WO2013025135A1

WO2013025135A1 - Cutting blade

Info

Publication number: WO2013025135A1
Application number: PCT/SE2011/050996
Authority: WO
Inventors: Patrik JÄGENSTEDT; Magnus ÖHRLUND
Original assignee: Husqvarna Ab
Priority date: 2011-08-18
Filing date: 2011-08-18
Publication date: 2013-02-21
Also published as: SE1450250A1; DE112011105538T5; DE112011105538B4; SE541461C2

Abstract

The invention relates to a rotary lawn mower cutting blade (110). The cutting blade (110) is arranged to rotate about a vertical axis of rotation (A) of a lawn mower (100). The cutting blade (110) includes a base portion (204), arranged to connect the cutting blade (110) to a rotating carrier member (108) attached to the lawn mower (100). The cutting blade (110) further includes a cutting portion (208) having at least one recess is formed in a peripheral edge of the cutting portion (208). The at least one recess define at least one concave cutting edge (210).

Description

CUTTING BLADE

TECHNICAL FIELD

The present invention relates to a rotary lawn mower used for lawn or garden maintenance. More particularly, the present invention relates to a cutting blade used in the rotary lawn mower.

BACKGROUND

Various type of rotary lawn mowers, for example, but not limited to, walk-behind lawn mowers, rider mowers, or robotic lawn mowers are used for garden or lawn maintenance. Typically, a rotary lawn mower includes one or more cutting blades which are arranged to rotate about a vertical axis. The cutting blades are attached to a rotating carrier member, such that the rotating carrier member is powered by a prime mover to rotate the cutting blades. Generally, a cutting blade includes a cutting edge arranged to cut the grass.

There is a need for an improved cutting blade to effectively mow and minimize the noise generation and energy consumption.

SUMMARY

It is an objective to provide an improved rotary lawn mower cutting blade.

The objective is achieved with a novel rotary lawn mower cutting blade according to claim 1. The cutting blade is arranged to rotate about a vertical axis of rotation of the lawn mower. The cutting blade includes a base portion, arranged to connect the cutting blade to a rotating carrier member of the lawn mower, and a cutting portion. Further, at least one recess is formed in a peripheral edge of the cutting portion, so as to define at least one cutting edge, having a concave shape. During operation, the concave shape of the cutting edge enables a slicing action of the vegetation, the slicing action is energy- saving as compared to a cutting action of the cutting blades having a straight cutting edges. Further, the slicing action during cutting of the vegetation also generates less noise. According to claim 2, the at least one cutting edge of the cutting blade extends between a leading end and a trailing end. Further, a radius of curvature of the at least one cutting edge decreases in a direction from the leading end to the trailing end. The cutting edge has an exponential shape such that the curvature at the leading edge follows a radius of rotation to collect and pre-process the vegetation. Finally, the curvature at the trailing end, having a smaller radius of curvature, pinches-off the vegetation.

According to claim 3, the at least one cutting edge is positioned such that, when the cutting blade rotates about the axis of rotation, an imaginary straight line intersecting the leading end and the trailing end of the cutting edge, is angled by an angle relative to a tangent line to a path of rotation of the trailing end, which tangent line intersects the trailing end. The angle is less than 60 degrees. Further, according to claim 4, the angle is preferably less than 45 degrees. The angle define a cutting angle for the cutting blade, by maintaining the cutting angle as low, based on the profile of the cutting edge, the cutting edge faces away from the axis of rotation for a smooth cutting operation.

According to claim 5, the cutting portion furthermore comprises a second cutting edge, neighboring the first cutting edge. Moreover, according to claim 6, the cutting blade is essentially symmetric with respect to a central symmetry line. Additionally, according to claim 7, the first and second cutting edges extend from a common point on the symmetry line. This allows using the cutting blade in both clockwise and counter- clockwise directions. The cutting blade may get blunt after a prolonged operation, by having a symmetric edge on the other side of the cutting blade; it may be easily switched to other cutting edge by changing the rotation or by turning over the mounting of the cutting blade.

According to claim 8, the cutting blade has a partly hyperbolic pentagonal shape, with first and second side edges, neighboring a respective cutting edge, and a base edge, arranged to face towards the axis of rotation.

According to claim 9, the base portion includes at least one connecting aperture which is adapted to receive a fastening member for attaching the cutting blade to the carrier member.

According to claim 10, the rotating carrier member is a rotating disc. According to claim 11 , the base portion is arranged to be pivotally connected to the rotating disc. According to claims 12, the cutting blade includes a second cutting portion such that the base portion is positioned between the two cutting portions.

Claim 13 discloses a cutting unit of a rotary lawn mower. Further, according to claim 14, the cutting unit includes a rotating member and a plurality of cutting blades. Moreover, claim 15 discloses a rotary lawn mower including the cutting unit. Claim 16 discloses a rotary lawn mower including a cutting blade. According to claim 17, the rotary lawn mower is a robotic lawn mower.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail with reference to the enclosed drawings, wherein:

FIG. 1 is a bottom view of a rotary lawn mower, according to an embodiment of the present invention;

FIG. 2 is a top view of a cutting blade attached to a rotating carrier member, according to an embodiment of the present invention;

FIG. 3 is a top view of the cutting blade, according to the embodiment of FIG. 2;

FIG. 4 is a top view of the cutting blade, according to another embodiment of present invention;

FIG. 5 is a top view of the cutting blade, according to yet another embodiment of present invention;

FIG. 6 is a top view of the cutting blade, according to a further embodiment of present invention; and

FIG. 7 is a bottom view of a rotary lawn mower having a cutting blade, according to the embodiment of FIG. 5.

DESCRIPTION OF EMBODIMENTS

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the invention incorporating one or more aspects of the present invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those ordinarily skilled in the art. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. In the drawings, like numbers refer to like elements.

FIG. 1 is a bottom view of a rotary lawn mower 100 (hereinafter referred to as

"the lawn mower 100"), according to an embodiment of the present invention. The lawn mower 100 may be a walk-behind lawn mower, a robotic lawnmower, or the like. The lawn mower 100 may be powered by prime mover (not shown) for example, an engine, an electric motor, or the like. Alternatively, the lawn mower 100 may also be a separate mowing deck configured to be attached to a vehicle, for example, a riding mower.

As illustrated in FIG. 1, the lawn mower 100 includes a body 102 and ground engaging wheels 104 attached to the body 102 via axles 106. In various embodiments of the present invention, two or more wheels 104 may be driven. Further, at least two caster wheels may be provided instead of two of the wheels 104.

As illustrated in FIG. 1, a cutting unit 107 is provided on the bottom side of the body 102. The cutting unit 107 includes a rotating carrier member 108 (hereinafter referred to as "the carrier member 108") which is configured to rotate about a vertical axis of rotation A (hereinafter referred to as "the axis A"). The carrier member 108 may be driven by the prime mover. In an embodiment, the carrier member 108 may be directly mounted on an output shaft of the prime mover. Alternatively, the carrier member 108 may be driven by the prime mover via a transmission assembly. According to the embodiment illustrated in FIG. 1, the carrier member 108 is a rotating disc. However, the carrier member 108 may be any other shape within the scope of the present invention. Further, at least one rotary lawn mower cutting blade 110 (hereinafter referred to as "the cutting blade 110") is attached to the carrier member 108. Thus, during an operation of the rotary lawn mower 100, the cutting blade 110 rotates along with the carrier member 108 to cut vegetation, such as, grass. In the exemplary embodiment, as illustrated in FIG. 1, the cutting unit 107 includes three cutting blades 110 which are connected to the carrier member 108. However, there may be any number of cutting blades 110 attached to the carrier member 108 within the scope of the present invention. In various embodiment of the present invention, a height of the carrier member 108 and/or each wheel 104 relative to the ground may be adjustable, thereby enabling modification in a cutting height of each cutting blade 110.

FIGS. 2 and 3 are top views of the cutting blade 110, according to an embodiment of the present invention. As illustrated in FIG. 2, the cutting blade 110 is attached to the carrier member 108 via at least one fastening member 202. In another embodiment, the cutting blade 110 may be attached to the carrier member 108 via multiple fasteners. However, the cutting blade 110 may be connected to the carrier member 108 by any other means, for example, welding, brazing, or the like. Further, as illustrated in FIG. 3, the cutting blade 110 includes a base portion 204 which is configured to be attached to the carrier member 108. The base member 204 includes at least one connecting aperture 206 for insertion of the fastening member 202. In an alternative embodiment, the base portion 204 may also be pivotally connected to the carrier member 108. The cutting blade 110 may be normally biased by at least one resilient member (E.g., a spring) in a retracted position. However, when the carrier member 108 rotates above a pre-determined speed, a centrifugal force may overcome the biasing force of the resilient member and the cutting blade 110 pivots to a cutting position. Further, if the cutting blade 110 encounters any obstruction (E.g., a wall, a tree, a rock, or the like) the cutting blade 110 automatically pivots to the retracted position. This may substantially reduce damage to the cutting blade 110. Moreover, overloading of the transmission assembly and/or prime mover may also be prevented.

As illustrated in FIG. 3, the cutting blade 110 includes a cutting portion 208. Further, at least one recess is formed in a peripheral edge of the cutting portion 208 so as to define at least one cutting edge 210. In an embodiment of the present invention, the cutting edge 210 has a concave shape. The concave shape of the cutting edge 210 enables a slicing action on the vegetation similar to that of a scythe. Such a slicing action may consume less energy as compared to a cutting action of a straight edge. Further, the slicing action may also generate less noise. Moreover, the cutting edge 210 extends between a leading end 210a and a trailing end 210b. In the exemplary embodiment, during operation, the leading end 210a is configured to encounter the vegetation before the trailing end 210b as the cutting blade 110 rotates in an anti-clockwise direction. According to an embodiment, the radius of curvature of the cutting edge 210 decreases in a direction from the leading end 210a to the trailing end 210b. Thus, the cutting edge 210 has a substantially exponential shape, reminding of the shape of a scythe. During a cutting operation, the curve of the cutting edge 210 initially collects a strip of vegetation that is to be cut. Finally, a smaller radius of curvature near the trailing end 210b pinches off the vegetation in a slicing action.

Further, as illustrated in FIGS. 2 and 3, the cutting edge 210 is positioned such that when the cutting blade 110 rotates about the axis A, an imaginary straight line L, which intersects the leading end 210a and the trailing 210b, is disposed at an angle a relative to a tangent line T to a path of rotation R of the trailing end 210b, wherein the tangent line T intersects the trailing end 210b. The angle a has a value which results in a low cutting angle as the cutting edge 210 is positioned such that the cutting edge 210 faces away from the axis of rotation A. In an embodiment of the present invention, the angle a is less than about 60 degrees. In another embodiment of the present invention, the angle a is less than about 45 degrees.

According to the embodiment illustrated in FIG. 3, the cutting portion 208 includes a second cutting edge 210' adjacent to the first cutting edge 210. Further, the cutting blade 110 is essentially symmetric with respect to a central symmetry line S. Consequently, the second cutting edge 210' is substantially a mirror image of the first cutting edge 210. Moreover, the first and second cutting edges 210 and 210' extend from a common point from the symmetry line S. The common point is coincident with the trailing end 210b of the first cutting edge 210. The second cutting edge 210' enables the cutting blade 110 to be used in two rotational directions, clockwise and anti-clockwise. Moreover, the cutting blade 110 has the same cutting characteristic irrespective of the direction of rotation as the cutting blade 110 has a central symmetry line S. As illustrated in FIG. 3, the cutting blade 110 has a partly hyperbolic pentagonal shape, with first and second side edges 212 and 214 adjacent to the cutting edges 210 and 210' respectively, and a base edge 216 facing towards the axis of rotation A.

FIG. 4 is a top view of a cutting blade 110, according to another embodiment of the present invention. The cutting blade 110 includes a base portion 204, and a cutting portion 208. Further, the cutting portion 208 includes a cutting edge 210. The cutting blade 110, as illustrated in FIG. 4, may be configured to rotate in an anti-clockwise direction for cutting vegetation.

FIG. 5 is a top view of a cutting blade 110, according to yet another embodiment of the present invention. The cutting blade 110 includes a base portion 204, and two cutting portions 208 and 208' at sides of the base portion 204. Further, each of the two cutting portions 208 and 208' includes a cutting edge 210. The cutting blade 110, as illustrated in FIG. 5, may be configured to rotate in an anti-clockwise direction for cutting vegetation. The presence of the two cutting portions 208 and 208' enable cutting of a larger strip of vegetation in a single rotation. FIG. 6 is a top view of a cutting blade 110, according to a further embodiment of the present invention. The cutting blade 110 includes a base portion 204, and two cutting portions 208 and 208' at opposite sides of the base portion 204. Further, each of the two cutting portions 208 and 208' includes first and second cutting edges 210 and 210'. Further, the cutting blade 110, as illustrated in FIG. 5, has a central symmetry line S. The second cutting edge 210' enables the cutting blade 110 to be used in two rotational directions, clockwise and anti-clockwise. Moreover, the cutting blade 110 has the same cutting characteristic irrespective of the direction of rotation as the cutting blade 110 has a central symmetry line S.

FIG. 7 illustrates a bottom view of a rotary lawn mower 700, according to another embodiment of the present invention. As illustrated in FIG. 7, the cutting blade 110, according to the embodiment illustrated in FIG. 5 is attached to a carrier member 108 of a lawn mower 700. However, the lawn mower 700 may be provided with the cutting blades 110, according to any of the embodiments illustrated in FIGS . 4 and 6. The carrier member 108 and the cutting blade 110 are configured to rotate about a rotational axis A. In the drawings and specification, there have been disclosed preferred embodiments and examples of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being set forth in the following claims.

Claims

1. A rotary lawn mower cutting blade (110), arranged to rotate about a vertical axis of rotation (A) of the lawn mower (100), the cutting blade (110) comprising:

a base portion (204), arranged to connect the cutting blade (110) to a rotating carrier member (108) of the lawn mower (100); and

a cutting portion (208);

characterized in that,

at least one recess is formed in a peripheral edge of the cutting portion (208), so as to define at least one cutting edge (210), having a concave shape.

2. The cutting blade (110) according to claim 1, wherein the at least one cutting edge (210) extends between a leading end (210a) and a trailing end (210b), and wherein a radius of curvature of the at least one cutting edge (210) decreases in a direction from the leading end (210a) to the trailing end (210b).

3. The cutting blade (110) according to any of the preceding claims, wherein the at least one cutting edge (210) is positioned such that, when the cutting blade rotates about the axis of rotation (A), an imaginary straight line (L) intersecting the leading end (210a) and the trailing end (210b) of the cutting edge (210), is angled by an angle (a) relative to a tangent line (T) to a path of rotation (R) of the trailing end (210b), which tangent line (T) intersects said trailing end (210b), wherein the angle (a) is less than 60 degrees.

4. The cutting blade (110) according to claim 3, wherein the angle (a) is less than 45 degrees.

5. The cutting blade (110) according to any of the preceding claims, wherein the cutting portion (208) furthermore comprises a second cutting edge (210'), neighboring the first cutting edge (210).

6. The cutting blade (110) according to claim 5, which cutting blade (110) is essentially symmetric with respect to a central symmetry line (S).

7. The cutting blade (110) according to claim 6, wherein the first and second cutting edges (210, 210') extend from a common point on the symmetry line (S).

8. A cutting blade (110) according to claim 7, which cutting blade (110) has a partly hyperbolic pentagonal shape, with first and second side edges (212, 214), neighboring a respective cutting edge (210, 210'), and a base edge (216), arranged to face towards the axis of rotation (A).

9. The cutting blade (110) according to any of the preceding claims, wherein the base portion (204) comprises at least one connecting aperture (206), which connecting aperture (206) is adapted to receive a fastening member (202) for attaching the cutting blade (110) to the carrier member (108).

10. The cutting blade (110) according to any of the preceding claims, wherein the rotating carrier member is a rotating disc (108).

1 1. The cutting blade (110) according to claim 9, wherein the base portion (204) is arranged to be pivotally connected to the rotating disc (108).

12. The cutting blade (110) according to any of claims 1-9, which cutting blade (110) comprises a second cutting portion (210'), and wherein the base portion (204) is positioned between the two cutting portions (208, 208').

13. A cutting unit (107) of a rotary lawn mower (100), which cutting unit (107) comprises a rotating member (108) and at least one cutting blade (110) according to any of the preceding claims.

14. A cutting unit (107) of a rotary lawn mower (100), which cutting unit (107) comprises a rotating member (108) and a plurality of cutting blades (110) according to any of claims 1-10.

15. A rotary lawn mower (100) comprising a cutting unit (107) according to any of claims 13-14.

16. A rotary lawn mower (100) comprising a cutting blade (110) according to any of claims 1 -12.

17. A rotary lawn mower (100) according to any of the previous claims, which rotary lawn mower (100) is a robotic lawn mower.