Patent Description:
Lawn care tasks are commonly performed using various tools and/or machines that are configured for the performance of corresponding specific tasks. Certain tasks, like grass cutting, are typically performed by lawn mowers. Lawn mowers may come in many different sizes and may have wide variances in their design and capabilities. However, beyond mere changes in design, size and function, lawn mowers have more recently also provided users with increased options in terms of powering the lawn mowers. While petrol or gasoline engines were dominant for decades, a market is quickly developing for battery powered lawn mowers.

Unlike petrol or gasoline engines that can be refueled very quickly at just about any location on a job site, battery powered devices need to be taken out of operation for a while in order to be recharged (unless a new and previously charged battery can be interchanged with the depleted battery). However, for large jobs, even battery replacement may not be fully enabling for completing the job if there is not sufficient time to charge depleted batteries while the substitute battery or batteries are themselves being depleted during operation. In other words, if the speed at which depleted batteries recharge is not as fast as the speed at which batteries in use are depleted, then even battery replacement may not enable a job to be completed without waiting at least some time for battery charging. The potential limitations of battery charging can make it even more important that the battery powered devices have sufficient capacity to complete a job at a job site on a single charge (or at least without having to wait for any charge time before completing the job) in order to secure the viability and growth of this emerging market.

In order to deliver on these expectations, improving the efficiency of the lawn mower may be helpful. Moreover, since turning the mower blade can be one of the main sources of power consumption in a battery powered lawn mower, improving the efficiency of the lawn mower blade itself may contribute significantly to achieving the usage time that is achievable for a given battery powered lawn mower.

In this sense, Great <CIT> discloses a device according to the preamble of appended claim <NUM>.

According to the invention there is provided a cutting blade for a lawn mower. The cutting blade includes a mounting portion and a plurality of cutting elements. The mounting portion includes a plurality of mounting arms and a mounting orifice formed at an axis of the cutting blade. The mounting orifice is configured to interface with a shaft of the lawn mower. Each of the cutting elements is operably coupled to a corresponding one of the mounting arms. Each of the cutting elements includes a wing portion at a distal end thereof, and a transition region configured to operably couple the wing portion to a respective one of the mounting arms. The cutting elements further include a first cutting edge disposed at the wing portion, and a second cutting edge disposed at the transition region.

Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Furthermore, as used herein, the term "or" is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other.

Some example embodiments may provide a lawn mower blade with design features and geometries that define a structure capable of delivering high performance with less power consumption. In this regard, for example, the high efficiency blade described herein includes multiple (e.g., four) blade elements that each include two cutting edges. The cutting edges are provided in a swept configuration with a lift geometry that produces more than a <NUM>% (in some cases as much as <NUM>% or more) lift than conventional blade designs with at least <NUM>% less drag. As a result, the structures provided herein deliver a highly efficient, yet quality cutting experience.

A description of an example embodiment will follow in reference to <FIG>. <FIG> illustrates a top perspective view of a high efficiency blade <NUM> according to an example embodiment. <FIG> illustrates a side view of the high efficiency blade <NUM>, and <FIG> and <FIG> illustrate top and bottom views, respectively, of the high efficiency blade <NUM>. <FIG> illustrates a perspective view (taken from a perspective at a blade axis of the high efficiency blade <NUM>) of a wing portion <NUM> and a transition region <NUM> of a single cutting element of the high efficiency blade <NUM>. <FIG> is a top, perspective view of the wing portion <NUM> and the transition region <NUM> of the single cutting element of <FIG>. Meanwhile, <FIG> is a perspective view of the single cutting element from a point situated in front of the wing portion <NUM>, while <FIG> is a perspective view from a point displaced from a distal end of the wing portion <NUM>. <FIG> shows a cross section view of the wing portion <NUM> taken along line A-A' of <FIG>, and <FIG> shows a cross section view taken along line B-B' of <FIG>.

Referring now to <FIG>, the high efficiency blade <NUM> includes a plurality of cutting elements (e.g., first cutting element <NUM>, second cutting element <NUM>, third cutting element <NUM>, and fourth cutting element <NUM>). The cutting elements are configured to define a balanced and symmetrical structure to improve the ease at which the high efficiency blade <NUM> can be rotated by a shaft driven by the engine of the lawn mower. The high efficiency blade <NUM> also includes a mounting portion <NUM> to which each of the cutting elements is attached. The mounting portion <NUM> may include a mounting orifice <NUM> at a center thereof. The mounting orifice <NUM> may have any desired shape for interfacing with the shaft of the lawn mower. Thus, for example, the mounting orifice <NUM> could have a circular shape (as shown) or other shapes such as a star shape, rectangular shape, triangular shape, or numerous other geometric shapes. The mounting portion <NUM> interfaces with the shaft of the lawn mower either directly or indirectly (e.g., via a mounting structure operably coupled to the shaft). In any case, the mounting portion <NUM> (and the mounting orifice <NUM> in particular) may define an axis <NUM> of rotation for the high efficiency blade <NUM>.

The mounting portion <NUM> also includes a corresponding instance of a mounting arm <NUM> for each respective one of the first cutting element <NUM>, the second cutting element <NUM>, the third cutting element <NUM>, and the fourth cutting element <NUM>. The mounting arms <NUM> may desirably have a significantly smaller width than the wing portions <NUM> in order to minimize the weight of the mounting portion <NUM>. By keeping the weight of the mounting portion <NUM> low, and by providing good aerodynamic characteristics for the wing portion <NUM>, the lift provided by the high efficiency blade <NUM> may be increased and the power needed to turn the high efficiency blade <NUM> may be decreased. Additionally, by employing a balanced configuration with four cutting elements spaced equally apart from each other, and having corresponding cutting edges and lifting surfaces may increase efficiency of the high efficiency blade <NUM> by greater than <NUM>% relative to a more conventional two cutting edge design.

A cutting portion of each of the cutting elements includes a first cutting edge <NUM> and a second cutting edge <NUM>. The first cutting edge <NUM> extends across a leading edge of the wing portion <NUM>, and the second cutting edge <NUM> extends across the leading edge of the transition region <NUM>. In an example embodiment, the first cutting edge <NUM> may extend entirely across the leading edge of the wing portion <NUM>, and the second cutting edge <NUM> may extend entirely across the leading edge of the transition region <NUM>. However, it is possible that the first and second cutting edges <NUM> and <NUM> could be formed to extend over only parts (and not all) of the leading edges of the wing portion <NUM> and transition region, respectively. In the context of this disclosure the leading edge should be understood in reference to a direction of rotation shown by arrow <NUM> (i.e., clockwise when viewed from above).

The wing portion <NUM> may be a plate-like piece of material (e.g., a fin or wing) shaped to have a substantially consistent shape from a proximal end <NUM> (see <FIG> and <FIG>) of the wing portion <NUM> to a distal end <NUM> of the wing portion <NUM>. The proximal end <NUM> of the wing portion <NUM> may be attached to a distal end <NUM> of the transition region <NUM>. A proximal end <NUM> of the transition region <NUM> is attached to the mounting portion <NUM>.

The first cutting edge <NUM> of each of the cutting elements is in a same plane (e.g., a cutting plane <NUM>) such that rotation of the high efficiency blade <NUM> carries the first cutting edges <NUM> of all of the cutting elements consistently through the cutting plane <NUM> (see <FIG>). As best seen in <FIG>, the wing portion <NUM> may be formed to curve (over a substantially consistent arc) from the first cutting edge <NUM> to a trail edge <NUM> of the wing portion <NUM>.

The trail edge <NUM> of each of the wing portions <NUM> of the cutting elements also lies in a same plane (e.g., a trail edge plane <NUM> shown in <FIG>) that is spaced apart from the cutting plane <NUM>. Meanwhile, the trail edge <NUM> and the first cutting edge <NUM> of each of the cutting elements extends from the proximal end <NUM> to the distal end <NUM> of the wing portion <NUM> substantially parallel to each other. The trail edge <NUM> may also be chamfered in order to further increase efficiency of the high efficiency blade <NUM> by about <NUM>% as compared to a similar design without the chamfered characteristic. The mounting portion <NUM> (and therefore the mounting arms <NUM>) lie in a plane substantially half way between the cutting plane <NUM> and the trail edge plane <NUM> (or in a range of between about <NUM>% to about <NUM>% of the way in between the cutting plane <NUM> and the trail edge plane <NUM>).

A chord length of the wing portion <NUM> may be selected to be about <NUM> inches. This chord length increases efficiency by about <NUM>% due to the aerodynamic characteristics of the resulting wing. As shown in <FIG>, for the chord length of about <NUM> inches at the wing portion <NUM>, an angular difference (i.e., wing angle of attack) measured from the cutting plane <NUM> to line passing directly from the first cutting edge <NUM> to the trail edge <NUM> may be about <NUM> degrees. However, any values from about <NUM> degrees to about <NUM> degrees may be employed in various example embodiments. A wing angle of attack in this range provides good lift and improved efficiency. Moreover, at the wing angle of attack of <NUM> degrees, an increased efficiency of about <NUM>% is experienced relative to designs without a wing angle.

As can be appreciated from <FIG>, the wing portion <NUM> is in a swept configuration relative to the transition region <NUM> (and corresponding portions of the mounting portion <NUM> that are operably coupled to each respective transition region <NUM> of the cutting elements). In particular, as shown in <FIG>, an angular difference between a line <NUM> extending along the first cutting edge <NUM> and a radial line <NUM> extending from the axis <NUM> at the mounting orifice <NUM> to the blade tip (i.e., an intersection between the distal end <NUM> of the wing portion <NUM> and the first cutting edge <NUM>) may be about <NUM> degrees. This angular difference defines a swept angle <NUM> or the degree to which the first cutting edge <NUM> is swept (forward in this example) in relation to the mounting arms <NUM>.

In an example embodiment, a width of the mounting arms <NUM> (as shown in <FIG>) may be about <NUM>% of the chord length of the wing portion <NUM>. Thus, in this example, the width of the mounting arms <NUM> may be about <NUM> inches since the chord length is <NUM> inches. The transition region <NUM> may be structured to provide the transition from the mounting arms <NUM> to the wing portion <NUM> both in terms of accommodating the swept angle <NUM>, the transition from a narrower (e.g., <NUM> inch) mounting arm <NUM> to a wider (e.g., <NUM> inch chord length) wing portion <NUM>, and the transition from a flat mounting arm <NUM> to a curved wing portion <NUM>. Accordingly, the transition region <NUM> may be configured to simultaneously broaden and twist while also bending from the proximal end <NUM> to the distal end <NUM> of the transition region <NUM>. In this regard, for example, the transition region <NUM> bends forward about <NUM> degrees (e.g., to the right as viewed from the top, but generally forward toward the leading edge of the wing portion <NUM>) to provide the swept angle <NUM>. The transition region <NUM> is also twisted since the mounting arms <NUM> are flat and located in between the trail edge plane <NUM> and the cutting plane <NUM> so that a rear part (or trail end) of the transition region <NUM> rises from the rear end or trail end of the mounting arms <NUM> to meet the trail edge <NUM> of the wing portion. Meanwhile, a front part or leading edge of the transition region <NUM> falls from the front part or trail end of the mounting arms <NUM> to meet the first cutting edge <NUM>. The second cutting edge <NUM> follows this transition and therefore includes a curve that extends upward away from the cutting plane <NUM> while simultaneously curving at an angle in a direction away from the trail edge <NUM> of the wing portion <NUM>. The extension of the second cutting edge <NUM> upward and away from the cutting plane <NUM> enables the second cutting edge <NUM> to act as a mulching blade in combination with the significant lift provided by the wing portion <NUM>.

In some example embodiments, an aerodynamic orifice <NUM> may be provided in the transition region <NUM> in order to further improve efficiency. The aerodynamic orifice <NUM> may be provided at an approximate midpoint of the transition region <NUM> between the distal end <NUM> and proximal end <NUM> thereof. In some cases, the aerodynamic orifice <NUM> may be round, rectangular or have another geometric shape. However, by employing a square shape (e.g., with rounded corners) at the midpoint of the transition region <NUM>, efficiency of the high efficiency blade <NUM> may be increased by about <NUM>% as compared to the same design without the aerodynamic orifice <NUM>.

The high efficiency blade <NUM> of an example embodiment employs the various efficiency improving features in combination to maximize efficiency. However, it should also be appreciated that subsets of the features described above could also be employed in various combinations in order to improve efficiency as well without necessarily combining all of the features. The combination of all of the features described above has been shown to provide as much as <NUM>% more lift per pound of drag, and <NUM>% less drag than a comparable lift provided by a standard mower blade offered today.

In an example embodiment, the cutting blade may include additional, optional features, and/or the features described above may be modified or augmented. Some examples of modifications, optional features and augmentations are described below. It should be appreciated that the modifications, optional features and augmentations may each be added alone, or they may be added cumulatively in any desirable combination. The first cutting edge of each of the cutting elements extends linearly across a leading edge of the wing portion from a proximal end of the wing portion to a distal end of the wing portion, and the first cutting edge of each of the cutting elements lie in a cutting plane. The wing portion further includes a trail edge disposed opposite the first cutting edge on the wing portion and extending substantially parallel to the first cutting edge, and the trail edge of each of the cutting elements lie in a trail edge plane. The mounting portion lies in a plane about half way between the trail edge plane and the cutting plane. In an example embodiment, the trail edge may be chamfered. In some cases, the second cutting edge may extend across a leading edge of the transition region from a proximal end of the transition region to a distal end of the transition region. In an example embodiment, the second cutting edge and the first cutting edge may form a continuous cutting surface, and the second cutting edge may extend away from the cutting plate as the second cutting edge moves away from the distal end of the transition region toward the proximal end of the transition region. In some cases, the second cutting edge bends away from the trail edge as the second cutting edge moves away from the distal end of the transition region toward the proximal end of the transition region. In an example embodiment, a chord length of the wing portion from the first cutting edge to the trail edge may be more than twice a width of the mounting arm. In some cases, the transition region may be configured to taper in width from a leading edge to a trailing edge thereof from the chord length of the wing portion at a distal end of the transition region to the width of the mounting arm at a proximal end of the transition region. In an example embodiment, the transition region may include an aerodynamic orifice disposed at a portion thereof. In some cases, the aerodynamic orifice may have a square shape with rounded corners. In an example embodiment, the aerodynamic orifice may be disposed at a center of the transition region. In some cases, the electronic connection assembly may include a corded connection between an electrical system of the host device and the electric motor. In an example embodiment, the wing portion may be configured to curve from the first cutting edge to the trail edge defining an attack angle of between about <NUM> degrees and <NUM> degrees. In some cases, the wing portion may be swept relative to the mounting arm at a swept angle of between about <NUM> degrees and <NUM> degrees. In an example embodiment, the swept angle may be about <NUM> degrees. In some cases, the cutting blade may include four cutting elements equidistantly spaced apart from each other. In an example embodiment, the wing portion may be curved and the mounting portion is flat. The transition region may be flat at a proximal end thereof and curved at a distal end thereof to transition from the mounting portion to the wing portion. In some cases, the distal end of the transition region may include a first portion that extends downward from a plane in which the mounting portion lies to the first cutting edge, and a second portion that extends upward from the plane to a trail edge of the wing portion.

Claim 1:
A cutting blade (<NUM>) for a lawn mower, the cutting blade (<NUM>) comprising:
a mounting portion (<NUM>) comprising a plurality of mounting arms (<NUM>) and a mounting orifice (<NUM>) formed at an axis (<NUM>) of the cutting blade (<NUM>), the mounting orifice (<NUM>) being configured to interface with a shaft of the lawn mower; and
a plurality of cutting elements (<NUM>, <NUM>, <NUM>, <NUM>), each of the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) operably coupled to a corresponding one of the mounting arms (<NUM>),
wherein each of the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) comprises a wing portion (<NUM>) at a distal end (<NUM>) thereof, and a transition region (<NUM>) configured to operably couple the wing portion (<NUM>) to a respective one of the mounting arms (<NUM>), and
wherein the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) further comprise a first cutting edge (<NUM>) disposed at the wing portion, and extending linearly across a leading edge of the wing portion (<NUM>) from a proximal end (<NUM>) of the wing portion (<NUM>) to a distal end (<NUM>) of the wing portion (<NUM>), and
wherein the first cutting edge (<NUM>) of each of the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) lies in a cutting plane (<NUM>) , wherein the wing portion (<NUM>) further comprises a trail edge (<NUM>) disposed opposite the first cutting edge (<NUM>) on the wing portion (<NUM>) and extending substantially parallel to the first cutting edge (<NUM>), and
wherein the trail edge (<NUM>) of each of the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) lies in a trail edge plane (<NUM>), characterized in that the mounting portion (<NUM>) lies in a plane about half way between the trail edge plane (<NUM>) and the cutting plane (<NUM>), and in that the cutting elements (<NUM>, <NUM>, <NUM>, <NUM>) further comprise a second cutting edge (<NUM>) disposed at the transition region (<NUM>).