Bush cutter and cord reel cassette used for bush cutter

Abstract

Provided is a technology for preventing a cord cutter from being tugged outward and pulled out to an unintended length by centrifugal force applied to the cord cutter during operation of a bush cutter. In this bush cutter 10, two cord reel cassettes 100 rotate integrally with a cover member 70 (upper cover 72 and lower cover 73). However, the two cord reel cassettes 100 are fixed to a fixing member 80, and therefore the cord reel cassettes 100 cannot freely rotate inside the cover member 70. Centrifugal force acts on a nylon cord 200 in association with the rotation of the cord reel cassettes 100, but because the cord reel cassettes 100 cannot freely rotate, there is no possibility that the nylon cord 200 will be pulled out by the centrifugal force.

Description

Brush cutter and cord reel cassette used in brush cutter

[0001] The present invention relates to a cord reel cassette that can be attached to a brush cutter, and to a brush cutter.

[0002] Conventionally, brush cutters (also called "brush trimmers") have been known that include a motor, a shaft, and a rotary saw, and are used by a user to cut grass or small trees by operating a handle fixed to the shaft. In some cases, a brush cutter can be used as a cord cutter for cutting edge grass by attaching a resin cord, such as a thick nylon cord, to the rotor where the rotary saw is attached (see Patent Document 1).

[0003] Patent No. 7282425

[0004] The brush cutter described in Patent Document 1, which was invented by the present inventor, is configured to cut grass by rotating two cord cutters. These two cord cutters are wound on separate cord reel cassettes. The brush cutter described in Patent Document 1 is equipped with two cord adjustment mechanisms for independently adjusting the lengths of the two cord cutters pulled out from the two cord reel cassettes.

[0005] In the brush cutter described in Patent Document 1, the two cord reel cassettes are configured to rotate freely within the storage chamber of the cover member while the brush cutter is in operation. The lengths of the two cord cutters pulled out from the two cord reel cassettes are adjusted by two cord adjustment mechanisms. When the brush cutter is in operation, centrifugal force acts on the cord cutters. However, the cord adjustment mechanisms prevent the cord cutters from being pulled outward by centrifugal force and pulled out to an unintended length. Therefore, during normal use, the two cord cutters are not pulled out to an unintended length by centrifugal force.

[0006] However, the inventors discovered a problem in that if a malfunction occurs in the cord adjustment mechanism and the force with which the cord adjustment mechanism secures the cord cutter weakens, the cord cutter cannot be secured against the centrifugal force acting on the cord cutter, and the two cord cutters are pulled out to an unintended length due to the centrifugal force.

[0007] The present invention is intended to solve the above-mentioned problems discovered by the inventor, and its object is to provide a technology for preventing a brush cutter using two cord cutters from being pulled outward and pulled out to an unintended length due to centrifugal force acting on the cord cutters while the brush cutter is in operation.

[0008] According to one aspect of the present invention, there is provided a brush cutter configured to be fitted with two independent cord reel cassettes, each having a different cord wound thereon, the brush cutter comprising: a rod provided with a handle; a rotating shaft arranged at one end of the rod; a drive source that applies a driving force to rotate the rotating shaft; a cover member fixed to the rotating shaft and configured to rotate with the rotation of the rotating shaft, the cover member having a hollow storage chamber therein for storing the two cord reel cassettes; a fixing member having a plate-shaped main body and engaging portions provided on the plate-shaped main body that engage with engaging receiving portions provided on the two cord reel cassettes to fix the two cord reel cassettes to the main body; and a locking mechanism provided on the cover member and the fixing member, configured to move the fixing member between a first position where the fixing member rotates independently of the cover member and a second position where the fixing member rotates integrally with the cover member. The brush cutter is characterized in that, when the fixing member is positioned in the second position during operation of the brush cutter, the two cord reel cassettes rotate integrally with the fixing member and the cover member while being fixed to the fixing member in the storage chamber of the cover member, and when the fixing member is positioned in the first position, the two cord reel cassettes and the fixing member rotate relative to the cover member, thereby making it possible to adjust the length of the cord wound around the two cord reel cassettes.

[0009] In the brush cutter of the present invention, when the fixing member is located in the second position during operation of the brush cutter, the two cord reel cassettes rotate integrally with the cover member. However, because the two cord reel cassettes are fixed to the fixing member, the cord reel cassettes are prevented from freely rotating in the storage chamber inside the cover member. Therefore, even if centrifugal force acts on the cord as the cord reel cassette rotates, the cord reel cassette cannot freely rotate, so there is no risk of the cord being pulled out to an unintended length due to centrifugal force. Furthermore, when the fixing member is located in the first position, the two cord reel cassettes and the fixing member are rotatable relative to the cover member, allowing the cord to be easily pulled out from the two cord reel cassettes.

[0010] FIG. 1 is a schematic diagram of a brush cutter 10. FIG. 2 is a schematic explanatory diagram of an upper cover 72, a lower cover 73, and a cord reel cassette 100. Note that in FIG. 2, the cross section of the cord reel cassette 100 is not shaded to make the drawing easier to see. FIG. 3 is a schematic explanatory diagram of the cord reel cassette 100. FIG. 4 is a schematic explanatory diagram of a fixing member 80. FIG. 5 is a schematic explanatory diagram illustrating a recess 731 provided in the lower cover 73. FIG. 6 is a schematic explanatory diagram illustrating a recess 102a as an example of an engagement receiving portion and a protrusion 80P as an example of an engagement portion.

[0011] The brush cutter 10 according to the present invention will be described with reference to the drawings. In the following description, the upper side, lower side, left side, and right side will be defined as shown in FIG.

[0012] As shown in Figure 1, the brush cutter 10 mainly comprises a cylindrical rod 20, a rotating shaft 30 (see Figure 2) provided at one end (lower end) of the rod 20, a drive unit 40 provided at the end (upper end) of the rod 20 opposite the rotating shaft 30, a handle 50 provided on the side of the rod 20 closer to the drive unit 20, a guard 60 provided on the side of the rod 20 closer to the rotating shaft 30, a cover member 70 that houses a cord reel cassette 100 (see Figure 2), and a fixing member 80 (see Figure 2) that fixes the cord reel cassette 100 to the cover member 70.

[0013] The cylindrical rod 20 is a hollow metal pipe with a length of approximately 1500 mm to 1700 mm, and has a drive unit 40 attached to its upper end. The drive unit 40 includes a motor 41 and a battery 42 for supplying power to the motor 41. A rotating shaft 30 (see FIG. 2) is provided at the lower end of the rod 20, and the rotating shaft 30 is configured to rotate by a rotational driving force transmitted from a rotating shaft 43 of the motor 41 via a transmission mechanism (not shown).

[0014] The handle 50 (see FIG. 1 ) is a roughly U-shaped grip that allows a user to hold the brush cutter 10. A switch 51 that is linked to the motor 41 is attached to one end of the handle 50. When the user turns on the switch 51, the motor 41 is driven, causing the rotation shaft 43 and the rotation shaft 30 to rotate.

[0015] As shown in FIG. 2 , the cover member 70 includes an upper cover 72 and a lower cover 73. In this embodiment, the upper cover 72 and the lower cover 73 of the cover member 70 are made of metal. The upper cover 72 includes a substantially cylindrical side wall 721 and a circular upper wall 722 that covers the upper side of the side wall 721. Two guide holes 723 are formed in the side wall 721 of the upper cover 72 for removing the nylon cord 200 from the cord reel cassette 100. A through hole 722h is formed in the center of the upper wall 722, through which the rotating shaft 30 is inserted. The rotating shaft 30 is inserted through the through hole 722h of the upper cover 72, and the upper cover 72 is fixed to the rotating shaft 30 with a fastening member 71, such as a nut.

[0016] Like the upper cover 72, the lower cover 73 is also a metal cover member and has an opening 73h in its center. Furthermore, as shown in FIG. 5 , a plurality of recesses 731 are provided surrounding the periphery of the opening 73h. As will be described later, the plurality of recesses 731 fit into a plurality of protrusions 840 (see FIG. 4 ) provided on the main body 810 (see FIG. 4 ) of the fixing member 80. As shown in FIG. 2 , the lower cover 73 is fixed below the upper cover 72 by screws or the like so as to cover the upper cover 72 from below. When the lower cover 73 is attached to the upper cover 72, a cylindrical space is formed inside the upper cover 72 and the lower cover 73 for accommodating two cord reel cassettes 100.

[0017] As described above, the upper cover 72 can be fixed to the rotating shaft 30 by the fastening member 71. Furthermore, the upper cover 72 and the lower cover 73 are fixed together by screws or the like. Therefore, as the rotating shaft 30 rotates, not only the upper cover 72 but also the lower cover 73 rotates.

[0018] Next, the two cord reel cassettes 100 disposed within the space defined by the upper cover 72 and the lower cover 73 will be described with reference to the drawings. As shown in FIG. 2, the two cord reel cassettes 100 are disposed one above the other in the vertical direction. The two cord reel cassettes 100 have the same configuration. As shown in FIG. 2, the cord reel cassette 100 has an upper wall 101, a lower wall 102, and a shaft 103 that connects the upper wall 101 and the lower wall 102 in the vertical direction. A nylon cord 200 is wound around each of the shafts 103 of the two cord reel cassettes 100. Although not shown, one end of the nylon cord 200 is fixed to the shaft 103 of the cord reel cassette 100. This prevents the nylon cord 200 from coming completely off the cord reel cassette 100. 3, the shaft portion 103 of the cord reel cassette 100 is provided with four fitting grooves 104 that fit onto four fixed shafts 820 (see FIG. 2) of the fixing member 80, which will be described later. The four fitting grooves 104 are an example of the engagement receiving portion of the present invention, and the four fixed shafts 820 are an example of the engagement portion of the present invention.

[0019] 4, the fixing member 80 includes a substantially disk-shaped main body 810, a circular groove 811 provided in the approximate center of the main body 810, four fixing shafts 820 arranged around the groove 811, a pressing portion 830 protruding downward at the approximate center of the main body 810, a plurality of protrusions 840 surrounding the pressing portion 830, and a spring 850 (see FIG. 2). Note that, as shown in FIG. 2, the lower end of the spring 850 is inserted into the groove 811 of the fixing member 80.

[0020] As shown in Figure 2, when two cord reel cassettes 100 are stacked vertically, the bottom wall 102 of the upper cord reel cassette 100 and the top wall 101 of the lower cord reel cassette 100 may be in contact with each other, or may be arranged facing each other with a predetermined gap between them.

[0021] As shown in FIG. 2, the two nylon cords 200 pulled out from the cord reel cassette 100 are pulled out from two main body guide holes 723 provided in the side wall 721 of the upper cover 72 .

[0022] Next, a method for replacing the cord reel cassette 100 in the brush cutter 10 according to the present invention will be described. When using the brush cutter 10 to mow edge grass, the tip of the nylon cord 200 gradually wears down. The user can purchase a cord reel cassette 100 with the nylon cord 200 wound around it and replace it. Two cord reel cassettes 100 can also be replaced simultaneously. Alternatively, only one of the two cord reel cassettes 100 can be replaced. The following description will be given taking the case of replacing two cord reel cassettes 100 simultaneously as an example.

[0023] When replacing the cord reel cassettes, first, the screws between the upper cover 72 and the lower cover 73 are removed, and the lower cover 73 is removed from the upper cover 72. At this time, the fixing member 80 and the two cord reels 100 are also removed along with the lower cover 73. Next, the two cord reel cassettes 100 to be replaced are lifted up and removed from the fixed shafts 820 of the fixing member 80. The fixing member 80 can also be removed from the lower cover 73.

[0024] Next, a new cord reel cassette 100 is prepared and attached to the fixing member 80. At this time, the four fitting grooves 104 (see FIG. 3 ) of the shaft portion 103 of the cord reel cassette 100 are fitted onto the four fixed shafts 820 of the fixing member 80. This prevents the cord reel cassette 100 from freely rotating relative to the fixing member 80. In other words, the cord reel cassette 100 and the fixing member 80 rotate together. Next, with the fitting grooves 104 of the cord reel cassette 100 fitted onto the fixed shafts 820, the fixing member 80 is attached to the lower cover 73. At this time, the pressing portion 830 of the fixing member 80 is inserted into the opening 73h of the lower cover 73 so that the pressing portion 830 protrudes downward from the opening 73h. At the same time, the convex portion 840 of the fixing member 80 is fitted into the concave portion 731 of the lower cover 73. With the fixing member 80 attached to the lower cover 73 in this manner, the lower cover 73 is fixed to the upper cover 72 with screws or the like. At this time, the spring 850 of the fixing member 80 is compressed from its natural length, and the upper end of the spring 850 abuts against the upper wall 722 of the upper cover 72. Because the upper end of the spring 850 abuts against the upper wall 722 of the upper cover 72 when the spring 850 of the fixing member 80 is compressed from its natural length, the fixing member 80 is biased downward, i.e., toward the lower cover 73, by the spring 850. As described above, the convex portion 840 of the fixing member 80 is fitted into the concave portion 731 of the lower cover 73, and therefore the fixing member 80 is biased toward the lower cover 73. This prevents the fixing member 80 from rotating independently of the lower cover 73, and the fixing member 80 and the lower cover 73 rotate together. In this way, the position where the convex portion 840 of the fixing member 80 is fitted into the concave portion 731 of the lower cover 73 corresponds to the second position of the fixing member 80. The combination of the convex portion 840 provided on the fixing member 80, the concave portion 731 provided on the lower cover 73, and the spring 850 is an example of the locking mechanism of the present invention.

[0025] As described above, the upper cover 72 is fixed to the rotating shaft 30 by a fastening member 71 such as a nut. The lower cover 73 is fixed to the upper cover 72 by a screw or the like. The fixing member 80 is fixed to the lower cover 73, and the lower cover 73 and the fixing member 80 rotate together. Furthermore, two cord reel cassettes 100 are fixed to the fixing member 80, and the fixing member 80 and the two cord reel cassettes 100 rotate together. As a result, as the rotating shaft 30 rotates, the upper cover 72, the lower cover 73, the fixing member 80, and the two cord reel cassettes 100 rotate together.

[0026] Next, a method for adjusting the length of the nylon cord 200 in the cord reel cassette 100 will be described. When the motor 41 is driven to rotate the rotating shaft 30, the two cord reel cassettes 100 also rotate integrally with the cover members 70 (upper cover 72 and lower cover 73) as described above, and the cord reel cassettes 100 cannot rotate freely inside the cover members 70. As the cord reel cassettes 100 rotate, centrifugal force acts on the nylon cord 200. However, because the cord reel cassettes 100 cannot rotate freely, there is no risk of the nylon cord 200 being pulled out by the centrifugal force. In contrast, when the rotating shaft 30 is rotating due to the drive of the motor 41, the pressing portion 830 of the fixing member 80 is pressed against the ground or the like, thereby momentarily pressing the pressing portion 830 upward. If the upward pressing force at this time is greater than the downward biasing force of spring 850, fixing member 80 moves upward against the downward biasing force of spring 850. At this time, convex portion 840 of fixing member 80 moves away from concave portion 731 of lower cover 73, allowing fixing member 80 to rotate freely relative to lower cover 73. In this manner, the position where convex portion 840 of fixing member 80 moves away from concave portion 731 of lower cover 73 corresponds to the first position of fixing member 80. When fixing member 80 is in the first position, fixing member 80 rotates due to inertia, and nylon cord 200 is pulled out by centrifugal force. Note that fixing member 80 momentarily moves upward and rotates relative to lower cover 73 when pressing portion 830 against the ground. However, immediately thereafter, fixing member 80 moves downward due to the biasing force of spring 850, and convex portion 840 of fixing member 80 fits into concave portion 731 of lower cover 73. This again prevents fixing member 80 from rotating independently of lower cover 73, and causes fixing member 80 and lower cover 73 to rotate together. In this way, nylon cord 200 is pulled out only while pressing portion 830 is momentarily moving upward by being pressed against the ground, so that no excess nylon cord 200 is pulled out, and the amount of nylon cord 200 pulled out can be adjusted by changing the number of times pressing portion 830 is pressed against the ground.

[0027] As described above, in the brush cutter 10 according to the present invention, the upper cover 72, the lower cover 73, the fixing member 80, and the two cord reel cassettes 100 rotate integrally with the rotation of the rotating shaft 30. Specifically, the convex portion 840 of the fixing member 80 fits into the concave portion 731 of the lower cover 73, and the fixing member 80 is biased toward the lower cover 73. This prevents the fixing member 80 from rotating independently of the lower cover 73, and the fixing member 80 and the lower cover 73 rotate integrally. Furthermore, the two cord reel cassettes 100 are fixed to the fixing member 80. As a result, the two cord reel cassettes 100 rotate integrally with the cover members 70 (the upper cover 72 and the lower cover 73). However, because they are fixed to the fixing member 80, the cord reel cassettes 100 cannot rotate freely within the cover members 70. As the cord reel cassette 100 rotates, centrifugal force acts on the nylon cord 200, but since the cord reel cassette 100 cannot rotate freely, there is no risk of the nylon cord 200 being pulled out by the centrifugal force.

[0028] In the brush cutter 10 according to the present invention, if the tip of the nylon cord 200 becomes worn, as described above, while the rotating shaft 30 is rotating due to the drive of the motor 41, the pressing portion 830 of the fixing member 80 is pressed lightly against the ground or the like, thereby momentarily pressing the pressing portion 830 upward. This simple operation allows the nylon cord 200 to be easily pulled out. Furthermore, since the fixing member 80 is constantly biased toward the lower cover 73 by the spring 850, the pressing portion 830 is pressed against the ground, causing the fixing member 80 to momentarily move upward and rotate relative to the lower cover 73. After that, the biasing force of the spring 850 causes the fixing member 80 to immediately move downward, and the convex portion 840 of the fixing member 80 engages with the concave portion 731 of the lower cover 73. This prevents the fixing member 80 from rotating independently of the lower cover 73 again, preventing excessive pulling out of the nylon cord 200.

[0029] In the brush cutter 10 according to the present invention, the nylon cord 200 is wound around the cord reel cassette 100. This allows the user to easily replace the nylon cord 200 along with the cord reel cassette 100. This eliminates the need to wind a long nylon cord around the rotor, as is the case with conventional brush cutters. This saves the user time and effort, and even users unfamiliar with machine operation can easily replace the nylon cord. Furthermore, when a user wishes to use nylon cord of a different thickness, they can simply replace the entire cord reel cassette 100, significantly reducing the time and effort required for replacement compared to conventional brush cutters. Furthermore, the two cord reel cassettes 100 are not integrated and connected to each other, but can be removed and replaced individually. Therefore, the two cord reel cassettes 100 do not necessarily need to be replaced at the same time; only one can be replaced, allowing for efficient cord use.

[0030] In the brush cutter 10 according to the present invention, the replaceable cord reel cassette 100 is covered by the metal upper cover 72 and lower cover 73, so even if pebbles or other objects fly in while cutting edge grass, there is no risk of them directly hitting the cord reel cassette 100. Therefore, the cord reel cassette 100 does not need to be made from a metal material, and can be made from a lightweight material such as plastic or resin, which makes it lightweight and inexpensive to manufacture.

[0031] In the brush cutter 10 according to the present invention, two cord reel cassettes 100 are individually and detachably arranged in a storage chamber formed by the upper cover 72 and the lower cover 73. This allows the user to replace each cord reel cassette 100 individually. Each cord reel cassette 100 has an upper wall 101 and a lower wall 102 that face each other in the vertical direction. Therefore, even when two cord reel cassettes 100 are stacked on top of each other, the lower wall 102 of one cord reel cassette 100 and the upper wall 101 of the other cord reel cassette 100 act as a barrier, preventing the two nylon cords 200 from becoming tangled.

[0032] The present invention is not limited to the above-described embodiment and may be modified without departing from the spirit and scope of the present invention. For example, while the nylon cord 200 is wound around the cord reel cassette 100, the cord does not necessarily have to be made of nylon and may be made of a cord made of other resins. Furthermore, the cover member 70 does not necessarily have to be made of metal and may be made of an appropriate material, such as resin. In the above-described embodiment, the cord reel cassette 100 has the nylon cord 200 wound around a spool (winding frame) formed of the upper wall 101, the lower wall 102, and the shaft 103. However, the present invention is not limited to such an embodiment. As long as the cord reel cassette 100 has portions corresponding to the upper wall, the lower wall, and the shaft, the outer shape of the cord reel cassette 100 may be any appropriate shape.

[0033] In the above embodiment, when the rotating shaft 30 is rotating due to the drive of the motor 41, the pressing portion 830 of the fixing member 80 is pressed lightly against the ground or the like, thereby momentarily pressing the pressing portion 830 upward, thereby unwinding the nylon cord 200. However, the present invention is not limited to such an embodiment. For example, when the motor 41 is not driven, i.e., when the rotating shaft 30 is not rotating, the user may press the pressing portion 830 so that the convex portion 840 of the fixing member 80 moves away from the concave portion 731 of the lower cover 73, and then rotate the fixing member 80 to unwind the nylon cord 200. In this case, the user can easily adjust the amount of nylon cord 200 unwound by adjusting the amount of rotation of the fixing member 80. Furthermore, the pressing portion 830 of the fixing member 80 may be provided with a protrusion or recess for the user to grip, so that the user can easily rotate the fixing member 80.

[0034] The brush cutter 10 of the present invention may also be configured so that the nylon cord 200 is pulled out only when the user presses the pressing portion 830 of the fixing member 80 while the rotating shaft 30 is not rotating. For example, the height of the pressing portion 830 may be adjusted so that the pressing portion 830 does not protrude downward from the lower cover 73, or a barrier may be provided on the underside of the lower cover 73 that protrudes downward beyond the pressing portion 830 to prevent the pressing portion 830 from directly hitting the ground. This configuration can prevent the pressing portion 830 from being unintentionally pressed and the nylon cord 200 from being pulled out while the brush cutter 10 is being driven.

[0035] In the above embodiment, the fixing member 80 includes a fixing shaft 820 as an example of an engaging portion, and the shaft portion 103 of the cord reel cassette 100 includes a fitting groove 104 as an example of an engaging receiver. However, the engaging portion and the engaging receiver of the present invention are not limited to this. For example, as shown in FIG. 6 , a recess 102a as an example of an engaging receiver may be provided on the bottom wall 102 of the cord reel cassette 100, and a protrusion 80P as an example of an engaging portion may be provided on the fixing member 80. Even in this case, the cord reel cassette 100 can be fixed to the fixing member 80. Note that if the bottom wall 102 of the cord reel cassette 100 includes a recess 102a as an example of an engaging receiver, a protrusion 101a that fits into the recess 102a may be provided on the top wall 101 of the cord reel cassette 100. As a result, when two cord reel cassettes 100 are stacked one on top of the other, the recessed portion 102a and the protruding portion 101a fit together, preventing the two cord reel cassettes 100 from rotating freely relative to each other.

[0036] In the above embodiment, the brush cutter 10 is provided with a battery 42 and is driven by electricity, but the present invention is not limited to this configuration and may be driven by, for example, an engine.

Claims

1. A brush cutter configured to be fitted with two cord reel cassettes, each with a different cord wound around it, comprising: a rod provided with a handle; a rotating shaft located at one end of the rod; a drive unit that applies driving force to rotate the rotating shaft; a cover member fixed to the rotating shaft and configured to rotate as the rotating shaft rotates, and having a hollow storage chamber provided therein for storing the two cord reel cassettes; a fixing member having a plate-shaped main body and engaging portions provided on the plate-shaped main body that engage with engaging receiving portions provided on the two cord reel cassettes to fix the two cord reel cassettes to the main body; and a locking mechanism provided on the cover member and the fixing member, configured to move the fixing member between a first position where the fixing member rotates independently of the cover member and a second position where the fixing member rotates integrally with the cover member. When the brush cutter is in operation, when the fixing member is in the second position, the two cord reel cassettes rotate integrally with the fixing member and the cover member while being fixed to the fixing member in the storage chamber of the cover member, and when the fixing member is in the first position, the two cord reel cassettes and the fixing member rotate relative to the cover member, thereby making it possible to adjust the length of the cord wound around the two cord reel cassettes.

2. A brush cutter as described in claim 1, wherein the locking mechanism comprises a pair of a convex portion provided on the fixing member and a concave portion provided on the cover member, or a pair of a concave portion provided on the fixing member and a convex portion provided on the cover member, and a biasing member that biases the fixing member towards the cover member.

3. The brush cutter according to claim 2, wherein the biasing member of the locking mechanism is configured to bias the fixing member toward the cover member.

4. A cord reel cassette that is removably stored in the storage chamber of the cover member of the brush cutter described in claim 1, characterized in that it has an upper wall and a lower wall that face each other in the vertical direction, and a shaft that connects the center of the upper wall to the center of the lower wall in the vertical direction, and the shaft or the lower wall has an engagement receiving portion configured to engage with the engagement portion of the fixing member.

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