Rotary mower including sharpener and method

Claim 1

In a rotary mower that includes a wheel mounted, downwardly opening housing and a vertical shaft rotatably depending in said housing having radially outwardly extending arms each supporting a cutting blade at its outer end for movement of the blades in an annular path in one direction at a relatively low idling speed and at a relatively high cutting speed, each blade having a cutting edge facing in said one direction, and a motor on said housing manually controllable for operation at a relatively low idling speed and a relatively high cutting speed, said motor being connected with said shaft for rotating said shaft, and arms as a unit about the axis of said shaft for moving said blades in said path at an idling speed and at said cutting speed, the improvement comprising: a. blade supporting means movable under the influence of centrifugal force upon movement of said blades in said annular path at said cutting speed for moving said blades about the axes of said arms from elevated non-cutting positions of the cutting edges of said blades to lowered cutting positions of said cutting edges and vice versa, b. yieldable means reacting between said blade supporting means and said arms for moving said blades from said lowered positions of their cutting edges to elevated non-cutting positions of said cutting edges upon the said blades moving in said annular path at said idling speed, c. an annular, planar blade sharpening stone coaxial with said shaft and path extending over and parallel with the plane of the latter, d. means supporting said sharpening stone for downward movement to a sharpening position with engagement with said blades along their cutting edges when said edges are in said elevated noncutting positions for sharpening said blades while they are moving in said path at said idling speed, and e. means connected with said stone for moving the latter downwardly to its said sharpening position and vice versa.