Abstract:
In one embodiment, a heater for a vehicle having an engine that generates hot exhaust gases includes a distribution pipe extending along a cargo carrying part of the vehicle. The distribution pipe is operatively connected to an engine exhaust pipe such that engine exhaust can flow through the distribution pipe when the engine is running. The distribution pipe has a plurality of openings therein through which exhaust is discharged to heat the cargo carrying part of the vehicle when the engine is running. Each opening has a cross-sectional area substantially smaller than a cross-sectional area of the distribution pipe.

Description:
BACKGROUND 
   Moist cargo materials hauled in dump bed trucks can freeze and stick to the truck bed in cold weather. Frozen cargo materials are difficult and sometimes dangerous to dump from the truck bed. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates one example of a dump bed truck that may be adapted for use with embodiments of the invention. 
       FIGS. 2-6  illustrate a dump bed truck with a truck bed heater constructed according to an embodiment of the invention. 
       FIGS. 7-9  illustrate a dump bed truck with a truck bed heater constructed according to an embodiment of the invention. 
       FIGS. 10-12  illustrate examples of discharge nozzles for the hot exhaust gases used to heat the truck bed. 
       FIGS. 13-14  illustrate an arrangement of valves that may be used to control the flow of exhaust between the truck bed heater and the truck muffler and exhaust stack. 
       FIGS. 15-16  illustrate a dump bed truck with a truck bed heater constructed according to an embodiment of the invention. 
       FIG. 17  illustrates a truck bed heating system according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   Embodiments of the invention were developed in an effort to make it easier and safer to dump frozen materials from a dump bed truck. Exemplary embodiments, therefore, will be described with reference to a dump bed truck. Embodiments of the invention, however, are not limited to use on dump bed trucks. Embodiments may be adapted for use with other exhaust generating vehicles including flat bed trucks, tractor-trailer rigs and pick-up trucks. The exemplary embodiments shown in the figures and described below illustrate but do not limit the invention. Other forms, details, and embodiments may be made and implemented. Hence, the following description should not be construed to limit the scope of the invention, which is defined in the claims that follow the description. 
     FIG. 1  illustrates a dump bed truck  10  that may be adapted for use with embodiments of the invention. Truck  10  includes a cab  12  and a dump bed  14  containing cargo  16 . The front of bed  14  may be hoisted up to dump cargo  16  out the back of bed  14 . Truck  10  also includes an engine (not shown) that generates hot exhaust gases discharged through an exhaust stack  18 . Dump bed truck  10  represents generally any vehicle that generates hot exhaust gases and includes a bed or container capable of holding cargo, including containers that are only temporarily attached to the truck (roll-on trash containers, for example). 
     FIGS. 2-6  illustrate a dump bed truck  20  with a truck bed heater  22  constructed according to one embodiment of the invention. Only the outline of the truck bed is shown in the plan view of  FIG. 4  so that the components of heater  22  under the bed are visible. The truck bed is shown in section in  FIGS. 5 and 6 . Referring to  FIGS. 2-6 , truck  20  includes a cab  24 , a dump bed  26  and a hydraulic hoist  28  that lifts bed  26  as shown in  FIGS. 3 and 6 . The truck engine (not shown) discharges hot exhaust gases to an exhaust pipe  30 . Exhaust pipe  30  carries exhaust to a muffler/stack  32  and/or to an intake pipe  34  for bed heater  22 . A pair of butterfly valves  37  and  39  ( FIGS. 13-14 ), for example, control the flow of exhaust from pipe  30  to stack  32  and intake pipe  34 . Heater intake pipe  34  carries exhaust to a manifold  38  from which exhaust is channeled to jetted distribution pipes  40 . In the embodiment shown, manifold  38  is a continuation of intake pipe  34 . Hot exhaust gases are discharged from each distribution pipe  40  through a series of openings  42  extending along the length of pipes  40 . Manifold  38  and distribution pipes  40  are mounted to a frame  44  that supports bed  26 . 
   Where distribution pipes  40  are mounted to the movable dump bed frame  44 , as shown in  FIGS. 4-6 , a quick disconnect  46  on intake pipe  34  allows bed heater  22  to more easily disconnect and connect to the truck exhaust as bed  26  is alternately raised and lowered. Quick disconnect  46  may include, for example, a hood that fits tightly down over the end of intake pipe  34  as best seen in  FIGS. 5 and 6 . The hood may be lined with rubber or another suitable sealing material to help seal the pipe connection at disconnect  46 . In the embodiment shown in  FIGS. 7-9 , in which distribution pipes  40  are attached to the stationary truck frame  47 , the quick disconnect is omitted. 
   In the embodiment shown in  FIGS. 2-9 , two distribution pipes  40  extend parallel to one another along nearly the full length of bed  26 . Each pipe  40  is positioned approximately mid-way between the center of bed  26  and the sides of bed  26 . Openings  42  are depicted in  FIGS. 4 and 5  as a series of evenly spaced nozzles that direct the flow of gas up out of pipes  40  onto the bottom of bed  26 . Other configurations are possible. Several factors may influence the configuration for any particular application including, for example, the size of the truck bed, the heat transfer characteristics of the bed, the nature of the cargo and the climatic conditions in which the bed will be used. Alternative configurations may include, for example, more or fewer distribution pipes, distribution pipes that diverge or converge along the length of the bed, more or fewer openings, openings that are clumped together along the pipe, and distribution pipes along the sides of the bed. 
     FIGS. 10-12  illustrate different exemplary embodiments for exhaust discharge openings  42  in distribution pipes  40 . In the embodiment shown in  FIG. 10 , opening  42  is constructed as a simple opening in the top of pipe  40 . In the embodiment shown in  FIG. 11 , opening  42  is constructed as a straight nozzle  48  protruding from the top of pipe  40 . In the embodiment shown in  FIG. 12 , opening  42  is constructed as a nozzle  50  that protrudes horizontally from the side of pipe  40  and makes a 90° bend to vertical. Nozzle  50  in  FIG. 12  includes an oxidizing catalyst  52  to increase the temperature of the exhaust gases discharged from nozzle  50 . An air injection venturi  54  feeds air into catalyst  52  to aid oxidation. 
     FIGS. 13 and 14  illustrate an arrangement of butterfly valves  37  and  39  for controlling the flow of engine exhaust from pipe  30  to heater intake pipe  34  and stack  32 . Valves  37  and  39  are opened and closed by a solenoid  56  acting through a linkage  58  connecting solenoid  56  to each valve  37  and  39 . In  FIG. 13 , solenoid slider  60  is fully extended so that valve  37  to heater intake pipe  34  is fully closed, valve  39  to stack  32  is fully open and all of the exhaust flows to stack  32 . In  FIG. 14 , solenoid slider  60  is fully retracted so that valve  39  to stack  32  is closed, valve  37  to intake pipe  34  is open and all of the exhaust flows through intake pipe  34 . It may be desirable under some operating conditions to have each valve  37 ,  39  partially open to split the flow of exhaust between stack  32  and heater intake pipe  34 . In this way, the flow of hot exhaust gases to bed heater  22  may be regulated to help achieve the desired heating of bed  26 . The valve control system illustrated in  FIGS. 13-14  is just one example of a suitable control system. Other systems are possible. For example, the valves may be operated manually or each valve may be operated by its own solenoid and connecting linkage. 
   In the embodiment shown in  FIGS. 15-16 , a gas burner  62  is added to truck bed heater  22  to increase the temperature of the hot gases used to heat truck bed  26 .  FIG. 17  illustrates a control system for a gas burner assisted truck bed heater  22 . Referring to  FIGS. 15-17 , gas burner  62  is connected to heater intake pipe  34 . Burner  62  includes an electronic ignitor  64  to ignite natural gas, propane or another suitable gas delivered to burner  62  from gas tank  66  through a feed pipe  68 . The flow of gas from tank  66  to burner  62  is controlled by a pressure regulator  69  and flow control valve  70 . Where gas tank  66  is located remote from burner  62 , mounted to the cab or truck frame for example, then a flexible tubing feed pipe  68  may be used along with a quick disconnect at control valve  70 . 
   An electronic programmable controller  72  may be used to achieve the desired flow of hot gases to heater intake pipe  34  by regulating flows from the engine exhaust and heat from gas burner  62 . Controller  72 , therefore, is operatively connected to gas burner flow control valve  70 , ignitor  64  and exhaust valve actuator solenoid  56 . Gas burner  62  is one example of a secondary heat source that may be used to supplement the heat provided by exhaust from engine  76 . Control inputs to controller  72  may include, for example, a temperature signal from a thermocouple  74  to monitor the temperature of gases entering manifold.  38 , air temperature, truck bed temperatures, engine exhaust flow rates and temperatures, and gas burner temperature. 
   While the configuration of components of heater  22  may be varied to achieve a desired performance for a particular truck bed, it is expected that two 4″-5″ diameter distribution pipes and a corresponding number of ¾″-1″ diameter nozzles will adequately heat the floor of a typical roll-on trash container carried by a diesel fueled truck engine. In one example, heater manifold  38  is a 5″ diameter steel pipe. Two 4″ diameter steel distribution pipes  40  connected to manifold  38  extend along the full length of the trash container/bed  26 . The floor of trash container dump bed  26  is 20′-0″ long and 7′-0″ wide and made from 3/16″ thick steel plate. Each distribution pipe  40  is positioned 2′-7″ from the side of bed  26 , leaving 1′-10″ between pipes  40 . Twelve 1″ diameter nozzles  48  are spaced 1′-6″ apart along the length of each distribution pipe  40 . The tip of each nozzle  48  is approximately 3″ below the underside of bed  26 . The ratio between the cross-sectional area of each distribution pipe and the cross-sectional area of each opening or nozzle for such a trash container configuration is in the range of 16 (for a 4″ diameter pipe and 1″ nozzles) to 45 (for a 5″ diameter pipe and ¾ nozzles). 
   The present invention has been shown and described with reference to the foregoing exemplary embodiments. It is to be understood, however, that other forms, details, and embodiments may be made without departing from the spirit and scope of the invention which is defined in the following claims.