Abstract:
A partial cover and tailgate seal is added to the bed of a truck or trailer to prevent a slurry-type load from overflowing the tailgate of the bed when traversing steep terrain and to help seal the interface between the tailgate and the bed.

Description:
BACKGROUND 
     This application claims priority from U.S. Provisional Application Ser. No. 61/386,105, filed Sep. 24, 2010, which is hereby incorporated herein by reference. The present invention relates to a partial bed cover and tailgate seal for use in many trucks, particularly dump trucks and articulated haulers. 
     Many dump trucks, including articulated haulers and off-road dump trucks, are used to haul material to an off-site location. Often times the material is a slurry, such as mud, containing a liquid, usually water. Strict regulations control the transport of this material to ensure that the mud does not escape from the bed of the truck or trailer. This is a particular problem in mountainous regions, because, when climbing a steep hill, the mud tends to flow to the rear of the trailer and may overflow over the top of the tail gate and leak along the full width of the truck bed along the line where the tailgate abuts the bed. 
     So far, the solution has been to load the truck with far less than a full load so that the trailer will not overflow. This makes the hauling very inefficient and expensive as well as adding undesirable traffic on mountain roads. It also does not solve the problem of leakage of liquid along the line where the tailgate abuts the bed. 
     SUMMARY 
     One embodiment of a solution to that problem is described herein. It includes a partial bed cover with a tailgate seal. The cover extends from the rear of the truck or trailer bed toward the front a distance that is sufficient to prevent the load from overflowing the tailgate while still allowing ample space for a bucket or other loader to load the truck or trailer bed. Preferably, the cover extends from one-eighth to one-half of the length of the bed. The cover further includes a flexible mud flap extending downwardly to seal along the line where the tailgate abuts the bed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an articulated hauler with a partial bed cover and tailgate seal installed, with the bed in the lowered or hauling position; 
         FIG. 2  is the same view as  FIG. 1 , but with the bed in the raised or dumping position; 
         FIG. 3  is a schematic side view of the bed of  FIG. 1  but without the cover and seal, showing the level of mud when the bed is fully loaded and on level ground: 
         FIG. 4  is the same as  FIG. 3 , but showing the condition when the truck is traveling uphill, with the mud shifting and overflowing the top of the tailgate; 
         FIG. 5  is a the same as  FIG. 4 , but with a partial bed cover and tailgate seal installed; 
         FIG. 6  is an enlarged, broken away side view of the bed of  FIG. 5 , with the truck on level ground, and showing the tailgate seal in phantom; 
         FIG. 7  is a side view of the partial bed cover and seal of  FIG. 6 ; 
         FIG. 8  is a broken-away, top view of the bed of  FIGS. 5 and 6  with the tailgate removed for clarity; and 
         FIG. 9  is a broken-away, side view of the bed of  FIG. 6 , shown in the raised position (dump position). 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  are side views of an articulated hauler or truck  10  including a cab  12  and a bed  14  with a tailgate  16 . The bed  14  is supported on wheels and is shown with an embodiment of a partial cover and tailgate seal  18  mounted on the bed  14  for increasing the load that can be carried by the bed  14 , as described in more detail below. The hauler  10  includes a hydraulic lift for raising and lowering the bed  14 , as is well known in the art. 
       FIG. 3  shows the bed  14  of the hauler  10  without the cover and seal  18  of  FIG. 1 . In this view, the hauler  10  is on level ground and the trailer bed  14  is in the lowered position, with a full load of mud depicted by the dotted line  20 . It can be appreciated that some muddy water  22  leaks past the tailgate  16  along the line where the tailgate  16  abuts the bottom edge of the rear opening of the bed  14 . 
       FIG. 4  shows the same bed  14  as  FIG. 3  when the truck  10  is climbing a moderate 10 degree grade. It may be appreciated that the load has shifted rearwardly, and a substantial amount of mud  24  is overflowing the top of the tailgate  16 , in addition to the muddy water  22  leaking through the gap between the bottom edge of the rear opening and the tailgate  16 , along which the tailgate  16  abuts the bed  14 . As the steepness of the grade traversed by the truck  10  is increased, this problem becomes even worse. 
       FIG. 5  shows the bed  14  when the hauler  10  is climbing the same 10 degree grade shown in  FIG. 4 , but this time the bed  14  is equipped with a rigid partial cover and tailgate seal assembly  18 . It may be appreciated that the mud is no longer able to overflow over the top of the tailgate  16 , and even the leak at the base of the tailgate  16  has been eliminated. 
     Referring now to  FIGS. 6-8 , the bed  14  has a generally horizontal bottom and generally vertical left, right, and front sides, extending upwardly to an open top edge. A rear opening is defined by the left and right sides and tapered rear side of the bed  14 . The rear opening is enclosed by a movable tailgate  16 . The top edge of the bed  14  is enclosed from the rear opening toward the front by a substantially flat plate  26 , which in this embodiment is a solid metal plate, which extends from the left side to the right side of the top edge. The plate  26  is bolted to the left and right top edges of the bed  14  and extends from the rear of the bed toward the front a distance from one-eighth to one-half of the full front-to-rear length of the bed  14 , leaving an opening of at least ten feet in the front-to-rear direction, and preferably at least twelve feet or more, or large enough to allow the bed  14  to be loaded easily using a bucket loader or other mechanical loader. 
     Two straight, parallel pieces of angle iron  28 ,  30  extend in the left-to-right direction across the width of the plate  26  and are welded to the plate  26  to serve as reinforcing beams to provide additional structural strength to the plate  26  in order to handle the pressure of the load of mud pushing against the plate  26  so the plate  26  will not bow or buckle. A third parallel straight piece of angle iron  32  is welded to the rear end of the plate  26  to provide a surface onto which to secure a flexible, rubber mud flap  36  to the plate  26 . In this embodiment, the mud flap  36  is secured to the plate  26  by means of bolts  34  that extend through the mud flap  36  and through the angle iron  32 . The reinforced plate  26  and mud flap  36  together form the partial cover and tailgate seal assembly  18  (See  FIG. 7 ). 
     Referring to  FIGS. 6 and 7 , the mud flap  36  extends slightly beyond the line  38 , which is the bottom edge of the rear opening, and which is where the bottom edge of the tailgate  16  abuts the truck bed  14 , such that, when the tailgate  16  is in the closed position, as shown in  FIG. 6 , the mud flap  36  lies inside the tailgate  16 , and the mud or other slurry inside the truck bed  14  pushes the mud flap against the truck bed and against the tailgate  16 , forming a seal along that line  38 . 
     The mud flap  36  also seals between the top of the tailgate  16  and the rigid plate  26 , since it is bolted to the rear edge of the rigid plate  26  and extends downwardly past the top of the tailgate  16 . 
     As shown in  FIGS. 6 and 8 , the mud flap  36  fits inside the bed  14  and inside the tailgate  16 , with a small clearance between the flap  36  and the left and right sides of the bed  14 . The rear face of the flap  36  abuts the tailgate  16 . Any mud in the bed  14  presses against the mud flap  36 , pushing it against the tailgate  16  and creating a seal that prevents the slurry from seeping out around the top or bottom of the closed tailgate  16 . The mud flap  36  is preferably made from a strong, yet flexible material, such as rubber, while the plate  26  is made from a much more rigid material, such as a thick, solid sheet of metal. 
     When the bed  14  is tilted rearwardly for unloading, as shown in  FIG. 9 , the bed  14  separates from the tailgate  16 , so the tailgate  16  no longer encloses the rear opening of the bed  14 , and mud flows out through the rear opening, pushing the mud flap  36  rearwardly, out of the way, so the mud flap  36  does not interfere with the material flowing out the rear opening of the bed  14 . 
     When the bed  14  is returned to its normal position, it moves back into alignment with the tailgate  16 , and the tailgate  16  pushes the mud flap  36  back into the bed  14 , to the position shown in  FIG. 6 . 
     Since the plate  26  and flap  36  do not interfere with the normal operation of the tailgate, various types of beds and tailgates can accommodate this same partial cover and tailgate seal  18 . For example, in a different known type of bed, the tailgate remains fixed along its top edge to the top rail of the bed and pivots rearwardly about the top edge to allow the load to flow out the open rear of the bed when the bed is raised for unloading. The bottom edge of the tailgate may be pinned to the bed and the pin may be removed in order to allow the tailgate to pivot for unloading, as is known in the art. In that case, again the flap  36  would seal the top and bottom edges of the tailgate when the tailgate is closed, would be pushed out of the way by the load when the bed is tilted for unloading, and would return to its initial position when the tailgate is closed. 
     In the embodiment shown here, the partial cover and tailgate seal assembly  18  is installed along the top rail (top edge) of the bed  14  with the mud flap  36  lined up against the rear edge of the bed, where the tailgate  16  closes the rear of the bed  14 . In order to install the partial cover and tailgate seal assembly  18 , the mud flap  36  is first bolted onto the plate  26 , and then the assembly is placed on top of the bed  14 . It may be lifted up with the aid of a crane or an A-frame and then secured. In this embodiment, it is secured to the top edge of the left and right sides of the bed  14  using bolts  40  as shown in  FIG. 8 . Of course, other methods for securing the plate  26  to the bed  14  may be used, such as welding, for instance. 
     The mud or other slurry may be loaded into the bed  14  through the remaining open area forward of the plate  26 . The shorter the length of the plate  26 , the more open area is available for loading the bed  14 , which is desirable for ease of loading. On the other hand, the longer the length of the plate  26 , the steeper the grade which can be negotiated without overflowing the load over the tailgate  16 , given a certain size load (or, conversely, the larger the load which can be handled without overflowing the tailgate  16 , given a certain degree of grade). Thus, a decision has to be made to determine the optimum length of the plate and the optimum length of the remaining opening to provide both ease of loading and securing of the mud or other slurry for the degree of grade or slope that is anticipated. 
     It will be obvious to those skilled in the art that various modifications may be made to the embodiments described above without departing from the scope of the present invention as claimed.