Grass cutting blade device

Abstract

To provide a mowing blade device capable of efficiently mowing grasses while suppressing flipping up stones and damaging a blade part in the mowing blade device which includes a rotary blade in a position decentered from a center between an upper panel and a lower panel disposed so as to be rotated around the center.SOLUTION: A lower panel 3 of a mowing blade device 1 has a plate-like outer peripheral part 33 protruding to the outside from an upper panel 2. The outer periphery of the outer peripheral part 33 includes a circular arc portion 34 formed in a circular art shape along a circumferential direction around the lower panel 3, and a notch portion 35 in a notched shape to a virtual circle 200 as a locus drawn by the circular arc portion 34 due to the rotation of the lower panel 3. The notch portion 35 is formed so as to be overlapped in a plain view on a blade part 56 of a rotary blade 5 from a position in front of the rotary blade 5 in the rotation direction of the lower panel 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a grass cutting blade.

Background Art

[0002] In Patent Documents 1 and 2 below, there is a proposal for a grass cutting blade device including an upper disk and a lower disk provided to rotate around a center, a guide pin connecting the upper disk and the lower disk at a position eccentric from the center, and a disk-shaped rotary blade rotatably provided around the guide pin between the upper disk and the lower disk, having a blade portion on the outer periphery, and the blade portion protruding outside the lower disk.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the grass cutting blade device of Patent Document 1, there is a risk that a stone may hit the blade portion deeply during grass cutting and the stone may be bounced up. If the stone bounces up, there is a risk that the bounced stone may hit a person or the like. Also, when the blade portion hits a hard object (obstacle) such as a tree, a wall, or a fence, there is also a risk that the blade portion may be severely damaged.

[0005] Therefore, an object of the present disclosure is to provide a grass cutting blade device that can efficiently cut grass while suppressing the bouncing of stones and damage to the blade portion in a grass cutting blade device including an upper disk, a lower disk, a guide pin, and a rotary blade.

Means for Solving the Problems

[0006] The grass cutting blade device of this disclosure is An upper plate and a lower plate are provided to rotate around the center, A guide pin connects the upper plate and the lower plate at an eccentric position from the center, The device comprises a disc-shaped rotating blade rotatably mounted between the upper plate and the lower plate with respect to the guide pin as its axis, having a cutting edge on its outer circumference, the cutting edge extending outward from the lower plate, The outer circumference of the lower plate includes an arc portion formed in an arc shape along the circumferential direction around the center, and a notched portion that is cut out from a virtual circle which is the trajectory traced by the arc portion due to the rotation of the lower plate. The notch is formed such that, when viewed in plan, it overlaps the blade portion of the rotating blade from a position in front of the rotating blade in the rotational direction of the lower platen. 、 The end of the notch located on the side of the lower plate that is in the direction of rotation is defined as the front end, and the end located on the opposite side of the direction of rotation is defined as the rear end. The notch includes a first portion that forms part of the front end, and a second portion that changes direction from the first portion toward the virtual circle and extends to the rear end while overlapping the rotating blade when viewed in plan. .

[0007] According to this design, a notch is provided on the outer circumference of the lower plate, around the rotating blade. This allows the blade portion of the rotating blade to extend outside the lower plate while increasing the diameter of the lower plate (in other words, the distance between the arc portion and the center of rotation of the lower plate). By increasing the diameter of the lower plate (arc portion), stones can be pushed outward by the arc portion, preventing them from hitting the blade. This reduces the amount of stones thrown up and damage to the blade. In addition, when grass comes into contact with the arc portion, it bends radially outward of the lower plate. However, when contact with the arc portion is released at the notch, the rebound from this bending can cause the grass to be displaced radially inward of the lower plate. This allows the grass to be guided along the notch to the blade, enabling efficient grass cutting. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view of the grass cutting blade device. [Figure 2] This is a side view of the grass cutting blade device. [Figure 3] This is a cross-sectional view of the grass cutting blade device along line III-III in Figure 1. [Figure 4]It is an exploded perspective view of a grass cutting blade device. [Figure 5] It is an enlarged view of part A in FIG. 1, showing the state where the rotary blade is in the outermost position. [Figure 6] It is an enlarged view of part A in FIG. 1, showing the state where the rotary blade is in the innermost position. [Figure 7] It is a bottom view (rear view) of the upper disk. [Figure 8] It is a perspective view of a lawn mower. [Figure 9] It is a perspective view of the rotary blade of the first embodiment. [Figure 10] It is a plan view (top view) of the rotary blade of the first embodiment. [Figure 11] It is a front view of the rotary blade of the first embodiment. [Figure 12] It is a right side view of the rotary blade of the first embodiment. [Figure 13] It is a cross-sectional view of the rotary blade of the first embodiment taken along line XIII-XIII in FIG. 10. [Figure 14] It is a cross-sectional view of the blade part (protruding part) of the rotary blade of the first embodiment taken along line XIV-XIV in FIG. 10. [Figure 15] It is a cross-sectional view of the rotary blade of the first embodiment taken along line XV-XV in FIG. 10. [Figure 16] It is a perspective view of the rotary blade of the second embodiment. [Figure 17] It is a plan view (top view) of the rotary blade of the second embodiment. [Figure 18] It is a front view of the rotary blade of the second embodiment. [Figure 19] It is a right side view of the rotary blade of the second embodiment. [Figure 20] It is a cross-sectional view of the blade part (protruding part) of the rotary blade of the second embodiment taken along line XX-XX in FIG. 17. [[ID=]] [Figure 21] It is a cross-sectional view of the rotary blade of the second embodiment taken along line XXI-XXI in FIG. 17. [Figure 22] It is a cross-sectional view of the rotary blade of the second embodiment taken along line XXII-XXII in FIG. 17. [Figure 23] It is a perspective view of the rotary blade of the third embodiment. [Figure 24] This is a plan view (top view) of the rotating blade of the third embodiment. [Figure 25] This is a front view of the rotating blade of the third embodiment. [Figure 26] This is a right side view of the rotating blade of the third embodiment. [Figure 27] This is a cross-sectional view of the rotating blade of the third embodiment along the line XXVII-XXVII in Figure 24. [Figure 28] This is a cross-sectional view of the rotary blade of the third embodiment along the line XXVIII-XXVIII in Figure 24. [Figure 29] This is a cross-sectional view of the blade portion (protruding portion) of the rotary blade of the third embodiment along the line XXIX-XXIX in Figure 24. [Figure 30] This is a perspective view of the rotating blade of the fourth embodiment. [Figure 31] This is a plan view (top view) of the rotating blade of the fourth embodiment. [Figure 32] This is a front view of the rotating blade of the fourth embodiment. [Figure 33] This is a right side view of the rotating blade of the fourth embodiment. [Figure 34] This is a cross-sectional view of the rotary blade of the fourth embodiment along the line XXXIV-XXXIV in Figure 31. [Figure 35] This is a cross-sectional view of the rotating blade of the fourth embodiment along the line XXXV-XXXV in Figure 31. [Figure 36] This is a cross-sectional view of the blade portion (protruding portion) of the rotary blade of the fourth embodiment along the line XXXVI-XXXVI in Figure 31. [Figure 37] This is a perspective view of the grass cutting blade device of the fifth embodiment. [Modes for carrying out the invention]

[0009] (First Embodiment) Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. Figures 1 to 4 show the grass cutting blade device 1 of this embodiment. The grass cutting blade device 1 constitutes part of a handheld grass trimmer 100 illustrated in Figure 8. The grass trimmer 100 includes a shaft 101, a drive shaft 102 provided at the tip of the shaft 101, a handle 103 provided in the middle of the shaft 101, and a drive source 104 provided at the rear end of the shaft 101. The grass cutting blade device 1 is attached to the drive shaft 102 at the tip of the shaft 101. The drive shaft 102 is attached so as to fit into the central hole 31c (see Figures 1 and 3) of the grass cutting blade device 1. The drive shaft 102 rotates the grass cutting blade device 1 around its centerline L0 (see Figure 3) by its own rotation.

[0010] The drive source 104 is an engine, motor, etc., that rotates the drive shaft 102. The shaft 101 is pipe-shaped, and a transmission shaft (not shown) is provided inside it to transmit the driving force from the drive source 104 to the drive shaft 102. The handle 103 is the part of the lawnmower 100 that is held by the user to control the direction and position of the shaft 101 and the grass cutting blade device 1 at its tip. The grass cutting blade device 1 is used to move along the ground where grass grows by operating the handle 103.

[0011] As shown in Figures 1 to 4, the grass cutting blade device 1 comprises an upper plate 2, a lower plate 3, a guide pin 4, a rotating blade 5, and a nut 6. The upper plate 2 may be entirely made of resin, for example, but may be partially or entirely made of metal. The upper plate 2 is positioned above the lower plate 3 and opposite the lower plate 3. In the plan view of Figure 1, the center O of the upper plate 2 coincides with the center of the lower plate 3. The center O is a point on the center line L0 in Figure 3. In the following, the center of the lower plate 3 may also be indicated by the symbol "O".

[0012] The upper plate 2 has an upper surface portion 21 and a side portion 22. The upper surface portion 21 is formed in a circular plate shape when viewed from above. The upper surface portion 21 is provided with a vertical gap between it and the lower plate 3 to form a space for arranging the rotating blade 5. A through hole 24 (hereinafter sometimes referred to as the center hole) is formed in the center of the upper surface portion 21. The upper end portion 31b of the central portion 31 of the lower plate 3 fits into this center hole 24 (see Figure 3). The upper end portion 31b fits into the center hole 24 so as to be flush with the upper surface 21a of the upper surface portion 21. Also, the diameter of the upper surface portion 21 (upper plate 2) is smaller than the diameter of the lower plate 3 (the diameter of the virtual circle 200 described later). Note that the diameter of the upper plate 2 may be the same as or larger than the diameter of the lower plate 3.

[0013] Furthermore, multiple through holes 25 (hereinafter sometimes referred to as outer peripheral holes) are provided on the outer circumference of the upper surface portion 21. In this embodiment, three outer peripheral holes 25 are formed. The multiple outer peripheral holes 25 are formed at equal intervals (i.e., 120° intervals) along the circumferential direction of the upper surface portion 21. As shown in Figure 4, each outer peripheral hole 25 includes a large-diameter hole 25a located on the upper surface 21a side of the upper surface portion 21 and a small-diameter hole 25b located on the lower surface (back side) side of the upper surface portion 21. These large-diameter holes 25a and small-diameter holes 25b are formed coaxially. The small-diameter hole 25b is formed to be smaller in diameter than the large-diameter hole 25a. The outer peripheral holes 25 are holes for fitting guide pins 4. Specifically, the head 41 of the guide pin 4 (see Figure 4) is fitted into the large-diameter hole 25a. The head portion 41 is fitted into the outer peripheral hole 25 (large hole 25a) so as to be flush with the upper surface 21a of the upper portion 21 (see Figure 3). The middle portion 42 of the guide pin 4 (see Figure 4) is fitted into the small diameter hole 25b.

[0014] The upper surface 21a of the upper portion 21 is formed as a surface without irregularities or steps, except for the central hole 24 and the outer peripheral hole 25. More specifically, the upper surface 21a does not have stepped surfaces parallel to the rotational centerline L0, except for the central hole 24 and the outer peripheral hole 25. Furthermore, the upper surface 21a does not have any parts (convex portions) that are displaced upward and then downward, or parts that are displaced downward and then upward, either from the radially inner side to the outer side of the upper plate 2, or along the circumferential direction of the upper plate 2. In addition, the upper surface 21a does not have any multiple horizontal planes (planes perpendicular to the rotational centerline L0) at different positions in the vertical direction, except for the central hole 24 and the outer peripheral hole 25.

[0015] More specifically, the portion of the upper surface 21a other than the central hole 24 and the outer peripheral hole 25 is formed as a flat surface (horizontal plane) perpendicular to the rotational centerline L0 (see Figure 3) of the upper plate 2 and the lower plate 3. That is, the upper surface 21a, except for the central hole 24 and the outer peripheral hole 25, has no irregularities, steps, or inclinations in the vertical direction, which is the direction of the rotational centerline L0. As described above, the guide pin 4 is fitted into the outer peripheral hole 25 so as to be flush with the upper surface 21a, and the central part 31 of the lower plate 3 is fitted into the central hole 24 so as to be flush with the upper surface 21a. Furthermore, the drive shaft 102 is fitted into the central hole 31c formed in the central part 31, and the central hole 31c is hidden by the drive shaft 102. Therefore, when the grass cutting blade device 1 is attached to the grass cutter 100, there are no irregularities or steps on the upper surface 21a (including the upper surface of the guide pin 4) other than the drive shaft 102. In other words, there are no stepped surfaces perpendicular to the horizontal plane (surfaces parallel to the rotation center line L0).

[0016] Figures 1 to 4 show an example in which the entire upper surface 21a (including the upper surface of the guide pin 4) is formed as a flat surface perpendicular to the rotation centerline L0. In other words, in the example in Figures 1 to 4, the upper surface 21a (including the upper surface of the guide pin 4) is formed as a surface in which the vertical position does not change along the circumferential direction around the rotation centerline L0, and in which the vertical position does not change along the radial direction. However, it is not limited to this, and the upper surface 21a is not limited to the example in Figures 1 to 4 as long as it is a surface without irregularities or steps along the circumferential and radial directions. Specifically, for example, the entire upper surface 21a (excluding through holes such as the center hole 24 and outer circumference hole 25) may be formed as a downward inclined surface in which the vertical position does not change along the circumferential direction around the rotation centerline L0, and which gradually displaces downward as it moves from the inside to the outside in the radial direction (not including a horizontal surface perpendicular to the rotation centerline L0 and a stepped surface parallel to the rotation centerline L0). In this case, the downward-sloping surface may be a straight line along the radial direction or a curved line. Furthermore, the inclination angle of the downward-sloping surface may be the same at any position along the circumferential direction around the rotation centerline L0.

[0017] Furthermore, for example, the entire upper surface 21a (excluding through holes such as the central hole 24 and the outer peripheral hole 25) may be formed as an upward inclined surface whose vertical position does not change along the circumferential direction around the rotation centerline L0, and which gradually displaces upward as it moves from the inside to the outside in the radial direction (excluding horizontal surfaces perpendicular to the rotation centerline L0 and stepped surfaces parallel to the rotation centerline L0). In this case, the upward inclined surface may be a surface that draws a straight line along the radial direction, or a surface that draws a curve. Also, the inclination angle of the upward inclined surface may be the same at any position along the circumferential direction around the rotation centerline L0.

[0018] Furthermore, for example, the upper surface 21a (excluding through holes such as the central hole 24 and the outer peripheral hole 25) does not change its vertical position along the circumferential direction around the rotation centerline L0, and a portion of the upper surface 21a in the radial direction may be formed as a horizontal surface, while the remaining portion may be formed as a downward-sloping surface. In this case, the inner radial side may be formed as a horizontal surface and the outer side as a downward-sloping surface, or conversely, the inner radial side may be formed as a downward-sloping surface and the outer side as a horizontal surface. Also, in this case, the upper surface 21a may not include an upward-sloping surface.

[0019] Furthermore, for example, the upper surface 21a (excluding through holes such as the central hole 24 and the outer peripheral hole 25) does not change its vertical position along the circumferential direction around the rotation centerline L0, and a portion of the upper surface 21a in the radial direction may be formed as a horizontal surface, while the remaining portion may be formed as an upwardly inclined surface. In this case, the inner radial side may be formed as a horizontal surface and the outer side as an upwardly inclined surface, or conversely, the inner radial side may be formed as an upwardly inclined surface and the outer side as a horizontal surface. Also, in this case, the upper surface 21a may not include a downwardly inclined surface.

[0020] As shown in Figure 7, the upper surface portion 21 has a hole perimeter portion 26 on its back side that surrounds each outer peripheral hole 25. The hole perimeter portion 26 is formed in a plane perpendicular to the rotation center line L0. The hole perimeter portion 26 contacts the center of the upper surface of the rotating blade 5 and restricts the upward movement of the rotating blade 5.

[0021] Furthermore, as shown in Figure 7, the upper surface portion 21 has a plurality of ribs 27 that protrude downward from its back surface. The ribs 27 are provided so as to extend radially from the upper surface portion 21. Specifically, the ribs 27 are provided so as to connect each hole perimeter portion 26 and the central hole 24. Multiple ribs 27 are provided for each hole perimeter portion 26. The tip of the rib 27 in the direction of protrusion from the back surface of the upper surface portion 21 (the lower end in the vertical direction) is provided at a position that is flush with the hole perimeter portion 26. The base end of the rib 27 (the upper end in the vertical direction) is located above the hole perimeter portion 26. The tip of each rib 27 contacts the upper surface of the rotating blade 5, or faces the upper surface of the rotating blade 5 with a slight gap between them. In addition to increasing the rigidity of the upper plate 2, the ribs 27 also function as restrictors that limit the upward movement of the rotating blade 5.

[0022] The side portion 22 is formed to extend downward (towards the lower plate 3) from the outer circumference of the upper portion 21 in a direction parallel to the rotation centerline L0. The side portion 22 is also formed in an arc shape along the outer circumference of the upper portion 21. Notches 23 are formed in the side portion 22 to allow each rotating blade 5 to exit (see Figure 4). The notches 23 are formed to penetrate between the outer and inner surfaces of the side portion 22. The notches 23 are also formed in a shape that is open at the bottom. There are three notches 23, one for each rotating blade 5. The three notches 23 are formed at equal intervals (i.e., 120° intervals) in the circumferential direction around the rotation centerline L0.

[0023] When the upper plate 2 and the lower plate 3 are connected, the lower end 22a of the side portion 22 (see Figures 3 and 4) contacts the upper surface of the lower plate 3. Specifically, the lower end 22a contacts the upper end of the outer peripheral wall portion 32b (see Figures 3 and 4) of the main body portion 32 of the lower plate 3, which will be described later. In other words, the side portion 22 functions as a closing portion that closes the outer periphery of the space formed between the upper surface portion 21 and the lower plate 3 (excluding the position where the rotating blade 5 is provided (notch 23)).

[0024] The upper platen 2, driven by the drive shaft 102 (see Figure 8), rotates in a counterclockwise direction E1 around the center O, as seen in the plan view of Figure 1, together with the lower platen 3 and each rotating blade 5.

[0025] The lower plate 3 may be entirely made of resin, for example, but may be partially or entirely made of metal. The lower plate 3 is positioned below the upper plate 2 and opposite to it. The diameter of the lower plate 3 (the diameter of the virtual circle 200 described later) is larger than the diameter of the upper plate 2.

[0026] The lower plate 3 comprises a central portion 31, a main body portion 32, and an outer peripheral portion 33. The central portion 31 is provided so as to protrude upward at the center of the lower plate 3 (main body portion 32). As shown in Figure 3, the central portion 31 has a cylindrical portion 31a that encloses the entire circumference around the rotation centerline L0 in a circular manner, and an upper end portion 31b that protrudes radially inward from the upper end of the cylindrical portion 31a and is formed in an annular (circular) shape around the rotation centerline L0. The lower end of the cylindrical portion 31a forms an opening that communicates with the space inside the cylindrical portion 31a.

[0027] As shown in Figure 3, the upper end portion 31b fits into the central hole 24 of the upper plate 2. A hole 31c for attaching the drive shaft 102 (see Figure 8) is formed in the center of the upper end portion 31b. Note that the upper end portion 31b and the hole 31c may be formed as part of the upper plate 2.

[0028] The main body portion 32 of the lower plate 3 has a main body bottom portion 32a and an outer peripheral wall portion 32b. The main body bottom portion 32a surrounds the entire circumference of the central portion 31 in an annular (circular) shape and is provided to extend radially outward from the lower end of the central portion 31. The main body bottom portion 32a is formed in a plate shape. The outer circumference of the main body bottom portion 32a forms a circle centered on the rotation center line L0. As shown in Figure 3, the lower surface of the main body bottom portion 32a (the surface opposite to the side facing the upper plate 2) is formed in an inclined shape that gradually displaces upward as it moves away from the rotation center line L0. This inclined surface may be a straight line or a curved surface when viewed in the cross-section of the lower plate 3 in Figure 3. Furthermore, the inclined surface is formed over the entire circumference around the rotation center line L0. In addition, the inclination angle of the lower surface of the main body portion 32 with respect to the ground surface is, for example, 30° or less. Furthermore, this inclination angle is the same at any position along the circumferential direction around the rotation center line L0.

[0029] The outer peripheral wall portion 32b of the main body portion 32 (see Figures 3 and 4) is formed in a shape that protrudes upward from the outer circumference of the main body bottom portion 32a. Furthermore, the outer peripheral wall portion 32b is formed to trace a circle (ring) around the rotation center line L0 along the outer circumference of the main body bottom portion 32a, in other words, it is formed over the entire circumference around the rotation center L0. As described above, the upper end of the outer peripheral wall portion 32b is in contact with the lower end 22a of the side portion 22 of the upper platen 2. Together with the side portion 22 of the upper platen 2, the outer peripheral wall portion 32b functions as a closing portion that closes the outer circumference of the space formed between the upper platen 2 and the lower platen 3.

[0030] As shown in Figure 4, a hole 37 (hereinafter sometimes referred to as an outer peripheral hole) is formed in the bottom 32a of the main body, penetrating between the upper and lower surfaces of the bottom 32a. Three outer peripheral holes 37 are formed, corresponding to the number of rotating blades 5. The multiple outer peripheral holes 37 are formed on the outer periphery side of the bottom 32a of the main body (closer to the outer peripheral wall portion 32b) at equal intervals (120° intervals in this embodiment) in the circumferential direction around the rotation centerline L0. In addition, each outer peripheral hole 37 is formed at a position coaxial with the outer peripheral hole 25 of the upper plate 2. The outer peripheral holes 37 are holes for fitting the guide pins 4. Specifically, the tip side portion 43 of the guide pin 4 (see Figure 4) and the nut 6 that fits onto it are fitted into the outer peripheral holes 37 (see Figure 3).

[0031] As shown in Figure 4, the main body bottom portion 32a has a hole perimeter portion 38 on its upper surface that surrounds each outer peripheral hole 37. The hole perimeter portion 38 is formed in a plane perpendicular to the rotation center line L0. The hole perimeter portion 38 contacts the center of the lower surface of the rotating blade 5 and acts as a restricting portion that restricts the downward movement of the rotating blade 5. The hole perimeter portion 38 also functions as a mounting surface on which the rotating blade 5 rests.

[0032] Furthermore, as shown in Figure 4, the bottom portion 32a of the main body has a plurality of ribs 39 that protrude upward from its upper surface. The ribs 39 are provided so as to extend radially from the bottom portion 32a of the main body. Specifically, the ribs 39 are provided so as to connect the area around each hole 38 and the central portion 31. Multiple ribs 39 are provided for each area around each hole 38. The tip of the rib 39 (the upper end in the vertical direction) is provided at a position that is flush with the area around the hole 38. The base end of the rib 39 (the lower end in the vertical direction) is located below the area around the hole 38. The tip (upper end) of each rib 39 contacts the lower surface of the rotating blade 5, or faces the lower surface of the rotating blade 5 with a slight gap between them. In addition to increasing the rigidity of the lower plate 3, the ribs 39 also function as restrictors that limit the downward movement of the rotating blade 5.

[0033] The outer periphery 33 of the lower plate 3 is formed to extend radially outward from the outer periphery of the main body 32 (main body bottom 32a). Furthermore, the outer periphery 33 extends outward from the upper plate 2 over the entire circumference around the center O or the rotation centerline L0. The outer periphery 33 is connected to the lower end of the outer periphery wall 32b of the main body 32. The outer periphery 33 is a part that prevents obstacles such as pebbles from hitting the blade portion 56 (see Figure 1) of the rotating blade 5 and guides grass to the blade portion 56. The outer periphery 33 is formed in an annular shape along the outer periphery (outer periphery wall 32b) of the main body 32. Furthermore, the outer periphery 33 is formed over the entire circumference in the circumferential direction around the rotation centerline L0. In addition, the outer periphery 33 is formed in a plate shape. Furthermore, the upper and lower surfaces of the outer periphery 33 are formed in an inclined shape that gradually displaces upward as it moves away from the rotation centerline L0. The inclined surface may be a straight line along the radial direction of the lower plate 3 when viewed in the cross-section of Figure 3, or it may be a curved surface. Also, the inclination angle of the lower surface of the outer peripheral portion 33 with respect to the ground surface may be different from or the same as the inclination angle of the main body bottom portion 32a. The inclination angle of the outer peripheral portion 33 may be a larger angle than the inclination angle of the main body bottom portion 32a. The inclination angle of the outer peripheral portion 33 is, for example, 45° or less. Also, the inclination angle is the same at any position along the circumferential direction around the rotation centerline L0. In this embodiment (the example in Figure 3), an example is shown where the inclination angle of the lower surface of the outer peripheral portion 33 is larger than the inclination angle of the main body bottom portion 32a.

[0034] As shown in Figure 1, the outer edge of the outer periphery 33 includes an arc portion 34 formed in an arc shape along the circumferential direction around the center O (rotation centerline L0) of the lower plate 3, and a notch portion 35 that is cut out of the virtual circle 200 which is the trajectory traced by the arc portion 34 due to the rotation of the lower plate 3. The notch portion 35 is formed at a position around the rotating blade 5 in the circumferential direction around the center O (rotation centerline L0). The arc portion 34 is formed at a position between one rotating blade 5 and the adjacent rotating blade 5 in the circumferential direction. The number of notches 35 is equal to the number of rotating blades 5 (3 in this embodiment). The multiple (3) notches 35 are formed at positions that are equally spaced (120° intervals in this embodiment) in the circumferential direction around the center O of the lower plate 3. The number of arc portions 34 is the same as the number of notches 35 (3 in this embodiment). Multiple (3) arc portions 34 are formed at positions that are equally spaced (120° intervals in this embodiment) in the circumferential direction of the lower plate 3. Each notch portion 35 is formed between the multiple arc portions 34. Each arc portion 34 is formed between the multiple notches 35.

[0035] In the following, the three rotating blades 5 may be distinguished by the designations "5A," "5B," and "5C," as shown in Figure 1. Similarly, the three notches 35 may be distinguished by the designations "35A," "35B," and "35C," as shown in Figure 1. Furthermore, the end 35c of the notch 35 located on the rotation direction E1 side is considered the front end, and the end 35d located on the opposite side of the rotation direction E1 is considered the rear end. The first notch 35A is formed around the first rotating blade 5A. The second notch 35B is formed around the second rotating blade 5B. The third notch 35C is formed around the third rotating blade 5C.

[0036] The front end 35c of the first notch 35A may be formed closer to the first rotating blade 5A than, for example, the rear end 35d of the second notch 35B and the second rotating blade 5B, which are located on the front side in the rotation direction E1. Also, the front end 35c of the first notch 35A may be formed further from the first rotating blade 5A than the rear end 35d of the first notch 35A. In other words, the distance between the front end 35c of the first notch 35A and the center of the guide pin 4 to which the first rotating blade 5A is mounted may be greater than the distance between the rear end 35d of the first notch 35A and the center of the guide pin 4. Furthermore, in a plan view of Figure 1, for example, a virtual straight line (not shown) connecting the front end 35c of the first notch 35A and the center O of the lower plate 3 may not intersect the first rotating blade 5A. For example, a hypothetical straight line (not shown) connecting the rear end 35d of the first notch 35A and the center O of the lower plate 3 may be assumed to intersect the first rotating blade 5A.

[0037] More specifically, the first notch 35A is formed so that the blade portion 56 located on the outer circumference of the first rotating blade 5A extends to the outside of the lower platen 3. In a plan view of Figure 1, the first notch 35A is formed to extend in the opposite direction E2 of the rotation direction E1 from a position in front of the first rotating blade 5A in the rotation direction E1 of the lower platen 3 toward the blade portion 56 of the rotating blade 5A, which is located radially outward from the guide pin 4. More specifically, the notch 35A includes a first portion 35a that constitutes a part of the front end 35c, and a second portion 35b that changes direction from the first portion 35a toward the virtual circle 200 and extends to the rear end 35d, overlapping (intersecting) with the blade portion 56 of the rotating blade 5A in a plan view of Figure 5. The rear end 35d is located behind (opposite side of) the rotation direction E1 of the rotating blade 5A.

[0038] The first part 35a is located in front of the rotating blade 5A in the rotation direction E1. The first part 35a is formed so that it gradually moves away from the virtual circle 200 as it moves in the opposite direction E2 to the rotation direction E1. Also, the range of the first part 35a along the circumferential direction around the center O is smaller than the range of the second part 35b. Here, the first virtual line (not shown) is defined as the line connecting the front end 35c and the center O of the lower plate 3. The second virtual line (not shown) is defined as the line connecting the front end 35c and the center 44 (see Figure 5) of the guide pin 4 to which the rotating blade 5A is mounted (in other words, the center of the outer circumference hole 37 into which the guide pin 4 is fitted). The angle θ (see Figure 5) between the first part 35a and the virtual circle 200 may be smaller than the angle between the first virtual line and the virtual circle 200. Also, the angle θ may be smaller than the angle between the second virtual line and the virtual circle 200.

[0039] As shown in Figure 5, the second part 35b is formed so that it gradually approaches the virtual circle 200 as it moves from a position 35e in front of the rotating blade 5A (the boundary between the first part 35a and the second part 35b) toward the opposite direction E2 of the rotation direction E1. Specifically, the second part 35b is formed in the shape of an arc that gradually bulges outward. The center of the circle (not shown) corresponding to the arc of the second part 35b is set on the side of the center of the virtual circle 200 (inside the virtual circle 200).

[0040] Furthermore, the notch portion 35A (first portion 35a and second portion 35b) may be formed so as not to overlap (intersect) with the inner portion 51 of the rotating blade 5A, as described later, when viewed in plan view in Figure 5. In other words, the second portion 35b may be formed so as not to overlap with the inner portion 51 of the rotating blade 5A, but only with the outer circumference 52 of the rotating blade 5A where the blade portion 56 is formed. As will be described later, the central hole 53 of the rotating blade 5 into which the guide pin 4 is inserted (see Figures 5 and 6) is formed to be larger in diameter than the diameter of the guide pin 4. Figure 5 shows the rotating blade 5A in its outermost position. The notch portion 35A may be formed so as to overlap only with the outer circumference 52 of the rotating blade 5A even when the rotating blade 5A is in its outermost position. Figure 6 shows the rotating blade 5A in its innermost position. The notch 35A may be formed so as to overlap only the outer circumference 52 of the rotating blade 5A, even when the rotating blade 5A is in its innermost position.

[0041] The second notch 35B and the third notch 35C are formed in the same shape as the first notch 35A. Furthermore, the three arc portions 34 are formed in the same shape (same curvature and same arc length). In addition, the circumferential range of one notch 35 around the center O (in other words, the arc length of the virtual circle 200 cut by the front end 35c and rear end 35d of the notch 35) is the same as the arc length of one arc portion 34 (the circumferential range around the center O). Note that the circumferential range of the notch 35 may be smaller or larger than the circumferential range of the arc portion 34, depending on conditions such as the rotational speed and diameter of the lower plate 3.

[0042] As described above, the diameter of the lower plate 3 in the peripheral portion of the rotating blade 5 (i.e., the notched portion 35) is smaller than the diameter of the lower plate 3 in the portion between one rotating blade 5 and the adjacent rotating blade 5 (i.e., the arc portion 34). Conversely, the diameter of the lower plate 3 in the portion between one rotating blade 5 and the adjacent rotating blade 5 is larger than the diameter of the peripheral portion of the rotating blade 5. The notched portion 35 is a small-diameter portion whose distance from the center O is smaller than that of the arc portion 34. The arc portion 34 is a large-diameter portion whose distance from the center O is larger than that of the notched portion 35. Thus, the lower plate 3 includes a small-diameter portion 35 and a large-diameter portion 34 along the circumferential direction around the center O. The small-diameter portion 35 is formed so that, when viewed in plan, it overlaps (intersects) with the cutting edge 56 of the rotating blade 5 from the front of the rotating blade 5 in the reverse direction E2. The large-diameter portion 34 is formed so as not to overlap with the blade portion 56 when viewed from above.

[0043] The guide pin 4 connects the upper plate 2 and the lower plate 3 at an eccentric position from the center O of the upper plate 2 and the lower plate 3, and is a pin that serves as the axis of the rotating blade 5. The axis of the guide pin 4 is parallel to the rotation center line L0 of the upper plate 2 and the lower plate 3. Guide pins 4 are provided in the same number as the rotating blade 5 (3 in this embodiment). The guide pins 4 are inserted into the outer peripheral holes 25 of the upper plate 2 and the outer peripheral holes 37 of the lower plate 3 (see Figure 3). The guide pins 4 are inserted into the outer peripheral holes 25 and 37 from the upper plate 2 side.

[0044] As shown in Figure 4, the guide pin 4 has a head portion 41, an intermediate portion 42, and a tip portion 43. These portions 41-43 are formed coaxially. The head portion 41 is formed to be larger in diameter than the intermediate portion 42 and the tip portion 43. The head portion 41 fits into the large-diameter hole 25a (see Figure 4) of the outer circumference hole 25 of the upper plate 2. The intermediate portion 42 is formed to be smaller in diameter than the head portion 41 and larger in diameter than the tip portion 43. The intermediate portion 42 fits into the small-diameter hole 25b (see Figure 4) of the outer circumference hole 25 of the upper plate 2 and is also inserted into the central hole 53 of the rotating blade 5 (see Figure 3). The diameter of the intermediate portion 42 is smaller than the diameter of the central hole 53. The tip portion 43 is formed to be smaller in diameter than the head portion 41 and the intermediate portion 42. The tip portion 43 fits into the outer circumference hole 37 of the lower plate 3. The tip portion 43 is also configured as a male threaded portion with a screw groove formed on its outer circumference. The tip side portion 43 is fitted with the nut 6 within the outer peripheral hole 37 of the lower plate 3 (see Figure 3). The upper plate 2 and the lower plate 3 form a single rotating plate by fastening them with the guide pin 4 and the nut 6. The upper plate 2 and the lower plate 3 can be separated from each other by releasing the fastening between the guide pin 4 and the nut 6.

[0045] The rotating blade 5 constitutes the blade (grass cutting blade) for the grass trimmer. Multiple rotating blades 5 are provided at equal intervals in the circumferential direction of the upper plate 2 and the lower plate 3. In this embodiment, three rotating blades 5 are provided. Multiple rotating blades 5 are identical in shape to each other. For example, the entire rotating blade 5 is made of resin. The blade portion 56 of the rotating blade 5 may be made of resin, and the other parts may be made of metal. Alternatively, the entire rotating blade 5 may be made of metal.

[0046] The rotating blade 5 is sandwiched between the upper platen 2 and the lower platen 3, and is rotatably mounted around the guide pin 4 as its axis. In other words, the rotating blade 5 is mounted to be rotatable around the guide pin 4 independently of the rotation of the upper platen 2 and the lower platen 3.

[0047] More specifically, the rotating blade 5 is formed in a disc shape with a smaller diameter than the upper plate 2 and the lower plate 3. As shown in Figures 9 to 12, the rotating blade 5 includes a disc-shaped inner portion 51 and an outer portion 52 provided along the outer circumference of the inner portion 51. A through hole 53 (hereinafter sometimes referred to as the center hole) is formed in the center of the inner portion 51 as a mounting hole that penetrates in the direction of the center line L1 of the inner portion 51. The center hole 53 is formed in a circular shape in the plan view of Figure 10. The diameter of the center hole 53 is larger than the diameter of the intermediate portion 42 of the guide pin 4. Therefore, the rotating blade 5 is provided so that it can move in a direction perpendicular to the center line L1 of the rotating blade 5 (in other words, the axis of the guide pin 4) by the difference between the diameter of the center hole 53 and the diameter of the intermediate portion 42.

[0048] As shown in Figure 13, the inner portion 51 has a hole perimeter portion 51a surrounding the central hole 53 and an intermediate portion 51b located between the hole perimeter portion 51a and the outer perimeter portion 52. The hole perimeter portion 51a is formed in a plane perpendicular to the center line L1. The hole perimeter portion 51a is in contact with the hole perimeter portion 26 of the upper plate 2 (see Figure 7) or the hole perimeter portion 38 of the lower plate 3 (see Figure 4). As shown in Figure 13, the intermediate portion 51b includes an inclined surface inclined with respect to a virtual horizontal plane perpendicular to the center line L1, such that the width of the inner portion 51 in the direction of the center line L1 gradually decreases as it extends radially outward from the hole perimeter portion 26. This inclined surface 51b is formed over the entire circumference around the center line L1. Furthermore, the angle of inclination of the inclined surface 51b with respect to the virtual horizontal plane is the same at any position in the circumferential direction around the center line L1. In Figure 10, the boundary position between the inner portion 51 and the outer portion 52 is indicated by a dashed line 150. The dashed line 150 is a circle that passes through point 56a, the point closest to the center P, on the surface constituting the blade portion 56 of the rotating blade 5. The intermediate portion 51b may be formed as an inclined surface up to the boundary position 150 with the outer portion 52, or it may be formed as an inclined surface up to a position just before the boundary position 150, with the area outside of that being a plane perpendicular to the center line L1.

[0049] The outer circumference 52 has a blade portion 56 along the circumferential direction. The blade portion 56 has a plurality of protrusions 54 that are equally spaced in the circumferential direction around the center P (see Figure 10) of the rotating blade 5. The center P is located on the center line L1 of the rotating blade 5. In this embodiment, 20 protrusions 54 are formed. In other words, the blade portion 56 has a plurality of notches 55 that are equally spaced in the circumferential direction around the center P. Each notch 55 is formed between one protrusion 54 and the adjacent protrusion 54. The plurality of protrusions 54 are formed to be the same shape as each other. The plurality of notches 55 are also formed to be the same shape as each other.

[0050] More specifically, the protruding portion 54 protrudes radially outward from the rotating blade 5 (inner portion 51), in other words, it protrudes in a direction perpendicular to the center line L1 of the rotating blade 5. The center line L2 (see Figure 10) extending in the direction of the protrusion of the protruding portion 54 intersects the center P (center line L1) of the rotating blade 5. As shown in Figure 10, the protruding portion 54 has a first side blade 57 facing a first direction F1 in the circumferential direction around the center P, and a second side blade 58 facing the opposite direction F2 of the first direction F1 in the circumferential direction. These side blades 57 and 58 face opposite directions with respect to the center line L2. Furthermore, the side blades 57 and 58 are formed in a symmetrical shape with respect to the center line L2.

[0051] As shown in Figure 14, the first side blade 57 is formed in a tapered shape, with its vertical width gradually decreasing as it moves toward the first direction F1. Specifically, the first side blade 57 includes a first inclined surface 57a and a second inclined surface 57b. These inclined surfaces 57a and 57b are formed inclined with respect to a virtual horizontal plane perpendicular to the center line L1 of the rotating blade 5. The first inclined surface 57a faces upward and is gradually displaced downward as it moves toward the first direction F1. The second inclined surface 57b faces downward and is gradually displaced upward as it moves toward the first direction F1. The first inclined surface 57a and the second inclined surface 57b are connected at the tip 57c on the first direction F1 side. This tip 57c is located in the middle of the vertical width of the protruding portion 54. Furthermore, the tip 57c is formed in a sharp shape. In other words, the angle between the first inclined surface 57a and the second inclined surface 57b at the tip 57c is set to an acute angle (an angle less than 90°).

[0052] The second side blade 58 has a first inclined surface 58a, a second inclined surface 58b, and a tip 58c, which are symmetrical to the first side blade 57 with respect to the center line L2 of the protruding portion 54.

[0053] Furthermore, the first inclined surface 57a of the first side blade 57 and the first inclined surface 58a of the second side blade 58 are directly connected (that is, without a plane perpendicular to the center line L1 of the rotating blade 5). The connection portion 59 between the first inclined surface 57a and the first inclined surface 58a forms a straight line extending radially when viewed in plan in Figure 10.

[0054] The second inclined surface 57b of the first side blade 57 and the second inclined surface 58b of the second side blade 58 are directly connected (that is, without a plane perpendicular to the center line L1 of the rotating blade 5). The connection portion 60 between the second inclined surface 57b and the second inclined surface 58b forms a straight line extending in the radial direction when viewed from above.

[0055] Thus, in this embodiment, the first side blade 57 and the second side blade 58, which are formed back-to-back, have common edges 59 and 60 on the opposite sides of their respective tapering directions, and these edges 59 and 60 form a straight line along the radial direction of the rotating blade 5.

[0056] As shown in Figure 14, the cross-section of the projection 54 perpendicular to the center line L2 is rhombic (approximately rhombic). The projection 54 also has a surface 61 at its tip in the projection direction (direction of the center line L2) (see Figures 9 and 11). The tip surface 61 is formed in a non-sharp form, specifically, it is rhombic, similar to the cross-section in Figure 14. The tip surface 61 may be formed as a plane perpendicular to the center line L2, or as a curved surface along the circumferential direction of the rotating blade 5.

[0057] Furthermore, the protruding portion 54 is formed in a columnar shape. A columnar shape refers to a shape in which the aspect ratio of the cross-section is between 0.3 and 3.0. Therefore, the ratio of the vertical width G1 to the horizontal width G2 of the protruding portion 54 in the cross-section shown in Figure 14 is between 0.3 and 3.0.

[0058] The notch 55 is formed to be U-shaped and recessed toward the center P when viewed in plan in Figure 10. The notch 55 is formed to be symmetrical with respect to its center line L3. The center line L3 extends radially from the rotating blade 5 (inner part 51) and intersects the center P of the rotating blade 5.

[0059] More specifically, the notch 55 has a first side blade 57 of one protrusion 54, a second side blade 58 of the adjacent protrusion 54, and a bottom blade 62. The bottom blade 62 is formed in an arc shape between the first side blade 57 of one protrusion 54 and the second side blade 58 of the adjacent protrusion 54. As shown in Figures 11 and 13, the bottom blade 62 includes a first inclined surface 62a and a second inclined surface 62b. These inclined surfaces 62a and 62b are formed inclined with respect to a virtual horizontal plane perpendicular to the center line L1 of the rotating blade 5. The first inclined surface 62a faces upward and gradually displaces downward as it moves radially outward from the rotating blade 5 or as it approaches the center line L3 of the notch 55. The second inclined surface 62b faces downward and gradually displaces upward as it moves radially outward from the rotating blade 5 or as it approaches the center line L3 of the notch 55. The first inclined surface 62a and the second inclined surface 62b are connected at a position radially outward of the rotating blade 5 or closer to the center line L3. The connecting part, the tip 62c (see Figures 11 and 13), is located midway through the vertical width of the rotating blade 5 (inner part 51). Furthermore, the tip 62c is formed in a sharp shape. That is, the angle between the first inclined surface 62a and the second inclined surface 62b at the tip 62c is set to an acute angle (an angle less than 90°).

[0060] Furthermore, the first inclined surface 62a of the bottom blade 62 is continuous with the first inclined surfaces 57a and 58a of the protruding portion 54, which are opposite each other with the notched portion 55 in between. In other words, the first inclined surfaces 57a and 58a of the protruding portion 54 and the first inclined surface 62a of the bottom blade 62 form a continuous surface that curves in a U-shape when viewed from above.

[0061] Similarly, the second inclined surface 62b of the bottom blade 62 is continuous with the second inclined surfaces 57b and 58b of the protruding portion 54, which are opposite each other with the notch portion 55 in between. That is, the second inclined surfaces 57b and 58b of the protruding portion 54 and the second inclined surface 62b of the bottom blade 62 form a continuous surface that curves in a U-shape when viewed from above.

[0062] Furthermore, the tip 62c of the bottom blade 62 is continuous with the tips 57c and 58c of the opposing side blades 57 and 58, with the notched portion 55 in between. In other words, the tips 57c and 58c of the side blades 57 and 58 and the tip 62c of the bottom blade 62 form a continuous sharp section that curves in a U-shape when viewed from above.

[0063] The rotating blade 5 is formed in a vertically symmetrical shape. That is, the bottom view of the rotating blade 5 is shown symmetrically to the top view (plan view) of Figure 10. Furthermore, the rotating blade 5 is formed in a shape that is 18° rotationally symmetrical (20 rotations symmetrical) around the center P. The rear view of the rotating blade 5 is shown symmetrically to the front view of Figure 11. The left side view of the rotating blade 5 is shown symmetrically to the right side view of Figure 12.

[0064] The rotating blade 5 is detachable from the upper and lower plates 2 and the lower plate 3. Specifically, the rotating blade 5 can be removed from the upper and lower plates 2 and 3 by releasing the fastening between the guide pin 4 and the nut 6, thereby separating the upper and lower plates 3. Alternatively, the rotating blade 5 can be inverted after separating the upper and lower plates 2 and 3, and then reattached to the upper and lower plates 3. Furthermore, it is possible to replace the rotating blade 5 with a new one.

[0065] The rotating blade 5 is positioned such that, when it is in the outermost position in Figure 5, the blade portion 56 extends outward from the notch portion 35 (second portion 35b) of the lower plate 3. Furthermore, when it is in the outermost position in Figure 5, the blade portion 56 may extend slightly outward from the virtual circle 200 (for example, by the same amount as or less than the radial width D of the blade portion 56 of the rotating blade 5). In this case, the virtual circle 200 overlaps (intersects) only the blade portion 56 of the rotating blade 5 when viewed in plan. Note that the outermost position in Figure 5 corresponds to the position of the rotating blade 5 when the upper plate 2 and lower plate 3 are rotating and no object such as grass is in contact with the blade portion 56. Also, when it is in the outermost position in Figure 5, only the outer circumference 52 where the blade portion 56 is formed may extend outward from the notch portion 35, while the inner portion 51 is located inside the notch portion 35. Furthermore, when in the innermost position shown in Figure 6, the blade portion 56 may be located inside the virtual circle 200 and outside the notch portion 35 (second portion 35b).

[0066] The following describes the operation and effects of this embodiment. The rotating blade 5 rotates around the rotational centerline L0 of the upper platen 2 and lower platen 3 as the upper platen 2 and lower platen 3 rotate. At this time, the rotating blade 5 rotates while locked in the outermost position shown in Figure 5 due to centrifugal force. Furthermore, if the rotating blade 5 hits a hard object (obstacle) such as wood, a wall, or a fence while rotating, it may be displaced to a position inward from the outermost position in Figure 5 (for example, the innermost position in Figure 6). Also, if the rotating blade 5 hits a hard object (obstacle) such as wood, a wall, or a fence while rotating, it may be displaced around the guide pin 4 in the opposite direction E2 to the rotational direction E1 of the upper platen 2 and lower platen 3. This reduces the impact on the blade portion 56 by the obstacle, and prevents damage to the blade portion 56 or the obstacle.

[0067] Furthermore, the lower plate 3 has an outer peripheral portion 33 that extends radially outward from its main body portion 32 (the portion corresponding to the diameter of the upper plate 2), so that stones can be pushed outward by this outer peripheral portion 33. Specifically, large-diameter arc portions 34 are provided on the outer circumference of the lower plate 3 (outer peripheral portion 33) at positions between the multiple rotating blades 5, so that pebbles and the like can be removed to the outside of the rotational trajectory of the rotating blades 5 by this arc portion 34. This prevents pebbles and the like from hitting the blade portion 56, and prevents the blade portion 56 from being damaged or pebbles and the like from being scattered around. In addition, the diameter of the arc portion 34 is set to be large enough so that the blade portion 56 protrudes slightly from the virtual circle 200 (when the rotating blade 5 is in its outermost position), or so that the blade portion 56 is recessed inside the virtual circle (when the rotating blade 5 is in its innermost position), so that pebbles and the like can be removed more effectively.

[0068] Furthermore, when the rotating blade 5 is in the outermost position in Figure 5, the blade portion 56 protrudes only slightly from the virtual circle 200 (specifically, by an amount less than or equal to the protrusion width D of the blade portion 56), so even if a pebble or the like comes towards the rotating blade 5, contact with the blade portion 56 can be suppressed. Also, when the rotating blade 5 is in the innermost position in Figure 6, the blade portion 56 retracts inside the virtual circle 200, so even if an obstacle comes into contact with the blade portion 56, that contact can be quickly resolved.

[0069] Furthermore, since a notch 35 is provided around the rotating blade 5 on the outer circumference of the lower plate 3 (outer circumference 33), the diameter of the lower plate 3 (in other words, the distance between the arc portion 34 and the center of rotation of the lower plate 3) can be increased while the blade portion 56 of the rotating blade 5 is extended to the outside of the lower plate 3. By increasing the diameter of the lower plate 3 (arc portion 34), obstacles such as stones can be pushed outward by the arc portion 34, preventing them from hitting the blade portion 56. In addition, the notch 35 allows grass to be efficiently guided to the blade portion 56. That is, when grass (especially hard, woody grass) comes into contact with the arc portion 34, it bends radially outward of the lower plate 3, but when the contact with the arc portion 34 is released at the position of the notch 35, the grass is displaced towards the notch 35 due to the recoil from that bending. As a result, the grass can be guided along the notch 35 to the blade portion 56, and the grass can be cut efficiently.

[0070] Furthermore, the second portion 35b of the notch 35 is formed to change direction from the first portion 35a toward the virtual circle 200, and is also formed in an arc shape that gradually approaches the virtual circle 200, thereby preventing stones from getting caught in the notch 35 and causing them to bounce.

[0071] Furthermore, since the space between the upper panel 2 and the lower panel 3 is closed off by the side surface 22 of the upper panel 2, it is possible to prevent grass and other debris from entering that space.

[0072] The lower surface of the main body bottom 32a and the outer peripheral portion 33 of the lower plate 3 is formed in a sloping shape that displaces upward from the inside to the outside (see Figure 3), thereby reducing the contact area between the lower plate 3 and the ground. This makes it easier to move the grass cutting blade device 1 along the ground. The lower surface of the lower plate 3 may be displaced linearly upward from the inside to the outside in the radial direction, or it may be displaced upward in a curved shape. Alternatively, as in the example in Figure 3, the lower surface of the lower plate 3 may be displaced linearly upward from the inside to the outside in the radial direction, and then displaced linearly upward at a different angle of inclination than the previous angle. In other words, the angle of inclination of the lower surface of the lower plate 3 may change in stages.

[0073] Since the upper surface 21a of the upper plate 2 is formed as a surface without irregularities or steps (for example, a flat surface perpendicular to the rotation center line L0), it is possible to prevent grass from getting entangled in the upper surface 21a.

[0074] Furthermore, since the rotating blade 56 has a large number of blade portions 56 (protruding portions 54), as many as 20, the wear distribution of the blade portions 56 is improved, and the durability of the blade portions 56 can be enhanced.

[0075] Furthermore, since the rotating blade 5 is vertically symmetrical, if the first side blade 57 on the rotation direction E1 side of the upper plate 2 and lower plate 3 becomes worn, the rotating blade 5 can be inverted and replaced so that the unworn second side blade 58 faces the rotation direction E1 side, and grass can be cut mainly using the second side blade 58.

[0076] Furthermore, since the tip 61 of the blade portion 56 in the protruding direction (see Figures 9 and 11) is formed as a flat surface (non-sharp shape), the pressure acting on the blade portion 56 when the tip 61 hits hard grass or tree trunks can be reduced, thereby suppressing wear on the side blades 57 and 58. This improves the durability of the blade portion 56.

[0077] Furthermore, as shown in Figure 14, the inclined surfaces 57a and 57b of the first side blade 57 of the blade portion 56 and the inclined surfaces 58a and 58 of the second side blade 58, which is back-to-back with the first side blade 57, are directly connected. In other words, the first side blade 57 and the second side blade 58 have common edges 59 and 60, so the width of the protruding portion 54 along the circumferential direction of the rotating blade 5 can be reduced. This makes it possible to increase the number of protruding portions 54 while suppressing a reduction in the width of the cutting portion 55. A larger number of protruding portions 54 improves the durability of each blade 57 and 58 of the protruding portion 54.

[0078] Furthermore, since the blade section 56 includes a bottom blade 62 in addition to the side blades 57 and 58, the grass cutting power can be increased even further.

[0079] Furthermore, since the inner portion 51 of the rotating blade 5 is formed in a slightly inclined shape (see Figure 13), it is possible to suppress the blade portion 56 from coming into contact with the upper platen 2 and the lower platen 3. Also, for example, when an obstacle hits the rotating blade 5, it is possible to make it easier to rotate the rotating blade 5 around the guide pin 4 in order to reduce the impact on the rotating blade 5.

[0080] Furthermore, since the blade portion (protruding portion 54) of the rotating blade 5 is formed in a columnar shape, its rigidity and durability can be increased compared to when it is formed in a plate shape.

[0081] (Second Embodiment) Next, a second embodiment of this disclosure will be described, focusing on the differences from the above embodiment. The grass cutting blade device of this embodiment differs from the first embodiment in that it is equipped with a rotating blade 7 shown in Figures 16 to 22 instead of the rotating blade 5 of the first embodiment, and is otherwise the same as the grass cutting blade device 1 of the first embodiment. The rotating blade 7 differs from the rotating blade 54 of the first embodiment in the number and shape of the protrusions 71 that constitute the blade portion, and is otherwise the same as the rotating blade 5 of the first embodiment. Furthermore, the rotating blade 7 is formed to be vertically symmetrical and rotationally symmetrical (12-degree rotational symmetry, 30° rotational symmetry).

[0082] The protrusions 71 project radially outward from the rotating blade 7 (in a direction perpendicular to the center line L4 (see Figure 16)) and are formed in multiples at equal intervals in the circumferential direction around the center line L4 of the rotating blade 7 on its outer circumference. In this embodiment, 12 protrusions 71 are formed. The multiple protrusions 71 are formed to be the same shape as each other. Each protrusion 71 has a first side blade 72 facing a first direction F3 (see Figures 17 and 20) in the circumferential direction around the center line L4 of the rotating blade 7, and a second side blade 73 facing the opposite direction F4 of the first direction F3.

[0083] The first side blade 72 is formed in the same manner as the first side blade 57 of the first embodiment. Specifically, as shown in Figure 20, the first side blade 72 includes a first inclined surface 72a and a second inclined surface 72b, and is formed in a tapered shape in which the width between the inclined surfaces 72a and 72b gradually decreases as it moves toward the first direction F3.

[0084] The second side blade 73 is formed in the same manner as the second side blade 58 of the first embodiment. Specifically, as shown in Figure 20, the second side blade 73 includes a first inclined surface 73a and a second inclined surface 73b, and is formed in a tapered shape in which the width between the inclined surfaces 73a and 73b gradually decreases as it moves toward the second direction F4.

[0085] As shown in Figure 20, surfaces 74 and 75 extending in the circumferential direction of the rotating blade 7 are interposed between the first side blade 72 and the second side blade 73. Specifically, surface 74 is interposed between the first inclined surface 72a of the first side blade 72 and the first inclined surface 73a of the second side blade 73. Surface 75 is interposed between the second inclined surface 72b of the first side blade 72 and the second inclined surface 73b of the second side blade 73. These surfaces 74 and 75 may be planes perpendicular to the center line L4 of the rotating blade 7. One surface 74 faces upwards towards the rotating blade 7. The other surface 75 faces downwards towards the rotating blade 7. In addition, the upper edge 72c of the first side blade 72 (see Figures 17 and 20) and the upper edge 73c of the second side blade 73 (see Figures 17 and 20) extend parallel to each other along the radial direction of the rotating blade 7. Similarly, the lower edge 72d of the first side blade 72 (see Figure 20) and the lower edge 73d of the second side blade 73 (see Figure 20) extend parallel to each other along the radial direction of the rotating blade 7. In addition, the cross-section of the projection 71 perpendicular to the radial direction of the rotating blade 7 is hexagonal (approximately hexagonal) (see Figure 20). Thus, in this embodiment, there is no common edge between the first side blade 72 and the second side blade 73, which are located back to back.

[0086] Furthermore, as shown in Figures 16 and 18, the projection 71 has a surface 76 at its tip in the projection direction. The tip surface 76 is formed in a non-sharp shape, specifically, in a hexagonal shape (approximately hexagonal) similar to the cross-section in Figure 20. The tip surface 76 may be formed as a plane perpendicular to the center line of the projection 71, or as a curved surface along the circumferential direction of the rotating blade 7.

[0087] According to this embodiment, the same effects as those of the first embodiment are achieved. In addition, since surfaces 74 and 75 are interposed between the first side blade 72 and the second side blade 73, the rigidity of the protruding portion 71 (blade portion) can be increased, and the durability of the protruding portion 71 can be increased.

[0088] The bottom view of the rotating blade 7 is shown symmetrically to the top view (top view) in Figure 17. The rear view of the rotating blade 7 is shown symmetrically to the front view in Figure 18. The left side view of the rotating blade 7 is shown symmetrically to the right side view in Figure 19.

[0089] (Third embodiment) Next, a third embodiment of this disclosure will be described, focusing on the differences from the above-described embodiment. The grass cutting blade device of this embodiment differs from the first embodiment in that it is equipped with a rotating blade 8 shown in Figures 23 to 29 instead of the rotating blade 5 of the first embodiment, and is otherwise the same as the grass cutting blade device 1 of the first embodiment. The shape of the protruding portion 81 that constitutes the blade portion of the rotating blade 8 differs from the shape of the protruding portion 54 of the first embodiment, and is otherwise the same as the rotating blade 5 of the first embodiment. Furthermore, the rotating blade 8 is formed to be vertically symmetrical and rotationally symmetrical (20-degree rotational symmetry, 18° rotational symmetry).

[0090] The protrusions 81 project radially outward from the rotating blade 8 (in a direction perpendicular to the center line L5 (see Figure 23)) and are formed in multiples at equal intervals in the circumferential direction around the center line L5 of the rotating blade 8 on its outer circumference. In this embodiment, 20 protrusions 81 are formed. The multiple protrusions 81 are formed to be the same shape as each other. Each protrusion 81 has a first side blade 82 facing a first direction F5 (see Figures 24 and 29) in the circumferential direction around the center line L5 of the rotating blade 8, and a second side blade 83 facing the opposite direction F6 (see Figures 24 and 29) to the first direction F5.

[0091] The first side blade 82 is formed in the same manner as the first side blade 57 of the first embodiment. Specifically, as shown in Figure 29, the first side blade 82 includes a first inclined surface 82a and a second inclined surface 82b, and is formed in a tapered shape in which the width between the inclined surfaces 82a and 82b gradually decreases as it moves toward the first direction F5.

[0092] The second side blade 83 is formed in the same manner as the second side blade 58 of the first embodiment. Specifically, as shown in Figure 29, the second side blade 83 includes a first inclined surface 83a and a second inclined surface 83b, and is formed in a tapered shape in which the width between the inclined surfaces 83a and 83b gradually decreases as it moves toward the second direction F6.

[0093] The protruding portion 81 has a tip blade 84 at its tip in the direction of protrusion (see Figures 23, 24, and 27). In other words, the tip of the protruding portion 81 is formed in a sharp shape. As shown in Figure 27, the tip blade 84 is formed in a tapered shape, with its vertical width gradually decreasing as it moves toward the direction of protrusion of the protruding portion 8 (radially outward from the rotating blade 8). Specifically, the tip blade 84 includes a first inclined surface 84a and a second inclined surface 84b. These inclined surfaces 84a and 84b are formed inclined with respect to a virtual horizontal plane perpendicular to the center line L5 of the rotating blade 8. The first inclined surface 84a faces upward and gradually displaces downward as it moves toward the direction of protrusion of the protruding portion 84. The second inclined surface 84b faces downward and gradually displaces upward as it moves toward the direction of protrusion of the protruding portion 84. The first inclined surface 84a and the second inclined surface 84b are connected to each other at the tip 84c in the direction of protrusion of the protruding portion 84. The tip 84c is located midway through the vertical width of the protrusion 81. Furthermore, the tip 84c is formed in a sharp shape. That is, the angle between the first inclined surface 84a and the second inclined surface 84b at the tip 84c is set to an acute angle (an angle less than 90°). Also, the tip 84c traces a straight or curved line along the circumferential direction of the rotating blade 8 (see also Figure 25).

[0094] The first inclined surface 84a and the second inclined surface 84b are formed in a substantially triangular shape (a shape having three sides) when viewed in a plan view in Figure 24 and a front view in Figure 25. The first side of the first inclined surface 84a constitutes the tip 84c described above. The second side of the first inclined surface 84a constitutes the edge of the first inclined surface 82a (see Figure 29) of the first side blade 82. The third side of the first inclined surface 84a constitutes the edge of the first inclined surface 83a (see Figure 29) of the second side blade 83.

[0095] The first edge of the second inclined surface 84b constitutes the tip 84c described above. The second edge of the second inclined surface 84b constitutes the edge of the second inclined surface 82b (see Figure 29) of the first side blade 82. The third edge of the second inclined surface 84b constitutes the edge of the second inclined surface 83b (see Figure 29) of the second side blade 83.

[0096] Thus, the first inclined surface 82a of the first side blade 82, the first inclined surface 83a of the second side blade 83, and the first inclined surface 84a of the tip blade 84 share a common edge 85 (see Figures 24 and 29), and this edge 85 is point-shaped when viewed in plan in Figure 24. In addition, the second inclined surface 82b of the first side blade 82, the second inclined surface 83b of the second side blade 83, and the second inclined surface 84b of the tip blade 84 share a common edge 86 (see Figure 29), and this edge 86 is point-shaped.

[0097] Furthermore, a surface 87 (see Figure 24) is interposed between the first inclined surface 82a of the first side blade 82 and the first inclined surface 83a of the second side blade 83. This surface 87 may be a plane perpendicular to the center line L5 of the rotating blade 8. The distance between the upper edge 82c (see Figure 24) of the first side blade 82 (first inclined surface 82a) and the upper edge 83c (see Figure 24) of the second side blade 83 (first inclined surface 83a), which constitute the edge of surface 87, gradually decreases towards the tip of the protruding portion 81. Finally, it converges to a single point 85.

[0098] Similarly, a surface (not shown) is interposed between the second inclined surface 82b of the first side blade 82 and the second inclined surface 83b of the second side blade 83. The distance between the lower edge (not shown) of the first side blade 82 (second inclined surface 82b) and the lower edge (not shown) of the second side blade 83 (second inclined surface 83b), which constitute the edge of this surface, gradually decreases as it approaches the tip of the protrusion 81. Finally, it converges to a single point 86 (see Figure 29).

[0099] This embodiment provides the same effects as the first embodiment. In addition, since the rotating blade 8 has a tip blade 84, grass can also be cut with this tip blade 84. Furthermore, since the first side blade 82 and the second side blade 83, which are positioned back to back, have common edges 59 and 60 on the edges opposite each other in the tapering direction, the width of the protruding portion 81 along the circumferential direction of the rotating blade 8 can be reduced. This allows for an increase in the number of protruding portions 81 while suppressing a reduction in the width of the cut portions between the protruding portions 81. By increasing the number of protruding portions 81, the durability of each blade 82 to 84 of the protruding portion 81 can be increased.

[0100] The bottom view of the rotary blade 8 is shown symmetrically to the top view (plan view) in Figure 24. The rear view of the rotary blade 8 is shown symmetrically to the front view in Figure 25. The left side view of the rotary blade 8 is shown symmetrically to the right side view in Figure 26.

[0101] (Fourth Embodiment) Next, a fourth embodiment of this disclosure will be described, focusing on the differences from the above embodiments. The grass cutting blade device of this embodiment differs from the first embodiment in that it is equipped with a rotating blade 9 shown in Figures 30 to 36 instead of the rotating blade 5 of the first embodiment, and is otherwise the same as the grass cutting blade device 1 of the first embodiment. The rotating blade 9 differs from the rotating blade 54 of the first embodiment in the number and shape of the protrusions 91 that constitute the blade portion, and is otherwise the same as the rotating blade 5 of the first embodiment. Furthermore, the rotating blade 9 is formed to be vertically symmetrical and rotationally symmetrical (12-degree rotational symmetry, 30° rotational symmetry).

[0102] The protrusions 91 project radially outward from the rotating blade 9 (in a direction perpendicular to the center line L6 (see Figure 30)) and are formed in multiples at equal intervals in the circumferential direction around the center line L6 of the rotating blade 9 on its outer circumference. In this embodiment, 12 protrusions 91 are formed. The multiple protrusions 91 are formed to be the same shape as each other. Each protrusion 91 has a first side blade 92 facing a first direction F7 (see Figures 31 and 36) in the circumferential direction around the center line L6 of the rotating blade 9, and a second side blade 93 facing the opposite direction F8 (see Figures 31 and 36) to the first direction F7.

[0103] The first side blade 92 is formed in the same manner as the first side blade 57 of the first embodiment. Specifically, as shown in Figure 36, the first side blade 92 includes a first inclined surface 92a and a second inclined surface 92b, and is formed in a tapered shape in which the width between the inclined surfaces 92a and 92b gradually decreases as it moves toward the first direction F7.

[0104] The second side blade 93 is formed in the same manner as the second side blade 58 of the first embodiment. Specifically, as shown in Figure 36, the second side blade 93 includes a first inclined surface 93a and a second inclined surface 93b, and is formed in a tapered shape in which the width between the inclined surfaces 93a and 93b gradually decreases as it moves toward the second direction F8.

[0105] As shown in Figure 36, surfaces 94 and 95 extending in the circumferential directions F7 and F8 of the rotating blade 9 are interposed between the first side blade 92 and the second side blade 93. These surfaces 94 and 95 are formed in the same way as surfaces 74 and 75 in the second embodiment (see Figure 20). In this embodiment, as in the second embodiment, there is no common edge between the first side blade 92 and the second side blade 93, which are located back to back.

[0106] The protruding portion 91 has a tip blade 96 at its tip in the direction of protrusion (see Figures 31 and 34). In other words, the tip of the protruding portion 91 is formed in a sharp shape. The shape of the tip blade 96 in the cross-section shown in Figure 34 is formed in the same way as the shape of the tip blade 84 of the third embodiment in the cross-section shown in Figure 27.

[0107] Furthermore, the upper first inclined surface 96a and the lower second inclined surface 96b of the tip blade 96 are each formed in a trapezoidal shape when viewed from the front in Figure 32. The base of this trapezoid constitutes the sharp tip portion 96c of the tip blade 96 (see Figure 34). The upper side of the trapezoid constitutes the edges of surfaces 94 and 95. The inclined portion of the trapezoid constitutes the edges of the first side blade 92 and the second side blade 93.

[0108] This embodiment provides the same effects as the first embodiment. In addition, since the rotating blade 9 has a tip blade 96, grass can also be cut with this tip blade 96. Furthermore, since surfaces 94 and 95 are interposed between the first side blade 92 and the second side blade 93, the rigidity of the protruding portion 91 (blade portion) can be increased, and the durability of the protruding portion 91 can be increased.

[0109] The bottom view of the rotating blade 9 is shown symmetrically to the top view (top view) in Figure 31. The rear view of the rotating blade 9 is shown symmetrically to the front view in Figure 32. The left side view of the rotating blade 9 is shown symmetrically to the right side view in Figure 33.

[0110] (Fifth embodiment) Next, a fifth embodiment of this disclosure will be described, focusing on the differences from the above embodiments. In the above embodiments, an example was shown in which the upper plate has a smaller diameter than the lower plate. In this embodiment, an example will be described in which the upper plate has the same diameter as the lower plate, and a notch is formed near the rotating blade on the outer circumference of the upper plate. Figure 37 shows the grass cutting blade device 300 of this embodiment. The grass cutting blade device 300 comprises an upper plate 301, a lower plate 302, a guide pin 303, and a rotating blade 304. The shapes of the upper plate 301 and the lower plate 302 differ from those of the first embodiment, but otherwise they are the same as the grass cutting blade device 1 of the first embodiment. That is, the guide pin 303 and the rotating blade 304 are the same as the guide pin 4 and the rotating blade 5 of the first embodiment. Note that the rotating blade 304 may be the rotating blade of the second to fourth embodiments.

[0111] The upper plate 301 and the lower plate 302 are formed in the same diameter disc shape and have the same outer circumference shape. The outer circumference shapes of the upper plate 301 and the lower plate 302 are the same as the outer circumference shape of the lower plate 3 in the first embodiment. That is, the outer circumference of the upper plate 301 has an arc portion 301a formed in the shape of an arc centered on the rotation center of the upper plate 301, and a notched portion 301b which is cut out with respect to the rotation trajectory (virtual circle) traced by the arc portion 301a. The arc portion 301a is formed in the same shape as, for example, the arc portion 34 in the first embodiment. The notched portion 301b is formed in the same shape as, for example, the notched portion 35 in the first embodiment and is formed at the peripheral position of each rotating blade 304. The upper surface of the upper plate 301 is formed as a flat surface, similar to the first embodiment.

[0112] The outer circumference of the lower plate 302 has an arc portion 302a formed in an arc shape centered on the rotation center of the lower plate 301, and a notched portion 302b that is cut out with respect to the rotation trajectory (virtual circle) traced by the arc portion 302a. The arc portion 302a is formed in the same shape as, for example, the arc portion 34 of the first embodiment. The arc portion 302a is also formed in the same shape as the arc portion 301a of the upper plate 301. The notched portion 302b is formed in the same shape as, for example, the notched portion 35 of the first embodiment and is formed at the peripheral position of each rotating blade 304. The notched portion 302b is also formed in the same shape as the notched portion 301b of the upper plate 301. The lower plate 302 does not have a plate-like outer circumference that extends outward from the upper plate 301.

[0113] In a plan view, the upper plate 301 and the lower plate 302 are connected by a guide pin 303 such that the arc portion 301a of the upper plate 301 coincides with the arc portion 302a of the lower plate 302, and the notch portion 301b of the upper plate 301 coincides with the notch portion 402b of the lower plate 302. Openings 305 are formed on the sides of the upper plate 301 and the lower plate 302 to allow the blade portions of each rotating blade 304 to protrude outwards. Except for these openings 305, the space between the upper plate 301 and the lower plate 302 is closed.

[0114] Thus, the same effects as those of the above embodiment can be obtained with this embodiment as well.

[0115] This disclosure is not limited to the embodiments described above, and various modifications are possible. For example, although the above embodiment shows an example with three rotating blades, the number of rotating blades can be any number, such as one, two, or four or more. Also, the number of blade portions (protrusions) formed on the outer circumference of the rotating blade can be any number.

[0116] Furthermore, in the above embodiment, an example was shown in which a closing portion (side surface) that closes the outer periphery of the space between the upper and lower panels is provided on the upper panel, but it may also be provided on the lower panel, or on both the upper and lower panels.

[0117] Furthermore, the rotary blade of this disclosure may be configured as follows. A disc-shaped rotating blade for a lawnmower, which is mounted on the rotating disc of the lawnmower so as to be rotatable at an eccentric position from the center of rotation of the rotating disc of the lawnmower, It has a plurality of protrusions that project radially outward along the outer circumference of the disc shape, The aforementioned protrusion is The first side blade is formed in a tapered shape in which the vertical width gradually decreases as it moves toward the first direction in the circumferential direction of the disc, It has a second side blade formed in a tapered shape, where the vertical width gradually decreases as it moves in the second direction opposite to the first direction in the circumferential direction of the disc shape, The tip of the protruding portion in the direction of protrusion is formed to be non-sharp. Rotary blade for lawnmowers.

[0118] In this case, the first side blade and the second side blade may have a common edge between them on the opposite side in the tapering direction.

[0119] When the rotating blade is configured in this way, the rotating disc may have a shape other than that of the embodiment described above. For example, a lower disc (rotating disc) without a notch formed on its outer circumference may be used.

[0120] Furthermore, the grass cutting blade device of this disclosure may be configured as follows. An upper plate and a lower plate are provided to rotate around the center, A guide pin connects the upper plate and the lower plate at an eccentric position from the center, The device comprises a disc-shaped rotating blade rotatably mounted between the upper plate and the lower plate with respect to the guide pin as its axis, having a cutting edge on its outer circumference, the cutting edge extending outward from the lower plate, The lower plate has an outer periphery that extends outward from the upper plate over its entire circumference around the center. Grass cutting blade device.

[0121] According to this design, the outer circumference of the lower plate can push the stones outwards, preventing them from hitting the blades of the rotating blades. This reduces stone bouncing. [Explanation of symbols]

[0122] 1,300 Grass cutting blade device 2, 301 Upper panel 3, 302 lower panel 34, 301a, 302a Arc section 35, 301b, 302b Notches 4, 303 Guide pins 5, 7, 8, 9, 304 Rotary blades 53. Center hole (mounting hole) of the rotating blade 54, 71, 81, 91 Protruding part (blade part) of the rotating blade 200 virtual yen

Claims

1. An upper plate and a lower plate are provided to rotate around the center, A guide pin connects the upper plate and the lower plate at an eccentric position from the center, The device comprises a disc-shaped rotating blade rotatably mounted between the upper plate and the lower plate with respect to the guide pin as its axis, having a cutting edge on its outer circumference, the cutting edge extending outward from the lower plate, The outer circumference of the lower plate includes an arc portion formed in an arc shape along the circumferential direction around the center, and a notched portion that is cut out from a virtual circle which is the trajectory traced by the arc portion due to the rotation of the lower plate. The notch is formed, when viewed in plan, from a position in front of the rotating blade in the rotational direction of the lower platen, and overlaps with the blade portion of the rotating blade. The end of the notch located on the side of the lower plate that is in the direction of rotation is defined as the front end, and the end located on the opposite side of the direction of rotation is defined as the rear end. The notch portion of the grass cutting blade device includes a first portion that constitutes a part of the front end, and a second portion that changes direction from the first portion toward the virtual circle and extends to the rear end while overlapping the rotating blade when viewed in plan.

2. The grass cutting blade device according to claim 1, wherein the upper plate or the lower plate has a side portion that closes the space between the upper plate and the lower plate.

3. The grass cutting blade device according to claim 1, wherein the rotating blade is mounted on the guide pin so as to be movable between an outermost position where the blade portion extends outside the virtual circle and an innermost position where the blade portion retracts inside the virtual circle.

4. The grass cutting blade device according to claim 1, wherein at least the outer circumference of the bottom surface of the lower plate is formed in an inclined shape that displaces upward from the inside to the outside.

5. The grass cutting blade device according to claim 1, wherein the upper surface of the upper plate is formed to be a surface without irregularities or steps.

6. The rotating blade has a plurality of protrusions that protrude radially outward from the rotating blade along its outer circumference, The aforementioned protrusion is The first side blade is formed in a tapered shape, with its vertical width gradually decreasing as it moves in the first direction in the circumferential direction of the rotating blade, The rotating blade has a second side blade that is formed in a tapered shape, with the vertical width gradually decreasing as it moves in the circumferential direction toward the second direction opposite to the first direction, The grass cutting blade device according to claim 1, wherein the tip of the protruding portion in the direction of protrusion is formed in a non-sharp shape.

7. The grass cutting blade device according to claim 6, wherein the first side blade and the second side blade have a common edge between them on the opposite side in the tapering direction.

Images