they tend to shrink. These effects frequently result in distortion in the assemblies so constructed. According to a practice of the invention, however, flowing a casting alloy or other molding material about the portions of the components to be joined will involve significantly lower and more uniformly distributed temperatures about the joints, and will thereby eliminate or minimize any resulting distortion.

An alternative embodiment of the invention may be utilized, wherein the fluid molding material is a thermoplastic resin. Preferably, in the use of such a material, the casting process is replaced with injection molding of a high-strength, impact-resistant, fiber-reinforced polymer, such as bis-phenol-A-epoxy, that has been mixed with relatively short, ultra-strong fibers, such as chopped AS-400 graphite fibers.

Preferred results have been obtained in such case when such carbon fibers, each having a length of less than about 2 millimeters, are suspended in the fluid molding material. Of course, the thermoplastic or composite materials selected for use in the practice of the invention must meet the structural reguirements of the assembly to be joined thereby.

The use of such thermoplastic molding materials in the assembly of lineals in accordance with the invention offers certain advantages over a use of casting alloys. It may be possible to mold more intricately shaped molded components, with a combination of structural and aesthetic functions. The molded plastic nodes could serve aesthetics by being designed for partial exposure to the exterior of a vehicle, for example. In addition, plastic nodes will shrink less upon curing or solidification than will aluminum alloy castings. A use of thermoplastic molding materials will completely eliminate the need to solution heat treat and age the nodes, and will avoid any associated difficulties, such as distortion of parts upon quenching, and extra handling that such treatments may involve. Furthermore, the use of plastic molded nodes will eliminate the possibility of an adverse metallurgical reaction between the cast alloys and the alloys of the lineals. The capital and operating costs of a system for molding with plastic or composite materials is expected to be less than that required for casting with molten alloys. Furthermore, the molds for use in mold/joining the lineals with thermoplastic or composite materials will be significantly lighter in weight and cheaper than those required for a use of casting alloys.

Regardless of the fluid molding material utilized in the practice of the invention, after placement of the lineals in the mold means and introduction of the fluid molding material therein, the molding material is allowed to solidify or cure around the elongated structural components in the mold, thereby forming an integral structure consisting of a plurality of elongated structural components that are joined together by a molded component. Upon solidification of the molded component, the mold

sections are separated, and the completed assembly or subassembly is removed preferably with the aid of pneumatically- or mechanically-actuated release pins built into the mold sections. An example of structural components joined according to a practice of the invention is illustrated in Figure 2, where lineals 22a and 22b of Figure 1A are shown as joined by molded component 86.

Figures 10, 11 and 12 illustrate how the invention may be utilized to join one end of a first structural component to a second component at a point intermediate from the end of the second component. As shown therein, one end of component 88 is joined to component 90 at an intermediate point away from the ends of component 90. The components are placed in close proximity to each other in lower mold section 92 (Figure 11) , and upper mold section 94 is lowered to mate with section 92. The mold is designed so that cavity 96 is provided around the portions of the components to be joined to accommodate the fluid joining material. Fluid joining material is introduced into the mold by conventional means (not shown) and allowed to solidify around the portions of components 88 and 90 to be joined. Figure 13 illustrates a structural assembly, subassembly or frame 98 that has been made according to the invention by the simultaneous joining of extruded components. As shown therein, components 100 and 102 are joined by molded component 108, components 102 and 104 are joined by molded component 110, components 104 and 106 are joined by molded component 112 and components 106 and 100 are joined by molded component 114.

Figure 14 illustrates the joining process by which the components of assembly 98 (Figure 13) are joined. As shown therein, lower mold sections 116, 118, 120 and 122 are mounted on base 124. Of course,

the base will be designed as needed for the particular application. It may not necessarily be a solid structure such as shown in Figure 14.

Component 100 is placed with the end to be joined to component 106 in section 116 and the end to be joined to component 102 in section 118. Component 102 is placed with the end to be joined to component 100 in section 118 and the end to be joined to component 104 in section 120. Component 104 is placed with the end to be joined to component 102 in section 120 and the end to be joined to component 106 in section 122. Component 106 is placed with the end to be joined to component 104 in section 122 and the end to be joined to component 100 in section 116. As shown, all components are placed with their ends to be joined in close proximity each to the other. Components 100, 102, 104 and 106 are all illustrated as being provided with anchoring holes 126 at each end to be joined. After the components to be joined are placed in the lower mold sections, upper mold sections 128, 130, 132 and 134 are lowered so as to mate respectively with lower sections 116, 118, 120 and 122. After the mold is assembled with the portions of the structural components to be joined therein, a fluid molding material, preferably an aluminum casting alloy, is introduced simultaneously into the separate molds. The fluid molding material may be introduced under pressure, by gravity feed, or by inducing a partial vacuum in the mold cavity. For simultaneous supply of the fluid molding material to the different molds, the launder system of supply is preferably utilized.

After placement of the lineals in the molds and introduction of the fluid molding material therein, the molding material is allowed to solidify or cure around the elongated structural components in the mold, thereby forming an integral structure consisting of a

plurality of elongated structural components that are joined together by a molded component. Upon solidification of the molded component, the mold sections are separated, and the completed assembly or subassembly is removed, preferably with the aid of pneumatically- or mechanically-actuated release pins built into the mold sections. It has been found that the simultaneous supply and solidification of the casting alloy at the different nodal points in the practice of the invention will provide a more balanced stress distribution throughout the assembly and reduced' assembly distortion than would be obtained if the lineals were joined to the nodes by welding.

Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus, the invention, as described herein, is susceptible to various modifications and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.