Rotary lawn mower, blade and sharpener

Claim 1

IN A ROTARY LAWN MOWER THAT INCLUDES A PORTABLE, WHEEL MOUNTED MOWER CHASSIS HAVING A MOTOR DRIVEN, ROTATABLE, VERTICAL SHAFT PROVIDED WITH BLADE SUPPORTING MEANS ON ITS LOWER END FOR SUPPORTING A PLURALITY OF SUBSTANTIALLY HORIZONTALLY EXTENDING CUTTING BLADES RIGID WITH SAID SHAFT FOR MOVEMENT OF SAID BLADES WITH SAID SHAFT IN ONE DIRECTION IN AN ANNULAR PATH ABOUT SAID SHAFT WHEN SAID SHAFT IS ROTATED IN SAID ONE DIRECTION: (A) A PLURALITY OF SUBSTANTIALLY HORIZONTALLY ELONGATED, FLAT-SIDED, CUTTING BLADES EXTENDING LONGITUDINALLY THEREOF RADIALLY OUTWARDLY OF SAID BLADE SUPPORTING MEANS, AND ONE OF THE LONGITUDINALLY EXTENDING EDGES OF EACH BLADE BEING A LEADING EDGE RELATIVE TO THE DIRECTION OF MOVEMENT THEREOF IN SAID PATH, AND EACH BLADE ALSO BEING BEVELLED ON ITS UNDERSIDE ALONG SAID LEADING EDGE TO THE UPPER SURFACE OF EACH BLADE WHEREBY SAID LEADING EDGE IS SHARPENED TO PROVIDE A CUTTING EDGE; (B) BLADE SECURING MEANS FOR RELEASABLY SECURING EACH BLADE TO SAID BLADE SUPPORTING MEANS FOR MOVEMENT OF EACH BLADE RELATIVE TO SAID BLADE SUPPORTING MEANS FROM A LOWERED CUTTING POSITION AT A LEVEL BELOW SAID SHAFT AND SAID BLADE SUPPORTING MEANS AND WITH SAID CUTTING EDGE LEADING RELATIVE TO SAID MOVEMENT OF SAID BLADE IN SAID PATH IN SAID ONE DIRECTION TO AN ELEVATED SHARPENING POSITION SPACED ABOVE SAID CUTTING POSITION WITH SAID CUTTING EDGE TRAILING RELATIVE TO SAID DIRECTION OF MOVEMENT OF SAID BLADE IN SAID PATH, AND WITH THE BEVELLED SURFACE ALONG SAID CUTING EDGE FACING UPWARDLY AND HORIZONTAL; (C) SAID BLADE SECURING MEANS INCLUDING MEANS FOR LOCKING SAID BLADE IN SAID CUTTING POSITION AND IN SAID SHARPENING POSITION RESPECTIVELY; (D) BLADE SHARPENING MEANS CARRIED BY SAID CHASSIS AT A POINT SPACED ABOVE SAID ANNULAR PATH OF SAID BLADES WHEN THE LATTER ARE IN SAID CUTTING POSITION AND IN A POSITION FOR ENGAGEMENT WITH THE BEVELLED SURFACE OF SAID BLADE ALONG SAID CUTTING EDGE WHEN SAID BLADE IS LOCKED IN SAID SHARPENING POSITION AND IS MOVED IN SAID ONE DIRECTION ABOUT THE AXIS OF SAID SHAFT.