Cutting tool sharpener

An apparatus for sharpening a cutting tool having opposing first and second side surfaces and a cutting edge therebetween, the apparatus comprising:

• a plurality of spaced apart rollers;
• a flexible abrasive belt having an abrasive top surface and an opposing backing surface, the flexible abrasive belt routed around the plurality of rollers to form a belt path defining respective first and second planar extents tangential to and on opposing sides of a first roller of the plurality of rollers, the first planar extent extending from the first roller to a second roller and the second planar extent extending from the first roller to a third roller, each of the first and second planar extents symmetric with and non-parallel to a centerline passing through a central axis about which the first roller rotates, the central axis bisecting an overall angle between the first and second planar extents, the plurality of spaced apart rollers comprising a belt tracking mechanism to nominally maintain the flexible abrasive belt positioned over the plurality of rollers;
• a motor adapted to drive the flexible abrasive belt in at least a first selected direction along the belt path;
• and
• a sharpening guide assembly secured adjacent the flexible abrasive belt and the first roller comprising a first guide slot adjacent the first planar extent of the flexible abrasive belt and a second guide slot adjacent the second planar extent of the flexible abrasive belt, wherein the first and second guide slots comprise first and second cutting edge guide surfaces adapted to contactingly engage the cutting edge of the cutting tool during presentation of the respective first and second sides of the cutting tool against first and second side guide surfaces, the first and second side guide surfaces symmetric about the centerline of the first roller so that each of the first and second side guide surfaces are disposed at a common acute angle with respect to the first and second planar extents of the flexible abrasive belt to support the opposing first and second side surfaces of the cutting tool as the cutting edge of the cutting tool is contactingly presented against the respective first and second planar extents.

An apparatus for sharpening a blade having opposing first and second side surfaces converging to a cutting edge, the apparatus comprising:

• a belt support assembly comprising a plurality of belt support surfaces providing a routing path for a flexible abrasive belt having an outer surface for supporting abrasive particles and an inner surface routed along the plurality of belt support surfaces, the plurality of belt support surfaces comprising at least a first rotatable support surface, a second rotatable support surface and a third rotatable support surface arranged such that a first belt extent along the routing path extends from the first rotatable support surface to the second rotatable support surface and a second belt extent along the routine path extends from the first rotatable support surface to the third rotatable support surface, the second and third rotatable support surfaces separated by a first distance and the first and second rotatable support surfaces separated by a second distance greater than the first distance;
• a main drive assembly comprising an electric motor, a motor control circuit and a torque transfer mechanism configured to drive the flexible abrasive belt at least one selected speed and at least one selected direction about the plurality of belt support surfaces;
• and
• a sharpening guide assembly comprising a first guide slot adjacent the first planar extent of the flexible abrasive belt and a second guide slot adjacent the second planar extent of the flexible abrasive belt, the first and second guide slots each comprising first and second cutting edge guide surfaces adapted to contactingly engage opposing distal ends of the cutting edge of the cutting tool during presentation of an intermediary portion of the cutting edge between the opposing distal ends of the cutting edge of the cutting tool against the flexible abrasive belt, the first guide slot further comprising a first side support surface configured to contactingly support the first side of the blade at a selected angle during presentation of the intermediary portion of the cutting edge to the first planar extent of the flexible abrasive belt, the second guide slot further comprising a second side support surface configured to contactingly support the second side of the blade at the selected angle during presentation of the intermediary portion of the cutting edge to the second planar extent of the flexible abrasive belt.

A method for sharpening a cutting tool having opposing first and second side surfaces and a cutting edge therebetween, the method comprising:

• installing a first flexible abrasive belt along a belt path about a plurality of spaced-apart rollers, the first flexible abrasive belt having a first linear stiffness, the belt path defining respective first and second planar extents tangential to and on opposing sides of a first roller of the plurality of rollers, each of the first and second planar extents symmetric with respect to a centerline passing through a central axis about which the first roller rotates, the central axis bisecting an overall angle between the first and second planar extents and equidistant from a second roller and s third roller of the plurality of spaced-apart rollers;
• driving the first flexible abrasive belt along the belt path in a selected direction, wherein a tensioner assembly applies a bias force to at least one of the rollers to establish a tension in the driven first flexible abrasive belt and maintain said first and second planar extents;
• providing a sharpening guide adjacent the flexible abrasive belt, the sharpening guide comprising a first guide slot adjacent the first planar extent and a second guide slot adjacent the second planar extent, wherein the guide slots are on opposing sides of the centerline;
• using the first guide slot of the sharpening guide to present the first side of the cutting tool against the first extent of the first flexible abrasive belt to induce bending of the flexible belt at a first radius of curvature determined in relation to the first linear stiffness to form a first convex shape on the first side of the cutting tool at said first radius of curvature, wherein the first guide slot establishes a selected angle of the cutting tool relative to a centerline that bisects an overall angle between the first and second planar extents;
• and
• using the second guide slot of the sharpening guide to present the opposing second side of the cutting tool against the second extent of the first flexible abrasive belt to induce bending of the flexible abrasive belt at the first radius of curvature to form a first convex shape on the second side of the cutting tool at said first radius of curvature, wherein the second guide slot maintains the cutting tool at the selected angle, and wherein a tensioner assembly exerts a bias force upon a selected one of the first, second and third rollers to oppose deflection of the belt during presentation of the cutting tool against the respective first and second extents of the driven first flexible abrasive belt.