JPH0311723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a rotary brush cutting saw blade that is attached to a brush cutter to cut down vegetation.

[Prior Art] Most conventional cutting blades are used by rotating only in a fixed direction, and therefore, the usage time is short, 1 to 2 hours.

The present inventor disclosed in Japanese Patent Application Laid-Open No. 56-158018 a rotary brush cutting saw blade that can be used interchangeably in both forward and reverse directions (in other words, can be used inside out). The present invention further improves and advances this.

For example, Utility Model Publication No. 49-17004, Utility Model Application No. 17004
-10333, etc., proposes a rotary brush cutting saw blade that can be rotated in both forward and reverse directions, but all of these blades are used for different purposes by rotating in the forward and reverse directions (used inside out).

[Problems to be solved by the invention] A mowing blade suffers much more wear due to collisions and contact with hard objects than the target object, which is plants, and the decline in sharpness is caused by adhesion near the roots of plants. Or damage or wear due to collision or contact with scattered earth, sand, pebbles, concrete pieces, etc.

The present invention takes advantage of the new discovery that when these hard objects come into contact with the cutting edge, the cutting edge in the direction of travel becomes dull, but the cutting edge in the direction opposite to the direction of travel is ground and sharpened. It is an object of the present invention to provide a saw blade that can be used in both forward and reverse directions (in other words, inside out).

In addition, the present invention cleverly arranges a square blade protruding in the radial direction and a scalene triangular blade having a tip (apex) on the inside in the radial direction compared to the square blade. The purpose of this blade is to have the ability to knock hard objects outward in the radial direction.

Note that in the present invention, the term "square blade" is an abbreviation for a blade whose outermost edge in the radial direction is generally arcuate, and refers to a blade that is approximately square.

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present invention provides; , the cutting edges on the outer periphery are: a plurality of square blades having cutting edges in the circumferential direction, arranged at equal angles and lengths, and a tip (apex) on the inside in the radial direction compared to the square blades.
and a scalene triangular blade having an integral multiple of the square blade, the long side and the short side of which are cutting edges; the radius of the scalene triangular blade passing through the circumferential center of the square blade This is a rotary brush cutting saw blade that can be used interchangeably in both forward and reverse directions, with the long side cutting edge facing the square blade symmetrically with respect to the square blade.

[Function] Wear of the rotary cutting saw blade occurs due to collision and contact with hard substances attached to the vicinity of the roots of plants, rather than from cutting the plants themselves.

In the present invention, by utilizing the small angle of attack of the long edge of the scalene triangular blade with respect to the rotation direction, hard objects are scattered outward in the radial direction, and when the square blade and triangular blade rotate, The cutting edge on the opposite side is polished based on the new discovery that the cutting edge on the opposite side becomes dull due to wear, but the blade on the opposite side to the advancing direction is ground by contact with a hard object.
This will be specifically explained in Examples.

[Example] FIG. 1 is a drawing showing an embodiment of the present invention.

The center hole of the thin disc 1 is a mounting hole for a drive unit of a brush cutter. On the outer periphery of the thin plate 1, three square blades 2 are arranged at equal angles and lengths in the case of the figure. Its circumferential surfaces 4, 4' are ground to form cutting edges. Scalene triangular blades 3 and 3' are arranged symmetrically with respect to a radius passing through the circumferential center of the square blade 2, with their long sides facing the square blade side. The cutting edges on the short side are shown as 5 and 5', and the cutting edges on the long side are shown as 6 and 6'. The radial outer end of the square blade 2 is
From the tip (apex) of the triangular blade 3, radially outward,
Only C stands out. The circumferential length of a square blade (also called a large blade) is a, and the circumferential length of a series of scalene triangular blades (also called a small blade) is shown as b and b'(b=b'). ).

The mode of action when performing brush cutting work using the brush cutting rotary saw blade shown in this embodiment is as follows.

The saw blade, which rotates at high speed, collides with and comes into contact with vegetation to cut the grass and trees, and also cuts down on hard objects (gravel, buried stones, concrete pieces, iron pieces, cans, etc.) that are present at or near the grass cutting area. etc.) causing collision or contact.

Substantial wear and tear on the saw blade is not caused by abrasion caused by mowing soft vegetation, but is mainly caused by collision and contact abrasion with the hard object. In other words, the brush cutting rotary saw blade is
While constantly in contact with substances harder than itself,
Cutting soft vegetation.

In Fig. 1, when the saw blade rotates in the R direction, the wear on the radial outer surface of the square blade is greatest in the A section facing the rotation direction, and
It gets smaller as you go to A′. Further, the cutting edge portion in the circumferential direction is the largest at the radially outer part A, and is the smallest at the inner part B. This relationship is also the same in the case of scalene triangular blades, where the wear is greatest at the apex.

Figure 2 A shows the worn state of the cutting blade parts 4, 5, and 6 of the cutting blade in Figure 1 when used in the R direction, and Figure 2 B shows the worn state of the cutting blade parts 4, 5, and 6 of the cutting blade used in the R direction. Cutting edges 4', 5', 6' and cutting edges 4, 5, 6 when used
Shows worn condition. In Figure 2 A and Figure 2 B,
The parts indicated by broken lines each show the state before use, and the outer peripheral edge 7 of the square blade 2 has a larger radius than the apex of the scalene triangular blades 3 and 3', so it is a scalene triangular blade. It is used to protect against hard objects that fly into the surface, causing severe wear.

The triangular blade 3 is connected to the square blade 2, and the long side cutting edge is connected to the radius passing through the circumferential center of the square blade 2.
The reason why they are arranged symmetrically in the direction of The long side cutting edge of the triangular blade 3 has a large angle of attack with respect to the rotation direction R' (in the case of rotation in the R' direction, the width b
The long side cutting edge of the triangular blade 3) that spans the length of the triangle blade 3) causes the blade to be blown away in the radial direction, and then the short side cutting edge with a small angle of attack (5 when rotating in the R direction, 5′ when rotating in the R' direction) removes vegetation. (It goes without saying that the long side cutting blade with a large angle of attack performs a mowing action in addition to the action of knocking away hard materials.) In this way, wear damage to the short cutting edge is prevented, thereby increasing the durability of the saw blade.

Next, reference will be made to the inventor's discovery that the cutting blade is worn in the direction of movement (mowing direction), but is polished in the direction opposite to the direction of movement.

FIG. 3 is a view of the state of the blade of the rotary saw blade when cutting grass, as seen from a viewpoint parallel to the ground. The forward end of the square blade 2 in the advancing direction is denoted by 4, the rear end 4', the long side cutting edges of the scalene triangular blade 3 are denoted by 6, 6', and the short side cutting edges are denoted by 5, 5'.

Here, we will focus on the cutting edges 4 and 4' of the square edge 2 as an example of the cutting edge.

It is well known that the advancing direction cutting edge 4 of the square blade 2 wears out due to friction during brush cutting. The theoretical explanation as to why the cutting edge 4' in the opposite direction of advancement is ground is currently unknown.

However, it is well known that when an object moves at high speed in a Newtonian fluid (a fluid that follows Newton's law of viscosity), a phenomenon called skin separation occurs at the rear of the object, disrupting the flow. Of course, air containing soil, sand, etc.
Although it is a non-Newtonian fluid, as the square blade moves at high speed, particularly severe flow turbulence occurs at the tail end of the blade, consuming mechanical energy. It is not surprising to think that this consumed energy grinds the square blade in the form of frictional energy. That is,
This is a problem in non-Newtonian fluid mechanics.

Now, the brush cutting rotary saw blade of the present invention has a symmetrical shape that remains the same even when turned over.

Therefore, when the saw blade loses its sharpness after being used in one direction, it can be used for a long period of time by turning the saw blade over and performing mowing work with the polished cutting edge, and repeating this turning over.

[Effects of the Invention] As described above, the brush cutting rotary saw blade of the present invention has a rectangular cutting blade and a scalene triangular cutting blade on the long side, by scattering hard objects such as sand and gravel outward in the radial direction. , prevents wear of the short side cutting edge and maintains sharpness for a long time.

In addition, for both square blades and scalene triangular blades, the cutting blade in the direction of rotation (progressive direction) wears out due to collisions and contact with hard objects, but the cutting blade in the opposite direction to the rotation direction wears out due to hard objects. The sharpness is restored by being polished by contact with the saw blade, so by attaching the saw blade upside down, the sharpness is restored, and by repeatedly turning the saw blade over, it can be used for a long period of time.

As described above, with the advent of the rotary brush cutting saw blade of the present invention, the service life of the rotating cutting saw blade has been significantly extended, and its economic effects are immeasurable.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the present invention in which three square blades (large blades) are arranged in the circumferential direction, and five scalene triangular blades (small blades) are arranged on each side of the square blade in the circumferential direction. It is a front view. Figure 2 is a diagram showing the state of wear due to hard objects in the embodiment shown in Figure 1. FIG. 3 is a diagram showing the state of wear when the rotary cutting saw blade shown in the figure is rotated in the R' direction. FIG. 3 is a diagram showing the state of the upper and lower surfaces of the cutting blade in a sectional view taken along the - arrow in FIG. 1. 1... Thin disc, 2, 2'... Square blade, 3, 3'... Scalene triangular blade, 4, 4'... Square blade cutting edge, 5, 5'... Scalene triangular blade short side cutting edge, 6. 6'... Scalene triangular blade long side cutting edge, 7... Square blade outer periphery.

Claims (1)

[Scope of Claims] 1. A rotary cutting saw blade made of a thin disc made of chemical plywood or steel plate having a mounting hole in the center and cutting blades on the outer periphery, wherein the blades on the outer periphery are arranged at equal angles and equal lengths. A plurality of square blades are provided with cutting edges in the circumferential direction, and a point (apex) is located radially inward compared to the square blades.
a scalene triangular blade having an integral multiple of the square blade, the long side and the short side of which are cutting edges; A rotary brush cutting saw blade that can be used interchangeably in both forward and reverse directions, characterized in that it is symmetrical with respect to the square blade, and its long side cutting edge faces the square blade.