Patent Description:
Robotic garden tools like robotic mowers may include a rotating blade assembly. Rotational cutting blades are e.g. known from <CIT>, <CIT>, <CIT> and <CIT>.

A rotational cutting blade configured to rotate about an axis of rotation, the rotational cutting blade including a hub defining the axis of rotation, a first arm extending radially from the hub to define a first distal end, where the first arm includes a first blade mounting point configured to at least partially receive a cutting element therein, where the first blade mounting point includes a first cutting boundary, and where the first cutting boundary is subdivided into at least one access slot and at least one guard, and a second arm extending radially from the hub to define a second distal end, where the second arm includes a second blade mounting point configured to at least partially receive a cutting element, therein, where the second blade mounting point includes a second cutting boundary, and where the second cutting boundary includes at least one access slot and at least one guard.

The rotational cutting blade includes where the at least one guard of the first blade mounting point is positioned at a first radial distance from the axis of rotation, where the at least one guard of the second blade mounting point is positioned at a second radial distance from the axis of rotation, and where the first radial distance is different than the second radial distance.

Alternatively or additionally, in any combination, the rotational cutting blade may include where the at least one guard of the first blade mounting point at least partially radially overlaps an at least one access slot of the second blade mounting point.

Alternatively or additionally, in any combination, the rotational cutting blade may include where the first blade mounting point includes a pocket formed into the first arm, and where the second blade mounting point includes a pocket formed into the second arm.

The invention is capable of other embodiments and of being practiced or of being carried out according to the claims.

<FIG> illustrate a robotic garden tool <NUM> having a cutting element. More specifically, the illustrated robotic garden tool <NUM> includes a robotic mower for use to cut vegetation such as grass in an enclosed cutting area <NUM>. The cutting area <NUM> generally includes, but is not limited to, a continuous area of grass or other vegetation that is enclosed by one or more barriers <NUM>. In the illustrated embodiment, the barriers <NUM> include a series of electrified wires enclosing the cutting area <NUM> while in alternative embodiments different form of barrier may be used such as, but not limited to, walls, pavers, virtual barriers created by GPS data points or beacons, and the like. As shown in <FIG>, such barriers <NUM> may be used to enclose the overall cutting area <NUM> and/or to segregate one or more interior regions from the cutting area <NUM>. While the illustrated robotic garden tool <NUM> is a robotic lawn mower, it is understood that in alternative embodiments the garden tool <NUM> may include, but is not limited to, other forms of robotic garden tools having cutting blades such as a robotic trimmer, and the like.

As shown in <FIG>, the tool <NUM> is an electrically powered, self-propelled device that includes a body <NUM>, a plurality of wheels <NUM> rotatably mounted to the body <NUM>, a cutting assembly <NUM> mounted to the body <NUM>, a controller <NUM>, and a battery <NUM>. The body <NUM>, in turn, includes a front or first end <NUM>, rear or second end <NUM> opposite the first end <NUM>, a right or first side <NUM>, and a left or second side <NUM> opposite the first side <NUM>. The body <NUM> also defines a longitudinal axis <NUM> extending along the length of the body <NUM> and centered between the first side <NUM> and the second side <NUM> (e.g., passing through both the first and second ends <NUM>, <NUM>). The body <NUM> also defines a lateral axis <NUM> extending along the width of the body <NUM> and centered between the first and second ends <NUM>, <NUM> (e.g., passing through both the first and second sides <NUM>, <NUM>). The body <NUM> also defines a central axis <NUM> generally positioned at the intersection of the longitudinal and lateral axes <NUM>, <NUM> and oriented perpendicular to both (e.g., in a generally vertical orientation).

As shown in <FIG>, the tool <NUM> includes four wheels 22a, 22b, 22c, 22d, each rotatably coupled to the body <NUM> and configured to support the tool <NUM> for self-driven movement along a support surface <NUM> (e.g., the surface of the cutting area <NUM>). In the illustrated embodiment, the wheels 22a, 22b, 22c, 22d include two steerable, undriven wheels 22a, 22b and two non-steerable, driven wheels 22c, 22d. However, in alternative embodiments, all or any sub-set of the wheels <NUM> may be driven and all or any sub-set of the wheels <NUM> may be steerable. Furthermore, while the illustrated steerable wheels are passive in nature (e.g., a caster-style wheel), it is understood that in alternative embodiments the steerable wheels 22a, 22b may be actively driven by the controller <NUM>. In still other embodiments, the tool <NUM> may include more or fewer wheels <NUM> positioned in different arrangements about the tool <NUM>. In still other embodiments, the wheels <NUM> may be replaced by other forms of propulsion such as, but not limited to, tracks, omni-wheels, walking legs, and the like.

The driven wheels 22c, 22d of the tool <NUM> are positioned proximate the second end <NUM> of the body <NUM> and rotate about a common rear axis <NUM> oriented perpendicular to the longitudinal axis <NUM>. In the illustrated embodiment, each rear wheel 22c, 22d is mounted to and driven by a dedicated electric motor 68a, 68b to provide propulsion for the tool <NUM> over the support surface <NUM>. In some embodiments, the wheels <NUM> may be mounted directly to a respective motor 68a, 68b while in other embodiments a gear reduction and the like may be used. In the illustrated embodiment, the driven wheels 22c, 22d are non-steerable. However, in alternative embodiments, the driven wheels 22c, 22d may also be steerable.

<FIG> illustrates the cutting assembly <NUM> of the tool <NUM>. More specifically, the cutting assembly <NUM> includes a cutting motor <NUM> mounted to the body <NUM>, and a cutting blade <NUM> in operable communication with the cutting motor <NUM> and configured to rotate with respect to the blade guard <NUM> about a blade axis <NUM>. In some embodiments, the cutting assembly <NUM> may also include a blade guard <NUM> to at least partially encompass and restrict access to the cutting blade <NUM> during use.

As shown in <FIG>, the cutting blade <NUM> of the cutting assembly <NUM> includes frame <NUM> and one or more blade elements <NUM> coupled to the frame <NUM> to produce a radial cutting region <NUM>. During use, the cutting blade <NUM> is configured to be coupled to the motor <NUM> for rotation with respect to the body <NUM> about the blade axis <NUM>.

The frame <NUM> of the blade <NUM> includes a central hub <NUM> defining the blade axis <NUM>, and one or more arms <NUM> extending radially outwardly from the central hub <NUM> to define a corresponding distal end <NUM>, a first or leading edge in the direction of rotation, and a second or trailing edge opposite the direction of rotation. The frame <NUM> also forms a first surface <NUM> and a second surface <NUM> opposite the first surface <NUM>. In the illustrated embodiment, both the first and second surfaces <NUM>, <NUM> are planar to produce a plate-like shape, however, in alternative embodiments one or both surfaces <NUM>, <NUM> may be curvilinear.

As shown in <FIG>, each arm <NUM> of the cutting blade <NUM> extends radially outwardly from the central hub <NUM> to form a respective distal end <NUM> to define a corresponding arm radial length <NUM>. Each arm <NUM> also includes a blade mounting point (BMP) <NUM> sized and shaped to receive a corresponding blade element <NUM> therein. In the illustrated embodiment, the frame <NUM> includes three arms <NUM> equally spaced from one other and having the same arm radial length <NUM>. However, in alternative embodiments more or fewer arms <NUM> may be present. In still other embodiments, the arm radial length <NUM> may vary between each arm <NUM>. For example, in some embodiments a first subset of arms <NUM> may have a first arm radial length <NUM> while a second subset of arms <NUM> may have a second arm radial length <NUM> different than the first arm radial length <NUM>. In still other embodiments, each arm <NUM> may have a unique arm radial length <NUM>.

In the illustrated embodiment, each arm <NUM> is linear in overall shape tapering in width as they extend radially outwardly away from the hub <NUM> to form a pair of side axes <NUM> generally corresponding to the lateral edges <NUM> thereof. However, in alternative embodiments, different width profiles and/or different shapes may be present. For example, the arms <NUM> may be curved and the like. Furthermore, while each arm <NUM> has the same shape and width profile, it is understood that in other embodiments each arm <NUM> or a subset of arms <NUM> may have a unique shape and/or width profile.

As shown in <FIG>, each arm <NUM> includes at least one BMP <NUM> formed integrally therein and sized and shaped to receive a corresponding blade element <NUM> therein. More specifically, the illustrated BMP <NUM> includes a pocket <NUM> formed into one of the first surface <NUM> and the second surface <NUM> with a pocket depth <NUM> generally corresponding to the height <NUM> of the blade element <NUM>. The pocket <NUM> also includes one or more cutting boundaries <NUM> generally corresponding to the boundary of the pocket <NUM> immediately opposite or adjacent to a cutting edge <NUM> of the cutting element <NUM> placed therein. More specifically, the pocket <NUM> includes a first cutting boundary 150a adjacent the first cutting edge 148a of the blade element <NUM> and a second cutting boundary 150b adjacent the second cutting edge 148b of the blade element <NUM>. During operation, only one of the first and second cutting edges 148a, 148b of a given cutting element <NUM> will actually cut vegetation at any given time depending upon the orientation of the cutting blade <NUM> relative to the body <NUM> (e.g., whether the blade <NUM> is installed first surface <NUM> up or first surface down <NUM>) and the direction of rotation of the blade <NUM>.

In the illustrated embodiment, the pocket <NUM> is completely positioned within the periphery of the corresponding arm <NUM> and integrally formed therein. As shown in <FIG>, the arm radial length <NUM> is greater than the maximum radial distance of the pocket <NUM> and the pocket <NUM> is completely positioned between both edge axes <NUM>.

The BMP <NUM> also includes one or more access slots <NUM> and one or more guards <NUM> positioned along the cutting boundaries 150a, 150b of the pocket <NUM>. More specifically, each access slot <NUM> includes a slot formed into the arm <NUM> and sized to provide access to the corresponding cutting edge <NUM> of the blade element <NUM>. In the illustrated embodiment, each access slot <NUM> is open to a lateral edge <NUM> of the arm <NUM> and extends circumferentially inwardly therefrom a distance greater than the distance between the lateral edge <NUM> and the cutting edge <NUM> of the blade element <NUM> (see <FIG>). In contrast, each guard <NUM> includes a portion of the arm <NUM> that remains in position adjacent the cutting edge <NUM> of the blade element <NUM> to restrict access thereto.

In the illustrated embodiment, each access slot <NUM> defines an access width <NUM> that is sized to permit grass to engage the cutting edge <NUM> of the blade element <NUM> during use but small enough to restrict access to the blade by a user's fingers, toes, and/or other appendages. More specifically, each access slot <NUM> of the cutting blade <NUM> have an access width <NUM> that is less than or equal to <NUM>. By limiting the maximum width of any given access slot <NUM>, the cutting blade <NUM> improves safety by restricting access to the sharp portions of the blade <NUM> (e.g., the cutting edges <NUM> of the blade element <NUM>) to any items larger than the maximum access width. In some embodiments, the access width <NUM> is between <NUM> and <NUM>. In other embodiments, the access width <NUM> may be less than or equal to <NUM>, <NUM>, <NUM>, or <NUM>. In still other embodiments, the access width <NUM> may be less than <NUM>.

As shown in <FIG>, the BMP <NUM> includes three access slots <NUM> and three guards <NUM> positioned along both the first and second cutting boundaries 150a, 150b. More specifically, each cutting boundary 150a, 150b of the BMP <NUM> includes a first guard 156a positioned at a first radial distance <NUM> from the axis <NUM>, a second guard 156b positioned at a second radial distance <NUM> from the axis <NUM>, and a third guard 156c positioned at a third radial distance <NUM> from the axis <NUM>. In the illustrated embodiment, the locations of each guard 156a, 156b, 156c of each arm <NUM> is located at the same radial distances of the same corresponding guards 156a, 156b, 156b of the remaining arms <NUM> (e.g., the BMP <NUM> of each arm <NUM> is identical). However, in alternative embodiments, the locations and number of the guards <NUM> in each arm <NUM> may be staggered to assure that, between all of the arms <NUM>, an un-guarded portion of a cutting edge <NUM> of a blade element <NUM> is continuously available over the entire radial cutting region <NUM> of the blade <NUM>. For example, the guards <NUM> of the BMPs <NUM> of blade <NUM> are positioned so that where a guard <NUM> is present in one arm <NUM> at least one access slot <NUM> is present in another arm <NUM> over the entire radial cutting region <NUM>. By doing so, the blade <NUM> is able to include the safety provided by the guards <NUM> but still assure a complete and unbroken radial cutting region <NUM> to improve efficiency. In still other embodiments, the guard <NUM> of one arm <NUM> is positioned so that it at least partially radially overlaps the access slot <NUM> of another arm <NUM>. In still other embodiments, the BMPs <NUM> may all be positioned at the same radial distance from the axis of rotation, in other embodiments, the BMPs <NUM> may be offset. In still other embodiments, the BMPs <NUM> may be staggered such that the at least partially radially overlap one another to produce a continuous cutting region <NUM> that is radially wider than any single given blade <NUM>.

<FIG> illustrates a blade element <NUM> of the cutting blade <NUM>. The blade element <NUM> is substantially rectangular in shape and includes a first cutting edge 148a and a second cutting edge 148b opposite the first cutting edge 148a. The cutting blade <NUM> also defines a blade height <NUM>, a first cutting plane coincident with the first cutting edge 148a and parallel to the bottom surface of the blade element <NUM>, and a second cutting plane coincident with the second cutting edge 148b and parallel to the top surface of the blade element. While the illustrated blade element <NUM> includes two linear cutting edges 148a, 148b, it is understood that in alternative embodiments different sizes and shapes of blade element <NUM> may be used having different number and contour of cutting edges thereon.

<FIG> illustrates another embodiment of a blade element <NUM>'. The blade element <NUM>' includes a body <NUM>' having a cutting edge <NUM>' sub-divided by one or more guard prongs <NUM>' formed integrally therewith and having a blunt or otherwise un-sharpened perimeter. In the illustrated embodiment, each pair of adjacent guard prongs <NUM>' define a gap distance <NUM>' therebetween. The gap distance <NUM>' between each pair of adjacent guard prongs <NUM>' is large enough to allow grass and other vegetation to gain access to and engage the cutting edge <NUM>' positioned therebetween but sufficiently small to restrict access to the cutting edge <NUM>' by a user's fingers, feet, and other appendages. More specifically, each gap distance <NUM>' of the blade element <NUM>' is less than or equal to <NUM>. In other embodiments, each gap distance <NUM>' is between <NUM> and <NUM>. In still other embodiments, the gap distance <NUM>' may be less than or equal to <NUM>, <NUM>, <NUM>, or <NUM>. In still other embodiments, the gap distance <NUM>' may be less than <NUM>. While the illustrated guard prongs <NUM>' are formed integrally with the body <NUM>' of the blade element <NUM>', it is understood that in alternative embodiments the guard prongs <NUM>' may be molded onto the body <NUM>' as a separate material.

Claim 1:
A rotational cutting blade (<NUM>) configured to rotate about an axis (<NUM>) of rotation, the rotational cutting blade (<NUM>) comprising:
a hub (<NUM>) defining the axis (<NUM>) of rotation,
a first arm (<NUM>) extending radially from the hub (<NUM>) to define a first distal end (<NUM>), wherein the first arm (<NUM>) includes a first blade mounting point (<NUM>) configured to at least partially receive a cutting element (<NUM>) therein, wherein the first blade mounting point (<NUM>) includes a first cutting boundary (150a, 150b), and wherein the first cutting boundary (150a, 150b) is subdivided into at least one access slot (<NUM>) and at least one guard (<NUM>); and
a second arm (<NUM>) extending radially from the hub (<NUM>) to define a second distal end (<NUM>), wherein the second arm (<NUM>) includes a second blade mounting point (<NUM>) configured to at least partially receive a cutting element (<NUM>), therein, wherein the second blade mounting point (<NUM>) includes a second cutting boundary (150a, 150b), and wherein the second cutting boundary (150a, 150b) includes at least one access slot (<NUM>) and at least one guard (<NUM>),
wherein the at least one guard (<NUM>) of the first blade mounting point (<NUM>) is positioned at a first radial distance from the axis (<NUM>) of rotation, wherein the at least one guard (<NUM>) of the second blade mounting point (<NUM>) is positioned at a second radial distance from the axis (<NUM>) of rotation, and wherein the first radial distance is different than the second radial distance,
characterized in that
the guards (<NUM>) of the blade mounting points (<NUM>) of the blade (<NUM>) are positioned so that where the guard (<NUM>) is present in the first arm (<NUM>) at least one access slot (<NUM>) is present in the second arm (<NUM>) over an entire radial cutting region (<NUM>).