Abstract:
An agricultural vehicle includes a frame, a wheel supporting the frame, and a rockshaft coupled to the frame and operable to pivot with respect to the frame. The rockshaft has an outer surface, an inner surface and an open end. An internal end cap is positioned on the open end of the rockshaft. The internal end cap has an inner surface and an outer surface. The inner surface of the internal end cap contacts the outer surface of the rockshaft. An external end cap is positioned on the open end of the rockshaft and contacts the outer surface of the internal end cap. A fastener connects the external end cap to the frame to retain the external end cap on the rockshaft.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    This disclosure relates generally to the protection of shafts or axles such as rockshafts used on agricultural implements. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Vehicle or implement rockshafts include shafts or axles that rotate or pivot backwards and forwards about their journals or the portion contained by a bearing. In agricultural implements like tillage cultivators or seeding planters, tubular rockshafts are utilized, for example, to control a height on the implement frames and disk gang attachments. The rockshaft pivots about a central axis so that the shaft and anything attached to the shaft moves with respect to the ground surface. Some bearing block assemblies support the shaft from a frame, and a hydraulic cylinder rotates the rockshaft to move objects hanging from the shaft with respect to the ground surface. As the rockshaft pivots, often under very heavy loading, wear occurs between the rockshaft and the bearing block. Grease lubrication is used to reduce the wear, but this leads to performance problems and down-time, among other issues. 
       SUMMARY OF THE DISCLOSURE 
       [0003]    Various aspects of example embodiments are set out below and in the claims. Embodiments include internal end caps that fit over the ends of a rockshaft. Other embodiments are disclosed in the detailed description, accompanying drawings and claims. 
         [0004]    Some embodiments provide an agricultural vehicle includes a frame, a wheel supporting the frame, and a rockshaft coupled to the frame and operable to pivot with respect to the frame. The rockshaft has an outer surface, an inner surface and an open end. An internal end cap is positioned on the open end of the rockshaft. The internal end cap has an inner surface and an outer surface. The inner surface of the internal end cap contacts the outer surface of the rockshaft. An external end cap is positioned on the open end of the rockshaft and contacts the outer surface of the internal end cap. A fastener connects the external end cap to the frame to retain the external end cap on the rockshaft. 
         [0005]    Some embodiments include an industrial task machine comprising a frame, a wheel supporting the frame, and a rockshaft coupled to the frame and operable to pivot with respect to the frame. The rockshaft has an outer surface, an inner surface, a first open end and a second open end. A first internal end cap is positioned on the first open end of the rockshaft. The internal end cap has an inner surface and an outer surface. The inner surface of the internal end cap contacts the outer surface of the rockshaft. A first external end cap is positioned on the first open end of the rockshaft. The external end cap contacts the outer surface of the internal end cap. A first fastener connects the external end cap to the frame to retain the external end cap on the rockshaft. A second internal end cap has an inner surface and an outer surface. The second internal end cap is positioned on the second open end of the rockshaft and contacts the outer surface of the rockshaft. A second external end cap is positioned on the second open end of the rockshaft and contacts the outer surface of the second internal end cap. A second fastener connects the second external end cap to the frame to retain the second external end cap on the rockshaft. 
         [0006]    Some embodiments provide a rockshaft end cap assembly connected to a rockshaft having an outer surface, an inner surface and an open end. The rockshaft end cap assembly includes an internal end cap positioned on the open end of the rockshaft. The internal end cap has an inner surface and an outer surface. The inner surface of the internal end cap contacts the outer surface of the rockshaft. The rockshaft end cap assembly further includes an external end cap positioned on the open end of the rockshaft. The external end cap contacts the outer surface of the internal end cap. The rockshaft end cap assembly further includes a fastener connecting the external end cap to a vehicle frame to retain the external end cap on the rockshaft. 
         [0007]    This disclosure includes embodiments of an internal end cap (e.g.  70  in  FIG. 5 ) positioned on an end of a shaft such as a rockshaft used in agricultural implements. The internal end cap acts like a smooth liner or buffer between the end region of the rockshaft and any outer external housing. The rockshaft together with the internal end cap can readily pivot in the outer external housing without a messy coat of grease, greasing or oiling or impregnating with the oil. 
         [0008]    Some embodiments of end caps include a tapered cup that is pushed or tucked over the end of the rockshaft. Outside of the rockshaft and internal end cap is an external housing (e.g., a tube) including an external end cap and flanges, usually made of steel casting, that fits over the rockshaft and over the internal end cap. The internal tapered end cap can be made of smooth material that is wear resistant and replaces the friction-reducing grease normally placed between the ends of the rockshaft and the external end cap. The smooth internal tapered end cap can prevent abrasive metal-to-metal (shaft-to-external end cap) contact under thrust or radial loading when the agricultural implement moves across the uneven soil. The coefficient of friction of the internal end cap material is low enough to maintain smooth, quiet rockshaft operation and to reduce frictional wear problems in all planes of contact with the external end cap in order to reduce or eliminate rockshaft and external end cap maintenance. Other embodiments of the internal end cap are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The Detailed Description refers to the following example figures: 
           [0010]      FIG. 1  depicts a perspective view of a cultivator containing at least two visible rockshafts. 
           [0011]      FIG. 2  depicts an upper side perspective magnified view of one rockshaft of  FIG. 1  with an external end cap of the rockshaft. 
           [0012]      FIG. 3  depicts a lower side perspective magnified view of the rockshaft of  FIG. 2  and external end caps on either side of the rockshaft of  FIG. 2 . 
           [0013]      FIG. 4  depicts an inside lower side perspective magnified view of  FIG. 2 . 
           [0014]      FIG. 5  depicts a partial exploded upper view of the rockshaft and internal and external end caps of  FIGS. 2-4 . 
           [0015]      FIG. 6  depicts another partial exploded view of the rockshaft and internal and external end caps of  FIG. 5 . 
           [0016]      FIG. 7  depicts a cutaway side view of the internal end caps and rockshaft taken along line  7 - 7  of  FIG. 2 . 
           [0017]      FIG. 7A  depicts a partial cutaway perspective view of the internal end caps and rockshaft of  FIG. 7 . 
           [0018]      FIG. 8  depicts an embodiment of an internal end cap having an example slit along the side. 
           [0019]      FIG. 9  depicts an embodiment of an internal end cap having protrusions that help retain the internal end cap to the rockshaft. 
           [0020]      FIG. 10  depicts an embodiment of an internal end cap that shrink wraps on an end of a rockshaft. 
           [0021]      FIG. 11  depicts an upper side view of an embodiment of an external end cap. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0023]      FIG. 1  shows an agricultural tillage implement in the form of a cultivator  10  having a main frame  12 . Other examples include seeding planters or towed spray tanks. The illustrated cultivator  10  includes multiple transversely extending rockshafts  20  and  21 . A magnified view of the shorter of the two rockshafts,  21 , is shown in  FIG. 2 . The illustrated rockshafts  21  has a circular cross section and are connected to a bearing block assembly or a lift yoke  14  (see  FIG. 2 ). 
         [0024]    In  FIGS. 2-4 , rockshaft  21  is capped on both ends by a respective external end cap  26  having an external end surface  24 . The external end caps  26  are mounted to a transverse frame tube  124  of the main frame  12 . A rectangular or V-shaped bolt  126  and nuts  122  (see, e.g.,  FIG. 5 ) attach the external end cap  26  to the transverse frame tube  124  of the main frame  12 . Hydraulic or hydro-electric cylinders (not shown) are connected to a lift yoke  14  by a bar  16 . The cylinders pull and push on the bar  16 , which in turn pulls or pushes the lift yoke  14  to pivot the rockshaft  21  about a transverse rockshaft central axis  20   a . The cultivator  10  is supported by a plurality of lift wheel assemblies  120 . Rockshaft  21  then lifts or lowers one or more of portions of the frame  12  with respect to the wheel assemblies  120  of the cultivator  10 . 
         [0025]    There are external end caps  26  on either side of the rockshaft  21 . As can be seen from  FIG. 3 , reaching one side of the rockshaft  21  is easier on the outer side of the cultivator  10 . By contrast, the other side of the rockshaft  21  is harder to reach with tools or to service (e.g. lubricate). Rockshaft  20  in the rear center of the cultivator  10  is even more difficult to service when the rockshaft  20  or its ends wear out, rust, or collect dirt and residue. To overcome this and other problems, an internal end cap is introduced on both ends of rockshafts  20  and  21 . 
         [0026]      FIG. 5  depicts a partially exploded upper view of the rockshaft  21  and internal end cap  70  and external end caps  26  of  FIGS. 2-4 . The illustrated internal end cap  70  is a one piece cylinder with an open end  74  and a closed end  72 . Internal end cap  70  is made of a material with a coefficient of kinetic or sliding friction that is low enough (e.g., less than 0.2) to maintain smooth, quiet rockshaft operation and to reduce frictional wear problems in all planes of contact with the external end cap  26 . For example, the material may include polyethylene and ultra high molecular weight polyethylene (UHMW, e.g. molecular weight of 3.1 million or higher). Other materials having low or lower friction coefficient and high abrasion resistance as UHMW does are also suitable. For example, hard molded nylon impregnated with oil or grease is another embodiment. UHMW is self-lubricating, which reduces a need for servicing or periodic lubricating of the rockshaft  21 . However, in some embodiments, the internal end cap  70  is still lubricated or impregnated with oil or grease to further reduce the amount of friction. 
         [0027]    In  FIG. 5 , the illustrated internal end cap  70  is tapered (e.g. by 0.25 to 0.5 degrees) from the open end  74  to the covered or closed end  72 . That is, the diameter of the circular open end  74  is slightly larger than the diameter of the closed end  72  in order to make it easier to mount the internal end cap  70  onto the rockshaft  21 . Most rockshafts are tubular with a circular cross section to permit a large range of motion about its central axis  20   a . However, if the needed range of motion is small or there is limited rotational motion, then in some embodiments the rockshaft  21  has a more oval, or hexagonal or octagonal cross section with rounded corners. In these embodiments, the internal end cap  70  has a corresponding cross sectional shape in order to fit snugly over the end of the rockshaft  21 . 
         [0028]      FIG. 6  depicts another partial exploded view of the rockshaft  21  and the external end cap  26  and internal end cap  70  illustrated in  FIG. 5 , but showing the open end  74  of the internal end cap  70 . The external end cap  26  has an inner surface  28  which is sized to receive the internal end cap  70  and the rockshaft  21 . The internal end cap  70  has a wall thickness of 5-7 mm. The interior and exterior wall of the illustrated internal end cap  70  is smooth. Part way along the length of the internal end cap, the inner diameter of the internal end cap  70  is the same as the outer diameter of the rockshaft  21 . The internal end cap  70  is pushed against an end of the rockshaft  21  with enough force so that the internal end cap  70  remains tightly on the end on the rockshaft  21  past where the two diameters match. In this embodiment, both ends of rockshaft  21  are covered by a respective internal end cap  70 . The external end cap  26  fits over the internal end cap  70 . 
         [0029]      FIG. 7  depicts a cutaway side view of two example internal end caps  70   a ,  70   b  and the rockshaft  21  of  FIG. 2 .  FIG. 7A  depicts a partial cutaway perspective view of the example internal end caps and rockshaft of  FIG. 7 . Each internal end cap  70   a  and  70   b  includes a respective closed end surface  72   a  and  72   b . The lengths of the illustrated internal end caps  70   a  and  70   b  differ and are based on where the lift yoke  14  is coupled to the rockshaft  21 . In  FIG. 7 , there is an air pocket  76   a ,  76   b  between the respective closed end surface  72   a ,  72   b  and a respective end surface  24  of the corresponding external end cap  26 . In the illustrated embodiment, the depth of each air pocket  76   a  and  76   b  is proportional to the length of the internal end cap  70 ; the longer the internal end cap  70 , the greater the depth of the associated air pocket. In profile cross-section as shown in  FIG. 7 , the air pockets span the outer diameter of the rockshaft  21  (or the inner diameter of the internal end caps  70   a  and  70   b ). In some embodiments, the air pockets can have a diameter corresponding to the inner diameter of the rockshaft  21 . In some embodiments, the air pockets are substantially smaller than the illustrated air pockets  76   a ,  76   b . In some embodiments, the air pockets are omitted and closed end surfaces  72   a ,  72   b  of the respective end caps  70   a ,  70   b  abut the respective end surface  24  of the respective external end cap  26 . 
         [0030]    The example air pockets  76   a  and  76   b  have rounded ends. That is, the inner closed-end surface of the external end cap  26  has rounded ends and comes to a trough point in the center rather than have a flat or planar surface. As can be seen in  FIG. 7 , the internal end caps  70   a ,  70   b  serve to line the space between the rockshaft  21  and the external end caps  26 . As shown, the cylindrical side wall of each internal end cap  70   a  and  70   b  contacts the surface of the rockshaft  21  and the cylindrical side wall of the respective external end cap  26 . 
         [0031]      FIG. 8  depicts another embodiment of an internal end cap  270  having a slit  282  along the length of the side wall of the cylindrical wall of  270 . The illustrated slit  282  is parallel to the central axis of the rockshaft. Although not shown, other example slits include slits along only part of the length of the cylindrical surface either parallel to or transverse to the central axis of the cylinder. In most embodiments, the arc distance  280  between the two sides of the slit  282  spans substantially zero degrees; that is, the slit  282  is a cut through the side wall. In some embodiments, the arc distance  280  is 0-2 millimeters. The slit  282  makes it easier to mount or pull the internal end cap  270  onto an end of the external rockshaft. Wth the slit  282 , the internal end cap  270  is either tapered or free of tapering (i.e., having a uniform radius from the open end  274  to the closed end  272 ). In some embodiments, the slit can include partial slits along only the cylindrical surface either parallel to or crosswise to the central axis of the cylinder. 
         [0032]      FIG. 9  depicts another embodiment of an internal end cap  370  having a first open end  372 , a second open end  374  and extending along axis  320   a . The illustrated internal end cap  370  includes two protrusions  376  that help retain the internal end cap  370  on the rockshaft. In some embodiments, the internal end cap  370  is tapered such that the diameter of the first open end  372  is less than the diameter of the second open end  374 . In some embodiments, the rockshaft also has corresponding recesses that mate with the respective protrusion  376  on the internal surface of the internal end cap  370 . In other embodiments, the end surface of the rockshaft has a protrusion and the inner surface of the internal end cap  370  is either smooth or has a corresponding recess that mates to the protrusion. The protrusions and recesses can help to keep the internal end cap  370  mounted more snugly or tightly on the end of the rockshaft. 
         [0033]      FIG. 10  depicts another embodiment of an internal end cap  470  having a closed end  472 , an open end  474  and extending along axis  420   a . The illustrated internal end cap  470  shrink wraps onto an end of a rockshaft  421 . The polyethylene material or other polymers (e.g., PVC or a combination of polyethylene and PVC or polypropylene) shrinks tightly over the end of the rockshaft  421  when heat is applied (e.g., over 90 degrees C.). A quick heat treatment (e.g., through a heat tunnel or by inserting a heated rockshaft  421  into the internal end cap  470 ) is applied just long enough to shrink the polyethylene material a little so that the internal end cap  470  still retains its shape and functions as a low friction liner that, together with the rockshaft  421 , can still readily rotate or pivot in the external end cap or other external housing. In this scenario, in one embodiment, the internal end cap  470  has either a uniform or a tapered diameter along the length of the internal end cap  470 . Whether uniform or tapered, the diameter is larger than the outer diameter of the rockshaft  421  for easy insertion without use of tools. Since the material of the internal end cap  470  shrinks, it will stay snugly on the rockshaft  421 . 
         [0034]    In some embodiments, a dense rubber material is used for the illustrated internal end cap  470  so that it withstands abrasion. For example, an industrial urethane rubber (e.g., PMC-790 urethane rubber) is used to form a cylindrical cup. The rubber cup is also impregnated with oil or greased from the outer surface inward so that the cup and its outer surface has a low coefficient of friction. The rubber cup is again tapered like the polyethylene version with the open end  472  having a larger diameter than the closed end  474  so that the internal end cap  470  can be readily mounted on the end of the rockshaft  421 . 
         [0035]      FIG. 11  depicts another embodiment of an external end cap  526  that includes a smooth cylinder on the outside, free of any collars, flanges or attachments. The illustrated external end cap  526  includes a closed end  524  and is coupled to rockshaft  521  and wheel assembly  620 . Since this is a free hanging external end cap  526 , not directly attached to the frame  512 , there tends to be less abrasive force on the external end cap  526  and on an internal end cap (a hard molded nylon internal end cap (not shown in  FIG. 11 ) impregnated with oil or grease is often sufficient). 
         [0036]    Although the focus of the aforementioned embodiments is on agricultural implements, construction machines or other uses of rockshafts also exist. For example, lift shafts in construction machines include rockshafts housed in external tubes. Positioning one of the example internal end caps in this equipment improves the life of the machine. The internal end cap liner eliminates a need for periodic greasing or metal-to-metal contact between the rockshaft and the external end housing. Also, although the disclosure focused on the shorter rockshaft  21 , any of the embodiments also apply to the longer rockshaft  20 . 
         [0037]    In the present disclosure, the descriptions and example embodiments should not be viewed as limiting. Rather, there are variations and modifications that may be made without departing from the scope of the appended claims.