Abstract:
A castor wheel support for a towed agricultural implement. The castor support has a spindle for supporting a castor mounting structure for pivoting movement. The castor mounting structure includes an annular friction element received over the spindle and a plurality of C-shaped shims removable laterally without disassembly of the mounting structure to allow the pressure on the friction element to be set to minimize wobbling.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0001]    The present invention relates to agricultural implements, and, more specifically, to castor wheel assemblies used in such implements. 
       2. Description of the Related Art 
       [0002]    One of the widely used support systems for allowing ground movement at a precise elevation above the ground utilizes trailing wheels and front castor wheels. Towed tillage implements advantageously use this type of support system to more closely follow the ground contours. The trailing wheels (and the front castor wheels) are usually movable up and down so that the height of the implement frame above the ground may be controlled. Along with the trailing wheels, which have a fixed axis of rotation, there are usually a pair of forward castor wheels, widely used, so that the towed direction of the implement is followed by pivoting of the castor wheels. In addition to the field position, the rear wheels and the front castor wheels may be placed in a transport position in which the ground engaging elements of the tillage implement are elevated above the surface level of the soil. 
         [0003]    While the castor wheels allow a simplified way of following the direction of movement set by a tractor pulling the implement, they do experience, under operating conditions, an oscillation that is considered to be wobbling. A number of factors can contribute to the wobble and they include weight balance, internal friction, towing speed and trailing arm geometry. 
         [0004]    Because many of these factors are dynamic and not controlled necessarily by the machine operator, it has been proposed to include friction elements in the pivoting support for the castor wheel so as to inhibit wobbling. The friction elements, at first glance, offer a direct solution to the problem. However, the wear incurred by friction elements over time, decreases the inhibiting force and results in less effective damping of the wobble. It has been proposed to use spring loaded brake elements to offer a consistent friction force to inhibit the wobbling over an extended period of time. However, this approach introduces additional cost and complexity. Furthermore, the friction mechanisms maybe prone to accumulation of soil and other debris to diminish their effectiveness. 
         [0005]    Accordingly, what is needed in the art is a simplified way to introduce friction in a castor wheel assembly. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention seeks to provide a simplified way of introducing friction into a castor wheel assembly allowing for flexible adjustment of the friction to reduce wobble. 
         [0007]    In one aspect of the present invention, a castor support assembly is provided for a wheel. The support assembly includes a base, a spindle extending downward from the base and a castor mounting structure having a bore received over the spindle to permit pivoting movement about the spindle and an axle for rotatably mounting the wheel. A thrust bearing is provided on the spindle between the base and the castor mounting structure. A removable disk is secured to the end of the spindle and an annular friction element is received over the spindle between the castor mounting structure and the removable disk. A plurality of shims of predetermined thickness are positioned between the end of the spindle and the removable disk for setting the clearance between the friction element and the end of the castor mounting structure to inhibit oscillation of the castor support assembly. 
         [0008]    In another aspect of the present invention, an agricultural implement is provided having a frame for towed movement along the ground and a base connected to the frame by an articulated connection. A spindle extends downward from the base and a castor mounting structure having a bore is received over the spindle to permit pivoting movement about the spindle. An axle assembly supporting a wheel extends from the castor mounting structure. A thrust bearing is received on the spindle between the base and the castor mounting structure. A removable disk is secured to the end of the spindle and an annular friction element is received over the spindle between the castor mounting structure and the removable disk. A plurality of shims of predetermined thickness are positioned between the end of the spindle and the removable disks for setting the clearance between the friction element and the end of the castor mounting structure to inhibit oscillation of the castor support assembly. 
         [0009]    An advantage of the present invention is a simplified and effective reduction in wobbling of the castor wheel assembly. 
         [0010]    Another advantage of the invention is the easy removal and installation of the elements that set the clearance and thus the friction force of a castor wheel assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a side view of a towed agricultural implement which may incorporate the present invention; 
           [0013]      FIG. 2  is a perspective view of a castor support assembly for a wheel embodying the present invention; 
           [0014]      FIG. 3  is a side view of the castor support assembly of  FIG. 2 ; 
           [0015]      FIG. 4  is a view of the castor support assembly of  FIGS. 2 and 3  taken on plane  4 - 4  of  FIG. 3 ; and 
           [0016]      FIG. 5  is an exploded perspective view of the castor support assembly of  FIGS. 2-4 . 
       
    
    
       [0017]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a tillage implement  10  which is towed by a tractor  12  having tractor drive wheels  14  over the soil  19 . The tillage implement  10  is connected to the tractor  12  by a tow bar  16  and has a frame  18  supported above the soil  19  by a pair of trailing wheel assemblies  20  and forward castor wheel assemblies  22 . The trailing wheel assemblies  20  and forward castor wheel assemblies  22  are configured to support the frame  18  at variable selected heights above the soil  19  according to the operational conditions and transport conditions of the tillage implement  10 . Tillage implement  10 , as illustrated, supports a plurality of cultivators  24 . However, it should be understood by those skilled in the art that a wide variety of tools may be supported for broadly tilling the soil  19 . During field operations, the trailing wheel assemblies  20  and the forward castor wheel assembly  22  support the frame so that the cultivators  24  are at a predetermined depth according to the particular requirements. During transport to the field, the trailing wheel assembly  20  and the forward caster wheel assemblies  22  elevate the frame  18  so that the cultivators  24  are clear of the soil  19 . The mechanism for articulating the trailing wheel assemblies  20  and the forward castor wheel assemblies is well known and is not described to enable a clearer focus on the invention. 
         [0019]    During field operation and transport between fields, the trailing wheel assemblies  20  track the tow bar  16  and the castor wheel assemblies  22  pivot so that their wheels  26  track and follow the path established by the tractor  12  and the trailing wheel assemblies  20 . 
         [0020]    While prior art castor wheel assemblies  22  adequately follow the movement, the fact that the castor wheel assemblies  22  may pivot can cause oscillation or wobbling, both in the field operation condition and in the transport condition. In accordance with the present invention, the castor support assembly illustrated in  FIGS. 2-5  minimizes, if not eliminates, such wobbling. Referring first to  FIG. 2 , the castor support assembly  22  includes a base  28  supported by parallel links  30  appropriately connected and articulated to frame  18 . Parallel links  30  connect to base  28  at pivotal connections  32 . The effect of the parallel link connection maintains the base  28  at a constant orientation relative to frame  18  and thus the soil  19 . The base  28  has a pair of side plates  34  extending from the pivotal connection  32  and is reinforced with a web  36 . A downwardly extending spindle  38  having a longitudinal axis A is connected to and supported by side plates  34  and web  36 . The spindle  38  may be secured to the structures in many different ways, including welding. A castor mounting structure  40  includes a thrust washer  42  positioned over spindle  38  and a sleeve  44  forming a central through bore that is received over spindle  38 . Thrust washer  42  may be formed from nylon or any other appropriate anti-friction material. Sleeve  44  is positioned between side plates  46  and interconnecting top and bottom webs  46  and  48  forming a structural unit. A box-like extension  50  extends laterally to an arm  52  which extends downwardly at an angle where a sleeve  54  extends at a right angle for supporting a removable axle assembly  56 . A pin  57 , extendable through the sleeve  54  and axle assembly  56 , permits removable mounting thereof. The wheel  26  shown by dashed lines in  FIGS. 2 and 3 , is appropriately mounted on the axle assembly  56 . A spacer  58  is positioned over spindle  38  below sleeve  44  and abuts an annular friction element  60 , herein shown as being formed from polyurethane or other suitable friction material. An abrasion resistant steel, AR400, is a preferred material for annular friction element  60 . A disk  62  is removably fastened to the lower end  39  of spindle  38  by means of a pair of screws  64 . A plurality of shims  66  are positioned between the end of spindle  38  and disk  62  and within the inner diameter of annular friction element  60 . The shims  66  each have predetermined thicknesses allowing for the mounting of the disk  62  at a variable distance from the end  39  of spindle  38  so as to control the compression of annular friction element  60  against spacer  58  and sleeve  44 . The shims  66  each have a circular circumference  68  co-incident with the outer diameter of spindle  38  to fit within the inner diameter of annular friction element  60 . The shims  66  also have recesses  70  so that the spacers form generally a C-shape in plan view. This permits removal of the spacers  66  in a lateral direction relative to the axis A of spindle  38 . In addition, the screws  64  act as guides for the spacers  66  during removal and installation. As illustrated, the shims  66  are stacked in staggered relation so that the adjacent recesses  70  point in opposite directions. 
         [0021]    In operation, an appropriate number of shims  66  are positioned with the screws  64  loosened to provide access. The number of shims are selected to provide the correct compression of the annular friction element  60  to minimize, if not eliminate, wobbling. Over time, the various components making up the castor support assembly  22  wear, thus reducing the compression on the friction element  60  and, in turn, the effect on damping. The plurality of shims  66  allows shims to be conveniently removed to increase the friction to the original level and thus maintain the damping. All this is done without the need to totally disassemble the castor support assembly by loosening the screws  64  and moving the shims laterally. The arrangement described above provides an extremely simplified and effective way of applying friction to a castor support assembly, thus permitting an economical beginning product and simplified field capable maintenance. In addition, because the shims  66  are internal to the structure, the possibility of debris fouling the mechanism is minimized. 
         [0022]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.