Grass cutting equipment

Abstract

To provide a grass mower which is capable of operating around an obstacle with a simplified configuration of a circuit for driving an arm.SOLUTION: A grass mower A comprises: a first work arm 21 which is capable of turning around a turning shaft 12; a second work arm 31 which is capable of turning between a first posture in which tips of the first work arm 21 and the second work arm 31 are oriented frontward and a second posture other than the first posture in which the first work arm 21 and the second work 31 arm are completely oriented backward; a first sensor 52A for detecting a contact of an obstacle with the first work arm 21; a second sensor 52B for detecting a contact of the first work arm 21 with the second work arm 31; and a third sensor 52C for detecting that the first work arm is in the first posture. The first work arm is switched between a state where the first work arm can be passively turned between the first posture and the second posture, and a state where the first work arm is forcibly turned between the second posture to the first posture, depending on the presence or absence of detections by the first sensor 52A, the second sensor 52B and the third sensor 52C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a grass cutting device. [Background technology]

[0002] Patent Document 1 has been published as a device for cutting vegetation on the ground around a post that is an obstacle. According to Patent Document 1, a mowing device adapted to be propelled by an associated vehicle includes a support, first and second arms, and first and second mower 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 mower element is attached to the first arm, and the second mower element is attached to the second arm. Each of the first and second arms is provided with a cylinder for pivoting drive, and these cylinders are in communication with each other. In addition, a hydraulic circuit that communicates the cylinders is provided with a plurality of various valves and an accumulator is used to realize mowing around the obstacle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Publication No. 2006 / 0026938A1 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the configuration of Patent Document 1 has a problem in that since there are many circuits for driving and cushioning the first and second arms, the configuration of the hydraulic circuits of the entire device is complicated. Therefore, the present invention has been made in consideration of the above-mentioned problems, and has an object to provide a grass cutting device that can work around obstacles by simplifying the configuration of the circuit that drives and damps the arm. The inventor proposed the body configuration of a grass cutting device in Japanese Patent Application No. 2020-119920 "Grass Cutting Device" and Japanese Patent Application No. 2020-134176 "Grass Cutting Device". The present invention proposes the mechanical, hydraulic, and electrical circuitry of these grass cutting devices. [Means for solving the problem]

[0005] The present invention relates to a first working arm provided so as to be rotatable about a rotation axis; a second work arm provided separately from the first work arm and rotatable about the rotation shaft; a first sensor that detects contact of the first work arm with an obstacle; a second sensor that detects contact of the first work arm with the second work arm; a third sensor that detects that the first work arm is in the first posture, the first work arm and the second work arm are rotatable between a first position, in which the tip ends of the first work arm and the second work arm face forward, and a second position, which is a position between the first position and the first work arm and the second work arm face completely backward, other than the first position, switching the first work arm between a state in which the first work arm can passively rotate between the first position and the second position and a state in which the first work arm can forcibly rotate between the second position and the first position depending on the presence or absence of detection by the first sensor, the second sensor, and the third sensor; A grass cutting device, relates to.

[0006] The present invention further comprises: When only the first sensor detects an abnormality, or when all of the first sensor, the second sensor, and the third sensor detect an abnormality, the first working arm is made passively rotatable. A grass cutting device, relates to.

[0007] The present invention further comprises: When only the second sensor detects the position, the first work arm is forced to rotate. A grass cutting device, relates to.

[0008] The present invention further comprises: When the second sensor and the third sensor detect the position, the first work arm is maintained in the first position. A grass cutting device, relates to. Effect of the Invention

[0009] According to the present invention, it is possible to provide a grass cutting device capable of working around obstacles by simplifying the configuration of the circuit that drives and damps the arm. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a grass cutting device according to an embodiment of the present invention, showing a first working arm in a receiving position (first position). The left side of the drawing is the front in the traveling direction, and the top of the drawing is the right side in the traveling direction, which is the traveling body side. [Diagram 2] 1 is a side view of a grass cutting device according to an embodiment of the present invention, with the back side facing forward in the direction of travel and the top side facing the right side in the direction of travel, which is the traveling machine body side. [Diagram 3] FIG. 2 is a front view of the grass cutting device according to the embodiment of the present invention, and is a cross-sectional view taken along line AA in FIG. 1, with a second fitting and an actuator partially cut away. [Figure 4] 1 is a plan view showing the operation of a grass cutting device according to an embodiment of the present invention; FIG. 2 shows a state in which the sensor arm does not detect an obstacle; FIG. 3 shows a state in which the first work arm is in contact with the second work arm; FIG. 4 shows a state in which the first work arm and the second work arm are in the first position (receiving position) which is the normal working position; FIG. 5 shows the first base member and link mechanism, and the second base member in cross section; and FIG. 6 shows position a, which indicates the device position. [Diagram 5]1 is a plan view showing the operation of a grass cutting device according to an embodiment of the present invention; FIG. 2 shows a state in which a sensor arm detects an obstacle; FIG. 3 shows a state in which a first work arm is in contact with a second work arm; FIG. 4 shows a state in which the first work arm and the second work arm are in a first position (receiving position) which is a normal working position; and FIG. 5 shows a cross section of the first base member and the second base member. FIG. 6 shows a position a indicating the device position. [Figure 6] FIG. 1 is a plan view showing the operation of a grass cutting device according to an embodiment of the present invention. FIG. 1 shows a state in which the sensor arm has detected an obstacle. FIG. 2 shows a state in which the first work arm has been separated from the second work arm. FIG. 3 shows a state in which the first work arm and the second work arm are in the middle of rotating from the first position (receiving position), which is the normal working position, to the second position (discharging position). The first work arm and the second work arm are freely rotatable due to switching of the switching valve (control valve) by sensor detection. For the sake of explanation, 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 device position. [Figure 7] FIG. 1 is a plan view showing the operation of a grass cutting device according to an embodiment of the present invention. It shows a state in which the sensor arm does not detect an obstacle (when an obstacle is separated from the sensor arm while the first work arm is being driven to rotate). It shows a state in which the first work arm is separated from the second work arm. It shows a state in which the first work arm and the second work arm are in the middle of rotating from the first position (receiving position), which is the normal working position, to the second position (discharging position). For the sake of explanation, 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 device position. [Figure 8] 1 is a plan view showing the operation of a grass cutting device according to an embodiment of the present invention; FIG. 2 shows a state in which the sensor arm does not detect an obstacle; FIG. 3 shows a state in which the first work arm is in contact with the second work arm; FIG. 4 shows a state in which both the first work arm and the second work arm have rotated to the second position (dischargeable position); FIG. 5 shows a case in which the obstacle has moved away from the first work arm and the second work arm after the first work arm and the second work arm have rotated to the second position (dischargeable position). For the sake of explanation, the first base member and the link mechanism are omitted, and the second base member is shown in cross section. This is position e, which shows the device position. [Figure 9]1 is a fluid pressure circuit diagram (hydraulic circuit diagram) of a grass cutting device according to an embodiment of the present invention (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] FIG. 1 is a fluid pressure circuit diagram (hydraulic circuit diagram) of a grass cutting device according to an embodiment of the present invention (circuit b when the device is in positions b, c, and d). The first control valve is in the no-load position, and the second control valve is in the open position. [Figure 11] 1 is a fluid pressure circuit diagram (hydraulic circuit diagram) of a grass mowing device according to an embodiment of the present invention (circuit c when the device is in position e). The first control valve is in the pumping position, and the second control valve is in the shutoff position. [Figure 12] This is a circuit diagram of a grass cutting device according to an embodiment of the present invention (electrical circuit a). This is the state of position a showing the device position. The first switching valve is in the no-load position, and the second switching valve is in the cut-off position. Neither the first switching valve nor the second switching valve is conductive. The actuator (cylinder) is contracted and restricted. [Figure 13] FIG. 1 is a circuit diagram (electrical circuit b) showing the state of electrical connections of the grass cutting device according to an embodiment of the present invention. This is a state of posture b showing the posture of the device. 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 energized via the first sensor. The actuator (cylinder) is in a freely extending and retracting state (freely displaceable state). [Figure 14] This is a circuit diagram (electrical circuit c) showing the state of electrical connections of the grass cutting device according to the embodiment of the present invention. This is the state of posture c showing the posture of the device. 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 energized via the first sensor. The actuator (cylinder) is in a freely extending and retracting state (freely displaceable state). [Figure 15] This is a circuit diagram (electrical circuit d) showing the state of electrical connections of the grass cutting device according to the embodiment of the present invention. This is the state of posture d showing the posture of the device. 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 conductive via the first sensor and the second sensor. The actuator (cylinder) is in a freely extending and retracting state (freely displaceable state). [Figure 16]This is a circuit diagram (electrical circuit e) showing the state of electrical connections of the grass cutting device according to an embodiment of the present invention. This is the state of posture e showing the posture of the device. The first switching valve is in the pressure-feeding position, and the second switching valve is in the cut-off position. The first switching valve is turned on via the first sensor to the third sensor. The actuator (cylinder) is driven to the extension side, and the first working arm and the second working arm are returned to the first posture (receiving posture). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A denotes a grass cutting device serving as a working machine. The grass cutting device A is attached to a traveling machine body (not shown) such as a tractor by one or more grass cutting device attachment arms (not shown). The grass cutting device A is connected to a boom device, etc. The boom device (telescopic means) is similar to the "Working Machine" of Patent Application No. 2019-194694 and the "Working Machine" of Patent Application No. 2020-14070, and is connected by the connecting mechanism of the "Detachable Mechanism and Working Machine Equipped with Detachable Mechanism" of Patent Application No. 2020-84471. Note that the grass cutting device A of the present application is not limited to only the exemplified boom device (telescopic means) as shown in the illustration of the "Grass cutting device" of the prior application Patent Application No. 2019-187386 (Patent Application No. 2018-087440).

[0012] In the grass cutting device A, reference numeral 11 denotes a base member. The base member 11 is made up of a first base member 111 and a second base member 112. Reference numeral 21 denotes a first working arm, and 31 denotes a second working arm. Reference numeral B denotes a parallel link mechanism. The first work arm 21 and the second work arm 31 are attached to a traveling machine body consisting of a tractor or the like via a grass cutting device mounting arm, also called a boom device, which is made up of multiple members, and the grass cutting device A works by being positioned in front of, behind or to the side of the traveling machine body. When attached 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 attached to the side of the traveling body via multiple grass cutting device attachment arms, or to the rear and side of the traveling body via grass cutting device attachment arms that can move left and right on the traveling body, or to the rear and side of the traveling body via grass cutting device attachment arms that can move left and right. Furthermore, the grass cutting device A may be attached directly to the traveling body or a three-point link lifting device that the traveling body has, without using a grass cutting device attachment arm. The grass cutting device A is capable of pinching an obstacle W between a first work arm 21 and a second work arm 31 which are provided rotatably in a scissors shape, and each of the first work arm 21 and the second work arm 31 can rotate to perform work. The tip sides of the scissors-shaped first work arm 21 and second work arm 31 away from the rotation fulcrum axis are directed in the direction of travel. The tip sides of the illustrated first work arm 21 and second work arm 31 are curved in an arc shape.

[0014] The base member 11 is provided 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 provided at one end on the tip side of the parallel link mechanism B. The second base member 112 (11) is horizontally movable relative to the first base member 111 (11) provided on the other end side of the parallel link mechanism B via the parallel link mechanism B.

[0015] Reference numeral 12 denotes a pivot shaft. The pivot shaft 12 is provided on the second base member 112 and is a vertical axis oriented in a direction intersecting the work surface. Each of the first work arm 21 and the second work arm 31 is capable of horizontal rotation about the pivot shaft 12 as a fulcrum axis. Furthermore, depending on the rotational position of the first work arm 21 and the second work arm 31, they take an acceptance position (first position) and an unloading position (second position). The first working arm 21 is provided so as to be rotatable between a first position and a second position about a rotating shaft 12. The second working arm 31 is provided separately from the first working arm 21, and is provided so as to be rotatable between the first position and the second position about the rotating shaft 12. These positions will be explained later.

[0016] The stopper 15 is provided on the second work arm 31. Reference numeral 16 denotes a first fitting and 17 a second fitting. The first fitting 16 and the second fitting 17 are attached so as to be connected to each other and to connect the second base member 112 (11) and the first working arm 21 around the rotating shaft 12. The first fitting 16 and the second fitting 17 rotate near the periphery of the rotating shaft 12 while remaining connected to each other as the first working arm 21 rotates about the rotating shaft 12.

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

[0018] The parallel link of the parallel link mechanism B is composed of a front arm 13A on the side closer to the obstacle W that contacts the working arm when it comes into contact with the obstacle, and a rear arm 13B on the side farther from the obstacle W. The parallel link mechanism B is rotatably attached to the first base member 111 (11) at one end and to the second base member 112 (11) at the other end, and is rotatable in a direction parallel to the working surface. In other words, the second base member 112 (11) is capable of moving in parallel with the first base member 111 (11). The parallel link mechanism B has an extended position or a retracted position depending on the rotational positions of the front arm 13A and the rear arm 13B. These positions will be described later.

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

[0020] The acceptable position (first position) in terms of the orientation of the first working arm 21 and the second working arm 31 refers to a positional state in which the first working arm 21 and the second working arm 31 are not in contact with the obstacle W as in the first working arm 21 and the second working arm 31 shown in Figures 1 and 4, or are in contact with the obstacle W but the tips of the first working arm 21 and the second working arm 31 face forward as in the first working arm 21 and the second working arm 31 shown in Figure 5. The positional state of the parallel link B in the acceptable position (first position) does not matter, as it may be in a deployed position or a retracted position, which will be described later. The dischargeable position (second position) in terms of the orientation, etc. of the first work arm 21 and the second work arm 31 refers to the position in which the first work arm 21 and the second work arm 31 come into contact with the obstacle W and are rotated horizontally inverted from the acceptance position (first position), as well as the subsequent position, as shown in Figures 6, 7, and 8.

[0021] The dischargeable position (second position) refers to a positional state of the first working arm 21 and the second working arm 31 before they face completely rearward, other than the receiving position (first position) of the first working arm 21 and the second working arm 31 shown in Figures 1, 4, and 5. The state in which only the first working arm 21 has rotated rearward relative to the traveling direction is also the dischargeable position (second position). The positional state of the parallel link B in the dischargeable position (second position) does not matter, and may be the deployed position or the retracted position described below. In this specification, the first posture (receiving posture) refers to a position in which the radial tip sides of the first work arm 21 and the second work arm 31 relative to the rotation center face forward, and the position (range) rotated (even slightly) backward from this position is referred to as the second posture (discharging posture).

[0022] The first working arm 21 is provided so as to be rotatable about a rotation shaft 12 between a receiving position (first position) and a dischargeable position (second position). The second working arm 31 is provided separately from the first working arm 21, and is provided rotatable about a rotating shaft 12 between a receiving position (first position) and the unloading position (second position).

[0023] The deployed position of the parallel link mechanism B is a state in which the first working arm 21 and the second working arm 31 of the parallel link mechanism B are deployed outwardly in the width direction relative to the direction of travel, i.e., the state shown in Figure 1. The retracted position of the parallel link mechanism B is a state in which the first working arm 21 and the second working arm 31 have been moved inward in the width direction relative to the traveling direction from the deployed position.

[0024] A 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 is made of a gas spring, a coil spring, etc., and in this embodiment of the present invention, a gas spring is used. As shown in Figure 1 and subsequent figures, 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 can change the position of the parallel link mechanism B 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 parallel link mechanism B is constantly biased forward and outward in the traveling direction by the first elastic body 41. When the parallel link mechanism B is not in contact with an obstacle W or the like, it returns to the deployed position and can wait for an obstacle W approaching as the vehicle travels.

[0026] Since the first elastic body 41 is disposed on the rear side of the rotating shaft 12, it does not come into direct contact with obstacles or the like that approach as the robot advances. Reference numeral 42 denotes a second elastic body. The second elastic body 42 is made up of a gas spring, a coil spring, or the like, and in this embodiment of the present invention, a gas spring is used. The second elastic body 42 spans and connects the first working arm 21 and the second working arm 31, and constantly urges the second working arm 31 towards the first working arm 21.

[0027] That is, the second elastic body 42 constantly biases the first work arm 21 and the second work arm 31 in a direction in which they approach each other. Therefore, the first work arm 21 and the second work arm 31 can perform grass cutting work while contacting the obstacle W, and can reliably cut vegetation around the obstacle W. Also, because the second elastic body 42 biases the second work arm 31 regardless of whether it is in the first position or the second position, the first work arm and the second work arm 31 can properly clamp the obstacle W even during position transition. The second elastic body 42 is provided on the outside of 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 will not come into contact with the obstacle.

[0028] The first working arm 21 and the second working arm 31 each consist of a substantially plate-shaped body. 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 rotatable in the horizontal direction about a rotating shaft 12 attached to the base member 112(11). The first working arm 21 and the second working arm 31 are provided at their respective tips with a first cutting blade unit 24 and a second cutting blade unit 34 that are rotationally driven by cutting blade motors 242, 342. The first working arm 21 and the second working arm 31 are capable of mowing grass with the first cutting blade unit 24 and the second cutting blade unit 34 while coming into contact with an obstacle W present on the work surface. The second work arm 31 is provided separately from the first work arm 21 and is rotatable about a pivot shaft 12 independently of the first work arm 21, and is positioned opposite the first work arm 21 with the obstacle W in between when the second work arm 31 comes into contact with the obstacle W.

[0029] The first working arm 21 is provided with an operating means (actuator, cylinder) 14 which is an operating means for driving the rotation of the first working arm 21. In this embodiment, the operating means 14 comprises an actuator and a hydraulic cylinder. The operating means 14 is attached to the base member 11. In this embodiment of the present invention, the operating means 14 is attached to the rear part of the second base member 112. Reference numeral 141 denotes a rod provided at the tip of the operating means 14. The rod 141 is extended and retracted by the operating means 14, which is a hydraulic cylinder. The operating means 14 drives the first work arm 21 to rotate.

[0030] The operating means (actuator, cylinder) 14 extends and retracts the rod 141 to rotate 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 rotatable about the rotation shaft 12, and can therefore perform a rotating operation by coming into contact with an obstacle W present on the work surface.

[0031] The stopper 15 provided on the second working arm 31 restricts the rotation of the second working arm 31 when it comes into contact with the first working arm 21 which is driven to rotate 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 position (first position), making it easy for the worker to adjust the contact position between the obstacle W and the second work arm 31 to an appropriate position. The stopper 15 is capable of coming into contact with the second base member 112 (11) and restricts its rotation. As shown in Figures 1, 4, 5 to 8, the stopper 15 comes into contact with the front end of the second base member 112 (11) and restricts the second working arm 31 from moving away from the first working arm 21 toward the traveling machine body, so that the receiving position (first position) can be maintained.

[0032] The operation of the rod 141 of the operating means 14 , which is extended and contracted by a hydraulic cylinder, restricts the operation of the first working arm 21 and the second working arm 31 to a movable range up to the point where they are restricted by the stopper 15 . The stopper 15 maintains the opening angle between the first work arm 21 and the second work arm 31 at an acute angle in the receiving position (first position) and when in the receiving position (first position), so that the working area of ​​the grass cutting device A does not expand unnecessarily and grass cutting work can be performed smoothly.

[0033] Reference numeral 23 denotes a contact portion. The contact portion 23 is provided between the pivot shaft 12 of the first working arm 21 and the first cutting blade portion 24, which is the working part. The contact portion 23 is provided in a concave shape. An obstacle W that reaches the contact portion 23 presses the contact portion 23, thereby causing the first working arm 21 to rotate backward. Reference numeral 24 denotes a first cutting blade unit. The first cutting blade unit 24 is a cutting blade, a cutting blade unit, or a working unit. The first cutting blade unit 24 is attached to the radial tip side of the lower part of the first work arm 21 relative to the rotating shaft 12. The first work arm 21 has one or more cutting blade units on its lower part.

[0034] The second work arm 31 has one or more cutting blade units at its lower part. In this embodiment, the second cutting blade unit 34 is provided at the radial tip side of the lower part of the second work arm 31 relative to the pivot shaft 12. An additional second cutting blade unit 34 may be provided near the pivot shaft 12 of the second work arm 31. The second cutting blade portion 34 is a cutting blade, a cutting blade portion, or a working portion.

[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 rotatable in the horizontal direction about a pivot shaft 12, and the first cutting blade unit 24 and the second cutting blade unit 34 are movable horizontally. Therefore, while the obstacle W is sandwiched between the opposing inner sides of the first work arm 21 and the second work arm 31, the grass all around the obstacle W is cut by the first cutting blade portion 24 and the second cutting blade portion 34.

[0036] Reference numerals 241 and 341 denote cutting blades. Four cutting blades 241 are provided at equal intervals on the rotation shaft of the first cutting blade unit 24, and four cutting blades 341 are provided at equal intervals on the rotation shaft of the second cutting blade unit 34. There is no limit to the number of cutting blades 241 and 341 provided on the first cutting blade unit 24 and the second cutting blade unit 34. As shown in Figs. 1 and 2, the cutting blades 241 and 341 provided on the first cutting blade unit 24 and the second cutting blade unit 34, respectively, rotate horizontally when viewed from the traveling direction.

[0037] Hydraulic motors 242 and 342 are attached to a motor base portion of the first working arm 21, on the central rotation axis of the first cutting blade unit 24. The hydraulic motor 242 may be replaced with an electrically operated electric motor. The hydraulic motors 342 are provided on the motor bases of the second work arms 31 and on the central rotation axis of the second cutting blade units 34 . The hydraulic motor 242 and the hydraulic motor 342 rotate the cutting blade 241 and the cutting blade 341 provided on the first cutting blade unit 24 and the second cutting blade unit 34, respectively.

[0038] A detection unit 5 is provided adjacent to the first cutting blade unit 24, which is the working unit, and is positioned so as to protrude laterally, that is, radially outward of the rotational diameter of the first cutting blade unit 24, which is the working unit, as shown in Fig. 1 and subsequent drawings. When the side of the detection unit 5 comes into contact with an obstacle W, it sinks toward the rotation center of the first cutting blade unit 24, thereby being able to detect the obstacle. A sensor arm 51 is provided on the detection unit 5. The sensor arm 51 is a contact sensor, and is provided along the front outer periphery of the first working arm 21.

[0039] The sensor arm 51 is made up of a first sensor arm 511 and a second sensor arm 512. The first sensor arm 511 and the second sensor arm 512 constituting the detection unit 5 are provided so as to be horizontally rotatable. 1 and 4 to 8, the first sensor arm 511 is attached such that one end protrudes outward from the left side toward the front side in the direction of travel of the first working arm 21. The second sensor arm 512 is attached to the outer end of the first sensor arm 511 that is attached to the first working arm 21. Therefore, it is attached on the inside side of the first working arm 21, which is the side through which the obstacle W passes.

[0040] The first sensor arm 511 and the second sensor arm 512 are installed so as to partially overlap each other. The first sensor arm 511 is rotatable horizontally about a rotation fulcrum shaft 511a provided at the outer end on the left side in the traveling direction, and the second sensor arm 512 is rotatable horizontally about a rotation fulcrum shaft 512a provided at the outer end on the left side in the traveling direction. As shown in FIG. 1, when the sensor arm 51 is not detecting an obstacle W, the first sensor arm 511 and the second sensor arm 512 protrude outward from the first cutting blade unit 24, which is the working part, 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, it is possible to improve detection accuracy while maintaining the distance between the tip of the first sensor arm 511, which is away from the pivot axis 511a, and the first cutting blade unit 24, which is the working part, within a certain range. Since the tip of the sensor arm 51 can be kept within a certain distance from the first cutting blade unit 24 which is the working part, it is possible to detect an obstacle within a certain distance from the first cutting blade unit 24 which is the working part.

[0042] The first sensor 52A is provided on the detection unit 5 so as to be capable of coming into contact with a contact portion 53A provided in the vicinity of the rotation fulcrum shaft 511a of the first sensor arm 511. The first sensor 52A is capable of issuing a signal indicating whether or not the sensor arm 51 has rotated by coming into contact with the abutting portion 53A.

[0043] 12 to 16 showing electrical circuit diagrams, the first sensor 52A is in contact with the contact portion 53A and in non-contact position 522 with the contact portion 53A not in contact. In other words, when the sensor arm 51 is not in contact with an obstacle, the first sensor 52A is in the non-contact position 522, and when the sensor arm 51 is in contact with an obstacle, the first sensor 52A is in the contact position 521. The contact portion 53A of the sensor arm 51 is a so-called cam piece. The contact portion 53A is rotatable together with the first sensor arm 511 and is capable of coming into contact with the first sensor 52A. By changing the shape of the periphery of the contact portion 53A, it is possible to change the timing at which the signal is emitted by the first sensor 52A.

[0044] A biasing body 54 is provided in the detection unit 5. The biasing body 54 biases the sensor arm 51 laterally outward in the radial direction relative to the rotation axis of the first cutting blade unit 24, which is the working unit. Reference numeral 55 denotes a connecting portion. The connecting portion 55 is made up of a sliding portion 551 and a pin 552. The sliding portion 551 is formed in the shape of an elongated hole in a 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 an intermediate portion of the second sensor arm 512. The connecting portion 55 connects one end of the first sensor arm 511 and the intermediate portion of the second sensor arm 512. Pin 552 is provided on second sensor arm 512, which is the other sensor arm, so as to protrude towards sliding portion 551, and is fitted into sliding portion 551. Pin 552 is slidable relative to sliding portion 551 within the range of an elongated hole provided in sliding portion 551.

[0046] The sliding portion 551 has an elongated hole shape and is provided on the first sensor arm 511. The sliding portion 551 is provided so as to become farther from the rotation fulcrum axis 511a of the first sensor arm 511 in the long diameter direction. A pin 552 provided on the second sensor arm 512, which is the other sensor arm, can link the rotation of the sensor arms 511, 512 with each other by sliding on the inner circumference of the elongated hole of the sliding portion 551. The shape of the sliding portion 551 and the positions of the sliding portion 551 and the pin 552 can be freely set in consideration of the detection sensitivity, the shape of the first cutting blade unit 24, which is the working part, and the like.

[0047] A curved portion 56 is formed on the sensor arm 51 so as to be curved along the first cutting blade portion 24 which is the working portion. The outer side surface of the curved portion 56 is provided so as to be positioned so as to substantially coincide with the outer peripheral edge of the side surface of the first cutting blade portion 24, which is the working part, in a plan view when the detection unit 5 is in the detection state. Alternatively, the curved portion 56 is provided so as to be positioned inside the outer peripheral edge of the side surface of the first cutting blade portion 24, which is the working part.

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

[0049] In a detection state in which the obstacle W contacts and presses the sensor arm 51, the sensor arm 51 is aligned with the outer periphery of the first work arm 21 or is located inside the outer periphery of the first work arm 21 and outside the rotation diameter of the first cutting blade unit 24, which is the working part. That is, the first cutting blade unit 24 can work at a position as close as possible to the obstacle W. In addition, when the obstacle W, which is sandwiched between the first work arm 21 and the second work arm 31 and headed toward the abutment part 23, passes by the side of the first cutting blade unit 24, which is the working part, the sensor arm 51 in the detection state does not protrude to the side from the working part, so it does not hinder the working part from approaching the obstacle W as much as possible. Therefore, the first cutting blade unit 24 and the second cutting blade unit 34 can cut grass growing around the obstacle W as close as possible to the obstacle W without being hindered by the sensor arm 51.

[0050] In the embodiment of the present invention, when an obstacle W heading toward the abutment portion 23 passes beside the first cutting blade portion 24 and the second cutting blade portion 34 which are the working portions, it is the first working arm 21, the second working arm 31 and the sensor arm 51 that come into contact with the obstacle W. Therefore, the obstacle W can be guided to the abutment portion 23 along the outer periphery of the first working arm 21 and the outer periphery of the second working arm 31.

[0051] Since the horizontally rotating sensor arm 51 is provided with the curved portion 34, even if the outer periphery of the first work arm 21 to which the sensor arm 51 is attached is curved, the sensor arm 51 can be positioned along this curve. Also, since the sensor arm 51 can be positioned so as to almost coincide with the edge of the first cutting blade unit 24, which is the working part, in a plan view in the detection state, the sensor arm 51 does not protrude from the first cutting blade unit 24, which is the working part, in the direction of the obstacle W, and excessive pressing force can be prevented from being applied to the sensor arm 51 and the obstacle W. The tip of the sensor arm 51, which is made up of multiple sensor arms, away from the pivot point does not protrude outward as much as when it is made up of only one sensor arm, so it requires less installation space. This allows for efficient use of space and allows for appropriate component placement.

[0052] When the obstacle W comes into contact with the sensor arm 51, the sensor arm 51 rotates rearward. Then, the first sensor 52A installed behind the sensor arm 51 is pressed via the contact portion 53A, and goes into a detection state. In this embodiment, the sensor arm 51 is provided along the front outer periphery of the first working arm 21, but it may also be provided along the front outer periphery of the second working arm 31 to perform the same function.

[0053] The sensor arm 51 of the detection unit 5 is composed of multiple parts, a first sensor arm 511 and a second sensor arm 512. However, since the first sensor arm 511 and the second sensor arm 512 of the sensor arms 51 have a linked structure, only one sensor that emits a signal is required. This simplifies the wiring and circuits that send signals, and the internal program of the control unit that processes these signals. Furthermore, the movement distance involved in the rotation of the tip of the sensor arm can be shortened by connecting multiple sensor arms 51. When each sensor arm 51 rotates upon contact and pressure from an obstacle W, the variation in the detection accuracy of the sensor caused by the difference in distance from each rotation fulcrum 511a, 512a to the position pressed by the obstacle W can be minimized, improving the reliability of detection of the obstacle W.

[0054] The rotation of the first sensor arm 511 is transmitted in conjunction with the other sensor arm, the second sensor arm 512, via the connecting portion 55, so that the other sensor arm, the second sensor arm 512, also rotates in the same direction. In addition, when the obstacle W presses against the other sensor arm, the second sensor arm 512, causing the second sensor arm 512 to rotate, the rotation of the other sensor arm, the second sensor arm 512, is transmitted to the first sensor arm 511 via the connecting portion 55, so that the first sensor arm 511 also rotates in the same direction, activating the switch.

[0055] Each sensor arm 51 (first sensor arm 511, second sensor arm 512) rotates horizontally and is arranged overlapping with parts of the sensor arms 51 horizontally. Since there are no horizontal gaps or steps between the sensor arms 51 (first sensor arm 511, second sensor arm 512), an obstacle W will not get caught or caught. This point is important because in the embodiment of the present invention, the obstacle W works while sliding horizontally relative to the sensor arm 51.

[0056] In order to rotate the first working arm 21 and the second working arm 31 from the receiving position (first position) to the unloading position (second position), or from the unloading position (second position) to the receiving position (first position), the rod 141 of the operating means 14 is extended or retracted. A sensor arm 51 is used to control the operation of the rod 141. By extending and retracting the rod 141 of the operating means 14, the first working arm 21 and therefore the second working arm 31 are caused to rotate around the obstacle W, thereby preventing damage caused by the arms colliding with the obstacle W. The sensor arm 51 serves as a sensing mechanism for enabling the device to actively rotate with respect to an obstacle W.

[0057] 52B is a second sensor. 53B is a contact portion. The second sensor 52B is provided near the periphery of the rotation fulcrum shaft 12 of the first work arm, and is provided so as to be able to come into contact with the contact portion 53B provided near the periphery of the rotation shaft 12 of the second work arm 31. Since the second sensor 52B and the contact portion 53B are provided near the rotation shaft 12, they can be placed away from the first cutting blade unit 24 and the second cutting blade unit 34, which are the working parts. This prevents the obstacle W from being erroneously detected or damaged due to grass or the like around it coming into contact with the second sensor 52B.

[0058] The abutment portion 53B comes into contact with the second sensor 52B when the first working arm 21 and the second working arm 31 are relatively closed and their tips come into contact with each other. Conversely, the abutment portion 53B does not come into contact with the second sensor 52B when the first working arm 21 and the second working arm 31 are relatively open and their tips are not in contact with each other. The second sensor 52B and the abutment portion 53B are provided near the periphery of the rotation fulcrum shaft 12 of the first working arm and near the periphery of the rotation shaft 12 of the second working arm 31, respectively, to achieve this positional relationship. The second sensor 52B can detect the relative opening and closing of the first working arm 21 and the second working arm 31 based on the presence or absence of contact with the abutment 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 is capable of issuing a signal indicating whether or not the second working arm 31 and the first working arm 21 have rotated relatively to each other, by coming into contact with or not coming into contact with the abutment portion 53B.

[0060] 12 to 16, the second sensor 52B is in an open position 523 where the first work arm 21 is open relative to the second work arm 31, and in a closed position 524 where the first work arm 21 is closed relative to the second work arm 31. The second sensor 52B switches an electric circuit within the second sensor 52B depending on whether or not there is contact with the abutment portion 53B, to detect 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, or in the closed position 524 shown in FIGS. 12 to 16, it detects that the first work arm 21 has come into contact with the second work arm 31.

[0061] The contact portion 53B has a so-called planar shape. The contact portion 53B is provided in the vicinity of the rotation shaft 12 which is the rotation fulcrum of the second work arm 31, and therefore rotates integrally with the second work arm 31. By changing the protruding or curved shape of the surface of the abutment portion 53B, it is possible to change the timing at which the signal is emitted by the second sensor 52B. Furthermore, in addition to the embodiment, the abutment portion 53B may be an abutment piece made of a so-called cam piece. In this case, the abutment portion 53B has a peripheral edge that protrudes from the second work arm 31 towards the first work arm side and is brought into contact with the second sensor 52B, thereby causing 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 working arm 31 and the first working arm 21 have closed relatively and come into contact.

[0062] The third sensor 52C is provided near the rotation shaft 12 of the second base member 112 (11). Abutment portion 53C is provided on the upper portion of first work arm 21 near the periphery of rotation shaft 12 which serves as the rotation fulcrum. Abutment portion 53C is formed integrally with first work arm 21 by a boss provided coaxially with rotation shaft 12, and rotates together with first work arm 21. The third sensor 52C is capable of issuing a signal indicating whether or not the first working arm 21 has rotated relatively to the second base member 112 (11) by coming into contact with the abutment portion 53C.

[0063] The third sensor 52C detects whether or not the first work arm 21 is in the first posture. 14 to 16, which show the electric circuit of the embodiment of the present invention, indicate a detection position 525 which detects that the first work arm 21 is in the second position when the circuit is energized by the third sensor 52C. In contrast, detection position 525 shown in Figs. 12 to 13 indicates that the circuit recognizes that the first work arm 21 is in the first position in which it does not rotate relative to the second base member 112 (11) when the circuit is interrupted by the third sensor 52C. The detection position 525 for the second position detects the position of the second work arm 31 by the third sensor 52C. The portion of the contact portion 53C that comes into contact with the third sensor 52C is made of a planar member in the example, but may be a so-called cam piece. By changing the shape of the periphery of the contact surface of the contact portion 53C, it is possible to change the timing at which the third sensor 52C issues a signal.

[0064] The configurations of the hydraulic circuit and the electric circuit will now be described. 9 to 11 showing fluid circuit diagrams, the operating means 14, also called an actuator or a cylinder, is made up of a bottom side chamber 143 and a rod side chamber 142. When hydraulic pressure flows into the bottom side chamber 143 and the rod side chamber 142, the rod 141 of the actuator 14 is extended or contracted. The actuator 14 rotates the first work arm 21 by extending and contracting the rod 141 . Reference numeral 73 denotes a storage tank. A fluid is stored in the storage tank 73. In this embodiment, the fluid is oil, which is a liquid.

[0065] A fluid pressure generation source (pump) 74 is connected to the storage tank 73 and sends the hydraulic pressure of the storage tank 73 to the downstream side. A first switching valve (first control valve) 75 is connected to the downstream side of a fluid pressure generating source (pump) 74 via a feed pipe 71a. The first switching valve (first control valve) 75 can be switched between a pumping position 751 in which fluid is pumped to the actuator 14 located downstream of the first switching valve (first control valve) 75, and an unloaded position 752 in which fluid is not pumped to the actuator 14. A second switching valve 76 is disposed downstream of the first switching valve 75 and upstream of the actuator 14, and communicates with the actuator 14 via a feed pipe 71b.

[0066] The second switching valve (second control valve) 76 communicates between the bottom side chamber 143 of the actuator 14 and the first switching valve (first control valve) via a feed pipe 71c. The second switching valve (second control valve) 76 is switchable between a blocking position 761 that blocks the fluid from the actuator 14 to the first switching valve (first control valve) 75 side, and an open position 762 that allows the fluid to freely flow in and out between the actuator 14 and the first switching valve (first control valve) 75 side. The rod side chamber 142 of the actuator 14 communicates with a first switching valve (first control valve) 75 via a return pipe 72a. The first switching valve (first control valve) 75 communicates with the storage tank 73 through a return line 72b. A relief valve 77 is provided between the feed pipe 71c and the return pipe 72a. The relief valve 77 will be described in detail later.

[0067] The configuration of the electric circuit will be described with reference to FIGS. The first sensor 52A detects the movement of the sensor arm 51 caused when an obstacle W comes into contact with the sensor arm 51. The first sensor 52A can be in a contact position 521 or a non-contact position 522. By switching the first sensor 52A to either the contact position 521 or the non-contact position 522, the electric circuit is selectively branched into a circuit toward the first switching valve 75 or a circuit toward the second switching valve 76.

[0068] The second sensor 52B detects whether the first working arm 21 and the second working arm 31 are closed and in contact with each other. The second sensor 52B can take an open position 523 where the first working arm 21 and the second working arm 31 are relatively open and not in contact, and a closed position 524 where the first working arm 21 and the second working 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 switches to a non-abutment position 522, and the electric circuit branched to the first switching valve 75 side can be branched again into the open position 523 which is a circuit toward the second switching valve 76 side, and the closed position 524 which is a circuit toward the first switching valve 75 side.

[0069] The third sensor 52C detects whether or not the second working arm 31 is in the first position. It is possible to branch off at the closed position 524 and disconnect the circuit leading to the first switching valve 75. When 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 when 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 pivoting movement of the first working arm 31 by means of fluid pressure. The fluid pressure generating source 74 can pump fluid pressure to the actuator 14 via a feed pipe 71a, a feed pipe 71b, and a feed pipe 71c. Return lines 72 a and 72 b return fluid pressure from actuator 14 to reservoir tank 73 . The second switching valve 76 is disposed between the actuator 14 and the first switching valve 75 side, and can be switched between a blocking position 761 as shown in Figures 9 and 11, which blocks fluid from the actuator 14 to the first switching valve 75 side while allowing fluid to move from the first switching valve 75 side, which is a check circuit, to the actuator 14 side, 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 side.

[0071] The relief valve 77 can form a communication state that communicates the feed pipe 71c between the second switching valve 76 and the actuator 14 and the return pipe 72a when the second switching valve 76 is in the shutoff position 761 and the first switching valve 75 is in the open position 762 as shown in Fig. 9 and the pressure in the feed pipe 71c increases. Also, the relief valve 77 can form a communication state that communicates the feed pipe 71c and the return pipe 72a when the second switching valve 76 is in the shutoff position 761 and the first switching valve 75 is in the pumping position 751 as shown in Fig. 11 and the pressure in the feed pipes 71a, 71b, and 71c increases. When the feed pipe 71c and the return pipe 72a are in communication with each other by the relief valve 77, no fluid pressure is applied to the actuator 14, so that the actuator 14 is free to move.

[0072] The first switching valve 75 is located between the fluid pressure generating source 74 and the second switching valve 76, and is switchable between a pumping position 751 in which fluid is pumped to the actuator 14, and an unloaded position 752 in which no fluid is pumped to the actuator 14. The communication state between the feed pipe 71 c and the return pipe 72 a by the relief valve 77 can be formed regardless of the pumping position 751 and the no-load position 752 of the first switching valve 75 .

[0073] The relationship between the posture of the grass cutting device A, the hydraulic circuit, and the electric circuit will be described. The grass mowing device A according to the embodiment of the present invention sequentially assumes the positions a through e indicating the device position. In accordance with each of the positions, the hydraulic circuit sequentially assumes the hydraulic circuit states a through c, and the electric circuit sequentially assumes the electric circuit states a through e.

[0074] (Position a showing the device position) The relationship between the position of the grass cutting device A in position a, which indicates the device position, and the hydraulic circuit and the electric circuit will be described. When the grass mowing device A is in position a, which indicates the device position, the first work arm 21 is in the accepting position (first position) as shown in Figures 1 and 4. This is a state in which the sensor arm 51 (511, 512) has not detected an obstacle W. This is a state in which the first work arm 21 is in contact with the second work arm 31. This is a state in which the first work arm 21 and the second work arm 31 are in the first position (acceptable position), which is a normal working position.

[0075] (Hydraulic circuit a) In the position a, which indicates the device position, the hydraulic circuit is in the hydraulic circuit a state shown in FIG. 9. The first control valve 75 is in the no-load position 752, and the second control valve 76 is in the shutoff position 761. Although the first switching valve (control valve) 75 and the second switching valve (control valve) 76 are both conductive, the first control valve 75 in the no-load position 752 connects the fluid pressure generated by the fluid pressure generating source 74 from the feed pipe 71a to the return pipe 72b that communicates inside the no-load position 752. Therefore, the fluid pressure does not flow from the fluid pressure generating source 74 to the feed pipe 71b. Furthermore, the check circuit in the shutoff position 761 prevents the fluid in the bottom side chamber 143 and the feed pipe 71c from flowing toward the feed pipe 71b, so that the actuator (cylinder) 14 is contracted and restricted. That is, the first working arm 21 and the second working arm 31 shown in FIG. 1 and FIG. 4 can maintain the first position (receiving position). 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 posture, the first switching valve (first control valve) 75 is switched to the unloaded position 752, and the second switching valve (second control valve) 76 is switched to the shut-off position 761.

[0076] (Electrical circuit a) In position a, which indicates the device position, the electric circuit is in the electric circuit state a shown in Fig. 12. The first sensor 52A is in the non-abutment position 522. The second sensor 52B is in the closed position 524 because the first working arm 21 and the second working arm 31 are relatively closed and in contact with each other. The third sensor 52C does not detect the detection position 525 because the second working arm 31 is not in the second position (dischargeable position). Therefore, no voltage is applied to the first switching valve 75 and the second switching valve 76, and the first switching valve 75 is brought to the no-load position 752, which are their respective return positions, and the second switching valve 76 is switched to the shut-off position 761.

[0077] (Position b showing the device position) The relationship between the position of the grass cutting device A in position b, which indicates the device position, and the hydraulic circuit and the electric circuit will be described. 5, when the grass cutting device A is in position b, which indicates the device position, the sensor arm 51 (511, 512) has detected an obstacle W. The first work arm 21 is in contact with the second work arm 31. This represents the first position (receiving position) in which the first work arm 21 and the second work arm 31 are in the normal working position.

[0078] (Hydraulic circuit b) In posture b, which indicates the device posture, the hydraulic circuit is the hydraulic circuit b shown in Fig. 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 by the fluid pressure generation 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 and the bottom side chamber 143 of the actuator 14 are in a communicating state via the second switching valve 76 and the first control valve 75, allowing fluid to pass between them, and the rod 141 of the actuator 14 is in a state in which it can freely protrude and retract.

[0079] (Electrical circuit b) In posture a, which indicates the device posture, the electric circuit is in the state of electric circuit b shown in Fig. 13. The first sensor 52A is in the contact position 521 because the sensor arm 51 (511, 512) is pressed and rotated by 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 does not detect the detection position 525 because the second work arm 31 is not in the second posture (ejectable posture). Since power is conducted to the second switching valve (control valve) 76 via the first sensor 52A which is at the abutment position 521 in the electric circuit, the second switching valve (control valve) 76 is switched to the open position 762. In contrast, since no electricity is applied to the first switching valve 75, the first switching valve 75 is in the unloaded position 752 which is the return position. Therefore, the actuator (cylinder) 14 is in a free extension / retraction state (freely displaceable state) where no fluid pressure is applied, and the first arm 21 can be rotated rearward by the pressure of the obstacle W against the first arm 21 as the aircraft advances.

[0080] (Position c showing the device position) The relationship between the attitude of the grass cutting device A in the attitude c, which indicates the device attitude, and the hydraulic circuit and the electric circuit will be described. When the grass cutting device A is in position c, which indicates the device position, as shown in Fig. 6, the sensor arm 51 (511, 512) has detected an obstacle W. Because 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 represents a state in which the first work arm 21 and the second work arm 31 are midway through rotation after moving from the first position (receiving position), which is the normal working position, to the second position (discharging position). The switch valve (control valve) is switched based on the detection of the sensor, and the first work arm 21 and the second work arm 31 are in a freely rotatable state.

[0081] (Hydraulic circuit b) In the position c showing the device position, the hydraulic circuit is the hydraulic circuit b shown in Fig. 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 details of the hydraulic circuit b are as described above in (Hydraulic circuit b), so repeated explanation will be omitted.

[0082] (Electrical Circuit C) In the position c, which indicates the device position, the electric circuit is in the electric circuit c state shown in FIG. 14. The first sensor 52A is in the abutment position 521. The second sensor 52B is in the open position 523 because the first working arm 21 and the second working arm 31 are relatively open with the obstacle W sandwiched between them. The third sensor 52C detects the detection position 525 because the second working arm 31 is sandwiching the obstacle W between the first working arm 21 and has rotated horizontally backward to the second position (dischargeable position). In the electric circuit, power is conducted to the second switching valve (control valve) 76 via the abutment position 521 of the first sensor 52A, and the valve is switched to the open position 762. In contrast, the first switching valve 75 is in the no-load position 752 because no voltage is applied thereto. Therefore, the actuator (cylinder) 14 is in a free extension / retraction state (freely displaceable state) without any fluid pressure applied, and following the above-mentioned posture b and hydraulic circuit b and electric circuit b states, the first arm 21 can continue to rotate backward due to the pressure of the obstacle W.

[0083] (Position d showing the device position) The relationship between the attitude of the grass cutting device A in the attitude d, which indicates the device attitude, and the hydraulic circuit and the electric circuit will be described. 7, in the position d indicating the device position, the grass cutting device A represents a state in which the first work arm 21 and the second work arm 31 are in the second position and the sensor arm 51 (511, 512) does not detect the obstacle W (this is the case in which the obstacle W has moved away from the sensor arm 51 (511, 512) when the first work arm 21 is driven to rotate). The obstacle W is sandwiched between the first work arm 21 and the second work arm 31, and the first work arm 21 is moved away from the second work arm 31. The first working arm 21 and the second working arm 31 are in the middle of rotating from the first position (receiving position), which is the normal working position, to the second position (ejecting position).

[0084] (Hydraulic circuit b) In the position d showing the device position, the hydraulic circuit is the hydraulic circuit b shown in Fig. 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 details of the hydraulic circuit b are as described above in (Hydraulic circuit b), so repeated explanation will be omitted.

[0085] (Electrical circuit d) In posture d, which indicates the device posture, the electric circuit is electric circuit d shown in Fig. 15. Since the obstacle W is away from the sensor arm 51, the first sensor 52A is in the non-abutment position 522. Since the first work arm 21 and the second work arm 31 are open to each other, the second sensor 52B is in the open position 523. Since the second work arm 31 is in the second posture (ejectable posture), the third sensor 52C detects the detection position 525. Since the second switching valve (control valve) 76 is in communication 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 freely expanding and contracting state (freely displaceable state).

[0086] In the illustrated posture d, the obstacle W is away from the sensor arm 51 and the first work arm 21, and the first work arm 21 is not pressed backward, so the actuator 14 in the free extension / retraction state does not extend or retract. When the sensor arm 51 and the first work arm 21 are pressed again by the obstacle W as the machine advances, the above posture c is reached, and the first work arm 21 rotates backward. For this reason, even if the postures c and e are alternately repeated depending on the contact state between the obstacle W and the sensor arm 51 and the first work arm 21 in the second posture, the actuator 14 will not extend or retract unless an external force, that is, a force caused by the obstacle W to rotate the first work arm 21, is applied to the rod 141. In other words, when the sensor arm 51 is pushed by an obstacle W, or when the first work arm 21 is in the second posture 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 freely rotate horizontally regardless of fluid pressure.

[0087] (Position e showing the device position) The relationship between the attitude of the grass cutting device A in the attitude e, which indicates the device attitude, and the hydraulic circuit and the electric circuit will be described. 8, in posture e, which indicates the posture of the grass mowing device A, the sensor arm 51 (511, 512) is not detecting an obstacle W. The first work arm 21 is in contact with the second work arm 31. Both the first work arm 21 and the second work arm 31 are in a state of having rotated to the second position (dischargeable position). In other words, after the tip sides of the first work arm 21 and the second work arm 31, which sandwich the obstacle W, both rotate backward to the second position (dischargeable position), the obstacle W is discharged from the first work arm 21 and the second work arm 31 and then separated, and the first work arm 21 and the second work arm 31 are in a closed state.

[0088] (Hydraulic circuit c) In the position e showing the device position, the hydraulic circuit is the hydraulic circuit c shown in FIG. 11. The first control valve 75 is in the pumping position 751, and the second control valve 76 is in the shutoff position 761. The fluid pressure generated from the fluid pressure generating source 74 is pumped to the second switching valve 76 through the feed pipes 71a and 71b by the pumping position 751. The feed pipes 71a and 71b in the pumping position 751 are not in communication with the return pipes 72a and 72b, so that the fluid is not returned to the storage tank 73. In other words, the upstream side and downstream side of the fluid are separate circuits. With the second control valve 76 in the shutoff position 761, which is a check circuit, the fluid pressure sent from the fluid pressure generating source 74 side is sent to the bottom side chamber 143 of the actuator 14, which is the downstream side, without being blocked. The fluid in the rod side chamber 142 passes through the further downstream return pipe 72a, the first control valve 75, and the return pipe 72b and returns to the storage tank 73. As a result, the rod 141 of the actuator 14 protrudes, and the actuator 14 can be extended.

[0089] (Electrical Circuit E) In the position e showing the position of the device, the electric circuit is the electric circuit e shown in FIG. The first sensor 52A is in a non-contact position 522 because the sensor arm 51 (511, 512) is not pressed against the obstacle W. The second sensor 52B is in a 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 a detection position 525 because the second work arm 31 is in the second position (dischargeable position). In the electric circuit e, by conducting and applying an electric current to the first switching valve 75 via the first sensor 52A to the third sensor, the first switching valve 75 is switched to the pumping position 751. Since the conducting state of the second switching valve 76 is released with respect to the first switching valve 75, no electric current is applied to it and it is returned to the cut-off position 761. The actuator (cylinder) 14 is driven to the extension side to return the first working arm 21 and the second working arm 31 to the first position (receiving position).

[0090] The operation of the grass cutting device A will now be described. 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 machine body to cut grass. During operation, an obstacle W may be encountered. The first elastic body 41 biases the second working arm 31 in a direction drawing it closer to the first working arm 21, so the first working arm 21 and the second working arm 31 are brought close to each other and the tip end between them is closed. The tip end of the first working arm 21 is directed forward by the operating means 14. At the same time, the second working arm 31 is pushed by the first working arm 21 and is directed forward against the biasing force of the second elastic body 42. Therefore, the first working arm 21 and the second working arm 31 are in a receiving position (first position).

[0091] (Position a showing the device position) 1 and 4, in a normal grass-cutting operation state, the first elastic body 41 that biases the second work arm 31 in a direction toward the first work arm 21 is stretched. At this time, the rod 141 of the operating means 14 is in an extended state. The sensor arm 51 (the first sensor arm 511 and the second sensor arm 512) is not in contact with the obstacle W and does not sense the obstacle W. The first working arm 21, the second working arm 31 and the sensor arm 51 are in a receiving position (first position) facing forward in the traveling direction, and the traveling machine body moves the grass cutting device A forward in the traveling direction. The electric circuit at this time is the electric circuit a shown in Figure 9, and a hydraulic circuit b is formed.

[0092] When the grass mowing device A encounters an obstacle W while traveling, the obstacle W comes into contact with the second work arm 31 as shown in Figs.

[0093] (Position b showing the device position) Fig. 5 shows the moment when the obstacle W comes into contact with the second work arm 31. In the case of the embodiment of the present invention illustrated in Fig. 4, the obstacle W is located between the hydraulic motor 242 arranged on the rotation shaft of the cutting blade 241 of the first work arm 21 and the hydraulic motor 342 arranged on the rotation shaft of the cutting blade 341 of the second work arm 31, and is in contact with the tips of the first work arm 21 and the second work arm 31. Furthermore, the obstacle W is pressing against the sensor arm 51, and the first sensor 52A detects that the obstacle W has come into contact with the first work arm 21.

[0094] When the traveling body advances from the state shown in FIG. 4 and hits an obstacle W, the state changes to that shown in FIG. As shown in Fig. 5, when an obstacle W abuts against the first work arm 21, the obstacle W comes into contact with the sensor arm 51, which detects it and rotates the sensor arm 51 rearward. The first sensor 52A installed at the rear of the sensor arm 51 is pressed, switching the electric circuit to the abutment position 521, resulting in a detection state. That is, the electric circuit becomes the state of electric circuit b shown in Fig. 13, and the hydraulic circuit forms the hydraulic circuit b shown in Fig. 10.

[0095] When the first sensor 52A takes the electric circuit b in the detection state, the hydraulic control valve of the operating means 14 The second switching valve 76, which is an electromagnetic valve, is operated to the open position 762 side to form a hydraulic circuit b. The rod 141 of the means 14 is made to be in a contractible state. In this case, the first switching valve 75 is Since the first working arm 21 remains in the unloaded position 752, it is free to rotate. The sensor arm 51 is used to control a series of operations until the rod 141 is retracted. Use.

[0096] (Position c showing the device position) As the traveling machine body continues traveling from the state shown in FIG. 5, it reaches the state shown in FIG. In the state shown in Fig. 6, the first work arm 21 is opened outward due to the pressure of obstacle W as the traveling body advances, and the obstacle W is positioned between the first work arm 21 and the second work arm 31. Obstacle W, represented by a two-dot chain line in Fig. 6, is in a position where it has moved further relative to the abutment part 23 as the traveling body advances, and the first work arm is in the middle of rotating backward due to the pressure of obstacle W. The second work arm 31 transitions to a second posture in which it has rotated to follow the first work arm 21.

[0097] When an obstacle W presses against the sensor arm 51 and gets between the first working arm 21 and the second working arm 31, the obstacle W causes the first sensor 52A, the second sensor 52B and the third sensor 52C to enter a detection state, causing the rod 141 of the operating means 14 to enter a retractable state. Then, as shown in Figure 6, the first working arm 21 rotates rearward, away from the second working arm 21, with the pivot shaft 12 as the center of rotation. At this time, the second elastic body 42 contracts, resulting in a state in which the repulsive force is further increased compared to when the obstacle W is in the receiving position (first position). As shown in Figure 6, when the obstacle W moves relatively near the abutment portion 23, the second working arm 31 is caused to pivot toward the first working arm 21 by the second elastic body 42. Therefore, the obstacle W is sandwiched between the first working arm and the second working arm while being in contact with them. That is, the electric circuit forms the electric 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 freely extendable and retractable, 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, preventing damage caused by the arms colliding with the obstacle W.

[0098] As shown in Figure 6, the second elastic body 42 brings the obstacle W into contact between the first work arm 21 and the second work arm 31, allowing the cutting blades 241 and 341 to mow as close as possible to the periphery of the obstacle W. While the obstacle W passes between the cutting blade 241 and the cutting blade 341 of the first work arm 21 and the second work arm 31 , the obstacle W can be efficiently sent to the contact portion 23 or near the pivot shaft 12 . Thereafter, the obstacle W is moved relatively toward the pivot shaft 12 which is the pivot point for the first working arm 21 and the second working arm 31 .

[0099] As shown in FIG. 6, the grass cutting device A advances further with the obstacle W sandwiched between the first work arm 21 and the second work arm 31. Then, the obstacle W abuts against the abutment 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 rotating shaft 12 and then presses against the abutment portion 23. The pressure of the sensor arm 51 causes the first sensor 52A to enter a detection state, and the first work arm 21 presses against the abutment portion 23 by the obstacle W, so that it rotates about the rotating shaft 12. The second work arm 31 connected to the first work arm 21 can also rotate in conjunction with the first work arm 21 due to the increased repulsive force of the second elastic body 42.

[0100] The traveling body and the grass cutting device A continue to advance. As the traveling body advances, the rod 141 of the operating means 14 further contracts, causing the first working arm 21 to further rotate rearward with the pivot shaft 12 as the center of rotation. The second work arm 31 is connected to the first work arm 21 which can now be driven to rotate, and so rotates in conjunction with the first work arm 21. The second work arm 31 is also capable of rotating separately from the first work arm 21, but is biased towards the first work arm 21 by the second elastic body 42, so it rotates while pinching the obstacle W near the rotation axis 12 and the abutment portion 23. As a result, the tips of the first work arm 21 and the second work arm 31 of the grass cutting device A that have come into contact with the obstacle W will face rearward.

[0101] (Position d showing the device position) If the traveling vehicle changes its travel speed from the state shown in Fig. 6, or if the first working arm 21 and the second working arm 31 are not rotated properly due to further obstruction of rotation, the state shown in Fig. 7 may occur. This state is a state in which the first working arm 21 and the second working arm 31 are in the dischargeable position (second position), the pressure on the sensor arm 51 by the obstacle W is released, and the first working arm 21 has rotated in a direction opening relative to the second working arm 31. That is, the electric circuit forms the electric circuit d shown in Fig. 15, and the hydraulic circuit forms the hydraulic circuit b shown in Fig. 10. Although the conduction path of the electric circuit d has changed compared to the cases of positions b and c, the hydraulic circuit is unchanged from the cases of positions b and c, so the first working arm 21 continues to be in a state in which it can rotate freely. When in the second position and 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 put the operating means 14 into a driven state. Therefore, the obstacle W and the grass cutting device A will not be damaged by an unexpected operation.

[0102] (Position e showing the device position) As the traveling machine body continues to move forward from the state shown in FIG. 6 and FIG. 7, it reaches the state shown in FIG. 8, as the traveling machine body advances, the obstacle W leaves the abutment portion 23 facing rearward and moves toward the tips of the first work arm 21 and the second work arm 31 facing rearward. Eventually, the obstacle W leaves the tips of the first work arm 21 and the second work arm 31 toward the rear.

[0103] In the dischargeable position (second position) shown in Fig. 8, as the traveling body advances, the obstacle W detaches from the first work arm 21 and the second work arm 31. When detaching, the obstacle W pushes aside the second work arm 31 and moves relatively backward. Because the second work arm 31 is biased by the second elastic body 42, after the obstacle W pushes aside the second work arm 31, it again rotates towards the first work arm 21.

[0104] When the obstacle W separates 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 sense the obstacle W. The first work arm 21 and the second work arm 31 are not sandwiching the obstacle W, so they are closed and in contact with each other. When the sensor arm 51 no longer senses the obstacle W in the dischargeable position (second position) and the first working arm 21 and the second working 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 that the electric circuit goes into the state of electric circuit e shown in Figure 16. The electric circuit e causes the hydraulic circuit to go into the state of hydraulic circuit c shown in Figure 11, and the rod 141 of the operating means 14 is extended. Then, the first working arm 21 returns to the original position, the first position which is the receiving position with the tip facing forward. The second working arm 31 moves in conjunction 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) Explain the effects of the hydraulic circuit. 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 a state where the circuit on the pump (fluid pressure generating source) 74 side and the circuit on the tank 73 side are in a communication state. Furthermore, the first switching valve (control valve) 75 is in a communication state with the circuit (feed pipes 71b, 71c) that communicates with the rod side chamber 142 of the actuator (cylinder) 14. That is, the circuit (return pipes 72a, 72b) leading to the rod side chamber 142 of the actuator (cylinder) 14 is in communication with the pump 74 side and the tank 73 side. Therefore, the fluid pressure pumped out from the pump 74 is returned to the tank 73 side without applying pressure to 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 tank 73.

[0106] (2) In the case of the embodiment of the present invention, the pump 74 is constantly driven by power from the traveling machine body, and therefore there is no need to switch this power or the fluid pressure generated by the pump 74. In other words, while the fluid pressure generating source (pump) 74 and the fluid storage tank (oil tank) 73 are shared, the supply side pipes (71b, 71c) and the return side pipes (72b, 72c) can be configured with as simple a circuit configuration as possible, thereby making it possible to simplify the configuration of the entire device as much as possible.

[0107] (3) As shown in Fig. 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 shutoff position 761, the flow of fluid from the bottom side chamber 143 of the actuator (cylinder) 14 to the first switching valve (control valve) 75 is stopped. Therefore, the actuator 14 can maintain the current extension / retraction position without contracting. In other words, the first position (receiving position), which is the position during normal operation, is maintained.

[0108] 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, fluid can freely flow between the bottom side chamber 143 and the first switching valve (control valve) 75. In other words, the rod side chamber 142 of the actuator (cylinder) 14 and the bottom side chamber 143 of the actuator (cylinder) 14 are in communication with the tank 73.

[0109] Furthermore, when in the no-load 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. Therefore, the fluid pressure pumped from the pump 74 is returned to the tank 73, and no pressure is applied to the actuator 14. Also, the rod 141 can be made freely extendable and retractable, and the first working arm 21 can passively rotate from the receiving position (first position) to the dischargeable position (second position) by the pressure of the obstacle W (rotation of the first working arm 21 towards the dischargeable position (second position) by the obstacle).

[0110] (5) As shown in FIG. 11, when the first switching valve (control valve) 75 is in the pumping position 751, the first switching valve (control valve) 75 connects the circuit (71a, 71b, 71c) on the pump 74 side to the bottom side chamber 143 of the actuator (cylinder) 14, and also connects the rod side chamber 142 of the actuator (cylinder) 14 to the circuits (72a, 72b) on the tank 73 side. Therefore, the fluid pressure pumped from the pump 74 is pumped to the bottom side 143 circuit (71a, 71b, 71c) of the actuator 14, and can extend the rod 141 of the actuator 14. The fluid in the rod side 142 circuit (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, whether the switching position of the second switching valve (control valve) 76 is the shutoff position 761 or the open position 762, there is no effect on the driving of the extension operation of the actuator 14. In the case of the embodiment of the present invention, the second switching valve (control valve) 76 is switched to the shutoff position 761 but does not impede the flow of fluid from the first switching valve (control valve) shutoff position 75 toward the bottom side chamber 143 (return operation from the dischargeable position (second position) to the receiving position (first position)).

[0112] (6) As shown in FIG. 11, when the first switching valve (control valve) 75 is in the pumping position 751, the second switching valve (control valve) 76 switches to the shutoff position 761 because a relay circuit is configured so that the electric circuits (details will be described later) that switch the first switching valve (control valve) 75 and the second switching valve (control valve) 76 are operated by three sensors (switches). The operations of (3) and (5) can be performed with a simple configuration. (If the second switching valve (control valve) 76 is set to the open position 762 in the case of (5) shown in FIG. 11, a separate control device is required, which is not a simple configuration.)

[0113] (7) Due to the configuration of the fluid pressure circuit in the embodiment of the present invention, the first working arm 21 and the second working arm 31 can be rotated by only one of the actuators 14. In other words, by installing a spring, which is an elastic body, the second working arm 31 can rotate so as to follow the first working arm 21.

[0114] (8) By simply switching the first switching valve (control valve) 75 having two switching positions, the actuator 14 can be switched between being driven in the extension direction and being freely moved in the extension / contraction direction. Therefore, it is possible to easily switch between the forced return of first working arm 21 to the receiving position (first position) and the passive operation when an obstacle is pinched.

[0115] (9) Since the actuator 14 is prevented from shortening by simply blocking the outflow of pressure from the bottom side chamber 143 of the actuator (cylinder) 14 when the second switching valve (control valve) 76 is in the blocking position 761, the circuit configuration can be simplified. (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) by relay circuits, the two switching valves (control valves) can operate without requiring a control device.

[0116] (11) Explain the effects of electrical circuits. The state of the electric circuit when the first working arm 21 and the second working arm 31 are in the receiving position (first position), which is the normal working position, will be described. As shown in FIG. 12, since the first sensor 52A is not in contact with an obstacle W or the like, 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 switches the circuit to the abutting position (working arms in closed position 524) and connects to the circuit leading to the third sensor, because the second work arm 31 and the first work arm 21 are in a closed state and in contact with each other, and the second work arm 31 and the first work arm 21 are in contact with each other. The third sensor is not conductive because the second work arm 31 is in the receiving position (first position) (it detects that it is in the receiving position (first position)). Therefore, the power supply to the first switching valve (control valve) 75 and the second switching valve (control valve) 76 (connected to both +12V and GND in the figure) is cut off, and the first switching valve (control valve) 75 is switched to the unloaded position 752, and the second switching valve (control valve) 76 is switched to the cut-off position 761, which are the return positions of the switching valves.

[0118] (12) The state of the electric circuit when an obstacle W comes into contact with the sensor arm 51 (first sensor arm 511, second sensor arm 512) provided on the first working arm 21 will be described. As shown in Fig. 13, the first sensor 52A detects the sensor arm 51 that has rotated by contacting an obstacle W or the like, and switches the circuit to the contact position 521, connecting it to the circuit leading to the second switching valve (control valve) 76. Therefore, the second switching valve (control valve) 76 is connected to the power source and switches to the open position 762. Thereafter, the fluid circuit goes to the state (4) shown in Fig. 10. Since the first switching valve (control valve) 75 is no longer electrically connected to the power source, it is in the unloaded position 752, which is the return position.

[0119] (13) We will explain the case where 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 toward the discharge-enabling position (second position). In this state, as shown in Fig. 14, the second sensor 52B switches and connects the circuit to the second switching valve (control valve) 76 side (the working arm is in the open position 523), and the third sensor is in a conductive state with the first switching valve (control valve) 75 (the detection position for the second attitude). However, the first sensor 52A contacts the abutment position 521 and connects the power source to the circuit leading to the second switching valve (control valve) 76, so that the second switching valve (control valve) 76 maintains the open position 762. In contrast, the first switching valve (control valve) 75 is in the unloaded position 752, which is the return position, because the power source is cut off. The fluid circuit is maintained in the state (4).

[0120] (14) The above state (10) is assumed (three sensors, namely, first sensor 52A, second sensor 52B and 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), and the sensor arm 51 (first sensor arm 511, second sensor arm 512) provided on the first work arm 21 is 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 is rotated towards the discharge-enabling position (second position). As shown in FIG. 15, since the first sensor 52A is not in contact with an obstacle W or the like, the circuit is switched to the non-contact position 522 and connected to the circuit leading to the second sensor 52B.

[0121] Because the second working arm 31 and the first working arm 21 are in an open state and the second working arm 31 has rotated to the ejection possible position (second position), the second sensor 52B detects no contact (the working arm is in the open position 523). Therefore, the second sensor 52B, which is connected to the power supply on the GND side, connects the circuit to the second switching valve (control valve) 76 side, and the second switching valve (control valve) 76 maintains its connection to the power supply.

[0122] The fluid circuit can maintain a state in which the second switching valve (control valve) 76 is in the open position 762. The third sensor detects that the second work arm 31 is not in the receiving position (first position) and brings the first switching valve (control valve) 75 and the third sensor into a conductive state (detection position 525 for the second position), but since the first switching valve (control valve) 75 is not in a conductive state with the power source, it remains in the no-load position 752. This allows the fluid circuit to maintain the state (4).

[0123] (15) A state will be described in which the first work arm 21 and the second work arm 31 are in an ejection position (second position), the obstacle W has been moved away from the sensor arm, 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. That is, as shown in Figure 8, after the obstacle W is clamped between the first work arm 21 and the second work arm 31, it rotates as the aircraft moves forward, and then the obstacle W is separated from the first work arm 21 and the second work arm 31.

[0124] 16, since the first sensor 52A is not in contact with an obstacle W or the like, the power supply circuit on the GND side is switched to the non-contact position 522 and connected to the circuit leading to the second sensor 52B. Since the second working arm 31 and the first working arm 21 are in contact with each other, the circuit is switched to the contact position (working arm closed position 524) and the power supply circuit on the GND side is connected to the circuit leading to the third sensor.

[0125] Since the second work arm 31 is in the dischargeable position (second position), the third sensor is in a conductive state (detects that it is in the dischargeable position (second position), second position detection position 525). Therefore, the second switching valve (control valve) 76 is disconnected from the power source and returns to the cut-off position 761, and the first switching valve (control valve) 75 is connected to the power source (connected to both +12V and GND in the figure), thereby switching to the pumping position 751. The fluid circuit is now in the state (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 of the hydraulic circuit and the electric circuit will now be described. (1) The bottom side chamber 143 of the actuator 14 is connected to the fluid pressure generating source (pump) 74 via feed lines 71a, 71b, and 71c, and the rod side chamber 142 of the actuator 14 is connected to the storage tank 73 via return lines 72a and 72b. A second switching valve 76 is disposed in the feed lines 71b and 71c, and when the second switching valve 76 is in the shutoff position 761, the fluid cannot move from the bottom side chamber 143 to the fluid pressure generating source 74 side, as shown in Fig. 9 (hydraulic circuit a, position a Figs. 1 and 4, electric circuit a Fig. 12) and Fig. 11 (hydraulic circuit c, position e Fig. 8, electric circuit e Fig. 16).

[0127] (2) As shown in Figures 9 and 11, when the second switching valve 76 is in the shutoff position, the relief valve 77 operates in response to an increase in pressure in the feed pipes 71a, 71b, and 71c. This allows the fluid in the feed pipes 71a, 71b, and 71c to escape into the return pipes 72a and 72b. In this embodiment of the present invention, the increase in pressure in the feed pipes 71a, 71b, and 71c is assumed to be caused when an obstacle W or the like comes into contact with the first working arm 21 or the second working arm 31 and is forcibly pressed toward the second position. That is, the pressure in the feed pipes 71a, 71b, and 71c between the bottom-side chamber 143 and the second switching valve 76 increases as the rod 141 of the cylinder 14, which is the actuator 14, is pressed in the direction of contraction. The pressure rise operates the relief valve 77, releasing the fluid (pressure) in the feed lines 71a, 71b, and 71c to the return lines 72a and 72b.

[0128] (3) When the relief valve 77 is in an operating state, both the bottom side chamber 143 and the rod side chamber 142 of the actuator 14 are connected to the storage tank 73. Furthermore, because the bottom side chamber 143 is in communication with the rod side chamber 142, the actuator 14, which is a cylinder, is in a state in which it is free to expand and contract (freely displaceable state). In light of the embodiment, the first working arm 21 or the second working arm 31 that is forcibly pressed towards the second position can rotate towards the second position 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 case, the forcible pressing refers to pressing in a state where the sensors 52A, 52B, 52C are not detecting anything and the switching valves 75, 76 are not operating normally.

[0129] (4) As shown in Fig. 10 (hydraulic circuit b, position d Fig. 7, electric circuit d Fig. 15), when the second switching valve 76 is in the open position and the first switching valve 75 is in the unloaded position, even if the pressure in the feed pipes 71a, 71b, 71c rises, the feed pipes 71a, 71b, 71c communicate with the return pipes 72a, 72b in the first switching valve 75 in the unloaded position, so that the fluid in the feed pipes 71a, 71b, 71c escapes into the return pipes 72a, 72b. Furthermore, since the bottom side chamber 143 is in communication with the rod side chamber 142, the actuator 14, which is a cylinder, is in a state in which it is free to expand and contract (freely displaceable state) without operating the relief valve 77. In light of the embodiment, the first working arm 21 or the second working arm 31 that is forcibly pressed toward the second position can rotate toward the second position without resisting the obstacle W (a normal operating state in the embodiment in which each switching valve 75, 76 is operated upon detection by each sensor 52A, 52B, 52C).

[0130] (5) However, even in the normal operating state described above, if the pressure in the feed pipelines 71a, 71b, 71c increases due to an abnormality such as the extension / contraction speed of the actuator 14 being too fast, the relief valve 77 will operate to prevent damage to the circuits and equipment. (6) As shown in FIG. 11 (hydraulic circuit c, position e in FIG. 8, electric circuit e in FIG. 16), even when the first switching valve 75 is in the pumping position, when the fluid pressure in the feed lines 71a, 71b, 71c increases, the relief valve 77 operates to release the pressure to the return circuit, regardless of the switching position of the second switching valve 76.

[0131] (7) The circuit configuration for switching the actuator 14 between the driven state and the non-driven state is simplified, while still achieving the drive mechanism and buffer mechanism for each arm. (8) In the embodiment, the actuator 14 has been described as a cylinder, but a fluid pressure motor may be used to rotate the first work arm 21. Furthermore, the extension and contraction 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 this embodiment of the present invention, the rotation axis 12 which is the rotation fulcrum axis of the first working arm 21 and the second working arm 31 may be the same axis. In the present invention, the first working arm 21 is rotated in accordance with the extension and contraction of the rod 141 . The second working arm 31 always pivots together with the first working arm 21 while being cushioned by the second elastic body 42 .

[0133] In the embodiment of the present invention, the front side of the abutting portion 23 can form a closed closed portion C when the first working arm 21 and the second working arm 31 are closed. As the traveling body advances, the rod 141 of the operating means 14 is extended and retracted to rotate the first working arm 21 and therefore the second working arm 31 around the obstacle W located within the closed section C, thereby preventing damage caused by the arms colliding with the obstacle W. In the embodiment described above, the sensor arm 51 is composed of two sensor arms, the first sensor arm 511 and the second sensor arm 512, but it may be composed of three or more sensor arms linked together. In this case, the moving distance involved in the rotation of the tip of each sensor arm can be shortened, which is expected to further improve the detection accuracy of the switch. In the diagram showing the electric circuit of the embodiment, +12V is written to indicate the voltage, but the voltage is not limited to this and can be changed appropriately according to the voltage used. Also, the electric circuit can be configured by switching the + side and the - side (GND side), and can be changed appropriately according to the specifications of the device to be used. [Explanation of symbols]

[0134] 11 Base member 111 First base member 112 Second base member 12 Swivel Axis 13 Arm 13A Forearm 13B Rear arm 14 Operating means (actuator, cylinder) 15 Stopper 21 First working arm 22 Turning restriction means guide (turning restriction means) 23 Contact part 24 1st cutting blade part (cutting blade, cutting blade part, working part) 31 Second working arm 32 Turning restriction protrusion (turning restriction 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 shaft of first sensor arm 512 Second Sensor Arm 512a: Pivot axis of second sensor arm 52A First Sensor 52B Second Sensor 52C 3rd sensor 53A Contact part 53B Contact part 53C Contact part 71a Feed Pipe 71b Feed pipe 71c Feed Pipe 72a Return pipe 72b Return pipe 73 Tank 74 Fluid pressure source (pump) 75 First switching valve (first control valve) 751 Pressure 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 provided so as to be rotatable about a rotation axis; a second working arm provided separately from the first working arm and rotatable about the rotation shaft; a first sensor that detects contact of the first work arm with an obstacle; a second sensor that detects contact of the first work arm with the second work arm; a third sensor that detects that the first work arm is in the first posture, the first work arm and the second work arm are rotatable between a first posture in which the tip ends of the first work arm and the second work arm face forward and a second posture which is a posture between the first posture and the first work arm and the second work arm face completely backward, switching the first work arm between a state in which the first work arm can passively rotate between the first position and the second position and a state in which the first work arm can forcibly rotate between the second position and the first position depending on the presence or absence of detection by the first sensor, the second sensor, and the third sensor; A grass cutting device characterized by the above.

2. When only the first sensor detects an abnormality, or when all of the first sensor, the second sensor, and the third sensor detect an abnormality, the first working arm is put into a passively rotatable state.

2. The grass cutting device according to claim 1.

3. When only the second sensor detects the position, the first work arm is forced to rotate.

2. The grass cutting device according to claim 1.

4. When the second sensor and the third sensor detect the position, the first work arm is maintained in the first position.

2. The grass cutting device according to claim 1.

Images