Abstract:
A trailerable load-transferring assembly is removably attachable to the rear portion of a load-bearing vehicle. The load-transferring assembly includes a pivot connection, an auxiliary axle, an elongate abutment member that extends between a free end and an abutment end, and an actuator assembly disposed between the free end of the abutment member and the auxiliary axle. When the load-transferring assembly is connected to the vehicle by the pivot connection, the actuator assembly is actuated such that it applies a lifting force on the free end relative to the auxiliary axle. The lifting force causes the abutment member to pivot about the pivot connection, bringing the abutment end of the abutment member into an abutting engagement with an abutment surface attached to the frame of the load-bearing vehicle. The lifting force and abutting engagement prevents transverse movement of the load-transferring assembly relative to the vehicle and transfers a portion of the load from the vehicle&#39;s rear axles to the auxiliary axle.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to trailer assemblies, and, more particularly, to a trailer assembly which, when attached to the rear of a load-bearing vehicle, transfers a portion of the load from the rear wheel axle of the load-bearing vehicle to the wheel axle of the trailer assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    Roadway surfaces and bridges experience stresses due to the weight of load-bearing vehicles which travel the roadway systems. To lessen the detrimental effect of such traffic on the roadway systems, federal and state laws regulate load-bearing vehicles which travel federal and state roadways. These regulations dictate maximum loading per vehicle axle, which is based on the load-bearing capacity of roadway surfaces in the system, and minimum distance between load-bearing axles, which ensures that the vehicle&#39;s load is properly distributed over individual structural members of a bridge in the roadway system. Thus, vehicle weight restrictions generally are specified as a combination of load per axle and distance between axles.  
           [0003]    To comply with such regulations, work vehicles that are designed to carry a substantial load often include some type of auxiliary axle that increases the vehicle&#39;s legal load-carrying capacity. Auxiliary axles generally include pusher axles, which typically are mounted forward of the vehicle&#39;s rear drive axle, and trailer or tag axles, which are mounted aft of the rear axle. Such auxiliary axles increase load-bearing capacity by redistributing the load on the vehicle&#39;s axles and/or extending the wheel base between load-bearing axles.  
           [0004]    Pusher axles and many tag axles typically are deployable between a lifted or stowed position and a lowered or load-bearing position. Stowable configurations for tag axles generally employ hydraulically actuated piston assemblies that vertically pivot the axle relative to the vehicle to raise and lower the device. In the stowed position, the tag axle typically is positioned in a raised position at the rear of the vehicle. For some vehicles, tag axles in the stowed position can hinder loading and unloading tasks, thus rendering such arrangements impractical or unusable, particularly for vehicles have a flat loading bed.  
           [0005]    Other trailer or tag axles may be configured as a detachable assembly. Typically, such assemblies include a pivotable connection that allows the assembly to pivot transversely relative to the vehicle such that the trailer axle can track behind the vehicle when turning. For some vehicles, however, transverse movement of the trailer relative to the vehicle can have detrimental effects on the stability of the vehicle during a turn as a result of the forces exerted by the trailer axle assembly on the vehicle frame which are necessary to redistribute the load on the axles. Further, transverse movement hinders maneuvers in a reverse direction. Thus, although a detachable trailer axle assembly does not present an obstacle to loading/unloading operations, other issues with respect to vehicle stability and maneuverability may arise.  
           [0006]    Accordingly, it would be desirable to provide an auxiliary axle assembly that overcomes the aforementioned disadvantages of known auxiliary axle assemblies.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed toward a trailer assembly that, when attached to the rear portion of a load-bearing vehicle, transfers a portion of the load from the vehicle&#39;s rear wheel axle to the wheel axle of the trailer assembly.  
           [0008]    In accordance with one aspect of the invention, a load-transferring assembly comprises a frame assembly having an auxiliary wheel axle, an abutment member connected to the frame assembly that has an abutment end and a free end, and an actuator assembly disposed between the free end of the abutment member and the frame assembly. When the frame assembly is connected to the rear portion of the vehicle and the abutment member abuts a vehicle abutment member that is disposed proximate the rear of the vehicle, transverse movement of the frame assembly relative to the vehicle is substantially restricted. Further, when the actuator assembly is actuated such that a lifting force is applied to the free end of the abutment member, a portion of the load on a rear axle of the vehicle is transferred to the auxiliary wheel axle of the frame assembly.  
           [0009]    In accordance with another aspect of the invention, a load-transferring trailer assembly comprises a frame assembly that includes a wheel axle assembly and an engagement member configured to detachably engage a rear portion of a load-bearing vehicle. The trailer assembly further comprises an elongate member connected to the frame assembly and extending between a static connection end and a free end. The static connection end is configured to form a static connection with the rear portion of the vehicle such that transverse movement of the frame assembly relative to the vehicle is substantially inhibited. A lifting member is arranged between the static connection end of the elongate member and the wheel axle assembly and is configured to apply a lifting force to the free end such that a portion of the load on the rear vehicle axle is transferred to the wheel axle assembly.  
           [0010]    In accordance with yet another aspect of the invention, a combination is provided that comprises a load-bearing vehicle and a load-transferring trailer assembly connected to the vehicle. The trailer assembly comprises a frame assembly having an auxiliary wheel axle, a elongate member connected to the frame assembly, and an actuator assembly. The elongate member has a static connection end and a free end. The actuator assembly is disposed between the free end and the frame assembly and is configured to apply a lifting force to the free end such that a portion of the load on the rear axle of the load-bearing vehicle is transferred to the auxiliary wheel axle.  
           [0011]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:  
         [0013]    [0013]FIG. 1 is a side view of a load-transferring assembly attached to a load-bearing vehicle;  
         [0014]    [0014]FIG. 2 is a plan view of a portion of the load-bearing vehicle of FIG. 1;  
         [0015]    [0015]FIG. 3 is a plan view of the load-transferring assembly of FIG. 1;  
         [0016]    [0016]FIG. 4 is a front view of the load-transferring assembly of FIG. 1;  
         [0017]    [0017]FIG. 5 is a rear view of the load-transferring assembly of FIG. 1;  
         [0018]    [0018]FIG. 6 is a cross-sectional view of the load-transferring assembly of FIG. 1, taken generally along the line  6 - 6  of FIG. 3;  
         [0019]    [0019]FIG. 7 is a side view of the load-transferring assembly of FIG. 6 attached to the load-bearing vehicle before the load has been transferred; and  
         [0020]    [0020]FIG. 8 is a side view of the load-transferring assembly of FIG. 6 attached to the load-bearing vehicle after the load has been transferred. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring first to FIG. 1, a trailerable load-transferring assembly  10  is shown attached to a load-bearing vehicle  12 . The load-bearing vehicle  12  includes a front cab  14  and a flat load-bearing bed  16 . The vehicle  12  has a front axle  18  and a rear tandem axle arrangement  20  and  22 . The trailerable load-transferring assembly  10 , which includes an auxiliary axle  24 , is detachably coupled to the rear portion of the bed  16  in a manner that will be described in detail below.  
         [0022]    In accordance with federal laws, the gross vehicle weight (i.e., the combined weight of the vehicle and its load) of a vehicle traveling on the interstate roadway system cannot exceed 80,000 lbs., the weight on any one axle cannot exceed 20,000 lbs., and the weight on any tandem axle cannot exceed 34,000 lbs. The maximum axle loads are further restricted by the federal bridge formula which dictates the maximum weight that may be borne by any two or more consecutive axles based on the inter-axle spacing. The bridge formula is as follows:  
           W= 500[( L ( N )/( N− 1))+12( N )+36] 
         [0023]    where W is the gross vehicle weight; L is the distance in rounded whole feet between the extreme of any group of two or more consecutive axles; and N is the number of axles in the group under consideration.  
         [0024]    Thus, if the load-transferring assembly  10  is not attached to the vehicle  12  in FIG. 1, then the load on the single front axle  18  may not exceed 20,000 lbs., and the load on the tandem axles  20  and  22  may not exceed 34,000 lbs., or 17,000 lbs. per axle. These weight limitations are further restricted by the inter-axle spacing. In one exemplary embodiment, the distance between axles  18  and  20  is 16 feet, and the distance between axles  20  and  22  is 4 feet, for an overall length of 20 feet. For a vehicle with three axles, the federal bridge formula limits the gross vehicle weight to 51,000 lbs. If the distance between axle  22  and the auxiliary axle  24  is 8 feet, then the gross vehicle weight can be increased to 60,500 lbs. (i.e., 28 feet and 4 axles).  
         [0025]    Referring now to FIG. 2, the bed  16  is supported by a chassis frame  26  coupled to the axles  20  and  22 . In the embodiment illustrated in the Figures, the chassis frame  26  includes a vehicle abutment member  28  that extends from the rear portion of the vehicle  12  and is configured to engage with the load-transferring assembly  10 . The vehicle abutment member  28  is generally disposed along a longitudinal axis  30  of the bed  16  that is generally centered transversely relative to a transverse axis  32  extending through the axle  22 . The chassis frame  26  further includes engagement members  34  and  36  which are configured to engage with and retain the load-transferring assembly  10  in such a manner that the assembly  10  may pivot vertically about a transverse axis  38  that is generally parallel to the transverse axis  32 . The engagement members  34  and  36  may be configured as any of a variety of structures suitable to retain the load-transferring assembly  10  attached to the vehicle  12  in a manner that allows vertical pivotal movement about the transverse axis  38 .  
         [0026]    Turning now to FIGS. 3, 4, and  5 , a plan view, a front view, and a rear view, respectively, of the load-transferring assembly  10  are illustrated. The load-transferring assembly  10  includes a frame assembly  40  having a pair of generally parallel side arms  42  and  44 , an elongate abutment member  46 , a pivot connection assembly  48 , and an auxiliary axle  50  extending between a pair of wheels  52  and  54  carrying tires  53  and  55 , respectively. The frame assembly  40  is connected to a pair of wheel fenders  56  and  58  via support struts  60  and  62  and to a rear fender  64  via support struts  66  and  68 . In the exemplary embodiment illustrated in the Figures, the rear fender  64  is configured to support various light fixtures (e.g., lights  70  and  72  in FIG. 5), such as brake lights, running lights, turn signal indicators, etc. A pair of mud flaps  74  and  76  (see FIG. 5) extend from the rear fender  64  proximate the region at which the rear fender  64  is connected to the wheel fenders  56  and  58 .  
         [0027]    The pivot connection assembly  48  is configured to pivotally connect to the pair of side arms  42  and  44  and to pivotally engage with the engagement members  34  and  36  to secure the assembly  10  to the vehicle  12 . In the exemplary embodiment illustrated in FIGS.  3 - 5 , the pivot connection assembly  48  includes a plurality of flanges  78 ,  80 ,  82 ,  84 , and  86  connected to a transverse bar  88 . The flanges  78  and  80  are generally parallel and spaced apart such that one end of the flanges  78  and  80  form a first cavity  90  for receiving the side arm  42  and the other end of the flanges  78  and  80  form a second cavity  92  for receiving the vehicle engagement member  34 . Similarly, one end of the flanges  82  and  84  form a cavity  94  for receiving the side arm  44 , while the other end of the flanges  82  and  84  cooperate with the flange  86  to form a second cavity  96  for receiving the vehicle engagement member  36 . The ends of the side arms  42  and  44  are respectively secured within the cavities  90  and  94  by pins  98  and  100 , which provide an axis about which the arms  42  and  44  may vertically pivot. With reference to FIG. 5, it can be seen that the other ends of the side arms  42  and  44  are attached to the axle  50 , such as by bolts, rivets, welded joints, etc.  
         [0028]    Turning now to FIG. 4 and FIG. 6 (which includes a cross-sectional view of the assembly  10  taken generally along the line  6 - 6  of FIG. 3), it can be seen that the transverse bar  88  also supports the elongate abutment member  46  via support members  102 ,  104 , and  106 . In the exemplary embodiment illustrated in the Figures, the support members  102 ,  104 , and  106  are disposed approximately midway between an abutment end  108  and a free end  110  of the abutment member  46  and fixedly attach the abutment member  46  to the transverse bar  88 . Although the Figures show the support members  102 ,  104 , and  106  as generally triangular, web-shaped structures, it should be understood that any of a variety of configurations and structures are possible which can provide adequate support and attachment of the abutment member  46 .  
         [0029]    An adjustable support leg  112  is disposed toward the abutment end  108  of the member  46  to stabilize the assembly  10  when not connected to the vehicle  12 . A rotatable handle  114  allows for extension and retraction of the support leg  112 , as desired.  
         [0030]    The free end  110  of the abutment member  46  is positioned generally above the auxiliary axle  50 . An actuator assembly is disposed between the free end  110  and the axle  50  and is operable to engage the abutment member  46  with the vehicle  12  in a manner that results in redistribution of a portion of the load on tandem axles  20  and  22  to the auxiliary axle  50  and the front axle  18 , as will be described in detail below. In the exemplary embodiment illustrated in the Figures, the actuator assembly includes a pair of pneumatically activated air bags or bellows  116  and  118 , such as air springs commercially available from Goodyear or Firestone. The free end  110  of the abutment member  46  terminates at a transverse portion  120  which connects the free end  110  to the top side of the bellows  116  and  118 . The bottom side of the bellows  116  and  118  are attached to the ends of the side arms  42  and  44 , which, in turn, are attached to the axle  50 . The bellows  116  and  118  are pneumatically actuated via an air hose  122  which is detachably connectable to an air supply in the vehicle  12 .  
         [0031]    The amount of air pressure provided to the bellows  116  and  118  through the air hose  122  is based on the desired amount of load redistribution. In one embodiment, the amount of air pressure to actuate the bellows  116  and  118  is fixed in accordance with a setpoint established by control and regulator circuitry associated with the vehicle  12 . In other embodiments, the control and regulator circuitry can be configured to have multiple setpoints that may be selected by an operator based on the gross vehicle weight. Alternatively, the control and regulator circuitry may be configured to determine a fixed setpoint based on monitored parameters, such as gross vehicle weight, tire pressure, etc. Or, the control and regulator circuitry may be configured to dynamically vary the amount of air pressure based on monitored parameters, such as terrain variations, load changes, direction of travel, etc.  
         [0032]    Although the actuator assembly in the illustrated embodiment includes pneumatically actuated bellows to lift the abutment member  46 , it should be understood that other types of actuator assemblies also are contemplated. Such assemblies may include hydraulically activated components, such as hydraulic pistons and cylinders, or any other type of structure that can lift the free end  110  of the abutment member  46  relative to the auxiliary axle  50 .  
         [0033]    Referring now to FIGS. 7 and 8, attachment of the load-transferring assembly  10  to the vehicle  12  is shown. In FIG. 7, the assembly  10  is attached, but not actuated such that the axle load can be redistributed. In FIG. 8, the assembly  10  is attached and actuated and the load is redistributed. Both FIGS. 7 and 8 present a side cross-sectional view of the assembly  10  taken generally along the line  6 - 6  of FIG. 3.  
         [0034]    Turning first to FIG. 7, the assembly  10  is positioned at the rear of the vehicle  10  such that the vehicle engagement members  34  and  36  are received within the cavities  92  and  96 , respectively, of the pivot connection assembly  48 . In FIG. 7, the flange  82  has been omitted to provide a better view of the pivot connection arrangement. When the members  34  and  36  are received within the cavities  92  and  96 , the transverse bar  88  rests within a concave portion  124  of the members  34  and  36 , and an aperture  126  through each of flanges  78 ,  80 ,  82 ,  84 , and  86  aligns with an aperture  128  in each of engagement members  34  and  36 . To securely attach the assembly  10  to the vehicle  12 , lock pins  130  are inserted through the apertures  128  and  126 . The lock pins  130  thus provide a pivot point about which the assembly  10  may vertically pivot relative to the vehicle  12 .  
         [0035]    To complete the engagement of the assembly  10  with the vehicle  12 , the support leg is retracted via the handle  114  and the bellows  116  and  118  are pneumatically actuated through air hose  122  as shown in FIG. 8. Upon actuation, the free end  110  of the abutment member  46  is lifted relative to the auxiliary axle  50 . As the lifting continues, the abutment member  46  pivots about the lock pins  130 , lowering the abutment end  108  such that an abutment surface  132  at the end  108  of the member  46  engages (i.e., abuts) an vehicle abutment surface  134  of the vehicle abutment member  28 . As long as the lifting force on the free end  110  is maintained, the abutment surfaces  132  and  134  remain statically engaged, effectively integrating the frame  40  of the assembly  10  with the frame  26  of the vehicle  12  and prohibiting any transverse movement of the assembly  10  relative to the vehicle  12 . As a result, a portion of the load on the tandem axles  20  and  22  is transferred to both the auxiliary axle  50  and the single front axle  18 .  
         [0036]    The following example illustrates the resultant redistribution of the load. Given the interaxle spacings discussed with respect to FIG. 1 above, and assuming the distance between the tandem axle  22  and the auxiliary axle  50  is eight feet, the gross vehicle weight is 57,000 lbs. and the air pressure provided to the airbags  116  and  118  is approximately 55 psi, then the load on auxiliary axle is approximately 8700 lbs., the combined load on axles  20  and  22  is approximately 33,500 lbs., and the load on the front axle  18  is approximately 14,800 lbs.  
         [0037]    In the exemplary embodiment illustrated in the Figures, a shim  136  is attached to the surface  132  of the abutment end  108 . Use of the shim  136  may be desirable to account for irregularities and mismatches between the abutment surfaces  132  and  134 . Thus, the shim  136  may be positioned as needed to optimize the engagement between the surfaces  132  and  134 .  
         [0038]    Also in the exemplary embodiment illustrated in the Figures, the static engagement between the vehicle  12  and the load-transferring assembly  10  is an abutment. In alternative embodiments, the static engagement may be accomplished by other configurations. For example, the vehicle  12  may include a receiving cavity for receiving the abutment end  108  of the assembly  10 . Such a cavity may be configured to lock the abutment end  108  into position while allowing the load-redistribution forces imparted from the lifting action to be transferred through the abutment member to the frame  26  of the vehicle  12 .  
         [0039]    As discussed, the engagement of the assembly  10  with the vehicle  12  prohibits transverse movement of the assembly  10  relative to the vehicle  12 . Thus, to facilitate tracking of the assembly  10  with respect to the vehicle  12 , which enables turning maneuvers and prevents scuffing and damage to the tires, the auxiliary axle  50  is configured as a self-steering axle.  
         [0040]    Referring back to FIGS. 3 and 5, the ends of auxiliary axle  50  are connected to the wheels  52  and  54  via pins  138  and  140 , respectively, such that the wheels  52  and  54  are positively castered. In addition, the wheels  52  and  54  may be toed in (not shown) to provide additional directional stability. Turning of the wheels  52  and  54  is synchronized by interconnecting the wheels  52  and  54  via tie rods  142  and  144 . The tie rods  142  and  144  are interconnected by attachment to a plate  146 . The plate  146  couples the tie rods  142  and  144  to the axle  50  through a pivot pin  148  which passes through apertures in a tongue  150 , which is fixedly attached to the axle  50 , and in the tie rod plate  146 . The pivot pin  148  provides a vertical pivot axis about which the tie rods  142  and  144 , and thus the wheels  52  and  54 , can pivot transversely relative to the axle  50 .  
         [0041]    The self-steering capability of the auxiliary axle  50 , however, may hinder reverse maneuvers of the vehicle  12  when the assembly  10  is attached. For example, when attempting to back the vehicle  12  along a straight line, irregularities in the roadway surface may cause the wheels  52  and  54  to pivot. Thus, as the vehicle  12  continues to move in reverse, the tires on the wheels  52  and  54  may drag and scuff, potentially damaging the tires and/or the axle  50 . Thus, in some embodiments, it may be desirable to lock the wheels  52  and  54  in a position suitable for straight movement in reverse.  
         [0042]    Referring to FIGS. 5 and 6, a lock pin assembly  152  is provided, which, when actuated, drops a pin which locks the tie rod plate  146  to the tongue  150 , thus preventing pivotal motion about the pivot pin  148 . In the exemplary embodiment, the lock pin assembly  152  is pneumatically actuated via the air hose  122 . Actuation may be performed manually by the operator of the vehicle  12  or may be performed automatically when the vehicle gears are placed in reverse. Alignment of the wheels  52  and  54  for reversing along a straight line may be performed manually simply by positioning of the vehicle  12 . Alternatively, actuation of the lock pin assembly  152  may be prohibited until control electronics sense that wheels  52  and  54  are properly aligned.  
         [0043]    It also may be desirable to further facilitate reverse maneuverability by removing at least a portion of the load on the auxiliary axle  50 . Removal of the load may be accomplished by relieving a portion of the lifting force on the free end  110  of the abutment member  46 . In the exemplary embodiment, the lifting force is removed by partially bleeding the air from the bellows  116  and  118  whenever the lock pin assembly  152  is actuated. Bleeding the air may be triggered manually by the vehicle operation or may be synchronized with actuation of the lock pin assembly  152  by control electronics in the vehicle  12 .  
         [0044]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.