Patent Publication Number: US-2021188360-A1

Title: Interlocking frame system and components therefor

Description:
TECHNICAL FIELD AND BACKGROUND 
     Recreational vehicle (RVs) components, such as walls (including interior walls and sidewalls), floors, and ceilings, are often formed from a laminated panel. 
     Traditional laminated RV panels are comprised of sheet material layers that are mounted to an aluminum tube frame with foam inserts placed in the frame openings to provide structure, sound dampening, and thermal protection. A typical sandwich panel (from its exterior finish to its interior finish) likely consists of fiber reinforced plastic sheet, a Luan wood sheet or other engineered sheet products, the aluminum frame and foam core, and then a Luan wood sheet with decor paper covering the interior side. This laminated panel configuration is used on RV side wall, floors, rear walls, slide-out walls, slide-out floors, and other smaller structural components used in the RV. 
     Central to each laminated structure is the aluminum tube frame. The aluminum frame is typically comprised of hollow thin aluminum tubes that are welded together. These frames typically provide enough structure to create the core of the panel, such as the side wall, but ultimately the integrity of the panel is defined by the laminated sandwich that combines the shear strength of its exterior sheets with the core (the frame and the foam inserts) to form a mechanically sound panel, such as a floor or wall. However, given the nature of RVs in that they are pulled her over varied terrain and subject to repeated vibration and shock loading from travel and transportation, the panels tend to take the brunt of the loading and can fail under extreme conditions. Often, these failure can be initiated or at least include the failure of a weld joint. 
     SUMMARY (P105B) 
     Accordingly, a structural assembly for a recreational vehicle is disclosed that includes a frame formed from a plurality of metal structural frame members, with hollow portions, that are interconnected in some cases at welded joints, with at least one or more of the welded joints configured such that at least one of the intersecting structural frame members engages the other structural frame member both internally in its hollow space and externally adjacent where it is welded to reduce the stresses at the weld. 
     Alternately, one or more of the joints are configured such that at least one of the intersecting structural frame member engages the other structural frame members both internally in its hollow space and externally to mechanically couple the two structural frame members together but without the need of a weld. 
     For example, a first structural frame member is mounted to an exterior surface of a sidewall of a second structural frame member and is configured to engage the interior surface of the side wall to redistribute the stresses at the joint. 
     In another example, a first structural frame member is mounted to a sidewall of a second structural frame member and is configured to transfer some of the forces to the upper wall of the second structural frame member from the sidewall of the second structural frame member to which the first structural frame member is mounted. 
     In one embodiment, a structural assembly for a recreational vehicle includes a first structural frame member with a hollow section and a second structural frame member. The side wall of the second structural frame member has a notch, for example, a narrow notch which forms a tab and a slot for receiving the side wall of the first structural frame member through a notch formed in the upper wall of the first structural frame member for receiving the tab into its hollow section. Further, the upper wall of the second structural frame member is located in the notch of the first structural frame member when the second structural frame member is engaged with the side wall of the first structural frame member with the slot wherein the structural assembly forms a component of a recreational vehicle frame. 
     In one embodiment, the notch of the first structural frame member extends into the side wall of the first structural frame member such that the upper wall of the second structural frame member is coplanar or flush with the upper wall of the first structural frame member when the second structural frame member is engaged with the side wall of the first structural frame member with the slot. 
     In another embodiment, the notch has a width, and the second structural frame member has a width being approximately equal to the width of the notch of the first structural frame member wherein the notch of the first structural frame member straddles the width of the second structural frame member. 
     In other embodiments, in any of the above, the side wall of the second structural frame member has a first section on one side of the slot with a first height and a second section on the opposed side of the slot with a second height that is shorter than the first height to thereby form the tab with a shorter height than the first section of the side wall for insertion into the notch of the first structural frame member. 
     In yet other embodiments, in any of the above, one or both of the first structural frame member and the second structural frame member comprise a hollow tubular structural frame member. 
     In yet other embodiments, in any of the above, the first structural frame member has a terminal end, and the notch of the first structural frame member extends along the upper wall to the terminal end. 
     In any of the above, the structural assembly may further include a third structural frame member having an upper wall and a side wall depending from the upper wall of the third structural frame member. The upper wall of the first structural frame member has a second notch, and the second structural frame member has a third notch in the upper wall of the second structural frame member. The side wall of the third structural frame member has a narrow notch that forms a second slot for engaging the side wall of the first structural frame member through the second notch of the first structural frame member and another narrow notch forming a third slot for engaging the side wall of the second structural frame member through the third notch of the upper wall of the second structural frame member. 
     In any of the above, the first structural frame member is orthogonal to the second structural frame member. 
     In any of the above, the first structural frame member is formed by first and second joined structural frame members, each of the first and second joined structural frame members having an upper wall forming the upper wall of the first structural frame member and a side wall forming the side wall of the first structural frame member. 
     For example, the first and second joined structural frame members may be joined in an abutting relationship with a portion of the notch of the first structural frame member being formed in the upper wall of the first joined structural frame member and in the upper wall of the second joined structural frame member. Further, the upper wall of the second structural frame member may be coplanar or flush with the upper walls of the first and second joined structural frame members. 
     In some embodiments, at least one weld joins the second structural frame member with the first structural frame member. For example, the weld may join the side wall of the second structural frame member with the side wall of the first structural frame member. 
     In another embodiment, a structural assembly for an recreational vehicle includes a first structural frame member having an upper wall and a side wall depending from the upper wall, with the upper wall having a notch at the side wall. The structural assembly further includes a second structural frame member having an upper wall and a side wall depending from the upper wall, with the upper wall of the second structural frame member having a notch at the side wall of the second structural frame member. The structural assembly also includes a channel-shaped member having an upper plate and a pair of downwardly depending flanges. Each of the flanges having a narrow notch forming a slot to engage with at least one of the side walls of the first and second structural frame members through the notches of the first and second structural frame members wherein the structural assembly forms a component of a recreational vehicle frame. 
     In a further embodiment, one or both of the notches of the first and second structural frame members extend into a respective side wall of the side walls of the first structural frame member and the second structural frame member, wherein the upper wall of the channel-shaped structural frame member is coplanar or flush with one or both of the upper walls of the first and second structural frame members. 
     In any of the above, the side wall of the first structural frame member abuts the side wall of the second structural frame member. 
     Optionally, the structural assembly further includes one or more welds joining the first and second structural frame members, with the weld being adjacent one side of the notch and, optionally, on either side of the notch. 
     In a further embodiment, the structural assembly further includes a third structural frame member having an upper wall and opposed side walls depending from the upper wall of the third structural frame member. The third structural frame member is disposed between the first and second structural frame members, with the upper wall of the third structural frame member having a notch in the upper wall extending between the opposed side walls. The upper wall of the channel-shaped member extends into the notch of the third structural frame member. 
     For example, in another embodiment, the slot comprises a first slot, and the opposed flanges have a second slot. The first slot is engaged with the side wall of the first structural frame member and one of the opposed side walls of the third structural frame member. The second slot is engaged with the side wall of the second structural frame member and the other of the opposed side walls of the third structural frame member. 
     In any of the above, the first, second, and third structural frame members may be parallel to each other. 
     According to yet another embodiment, a structural assembly for an recreational vehicle includes a first structural frame member having a first upper wall and a pair of opposed first side walls depending from the first upper wall, with the first upper wall having a first notch extending between the opposed first side walls. The structural assembly further includes a second structural frame member having a second upper wall, a bottom wall, and a pair of opposed second side walls extending between the second upper wall and the bottom wall. The bottom wall has a second notch extending between the second side walls, with the second notch being approximately equal in size to the first notch to allow the second structural frame member to straddle and be interlocked with the first structural frame member at the first notch and, further, wherein the second upper wall of the second structural frame member is coplanar or flush with the first upper wall of the first structural frame member. 
     Optionally, the structural assembly may also include one or more welds joining the first and second structural frame members together wherein the structural assembly forms a component of a recreational vehicle frame. For example, the weld or welds may be located adjacent the first and second notches. 
     In further embodiments, one or both of the first structural frame member and the second structural frame member comprise a hollow tubular structural frame member. 
     In yet another embodiment, a frame system for a recreational vehicle includes a plurality of structural frame members arranged in a plane and welded together to form a frame. At least two structural frame members of the structural frame members have a welded joint and have notches formed therein to allow the two structural frame members to be mechanically interlocked at the joint to reduce the size of the weld for the welded joint. 
     For example, at least two structural frame members may be formed by any one of the above structural assemblies. 
     Accordingly, a frame is disclosed that can be easily assembled and, further, that can exhibit added rigidity and/or controlled flexibility. 
    
    
     
       DETAILED DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of an exemplary recreational vehicle; 
         FIG. 1A  is similar view to  FIG. 1  but with the outer layers of the various panels removed to show the underlying frames; 
         FIG. 2  is a side view of a recreational vehicle side panel with the outer layers removed to show the underlying frame and frame members; 
         FIG. 3  is an enlarged view of detail III-III of  FIG. 2 ; 
         FIG. 4  is an enlarged view of a section of the frame of  FIG. 3 ; 
         FIG. 5  is an enlarged view of another section of the frame of  FIG. 3 ; 
         FIG. 6  is an enlarged fragmentary perspective view of two joined structural frame members; 
         FIG. 6A  is a cross-section view taken along line VIA-VIA of  FIG. 6 ; 
         FIG. 7  is an exploded perspective view illustrating the joint of the two joined members of  FIG. 6 ; 
         FIG. 7A  is a top plan view of similar joint to the joint shown in  FIG. 7  but with a third structural frame member illustrating optional weld or adhesive locations; 
         FIG. 7B  is a top plan view of the joint of  FIG. 7A  illustrating adhesive applied to the upper walls of the joined structural frame members; 
         FIG. 8  is an enlarged fragmentary perspective view of another joint; 
         FIG. 8A  is a cross-section view taken along line VIIIA-VIIIA of  FIG. 8 ; 
         FIG. 9  is an exploded perspective view illustrating the joint of  FIG. 8 ; 
         FIG. 10  is an enlarged fragmentary perspective view of another joint; 
         FIG. 10A  is a cross-section view taken along line XA-XA of  FIG. 10 ; 
         FIG. 11  is an exploded perspective view illustrating the joint of  FIG. 10 ; 
         FIG. 12  is an enlarged fragmentary perspective view of another joint; 
         FIG. 12A  is a cross-section view taken along line XIIA-XIIA of  FIG. 12 ; 
         FIG. 13  is an exploded perspective view illustrating the joint of  FIG. 12 ; 
         FIG. 14  is an enlarged fragmentary perspective view of another joint; 
         FIG. 14A  is a cross-section view taken along line XIVA-XIVA of  FIG. 14 ; 
         FIG. 14B  is a cross-section view taken along line XIVB-XIVB of  FIG. 14 ; 
         FIG. 15  is an exploded bottom perspective view illustrating the joint of  FIG. 14 ; 
         FIG. 16  is an enlarged fragmentary perspective view of another joint; 
         FIG. 17  is an exploded perspective view illustrating the joint of  FIG. 16 ; 
         FIG. 18  is an enlarged fragmentary perspective view of another joint; 
         FIG. 18A  is a cross-section view taken along line XVIIIA-XVIIIA of  FIG. 18 ; 
         FIG. 19  is an exploded perspective view illustrating the joint of  FIG. 18 ; 
         FIG. 20  is an enlarged fragmentary perspective view of another joint; 
         FIG. 21  is an exploded perspective view illustrating the joint of  FIG. 20 ; 
         FIG. 21A  is a similar view to  FIG. 21  illustrating the opposed end of one of the structural frame members joined with a third structural frame member using a joint illustrated in  FIGS. 6, 6A, and 7 ; 
         FIG. 21B  is an exploded perspective view the structural frame members of  FIG. 21A ; 
         FIG. 21C  is a cross-section view taken along line XXIC-XXIC of  FIG. 21A ; 
         FIG. 22  is an enlarged fragmentary perspective view of another joint; 
         FIG. 23  is an exploded perspective view illustrating the joint of  FIG. 22 ; 
         FIG. 24  is an enlarged fragmentary perspective view of another joint; 
         FIG. 25  is an unfolded perspective view illustrating the joint of  FIG. 24 ; 
         FIG. 26  is an enlarged fragmentary perspective view of another joint; 
         FIG. 27  is an exploded perspective view illustrating the joint of  FIG. 26 ; 
         FIG. 28  is a perspective view illustrating another joint with one or more injection ports; 
         FIG. 29  is an exploded perspective view of the joint of  FIG. 28 ; 
         FIG. 30  is an enlarged fragmentary perspective view of one of the structural frame members of the joint of  FIG. 28 ; 
         FIG. 31  is an enlarged fragmentary perspective view of another structural frame member of the joint of  FIG. 28 ; 
         FIG. 32  is a similar view to  FIG. 28  illustrating the joint reinforced with a foam material; 
         FIG. 32A  is a cross-section taken through line XXXIIA-XXXIIA of  FIG. 32 ; 
         FIG. 32B  is a cross-section taken through line XXXIIB-XXXIIB of  FIG. 32 ; 
         FIG. 32C  is a similar cross-section to  FIG. 32A  but illustrating another embodiment of the foam inserts; 
         FIG. 33  is an end perspective view of the joint of  FIG. 32 ; 
         FIG. 34  is similar view to  FIG. 33 ; 
         FIG. 35  is a perspective view illustrating another joint similar to the joint illustrated in  FIG. 28  with multiple injection ports; 
         FIG. 36  is an end perspective view of the joint of  FIG. 35  illustrating one or more foam inserts injected into the joint of  FIG. 35 ; 
         FIG. 37  is an enlarged fragmentary perspective view of another embodiment of the end of one the structural frame members of the joint of  FIG. 35 ; 
         FIG. 38  is an enlarged fragmentary perspective view of yet another embodiment of the end of one the structural frame members of the joint of  FIG. 35 ; 
         FIG. 39  is a cross-section view similar to  FIG. 6  illustrating the joint with an insert; 
         FIG. 40  is a cross-section view similar to  FIG. 10A  illustrating the joint with an insert; 
         FIG. 41  is a cross-section view similar to  FIG. 12A  illustrating the joint with an insert; 
         FIG. 42  is a cross-section view similar to  FIG. 14A  illustrating the joint with an insert; 
         FIG. 43  is a cross-section view similar to  FIG. 14B  illustrating the joint with an insert; 
         FIG. 44  is a cross-section view similar to  FIG. 18A  illustrating the joint with an insert; 
         FIG. 45  is a cross-section view similar to  FIG. 25  illustrating the joint with an insert; and 
         FIG. 46  is a cross-section view similar to  FIG. 21C  illustrating the joint with an insert. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 1A , the numeral  10  generally designates a recreational vehicle (RV). Recreational vehicle  10  includes a chassis  12 , a plurality of wheels  14 , which are mounted to chassis  12 , and a plurality of frames  16  that form structural panels (or are covered with panels) to form walls, such as sidewalls  18  and interior walls (not shown), a floor  20  ( FIG. 4 ), and/or ceiling/roof  22 , which are mounted to the chassis  12  and assembled together form the RV cabin. As will be more fully described below, the frames  16  that form the structural panels (including sidewalls  18 , floors  20 , and ceiling/roof  22 , as well as interior or partitions walls, including accessory compartments frames (not shown)) or to which the structural panels are mounted, may be formed using the frame and frame assembly method described below. Although described in reference to a structural frame for an RV, it should be understood that the frame and frame assembly method described below may be used to form or assemble other frames. For the purposes of this disclosure, the focus of the description will be on how the structural frame members of the frame  16  are joined. 
     Referring to  FIG. 2 , for example, the frame  16  of side wall  18  includes a plurality of horizontal and generally horizontal structural frame members  16   a - 16   q , vertical and generally vertical structural frame members  17   a - 17   t , a plurality of structural frame members  18   a ,  18   b , and  18   c  that form connectors, structural frame members  19   a,    19   b , and  19   c  that form brace members, and structural frame members S that form offset supports or spacers, which are joined to form the frame  16 . Several variations of joining methods are described below, including interlocking of the structural frame members and then optionally welding the structural frame members together. Further, as will be more fully described the structural frame members may be marked, such as by lettering or color coding, to assist in the assembly of the interlocking parts, which may eliminate the need for fixturing. 
     The terms upper and lower, left, right, vertical and horizontal are just used in reference to the orientation shown in  FIG. 2 . Further, it should be understood that additional structural frame members (not illustrated) may form part of the frame, including curved frame members and frame members that are arranged to frame in and reinforce other openings, such as for doors or windows. Therefore, it should be understood that the frame and method of assembling the frame described below may be adjusted and configured to form a variety of different frame configurations. 
     Referring to  FIGS. 3 and 4 , for example, some of the structural frame members may be joined: At right angles (i.e. orthogonal) to each other, such as using a joint J 1  (e.g.  FIG. 6, 6A, 7, 16, 17, 21A, 21B, 21C ), joint J 2  (e.g. FIGS,  8 ,  8 A, and  9 ), joint J 5  (e.g.  FIGS. 14, 14A, 14B, and 15 ), joint J 7  (e.g.  FIGS. 18, 18A, and 19 ), joint J 8  (e.g.  FIGS. 20, 21, 21A, 21B, 21C ), joint J 9  (e.g.  FIGS. 22 and 23 ), joint  11  (e.g.  FIGS. 32 -,  33 ); joined parallel to each other, such as by joint J 3  (e.g.  FIGS. 10, 10A, and 11 ), joint J 4  (e.g.  FIGS. 12, 12, and 13 ); or joined at a non-orthogonal angle to each other, such as joint J 6  (e.g.  FIGS. 16 and 17 ) or joint J 10  (e.g.  FIGS. 24 and 25 ), or using a combination of joints (see for example  FIGS. 16, 21A, 22, 23, and 26 ), which interlock one or more structural frame members together. 
     Referring to  FIGS. 6, 6A, and 7 , joint J 1  is formed by two or more orthogonal structural frame members—for example, a first structural frame member  17   h  and a second structural frame member  16   b,  which form a T-shaped joint. Though, as described below, a third structural frame member may be attached to first structural frame member  17   h  on the opposed side from structural frame member  16   b  using the same joint to form a cross-shaped joint. The reference to first and second (or third) in regard to the structural frame members should not be construed to be limiting and is just used to provide a frame of reference. 
     As understood from  FIG. 7 , each of the side walls  30  of the second structural frame member  16   b  has a narrow notch  32  in the form of a slot to form tabs  32   a . Slots  32  are sized and configured for receiving the side wall  34  of the first structural frame member  17   h  through a notch  36  formed at least in the upper wall  38  of the first structural frame member  17   h , and, optionally, in both the upper wall  38  and the side wall  34  of the first structural frame member  17   h.    
     Slots  32  extend up into side walls  30  from their lower ends or sides (as seen in  FIG. 7 ) to form tabs or fangs  32   a  that are used to extend into the notch  36  to thereby engage the side wall  34  from the interior side of the of first structural frame member  17   h.  Optionally, the height of each of the tabs  32   a  may be the same or less than the height of the side walls  30  of first structural frame member  16   b . Thus, each of the side walls of the second structural frame member has a first section on one side of the slot  32  with a first height and a second section on the opposed side of the slot  32  with a second height that is different, e.g. shorter, than the first height to thereby form tabs  32   a  with a shorter height than the first sections (e.g. remainder) of the side walls for insertion into the notch in the first structural frame member. As it would be understood with tight tolerances, the shorter the slot  32 , the easier it may be to assemble. 
     Further, the upper wall  40  of the second structural frame member  16   b  may extend to the distal end of the second structural frame member. In this manner, upper wall  40  can extend into and be located in the notch  36  when the second structural frame member  16   b  is engaged with the first structural frame member  17   h,  such as shown in  FIG. 6A . As a result, the notch  36  straddles the upper wall at the end of the second structural frame member  16   b.  Further, upper wall  40  may be coplanar or flush with the upper wall  38  of first structural frame member  17   h.    
     In the illustrated embodiment, first structural frame member  17   h  and second structural frame member  16   b  each have closed rectangular tubular cross-sections with both upper walls  38 ,  40  and lower walls  42 ,  44 . However, it should be understood that the structural frame members may have open cross-sections, such as L or C shaped cross sections, such as in structural angles or channels, etc. Optionally, in additional to upper wall  40  of second structural frame member  16   b  being coplanar with or coplanar or flush and extending into upper wall  38  of first structural frame member  17   h,  lower wall  44  may also be coplanar or flush, but adjacent lower wall  42  of first structural frame member  17   h  ( FIG. 6A ). 
     Optionally, as best understood from  FIG. 6A , the illustrated embodiment, the notches  32  and  36  are sized to form a snug fit between the first structural frame member  17   h  and the second structural frame member  16   b  so that they form a tight, rigid connection. For example, the clearance between the notch  36  and the second structural frame member  16   b  may be an air gap, in a range of about 0 to 0.006 inches or in a range of 0 to 0.020 inches. Similarly, the clearance between the notch  32  and the side wall of the first structural frame member  17   h  may be an air gap, for example, in a range of about 0 to 0.006 of an inch or in a range of 0 to 0.02 of an inch. Alternately, the notches may be sized to provide a larger gap, for example, in a range of 1/64 th  of an inch to 1/16 th  of an inch or greater to provide some flexibility at the joint. 
     Consequently, when the second structural frame member  16   b  is fully engaged with the first structural frame member  17   h,  structural frame number  16   b  will transfer some of the forces at the joint to the upper wall of the first structural frame member  17   h.  Similarly, tabs  32   a  will engage the interior surface of the sidewall of the first structural frame member  17   h  thereby re-distribute some the stresses from the weld of welds, at the joint when welded, to other portions of the first structural frame member, which has been found to reduce stresses in the weld or welds. In other embodiments, when no welds are provided, this interlocking of the two structural frame members provide a sufficiently rigid joints for the frame, especially when combined with the laminations described below. 
     Referring again to  FIG. 6A , optionally the ends  32   b  of tabs  32   a  may be rounded or tapered to facilitate insertion, but without significantly reducing the bearing surface between the tabs and the side wall of the first structural frame member  17   h.  For example, the tabs  32   a  and rounded tapered ends may be sized so that the tabs still contact at least 30% of the height of the side wall or greater of the first structural frame member  17   h . As described below, by providing this internal interface and interlock between the two structural frame members, the stresses on any welds provided, for example, tack welds between the respective side walls of the structural frame members (for example, one of each side of the joint) may be reduced. Further, in some configurations the welds may be eliminated, with the strength of the panel relying on the laminated layers that are applied to both sides of the frame when forming the panels. 
     Referring to  FIGS. 7A and 7B , a third structural frame member  16   b ′ may be joined with structural frame member  17   h  using the same connection described above in reference to structural frame member  16   b  so that together structural frame members  16   b ,  16   b ′ and  17   h  form a cross shaped configuration. As noted below, the structural frame members may be welded together using stitch welding or continuous welds W at their respective sidewalls, including a corner bead weld or welds, such as shown in  FIG. 7A  . Additionally or in lieu of the corner bead weld or welds, the structural frame members may be joined by one or more surface bead welds, for example on their upper and/or lower walls, such as understood from  FIG. 7B . However, as noted above, sufficient strength to the frame may be provided by the laminated layers that are applied to both sides of the frame when forming the panels. 
     Although illustrated as hollow closed rectangular tubular members, as noted above, it should be understood that either one or both of the first structural frame member and the second structural frame member may have an open section and/or comprise a partially hollow member or a solid structural frame member but with a space formed in at least one of the structural frame members to allow for the internal interface and interlocking of the two members. Further, while illustrated with a rectangular cross-section, the shape of the cross-sections of both or any of the members may be varied. 
     Referring to  FIG. 8 , in another embodiment, namely in joint  2 , the upper wall  38 ′ of the first structural frame member includes two notches  36 ′, which are spaced apart by a section  36   a ′ of upper wall  38 ′, with each sized to receive a respective tab of tabs  32   a ′. Tabs  32   a ′ are also formed by narrow notches  32 ′ in the form of slots that extend up into the opposed side walls  30 ′ of the second structural frame member. In this embodiment, the upper wall  40 ′ of the second structural frame member has a forked or bifurcated end  40   a ′ so that only portions of the upper wall  40  extend into the notches  36  of the first structural frame member. Further, the portions of the upper wall  40 ′ that extend into the notches  36 ′ may be coplanar or flush with the upper wall  38 ′ of the first structural frame member. 
     Again, the slots  32 ′ are configured for receiving the side wall  34 ′ of the first structural frame member through notches  36 ′. Optionally, similar to the previous embodiment, the height of each of the tabs  32   a ′ may be the same or less than the remainder of the side walls  30 ′ of the first structural frame member. Additionally, as noted in reference to the above embodiment, and as shown in  FIG. 8A , the slots and notches may be sized to form a snug fit connection at the joint or may provide gaps to introduce some flexibility into the joint. 
     In the above embodiments, the structural frame members are angle at ninety degrees (orthogonal) to each other. Referring to  FIGS. 10, 10A, 11, 12, 12A, and 13 , the structural frame members may be parallel, with another structural frame member straddling at least a portion of the parallel structural frame members to interlock them together. 
     As best seen  FIGS. 10, 10A, and 11 , first and second structural frame members  17   r  and  17   q  are interlocked by a third channel shaped structural frame member  46 . Each of the first and second structural frame members  17   r  and  17   q  has an upper wall  48 ,  50  and a pair of opposed side wall  52 ,  54  depending from their respective upper wall  48 ,  50 . In the illustrated embodiment, the inner side walls  52   a,    54   a  of each of the first and second structural frame members  17   r  and  17   q  contact and abut each other—but it should be understood that they may be spaced from each other with the channel shaped structural frame member  46  lengthened to extend and span between the two structural frame members, and further provided with a slot for each of the side walls (such as shown in  FIG. 13 ) rather than a shared slot, which is shown in  FIGS. 10A and 11 . For example, see structural frame member  18   b  ( FIG. 2 ). 
     Each upper wall  48 ,  50  has a notch  56 ,  58  at its respective side wall, which optionally extends into the side wall (similar to the previous embodiments). The channel-shaped structural frame member  46  has a web that forms an upper wall  60 , and a pair of downwardly depending flanges that form opposed side walls  62 . Each of the side walls  62  has a narrow notch in the form of a slot  64 , which divides the side walls  62  into two tabs  66  (or fangs). Optionally, each tab is substantially the same size, for engaging and straddling both of the abutting side walls of the first and second structural frame members through the notches  56 ,  58  ( FIG. 10A ). Although illustrated as having the same heights, tabs  66  may have different heights to provide different stiffnesses to the joint or simply to facilitate assembly. Further, the widths of the tabs may vary to vary the stiffness of the joint or simply to accommodate different size first and second structural frame members  17   q  and  17   r.    
     Optionally, similar to the first two embodiments, the upper wall of the channel-shaped structural frame member may be coplanar or flush with one or both of the upper walls of the first and second structural frame members. Again, the size of the notches ( 56 ,  58 ,  64 ) are selected to provide a snug fit connection, such as shown in  FIG. 10A , or may be increased to introduce flexibility, such as described above. Additionally, similar to joint J 2 , notches  56  and  58  may be each formed from a pair of notches (both or just one), with upper wall  60  of member  46  having one or both sides having a forked configuration to extend into the spaced notches. 
     As best seen  FIGS. 12, 12A, and 13 , three parallel structural frame members, such structural frame members  16   i ,  16   i , and  16   l , may be interlocked using structural frame member  18   a.  Similar to the previous embodiment, structural frame member  18   a  straddles between the three structural frame members  16   i,    16   i,  and  16   l  and is also formed by channel shaped structural frame member  70 . Each of the structural frame members has an upper wall  72 ,  74 ,  76  and a pair of opposed side wall  78 ,  80 ,  82  depending from their respective upper wall  72 ,  74 ,  76 . In the illustrated embodiment, the inner side walls  78   a  and  82   a  contact and abut the respective side walls  80  of the middle, second structural frame member  16   i.  Again it should be understood that they may be spaced from each other with the channel shaped structural frame member  46  lengthened to extend and span between the spaced structural frame members, and further provided with additional notches to independently engage each of the side walls. 
     Each upper wall  72 ,  74 , and  76  has a notch  84 ,  86 ,  88  at the side wall, which optionally extend into the respective side wall, as seen in  FIG. 13 , with sufficient depth to allow member  16   i  be coplanar or flush with each of the structural frame members. Further, notch  86  of the central structural frame member  16   i  spans the full width of the upper wall  74 . As noted, notch  86  optionally extends into each of its side walls  80  at a sufficient depth so that channel-shaped member  70  may traverse and nest in the central structural frame member in notch  86  and similarly extend and nest in notches  84  and  88  of structural frame members  16   i  and  16   l  so that channel-shaped member  70  nests in all three structural frame members to form a coplanar or flush arrangement. 
     Channel-shaped member  70  has a web  92 , which forms an upper wall (which optionally is coplanar or flush with upper walls  72 ,  74 , and  76 ), and a pair of downwardly depending flanges  94 , which form opposed side walls. Each of the flanges  94  has a pair of narrow notches that form slots  96 , which divide the respective side walls into three tabs  98  (or fangs) for engaging the abutting side walls of the first, second, and third second structural frame members through the notches  84 ,  86 , and  88 . Similar to the previous embodiment, slots  96  may be sized to engage two side walls, which may or may not have the same thickness. 
     Although illustrated as having the same heights, tabs  98  may have different heights. Further, the width of each tab may vary—for example, in the illustrated embodiment, the outer tabs  94   a are narrower in width than the central tab  94   b,  which spans across the full internal width of the central structural frame member  16   i.  However, it should be understood that the central tab  94   b  may be at least partially bifurcated with a central narrow notch dividing the central tab into two tabs. For example, the central narrow notch may have the same height as notches  96  or may be shorter or longer and/or narrower or wider. 
     Optionally, similar to the first two embodiments, as noted, the upper wall of the channel-shaped structural frame member may be coplanar or flush with one, two or all of the upper walls of the first, second, and third structural frame members. For further optional additional details about the tabs and about clearances or gaps between member  18   a  and members  16   i,    16   j,  and  16   l , reference is made to the above description. 
     Referring to  FIGS. 14, 14A, 14B, and 15 , two structural frame members, such as structural frame members  16   f,    17   h  may be arranged so that one structural frame member crosses or transverses the other frame member to form a cross-shaped interlocking joint J 5 . As best seen in  FIG. 15 , the interlocking joint J 5  is formed by a notch  102 ,  104  formed in each structural frame member  16   f,    17   h.  One of the notches  104  has extended portions on its opposed sides forming slots  106  ( FIGS. 14B and 15 ) to receive the side wall of the other structural frame member to form a central, elongated tab  106   a  on each side to extend into the hollow space  102   a  of structural frame member  17   h.  Each notch  102  and  104  transverses the width of each respective structural frame member and, further, is sized so that the upper wall of each structural frame member is coplanar or flush with the upper wall of the other structural frame member. 
     Although illustrated with a single, sold tab  106   a  on each side of structural frame member  16   f,  which extends the full width of the structural frame member  17   h,  it should be understood that one or both tabs may be bifurcated by an additional central narrow notch. 
     In yet other embodiment, as shown in  FIG. 16 , two structural frame members, such as structural frame members  19   c  and  16   i,  may be arranged so that one structural frame member forms a non-orthogonal angle with respect to the other. For example, interlocking joint J 6  may be formed by an angled notch  110  in one structural frame member  16   i  and a pair of the slots  114  ( FIG. 17 ) formed in the opposed side walls of the other structural frame member  19   c , but which are offset from each other so that they can engage the angled side wall and notch of the respective side wall of structural frame member  19   c.  Similarly, the opposed end of the angled structural frame member  19   c  may have a pair of slots  116  to engage an angled notch  112  formed in a third structural frame member, such as structural frame member  17   s.  Structural frame member  17   s  may be orthogonal to member  16   i  and, further, may be interlocked to member  16   i  using joint J 1  or J 2 , described above. 
     Additional joints may be formed, for example at the ends of two abutting structural frame members, such as first and second structural frame members  17   j  and  16   o  ( FIG. 2 ). For example, referring to  FIG. 18 , a notch  118  may be provided that extends through the upper wall  120  of structural frame member  17   j  and into side wall  122  and, further, to the terminal end  124  of first structural frame member  17   j.  Notch  126 , which forms a slot, may be formed in one side wall  128  of second structural frame member  16   o  to form a tab  128   a  to engage the side wall  122  of the first structural frame member, so that the opposed side wall  130  of the second structural frame member  16 o abuts the distal end  124  of the first structural frame member  17   j  (see  FIG. 18 ). 
     Similarly the upper wall  132  of the second structural frame member may extend into the notch  120  and, further, be coplanar or flush with the upper wall  122  of the first structural frame member. Optionally, as noted above, one or more welds may be provided between the respective side walls of the two structural frame members. 
     Referring to  FIGS. 20 and 21 , any one of the structural frame members may be formed as a composite structural frame member  148 . For example, in the illustrated embodiment, composite structural frame member  148  may be formed from abutting first and second joined structural frame members  148   a ,  148   b.  Each of the first and second joined structural frame members  148   a,    148   b  has an upper wall and a lower wall  152 ,  154 , and a pair of opposed side walls  158 ,  160 . First and second joined structural frame members  148   a,    148   b  are joined by upper and lower tabs  162  formed in the upper and lower walls of one member, e.g. joined structural frame member  148   a,  which extend into corresponding notches  164  formed in the upper and lower walls of the other member, e.g. joined structural frame member  148   b.  The other structural frame member  150  abuts and straddles the side walls of both joined structural frame members  148   a,    148   b,  which forms a joint similar to J 1 . 
     Referring to  FIG. 21 , structural frame member  150  includes slots  162   a  in its opposed side walls  162  that form tabs  162   b  that extend into a respective notch  166 ,  168  formed in each structural frame members  148   a,    148   b  at their respective distal ends similar to notches  118 ,  120  described above. 
     It should be understood that the various joints described herein may be used with other structural frame members, such as structural frame members S, and further combined with other joints (see  FIGS. 21A, 21B, 21C, 22 and 26 ). Further, the shape of the structural frame members may vary and include rectangular, as shown, or rounded cross-sections, including circular. Additionally, while illustrated with closed cross-sections, the structural frame members may have open cross-sections, such as structural angles, channels, half-angles, half tubes, or the like or composite shaped members, for example, with one portion having a closed cross-section and the other extending from the closed-cross-section, such as P-shaped member. Other structural member may have two closed hollow sections, such as side-by-side tubular members. 
     Referring to  FIGS. 21A, 21B, and 21C , as noted above multiple structural frame members may be assembled using two more joints, and further, as will be described below, the joints may be configured so that one joint may have a rigid connection, while another joint may have a flexible connection, for example, to relieve stresses in the overall frame. 
     For example, structural frame member  16   b  may be connected to structural frame member  17   e  using joint J 1 , with notches  32  receiving the side wall  180  of structural frame member  16   b  and tab  32   a  extended into the interior space  180   a  of structural frame member  16   b  through notch  181 , similar to as described above in reference to  FIGS. 6, 6A, and 7 . Structural frame member  17   e  in turn may be connected to structural frame member  16   a  using joint J 8 , with notches  162   a  receiving the side walls  182 ,  182 ″ of structural frame member  16   a  and tabs  162   b  extended into the interior spaces  182   a ′,  182   a ″ of structural frame members  16   a ′, and  16   a ″ through notches  183 ′,  183 ″, similar to as described above in reference to  FIG. 21 . 
     In the illustrated arrangement joint J 8  may be a rigid joint, especially given that it is formed at the juncture of two abutting structural frame members  16   a ′ and  16   a ″ that are joined together in a similar manner to members  148   a,    148   b  described below in reference to  FIG. 20 . 
     Joint J 1  may be formed with greater tolerances between the mating tabs, notches, and/or side walls, as noted above, to provide some flexibility at the joint to thereby reduce stress in the frame. Further, as will be described more fully below, as with all the above joints, inserts may be located internally at one or both joints (J 1  or J 8 ) to reinforce the joint or joints or to introduced greater flexibility about one or more axes to modify the degrees of freedom at the respective joint. 
     Referring to  FIG. 22 , joint J 9  may be used to join a spacer structural frame member S with two other structural frame members, such as members  17   b  and  17   c,  with tabs  170  formed on the upper wall of spacer S and corresponding notches formed in the upper walls of members  17   b,    17   c.    
     Other joints, such as joints J 10  shown in  FIGS. 22, 24, and 25 , may be formed by forming an angled notch  174 , such as a 90 degree notch, in the upper, lower and side walls  176   a,    176   b,    178   a,    178   b  of a structural frame member and then folding the structural frame member about the notch (or notches when multiple bends are desired) and, thereafter, welding the bent portions of the member together, such as best understood in  FIGS. 24 and 25 . For example, joints J 10  may also be suitable for structural frame members  17   c,    16   d ,  16   e,    17   f,  and  17   t  or structural frame members  17   i,    16   g,  and  16   hc,  which are used for framing a slide out or window. 
     In any of the above, the structural assembly may further include an additional structural frame member or members joined with other structural frame members using any combination of joints, such joints J 1 , J 3 , J 6 , and/or J 10 , such as shown in  FIGS. 26 and 27 . 
     In any of the above, at least one weld may join the structural frame members together. For example, the side walls of the structural frame members may be joined together by a weld or welds or an adhesive, for example using a corner bead, including stitch corner beads ( FIG. 7A ). Optionally, the upper and lower sides of the structural frame members may be welded at their intersections. A full wrap around bead, such as full wrap around weld, may also be used. Further, to adhere the laminations described below, adhesive may be applied to the upper and lower walls of the respective structural frame members (see  FIG. 7B ). However, the weld or welds may be omitted completely and, instead, rely on the external laminations L (shown only partially in  FIG. 2 ) for strength, which are secured to the frame by adhesive, such as described in U.S. patent application Ser. No. 16/346,716, filed on Mar. 18, 2019, owned by Jayco, which is incorporated by reference herein its entirety. 
     Referring to  FIGS. 28-34 , in another embodiment of the various joints described herein, an insert or inserts maybe provided internally to the joint to reinforced the joint internally and, optionally, replace any exterior welds. Further, the joints may be tailored to customize the rigidity or flexibility of the joint as desired, for example to increase or decrease the rigidity or flexibility of the joint about one or more axes. Although illustrated in reference to only some of the joints, it should be understood that any or all of the joints disclosed herein may incorporate the insert described below. 
     As best seen in  FIGS. 28 and 29 , an exemplary joint J 11 , which is similar to joint J 2 , includes a three structural frame members  217 ,  216   a,  and  216   b,  with structural frame members  216   a  and  216   b  mounted to structural frame member  217  on opposed sides of structural frame member  217 . In the illustrated embodiment, structural frame members  216   a  and  216   b  are mounted to structural frame member  217  on opposed sides of structural frame member  217  at ninety degree angles (orthogonal) to form a cross-shaped joint. However, it should be understood that the structural frame members  216   a  and  216   b  may be mounted to structural frame member  217  at non-orthogonal angles, such as shown in joint J 6  ( FIG. 16 ). 
     Similar to joint J 2 , each of structural frame members  216   a  and  216   b  is coupled to and engaged with a respective side wall  234  of the opposed sidewalls  234  of structural frame member  217  by a pair of tabs  232   a,    233   b.  Tabs  232   a,    233   a are formed by slots  232  and  233  that extend up and into side walls  230  and  231  of the respective structural frame members  216   a,    216   b.  Similar to the previous embodiments, in the illustrated embodiment tabs  232   a,    233   a have a shorter height than the remainder of the side walls  230 ,  231 , which helps facilitate installation, though they may have the same height as the respective side walls. 
     Tabs  232   a,    233   a extend into the hollow space inside structural frame member  217  through corresponding pairs of notches  236  formed in structural frame member  217  (on opposed side walls  234 ) to form a mechanical internal interface with the side walls  234  of structural frame member  217 . The size of the notches and slots may vary. For example, in the illustrated embodiment, notches  236  may be sized to be approximately the same thickness as the sidewalls  230 ,  231  of structural frame number  216   a,    216   b  (and the slots  232 ,  233  may be sized to be approximately the same size as the wall thickness of structural frame member  217 ) to form a snug fit between the structural frame members so that they optionally form a tight, rigid connection. Further, the terminal edges  240   a,    242   a  ( FIG. 31 ) of the respective upper walls  240 ,  242  of structural frame members  216   a,    216   b  may be offset from the terminal edges  232   b,    233   b  of tabs  232   a,    233   a so that they align with the inner edge  232   c,    233   c  of slots  232 ,  233  and, therefore, abut the side walls  234  of structural frame member  217  at upper wall  238 . In this manner, the upper walls  240 ,  242  of structural frame members  216   a,    216   b  are generally coplanar with, but adjacent the upper wall  238  of structural frame number  217 . 
     As noted, structural frame members  216   a,    216   b  may form a tight fit connection with structural frame member  217 . Alternately, the notches and slots may be sized to allow for some flexibility at one or more selected joints to reduce stresses on the frame. As noted above, some of the panels, for example, the panels that form the side walls, floors, and roof in a recreational vehicle tend to be subject to repeated dynamic loading. Hence, it may be beneficial to make the panel more flexible in areas of the frame that are subjected to increased stress from dynamic loading. 
     For example, to introduce some flexibility, the clearance between the notch and the side wall of structural frame member  216   a  or  216   b  (and between the slot and the side wall of structural frame member  217 ) may be increased (from the above stated exemplary ranges of about 0 to 0.006 inches, 0 to 0.02 inches, or 0 to 0.04 inches) to provide more than an air gap, for example, a gap in a range of 1/64 th  to 1/32 th  of an inch, in a range of 1/64 th  to 1/16 th  of an inch, or in a range of 1/64 th  to ⅛ th  of an inch to provide the desired flexibility and/or to allow the foam, described below, to flow in the gap or gaps to provide some controlled flexibility at the joint. Alternately, the gaps may be provided to ease installation and allow the foam insert described below to flow and, depending on the foam formulation, form an adhesive bond between the structural frame members, as a well as form bearing members (or in some cases springs) to control the rigidity or flexibility of the joint. 
     Referring to again  FIGS. 28 and 29 , one or more expanding foams may be injected into the space formed in one or more of the structural frame members at the joint to internally reinforce the interlock between the joined structural frame members. For example, one of structural frame members, such as structural frame member  217 , optionally includes at least one injection port  244  ( FIG. 29 ) for injecting one or more expanding foams into the space adjacent the interlocked sections of the structural frame members. For example, a suitable foam may become rigid when cured or may cure or set to a compressible or flexible state to provide a more flexible joint. Optionally, as noted above, the foam may be formulated to provide an adhesive bond between the foam and the structural frame members. Further, a portion of the joint may have one foam injected, and another portion of the joint may have another foam injected so that the stiffness of the joint and other components mounted thereto may be varied. 
     Referring to  FIGS. 32A and 32B , when foam is injected into the hollow space in the structural frame member (e.g. structural frame member  217 ), for example, through an injection port  231 , between tabs  232   a,    233   a , depending on the size of the tabs, the foam may flow between the distal vertical edges  232   b  and  233   b  of the tabs ( FIG. 32A ), and further between the inwardly facing sides  232   c,    233   c  of tabs  232   a,    233   a ( FIG. 32B ). Again depending on the height of the tabs, the foam may flow between the lower distal edges  232   d  and  233   d  of the tabs  232   a,    233   a ( FIG. 32B ) and the bottom wall of the structural frame member. In this manner, when the foam expands, the foam can form a bearing member that provides restraint in X, Y, and Z axes as shown in  FIGS. 32A and 32B . Depending on the foam, the bearing member may be rigid or may be compressible with a varying spring force, again depending on the formulation. When formed from a compressible foam, therefore, the bearing member may also form a spring or springs along the X, Y, and/or Z axis. 
     Additionally, as noted above depending on the formulation, the foam may form an adhesive bond with the tabs and/or side walls, with the adhesive bond being enhanced depending on the material forming the structural frame members. For example, in polymer based structural frame members a greater bond may be achieved than with aluminum structural frame members, again depending on the formulation of the foam. 
     As best seen in  FIG. 32C , a joint may have two side by side injections ports for injecting two different foams. Referring to  FIG. 32C , when foam is injected into the hollow space in the structural frame member (e.g. structural frame member  217  and into joints similar to J 1  and J 2  except with narrower notches) it may be injected through two ports, e.g. ports  244   a and  244   b,  which are provided in the upper wall  238  and between tabs  232   a,    233   a , so that the foams flow into the hollow space between tabs  232   a  and  233   a and can form foam inserts  250  and  250 ′ with different properties. In this manner, when the foams expand, foam insert  250  can form a bearing member that provides restraint in X, Y, and/or Z axes for tab  233   a , while foam insert  250 ′ can form a bearing member that provides restraint in X, Y, and/or Z axes for tab  232   a  as shown in  FIG. 32C . For example, one foam may form a rigid insert, while the other may form a flexible, resilient insert. 
     Additionally, as noted above depending on the formulation, the foam may form an adhesive bond with the tabs and/or side walls, with the adhesive bond being enhanced depending on the material forming the structural frame members. For example, in polymer based structural frame members a greater bond may be achieved than with aluminum structural frame members, again depending on the formulation of the foam. 
     Suitable foams may include foams from Alumilite of Kalamazoo, Mich. or foams from Smooth-On of Macungie, Pa. For example, suitable foams include ALUMIFOAM, which is a rigid expanding urethane foam; FLEX URETHANE , which is an expanding flexible urethane foam; FOAM IT! RIGID , which is a rigid expanding urethane foam; and SOMA FOAMA, which is an expanding flexible silicone foam. 
     Referring again to  FIGS. 28 and 29 , injection port  244  may be located in upper wall  238  of structural frame member  217  between notches  236  so that port  244  can direct foam  250  into the hollow space in structural frame member  217  between tabs  232   a  and between tabs  233   a and side walls  234 . Further, depending on the depths and heights of the respective tabs, the foam  250  may flow between the vertical edges  232   b,    233   b  of tabs  232   a  and  233   a to form a bearing member (when cured or set) between the respective tabs  232   a  and  233   a , and also under each lower edge of the tabs. 
     As best seen in  FIG. 32A , in one embodiment, as noted above, the depth and height of each of the tabs allows the foam  250  to flow between the inwardly facing vertical edges  232   b,    233   b  of tabs  232  and  233  as well as between the inwardly facing sides  232   d,    233   d  and beneath the lower edges  232   e,    233   e  of each tab  232 ,  233 . Additionally, as noted above, depending on the size of the clearance or gaps between the respective structural frame members, and the viscosity of the foam, the foam  250  may flow up through the upper wall  238  of structural frame member  217  adjacent upper walls  240 ,  242  of the structural frame members  216   a,    216   b,  such as shown in  FIG. 32 . 
     Referring again to  FIG. 29 , structural frame member  217  may include additional injection ports, for example, that direct the flow of foam into adjacent structural frame members or allow two different foams to be injected. For example, structural frame member  217  may have injection ports  246  provided in one or each of the opposed sidewalls  234 , between notches  236  and between tabs  232   a  and  233   a , to direct the flow of foam  250  into the hollow space provided in structural frame members  216   a  and  216   b  adjacent side walls  234  of structural frame members  217 . 
     In the illustrated embodiment, each of the structural frame members  217 ,  216   a  and  216   b  is a hollow tubular member so that the space provided in each structural frame member is defined by and bounded by their respective upper walls, side walls, and bottom walls. It should be understood that solid or at least partially hollow members may be used to form the respective structural frame members as well. 
     In this manner, when the foam cures, the internal interface between the tabs and the side walls and bottom wall, for example, is joined either with a connection formed by the foam forming a bearing member adjacent the tabs. For example, when using foam that cures into a rigid form the connection forms a rigid bearing member. When the foam forms a compressible or flexible bearing member adjacent the tabs, the bearing member is flexible and further can have spring properties when the cured or set foam exhibits elastic properties. Additionally, as noted above, one joint (e.g. between structural frame member  216   a  and structural frame member  217 ) may include a rigid foam (when cured) and other the other joint (e.g. between structural frame member  216   b  and structural frame member  217 ) may include a compressible or flexible foam. The location of the differing foams may be controlled in a manner to allow the rigidity or flexibility of the frame to be customized. 
     For example in one embodiment, the space in structural frame member  217  may be filled with a foam  250   a  ( FIG. 28 ) that retains some flexibility or compressibility after it cures to allow the structural frame members  216   a,    216   b  to flex about structural frame member  217 . In contrast, the space in structural frame members  216   a,    216   b  may be filled (for example, via injection ports  248  ( FIG. 31 )) with a foam  250   b  ( FIG. 28 ) that becomes rigid upon curing so that when other components are mounted to one or both the structural frame members  216   a  or  216   b,  the foam can provide rigidity to each connection. For example, ports  248  (see  FIGS. 31 and 35 ) may be provided in one or both side walls or upper wall of the respective structural frame members  216   a,    216   b.    
     In another embodiment, foam  250  may be injected through all the accessible injection ports, such as shown in  FIG. 36 , which when cures becomes rigid. Foam  250 , therefore not only internally couples the tabs of structural frame members  216   a,    216   b  to the interior of structural frame member  217 , but also internally couples structural frame members  216   a,    216   b  to the exterior of structural frame member  217  to form a very rigid joint. This may be further enhanced if the foam is formulated with adhesive properties. 
     Optionally, to further enhance the mechanical coupling of the structural frame members together, one or both tabs  232   a,    233   a may include recesses  252  to enhance the mechanical coupling of the foam to the tabs  232   a,    233   a and, hence, to the structural frame members  216   a,    216   b.  For example referring to  FIG. 37 , recess  252  may be formed in tabs  232   a,    233   a inward of their outer perimeters by transverse through holes or circular indentations  254  formed in the respective tabs. 
     Alternately, recesses  252  may be formed along the distal edges  232   b,    233   b  of one or both of the tabs  232   a,    233   a in the form of cutouts or notches  256  ( FIG. 38 ). Again in this manner, the foam will flow into the respective recesses to mechanically couple the foam to the tabs  232   a,    233   a and, hence, structural frame members  216   a,    216   b.    
     As noted above, any of the above-described joints may be enhanced or modified by the addition of a foam insert or inserts. For example, referring to  FIG. 39 , joint J 1  (or joint J 2 ) may include an injection port  260  in its upper wall  38  between its opposed ends of notch  36  (and hence between tabs  32   a ) to inject a foam insert  250 , which can at least partial fill the hollow space between tabs  32  and adjacent tabs  32   a  to extend between their distal vertical free edges  32   c  and the opposed side wall  34  of structural frame member  17   h.  Further, the foam may flow under distal bottom free edges  32   d  and extend between edges  32 d and bottom wall  42 . In this manner, the foam forms a bearing member to provide reactive forces on tabs  32   a  in the X, Y, and Z axes. As noted above, these may be spring forces if the foam is selected to have elastic properties when cured or set. 
     Optionally, side wall  34  adjacent structural frame member  16   b  may include an injection port to direct some of the foam into the hollow space in structural frame member  16   b  adjacent side wall  34  between its respective side walls  30 . Alternately as described above, structural frame member  16   b  may have a port in its upper wall or side wall to inject the same or a different foam to provide an attachment point for another component, including another structural frame member. 
     Referring to  FIG. 40 , joint J 3  may include injection ports  264  in upper wall  60  of structural frame member  46  between its opposed side walls  62  (but which straddle the abutting side walls  52   a,    54   a ) to inject a foam insert  250  into the hollow spaces in structural frame members  17   q  and  17   r.  In this manner, the foam can fill the hollow space between side walls  62  and between the distal vertical edges  66   a  of tabs  66  and opposed side walls  52  and  54 . And depending on the height of the tabs  66 , the foam may fill and extend between distal bottom edges  66   b  of tabs  66  and bottom walls  49  and  51  of structural frame members  17   q  and  17   r . Alternately or in addition, injection ports may be provided in upper walls  48  and  50  of structural frame members  17   q  and  17   r.    
     Referring to  FIG. 41 , joint J 4  may similarly include one or more foam inserts  250 , which may be injected through injections ports provided in structural frame member  18   a  (for example by three injection ports provided in upper wall  70 ) or in structural frame members  16   i,    16   i,  and  161  (for example by three injection ports in upper walls  72 ,  74 , and  76 ). In this manner, the foam can fill the hollow space between side walls  94  and between the distal vertical edges  94   c  of tabs  94   a and opposed side walls  78  and  82 . And depending on the height of the tabs  94   a ,  94   b,  the foam may fill and extend between distal bottom edges  94   d ,  94   e  of tabs  94   a ,  94   b  and bottom walls  73 ,  75 , and  77  of structural frame members  16   i,    16   i,  and  16   l . Alternately or in addition, injection ports may be provided in upper walls  72 ,  74 , and  76  of structural frame members  16   i,    16   i,  and  16   l.    
     Referring to  FIGS. 42 and 43 , joint J 5  may similarly include one or more foam inserts  250 , which may be injected through an injections port  270  provided in the upper wall or bottom wall of structural frame member  16   f  or  17   h  located between their respective side walls and between the opposed ends of notches  102  and  104 . Further, to allow the foam to flow into the hollow spaces adjacent their respective abutting side walls, as shown in  FIGS. 42 and 43 , side wall  272  of structural frame member  17 h may include an injection port  274 . Further, when tabs  106   a  are shorter that the side walls of structural frame member  17   h,  the foam may flow under the tabs  106   a  into the adjacent hollow space (see  FIG. 43 ). 
     In this manner, the foam can form a bearing member between the distal bottom free edges  106   b  of tabs  106   a  and the bottom wall of structural frame member  17   h  and between the vertical edges of tabs  106   a  and the side walls of structural frame member  17   h  when the slots  106  have more than an air gap to allow foam to flow into the slots adjacent the edges of tabs  106   a.    
     Referring to  FIG. 44 , joint J 7  may also include a foam insert or inserts similar to joint J 1  and J 3 , with an injection port provided in either upper wall  120  or upper wall  132  of structural frame members  17   j  or  16   o , or side walls  122  or  130 . 
     Referring to  FIG. 45 , a foam insert  250  may also be used in joint J 10 , which may be particularly suitable for foam with adhesive properties to enhance the joint one the structural frame member is bent and folded as shown in FIG .  24 . Again, one or more injection ports may be provided in the upper, lower and/or side walls  176   a,    176   b,    178   a,    178   b  of the structural frame member so that the foam forms a bearing member inside the hollow spaces of the two sectioned parts of the structural frame member to resist bending and torsion at the joint to help keep the joint in its folded configuration. 
     As described above, two different foams may be used to provide different joint characteristics. For example, structural frame members may be connected using two or more joints, including two or more different joints, with one joint being provided with a rigid foam insert and another joint being provided with compressible and, optionally elastic, foam insert. 
     For example, referring to  FIG. 46 , three structural frame members are arranged and connected in an H frame configuration with a central structural frame member  17   e  connected to structural frame member  16   b  using joint J 1  on one end connected to structural frame member  16   a  using joint J 8 . Joint  1 , for example, may include a foam insert  250  formed from one foam, and joint J 8  may include a foam insert  250 ′ formed from a different foam that joint J 1 . In the illustrated embodiment, joint J 1  is provided with a rigid foam insert, while joint J is provided with greater gaps and a flexible, foam insert, and optionally with elastic properties to allow joint J 1  to flex under certain loading conditions, such as dynamic loading above a certain threshold. 
     As noted above, the structural frame members forming the frames described above, may be formed from metal, such as aluminum, or may be formed from a polymer or a composite material. Further, while shown as having rectangular or square hollow closed cross-sections, the shape of the structural frame members may vary and, further, may have solid sections or open sections, and may have a composite section—one part closed and the other part open or solid. The joints may be orthogonal or angled as shown, with angle varying from zero degrees to 90 degrees. Further, as noted, the joints may have a weld or an adhesive on their exterior surfaces. Additionally, the joints may have air gaps or gaps that allow some degree of freedom along or about one or more axes. 
     It should be understood that in any of the above joints, depending on the forces and vibrations at the joint, welds may be used or omitted. Further, foam inserts may be used to reinforce the joint and/or provided added flexibility when desired. Accordingly, the structural assemblies described herein may provide enhanced connections between the respective structural frame members to varying degrees and, further, provide a greater joining interface or surface to hold the members together, which may provide a greater distribution of load across the joined members. As described above, in some embodiments welding may be used in which case the stresses in the welds may be reduce. In other cases, the welds may be eliminated, which can avoid burn through or gouging that can occur during welding.