JP2024088100A - Grass trimmer blades - Google Patents

Abstract

To provide a mower blade, which is attached to a mower mounted on a rear part of a tractor or the like to cut weeds or finely crush the cut weeds and is excellent in durability while it is formed by bending one plate of material and yet is hardly damaged.SOLUTION: The mower blade is formed by bending one plate of material and attached to a rotary shaft of a mower through a fixing tool so as to be freely fluctuated and includes: a base part 1 in which an insertion hole 11 for inserting the fixing tool is bored, and plate members are formed in a manner of facing each other by a folded part 12; and a blade part 2 having a first ridge line R1 and a second ridge line R2 branching into two with the interval widening from the folding part 12 toward a blade edge 21 and having a surface held between the first ridge line R1 and the second ridge line R2. The folding part 12 has a projecting part 3 formed to project from a top surface 1a of the base part 1.SELECTED DRAWING: Figure 1

Description

The present invention relates to a blade for a grass cutter that is attached to a grass cutter, such as a flail mower or hammer knife mower, which is attached to the rear of a tractor or the like in order to cut weeds and finely crush the cut weeds.

Conventionally, there are several types of grass cutter blades that are attached to the above-mentioned grass cutter and used as a set of two blades.

For example, Patent Document 1 discloses a cutting claw that is detachably attached to a claw attachment portion provided on a rotating shaft, and is used as a set of two plate blade members with a "H"-shaped cross section that form a roughly Y-shape.

Patent Document 2 also discloses a flail mower blade that is freely rotatably attached to a blade holder by an attachment member, and is made up of two divided halves that come into contact with each other at their contact surfaces, each of which is made up of a plate-like body that is symmetrical about the contact surface as its axis of symmetry, with the lower portion of each plate-like body twisted approximately 90 degrees from the contact surface in the opposite lateral direction and forward direction, and the tip edge of the plate-like body facing the direction of rotation is formed as a flat front blade.

JP 2009-089660 A JP 2009-268444 A

However, in the cutting claws disclosed in Patent Document 1, the cutting edges of each blade are also approximately "H" shaped, and as a set they form an approximately Y shape, so the cutting edges are slanted relative to the ground, making it impossible to cut some weeds from the roots. In the cutting blade disclosed in Patent Document 2, the cutting edges are approximately horizontal relative to the ground, solving the above problem, but the two divided halves are each made of a single plate-like body that is symmetrical with the contact surface as the axis of symmetry, and each plate-like body has a shape in which the lower part of the contact surface is twisted approximately 90 degrees from the contact surface to the opposite side and forward, respectively, so that if the two divided halves open during cutting work, weeds and the like can get into the gap between the contact surfaces, and it may not be possible to cut the weeds evenly.

In addition, there are also commercially available grass cutter blades with a shape in which a single plate member is bent so that the cutting edge is roughly parallel to the ground, such as the one disclosed in Patent Document 2, which is connected to the front side of the cutting blade. These blades are called ginkgo-shaped claws, but because the rotating shaft of the grass cutter rotates at high speed, various strong impact forces are applied during grass cutting work, and there is an issue that the bent part cracks and breaks over time.

The present invention aims to provide a blade for a grass cutter that is attached to a grass cutter, such as a flail mower or hammer knife mower, which is attached to the rear of a tractor, etc., to cut weeds and finely crush them, and that is formed by bending a single member, yet has excellent durability and is resistant to breakage.

[1] That is, the present invention is a grass cutter blade formed by bending a plate member and attached to the rotating shaft (A) of a grass cutter via a fixture (F) so as to be freely swingable, the grass cutter blade being characterized in that it has a base portion (1) formed with an insertion hole (11) for inserting the fixture (F) and a bent portion (12) in which the plate member faces each other, a first ridgeline (R1) and a second ridgeline (R2) that branch from the bent portion (12) toward the cutting edge (21) with the distance between them increasing, a blade portion (2) having a surface sandwiched between the first ridgeline (R1) and the second ridgeline (R2), and the bent portion (12) has a protruding portion (3) formed to protrude from the top surface (1a) of the base portion (1).

[2] The blade for a grass cutter described in [1] above is characterized in that the protruding portion (3) is formed so that the thickness (t) of the plate member: the height (3h) of the protruding portion (3) = 1:0.03 to 10.

[3] The blade for a grass cutter described in [1] or [2] is characterized in that the base (1) is formed by bending and partially joining opposing plate members.

The tilling tines of the present invention are blades for lawnmowers that are attached to lawnmowers such as flail mowers and hammer knife mowers that are attached to the rear of tractors to cut weeds and finely crush them. Although they are formed by bending from a single member, they are highly durable and resistant to breakage.

1 is a perspective view of an embodiment of a grass cutter blade according to the present invention. FIG. 1 is a front view of an embodiment of a grass cutter blade according to the present invention. FIG. FIG. 2 is a right side view of the embodiment of the grass cutter blade of the present invention. 1 is a plan view of an embodiment of a grass cutter blade according to the present invention. FIG. 1 is a reference diagram showing a state in which a blade for a grass cutter according to an embodiment of the present invention is attached to a pivot shaft A via a fixture F so as to be freely swingable. FIG. 6 is a cross-sectional view taken along a plane perpendicular to the axial direction of a rotation axis A in FIG. 5 . FIG. 2 is a perspective view showing a load direction and a confirmed location of stress concentration in an analysis test of the grass cutter blade according to the first embodiment of the present invention. FIG. 11 is a perspective view showing the load direction and the location where stress concentration was confirmed in an analysis test of the comparative example 1 of the grass cutter blade.

The following is a detailed description of an embodiment of the grass cutter blade according to the present invention, based on the accompanying drawings. The embodiment described below is a preferred example for implementing the present invention, and therefore various technical limitations are imposed. However, the present invention is not limited to this embodiment unless otherwise specified in the following description. In addition, the up-down direction in the description refers to the up-down direction in FIG. 2, the forward direction refers to the front direction of the paper in FIG. 2, and the rearward direction refers to the back direction of the paper in FIG. 2. In addition, in a numerical range represented by the symbol "~", the upper and lower limit numerical values are included in the range.

As described above, the grass cutter blade according to the present invention is attached to a grass cutter attached to the rear of a tractor. Specifically, the grass cutter is provided with a cylindrical or other rotating shaft A that rotates by a power source that is mounted on the grass cutter. A pair of plate-shaped brackets B are erected facing each other from the surface of the rotating shaft A. Each of the pair of brackets B has a through hole, and the fixing part F can be attached to the pair of brackets B by inserting the rod-shaped part of the fixing part F into the hole. Furthermore, the grass cutter blade of the present invention can be attached to the fixing tool F by inserting the grass cutter blade into the approximately U-shaped base part of the fixing part F. In this way, the grass cutter blade of the present invention is attached to the rotating shaft A of the grass cutter via the fixing tool F so as to be able to swing freely. Note that since a pair of brackets B are provided on the surface of the rotating shaft A at a predetermined interval, the grass cutter blade of the present invention is also provided on the surface of the rotating shaft A in multiple numbers.

In this embodiment, as shown in Figures 5 and 6, the fixing device F has a substantially U-shaped base portion and a rod-shaped portion having a screw portion that passes through the open end side of the base portion. The grass cutter blade of the present invention can be attached to the fixing device F by inserting the grass cutter blade of the present invention into the substantially U-shaped base portion of the fixing device F. However, in other embodiments, the base portion can be U-shaped or V-shaped, or can have only a rod-shaped portion without a base portion, or can have various other shapes, so long as the grass cutter blade of the present invention can be attached to the rotation shaft A of the grass cutter freely swinging via the fixing device F.

The grass cutter blade of the present invention is formed by bending a plate member. Specifically, the upper part of the plate member is folded roughly in half, and the lower part is curved so that it juts out forward. In order to disperse the stress applied to the grass cutter blade during use and make it less likely to break, it is preferable that the various bent and curved parts have gently curved shapes rather than sharp shapes.

The plate member used in the grass cutter blade is preferably made of a metal such as steel, iron, titanium or a titanium alloy, or an aluminum alloy. The grass cutter blade of the present invention is preferably made of a plate member having a thickness t of 1 to 10 mm, more preferably 2 to 7 mm, and most preferably 2.5 to 5 mm. If the plate member used in the grass cutter blade is made of metal and has a thickness within the above range, it will not easily break even if it comes into contact with a small stone when it is attached to the rotating shaft A of the grass cutter via a fixing device F and cuts weeds, and it has an appropriate mass as a grass cutter blade, and can cut weeds by the centrifugal force generated by the rotation of the rotating shaft A. The plate member used in the grass cutter blade may be coated with paint, plating, etc. for the purpose of rust prevention, etc.

The base 1 of the grass cutter blade of the present invention is a portion in which an insertion hole 11 for inserting the fixing device F is drilled, and a plate member is formed facing the bent portion 12 by bending. By inserting the fixing device F into the insertion hole 11, the grass cutter blade is attached in a state in which it can move relative to the fixing device F. The insertion hole 11 may be drilled before one plate member is bent, or it may be drilled after it is bent. In this embodiment, the insertion hole 11 is a long hole that is long in the vertical direction, but in other embodiments, the insertion hole 11 may be a circular, elliptical, or other shape as long as it can move more than the fixing device F relative to the fixing device F.

In addition, in this embodiment, the base 1 is bent at the bent portion 12 so that the opposing plate members are spaced apart by a distance of about 0.1 to 1 mm and do not come into contact with each other, but in other embodiments, the opposing plate members may be partially joined by welding or the like.

The blade section 2 is a portion having a surface sandwiched between the first ridgeline R1 and the second ridgeline R2, with a first ridgeline R1 and a second ridgeline R2 that branch into two with the distance between them increasing from the bent portion 12 toward the cutting edge 21. The blade section 2 has a curved shape with the cutting edge 21 located at the lower end of the blade section 2 projecting furthest forward. When the grass cutter blade of the present invention is attached to the rotation shaft A of the grass cutter via the fixing device F, the cutting edge 21 makes it approximately horizontal to the ground, so that weeds can be cut from the roots and the cut weeds can also be finely crushed. The cutting edge 21 is preferably formed at an acute angle to make it easier to cut and crush weeds.

In this embodiment, the blade portion 2 has a first ridgeline R1 and a second ridgeline R2 that are gently curved, and as shown in FIG. 2, has a ginkgo shape, a triangular shape with the left and right sides recessed inward, or an inverted approximately T-shape, but it may also have a triangular shape with the two left and right sides bulging outward, an approximately semicircular shape, or the like.

The protruding portion 3 is a portion formed by bending the bent portion 12 protruding upward from the top surface 1a of the base 1. The protruding portion 3 provides excellent durability and resistance to breakage compared to a grass cutter blade that does not have the protruding portion 3. The protruding portion 3 may be formed by bending a plate member with a protruding upper edge at approximately the center, or by bending a plate member with a flat upper edge at approximately the center and then performing press cutting, laser cutting, grinding, or the like.

As shown in FIG. 3, the height 3h of the protruding portion 3 is the height in the vertical direction from the top surface 1a of the base 1, more specifically from the top of the top surface 1a. The height 3h of the protruding portion 3 is preferably formed so that the ratio of the thickness t of the plate member forming the grass cutter blade of the present invention to the height 3h of the protruding portion 3 is (thickness t of plate member): (height 3h of protruding portion 3) = (1): (0.03 to 10), more preferably (1): (0.1 to 7.0), and most preferably (1): (0.3 to 5.0). In this embodiment, the thickness t of the plate member forming the grass cutter blade is 3.2 mm, and the height 3h of the protruding portion 3 is 3 mm, so that (thickness t of plate member): (height 3h of protruding portion 3) = 1: 0.94. When the ratio of the thickness t of the plate member forming the grass cutter blade of the present invention to the height 3h of the protruding portion 3 is within this range, cracks are less likely to occur on the top surface 1a side of the bent portion 12 when the grass cutter blade is in use, interference with the grass cutter's rotation axis A and fixing device F is prevented, and the center of gravity balance of the grass cutter blade can be maintained. In this embodiment, the protruding portion 3 has a substantially trapezoidal shape as shown in FIG. 3, but in other embodiments, it may have a shape other than the substantially trapezoidal shape, such as a substantially triangular shape, a substantially rectangular shape, or a substantially fan shape. In FIG. 3 showing this embodiment, the shape of the top surface 1a is a shape that combines straight lines and curved lines, but in other embodiments, it may have a shape represented by only straight lines or only curved lines.

The width 3w, which is the length in the front-to-rear direction of the protrusion 3, is preferably equal to or greater than the thickness t of the plate member forming the grass cutter blade and equal to or less than two-thirds of the width 1W, which is the length in the front-to-rear direction of the base 1, more preferably equal to or greater than 1.1 times the thickness t of the plate member and equal to or less than three-fifths of the width 1W of the base 1, and most preferably equal to or greater than 1.5 times the thickness t of the plate member and equal to or less than one-half of the width 1W of the base 1. When the width 3w of the protrusion 3 is in this range, cracks are less likely to occur on the top surface 1a side of the bent portion 12 when the grass cutter blade is in use.

As shown in FIG. 4 and other figures, the side portion 4 is located below the base portion 1 and is located behind the blade portion 2 via the first ridgeline R1 and the second ridgeline R2. The side portion 4 supports the blade portion 2 while dispersing and absorbing the stress applied to the blade portion 2 when the grass cutter blade is in use, thereby preventing damage or deformation of the blade portion 2. The side portion 4 is formed continuously with the base portion 1 on the right or left side of the grass cutter blade, with the curvature start line L as the boundary.

[Analysis test]
In the grass cutter blade of this embodiment, the bent portion 12 is provided with a protruding portion 3 formed by protruding from the top surface 1a of the base 1, but the extent to which the stress applied to the top surface 1a side of the bent portion 12 changes was confirmed by computer analysis, compared to a comparative example in which the protruding portion 3 is not provided. Specifically, using Pro ENGINEER from Parametric Technology Corporation, as shown in Figures 7 and 8, a load of 5 kN was applied to both sides of the cutting edge 21 in the direction of the reaction force (direction of the arrow) of the impact force applied when the grass cutter blade is used, and the bent portion 12 side on the right side of the edge near the insertion hole 11 of the base 1 was set as a stationary area fr that does not displace, and the stress applied to the α and β parts on the top surface 1a side of the bent portion 12 was calculated. The α and β portions are portions where stress is concentrated and cracks easily form and break when the grass cutter blade is actually used, and the cracks grow and extend downward in the vertical direction of the bent portion 12, causing breakage and making the grass cutter blade unusable. A similar analysis was also performed on grass cutter blades in which the height 3h of the protruding portion 3 was changed. The results are shown in Table 1. In Comparative Example 1, the height 3h of the protruding portion 3 is -5 to 0 mm because, as shown in FIG. 8, the top surface 1a of the base 1 is gently curved toward the bent portion 12, and therefore has the above-mentioned width when measured from the horizontal tangent at the top of the top surface 1a.

As shown in Table 1, the grass cutter blades of Examples 1 to 7, which have protrusions 3, have a significantly reduced stress in the α portion, which is the portion that is prone to cracking and breakage, compared to the β portion of the grass cutter blade of Comparative Example 1, which does not have protrusions 3. This shows that the grass cutter blades have excellent durability and are less likely to break when used for cutting grass.

[Field Test]
Next, the grass cutter blade of Example 1 having the projection 3 and the grass cutter blade of Comparative Example 1 having no projection 3 were actually attached to the rotating shaft A of the grass cutter via a fixture F so as to be freely swingable, grass was cut, and the condition of cracks, etc. was checked at predetermined intervals. Specifically, as shown in Fig. 5, six grass cutter blades of Example 1 were attached to the rotating shaft A of the grass cutter via a fixture F so as to be freely swingable at predetermined intervals along the axial direction of the rotating shaft A, and similarly, six grass cutter blades of Comparative Example 1 were attached to different positions of the same rotating shaft A via fixtures F so as to be freely swingable at similar intervals along the axial direction of the rotating shaft A, grass was cut for about 35 hours in cultivated land scattered with stones and overgrown with weeds, and the condition of cracks, etc. was checked visually at appropriate times. The six grass cutter blades of Example 1 and Comparative Example 1 were numbered 1 to 6, and those with no visible cracks in the α portion were rated as ◯, those with visible cracks in the α portion as △, and those with cracks growing downward in the vertical direction of the bent portion 12 as ×. The results are shown in Table 2.

As shown in Table 2, it was found that as time passed during mowing, the grass cutter blade of Example 1 was less susceptible to cracks and the cracks were less likely to grow compared to the grass cutter blade of Comparative Example 1. Specifically, 35.6 hours after the start of the test, only one grass cutter blade of Example 1 had a crack in the α portion, but the remaining five had no cracks at all, while three grass cutter blades of Comparative Example 1 had cracks in the β portion, and the remaining three had cracks that did not stop at the β portion but instead grew downward in the vertical direction of the bent portion 12. These results well supported the results of the analytical test described above.

1: Base 11: Insertion hole 12: Bent portion 1a: Top surface 1W: Width of base 1 2: Blade portion 21: Blade tip 3: Protruding portion 3w: Width of protruding portion 3 3h: Height of protruding portion 3 4: Side portion R1: First ridge line R2: Second ridge line A: Rotating shaft F: Fixing device B: Bracket t: Thickness of plate member forming the grass cutter blade L: Curve start line

Claims (3)

A grass cutter blade is formed by bending a plate member and is attached to a rotating shaft (A) of a grass cutter via a fixing device (F) so as to be able to swing freely,
a base portion (1) in which an insertion hole (11) for inserting the fixing device (F) is drilled and in which the plate members are formed facing each other by a bent portion (12);
The blade (2) has a first ridge line (R1) and a second ridge line (R2) that are bifurcated with the distance between them increasing from the bent portion (12) toward the blade tip (21), and the blade (2) has a surface sandwiched between the first ridge line (R1) and the second ridge line (R2);
A grass cutter blade, characterized in that the bent portion (12) has a protruding portion (3) formed to protrude from a top surface (1a) of the base portion (1). The blade for a grass cutter as described in claim 1, characterized in that the protrusion (3) is formed so that the thickness (t) of the plate member: the height (3h) of the protrusion (3) = 1:0.03 to 10. The blade for a grass cutter according to claim 1 or 2, characterized in that the base (1) is formed by bending and partially joining opposing plate members.

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