Grass cutting device

Abstract

To provide a grass mower that can work around obstacles by simplifying the configuration of a circuit that drives an arm.SOLUTION: A grass mower comprises a first work arm 21 rotatably mounted on a pivot shaft 12, a second work arm 31 provided separately from the first work arm 21 and rotatably mounted on the pivot shaft 12, a first sensor 52A for detecting that an obstacle comes into contact with the first work arm 21, a second sensor 52B for detecting that the first work arm 21 comes into contact with the second work arm 31, and a third sensor 52C for detecting that the first work arm 21 is in a position in which the tip of the first work arm 21 is facing forward. The first work arm 21 is switched between a state in which it can be passively rotated and a state in which it is forced to rotate depending on whether or not the first sensor 52A, the second sensor 52B, and the third sensor 52C are detected.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0003] , , , ,

[0001] This invention relates to a grass cutting device.

Background Art

[0002] Patent Document 1 discloses a device for cutting plants on the ground around a support column that serves as an obstacle. According to Patent Document 1, a grass cutting device adapted to be propelled by an associated vehicle includes a support, first and second arms, and first and second grass cutting machine elements. The support is adapted to be attached to an associated boom extending from the associated vehicle. The first arm and the second arm are pivotally attached to the support. The first grass cutting machine element is attached to the first arm, and the second grass cutting machine element is attached to the second arm. Each of the first and second arms is provided with a cylinder for pivotal drive, and these cylinders are connected to each other. Also, by arranging a plurality of various valves in a hydraulic circuit connecting the cylinders and using an accumulator, grass cutting around an obstacle is realized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration of Patent Document 1, there are many circuits for driving and buffering the first and second arms, so there is a problem that the configuration of the hydraulic circuit of the entire device is complicated. That is. Therefore, the present invention has been made in view of the above problems, and for driving and buffering the arm The objective is to simplify the circuit configuration and provide a grass-cutting device that can operate around obstacles. Let's assume that. The inventors have filed Japanese Patent Application No. 2020-119920 "Grass Cutting Device" and Japanese Patent Application No. 2020-134 In publication No. 176, "Grass Cutting Device," we proposed the machine configuration of a grass cutting device. This invention relates to these grass cutting devices I will propose solutions related to mechanical systems, hydraulic systems, and electrical circuits. [Means for solving the problem]

[0005] This invention is A first working arm is provided that can rotate around a pivot axis, A second work arm is provided separately from the first work arm and is rotatable about the pivot axis, A first sensor that detects when an obstacle comes into contact with the first working arm, A second sensor detects when the first work arm comes into contact with the second work arm, The system includes a third sensor that detects that the first working arm is in a first position, The first work arm and the second work arm are rotatable between a first posture in which the tips of the first work arm and the second work arm are facing forward, and a second posture which is a posture other than the first posture, until the first work arm and the second work arm are completely facing backward. Depending on whether the first sensor, the second sensor, and the third sensor detect anything, the first work arm is switched between a state in which it can passively rotate between a first posture and a second posture, and a state in which it is forcibly rotated between a second posture and a first posture. When the second and third sensors detect something, the first working arm maintains the first posture in which the tip of the arm is facing forward. height, When the first sensor and the second sensor detect an object, the first work arm is made passively rotatable from the first position to the second position. A grass cutting device characterized by the following: It relates to.

[0007] This invention is Furthermore, If at least the third sensor is in a detection state while the first work arm passively rotates from the first position to the second position, then passive rotation of the first work arm toward the second position is possible. A grass cutting device characterized by the following: It relates to. [Effects of the Invention]

[0009] This invention simplifies the configuration of the circuit that drives and cushions the arm, providing a grass-cutting device that can work around obstacles. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view of a grass-cutting device according to an embodiment of the present invention. The first working arm is shown in a receiving position (first position). In the figure, the left is the front in the direction of travel, and the top is the right in the direction of travel, which is the side of the traveling machine. [Figure 2] This is a side view of a grass-cutting device according to an embodiment of the present invention. In the figure, the back is the front in the direction of travel, and the top of the figure is the right side in the direction of travel, which is the side of the traveling machine. [Figure 3] This is a front view of a grass cutting device according to an embodiment of the present invention, and the second fitting and actuator are partially cut out, as shown in Figure 1, section AA. [Figure 4] This is a plan view showing the operation of a grass-cutting device according to an embodiment of the present invention. It shows the state in which the sensor arm has not detected an obstacle. It shows the state in which the first working arm is in contact with the second working arm. It shows the first position (acceptable position) in which the first working arm and the second working arm are in their normal working position. The first base member and link mechanism are omitted, and the second base member is shown in cross-section. This is position a, showing the position of the device. [Figure 5] This is a plan view showing the operation of a grass-cutting device according to an embodiment of the present invention. It shows the state in which the sensor arm has detected an obstacle. It shows the state in which the first working arm is in contact with the second working arm. It shows the first working position (acceptable position) in which the first working arm and the second working arm are in their normal working position. For explanatory purposes, the first base member and the second base member are shown in cross-section. This is position b, which shows the position of the device. [Figure 6]This is a plan view showing the operation of a grass-cutting device according to an embodiment of the present invention. It shows the state in which the sensor arm has detected an obstacle. It shows the state in which the first working arm has moved away from the second working arm. It shows the state in which the first working arm and the second working arm are in the process of rotating from the first position (receiving position), which is the normal working position, to the second position (discharging position). The first working arm and the second working arm are in a state in which they can rotate freely due to the switching of the switching valve (control valve) by the detection of the sensor. For explanatory purposes, the first base member and link mechanism are omitted, and the second base member is shown in cross-section. This is position c, which shows the position of the device. [Figure 7] This is a plan view showing the operation of a grass-cutting device according to an embodiment of the present invention. It shows the state in which the sensor arm has not detected an obstacle (this is when the obstacle has moved away from the sensor arm while the first working arm is being driven to rotate). It shows the state in which the first working arm has moved away from the second working arm. It shows the state in which the first working arm and the second working arm are in the process of rotating from the first position (receiving position), which is the normal working position, to the second position (discharging position). For explanatory purposes, the first base member and link mechanism are omitted, and the second base member is shown in cross-section. This is position d, which shows the position of the device. [Figure 8] This is a plan view showing the operation of a grass-cutting device according to an embodiment of the present invention. It shows the state in which the sensor arm has not detected an obstacle. It shows the state in which the first working arm is in contact with the second working arm. It shows the state in which both the first and second working arms have rotated to the second posture (dischargeable posture). This shows the state in which the obstacle has moved away from the first and second working arms after the first and second working arms have rotated to the second posture (dischargeable posture). For explanatory purposes, the first base member and link mechanism are omitted, and the second base member is shown in cross-section. This is posture e, which shows the posture of the device. [Figure 9] This is a fluid pressure circuit diagram (hydraulic circuit diagram) of a grass cutting device according to an embodiment of the present invention (this is circuit a when the device is in position a). The first control valve is in the no-load position and the second control valve is in the shut-off position. [Figure 10]This is a hydraulic circuit diagram of the lawn mowing device according to an embodiment of the present invention (hydraulic circuit diagram). (When in the device postures b, c, d indicating the device posture, it is circuit b). The first control valve is in the no-load position, and the second control valve is in the open position. [Figure 11] This is a hydraulic circuit diagram of the lawn mowing device according to an embodiment of the present invention. (When in the posture e indicating the device posture, it is circuit c). The first control valve is in the pressure feeding position, and the second control valve is in the shut-off position. [Figure 12] This is a circuit diagram of the lawn mowing device according to an embodiment of the present invention (electrical circuit a). It is in the state of posture a indicating the device posture. The first switching valve is in the no-load position, and the second switching valve is in the shut-off position. Both the first switching valve and the second switching valve are non-conductive. The actuator (cylinder) is restricted from contracting. [Figure 13] This is a circuit diagram showing the electrical connection state of the lawn mowing device according to an embodiment of the present invention (electrical circuit b). It is in the state of posture b indicating the device posture. The first switching valve is in the no-load position, and the second switching valve is in the open position. The second switching valve is made conductive via the first sensor. The actuator (cylinder) is in a freely expandable and contractible state (displaceable state). [Figure 14] This is a circuit diagram showing the electrical connection state of the lawn mowing device according to an embodiment of the present invention (electrical circuit c). It is in the state of posture c indicating the device posture. The first switching valve is in the no-load position, and the second switching valve is in the open position. The second switching valve is made conductive via the first sensor. The actuator (cylinder) is in a freely expandable and contractible state (displaceable state). [Figure 15] This is a circuit diagram showing the electrical connection state of the lawn mowing device according to an embodiment of the present invention (electrical circuit d). It is in the state of posture d indicating the device posture. The first switching valve is in the no-load position, and the second switching valve is in the open position. The second switching valve is made conductive via the first sensor and the second sensor. The actuator (cylinder) is in a freely expandable and contractible state (displaceable state). [Figure 16]This is a circuit diagram (electrical circuit e) showing the electrical wiring state of a grass cutting device according to an embodiment of this invention. The device is in state e, which is the orientation of the device. The first switching valve is in the pressurized load position, and the second switching valve is in the shut-off position. The first switching valve is made electrically connected via the first to third sensors. The actuator (cylinder) is driven to the extension side, returning the first working arm and the second working arm to the first orientation (receiving orientation). [Modes for carrying out the invention]

[0011] A is a grass cutting device used as a work machine. The grass cutting device A is attached to a traveling machine (not shown), such as a tractor, by one or more grass cutting device mounting arms (not shown). The grass cutting device A is connected to a boom device, etc. The boom device (extension mechanism) is the same as in Japanese Patent Application No. 2019-194694 "Work Machine", Japanese Patent Application No. 2020-14070 "Work Machine", etc., and is connected by the connection mechanism of Japanese Patent Application No. 2020-84471 "Attachment Mechanism and Work Machine Equipped with Attachment Mechanism". Note that the grass cutting device A of this application is not limited to the example boom device (extension mechanism) as illustrated in the prior application Japanese Patent Publication No. 2019-187386 (Japanese Patent Application No. 2018-087440) "Grass Cutting Device".

[0012] In the grass cutting device A, 11 is a base member. The base member 11 consists of a first base member 111 and a second base member 112. 21 is the first working arm, and 31 is the second working arm. B is a parallel link mechanism. The first working arm 21 and the second working arm 31 are attached to a traveling machine such as a tractor via a multiple component called a boom device, which is a grass cutting device mounting arm, and the grass cutting device A operates at the front, rear, or side of the traveling machine. When attaching to the grass cutting device mounting arm, it is connected to the tip of the grass cutting device mounting arm by a connecting part 61 provided on the first base member 111.

[0013] The grass cutting device A can be mounted to the side of the vehicle via multiple grass cutting device mounting arms, or mounted to the rear and side of the vehicle via grass cutting device mounting arms that can move left and right on the vehicle, or mounted to the rear and side of the vehicle via grass cutting device mounting arms that can move left and right on the vehicle. Furthermore, the grass cutting device A may be mounted directly to the vehicle or to a three-point linkage lifting device etc. on the vehicle without using grass cutting device mounting arms. The grass-cutting device A is capable of gripping an obstacle W between a first working arm 21 and a second working arm 31, which are rotatably mounted in a scissor-like shape, and each of the first working arm 21 and the second working arm 31 can rotate to perform work. The tips of the scissor-shaped first working arm 21 and the second working arm 31, away from the pivot axis, are oriented in the direction of travel. The tips of the illustrated first working arm 21 and second working arm 31 are curved in an arc shape.

[0014] The base member 11 is installed on the grass cutting device A. The first base member 111(11) is attached to the traveling body side of the parallel link mechanism B. The second base member 112(11) is installed at one end of the front side of the parallel link mechanism B. The second base member 112(11) is horizontally movable relative to the first base member 111(11) installed at the other end of the parallel link mechanism B via the parallel link mechanism B.

[0015] 12 is a pivot axis. The pivot axis 12 is provided on the second base member 112 and consists of a vertical axis oriented in a direction intersecting the work surface. The first work arm 21 and the second work arm 31 are each capable of horizontal rotation with the pivot axis 12 as the pivot axis. Furthermore, depending on the rotational posture of the first work arm 21 and the second work arm 31, they can assume a receiving posture (first posture) and a discharge posture (second posture). The first working arm 21 is provided so as to be able to rotate between a first and second position on a pivot axis 12. The second working arm 31 is provided separately from the first working arm 21 and is also provided so as to be able to rotate between a first and second position on a pivot axis 12. An explanation of these attitudes will follow later.

[0016] 15 is a stopper. The stopper 15 is provided on the second working arm 31. 16 is the first fitting, and 17 is the second fitting. The first fitting 16 and the second fitting 17 are connected to each other and are attached to connect the second base member 112(11) around the pivot axis 12 to the first work arm 21. As the first work arm 21 rotates around the pivot axis 12, the first fitting 16 and the second fitting 17 rotate in the vicinity of the pivot axis 12 while remaining connected to each other.

[0017] The pivot axis 12 is positioned closer to the mounting position of the front arm 13A attached to the second base member 112(11) than to the mounting position of the rear arm 13B attached to the second base member 112(11). In other words, since the pivot axis 12 is located on the front side of the second base member 112(11), the tips of the first work arm 21 and the second work arm 31 connected to the pivot axis 12 can be positioned further forward.

[0018] The parallel link of the parallel link mechanism B consists of a front arm 13A on the side closer to the obstacle W that the work arm contacts when it comes into contact with the obstacle, and a rear arm 13B on the side further away from the obstacle W. The parallel link mechanism B is rotatably mounted on the first base member 111(11) at one end and on the second base member 112(11) at the other end, and is rotatable in a direction parallel to the work surface. That is, the second base member 112(11) is capable of parallel movement relative to the first base member 111(11). Depending on the rotational position of the front arm 13A and the rear arm 13B, the parallel link mechanism B has an extended position or a retracted position. These positions will be described later.

[0019] The parallel link mechanism B, in the deployed position described later, is oriented outward to the left and right relative to the direction of travel from the first base member 111(11). As a result, when the first work arm 21 and the second work arm 31 come into contact with an obstacle W, the first work arm 21 and the second work arm 31 can passively move horizontally or parallel to the ground toward the traveling machine body, which is inward in the width direction relative to the rear and direction of travel, so as to sandwich the obstacle W between the first work arm 21 and the second work arm 31.

[0020] The acceptable posture (first posture) in terms of the orientation and other aspects of the first work arm 21 and the second work arm 31 refers to a posture where the first work arm 21 and the second work arm 31 are not in contact with the obstacle W, as shown in Figures 1 and 4, or where they are in contact with the obstacle W, as shown in Figure 5, but the tips of the first work arm 21 and the second work arm 31 are facing forward. The posture of the parallel link B in the acceptable posture (first posture) does not matter, regardless of the position of the deployed position or the retracted position, which will be described later. The dischargeable posture (second posture) in terms of the orientation and other aspects of the first work arm 21 and the second work arm 31 refers to the posture in which the first work arm 21 and the second work arm 31 are in contact with the obstacle W and have rotated horizontally in a reverse direction from the receiving posture (first posture), as shown in Figures 6, 7, and 8, and the posture thereafter.

[0021] The dischargeable posture (second posture) refers to the posture state of the first work arm 21 and the second work arm 31, other than the receiving posture (first posture) shown in Figures 1, 4, and 5, until the first work arm 21 and the second work arm 31 are completely facing backward. The state in which only the first work arm 21 is rotated backward relative to the direction of travel is also the dischargeable posture (second posture). The posture state of the parallel link B in the dischargeable posture (second posture) does not matter, regardless of whether it is in the deployed position or the retracted position, which will be described later. In this specification, the first posture (acceptable posture) refers to the position in which the radial tip sides of the first work arm 21 and the second work arm 31 with respect to the pivot center face forward, and the position (range) rotated (even slightly) backward from this position is referred to as the second posture (dischargeable posture).

[0022] The first working arm 21 is provided so as to be able to rotate around the pivot axis 12 between a receiving position (first position) and an ejection position (second position). The second working arm 31 is provided separately from the first working arm 21 and is rotatable around the pivot axis 12 between a receiving position (first position) and a discharge position (second position).

[0023] The deployed position of the parallel link mechanism B is the state in which the arms of the first work arm 21 and the second work arm 31 of the parallel link mechanism B are deployed outward in the width direction relative to the direction of travel, that is, the state shown in Figure 1. The retracted position of the parallel link mechanism B is the state in which the first working arm 21 and the second working arm 31 are moved inward in the width direction relative to the direction of travel from the deployed position.

[0024] 41 is the first elastic body. The first elastic body 41 is provided on the side of the rear arm 13B of the parallel link mechanism B. The first elastic body 41 consists of a gas spring, a coil spring, etc., and in this embodiment of the invention, a gas spring is used. As shown in Figures 1 and below, both ends of the first elastic body 41 are attached to the first base member 111(11) and the second base member 112(11) side of the rear arm 13B.

[0025] The first elastic body 41 allows the parallel link mechanism B to be repositioned between an extended position and a retracted position, and constantly biases the second base member 112(11) toward the extended position relative to the first base member 111(11). The first elastic body 41 constantly biases the parallel link mechanism B forward and outward relative to the direction of travel. When the parallel link mechanism B is not in contact with an obstacle W, it can return to its deployed position and wait for the obstacle W that approaches as it moves forward.

[0026] Since the first elastic body 41 is positioned behind the pivot axis 12, it does not come into direct contact with obstacles or other objects that approach as the vehicle moves forward. 42 is a second elastic body. The second elastic body 42 consists of a gas spring, a coil spring, etc., and in this embodiment of the invention, a gas spring is used. The second elastic body 42 is spanned and connected to the first work arm 21 and the second work arm 31, and constantly biases the second work arm 31 toward the first work arm 21.

[0027] In other words, the second elastic body 42 constantly biases the first working arm 21 and the second working arm 31 toward each other. As a result, the first working arm 21 and the second working arm 31 can perform grass cutting work while in contact with the obstacle W, and the plants around the obstacle W can be reliably cut. Furthermore, since the second elastic body 42 biases the second working arm 31 regardless of whether it is in the first or second position, the first working arm and the second working arm 31 can properly grip the obstacle W even during position transitions. The second elastic body 42 is positioned outside the second work arm 31, not on the inside where the obstacle W is sandwiched between the first work arm 21 and the second work arm 31. Therefore, when working with the obstacle W sandwiched between the first work arm 21 and the second work arm 31, the second elastic body 42 does not come into contact with the obstacle.

[0028] The first working arm 21 and the second working arm 31 are each made up of a roughly plate-like body. As shown in Figures 2 and 3, the first working arm 21 and the second working arm 31 are stacked and attached to the second base member 112(11) so as to be able to rotate horizontally around a pivot shaft 12 attached to the base member 112(11). The first working arm 21 and the second working arm 31 are each provided with a first cutting blade section 24 and a second cutting blade section 34 at their tip ends, which are rotationally driven by cutting blade motors 242 and 342, respectively. The first working arm 21 and the second working arm 31 can perform grass cutting work with the first cutting blade section 24 and the second cutting blade section 34 while in contact with obstacles W present on the work surface. The second working arm 31 is provided separately from the first working arm 21 and is rotatable independently of the first working arm 21 around the pivot axis 12, and is positioned opposite the first working arm 21 with the obstacle W in between when it comes into contact with the obstacle W.

[0029] The first working arm 21 is equipped with an operating means (actuator, cylinder) 14, which is an operating means that drives the rotation of the first working arm 21. In this embodiment, the operating means 14 consists of an actuator and a hydraulic cylinder. The operating means 14 is attached to the base member 11. In this embodiment of the invention, the operating means 14 is attached to the rear part of the second base member 112. 141 is a rod provided at the tip of the operating means 14. The rod 141 extends and retracts by the operating means 14, which is a hydraulic cylinder. The operating means 14 rotates the first work arm 21.

[0030] The operating means (actuator, cylinder) 14 extends and retracts the rod 141, and rotates the first working arm 21 via the first fitting 16 and the second fitting 17. The first working arm 21 is provided so as to be able to rotate around the pivot axis 12, and can rotate by coming into contact with an obstacle W present on the work surface.

[0031] The stopper 15 on the second work arm 31 restricts the rotation of the second work arm 31 when it comes into contact with the first work arm 21, which is rotated by the operating means 14. The stopper 15 can stably maintain the positions of the first work arm 21 and the second work arm 31 in the receiving posture (first posture), and it is easy for the worker to adjust the contact position between the obstacle W and the second work arm 31 to the appropriate position. The stopper 15 can contact the second base member 112(11) and restricts its rotation. As shown in Figures 1, 4, 5 to 8, the stopper 15 contacts the front end of the second base member 112(11) and restricts the movement of the second work arm 31 toward the travel body, which is the direction toward separating it from the first work arm 21, thereby maintaining the acceptance posture (first posture).

[0032] The operation of the rod 141 of the hydraulic cylinder-operated operating means 14 restricts the movement of the first working arm 21 and the second working arm 31 to a range of motion until it is restricted by the stopper 15. The stopper 15 maintains an acute angle in the receiving posture (first posture) and between the first work arm 21 and the second work arm 31 in the receiving posture (first posture), so that the working area of ​​the grass cutting device A does not expand unnecessarily, and grass cutting work can be performed smoothly.

[0033] 23 is a contact portion. The contact portion 23 is provided between the pivot axis 12 of the first working arm 21 and the working part, the first cutting blade portion 24. The contact portion 23 is provided in a concave shape. When an obstacle W reaches the contact portion 23, it presses against the contact portion 23, causing the first working arm 21 to rotate to the rear. 24 is the first cutting blade section. The first cutting blade section 24 is a cutting blade, a cutting blade section, or a working section. The first cutting blade section 24 is attached to the radial end side of the lower part of the first working arm 21 relative to the pivot axis 12. The first working arm 21 has one or more cutting blade sections at its lower end.

[0034] The second working arm 31 has one or more cutting blades at its lower end. In this embodiment, the second cutting blade 34 is located at the radial end of the lower part of the second working arm 31 relative to the pivot axis 12. Additional second cutting blades 34 may be provided near the pivot axis 12 of the second working arm 31. The second cutting blade section 34 is a cutting blade, a cutting blade section, or a working section.

[0035] The first working arm 21 and the second working arm 31 are attached to the second base member 112(11) so as to be able to rotate horizontally around the pivot axis 12, and the first cutting blade section 24 and the second cutting blade section 34 are horizontally movable. Therefore, the first working arm 21 and the second working arm 31 grip the obstacle W between their opposing inner sides, and the first cutting blade section 24 and the second cutting blade section 34 cut the grass all around the obstacle W.

[0036] 241 and 341 are cutting blades, respectively. Four cutting blades 241 are provided at equal intervals on the rotation axis of the first cutting blade section 24, and four cutting blades 341 are provided at equal intervals on the rotation axis of the second cutting blade section 34. There is no limit to the number of cutting blades 241 and 341 provided on the first cutting blade section 24 and the second cutting blade section 34. As shown in Figures 1 and 2, the cutting blades 241 and 341 provided on the first cutting blade section 24 and the second cutting blade section 34, as viewed from the direction of travel, rotate horizontally.

[0037] 242 and 342 are hydraulic motors. Hydraulic motor 242 is mounted on the rotational axis of the first cutting blade section 24, on the motor base of the first working arm 21. Alternatively, an electrically operated electric motor may be used instead of the hydraulic motor 242. The hydraulic motors 342 are each mounted on the rotational axis of the second cutting blade section 34, on the motor base of the second working arm 31. The hydraulic motors 242 and 342 rotate the cutting blades 241 and 341, which are provided on the first cutting blade section 24 and the second cutting blade section 34, respectively.

[0038] 5 is a detection unit. The detection unit 5 is provided in close proximity to the first cutting blade unit 24, which is the working unit, and is positioned to protrude laterally, which is radially outward from the rotational diameter of the first cutting blade unit 24, as shown in Figures 1 and below. The side portion of the detection unit 5 can detect an obstacle W by contacting the obstacle and retracting toward the rotational center side of the first cutting blade unit 24. 51 is a sensor arm. The sensor arm 51 is installed on the detection unit 5. The sensor arm 51 is a contact sensor and is installed along the front outer circumference of the first work arm 21.

[0039] The sensor arm 51 consists of a first sensor arm 511 and a second sensor arm 512. The first sensor arm 511 and the second sensor arm 512, which constitute the detection unit 5, are provided to be able to rotate horizontally. As shown in Figures 1, 4 to 8, the first sensor arm 511 is attached so that one end protrudes outward from the left side in the direction of travel of the first work arm 21 towards the front. The second sensor arm 512 is attached on the inside side of the first work arm 21, on the side through which the obstacle W passes, from the outer end of the first sensor arm 511 that attaches to the first work arm 21.

[0040] The first sensor arm 511 and the second sensor arm 512 are installed with some overlap. The first sensor arm 511 is rotatable horizontally by a pivot shaft 511a located at its outer end on the left side in the direction of travel, and the second sensor arm 512 is rotatable horizontally by a pivot shaft 512a located at its outer end on the left side in the direction of travel. As shown in Figure 1, the first sensor arm 511 and the second sensor arm 512, which are sensor arms 51 in a state where they do not detect an obstacle W, protrude outward from the first cutting blade section 24, which is the working section, in a plan view.

[0041] By configuring the sensor arm 51 of the detection unit 5 with multiple first sensor arms 511 and second sensor arms 512, detection accuracy can be improved while maintaining a certain distance between the tip of the first sensor arm 511, which is away from the pivot axis 511a, and the first cutting blade 24, which is the working part. Since the tip of the sensor arm 51 can be kept within a certain distance from the working part, the first cutting blade 24, obstacles can be detected within a certain distance from the working part, the first cutting blade 24.

[0042] The first sensor 52A is provided on the detection unit 5 so as to be able to contact a contact portion 53A provided near the pivot axis 511a of the first sensor arm 511. The first sensor 52A contacts the contact portion 53A to determine whether or not the sensor arm 51 has rotated. It is possible to emit that signal.

[0043] The first sensor 52A takes the contact position 521 shown in Figures 12 to 16, which represent the electrical circuit diagram, when the contact portion 53A makes contact, and the non-contact position 522 when the contact portion 53A does not make contact. In other words, if the sensor arm 51 does not come into contact with an obstacle, the first sensor 52A is in the non-contact position 522, and if the sensor arm 51 comes into contact with an obstacle, the first sensor 52A is in the contact position 521. The contact portion 53A of the sensor arm 51 is made of a so-called cam piece. The contact portion 53A is rotatable together with the first sensor arm 511 and can contact the first sensor 52A. By changing the shape of the periphery of the contact portion 53A, the timing of the signal emitted by the first sensor 52A can be changed.

[0044] 54 is a biasing element. The biasing element 54 is provided on the detection unit 5. The biasing element 54 biases the sensor arm 51 toward the radially outward side of the rotation axis of the first cutting blade unit 24, which is the working unit. 55 is a connecting portion. The connecting portion 55 consists of a sliding portion 551 and a pin 552. The sliding portion 551 is formed in the shape of an elongated hole in the first sensor arm 511, which is one of the sensor arms.

[0045] The connecting portion 55 connects one end of the first sensor arm 511, which is the sensor arm 51, to the middle portion of the second sensor arm 512. The connecting portion 55 connects one end of the first sensor arm 511 to the middle portion of the second sensor arm 512. The pin 552 is provided on the second sensor arm 512, which is the other sensor arm, so as to protrude toward the sliding part 551, and is fitted into the sliding part 551. The pin 552 is slidable relative to the sliding part 551 within the range of the elongated hole provided in the sliding part 551.

[0046] The sliding part 551 is elongated and is provided on the first sensor arm 511. The sliding part 551 is positioned so that it moves further away from the pivot axis 511a of the first sensor arm 511 as it moves in the direction of its major axis. A pin 552 provided on the second sensor arm 512 slides along the inner circumference of the elongated hole in the sliding part 551, thereby linking the rotation of the two sensor arms 511 and 512. The shape of the sliding part 551 and the positions of the sliding part 551 and the pin 552 can be freely set, taking into consideration the detection sensitivity and the shape of the first cutting blade part 24, which is the working part.

[0047] 56 is a curved section. The curved section 56 is formed on the sensor arm 51 so as to curve along the working section, which is the first cutting blade section 24. The outer side surface of the curved portion 56 is positioned such that, in a plan view when the detection unit 5 is in detection mode, it roughly coincides with the outer peripheral edge of the side surface of the first cutting blade portion 24, which is the working portion. Alternatively, it is positioned inward from the outer peripheral edge of the side surface of the first cutting blade portion 24, which is the working portion.

[0048] In a plan view, the tip of the first working arm 21 is positioned to cover the first cutting blade 24, so that the first cutting blade 24 does not protrude from the first working arm 21 and does not come into contact with the obstacle W. In this embodiment of the invention, the tip of the first working arm 21 is curved in an arc shape, so that the outer edge of the first working arm 21 rotates while in contact with the obstacle W, thereby smoothly guiding the obstacle W to the contact portion 23.

[0049] When an obstacle W is detected to be in contact with and pressed against the sensor arm 51, the sensor arm 51 is positioned to coincide with the outer edge of the first work arm 21 or to be inside the outer edge of the first work arm 21 and outside the rotational diameter of the first cutting blade 24, which is the work part. In other words, the first cutting blade 24 can work at a position as close to the obstacle W as possible. Furthermore, when the obstacle W, which is sandwiched between the first work arm 21 and the second work arm 31 and heading towards the contact part 23, passes to the side of the first cutting blade 24, which is the work part, the sensor arm 51 in the detected state does not protrude laterally from the work part, so it does not hinder the work part from getting as close to the obstacle W as possible. Therefore, the first cutting blade 24 and the second cutting blade 34 can cut the grass growing around the obstacle W as close to the obstacle W as possible without the sensor arm 51 getting in the way.

[0050] In this embodiment of the invention, when an obstacle W heading toward the contact portion 23 passes to the side of the working portions, namely the first cutting blade portion 24 and the second cutting blade portion 34, the first working arm 21, the second working arm 31, and the sensor arm 51 are the ones that contact the obstacle W. Therefore, the obstacle W can be guided to the contact portion 23 along the outer circumference of the first working arm 21 and the outer circumference of the second working arm 31.

[0051] Since the horizontally rotating sensor arm 51 is equipped with a curved portion 34, the sensor arm 51 can be positioned along the curve even when the outer edge of the first work arm 21 to which the sensor arm 51 is attached is curved. Furthermore, in a plan view of the detection state, it can be positioned so as to almost coincide with the edge of the first cutting blade portion 24, which is the work portion, so that the sensor arm 51 does not protrude from the first cutting blade portion 24 towards the obstacle W, thereby preventing excessive pressing force from being applied to the sensor arm 51 and the obstacle W. Since the tip of the sensor arm 51, which is composed of multiple sensor arms, does not protrude significantly outward compared to when it is composed of only one sensor arm, it requires less installation space. This allows for efficient use of space and proper placement of components.

[0052] When an obstacle W comes into contact with the sensor arm 51, the sensor arm 51 rotates backward. As a result, the first sensor 52A, which is installed behind the sensor arm 51, is pushed via the contact portion 53A and enters a detection state. In this embodiment, the sensor arm 51 is provided along the front outer circumference of the first work arm 21, but it may also be provided along the front outer circumference of the second work arm 31 to perform a similar function.

[0053] The sensor arm 51 of the detection unit 5 is composed of multiple first sensor arms 511 and second sensor arms 512. However, since the first sensor arm 511 and the second sensor arm 512 are connected to each other, only one sensor is needed to emit a signal. Therefore, the wiring and circuits for sending the signal, as well as the internal program of the control unit that processes this signal, can be simplified. Furthermore, by connecting multiple sensor arms 51, the travel distance required for rotation of the tip of each sensor arm can be shortened. When an obstacle W makes contact and presses against each sensor arm 51, the variation in sensor detection accuracy caused by the difference in distance from each pivot point 511a, 512a to the position where the obstacle W presses against it can be minimized as much as possible, thereby improving the reliability of obstacle W detection.

[0054] The rotation of the first sensor arm 511 is transmitted to the second sensor arm 512 via the connecting part 55, causing the second sensor arm 512 to rotate in the same direction. Furthermore, if an obstacle W presses against the second sensor arm 512, causing the second sensor arm 512 to rotate, the rotation of the second sensor arm 512 is transmitted to the first sensor arm 511 via the connecting part 55, causing the first sensor arm 511 to rotate in the same direction and activate the switch.

[0055] Each sensor arm 51 (first sensor arm 511, second sensor arm 512) rotates horizontally, and multiple sensor arms are arranged so that parts of them overlap horizontally. Because there are no horizontal gaps or steps between the sensor arms 51 (first sensor arm 511, second sensor arm 512), obstacles W cannot get caught or snagged. In the embodiment of the present invention, the obstacle W slides horizontally relative to the sensor arm 51 during the operation, so this point is important.

[0056] To rotate the first work arm 21 and the second work arm 31 from a receiving position (first position) to a discharge position (second position), or from a discharge position (second position) to a receiving position (first position), the rod 141 of the operating means 14 is extended or retracted. The sensor arm 51 is used to control the operation of this rod 141. The extension and retraction of the rod 141 of the operating means 14 causes the first working arm 21 and subsequently the second working arm 31 to rotate around the obstacle W, thereby preventing damage from collisions between the arms and the obstacle W. The sensor arm 51 is a sensing mechanism that allows the device to actively rotate in response to an obstacle W.

[0057] 52B is a second sensor. 53B is a contact part. The second sensor 52B is installed near the pivot axis 12 of the first work arm and is installed so as to be able to contact the contact part 53B installed near the pivot axis 12 of the second work arm 31. Since the second sensor 52B and the contact part 53B are installed near the pivot axis 12, they can be kept away from the work parts, the first cutting blade section 24 and the second cutting blade section 34. Therefore, it is possible to prevent false detection or damage caused by grass or other debris around the obstacle W coming into contact with the second sensor 52B.

[0058] The contact portion 53B contacts the second sensor 52B when the first work arm 21 and the second work arm 31 are relatively closed and their tips come into contact. Conversely, the contact portion 53B does not come into contact with the second sensor 52B when the first work arm 21 and the second work arm 31 are relatively open and their tips are not in contact. The second sensor 52B and the contact portion 53B are positioned near the pivot axis 12 of the first work arm and near the pivot axis 12 of the second work arm 31, respectively, so as to be in this relative position. The second sensor 52B can detect the relative opening and closing of the first work arm 21 and the second work arm 31 by whether or not it comes into contact with the contact portion 53B.

[0059] The second sensor 52B detects whether the second work arm 31 and the first work arm 21 are in a closed state and are in contact with each other, or whether the second work arm 31 and the first work arm 21 are in an open state and are not in contact with each other. The second sensor 52B can emit a signal indicating whether or not the second work arm 31 and the first work arm 21 have rotated relative to each other by contacting or not contacting the contact portion 53B.

[0060] The second sensor 52B takes an open position 523, where the first work arm 21 is open relative to the second work arm 31, and a closed position 524, where the first work arm 21 is closed relative to the second work arm 31, as shown in the circuit diagrams in Figures 12 to 16. The second sensor 52B switches the electrical circuit inside the second sensor 52B based on whether or not it is in contact with the contact portion 53B, thereby detecting the opening and closing of the first work arm 21 relative to the second work arm 31. When the first work arm 21 is in the open position 523 and when it is in the closed position 524 as shown in Figures 12 to 16, it is detected that the first work arm 21 has come into contact with the second work arm 31.

[0061] The contact portion 53B is a so-called surface. Since the contact portion 53B is located near the pivot axis 12, which is the pivot point of the second work arm 31, it rotates together with the second work arm 31. By changing the protruding or curved shape of the contact portion 53B, the timing of the signal emitted by the second sensor 52B can be changed. In addition, the contact portion 53B may be a contact piece made of a so-called cam piece, in addition to the embodiment. In this case, the contact portion 53B makes contact with the second sensor 52B by bringing the peripheral edge that protrudes from the second work arm 31 toward the first work arm side into contact with the second sensor 52B, thereby allowing the second sensor 52B to detect the open / closed state of the second work arm 31 and the first work arm 21. The second sensor 52B is pressed via the contact portion 53B and detects that the second work arm 31 and the first work arm 21 have closed relative to each other and are in contact.

[0062] 52C is a third sensor. The third sensor 52C is installed near the pivot axis 12 of the second base member 112(11). 53C is a contact portion. The contact portion 53C is located on the upper part of the first work arm 21 and near the pivot axis 12, which serves as the pivot point. The contact portion 53C is integrally formed with the first work arm 21 by a boss provided coaxially with the pivot axis 12, and rotates together with the first work arm 21. The third sensor 52C can emit a signal indicating whether or not the first working arm 21 has rotated relative to the second base member 112(11) by contacting the contact portion 53C.

[0063] The third sensor 52C detects whether the first working arm 21 is in the first position. Figures 14 to 16 illustrating the electrical circuit of an embodiment of this invention show a detection position 525 where, when the circuit is made conductive by the third sensor 52C, it is detected that the first work arm 21 is in the second posture. In contrast, the detection position 525 shown in Figures 12 to 13 is where, when the circuit is disconnected by the third sensor 52C, the circuit recognizes that the first work arm 21 is in the first posture, where it does not rotate relative to the second base member 112(11). The detection position 525 for the second posture is where the position of the second work arm 31 is detected by the third sensor 52C. The portion of the contact portion 53C that contacts the third sensor 52C is made of a planar member in this example, but it may also be a so-called cam piece. By changing the shape of the peripheral edge of the contact surface of the contact portion 53C, the timing of the signal emitted by the third sensor 52C can be changed.

[0064] The configuration of the hydraulic and electrical circuits will be described. As shown in Figures 9 to 11, which represent the fluid circuit diagram, the operating means 14, also called an actuator or cylinder, consists of a bottom chamber 143 and a rod chamber 142. When hydraulic pressure flows into the bottom chamber 143 and the rod chamber 142, the rod 141 of the actuator 14 extends and retracts. The actuator 14 rotates the first working arm 21 by extending and retracting the rod 141. 73 is a storage tank. Storage tank 73 stores a fluid. In this embodiment, the fluid is oil, which is a liquid.

[0065] 74 is a fluid pressure source (pump). The fluid pressure source (pump) 74 is connected to the storage tank 73 and sends the hydraulic pressure from the storage tank 73 to the downstream side. 75 is the first switching valve (first control valve). The first switching valve 75 is connected to the downstream side of the fluid pressure source (pump) 74 via the supply pipeline 71a. The first switching valve (first control valve) 75 can be switched between a pumping position 751, which pumps fluid to the actuator 14 located downstream of the first switching valve (first control valve) 75, and a no-load position 752, which does not pump fluid to the actuator 14. 76 is a second switching valve. The second switching valve 76 is located downstream of the first switching valve 75 and upstream of the actuator 14, and is in communication with it via the supply pipeline 71b.

[0066] The second switching valve (second control valve) 76 communicates with the bottom chamber 143 of the actuator 14 and the first switching valve (first control valve) via a supply pipeline 71c. The second switching valve (second control valve) 76 can be switched between a shut-off position 761 that shuts off the fluid flow from the actuator 14 to the first switching valve (first control valve) 75, and an open position 762 that allows fluid to freely enter and exit between the actuator 14 and the first switching valve (first control valve) 75. The rod-side chamber 142 of the actuator 14 is in communication with the first switching valve (first control valve) 75 via the return pipe 72a. The first switching valve (first control valve) 75 is connected to the storage tank 73 by a return pipe 72b. A relief valve 77 is provided between the supply pipe 71c and the return pipe 72a. Details of the relief valve 77 will be described later.

[0067] The configuration of the electrical circuit will be explained with reference to Figures 12 to 16. The first sensor 52A detects the movement of the sensor arm 51 due to contact with an obstacle W. The first sensor 52A can take on a contact position 521 and a non-contact position 522. By switching to either the contact position 521 or the non-contact position 522, the electrical circuit is selectively branched to either a circuit leading to the first switching valve 75 or a circuit leading to the second switching valve 76.

[0068] The second sensor 52B detects whether the first work arm 21 and the second work arm 31 are closed and in contact with each other. The second sensor 52B can take on an open position 523 in which the first work arm 21 and the second work arm 31 are relatively open and not in contact, and a closed position 524 in which the first work arm 21 and the second work arm 31 are relatively closed and in contact. By switching the second sensor 52B to either the open position 523 or the closed position 524, the first sensor 52A is switched to the non-contact position 522, and the electrical circuit that branched to the first switching valve 75 side is branched again into an open position 523, which is a circuit that goes towards the second switching valve 76 side, and a closed position 524, which is a circuit that goes towards the first switching valve 75 side.

[0069] The third sensor 52C detects whether the second working arm 31 is in the first position. It is possible to interrupt the circuit leading to the first switching valve 75 by branching it with the closed position 524. If the second working arm 31 is in the first position, the third sensor 52C can interrupt the circuit leading to the first switching valve 75, and if the second working arm 31 is in the second position, it can connect the circuit leading to the first switching valve 75.

[0070] The actuator 14 drives the rotational movement of the first work arm 31 by fluid pressure. The fluid pressure source 74 can supply fluid pressure to the actuator 14 via the supply pipelines 71a, 71b, and 71c. The return pipelines 72a and 72b return the fluid pressure from the actuator 14 to the storage tank 73. The second switching valve 76 is positioned between the actuator 14 and the first switching valve 75, and can be switched between two positions: a shut-off position 761, as shown in Figures 9 and 11, which allows fluid to move from the first switching valve 75 (which is a check circuit) to the actuator 14 while blocking fluid from flowing from the actuator 14 to the first switching valve 75; and an open position 762, as shown in Figure 10, which allows fluid to freely flow in and out between the actuator 14 and the first switching valve 75.

[0071] The relief valve 77 can create a communication state between the supply pipeline 71c and the return pipeline 72a when the pressure in the supply pipeline 71c increases, as shown in Figure 9, when the second switching valve 76 is in the shut-off position 761 and the first switching valve 75 is in the open position 762. Furthermore, as shown in Figure 11, the relief valve 77 can create a communication state between the supply pipeline 71c and the return pipeline 72a when the pressure in the supply pipelines 71a, 71b, and 71c increases, as shown in Figure 11. When the relief valve 77 connects the supply pipeline 71c and the return pipeline 72a, no fluid pressure is applied to the actuator 14, allowing the actuator 14 to move freely.

[0072] The first switching valve 75 is located between the fluid pressure source 74 and the second switching valve 76, and can be switched between a pumping position 751, which pumps fluid to the actuator 14, and a no-load position 752, which does not pump fluid to the actuator 14. The relief valve 77 can establish communication between the supply pipeline 71c and the return pipeline 72a regardless of the pressure position 751 and the no-load position 752 of the first switching valve 75.

[0073] This section explains the relationship between the orientation of the grass-cutting device A, its hydraulic circuit, and its electrical circuit. The grass-cutting device A according to this embodiment of the invention sequentially takes on postures a to e, which represent the device posture. Depending on the posture, the hydraulic circuit sequentially takes on states a to c, and the electrical circuit sequentially takes on states a to e.

[0074] (Posture a showing the device orientation) This section explains the relationship between the posture of the grass-cutting device A, as shown in posture a, and the hydraulic and electrical circuits. In posture a, which indicates the posture of the grass cutting device A, the first working arm 21 is in a receiving posture (first posture), as shown in Figures 1 and 4. The sensor arms 51 (511, 512) are not detecting any obstacles W. The first working arm 21 is in contact with the second working arm 31. The first working arm 21 and the second working arm 31 are in their normal working posture, the first posture (receiving posture).

[0075] (Hydraulic circuit a) In posture a, which shows the device posture, the hydraulic circuit is in the state of hydraulic circuit a as shown in Figure 9. The first control valve 75 is in the no-load position 752, and the second control valve 76 is in the shut-off position 761. Although both the first switching valve (control valve) 75 and the second switching valve (control valve) 76 are conductive, the first control valve 75 in the no-load position 752 causes the fluid pressure generated by the fluid pressure source 74 to connect from the supply pipeline 71a to the return pipeline 72b which communicates inside the no-load position 752. Therefore, the fluid pressure does not flow from the fluid pressure source 74 to the supply pipeline 71b. Furthermore, the check circuit in the shut-off position 761 prevents the fluid in the bottom chamber 143 and the supply pipeline 71c from flowing towards the supply pipeline 71b, thus restricting the contraction of the actuator (cylinder) 14. In other words, the first working arm 21 and the second working arm 31 shown in Figures 1 and 4 can maintain the first posture (acceptable posture). As shown in Figures 1, 4, 9, and 12, when the first sensor 52A does not detect an obstacle W, the second sensor 52B detects contact between the second work arm and the first work arm, and the third sensor 52C detects that the second work arm is in the first position, the first switching valve (first control valve) 75 is switched to the no-load position 752, and the second switching valve (second control valve) 76 is switched to the shut-off position 761.

[0076] (Electrical circuit a) In the device orientation a, the electrical circuit is in the state shown in Figure 12. The first sensor 52A is in the non-contact position 522. The second sensor 52B is in the closed position 524 because the first work arm 21 and the second work arm 31 are relatively closed and in contact. The third sensor 52C does not detect the detection position 525 because the second work arm 31 is not in the second orientation (dischargeable orientation). Therefore, no voltage is applied to the first switching valve 75 and the second switching valve 76, and the first switching valve 75 is returned to the no-load position 752, while the second switching valve 76 is switched to the shut-off position 761.

[0077] (Position b showing the device's orientation) This section explains the relationship between the posture of the grass-cutting device A, the hydraulic circuit, and the electrical circuit in posture b, which represents the device's orientation. In posture b, which shows the posture of the grass cutting device A, the sensor arms 51 (511, 512) have detected an obstacle W, as shown in Figure 5. The first working arm 21 is in contact with the second working arm 31. This represents the first posture (acceptable posture) where the first working arm 21 and the second working arm 31 are in their normal working posture.

[0078] (Hydraulic circuit b) In posture b, which shows the device posture, the hydraulic circuit is hydraulic circuit b as shown in Figure 10. The first control valve 75 is in the no-load position 752, and the second control valve is in the open position 762. The fluid pressure generated from the fluid pressure source 74 is returned to the storage tank 73 by the no-load position 752, and no pressure is applied to the actuator 14. The rod side chamber 142 of the actuator 14 and the bottom The interior chamber 143 on the side of the tube is in communication with the second switching valve 76 and the first control valve 75, allowing fluid to flow between them, and the rod 141 of the actuator 14 is able to extend and retract freely.

[0079] (Electrical circuit b) In posture a, which shows the device's orientation, the electrical circuit is in state b, as shown in Figure 13. The first sensor 52A is in contact position 521 because the sensor arm 51 (511, 512) is rotating due to being pressed against the obstacle W. The second sensor 52B is in closed position 524 because the first work arm 21 and the second work arm 31 are closed and in contact with each other. The third sensor 52C does not detect position 525 because the second work arm 31 is not in the second orientation (dischargeable orientation). In the electrical circuit, power is supplied to the second switching valve (control valve) 76 via the first sensor 52A located at the contact position 521, so the second switching valve (control valve) 76 switches to the open position 762. In contrast, no electrical force is applied to the first switching valve 75, so the first switching valve 75 is in the unloaded position 752, which is its return position. Therefore, the actuator (cylinder) 14 is in a state of free extension and retraction (displaceable state) without fluid pressure, and the pressure of the obstacle W against the first arm 21 as the machine moves can cause the first arm 21 to rotate to the rear.

[0080] (Position c showing the device's orientation) This section explains the relationship between the posture of the grass-cutting device A, the hydraulic circuit, and the electrical circuit in posture c, which represents the device's orientation. In posture c, which shows the posture of the grass cutting device A, the sensor arms 51 (511, 512) have detected an obstacle W, as shown in Figure 6. Since the obstacle W is sandwiched between the first work arm 21 and the second work arm 31, the first work arm 21 is separated from the second work arm 31. This shows the state in which the first work arm 21 and the second work arm 31 have transitioned from the first posture (receiving posture), which is the normal working posture, to the second posture (discharging posture) and are in the process of rotating. The sensor detection switches the switching valve (control valve), and the first work arm 21 and the second work arm 31 are in a state where they can rotate freely.

[0081] (Hydraulic circuit b) In posture c, which shows the device orientation, the hydraulic circuit is hydraulic circuit b as shown in Figure 10. The first control valve 75 is in the no-load position 752, and the second control valve is in the open position 762. Details of hydraulic circuit b are as described above in (hydraulic circuit b), so a repeated explanation will be omitted.

[0082] (Electrical circuit c) In the device orientation c, the electrical circuit is in the state shown in Figure 14. The first sensor 52A is in contact position 521. The second sensor 52B is in open position 523 because the first work arm 21 and the second work arm 31 are relatively open with the obstacle W in between. The third sensor 52C detects position 525 because the second work arm 31 is gripping the obstacle W with the first work arm 21 and has rotated horizontally to the rear, resulting in the second orientation (dischargeable orientation). In the electrical circuit, power is supplied to the second switching valve (control valve) 76 via the contact position 521 of the first sensor 52A, switching it to the open position 762. In contrast, the first switching valve 75 is in the no-load position 752 because no voltage is applied to it. Therefore, the actuator (cylinder) 14 is in a state of free extension and retraction (displaceable state) without fluid pressure, and following the above-mentioned posture b and the state of hydraulic circuit b and electrical circuit b, the rotation of the first arm 21 toward the rear due to the pressing of the obstacle W can be continued.

[0083] (Position d showing the device's orientation) This section explains the relationship between the posture of the grass-cutting device A, the hydraulic circuit, and the electrical circuit in posture d, which represents the device's orientation. In posture d, which indicates the posture of the grass cutting device A, as shown in Figure 7, the first working arm 21 and the second working arm 31 are in the second posture, and the sensor arm 51 (511, 512) has not detected the obstacle W (this is the case when the obstacle W is separated from the sensor arm 51 (511, 512) when the first working arm 21 is rotated). The obstacle W is sandwiched between the first working arm 21 and the second working arm 31, and the first working arm 21 is separated from the second working arm 31. The first working arm 21 and the second working arm 31 are in a state of rotation from the first position (receiving position), which is the normal working position, to the second position (discharging position).

[0084] (Hydraulic circuit b) In position d, which shows the device orientation, the hydraulic circuit is hydraulic circuit b as shown in Figure 10. The first control valve 75 is in the no-load position 752, and the second control valve is in the open position 762. Details of hydraulic circuit b are as described above in (hydraulic circuit b), so a repeated explanation will be omitted.

[0085] (Electrical circuit d) In the orientation d of the device, the electrical circuit is the electrical circuit d shown in Figure 15. Since the obstacle W is away from the sensor arm 51, the first sensor 52A is in the non-contact position 522. The second sensor 52B is in the open position 523 because the first work arm 21 and the second work arm 31 are open to each other. The third sensor 52C detects the detection position 525 because the second work arm 31 is in the second orientation (dischargeable orientation). Since the second switching valve (control valve) 76 is electrically connected via the first sensor 52A and the second sensor 52C, the second switching valve (control valve) 76 is in the open position 762. Therefore, the actuator (cylinder) 14 is in a state of free extension and retraction (a state of free displacement).

[0086] In the example posture d, the obstacle W is separated from the sensor arm 51 and the first work arm 21, and the first work arm 21 is not pushed backward, so the actuator 14, which is in a freely extendable / extendable state, does not extend or extend. As the machine moves, the sensor arm 51 and the first work arm 21 are pushed again by the obstacle W, resulting in the state described above as posture c, and the first work arm 21 rotates backward. Therefore, in the second posture, even if the state of posture c and posture e alternates depending on the contact state between the obstacle W and the sensor arm 51 and the first work arm 21, the actuator 14 will not extend or extend unless an external force, such as the obstacle W, acts on the rod 141 to rotate the first work arm 21. In other words, when the sensor arm 51 is being pushed by an obstacle W, or when the first work arm 21 is in the second position and the first work arm 21 and the second work arm 31 are relatively open, the second switching valve (control valve) 76 is in the open position 762, so that the first work arm 21 can rotate horizontally freely regardless of fluid pressure.

[0087] (Position e showing the device's orientation) This section explains the relationship between the posture of the grass-cutting device A, the hydraulic circuit, and the electrical circuit in posture e, which represents the device's orientation. In posture e, which shows the posture of the grass cutting device A, the sensor arms 51 (511, 512) are not detecting the obstacle W, as shown in Figure 8. The first working arm 21 is in contact with the second working arm 31. Both the first working arm 21 and the second working arm 31 are rotated to the second position (dischargeable position). In other words, after the tips of the first working arm 21 and the second working arm 31, with the obstacle W in between, have both rotated backward to the second position (dischargeable position), the obstacle W has been discharged from the first working arm 21 and the second working arm 31 and separated from them, and the first working arm 21 and the second working arm 31 are in a closed position.

[0088] (Hydraulic circuit c) In position e, which shows the orientation of the device, the hydraulic circuit is hydraulic circuit c as shown in Figure 11. The first control valve 75 is in the pumping position 751, and the second control valve 76 is in the shut-off position 761. The fluid pressure generated from the fluid pressure source 74 is pumped to the second switching valve 76 via the supply pipeline 71a and supply pipeline 71b by the pumping position 751. Since the supply pipeline 71a and supply pipeline 71b at the pumping position 751 are not in communication with the return pipeline 72a and return pipeline 72b, the fluid is not returned to the storage tank 73. In other words, the upstream and downstream sides of the fluid are separate circuits. With the second control valve 76 in the shut-off position 761, which is a check circuit, the fluid pressure sent from the fluid pressure source 74 is sent to the bottom chamber 143 of the actuator 14, which is the downstream side, without being interrupted. The fluid in the rod-side chamber 142 returns to the storage tank 73 via the downstream return pipe 72a, the first control valve 75, and the return pipe 72b. As a result, the rod 141 of the actuator 14 protrudes, allowing the actuator 14 to be extended.

[0089] (Electrical circuit e) The electrical circuit in orientation e, which indicates the orientation of the device, is shown in Figure 16. The first sensor 52A is in the non-contact position 522 because the sensor arm 51 (511, 512) is not being pressed against the obstacle W. The second sensor 52B is in the closed position 524 because the first work arm 21 and the second work arm 31 are closed and in contact with each other. The third sensor 52C detects the detection position 525 because the second work arm 31 is in the second posture (dischargeable posture). In the electrical circuit e, the first switching valve 75 is switched to the pressurized position 751 by conducting and applying power to it via the first sensor 52A to the third sensor. Since the conduction state of the second switching valve 76 is released from the first switching valve 75, it returns to the shut-off position 761 without any electrical application. The actuator (cylinder) 14 is driven in the extension direction, returning the first work arm 21 and the second work arm 31 to the first position (receiving position).

[0090] The operation of the grass cutting device A will now be explained. As shown in Figures 1 to 8, the grass cutting device A is driven by being pushed or pulled forward in the direction of travel by the traveling body to cut grass. Obstacles W may be present during operation. The first elastic body 41 biases the second work arm 31 toward the first work arm 21, so that the first work arm 21 and the second work arm 31 are close together and their ends are closed. Also, the first work arm 21 is directed forward by the operating means 14. At the same time, the second work arm 31 is pushed by the first work arm 21 and is directed forward against the biasing force of the second elastic body 42. Therefore, the first work arm 21 and the second work arm 31 are in a receptive position (first position).

[0091] (Posture a showing the device orientation) In a normal grass-cutting operation, as shown in Figures 1 and 4, the first elastic body 41 that biases the second working arm 31 toward the first working arm 21 is extended. At this time, the rod 141 of the operating means 14 is in an extended state. The sensor arms 51 (first sensor arm 511, second sensor arm 512) are not in contact with the obstacle W and are not detecting the obstacle W. The first working arm 21, the second working arm 31, and the sensor arm 51 assume a forward-facing position in the direction of travel, which is the receiving posture (first posture), and the traveling machine moves the grass cutting device A forward in the direction of travel. The electrical circuit at this time is the electrical circuit a shown in Figure 9, which forms the hydraulic circuit b.

[0092] If the grass-cutting device A encounters an obstacle W while moving, the obstacle W will come into contact with the second working arm 31, as shown in Figures 4 to 8.

[0093] (Position b showing the device's orientation) Figure 5 shows the moment when the obstacle W and the second working arm 31 come into contact. In the embodiment of this invention illustrated in Figure 4, the obstacle W is located between the hydraulic motor 242 positioned on the rotation axis of the cutting blade 241 of the first working arm 21 and the hydraulic motor 342 positioned on the rotation axis of the cutting blade 341 of the second working arm 31, and is in contact with the tips of the first working arm 21 and the second working arm 31. Furthermore, the obstacle W is pressing against the sensor arm 51, and the first sensor 52A is detecting that the obstacle W has come into contact with the first working arm 21.

[0094] As the vehicle moves forward from the state shown in Figure 4 and comes into contact with the obstacle W, it reaches the state shown in Figure 5. As shown in Figure 5, when the obstacle W comes into contact with the first work arm 21, the obstacle W also comes into contact with the sensor arm 51 and is detected, causing the sensor arm 51 to rotate backward. The first sensor 52A, which is installed behind the sensor arm 51, is pressed, and the electrical circuit is switched to the contact position 521, resulting in a detection state. That is, the electrical circuit becomes the state of electrical circuit b shown in Figure 13, and the hydraulic circuit forms the hydraulic circuit b shown in Figure 10.

[0095] When the first sensor 52A detects an electrical circuit b, the second switching valve 76, which is the solenoid valve of the hydraulic control valve of the operating means 14, is activated to the open position 762 to form the hydraulic circuit b, and the rod 141 of the operating means 14 is made retractable. Also, in this case, the first switching valve 75 remains in the unloaded position 752, so the first working arm 21 becomes freely rotatable. The sensor arm 51 is used to control the series of operations until the rod 141 is retracted.

[0096] (Position c showing the device's orientation) If the vehicle continues to travel from the state shown in Figure 5, it will reach the state shown in Figure 6. In the state shown in Figure 6, the first work arm 21 opens outward due to the pressure on the obstacle W caused by the movement of the mobile machine, and the obstacle W is positioned between the first work arm 21 and the second work arm 31. The obstacle W shown by the dashed line in Figure 6 is in a position where the mobile machine has moved further toward the contact portion 23, and the first work arm is in the process of rotating backward due to the pressure of the obstacle W. The second work arm 31 has moved to a second position, rotating to follow the first work arm 21.

[0097] When the obstacle W presses against the sensor arm 51 and enters the space between the first work arm 21 and the second work arm 31, the obstacle W causes the first sensor 52A, the second sensor 52B, and the third sensor 52C to enter a detection state, and the rod 141 of the operating means 14 to be retractable. As shown in Figure 6, the first work arm 21 then rotates backward, away from the second work arm 21, with the pivot axis 12 as the pivot point. At this time, the second elastic body 42 shortens, resulting in a further increase in repulsive force compared to the receiving posture (first posture). As shown in Figure 6, when the obstacle W moves relative to the contact portion 23, the second work arm 31 pivots towards the first work arm 21 due to the second elastic body 42. Therefore, the obstacle W is sandwiched between the first and second work arms while in contact with them. In other words, the electrical circuit forms the electrical circuit c shown in Figure 14, and the hydraulic circuit forms the hydraulic circuit b shown in Figure 10. Since the rod 141 of the operating means 14 is in a state where it can freely extend and retract, the first working arm 21 and the second working arm 31 connected to the first working arm 21 are passively rotated around the obstacle W by contact with the obstacle W, thereby preventing damage from the arms colliding with the obstacle W.

[0098] As shown in Figure 6, the second elastic body 42 brings the obstacle W into contact with the first working arm 21 and the second working arm 31, so that the cutting blades 241 and 341 can cut as close as possible to the periphery of the obstacle W. While the obstacle W is passing between the cutting blades 241, 341 of the first working arm 21 and the second working arm 31, the obstacle W can be efficiently fed towards the contact portion 23 or the vicinity of the pivot axis 12. Subsequently, the obstacle W is moved relative to the pivot axis 12, which is the pivot point of the first work arm 21 and the second work arm 31.

[0099] As shown in Figure 6, the grass-cutting device A moves forward with the obstacle W between the first working arm 21 and the second working arm 31. Then the obstacle W comes into contact with the contact portion 23 and the sensor arm 51 (first sensor arm 511, second sensor arm 512). At the same time, the obstacle W continues to move toward the pivot axis 12 and presses against the contact portion 23. Due to the pressing by the sensor arm 51, the first sensor 52A enters a detection state, and the first working arm 21 rotates around the pivot axis 12 as the obstacle W presses against the contact portion 23. The second working arm 31, which is connected to the first working arm 21, can also rotate in conjunction with the first working arm 21 due to the increased repulsive force of the second elastic body 42.

[0100] The mobile machine and the grass-cutting device A move forward further. As the mobile machine moves forward, the rod 141 of the operating means 14 retracts further, causing the first working arm 21 to rotate further backward around the pivot axis 12 as the center of rotation. The second working arm 31 is connected to the first working arm 21, which has been made capable of rotational drive, and therefore rotates in conjunction with the first working arm 21. In addition, although the second working arm 31 can rotate independently of the first working arm 21, it is biased toward the first working arm 21 by the second elastic body 42, so it rotates while gripping the obstacle W near the rotation axis 12 and the contact portion 23. As a result, the tips of the first working arm 21 and the second working arm 31 of the grass-cutting device A, which have come into contact with the obstacle W, face towards the rear.

[0101] (Position d showing the device's orientation) If the traveling machine changes its speed while moving from the state shown in Figure 6, or if the rotation of the first work arm 21 and the second work arm 31 is not properly performed due to further obstruction of rotation, the machine may reach the state shown in Figure 7. In this state, the first work arm 21 and the second work arm 31 are in the discharge-ready position (second position), the pressure on the sensor arm 51 by the obstacle W is released, and the first work arm 21 has rotated in the direction of opening relative to the second work arm 31. That is, the electrical circuit forms the electrical circuit d shown in Figure 15, and the hydraulic circuit forms the hydraulic circuit b shown in Figure 10. Although the conductive path of the electrical circuit d is changed compared to the cases of positions b and c, the hydraulic circuit remains unchanged from the cases of positions b and c, so the first work arm 21 can continue to rotate freely. In the second position, and when the first working arm 21 is open relative to the second working arm, even if the pressure on the sensor arm 51 is released, the hydraulic circuit configuration does not result in the operating means 14 being driven. Therefore, unexpected movements will not damage the obstacle W or the grass cutting device A.

[0102] (Position e showing the device's orientation) If the vehicle continues to move from the state shown in Figures 6 and 7, it will reach the state shown in Figure 8. As shown in Figure 8, as the vehicle moves forward, the obstacle W moves away from the contact point 23 facing the rear and towards the tips of the first work arm 21 and the second work arm 31, which are also facing the rear. Eventually, the obstacle W detaches from the tips of the first work arm 21 and the second work arm 31 towards the rear.

[0103] In the dischargeable posture (second posture) shown in Figure 8, as the mobile machine moves forward, the obstacle W detaches from the first work arm 21 and the second work arm 31. Upon detachment, the obstacle W pushes the second work arm 31 aside and moves relative to it towards the rear. Since the second work arm 31 is biased by the second elastic body 42, after the obstacle W pushes the second work arm 31 aside, it rotates again towards the first work arm 21.

[0104] When the obstacle W detaches from the first work arm 21 and the second work arm 31, the sensor arm 51 does not come into contact with the obstacle W and therefore does not detect the obstacle W. The first work arm 21 and the second work arm 31 are not sandwiching the obstacle W and are therefore in contact with each other in a closed position. In the dischargeable position (second position), when the sensor arm 51 no longer detects the obstacle W and the first work arm 21 and the second work arm 31 close to each other, the first sensor 52A takes the non-contact position 522 and the second sensor 52B takes the closed position 524, so the electrical circuit is in the state of electrical circuit e shown in Figure 16. Electrical circuit e causes the hydraulic circuit to form the state of hydraulic circuit c shown in Figure 11, and extends the rod 141 of the operating means 14. Then the first work arm 21 returns to the first position, which is the receiving position, with its tip pointing forward. The second working arm 31 moves along with the first working arm 21, which rotates due to the elastic force of the second elastic body 42, and returns to the first position.

[0105] (1) The effects and functions of the hydraulic circuit will be explained. As shown in Figure 10, when the first switching valve (control valve) 75 is in the no-load position 752, the first switching valve (control valve) 75 is in communication with the circuit on the pump (fluid pressure source) 74 side and the circuit on the tank 73 side. Furthermore, the circuits (supply lines 71b, 71c) connecting the first switching valve (control valve) 75 to the rod-side chamber 142 of the actuator (cylinder) 14 are in communication. In other words, the circuits (return lines 72a, 72b) leading to the rod-side chamber 142 of the actuator (cylinder) 14 are in communication with the pump 74 side and the tank 73 side. Therefore, the fluid pressure pumped from the pump 74 is returned to the tank 73 side without pressurizing the rod-side circuit 142 of the actuator 14. Furthermore, since the fluid pressure generated by the pump 74 is returned to the tank 73 side without being forcibly stopped, there is no need to add a control valve or the like to the circuit between the first switching valve (control valve) 75 and the pump 74 and the tank 73.

[0106] (2) In the embodiment of this invention, the pump 74 is always driven by power from the traveling machine, so there is no need to switch the power source or the fluid pressure generated by the pump 74. In other words, while the fluid pressure source (pump) 74 and the fluid storage tank (oil tank) 73 are common, the supply lines (71b, 71c) and return lines (72b, 72c) can be made into the simplest possible circuit configuration, making the entire device as simple as possible.

[0107] (3) As shown in Figure 9, when the first switching valve (control valve) 75 is in the no-load position 752, and the second switching valve (control valve) 76 is switched to the shut-off position 761, the fluid flow from the bottom chamber 143 of the actuator (cylinder) 14 toward the first switching valve (control valve) 75 is stopped. Therefore, the actuator 14 can maintain its current extension / retraction position without shortening. In other words, it maintains the first position (acceptable position), which is the position during normal operation.

[0108] (4) As shown in Figure 10, when the first switching valve (control valve) 75 is in the no-load position 752 and the second switching valve (control valve) 76 is switched to the open position 762, the fluid flow between the bottom chamber 143 and the first switching valve (control valve) 75 becomes freely accessible. That is, the rod-side chamber 142 and the bottom chamber 143 of the actuator (cylinder) 14 are in communication with the tank 73.

[0109] Furthermore, in the unloaded position 752, the first switching valve (control valve) 75 connects the rod-side chamber 142 and the bottom-side chamber 143 of the actuator (cylinder) 14. Consequently, the fluid pressure pumped from the pump 74 is returned to the tank 73, and no pressure is applied to the actuator 14. In addition, the rod 141 can be freely extended and retracted, and the first working arm 21 can be passively rotated from the receiving position (first position) to the discharge position (second position) by the pressure of the obstacle W (rotation of the first working arm 21 towards the discharge position (second position) due to the obstacle).

[0110] (5) As shown in Figure 11, when the first switching valve (control valve) 75 is in the pressurizing position 751, the first switching valve (control valve) 75 connects the circuits on the pump 74 side (71a, 71b, 71c) to the bottom chamber 143 of the actuator (cylinder) 14, and also connects the rod chamber 142 of the actuator (cylinder) 14 to the circuits on the tank 73 side (72a, 72b). Therefore, the fluid pressure pumped from the pump 74 is sent to the bottom-side circuits 143 (71a, 71b, 71c) of the actuator 14, allowing the rod 141 of the actuator 14 to extend. The fluid in the rod-side circuits 142 (72a, 72b) of the actuator 14 is returned to the tank 73 side via the first switching valve (control valve) 75.

[0111] At this time, the switching position of the second switching valve (control valve) 76, whether it is the shut-off position 761 or the open position 762, does not affect the drive of the extension operation of the actuator 14. In this embodiment of the invention, the second switching valve (control valve) 76 switches to the shut-off position 761, but does not obstruct the fluid flow from the shut-off position 75 of the first switching valve (control valve) toward the bottom chamber 143 (return operation from dischargeable position (second position) to receiving position (first position)).

[0112] (6) As shown in Figure 11, when the first switching valve (control valve) 75 is in the pressurized position 751, the second switching valve (control valve) 76 switches to the shut-off position 761 because the relay circuit is configured to operate the electrical circuits (details described later) that switch the two switching valves (control valves), the first switching valve (control valve) 75 and the second switching valve (control valve) 76, using three sensors (switches). This achieves the operation of (3) and the operation of (5) with a simple configuration. (If, for example, the second switching valve (control valve) 76 were to be set to the open position 762 in the case of (5) shown in Figure 11, a separate control device would be required, and it would not be a simple configuration.)

[0113] (7) With the configuration of the fluid pressure circuit in this embodiment of the present invention, the first work arm 21 and the second work arm 31 can be rotated by only one of the actuators 14. That is, by installing an elastic spring, the second work arm 31 is able to rotate in accordance with the first work arm 21.

[0114] (8) The actuator 14 can be switched between operation driving in the extension direction and free movement in the extension direction solely by the switching operation of the first switching valve (control valve) 75, which has two switching positions. Therefore, it is possible to easily switch between the forced return of the first working arm 21 to the acceptable position (first position) and the passive operation when an obstacle is caught.

[0115] (9) By simply blocking the outflow of pressure from the bottom chamber 143 of the actuator (cylinder) 14 at the shut-off position 761 of the second switching valve (control valve) 76, the shortening of the actuator 14 is prevented, thus simplifying the circuit configuration. (10) Three sensors, a first sensor 52A, a second sensor 52B, and a third sensor 52C, are used to switch the first switching valve (control valve) 75 and the second switching valve (control valve) 76. By connecting these three sensors and the two switching valves (control valves) with a relay circuit, the two switching valves (control valves) can operate without the need for a control device.

[0116] (11) The effects of electrical circuits will be explained. This section describes the state of the electrical circuit when the first work arm 21 and the second work arm 31, which are in their normal working positions, are in a receiving position (first position). As shown in Figure 12, since the first sensor 52A is not in contact with an obstacle W, the circuit is switched to the non-contact position 522 and connected to the circuit leading to the second sensor 52B.

[0117] The second sensor 52B detects that the second work arm 31 and the first work arm 21 are in a closed position and are in contact with each other, so it switches the circuit to the contact position (work arm closed position 524) and connects to the circuit leading to the third sensor. The third sensor does not conduct because the second work arm 31 is in an acceptable position (first position) (detecting that it is in an acceptable position (first position)). Consequently, the power supply connection (connected to both +12V and GND in the diagram) is severed to the first switching valve (control valve) 75 and the second switching valve (control valve) 76, and the first switching valve (control valve) 75 is switched to the no-load position 752, and the second switching valve (control valve) 76 is switched to the shut-off position 761, which are the return positions of the switching valves.

[0118] (12) The state of the electrical circuit when an obstacle W comes into contact with the sensor arm 51 (first sensor arm 511, second sensor arm 512) attached to the first work arm 21 will be explained. As shown in Figure 13, the first sensor 52A detects the sensor arm 51 which has rotated after coming into contact with an obstacle W, etc., and switches the circuit to the contact position 521, connecting to the circuit leading to the second switching valve (control valve) 76. As a result, the second switching valve (control valve) 76 is connected to the power supply and switches to the open position 762. After that, the fluid circuit enters the state shown in (4) in Figure 10. Since the first switching valve (control valve) 75 has lost its connection to the power supply, it is in the return position, the no-load position 752.

[0119] (13) When an obstacle W comes into contact with the sensor arm 51, the second work arm 31 and the first work arm 21 are in an open state, and the second work arm 31 rotates to the discharge-capable position (second position) side. In this state, as shown in Figure 14, the second sensor 52B switches on and connects the circuit to the second switching valve (control valve) 76 (working arm in the open position 523), and the third sensor becomes conductive with the first switching valve (control valve) 75 (second posture detection position). However, the first sensor 52A makes contact with the contact position 521 and connects the power supply to the circuit leading to the second switching valve (control valve) 76, so the second switching valve (control valve) 76 maintains the open position 762. In contrast, the first switching valve (control valve) 75 is disconnected from the power supply and is in the return position, the no-load position 752. The fluid circuit remains in state (4).

[0120] (14) The following describes the state described in (10) above (three sensors, the first sensor 52A, the second sensor 52B, and the third sensor 52C, are used to switch the first switching valve (control valve) 75 and the second switching valve (control valve) 76. These three sensors and the two switching valves (control valves) are connected by a relay circuit), where the sensor arms 51 (first sensor arm 511, second sensor arm 512) provided on the first work arm 21 are not in contact with the obstacle W, the second work arm 31 and the first work arm 21 are open, and the second work arm 31 has rotated to the discharge-ready position (second position) side. As shown in Figure 15, since the first sensor 52A is not in contact with an obstacle W, the circuit is switched to the non-contact position 522 and connected to the circuit leading to the second sensor 52B.

[0121] Since the second work arm 31 and the first work arm 21 are in the open position, and the second work arm 31 has rotated to the discharge-ready position (second position), the second sensor 52B detects non-contact (work arm in the open position 523). Therefore, the second sensor 52B, which is connected to the power supply on the GND side, connects its circuit to the second switching valve (control valve) 76, and the second switching valve (control valve) 76 remains connected to the power supply.

[0122] The fluid circuit can maintain the state in which the second switching valve (control valve) 76 remains in the open position 762. The third sensor detects that the second working arm 31 is not in the acceptable position (first position) and causes the first switching valve (control valve) 75 and the third sensor to become conductive (second position detection position 525). However, since the first switching valve (control valve) 75 does not become conductive with the power supply, it remains in the no-load position 752. As a result, the fluid circuit can maintain state (4).

[0123] (15) The first work arm 21 and the second work arm 31 are in a dischargeable position (second position), the obstacle W is separated from the sensor arm and the first sensor 52A does not detect contact with the obstacle, and the first work arm 21 and the second work arm 31 are closed. Specifically, as shown in Figure 8, the obstacle W is grasped between the first working arm 21 and the second working arm 31, then rotates as the machine moves forward, and the state in which the obstacle W is then separated from the first working arm 21 and the second working arm 31 is described.

[0124] As shown in Figure 16, the first sensor 52A is not in contact with an obstacle W, so the GND-side power supply circuit is switched to the non-contact position 522 and connected to the circuit leading to the second sensor 52B. The second work arm 31 and the first work arm 21 are in contact with each other, so the circuit is switched to the contact position (work arm in the closed position 524), and the GND-side power supply circuit is connected to the circuit leading to the third sensor.

[0125] The third sensor becomes conductive (detects that the second working arm 31 is in the discharge-ready position (second position), detection position 525) because the second working arm 31 is in the discharge-ready position (second position). Consequently, the second switching valve (control valve) 76 is disconnected from the power supply and returns to the shut-off position 761, and the first switching valve (control valve) 75 is switched to the pressurized position 751 by connecting to the power supply (connected to both +12V and GND in the figure). The fluid circuit enters the state described in (5) above, and the first working arm 21 and the second working arm 31 are driven to rotate to the receiving position (first position).

[0126] The effects and behaviors of hydraulic and electrical circuits will be explained. (1) The bottom chamber 143 of the actuator 14 is connected to the fluid pressure source (pump) 74 by supply lines 71a, 71b, and 71c, and the rod chamber 142 of the actuator 14 is connected to the storage tank 73 by return lines 72a and 72b. Second switching valves 76 are located in the supply lines 71b and 71c, and as shown in Figure 9 (hydraulic circuit a, posture a Figure 1, Figure 4, electrical circuit a Figure 12) and Figure 11 (hydraulic circuit c, posture e Figure 8, electrical circuit e Figure 16), when the second switching valves 76 are in the shut-off position 761, fluid cannot move from the bottom chamber 143 to the fluid pressure source 74.

[0127] (2) As shown in Figures 9 and 11, when the second switching valve 76 is in the shut-off position, the relief valve 77 operates in response to the pressure rise in the supply lines 71a, 71b, and 71c. This releases the fluid in the supply lines 71a, 71b, and 71c into the return lines 72a and 72b. In this embodiment of the invention, the pressure rise in the supply lines 71a, 71b, and 71c is assumed to be caused by an obstacle W or the like coming into contact with the first working arm 21 or the second working arm 31, and being forcibly pushed toward the second posture side. That is, the pressure in the supply lines 71a, 71b, and 71c between the bottom chamber 143 and the second switching valve 76 increases due to the rod 141 of the cylinder 14, which is the actuator 14, being pushed in the direction of shortening. Due to the pressure increase, the relief valve 77 operates, releasing the fluid (pressure) in the supply lines 71a, 71b, and 71c into the return lines 72a and 72b.

[0128] (3) When the relief valve 77 is operating, both the bottom chamber 143 and the rod chamber 142 of the actuator 14 are connected to the storage tank 73. Furthermore, since the bottom chamber 143 is in communication with the rod chamber 142, the actuator 14, which is a cylinder, is in a state of free extension and retraction (a state of free displacement). In accordance with the embodiment, the first working arm 21 or the second working arm 31, which is forcibly pressed to the second posture side, can rotate to the second posture side without resisting the obstacle W. Therefore, damage to the grass cutting device A, including the first working arm 21 or the second working arm 31, can be prevented. In this context, forced pressing refers to pressing that occurs when the respective sensors 52A, 52B, and 52C are not detecting anything and the respective switching valves 75 and 76 are not operating normally.

[0129] (4) As shown in Figure 10 (hydraulic circuit b, posture d Figure 7, electrical circuit d Figure 15), when the second switching valve 76 is in the open position and the first switching valve 75 is in the no-load position, even if there is a pressure increase in the supply lines 71a, 71b, and 71c, the supply lines 71a, 71b, and 71c and the return lines 72a and 72b are in communication within the first switching valve 75 in the no-load position, so the fluid in the supply lines 71a, 71b, and 71c is released into the return lines 72a and 72b. Furthermore, since the bottom side chamber 143 is in communication with the rod side chamber 142, the actuator 14, which is a cylinder, becomes free to extend and retract (displaceable) without operating the relief valve 77. In accordance with the embodiment, the first work arm 21 or the second work arm 31, which is forcibly pressed toward the second posture, can rotate toward the second posture without resisting the obstacle W (a normal operating state in the embodiment, in which the respective switching valves 75 and 76 are operated by the detection of each sensor 52A, 52B, and 52C).

[0130] (5) However, even under the normal operating conditions described above, if the pressure in the supply lines 71a, 71b, and 71c rises due to an abnormality such as the actuator 14 extending and retracting too quickly, the relief valve 77 will operate to prevent damage to the circuit and the device. (6) As shown in Figure 11 (hydraulic circuit c, position e Figure 8, electrical circuit e Figure 16), even when the first switching valve 75 is in the pressurized position, if the fluid pressure in the supply lines 71a, 71b, and 71c rises, the relief valve 77 can operate regardless of the switching position of the second switching valve 76 to release the pressure into the return circuit.

[0131] (7) The circuit configuration for controlling the drive and non-drive states of the actuator 14 is simplified while still realizing the drive mechanism and shock absorption mechanism for each arm. (8) In the embodiment, the actuator 14 has been described as a cylinder, but the first work arm 21 may be rotated using a fluid pressure motor. Furthermore, the extension and retraction movement of the actuator 14 as a cylinder and the rotation direction of the first work arm 21 are not necessarily limited to those exemplified.

[0132] In the embodiments of the present invention, the pivot axis 12, which is the pivot point axis for the first work arm 21 and the second work arm 31, can be the same axis. In the present invention, the first working arm 21 is rotated in accordance with the extension and retraction of the rod 141. The second working arm 31 rotates while being cushioned by the second elastic body 42, always attached to the first working arm 21.

[0133] In the embodiment of the present invention, the front side of the contact portion 23 can form a closed portion C when the first working arm 21 and the second working arm 31 are closed. While the mobile body moves forward, the extension and retraction of the rod 141 of the operating means 14 causes the first working arm 21 and subsequently the second working arm 31 to rotate around the obstacle W located within the closed section C, thereby preventing damage from collisions between the arms and the obstacle W. In the embodiment described, the sensor arm 51 is composed of two sensors, a first sensor arm 511 and a second sensor arm 512. However, it may also be composed of three or more sensor arms connected together. In this case, the travel distance required for the rotation of the tip of each sensor arm can be shortened, which can lead to a further improvement in the detection accuracy of the switch. In the diagram showing the electrical circuit of the example, the voltage is indicated as +12V, but the voltage is not limited to this and can be changed as appropriate depending on the voltage used. Furthermore, the electrical circuit can be configured by swapping the + side and the - side (GND), allowing for modifications to suit the specifications of the equipment being used. [Explanation of symbols]

[0134] 11 Base member 111 First base member 112 Second base member 12. Swivel axis 13 Arms 13A Front Arm 13B Rear Arm 14. Operating means (actuator, cylinder) 15 Stopper 21. First working arm 22. Swing restriction means guide (swing restriction means) 23 Contact part 24 1st cutting blade part (cutting blade, cutting blade part, working part) 31. Second working arm 32. Swivel restricting projection (swivel restricting means) 34 2nd cutting blade part (cutting blade, cutting blade part, working part) 41 First elastic body 42 Second elastic body 5. Detection Unit 51 Sensor Arm 511 First Sensor Arm 511a Pivot axis of the first sensor arm 512 Second Sensor Arm 512a Pivot axis of the second sensor arm 52A First Sensor 52B Second Sensor 52C Third Sensor 53A Contact part 53B Contact part 53C Contact part 71a Supply pipeline 71b Supply pipeline 71c supply pipeline 72a Return pipeline 72b Return conduit 73 tanks 74. Fluid pressure source (pump) 75. First switching valve (first control valve) 751 Pressure feeding position 752 No load position 76. Second switching valve (second control valve) 761 Blocking position 762 Open position 77 Relief valve A grass cutting device S work equipment W Obstacle

Claims

1. A first working arm is provided that can rotate around a pivot axis, A second work arm is provided separately from the first work arm and is rotatable about the pivot axis, A first sensor that detects when an obstacle comes into contact with the first working arm, A second sensor detects when the first work arm comes into contact with the second work arm, The system includes a third sensor that detects that the first working arm is in a first position, The first work arm and the second work arm are rotatable between a first posture in which the tips of the first work arm and the second work arm are facing forward, and a second posture in which the first work arm and the second work arm are facing completely backward, Depending on whether the first sensor, the second sensor, and the third sensor detect anything, the first work arm is switched between a state in which it can passively rotate between a first posture and a second posture, and a state in which it is forcibly rotated between a second posture and a first posture. When the second and third sensors detect something, the tip of the first work arm is made to maintain the first posture in which it is facing forward. When the first sensor and the second sensor detect an event, the first work arm is made passively rotatable from the first position to the second position. A grass cutting device characterized by the following features.

2. If at least the third sensor is in a detection state while the first work arm passively rotates from the first position to the second position, then passive rotation of the first work arm toward the second position is possible. The grass cutting device according to feature 1.

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