Patent Publication Number: US-8528291-B2

Title: 3-dimensional universal tube connector system

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application Ser. No. 61/323,046, filed Apr. 12, 2010, entitled “3-DIMENSIONAL UNIVERSAL TUBE CONNECTOR SYSTEM”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     This application is also a continuation-in-part application of application Ser. No. 12/698,220, filed Feb. 2, 2010, entitled “3-DIMENSIONAL UNIVERSAL TUBE CONNECTOR SYSTEM”, which claimed the benefit of Provisional Application Ser. No. 61/149,439, filed Feb. 3, 2009, entitled “3-DIMENSIONAL UNIVERSAL TUBE CONNECTOR SYSTEM”.The aforementioned applications are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to fabricated tubular truss and frame structures, and in particular to structures assembled using carbon-fiber tubes or rods. 
     2. Description of Related Art 
     Trusses and frame type structures have been used for many years as an efficient method to create lightweight, yet extremely stiff support structures. Trusses are particularly useful when a load must be carried over long distances, such as in building roofs, bridges, and cranes. 
     Prior art exists for various types of truss connector systems. U.S. Pat. No. 435,156 (Schmemann) discloses a design for an arch pipe truss for use in roofs. Schmemann uses rod members with threaded ends, which are threaded in joint connectors with mating receptacles. This design, however, does not allow the user to select the angle for the diagonal arbitrarily. 
     U.S. Pat. No. 2,487,169 (Newell) discloses a joint connector used for creating pipe trusses. This connector is fabricated by intersecting plates fitted axially into the pipe end. This joint must be welded together, especially for each individual joint. 
     U.S. Pat. No. 3,985,459 (Gilb) discloses a ridge joint connector assembly. In this joint, two pairs of sheet metal fastener plates are placed on the inside and outside faces of the ends of lumber members. This joint does not allow for the connection of tubes and rods, nor does it permit the connection of members orthogonal to the first two members. U.S. Pat. No. 4,050,210 (Gilb) also discloses a ridge connector for light composite trusses composed of lumber top chords and metal webs. Here, pairs of U-shaped connectors are used, along with pins and slots to hold the members together. 
     U.S. Pat. No. 4,161,088 (Gugliotta) discloses a pipe-and-ball truss array for supporting deck surfaces. This joint includes a spherically shaped joint center, with tubular members bolted to various locations on the sphere. U.S. Pat. No. 4,915,533 (De la Haye) discloses a coupling piece for joining two or more rods. This patent uses a round or polygonal shaped piece, into which the rods are bolted at specific locations. U.S. Patent No. 5,310,273 (Hara) discloses a joint structure for removably attaching a ball member to an end of a bar to form a truss structure, which engages using a tension rod. 
     U.S. Pat. No. 4,650,361 (Seuster) discloses a joint for truss structures including fiber composite material. In particular, the joint attaches reflector panels in a truss support structure for a radio telescope, and the truss bars and reflector panels are made from carbon-fiber composites. Here, the joint includes a ball into which bolts are fastened, with the ends attached to the fiber composite bars. 
     U.S. Pat. No. 3,229,998 (Pennington), U.S. Pat. No. 4,667,505 (Sharp), U.S. Pat. No. 4,870,856 (Sharp), U.S. Pat. No. 4,840,201(Botsolas), U.S. Pat. No. 5,007,666 (Kyfes), and U.S. Design Patent No. D362,916 (Cetrulo) disclose various types of split or clam-shell shaped joiners. These methods, however, do not incorporate means to connect diagonal connectors, and hence cannot be used exclusively to form a truss structure. Similarly, U.S. Pat. No. 6,032,430 (Soukup), U.S. Pat. No. 5,346,237 (Wang), U.S. Pat. No. 6,604,710 (Ohmer), and U.S. Pat. No. 5,711,131 (Thomas) all disclose connection methods for bars; however, in each case the directions of the individual members is predetermined by the specific connector. That is, the user needs multiple types of connectors to fabricate an entire structure with multiple internal angles. 
     U.S. Pat. No. 7,171,792 (Windahl et al.) discloses a pipe and cable truss system. Here, two inclined members are joined at an angle, forming the peak of the truss. Vertical members and tension cables are used to hold the structure together. In order to connect the tension cables, tabs with holes are attached to the rigid pipe members. These tabs, however, would not be adequate for high compression or out-of-plane loads. In addition, the use of tabs prohibits the attachment of tubes and rods in place of the tension cables. 
     Several companies offer joints for connecting tubes. Hy-Gain Corporation (Lincoln, Nebraska) manufactures antenna support structures. Hy-Gain Model LJ-105CA contains a clamshell type joint that is used to connect multiple tubes inline and at 90 degree angles. Using these connectors, however, one is unable to attach tubes along the third axis. In addition, there is no means to connect compressional diagonal members through this type of joint. Cushcraft Corporation (Manchester, New Hampshire) also supplies clamshell type attachment joints for antenna support structures (Big Thunder Series); however, like with the Hy-Gain models, a single universal joint cannot be utilized to create an entire truss or frame. 
     AirDynamics Corporation (New York, N.Y.) provides fittings to connect carbon fiber tubes. These fittings are tube splices used by sliding one end into each tube. Adhesive is applied to the fitting prior to insertion within the tube, and the glue line lies between the outer periphery of the fitting and the inner tube wall. 
     SUMMARY OF THE INVENTION 
     A system connects uni-directional pultruded, filament wound, or roll-wrapped tubes or rods together to form trusses and other structures using a series of connector pieces bonded together. The tubes or rods are preferably carbon fiber tubes or rods. The connector pieces are preferably bonded together with adhesive. In one embodiment, the adhesive is an epoxy adhesive. 
     A universal joint connector allows simple, easy, and inexpensive fabrication of complex structures from pultruded, filament wound, or roll-wrapped carbon-fiber tubes or rods. This method is applicable to all types of materials for both the tubes and rods, as well as the connectors; however, the preferred embodiment uses pultruded, filament wound, or roll-wrapped carbon fiber tubes and/or rods and injection molded carbon-fiber reinforced plastic connectors. The universal connectors are preferably fabricated from three parts: an outer piece, an inner piece, and preferably one to four diagonal tube connectors. 
     In one embodiment, a connector system includes tubes or rods and universal connectors. Each universal connector includes a first connector bracket and a second connector bracket, where the first connector bracket and the second connector bracket attach together to form a structure having at least one opening into which the tubes or rods can be placed. The universal connector also includes at least one diagonal member having an opening into which a tube or rod can be placed. The diagonal member is aligned at an angle in relation to at least one of the openings in the structure. The universal connector also includes adhesive ridge gauges on an inner surface of the opening of the diagonal member and in the opening of the structure. 
     In another embodiment, a universal connector includes a first connector bracket and a second connector bracket, where the first connector bracket and the second connector bracket attach together to form a structure having at least one opening into which the tubes or rods can be placed. The universal connector also includes at least one diagonal member having an opening into which a tube or rod can be placed. The diagonal member is aligned at an angle in relation to at least one of the openings in the structure. The universal connector also includes adhesive ridge gauges on an inner surface of the opening of the diagonal member and in the opening of the structure. 
     In yet another embodiment, a truss structure includes universal connectors. The universal connectors each include a first connector bracket and a second connector bracket, where the first connector bracket and the second connector bracket attach together to form a structure having at least one opening into which the tubes or rods can be placed. The universal connector also includes at least one diagonal member having an opening into which a tube or rod can be placed. The diagonal member is aligned at an angle in relation to at least one of the openings in the structure. The truss structure also includes tubes or rods, which are connected by the universal connectors to form longitudinal members, a plurality of cross-members orthogonal to the longitudinal members, and a plurality of diagonal elements connecting the longitudinal members on a diagonal. 
     A method constructs a truss structure from tubes or rods and universal connectors. Each universal connector includes a first connector bracket and a second connector bracket, where the first connector bracket and the second connector bracket attach together to form a structure having at least one opening into which the tubes or rods can be placed. The universal connector also includes at least one diagonal member having an opening into which a tube or rod can be placed. The diagonal member is aligned at an angle in relation to at least one of the openings in the structure. The method includes the step of forming longitudinal members by connecting the tubes or rods linearly with universal connectors. The method also includes the steps of connecting the longitudinal members with a plurality of cross-members using universal connectors such that the cross-members are orthogonal to the longitudinal members and bracing the truss structure by connecting a plurality of diagonal elements on two different longitudinal members and two different cross-members using universal connectors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an assembled 90 degree angle universal connector with 4 diagonal members attached in an embodiment of the present invention. 
         FIG. 2   a  shows an outer connector bracket of the universal connector of  FIG. 1 . 
         FIG. 2   b  shows an inner connector bracket of the universal connector of  FIG. 1 . 
         FIG. 3  shows a close-up of the outer connector bracket of  FIG. 2   a , including adhesive ridge gauges. 
         FIG. 4  shows diagonal members of  FIG. 1  in various orientations. 
         FIG. 5  shows a diagonal member attached to an outer connector bracket at an arbitrary angle. 
         FIG. 6   a  shows a front side view of an assembled 90 degree angle universal connector with four diagonal members attached and tubes bonded into place. 
         FIG. 6   b  shows a back side view of the assembled 90 degree angle universal connector shown in  FIG. 6   a . 
         FIG. 7  shows the universal connector of  FIGS. 6   a  and  6   b  with the inner connector bracket hidden. 
         FIG. 8  shows a rectangular truss made from tubes and universal tube connectors. 
         FIG. 9  shows a close-up of one end of the truss structure of  FIG. 8 . 
         FIG. 10   a  shows a top down view of a 60 degree angle connector of the present invention. 
         FIG. 10   b  shows a cross-sectional side view of a 60 degree angle connector of the present invention. 
         FIG. 11  shows the outer connector bracket of the 60 degree angle connector of  FIG. 10 . 
         FIG. 12   a  shows a portion of the outer connector bracket of  FIG. 11 . 
         FIG. 12   b  shows a cross-sectional view along lines  12   b - 12   b  of  FIG. 12   a , through the midplane of the outer connector bracket of  FIG. 11 , showing the tube stop feature. 
         FIG. 13  shows a tube end connector of the present invention. 
         FIG. 14  shows a triangular truss including the 60 degree angle connectors of  FIG. 10  and the tube end connectors of  FIG. 13 . 
         FIG. 15  shows the structure of  FIG. 14  with a triangular plate bonded to the tube end connectors of  FIG. 13 . 
         FIG. 16  shows a close-up view of the end of the structure shown in  FIG. 15 , showing the plate and tube end connectors. 
         FIG. 17   a  shows a tube side connector of the present invention. 
         FIG. 17   b  shows another view of the tube side connector of  FIG. 17   a.    
         FIG. 18  shows a truss structure with tube side connectors bonded into place. 
         FIG. 19   a  shows the truss structure of  FIG. 18  with a rectangular plate bonded to the tube side connectors. 
         FIG. 19   b  shows another view of the truss structure of  FIG. 19   a.    
         FIG. 20   a  shows a 3-way 90 degree connector of the present invention. 
         FIG. 20   b  shows the outer portion of the 3-way connector of  FIG. 20   a.    
         FIG. 20   c  shows the inner portion of the 3-way connector of  FIG. 20   a.    
         FIG. 21  shows a 3-way 90 degree connector with diagonal members and tubes or rods bonded in place. 
         FIG. 22   a  shows a 2-dimensional T connector of the present invention. 
         FIG. 22   b  shows an exploded view of the two brackets that make up the T connector of  FIG. 22   a.    
         FIG. 23  shows a 2-dimensional T connector of  FIG. 22  with diagonal members bonded in place. 
         FIG. 24   a  shows a 2-dimensional 90 degree connector of the present invention. 
         FIG. 24   b  shows an exploded view of the two brackets that form the connector of  FIG. 24   a.    
         FIG. 25  shows a 2-dimensional 90 degree connector of  FIG. 24  with a diagonal member bonded in place. 
         FIG. 26   a  shows a 2-dimensional 135 degree connector of the present invention. 
         FIG. 26   b  shows an exploded view of the two brackets that form the connector of  FIG. 26   a.    
         FIG. 27  shows a 2-dimensional 135 degree connector of  FIG. 26  with a diagonal member bonded in place. 
         FIG. 28   a  shows an inline connector of the present invention. 
         FIG. 28   b  shows an exploded view of the two brackets that form the connector of  FIG. 28   a.    
         FIG. 29   a  shows a 2-dimensional 4-way connector of the present invention. 
         FIG. 29   b  shows an exploded view of the two brackets that form the connector of  FIG. 29   a.    
         FIG. 30  shows a 2-dimensional 4-way connector of  FIG. 29   a  with diagonal members bonded in place. 
         FIG. 31  shows a structure with several different types of connectors and carbon-fiber tubes or rods. 
         FIG. 32   a  shows a back side view of another 90 degree universal connector of the present invention. 
         FIG. 32   b  shows a front side view of the 90 degree universal connector of  FIG. 32   a.    
         FIG. 33   a  shows a back side of the universal connector of  FIG. 32   a  with diagonal members bonded in place. 
         FIG. 33   b  shows a front side of the universal connector of  FIG. 32   a  with diagonal members bonded in place. 
         FIG. 34   a  shows a back side view of another 60 degree universal connector of the present invention. 
         FIG. 34   b  shows a front side view of the 60 degree universal connector of  FIG. 34   a.    
         FIG. 35   a  shows a back side of the universal connector of  FIG. 34   a  with diagonal members bonded in place. 
         FIG. 35   b  shows a front side of the universal connector of  FIG. 34   a  with diagonal members bonded in place. 
         FIG. 36  shows the diagonal member of  FIG. 1  with a smaller receptacle. 
         FIG. 37   a  shows an angle termination connector in an embodiment of the present invention. 
         FIG. 37   b  shows the angle termination connector of  FIG. 37   a  with a diagonal member attached. 
         FIG. 38   a  shows an inline connector in an embodiment of the present invention. 
         FIG. 38   b  shows the inline connector of  FIG. 38   a  with a diagonal member attached. 
         FIG. 39  shows an alternate embodiment for the inline connector of  FIG. 38   a.    
         FIG. 40   a  shows an alternate embodiment for the inline connector of  FIG. 39 . 
         FIG. 40   b  shows the inline connector of  FIG. 40   a  with four diagonal members attached. 
         FIG. 41   a  shows a tube end insert piece in an embodiment of the present invention. 
         FIG. 41   b  shows the tube end insert of  FIG. 41   a  placed inside the end of a tube. 
         FIG. 42  shows eight universal connector pieces combined to form a 3-dimensional 90 degree universal connector in an embodiment of the present invention. 
         FIG. 43   a  shows an outer view of a 3-dimensional 90 degree universal connector piece in an embodiment of the present invention. 
         FIG. 43   b  shows an inner view of the 3-dimensional 90 degree universal connector piece of  FIG. 43   a.    
         FIG. 44  shows the 3-dimensional 90 degree universal connector of  FIG. 42  with tubes inserted into the receptacles for each primary orthogonal axis and three diagonal members attached. 
         FIG. 45  shows a 3-dimensional 90 degree universal connector utilizing four components and attached to a plate. 
         FIG. 46   a  shows a universal connector including four individual connector pieces and a 2-dimensional 4-way connector. 
         FIG. 46   b  shows an alternate view of the connector of  FIG. 46   a.    
         FIG. 47  shows two 3-dimensional 90 degree universal connectors and one 90 degree angle universal connector bonded together. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention includes a system for connecting tubes or rods together to form trusses and other structures using a series of connector pieces bonded together. Either tubes or rods, or any combination of both tubes and rods, may be used in the connector system of the present invention. The connector system of the present invention is preferably designed for uni-directional pultruded, filament wound (fiber wound), or roll-wrapped tubes or rods. In a preferred embodiment, the tubes or rods are made of carbon fiber. Carbon-fiber products, such as carbon-fiber tubes or rods, can be used for a wide range of applications. There is great interest in purchasing these raw building materials and using them to fabricate custom structures. 
     In a preferred embodiment, the connectors and the tubes or rods form a truss structure. The connector pieces are preferably bonded together with adhesive. In one embodiment, the adhesive is an epoxy adhesive. 
     A universal joint connector allows simple, easy, and inexpensive fabrication of complex structures from tubes or rods. This method is applicable to all types of materials for both the tubes and rods, as well as the connectors; however, the preferred embodiment uses pultruded, filament wound, or roll-wrapped carbon fiber tubes/rods and injection molded carbon-fiber reinforced plastic connectors. 
     The present invention includes a universal joint for constructing trusses, where the diagonals can be set at any angle, and the diagonal members can be either in tension or compression. In preferred embodiments, the diagonal members are tubes. A single joint can be used to construct an entire truss or frame structure out of tubes or rods, regardless of the size and diagonal angles. In other words, one only needs to design the shape of the truss and not any individual connectors. 
     Unlike prior art brackets, which can only connect elements in one plane, the present invention includes a method and system for connecting a tube or rod out of plane (that is, perpendicular to the two in-plane directions). Also unlike the prior art, the connectors of the present invention can connect the tubes or rods at any angle, giving a high degree of versatility to a single connector design. When constructing a truss structure, both of these connection methods preferably need to be utilized. The third dimension gives the truss both depth and width, and the diagonal members are necessary for rigidity due to shear and torsional loads. 
     While screws or other fasteners are used in the present invention, they are preferably used to simply hold the part together during bonding. All of the strength preferably comes from an adhesive bond. 
     The universal connector is preferably fabricated from three parts: an outer piece (outer connector bracket), an inner piece (inner connector bracket), and one or more diagonal tube connectors (diagonal members). In preferred embodiments, there are one to six diagonal members. 
     An embodiment of the present invention is shown in  FIG. 1 , which depicts an assembled 90 degree angle universal connector  100 . The universal connector  100  includes an inner connector bracket  1  and an outer connector bracket  2  that form a clamshell. Since diagonal elements are an integral part of most truss structures, this capability is preferably added to the design through an additional diagonal member  3 . The diagonal member  3  is shown in  FIG. 1  secured in place by adhesive; however, there are other ways of securing the diagonal member  3  including, but not limited to, fasteners, clips and weldments. In order to facilitate ease of assembly and proper pressure during adhesive curing, a fastener  4  is preferably used. 
     The outer connector bracket  2  and the inner connector bracket  1  are shown separated in  FIGS. 2   a  and  2   b , respectively. The holes  20  located on the flat surfaces are used to align the parts correctly during assembly and bonding. In preferred embodiments, fasteners  4 , shown in  FIG. 1 , for example rivets, screws, or bolts with nuts, are placed through the holes to align the parts and draw them together for proper bonding. If screws are used, then one connector piece would include a through hole, and the other piece would include a tapped hole. The fastener is inserted during bonding, and can optionally be removed once the adhesive is fully cured. 
     Adhesive ridge gauges, or ribs,  21 , preferably located on the interior surfaces of the connector brackets  1  and  2 , help to properly align the tubes or rods, as well as provide proper spacing between the wall surfaces to ensure adequate adhesive thickness.  FIG. 3  shows a close-up of the outer connector bracket  2  and the adhesive ridge gauges  21 . 
     Diagonal members  3  are shown in various orientations in  FIG. 4 . Each diagonal member  3  includes a tab  7  and a receptacle  8 . Like with the inner connector bracket  1  and the outer connector bracket  2 , adhesive ridge gauges  41 , or ribs, are preferably included on the inner surfaces of the diagonal members for proper tube or rod alignment and to ensure adequate adhesive thickness. 
     An important feature of this design is the ability to align the diagonal members  3  at any angle  51 , since this angle is not pre-determined In other words, the determination of the diagonal angle can be made by the fabricator when bonding the diagonal member  3  to the inner connector bracket  1  and the outer connector bracket  2 . Eliminating design restrictions on this angle in turn removes geometric restrictions on the assembled structure. For example, if the connector angle  51  was restricted to 45 degrees, the user would be required to design the complete truss or frame structure to include only this angle, which would severely limit the use of the system. The ability to allow angle  51  to vary between 0 and 90 degrees allows the designer great latitude in truss construction. 
     The universal connector  100  is shown in  FIGS. 6   a  and  6   b  with carbon-fiber tubes  60  inserted and bonded into place. Although tubes are shown, carbon fiber rods or other tubes or rods could alternatively be used. The user bonds a tube or rod into the diagonal member  3  by either sliding it in or placing it first into the outer connector bracket  2 , and then fixing the inner connector bracket  1  into place. Adhesive is preferably added to all mating surfaces, and the tubes or rods are then placed in the requisite channels. In one embodiment, the adhesive is an epoxy adhesive. The combination of the two-piece configuration, the internal adhesive-control ridges/ribs, diagonal members, and the holes for fasteners, make up the primary gusset assembly system. The connector system is shown in  FIG. 7  with the inner connector bracket  1  hidden. 
     An assembled rectangular truss structure  400  is shown in  FIG. 8 . The truss is made up of universal connectors  100  and tubes or rods  60 . The tubes or rods are preferably made of carbon fiber. A close-up of one end of the truss structure  400  is shown in  FIG. 9 . The corner brackets  91  at the terminal end of the truss structure  400  are preferably made by cutting one leg off of the inner connector bracket  1  and the outer connector bracket  2 . 
     The inner connector bracket  1  and the outer connector bracket  2  can be manufactured in different shapes to facilitate creation of other truss geometries, and are not restricted to purely 90 degree connectors. One example of non-right angle connector geometries is shown in  FIGS. 10   a  and  10   b , which show a 60 degree angle connector  500 . The 60 degree angle connector  500  is made up of an inner connector bracket  15  and an outer connector bracket  16 . The two pieces form a clamshell structure, and allow for diagonal members  3  to be added in the same manner as shown in  FIG. 1 . 
       FIGS. 11 and 12   a  show the inside surfaces of the outer connector bracket  16  of the 60 degree angle connector  500 . Internal ribs  21  are included, similar to those in the universal connector  100 , for proper tube or rod positioning and adhesive thickness control. In addition, tube stops  71  are preferably included in the connector  500  to make sure the two tubes that make the 60 degree angle are set at the proper depth.  FIG. 12   b  shows a section view along lines  12   b - 12   b  of  FIG. 12   a , showing the tube stops  71  and internal ribs  21 . 
     To facilitate the attachment of truss structures to foundations, as well as add mounting plates to the ends of the truss, a tube end connector  131 , as shown in  FIG. 13 , can be utilized. The tube end connector  131  has a flange portion  132 , holes for mounting fasteners  133 , and a tubular portion  134  to accept a tube or rod, which is preferably a carbon-fiber pultruded or filament wound tube or rod. 
       FIG. 14  shows a triangular truss  600  with 60 degree angle universal connectors  500 , tubes or rods  60 , and tube end connectors  131 .  FIG. 15  shows a plate  151  optionally bonded to the tube end connectors  131  of the truss structure  600 .  FIG. 16  shows an alternate view of the end of the truss structure  600  of  FIG. 15 . 
     In addition to the tube end connectors, other mounting pieces can be optionally added to the truss structures. One example is a tube side connector  171  shown in  FIGS. 17   a  and  17   b . This connector includes a semi-circular channel  172 , one or more internal ribs  21 , and a flat side  173 . The tube side connector  171  is preferably included in a truss or frame structure by bonding a tube or rod, which is preferably a carbon-fiber tube or rod, into the semi-circular channel  172  and using the flat side  173  for bonding to a support structure or for affixing a mounting plate to the truss. One example of the tube side connector included in a truss structure  700  is shown in  FIG. 18 .  FIGS. 19   a  and  19   b  show the truss structure  700  with a flat plate  191  optionally bonded to the tube side connectors. 
     The universal connector can be cut at various positions in order to form simpler connectors. For example, the flange in the third dimension can be removed to form a 2-dimensional T-shaped connector. Similarly, both 2-dimensional and 3-dimensional corner pieces, as well as 2-dimensional straight splice connectors, can be formed using the same method. In this way, the universal connector assembly can be utilized for virtually any type of structural joint including, but not limited to, 2-dimensional, 3-dimensional, corner, T-shape, and diagonal angles. 
     Individual connectors for each type of joint can also be manufactured for end-users who do not wish to cut down the universal connector. A sampling of some of these simplified connectors is shown in  FIGS. 20 through 31 .  FIGS. 20   a  through  20   c  show a 3-dimensional corner bracket connector  201 . The inner connector bracket  202  and the outer connector bracket  203  are utilized using the aforementioned methods for the universal connector  100 . The 3-dimensional corner bracket connector  201  is shown in  FIG. 21  with three diagonal members  3  bonded into place at arbitrary angles. Also, six tubes  60  are shown bonded into the connectors  201 . 
       FIGS. 22   a  and  22   b  show a 2-dimensional T connector  221 . Due to symmetry, both the top  222  and bottom  222  halves of the clamshell which make up the T connector  221  are identical. The complete 2-dimensional T connector  221  is shown in  FIG. 23  with two diagonal members  3  attached. 
       FIGS. 24   a  and  24   b  show a 2-dimensional 90 degree connector  241 . The top half  242  of the connector and the bottom half  243  of the connector form the 90 degree connector  241 . The complete 2-dimensional 90 degree connector  241  is shown in  FIG. 25  attached to a diagonal member  3 . 
       FIGS. 26   a  and  26   b  show a 2-dimensional 135 degree connector  261 . The top half  262  of the connector and bottom half  263  of the connector form the 135 degree connector  261 . The complete 2-dimensional 135 degree connector  261  is shown in  FIG. 27  with a diagonal member  3  attached. 
       FIGS. 28   a  and  28   b  show an inline connector  281 . Due to symmetry, both the top  282  and bottom  282  halves of the clamshell which comprise the inline connector  281  are identical. 
       FIGS. 29   a  and  29   b  show a 2-dimensional 4-way connector  291  of the present invention. Due to symmetry, both the top  292  and bottom  292  halves of the clamshell which make up the 4-way connector  291  are identical. The complete 4-way connector  291  is shown in  FIG. 30  with four diagonal members  3  attached. 
       FIG. 31  shows an example of how each simplified connector can be utilized to form a structure  800 . This structure includes 3-dimensional corner bracket connectors  201 , 2-dimensional T connectors  221 , 2-dimensional 90 degree connectors  241 , 2-dimensional 135 degree connectors  261 , inline connectors  281 , and 2-dimensional 4-way connectors  291 . As exemplified in this figure, there are a very large number of possibilities for the shape of the resulting structure. 
     An alternative embodiment for the 90 degree angle universal connector  100  is shown in  FIG. 32 .  FIG. 32   a  shows a back side view of a 90 degree angle universal connector  350  and  FIG. 32   b  shows a front side view of the 90 degree angle universal connector  350 . 
     This connector differs from the connector  100  shown in  FIG. 1  by replacing the center tube receptacles with alignment holes for diagonal members  3 , as shown in  FIGS. 33   a  and  33   b . The inner connector bracket  1  shown in  FIG. 1  is replaced by an inner connector bracket  351 , and the outer connector bracket  2  is replaced by an outer connector bracket  352 . 
     An alternative embodiment for the 60 degree angle universal connector  500  is shown in  FIG. 34 .  FIG. 34   a  shows a back side view of a 60 degree angle universal connector  550  and  FIG. 34   b  shows a front side view of the 60 degree angle universal connector  550 . This connector differs from the connector  500  shown in  FIG. 10  by replacing the center tube receptacles with alignment holes for diagonal members  3 , as shown in  FIGS. 35   a  and  35   b . The inner connector bracket  15  shown in  FIG. 10  is replaced by an inner connector bracket  555 , and the outer connector bracket  16  is replaced by an outer connector bracket  556 . 
       FIG. 36  shows an alternative embodiment for a diagonal member  360  where the tab portion  361  is the same as shown in  FIGS. 1 and 4 , but the receptacle portion  362  has a reduced diameter to accommodate a smaller tube. Other potential variations include, but are not limited to, a larger receptacle, a smaller tab, or a larger tab. These additional embodiments of the diagonal member give greater versatility to a structural design including tubes and the connectors in embodiments of the present invention. Some examples for receptacle diameters include, but are not limited to, ¼″, ⅜″, ½″ ¾″, and 1″ (to accept tubes with those diameters). Some examples of tab widths include, but are not limited to, approximately ¾″, 1″, 1.5″ and 2″. The larger widths and diameters would be preferably used to accommodate larger diameter tubes. A preferred embodiment for a diagonal member includes a ½″ receptacle (which fits a ½″ diameter tube) and an approximately 1″ width for the tabs. Other receptacle diameters and tab widths for the diagonal members may alternatively be used, and any combination of receptacle diameter and tab width may be chosen for particular designs to accommodate the needs of that particular design. 
     The diagonal members  3  and  360  and the variations of the diagonal members discussed herein are preferably attached to the connectors shown in the figures by adhesive; however, there are other ways of securing the diagonal member  3  and  360  including, but not limited to, fasteners, clips and weldments. The diagonal member  360  shown in  FIG. 36 , as well as the variations for the diagonal member discussed in this paragraph, may be used in any combination with any of the connectors discussed herein. 
       FIGS. 37   a  and  37   b  show an angle termination connector  370  in an embodiment of the present invention. The flat side  371  bonds to another flat surface, such as a plate, while the diagonal member  3 , shown in  FIG. 37   b , connects to the angled side  372  and is used to connect to the end of a tube of the structure. Note that, in this figure and those that follow, the diagonal member  3  is attached to the connector by adhesive. While this attachment method is preferred, other attachment means, including, but not limited to, fasteners, clips and weldments, could alternatively be used. 
       FIGS. 38   a  and  38   b  show an inline connector  380  in an embodiment of the present invention. This connector can be used as a splice to join two inline tubes, or as a means to add another tube at an arbitrary angle relative to the primary tube. This is accomplished using a diagonal members  3 , as shown in  FIG. 38   b . An alternate embodiment of the inline connector  390 , which has a double flange  381  instead of the single flange  381  shown in  FIG. 38   a , is shown in  FIG. 39 . Connector  390  can accept diagonal members on either side of the inline portion  382 . Another embodiment of the inline connector  405 , which has an alternatively shaped double flange  406  able to accept multiple diagonal members  3 , is shown in  FIGS. 40   a  and  40   b.    
     A tube end insert  410  is shown in  FIG. 41   a . This component is used to attach additional parts to the truss structure off the end of a tube.  FIG. 41   b  shows the tube end insert  410  bonded into place within the end of a tube  60 . The hole  411  in the end of the tube insert  410  can be smooth or threaded, and allows for additional connections. 
     One example of a 3-dimensional 90 degree universal connector  420  for creating truss and frame structures is shown in  FIG. 42 . This connector includes up to eight pieces  421  bonded together. Individual components  421  are shown in  FIGS. 43   a  and  43   b . In  FIG. 44 , connector  420  is shown with tubes  60  bonded into place in the three primary orthogonal directions. In addition to tubes  60  being inserted into the receptacles, diagonal members  3  can be attached to one or more of the flat sides of a universal connector  420 .  FIG. 44  shows the universal connector  420  with three diagonal members attached; however, up to twelve diagonal members can be attached simultaneously in the embodiment shown, giving great versatility to the design. 
     In addition to the complete connector, individual components of the universal connector  420  can be excluded, giving further versatility. For example,  FIG. 45  shows a universal connector  450  comprised of four individual connector pieces  421 , and providing a flat surface convenient for bonding to a flat plate  451 . The connectors  421  are preferably bonded to the flat plate  451  with an adhesive. 
       FIGS. 46   a  and  46   b  show a universal connector  450  and a 2-dimensional 4-way connector piece  292  bonded together to form a new connector  460 . 
       FIG. 47  shows two 3-dimensional 90 degree universal connector pieces  421  and one 90 degree angle universal connector outer bracket  2  in an embodiment of the present invention. The design of these connectors allows them to be bonded together as shown in  FIG. 47 . 
     In addition to the manufacturing method presented here, instead of fabricating and assembling the inner connector bracket  1  and outer connector bracket  2  as two separate pieces, an alternative embodiment utilizes a single injection molded part, with the two halves combined into one. In this embodiment, the tubes or rods would slide into the connector in a similar fashion to standard plastic tube fittings, instead of the connector assembled in two halves. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.