Abstract:
A bushing is provided for mounting a pivot arm that has both a threaded portion as well as one or two smooth cylindrical portions. The threaded portion enables the pivot arm to be a laterally adjusted by rotating the bushing while the smooth portion or portions provide a bearing surface or surfaces for the pivot arm loads. This removes the load from the threads, reducing wear of both the bushing and the pivot arm, thereby reducing maintenance cost.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a bushing for mounting a laterally adjustable pivot arm and in particular to such a bushing having a threaded portion for laterally adjusting the pivot arm and allowing the arm to pivot and a smooth cylindrical portion bearing the load on the pivot arm. 
     BACKGROUND 
     A typical structure for an agricultural planter row unit includes a frame to which a furrow opener is mounted. A depth control member, such as a gauge wheel, is positioned adjacent the furrow opener to limit the depth to which the opener penetrates into the soil. The gauge wheel is mounted to an arm that is pivotally mounted to the frame. The gauge wheel and pivot arm are laterally adjustable relative to the frame so that the gauge wheel can be placed close to, or in light contact with the opener disks. This enables the gauge wheel to prevent moist soil from sticking to the opener. To provide for a lateral adjustment of the gauge wheel, the pivot arm is attached to the frame through a bushing assembly having a threaded a bushing and a through bore that receives a mounting bolt threaded into the frame. The threads on the bushing engage the threads in the pivot arm. By rotating the bushing, the pivot arm is moved laterally toward or away from the opener disk. This structure applies the load on the gauge wheel to the threads of the bushing and the pivot arm. 
     SUMMARY 
     A bushing is provided for mounting the pivot arm that has both a threaded portion as well as one or two smooth cylindrical portions. The threaded portion enables the pivot arm to be a laterally adjusted while the smooth portion or portions provide a bearing surface or surfaces for the pivot arm loads. This removes the load from the threads, reducing wear of both the bushing and the pivot arm, thereby reducing maintenance cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a planter row unit having the bushing described below; 
         FIG. 2  is an exploded perspective view of the bushing and pivot arm; 
         FIG. 3  is a sectional view of the bushing and pivot arm; and 
         FIGS. 4 and 5  are side views of alternative embodiments of the bushing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIG. 1 , a planter row unit  10  is shown mounted to transversely extending tool bar  12  in a conventional manner. The row unit  10  is provided with a central frame member  14  coupled to the tool bar by a parallelogram linkage  16  to enable vertical relative movement between the row unit and the toolbar in a known manner. Seed is stored in seed hopper  24  and provided to a seed meter  26 . The seed meter singulates seed from a seed pool and drops the individual seeds through a seed tube  28  into a planting furrow. The furrow is formed in the soil by a double disk furrow opener having a pair of closely spaced disks  30 . Gauge wheels  32  control the depth of the furrow and are mounted to the frame member  14  by pivot arms  36 . There is one gauge wheel adjacent the outer side of each opener disk. One disk and gauge wheel are shown in  FIG. 1 . The arm  36  pivots about a bushing assembly at the end of the arm mounted to the frame member  14 . A gauge wheel depth adjustment mechanism, not show, acts on the arm  36  to limit upward rotation of the arm, thereby setting the relative position of the gauge wheel and opener disk. The arm pivots for two reasons, one reason is to adjust the amount of penetration of the opener disk. The other reason is to allow the gauge wheel to move upward during operation when the wheel encounters rocks or other obstacles. The gauge wheel must also be adjustable laterally. The gauge wheel must be close to or even lightly touching the opener disk. This allows the gauge wheel to remove moist soil that tends to adhere to the disk and prevents the disk from pulling soil upward from the side wall of the seed furrow. Lateral adjustability is needed to compensate for wear of the gauge wheel over time and to allow for variability in the size and shape of the resilient gauge wheel material. 
     The bushing assembly  40  includes a bushing  42  and through bolt  44  as shown in  FIGS. 2 and 3 . The pivot arm  36  has a busing block  46  at the end of the arm where the arm is mounted to the central frame member  14 . The arm  36  and bushing block may be integrally formed as one piece or may be a multiple piece assembly. The bushing  42  extends through a bore  48  in the block  46 . The through bolt  44  has a head  45  and is threaded into the hole  50  in the central frame member  14 . When the bolt  44  is tightened, the bushing distal end  52  bears against the frame member  14  and the bushing is prevented from rotating. With the bolt  44  slightly loosened but still in the hole  50 , the bushing  42  can be rotated to laterally adjust the pivot arm  36  and gauge wheel  32 . 
     The bushing  42  has a cylindrical body  56  with a head  58  at a proximal end. The head  58  is hex shaped to enable a tool to be used to rotate the bushing. Shapes other than a hex can be used as desired. A through bore  60  extends through the bushing  42  for the bolt  44  with the bolt head  45  adjacent the bushing head  58 . A washer  47  maybe provided between the bolt head and the bushing head. The cylindrical body  56  is formed with a threaded center portion  62  having threads  63  and two smooth portions  64  and  66 . Smooth portion  64  is located between the head  58  and the threaded portion  62  while the smooth portion  66  is located between the threaded portion  62  and the distal end  52  of the bushing  42 . The diameter of the smooth portion  64  is larger than the outside diameter of the threads  63 . The diameter of the smooth portion  66  is smaller than the root diameter of the threads  62 . 
     The bore  48  in the bushing block  46  is complementarily shaped to receive the bushing  42 . The bore  48  has a larger diameter smooth portion  70 , a threaded portion  72  and a smaller diameter smooth portion  74 . When assembled, the smooth portions of the bushing and the smooth portions of the bushing block  46  form bearing surfaces to support the loads on the gauge wheel. By “smooth” it is meant the surfaces are free of threads and have a surface finish suitable for the loads on the gauge wheel and the amount of rotation desired. The bushing maybe lubricated by grease in a conventional manner. Lateral adjustment of the gauge wheel position is accomplished by rotating the bushing, causing the bushing block to move axially along the threads  63  of the bushing. Once the gauge wheel is in the desired position, the bolt  44  is tightened, securing the bushing in place against the face  76  of the central frame member  14 . This prevents rotation of the bushing, keeping the gauge wheel arm in position axially along the length of the bushing. The pivot arm  36  remains free to rotate about the bushing as the gauge wheel moves up and down during normal operation. 
     Alternative embodiments of the bushing are shown in  FIGS. 4 and 5 . In  FIG. 4 , a bushing  142  is shown in which the cylindrical body  152  has a single smooth portion  164  and a threaded portion  162 . In this embodiment, the smooth portion is between the head  158  and the threaded portion  162 . In  FIG. 5 , a bushing  242  is shown in which the cylindrical body  256  has a threaded portion  262  and a smooth portion  266 . In this embodiment, the smooth portion  266  is between the threaded portion  262  in the distal end  252 . The bushings  142  and  242  provide the benefit of having a cylindrical bearing surface but do not provide the benefits of the bushing  42  of two, spaced apart, bearing surfaces to better carry lateral load on the gauge wheel. The bushing block will be shaped complementary to the bushing. In all embodiments, the loads are no longer carried by the threads of the bushing and bushing block, eliminating a source of wear on the threads. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.