Rotary lawn mower cutting blade

A rotary lawn mower cutting blade with reduced drag and improved cutting ability includes a central mounting section, intermediate sections, and outboard sections along a common longitudinal axis and disposed about a common center of rotation. The outboard sections includes downward and inward projecting sections. The cutting blade also preferably includes cutting edges on the full extent of the leading edge of the outboard section including the downward and inward projecting sections. Additionally, the outer section can be twisted slightly to enhance airflow upward.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cutting blade for rotary lawn mowers.

2. Prior Art

Conventional rotary lawn mower cutting blades are made of an elongated flat metal plate, rectangular in shape, with a central mounting portion and an outer portion having a leading beveled cutting edge, and a bend or twist of either the entire outer portion of the blade or just the trailing edge of the outer portion to generate airflow used to draw the uncut grass upward into the path of the cutting edge and to expel the cuttings from the cutting area. Raised teeth may be added to the trailing edge of the outer portion of the blade to produce a mulching action.

The problem with present art rotary lawn mower cutting blades is that the central mounting portion is generally in the same plane as the cutting portion, resulting in lost energy as the central mounting portion passes over and impinges upon the top edge of the cut grass and residual clippings. Energy is wasted, efficiency of the lawn mower is impaired, and airflow through the cutting area is restricted.

It is the object of this invention to provide a novel rotary lawn mower cutting blade which has improved cutting abilities and can operate with greater efficiency.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a rotary lawn mower cutting blade which provides for improved cutting action with greater efficiency, comprises a central mounting portion, two oppositely extending intermediate portions connecting to outer portions which are in turn joined to downward-turned end portions which are in turn joined to inward turned cutting portions.

According to the invention, the downward-turned end portions may be straight or curved and may be directed downward in a perpendicular orientation from the plane of the central mounting portion, or at some obtuse or acute angle therefrom. The downward-turned end portion may also be skewed to the axis of rotation of the cutting blade, which places the leading edge of the end portion at a greater or less distance from the center of rotation than the trailing edge.

According to the invention, airflow can be enhanced during rotation of the blade by applying a slight twist to the intermediate or outer portion of the blade, the trailing edge of the outer portion, the trailing edge of the cutting portion, or some combination thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIG. 1andFIG. 2, there is shown a rotary mower cutting blade101that is an embodiment of the present invention having a central portion2which includes a central bore1for attaching blade101to a source of rotating power. The cutting blade is further provided with outer portions7which are joined to the central portion2by intermediate portions8along a common longitudinal blade axis. The cutting portions10, which have leading cutting edges6and trailing edges5, are joined to the outer portions7through the downward portions9. The outer portion7has a trailing edge3and the downward portion9has a trailing edge4. As seen inFIG. 1, the central portions, intermediate portions, and outer portions can be generally planar and can be disposed generally in a common plane. The leading cutting edges6of the cutting portions10, which are beveled from the inner surface of the cutting portion10downward in this embodiment, are continued through the downward portions9where the bevel direction becomes outward and outer portions7where the bevel direction becomes upward, however it of course may be understood that the direction of bevel and portions of the blade which are beveled to form a cutting edge can vary.

In this embodiment, the cutting blade is twisted slightly in the intermediate portion8. This will facilitate directing air upward during rotation of the cutting blade as air is directed upward along the surface of the outer portion7and the cutting portion10. As an alternative, trailing edge5and/or trailing edge3can be bent or twisted upward to create upward airflow during rotation of the cutting blade, and can also be formed into teeth as in U.S. Pat. No. 6,487,840 to create a mulching action of the grass clippings.

In this embodiment, the plane of the downward portions9are perpendicular to the plane of the central portion2, however this angular relationship may be acute or obtuse. Therefore, where in this specification and claims I employ the term “downward”, I intend an angular relationship which will result in a general downward projection. The plane of the downward portion9can also be skewed or twisted in the vertical plane so as to cause the trailing edge4to be further away from the center of rotation of the cutting blade than any other point on the surface of the downward portion9. This vertical twist will result in airflow being directed outward during rotation of the cutting blade which will improve removal of the grass clippings from the cutting area.

FIG. 3andFIG. 4illustrates a cutting blade201that is a second preferred embodiment of the invention. The cutting blade201is substantially identical to cutting blade101, with the exception that the downward portion9is curved rather than straight.

FIG. 3andFIG. 4illustrates a cutting blade201that is a second preferred embodiment of the invention. The cutting blade201is substantially identical to cutting blade101, with the exception that the downward portion9is curved rather than straight. Edge11that is shown as being intermediate of edge5and edge6and which is labeled inFIGS. 2 and 4and shown through the views can be regarded as an interior edge of the respective cutting portion on which it is included. As shown inFIGS. 1 and 3, an interior edge of a first cutting portion can generally face an interior edge of a second cutting portion.

While this invention has been described in the specification and illustrated in the drawings with respect to a preferred embodiment, it is understood that all changes and modifications that come within the spirit of the invention are desired to be protected. Undoubtedly, many variations or equivalents may be substituted for elements of the invention by one having ordinary skill in the art to which the present invention most nearly pertains, and such variations are intended to be within the scope of the invention, as disclosed herein;