Abstract:
A motor grader with an adjustable wheelbase. The motor grader may include front and rear wheels supporting a chassis and a main frame. A working blade may downwardly depend from the main frame between the front wheels and rear wheels to perform work on the ground below. The motor grader may also provide an adjustable wheel base to allow the center of gravity of the motor grader to better match the work load being addressed. The adjustable wheel base may also provide more swing clearance for the blade relative to the rear wheels, allow for an adjustable articulation angle, and minimize structural loads on the motor grader, particularly during ripping operation. The wheel base may be adjustable by providing structure through which the relative positions of the rear wheels can be altered automatically, manually, and dynamically.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a non-provisional application claiming priority under 35 USC §119 (e) to U.S. Provisional Application Ser. No. 61/258,897 filed on Nov. 6, 2009. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to construction vehicles and, more particularly, relates to motor graders. 
     BACKGROUND 
     Motor graders are common vehicles used in, among other things, road construction and maintenance for displacing, distributing, and leveling material such as soil, gravel, snow, and the like. Such machines typically include front and rear wheels with a relatively high main frame connecting the two. A work blade downwardly depends from the main frame. When in use the blade can be lowered so as to contact the ground below and when the vehicle moves forward, the material on the ground is pushed forward by the blade. The blade is also rotatable so as to displace more or less material as is desired for the given job. 
     With some motor graders, the rear of the vehicle is provided with tandem rear drives such that the overall machine has six wheels. Tandem rear drives provide the motor grader with additional power, traction and stability. Another feature common on motor graders is the attachment of a ripper tool on the rear of the vehicle. Such tools have a plurality of downwardly directed tines or claws which penetrate and drag along the ground when the vehicle moves forward. Ripper attachments are useful for breaking the top surface of the ground, be it compacted soil, turf, gravel or pavement. Once ripped, the ground can then be graded with the aforementioned blade. 
     While such machines are very useful and have been met with substantial commercial success since their introduction, improvements continue to be sought. For example, it would be advantageous to provide a motor grader with an adjustable center of gravity. One instance where this would be desirable would be when using the ripper attachment. As such a tool is placed behind the vehicle and creates a significant downward drag, it would be beneficial to have a vehicle with a center of gravity positionable to best address that load. 
     In addition, in certain operations it may be desirable to operate the grader with the blade rotated at an aggressive angle, i.e., up to being practically parallel with the longitudinal axis of the grader. However, with current technology this may inadvertently result in tire or wheel damage if the blade is rotated into engagement with the rear tandem wheel. 
     In still further instances, the motor grader might be tasked with grading the surface in question down to a tenth of an inch or less. For example, if finish grading a road surface just prior to application of concrete or asphalt, every deviation from that tolerance will result in additional concrete or asphalt being required, thereby increasing the cost of the job. With current graders, no ability exists to adjust the wheel base and thus if a surface to be graded is particularly uneven, this will result in a limited ability to meet that tolerance as the movement of one wheel due to an obstruction or the like on the surface to be graded will result in vertical displacement of the grader and blade. Alternatively, the grader will have to make multiple passes to meet the tolerance, also resulting in additional cost. 
     Finally, the main frame of a typical grader is able to turn or articulate with respect to the chassis or rear of the grader. As currently available graders have a wheel base of fixed length, the articulation angle and turning radius of the grader are also fixed. However, in certain situations it may be desirable to have an adjustable articulation angle. One example would be when grading a surface provided at an incline to the roadway such as a berm, culvert, ditch or the like. In such situations, the rear wheels of the grader may be on a flat level surface with the front wheel, main frame and blade articulated away from the rear wheels so as to be over the inclined surface being graded. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the disclosure, a motor grader is disclosed which comprises a chassis, a main frame extending from the chassis, a blade extending downwardly from the main frame, front wheels supporting the main frame, an engine supported by the chassis, and rear wheels supporting the chassis, the rear wheels having an adjustable position relative to a longitudinal axis of the chassis. 
     In accordance with another aspect of the disclosure, a method of operating a motor grader is disclosed, which comprises providing wheels on the motor grader with adjustable positions relative to a longitudinal axis of the motor grader, and moving the wheels to adjust a wheel base of the motor grader. 
     In accordance with a still further aspect of the disclosure, a motor grader is disclosed which comprises a main frame, a blade extending downwardly from the frame, and front and rear wheels mounted relative to the frame and each supporting a percentage of the overall weight of the motor grader, the percentage of weight being supported by each wheel being adjustable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of one embodiment of a motor grader constructed in accordance with the teachings of this disclosure; 
         FIG. 2  is a side elevational view similar to  FIG. 1 , but with the rear axles moved rearward; 
         FIG. 3  is a top schematic view of a motor grader constructed in accordance with the teachings of the disclosure; 
         FIG. 4  is a side elevational view similar to  FIG. 1 , but with the rear axles moved apart; 
         FIG. 5  is a side elevational view similar to  FIG. 1 , but with a V-blade attachment; 
         FIG. 6  is a schematic representation of a hydraulic embodiment for moving the axles; 
         FIG. 7  is a schematic representation of a rack &amp; pinion embodiment for moving the axles; 
         FIG. 8  is a schematic representation of a linear actuator embodiment for moving the axles; 
         FIG. 9  is a schematic representation of an operator interface and control system according to one embodiment of the present disclosure; and 
         FIG. 10  an isometric view of a chassis of a grader constructed in accordance with the teachings of this disclosure and showing a mounting plate with a plurality of mounting locations for manual positioning of the grader wheels. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and with specific reference to  FIG. 1 , a motor grader constructed in accordance with the present disclosure is generally referred to by reference numeral  100 . The motor grader  100  may include a chassis  102  from which forwardly extends a main frame  104 . A forward end  106  of the main frame  104  may be supported by front wheels  108 ,  110 . The chassis  102  may be supported by a tandem drive  112  including a first set of rear wheels  114 ,  116 , and a second set of rear wheels  118  and  120 , as shown best in  FIG. 3 . In alternative embodiments only a single set of rear wheel wheels may be provided, however, with a tandem drive system all four rear wheels are powered. The chassis  102  may support an engine  122  and an operator cab  124  as one of ordinary skill in the art will readily understand. 
     Each of the wheels  114 ,  116 ,  118  and  120  may be powered by a hydrostatic (Hystat) transmission  126 . In such an arrangement, as shown schematically in  FIG. 8 , the engine  122  powers a hydraulic pump  128 . Pressurized hydraulic fluid from the pump  128  is then communicated by suitable hoses  130  to one or more hydrostatic motors  132  to drive same. A rotating shaft  134  extending from the motor  132  is then connected directly to one of the wheels  114 ,  116 ,  118 ,  120  by way of a final drive  136  or the like. A separate motor  132  may be provided for each wheel  114 ,  116 ,  118 ,  120 , or through suitable couplings such as chains and sprockets one motor  132  could be used to power more than one wheel  114 ,  116 ,  118 ,  120 . 
     In any event, by using such a hydrostatic transmission  126 , the wheels and associated motors can be more easily moved compared to conventional mechanical drive shaft arrangements in that the engine  122  and pump  128  can stay fixed, and the motor(s)  132  and associated wheel(s)  114 ,  116 ,  118 ,  120  can move using one of the structural arrangements described later herein, with the flexible hoses  130  being provided with sufficient lengths to accommodate such changes in position. In other embodiments, the wheels  114 ,  116 ,  118 ,  120  may be mechanically driven by other mechanisms including, but not limited to, a driveshaft connecting the engine to axles extending between laterally mounted pairs of wheels, chains and sprockets, electric drives and motors, and other systems known to those of ordinary skill in the art. 
     Referring again to  FIG. 1 , rearward of the engine  122 , a ripper attachment  138  may be coupled to the motor grader  100 . The ripper attachment  138  may include a plurality of downwardly directed tines or claws  140  extending from a frame  142 , as well as a hydraulic cylinder  144  for raising and lowering the ripper attachment  138 . When lowered, the tines  140  engage ground  146  such that when the motor grader  100  moves forward the ground  146  is displaced. As used herein, the ripper attachment  138  may also be interpreted to include a scarifier, which is basically a lighter weight ripper typically mounted in front of the blade. Both rippers and scarifiers can have a variable number of tines. 
     Downwardly depending from the main frame  104  is a work blade  148 . The work blade  148  may be mounted on a drawbar-circle-moldboard (DCM)  150 . The DCM  150  may include a drawbar  152  connected to a circle  154 . The circle  154  may include a set of circular gear teeth (not shown) for allowing rotation of the blade  148 . In other embodiments, different mechanical or hydraulic arrangements can be provided to allow for rotation of the blade  148 , while in still other embodiments, specialized tools other than a blade  148  may be mounted on the DCM  150 . Hydraulic cylinders  156  may also be provided to raise and lower the DCM  150  and blade  148  as a whole. 
     Referring now to  FIG. 2 , it will be seen to be very similar to  FIG. 1 , but for the positions of the rear wheels  114 ,  116 ,  118 ,  120  relative to a longitudinal axis  158  of the motor grader  100 . As shown, all wheels  114 ,  116 ,  118 ,  120  have been moved rearward. By moving the rear wheels  114 ,  116 ,  118 ,  120  rearward this alters the center of gravity of the motor grader  100 . For example, with typical motor graders currently on the market the weight distribution on the front and rear wheels is typically 30/70, i.e., 30% on the front wheels and 70% on the rear wheels. However, by moving the wheels  114 ,  116 ,  118 ,  120  rearward this ratio can be changed to a 20/80 distribution or more. Similarly, while not depicted, the rear wheels  114 ,  116 ,  118 ,  120  can all be moved forward of their position in  FIG. 1 , to thus place the weight distribution more toward a 40/60 split or less. In other embodiments, the rear wheels  114 ,  116 ,  118 ,  120  can all be moved to create an even wider range of load distributions on the front and rear wheels. The percentage of grader weight A supported by the front wheels could range anywhere from 10 to 90 percent, and the percentage of grader weight B supported by the rear wheels could range anywhere from 90 to 10 percent as well. As a frame of reference, typical motor graders manufactured by the present assignee have overall gross weights (A plus B) of between 30,000 and 50,000 pounds. 
     One application where rearward movement may be advantageous is when using the ripper attachment  138 . To reduce mechanical stress on the chassis  102 , the wheel wheels  114 ,  116 ,  118 ,  120  may all be moved rearward and thus closer to the ripper attachment  138 . This has the effect of shortening the lever arm between rear wheels  114 ,  116 ,  118 ,  120  and the ripper attachment  138 . Not only does this reduce the stress in the chassis  102 , but it also reduces the downward moment created by the ripper attachment  138  and thus makes the motor grader  100  more stable. This is a significant improvement over prior art motor graders having the fixed 30/70 split mentioned above in that such motor graders often need to attach large counterweights to the front of the motor grader in order to offset the downward moment created when the ripper attachment  138  is in use. By having movable wheels, the need for as much or any counterweight can be reduced. In so doing, not only is the manufacturing cost of the motor grader reduced, but so is its operating cost in that the motor grader can operate with less weight and thus better fuel economy. 
     Moving the rear wheels  114 ,  116 ,  118 ,  120  may also allow the work blade  148  to have a greater swing clearance with respect to the chassis  102  and particularly with respect to the forewardmost rear wheels  114  and  116 . For example, as shown in  FIG. 3 , if the blade  148  is operated at a particularly aggressive angle  160 , such as up to being almost parallel to a longitudinal axis  158  of the grader  100 , the rear wheels  114 ,  116  can be moved rearward to allow such movement and avoid damage to the tires on the wheels  114  and  116 . This also is a significant improvement over prior art motor graders which either can not operate the blade at such aggressive angles or can only do so at the risk of damaging the rear tires on the motor grader. 
     In the embodiment of  FIG. 4 , it can be seen that the rear wheels  114 ,  116 ,  118 ,  120  have been moved apart, with wheels  114  and  116  moving forward and wheels  118  and  120  moving rearward. With such an arrangement the weight distribution is more evenly spread over all the motor grader wheels. One application where this may be advantageous is when the work blade  148  is being tasked with finely grading a surface. For example, in certain situations such as when finish grading soil just prior to applying the top layer of asphalt or concrete, it may be desirable to grade the ground  146  down to a tight tolerance, e.g., down to a tenth of an inch or less. If the grading deviates from that, any lowered or raised surface will require additional concrete or asphalt to be added and thus raise the overall cost of the construction project. Alternatively, the grader  100  may be required to make multiple passes before reaching the desired tolerance, again adding to the cost of the project. With currently available graders, this is problematic in that any obstructions in, rocks on, or other significantly uneven portions of, the surface to be graded will cause the grader  100  as a whole to be vertically displaced and thus cause the blade  148  to move as well causing deviations from that desired tolerance. However, the present disclosure allows the wheels  108 ,  110 ,  114 ,  116 ,  118 ,  120  to be extended as far apart as possible along the longitudinal axis  158  to thereby lengthen the grader wheel base  162  and abate the effects of those obstructions in the surface  146  to be graded. 
     Referring now to  FIG. 5 , it can be seen to be very similar to  FIG. 1 , but for a V-blade attachment  164  on motor grader  100  for use in snow plowing applications. 
       FIGS. 6-8  set forth various arrangements for dynamically moving the wheels  114 ,  116 ,  118 , and  120 . As it would be desirable to be able to move the wheels on-the-fly in the field of use, mechanical structure may be provided to allow for such dynamic change in a safe and repeatable manner. In the first arrangement of  FIG. 6 , it can be seen that in the case of the rear wheels  114 ,  116 ,  118 , and  120 , a hydraulic cylinder  168  can be attached between the chassis  102  and each of the wheels  114 ,  116 ,  118 , and  120 . The hydraulic cylinder  168  may be fluidically connected to the hydraulic pump  128  powered by the engine  122 . When it is desired to move the wheels fore or aft along the longitudinal axis  158 , the cylinder  168  can be engaged. Rails  170  can be mounted on the chassis  102  with corresponding slider joints  172  on the motor shafts  134  or final drives  136  to allow for such motion. 
     Similarly, with the embodiment of  FIG. 7 , a rack and pinion arrangement can be provided. A rack  174  can be mounted on the chassis  102 , with pinions  176  being rotatably associated with each of the wheels  114 ,  116 ,  118 , and  120 . A drive gear or shaft or similar mechanical transmissions components  128  can be connected between the engine  122  and pinions  176  to provide for the power needed to move the wheels  114 ,  116 ,  188 , and  120 . 
     The embodiment of  FIG. 78  provides a linear actuator  180  to move the wheels  114 ,  116 ,  118 , and  120 . Other arrangements for dynamically moving the wheels  114 ,  116 ,  118 , and  120  will also be apparent to one of ordinary skill in the art and are encompassed by the scope of this disclosure. 
     With any of the aforementioned systems, the motor grader  100  can move the wheels  114 ,  116 ,  118 , and  120  on-the-fly. As shown in  FIG. 9 , this feature can be incorporated into an operator interface  182  provided in the cab  124 . The operator interface  182  may include a display  184  and be electronically coupled to a processor  186  and memory  188 . The display  184  may include individual controls or switches for selecting various modes of operation. A manual control  190  may be used if the operator wishes to manually select the positioning of the wheels. A pre-set configuration control  192  may be used if the operator wishes to select one or more default settings programmed into the memory  188 . For example, one setting may be for “RIPPING” in which case the rear wheels  114 ,  116 ,  118  and  120  may be moved rearward as indicated above. Another setting may be for “SNOW-PLOWING” wherein the wheels  114 ,  116 ,  118 , and  120  may be moved forward. 
     Another mode may be accessed with automatic control  194 . In such a mode, the longitudinal positioning of the wheels may be adjusted according to feedback received from sensors  196  operatively associated with each wheel. As shown in  FIG. 9 , the sensors  196 , which may be load sensors or other types of sensors, may provide a closed loop feedback system to the operator interface  182 . The operator interface  182  can then direct the hydraulic cylinders  168  (or the rack  174  &amp; pinion  176 , linear actuator  180 , or other arrangement as the case may be) to move the wheels  114 ,  116 ,  118 , and  120  to best balance the loads on each given the operating conditions and task being performed. 
     In addition to the above examples, one application where this may be particularly advantageous is when the motor grader  100  is being operated at speeds having known harmonic difficulties. More specifically, in current motor graders, resonance is commonly reached at certain speeds of operation, such as six or twelve miles per hour. At such speeds, the resulting harmonics cause the motor grader to bounce, thus disturbing the operator and detrimentally affecting the task being performed. However, in the automatic mode disclosed above, this disturbance could be sensed by providing the sensors  196  in the form of speed sensors, vibration sensors, frequency sensors, or the like and then feeding the sensed data back to the operator interface  182 . The operator interface  182  could then automatically adjust the relative longitudinal positions of the wheels to dampen such vibrations. 
     In addition, the relative positions of the rear wheels  114 ,  116 ,  118 ,  120  may also be automatically adjusted based on a sensed position of the ripper attachment. For example, as the ripper attachment is lowered beyond a predetermined position as determined by a position sensor  196  or the like, the rear wheels  114 ,  116 ,  118 ,  120  may automatically be moved rearward to a location that better supports a ripping operation. Then, as the ripper is returned to a stowed position, the rear wheels may be automatically returned to a previous or default position. 
       FIG. 10  provides an additional embodiment wherein the wheels  114 ,  116 ,  118 , and  120  can be moved manually. In such embodiments, a mounting plate  198  can be provided with a plurality of mounting locations defined by mounting holes  200 . By moving the desired wheel and associated drive shaft  134  and final drive  136 , the overall wheel base  162  of the grader  100  can be manually altered as well. Again this points out one of the advantages afforded by having the wheels powered by a hydrostatic transmission in that the engine  122  and hydraulic pump  128  can stay fixed in position, with the hydraulic hoses  130  accommodating movement of the motors  132 , drive shafts  134 , final drives  136  and wheels  114 ,  116 ,  118 , and  120 . 
     Through all of the above embodiments, it can be seen that a wheel base  162  of the motor grader  100  is alterable. In addition, depending on the direction of movement of the wheels  114 ,  116 ,  118 , and  120 , the turning radius or articulation angle  166  of the motor grader  100  are able to be increased or decreased as needed. Finally, also depending on the direction of movement, blade clearance  160  and the ability of the grader  100  to finely grade are modifiable as well. 
     INDUSTRIAL APPLICABILITY 
     The technology disclosed herein has industrial applicability in a variety of settings such as, but not limited to, changing the center of gravity or wheel base of a motor grader. If a shorter turning radius is desired, the wheels of the motor grader can simply be moved closer together. If a ripper attachment is being used on the rear of the grader, the rear wheels can be moved rearward to reduce stress in the chassis of the motor grader, increase stability, and lessen the need for counterweights on the front of the grader. Conversely, if a snow plow is being implemented on the front of the grader, the wheels can be moved forward to distribute more weight to the front of the grader and thus greater downward force on the snowplow. Depending on the material or terrain being graded or pitch or incline of the ground it may be advantageous to adjust the wheel base as well. 
     In addition, given the tolerances currently expected with finish grading, the present disclosure can allow for maximum lengthening of the wheel base along a longitudinal axis of the motor grader to thereby limit the vertical displacement of the blade when the grader rolls over an obstruction in the surface being graded. The wheel base can also be adjusted to dampen resonance harmonics typically resulting a certain speeds of operation. Finally, by moving the rear wheels rearward, the grader is able to allow the blade to be rotated to a very aggressive angle without damaging the rear wheels, chassis or tires. The present disclosure sets forth arrangements allowing the grader to do all of the above safely, repeatably, and dynamically.