Abstract:
An apparatus for improving the stability of a payload of granular material loaded onto the bed of a vehicle that will traverse at least one grade is disclosed. The bed of the vehicle may be coupled to a hoist mechanism which may be linked to a controller with a memory for entering a value for the grade the vehicle may traverse while carrying the payload on the bed. The controller may send a signal to the hoist mechanism to tilt the bed to a tilted position having an angle about the value of the grade. An optional tilt support mechanism may be used to engage and support the bed after the bed has been tilted by the hoist mechanism to support the bed in the tilted position while the bed is loaded with the granular material. The hoist mechanism can be used to move the bed back to the horizontal position after the payload has been deposited on the bed.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to a system and method for stabilizing a load of granular material on the bed of a vehicle. 
       BACKGROUND 
       [0002]    Dump trucks and other machines for hauling payloads of granular material are equipped with bodies or beds that are designed to limit the material that may fall off or out of the bed during transport. The designs of these machines must take account for steep grades and, as a consequence, the use of tail-gates or tail-barriers becomes necessary. The effectiveness of a tailgate may be limited as a payload of granular material is typically loaded high on the bed and it may not be practical to design a tailgate as high as the top of the payload. Further, large tailgates are heavy, which limit the weight of the payload that the truck or machine may safely carry. 
         [0003]    An alternative to large tailgates is a cover or tarp draped over the top of the payload. Many cover designs are available, including mechanisms that automatically deploy the cover. However, covers are only practical when the granular material is lightweight and will not tear or cut the cover. Covers are not practical for heavy dump trucks that carry material like rocks that weigh several kilograms to several hundred kilograms. Further, covers are often not preferred because of the time it takes to deploy a cover, which consumes valuable haulage time. For example, in a mining operation where a truck may be constantly hauling granular material from one location to another, the time consumed by deploying a cover each time the truck is loaded would reduce the number of loads per day the truck can haul. 
         [0004]    Because large tailgates and covers are usually impractical for heavy dump trucks, heavy dump trucks are designed with deep beds. A deep bed can limit material spillage as long as the material is properly distributed on the bed. However, deep beds require a severe, near vertical tilt during the dumping process. A severe, near vertical tilt requires a hoist mechanism with a larger and heavier piston and, therefore, a heavier hoist mechanism. Such a heavier hoist mechanism can limit the weight of the payload the truck can safely carry. Thus, there may be a tradeoff between the depth of the bed, which enables larger payloads, and the tilt angle required to dump the payload from the bed, which may ultimately limit the weight of the payload. 
         [0005]    The overall size of a bed presents an additional limitation. If the granular material is lightweight, the granular material may be loaded very high in an attempt to reach the maximum haulage capacity of the truck or vehicle. The higher the material is loaded, the more likely it is to spill, especially on steep grades. As a result, for lighter materials, the beds must be designed deeper and larger and, therefore heavier. Eventually a point may be reached where making the bed any larger would require a payload weight reduction. 
         [0006]    When granular materials are poured onto a horizontal surface, such as a truck bed, a conical pile will form. The internal angle between the surface of the pile and the horizontal surface is known as the angle of repose (γ). For a conically-shaped payload disposed on a truck bed, the angle of repose is the angle between the surface of the pile and the truck bed. Materials with a low angle of repose form flatter piles than materials with a high angle of repose. The angle of repose represents the steepest slope possible relative to the truck bed, or, when the granular material on the slope face is on the verge of sliding. The angle of repose is related to the density, the surface area of the granular particles, the shapes of the particles and the coefficient of friction of the granular material. 
         [0007]    When hauling a payload of granular material up a grade, if the granular material is loaded into a conical pile and the surface of the top of the pile is at or near the angle of repose, the angle of the grade will destabilize the payload, possibly causing spillage. Vibrations can also destabilize a conical pile of granular material. If the granular material includes sharp or large rocks, spillage can present a safety hazard to following vehicles or trucks. As truck tires are very expensive, the economics of a mining or hauling operation can also be compromised. 
         [0008]    Therefore, there is a need for an improved system and method for loading dump truck beds and other hauling vehicle beds with granular material that maximizes the payload while minimizing spillage during both flat hauls and hauls proceeding up a grade. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    This disclosure describes apparatuses, vehicles, systems and methods that add stability to granular material loaded on a bed and that is hauled from one location to another and where the haul path includes traversing a grade. The disclosed apparatuses, vehicles, systems and methods reduce the likelihood of spillage of the granular material when traversing a grade. 
         [0010]    A disclosed apparatus improves the stability of a payload of granular material loaded onto the bed of a vehicle that will traverse at least one grade while carrying the payload. The bed of the vehicle is coupled to a hoist mechanism. The apparatus may include a controller with a memory for entering a value for the grade the vehicle may traverse while carrying the payload. The controller may send a signal to the hoist mechanism to tilt the bed to a tilted position having an angle about the value of the grade. The bed, in the tilted position, may then be loaded with the granular material. The hoist mechanism may then move the bed to a horizontal position after the payload had been loaded onto the bed. 
         [0011]    A vehicle for transporting payloads of granular material is disclosed. The vehicle may include a bed coupled to a hoist mechanism and a tilt support mechanism. The vehicle may also include an interface linked to a controller having a memory with a value of a grade the vehicle may traverse stored in the memory. The controller may send a signal to the hoist mechanism to tilt the bed an amount having an angle about the value of the grade. The bed, in the tilted position, may then be loaded with the granular material. The hoist mechanism may then move the bed to a horizontal position after the payload had been loaded onto the bed. 
         [0012]    A method is disclosed for loading the bed of a vehicle with a payload of granular material that will traverse at least one grade. The method may include: identifying the steepest grade the vehicle will traverse; tilting the bed to an angle from a horizontal position to a tilted position having an angle about the value of the grade; supporting the bed at the angle; loading a payload onto the bed; and lowering the bed to the horizontal position thereby causing the payload to move forward on the bed. 
         [0013]    In a refinement of any one or more embodiments disclosed herein, a tilt support mechanism may be included that is engages and supports the bed after the bed has been tilted by the hoist mechanism to support the bed in the tilted position while the bed is loaded with the granular material. The tilt support mechanism may be employed to protect the hoist mechanism from damage while the bed is loaded in the tilted position. The tilt support mechanism may then be releasable from supporting the bed so the hoist mechanism can move the bed to a horizontal position after the payload has been deposited on the bed. 
         [0014]    In a refinement of any one or more embodiments disclosed herein, the tilt support mechanism may be moved into and out of engagement with the bed by hand. 
         [0015]    In a refinement of any one or more embodiments disclosed herein, the tilt support mechanism may be coupled to an actuator that may be linked to the controller, and the tilt support mechanism may be moved into and out of engagement with the bed by the actuator that may receive signals from the controller. 
         [0016]    In a refinement of any one or more embodiments disclosed herein, the controller may be part of an ECM. 
         [0017]    In a refinement of any one or more embodiments disclosed herein, the tilt support mechanism actuator may be a hydraulic motor. 
         [0018]    In a refinement of any one or more embodiments disclosed herein, the memory of the controller includes a plurality of angle of reposes for various granular materials. 
         [0019]    In a refinement of any one or more embodiments disclosed herein, an interface may be included for initiating the controller sending the signal to the hoist mechanism. In a refinement of any one or more embodiments disclosed herein, the interface may be a button. 
         [0020]    In a refinement of any one or more embodiments disclosed herein, the value for the grade may be inputted to the controller remotely. 
         [0021]    In a refinement of any one or more embodiments disclosed herein, the angle of repose can be inputted to the controller remotely. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a side elevational view of a vehicle with a granular load on level ground, particularly illustrating the angle of repose γ of the granular load. 
           [0023]      FIG. 2  is a side elevational view of the vehicle with the granular load traversing a grade. 
           [0024]      FIG. 3  is a side elevational view of the vehicle on level ground during loading of a granular load while supporting the bed of the vehicle at an angle β that accounts for the angle of repose γ of the granular material and the angle θ of the grade illustrated in  FIG. 2 . 
           [0025]      FIG. 4  is a side elevational view of the vehicle and granular load of  FIG. 3  traversing the grade illustrated in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    As shown in  FIG. 1 , during a typical loading process, a truck  10  may be disposed on a level surface  11  and the bed  13  may be loaded close to 100% of the payload capacity of the truck  10  with a granular material  12 . The bed  13  may be designed large enough to hold as much granular material  12  as the truck  10  can safely carry, but not past a threshold where increasing the size and weight of the bed  13  would reduce the amount of payload the truck  10  can safely carry. In addition to the size and weight of the bed and the haulage capacity of the truck  10 , the cost of transporting the bed  13  (e.g. fuel, etc.) is usually taken into consideration when designing the bed  13  so the size of the bed  13  does not reduce the profit of carrying the payload  14 . 
         [0027]    Another factor considered in the design of the bed  13  includes a physical property of the conical pile of the granular material  12  that will be hauled on the bed  13 . The physical property is known as the angle of repose γ. In  FIG. 1 , the granular material  12  will tend to form a conical pile having a natural static stability slope referred to as the angle of repose γ. The angle of repose γ represents a maximum static slope of the surface  17  of the payload  14  before the surface  17  starts to slide downward. The angle of repose γ, however, usually cannot be sustained when the granular material  12  is subjected to vibrations or movement over an unlevel surface. Thus, for a heavy dump truck  10  with a fully loaded bed  13 , the slope of the payload  14  should be less than the angle of repose γ. Because reducing the slope of the surface  17  results in a flatter pile, changing the slope of the payload  14  from the angle of repose γ to a flatter dynamic stability angle that will be less than the angle of repose γ requires that the bed  13  of the truck  10  to be larger to prevent spillage. In many situations, such as hauling rocks on a mining road, spillage can be a safety hazard not only to the truck  10  but to trucks or other vehicles following behind the truck  10 . 
         [0028]      FIG. 2  shows the load distribution of  FIG. 1  on a 10° grade  111  (θ=10°; 17.6% grade). As the truck  10  was loaded to capacity while on level surface  11  ( FIG. 1 ), the slope of the grade  111  indicated by θ in  FIG. 2 , when combined with angle of repose γ, which was created on the level surface  11 , will be beyond the dynamic stability slope for the granular material  12  as the slope of the grade θ in combination with the angle of repose γ exceeds the angle of repose γ (θ+γ&gt;γ). Because the angle of repose γ represents a maximum slope available for the particular granular material  12  on level ground, not the slanted grade  111 , the payload  14  as shown in  FIG. 2  is unstable and the surface  17  will slide downward thereby causing spillage when truck  10  hauls the payload  14 . Therefore, the bed  13  should be designed larger in order to account for both displacement of the payload  14  due to the different grades the truck  10  may traverse and vibrations. 
         [0029]    Even with a larger bed  13 , the payload  14  should be correctly placed on the bed  13 , not too close to the rear  15  of the bed  13  and not too close to the front end  16  of the bed  13 , or spillage may still occur. As shown in  FIG. 1 , the payload  14  was deposited onto the bed  13  at or about the position  18 . As shown in  FIG. 2 , the payload  14  is loaded closer to the front end  16  of the bed  13  to limit spillage off of the rear end  15  of the bed  13  when the truck  10  is proceeding up the grade  111 . As a result, the operators that load the truck  10  may take into consideration the highest grade  111  that the truck  10  needs to traverse and exercise the judgment to properly place the payload  14  on the bed  13  to limit spillage over the rear  15  of the bed  13 . 
         [0030]    To reduce the amount of judgment that operators must exercise,  FIG. 3  illustrates a technique for loading the bed  13  while the bed  13  is in a tilted position, shown by the angle α. In the example shown in  FIG. 3 , a tilt support mechanism  20  is employed to support the bed  13  at an angle β during the loading process. The tilt support mechanism  20  may be used to support the bed  13  in the tilted position shown in  FIG. 3  while the payload  114  is deposited on the bed  13 . When the truck  10  has been fully loaded, the bed  13  may then lowered by the hoist mechanism  21  and haulage may commence. 
         [0031]    However, the hoist mechanism  21  may be used to both tilt the bed  13  and support the bed  13  while the bed  13  is being loaded. Further, the bed  13  may be tilted using a mechanism other than the hoist mechanism  21  of the truck  10 ; a separate hoist mechanism, pulley mechanism or other type of mechanism (not shown) may be employed. In some cases, the hoist mechanism  21  may be prone to damage if the bed  13  is loaded when the hoist mechanism  21  is supporting the bed  13  in a tilted position like shown in  FIG. 3 . Therefore, use of the tilt support mechanism  20  may provide protection to the hoist mechanism  21  from damage caused by loading the bed  13  while the hoist mechanism  21  is supporting the bed  13  in a tilted position. 
         [0032]    As shown in  FIG. 4 , the introduction of β during the loading process ensures that the angle γ 2  of the slope of the granular material  12  is reduced by the angle β when the bed  13  is lowered. The flatter angle γ 2  for the slope of the surface  117  may be controlled by controlling β during the loading process so the conical pile of granular material  12  may remain stable for the steepest grade in the haul path, even when subjected to vibrations. The introduction of the load angle β may reduce the possibility of spillage because it may result in a flatter slope for the surface  117 . 
         [0033]    Another benefit shown in  FIG. 3  that will reduce the possibility of spillage is allowing the payload  114  to shift forward on the bed  13  to a position  118  that is closer to the front end  16  of the bed  13  than the position  18  illustrated in  FIG. 1 . By allowing the load position  118  to move forward when the bed  13  is lowered, the risk of spillage off the rear end  15  of the bed  13  while traversing up a steep grade  111  may be reduced. Further, the bed  13  may be designed as such that when the bed  13  reaches close to 100% weight capacity, the granular material  12  will spill from the rear  15  of the bed  13 . Using one or more of these techniques, accidental overloading of the bed  13  becomes less likely with the increased stability of the surface  117 . The loading process illustrated in  FIG. 3  may also lead to improved designs for the bed  13  with an improved approach to the economically ideal bed size, making each haul cycle more profitable. Because spilled rocks of certain sizes are typical causes for damage to truck tires, a reduction of spillage provides both safety and economic benefits the haulage process. Another possible technique shown in  FIG. 3  that will reduce the possibility of spillage is to deposit the payload  114  on the bed  13  at a position  118  that is closer to the front end  16  of the bed  13  than the position  18  illustrated in  FIG. 1 . By moving the load position  118  forward, the risk of spillage off the rear end  15  of the bed  13  while traversing up a steep grade  111  may be reduced. 
         [0034]    A fixed loading angle may not fit all types of payloads, so it may be preferable to introduce an adjustable loading angle β. Such an adjustable angle β would be used for variations in the grade angle θ of the haulage paths from one location to another, for variations in the angle of repose γ of various materials and by limiting the loading capabilities of the bed  13  before the granular material  12  begins to fall off the rear end  15  of the bed  13 . 
         [0035]    The hoist mechanism  21  may be controlled and activated by a controller  22  which may be a separate or dedicated controller or part of the engine control module (ECM) of the truck  10 . The controller  22  may include a memory  23  for the storage of the angle of repose γ of the granular material  12  being transported or various angles of repose γ for various granular materials that the truck  10  is expected to transport. The tilt support mechanism  20  may be moved into an out of a position supporting the bed  13  by an actuator  24  which, in turn, may be activated and controlled by the controller  22 . A value for the grade, such as the angle θ or various grade angles or various values for the grade such as the commonly used degree or percentage of the grade (tan(θ)) may also be stored in the memory  23  of the controller  22 . 
         [0036]    The controller  22  may include a wireless connection so that the angle of repose γ may be inputted to the controller  22  and into the memory  23  remotely. For that matter, the grade angle θ and/or modified angle of repose γ 2  may be inputted remotely as well. An interface  25  may be provided on the truck  10  for inputting the grade angle θ, the angle of repose γ, the modified angle of repose γ 2  or any combination thereof. As an alternative, the memory  23  of the controller  22  may be programmed remotely or the grade angle θ, the angle of repose γ, the modified angle of repose γ 2  or any combination thereof may be stored in the memory  23  ahead of time and the interface  25  on the truck  10  may be a simplified pushbutton device. 
       INDUSTRIAL APPLICABILITY 
       [0037]    In an ideal bed design, the load will spill once 100% of the capacity is reached. In practice, however, an ideal bed design may not be practical as the density of the granular material may vary, rainwater may affect the physical characteristics of the payload, the severity of vibrations may vary and/or grades the truck will traverse can vary. Use of the hoist mechanism to tilt the bed prior to loading, the optional implementation of the disclosed tilt support mechanism and the disclosed loading methods greatly reduce the need for extending the size of the bed in order to reduce spillage. By avoiding beds that are larger and therefore heavier than necessary, the economics of the hauling process are improved. 
         [0038]    To safely load a bed with granular material that will be exposed to vibrations and an unlevel haul path, the steepest grade in the haul path is identified. The bed may then be tilted to an angle from horizontal to a tilted position having an angle about the value of the grade. The bed may then be supported at the angle by the hoist mechanism, a tilt support mechanism or other mechanism because many truck bed hoist systems can be damaged if the bed is loaded in a tilted position. A payload of granular material may then be loaded onto the bed. The bed may then be lowered to the horizontal position which may cause the load to shift forward on the bed. 
         [0039]    The disclosed apparatuses, systems, trucks and methods simplify the loading of granular materials onto a truck or vehicle bed that will traverse one or more grades along the haul path. By simplifying the loading process, and reducing the guesswork associated with loading a payload of granular materials onto a truck or vehicle bed, safety is enhanced because the likelihood of spillage is reduced. By reducing the likelihood of spillage, the economics of the hauling operation are enhanced.