Abstract:
A monolithic dual-purpose trailer for transporting cargo includes a frame including two longitudinally extending side rails and a central reinforcing member in the form of an engineered truss is located between the two side rails. Wheels are mounted to the frame. A deck including a load bearing surface with a grate is formed on the frame. Hoppers are positioned below the grate. The frame is formed as one solid welded unit. The deck has a portion formed of flat aluminum. A perimeter frame rail is located around the deck. The trailer can transport multiple types of loads and does not have to be converted from one mode to another and additionally has reduced longitudinal flexing.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains to the art of hauling cargo from place to place and more particularly to trailers used to haul either discrete cargo that is typically transported on a flat bed and loose bulk cargo such as crushed stone or sand that is typically transported in a hopper. 
   2. Discussion of the Prior Art 
   In the past large discrete items of cargo have been traditionally transported on flatbed trailers and loose bulk cargo has been transported in trailers that have hoppers. Since such trailers are designed to transport only one type of load, often the trailers made a trip one-way loaded and make a return trip empty. Traveling in a non-loaded condition is wasteful and considered undesirable because of the large cost of fuel and labor costs associated with moving an empty trailer. 
   In response to this problem Schmidt et al have proposed in U.S. Pat. No. 4,082,357 to start with a box-type semi-trailer and adding a grate type floor and hoppers. The patent then teaches a relatively complicated conversion system which supposedly allows an operator to convert the trailer from a hopper configuration to a box configuration. Numerous walls and partitions must be moved and sealed to change the trailer from one configuration to the other. 
   Sentle, Jr. et al. have proposed a dual purpose trailer body for converting between a first configuration for handling freight of a bulk nature such as coils of steel or paper and to a second configuration for handling comminuted material such as dolomite or grain. The patent teaches moving large floor panels from a horizontal position to a vertical position to convert the trailer from the first to second positions. 
   Apparently the difficulties involved with these types of convertible trailers in terms of the effort required to convert them from one configuration to another has been so great that none of them are currently in mass production except for a trailer produced by Western Trailers. Even the Western Trailer unit has so many problems with the conversion process that divers will only convert them seasonally. The trailers still often travel in a non-load condition because of the labor and safety issues involved with converting the trailer is so great it is cheaper to run the trailer empty. 
   Also in all of the above-mentioned convertible trailers and indeed for flat bed trailers generally there is the additional problem of the trailers having weakness in the longitudinal direction that allows undesirable longitudinal flexing. 
   Based on the above, there is a need in the art for a trailer that can transport multiple types of loads and does not have to be converted from one mode to another and additionally reduces longitudinal flexing. 
   SUMMARY OF THE INVENTION 
   In accordance with the invention a monolithic dual-purpose trailer for transporting cargo includes a frame including two longitudinally extending side rails and a central reinforcing member in the form of an engineered truss is located between the two side rails. Wheels are mounted to the frame. A deck including a load-bearing surface with a grate is formed on the frame. A hopper is positioned below the grate. The frame is formed as one solid welded unit. The deck has a portion formed of flat aluminum. A perimeter frame rail is located around the deck. 
   A second hopper is located behind the hopper and wherein the grate includes a front portion and a rear portion and the hopper is located below the front portion and the second hopper is located below the rear portion. A hopper divider is located between the hoppers and attached to the frame. Actuators are use for opening a closing the hoppers. Lateral rails extend between the side rails, the lateral and side rails being located along the perimeter. An upper cross beam and a lower cross beam each extend between the side rails and connected to the truss. 
   Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top perspective view of the vehicle trailer incorporating a preferred embodiment of the invention; 
       FIG. 2  is a top perspective view of the trailer of  FIG. 1  with the grate removed; 
       FIG. 3  is a bottom perspective view of the trailer of  FIG. 1  showing one hopper gate open and the other hopper gate closed; 
       FIG. 4  is a side view of the trailer of  FIG. 1 ; 
       FIG. 5  is a cross-section view of along the line  5 - 5  of  FIG. 1 ; 
       FIG. 6  is an end view of the trailer of  FIG. 1 ; and 
       FIG. 7  is a top perspective view of the hoppers removed from the trailer. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With initial reference to  FIGS. 1-3 , there is illustrated a nonconvertible monolithic dual-purpose trailer  10  constructed in accordance with a preferred embodiment of the invention. Trailer  10  has a longitudinally extending deck  20  that is preferably flat. First and second hoppers  30 ,  31  are located below deck  20 . Deck  20  is capable of transporting any load typically loaded on a flatbed trailer. For example, discrete cargo such paper rolls, coils of steel, lumber and the like are transported on deck  20 . The first and second hoppers  30 ,  31  are capable of carrying comminuted, loose bulk material such as sand or crushed stone. 
   Generally trailer  10  is supported by a king pin  50  at a first end  54  and by wheels  60  at a second end  64 . Wheels  60  are mounted on axles  65  that in turn are mounted to trailer  10  by a suspension system (not shown) as is well known in the art. As shown there are eight wheels however it is envisioned that the number and placement of the wheels could change depending on load requirements. Pin  50  is designed to engage a tractor (not shown) to form a tractor-trailer unit as is well known in the art. Pin  50  is welded securely to trailer  10 . Of course other structural arrangements could be used to attach the trailer to a tractor. 
   Deck  20  includes a first flat portion  70  at first end  54  that is generally rectangular and is strong enough to support discrete cargo. A second flat portion  75  of similar construction to first portion  70  is located at second end  64  of deck  20 . Flat portions  70 ,  75  are preferably made of aluminum but may be made of any suitable material. Aluminum is preferred because it is light and has sufficient strength to carry typically cargo hauled by flatbed trailers. Steel or other similar materials could be used. The flat portions  70 ,  75  are permanently fixed to a frame  77  preferably by welding. While not shown, flat portions  70 ,  75  may be fitted with metal hoops set in recesses. The hoops may either lay flat or be pivoted upright so that a rope or cable may be passed therethrough to secure cargo placedon deck  20 . 
   A steel or aluminum grate  80  is located between flat portions  70 ,  75 . Preferably grate  80  is permanently welded to trailer  10 . Grate  80  is made of two portions  81 ,  82 , one portion being located over each hopper  30 ,  31 . Grate  80  is shown as being removed in  FIG. 2 . Grate  80  has openings large enough to allow loose bulk cargo to pass though into hoppers  30 ,  31 . Grate  80  is also strong enough to hold discrete cargo. A hopper divider  100  is welded between first and second portions  81 ,  82  of grate  80  and provides extra strength for deck  20 . 
   Located below deck  20  is main frame  77  of trailer  10 . Frame  77  includes two longitudinal side rails  110 ,  120  that extend the entire length of trailer  10 . A central truss  130  also extends longitudinally and is located between side rails  110 ,  120 . Front and rear end rails  140 ,  150  are located at each end of trailer  10 . A plurality of crossbeams  160  are located under each flat portion  70 ,  75  of deck  20 . 
   Turning now to first end  54  of trailer  10  as best seen in  FIG. 3 , longitudinal side rails  110 ,  120  support the edges of flat portions  70 ,  75  of deck  20 . Cross beams  160  extend laterally between first and second side rails  110 ,  120  and also provide support for deck portion  20 . A generally circular support  170  is attached to several of cross beams  160  and pin  50  is attached to circular support  170 . Holes  165  are provided in cross beams  160  to allow central truss  130  to pass therethrough. A pair of extendable supports (not shown) may be attached to crossbeams  160 . Such supports allow trailer  10  to remain upright when not attached to a tractor. 
   Turning now to second end  64  of trailer  10  as shown in  FIGS. 1 and 3 , longitudinal side rails  110 ,  120  support the edges of flat portions  70 ,  75  of deck  20 . Cross beams  160  extend laterally between side rails  110 , 120  and also provide support for flat portions  70 ,  75 . An end rail  140  is provided with lights  180  to indicate when trailer  10  is braking or turning. Central truss  130  passes below cross beams  160  and ends at rail  150 . Wheels  60  and associated axles  65  are attached to cross beams  160  in a known manner. 
     FIG. 2  shows grate  80  removed from trailer  10  so that gates  201 ,  202 ,  203 ,  204  of hoppers  30 ,  31  can be clearly seen. First hopper  30  is shown with gates  201 ,  202  in the closed position while second hopper  31  is shown with gates  203 ,  204  in the open position. Gates  201 ,  202 ,  203  and  204  are used to unload hoppers  30 ,  31  of their cargo. Additionally engineered truss  130  passes between gates  201 ,  202 ,  203 ,  204 . 
   Turning now to  FIGS. 4 and 5  engineered truss  130  can be seen in more detail.  FIG. 4  shows a side view of trailer  10  while  FIG. 5  shows a cross section of trailer  10  along the line  5 - 5  of  FIG. 1 . Truss  130  is centered between side rails  110 ,  120  and between gates  201 ,  202 ,  203 ,  204 . Truss  10  has a deck support rail  210  and a base support rail  220 . Connecting beams  230  extend between deck support rail  210  and base support rail  220  and thus forming a truss structure. Generally triangular openings  250  are formed between connecting beams  230  and support rails  210 ,  220 . The geometry of truss  130  substantially eliminates the longitudinal flexure usually found in conventional flat bed trailers and bottom dump trailers. 
   Trailer  10  as described above is essentially a monolithic one-piece welded unit with a low center of gravity. In use trailer  10  can carry loads in both hoppers  30 ,  31  and on deck  20  simultaneously. Further since trailer  10  is not convertible and stays in the same configuration at all times hoppers  30 ,  31  are easily sealed when they are manufactured and do not have the sealing problems present in convertible trailers 
   As shown in  FIGS. 6 and 7 , air cylinders  280  control gates  201 ,  202 ,  203 ,  204  for each hopper  30 ,  31 . While air cylinders are preferred, other types of actuators may be used. For example it is also possible to use hydraulic or electrically operated actuators. Cylinders  280  may be remotely controlled so a driver does not need to leave truck&#39;s cab to unload trailer  10 . The operation of gates  201 ,  202 ,  203 ,  204  can be seen in  FIG. 6  in which gates  201 ,  202  are shown in an open position and gates  203 ,  204  are shown in a closed position. A cross member  290  is secured to truss  130  and supports hoppers  30 ,  31 . A deck cross member  300  is also connected to truss  130  and supports deck  20 . 
   As best seen in  FIG. 6 , a downward sloping seal guard  310  is attached to truss  130 . Seal guard  310  keeps most of the cargo in hopper  31  from passing between truss  130  and the edge of gates  203  and  204 . Seals  320  are preferably made of hard rubber and are bolted to truss  130 . Seals  320  are struck by gates  203  and  204  as they close thus prevent any small amount of cargo that does pass seal guard  310  from dropping onto the road. A skid plate  340  is provided on truss  130  to protect seals  320  and gates  203  and  204  from damage. 
   In operation trailer  10  may be loaded with one type of cargo when traveling in one direction and then loaded with another type of cargo on a return trip. Since there is a greater chance trailer  10  will be loaded on each trip as compared to either a flatbed or a hopper significant saving will occur. Additionally drivers may be able to service more customers because they can haul more varied types of cargo. Since trailer  10  does not have to be converted between two separate configurations time is saved because the conversion process does not have to occur. Further the operator does not have to risk injuries that may occur during the conversion process. 
   Although described with reference to a preferred embodiment of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. In general, the invention is only intended to be limited by the scope of the following claims.