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A device and method for sharpening a mower blade are provided, in which a mounting device for mounting a rotary blade having two opposite cutting edges to be sharpened, wherein the mounting device is capable of positioning the blade in a first fixed state and a second, axially pivoting state. One or

A device and method for sharpening a mower blade are provided, in which a mounting device for mounting a rotary blade having two opposite cutting edges to be sharpened, wherein the mounting device is capable of positioning the blade in a first fixed state and a second, axially pivoting state. One or more grinding head assemblies are each positioned on an opposite end of the blade, wherein the grinding head assemblies respectively grind the two opposite cutting edges to be sharpened. A control system controls movement of the two grinding head assemblies. The mounting device positions the blade in the first fixed state to enable the two grinding head assemblies to grind the cutting edges in a direction substantially parallel to the cutting edges of the blade to perform a straight grind, and then may position the blade in the second axially pivoting state to enable the blade to pivot around its blade rotation axis away from the grinding head assemblies upon completion of the straight grind, thereby forming a curve at the end of each cutting edge. The mounting assembly also holds the blade in a third, freely rotating state in which the blade may substantially freely rotate around its blade rotation axis to enable balancing of the blade after sharpening.

대표청구항 ▼

What is claimed: 1. A device for sharpening a rotary mower blade with a rotational axis at its center, a longitudinal axis and a pair of cutting edges, one cutting edge on each of opposed sides of the longitudinal axis, comprising: a blade mounting assembly for supporting a blade to be sharpened fo

What is claimed: 1. A device for sharpening a rotary mower blade with a rotational axis at its center, a longitudinal axis and a pair of cutting edges, one cutting edge on each of opposed sides of the longitudinal axis, comprising: a blade mounting assembly for supporting a blade to be sharpened for pivoting about the blade's rotational axis, said mounting assembly being held in a fixed state relative to a main base during sharpening; at least one grinder wheel having an axis of rotation and a grinding surface oriented perpendicular to the grinder wheel's axis of rotation; a grinder wheel carriage operably connected to the at least one grinder wheel and mounted to the main base to provide the grinder wheel linear motion along a grinding path generally parallel to and in grinding engagement with a cutting edge of the blade; means for moving the carriage and grinder wheel along the grinding path; and a lock for selectively holding and releasing the blade mounting assembly from its fixed state into a freely pivoting state sufficient to reveal rotational imbalance in the blade. 2. The device of claim 1, wherein each cutting edge has a distal end and an inner end nearer its center, further comprising means for causing relative motion between the blade and the grinding surface as the grinding surface reaches the inner end of the cutting edge to form a radius there. 3. The device of claim 2, wherein the means for causing relative motion between the blade and the grinding surface comprises means for releasing the blade mounting assembly from its fixed state to a controlled tilting state and means for causing the blade to tilt in a direction away from the grinding surface as the grinding surface reaches the inner end of the cutting edge. 4. The device of claim 3 wherein the means for causing the blade to tilt in a direction away from the grinding surface as the grinding surface reaches the inner end of the cutting edge comprises a cam actuated by travel of the at least one grinder wheel carriage in a direction generally toward the center of the blade. 5. The device of claim 2, wherein the means for causing relative motion between the blade and the grinding surface comprises means for retracting the grinding surface in a direction away from the cutting edge as the grinding surface reaches the inner end of the cutting edge. 6. The device of claim 1, wherein each grinder wheel carriage further comprises means for selectively adjusting the angle at which the grinding surface achieves grinding engagement with each cutting edge. 7. The device of claim 1 wherein the at least one grinder wheel comprises two grinder wheels, each mounted on a carriage for linear motion along a grinding path, the respective grinding paths being opposed and substantially symmetrical relative to the blade center. 8. The device of claim 1, wherein the blade mounting assembly comprises an opposed pair of clamping blocks for engaging opposed sides of the blade to be sharpened. 9. The device of claim 8, wherein the clamping blocks are controlled for symmetrical clamping motion by a cam plate, opposed ends of which drive the clamping blocks toward and away from each other. 10. The device of claim 1, wherein the freely pivoting state permits the longitudinal axis of the blade to be substantially horizontal. 11. A device for sharpening a mower blade, comprising: a mounting assembly for mounting a blade having a rotational axis at its center and a pair of cutting edges, one cutting edge on each of opposed sides of the longitudinal axis, wherein the mounting assembly holds the blade in a fixed state or in free pivoting state allowing pivoting from the horizontal that reveals blade rotational imbalance; at least one grinding head assembly positionable adjacent one end of the blade and in engagement with a cutting edge to be sharpened; and a control system for controlling movement of the at least one grinding head assembly along the cutting edge, wherein the mounting assembly selectively holds the blade in the fixed state to enable the at least one grinding head assembly to grind a cutting edge in a direction substantially parallel to the at least one cutting edge of the blade, and in the free pivoting state to enable the blade to pivot around its rotational axis for balance testing. 12. The device of claim 11, wherein each cutting edge has a distal end and an inner end nearer its center and further comprising means for pivoting the blade away from the at least one grinding head assembly when a linear grind approaches the inner end of a cutting edge, thereby forming a curve at the inner end of such cutting edge. 13. The device according to claim 11, wherein the mounting assembly comprises a locking means for selectively holding the blade in the fixed state or in the free pivoting state when the locking means is released. 14. The device according to claim 13, wherein the mounting assembly is configured with a latch/release to release selectively the blade into a controlled tilting state. 15. The device according to claim 14, wherein the mounting assembly comprises a latch/release that is engaged when the blade is held in the fixed state and provides a controlled tilting state when the latch/release is released. 16. The device according to claim 11, wherein the at least one grinding head assembly comprises a first and a second grinding head assembly and the control system comprises a drive control for symmetrically moving the first and a second grinding head assemblies to substantially simultaneously grind two opposed cutting edges of the blade. 17. The device according to claim 16, wherein the drive control means comprises a controller for a belt drive coupled to the grinding head assemblies, each comprising a carriage, and a drive wheel coupled to the belt drive for providing movement to the grinding head assemblies. 18. A method for sharpening a rotary mower blade, comprising the steps of: using a mounting assembly, mounting a blade having two cutting edges to be sharpened on opposite sides of the blade's longitudinal axis, wherein the mounting assembly is configured to position the blade in a fixed state and a freely pivoting state; and controlling coordinated movement of two grinding head assemblies, each grinding head assembly being positioned adjacent an opposite end of the blade, wherein each grinding head assembly respectively grinds one of the two opposed cutting edges to be sharpened; and using the mounting assembly, first positioning the blade in the fixed state to enable each grinding head assembly to grind a cutting edge in a direction substantially parallel to the cutting edges of the blade, then positioning the blade substantially horizontally in the freely pivoting state to test the blade for rotational imbalance. 19. The method according to claim 18, wherein the step of using the mounting assembly comprises using a first lock for holding the blade in the fixed state and to release the blade into the free pivoting state when the first lock is released. 20. The method according to claim 18, further comprising using the mounting assembly, positioning the blade in a controlled tilting state, to pivot around its blade rotation axis away from the grinding head assemblies when a linear grind reaches an inner end of the cutting edge, thereby forming a curve at the inner end of each cutting edge. 21. The method according to claim 20, wherein the grinding head assemblies are mounted on a main base and the step of using the mounting assembly to position the blade in a controlled tilting state comprises selectively applying a latch/release that selectively fixes the mounting assembly to the main base and selectively releases the mounting assembly for controlled tilting. 22. The method according to claim 18, further comprising, in response to a rotational imbalance, placing the blade again in the fixed state and controlling the movement of one grinding head assembly to grind a cutting edge associated with a heavier end of the blade. 23. The method according to claim 18, wherein the step of controlling coordinated movement of the two grinding head assemblies is performed using a drive means for symmetrically moving the grinding head assemblies to substantially simultaneously grind the two cutting edges of the blade. 24. The method according to claim 18, wherein the step of first positioning the blade in the fixed state to enable each grinding head assembly to grind a cutting edge in a direction substantially parallel to the cutting edges of the blade, then positioning the blade substantially horizontally in the freely pivoting state to test the blade for rotational imbalance is performed without removing the blade from the mounting assembly.