Patent Publication Number: US-8535120-B2

Title: Blade sharpening system for agricultural implements

Description:
BACKGROUND 
     The invention relates generally to ground working equipment, such as agricultural equipment, and more specifically, to a blade sharpening system for agricultural implements. 
     It is well known that to attain the best agricultural performance from a piece of land, a farmer must cultivate the soil, typically through a tilling operation. Common tilling operations include plowing, harrowing, and sub-soiling. Modern farmers perform these tilling operations by pulling a tilling implement behind a motorized tractor. Depending on the crop selection and the soil conditions, a farmer may need to perform several tilling operations at different times over a crop cycle to properly cultivate the land to suit the crop choice. In one type of tilling operation, rows of blades are pulled through soil to break up clods or lumps of soil, as well as old plant material to provide a more amenable soil structure for planting and to level the soil surface. 
     As will be appreciated, maintaining a sharp edge on the blades enables the blades to cut plant residue efficiently. Unfortunately, contact with the soil causes the edge of the blades to become dull over time. Therefore, a farmer may periodically (e.g., every few months) sharpen the blades to maintain efficient operation of the tillage implement. Due to the large number of blades on a typical tillage implement, the process of sharpening each blade may be exceedingly time consuming. For example, a farmer may remove each blade from the implement and sharpen the edge of the blade with a handheld grinder. Alternatively, the farmer may utilize a portable blade sharpener having transport wheels. The portable sharpener may be successively rolled into alignment with each blade to sharpen the edge of the respective blade. While this configuration enables the blades to be sharpened while on the implement, the portable sharpener typically requires a substantially flat surface to facilitate alignment between a grinding disc and the blade. Consequently, the portable sharpener may not be utilized to sharpen blades in the field. Moreover, because the position of the grinding disc is fixed with respect to the blade, the portable sharpener may be unable to effectively sharpen fluted or wavy blades. 
     BRIEF DESCRIPTION 
     A blade sharpening system is provide that includes a base and a pendulous arm having a first end rotatably coupled to the base by a pivot joint. The blade sharpening system also includes a sharpener suspended by the pendulous arm and configured to engage a generally circular agricultural implement blade while mounted on the agricultural implement. The pendulous arm is configured to enable movement of the sharpener to accommodate lateral variations in blade profile. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a perspective view of an exemplary agricultural implement; 
         FIG. 2  is a perspective view of an exemplary blade sharpening system that may be employed to sharpen blades of the agricultural implement; 
         FIG. 3  is a side view of the blade sharpening system of  FIG. 2  mounted to a row of blades, showing a sharpening assembly and a drive unit of the blade sharpening system; 
         FIG. 4  is a back perspective view of the sharpening assembly shown in  FIG. 2 ; 
         FIG. 5  is a rear view of the sharpening assembly shown in  FIG. 2 , showing a centering assembly; 
         FIG. 6  is a perspective view of the blade sharpening system shown in  FIG. 2 ; 
         FIG. 7  is a perspective view of the drive unit shown in  FIG. 3 ; and 
         FIG. 8  is a flow diagram of an exemplary method of operating the blade sharpening system. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now to the drawings,  FIG. 1  is a perspective view of an exemplary agricultural implement  10 . While a vertical tilling implement  10  is shown and described below, it should be appreciated that the blade sharpening system may be utilized to sharpen blades on any other suitable agricultural implement. As will be appreciated, an agricultural vehicle is configured to pull the vertical tilling implement  10  in a direction of motion A. The vertical tilling implement  10  includes a main frame  12 . The main frame  12  has a hitch  14  on the front end that may be used to connect the vertical tilling implement  10  to the agricultural vehicle, such as a tractor or other prime mover. Additionally, a set of wheels  16  is connected to the main frame  12 . The set of wheels  16  is oriented in a direction that is in general alignment with the direction of motion A. The set of wheels  16  includes a set of center wheels  18  and a set of pivoting wheels  20 . The set of center wheels  18  is attached across the main frame  12  at positions, for example, roughly midway between the front and rear ends of the main frame  12 . The set of center wheels  18  may include a system for adjusting the distance between the main frame  12  and the set of center wheels  18 . This system for adjusting may permit the set of center wheels  18  to be statically fixed during the movement of the vertical tilling implement  10  or to be dynamically adjustable as the vertical tilling implement  10  travels. The set of pivoting wheels  20  is connected to the front distal ends of the main frame  12 , and may reduce the amount of lateral movement of vertical tilling implement  10  as it is pulled. 
     The vertical tilling implement  10  also includes multiple rows of fluted-concave blades  22  attached to the main frame  12 . In certain configurations, the rows of fluted-concave blades  22  are indexed. In particular, the rows of fluted-concave blades  22  includes a front left row  24 , a front right row  26 , a rear left row  28 , and a rear right row  30 . When indexed, the front left row  24  and the front right row  26  are aligned with the rear left row  28  and the rear right row  30  such that areas of ground between the blades in the front left rows  24  and the front right row  26  are engaged by the blades in the rear left row  28  and the rear right row  30  as the tilling implement is pulled forward. 
     In the illustrated embodiment, the front left row  24  is symmetric about a centerline  32  of the vertical tilling implement  10  with the front right row  26 . Likewise, the rear left row  28  is symmetric about the centerline  32  of the vertical tilling implement  10  with the rear right row  30 . Additionally, the front left row  24  is substantially symmetric about a line perpendicular to the direction of motion A with the rear left row  28 . Likewise, the front right row  26  is substantially symmetric about a line perpendicular to the direction of motion A with a rear right row  30 . These general symmetries may involve some of the rows being offset relative to the others to achieve the indexing of the blades as described above. 
     When the rows of concave blades  22  are arranged in a symmetrical arrangement about the centerline  32 , such as illustrated in  FIG. 1 , a gap between each side of symmetrical rows may be created. A center tilling member  34  may be placed in this gap to ensure that all the soil passing under the vertical tilling implement  10  is tilled as the tilling implement is pulled forward. The center tilling member  34  may be a coulter, as shown in  FIG. 1 , another fluted blade, or the like. 
     While four rows of fluted-concave blades  22  are employed in the illustrated embodiment, it should be appreciated that more or fewer rows may be utilized in alternative embodiments. Additionally, while the illustrated embodiment shows the rows of fluted-concave blades  22  having an x-shaped configuration based on the described symmetry, the rows of fluted-concave blades  22  may have a different configuration. For example, the rows of fluted-concave blades  22  may have a diamond configuration, a k-shaped configuration, or all may be parallel with each other in a direction perpendicular to the direction of motion A. Furthermore, it is contemplated that some or all of the rows may be configured in asymmetric arrangements. 
     Rolling basket assemblies  36  are connected to the rear end of the main frame  12  to provide downward pressure. As will be appreciated, the rolling basket assemblies  36  may be replaced with any other acceptable member that is capable of exerting a desired downward pressure, including drag harrows, and the like. Although  FIG. 1  shows three rolling basket assemblies  36 , two of which having rotational axes which are not collinear with the third, the rolling basket assemblies  36  may include fewer or more members providing downward force. 
     As discussed in detail below, a blade sharpening system may be employed to sharpen the edges of the fluted-concave blades  22 , thereby maintaining efficient operation of the implement  10 . As will be appreciated, maintaining a sharp edge on the blades  22  enables the blades  22  to cut plant residue efficiently. Consequently, it may be desirable to periodically (e.g., every few months) sharpen each blade  22  on the implement  10 . The blade sharpening system described below includes a sharpener configured to engage a blade  22  of the agricultural implement  10 . The blade sharpening system also includes a rail configured to support the sharpening assembly and to facilitate movement of the sharpening assembly along the rail. The blade sharpening system further includes a mounting feature coupled to the rail and configured to engage a structural member of the agricultural implement  10  to support the rail and sharpening assembly. In this configuration, the sharpening assembly may be translated along the rail and aligned with successive blades  22 , thereby facilitating blade sharpening operations. 
     While the implement  10  shown and described below utilizes generally circular fluted-concave blades, it should be appreciated that alternative implements may employ other blade configurations. For example, certain implements may include fluted blades having no concavity (i.e., substantially flat). Alternative implements may include smooth-edged concave blades, i.e., blades having no flutes. Yet further implements may employ wavy blades, flat blades, or other blade configurations. In addition, certain implements may utilize a combination of blades. Because certain embodiments of the blade sharpening system are configured accommodate lateral variations in blade profile, the blade sharpening system may be utilized to sharpen any of the blade configurations described above, or other suitable blade configurations. 
       FIG. 2  is a perspective view of an exemplary blade sharpening system  38  that may be employed to sharpen blades  22  of the agricultural implement  10 . As illustrated, the blade sharpening system  38  is coupled to a gang  40  of blades  22 . As will be appreciated, the gang  40  may form part of a row (e.g.,  24 ,  26 ,  28 , or  30 ) of blades  22  within the implement  10 . The blades  22  within the gang  40  are configured to rotate together, and each row may include multiple (e.g., 1, 2, 3, 4, or more) gangs  40 . In the illustrated embodiment, a gang tube  42  extends along a direction substantially parallel to an axis of rotation of the blades  22 . Consequently, the blades  22  are oriented perpendicularly to the gang tube  42 . As illustrated, multiple support members  44  extend between the gang tube  42  and an axle  46  of the gang  40 , thereby supporting the blades  22 . In the present embodiment, the gang tube  42  is secured to the frame  12  of the implement  10  at a desired angle for tilling operations. The gang  40  also includes an angled beam  48  configured to support scrapers positioned adjacent to the blades  22  and configured to remove accumulated dirt and debris from the blades  22 . The angled beam  48  may be secured to the gang tube  42 , the implement frame  12 , or a combination thereof. 
     In the illustrated embodiment, the blade sharpening system  38  includes a sharpening assembly  50  and a drive unit  52 . As discussed in detail below, the sharpening assembly  50  is configured to sharpen an edge  54  of each blade  22 , while the drive unit  52  rotates the blade  22  relative to the sharpening assembly  50 . In this manner, the sharpening assembly  50  may evenly sharpen the edge  54  along the entire circumference of the blade  22 . As illustrated, the drive unit  52  is secured to the gang tube  42 , and the sharpening assembly  50  is secured to the angled beam  48 . Consequently, the entire blade sharpening system  38  is supported by structural elements of the implement  10 . Specifically, the blade sharpening system  38  includes a rail  56  configured to support the sharpening assembly  50  and to facilitate movement of the sharpening assembly  50  along the rail  56 . The blade sharpening system  38  also includes mounting features, such as the illustrated hooks  58 , coupled to the rail  56  and configured to engage the angled beam  48  of the agricultural implement  10  to support the rail  48  and sharpening assembly  50 . In this configuration, the sharpening assembly  50  may be translated along the rail  56  and aligned with successive blades  22 , thereby facilitating blade sharpening operations. While the drive unit  52  is coupled to the gang tube  42  and the hooks  58  are coupled to the angled beam  48  in the present embodiment, it should be appreciated that the drive unit  52  and/or sharpening assembly  50  may be coupled to other structural members of the agricultural implement  10  in alternative embodiments. Furthermore, while the sharpening assembly  50  and the drive unit  52  are separate components in the present embodiment, it should be appreciated that alternative embodiments may employ a single assembly including the sharpening assembly  50  and the drive unit  52 . 
     In the illustrated embodiment, the sharpening assembly  50  includes a sharpener  60  configured to engage each blade  22  of the gang  40 . The sharpener  60  includes a grinding disc  62  configured to sharpen the edge  54  of the blade  22 , and a motor  64  configured to drive the grinding disc  62  to rotate. As will be appreciated, contact between the rotating grinder disc  62  and the blade  22  removes a small amount of material from the edge  54  of the blade  22 , thereby increasing blade sharpness. As discussed in detail below, operation of the sharper  60  may be coordinated with operation of the drive unit  52  such that the blade  22  is driven to rotate as the grinder disc  62  sharpens the edge  54  of the blade  22 . Consequently, the present blade sharpening system  38  may provide a substantially uniform blade edge  54 , thereby increasing the plant residue cutting effectiveness of the blade  22 . In addition, while the drive unit  52  is configured to drive a single blade  22 , rotation of the single blade  22  will drive each blade  22  in the gang  40  to rotate because the blades  22  are keyed to the axle  46 . Consequently, the drive unit  52  may remain in one location as the sharpening assembly  50  is moved between blades  22 . 
     As previously discussed, the sharpening assembly  50  is configured to translate along the rail  56  in a first direction  66  and a second direction  68 , thereby enabling the sharpening assembly  50  to access each blade  22  within the gang  40 . In the illustrated embodiment, the sharpening assembly  50  includes a carrier  70  configured to engage the rail  56  and to facilitate movement of the sharpening assembly  50  along the rail  56 . The sharpening assembly  50  also includes a sharpener support  72  configured to support the sharpener  60 . In the present embodiment, the sharpener support  72  is rotatable in a direction  74  relative to the carrier  70  between a blade-engaged position and a blade-disengaged position. Specifically, to facilitate movement of the sharpening assembly  50  from presently engaged blade to another blade  22  on the gang  40 , an operator may lift a handle  76  upwardly, thereby inducing the sharpener support  72  to rotate about a pivot  78  in the direction  74  relative to the carrier  70 . Rotating the sharpener  60  in the direction  74  extracts the sharpener  60  from a region between adjacent blades  22 , thereby substantially reducing or eliminating the possibility of contact between the sharpener  60  and the blades  22  as the sharpener  60  translates in the direction  66  or  68 . 
     As illustrated, the carrier  70  includes a locking mechanism, such as the illustrated set screw  80 , configured to selectively block movement of the sharpening assembly  50  along the rail  56 . Consequently, to facilitate movement of the sharpening assembly  50 , an operator may rotate the set screw  80 , thereby reducing the contact force between the screw  80  the rail  56  and enabling movement of the sharpening assembly  50  in the direction  66  or  68 . Once the locking mechanism has been released, the operator may translate the sharpening assembly  50  to a position substantially aligned with a subsequent blade  22 . The operator may then tighten the set screw  80  to block movement of the sharpening assembly  50  with respect to the rail  56 , and move the handle  76  downwardly, thereby rotating the sharpener  60  in the direction  82  about the pivot  78 . In this manner, the sharpening assembly  50  may be positioned to sharpen each blade  22  within the gang  40 . Because the blade sharpening system  38  is fully supported by structural elements of the implement  10 , blade sharpening operations may be performed while the implement  10  is positioned on substantially any surface, even the soil of a field. Consequently, the duration associated with sharpening blades of a tillage implement may be substantially reduced, thereby increasing the availability of the implement  10  for tillage operations. 
     As previously discussed, the present implement  10  includes concave-fluted blades  22 . As illustrated, each blade  22  includes a flat center portion  84  and a series of crests and troughs  86  extending a-radially inward from the outer periphery of the blade  22 . The series of crests and troughs  86  forms multiple flutes  88 . As will be appreciated, employing fluted concave blades  22  may permit the use of more aggressive gang angles without resulting in increased blade failures or the generation of large clumps of soil requiring multiple passes, and/or may enable the implement  10  to travel at greater speeds than the known tilling systems having freely-rotatable blades. Unfortunately, blade sharpening systems employing fixed sharpeners may be unable to follow the contours of the fluted blades  22 , thereby resulting in an uneven edge  54  that is less effective for cutting plant residue. Consequently, certain embodiments of the blade sharpening system  38  are configured to accommodate lateral variations in blade profile, thereby enabling the blade sharpening system  38  to be utilized for sharpening fluted-concave blades  22 , or other suitable blade configurations. 
     In certain embodiments, the blade sharpening assembly  50  includes a base member, such as the illustrated carrier  70 , and a pendulous arm  90  having a first end rotatably coupled to the carrier  70  by a pivot joint  92 . The blade sharpening assembly  50  also includes the sharpener  60  coupled to a second end of the pendulous arm  90  and configured to engage the blade  22  of the agricultural implement  10 . The pendulous arm  90  is configured to enable movement of the sharpener  60  relative to a neutral position to accommodate lateral variations in blade profile. As discussed in detail below, the blade sharpening assembly  50  also includes a centering assembly  94  configured to bias the sharpener  60  toward to the neutral position. For example, when aligning the sharpener  60  with a blade  22 , the carrier  70  may be translated in the direction  68  until the grinding disc  62  contacts the blade  22 . The carrier  70  may then be translated an additional small distance in the direction  68 , thereby inducing the sharpener  60  to rotate in the direction  96  about the pivot  92 . As will be appreciated, due to the weight of the sharpener  60  and/or the bias of the centering assembly  94 , the sharpener  60  will be driven in the direction  98 , thereby establishing a contact force between the grinding disc  62  and the blade  22 . As the drive unit  52  induces the blade  22  to rotate, the contours of the fluted blade  22  will induce the sharpener  60  to rotate in the directions  96  and  98  about the pivot  92 . As a result, the illustrated sharpening assembly  50  may provide the fluted blade  22  with a substantially uniform sharp edge  54 , thereby enabling the blade  22  to efficiently cut plant residue. 
     While the illustrated sharpener  60  is configured to sharpen a first side of each blade  22 , it should be appreciated that the sharpener  60  may be configured to sharpen a second side of each blade  22 . For example, a guard  100  covering a first side of the grinder disc  62  may be attached to a second side of the grinder disc  62 , thereby facilitating contact between the first side of the grinder disc  62  and the second side of each blade  22 . In addition, it should be appreciated that the grinder disc  62  of the illustrated embodiment may be replaced with an alternative device, such as an edge roller, a polishing wheel or a wire wheel brush in alternative embodiments to sharpen the blades  22 . 
       FIG. 3  is a side view of the blade sharpening system of  FIG. 2  mounted to a row of blades  22 , showing the sharpening assembly  50  and the drive unit  52  of the blade sharpening system  38 . As previously discussed, the sharpening assembly  50  includes a hook  58  coupled to the rail  56  and configured to engage the angled beam  48  of the agricultural implement  10  to support the rail  56  and sharpening assembly  50 . As illustrated, the hook  58  includes first flat surface  102  configured to contact a second flat surface  104  of the angled beam  48 , and a third flat surface  106  configured to contact a fourth flat surface  108  of the angled beam  48 . In addition, the hook  58  includes a recess  110  configured to capture an end  112  of the angled beam  48 . In this configuration, the hook  58  may be coupled to the angled beam  48  by disposing the recess  110  about the end  112 , and then rotating the sharpening assembly  50  in the direction  82  until the first surface  102  contacts the second surface  104 , and the third surface  106  contacts the fourth surface  108 . Once engaged, contact between the hook  58  and the angled beam  48  will block rotation of the rail  56  and sharpening assembly  50  in the direction  82  and translation in the direction  114 . To remove the rail  56  and sharpening assembly  50 , the sharpening assembly  50  may be rotated in the direction  74  and lifted upwardly in the direction  116 . The blade sharpening system  38  may then be transferred to another gang  40  for additional blade sharpening operations. Because the hook  58  is configured to secure the rail  56  and sharpening assembly  50  to the implement  10  without fasteners, the blade sharpening system  38  may be readily transferred between gangs  40 . 
     The drive unit  52  also includes a mounting feature, such as the illustrated clamp  118 , configured to removably secure the drive unit  52  to the gang tube  42  of the agricultural implement  10 . As illustrated, the clamp  118  includes a fixed upper jaw  120  and a movable lower jaw  122 . In the illustrated embodiment, rotation of a set screw  124  drives the lower jaw  122  in the downward direction  114  or the upward direction  116 . In this configuration, the drive unit  52  may be readily uncoupled from the gang tube  42  of a first gang  40  and secured to the gang tube  42  of a second gang  40 . In addition, because the position of the lower jaw  122  is adjustable (e.g., vertically and horizontally with respect to the fixed upper jaw  120 ), the drive unit  52  is mountable to various tubes  42  having different heights and widths. 
       FIG. 4  is a back perspective view of the sharpening assembly  50  shown in  FIG. 2 . As illustrated, the carrier  70  includes four wheels  126  configured to engage the rail  56 . The wheels  126  are configured to secure the sharpening assembly  50  to the rail  56  and to facilitate movement of the sharpening assembly  50  along the rail  56 . Specifically, each wheel  126  includes a recess  128  configured to capture the rail  56 . As a result, movement of the sharpener assembly  50  with respect to the rail  56  is blocked in each direction, except the directions  66  and  68 . In addition, as previously discussed, the carrier  70  includes a set screw  80  configured to selectively block movement of the sharpening assembly  50  along the rail  56 . While the illustrated embodiment employs a set screw  80 , it should be appreciated that alternative embodiments may utilize other locking mechanisms to selectively block movement of the sharpening assembly  50  with respect to the rail  56 . 
     In the illustrated embodiment, the sharpening assembly  50  also includes an adjustment mechanism  130  configured to vary a position of the sharpener  60  relative to the blade  22 . As illustrated, the adjustment mechanism  130  includes a set screw  132  configured to drive a sharpener mount  134  in a forward direction  136  or a rearward direction  138  relative to the blade  22 . Consequently, the grinder disc  62  may be aligned with the edge  54  of blades  22  having varying diameters. For example, for smaller diameter blades  22 , the set screw  132  may be rotated to drive the sharpener  60  in the direction  136 , thereby aligning the grinder disc  62  with the edge  54  of the blade  22 . Conversely, for larger diameter blades  22 , the set screw  132  may be rotated to drive the sharpener  60  in the direction  138 , thereby aligning the grinder disc  62  with the edge  54  of the blade  22 . 
       FIG. 5  is a rear view of the sharpening assembly  50  shown in  FIG. 2 , showing a centering assembly  94 . As previously discussed, the sharpening assembly  50  includes the pendulous arm  90  having a first end rotatably coupled to the carrier  70  by a pivot joint  92 . The blade sharpening assembly  50  also includes the sharpener  60  coupled to a second end of the pendulous arm  90  and configured to engage the blade  22  of the agricultural implement  10 . The pendulous arm  90  is configured to enable movement of the sharpener  60  relative to a neutral position to accommodate lateral variations in blade profile. The blade sharpening assembly  50  also includes a centering assembly  94  configured to bias the sharpener  60  toward to the neutral position. As illustrated, the centering assembly  94  includes a first arm  140  rotatably coupled to the pivot joint  92  and in contact with a first side  142  the pendulous arm  90 . The centering assembly  94  also includes a second arm  144  rotatably coupled to the pivot joint  92  and in contact with a second side  146  of the pendulous arm  90 . In addition, the centering assembly  94  includes a spring  148  extending between the first arm  140  and the second arm  144 . The spring  148  is configured to bias the first arm  140  and the second arm  144  toward the pendulous arm  90 . 
     For example, if the sharpener  60  is rotated in the direction  96 , contact between the first side  142  of the pendulous arm  90  and the first arm  140  will drive the first arm  140  to rotate in the direction  150 . Because rotation of the second arm  144  in the direction  150  is block, rotation of the first arm  140  will expand the spring  148 , thereby inducing a force driving the sharpener to return to the illustrated neutral position. Conversely, if the sharpener  60  is rotated in the direction  98 , contact between the second side  146  of the pendulous arm  90  and the second arm  144  will drive the second arm  144  to rotate in the direction  152 . Because rotation of the first arm  140  in the direction  152  is block, rotation of the second arm  144  will expand the spring  148 , thereby inducing a force driving the sharpener to return to the illustrated neutral position. As a result, the illustrated sharpening assembly  50  may enable the grinder disc  62  to accommodate lateral variations in blade profile, thereby providing the fluted blade  22  with a substantially uniform sharp edge  54 . 
       FIG. 6  is a perspective view of the blade sharpening system  38  shown in  FIG. 2 . As previously discussed, the blade sharpening system  38  includes a sharpening assembly  50  and a drive unit  52 . The sharpening assembly  50  is configured to sharpen an edge  54  of each blade  22 , while the drive unit  52  rotates the blade  22  relative to the sharpening assembly  50 . In this manner, the sharpening assembly  50  may evenly sharpen the edge  54  along the entire circumference of the blade  22 . As illustrated, the drive unit  52  includes a rotating drive wheel  154  configured to engage the edge  54  the blade  22 , and a motor  156  configured to drive the wheel  154 . As discussed in detail below, the drive unit  52  includes an adjustment mechanism  158  configured to adjust the position of the wheel  154  relative to the clamp  118  to accommodate varying blade diameters. Because the drive unit  52  is coupled to the gang tube  42  by the clamp  118 , the drive unit  52  may be readily detached from the illustrated gang  40  and coupled to a subsequent gang  40  for continued sharpening operations. 
       FIG. 7  is a perspective view of the drive unit  52  shown in  FIG. 3 . As previously discussed, the drive unit  52  includes a motor  156  configured to drive a wheel  154 . In certain embodiments, the motor  156  may be coupled to the wheel  154  by a belt or chain. For example, an enclosure  160  may house the belt or chain configured to transfer power from the motor  156  to the wheel  154 . In addition, the drive unit  52  includes an adjustment mechanism  158  configured to adjust the position of the wheel  154  relative to the clamp  118  to accommodate varying blade diameters. As illustrated, the adjustment mechanism  158  includes a set screw  162  configured to rotate a frame  164  in a direction  166  relative to the clamp  118 . Because the wheel  154  is rotatably coupled to the frame  164 , rotation of the frame  164  in the direction  166  will drive the wheel  154  closer to the blade  22 . Consequently, the drive unit  52  may be configured to drive blades  22  of varying diameters. 
       FIG. 8  is a flow diagram of an exemplary method  168  of operating the blade sharpening system  38 . As previously discussed, operation of the sharper  60  may be coordinated with operation of the drive unit  52  such that the blade  22  is driven to rotate as the grinding disc  62  sharpens the edge  54  of the blade  22 . First, as represented by block  170 , the drive unit motor  156  is activated. Next, as represented by block  172 , the sharpener motor  64  is activated. Ensuring that the drive unit motor  156  is running prior to activating the sharpener motor  64  substantially reduces or eliminates the possibility of excessive wear due to the grinder disc  62  continuously removing material from a portion of the blade  22 . After the blade  22  has been sharpened, the sharpener motor  64  is deactivated, as represented by block  174 . Next, as represented by block  176 , a predetermined delay is employed to allow the grinder disc  62  to stop rotating. Finally, the drive unit motor  156  is deactivated, as represented by block  178 . Waiting unit the grinder disc  62  has stopped before deactivating the drive unit motor  156  may provide a substantially uniform blade edge  54 , thereby increasing the plant residue cutting effectiveness of the blade  22   
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.