Jig for sharpening mower blades

Abstract

A jig assembly is disclosed herein for holding a mower blade and a grinding tool during a sharpening operation on the mower blade. The jig assembly includes a mast, a fixture portion, and a jig portion. The fixture portion and jog portion can be mounted to the mast. The jig portion can include an arm and a tool-seat. The arm can include at least a first link and a second link movable relative to one another. The first link can be pivotally connected to the mast with a first pin defining an arm pivot axis. The first link and the second link can be interconnected whereby the second link is prevented from rotating in any plane that contains the arm pivot axis. The tool-seat can be disposed on the second link.

What is claimed is: 
     
         1 . A jig assembly for holding a mower blade and for controlling movement of a grinding tool having a grinding wheel during a sharpening operation on a cutting edge of the mower blade, said jig assembly comprising:
 a mast extending between a first end and a second end;   a fixture portion mounted to said mast, said fixture portion including a work-supporting surface extending in a first plane and configured to receive the mower blade, a back surface of the mower blade resting on said work-supporting surface during the sharpening operation of the cutting edge of the mower blade exposed on a front surface of the mower blade; and   a jig portion pivotally mounted to said mast, said jig portion comprising:
 an arm with a plurality of links interconnected to one another, said arm including at least a first link and a second link movable relative to one another, said first link extending between a first end and a second end, said first end of said first link pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, said first end of said first link rectilinearly fixed relative to said mast at said first pin, said first link and said second link interconnected whereby said second link is prevented from rotating in any plane that contains the arm pivot axis, and 
 a tool-seat disposed on said second link, the grinding wheel connected to said second link during the sharpening operation through said tool-seat. 
   
     
     
         2 . The jig assembly of  claim 1  wherein said first link and said second link are further defined as interconnected for one of relative pivoting movement and telescoping rectilinear movement. 
     
     
         3 . The jig assembly of  claim 2  wherein said first link is pivotally connected to said second link with a second pin, said second pin defining a link pivot axis, said arm pivot axis and said link pivot axis parallel to one another. 
     
     
         4 . The jig assembly of  claim 1  wherein said first link and said second link are further defined as having different lengths. 
     
     
         5 . The jig assembly of  claim 1  wherein said arm pivot axis is coplanar with a vector normal to said first plane. 
     
     
         6 . The jig assembly of  claim 1  wherein said tool-seat further comprises:
 a second pin pivotally engaged with said second link, said second pin defining a pitch axis about which the grinding wheel can pivot during the sharpening operation, said pitch axis and said arm pivot axis parallel to one another. 
 
     
     
         7 . The jig assembly of  claim 6  wherein said second pin further comprises:
 a first portion of outwardly-facing cylindrical surface that is smooth; and 
 a second portion of outwardly-facing cylindrical surface that is threaded. 
 
     
     
         8 . The jig assembly of  claim 6  wherein said tool-seat further comprises:
 a sleeve defining inwardly-facing surface, said second pin received in said inwardly-facing surface. 
 
     
     
         9 . The jig assembly of  claim 1  wherein said second link and said tool-seat are engaged with one another such that at least a first portion of said tool-seat is movable in a first rectilinear direction that includes at least a first orthogonal component that is parallel to said arm pivot axis and passes through said second link, said tool-seat further comprising a second portion fixed with said first portion during movement the first rectilinear direction, said second portion extending farther than said first portion in a direction normal to the first rectilinear direction, movement of said first portion and said second portion in the first rectilinear direction limited by a hard stop defined when said second portion directly or indirectly contacts said second link, and said first portion and said second portion are unrestrained in movement in a second rectilinear direction that is opposite to the first rectilinear direction such that said first portion and said second portion are freely separable from said second link. 
     
     
         10 . The jig assembly of  claim 9  wherein said first portion is a further defined as a second pin having a cylindrical profile. 
     
     
         11 . The jig assembly of  claim 9  wherein said second portion is further defined as engaging said second link indirectly, through a third portion of said tool-seat. 
     
     
         12 . The jig assembly of  claim 1  wherein said fixture portion is further defined as pivotally mounted to said mast with a third pin, said third pin defining a fixture pivot axis. 
     
     
         13 . The jig assembly of  claim 12  wherein said fixture pivot axis is further defined as transverse to said arm pivot axis. 
     
     
         14 . The jig assembly of  claim 13  wherein said fixture pivot axis is further defined as perpendicular to said arm pivot axis. 
     
     
         15 . The jig assembly of  claim 12  wherein a longitudinal axis passes through an interior of said mast, said fixture pivot axis intersecting said longitudinal axis within said interior and said arm pivot axis intersecting said longitudinal axis within said interior. 
     
     
         16 . The jig assembly of  claim 12  wherein said fixture portion further comprises:
 at least one stop extending above said work-support surface and limiting movement of the mower blade along said work-supporting surface, a leading edge of the mower blade resting against said at least one stop during the sharpening operation of the cutting edge of the mower blade, an intersection between the leading edge of the mower blade and said at least one stop during the sharpening operation of the cutting edge of the mower blade extending along an intersection axis, and said intersection axis and said fixture pivot axis parallel to one another, wherein said intersection axis moves about said fixture pivot axis during pivoting movement of said fixture portion, said intersection axis moving along an arcuate path in a second plane that is normal to said first plane, wherein said intersection axis and said fixture pivot axis are spaced a first distance from one another along a third axis normal to both of said intersection axis and said fixture pivot axis, wherein a third plane contains said fixture pivot axis and is normal to said arm pivot axis, wherein during the pivoting movement of said fixture portion said intersection axis moves over a range of distances from said third plane, an absolute value of a distance between endpoints of said range defining a second distance, and wherein said second distance less than one third of said first distance. 
 
     
     
         17 . The jig assembly of  claim 16  wherein said range extends across said third plane. 
     
     
         18 . The jig assembly of  claim 12  wherein:
 said fixture portion further comprises at least one protuberance and a spring biasing said at least one protuberance outward; and 
 said mast further comprises a plurality of detents spaced along an arc centered on said fixture pivot axis, said at least one protuberance selectively positioned in one of said plurality of detents to maintain said fixture portion in one of a plurality of different orientations relative to said mast. 
 
     
     
         19 . The jig assembly of  claim 12  wherein said fixture portion further comprises:
 first and second jaws that are movable relative to one another along a jaw axis that is parallel to said work-supporting surface. 
 
     
     
         20 . The jig assembly of  claim 1  wherein said mast is further defined as a unitary and integrally-formed. 
     
     
         21 . A jig assembly for holding a mower blade and for controlling movement of a grinding tool having a grinding wheel during a sharpening operation on a cutting edge of the mower blade, the jig assembly comprising:
 a mast extending between a first end and a second end;   a fixture portion mounted to said mast, said fixture portion including a work-supporting surface extending in a first plane and configured to receive the mower blade, a back surface of the mower blade resting on said work-supporting surface during the sharpening operation of the cutting edge of the mower blade exposed on a front surface of the mower blade; and   a jig portion pivotally mounted to said mast, said jig portion comprising:
 an arm pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, 
 a tool-seat disposed on said arm, the grinding wheel connected to said arm during the sharpening operation through said tool-seat, and 
 wherein said arm and said tool-seat are engaged with one another such that at least a first portion of said tool-seat is movable in a first rectilinear direction that includes at least a first orthogonal component that is parallel to said arm pivot axis and passes through said arm, said tool-seat further comprising a second portion fixed with said first portion during movement the first rectilinear direction, said second portion extending farther than said first portion in a direction normal to the first rectilinear direction, movement of said first portion and said second portion in the first rectilinear direction limited by a hard stop defined when said second portion directly or indirectly contacts said arm, and said first portion and said second portion are unrestrained in movement in a second rectilinear direction that is opposite to the first rectilinear direction such that said first portion and said second portion are freely separable from said arm in the second rectilinear direction. 
   
     
     
         22 . A jig assembly for holding a mower blade and for controlling movement of a grinding tool having a grinding wheel during a sharpening operation on a cutting edge of the mower blade, said jig assembly comprising:
 a mast extending between a first end and a second end;   a fixture portion mounted to said mast, said fixture portion including a work-supporting surface extending in a first plane and configured to receive the mower blade, a back surface of the mower blade resting on said work-supporting surface during the sharpening operation of the cutting edge of the mower blade exposed on a front surface of the mower blade;   a jig portion pivotally mounted to said mast, said jig portion comprising:
 an arm pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, and 
 a tool-seat disposed on said arm, the grinding wheel connected to said arm during the sharpening operation through said tool-seat; 
   wherein said fixture portion is further defined as pivotally mounted to said mast with a third pin, said third pin defining a fixture pivot axis; and   wherein said fixture portion further comprises at least one stop extending above said work-support surface and limiting movement of the mower blade along said work-supporting surface, a leading edge of the mower blade resting against said at least one stop during the sharpening operation of the cutting edge of the mower blade, an intersection between the leading edge of the mower blade and said at least one stop during the sharpening operation of the cutting edge of the mower blade extending along an intersection axis, and said intersection axis and said fixture pivot axis parallel to one another, wherein said intersection axis moves about said fixture pivot axis during pivoting movement of said fixture portion, said intersection axis moving along an arcuate path in a second plane that is normal to said first plane, wherein said intersection axis and said fixture pivot axis are spaced a first distance from one another along a third axis normal to both of said intersection axis and said fixture pivot axis, wherein a third plane contains said fixture pivot axis and is normal to said arm pivot axis, wherein during the pivoting movement of said fixture portion said intersection axis moves over a range of distances from said third plane, an absolute value of a distance between endpoints of said range defining a second distance, and wherein said second distance less than one third of said first distance.