Patent Publication Number: US-8978338-B2

Title: Structural trusses with monolithic connector plate members

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present case claims the benefit of U.S. Patent Application No. 61/641,604 filed on 2 May 2012, which application is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The technical field relates generally to structural trusses for supporting loads. 
     BACKGROUND 
     Structural trusses are very useful in a wide variety of situations. They can be used vertically, horizontally or in any other possible orientation. They generally include an elongated framework having three or more spaced-apart tubes extending in the lengthwise direction. The longitudinal tubes are rigidly interconnected to one another using a network of intervening members. 
     In most implementations, at least one end of each structural truss needs to be connected to an adjacent element in a construction assembly. The adjacent element can be a supporting structure or another structural truss. For instance, two adjacent structural trusses can be connected directly end-to-end or through another element. Various factors can impose limitations to the length of a structural truss and, for instance, it may be required and/or more desirable to attach two or more smaller structural trusses instead of using a single but longer structural truss. A very long structural truss can create complications in terms of handling and transportation, for example. Using smaller lengths of structural trusses assembled together is generally desirable. 
     In use, bending moment in a structural truss set at the horizontal is carried by tension or compression in the chords and the shear force is carried by the diagonals. The purpose of a connection is to transfer the bending moment and shear force from one structural truss or module to the next. The connection must also be stable. 
     Connecting one end of a structural truss to an adjacent element create some challenges, especially when welding is involved. The known connector arrangements have used parts such as small plates or gussets welded to the end face of the framework so as to provide a supporting interface for fasteners, in particular removable fasteners such as sets of bolts, nuts and washers. The welding process typically creates heat affected zones. These zones are generally extending up to one inch from the weld beads. The metal in the heat affected zones is more ductile than before the welding and the allowable stress in the heat affected zones is reduced by a substantial factor. Using larger tubes and/or plates can compensate for the heat affected zones but this adds weight and costs. It also reduces the space available for the fasteners. The fasteners must be located as close as possible to the corners of the structural truss to increase strength. 
       FIG. 22  illustrates an example of a structural truss  500  as found in the prior art. This structural truss  500  has end plates  502  welded to four interconnected tubes forming the end of the framework  504 . The end plates  502  include holes made through their thickness to receive the shank of the connecting bolts. When connecting two of these structural trusses  500  together, the head of the bolts will be on the inner side of the end plates  502  of one structural truss  500 , and the opposite nuts will be on the inner side of the end plates  502  of the other structural truss. Annular washers are provided between the head of the bolts and the back side surface of the end plates to distribute the forces on a wider area. Annular washers are also used between the nuts and the back side surface of the opposite end plates  502  for the same reasons. Moreover, since the end frame is also welded onto the framework, this part of the structural truss also includes heat affected zones. 
     The typical route which the retaining forces in such arrangement is as follows: 
     chord—weld—end frame—weld—end plate—washer—bolt—nut—washer—end plate—weld—end frame—weld—chord. 
     The bolts, nuts and/or washers transmit the load into the end plates  502 , which induce a considerable amount of local stress and deformation. Since the distance between the neutral axis of the bolt and the chords are distanced depending of the industry standard of holes position, it is often not possible to use oversized washers in order to distribute the load on a wider area in order to lower the mechanical stress on the end plates  502  around the holes. This can significantly reduce the end plate capacity. The use of larger tubes at the end frame to compensate for the head affected zones can force designers to move the fastener holes further away from the corners, which again can reduce the load bearing capacity. 
     Clearly, room for improvements exists in this area. 
     SUMMARY 
     In one aspect, there is provided a structural truss having a tubular framework with opposing ends and that extends lengthwise along a main longitudinal axis, at least one of the opposing ends of the structural truss including at least one connector plate member welded to the framework between two corresponding longitudinal tubes, the connector plate member being made of a monolithic piece having an outer side and a rear side, the connector plate member including: a corner beam section extending between the two corresponding longitudinal tubes, the corner beam section protruding from the rear side of the connector plate member, the corner beam section including two opposite ends, each having a corresponding first cutout configured and disposed to fit around an end of the corresponding longitudinal tubes; a main plate section extending perpendicularly inwards on a side of the corner beam section and in a direction that is substantially perpendicular to the longitudinal axis, the main plate section including at least one fastener hole to receive a mounting bolt, the main plate section and the corner beam section defining together a planar outer abutment plate surface; and a lip projecting at right angle from the main plate section on the rear side of the connector plate member, the lip extending substantially parallel to the corner beam section. 
     In another aspect, there is provided a connector plate member for use with a structural truss, the connector plate member being made of a monolithic piece having an outer side and a rear side, the connector plate member including: an elongated corner beam section extending between the two corresponding longitudinal tubes, the corner beam section including two opposite ends, each having a corresponding first cutout; 
     a main plate section extending perpendicularly on a side of the corner beam section, the main plate section including at least one fastener hole to receive a mounting bolt, the main plate section and the corner beam section defining together a planar outer abutment plate surface; and a lip projecting at right angle from the main plate section on the rear side of the connector plate member, the lip extending substantially parallel to the corner beam section. 
     In another aspect, there is provided a junction block connector for use with at least one structural truss, the junction block connector including two connector plate members provided at least one side of the junction block connector, each connector plate member being made of a monolithic piece having an outer side and a rear side, each connector plate member including: an elongated corner beam section extending between the two corresponding longitudinal tubes, the corner beam section including two opposite ends, each having a corresponding first cutout; a main plate section extending perpendicularly on a side of the corner beam section, the main plate section including at least one fastener hole to receive a mounting bolt, the main plate section and the corner beam section defining together a planar outer abutment plate surface; and a lip projecting at right angle from the main plate section on the rear side of the connector plate member, the lip extending substantially parallel to the corner beam section. 
     Further details on these aspects as well as other aspects of the proposed concept will be apparent from the following detailed description and the appended figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a side view of an example of a structural truss incorporating the proposed concept; 
         FIG. 2  is a top view of the structural truss shown in  FIG. 1 ; 
         FIG. 3  is an isometric view illustrating a portion of the structural truss shown in  FIG. 1 ; 
         FIG. 4  is an end view of the portion of the structural truss shown in  FIG. 3 ; 
         FIG. 5  is an enlarged isometric and semi-schematic view of one of the connector plate members shown in  FIG. 3 ; 
         FIG. 6  is a cross section view of the connector plate member taken along line  6 - 6  in  FIG. 5 ; 
         FIG. 7  is an isometric view illustrating an example of two adjacent structural trusses of  FIG. 1  being adjoined end-to-end; 
         FIG. 8  is an isometric view illustrating an example of a plurality of adjacent structural trusses being connected to one another through a junction block connector; 
         FIG. 9  is an enlarged isometric view of the junction block connector of  FIG. 8 ; 
         FIGS. 10 ,  11  and  12  are top, front and right side views, respectively, of the junction block connector shown in  FIG. 9 ; 
         FIG. 13  is an enlarged isometric and semi-schematic view of one of the double-sided connector plate members on the junction block connector shown in  FIG. 9 ; 
         FIG. 14  is a cross section view of the double-sided connector plate member taken along line  14 - 14  in  FIG. 13 ; 
         FIG. 15  is an enlarged isometric view of one of the second connector plate members on the junction block connector shown in  FIG. 9 ; 
         FIG. 16  is an isometric view illustrating another example of a plurality of adjacent structural trusses with framework extensions being connected to one another through a junction block connector; 
         FIG. 17  is an isometric view of one of the framework extensions shown in  FIG. 16 ; 
         FIG. 18  is a rear view of the framework extension shown in  FIG. 17 ; 
         FIG. 19  is a front view of the framework extension shown in  FIG. 17 ; 
         FIG. 20  is a side view of the framework extension shown in  FIG. 17 ; and 
         FIG. 21  is an isometric view illustrating an example of two adjacent and perpendicular structural trusses being connected end-to-end through an adaptor unit; and 
         FIG. 22  is an example of end plates welded to the end portion of a structural truss as found in the prior art. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side view of an example of a structural truss  100  incorporating the proposed concept. This structural truss  100  is suitable for a very wide variety of applications. To name just a few, this including for instance building or the like, bridges or similar structures, exhibition stages, lightning equipment or other scenic elements for live performance and events. The structural truss  100  can be used in a permanent or temporary construction. 
     The structural truss  100  can be made entirely of metal, although variants are possible as well. Aluminum or an alloy thereof is an example of a possible material. 
     The illustrated structural truss  100  has a quadrilateral tubular framework  102  with opposing ends  102   a ,  102   b . The framework  102  extends lengthwise along a main longitudinal axis  104  and includes four spaced-apart longitudinal tubes  106  running substantially parallel to one another. 
     The illustrated framework  102  has a substantially rectangular cross section, with one corresponding longitudinal tube  106  for each corner of the framework  102 . The illustrated framework  102  is thus a generic example and the exact configuration of the framework  102  can vary from one implementation to another. For instance, the structural truss  100  can be provided with three longitudinal tubes  106  or even more than four longitudinal tubes  106 . Also, although the framework  102  is shown as being rectilinear in the lengthwise direction, the framework  102  can be arc-shaped or be otherwise curved. In such situation, the longitudinal axis  104  will thus be arc-shaped or otherwise curved as well. 
     The longitudinal tubes  106  can be circular in cross section, as shown, or can be rectangular in cross section, depending on the needs. Variants are possible as well. 
     The longitudinal tubes  106  are interconnected by a plurality of bracing members  110  that are obliquely disposed in-between the longitudinal tubes  106 . The bracing members  110  are in the form of rigid tubes made of the same material as the longitudinal tubes  106 , for instance aluminum or an alloy thereof. The ends of the bracing members  110  are welded or otherwise rigidly connected to the longitudinal tubes  106 . The illustrated example includes two sets of bracing members  110  disposed in the vertical plane. They create a zigzag pattern in the lengthwise direction. Variants are also possible. 
       FIG. 1  further shows diagonal cross members  112  extending across the open space  114  located inside the structural truss  100 . The diagonal cross members  112  are in the form of rigid tubes made of the same material as the longitudinal tubes  106 , for instance aluminum or an alloy thereof. Variants are possible as well. 
     The ends of the diagonal cross members  112  are welded or otherwise rigidly attached to the corresponding longitudinal tubes  106 . These diagonal cross members  112  are also visible in  FIG. 2 , which is a top view of the structural truss  100  shown in  FIG. 1 . This structural truss  100  includes a plurality of spaced-apart transversal cross members  116  extending horizontally at right angle with reference to the longitudinal axis  104  and running parallel to the top and bottom side of the framework  102 . The ends of the transversal cross members  116  are welded or otherwise rigidly attached at right angle to the corresponding longitudinal tubes  106 . Transversal cross members  116  are located at the opposite ends  102   a ,  102   b  of the framework  102 . 
     If desired, one can provide additional bracing members in a zigzag pattern across the top and/or bottom side of the framework  102 . Other variants are possible as well. 
       FIG. 3  is an isometric view illustrating a portion of the structural truss  100  shown in  FIG. 1 , namely the portion where the end  102   a  is located.  FIG. 3  shows the structural truss  100  from the top side. As can be seen, the end  102   a  of the framework  102  includes two transversal cross members  116  welded near the corresponding free ends of the longitudinal tubes  106 . The transversal cross members  116  are positioned horizontally in the illustrated example. One is adjacent to the top side and the other is adjacent to the bottom side. 
     Also provided are two spaced-apart connector plate members  120 . The ends of the connector plate members  120  are welded to the framework  102 . Both connector plate members  120  extend parallel to one another between two corresponding longitudinal tubes  106 . They are also symmetrically disposed. Each connector plate member  120  is made of an elongated rectilinear monolithic piece and is manufactured using a machined extruded workpiece. Each of these connector plate members  120  are integrated into the framework  102  in a way that will minimize the welding beads required for rigidly connecting them to the rest of the framework  102 . This way, the assembly time will be significantly reduced and the tubes used in making the end portions of the structural truss  100  can be smaller since the heat affected zones will be minimal. 
       FIG. 4  is an end view of the portion of the structural truss  100  shown in  FIG. 3 . This figure shows that the connector plate members  120  are welded to the longitudinal tubes  106  and the transversal cross members  116  only at the opposite ends thereof. The welding beams are also visible in  FIG. 5 .  FIG. 5  is an enlarged isometric and semi-schematic view of one of the connector plate members  120  shown in  FIG. 3 . 
       FIG. 6  is a cross section view of the connector plate member  120  taken along line  6 - 6  in  FIG. 5 . As can be seen, each plated connector member  120  has substantially a somewhat lowercase-a-shaped cross section. 
     Each connector plate member  120  includes an outer abutment plate surface  122 , which surface  122  is substantially flat and uninterrupted in the illustrated example. The outer abutment plate surface  122  is part of both a corner beam section  124  and a main plate section  126 . 
     The corner beam section  124  has a hollow interior space  130  surrounded by walls forming a rectangular cross section and having rounded edges between them. The corner beam section  124  includes two opposite ends. In the illustrated example, one end is at the top side and the other end is at the bottom side. The corner beam section  124  extends between the two corresponding longitudinal tubes  106  once the connector plate members  120  are welded to the framework  102 , as shown best in  FIGS. 4 and 5 . The corner beam section  124  protrudes from a rear side of the connector plate member  120 , which rear side is opposite the outer abutment plate surface  122 . 
     It should be noted that the corner beam section  124  can have a different shape than that shown and described herein. For instance, it can have a rounded shape. Some implementations may omit the hollow interior space. 
     Each end of the corner beam section  124  has a corresponding first cutout  140  provided to fit around the free end of the corresponding longitudinal tubes  106 . These first cutouts  140  can be machined on the extruded workpiece when the connector plate members  120  were manufactured. 
     The main plate section  126  of each connector plate member  120  extends perpendicularly on a side of the corner beam section and in a direction that is substantially parallel to the outer abutment plate surface  122 . The main plate section  126  includes at least one fastener hole  150  to receive a bolt  152  ( FIG. 5 ) when connecting the corresponding connector plate member  120  to an adjacently-disposed connector plate member  120 . The number of holes  150  will depend on various factors and the implementations. Two holes  150  having a similar diameter are provided in the illustrated example. Variants are possible as well. 
     Each connector plate member  120  further includes a lip  142  projecting at right angle from an inner side of the main plate section  126 . The lip  142  extends substantially parallel to the corner beam section  124  and is positioned at the edge of the main plate section  126  in the illustrated example. The lip  142  includes two opposite ends, each having a corresponding second cutout  144 . These second cutouts  144  are configured and disposed to fit around a corresponding one of the transversal cross members  116 . 
       FIG. 7  is an isometric view illustrating an example of two adjacent structural trusses  100  of  FIG. 1  being adjoined end-to-end. As can be seen, the structural trusses  100  are configured and disposed so that corresponding holes  150  on both sides of the interface will be in registry with one another to receive the bolts  152 . The outer abutment plate surfaces  122  will be brought into a mating engagement and tightening the bolts  152  and nuts  154  will create a very solid connection between these two structural trusses  100 . 
       FIG. 8  is an isometric view illustrating an example of a plurality of adjacent structural trusses  100  being connected to one another through a junction block connector  200 . The junction block connector  200  provides the interface between the adjacent ends of these structural trusses  100 .  FIGS. 10 ,  11  and  12  are top, front and right side views, respectively, of the junction block connector  200  shown in  FIG. 9 . 
     The junction block connector  200  includes a small square-shaped framework  202  formed by four spaced-apart tubes to which a number of connector plate members  204 ,  206  are welded. In the illustrated example, the first connector plate members  204  are disposed vertically and are double sided. The second connector plate members  206  are disposed horizontally, namely at the top and bottom sides, and are similar to the connector plate members  120 . Such arrangement provides a very resistant construction that is easier to manufacture compared to an arrangement made of tubes welded at right angle. 
       FIG. 13  is an enlarged isometric and semi-schematic view of one of the double-sided connector plate members  204  on the junction block connector  200  shown in  FIG. 9 . 
       FIG. 14  is a cross section view of the double-sided connector plate member  204  taken along line  14 - 14  in  FIG. 13 . This connector plate member  204  includes a corner beam member  210  and two main plate sections  212 ,  214 , each projecting from a respective side of the corner beam member  210 . The two main plate sections  212 ,  214  are disposed at right angle from one another. They each include a corresponding lip  216 ,  218 . 
       FIG. 15  is an enlarged isometric view of one of the second connector plate members  206  on the junction block connector  200  shown in  FIG. 9 . 
       FIG. 16  is an isometric view illustrating another example of a plurality of adjacent structural trusses  100  with framework extensions  300  being connected to one another using the junction block connector  200 . As can be seen, the ends of the structural trusses  100  in  FIG. 16  are removably attached to the rest of their framework  102 . These framework extensions  300  can quickly adapt one model of structural truss  100  to the interface of the junction block connector  200 . Once connected to the structural trusses  100 , they form a part thereof. 
       FIG. 17  is an isometric view of one of the framework extensions  300  shown in  FIG. 16 . The framework extension  300  includes four spaced-apart spigots  302  to which are connected two transversal members  304  and two connector plate members  306 . These connector plate members  306  are similar in construction to the connector plate members  120 . 
     Each spigot  302  is configured and disposed to fit over the tip of a corresponding one of the longitudinal tubes  106 . In the illustrated example, the tips of the longitudinal tubes  106  have male and/or female connectors and the framework extensions  300  have corresponding opposite connectors. The exact configuration can vary from one implementation to another. 
       FIG. 18  is a rear view of the framework extension  300  shown in  FIG. 17 .  FIG. 19  is a front view of the framework extension  300  shown in  FIG. 17 .  FIG. 20  is a side view of the framework extension  300  shown in  FIG. 17 . 
       FIG. 21  is an isometric view illustrating an example of two adjacent and perpendicular structural trusses  100  being connected end-to-end through an adaptor unit  400 . The adaptor unit  400  is made of two framework extensions  300  disposed at right angle from one another. They are directly connected together at a mating side using pins  402  or the like. The other spigots are connected using two obliquely-disposed linking rods  404 . 
     The present detailed description and the appended figures are meant to be exemplary only, and a skilled person will recognize that many changes can be made while still remaining within the proposed concept.