Cutting knife for a cutting head of a trimmer

Patent metadata

Field	Value
Publication number	US-10194584-B2
Application number	US-201715408461-A
Country	US
Kind code	B2
Filing date	Jan 18, 2017
Priority date	Jan 23, 2016
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

The cutting knife has a base member with first and second faces. One face has a topographic disturbance element arranged between knife edge and longitudinal center axis and shaping the elevation profile of the face. On the opposite face relative to the center plane an opposite elevation profile with contour line is formed. The contour line points of the contour line of the first elevation profile are positioned opposite the contour line points of the opposite contour line on perpendiculars to the center plane. The contour line of the first elevation profile and the opposite contour line are noncongruent. The contour line of the first elevation profile extends transversely to the longitudinal center axis of the base member across the disturbance element and has an ascending line section and a descending line section. A turning point positioned between these line sections is a component of the disturbance element.

First claim

What is claimed is:

1. A cutting knife for a cutting head of a trimmer, the cutting knife comprising:
a flat elongate base member comprising a first end and a second end, wherein a longitudinal center axis of the base member extends from the first end to the second end;
the base member comprising first and second longitudinal edges extending at a spacing to the longitudinal center axis from the first end to the second end;
the base member having a first face and a second face between which a center plane is positioned, wherein the first and second faces each are delimited in a first direction transverse to the longitudinal center axis by the first and second longitudinal edges of the base member and, in a second direction along the longitudinal center axis, delimited by the first end and the second end of the base member;
a fastening contour for mounting the cutting knife on the cutting head connected to the first end of the base member, wherein the second end of the base member is a free knife end of the cutting knife;
wherein on the first and second longitudinal edges of the base member a knife edge is formed, respectively, wherein, when the cutting head is rotating in a rotational direction in operation, either the knife edge of the first longitudinal edge is leading in the rotational direction and is a first active knife edge or the knife edge of the second longitudinal edge is leading in the rotational direction and is a second active knife edge;
at least the first face comprising at least one topographic disturbance element in an area between the first active knife edge or the second active knife edge and the longitudinal center axis of the base member;
wherein the at least one topographic disturbance element shapes a first elevation profile of the first face, wherein a contour line of the first elevation profile extends, transverse to the longitudinal center axis of the base member, from the first active knife edge or the second active knife edge in a direction toward the longitudinal center axis across the at least one topographic disturbance element;
wherein an oppositely positioned second elevation profile is formed on the second face that is positioned opposite the first face relative to the center plane, wherein a contour line of the oppositely positioned second elevation profile extends from the first active knife edge or the second active knife edge in the direction to the longitudinal center axis;
wherein the contour line of the first elevation profile comprises first contour line points and wherein the contour line of the oppositely positioned second elevation profile comprises second contour line points, wherein the first contour line points are positioned opposite the second contour line points on perpendiculars to the center plane of the base member;
wherein the contour line of the first elevation profile and the contour line of the oppositely positioned second elevation profile are noncongruent;
wherein the at least one topographic disturbance element arranged on the first face has no topographic disturbance element arranged opposite thereto at a same level on the second face so that a flow path of air that is flowing across the first face is disturbed by the at least one topographic disturbance element while a flow path of air flowing across the second face at said same level where there is no topographic disturbance element flows substantially without disturbance across the second face;
wherein the contour line of the first elevation profile in the area of the at least one topographic disturbance element comprises a first increasing line section and a second descending line section;
wherein the contour line of the first elevation profile comprises at least one turning point positioned between the first increasing line section and the second descending line section, wherein the at least one turning point is a part of the at least one topographic disturbance element.

2. The cutting knife according to claim 1 , wherein the at least one turning point is arranged on a perpendicular to the center plane and has a first spacing to the center plane, wherein a reference point is provided on the second face and is positioned directly opposite the turning point relative to the same perpendicular to the center plane, wherein the reference point has a second spacing relative to the center plane, and wherein the first spacing is unequal to the second spacing.

3. The cutting knife according to claim 2 , wherein the first spacing and the second spacing differ from each other by a spacing difference of up to ±100% of the second spacing.

4. The cutting knife according to claim 1 , wherein the base member comprises a knife back surface and edge surfaces, wherein the first and second longitudinal edges are edges of the edge surfaces, wherein the edge surfaces and the knife back surface together form the first face of the base member, wherein the knife back surface is divided by the longitudinal center axis of the base member, and wherein the at least one topographic disturbance element is positioned in an area between one of the edge surfaces and the longitudinal center axis of the base member.

5. The cutting knife according to claim 1 , wherein the at least one topographic disturbance element extends along the first active knife edge or the second active knife edge and has a width measured transverse to the first active knife edge or the second active knife edge along which the at least one topographic disturbance element is extending.

6. The cutting knife according to claim 1 , wherein the at least one topographic disturbance element is an elevation that is projecting from the first face.

7. The cutting knife according to claim 1 , wherein the at least one topographic disturbance element is a longitudinal rib or a longitudinal groove.

8. The cutting knife according to claim 7 , wherein the longitudinal rib or the longitudinal groove is positioned relative to the longitudinal center axis at an angle in a range of 0° to 10°.

9. The cutting knife according to claim 8 , wherein the angle is in a range of 2° to 4°.

10. The cutting knife according to claim 7 , wherein the longitudinal groove or the longitudinal rib extends across at least a partial length of the base member from the first end of the base member in a direction toward the free knife end.

11. The cutting knife according to claim 7 , wherein the longitudinal groove or the longitudinal rib is extending without interruption from the first end of the base member all the way to the free knife end.

12. The cutting knife according to claim 7 , wherein the longitudinal rib or the longitudinal groove tapers off in a direction toward the free knife end.

13. The cutting knife according to claim 1 , wherein the base member comprises a knife back surface that is embodied as a flat plane in at least one partial area of the base member.

14. The cutting knife according to claim 1 , wherein the base member is comprised of plastic material.

15. The cutting knife according to claim 1 , wherein the at least one topographic disturbance element effects a constructive non-symmetric cross section shape of the base member between the first active knife edge or the second active knife edge and the longitudinal center axis of the base member.

16. The cutting knife according to claim 1 , wherein the at least one topographic disturbance element generates an asymmetric cross section in an area between the first active knife edge or the second active knife edge and the longitudinal center axis so that the first and second elevation profiles differ in an active knife ar

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Günther David
• Pöhler Fabian

Classifications

• A01D34/826

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