Patent Publication Number: US-2007099734-A1

Title: Bushingless variable speed separator drive

Description:
FIELD OF THE INVENTION  
      The present invention relates to agricultural combines, and, more particularly, to variable speed belt drives for driving a separator in such combines.  
     BACKGROUND OF THE INVENTION  
      An agricultural combine includes a head and a feeder housing which remove the crop material from the field, gather the crop material and transport the crop material to a separator. The separator removes the grain crop material from the non-grain crop material. The grain is transported to a grain tank, and the non-grain crop material is discharged to the field. The separator typically includes a rotary element which is belt driven. The belt drive is in the form of a variable speed belt drive having a spring loaded movable sheave half which can move in an axial direction on the outside diameter of the hub. A relatively large clearance space is provided between the movable sheave half and the hub which accommodates polymer bushings therebetween. The relatively large clearance space along with the somewhat elastomeric properties of the polymer bushings allow the movable sheave half to wobble during use, which may shorten belt life.  
      What is needed in the art is a variable speed belt drive for a separator in an agricultural combine which has decreased wear between the movable sheave half and hub, and increased belt life.  
     SUMMARY OF THE INVENTION  
      The present invention provides a variable speed separator drive which eliminates bushings between the hub and movable sheave half by forming the hub from hardened chrome plated steel and forming the movable sheave half from nodular cast iron with a spiral lubricating groove at the inside diameter.  
      The invention comprises, in one form thereof, a variable speed separator drive for an agricultural combine, including a hub formed of chrome plated steel, and a movable sheave half carried by the hub. The movable sheave half is formed from nodular cast iron and includes an inside diameter with at least one spiral lubricating groove. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of an embodiment of a variable speed separator drive of the present invention;  
       FIG. 2  is a cross-sectional view through the variable speed separator drive taken along line  2 - 2  in  FIG. 1 ; and  
       FIG. 3  is a fragmentary, perspective view of the movable sheave half shown in  FIG. 2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an embodiment of a variable speed belt drive  10  of the present invention which receives input power from a belt  12  driven by a drive pulley  14 . In the embodiment shown, variable speed belt drive  10  is in the form of a variable speed separator drive for rotatably driving a separator in an agricultural combine. Drive pulley  14  may thus be driven, e.g., by a transmission coupled to an internal combustion (IC) engine.  
      Variable speed belt drive  10  generally includes a housing  16 , hub  18 , fixed sheave half  20  and movable sheave half  22 . Fixed sheave half  20  is coupled with an end of hub  18 , and is positioned in opposition to movable sheave half  22 . Fixed sheave half  20  may be formed from any suitable material, such as steel.  
      Hub  18  is formed from hardened and chrome plated steel. The chrome plating provides a highly finished surface for carrying movable sheave half  22 .  
      Movable sheave half  22  is carried by hub  18  and is movable in an axial direction along hub  18 . Movable sheave half  22  is biased toward fixed sheave half  20  using a spring  24 . An opposed base  26  is keyed to and carried by hub  18 , and provides an opposed fixed surface against which spring  24  acts to bias movable sheave half  22  toward fixed sheave half  20 .  
      Housing  16  is coupled to and moves with movable sheave half  22 . Housing  16  encloses hub  18 , spring  24  and cam  26 .  
      Movable sheave half  22  is carried by and slidably movable relative to hub  18 . Movable sheave half  22  includes an inside diameter  28  which defines a clearance distance relative to outside diameter  30  of hub  18  which is smaller than the clearance distance in conventional variable speed belt drives using bushings between the hub and movable sheave half. More particularly, movable sheave half  22  has an inside diameter  28  which is approximately between 0.01 to 0.04 millimeters less than outside diameter  30  of hub  18 . In the embodiment shown, the clearance distance is approximately 0.01 millimeters between inside diameter  28  and outside diameter  30 . A smaller clearance distance between hub  18  and movable sheave half  22  results in less oscillation of movable sheave half  22 , which in turn significantly improves the operating life of belt  12  carried by variable speed belt drive  10 .  
      Movable sheave half  22  is formed from cast iron, preferably nodular cast iron having interspersed graphite nodules. The graphite nodules which are exposed at inside diameter  28  of movable sheave half  22  provide reduced wear during operation.  
      Movable sheave half  22  also includes one or more lubricating grooves  32  formed in inside diameter  28 . In the embodiment shown, movable sheave half  22  includes a continuous spiral lubricating groove formed in inside diameter  28 . Lubricating groove  32  is configured with a shape and size to ensure proper lubrication between movable sheave half  22  and hub  18 , and may vary depending upon the application or lubricant (e.g., grease or oil).  
      During use, the torque which is applied to the output shaft of variable speed belt drive  10  (extending from the center of hub  18 ) controls the axial movement of movable sheave half  22 , and thus in turn the spacing between movable sheave half  22  and fixed sheave half  20 . The reduced clearance distance between inside diameter  28  of movable sheave half  22  and outside diameter  30  of hub  18  reduces wobble of movable sheave half  22  and improves belt life. The nodular graphite and grease grooves at inside diameter  28  of movable sheave half  22 , and the chrome plated outside diameter  30  of hub  18 , provide reduced friction and wear between movable sheave half  22  and hub  18 .  
      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.