SPACE FRAME APPARATUS AND PROCESS FOR THE MANUFACTURE OF SAME

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to frame structures, and, more particularly, to space frame apparatuses, and the process for manufacturing same, wherein such a space frame apparatus is used in the construction of various vehicles, such as automotive and aviation vehicles, and wherein the space frame apparatus is intended to structurally bear a sub¬ stantial load of such a vehicle when fully assem¬ bled.

2. Background Art

Space frame structures for use in the construction of vehicles have been know in the art for several years. Typically, such space frames have been constructed from a plurality of individual aluminum alloy extrusions which are joined together at nodes generally fabricated from cast or wrought shapes. Each of the nodes generally comprise three to four connecting regions which each fit into the hollow sections of the ends of corresponding ones of the individual extrusions. The ends of the extrusions may then be secured to the respective nodes through welding or adhesive bonding. Two examples of such a

node-type construction can be found in Browning, U.S. Pat. No. 4,735,355, and, in an article in the May 1991 Materials Engineering Magazine, referring to "Automotive Aluminum." Although use of nodes for attachment of individu¬ al, segmented extrusions, have indeed been utilized, such a construction has resulted in concerns rela¬ tive to the structural integrity of such connections -- especially inasmuch as both welds and adhesive bonding have a tendency to fatigue upon exposure of excessive vibration and stress typically imparted to such connections during normal operation of a vehi¬ cle employing such a space frame structure. Fur¬ thermore, when nodes, or the like, are used in a space frame, the space frame requires numerous individual extruded frame segments and numerous nodes for connection therewith. Accordingly, the costs associated with such a construction, coupled with concerns from a structural perspective, have resulted in the need for a better alternative.

Although the above-identified prior art utilizes a plurality of individual, segmented frame portions in combination with connecting nodes, other prior art space frames have been constructed from continuous frame portions, without reliance upon nodes. One example of such prior art is Malmurno. U.K. Pat. Apln. GB 2 131 361 A. Although Malmurno does uti¬ lize continuous frame portions, the cross-members which maintain the outer frame portions in an erect- ed orientation appear to be merely welded to the frame. Accordingly, the same concerns pertaining to fatigue of the connection between the cross-member and the outer frame portions persist -- even without the use of nodes.

Although prior art space frames disclose continu¬ ous outer frame portions, as well as means for connecting cross-members to the frames, none of such prior art teaches, much less discloses, one or more continuous outer frame portions which include pre¬ liminarily pre-softened regions, which are softened through localized heat induction, and, wherein the one or more continuous outer frame portions are then bendable to varying radii in any predetermined direction relative to a particular vehicle configu¬ ration. Furthermore, none of such prior art teach¬ es, much less discloses attachment of cross-members to the continuous outer frame portions of a space frame wherein the respective ends of the cross- members are insertable into corresponding slots within the continuous frame portions, and wherein the ends of the cross-members include a flange and collar portion each formed upon softening through localized heat induction and then deformation -- for purposes of securely pinching the cross-member to the inner and outer peripheral surfaces of the corresponding slots.

It is thus an object of the present invention to provide a space frame apparatus constructed from one or more continuous outer frame portions which are secured in an erected orientation through coopera¬ tion with one or more cross-members -- without reliance upon separate connecting elements, or nodes. it is also an object of the present invention to provide a space frame apparatus wherein secured connection of the one or more cross-members to the one or more continuous outer frame portions is maintained by a compression fit between the flange

and collar portion of the ends of the cross-members about the inner and outer peripheral surfaces of the corresponding slot shoulders, and wherein such flange and collar portions are formed by softening the distal and proximal ends of the cross-members through localized heat induction and then deforming same into such a flange and collar configuration.

It is still further an object of the present invention to provide a space frame apparatus wherein the one or more continuous outer frame portions are constructed from aluminum extrusions which have a plurality of predetermined areas pre-softened through localized heating so that continuous extru¬ sions can be bent to varying predetermined radii in predetermined directions relative to a specific vehicle configuration, and wherein the bent regions are then allowed to harden toward their original hardness.

It is yet another object of the present invention to provide a space frame apparatus having superior structural integrity at the connecting joint between the cross-members and the continuous outer frame portions, and which can be manufactured at relative¬ ly low costs. These and other objects of the present invention will become apparent in light of the present Speci¬ fication, Claims and Drawings.

DISCLOSURE OF THE INVENTION

The present invention comprises a space frame apparatus for use in the construction of various vehicles, such as automotive and aviation vehicles, wherein the space frame apparatus is intended to structurally bear a substantial load of such a vehi¬ cle when fully assembled.

The space frame apparatus includes one or more continuous outer frame means, having one or more pre-selected attachment regions, for providing an outer frame for a vehicle, and one or more cross- member means each having at least a first end opera¬ bly attached to the one or more frame means at corresponding ones of the one or more pre-selected attachment regions. Such cross-member means serve to increase the structural rigidity of the appara¬ tus, as well as to enable articulation of the one or more continuous outer frame means into an erected orientation.

Slot means, having an inner and outer peripheral surface, are integrally formed through at least a portion of the one or more pre-selected attachment regions for operably accepting at least a portion of corresponding respective ones of the at least first ends of the one or more cross-member means. Secure- ment means are operably associated with at least a portion of each of the first ends of the one or more cross-member means and the corresponding slot means for operably securing the first ends within the corresponding slots means, to, in turn, securely maintain the space frame apparatus in the erected orientation. The securement means further include at least a portion of the first ends of the cross-

member means being softened through localized heat¬ ing, and then deformed, so as to maintain the re¬ strained operable positioning of the first end within the corresponding slot means. In the preferred embodiment of the invention, the operable acceptance of the first ends of the cross- member means within the corresponding slot means describes a joint therebetween the cross-member means and the one or more continuous outer frame means. Furthermore, strength enhancement means are operably associated with the joint for imparting increased structural integrity thereto, to, in turn, increase rigidity against imparted stress at the joint. In this preferred embodiment of the invention, the one or more cross-member means further includes an interior surface defining a channel region and a wall having a finite thickness. The strength en¬ hancement means comprises at least one sleeve mem- ber, or ferrule, operably positioned within at least a portion of the channel region of the one or more cross-member means adjacent the interior surface of at least the first end of same -- so as to reinforce the finite wall thickness of the cross-member means within the joint.

Each of the at least first ends of the one or more cross-member means have an inner dimension, and, the at least one sleeve member has an outer dimension so as to collectively describe an interference fit therebetween. Accordingly, the interference fit additionally serves to maintain the sleeve member within at least a portion of the channel region of the first end of a corresponding one of the one or more cross-member means.

In one preferred embodiment of the invention, the sleeve member includes an inner edge operably posi¬ tioned within the channel region of a corresponding one of the at least first ends of the one or more cross-member means, and an outer edge extending through and past a corresponding one of the slot means.

The securement means further includes at least a portion of the outer edge of the sleeve member being softened through localized heating, and then de¬ formed, so as to result in a flange portion operably positioned adjacent the outer peripheral surface of the slot means to, in turn, further enhance secure¬ ment of respective ones of the at least first ends of the one or more cross-member means within the corresponding slot means.

The at least first ends of the more or more cross- member means each include a proximal end operably positionable adjacent the inner peripheral surface of the slot means. Each of the proximal ends may be softened through localized heating, and then de¬ formed, so as to form a detent, or collar portion, adjacent the inner peripheral surface of a corre¬ sponding one of the slot means. In one embodiment of the invention, the slot means have an inner dimension, and each of the at least first ends of the one or more cross-member means have an outer dimension so as to collectively de¬ scribe an interference fit therebetween. The inter- ference fit serves to maintain at least a portion of the first ends of the one or more cross-member means within at least a portion of a corresponding one of the slot means.

In the preferred embodiment of the invention, the

at least first ends of the one or more cross-member means each include a distal end and a proximal end wherein the distal end extends through and past the corresponding slot means in which the first end is positioned. The securement means further includes the distal and proximal ends being softened through localized heating, and then deformed, so as to form a detent, or collar portion, adjacent the inner peripheral surface of a corresponding one of the slot means, and, one or more flanged regions opera¬ bly positioned adjacent the outer peripheral surface of the corresponding slot means. Accordingly, such a flange/collar configuration creates a substantial¬ ly locked joint relative to the at least first end of the one or more cross-member means and the corre¬ sponding slot means.

In another preferred embodiment of the invention, the one or more continuous outer frame means com¬ prise two or more continuous outer frame portions. The two or more continuous outer frame portions include one or more pre-softened regions softened through localized heating for facilitating bending of the two or more continuous outer frame portions at varying radii in any desired direction. Each of these continuous outer frame means may be construct¬ ed from a single unitary member, or, alternatively, from a first half and a second half which are opera¬ bly secured together so as to collectively form a unitary frame portion. In the preferred embodiment of the invention, the one or more continuous outer frame means and the one or more cross-member means are each constructed of an aluminum material from the group comprising 6000- series alloys of varying hardnesses, such as a 6061-

T6 aluminum alloy.

The invention includes the process of manufactur¬ ing a space frame apparatus wherein the space frame apparatus is constructed with one or more bendable outer frame members having pre-selected attachment regions located thereon. The process includes the steps of a) forming slots in the one or more bend- able outer frame members at the pre-selected attach¬ ment regions, wherein the slots include an inner peripheral surface and an outer peripheral surface; b) softening predetermined areas on the one or more outer frame members through localized heating; c) bending the one or more bendable outer frame members at each of the predetermined areas to varying prede- termined radii in predetermined directions relative to a specific vehicle configuration; d) at least partially hardening the predetermined softened areas after bending the one or more bendable outer frame members so as to increase structural integrity to the predetermined areas; e) forming at least one cross-member with at least a first end having a distal end, a proximal end and a cross-sectional configuration; f) softening the proximal ends of the at least one cross-member through localized heating; g) deforming at least a portion of the softened proximal ends of each of the first ends so as to alter the pre-deformed cross-sectional config¬ uration of same, to, in turn, create a detent por¬ tion operably positioned adjacent the inner periph- eral surface of a corresponding slot for precluding over insertion of the first ends into the corre¬ sponding slots in the one or more outer frame mem¬ bers; h) inserting the first end of the at least one cross-member in a corresponding one of the slots in

the bent one or more outer frame members so as to form a joint therebetween each respectively; and i) hardening the locally softened proximal ends back toward the pre-softened hardness. In the preferred embodiment of the invention, the process for manufacturing a space frame apparatus further includes the steps of softening the distal ends of the first ends of the at least one cross- member through localized heating; deforming at least a portion of the softened distal ends of the first ends of the at least one cross-member so as to form a flange portion operably positioned adjacent the outer peripheral surface of corresponding ones of the slots; and, hardening the locally softened distal ends back toward their pre-softened hardness, after the step of softening the proximal ends of the at least one cross-member through localized heating. Accordingly, these flanged portions, in cooperation with the detent/collar portions, serve to lockably secure the cross-members to the continuous outer frame members by way of a compression fit.

In another embodiment of the invention, the proc¬ ess of manufacturing a space frame apparatus further includes the step of increasing structural integrity to the joint after the step of forming the at least one cross-member. This step of increasing the structural integrity to the joint comprises the step of inserting at least a portion of a sleeve member, or ferrule, within at least a portion of the at least first end of the at least one cross-member prior to the step of inserting the at least first end of the at least one cross-member in correspond¬ ing ones of the slots.

In this preferred embodiment, the sleeve member

includes an outer end and an inner end, and the at least first ends of the at least one cross-member includes a channel region. The step of inserting the at least first ends of the at least one cross- member in corresponding ones of the slots further includes the steps of inserting the inner end of the sleeve member within the channel regions of the at least one cross-member; inserting the at least first ends of the at least one cross-members, and, in turn, the sleeve member, into a corresponding one of the slots until at least a predetermined portion of the outer end of the sleeve member extends past the outer peripheral surface of a corresponding one of the slots; softening the outer end of the sleeve member through localized heating; deforming at least a portion of the softened outer end of the sleeve member so as to form a flange portion operably positioned adjacent the outer peripheral surface of the corresponding slot; and hardening the locally softened outer end of the sleeve member back toward its pre-softened hardness.

In yet another embodiment, the process of manufac¬ turing a space frame apparatus further includes the steps of extruding a billet so as to form one or more substantially straight extrusions to be used as the one or more bendable outer frame members, prior to the step of forming slots in the one or more bendable outer frame members at the pre-selected attachment regions. In addition, the step of bend- ing the one or more bendable outer frame members at each of the predetermined areas to varying predeter¬ mined radii in predetermined directions relative to a specific vehicle configuration further includes the step of positioning the bent portions of the one

or more bendable outer frame members in any desired dimension, so as to form a space frame apparatus constructed from one or more continuous outer frame members.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 of the drawings is a perspective view of a prior art automotive space frame showing, in partic- ular, the plurality of individual segmented frame portions and the plurality of connecting nodes used for connecting each of the individual segments together;

Fig. 2 of the drawings is an enlarged sectional view, in partial cross-section, of a prior art connecting node of Fig. 1, showing, in particular, the operable positioning of the ends of the nodes into hollow end regions of corresponding ones of the individual segmented frame portions, and, into the hollow ends of the corresponding cross-members;

Fig. 3 of the drawings is a perspective view of the present space frame apparatus showing, in par¬ ticular, the substantially uninterrupted continuous outer frame means, the cross-member means used to maintain the continuous outer frame means in an erected orientation, as well as the flanged portions of one of the ends of each of the cross-member means operably secured against the outer peripheral sur¬ face of a corresponding slot means; Fig. 4 of the drawings is a perspective view of a substantially linear shaft which is used to form one of the continuous outer frame means of Fig. 3, showing, in particular, the slot means operably formed at predetermined locations thereon, as well as the pre-softened regions which will facilitate appropriate bending thereat;

Fig. 5 of the drawings is an enlarged cross-sec¬ tional view of one of the cross-member means of Fig. 1 as well as the corresponding slot means of the

continuous outer frame means, showing, in particu¬ lar, the collar portion and flange portion of the end of the cross-member means operably compressing the inner and outer peripheral surfaces, respective- ly, of the slot means so as to result in a locked compression fit of the cross-member to the continu¬ ous outer frame means, as well as showing an option¬ al ferrule inserted within the channel region of the end of the cross-member means; Fig. 6 of the drawings is an enlarged cross-sec¬ tional view of a cross-member means secured to a corresponding slot means in the continuous outer frame means, showing, in particular, the pinched, or crimped, collar portion of the cross-member means operably positioned adjacent the inner peripheral surface of the slot means;

Fig. 7 of the drawings is an enlarged cross-sec¬ tional view of an alternative embodiment of the invention, showing, in particular, a substantially solid I-beam construction for the continuous outer frame means, as well as the lockable securement of one end of the cross-member means to a slot in the I-beam, as well as showing an alternative double- backed flange portion of the cross-member means operably positioned adjacent the outer peripheral surface of the corresponding slot;

Fig. 8 of the drawings is an enlarged cross-sec¬ tional view of the cross-member means of Fig. 7, showing, in particular, the operable positioning of a sleeve member within the channel region of the end of the cross-member, as well as showing the flanged outer end of the sleeve member operably positioned adjacent the flange portion of the cross-member means;

Fig. 9 of the drawings is an enlarged cross- sectional view of a cross-member means operably secured within a slot of an alternative embodiment of the continuous outer frame means, showing, in particular, the first and second halves of the con¬ tinuous outer frame means which collectively de¬ scribe a single, unitary frame portion; and

Fig. 10 of the drawings is an elevated enlarged break-away perspective view of the continuous outer frame means of Fig. 9, showing, in particular, the collar and flange portion of a corresponding cross- member means operably positioned adjacent the inner and outer peripheral surfaces, respectively, of the corresponding slot means.

BEST MODE FOR CARRYING OUT THE INVENTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail, several specific embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the inven¬ tion and is not intended to limit the invention to the embodiments illustrated.

Prior art automotive space frame 20 is shown in Fig. 1 as including a plurality of tubular individu¬ al frame portions, such as individual frame portions 22 through 24, a plurality of tubular cross-members, such as cross-members 26 and 27, and a plurality of connecting elements, or nodes, such as node 21 (Fig. 2) . As shown in detail in Fig. 2, each of the nodes include insertion ends, such as insertion ends 28 and 29, which are insertable into the hollow end portions of corresponding ones of the individual frame portions, such as frame portions 22 and 23, and into the hollow end portions of corresponding ones of the cross-members, such as cross-members 26 and 27. Actual securement of the insertion ends of the nodes within the hollow ends of the prior art cross-members and within the individual frame por¬ tions can be accomplished through conventional welding techniques and/or through the use of adhe¬ sive bonding. Once fully connected, prior art space frame 20 will include two outer frame members 25 and

25' comprised of a plurality of individually con¬ nected frame portions, a plurality of connecting nodes, and a plurality of cross-members which will maintain the outer frame members in an erected

orientation.

Space frame apparatus 30 of the present invention is shown in Fig. 3 as comprising two continuous outer frame means 31 and 32 and cross-member means 34 through 48. Continuous outer frame means 31 and 32 both include a plurality of pre-selected attach¬ ment regions (slot means) , such as slot means 50 through 58, as shown more clearly on substantially linear shaft 31' (Fig. 4), which will be used to form continuous outer frame means 31, and a plural¬ ity of bent regions, such as bent regions 61 through 66. As will be further explained in detail herein- below, each of the bent regions are formed as the result of softening predetermined locations 61' through 66' on substantially linear shaft 31' ' (Fig. 4) through localized heating, and then bending the shaft at each of the predetermined softened loca¬ tions to varying predetermined radii in predeter¬ mined directions so as to conform to a specific vehicle configuration, such as the vehicle configu¬ ration shown in Fig. 3. Slots, such as slot 52 (Fig. 5) , which operably accept a portion of corre¬ sponding ones of the cross-member means, such as cross-member means 36, each include an inner periph- eral surface 90, an outer peripheral surface 91 and an inner dimension 92.

Cross-member means, such as cross-member means 36, is shown in Fig. 5, as including a first end, such as first end 70, a second end (not shown) , an inte- rior surface, such as interior surface 72, and an inner dimension defining a channel region 73. The first and second ends of the cross-member means each include a distal end, such as distal end 80, having a flange portion, such as flange portion 83, and a

proximal end, such as proximal end 81, having a detent, or collar portion, such as collar portion 82. In this embodiment, collar portion 82 may be formed by swaging first end 70 of the cross-member means -- although other techniques for forming the collar, such as by pinching or crimping, are also contemplated.

Each of the first and second ends of the cross- member means are operably inserted into a corre- sponding slot, such as corresponding slot 52 (Fig. 5) where they are then secured in place so as to maintain space frame apparatus 30 in an erected orientation, as shown in Fig. 3. As will be ex¬ plained in detail, such securement results from a locked joint between the ends of the cross-member means and the corresponding slots. Such a locked joint is achieved as the result of the collar por¬ tion, such as collar portion 82, of the cross-member means, such as cross-member means 36, compressing against inner peripheral surface, such as inner peripheral surface 90, of corresponding slot 52, and then forming and positioning flange portion, such as flange portion 83, so that it is squeezing against outer peripheral surface, such as outer peripheral surface 91, of corresponding slot 52 -- so as to result in a compression fit therebetween. As will also be explained, such flanged and collared por¬ tions are formed by softening the respective distal and proximal ends of the cross-member means through localized heating, and then deforming same until the collar and flange portions are created.

Strength enhancement means 95 is shown in alterna¬ tive form in Fig. 5 as comprising a sleeve member, or ferrule, having an outer surface 96, an inner

edge 97, and an outer edge 98. The sleeve member is inserted within channel region 73 of a respective end, such as first end 70, of cross-member means, such as cross-member means 36, so as to increase rigidity to the joint formed upon insertion of the respective ends of the cross-member means within the corresponding slot means, such as slot means 52. Securement of sleeve member 95 to the cross-member means can be obtained by way of an interference fit between outer surface 96 of the sleeve member and at least a portion of channel region, such as channel region 73 (Fig. 5) , of the respective end of the corresponding cross-member means -- although other conventional securement techniques, such as welding or adhesive bonding of the sleeve member to the cross-member means are also contemplated. Also shown in Fig. 5 is an alternative construction of the continuous outer frame means wherein the contin¬ uous outer frame means may be constructed from two halves 125 and 126 which are secured together by keyed portions 127 and 128. In addition to such keyed portions, further securement can be maintained by, for example, welding.

An alternative construction of collar portion 82' is shown in Fig. 6 wherein the collar portion is operably positioned adjacent inner peripheral edge 90 of corresponding slot means 52. Such a collar portion is formed as the result of pre-softening proximal end 81 of first end 70 of the cross-member means, and then-pinching the softened region until the collar is formed -- as opposed to swaging. Although this embodiment is shown without the use of a ferrule, such reinforcement is indeed contemplat¬ ed.

Cross-member means 36' is shown in Fig. 7 and Fig. 8 as being operably attached within a corresponding slot means, such as slot means 52', of continuous outer frame means 100 (Fig. 7) having I-beam config- uration. The corresponding cross-members means, such as cross-member means 36', is operably secured within slot means 52', and, in turn, to continuous outer frame means 100, through a compression fit, wherein the flange and collar portions 83' and 82'', respectively, of the cross-member means, are opera¬ bly squeezed and maintained about extending portions 103 and 104 of the I-beam.

Also shown in Fig. 7 and Fig. 8, is alternative double-backed flange portion 106 (Fig. 7) which may be used for providing additional securement to the locked joint, as well as utilization of sleeve member 110 (Fig. 8) . Although the sleeve member has substantially the same configuration as that of sleeve member 95, as shown in Fig. 5, sleeve member no additionally includes outer end 98' having a flange portion 112 which extends beyond the outer peripheral surface of the corresponding slot means, as well as past flange portion 83' (Fig. 8) of the corresponding cross-member means. Such a flange on the sleeve member can be used to provide additional securement to the joint, and/or additional secure¬ ment to the cross-member means itself. Although not shown, such additional securement can be further obtained through welding or bending the sleeve member, through adhesive, to the end of a corre¬ sponding cross-member means. Furthermore, it is also contemplated that when such a flanged sleeve member is used, the distal end of the corresponding end of the cross-member means may be constructed

without a flange portion. Accordingly, lockable engagement of the cross-member means to the continu¬ ous outer frame means will occur through a compres¬ sion fit, adjacent a corresponding slot, as a result of the flange on the sleeve member, and the collar portion on the proximal end of a respective end of the cross-member means, squeezing the respective inner and outer peripheral surfaces of the corre¬ sponding slot means. An alternative embodiment of continuous outer frame means 130 is shown in Fig. 9 and Fig. 10 as comprising first half 131 and second half 132. Each of these halves include lip portions 133, 134 and 135, 136, respectively, which are secured together so as to form a single unitary frame portion. When such a configuration is utilized, a predetermined segment of the lip portions will be removed upon formation of the slots so as to facilitate operable acceptance of the corresponding ends of the cross- member means, and in turn, formation and position of the flange and collar portions about same. Although substantially rectangular and I-beam configured continuous outer frame means have been shown, other configurations, such as circular and hexagonal, among others, are also contemplated.

The process for constructing space frame apparatus 30 (Fig. 1) is achieved by first extruding linear sections, such as linear section 31' (Fig. 4) and then quenching the extrusions at press. Although several types of material can be used for such extrusions, aluminum alloys of the 6000-series of having varying hardnesses are preferred. Further¬ more, although hollow extrusions are preferred for purposes of fabricating the one or more continuous

outer frame means 31 and 32 (Fig. 1) (due to their relatively light weight and minimized material requirements) solid extrusions, such as extrusions having an I-beam configuration 100 (Fig. 7) , as well as non-extruded sections, are also contemplated for use.

After the extrusions have been quenched, they are substantially straightened and then heat treated and cut to a particular length suitable for the particu- lar vehicle configurations required. Accordingly, once cut to length, a required number of slots, such as slots 50 through 58 (Fig. 4) , are formed in the extrusions for eventual acceptance of the end por¬ tions of corresponding cross-members 34-48 (Fig. 3) . Such slots can be formed through a punching opera¬ tion, in conformance with a predetermined pattern relative to the structural connection required for a specific vehicle configuration, or, they may be formed by any other conventional slot forming tech- niques.

After the slots have been formed in the extru¬ sions , a specified number of predetermined regions , such as predetermined regions 61 ' through 66 ' (Fig . 4 ) , are softened through localized heating so as to at least temporarily increase ductility to the linear extrusions at the predetermined sof tened regions . One such acceptable method for softening the predetermined regions by localized heating is disclosed in U . S . Pat . No . 4 , 766 , 664 , issued to Joseph C . Benedyk, for a Process for Formation of High Strength Aluminum Ladder Structures . In such a process , an induction coil is placed in operable contact with the specific area to be heated, and, in turn, softened - - with only minimal conductivity to

adjacently positioned portions of the softened region. Although the use of an induction coil can be used (such as disclosed in U.S. Pat. No. 4,766,664) , other types of conventional heating processes for temporarily increasing ductility to localized areas are also contemplated.

After the longitudinal extrusions have been local¬ ly softened, each of the predetermined regions are bent to varying radii in predetermined directions relative to a specific vehicle configuration. It is contemplated that such bending be performed either manually, or on automated bending equipment pre¬ programmed with the particular bending requirements and bending locations relative to specific vehicle configurations. Accordingly, such bending will result in the formation of one or more continuous outer frame portions, such as outer frame portions 31 and 32 (Fig. 3) , constructed substantially from a single, substantially uninterrupted extrusion. Upon completion of the formation of the continuous outer frame portions, each of the locally softened regions are then allowed to harden toward their pre- softened hardness, as desired. The amount of hard¬ ness which will be regained will be dependent upon the specific type of alloy used for formation of the continuous outer frame portions, the amount of precipitation in the alloy prior to heating, inten¬ sity of the heat applied, as well as the length of time in which the heat is applied to the specific predetermined regions.

In addition to the continuous outer frame members being extruded, the process also includes extruding cross-members 34-48 (Fig. 3) to have first ends, such as first end 70 (Fig. 5) , second ends (not

shown) , and a distal and proximal end, such as distal and proximal ends 80 and 81 (Fig. 5) , respec¬ tively, at each of the first and second ends. After the cross-members have been extruded, the respective proximal ends are locally softened by the same or similar localized heating process as that used for the continuous outer frame members. Once softened, the proximal ends are deformed so as to form a collar portion, such as collar portions 82 (Fig. 5) and 82' (Fig. 6). The formation of collar portion 82 (Fig. 5) may be accomplished through the use of conventional swaging techniques, while formation of collar portion 82' (Fig. 6) may be formed by merely pinching, or crimping the softened portion of the cross-member. After the collar portions are formed, they are allowed to harden back toward their pre- softened hardness through conventional hardening methods.

Once the collar portions have been formed, the respective first and second ends of the cross-member means can be operably inserted within a correspond¬ ing slot, such as slot 52 (Fig. 5), until distal ends, such as distal end 80, extends through and past outer peripheral surface, such as outer periph- eral surface 91, of the slot so as to form a joint therebetween. After the joint has been created, distal ends, such as distal end 80, can be softened through localized heating and then deformed so as to form a flange portion, such as flange portion 83 (Fig. 5) which is then allowed to harden back toward its pre-softened hardness. The flange portion and the collar portion will be situated so that the flange portion is squeezing against the outer pe¬ ripheral surface, such as outer peripheral surface

91 (Fig. 5) of the corresponding slot 52, and collar portion 82 will be squeezing against the inner peripheral surface, such as inner peripheral surface 90, of the slot so as to result in a compression fit therebetween, to, in turn, lock the respective cross-members to the continuous outer frame por¬ tions.

Should additional reinforcement of the joint be required, insertion of a sleeve member, or ferrule, such as sleeve member 95 (Fig. 5) , or sleeve member 110 (Fig. 8) within the channel region, such as channel region 73 (Fig. 5) of the first and second ends of the cross-members can be used. As shown in Fig. 5, such a sleeve member can be inserted com- pletely within the channel region of the respective ends of the cross-members, and, in turn, completely within the corresponding slot. Alternatively, the sleeve members can have their outer ends, such as outer end 98' (Fig. 8), extending beyond the distal ends of the respective end of the corresponding cross-member. Accordingly, when such an end extend¬ ing sleeve member is used, its outer end can be softened through localized heat induction, and then deformed so as to create a flange portion 112 (Fig. 8) for further securement with and/or to the cross- member. Such a sleeve member can be further at¬ tached to the cross-member through an interference fit therebetween and/or through welding or adhesive bonding. The foregoing description and drawings merely explain and illustrate the invention and the inven¬ tion is not limited thereto except insofar as the appended claims are so limited as those skilled in the art who have the disclosure before them will be

able to make modifications and variations therein without departing from the scope of the invention.