Anti-scalping blade for rotary lawn mower

In a lawn mower of the type which includes a shroud supported on wheels for horizontally traversing the surface of a lawn, a rotatably driven shaft near the horizontal center of the shroud and extending downwardly for rotatably driving a blade attached thereto, and an opening in the upper portion of the shroud for the exit of cuttings from the lawn, an anti-scalping blade comprising:

• formed metallic member of generally
• (a) an integrally flat configuration having a central section with a center balance point, said member being disposed horizontally within the shroud;
• (b) means for securing the driving shaft to said member in concentric relation to said center balance point;
• (c) said member also having three blade arms which are symmetrically circumferentially spaced about said central section and extend radially outwardly therefrom, each of said blade arms having a forward side sharpened to form a cutting edge and having a portion of its width adjacent its rearward side inclined upwardly to create an air lift for lifting cuttings toward the exit port;
• and
• (d) said central section being of circular configuration concentric to said balance point, its diameter being at least one-third the diameter of the outer perimeter of said blade arms, both said air lifts and said cutting edges extending substantially the full length of the respective blade arms up to and adjacent said central section, and the under surface of said central section being relatively smooth, so that
• (1) any tendency of said blade member to knock down grass without cutting it is minimized;
• (2) the spaces between blade arms through which a vacuum force is created by the combined action of said air lifts have a combined cross-sectional area which is less than twice the cross-sectional area of said member;
• and
• (3) the minimum speed of each blade arm cutting edge adjacent said central circular section is more than onethird its maximum speed at its outer end.