Blades for lawnmowers

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

Technical Field

[0001] The present invention relates to a blade for a lawn mower that is attached to a lawn mower such as a flail mower or a hammer knife mower attached to the rear part of a tractor or the like in order to cut weeds or finely crush the cut weeds.

Background Art

[0002] Conventionally, there are known a plurality of types of blades for lawn mowers that are used by mounting two blades as a set.

[0003] For example, Patent Document 1 discloses a mowing claw that is detachably attached to a claw mounting portion provided on a rotating shaft body, and two plate blade members having a "C" - shaped cross - section are used as a set to form a substantially Y - shape.

[0004] Further, Patent Document 2 discloses a flail mower blade that is provided on a mowing blade holder by an attachment member so as to be freely rotatable, and is composed of two split halves that contact each other on their contact surfaces. The two split halves are each composed of a single plate - like body having a shape symmetric about a contact surface as a symmetry axis plane. Each plate - like body has a shape in which the lower part of the contact surface portion is sequentially twisted by approximately 90 degrees each in the lateral direction and the forward direction opposite to the contact surface, and a planar front edge of the plate - like body facing the rotation direction is formed as a front blade.

[0005]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0006] However, in the cutting claws disclosed in Patent Document 1, each blade tip is roughly "V" shaped, and as a pair they form roughly Y-shapes, so the blade tips are at an angle to the ground, which presents the problem of not being able to cut some weeds from the root. In the cutting blades disclosed in Patent Document 2, the blade tip is roughly horizontal to the ground, which solves the aforementioned problem, but the two divided halves each consist of a single plate-like body with a symmetrical shape 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 by approximately 90 degrees sequentially in the opposite lateral direction and forward direction from the contact surface, so if the two divided halves open during cutting, weeds and other debris may enter the gap between the contact surfaces, which may prevent uniform cutting of weeds.

[0007] In addition, there are commercially available brush cutter blades, such as those disclosed in Patent Document 2, which have a shape in which a single plate member is bent so that the cutting edge is approximately parallel to the ground, with the front side of the cutting blade connected. However, because the rotation axis of the brush cutter rotates at high speed, various strong impact forces are applied during brush cutting work, and as the usage time increases, cracks form at the bent part and the blade breaks.

[0008] Therefore, the present invention aims to provide a brush cutter blade that is used with brush cutters such as flail mowers and hammer knife mowers, which are attached to the rear of a tractor or the like for cutting weeds or finely shredding cut weeds, and that is formed by bending a single component while being highly durable and resistant to breakage. [Means for solving the problem]

[0009] [1] That is, the present invention is a blade for a grass trimmer, formed by bending a plate member and pivotably attached to the pivot shaft (A) of the grass trimmer via a fixing device (F), characterized in that it has a through hole (11) through which the fixing device (F) is inserted, and a base portion (1) formed by a bent portion (12) through which the plate member faces each other, and a blade portion (2) having a surface sandwiched between the first ridge line (R1) and the second ridge line (R2) which are formed by branching from the bent portion (12) toward the cutting edge (21) with the distance between them increasing, and the bent portion (12) has a protruding portion (3) formed to protrude from the top surface (1a) of the base portion (1).

[0010] [2] The blade for a grass trimmer according to [1] is characterized in that the protruding portion (3) is formed such that the thickness of the plate member (t) : the height of the protruding portion (3) (3h) = 1 : 0.03 to 10.

[0011] [3] The base (1) is formed by bending and joining together a portion of opposing plate members, and is a blade for a grass trimmer according to [1] or [2]. [Effects of the Invention]

[0012] The tilling claws of the present invention are blades for a grass cutter, such as a flail mower or hammer knife mower, which is attached to the rear of a tractor or the like for cutting weeds or finely shredding the cut weeds. They are formed by bending a single component, yet are highly durable and resistant to breakage. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of an embodiment of the blade for a grass trimmer of the present invention. [Figure 2] This is a front view of an embodiment of the grass trimmer blade of the present invention. [Figure 3] This is a right side view of an embodiment of the grass trimmer blade of the present invention. [Figure 4] This is a plan view of an embodiment of a brush cutter blade of the present invention. [Figure 5] This is a reference diagram showing an embodiment of the grass trimmer blade of the present invention, in which it is pivotably mounted on the pivot shaft A via a fixing device F. [Figure 6] This is a cross-sectional view taken when the pivot axis A in Figure 5 is cut by a plane perpendicular to the axial direction. [Figure 7] This is a perspective view showing the load application direction and stress concentration points confirmed in the analysis test of Embodiment 1 of the present invention for a grass trimmer blade. [Figure 8] This is a perspective view showing the load application direction and stress concentration points confirmed in the analysis test of Comparative Example 1 of the brush cutter blade. [Modes for carrying out the invention]

[0014] The embodiments relating to the brush cutter blade according to the present invention will be described in detail below with reference to the attached drawings. The embodiments described below are preferred specific examples for carrying out the present invention and therefore have various technical limitations. However, the present invention is not limited to these embodiments unless otherwise explicitly stated in the following description. In the description, the vertical direction refers to the vertical direction in Figure 2, the forward direction refers to the direction towards the viewer in Figure 2, and the backward direction refers to the direction towards the viewer in Figure 2. In addition, in numerical ranges represented by the symbol "~", the upper and lower limits are included within that range.

[0015] As described above, the brush cutter blade according to the present invention is used when mounted on a brush cutter attached to the rear of a tractor or the like. Specifically, the brush cutter is provided with a cylindrical or other rotating shaft A that rotates with a power source mounted on it. 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 through the hole. Furthermore, the brush cutter blade of the present invention can be attached to the fixing part F by inserting the brush cutter blade of the present invention through the substantially U-shaped base material part of the fixing part F. In this way, the brush cutter blade of the present invention is swingably mounted on the rotating shaft A of the brush cutter via the fixing part F. Since multiple pairs of brackets B are provided on the surface of the rotating shaft A at predetermined intervals, multiple brush cutter blades of the present invention are also provided on the surface of the rotating shaft A.

[0016] Furthermore, in this embodiment, as shown in Figures 5 and 6, the fixing device F comprises a substantially U-shaped base portion and a rod-shaped portion having a screw thread that is inserted through the open end of the base portion. The blade for the grass trimmer of the present invention can be attached to the fixing device F by inserting the blade for the grass trimmer of the present invention into the substantially U-shaped base portion of the fixing device F. However, in other embodiments, the blade for the grass trimmer of the present invention can be swingably attached to the pivot axis A of the grass trimmer via the fixing device F, and the base portion can be made into various shapes, such as a "U" shape, a V shape, or even just a rod-shaped portion without a base portion.

[0017] The blade for a grass trimmer of the present invention is formed by bending a single plate member. Specifically, the upper part of the single plate member is bent in half, and the lower part is curved so as to protrude forward. In order to distribute the stress applied when using the grass trimmer blade and make it less likely to break, it is preferable that the parts that are bent or curved in various ways have a gently curved shape rather than a pointed shape.

[0018] As the plate member used for the blade of the lawn mower, it is preferably formed of a metal such as steel, iron, titanium or a titanium alloy, or an aluminum alloy. Further, the blade for the lawn mower of the present invention is preferably formed of a plate member having a thickness t of 1 to 10 mm, more preferably formed of a plate member of 2 to 7 mm, and most preferably formed of a plate member of 2.5 to 5 mm. When the plate member used for the blade of the lawn mower is made of a metal and within the above thickness range, when it is swingably attached to the rotating shaft A of the lawn mower via the fixture F to cut weeds, even if it abuts against small stones or the like, it will not be easily damaged, and it will have an appropriate mass as a blade for the lawn mower, and weeds can be cut by the centrifugal force generated by the rotation of the rotating shaft A. The plate member used for the blade of the lawn mower may have a paint, plating, etc. attached to the surface for the purpose of rust prevention or the like.

[0019] The base portion 1 of the blade for the lawn mower of the present invention is a portion where an insertion hole 11 through which the fixture F is inserted is formed, and the plate members are opposed to each other by the bent bent portion 12. By inserting the fixture F into the insertion hole 11, the blade for the lawn mower is attached in a state where it can move with respect to the fixture F. The insertion hole 11 may be formed before one plate member is bent, or may be formed after being bent. Further, the insertion hole 11 is a long hole that is long in the vertical direction in the present embodiment, but in other embodiments, if it is larger than the fixture F and can move with respect to the fixture F, it can be formed in a shape such as a circle or an ellipse.

[0020] Further, in the present embodiment, the base portion 1 has a gap of about 0.1 to 1 mm between the opposing plate members formed by the bent bent portion 12 and they are not in contact, but in other embodiments, the opposing plate members may be partially joined by welding or the like.

[0021] The blade portion 2 has a first ridge line R1 and a second ridge line R2 that branch out from the bent portion 12 toward the cutting edge 21, with the gap between them widening, and the blade portion 2 has a surface sandwiched between the first ridge line R1 and the second ridge line R2. The blade portion 2 has a curved shape in which the cutting edge 21, located at the lower end of the blade portion 2, protrudes the furthest forward. Due to the cutting edge 21, when the brush cutter blade of the present invention is attached to the rotation axis A of the brush cutter via a fixing device F, it becomes approximately horizontal to the ground, so that weeds can be cut from the roots, and the cut weeds can also be finely shredded. The cutting edge 21 is preferably formed at an acute angle to facilitate cutting and shredding of weeds.

[0022] In this embodiment, the blade portion 2 has a ginkgo leaf shape, a triangular shape with the left and right sides recessed inward, or an inverted T-shape, as shown in Figure 2, due to the gently curved first ridge line R1 and second ridge line R2. However, it may also have a triangular shape with the left and right sides bulging outward, or an approximate semicircle shape.

[0023] The protruding portion 3 is the part formed by the bent portion 12 protruding upward from the top surface 1a of the base portion 1. The protruding portion 3 provides superior durability and resistance to breakage compared to a brush cutter blade without the protruding portion 3. The protruding portion 3 may be formed by bending a plate member with a protruding portion approximately in the center of its upper edge, or by bending a plate member with a flat upper edge approximately in the center and then forming it by press cutting, laser cutting, grinding, etc.

[0024] The height 3h of the protruding portion 3 is the vertical height from the top surface 1a of the base portion 1, more specifically from the top of the top surface 1a, as shown in Figure 3. The height 3h of the protruding portion 3 is preferably formed such that the ratio of the thickness t of the plate member forming the blade for the grass trimmer of the present invention to the height 3h of the protruding portion 3 is (thickness t of the plate member):(height 3h of the protruding portion 3) = (1):(0.03~10), more preferably (1):(0.1~7.0), and most preferably (1):(0.3~5.0). In this embodiment, the thickness t of the plate member forming the blade for the grass trimmer is 3.2 mm, and the height 3h of the protruding portion 3 is 3 mm, so (thickness t of the plate member):(height 3h of the protruding portion 3) = 1:0.94. When the ratio of the thickness t of the plate member forming the blade for the brush cutter 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 brush cutter blade is in use, interference with the rotation axis A and fixing device F of the brush cutter is prevented, and the balance of the center of gravity of the brush cutter blade can be maintained. In this embodiment, the protruding portion 3 has a substantially trapezoidal shape as shown in Figure 3, but in other embodiments, it may have a shape other than a substantially trapezoidal shape, such as a substantially triangular shape, a substantially square shape, or a substantially fan shape. Also, in Figure 3 showing this embodiment, the shape of the top surface 1a is a shape that combines straight lines and curves, but in other embodiments, it may be a shape shown only by straight lines or a shape shown only by curves.

[0025] The width 3w of the protruding portion 3, which is its length in the front-rear direction, is preferably greater than or equal to the thickness t of the plate member forming the blade for the grass trimmer and less than or equal to two-thirds of the width 1W of the base portion 1, more preferably greater than or equal to 1.1 times the thickness t of the plate member and less than or equal to three-fifths of the width 1W of the base portion 1, and most preferably greater than or equal to 1.5 times the thickness t of the plate member and less than or equal to half of the width 1W of the base portion 1. When the width 3w 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 trimmer blade is in use.

[0026] As shown in Figure 4, the side portion 4 is located below the base portion 1 and is positioned behind the blade portion 2 via the first ridge line R1 and the second ridge line R2. The side portion 4 supports the blade portion 2 while distributing and absorbing the stress applied to the blade portion 2 when using the brush cutter blade, thereby preventing damage and deformation of the blade portion 2. Furthermore, the side portion 4 is formed continuously with the base portion 1 on the right or left side of the brush cutter blade, with the curvature start line L as the boundary.

[0027] [Analysis Test] In this embodiment of the brush cutter blade, a protruding portion 3 is provided, which is formed by the bent portion 12 protruding from the top surface 1a of the base portion 1. Compared to a comparative example in which the protruding portion 3 is not provided, the extent to which the stress applied to the top surface 1a side of the bent portion 12 changes was confirmed by computer analysis. Specifically, using Pro ENGINEER from Parametric Technology Corporation, as shown in Figures 7 and 8, a load of 5kN was applied to both sides of the blade tip 21 in the direction of the reaction force of the impact force applied when using the brush cutter blade (direction of the arrow), and the stress applied to the α and β portions, which are the top surface 1a side of the bent portion 12, was calculated when the right side of the edge near the insertion hole 11 of the base portion 1 on the bent portion 12 side was set as a fixed region fr where it does not displace. Sections α and β are areas where stress concentrates and cracks easily form, leading to breakage, when the brush cutter blade is actually used. These cracks grow and extend downward in the vertical direction of the bent section 12, causing breakage and rendering the brush cutter blade unusable. The same analysis was performed on brush cutter blades with a modified height 3h of the protruding section 3. The results are shown in Table 1. In Comparative Example 1, the height 3h of the protruding section 3 is -5 to 0 mm because, as shown in Figure 8, the top surface 1a of the base 1 is gently curved toward the bent section 12, and the above width is obtained by measuring from the horizontal tangent at the top of the top surface 1a.

[0028] [Table 1]

[0029] As shown in Table 1, the brush cutter blades of Examples 1 to 7, which have the projection 3, showed significantly less stress in the α portion, which is the part that is actually prone to cracking and breakage, compared to the β portion of the brush cutter blade of Comparative Example 1, which does not have the projection 3. This indicates that they have excellent durability and are less likely to break during brush cutting.

[0030] [Practical Examination] Next, the brush cutter blades of Example 1, which have the protrusion 3, and the brush cutter blades of Comparative Example 1, which do not have the protrusion 3, were actually attached to the rotation axis A of the brush cutter via a fixing device F so as to be swingable, and grass cutting was performed, while the condition of cracks and other issues was checked at predetermined intervals. Specifically, as shown in Figure 5, six brush cutter blades of Example 1 were attached to the rotation axis A of the brush cutter via a fixing device F so as to be swingable at predetermined intervals along the axial direction of the rotation axis A, and similarly, six brush cutter blades of Comparative Example 1 were attached to different positions on the same rotation axis A via a fixing device F so as to be swingable, and grass cutting was performed for approximately 35 hours in a cultivated field with scattered stones and overgrown weeds, and the condition of cracks and other issues was checked visually at appropriate intervals. The six brush cutter blades from Example 1 and Comparative Example 1 were numbered 1 to 6, respectively. Blades with no cracks in section α were marked with ○, those with cracks in section α were marked with △, and those with cracks growing downwards in the vertical direction of the bent section 12 were marked with ×. The results are shown in Table 2.

[0031] [Table 2]

[0032] As shown in Table 2, it was found that, as the grass cutting time progressed, the grass cutting blade of Example 1 was less prone to cracking and less prone to crack growth compared to the grass cutting blade of Comparative Example 1. Specifically, 35.6 hours after the start of the test, only one grass cutting blade of Example 1 showed a crack in section α, while the remaining five showed no cracks at all. In contrast, three grass cutting blades of Comparative Example 1 showed cracks in section β, and the remaining three showed crack growth not only in section β but also downward in the vertical direction of the bent section 12. These results strongly supported the results of the analysis tests described above. [Explanation of Symbols]

[0033] 1...Base 11... Through hole 12...Bending part 1a...Top surface 1W...Width of base 1 2...Blade 21...Blade tip 3. Protruding section 3w...Width of protruding section 3 3h... Height of protruding section 3 4. Side R1...First ridgeline R2...Second ridgeline A... Rotating axis F... Fixture B...bracket t...Thickness of the plate material that forms the blade for the lawnmower. L... Curved starting line

Claims

1. A blade for a grass trimmer is formed by bending a plate member and is pivotably attached to the rotating shaft (A) of the grass trimmer via a fixing device (F), An insertion hole (11) for inserting the fixing device (F) is drilled, and the plate members are formed facing each other by the bent portion (12), From the bent portion (12) toward the cutting edge (21), a first ridge (R1) and a second ridge (R2) are formed, with the distance between them increasing as they branch out, and the cutting edge (2) has a surface sandwiched between the first ridge (R1) and the second ridge (R2). A brush cutter blade characterized in that 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 trimmer according to claim 1, characterized in that the protruding portion (3) is formed such that the thickness of the plate member (t) : the height of the protruding portion (3) (3h) = 1 : 0.03 to 10.

3. The base portion (1) is formed by partially joining together two bent plate members, as described in claim 1 or 2 for a grass trimmer blade.

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