Patent Publication Number: US-11643153-B2

Title: Spline joints and container having same

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/852,646, filed Apr. 20, 2020, now U.S. Pat. No. 11,136,073, which is a continuation of U.S. application Ser. No. 15/962,341, filed Apr. 25, 2018, now U.S. Pat. No. 10,625,790, the entire contents of both of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to containers, and in particular, to joints for connecting wall panels of containers. 
     BACKGROUND 
     Containers, for example commercial containers transported by trucks, commercial nautical vessels, trains, and the like include a set of walls that enclose the space of the container. The walls and connections therebetween are typically formed by assembling respective wall panels together forming a joint, often including additional splice plates, and then fastening the joints with numerous fasteners such as screws or rivets. 
     SUMMARY 
     In one aspect, the invention provides a container defining a cargo receiving interior defined by a plurality of panels. The container includes a first panel having a first edge. The first edge including a first protrusion with a first contoured profile. The first contoured profile includes at least one projection. The container also includes a second panel with a second edge. The second edge includes a second protrusion with a second contoured profile. The contoured profile includes at least one projection. The container further includes a spline having a first channel that defines a recess with an interior profile and a second channel separate from the first channel that defines a recess with an interior profile. The first channel receives the first protrusion of the first panel such that the first contoured profile is complementary to a portion of the interior profile. The second channel receives the second protrusion of the second panel such that the second contoured profile is complementary to a portion of the interior profile. The first panel further includes a mid-section extending from the first edge and the second panel further includes a mid-section extending from the second edge. The first edge has a greater thickness than the thickness of the mid-section of the first panel and the second edge has a greater thickness than the thickness of the mid-section of the second panel. 
     In another aspect, the invention provides a container defining a cargo receiving interior defined by a plurality of panels. The container including a first contoured edge of a first panel, a second contoured edge of a second panel, and a spline with a first channel that receives the first contoured edge and a second channel that receives the second contoured edge to form a spline joint securing the first and second panels together. The first and second channels are symmetrical with openings in opposite directions. Each of the first and second contoured edges includes a concavity containing an adhesive that bonds a surface of the respective first and second contoured edges with a surface of respective first and second channels of the spline. 
     In another aspect, the invention provides a method of assembling a container. The container defines a cargo receiving interior defined by a plurality of panels. The method includes providing a first panel with a first contoured edge and a second panel with a second contoured edge. The first panel and the second panel are held fixed relative to each other to define a space between the first and second contoured edges. The method also includes providing a spline with two symmetrical channels that open in opposite directions and sliding the spline axially and simultaneously onto the first and second contoured edges and into the space therebetween so that a first one of the two symmetrical channels receives the first contoured edge and a second one of the two symmetrical channels receives the second contoured edge to from a spline joint securing the first panel to the second panel. The method further includes, after the first and second panels are secured, applying an adhesive to a concavity on the first contoured edge to bond a surface of the first contoured edge with a surface of one of the two symmetrical channels, and applying an adhesive to a concavity on the second contoured edge to bond a surface of the second contoured edge with a surface of the other of the two symmetrical channels after the first and second panels are secured. 
     In another aspect, the invention provides a container defining a cargo receiving interior defined by a plurality of panels. The container includes a first panel having a first edge. The first edge including a first protrusion with a first contoured profile. The first contoured profile includes at least one projection. The container also includes a second panel with a second edge. The second edge includes a second protrusion with a second contoured profile. The contoured profile includes at least one projection. The container further includes a spline having a first channel that defines a recess with an interior profile and a second channel separate from the first channel that defines a recess with an interior profile. The first channel receives the first protrusion of the first panel such that the first contoured profile is complementary to a portion of the interior profile. The second channel receives the second protrusion of the second panel such that the second contoured profile is complementary to a portion of the interior profile. Each of the first and second contoured profiles includes a concavity containing an adhesive that bonds a surface of the respective first and second contoured profiles with a surface of the interior profile of the respective first and second channels of the spline. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a first perspective view of a container. 
         FIG.  2    is a second perspective view of the container of  FIG.  1   . 
         FIG.  3    is a perspective view of the container of  FIG.  1    without walls. 
         FIG.  4    is a perspective view of a spline joint on the container of  FIG.  1     
         FIG.  5    is a perspective view of a spline according to one embodiment of the invention. 
         FIG.  6    is a top view of the spline of  FIG.  5   . 
         FIG.  7    is a perspective view of a spline according to another embodiment of the invention. 
         FIG.  8    is a top view of the spline of  FIG.  7   . 
         FIG.  9    is a perspective view of a spline according to another embodiment of the invention. 
         FIG.  10    is a top view of the spline of  FIG.  9   . 
         FIG.  11    is a side view of the spline of  FIG.  9   . 
         FIG.  12    is a perspective view of a wall panel of the container of  FIG.  1   . 
         FIG.  13    is a detail view of a side edge of the wall panel of  FIG.  12    according to one embodiment of the invention. 
         FIG.  14    is a detail view of a side edge of the wall panel of  FIG.  12    according to another embodiment of the invention. 
         FIG.  15    is a top view of the spline joint of  FIG.  4   . 
         FIG.  16    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  17    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  18    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  19    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  20    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  21    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  22    is a top view of a spline joint according to another embodiment of the invention. 
         FIG.  23    is a perspective view of an interior of the container of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. It should be understood that the description of specific embodiments is not intended to limit the disclosure from covering all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     The term “laterally” or variations thereof refer to a sideways direction. The terms “top,” “upper,” “bottom,” and “lower” are intended to indicate directions when viewing the container when positioned for use. The term “coupled” means connected to or engage with, whether either directly or indirectly, for example with an intervening member, and does not require the engagement to be fixed or permanent, although engagement can be fixed or permanent. It should be understood that the use of numerical terms “first,” “second,” “third,” etc. as used herein does not refer to any particular sequence or order of components; for example, “first” and “second” portions may refer to any sequence of such components, and is not limited to the first and second components of a particular configuration. 
       FIGS.  1  and  2    illustrate a container, embodied here as a trailer  10  for over-the-road use with a truck to transport large cargo volumes. In other embodiments, the container may be a fixed storage construction, a cargo container, a shipping container, a straight truck, or the like. As shown, the trailer  10  is a semi-trailer configured for use with a road tractor (i.e., in forming a so called 18-wheeler). Aspects of the invention are not necessarily limited to such a trailer  10 , and aspects of the disclosure will be understood as also applying to other trailers and containers of various configurations. The trailer  10  includes a chassis  14  having axles with multiple sets of wheels  18 , although similar containers may be provided with alternate rolling chassis configurations or none at all. The trailer  10  defines a length L in a longitudinal or transport direction. The length L can be 53 feet in some constructions, although the trailer  10  can be manufactured in other lengths greater than or less than 53 feet. Perpendicular to the longitudinal direction, the trailer  10  defines a width W and a height H. The width W cooperates with the length L to define a plan view footprint of the trailer  10 , while the height H of the trailer  10  is measured perpendicular to the footprint (i.e., perpendicular to the ground). Subtracting for wall thicknesses, the length L, the width W, and the height H cooperate to define a cargo receiving interior  22  ( FIG.  2   ) of the trailer  10 . 
     The trailer  10  includes a first side defined by a first side wall  26 , a second side defined by a second side wall  30  opposite the first side wall  26 , a front defined by a front wall  34 , and a rear  38 . Wall panels  42  may form walls that span the first side wall  26 , second side wall  30 , and front wall  34 . Each of the first side wall  26 , second side wall  30 , and front wall  34  can be constructed of one or more wall panels  42 . Further in some embodiments, a wall panel may wrap around a corner of the trailer and form parts of multiple walls (e.g., the front wall and one of the first and second side walls). All of the wall panels  42  extend between a roof  46  of the trailer  10  and a floor  50  of the trailer  10 . Consecutive wall panels  42  can be joined together by a spline  54  forming a joint (e.g., spline joint  58 ,  FIG.  4   ) that extends parallel to the direction of the height H of the trailer  10  between the roof  46  and floor  50  of the trailer  10 . As shown in  FIG.  2   , the rear  38  of the trailer  10  includes at least one door panel  62  provided to selectively open for accessing the interior  22  for loading and unloading. 
     As shown in  FIG.  3   , the trailer  10  includes a frame  66  including, on each side, a top rail  78  adjacent the roof  46 , a bottom rail  82  adjacent the floor  50 , and support posts  84 . The top rail  78  and the bottom rail  82  extend parallel to the longitudinal or lengthwise direction of the trailer  10 . The support posts  84  are positioned perpendicular to the longitudinal direction and spaced along the length L of the trailer  10 . 
     With reference to  FIGS.  5  and  6   , the spline  54  includes a first end  86 , a second end  90  opposite the first end  86 , and a length L 1  between the first and second ends  86 ,  90 . The length L 1  of the spline  54  defines the length of the spline joint  58 . The spline  54  also includes a first channel  94  that defines a first recess  98  and a second channel  102  that defines a second recess  106 . Each of the first and second channels  94 ,  102  is formed as an open-channel or structure and the first and second channels  94 ,  102  forming the spline  54  can be integrally formed as a single piece or separately formed and joined together. The first and second channels  94 ,  102  both have openings  110  to their respective recesses  98 ,  106  that open in opposite directions of one another. The first and second channels  94 ,  102  are also symmetrical about an axis  114  that extends through the center of the spline  54 . Each of the first and second recesses  98 ,  106  includes a respective interior profile  118  that spans the inside of their respective channels  94 ,  102 . The interior profiles  118  are defined along four sides  122 A-D that form a rectangular arrangement with adjacent sides  122 A-D being perpendicular to one another. The two directly adjacent sides  122 C of the respective first and second channels  94 ,  102  cooperatively form a web  124  of the spline  54  that extends between, on one end of the web  124 , the sides  122 C arranged toward the interior and, on the other end of the web  124 , the sides  122 D arranged toward the exterior. Although referred to herein as individual sides, the two sides  122 C are arranged in the illustrated construction to be coextensive, forming one side of the spline  54  as a whole, and the same may be said of the two sides  122 D. For example, the spline  54  may be viewed as having a modified I-beam shape, where the web  124  extends between the midsections of two parallel, spaced sides. 
     Each of the interior profiles  118  of the spline  54  includes a male projection  126  that extends from one side (e.g., the exterior side  122 D) of the channel  94 ,  102  into the open space that otherwise forms the female recess  98 ,  106 . As illustrated, each projection  126  extends perpendicularly from the side  122 D. In the case that the projections  126  extend from the exterior sides  122 D in both channels  94 ,  102 , this means that the projections  126  extend in a direction toward the interior of the trailer  10 . As shown in  FIG.  6   , one side of each projection  126  is flat while another side (e.g., an opposite side) is curved. As shown, the two projections  126  of the spline  54  are arranged so that the two curved sides are facing each other and the two flat sides are facing away from each other. Although the interior profiles  118  are shown to include exactly one pair of mirror-image projections  126 , one or both of the interior profiles  118  can alternately include more or fewer projections  126 . Further, the projections  126  are not mirror-images in other constructions, and each projection  126  can have any convenient number of flat and/or round sides. In further embodiments, each interior profile  118  may include more or less than the four sides as illustrated, and the sides of the interior profiles may differ in shape from that shown. 
       FIGS.  7  and  8    illustrate a spline  130  according to another embodiment. The spline  130  is similar to the spline  54 , with like features being represented by like reference numerals. The spline  130  includes an additional channel  134  (e.g., a central channel  134 ) that extends the length L 1  of the spline  130  at a position between the first and second channels  94 , 102 . The central channel  134  can be positioned exactly centrally within the spline  130 , or offset therefrom. Although the central channel  134  has a regular, symmetrical shape, alternate shapes are optional. The central channel  134  is defined between the separate, spaced apart sides  122 C of the first channel  94  and the second channel  102 . These two sides  122 C form parallel webs that bound the central channel  134 . The central channel  134  defines an interior  138  that is rectangular, notwithstanding the rounded corners, and is positioned between the first and second channels  94 ,  102 . 
       FIGS.  9 - 11   , illustrate a spline  140  according to another embodiment. The spline  140  is similar to the splines  54 ,  130  with like features being represented by like reference numerals. The spline  140  includes the central channel  134  and a plurality of slots  142  (e.g., logistic slots) that extend into the interior  138  of the central channel  134  through an interior-facing wall  146  of the spline  140 . The slots  142  extend the entire length L 1  of the spline  140  from the first end  86  to the second end  90  of the spline  140 . The slots  142  may take any number of different shapes, including the simple elongate holes as illustrated. When a spline joint  58  including a spline  140  is assembled, the logistic slots  142  are exposed to the interior  22  of the trailer  10  so as to provide attachment points for load separators or other restraints that may be secured to the interior  22  of the trailer  10 . 
     Referring to  FIG.  12   , some or all of the wall panels  42  of the trailer  10  include a top edge  150 , a bottom edge  154  opposite the top edge  150 , a first side edge  158  (right), a second side edge  162  (left) opposite the first side edge  158 , and a mid-section  166  spanning between the first and second side edges  158 ,  162 . In the illustrated embodiment, the first and second side edges  158 ,  162  extend the entire length of the wall panels  42  from the bottom edge  154  to the top edge  150 . In other embodiments, the first and second side edges  158 ,  162  only extend a majority portion of the length between the top and bottom edges  150 ,  154 . Referring now to  FIG.  13   , the first and second side edges  158 ,  162  of any respective wall panel  42  are oblong shaped and include a protrusion  170  that extends towards the interior  22  of the trailer  10  when the wall panel  42  is positioned for use. In other words, the protrusion  170  is offset inwards from a plane P that is defined by an interior surface of the wall panel  42  at a location (e.g., the mid-section  166 ) along the wall panel  42  that is spaced away from the protrusion  170 . Each of the protrusions  170  on respective first and second side edges  158 ,  162  of the wall  42  include a contoured profile  174 . In other words, the contoured profiles  174  are irregularly shaped and not strictly defined by flat or straight ends. The contoured profile  174  includes a projection  176  that extends towards the plane P (e.g., extending toward the exterior when assembled for use). In the illustrated embodiment, the contoured profile  174  of the protrusion  170  on the first side edge  158  of the wall panel  42  corresponds to the interior profile  118  of the first channel  94  of the spline  54  and the contoured profile  174  of the protrusion  170  on the second side edge  162  of the wall panel  42  corresponds to the interior profile  118  of the second channel  102  of the spline  54 . The protrusion  170  on the first edge  158  of the wall  42  is complementary in shape to the first channel  94 , and the protrusion  170  on the second edge  162  of the wall panel  42  is complementary in shape to the second channel  102  of the spline  54 . The protrusions  170  are oversized with respect to the openings  110  of the channels  94 ,  102  of the spline  54  to preclude passage of the edges  158 ,  162  of the wall panel  42  through the openings of the channels  94 ,  102 . Although in the illustrated embodiment, the contoured profiles  174  are mirror-images of one another, each including a single projection  176 , the contoured profiles  174  are, in some constructions, different from each other and either one or both may differ in shape from that shown herein, e.g., the contoured profile  174  may include more or fewer projections  176  or projections  176  of alternate shapes. It is noted here that the projections  176  as shown, similar to the spline projections  126 , include one flat side and one curved side opposite the flat side. In some embodiments, the contoured profiles  174  may correspond (e.g., form fit) to the interior profiles  118  of the channels  94 ,  102 . In further embodiments, the contoured profile  174  may be complementary in shape to only a portion(s) of the shape of the interior profiles  118  of the spline  54 . In other embodiments, the contoured profiles  174  may be entirely complementary in shape to the interior profiles  118  of the spline  54 . In other words, the contoured profiles  174  may fully occupy the space provided by the recesses  98 ,  106  of the spline  54  with no void space. However, some gaps between the contoured profiles  174  and the interior profiles  118  may exist due to manufacturing tolerances or assembly clearances but the general shapes of the interior profiles  118  and contoured profiles do not vary. The first and second side edges  158 ,  162  of the wall panels  42  have a thickness T that is greater than the thickness t of the mid-section  166  of the wall panels  42  when measured in a common direction, i.e., the direction transverse to a direction of extension, or width, of the wall panel  42  between the respective first and second side edges  158 ,  162 . 
     As discussed earlier, the wall panels  42  can span along the side walls  26 ,  30 , and front wall  34  of the trailer  10 , or a wall panel  42  can span the entire length of one of the side walls  26 ,  30 , or front wall  34  of the trailer  10 . As such, the length between the first and second side edges  158 ,  162  of the wall panels  42  can vary significantly, along with the resulting aspect ratio of length to width. The thicknesses T, t may also vary as needed, based on construction material and strength requirements. In some embodiments, the first and second side edges  158 ,  162  of the wall panels  42  may be reinforced with a coating. In some embodiments, the wall panels  42  may be made out of a composite material. In further embodiments, the wall panels  42  may be made out of a sheet metal material such as aluminum. 
       FIG.  14    illustrates an alternate protrusion  177  for the first and second side edges  158 ,  162  of the wall panels  42  according to the preceding description. The protrusion  177  is similar to the protrusion  170 , with like features being represented by like reference numerals. However, the protrusion  177  of  FIG.  14    further includes an additional concavity  178 . The concavity  178  extends the entire length of the first and second side edges  158 ,  162 . The concavity  178  provides a volume and a surface for an adhesive to be applied between the spline  54  and the respective side edges  158 ,  162 . The adhesive may be applied along the surface of the concavity  178  to bond the first and second side edges  158 ,  162  to the first and second channels  94 , 102  of the spline  54 , respectively. 
     To assemble one of the spline joints  58  according to the present disclosure, the spline  54  is installed axially or lengthwise onto the two side edges  158 ,  162  of respective wall panels  42  being joined. Although reference is made directly to the spline  54  in the discussion of the assembly, it will be appreciated that the discussion also applies to splines of any number of alternate constructions, such as splines  130 ,  140 . Before the spline  54  is installed, a first side edge  158  of a respective first wall panel  42  is positioned parallel to a second side edge  162  of a respective second wall panel  42 . The first side edge  158  and the second side edge  162  are positionally fixed relative to each other to define a space therebetween, which space corresponds directly to the spacing between the channels  94 ,  102  of the spline  54 . Next, the spline  54  is arranged such that the first channel  94  is positioned above and aligned with the first side edge  158  of the first wall panel  42 , and the second channel  102  is positioned above and aligned with the second side edge  162  of the second wall panel  42 . The spline  54  is then moved axially in a direction parallel to its lengthwise direction into the space between the two wall panels  42  such that the contoured profiles  174  of the first and second side edges  158 ,  162  align with and slide into engagement with the interior profiles  118  of the first and second channels  94 ,  102  of the spline  54 . In some constructions, the spline joints  58  are established with the wall panels  42  in their final position within the trailer  10 , in which case the spline  54  is installed parallel to the trailer height H direction. During lengthwise installation of the spline  54 , the projections  126  on the interior profiles  118  of the first and second channels  94 ,  102  are aligned with and received by complementary recesses formed in the protrusions  170  along the first and second side edges  158 ,  162 . Furthermore, the projections  176  on the contoured profiles  174  of the first and second side edges  158 ,  162  are installed to be positioned directly alongside the projections  126 . Finally, the spline  54  is slid axially further along the contoured profiles  174  of the first and second protrusions  170  to occupy an entire lengthwise extent of the space therebetween, or a majority thereof. The first wall panel  42  is mechanically secured to the second wall panel  42  immediately upon installation of the spline  54 . In the illustrated embodiment, the contoured profile  174  of the first wall panel  42  is entirely complementary to the first interior profile  118  of the first channel  94  and the contoured profile  174  of the second wall panel  42  is entirely complementary to the interior profile  118  of the second channel  102 , with the exception of assembly clearances that may exist between the interior profiles of the first and second channels  94 ,  012  and the contoured profiles  174  of the first and second contoured profiles. Multiple spline joints  58  can then be assembled around the side walls  26 ,  30 , and front wall  34  of the trailer  10  in a similar manner to connect multiple wall panels  42  together. In some constructions, every joint between adjacent pairs of wall panels  42  throughout the entire trailer  10  is made by a spline joint  58  as described herein. 
     As mentioned above, in some embodiments, the first and second side edges  158 ,  162  of the wall panels  42  include a concavity  178  in the contoured profile  174 . When the spline joint  58  is assembled, the sides  122 C of the interior profiles  118  of respective first and second channels  94 ,  102  close the concavity  178 . Once the first wall panel  42  has been secured to the second wall panel  42 , adhesive can be applied to the concavities  178  on both the contoured profiles  174 . The adhesive fills the concavities  178  for the entire length of the spline  54 , or portions thereof, to bond the surface of the concavity  178  with the sides  122 A-D of the interior profiles  118 . The interior profiles  118  are completely filled and have no voids, although in this construction the protrusions  174  along with the adhesive cooperatively fill the interior profiles  118 . 
     It should be noted that each of the protrusions  170  on the first and second side edges  158 ,  162  cannot be forced in a direction perpendicular to the length L 1  of the spline  54 ,  130 ,  140  into the respective first and second channels  94 ,  102  of the spline  54 ,  130 ,  140  in order to form the spline joint  58  therebetween. In other words, the spline joints  58  are not capable of being established by snapping or clicking into place via elastic deformation of one or both mating components, and the protrusions  170  will only fit into respective first and second channels  94 ,  102  if the spline  54 ,  130 ,  140  is slid axially onto the first and second side edges  158 ,  162  of the wall panels  42 . 
       FIG.  15    illustrates a spline joint  58  including a spline  54  without the central channel  134 . The spline joint  58  includes a first side edge  158  of a first wall panel  42  received within a first channel  94  and a second side edge  162  of a second wall panel  42  received within a second channel  102 .  FIG.  16    illustrates a spline joint  58  including a spline  130  with the central channel  134 . The spline joint  58  also includes a first side edge  158  of a first wall panel  42  received within a first channel  94  and a second side edge  162  of a second wall panel  42  received within a second channel  102 . 
     As discussed earlier, the wall panels  42  of the trailers  10  may span in a multitude of ways around the side walls  26 ,  30 , and front wall  34  of the trailer  10 . For example, a spline joint  130  may join two wall panels  42  on the first side wall  26  or the second side wall  30  of the trailer  10  ( FIG.  21   ) or a spline joint  130  may join two wall panels  42  on the front wall  34  of the trailer  10  ( FIG.  22   ). As such, the spline joints  58  may be spaced around the side walls  26 ,  30 , and front wall  34  of the trailer  10  in a variety of ways. In addition, the side walls  26 ,  30 , and front wall  34  of the trailer  10  may meet in different ways to form different kinds of corners (e.g., beveled  182 , square  186 , rounded  190 , etc.). For example, as shown in  FIG.  17   , a spline joint  58  including a spline  130  with the central channel  134  may be positioned on either the first or second side wall  26 ,  30  of the trailer  10  next to a beveled corner  182  connecting a wall panel  42  on the front wall  34  to a wall panel  42  on one of the side walls  26 ,  30 . With reference to  FIG.  18   , a spline joint  58  including a spine  130  may be positioned on a beveled corner  182  connecting a wall panel  42  on the front wall  34  to a wall panel  42  on one of the side walls  26 ,  30 . Another example of a spline joint  58  with a spline  130 , as shown in  FIG.  19   , may be positioned on either the first or second side wall  26 ,  30  of the trailer  10  next to a square corner  186  connecting a wall panel  42  on one of the side walls  26 ,  30  to a wall panel  42  on the front wall  34 . A further example, as shown in  FIG.  20   , a spline joint  58  including the spline  130  with the central channel  134  may be positioned on either the first or second sidewalls  26 ,  30  of the trailer  10  next to a rounded corner  190  connecting a wall panel  42  on one of the side walls  26 ,  30  to a wall panel  42  on the front wall  34 . Although  FIGS.  17 - 22    illustrate spline joints  58  including the spline  130  of  FIGS.  7  and  8    and no concavities  178 , any or all of these joints can also be made with other embodiments disclosed herein, or various feature combinations thereof (e.g., with or without the central channel  134  and with or without the concavities  178  in any particular combination). 
       FIG.  23    illustrates the interior  22  of the trailer  10  with all the wall panels  42  secured. The spline joints  58  are spaced around the first side wall  26 , the second side wall  30 , and the front wall  34 . The splines  140  of the spline joints  58  all include logistic slots  142  that are configured to support fastening of additional structures inside the interior  22  of the trailer  10 . In other embodiments, only selected splines  140 , or none of the spline  140 , include logistic slots  142 . 
     In some embodiments, the spline  54 ,  130 ,  140  of the spline joint  58  does not extend the entire length between the top edge  150  and bottom edge  154  of the first and second wall panels  42 . The spline  54 ,  130 ,  140  may only extend partially between the top and bottom edges  150 ,  154  of the first and second wall panels  42  to allow space for additional fastening means above and below the spline joint  58 . In further embodiments, the spline  54 ,  130 ,  140  may extend further than the first and second wall panels  42  to establish direct or indirect engagement with the top and bottom rails  78 ,  82 . 
     Various features and advantages of the invention are set forth in the following claims.