Abstract:
An apparatus is disclosed for connecting a drive wheel axle and a track roller frame in a tracked vehicle. The apparatus includes an arm portion for attachment to the track roller frame; a yoke comprising a pivotal connection to the arm portion about a first pivot axis; a bearing housing comprising a pivotal connection to the yoke about a second pivot axis; a bearing assembly disposed adjacent the bearing housing; and a collet separated from the bearing housing by the bearing assembly, wherein the collet is configured for affixation to the drive wheel axle. A method is disclosed for accommodating forces in a vehicle on a drive wheel axle transmitted through a track roller frame, the method including providing an apparatus connecting the drive wheel axle and the track roller frame. The method further includes pivoting portions of the apparatus relative to each other about first and second pivot axes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase application of international patent application number PCT/US2013/076089, filed Dec. 18, 2013, which claims priority to U.S. provisional application Ser. No. 61/740,693, filed Dec. 21, 2012. The full disclosures, in their entireties, of international patent application number PCT/US2013/076089 and U.S. provisional application Ser. No. 61/740,693 are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to connecting a drive wheel axle and a track roller frame on a vehicle, and more particularly to accommodating forces in a drive wheel axle transmitted through a track roller frame. 
     2. Description of Related Art 
     A tractor for agricultural use can have wheels or tracks in contact with the ground surface. A cultivator is one agricultural implement that is often pulled by a tracked tractor, which has an advantage in a planted field over a wheeled tractor of having its weight more evenly distributed on the ground surface. A tracked tractor generally has two track assemblies, one on each of the left and right sides of the tractor. A track assembly typically includes a rubber track that forms a loop around a drive wheel, a number of mid-rollers, and an idler wheel. During use of the tractor, the drive wheel rotates and engages the rubber track, thereby causing the rubber track to rotate around a path defined by the drive wheel and the idler wheel. The rotation of the rubber track causes it to engage the ground, thereby propelling the tractor on the ground surface of the crop field. 
     A drive wheel of the tractor is rotatably attached to the drive wheel axle. Typically, the drive wheel axle has no freedom of movement other than the rotational motion provided by gears of a power train. However, in some tractor models, the track roller frame between a drive wheel and a corresponding idler wheel slightly twists and shifts from side to side in use as the tractor travels, especially over uneven terrain. Accordingly, there is a need for a structure for connecting the drive wheel axle and the track roller frame that has an ability to absorb or oppose the load caused by the positional misalignments between the drive wheel axle and the track roller frame. 
     OVERVIEW OF THE INVENTION 
     In one embodiment, the invention is directed to an apparatus for connecting a drive wheel axle and a track roller frame in a tracked vehicle. The apparatus comprises an arm portion for attachment to the track roller frame; a yoke comprising a pivotal connection to the arm portion about a first pivot axis; a bearing housing comprising a pivotal connection to the yoke about a second pivot axis; a bearing assembly disposed adjacent the bearing housing; and a collet separated from the bearing housing by the bearing assembly, wherein the collet is configured for affixation to the drive wheel axle. 
     In another aspect, a method is disclosed for accommodating forces in a vehicle on a drive wheel axle transmitted through a track roller frame, the method comprising providing an apparatus connecting the drive wheel axle and the track roller frame. The method further comprises pivoting a second portion of the apparatus relative to a first portion of the apparatus about a first pivot axis, wherein the first portion of the apparatus is connected to the track roller frame. Moreover, the method comprises pivoting a third portion of the apparatus relative to the second portion of the apparatus about a second pivot axis, wherein the third portion of the apparatus is connected to the drive wheel axle. 
     These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of the front frame, power train, and track assemblies of a tracked tractor embodying an exemplary embodiment of a multi-axis reaction arm of the present disclosure; 
         FIG. 2  is a top view of the parts of a tracked tractor of  FIG. 1 ; 
         FIG. 3  is a perspective view of the left track assembly of  FIG. 1 , with the outer idler wheel and the outer drive wheel removed; 
         FIG. 4  is a perspective view of an exemplary embodiment of a multi-axis reaction arm of the present disclosure; 
         FIG. 5  is a top view of the reaction arm of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of the reaction arm of  FIGS. 4 and 5 , taken along the line  6 - 6  of  FIG. 5 ; and 
         FIG. 7  is a cross-sectional view of the reaction arm of  FIGS. 4-6 , taken along the line  7 - 7  of  FIG. 5 . 
         FIG. 8  is a cross-sectional view of the reaction arm of  FIGS. 4-6 , taken along the line  8 - 8  of  FIG. 4 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the views of the drawings. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description. 
       FIG. 1  is a perspective view and  FIG. 2  is a top plan view of the front frame  10 , power train  12 , and track assemblies  14  of a tracked tractor embodying an exemplary embodiment of a multi-axis reaction arm of the present disclosure. Many of the illustrated components may be found in the commercially available Challenger MT765D tracked tractor, available from AGCO Corporation of Duluth, Ga. However, the Challenger MT765D tractor does not include a reaction arm as described in this disclosure. 
     The illustrated tracked tractor generally has two track assemblies  14 , one on each of the left and right sides of the tractor. A track assembly  14  typically includes a rubber track  16  that forms a loop around a drive wheel  18 , a number of mid-rollers  20  and an idler wheel  22 . During use of the tractor, drive wheel  18  rotates and engages rubber track  16 , thereby causing the rubber track  16  to rotate around a path defined by drive wheel  18  and idler wheel  22 . The rotation of rubber track  16  causes it to engage the ground, thereby propelling the tractor over the ground surface. 
     Both drive wheels  18  of the tractor are rotatably attached to the common drive wheel axle  24  extending from a transmission casing  25  of power train  12 ; drive wheel axle  24  has no freedom of movement relative to transmission casing  25  other than this rotational motion. Hard bar  26  passes through both track assemblies  14  and oscillates within front frame  10 , thereby providing a suspension function by allowing the undercarriage to move up and down relative to front frame  10 . Each drive wheel  18  comprises an inner drive wheel  18   a  and an outer drive wheel  18   b,  with guide blocks  28  (visible in  FIG. 3 ) of track  16  disposed between inner drive wheel  18   a  and an outer drive wheel  18   b.  Similarly, each idler wheel  22  comprises an inner idler wheel  22   a  and an outer idler wheel  22   b,  with guide blocks  28  of track  16  disposed between inner idler wheel  22   a  and an outer idler wheel  22   b.  Accordingly, guide blocks  28  prevent track  16  from sliding sideways off of the wheels  18 ,  22  and mid-rollers  20  of its respective track assembly  14 . The inner and outer wheel configurations effectively capture guide blocks  28  between them, thereby retaining each track  16  on its respective drive wheel  18  and idler wheel  22  as the tractor moves. 
       FIG. 3  is a perspective view of the left track assembly  14  of  FIG. 1 , with the outer drive wheel  18   b  and the outer idler wheel  22   b  removed. While this discussion will focus on the illustrated left track assembly  14 , it is to be understood that the concepts described herein equally apply to the right track assembly  14 . For proper operation, it is desirable that track  16  be tensioned tautly on its path around drive wheel  18  and idler wheel  22 . In the illustrated tractor, this goal is accomplished with the use of tensioner  30 . A bottom portion  40  of tensioner  30  is attached to track roller frame  42 . A left side of tensioner includes hydraulic cylinder  32 , which may lengthen and shorten, as known in the art. An end of cylinder  32  is pivotally connected to swing link  34 , which carries front hub  36  onto which idler wheel  22  is mounted. As cylinder  32  lengthens, it moves swing link  34 , which in turn moves front hub  36  forward. As a result, a distance between idler wheel  22  and drive wheel  18  increases, thereby tightening track  16  on its path around idler wheel  22  and drive wheel  18 . If track  16  is too tight, cylinder  32  is shortened to decrease the distance between idler wheel  22  and drive wheel  18 , thereby loosening track  16  on its path around idler wheel  22  and drive wheel  18 . 
     Mid-rollers  20  help to support the weight of the tractor. A mid-roller  20  is connected by a pivot joint  44  to track roller frame  42 . Pivot joints  44  allow mid-rollers  20  to oscillate up and down and serve a suspension function. Hard bar  26  (shown in  FIGS. 1 and 2 ) is held by bracket  46  of track roller frame  42  and is also connected to front frame  10  (as shown in  FIG. 2 ). Hard bar  26  passes through both track assemblies  14  and oscillates within front frame  10 , thereby providing a suspension function by allowing the undercarriage to move up and down relative to front frame  10 . As hard bar  26  moves, track roller frame  42  moves along with it. Thus, track roller frame  42  is allowed to slightly twist and shift from side to side in use as the tractor travels over uneven terrain. However, no oscillating or up/down movement is accommodated at drive wheel axle  24 . Accordingly, a multi-axis reaction arm  50  of the present disclosure is provided between track roller frame  42  and drive wheel axle  24  to take up the load forces created by the movement of track roller frame  42  relative to drive wheel axle  24  (such load forces typically being created by the tractor traversing uneven terrain). 
       FIG. 4  is a perspective view of an exemplary embodiment of the multi-axis reaction arm  50  of the present disclosure.  FIG. 5  is a top view of reaction arm of  50 .  FIG. 6  is a cross-sectional view of reaction arm  50 , taken along the line  6 - 6  of  FIG. 5 .  FIG. 7  is a cross-sectional view of reaction arm  50 , taken along the line  7 - 7  of  FIG. 4 . Reaction arm  50  comprises arm portion  52 , yoke  54 , bearing housing  56  (see  FIGS. 5-7 ), bearing assembly  58 , collet  60  and drive wheel hubs  72 . Arm portion  52  is mounted by fasteners (not shown) via flange  62  to track roller frame  42  (such as shown in assembled form, e.g., in  FIG. 3 ). On the opposite end of reaction arm  50 , collet  60  is secured by fasteners, such as bolts, to drive wheel axle  24  (again, as illustrated, for example, in  FIG. 3 ). Thus, collet  60  rotates with drive wheel axle  24 . Inner and outer drive wheels  18   a,    18   b  are fastened, such as by bolts, to drive wheel hubs  72  (see again, e.g.,  FIG. 3 ). In an exemplary embodiment, drive wheel hubs  72  are fixed to collet  60 , such as by integral formation or by fasteners, so that drive wheel hubs  72  rotate with drive wheel axle  24 . As shown in  FIG. 7 , bearing assembly  58  is disposed between collet  60  and bearing housing  56  to allow bearing housing  56  to remain relatively stationary even while collet  60  rotates with drive wheel axle  24 . Moreover, bearing assembly  58  extends between drive wheel hubs  72  and bearing housing  56  to allow bearing housing  56  to remain relatively stationary even while drive wheel hubs  72  rotate with drive wheel axle  24 . In an exemplary embodiment, bearing assembly  58  comprises a plurality of roller bearings  59 . 
     Referring to  FIGS. 6 and 7 , bearing housing  56  is connected by pins  64  to yoke  54  in a manner that allows bearing housing  56  to pivot about pivot axis  66 , which is substantially vertical when the tractor is disposed upright on a substantially horizontal ground surface. In an exemplary embodiment, pivot axis  66  corresponds to a longitudinal axis of pins  64 . Thrust washers  74  are disposed between bearing housing  56  and yoke  54  and around pins  64 . Thrust washers  74  are used to control vertical axial forces from the tractor&#39;s weight. A thrust washer is a type of bearing that provides a bearing surface for forces acting axial to the corresponding pin  64 . Yoke  54  is connected by shaft  68  to arm portion  52  in a manner that allows yoke  54  to pivot about pivot axis  70 , which is substantially horizontal when the tractor is disposed upright on a substantially horizontal ground surface. In an exemplary embodiment, pivot axis  70  corresponds to a longitudinal axis of shaft  68 . In an exemplary embodiment, the two pivot axes  66 ,  70  are substantially orthogonal to each other. 
     Thus, the present disclosure describes a multi-axis reaction arm  50  that is able to resolve both the horizontal force from the track tension (the direction of which is illustrated by arrow  76  in  FIGS. 5, 6 and 8 ) and the vertical force from the weight of the tractor (the direction of which is illustrated by arrow  78  in  FIGS. 6 and 7 ). This is accomplished by attaching drive wheel hubs  72  and drive wheel axle  24  to track roller frame  42  in a manner that allows track roller frame  42  to pivot about both horizontal pivot axis  70  and vertical pivot axis  66 . Thus, all twisting and side-to-side motions of track roller frame  42  relative to drive wheel hubs  72  and drive wheel axle  24  are accommodated by the two degrees of freedom provided by multi-axis reaction arm  50 . 
     The foregoing has broadly outlined some of the more pertinent aspects and features of the present invention. These should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be obtained by applying the disclosed information in a different manner or by modifying the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings.