Abstract:
A tread assembly has front and rear main idler wheels supported by a frame. A continuous tread is provided around the idler wheels for supporting a cart on a bottom portion of the tread between the front and rear main idler wheels. An assembly is provided to permit the front idler wheels to pivot laterally as the cart encounters uneven ground, in order to improve weight distribution across the tread and the idler wheels. The rear idler wheel also has an assembly to permit the rear idler wheel to pivot laterally. An alignment feature is incorporated into the front idler wheel assembly to permit adjustment of the alignment of the front idler wheel relative to the rear idler wheel. A tensioning mechanism is provided at the rear idler wheel to maintain the tread in tension. A pivot is provided between the frame and the rear idler wheel, and located forward from the hub of the idler wheel, such that increased load on the frame tends to push the idler wheel rearward to further tension the tread.

Description:
PRIORITY CLAIM  
       [0001]     This application is a continuation-in-part of U.S. Utility application Ser. No. 09/,847,264, filed on May 2, 2001, entitled “Agricultural Implement Frame and Cart,” the contents of which are incorporated herein by reference in their entirety. 
     
    
     FIELD  
       [0002]     The present invention relates to idler wheel assemblies for use with continuous tracks, such as might be found on agricultural carts. More particularly the present invention relates to front and rear idler wheel assemblies that permit the front and rear idler wheels to pivot transversely to the direction of travel of the continuous track, in order to permit the bottom tread portion of the track to match the contours of uneven ground and encourage equal weight distribution on the idler wheels, and to an idler wheel assembly that self adjusts the tension in the continuous track in response to increased loading.  
       BACKGROUND  
       [0003]     Vehicles that utilize continuous tracks, rather than wheels are well known. These continuous tracks have several advantages over wheels. Most notably, they spread the weight of the vehicle across a greater surface area than would be practical with wheels. These tracks are provided on track assemblies that include front and rear idler wheels around which the continuous track is provided. The frame is provided with some means to hold the front and rear idler wheels, in order to place the track in tension. As the vehicle is moved along the ground, the track translates with respect to the frame, and front and rear idler wheels are rotated. Intermediate idler wheels may be used to provide additional support to the bottom span of the track, which contacts the ground. Typically, two such track assemblies are provided, laterally spaced apart, to support a cart or other vehicle.  
         [0004]     As the cart moves across the ground, it commonly will encounter uneven areas. Typically the front and rear idler wheels are mounted to rotate in a fixed plane relative to the frame. Therefore, as the tread encounters irregularities, and especially irregularities across the width of the tread, a twisting force may result on the tread, which can result in uneven loading of the tread and the idler wheels. This problem has been partially solved by applicant&#39;s co-pending U.S. application Ser. No. 09/,847,264 by making the intermediate idler wheels pivotal in both longitudinal and lateral directions. However, the weight distribution could be further improved if the front and rear idler wheels were also designed to pivot laterally as the tread encounters uneven ground.  
         [0005]     One complicating factor with pivoting the front idler wheels involves the need to include an alignment feature that allows adjustment of the alignment of the front idler wheel relative to the rear idler wheel. In order to compensate for small variations in the treads and the frame, it is desirable to allow some adjustment of the plane in which the front idle wheel rotates relative to the frame in order to match the plane of the rear idler wheel in order to have them properly aligned during use. This means that a simple pivoting feature for the front idler wheel may not be sufficient in all cases.  
         [0006]     Another difficulty associated with rigidly mounted front and rear idler wheels is that because they do not pivot to match the contours of the land, the loading of the components is uneven. Therefore, the components, such as the frame, hub must be made stronger than would be required if the loading was shared equally. Therefore, the uneven loading of the parts leads to over engineering and increased costs. For example the tensioning device that holds the track in tension needs to handle a larger load if the loading of the components is not evenly distributed. That means that a larger capacity hydraulic shock must be used, or if air shocks are used, they must be inflated to a greater pressure than desired.  
         [0007]     In order to retain the track in place on the idler wheels it is necessary to keep the track in tension. As heavier loads are added, it is desirable to increase the tension in the track. This can be done manually to compensate for a heavy or light load as it is added. However, it would be desirable to have the tension self-adjust to some extent, and to adjust as the load applied to the frame changes during travel, as for example on encountering a bump.  
         [0008]     Therefore, a need exists to overcome one of more of the above-identified disadvantages of the current designs.  
       SUMMARY  
       [0009]     According to one embodiment of the invention a track assembly includes an elongated spindle tiltably connected to a frame to tilt from side to side. A first idler wheel is mounted on the spindle. A second idler wheel is operationally associated with the frame, and a continuous track is provided around the first and second idler wheels with a lower span between the first and second idler wheels forming a tread portion. The second idler wheel may also be mounted on a tiltable spindle. An alignment mechanism may be provided to selectively vary an alignment of the first idler wheel. The alignment mechanism can include an alignment bracket attached to the spindle at one end and an adjustment mechanism at the opposite end. The adjustment mechanism may be an eccentric bushing. A cart may be formed that includes two of the track assemblies.  
         [0010]     According to another embodiment of the invention a track assembly includes a frame having a first end and a second end. A first idler wheel is operably associated with the frame at the first end of the frame. A link is pivotally connected to the rear of the frame for pivoting in a generally vertical plane around a pivot member. An imaginary dividing plane is defined by extending the pivot axis of the pivot member vertically. A second idler wheel is operably provided on the link. A tensioning device maintains the axis of the second idler wheel on the opposite side of the imaginary dividing plane from the first idler wheel. A continuous track is provided around the first and second idler wheels with a lower span between the first and second idler wheels forming a tread portion. The idler wheels may be mounted on tiltable spindles to permit the idler wheels to tilt with tread portion as the track assembly is moved across uneven ground. A mechanism may be provided for varying the alignment of the first idler wheel. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]      FIG. 1  is a top plan view of a cart incorporating two track assemblies according to the present invention;  
         [0012]      FIG. 2  is a side view of an embodiment of a tread assembly according to the present invention;  
         [0013]      FIG. 3  is a partial side view of an embodiment of a front idler wheel assembly according to the present invention;  
         [0014]      FIG. 4  is a bottom view of the front idler wheel assembly of  FIG. 3 ;  
         [0015]      FIG. 5  is a front view of the front idler wheel assembly of  FIG. 3 ;  
         [0016]      FIG. 6  is a detail front view of an eccentric bushing according to one embodiment of the present invention;  
         [0017]      FIG. 7  is a partial side view of a rear idler wheel assembly according to one embodiment of the present invention;  
         [0018]      FIG. 8  is a top view of the rear idler wheel assembly of  FIG. 7 , with the tensioning member removed for illustration purposes;  
         [0019]      FIG. 9  is a bottom view of the rear idler wheel assembly of  FIG. 7  with the tensioning member removed for illustration purposes; and  
         [0020]      FIG. 10  is a rear view of the rear idler wheel assembly of  FIG. 7 , with broken lines indicating a tilted position for the spindles. 
     
    
     DETAILED DESCRIPTION  
       [0021]     The features and other details of the invention will now be more particularly described and pointed out in the claims. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principle features of this invention can be employed in various embodiments without departing from the scope of the invention.  
         [0022]      FIG. 1  is a top plan view of a cart  5  that is provided with a pair of track assemblies  10  mounted on a frame  18 . The inventive aspects of this disclosure relate to the track assemblies and the particular arrangement of the frame is not critical. The embodiments shown are intended to be pulled in a generally forward direction, but may also be pushed in reverse. It may also be possible to make the units self propelled by including a motor to drive the idler wheels.  
         [0023]     With reference to  FIG. 2 , a track assembly  10  is shown in a side elevation view. The track assembly  10  includes a frame  18 , front idler wheel  14 , and rear idler wheel  16 . The front and rear idler wheels are mounted on front and rear spindles  20  &amp;  22 . A continuous track  12  is wrapped round the idler wheels  14  &amp;  16  with a top span  13  and a bottom span  15  between the idler wheels  14  &amp;  16 . The bottom span  15 , forms a tread which provides a contact surface for engaging the ground. Is should be understood that typically (though not required) there will be two side-by-side front idler wheels and two side-by-side rear idler wheels, and the spindles  20 ,  22  will be double ended to support a pair of idler wheels. Alternatively, in place of the double ended spindle, a pair of opposing axially-aligned spindles could be used. Only one front idler wheel  14  and rear idler wheel  16  is shown in  FIG. 2 , in order to expose the construction of the track assembly  10 . The track may be provided with a ridge that rides between groove formed between each pair of idler wheels to help retain the track in place aligned with the idler wheels. The track assembly  10  may be incorporated into a cart for providing a tracked support for the cart. Typically, two such track assemblies  10  will be provided that are laterally spaced apart to support the cart.  
         [0024]     With further reference to  FIG. 2 , a front idler wheel assembly  100  is provided at a forward end of the frame  18 . The front idler wheel assembly  100  provides structure that allows the front idler wheel to pivot about a generally horizontal, longitudinal axis (roll axis) (not shown) so that as the tread  15  encounters irregularities, the front idler wheel  14  and track  12  can pivot to better match those contours. The front idler wheel assembly  100  also permits the angular alignment (yaw) of the front idler wheel  14  to be adjusted left or right (into or out of the page in  FIG. 2 ) with respect to the frame  18 , in order to be aligned properly with the rear idler wheel  16 .  
         [0025]     A side view of the front idler wheel assembly  100  is provided in  FIG. 3 . A bottom plan view of the front idler wheel assembly  100  is provided in  FIG. 4 . Starting at the right of  FIG. 3  (viewed from the opposite side as compared to  FIG. 2 ), the front idler wheel assembly  100  includes an eccentric bushing  32  mounted below the frame  18 . A front alignment shaft  30  is provided with a ball (not shown) that engages a ball socket  62  (not shown in  FIG. 2  or  3 , but see  FIG. 6 ), provided as part of the eccentric bushing  32 . A front alignment tube  28  is journalled around the alignment shaft  30 . An alignment bracket  26  is fixedly attached, as for example by welding, to the exterior of the front alignment tube. The alignment bracket  26  is fastened to the front spindle  20 . In the embodiment of  FIG. 2 , the alignment bracket is fastened to the front spindle  20  by wrapping around the front spindle  20  on each side of a centrally located housing  24 . The housing  24  contains a spherical bushing  76  (not shown in  FIG. 2 ) to which the front spindle  20  is attached. The spherical bushing contained in the housing  24  permits the front spindle  20  to pivot universally. The housing  24  is mounted, for example by a weldment, to an end plate  38  provided at the front end of the frame  18 . Braces  40  and  42  may be provided between the frame  18  and the housing  24  to provide additional support. A pair of stops  44  (only one is visible in  FIG. 2 ) are provided on the top of the attachment bracket  26 . These stops prevent the spindle  20  from pivoting too far, which can result in the idler wheels  14  rubbing against the frame  18 .  
         [0026]     The alignment feature of the front idler wheel assembly  100  is accomplished through the combination of the eccentric bushing  32 , the ball socket  62  in the eccentric bushing  32 , and the spherical busing in housing  24 . A detailed front view of the eccentric bushing  32  is provided in  FIG. 6 . The alignment of the front idler wheel  14  is accomplished by loosening the set screws  34 , and then rotating the rotating member  64  to adjust the position of the ball socket  62 . The set screws  34  are then retightened to retain the rotating member  64  in the second position. The knob  36 , provided on the back side of the rotating member  64  may be used to help turn the rotating member  64 . In the embodiment shown, the knob  36  is formed by a bolt head welded to the rotating member  64  so that a wrench, can be used to grasp the knob and make the adjustment.  FIG. 6  shows in broken lines a second position for the rotating member  64 , wherein the rotating member  64  has been rotated clockwise to move the ball socket  62 , and hence the rear end of alignment shaft  30  to the left. The front idler wheel  14  is thereby toed inward, if the front idler wheel assembly  100  is mounted on a left track assembly  10 , or, toed outward if the front idler wheel assembly is mounted to a right track assembly  10 . It should be understood that rather than a rotating eccentric bushing, any alternative structure could be used that permits selective sliding of the ball socket  62  from side to side.  
         [0027]     The side-to-side tilting of the spindle  22  is accomplished through the spherical bushing  66  within the housing  24 . This spherical bushing  66  permits the spindle  22  to tilt as the front idler wheels  14  attached to it are subjected to tilting forces through the tread  15  as the tread passes over uneven ground. The tilting of the spindle  22  causes a corresponding rotation of the alignment bracket  26 , which rotation is permitted because of the rotatable connection between the alignment tube  28  and the alignment shaft  30 . As best seen in  FIG. 5 , front tilt stops  44  on the top of the alignment bracket  26  bump up against the top plate  38  to prevent the spindle  20  and front idler wheels  14  from tilting too far. Typically these tilt stops  44  are set to limit the tilt to no more than 5 degrees of rotation for a wide track  12 , or as little as 1 degree for a narrow track  12 .  
         [0028]     Therefore, as with the front idler wheel assembly  100  discussed above, the rear idler wheel assembly  200  permits the rear idler wheels  16  to tilt along with the track  12 , when the tread  15  passes over uneven ground. As a result the weight of the cart remains evenly distributed across the entire width of the tread  15 , rather than being localized. This reduces stress on the tread  12  and spindles  20 ,  22 , and other components, and improves handling.  
         [0029]     The rear idler wheel assembly  200  is best seen in  FIG. 7 , which is a detail view of the rear portion of the track assembly  10  of  FIG. 2 . As seen in  FIG. 7 , a rear frame bracket  54  is fixedly attached at the rear of frame member  18 . A tension bracket  50  is pivotally attached to the frame bracket  54  by a pivot member  56 , such that the tension bracket  50  pivots about the pivot member  56  in a generally vertical plane. The tension bracket  50  has a pair of opposing faces  68  that are spaced apart. The rear spindle  22  is provided between the opposing faces, and a pivot bolt  52  is passed though both faces  68  and through a passageway in the rear spindle  22 , to pivotally connect the rear spindle to the tension bracket  50 . Rear stops  70  are provided to limit the amount of tilt that can be introduced to the rear spindle  22 . These rear stops  70  may take the form of plates provided between the opposing faces  68 , or any other device that will limit the amount the rear spindle  22  can pivot around the pivot bolt  52 .  
         [0030]     Additional views of the rear idler wheel assembly are shown in  FIGS. 8, 9 , and  10 .  FIG. 8  is top view of the rear idler wheel assembly, and  FIG. 9  is a bottom view with the tensioning device removed. The tensioning device shown in  FIG. 8  is an inflatable air shock. The tension provided can be adjusted by filling the bladder of the air shock to different pressure levels.  FIG. 10  is a rear view of the rear idler wheel assembly.  FIG. 10  illustrates the tilting feature of the spindles in broken lines.  
         [0031]     Intermediate idler wheels may be provided to provide additional support to the tread  15  portion of the track  12 . Preferably these idler wheels are of the form described in prior application U.S. Ser. No. 09/847,264, which has been fully incorporated by reference herein. In particular the tandem arm and idler wheels shown in  FIGS. 18, 19A ,  19 B,  22 , and  24  and the accompanying discussion are preferred. These intermediate idler wheels also match the tilt of the tread  15  to more evenly distribute the weight of the cart across the entire face of the tread  15  and among the idler wheels.  
         [0032]     A tensioning device  60 , such as an air shock, is provided between the bottom of the frame member  18  and a shock attachment bracket  70 . The shock attachment bracket is fixedly attached to the tension bracket  50 , and operable forms a part of the tension bracket  50 . If an air shock is used, the amount of tension provided to the track  12  can be adjusted by inflating and deflating the air shock. A tensioner base  50  may be provided on the bottom of frame member  18  for mounting one end of the tensioning device. The tensioning device  60  maintains the rear spindle  22  at an appropriate distance behind the frame member  18 .  
         [0033]     Importantly, the centerline of pivot member  56  is situated above and forwardly from the rear spindle  22 . An imaginary dividing plane  74  extending vertically above and below the pivot member can be used to determine whether the centerline of the rear spindle is behind the pivot member. Therefore, as greater load is applied downwardly to the frame  18  (as by a large payload), or upwardly to the spindle  22  (as by a jolt when passing over a bump), it tends to rotate the tension bracket  50  rearward, which adds tension to the track  12  by virtue of pulling the rear idler wheels  16  farther apart from the front idler wheels  14 . It should be noted that the tensioning structure described herein could be used on the front end of a track assembly as opposed to the rear end. Because of the tendency of the assembly  200  to automatically increase the tension in the tread  12  as additional load is added, it is not necessary to use as high a capacity tensioning device  60  as would otherwise be required. Therefore smaller hydraulic shocks may be used, or if an air shock is used, it need not be filled to as great a pressure as otherwise would be necessary.  
         [0034]     One of ordinary skill in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein, including those in the background, are expressly incorporated herein by reference in their entirety.