Abstract:
The present invention provides a tag axle attachment for an off-road agricultural vehicle. The tag axle attachment allows agricultural vehicles to meet roadway weight restrictions imposed by the federal and state governments while also allowing the vehicle to perform optimally in the field. The tag axle is assembled such that it can be hydraulically lowered into a deployed position when the agricultural vehicle is on the roadway and hydraulically raised into a stowed position when the agricultural vehicle is in the field. The tag axle assembly is mounted to the chassis rails of an agricultural vehicle and positioned to fit between the chassis rails when stowed and minimizes the load per axle of the vehicle when deployed.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of agricultural vehicles, and more particularly, to a tag axle attachment for an off road agricultural applicator vehicle. 
     BACKGROUND 
     When operating agricultural vehicles on public roads, operators must abide by vehicle weight restrictions imposed by state and federal governments. Vehicle weight restrictions are government imposed to reduce damage to roadways caused by heavy vehicles and minimize fatal accidents. Most commonly, vehicle weight restrictions are measured in terms of load per axle and the overall spacing between axles. Thus, if the number of axles on the vehicle and the spacing thereof is increased, a given vehicle may carry more weight than would otherwise be permitted. 
     To satisfy vehicle weight restrictions, an agricultural vehicle can be made smaller to alleviate the weight per axle of the vehicle. This is not an adequate solution, however, because small agricultural vehicles fail to meet the needs of farmers operating the vehicles in the field. Another option is to add a permanent axle to the agricultural vehicle, which would distribute the weight of the vehicle to more axles and would in turn decrease the weight per axle of the vehicle. This is not a desirable solution because an additional permanent axle may impede the operation of the vehicle when in the field. A third option is to add an axle that can be deployed to engage the road only when necessary. This axle is commonly called a “tag axle.” A tag axle is an axle that can be deployed from a stowed position when necessary to distribute the weight of a vehicle over more axles thereby reducing the weight per axle of the vehicle. 
     Tag axles are commonly used on large commercial trucks, many of which often travel through many states, with each state having its own weight restrictions. Although tag axles are commonly used for large commercial trucks, they are not used for agricultural vehicles. Accordingly, there is a need in the art for a device that allows an agricultural vehicle to optimally operate both on the field and on roadways without exceeding weight restrictions. Unfortunately, conventional tag axles are not suitable for agricultural use due to incompatibility with agricultural vehicles and potential interference with the ground when used off-road. Therefore, there is a need for a tag axle that is compatible with agricultural vehicles yet also does not interfere with off-road operation. 
     BRIEF SUMMARY OF THE INVENTION 
     It is a primary objective of the present invention to provide a tag axle for an off-road agricultural vehicle. The tag axle enables agricultural vehicles to meet roadway weight restrictions imposed by the federal and state governments while also allowing the vehicle to optimally perform in the field. The tag axle is preferably provided such that it can be hydraulically lowered into an operational position when the agricultural vehicle is on a roadway and hydraulically raised into a stowed position when the agricultural vehicle is operating off-road. 
     The tag axle assembly can have one or more wheel assemblies depending on the weight and configuration of the agricultural vehicle. In some embodiments, the tag axle assembly can be used on, for example and not a limitation, three, four, or six wheeled agricultural vehicles. The tag axle can be centrally aligned with the rear axle, which allows for optimal operation of the agricultural vehicle when the tag axle is lowered to the operational position. The width of the tag axle is preferably narrow enough to fit between the chassis rails of the agricultural vehicle so that when the tag axle is stowed, it does not interfere with the operation, e.g., the ground clearance, of the agricultural vehicle in the field. When deployed in the operational position, the tag axle successfully decreases the agricultural vehicle&#39;s overall weight per axle. 
     These and other features as well as advantages, which characterize the various embodiments of the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-D  are illustrations of a tag axle, in accordance with an exemplary embodiment of the present invention, installed behind the rear axle and in between two chassis rails of the agricultural vehicle. 
         FIG. 2  is a left side sectional-view illustration with the rear axle removed of a tag axle, in accordance with an exemplary embodiment of the present invention, in the stowed position attached to the chassis rail by a mounting bracket. 
         FIG. 3  is an angled, aerial sectional-view illustration with the chassis rail and rear axle removed of a tag axle, in accordance with an exemplary embodiment of the present invention. 
         FIG. 4  is an angled, sectional aerial-view illustration of a tag axle, in accordance with an exemplary embodiment of the present invention, in the stowed position mounted to the chassis rail. 
         FIG. 5  is a left side sectional-view illustration of a tag axle, in accordance with an exemplary embodiment of the present invention, in both the stowed and deployed positions with the rear axle and rear wheel shown. 
         FIG. 6  is a front angled-view illustration of a tag axle, in accordance with an exemplary embodiment of the present invention, showing the valve block attached to the mounting bracket and two hydraulic accumulators, ACC 1  and ACC 2 . 
         FIG. 7  graphically shows the relationship between the tag axle hydraulic pressure and the weight of the agricultural vehicle applied to the front, rear, and tag axles. 
         FIG. 8  is a top-view illustration of Switch  1  and Switch  2 , which are used to power and disable, and raise and lower the tag axle, respectively, in accordance with an exemplary embodiment of the present invention. 
         FIGS. 9A-B  are illustrations of a tag axle, in accordance with an exemplary embodiment of the present invention, installed behind the rear axle and in between two chassis rails of the agricultural vehicle. 
         FIG. 10  is an angled, aerial sectional-view illustration with the chassis rail and rear axle removed of a tag axle, in accordance with an exemplary embodiment of the present invention. 
         FIG. 11  is an angled, sectional aerial-view illustration of a tag axle, in accordance with an exemplary embodiment of the present invention, in the stowed position mounted to the chassis rail. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, in which like numerals represent like elements, exemplary embodiments of the present invention are herein described. 
       FIGS. 1A-D  are illustrations of a tag axle  100 , in accordance with an exemplary embodiment of the present invention, installed behind the rear axle  102  and in between two chassis rails  101  of the agricultural vehicle. Those of skill in the art will appreciate that the vehicle shown is but one example of a suitable vehicle for use with the tag axle of the present invention. The tag axle  100  is preferably attached proximate to the rear of the chassis rails  101  by a mounting bracket. Moreover, the tag axle  100  is preferably centrally aligned with, and located behind, the rear axle  102 . In other words, the tag axle  100  is preferably located behind the rear axle  102  and in between the two rear wheels  104  located at proximate ends of the rear axle  102 . This preferred location allows the tag axle  100  to absorb some of the load from the rear axle  102  thereby reducing the overall weight per axle of the agricultural vehicle. In vehicles having an alternative chassis design, the tag axle may be positioned in alternate locations based on the desire to allow tag axle operation without significantly compromising ground clearance when in off-road environments. 
       FIGS. 2-5  further illustrate the tag axle  100 . More specifically,  FIG. 2  is a left side sectional-view illustration of a tag axle  100 , in accordance with an exemplary embodiment of the present invention, in the stowed position attached to the chassis rail  101  by a mounting bracket  202  with the rear axle  102  removed. The tag axle  100 , as illustrated in  FIG. 2 , includes a hydraulically actuated swing arm assembly  220 , an axle assembly  201 , preferably having at least one wheel  215 , a mounting bracket  202 , and two hydraulic cylinders  203  (only one is visible in  FIG. 2 ). The mounting bracket  202  has a first end  208  and a second end  209 . The first end  208  of the mounting bracket  202  is attached to the rear end of the chassis rails  101  of the agricultural vehicle. The mounting bracket  202  is preferably bolted to the chassis, but may be attached using alternate methods, such as by welding. The swing arm assembly  220  has a first end  204  and a second end  205 . The first end  204  of the swing arm assembly  220  is pivotally attached proximate to the second end  209  of the mounting bracket  202 . The second end  205  of the swing arm assembly  220  is pivotally attached to the axle assembly  201 . The hydraulic cylinders  203  also have a first end  206  and a second end  207 . The first end  206  of the hydraulic cylinder  203  is pivotally connected to the first end  208  of the mounting bracket  202 . The second end  207  of the hydraulic cylinder  203  is pivotally connected to the axle assembly  201  by way of the swing arm assembly  220 . The hydraulic cylinder  203  actuates the raising and the lowering of the swing arm assembly  220 , which in turn raises and lowers the axle assembly  201  to the stowed and deployed positions, respectively. Those skilled in the art will appreciate that there are different telescoping devices, aside from hydraulic cylinders, that can actuate raising and lowering of the swing arm assembly. For example, and not limitation, the telescoping device may be actuated by a hand crank or an electric motor. Although  FIG. 2  is a left side sectional-view illustration of the tag axle assembly  100 , those of skill in the art will appreciate that the right side of the tag axle assembly  100  is substantially similar to the left side. 
       FIG. 3  is an angled, aerial sectional-view illustration of a tag axle  100 , in accordance with an exemplary embodiment of the present invention, with the chassis rail  101  and rear axle  102  removed. The tag axle  100  can be attached to the chassis rails  101  of the agricultural vehicle by a mounting bracket  202 . The mounting bracket  202  is adapted to install and remove the tag axle  100  from the agricultural vehicle as desired. Further, to supply hydraulic pressure to the axle assembly  201 , hydraulic pressure and return plumbing lines  300  are attached. 
       FIG. 4  is an angled, sectional aerial-view illustration of a tag axle  100 , in accordance with an exemplary embodiment of the present invention, in the stowed position mounted to the chassis rails  101  of the agricultural vehicle. The width of the axle assembly  201  is preferably narrow enough so that it fits in between the two chassis rails  101  when in the stowed position. It is desirable for the axle assembly  201  to be stowed between the chassis rails  101  so that the axle assembly  201  does not interfere with the operation of the agricultural vehicle when traveling uphill, downhill, or over obstructions in the field. Alternatively, the axle assembly  201  may be stowed in another position that does not interfere with the operation of the vehicle, such as directly behind the rear wheels. 
       FIG. 5  is a left side sectional-view illustration of a tag axle  100 , in accordance with an exemplary embodiment of the present invention, in both the stowed and deployed positions with the rear axle  201  and rear wheel  104  shown. The raised axle assembly  201  is in the stowed position. The lowered axle assembly  201  is in the deployed position. As shown in  FIG. 5 , the axle assembly&#39;s  201  axis of rotation is aligned with the central axis of the agricultural vehicle. To transition the axle assembly  201  to the deployed position, the hydraulic cylinders  203  expand to actuate the swing arm assembly  220  which pivots towards the ground to facilitate the movement of the axle assembly  201  to the ground-engaging position. 
       FIG. 6  is a front angled-view illustration of a tag axle assembly  100 , in accordance with an exemplary embodiment of the present invention, showing the valve block  600  attached to the mounting bracket  202  and two hydraulic accumulators, ACC 1   601  and ACC 2   602 . Specifically, the valve block  600  is attached to the second end  209  of the mounting bracket  202 . The valve block  600  controls the amount of hydraulic pressure provided to the axle assembly  201 . Contained within the valve block  600  are two adjustable pressure valves, UP and RV 2  (not shown). Valve UP sets the axle assembly operating pressure and RV 2  is the main pressure relief valve for the axle assembly and is preferably set  300  psi higher than the UP pressure setting. Hydraulic pressure and return plumbing lines  300  (not shown) are connected to the valve block  600  from a common supply tank, which also may supply hydraulic oil to the vehicle steering and boom control valves. Those skilled in the art will appreciate that a common supply tank is not required and that a plurality of supply tanks can be used. Two hydraulic accumulators are mounted to the valve block  600  on ports ACC 1   601  and ACC 2   602 . Accumulator ACC 1   601  preferably stores energy when the axle assembly  201  is deployed and provides suspension capabilities for the axle assembly  201  so it can properly absorb bumps or small obstructions. In an alternate embodiment in which hydraulics are not used, a spring or shock absorber may be added to provide suspension capabilities. ACC 1   601  may be pre-charged to different pressures depending on the load of the axle assembly  201 . ACC 2   602  preferably stores energy when the axle assembly  201  is in the stowed position to prevent cycling of the UP valve. 
       FIG. 7  graphically shows the relationship between the tag axle hydraulic pressure and the weight of the agricultural vehicle applied to the front, rear, and tag axles. Because the axle assembly  201  is raised and lowered using hydraulic pressure, this graph shows the axle pressure and its affect on the front and rear axles, thereby indicating how far the axle assembly  201  should be lowered in order to effectively distribute the weight of the vehicle across axles and reduce the overall weight per axle of the vehicle. Those skilled in the art will appreciate that this graph is provided to illustrate loading off the various axles specific for an axle assembly  201  and associated vehicle. If the location of the axle assembly differs, the load weights are altered, or the axle assembly is raised and lowered by a different means, the graph may change. 
       FIG. 8  is a top-view illustration of Switch  1   800  and Switch  2   801 , which are used to power and disable, and raise and lower the tag axle assembly  100 , respectively, in accordance with an exemplary embodiment of the present invention. Operator actuation of the axle assembly  201  is controlled through the use of Switch  1   800  and Switch  2   801 , which are preferably mounted in the vehicle cab. Alternatively, those skilled in the art are aware of different ways, other than the use of operator switches, to power, disable, raise, and lower the axle assembly  201 . Switch  1   800  is preferably a momentary switch adapted to power and disable the axle assembly  201 . Switch  2   801  is preferably a 3-position switch adapted to raise and lower the axle assembly  201 . Switch  1   800  and Switch  2   801  are preferably connected by a harness to a power source within the cab relay panel (not shown). A second wire harness connects Switch  2   800  to two solenoids SV 1  and SV 2  (not shown), which are located on the valve block  600 . SV 1  controls the raise and lower functions of the axle assembly  201  and SV 2  controls the ability of hydraulic oil to flow in or out of the hydraulic cylinders  203 . As a safety mechanism, Switch  2   801  can be configured to be powered only when Switch  1   800  is in the “on” position. Hydraulic pressure to the tag axle assembly  100  when in the stowed or deployed position is maintained even if Switch  1   800  is turned off, thereby holding the axle assembly  201  in either the stowed or deployed position until the next cycling of Switch  1   800  and Switch  2   801 . 
     In yet another embodiment, shown in  FIGS. 9A and 9B  the tag axle assembly  900  may be installed on a four wheeled agricultural vehicle. In this embodiment, due to the increased number of wheels on the vehicle, it may be possible to use only one wheel assembly  910  on the tag axle assembly  900 . This can reduce manufacturing and maintenance costs and decrease the weight of the tag axle assembly  900 . 
       FIGS. 9A-B  are illustrations of a tag axle assembly  900 , in accordance with yet another exemplary embodiment of the present invention, installed behind the rear axle  902  and in between two chassis rails  901  of the agricultural vehicle. Those of skill in the art will appreciate that the vehicle shown is but one example of a suitable vehicle for use with the tag axle assembly  900  of the present invention. The tag axle assembly  900  is preferably attached proximate to the rear of the chassis rails  901  by a mounting bracket. Moreover, the tag axle assembly  900  is preferably centrally aligned with, and located behind, the rear axle  902 . In other words, the tag axle assembly  900  is preferably located behind the rear axle  902  and in between the two rear wheels  904  located at proximate ends of the rear axle  902  of the vehicle. This preferred location allows the tag axle assembly  900  to absorb some of the load from the rear axle  902  thereby reducing the overall weight per axle of the agricultural vehicle. In vehicles having an alternative chassis design, the tag axle assembly may be positioned in alternate locations selected based on the desire to allow tag axle operation without significantly compromising ground clearance when in off-road environments. 
       FIGS. 10-11  further illustrate the tag axle assembly  900 .  FIG. 10  is an angled, aerial sectional-view illustration of a tag axle assembly  900 , in accordance with an exemplary embodiment of the present invention, with the chassis rails  901  and rear axle  902  removed. The tag axle assembly  900  can be attached to the chassis rails  901  of the agricultural vehicle by a mounting bracket  1003 . The mounting bracket  1003  is adapted to install and remove the tag axle assembly  900  from the agricultural vehicle as desired. Further, to supply hydraulic pressure to the tag axle assembly  900 , hydraulic pressure and return plumbing lines  1004  are attached. 
       FIG. 11  is an angled, sectional aerial-view illustration of a tag axle assembly  900 , in accordance with an exemplary embodiment of the present invention, in the stowed position mounted to the chassis rails  901  of the agricultural vehicle. The width of the tag axle assembly  900  is preferably narrow enough so that it fits in between the two chassis rails  901  when in the stowed position. It is desirable for the tag axle assembly  900  to be stowed between the chassis rails  901  so that the tag axle assembly  900  does not interfere with the operation of the agricultural vehicle when traveling uphill, downhill, or over obstructions in the field. Alternatively, the tag axle assembly  900  may be stowed in another non-obstructing position, such as directly behind the rear wheels  904 . 
     While the various embodiments of this invention have been described in detail with particular reference to exemplary embodiments, those skilled in the art will understand that variations and modifications can be effected within the scope of the invention as defined in the appended claims. Accordingly, the scope of the various embodiments of the present invention should not be limited to the above discussed embodiments, and should only be defined by the following claims and all applicable equivalents. 
     For example, the use of the tag axle assembly  100 ,  900  is not limited to use on the particular agricultural vehicles shown. Also, the number of wheel assemblies  215 ,  910  used on the tag axle assembly  100 ,  900  can change and is dictated by, among other things, the weight of the vehicle, the number of wheels and axles on the vehicle, and local vehicle weight restrictions. In other words, the two wheeled tag axle assembly  100  is not limited to use on a three wheeled agricultural vehicle; and, the use of the one wheeled tag axle assembly  900  is not limited to use on a four wheeled agricultural vehicle. Nor is the present invention limited to at most two wheels. The embodiments pictured in the figures are illustrative only and should in no way be construed as a limitation on this invention.