METHOD FOR MANUFACTURING A TUBULAR FRAME STRUCTURE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 61/196,934 filed October 22, 2008, the contents of which are incorporated by reference herein.

TECHNICAL FIELD OF INVENTION

[0002] The invention relates to a method for manufacturing tubular structure frames for Deformation Welding.

BACKGROUND OF THE INVENTION

[0003] Resistance welding of a first metal member to a second metal member (also known as electric-resistance welding) is a known metallurgical process in which the first and second metal members are heated by their own electrical resistance to a semi- fused or a fused state by the passage of very heavy electrical currents through the members for very short lengths of time. By forcing the first and second members together under pressure while the welding current is applied across the members, the members are then welded together. Resistance welding has many advantages in efficiently and effectively providing consistently reliable welds in high- volume manufacturing operations, when compared to alternative brazing or welding methods using gas torches or electrical arcs.

[0004] In order to achieve a complete resistance weld of the interface between the two mating members, the members must fit together very tightly at the interface at the time welding current is applied. It has been difficult to economically resistance weld together thin-walled metal members together, due to the need for having the members fit together tightly. Metal members where this was difficult include metals in the form of sheets, tubes, or similar shapes. In high- volume production, even where the configuration of the members is fairly simple, such members have been typically brazed or arc welded together rather than being resistance welded.

[0005] For example, in order to resistance weld a metal sheet or tube to another tube, the mating edges or surfaces of the members to be joined had to be cut or prepared along a three-dimensional contour so that the intersection between the members would fit together tightly enough before welding - to allow a good weld joint to be made. This can be difficult to achieve in thin-walled members that tend to flex under the pressure of the tooling used for preparing the mating edges or surfaces. The manufacturing costs for preparing the edges of the members to achieve an acceptably tight fit before welding, together with the cost of engineering for designing the members themselves and the equipment used for machining the members to achieve a tightly filling interface has been expensive. In addition to the cost associated with machining the members, complex fixtures were required to hold the members in position and to apply pressure along an interface, which is often three- dimensional, during resistance welding of the interface.

[0006] United States Patent Number 6,552,294, to Ananthanarayanan, et al, and United States Patent Number 6,717,091 to Ananthanarayanan, et al, each of which is hereby incorporated by reference herein, provide methods for attaching tubular assemblies using resistance welding. These and other methods do not contemplate manufacturing structural frames in which a plurality of tubes are capable of forming a large structure. Such a structure must be capable of connecting multiple tubes at a single node.

SUMMARY OF INVENTION

[0007] A method of making a tubular node and a structural frame using the node is provided. Conventional structural tubular members are welded together using a node with a deformation resistance welding process.

[0008] According to one aspect of the invention, a method of making a tubular node by deformation resistance welding is provided. It comprises providing a first tubular structure, providing a second tubular structure and deforming the first tubular structure to create an angular bend to a predetermined angle. An access port is created in the first tubular structure and the second tubular structure is assembled to

the access port of the first tubular structure. The first tubular structure is structurally connected to the second tubular structure at the access port by deformation resistance welding.

[0009] According to another aspect of the invention, a method of manufacturing a tubular frame structure by deformation resistance welding is provided. It comprises providing a three dimensional node having at least three axially extending legs which intersect at a common node intersection, at least two of the three legs having an axis lying in a first common plane, at least one of the three legs lying in a second common plane. A tubular structural member is provided and assembled to one of the at least three axially extending legs. The tubular structural member is forced into abutting contact with a portion of one of the at least three axially extending legs and a structural connection is made by deformation resistance welding the tubular structural member to one of the at least three axially extending legs.

[0010] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0012] FIG. 1 is an isometric view of a structural node in accordance with the invention;

[0013] FIG. 2 is an illustration, partially in cross-section, showing one aspect of the method of the invention;

[0014] FIG. 3 is an illustration, showing another aspect of the method of the invention;

[0015] FIG. 4 is an illustration showing a structural node manufactured in accordance with at least one of the methods illustrated in FIGS. 2 or 3;

[0016] FIG. 5 is an illustration, partially in cross-section, one aspect of a structural node of the invention as part of a structural frame of the invention;

[0017] FIG. 6 is an illustration, partially in cross-section, of another aspect of a method of attaching a structural node of the invention to a structural frame of the invention;

[0018] FIG. 7 is an illustration, partially in cross-section, of the method of FIG. 6;

[0019] FIG. 8 is an illustration, partially in cross-section, of yet another aspect of a method of attaching a structural node of the invention to a structural frame of the invention;

[0020] FIG. 9 is an illustration, partially in cross-section, of the method of FIG. 8;

[0021] FIG. 10 is a cross-sectional view showing one step of forming a structural node in accordance with an exemplary embodiment of the invention;

[0022] FIG. 11 is a cross-sectional view showing another step of forming a structural node in accordance with an exemplary embodiment of the invention;

[0023] FIG. 12 is a cross-sectional view showing an alternative step to that of FIG. 10 of forming a structural node in accordance with an exemplary embodiment of the invention;

[0024] FIG. 13 is a cross-sectional view of yet another step of forming a structural node in accordance with an exemplary embodiment of the invention;

DETAILED DESCRIPTION OF INVENTION

[0025] Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same, the invention provides a node and method of manufacturing a node and tubular structural frames using a Deformation Resistance Welding process (DRW). Where alternative embodiments are shown in the Figures, like numerals are used for like elements.

[0026] An exemplary embodiment of a node 10, useful as connection point or redistribution point for a structural frame is shown in FIG. 1. Node 10 is comprised of three equidistant node legs - first leg 14, second leg 15 and third leg 16. Each leg 14, 15 and 16 is generally cylindrical in shape and defined by an axis A, B and C, respectively, and each leg 14, 15 and 16 has an exterior diameter. As shown the arc angle, α, β, and γ, between adjacent axes A, B, C is 120 degrees. It will be appreciated that other alternative embodiments of node 10 may include elliptical or oval shaped legs 14, 15 or 16, when viewed in cross-section, or the arc angles , α, β, and γ, may be of varying angles such that only two are the same or that none of the angles are the same. Each of the varying embodiments fall within the scope of the invention, and the exemplary embodiment shown is not meant to limit the invention.

[0027] The axes A, B fall within a first common plane, while axis C falls in a second plane. It is contemplated that other embodiments may include one or more of axes A, B and C falling in different planes, though corresponding legs 14, 15 or 16 will still intersect at a common node intersection point 21. Each of legs 14, 15 has a generally contiguous inside surface wall 25 defining an interior portion 27 of node 10 and a generally contiguous outer surface wall 26 of node 10. Outer edges 28a, 28b and 28c extend between inside surface wall 25 and outside surface wall 26. Outer edges 28a, 28b and 28c have a generally uniform thickness extending between the inner and outer surface walls 25, 26. In one non-limiting embodiment, node 10 is comprised of a low carbon steel such as AISI 1008 to 1010 having the generally uniform edges 28a -28c with a thickness of generally 2 millimeters or less.

[0028] Legs 14 and 15 of node 10 are generally formed from a single common tube stock 12. In a method of manufacturing node 10, tube stock 12 is bent with a

predetermined angle α that is dependent on the desired resultant node 10 geometry, hi the exemplary embodiment shown, α is about 120 degrees. Deformation may be performed in many ways. In the example shown in FIGS. 1-4, tube stock 12 has been bent by hydro-forming. In hydro-forming, the hydraulic pressure within tubular stock 12 results in material flow and forming the bent tubular shaped growth seen in FIGS. 1-4.

[0029] As shown in FIG. 2, a punching or piercing tool 30 (shown in phantom) creates two access ports or aligned openings 31 and 32 through tube stock 12 and intersection point 21 of axes A and B. Collars 33 and 34 define the bounds of aligned openings 31 and 32, respectively. Collars 33 and 34 have flared edges 35 and 36 created by punching tool 30 and have diameters Dl and D2, where Dl is greater than D2.

[0030] In an alternative method, shown in FIG. 3 two aligned openings 131 and 132 through tube stock 12 are created by drilling openings 131 and 132 through the intersection point 21 of axes A and B. Collars 133 and 134 define the bounds of aligned openings 131 and 132, respectively. Collars 133 and 134 have clean edges 135 and 136 and have diameters DI l and D 12, where Dl 1 is greater than D 12. hi the exemplary embodiment shown, each of legs 14 and 15 have an inside diameter D 14, both DI l and D12 being greater than D 14.

[0031] FIG. 4 is an illustration showing a structural node 10 manufactured in accordance with at least one of the methods illustrated in FIGS. 2 or 3, and further manufactured in accordance with the methods described corresponding to FIGS. 10- 13.

[0032] Referring now to FIGS. 10-13, a second tube stock 50 is provided to weld to tube stock 12 to form node 10. Tube stock 50 has an inside surface 51 and an outside surface 52 having a uniform edge 53 extending therebetween. Adjacent uniform edge 53 is a circumferential radially extending rib 54, which extends radially outward from outside surface 52. Rib 54 is formed by is generally formed by stamping, kinking other known means to deform tube stock 50.

[0033] As shown in FIGS. 10 and 11, tube stock 50 is inserted within aligned opening 32 in order that outside surface 52 abuts collar 34. A leading edge 55 of radially extending rib 54 abuts flared edge 36 created by the punching or piercing tool 30 from the method shown in FIG. 2. By providing a stationary electrode 61 with an electrode extension portion 62 extending through aligned opening 31, circumferential ridge 63 of extension portion 62 can contact inside surface wall 25 of tube stock 12. It will be appreciated that the inside diameter D4 of circumferential ridge 63 is about equal to or greater than diameter D2 of collar 34.

[0034] Moveable ring electrode 65 is placed over outside surface 52 of tube stock 50 and applies a force F2 against trailing edge 56 of rib 54 that co-acts against force Fl exerted by circumferential ridge 63 bearing against inside surface wall 25. Electrodes 61 and 65 are energized and a deformation resistance welding step is implemented. The resulting formed joint 70 is shown in FIG. 11. There it can be seen that rib54 collapsed upon itself and allowed for relative motion of tube stock 50 and tube stock 12 during welding to form joint 70. While rib 54 remains, it will be appreciated that the combination of resistance heating and plastic deformation caused rib 54 to generally collapse onto itself in an interior portion 57 of tube stock 50. The resistance heating is due to the application of the welding current and the plastic deformation is due to the opposite Forces Fl and F2. This combination results in the weld nuggets 71 shown in Fig. 11 at the surfaces that were abutting prior to welding. A self threading nut 80 can be placed within opening 31 to seal the interior of node 10 once electrode 61 has been removed - though nut 80 is not generally required for the structural integrity of the node 10.

[0035] As shown in FIG. 12, tube stock 50 is inserted within aligned opening 132 of the drilled tube stock 12 created in the method shown in FIG. 3, in order that outside surface 52 abuts collar 134. By providing stationary electrode 61 with electrode extension portion 62 extending through aligned opening 131, circumferential ridge 63 of extension portion 62 can contact inside surface wall 25 of tube stock 12. It will be appreciated that the inside diameter D4 of circumferential ridge 63 is about equal to or greater than diameter D 12 of collar 134.

[0036] Moveable ring electrode 65 is placed over outside surface 52 of tube stock 50 and applies a force F2 against trailing edge 56 of rib 54 that co-acts against force Fl exerted by circumferential ridge 63 bearing against inside surface wall 25. Electrodes 61 and 65 are energized and a deformation resistance welding step is implemented. The resulting formed joint looks like that shown in FIG. 11. There it can be seen that rib54 collapsed upon itself and allowed for relative motion of tube stock 50 and tube stock 12 during welding to form joint 70. A self threading nut (not shown) can be placed within opening 131 to seal the interior of node 10 once electrode 61 has been removed.

[0037] As shown in FIGS. 13, tube stock 50 is inserted within aligned opening 132 of the drilled tube stock 12 created in a manner similar to the method shown in FIG. 3, in order that outside surface 52 abuts collar 134. By providing a stationary bottom electrode 81 , a corresponding hole 131 need not be drilled within tube 12. Bottom electrode 81 abuts outer surface wall 26. hi a method similar to that illustrated in FIGS. 10-12, moveable ring electrode 65 is placed over outside surface 52 of tube stock 50 and applies a force F2 against trailing edge 56 of rib 54 that co- acts against force Fl exerted by bottom electrode bearing against outer surface wall 26. Electrodes 81 and 65 are energized and a deformation resistance welding step is implemented. The resulting formed joint looks like that shown in FIG. 11. There it can be seen that rib54 collapsed upon itself and allowed for relative motion of tube stock 50 and tube stock 12 during welding to form joint 70. Electrode 81 is removed and, unlike the embodiment of FIGS 10 and 12 no opening is left and no nut is needed.

[0038] FIGS. 5-9 show exemplary embodiments of a tubular structural frame 200 manufactured by deformation resistance welding. Tubular structural frame 200 includes multiple nodes 10 and multiple structural tubular members 210, one node 10 and one structural tubular member 210 being shown in the illustrations of FIGS. 5-9. Where alternative embodiments are shown in the FIGS. 5-9, like numerals are used for like elements.

[0039] It will be appreciated that in a structural frame 200 contemplated by this invention, structural members 210 can be attached to any or all of first, second or third legs 14, 15, and 16 of node 10. An opposite end of a structural member 210 will be attached to another leg 14, 15 or 16 of another node 10, attachment being done by deformation resistance welding as will be further described herein. For illustrative purposes, only one node 10 and attachment of tubular member 210 to form structural frame 200 is shown. A person skilled in the art will recognize how multiple nodes 10 and members 210 fit together in frame 200. As such, a three-dimensional structural frame 200 can be constructed to fit any design criteria.

[0040] Referring now to FIG. 5, a simple deformation resistance weld is formed between structural member 210 and node 10. Structural member 210 includes an outside surface 211 and an inside surface 212 defining an interior portion 214. A complementary pair of arc shaped electrodes 220 and 221 apply radial co-acting forces F21 and F22 to outside surface 211 of structural member 210 causing inside surface 212 to bear against outside surface 52 of leg 16. By energizing electrodes 220 and 221, a welded joint is formed between inside surface 212 and outside surface 52.

[0041] Referring now to FIGS. 6-9, structural tubular member 210 is prepared for welding by providing a circumferential radially extending rib 231 having a leading edge 232 and a trailing edge 233. Rib 231 is formed by is generally formed by stamping, kinking other known means to deform structural tubular member 210. As shown, the method comprises placing structural member 210, having an outside diameter D31 about the same or slightly smaller than the inside diameter D32 of leg 16, inside leg 16.

[0042] Referring specifically to FIGS 6 and 7, a ring electrode 240 is placed over structural member 210 and bears against trailing edge 233 of rib 231, causing leading edge 232 to bear against outer edge 28c of third leg 16. A stationary bottom electrode 241, located axially opposite third Iegl6, supports node 10. Electrode 241 causes opposite co-acting forces F31 and F32 to deform circumferential radially extending rib 231 and, when electrodes 240 and 241 are energized causes deformation resistance welding at joint 250. The resulting welded joint is shown in FIG. 7. There

it can be seen that rib 231 collapsed upon itself and allowed for relative motion of structural member 210 and leg 16 of node 10 during welding to form joint 250.

[0043] Referring specifically now to FIGS. 8 and 9, deformation resistance welding is carried out by the use of ring electrode 240 placed over structural member 210. Ring electrode 240 co-acts with arc shaped electrodes 244 and 245 supported on complementary portions of a flange 260. Third leg 16 of node 10 has been deformed with a circumferential radially extending flange 116 having an underside surface 117 and an upper surface 118. Complementary flange portions 264 and 265 are brought together around outer surface wall 26 of third leg 16. hi a like manner, arc shaped electrodes 244 and 245 are brought together around third leg 16 between flange 260 and the underside surface 117 of flange 116. Forces F41 causes ring electrode 240 to bear against trailing edge 233 of rib 231, causing leading edge 232 to bear against upper surface 118 of flange 116 of third leg 16. Force F42 causes flange 260 to bear against arc shaped electrodes 244 and 245, which in turn bear against underside surface 117 of flange 1 16 of third leg 16. When electrodes 240, 244 and 245 are energized, deformation resistance welding is accomplished at joint 270, best shown in FIG. 9. There it can be seen that rib 231 collapsed upon itself and allowed for relative motion of structural member 210 and leg 16 of node 10 during welding to form joint 270.

[0044] The invention relates to a tubular structure node for tubular frames and tubular support structures that is manufactured using Deformation Welding Process (DRW). The common feature includes a bend tube that through different processes is connected with additional tubular structure to form a three dimensional 3 -leg node. The DRW process is applied to the node during which a force must be applied bringing both parts together. This tubular node replaces more conventional cast or stamped stand alone tubular nodes. It eliminates additional parts during the tubular structure assembly process since the tubular node is formed out of existing structural tubular elements that may be more desirable for high volume mass production.

[0045] Both electrodes are exposed to external mechanical forces at least one of that moves to bring the two welded parts together. The movable electrode(s) are accommodating to the recess shape applying pressure to the surface of the parts.

[0046] In one exemplary embodiment, pulses (totaling 1/3 of a second) of electric current of generally 5,000 amperes (and in one variation 15,000 to 20,000 amperes) are applied while applying the forces shown in the Figures of generally 300 to 800 pounds to the electrodes which abut against ribs and flanges. The joining of materials by the deformation resistance welding is not limited to specific materials, dimensions, electric current, and forces, as is understood by those skilled in the art. Any materials capable of being welded, such as copper, aluminum alloy, stainless steel, etc. can be used, as can be appreciated by the artisan. The particular choice of electric current, forces, and part dimensions, etc. are within the ordinary level of skill of the artisan.

[0047] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.