JPH0441800Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a string-shaped cutting blade for brush cutters used for mowing lawns and weeds, etc. This relates to cutting blades.

[Conventional technology]

Conventional string-shaped cutting blades of brush cutters used for mowing lawns and weeds are made of solid and homogeneous string material (eg, Japanese Patent Publication No. 59-39090).

Further, in Japanese Utility Model Publication No. 56-40277, the cord-like cutting blade has a two-layer structure consisting of a core made of twisted metal wire and a surface material such as rubber that covers this core.

[Problem that the invention attempts to solve]

During rotation of the string-like cutting blade, centrifugal force and accompanying tensile force are applied to the string-like cutting blade.

If the string-like cutting blade is made of a solid and homogeneous string material, when a crack that becomes a radial cut occurs in the string-like cutting blade, there is a possibility that the cutting blade will instantly break due to a large centrifugal force. Further, when a longitudinal tear occurs at the tip of the string-like cutting blade, it tends to rapidly advance toward the base end of the string-like cutting blade.

The cord-like cutting blade disclosed in Japanese Utility Model Publication No. 56-40277 requires a metal strand for the core material, resulting in a complicated structure.

The object of this invention is to provide a cord-like cutting blade for a brush cutter that is highly resistant to cracking, has improved durability and service life, and does not require expensive metal strands.

[Means for solving problems]

This invention will be explained using reference numerals in the drawings that correspond to the embodiments. The inside of the string-like cutting blade 22 for a brush cutter has a structure in which hollow portions 24 and partition wall portions 26 are arranged alternately in the longitudinal direction of the string-like cutting blade 22.

In the invention of claim 2, the string-like cutting blade 22 is made of a synthetic resin material.

[Effect]

As the string-like cutting blade 22 rotates, centrifugal force acts on the string-like cutting blade 22. Since the hollow portions 24 are arranged in the longitudinal direction within the string-like cutting blade 22, the weight of the string-like cutting blade 22 is reduced, and as a result, the centrifugal force is also reduced.

When a radial crack 28 occurs in the string-like cutting blade 22,
Due to the presence of the cavity 24 within the string-like cutting blade 22, the radial crack 28 grows in the circumferential direction of the string-like cutting blade 22. Further, the centrifugal force that causes the growth of the radial crack 28 is small.

When a longitudinal crack 30 is formed at the tip of the string-like cutting blade 22, the longitudinal crack 30 grows toward the base end of the string-like cutting blade 22. When the longitudinal crack 30 reaches the partition wall 26, it is blocked by the partition wall 26 and is prevented from advancing toward the proximal end of the string-like cutting blade 22.

〔Example〕

This invention will be described below with reference to embodiments shown in the drawings.

FIG. 5 is a schematic diagram of the tip of the brush cutter. The brush cutter 10 includes a pipe 12, and an engine (not shown) is attached to the upper end of the pipe 12.
The gear case 14 is attached to the lower end of the pipe 12 and receives power from the above-mentioned engine via a transmission shaft within the pipe 12. The head 16 is disposed below the gear case 14, and rotates by receiving rotation from the output portion of the gear case 14 via the shaft 18. The string-like cutting blades 22 are made of synthetic resin such as nylon, and are attached to the circumference of the head 16 at equal angular intervals, rotate integrally with the head 16, and cut grass and the like.

FIG. 1 is a longitudinal sectional view of the string-like cutting blade 22, and FIG. 2 is a sectional view taken along the line - in FIG. String cutting blade 2
2 has a circular cross section, and inside the string-like cutting blade 22, a cylindrical hollow part 24 and a partition wall part 26 that partitions between the hollow parts 24 are arranged alternately in the longitudinal direction of the string-like cutting blade 22. The structure is arranged in . As a result of the cavity 24 being formed within the string-like cutting blade 22, the string-like cutting blade 22
is reduced in weight, the centrifugal force generated in the string-like cutting blade 22 when it rotates is reduced, the tensile force of each part of the string-like cutting blade 22 is reduced, and the growth of cracks is also suppressed. Note that the string-like cutting blade 22 having the structure shown in FIG.
Regarding manufacturing, there is a method of first manufacturing the halves of the string-like cutting blade 22 and then joining them together.

FIGS. 3a and 3b are cross-sectional views showing the growth direction of the radial cracks 28 when they occur in the conventional string-like cutting blade 22b and the string-like cutting blade 22 of this invention. Since the conventional string-like cutting blade 22b is made of a material that is homogeneous and solid in the cross-sectional direction, the radial crack 2
8, it grows toward the center of the string-like cutting blade 22, and the growth rate is high. On the other hand, in the string-like cutting blade 22 , the radial crack 28 needs to advance in the circumferential direction of the string-like cutting blade 22 due to the existence of the cavity 24 . Since the force that advances the cutting blade in the circumferential direction is weaker than the force that advances the string-shaped cutting blade 22 toward the center, the growth of the radial crack 28 becomes gradual.

FIG. 4 shows a case where a longitudinal tear 30 has occurred at the tip of the string-like cutting blade 22. When a longitudinal crack 30 is formed at the tip of the string-like cutting blade 22, the longitudinal crack 30 grows toward the base end of the string-like cutting blade 22. When the longitudinal crack 30 reaches the partition wall 26, it is blocked by the partition wall 26, preventing the string-like cutting blade 22 from advancing toward the proximal end. Increase of radial cracks 28 is prevented.

[Effect of idea]

As described above, according to this invention, the inside of the string-like cutting blade has a structure in which the hollow portions and the partition wall portions are arranged alternately in the longitudinal direction of the string-like cutting blade. Therefore,
The string-shaped cutting blade is lighter, the centrifugal force during rotation is reduced, and the growth of cracks in the string-shaped cutting blade is suppressed. When a radial crack occurs in the string-like cutting blade, the radial crack propagates along the circumferential direction of the string-like cutting blade, not toward the center of the string-like cutting blade, so the radial crack increases. suppressed. Further, when a longitudinal tear occurs at the tip of the string-like cutting blade, the growth of the longitudinal crack in the proximal direction of the string-like cutting blade is prevented by the partition wall portion and is suppressed.

[Brief explanation of drawings]

The drawings relate to an embodiment of this invention, in which Fig. 1 is a longitudinal sectional view of a string-like cutting blade, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 a and b are views of the conventional and this invention, respectively. A cross-sectional view showing the growth direction of a radial crack when a radial crack occurs in the string-like cutting blade, FIG. 4 is a diagram showing a case where a longitudinal crack occurs at the tip of the string-like cutting blade, and FIG. It is a schematic diagram of the tip part of a brush cutter. 10...Brush cutter, 22...String-like cutting blade, 24...
Cavity part, 26... partition part.

Claims (1)

[Claims for Utility Model Registration] (1) A mower characterized in that inside the string-like cutting blade 22, hollow portions 24 and partition wall portions 26 are arranged alternately in the longitudinal direction of the string-like cutting blade 22. String-shaped cutting blade for haircut. (2) The string-like cutting blade for a brush cutter according to claim 1, wherein the string-like cutting blade 22 is made of a synthetic resin material.