Abstract:
A bearing assembly ( 20 ) with a self-lubricated liner interface ( 70 ) supported between a spherical outside surface ( 72 ) of a sealed agricultural bearing ( 20   b ) and a steel containment housing ( 60,62 ). The interface ( 70 ) includes a lubrication-impregnated plastic interposed between the housing ( 60,62 ) and the spherical surface ( 72 ) to relieve the bearing from the high forces of shaft misalignment. The plastic liner includes a compressible portion such as radially projecting protrusions ( 82 ), O-rings ( 82   a ) or other resilient band, or compressible molded plastic (H 2 ) to accommodate varying tolerances between the outside spherical surface ( 72 ) and housing cavity surfaces ( 68 ) and liner ( 70 ) and to bias the liner ( 70 ) against the spherical surface ( 72 ) to prevent bearing rotation. The plastic liner halves ( 70   a,   70   b ) fit firmly over the outside bearing surface to reduce entry of dirt and contaminants into the housing and onto the spherical bearing surface ( 74 ). The sealed bearing ( 20   b ) and self-lubricated interface ( 70 ) eliminate need for external grease ports.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to disk implements and, more specifically, to a disk bearing mounting. 
       BACKGROUND OF THE INVENTION 
       [0002]    A disk gang typically includes an arbor bolt or shaft supported by standard-mounted spherical bearings located between disks spaced along the length of the shaft. The spherical bearings are designed to facilitate self-alignment during assembly of the disk gang and to allow some oscillation from an initial in-line alignment as the gang shaft axis shifts with variable shaft loading as the disks impact objects and as ground conditions vary. In most previously available disk bearing assemblies, a lubrication point such as a grease fitting or oil reservoir is provided and requires regular maintenance. The maintenance procedures can be awkward and time-consuming. 
         [0003]    Tolerances between the outer surface of the disk bearing and bearing mounting frequently cause problems. Without careful and expensive manufacturing processes, the stacked tolerances between the bearing inserts and housing often can result in a loose fit that allows the entire bearing to rotate with the shaft within the housing. As a result, the bearing assembly will fail prematurely. In addition, lubrication is required between the housing and the spherical outer surface of the bearing to facilitate bearing self-alignment to accommodate shaft misalignments caused by axis tolerances and the slight shifting of the axis during operation as the loading on the gang varies. Without the proper lubrication between the housing and bearing, a spherical radius bearing will wear on the outside diameter, and eventually fail due to friction from rotating in the housing. 
       SUMMARY OF THE INVENTION 
       [0004]    A self-lubricated liner interface is supported between a spherical outside surface of an agricultural bearing and a steel containment housing. The steel containment housing protects the bearing and interface from dirt and field residue. The interface is fabricated from a lubrication-impregnated plastic and is interposed between the steel housing and the spherical surface to facilitate radial sliding for dynamic self-alignment of the bearing to relieve the bearing from the high forces of shaft misalignment. Radially projecting members extend beyond a generally spherical surface of the liner to accommodate varying tolerances between the outside spherical surface of the bearing and the housing and liner and to bias the interface into gripping relationship with the bearing prevent the bearing from rotating about the shaft axis relative to the containment housing. 
         [0005]    In one embodiment a radially split liner includes halves assembled over the spherical outside surface of the bearing. The liner has protrusions to bias the liner into gripping relationship with the bearing surface and eliminate problems caused by tolerance stacking. Anti-rotation locator tabs fit in corresponding recesses in a two-piece containment housing assembled over the halves. In another embodiment, each of the halves receive a tolerance-accommodating cushion member such as an O-ring in a groove formed in the half. The protrusions or cushion members help bias the liner against the outer surface of the bearing to provide sufficient grip between the housing and the spherical outside surface of the bearing to prevent the bearing from rotating within the housing. The plastic liner halves have outwardly directed circular openings that fit firmly over the bearing surface and provide seals between the surface and the openings on the opposite sides of housing to reduce or eliminate entry of dirt and contaminants into the housing and onto the spherical bearing surface. By using a sealed lubricated bearing in combination with a self-lubricated liner protected from contamination, external grease ports can be eliminated and maintenance requirements are reduced. 
         [0006]    In one embodiment, a lubrication impregnated plastic is integrally molded in the steel housing to provide a self lubricated interface between a spherical outside diameter bearing and the containment housing. Eliminating the machined surfaces on a cast bearing housing reduce need for secondary machining operations and reduce part cost. A lubrication impregnated plastic can be dually molded with a plastic or rubber material with a lower durometer. The lubricated high strength plastic would provide a rugged, long-wearing contact surface for the spherical diameter of the bearing, while the second portion of the bearing liner would provide material that can be displaced within depressed sections of the housing. An interference fit is thereby established between the liner and housing that creating a tight grip on the bearing, but allowing it to rotate spherically. The steel housing provides a protection system for the bearing and liner system from soil and field residue, while the interface between the liner and bearing remains free to slide radially to provide a dynamic self alignment of the bearing to relieve the bearing from the high forces of shaft misalignment. 
         [0007]    The containment housing protects the bearing and liner system from soil and field residue, while the interface between the liner and bearing remains free to slide radially for dynamic self-alignment that relieves the bearing from the high forces of shaft misalignment. The addition of a plastic liner integrally connected to the bearing housing eliminates the need for any secondary machining operation for tighter tolerances in the main housing to capture the bearing. The plastic liner eliminates the need for lubricant and therefore the problems of dirt and debris adhering to the surfaces and causing wear is reduced. The problem of dirt causing liner and bearing surface wear is also lessened because the liner can compress. 
         [0008]    These and other objects, features and advantages of the present invention will become apparent from a reading of the description which follows when taken with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a portion of a disk gang assembly. 
           [0010]      FIG. 2  is an exploded view of the disk gang assembly shown in  FIG. 1  showing the disk shaft liner and support bearing. 
           [0011]      FIG. 3  is an enlarged view of the liner and adjacent spacers removed from the disk shaft. 
           [0012]      FIG. 4  is a view similar to  FIG. 1  but with the bearing assembly partially disassembled to more clearly show the interface between the bearing and the containment housing. 
           [0013]      FIG. 5  is an exploded view of the bearing assembly of  FIG. 4 . 
           [0014]      FIG. 6  is an enlarged perspective view of a portion of the bearing assembly of  FIG. 4 . 
           [0015]      FIG. 7  is a view similar to that of  FIG. 6  but showing an alternate embodiment of the interface. 
           [0016]      FIG. 8  is an exploded view of another embodiment of the invention wherein the interface is molded directly into the containment housing. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring to  FIG. 1 , therein is shown a portion of an agricultural disk  8  with a disk gang assembly  10 . The disk  8  includes a disk frame  12  adapted for movement in the forward direction F over the ground to till the ground, break up clods, and incorporate plant residue into the soil. The frame  12  extends generally transversely to the forward direction F and supports a plurality of spaced C-spring gang mounting standards  16  made of spring steel. The standards  16  include upper ends connected by mounting brackets  18  to the frame  12 . 
         [0018]    A disk gang bearing assembly  20  includes a bearing  20   b  with a bearing inner race  20   a  is connected by bolts  22  to a lower horizontally extending leg  26  of each of the standards  16 . A disk gang bolt or shaft  30  with an axis  30   a  extends through the inner race  20   a  of the bearing assemblies  20  and supports a plurality of transversely spaced disk blades  32 ,  32   a  and  32   b  having central circular apertures  32   c  received over the shaft  30 . Spacing components  34 ,  36 ,  37  and  38  are interposed between the disk blades  32 ,  32   a  and  32   b . As shown, the spacing component  34  comprises a full spool sandwiched between a pair of adjacent disk blades at locations other than the locations of the bearing assemblies  20 . The spacing component  36  is a half spool positioned between inner race  20   a  of the bearing assembly  20  and the hub of the adjacent disk blade  32   b . The components  37  and  38  include a cylindrical spacer and a washer, respectively, sandwiched between the inner race  20   a  and the hub of the disk blade  32   a . A tensioning nut  40  is tightened on a threaded end  30   t  of the disk gang shaft  30  against end washers  42  abutting the outermost disk blade  32  to sandwich the mounted disk blades  32 ,  32   a  and  32   b , spacing components  36 ,  37  and  38  and inner races  20   a  of the supporting bearing assemblies  20  for rotation in unison about the shaft axis  30   a . A nut retaining assembly  46  is supported in the end of the shaft  30  to prevent the tensioning nut  40  from unthreading from the shaft. A conventional disk blade scraper assembly  48  is supported from the frame  12  for clearing mud and debris. 
         [0019]    As shown, the disk gang shaft  30  has a cylindrical surface. The inner diameter of the inner race  20   a  is slightly larger than the shaft diameter to receive the shaft  30  and accommodate manufacturing tolerances between the inner race  20   a  and the shaft  30 . As a result, slight gaps may exist at a mounting portion  30   m  between the shaft  30  and the inner race  20   a . The harsh operating environment of an agricultural disk and the subjection of the disk gang assembly  10  to corrosive conditions can result in damage to the mounting portion  30   m  and corrosion between the surface  30   c  of the mounting portion and the inner race  20   a.    
         [0020]    To fill any gaps between the inner race  20   a  and the mounting portion  30   m , prevent seizure of the bearing relative to the shaft  30 , and reduce damage to the mounting portion, an anti-corrosive shaft liner  50  is supported over the mounting portion  30   m  between the disk bearing inner race  20   a  and mounting portion. The shaft liner  50  is described in our co-pending and commonly assigned patent application Ser. No. 12/722,687, filed 5 Mar. 2010 and entitled Shaft Alignment and Anti-Corrosion Liner for a Disk Gang. The liner  50  is shown as a plastic cylinder with an axis  50   a  and an inner circumference approximately equal to the circumference of the mounting portion  30   m . To facilitate assembly of the liner  50  to the shaft  30  with completely disassembling the disks  34  and components  36  and  38  from the shaft  30 , the liner  50  may be spit as shown at  52  in  FIG. 3  generally parallel to or at a slight angle relative to axis  50   a  of the cylinder and axis  30   a  of the disk gang shaft  30 . The shaft liner  50  is formed from a tough plastic such as polyvinylchloride or similar material that is resistant to corrosion but is sufficiently flexible to fill the area of any gaps between the inner race  20   a  and the shaft surface  30   c.    
         [0021]    As shown in  FIG. 3 , the length of the liner  50  is selected to span the inner race  20   a  and project into the shaft-mounted spacer components  36 ,  37  and  38  adjacent the bearing assembly  20  to help take up tolerances between the inner diameters of the mounted components and the outer surface  30   c  of the shaft  30 . In the configuration shown, the spacer component  37  fits snugly over the liner  50  and abuts the inner circumference of the component  38 . The liner  50  also helps center the bearing inner race  20   a  and the components  36 ,  37  and  38  on the shaft  30  during assembly and protects the shaft  30  from damage. Slight misalignments between the shaft  30  and one or more of the spacing components  34 ,  36 ,  37  and the bearing inner race  20   a  can be accommodated by the shaft liner  50 . 
         [0022]    Referring now to  FIGS. 4-8 , the disk gang bearing assembly  20  will be described in further detail. The bearing assembly  20  includes mating upper and lower containment housing sections  60  and  62 , respectively, having a bearing housing cavity  66  defined by cavity surfaces  68 . A bearing liner  70  is interposed between an outer surface  72  of a spherically shaped outer race  74  of the bearing  20   b  and the surfaces  68  defining the bearing housing cavity  66 . The bearing liner  70  is a formed assembly of non-metallic material that includes an inner spherically shaped surface  78  conforming to a portion of the outer spherical surface  72  and an outer portion  80  conforming generally to the housing cavity  66 . As shown, the bearing liner  70  is molded from a lubricant-impregnated high strength plastic such as Teflon®-impregnated nylon. The inner spherical surface  78  of the liner  70  and the outer surface  72  of the bearing  20   b  have radii of approximately equal dimensions and centered at the same point. The outer race ring  74  can oscillate within the bearing liner  70  to facilitate self-alignment of the bearing inner race  20   a  with the with the shaft axis  30   a  during assembly of the disk gang assembly  10 . In addition, shifting of the shaft axis  30   a  caused by variable operational loading on the disks  32 ,  32   a  and  32   b  is also accommodated by the mounting. However, to avoid destruction of the liner  70 , the outer ring  74  of the bearing must be firmly held against rotation relative to the liner  70 . 
         [0023]    To provide adequate outer bearing race grip to prevent bearing rotation while allowing bearing self-alignment, the bearing liner  70  is fabricated with at least a portion indicated generally at  82  that can compress to take up manufacturing tolerances between the outer race  74  and the housing cavity  66  and provide a tight grip of the outer race  74  by the liner. Diametrically opposed locator tabs  84  project radially from the liner  70  and are received within mating tab-receiving cavities  85  at planar housing junctures  86 . 
         [0024]    As show in  FIGS. 5 and 6 , the liner  70  includes identical liner halves  70   a  and  70   b  molded from a lubrication-impregnated high strength plastic such as Lubriloy RW-HI. Each half has an innermost planar face lying in a plane generally perpendicular to the shaft axis  30   a . The formed halves  70   a  and  70   b  are assembled axially over the outer race  74  and abut at radially projecting lips  75   a  and  75   b  which are received within mating grooves  75   c  in the bearing housing cavity. The thickness of the liner  70  is approximately equal to the space between the surfaces  68  of the housing cavity  66  and the outer surface  72  of the outer race  74 . The compressible liner portion  82  as shown in  FIGS. 5 and 6  includes projections  82   p  spaced at regular intervals on the outer portion of the liner for accommodating tolerance between the containment cavity  66  of the containment housing and the outer spherical surface of the bearing of the outer race  74 . As the bolts  22  are tightened to secure the bearing  20   b , the projections  82   p  bias the inner surfaces of the liner halves  70   a  and  70   b  against the spherical surface of the outer race  74  to prevent rotation of the bearing  20   b  within the housing about the shaft axis  30   a . The liner material can compress to fill any gaps that otherwise would exist between the bearing and housing. Alternatively, a compressible liner portion  82   a  can include O-rings  82   r  ( FIG. 7 ) or other band structures which provide sufficient biasing to cause the liner  70  to adequately grip the bearing  20   b.    
         [0025]    In another embodiment, a liner  70   m  ( FIG. 8 ) can be integrally molded into a housing cavity  66   m  having cavity surfaces  68   m . The liner  70   m  can include a first or inner high strength self-lubricating plastic material surface H 1  defining the surface  78  and a more compressible second or outer liner portion H 2  of a material of durometer less than that of the first plastic material of surface H 1  to conform to the cavity  66   m  and provide sufficient compression to firmly hold the outer race  74  against rotation. A mold or injection port  90  is centrally located in the cavity  66   m  for injecting the liner material. As shown in the exploded view of  FIG. 8 , each half liner portion  62   m  is formed by a corresponding cavity  66   m  to include a central alignment rib  92   m  which conforms to a central groove  94   m  in housing section  62   m  and radially projecting tabs  84   m  which are received within mating cavities  85   m  at planar junctures  86   m  of the housing section  62   m  and the corresponding upper housing section (not shown). In the embodiment of  FIG. 8 , the liner is split along a plane that is generally parallel to the shaft axis  30   a . An injection port appendage  106  thermoplastically seals the port  90  and provides added resistance to liner misalignment and rotation. If housing maintenance requires removal and replacement of the liner  70   m , the appendage  106  can be severed and the liner  70   m  removed from the housing cavity  66   m  for replacement by a standard formed liner conforming to the cavity  66   m.