Cutting blades for grass cutter

Abstract

To reduce situations in which pebbles or the like on the ground are hit by a base part of cutting blades and jump outside a housing of the grass cutter in the cutting blades for a grass cutter.SOLUTION: Cutting blades for a grass cutter include: a base part 60 which has a first extension part 60a extended in one direction from a lower part of a driving shaft and a second extension part 60b extended in the other direction opposite from the lower part of the driving shaft; a first cutting blade part 61 which is provided for the first extension part 60a so that it extends outward from the first extension part 60a; and a second cutting blade part 62 which is provided for the second extension part 60b so that it extends outward from the second extension part 60b. An edge part on an upstream side in a rotary direction of the base part 60 in the first extension part 60a and a second extension part 60b is formed on inclined surfaces 60c, 60d which face diagonally upward or diagonally downward in the rotation direction.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a cutting blade equipped on a walking-type lawn mower or a riding-type lawn mower, and a cutting blade equipped on a lawn mower attached to a tractor or the like for use.

Background Art

[0002] Patent Document 1 discloses a cutting blade equipped on a walking-type lawn mower. In the cutting blade of Patent Document 1, the base of the cutting blade is attached to the lower part of a drive shaft along the vertical direction of the housing of the lawn mower, and the cutting blade part is attached to both ends of the base so as to be freely swingable around the axis along the vertical direction.

[0003] Patent Document 2 discloses a cutting blade equipped on a riding-type lawn mower. In the cutting blade of Patent Document 2, the base of the cutting blade is attached to the lower part of a drive shaft along the vertical direction of the housing of the lawn mower, the base extends from the lower part of the drive shaft, and the cutting blade part is formed on the extending part of the base.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the cutting blades of Patent Documents 1 and 2, the base of the cutting blade is rotationally driven by the drive shaft, and the grass is cut by the cutting blade part of the cutting blade. In this case, since no blade part for cutting grass is formed on the base of the cutting blade, when the base of the cutting blade hits small stones or the like on the ground, the small stones or the like are bounced off and may fly out of the housing of the lawn mower to the outside.

[0006] The object of the present invention is to reduce the situation where small stones on the ground are bounced off by the base of the cutting blade and fly out of the housing of the lawn mower to the outside.

Means for Solving the Problems

[0007] The present invention is a cutting blade for a lawn mower that is attached to the lower part of a drive shaft along the vertical direction of the housing of the lawn mower and is rotationally driven by the drive shaft. The cutting blade has a flat base portion having a first extension portion attached to the lower part of the drive shaft and extending outward from the lower part of the drive shaft in one direction, and a second extension portion extending outward from the lower part of the drive shaft in the other direction opposite to the first extension portion. The cutting blade also includes a first cutting blade portion provided on the first extension portion so as to extend outward from the first extension portion, and a second cutting blade portion provided on the second extension portion so as to extend outward from the second extension portion. The upper edges of the base portion in the rotational direction of the base portion in the first extension portion and the second extension portion are formed as inclined surfaces that are obliquely upward or obliquely downward with respect to the rotational direction.

[0008] The cutting blade of the present invention includes a base portion having a first extension portion and a second extension portion, a first cutting blade portion provided on the first extension portion of the base portion, and a second cutting blade portion provided on the second extension portion of the base portion. The upper edges of the base portion in the rotational direction of the base portion in the first extension portion and the second extension portion are formed as inclined surfaces that are obliquely upward or obliquely downward with respect to the rotational direction of the base portion.

[0009] Thereby, when the base portion of the cutting blade is rotationally driven, even if the upper edges of the base portion in the first extension portion and the second extension portion bounce off small stones on the ground, the small stones are not bounced off in the direction along the rotational direction of the base portion, but are often bounced off obliquely upward or obliquely downward with respect to the rotational direction of the base portion.

[0010] When the small stones are bounced off obliquely upward or obliquely downward as described above, the small stones hit the ceiling surface or the ground of the housing of the lawn mower in which the cutting blade is accommodated. Therefore, the possibility of flying out of the housing of the lawn mower to the outside later is suppressed. Even if small stones or the like that have been bounced off hit the outside of the housing of the lawn mower, the small stones or the like will hit the ceiling surface or the ground surface of the housing of the lawn mower and then bounce out of the outside of the housing of the lawn mower. Therefore, the momentum of the small stones or the like bouncing out can be greatly suppressed.

[0011] As described above, in the cutting blade for a lawn mower, even if small stones or the like on the ground are bounced off by the base of the cutting blade, it is possible to reduce the situation of bouncing out of the outside of the housing of the lawn mower.

[0012] In the present invention, the base can be attached to the lower part of the drive shaft by being turned upside down, and blade parts are formed at both the upper and lower edges in the rotational direction of the first cutting blade part and the second cutting blade part, and it is preferable that both the upper and lower edges in the rotational direction of the first extension part and the second extension part are formed on the inclined surface.

[0013] According to the present invention, when the base is rotationally driven, the upper blade parts of the first cutting blade part and the second cutting blade part function for cutting grass. When wear progresses on the upper blade parts of the first cutting blade part and the second cutting blade part, the base can be removed from the drive shaft of the lawn mower, the base can be turned upside down, and then attached to the drive shaft of the lawn mower again. Thereby, the upper and lower sides of the first cutting blade part are interchanged, and the upper and lower sides of the second cutting blade part are interchanged. Therefore, the lower blade part of the first cutting blade part can be used as the upper blade part, and the lower blade part of the second cutting blade part can be used as the upper blade part, and the cutting blade can function without problems even when turned upside down.

[0014] According to the present invention, since both the upper and lower edges of the first extension part and the second extension part of the base are formed on the inclined surface, even if the base is turned upside down and attached to the drive shaft of the lawn mower as described above, the upper edges of the first extension part and the second extension part of the base are inclined surfaces. This makes it possible to reduce the situation where small stones on the ground are bounced off by the base of the cutting blade and fly out of the housing of the lawn mower even when the cutting blade is used with the top and bottom reversed.

[0015] In the present invention, it is preferable that the upper edge portion in the rotational direction in the first extension portion and the upper edge portion in the rotational direction in the second extension portion are formed on one of the inclined surfaces of the obliquely upward and obliquely downward inclined surfaces, and the lower edge portion in the rotational direction in the first extension portion and the lower edge portion in the rotational direction in the second extension portion are formed on the other inclined surface of the obliquely upward and obliquely downward inclined surfaces.

[0016] According to the present invention, if the upper edge portions of the first extension portion and the second extension portion of the base are formed on the obliquely upward inclined surface, the lower edge portions of the first extension portion and the second extension portion of the base are formed on the obliquely downward inclined surface. Conversely, if the upper edge portions of the first extension portion and the second extension portion of the base are formed on the obliquely downward inclined surface, the lower edge portions of the first extension portion and the second extension portion of the base are formed on the obliquely upward inclined surface.

[0017] This makes it easy to form the base symmetrically with respect to the drive shaft of the lawn mower, and even when the base is turned upside down, it is easy to form the base symmetrically with respect to the drive shaft of the lawn mower, which is advantageous in terms of facilitating the manufacture of the cutting blade.

[0018] In the present invention, it is preferable that the first cutting blade portion is attached to both the upper and lower portions on one side and the upper and lower portions on the other side in the first extension portion so as to be freely swingable around a first axis along the vertical direction, and the second cutting blade portion is attached to both the upper and lower portions on one side and the upper and lower portions on the other side in the second extension portion so as to be freely swingable around a second axis along the vertical direction.

[0019] According to the present invention, the first cutting blade portion and the second cutting blade portion are attached to the first extension portion and the second extension portion of the base so as to be freely swingable, and the base, the first cutting blade portion, and the second cutting blade portion are configured as separate members. As a result, it becomes easy to form inclined surfaces on both the upper and lower edges of the first and second extending portions of the base portion, which is advantageous in terms of facilitating the manufacture of the cutting blade.

[0020] According to the present invention, the first cutting blade portion is attached to both the upper and lower portions on one side and the upper and lower portions on the other side of the first extending portion of the base portion, and the second cutting blade portion is attached to both the upper and lower portions on one side and the upper and lower portions on the other side of the second extending portion of the base portion. As described above, when the base portion is turned upside down and attached to the drive shaft of the lawn mower, the first cutting blade portions on the upper and lower one sides and the upper and lower other sides also turn upside down and function, and the second cutting blade portions on the upper and lower one sides and the upper and lower other sides also turn upside down and function. Therefore, the cutting blade functions smoothly even when turned upside down.

[0021] In the present invention, it is preferable that the length extending between the first axis and the outer end portion of the first cutting blade portion and the length extending between the second axis and the outer end portion of the second cutting blade portion are set to be longer than the length extending between the axis of the drive shaft and the first axis and the length extending between the axis of the drive shaft and the second axis.

[0022] According to the present invention, since the first cutting blade portion and the second cutting blade portion are configured to be long, it is possible to improve the cutting performance. In addition, it is possible to expect an extended service life of the first cutting blade portion and the second cutting blade portion and prevention of damage to the drive system of the lawn mower.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Best Mode for Carrying Out the Invention

[0024] In FIGS. 1 to 17, a walk-behind lawn mower equipped with a first cutting blade 11 and a second cutting blade 12 is shown, where F indicates the forward direction, B indicates the rear direction, U indicates the upward direction, D indicates the downward direction, R indicates the right direction, and L indicates the left direction.

[0025] (Overall Configuration of Walk-Behind Lawn Mower) As shown in FIGS. 1 and 2, the walk-behind lawn mower includes a first housing 21 that houses the first cutting blade 11 which is a cutting blade, a second housing 22 that houses the second cutting blade 12 which is a cutting blade, front wheels 1 and rear wheels 2 attached to the first housing 21, an engine 3, a steering handle 4, an auxiliary wheel 33 attached to the second housing 22, and the like.

[0026] (Configuration of the First Housing) As shown in FIGS. 2, 6, 7, 8, and 12, the first housing 21 has a top plate portion 23, a vertical surface portion 24 located on the right side of the first housing 21, a fixed vertical side member 25 which is the rear surface portion of the first housing 21, a cover 27, and the like.

[0027] The vertical surface portion 24 is bolt - connected to the right portion of the top plate portion 23 and can be replaced with another vertical surface portion 24 by removing the bolts. The fixed vertical side member 25 is bolt - connected to the rear portion of the top plate portion 23 and can be replaced with another fixed vertical side member 25 by removing the bolts. The cover 27 is composed of a flexible rubber plate and is attached to the right and left portions of the front portion of the top plate portion 23.

[0028] As shown in FIG. 8, the vertical surface portion 24 has a front portion 24a and a rear portion 24b, and is formed by being bent at an intermediate portion of the vertical surface portion 24 such that the direction of the front portion 24a and the direction of the rear portion 24b intersect.

[0029] The front portion 24a of the vertical surface portion 24 becomes the lateral surface portion on the opposite side of the axis P3 (refer to (Configuration of the second housing) described later) in the first housing 21, and the rear portion 24b of the vertical surface portion 24 becomes the connection portion between the front portion 24a of the vertical surface portion 24 and the fixed vertical side member 25 which is the rear surface portion of the first housing 21. The rear portion 24b of the vertical surface portion 24 is formed so as to follow the rotation locus C1 (refer to (States of the first cutting blade and the second cutting blade) described later) of the outer peripheral portion of the first cutting blade 11 in a plan view.

[0030] (Configuration of the second housing) As shown in FIGS. 2, 6, 7, 8, 12, and 13, the second housing 22 has a top plate portion 28, a vertical surface portion 29, a vertical side member 30 which is an opening area changing portion, a cover 31, a guard member 32, an auxiliary wheel 33, and the like.

[0031] As shown in FIGS. 6, 8, 12, and 13, the vertical surface portion 29 has a horizontal surface portion 29a located on the left portion of the second housing 22, a rear surface portion 29b located on the rear portion of the second housing 22, and an intermediate portion 29c. The vertical surface portion 29 is bolt-connected to the top plate portion 28 and can be replaced with another vertical surface portion 29 by removing the bolts.

[0032] The vertical side member 30 is attached to the rear surface portion 29b of the vertical surface portion 29 by bolts 34 which are an opening area changing portion and a position changing portion, and can be replaced with another vertical side member 30 by removing the bolts 34.

[0033] As shown in FIG. 2, the cover 31 is composed of a flexible rubber plate and is attached to the front portion of the top plate portion 28. The guard member 32 is composed of a round bar and is attached to the front portion of the top plate portion 28.

[0034] As shown in FIGS. 2, 6, 7, and 8, the right portion of the top plate portion 28 is attached to the left portion of the top plate portion 23 so as to be swingable up and down around the axis P3, and the second housing 22 is supported by the left portion of the first housing 21 so as to be posture-changeable up and down around the axis P3 which is a front-rear axis along the front-rear direction.

[0035] A wire (not shown) is connected across the angle adjustment lever 13 (see (Configuration of the steering handle) described later and FIG. 2) provided on the steering handle 4 and the second housing 22. By the angle adjustment lever 13, the second housing 22 can be set to a horizontal posture parallel to the first housing 21 and a downward posture facing obliquely downward from the first housing 21 (see FIGS. 6 and 7).

[0036] By the angle adjustment lever 13, a plurality of downward postures with different angles can be set. In this case, in each of the plurality of downward postures, the second housing 22 is stopped from swinging downward from the set angle and is allowed to swing upward from the set angle.

[0037] As shown in FIGS. 8 and 13, in the vertical surface portion 29, the horizontal surface portion 29a of the vertical surface portion 29 becomes the horizontal surface portion on the opposite side of the axis P3 in the second housing 22, the rear surface portion 29b of the vertical surface portion 29 becomes the rear surface portion of the second housing 22, and the intermediate portion 29c of the vertical surface portion 29 becomes the connecting portion between the horizontal surface portion 29a and the rear surface portion 29b of the vertical surface portion 29.

[0038] The intermediate portion 29c of the vertical surface portion 29 is formed in an arc shape in plan view, and the intermediate portion 29c of the vertical surface portion 29 is formed along the rotation locus C2 (refer to (the states of the first cutting blade and the second cutting blade) described later) of the outer peripheral portion of the second cutting blade 12 in plan view.

[0039] (Configuration regarding the engine, steering handle, and support of the rear wheels) As shown in FIGS. 2, 6, and 8, in the first housing 21, the frame 5 is connected along the left - right direction to the rear portion of the top plate portion 23, and the engine 3 is supported by the frame 5.

[0040] The frame 6 is connected along the up - down direction to the right portion of the frame 5, and the angled frame 7 is connected along the up - down direction to the left portion of the frame 5. The handle base 8 is connected along the up - down direction to the frame 7, and the steering handle 4 is attached to the handle base 8. The steering handle 4 is attached to the first housing 21 via the handle base 8 so as to extend rearward from the first housing 21.

[0041] As shown in FIGS. 1 and 2, a rear - wheel support case 9 is provided, and the rear wheel 2 is supported at the lower portion of the rear - wheel support case 9. The upper portion of the rear - wheel support case 9 is connected to the handle base 8, the front portion of the rear - wheel support case 9 is connected to the upper portion of the frame 6 via the bracket 10, and the lower portion of the rear - wheel support case 9 is connected to the right portion of the frame 5 and the lower portion of the frame 6. As described above, the rear wheel 2 that supports the first housing 21 is attached to the first housing 21 so as to be provided behind the first housing 21.

[0042] (Configuration of the steering handle) As shown in FIGS. 1 and 2, the steering handle 4 has a right handle portion 81 and a left handle portion 82 made of round pipes. The right handle portion 81 has a right first portion 81a, a right second portion 81b, and a right grip portion 81c, and the left handle portion 82 has a left first portion 82a, a left second portion 82b, and a left grip portion 82c.

[0043] The right first portion 81a of the right handle portion 81 extends obliquely rearward to the right from the handle base 8 (the first housing 21) in a plan view, and extends obliquely upward and rearward in a side view. A hook portion 81f is connected to the rear surface portion of the right first portion 81a.

[0044] The right second portion 81b of the right handle portion 81 extends obliquely rearward to the right, which is a little more toward the left - right center side of the steering handle 4 than the extending direction of the right first portion 81a, from the rear portion 81d of the right first portion 81a in a plan view, and extends substantially horizontally rearward from the rear portion 81d of the right first portion 81a in a side view.

[0045] The right grip portion 81c of the right handle portion 81 extends rearward along the front - rear direction from the rear portion 81e of the right second portion 81b in a plan view, and extends substantially horizontally rearward from the rear portion 81e of the right second portion 81b in a side view.

[0046] The left first portion 82a of the left handle portion 82 extends obliquely rearward to the left from the handle base 8 (the first housing 21) in a plan view, and extends obliquely upward and rearward in a side view. A hook portion 82f is connected to the rear surface portion of the left first portion 82a.

[0047] The left second portion 82b of the left handle portion 82 extends obliquely rearward to the left, which is a little more toward the left - right center side of the steering handle 4 than the extending direction of the left first portion 82a, from the rear portion 82d of the left first portion 82a in a plan view, and extends substantially horizontally rearward from the rear portion 82d of the left first portion 82a in a side view.

[0048] The left handle part 82c of the left handle section 82 extends rearward along the front-rear direction from the rear part 82e of the left second part 82b in a plan view, and extends substantially horizontally rearward from the rear part 82e of the left second part 82b in a side view.

[0049] An angle adjustment lever 13, a shift lever 55, a cutting clutch lever 72, and an accelerator lever 83 of the engine 3 are provided on the right handle section 81. A positioning lever 37, a traveling clutch lever 56, and a stop switch 84 of the engine 3 are provided on the left handle section 82.

[0050] (State of the steering handle) As shown in FIGS. 1 and 2, an operator standing behind the walking type lawn mower holds the right handle part 81c of the right handle section 81 and the left handle part 82c of the left handle section 82. In this case, the lateral interval W1 between the right handle part 81c of the right handle section 81 and the left handle part 82c of the left handle section 82 is substantially uniquely determined by the general build of the operator and the like.

[0051] According to the description of the above-mentioned (Configuration of the steering handle), the lateral interval W2 between the rear part 81d of the right first part 81a of the right handle section 81 and the rear part 82d of the left first part 82a of the left handle section 82 is large and close to the interval W1.

[0052] As described in the following (Operations related to the attitude change of the support member and the auxiliary wheel), when setting the inclined attitude of the support member 46 and the support base 45 (auxiliary wheel 33), or when changing the attitude of the support member 46 up and down, an operator standing behind the walking type lawn mower can fully insert his body between the right handle section 81 and the left handle section 82 of the steering handle 4.

[0053] Thereby, the operator can easily perform an operation of setting the inclined attitude of the support member 46 and the support base 45 (auxiliary wheel 33) and an operation of changing the attitude of the support member 46 up and down by extending his hand forward.

[0054] When the walking type lawn mower is mounted on the loading platform of a truck (not shown) for transportation, the walking type lawn mower can be fixed to the loading platform of the truck by hanging a rope across the hook portion of the loading platform of the truck and the hook portions 81f and 82f of the steering handle 4 (right handle portion 81 and left handle portion 82).

[0055] (Configuration regarding the support of the front wheels in the left - right direction) As shown in FIGS. 4 and 5, in the first housing 21, a front - wheel support member 14 is provided at the front portion of the top plate portion 23. The front - wheel support member 14 is formed by bending a plate material. The right portion of the substrate portion 14a of the front - wheel support member 14 is attached to the top plate portion 23 so as to be changeable in direction left and right around the axis P4 along the vertical direction.

[0056] A long hole 14b extending along the front - rear direction is opened in the left portion of the substrate portion 14a of the front - wheel support member 14. A bolt 15 fixed upward to the top plate portion 23 is inserted into the long hole 14b of the front - wheel support member 14, and a fixing handle 16 having a female screw portion is attached to the bolt 15.

[0057] Right and left support portions 14c are provided on the substrate portion 14a of the front - wheel support member 14, and the front - wheel support case 17 is supported so as to be swingable up and down around the axis P5 along the left - right direction. As shown in FIGS. 1 and 2, the front - wheel support member 14 extends forward through between the covers 27 (refer to the above - mentioned (Configuration of the first housing)), and the front wheel 1 is supported at the front portion of the front - wheel support case 17.

[0058] As shown in FIGS. 2 and 5, within the range of the long hole 14b of the front - wheel support member 14, in a plan view, the posture of the front - wheel support case 17 and the front - wheel support member 14 can be changed left and right across the straight - ahead posture A11 in which the front wheel 1 rotates along the front - rear direction and the inclined posture A12 in which the front wheel 1 rotates along the virtual direction extending obliquely forward on the opposite side of the second housing 22 with respect to the front - rear direction.

[0059] The operator can fix the posture of the front-wheel support member 14 by turning the fixed handle 16 to tighten the substrate portion 14a of the front-wheel support member 14. The operator can change the postures of the front-wheel support case 17 and the front-wheel support member 14 left and right within the range of the long hole 14b of the front-wheel support member 14 by turning the fixed handle 16 to loosen the tightening of the substrate portion 14a of the front-wheel support member 14. Thus, the inclination postures of the front-wheel support case 17 and the front-wheel support member 14 (front wheel 1) can be set at any position between the straight-ahead posture A11 and the inclined posture A12.

[0060] (Configuration regarding support of the front wheel in the vertical direction) As shown in FIGS. 4 and 5, the positioning member 18 is connected to the front-wheel support case 17 and extends rearward. The positioning member 19 is connected to the rear portion of the positioning member 18, and three locking holes 19a are opened in the positioning member 19 so as to be arranged along the vertical direction.

[0061] The cylindrical member 20 is connected to the front-wheel support member 14. The positioning pin 35 is provided on the cylindrical member 20 so as to be slidable along the front-rear direction, and a spring 36 that biases the positioning pin 35 toward the protruding side is provided. A wire 38 is connected across the positioning lever 37 (see the (Configuration of the steering handle) above and FIG. 2) and the positioning pin 35.

[0062] While holding the steering handle 4, the operator operates the positioning lever 37 to pull out the positioning pin 35 from the locking hole 19a of the positioning member 19, and operates the front portion of the first housing 21 up and down with the rear wheel 2 as a fulcrum. Since the front wheel 1 is in contact with the ground due to the weight of the front wheel 1 and the front-wheel support case 17, the posture of the front-wheel support case 17 with respect to the first housing 21 is changed up and down.

[0063] When the front part of the first housing 21 reaches the desired height, the operator can operate the positioning lever 37 to insert the positioning pin 35 into one of the locking holes 19a of the positioning member 19, thereby setting the posture of the front wheel support case 17 relative to the first housing 21 in three steps up and down. Thus, the cutting height by the first cutting blade 11 can be set to the desired height. As described above, the front wheel 1 that supports the first housing 21 is attached to the first housing 21 so as to be provided in front of the first housing 21.

[0064] (Configuration regarding auxiliary wheels) As shown in FIGS. 2, 12, and 14, in the second housing 22, a support base 45, which is a posture-changing part formed by bending a plate material into a channel shape, is provided. The support base 45 is attached to the top plate part 28 so as to be able to change its posture left and right around the axis P6, which is the vertical axis along the vertical direction.

[0065] A round pipe-shaped support member 46 is provided. The support member 46 is attached to the support base 45 so as to be able to change its posture up and down around the axis P7 along the left-right direction. The support member 46 is attached to the second housing 22 via the support base 45 so as to protrude forward from the second housing 22. The auxiliary wheel 33 is attached to the front end part of the support member 46 so as to be located in front of the second housing 22.

[0066] A lock lever 47 is attached to the rear part of the support member 46 so as to be able to swing up and down around the axis P8 along the left-right direction. By engaging the pin 47a of the lock lever 47 with one of the plurality of engaging parts 45a of the support base 45, the up and down posture of the support member 46 can be fixed. A spring 48 is connected across the lock lever 47 and the support member 46. By the spring 48, the lock lever 47 is biased toward the side where the pin 47a of the lock lever 47 engages with the engaging part 45a of the support base 45.

[0067] As shown in FIGS. 2, 12, 15, and 16, the substrate member 49 is fixed to a portion immediately to the right of the rear portion of the support base 45 on the top plate portion 28, and a nut 49a is fixed to the upper portion of the substrate member 49. A flat fixing member 50, which is a posture changing portion and a fixing portion, is connected to the right portion of the rear portion of the support base 45 and extends rightward from the support base 45 so as to be positioned above the substrate member 49.

[0068] A long hole 50a is opened in the fixing member 50, and the right end portion 50b of the fixing member 50 is bent downward. A fixing handle 51, which is a posture changing portion and a fixing portion, is provided, and a male screw portion is provided at the lower portion of the fixing handle 51.

[0069] (Operations related to the posture change of the support member and the auxiliary wheel) As shown in FIGS. 2, 12, 15, and 16, within a range where the rear portion of the support base 45 contacts the left portion of the substrate member 49 and the end portion 50b of the fixing member 50 contacts the right portion of the substrate member 49, the support base 45 can be changed in posture left and right around the axis P6.

[0070] Thereby, as shown in FIG. 2, in a plan view, a straight - ahead posture A21 in which the auxiliary wheel 33 rotates along the front - rear direction (a position where the rear portion of the support base 45 contacts the left portion of the substrate member 49), and an inclined posture A22 in which the auxiliary wheel 33 rotates along a virtual direction extending obliquely forward on the side of the first housing 21 with respect to the front - rear direction (a position where the end portion 50b of the fixing member 50 contacts the right portion of the substrate member 49), the postures of the support member 46 and the support base 45 can be changed left and right.

[0071] As shown in FIGS. 2, 12, 15, and 16, by attaching the male screw portion of the fixing handle 51 from the long hole 50a of the fixing member 50 to the nut 49a of the substrate member 49 and turning the fixing handle 51 to tighten the fixing member 50, the support base 45 can be fixed to the second housing 22.

[0072] The operator can release the fixation of the support base 45 and change the posture of the support member 46 and the support base 45 left and right by turning the fixed handle 51 to loosen the tightening of the fixing member 50. By turning the fixed handle 51 to tighten the fixing member 50, the inclination posture of the support member 46 and the support base 45 (auxiliary wheel 33) can be set at an arbitrary position between the straight-ahead posture A21 and the inclined posture A22.

[0073] The operator can change the posture of the support member 46 up and down by gripping and operating the rear part of the support member 46 and the lock lever 47 and pulling out the pin 47a of the lock lever 47 from the engaging portion 45a of the support base 45. By engaging the pin 47a of the lock lever 47 with a desired engaging portion 45a of the support base 45, the cutting height by the second cutting blade 12 can be set to a desired height.

[0074] (Transmission structure to the front and rear wheels) As shown in FIGS. 1, 2, and 3, the transmission 53 is provided above the rear-wheel support case 9. A transmission belt 54 is attached across the pulley 3b of the output shaft 3a of the engine 3 and the pulley 53b of the input shaft 53a of the transmission 53.

[0075] The transmission 53 is provided with a traveling clutch (not shown) and is configured to be shiftable into three forward speeds and one reverse speed. A wire (not shown) is connected across the shift lever 55 (refer to the above-mentioned (Configuration of the steering handle) and FIGS. 1 and 2) and the transmission 53, and the transmission 53 can be operated into three forward speeds and one reverse speed by the shift lever 55.

[0076] In the transmission device 53, the traveling clutch is biased to the disengaged state, and a wire (not shown) is connected across the traveling clutch lever 56 (refer to (the configuration of the steering handle) and FIG. 2 described above) and the traveling clutch. When the operator grips and operates the traveling clutch lever 56 and pulls the wire toward the traveling clutch lever 56 side, the traveling clutch is operated to the engaged state. When the operator releases the hand from the traveling clutch lever 56, the traveling clutch is operated to the disengaged state.

[0077] Inside the rear wheel support case 9, a transmission chain 58 is attached across the sprocket 53d of the output shaft 53c of the transmission device 53 and the sprocket 57a of the axle 57 that supports the rear wheel 2. A transmission shaft 59 is provided at the upper and lower middle portion of the rear wheel support case 9, and the sprocket 59a of the transmission shaft 59 meshes with the transmission chain 58.

[0078] As shown in FIGS. 1 to 5, a transmission shaft 63 is supported at the right front portion of the first housing 21, and a transmission chain 64 is attached across the sprocket 59b of the transmission shaft 59 and the sprocket 63a of the transmission shaft 63.

[0079] The input shaft 65 of the front wheel support case 17 is disposed at the position of the axis P5, and the input shaft 65 and the transmission shaft 63 are connected via a universal joint 66. Inside the front wheel support case 17, a transmission chain 68 is attached across the sprocket 65a of the input shaft 65 and the sprocket 67a of the axle 67 that supports the front wheel 1.

[0080] With the above configuration, as shown in FIG. 3, the power of the engine 3 is transmitted to the transmission device 53 via the transmission belt 54. The power shifted by the transmission device 53 is transmitted to the rear wheel 2 via the transmission chain 58, and is transmitted to the front wheel 1 via the transmission chain 58, the transmission shaft 59, the transmission chain 64, the transmission shaft 63, the input shaft 65, and the transmission chain 68. When the traveling clutch of the transmission device 53 is operated to the disengaged state, the front wheel 1 and the rear wheel 2 stop.

[0081] In this case, since the universal joint 66 is arranged so as to be located on the extension line of the axis P4, as described in the above (configuration related to the support of the front wheels in the left - right direction), even if the postures of the front - wheel support case 17 and the front - wheel support member 14 are changed left - and - right around the axis P4, the power transmission from the drive shaft 63 to the input shaft 65 can be performed without difficulty.

[0082] (Configuration of the first cutting blade and the second cutting blade) As shown in FIGS. 9, 10, and 11, the first cutting blade 11 and the second cutting blade 12 each have an elongated rhombus - shaped base portion 60 in plan view, two first cutting blade portions 61, and two second cutting blade portions 62.

[0083] A large opening 60e is opened at the central portion of the base portion 60, and openings 60f are opened on both sides of the opening 60e. A first extending portion 60a extending from the opening 60e in one direction and a second extending portion 60b extending from the opening 60e in the opposite direction are provided on the base portion 60.

[0084] In this case, the length of the base portion 60 of the second cutting blade 12 (the length across the end of the first extending portion 60a and the end of the second extending portion 60b) is configured to be longer than the length of the base portion 60 of the first cutting blade 11 (the length across the end of the first extending portion 60a and the end of the second extending portion 60b).

[0085] In the base portion 60, one edge of the first extending portion 60a and the opposite edge of the second extending portion 60b are formed as inclined surfaces 60c, and the other edge of the first extending portion 60a and the opposite edge of the second extending portion 60b are formed as inclined surfaces 60d. In FIG. 10, the inclined surface 60c of the base portion 60 faces obliquely downward, and the inclined surface 60d of the base portion 60 faces obliquely upward.

[0086] In the first cutting blade 11 and the second cutting blade 12, all four first cutting blade portions 61 and all four second cutting blade portions 62 are configured to have the same shape, and cutting edges 61a, 61b, 62a, 62b are formed on both edges of one and the other of the first cutting blade 11 and the second cutting blade 12.

[0087] In the first cutting blade 11, the first cutting blade portion 61 is attached to both the upper and lower portions on one side and the upper and lower portions on the other side of the first extension portion 60a of the base portion 60 by the support pin 52 so as to be freely swingable around the axis P11 which is the first axis along the vertical direction. Thereby, the first cutting blade portion 61 is provided on the first extension portion 60a of the base portion 60 so as to extend outward from the first extension portion 60a of the base portion 60.

[0088] In the second cutting blade 12, the second cutting blade portion 62 is attached to both the upper and lower portions on one side and the upper and lower portions on the other side of the second extension portion 60b of the base portion 60 by the support pin 52 so as to be freely swingable around the axis P12 which is the second axis along the vertical direction. Thereby, the second cutting blade portion 62 is provided on the second extension portion 60b of the base portion 60 so as to extend outward from the second extension portion 60b of the base portion 60.

[0089] (Configuration regarding the support of the first cutting blade and the second cutting blade) As shown in FIGS. 2, 6, 7, and 8, in the first housing 21, the cutting blade case 26 is connected to the top plate portion 23. The drive shaft 41 is supported by the cutting blade case 26 so as to be rotatable around the axis P1 which is the first vertical axis along the vertical direction, and the bracket 41a is connected to the lower portion of the drive shaft 41 by the nut 39.

[0090] In the second housing 22, the cutting blade case 43 is connected to the top plate portion 28. The drive shaft 42 is supported by the cutting blade case 43 so as to be rotatable around the axis P2 which is the second vertical axis along the vertical direction, and the bracket 42a is connected to the lower portion of the drive shaft 42 by the nut 39.

[0091] As shown in FIGS. 7 and 8, a bottomed cylindrical cover 44 is provided. In the first housing 21, while the bottom of the cover 44 is sandwiched between the base 60 of the first cutting blade 11 and the bracket 41a of the drive shaft 41, the nut 39 is inserted into the opening 60e (see FIG. 11) of the base 60 of the first cutting blade 11, and the bolt 40 is connected across the opening 60f (see FIG. 11) of the base 60 of the first cutting blade 11 and the bracket 41a of the drive shaft 41. Thus, the first cutting blade 11 and the cover 44 are attached to the lower part of the drive shaft 41.

[0092] In the second housing 22, while the bottom of the cover 44 is sandwiched between the base 60 of the second cutting blade 12 and the bracket 42a of the drive shaft 42, the nut 39 is inserted into the opening 60e (see FIG. 11) of the base 60 of the second cutting blade 12, and the bolt 40 is connected across the opening 60f (see FIG. 11) of the base 60 of the second cutting blade 12 and the bracket 42a of the drive shaft 42. Thus, the second cutting blade 12 and the cover 44 are attached to the lower part of the drive shaft 42.

[0093] With the above configuration, in the first cutting blade 11 and the second cutting blade 12, the base 60 is attached to the lower parts of the drive shafts 41 and 42. The base 60 has a first extension 60a extending from the lower parts of the drive shafts 41 and 42 in one direction, and a second extension 60b extending from the lower parts of the drive shafts 41 and 42 in the other direction opposite to the first direction.

[0094] In the first cutting blade 11 and the second cutting blade 12, the bolt 40 is removed, the base 60 is removed from the brackets 41a and 42a of the drive shafts 41 and 42, the first cutting blade 11 and the second cutting blade 12 are turned upside down, and then the base 60 is attached to the brackets 41a and 42a of the drive shafts 41 and 42 by the bolt 40 again, so that the first cutting blade 11 and the second cutting blade 12 can be attached to the lower parts of the drive shafts 41 and 42.

[0095] As shown in the following (transmission structure to the first cutting blade and the second cutting blade) and FIGS. 8, 9, and 10, the first cutting blade 11 is rotationally driven in the rotational direction B1, and the second cutting blade 12 is rotationally driven in the rotational direction B2. The rotational direction B1 is counterclockwise in a plan view of the first housing 21, and the rotational direction B2 is clockwise in a plan view of the second housing 22.

[0096] With the above configuration, the first cutting blade 11 is rotatably supported around the axis P1, which is the first vertical axis along the vertical direction, and is accommodated in the first housing 21. The second cutting blade 12 is rotatably supported around the axis P2, which is the second vertical axis along the vertical direction, and is accommodated in the second housing 22.

[0097] (States of the first cutting blade and the second cutting blade) As shown in FIGS. 9 and 10, since the length of the base 60 of the second cutting blade 12 is longer than the length of the base 60 of the first cutting blade 11 (see the previous item (Configuration of the first cutting blade and the second cutting blade)), the diameter D2 of the rotation locus C2 of the second cutting blade 12 is larger than the diameter D1 of the rotation locus C1 of the first cutting blade 11.

[0098] Below the connection portion (axis P3) between the first housing 21 and the second housing 22, the rotation locus C1 of the first cutting blade 11 and the rotation locus C2 of the second cutting blade 12 partially overlap in a plan view.

[0099] Since all four first cutting blade portions 61 and four second cutting blade portions 62 are configured in the same shape (see the above-mentioned (Configuration of the first cutting blade and the second cutting blade)), in the first cutting blade 11 and the second cutting blade 12, the length L11 extending from the axis P11 to the outer end of the first cutting blade portion 61 and the length L12 extending from the axis P12 to the outer end of the second cutting blade portion 62 are the same length.

[0100] In the first cutting blade 11, the length L21 extending from the axis P1 of the drive shaft 41 to the axis P11 and the length L22 extending from the axis P1 of the drive shaft 41 to the axis P12 are the same length, and L11 and L12 are set to be longer than the lengths L21 and L22.

[0101] In the second cutting blade 12, the length L31 extending between the axis P2 of the drive shaft 42 and the axis P11, and the length L32 extending between the axis P2 of the drive shaft 42 and the axis P12 are the same length, and L31 and L32 are set to be longer than the lengths L11 and L12.

[0102] As shown in FIGS. 8 to 11, when the first cutting blade 11 and the second cutting blade 12 are rotationally driven in the rotational directions B1 and B2, cutting edges 61a, 61b, 62a, and 62b are formed at both the upper and lower edges in the rotational directions B1 and B2 in the first cutting blade portion 61 and the second cutting blade portion 62. Both the upper and lower edges in the rotational directions B1 and B2 of the first extension portion 60a and the second extension portion 60b of the base portion 60 are formed as inclined surfaces 60c and 60d.

[0103] The upper edge in the rotational directions B1 and B2 of the first extension portion 60a of the base portion 60 and the upper edge in the rotational directions B1 and B2 of the second extension portion 60b of the base portion 60 are formed as an inclined surface 60c that slopes downward obliquely with respect to the rotational directions B1 and B2.

[0104] The lower edge in the rotational directions B1 and B2 of the first extension portion 60a of the base portion 60 and the lower edge in the rotational directions B1 and B2 of the second extension portion 60b of the base portion 60 are formed as an inclined surface 60d that slopes upward obliquely with respect to the rotational directions B1 and B2.

[0105] As described in the above (configuration regarding the support of the first and second cutting blades), when the first cutting blade 11 and the second cutting blade 12 are turned upside down and attached to the lower portions of the drive shafts 41 and 42, the upper edge and the lower edge in the rotational directions B1 and B2 of the first extension portion 60a of the base portion 60 are interchanged, and the upper edge and the lower edge in the rotational directions B1 and B2 of the second extension portion 60b of the base portion 60 are interchanged.

[0106] As a result, the upper edges of the first extension part 60a and the second extension part 60b of the base part 60 in the rotation directions B1 and B2 become the downwardly inclined surfaces 60d, and the lower edges of the first extension part 60a and the second extension part 60b of the base part 60 in the rotation directions B1 and B2 become the upwardly inclined surfaces 60c.

[0107] (Transmission Structure for the First Cutting Blade and the Second Cutting Blade) As shown in FIGS. 1, 2, 3, and 7, in the first housing 21, the transmission shaft 69 is supported by the cutting blade case 26, and a transmission belt 70 is attached across the pulley 3c of the output shaft 3a of the engine 3 and the pulley 69a of the transmission shaft 69. Inside the cutting blade case 26, the bevel gear 41b of the drive shaft 41 and the bevel gear 69b of the transmission shaft 69 are engaged with each other.

[0108] A cutting clutch 71 of the tension pulley type is provided for the transmission belt 70. A wire (not shown) is connected across the cutting clutch lever 72 (refer to the above-mentioned (Configuration of the Steering Handle) and FIGS. 1 and 2) and the cutting clutch 71, and the cutting clutch 71 can be operated to a transmission state and a cutoff state by the cutting clutch lever 72.

[0109] In the second housing 22, the transmission shaft 73 is supported by the cutting blade case 43, and the transmission shaft 69 and the transmission shaft 73 are connected via two universal joints 74 and an extendable transmission shaft 75. Inside the cutting blade case 43, the bevel gear 42b of the drive shaft 42 and the bevel gear 73a of the transmission shaft 73 are engaged with each other.

[0110] As shown in FIGS. 1, 2, and 3, a metal cover 76 is attached to the first housing 21, and the cover 76 covers the output shaft 3a and pulleys 3b, 3c of the engine 3, the transmission belt 54, the input shaft 53a and pulley 53b of the transmission 53, the transmission shaft 59 (sprocket 59b), the transmission chain 64, the transmission shaft 63 (sprocket 63a), the transmission shaft 69 (pulley 69a), the transmission belt 70, the cutting clutch 71, etc.

[0111] As shown in FIGS. 2, 6, and 7, a cylindrical cover 77 that is stretchable and flexible is attached across the cutting blade case 26 and the cutting blade case 43, and a universal joint 74 and a transmission shaft 75 are accommodated inside the cover 77.

[0112] With the above configuration, as shown in FIG. 3, the power of the engine 3 is transmitted to the drive shaft 41 via the transmission belt 70 and the transmission shaft 69, and is transmitted to the drive shaft 42 via the transmission shaft 69, the universal joint 74, the transmission shaft 75, and the transmission shaft 73.

[0113] As shown in FIGS. 8, 9, and 10, the drive shaft 41 and the first cutting blade 11 are rotationally driven in the rotational direction B1, and the drive shaft 42 and the second cutting blade 12 are rotationally driven in the rotational direction B2. The rotational trajectories C1, C2 and the rotational directions B1, B2 are set so that the first cutting blade 11 and the second cutting blade 12 move rearward at the position of the axis P3. When the cutting clutch 71 is operated to the disengaged state, the first cutting blade 11 and the second cutting blade 12 stop.

[0114] In this case, as described in the above (Configuration of the second housing), even if the posture of the second housing 22 is changed vertically, the universal joint 74 bends and the transmission shaft 75 expands and contracts, so that the power transmission from the transmission shaft 69 to the transmission shaft 73 is performed smoothly.

[0115] (Configuration regarding the opening for discharging the cut grass cut by the first cutting blade and the second cutting blade) As shown in FIGS. 6, 8, and 12, in the first housing 21, the left end portion of the fixed vertical side member 25 is located on the left and right center side (drive shaft 41 side) of the first housing 21 rather than the left end portion of the top plate portion 23.

[0116] As a result, an opening 78 for discharging the cut grass rearward is formed in a portion of the fixed vertical side member 25 of the first housing 21 adjacent to the second housing 22 so as to be located behind the axis P3 (connection portion between the first housing 21 and the second housing 22). The opening 78 is provided so as to be located on the left side, which is the side of the second housing 22, with respect to the rear wheel 2 in a rear view and a plan view (see FIG. 2).

[0117] In a plan view, the left rear portion of the top plate portion 23 of the first housing 21 and the fixed vertical side member 25 are located in front of the vertical side member 30 of the second housing 22. In a rear view, the left rear portion of the top plate portion 23 of the first housing 21, the fixed vertical side member 25, and the vertical side member 30 of the second housing 22 form the outer peripheral portion of the opening 78.

[0118] The vertical side portion 25a of the fixed vertical side member 25 becomes the right vertical side portion on the rear wheel 2 side at the right and left vertical side portions of the opening 78. In a rear view, the lower portion of the vertical side portion 25a of the fixed vertical side member 25 is located laterally outward from the upper portion of the vertical side portion 25a of the fixed vertical side member 25 with respect to the left and right center of the opening 78 (so as to be located on the rear wheel 2 side), and the vertical side portion 25a of the fixed vertical side member 25 is inclined and arranged in a rear view.

[0119] The extension portion 25b of the fixed vertical side member 25 extends obliquely rearward and toward the left and right center of the opening 78 from the vertical side portion 25a of the fixed vertical side member 25, and the extension portion 25b of the fixed vertical side member 25 becomes the extension portion provided on the right vertical side portion of the opening 78.

[0120] The vertical side portion 30a of the vertical side member 30 becomes the left vertical side portion on the opposite side of the rear wheel 2 at the right and left vertical side portions of the opening 78. In a rear view, the lower portion of the vertical side portion 30a of the vertical side member 30 is located laterally outward from the upper portion of the vertical side portion 30a of the vertical side member 30 with respect to the left and right center of the opening 78 (so as to be located on the opposite side of the rear wheel 2), and the vertical side portion 30a of the vertical side member 30 is inclined and arranged in a rear view.

[0121] The extension portion 30b of the vertical side member 30 extends obliquely rearward and toward the left and right center of the opening 78 from the vertical side portion 30a of the vertical side member 30, and the extension portion 30b of the vertical side member 30 becomes the extension portion provided on the right vertical side portion of the opening 78.

[0122] As described above (configuration of the second housing) and as shown in FIG. 6, when the second housing 22 is set to a downward posture facing obliquely downward from the first housing 21, the vertical side portion 30a and the extending portion 30b of the vertical side member 30 approach an upright posture. When the second housing 22 is set to a horizontal posture parallel to the first housing 21, the vertical side portion 30a and the extending portion 30b of the vertical side member 30 are in the inclined posture as described above.

[0123] As shown in FIGS. 2 and 6, a bracket 79 is connected to the lower part of the frame 7 so as to face rearward. A pressing member 80 made of a flexible rubber plate is attached to the bracket 79 and extends obliquely rearward and downward, and the pressing member 80 is disposed behind the opening 78.

[0124] (Configuration regarding changing the opening area of the opening for discharging the cut grass by the first cutting blade and the second cutting blade) As shown in FIGS. 6, 8, 12, and 13, a long hole 30c, which is an opening area changing portion and a position changing portion, is formed in the vertical side member 30 along the left-right direction. When a bolt 34 is inserted into the long hole 30c of the vertical side member 30 and tightened to the rear surface portion 29b of the vertical surface portion 29, the vertical side member 30 is fixed to the rear surface portion 29b of the vertical surface portion 29.

[0125] By loosening the bolt 34, the vertical side member 30 can be moved in the left-right direction with respect to the rear surface portion 29b of the vertical surface portion 29. When the vertical side member 30 is moved to the left and separated from the fixed vertical side member 25, the opening area of the opening 78 becomes larger. When the vertical side member 30 is moved to the right and brought closer to the fixed vertical side member 25, the opening area of the opening 78 becomes smaller.

[0126] (State of the ridge mowing operation) When performing the ridge mowing operation with a walk-behind mower, as shown in FIGS. 6, 7, and 17, the first housing 21 is run on the upper surface portion E1 of the ridge by the front wheels 1 and the rear wheels 2, and the second housing 22 is run on the side surface portion E2 of the ridge by the auxiliary wheels 33, thereby performing the mowing operation on the upper surface portion E1 and the side surface portion E2 of the ridge.

[0127] As described above (configuration related to the vertical support of the front wheels) and as shown in FIG. 4, the vertical posture of the front wheel support case 17 with respect to the first housing 21 is set to set the cutting height by the first cutting blade 11. As described above (operation related to the posture change of the support member and the auxiliary wheel) and as shown in FIG. 14, the cutting height by the second cutting blade 12 is set by changing the posture of the support member 46 up and down.

[0128] The front wheel 1 and the rear wheel 2 are rotationally driven, and the first housing 21 receives the driving force for forward movement from the front wheel 1 and the rear wheel 2, while the auxiliary wheel 33 is not rotationally driven, so the second housing 22 does not receive the driving force for forward movement from the front wheel 1 and the rear wheel 2. As a result, as the walking type lawn mower moves forward, when the second housing 22 receives resistance from the grass on the side face E2 of the ridge, the second housing 22 may try to move downward toward the lower side of the side face E2 of the ridge with the rear wheel 2 as a fulcrum (see arrow F1).

[0129] When the above situation occurs, as described above (operation related to the posture change of the support member and the auxiliary wheel) and as shown in FIG. 2, the left and right postures of the support member 46 and the support base 45 are set to an arbitrary inclined posture between the inclined posture A22 or the straight-ahead posture A21 and the inclined posture A22.

[0130] As the walking type lawn mower moves forward, the auxiliary wheel 33 rotates while contacting the side face E2 of the ridge and tries to climb diagonally upward on the side face E2 of the ridge (see arrow F2). Accordingly, a force (see arrow F3) that tries to lift the second housing 22 above the side face E2 of the ridge is generated.

[0131] As a result, the situation where the second housing 22 tries to move downward toward the lower side of the side face E2 of the ridge with the rear wheel 2 as a fulcrum is suppressed by the moment caused by the length (moment arm) of the support member 46 extending forward from the first housing 21 and the above-mentioned force (arrow F3).

[0132] If simply setting the left and right postures of the support member 46 and the support base 45 to the inclined posture A22 cannot suppress the situation where the second housing 22 tends to move downward toward the lower side of the ridge normal surface portion E2 with the rear wheel 2 as a fulcrum, as described above (the configuration related to the support of the front wheels in the left - right direction) and as shown in FIG. 2, set the left and right postures of the front wheel support case 17 and the front wheel support member 14 to an inclined posture A12 or an arbitrary inclined posture between the straight - ahead posture A11 and the inclined posture A12.

[0133] As a result, a force (refer to arrow F4) is generated to move the first housing 21 to the opposite side of the ridge normal surface portion E2 by the front wheel 1, and the second housing 22 is pulled upward to the upper surface portion E1 of the ridge via the first housing 21. Thus, the function of the auxiliary wheel 33 described above is assisted.

[0134] (Cutting state by the first cutting blade and the second cutting blade) As described above (the state of the ridge mowing operation) and as shown in FIGS. 6, 7, and 8, when the first housing 21 travels on the upper surface portion E1 of the ridge, the first cutting blade 11 is rotationally driven in the rotational direction B1. Thus, in the vicinity of the front portion of the first housing 21, grass is cut by the first cutting blade 11, and the cut grass moves rearward the position of the axis core P3 as the first cutting blade 11 rotates, and mainly exits rearward from the opening 78.

[0135] There may be a case where the cut grass does not exit rearward from the opening 78 but moves along the rear portion 24b and the front portion 24a of the vertical surface portion 24 from the fixed vertical side member 25 together with the first cutting blade 11. In this case, as described above (the configuration of the first housing) and as shown in FIG. 8, since the rear portion 24b of the vertical surface portion 24 is formed to follow the rotational locus C1 of the outer peripheral portion of the first cutting blade 11 in a plan view, the cut grass rarely stays near the rear portion 24b of the vertical surface portion 24.

[0136] As described above (the state of the weeding operation on the ridge) and as shown in FIGS. 6, 7, and 8, when the second housing 22 travels on the ridge side face E2, the second cutting blade 12 is rotationally driven in the rotational direction B2. As a result, near the front part of the second housing 22, grass is cut by the second cutting blade 12, and the cut grass moves backward along the position of the axis P3 as the second cutting blade 12 rotates, and mainly exits backward from the opening 78. There is little cut grass that exits backward from between the rear face part 29b of the second housing 22 (vertical face part 29) and the ridge side face E2, or from between the vertical side member 30 and the ridge side face E2.

[0137] There are cases where the cut grass does not exit backward from the opening 78, but instead moves along the intermediate part 29c and the horizontal face part 29a of the vertical face part 29 together with the second cutting blade 12 from the rear face part 29b of the vertical face part 29. In this case, as described above (the configuration of the second housing) and as shown in FIG. 8, since the intermediate part 29c of the vertical face part 29 is formed in an arc shape so as to follow the rotation locus C2 of the outer peripheral part of the second cutting blade 12 in plan view, the cut grass rarely stays near the intermediate part 29c of the vertical face part 29.

[0138] When the first cutting blade 11 and the second cutting blade 12 are rotationally driven, it is assumed that the upper edges of the first extension part 60a and the second extension part 60b of the base part 60 bounce off small stones and the like on the upper face part E1 and the side face part E2 of the ridge.

[0139] As shown in FIGS. 8 and 11, in the first cutting blade 11 and the second cutting blade 12, since the upper edges of the first extension part 60a and the second extension part 60b of the base part 60 are formed on the inclined surface 60c that is obliquely downward with respect to the rotational directions B1 and B2, the small stones and the like are not bounced off in the direction along the rotational directions B1 and B2 of the base part 60, but are bounced off obliquely downward with respect to the rotational directions B1 and B2 of the base part 60 and hit the upper face part E1 and the side face part E2 of the ridge.

[0140] As a result, the possibility that small stones and the like fly out from the first housing 21 and the second housing 22 to the outside is small. Even if small stones and the like fly out from the first housing 21 and the second housing 22 to the outside, the momentum of the small stones and the like flying out is greatly suppressed.

[0141] As described in the foregoing (configuration regarding support of the first cutting blade and the second cutting blade), even if the first cutting blade 11 and the second cutting blade 12 are turned upside down and attached to the lower portions of the drive shafts 41 and 42, the upper edges and the lower edges in the rotational directions B1 and B2 at the first extension portion 60a of the base portion 60 are interchanged, and the upper edges and the lower edges in the rotational directions B1 and B2 at the second extension portion 60b of the base portion 60 are interchanged.

[0142] As a result, the upper edges in the rotational directions B1 and B2 at the first extension portion 60a and the second extension portion 60b of the base portion 60 become the downwardly inclined inclined surfaces 60d, so that the same situation as described above is obtained.

[0143] (Discharge state of the cut grass from the opening by the first cutting blade and the second cutting blade) As described in the foregoing (cutting state by the first cutting blade and the second cutting blade) and shown in FIGS. 2 and 17, when the cut grass comes out from the opening 78 rearward, the cut grass is formed into a single continuous streak-like (mountain range-like) mass. The streak-like (mountain range-like) mass of the cut grass is formed near the connecting portion between the upper surface portion E1 and the side surface portion E2 of the ridge, or near the top of the side surface portion E2 of the ridge (see state G1).

[0144] As described in the foregoing (configuration regarding the opening for discharging the cut grass cut by the first cutting blade and the second cutting blade) and shown in FIGS. 2 and 6, due to the fact that the vertical side portion 25a of the fixed vertical side member 25 is inclined in a rear view, and the vertical side portion 30a of the vertical side member 30 is inclined in a rear view, the streak-like (mountain range-like) mass of the cut grass is easily formed into a trapezoidal cross-section.

[0145] Due to the fact that the extension portion 25b of the fixed vertical side member 25 extends obliquely rearward and toward the left and right center of the opening 78 from the vertical side portion 25a of the fixed vertical side member 25, and the extension portion 30b of the vertical side member 30 extends obliquely rearward and toward the left and right center of the opening 78 from the vertical side portion 30a of the vertical side member 30, the lateral portions of the streak-like (mountain range-like) mass of the cut grass are pressed and consolidated by the extension portion 25b of the fixed vertical side member 25 and the extension portion 30b of the vertical side member 30.

[0146] The pressing member 80 is disposed behind the opening 78 and extends obliquely rearward and downward, so that the upper portion of the strip-shaped (mountain-shaped) mass of mowed grass is pressed firmly by the pressing member 80.

[0147] Depending on the amount of grass on the ridge and the state of the grass (e.g., wet or dry after rain), the position of the vertical side member 30 can be changed left and right to increase or decrease the opening area of the opening 78. Since the opening 78 is located on the side of the second housing 22 with respect to the rear wheel 2, the strip-shaped (mountain-shaped) mass of mowed grass coming out of the opening 78 will not be crushed by the rear wheel 2.

[0148] As a result, the strip-shaped (mountain-shaped) mass of mowed grass is difficult to slide down the normal surface portion E2 of the ridge. Even if the strip-shaped (mountain-shaped) mass of mowed grass slides down the normal surface portion E2 of the ridge, the strip-shaped (mountain-shaped) mass of mowed grass is likely to stop in the middle portion of the normal surface portion E2 of the ridge and is less likely to slide down to the field.

[0149] (First alternative form of the invention) In the first cutting blade 11 and the second cutting blade 12, the upper edge portions in the rotational directions B1 and B2 (hereinafter referred to as edge portion H11) of the first extension portion 60a of the base portion 60, the lower edge portions in the rotational directions B1 and B2 (hereinafter referred to as edge portion H12) of the first extension portion 60a of the base portion 60, the upper edge portions in the rotational directions B1 and B2 (hereinafter referred to as edge portion H21) of the second extension portion 60b of the base portion 60, and the lower edge portions in the rotational directions B1 and B2 (hereinafter referred to as edge portion H22) of the second extension portion 60b of the base portion 60 can have the following various combinations of downwardly inclined surfaces and downwardly inclined surfaces.

[0150] (1) The edge portion H11 is an upwardly inclined surface, the edge portion H12 is a downwardly inclined surface, the edge portion H21 is an upwardly inclined surface, and the edge portion H22 is a downwardly inclined surface. (2) The edge portion H11 is a downwardly inclined surface, the edge portion H12 is a downwardly inclined surface, the edge portion H21 is an upwardly inclined surface, and the edge portion H22 is an upwardly inclined surface.

[0151] (3) The edge portion H11 is an inclined surface slanting upward, the edge portion H12 is an inclined surface slanting upward, the edge portion H21 is an inclined surface slanting downward, and the edge portion H22 is an inclined surface slanting downward. (4) The edge portion H11 is an inclined surface slanting downward, the edge portion H12 is an inclined surface slanting upward, the edge portion H21 is an inclined surface slanting upward, and the edge portion H22 is an inclined surface slanting downward.

[0152] (5) The edge portion H11 is an inclined surface slanting upward, the edge portion H12 is an inclined surface slanting downward, the edge portion H21 is an inclined surface slanting downward, and the edge portion H22 is an inclined surface slanting upward. (6) All of the edge portions H11, H12, H21, and H22 are inclined surfaces slanting downward. (7) All of the edge portions H11, H12, H21, and H22 are inclined surfaces slanting upward.

[0153] (Second alternative form of the invention implementation) When the first cutting blade 11 and the second cutting blade 12 are not used by being turned upside down, only the upper edges of the first extension portion 60a and the second extension portion 60b of the base portion 60 in the rotational directions B1 and B2 may be formed as inclined surfaces 60c that are slanting upward or slanting downward with respect to the rotational directions B1 and B2.

[0154] In the above-described configuration, in the upper edges of the first extension portion 60a of the base portion 60 in the rotational directions B1 and B2 and the upper edges of the second extension portion 60b of the base portion 60 in the rotational directions B1 and B2, one may be an inclined surface 60c slanting downward and the other may be an inclined surface 60d slanting upward.

[0155] When the first cutting blade 11 and the second cutting blade 12 are not used by being turned upside down, the blade portions 61a and 62a may be formed only on the upper edges of the first cutting blade portion 61 and the second cutting blade portion 62 in the rotational directions B1 and B2.

[0156] (Third alternative form of the invention implementation) In the first cutting blade 11 and the second cutting blade 12, instead of attaching the first cutting blade portion 61 and the second cutting blade portion 62 to the base portion 60 so as to be freely swingable, the first cutting blade portion 61 may be formed at one end of a single plate material, and the second cutting blade portion 62 may be formed at the other end of the single plate material.

[0157] According to this configuration, in a single plate material, the portion between the first cutting blade portion 61 and the second cutting blade portion 62 becomes the base portion 60, and the first cutting blade portion 61 and the second cutting blade portion 62 are in a fixed state without freely swinging on the base portion 60.

[0158] (Fourth alternative form of the invention) In a cross-sectional view of the base portion 60, the inclined surfaces 60c and 60d may be formed in an arc shape instead of a linear shape.

Industrial applicability

[0159] The present invention is applicable not only to the first cutting blade 11 and the second cutting blade 12 used in a walking type lawn mower including the first housing 21 and the second housing 22, but also to a single cutting blade used in a walking type lawn mower including one housing, and a cutting blade used in a riding type lawn mower having three or more cutting blades. The present invention is also applicable to a cutting blade used in a lawn mower attached as an attachment to a work vehicle such as a tractor.

Explanation of reference numerals

[0160] 41 Drive shaft 42 Drive shaft 60 Base 60a First extending portion 60b Second extending portion 60c Inclined surface 60d Inclined surface 61 First cutting blade portion 61a Blade portion 61b Blade portion 62 Second cutting blade portion 62a Blade portion 62b Blade portion B1 Rotation direction B2 Rotation direction P1 Axis center P2 Axis P11 Axis (First Axis) P12 Axis (Second Axis) L11 Length L12 Length L21 Length L22 Length

Claims

Claim 1 A cutting blade for a lawn mower, which is attached to the lower part of a drive shaft along the vertical direction of the housing of the lawn mower and is rotationally driven by the drive shaft, a base portion having a first extension portion attached to the lower part of the drive shaft and extending outward from the lower part of the drive shaft in one direction, and a second extension portion extending outward from the lower part of the drive shaft in the other direction opposite thereto, a first cutting blade portion provided on the first extension portion so as to extend outward from the first extension portion, a second cutting blade portion provided on the second extension portion so as to extend outward from the second extension portion, and a cutting blade for a lawn mower, wherein the upper edge portions in the rotational direction of the base portion in the first extension portion and the second extension portion are formed on inclined surfaces that are obliquely upward or obliquely downward with respect to the rotational direction.

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