Abstract:
A cargo container is disclosed having removable panels secured between roof bows that extend across the width of the cargo container. The roof bows may be constructed out of a metal or high strength composite material while the panels may be constructed from a similar high strength material or a lightweight plastic depending on the intended use of the trailer. A top sheet over the roof bows maybe required to secure the panels to the bows, or the top sheet may be optional for additional protection from the weather. Insulation may also be placed between the top sheet and panels if the container is to be used to carry refrigerated cargo.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a roof construction for a cargo container, and more particularly to a roof construction with anti-snag removable panels secured between roof bows. 
       BACKGROUND OF THE INVENTION 
       [0002]    Refrigerated containers and dry van trailers are extensively used internationally. The lower portions of the container typically experience far more wear and abuse than the upper portions, however the roofs are occasionally damaged due to improper loading of cargo or by a fork lift operator&#39;s carelessness. 
         [0003]    Trailers have typically been constructed as open top containers for bulk materials or as closed top containers for dry goods. Open top cargo containers allow for easy loading of bulk goods, such as corn and other food stuffs, but are not sufficiently watertight to carry goods that may be damaged by exposure to moisture. Conversely, closed top over the road containers provide their cargo with excellent protection from the elements, but are more difficult to load. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides an improved roof for a cargo container having removable panels secured between roof bows that extend across the width of the cargo container. The roof bows are preferably constructed out of a metal or high strength composite material while the panels may be constructed from a similar high strength material or a lightweight plastic depending on the intended use of the cargo container. A top sheet over the roof bows maybe required to secure the panels to the bows, or the top sheet may be optional for additional protection from weather. Insulation may also be placed between the top sheet and panels if the container is to be used to carry refrigerated cargo. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a perspective example of a trailer having a roof with multiple panels secured between roof bows where some of the panels have been removed to allow for top loading of the trailer. 
           [0006]      FIG. 2  shows a side view of a trailer roof constructed from roof bows and panels. 
           [0007]      FIG. 3  shows a cross section of an isolated roof bow. 
           [0008]      FIG. 4  shows a perspective view of an isolated roof bow. 
           [0009]      FIG. 5  shows a cross-sectional view of a roof bow secured to a roof liner and a panel. 
           [0010]      FIG. 6  shows a perspective view of an isolated panel. 
           [0011]      FIG. 7  shows a cross-sectional view of a roof bow secured to a panel. 
           [0012]      FIG. 8  shows a perspective view of a roof bow secured to two panels. 
           [0013]      FIG. 9  shows a perspective view of roof bows and panels in relation to the surface of a geometric cylinder. 
           [0014]      FIG. 10  shows a side view of roof bows and panels in relation to the surface of a geometric cylinder. 
           [0015]      FIG. 11  shows a perspective view of a trailer having a roof with multiple panels secured between roof bows where a roof liner has been added above the bows and panels. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present invention may be used with any type of cargo container roof and is particularly suited for containers that experience a great deal of wear and/or need to be highly configurable. However, for descriptive purposes, the present invention will be described in use with over the road trailers. 
         [0017]      FIGS. 1 and 2  show an over the road trailer  10  having a plurality of roof bows  15  spanning over and across a storage area  20  within the trailer  10 . The storage area is generally defined by the sidewalls  25  of the trailer, the front (not pictured), rear wall  30 , and floor  35  of the trailer. Panels  40  are secured between the roof bows  15  to form the roof of the trailer. The arced curvature of the roof increases the structural integrity of the container by resisting downward forces and also acts to help shed precipitation from the top of the trailer. In northern climates where heavy snow may pile up on the roof of the trailer, the structural integrity and ability to shed precipitation are of key importance. Typical bow rises are expected to be on the order of an inch across the width of the trailer, however smaller or greater bowing may be used based on the intended usage of the trailer. 
         [0018]      FIGS. 3 and 4  illustrate a cross sectional and perspective view of a roof bow  15 , respectively. The roof bows act to support the weight of the panels and other roof components and are preferably made from resilient materials such as metal or fiber reinforced resin that are both strong and resistant to wear and accidental damage. The roof bow includes a horizontally arced first bow slat  45  or first lower slat that extends between the sidewalls of the container. At the lateral end of the first bow slat  45  a first bow flange  50  extends upward away from the first bow slat  45 . In the illustrated example, the first bow flange  50  extends away from the first bow slat  45  at 60 degrees  55  relative to the width  60  of the first bow slat. Preferred angles of extension for the flange from the first bow slat  45  are 45 to 70 degrees relative to the width  60  of the first bow slat  45 . Angles between 45 and 70 degrees allow for tight locking between the roof bows and the panels while also providing a steeply angled surface that the flanges of the panels may be pushed upwardly against while installing the panels from within the trailer. The steep angle of the bow flange also facilitates deflection of the panel flange before it snaps into place. 
         [0019]    A first vertical wall  65  extends from the first bow slat  45  to a second bow slat  70  or top slat. The joints  75  between the slats and the walls and flanges are preferably rounded to reduce the number of snag points on the ceiling of the trailer. A second wall  80  extends downward from the second bow slat  70  to a third bow slat  85  or second lower slat. A second bow flange  90  extends away from a third bow slat  85 . In the illustrated example, the roof bow  15  is symmetric about an axis of symmetry  95  that bisects the second bow slat  70 . While symmetric roof bows are not needed for the present invention, they assist in simplifying the manufacturing process. In the illustrated example, the thickness  100  of the roof bow  15  is substantially uniform throughout the entire roof bow. Substantially uniform is herein defined to mean uniform with slight variations at the joints and/or bends. While folding a single sheet of metal into a roof bow will generally yield a uniform thickness piece, it should be appreciated that certain areas of the roof bow may be thickened to increase the resilience of the roof bow, while other areas may be thinned to help reduce the weight of the cargo container. 
         [0020]      FIG. 5  shows a cross sectional view of a roof bow  15 , panel  40 , and a liner  115 . The panel includes a panel flange  120  that extends upward from a panel slat  125  between two roof bows. When not interconnecting with a roof bow, the panel flange  120  extends inwards to the panel slat  125  at an angle complimentary with the angle of the bow flanges. However, when interconnecting with the roof bow  15 , the panel flange  15  is deflected away from the roof bows  15 . The deflection of the panel flange causes the flange to be pressed against the bow flange thereby locking the panel in place. Extending from the panel flange is a locking flange  130  that contacts the tip of the bow flange and prevents the panel from moving downwardly from the roof bow  15 . In the illustrated example, the locking flange  130  is located directly between the bow flange and the liner  115 . 
         [0021]    In  FIG. 5 , the liner  115  is secured to the second bow slat  70  of the roof bow  15 . In practice, the liner  115  contacts numerous roof bows at their second bow slats and may extend for the entire length of the cargo container as seen in  FIG. 11 . A mechanical fastener may be used to secure the liner to the roof bows, or adhesives may be used. The liner  115  adds additional protection from precipitation, but also limits access to the flanges of the panels and roof bows. Thermal insulation  123  may be placed between the liner and the panels for trailers configured to carry refrigerated goods. 
         [0022]      FIG. 6  shows an example of an isolated panel  40  with a panel slat  125  extending between two panel flanges  120 . The panels  40  may be constructed of a resilient material such as metal or fiber reinforced resin to resist wear, or they may be constructed from lightweight plastic to decrease the overall weight of the cargo container. If the panels are damaged or worn, they may be easily removed from between the roof bows by either retracting the panel flanges from above, or by forcefully pulling them down if they are constructed from plastic or other moderately resilient materials. In the illustrated example, the panel is constructed with an arched shape that matches the shape of the roof bows, however if the panels are constructed from sufficiently flexible materials they may be produced with flat slat portions and then bent to the shape of the roof bows during installation. 
         [0023]      FIG. 7  shows an example of an all weather roof bow  135  with improved precipitation resistance when a liner is not utilized. The all weather roof bow  135  has a t-top section  140  with t-slats  145  that extend from the first wall  65  to the second wall  80 . The t-slats extend past the first and second bow flanges ( 50 ,  90 ) to secure and cover the locking flanges  130  of the panels. Additionally, in the illustrated example the panel includes a securing flange  150  that directs any precipitation that enters the gap between the t-slat and the locking flange  130  to the gutter-like area above the first or third slats of the roof bow where it is shed from the roof of the trailer.  FIG. 8  shows a perspective view of an all weather roof bow  135  secured to two panels  40 . 
         [0024]      FIGS. 9 and 10  show a cargo container roof in relation to a geometric cylindrical surface  155 . In the illustrated example, the first bow slats  45  and the third bow slats  85  of the roof bows, and the panel slats  125  are all positioned upon and extend upon a single geometric cylindrical surface  155 . Having the numerous slats positioned upon and extending upon a single geometric surface creates a fairly smooth interior roof surface that is less likely to snag machinery or cargo. Due to the shape of the roof, the radius  160  of the geometric cylindrical surface  155  is generally expected to be substantially greater than the total height of the cargo container. 
         [0025]      FIG. 11  illustrates an example of an over the road trailer  10  with roof bows and panels that have been fully covered by a liner  115 . In the illustrated example, the gutters formed by the walls and first and third slats of the roof bows are not used to shed precipitation from the top of the trailer, so the sidewalls  25  extend up to and form water tight seals with the liner  115 . 
         [0026]    The inventors contemplate several alterations and improvements to the disclosed invention. Other alterations, variations, and combinations are possible that fall within the scope of the present invention. Although various embodiments of the present invention have been described, those skilled in the art will recognize more modifications that may be made that would nonetheless fall within the scope of the present invention. Therefore, the present invention should not be limited to the specific examples described.