Four-armed lawnmower blade in same cutting plane from a single metal sheet
View Patent ↗A lawnmower blade stamped or laser cut from a single metal sheet arranged as four blade arms of equal length on a single cutting plane that can resemble a cruciform shape. This design yields a uniform strength and reliability and does not rely on nuts, bolts, and multipart construction, and with minimal effect on overall weight. Each blade extends outward from a center mounting, possesses an offset, a sharpened leading edge and oppositely a deflection portion that is curved upward to produce a consistent suction force and circulating air flow useful during high moisture conditions. The leading edges all rotate in a single cutting plane to produce a level grass cut. The blade is capable of easy installation on a wide range of lawnmowers, but with a focus on commercial models and applications.
1 . A lawnmower blade apparatus comprising:
a. four blade arms of equal length on a single cutting plane arranged such that they appear as if two identical blades overlap and the resulting said four blade arms are from the range of 45 degrees to 90 degree angles, inclusive, to each other on opposite sides of the narrowest identical angles where they cross to form an angle of separation;
b. wherein said blade arms are sharpened on a leading edge in the direction of rotation in the range of 30 to 60 percent of said length and extending to the end of said blade arms;
c. wherein said apparatus is laser cut or stamped on one mold from a single metal sheet which contains a circular hole at the center of a recessed depth for mounting onto a spindle or motor shaft from a lawnmower motor or engine, such that said four blade arms, including their offsets and deflection areas, are integrally formed from said single metal sheet;
d. wherein said apparatus further contains said offset beginning anywhere from 3.5 to 4.5 inches on each of said four blade arms measured from the center axis of rotation;
e. wherein said offset is angled uniformly in the range of 10 to 20 degrees to reach the depth of said offset;
f. wherein each of said four blade arms has an upward deflection angle in the range of 20 to 40 degrees on the side opposite of said leading edge beginning at said end of said blade arms and extending inward in the range of 20 to 60 percent of said radial length and extending to said end of said blade arms to create said deflection area;
g. wherein said deflection area is raised beginning on each of said blade arms and extending in a straight line at 27 degrees until reaching its height and the top portion of said deflection area is parallel to said leading edge;
h. wherein there is a curved radius between any two said blade arms positioned next to each other, where said end to said blade arms is generally uniform and on the same horizontal plane; and
i. wherein said blade arms have a thickness of 0.125 to 0.25 inches.
2 . Said apparatus of claim 1 , wherein an angle of separation is from 75 to 90 degrees inclusive for said blade arms.
3 . Said apparatus of claim 1 , where said deflection area is in a range of 30 to 36 percent of said length.
4 . Said apparatus of claim 1 , where said deflection angle of said blade arms is in a range of 25 to 29 degrees.
5 . Said apparatus of claim 1 , wherein said offset begins at 3.5 inches measured from said center axis of rotation.
6 . Said apparatus of claim 2 , wherein said angle of separation is 90 degrees.
7 . Said apparatus of claim 3 , wherein said deflection area is 33 percent of said length.
8 . Said apparatus of claim 1 , wherein said recessed depth contains a plurality of evenly distributed mounting holes.
9 . A process of making said apparatus comprising the steps of:
a. selecting a single metal or metal alloy sheet of the desired thickness and composition;
b. cutting, stamping, or laser cutting said sheet into a shape that corresponds to the desired blade dimensions arranged as said four blade arms;
c. bending and pressing said offset on each of said blade arms;
d. raising a deflection angle to create a deflection area on each of said blade arms;
e. sharpening said blade arms on said leading edge in the range of 30 to 60 percent of said length; and
f. tempering said apparatus to within industry recognized standards to produce a uniform hardness.