Cutlery – Blades – Rotary
Reexamination Certificate
2001-11-05
2003-11-04
Payer, Hwei-Siu (Department: 3724)
Cutlery
Blades
Rotary
C056S255000, C056S295000
Reexamination Certificate
active
06640449
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cutting blade for a trimmer or brush cutter.
Trimmers essentially comprise a guide tube, which is provided at one end with a cutter head and at the other end with a drive motor that drives the cutter head. The cutting tool in the cutter head is exchangeable, so that with different cutting blades, not only grass, weeds, reeds and bushes, but also thin trees can be cut. The cut material is generally collected and reduced in size at another location.
It is an object of the present invention to provide a cutting blade for a trimmer by means of which not only good cutting results can be achieved, but also at the same time a chopping of the cut material is achieved.
SUMMARY OF THE INVENTION
This object is inventively realized.
By angling off the end portions that carry the cutting edges, the effective cutting edge extends not only in the plane of rotation of the central portion, but also transverse to the plane of rotation over a height that can be prescribed.
As a result, stems, stalks, or the like are cut several times, in other words, are chopped.
Pursuant to an advantageous further embodiment of the present invention, the end portion is angled off several times, especially in two stages, in the same direction, resulting in a reduced amount of mass in the outer region of the blade. Consequently, there is achieved a higher inherent frequency of the cutting blade with otherwise high service life and low inertia.
To protect the vertical cutting edge at the blade end, a nose-shaped deflector is provided at the approximately horizontal end portion of the cutting blade and projects beyond the path of the blade end. This deflector protects the blade end from obstacles and also serves to protect the cutting edge to the extent that in the direction of rotation of the cutting blade, the deflector leads the blade end, i.e. the cutting edge thereof.
To achieve a good chopping effect, the effective cutting edge extends from the edge of the end portion that leads in the direction of rotation into the free, angled-off blade end, whereby the cutting edge ends in particular at the front end of the free blade end is disposed approximately parallel to the central portion. The cutting edge can be made continuous, or can be composed of two cutting edge portions.
If the horizontal cutting edge portion is inclined counter to the direction of rotation, and in particular has a curved configuration, the inner end of the horizontal cutting edge portion, which faces the axis of rotation, will, in the direction of rotation of the cutting blade, lead the outer end of the horizontal cutting edge portion. Thus, a deflecting effect is achieved upon encountering obstacles, thereby reducing the stress on the drive or gear mechanism as well as on the cutting blade. A further reduction of the stress is achieved in that at least the essentially vertical cutting edge portion is sharpened not only on the side facing the axis of rotation but also on the side remote from the axis of rotation.
Pursuant to an advantageous further embodiment of the present invention, the width of the base body, as measured in the plane of the central portion, is tapered from the region of the fastening opening to the bent or angled off free blade ends of the end portions. As a result, the amount of mass in the outer blade radius is reduced, which leads to an increased inherent frequency of the cutting blade and thus to a reduced dynamic stressing of the cutting blade. Due to the tapered configuration, the tortional rigidity of the blade ends is also reduced. The construction is preferably such that when the blade ends strike an obstacle, a portion of the impact energy is converted into deformation, thereby again lowering the stress of the gear mechanism in the cutter head.
The inventive cutting blade thus forms a chopping blade, which exhibits excellent cutting efficiency along with a long service life, low development of noise, and a high protective effect.
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Hoffmann Joachim
Schneider Andreas
Schweigert Thomas
Andreas Stihl AG & Co.
Becker R W
Payer Hwei-Siu
R W Becker & Associates
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