JP6598292B2 - Mower - Google Patents

Description

  The present invention relates to an arm-coupled agricultural mowing machine that is mounted on a three-point link mechanism of a tractor and performs mowing work, and more particularly to a posture operation mechanism for a working unit during mowing work.

  Japanese Patent No. 3806465 and Japanese Patent No. 5521151 are disclosed as conventional techniques of this type of reaping device.

  In Japanese Patent No. 3806465, “the upper part of the second arm (12) is rotatably supported in the vehicle width direction (W) near the tip of the first arm (11), and the second arm (12) The third arm (13) is supported at the lower portion so as to be rotatable in the front-rear direction of the vehicle body (2), and the work implement (30) is rotatable at the lower portion of the third arm (13) in the vehicle width direction (W). A work device is disclosed that is provided with stop means (B) that supports and supports the third arm (13) so as to be rotatable also in the vehicle width direction (W) and restricts the rotation. Japanese Patent No. 551151 discloses "a first arm pivotally supported at one end of the support member in the vehicle width direction and a second arm pivotally connected to the first arm and having a mower body attached to the tip. In an arm-coupled mower having an arm, an arm-coupled mower can be easily switched between a mowing operation state and a retracted state by a lift cylinder, a first link, and a second link. ing.

Japanese Patent No. 3806465 Japanese Patent No. 5512151

  In the case of an arm-coupled mower used by being attached to a tractor, at least the joints of the coupling parts of the first arm, the second arm, and the mowing work part are rotated by the expansion and contraction of the hydraulic cylinder to move the mowing work part. The work is carried out by grounding the mowing field. As described above, the operation is performed while operating at least three hydraulic cylinders. However, there are always irregularities in the harvested farm scene, and each hydraulic cylinder is adjusted to correspond to the irregularities in the farm scene along with the driving operation of the tractor. If the mowing operation unit is not allowed to follow while operating, uncutting or the like occurs. For this reason, there was a problem that the mowing work can only be performed by a skilled worker.

  The work device disclosed in Patent Document 1 of the prior art enables the connection portion of the third arm supporting the work machine to be rotated in the front-rear direction of the vehicle body in order to make it easy to match the uneven farm scene, and the second Since the connecting portion with the arm can be rotated in the vehicle width direction and stop means for restricting the rotation is provided, the follow-up range is limited. Moreover, patent document 2 is the content of the technique which stores the mowing working part of an arm connection type mower easily.

  Therefore, an object of the present invention is to provide an arm-coupled mower that can easily follow the unevenness of the field with a simple operation in the arm-coupled mower. .

In order to solve the above problem, the mower according to claim 1 is:
A support frame attached to an agricultural tractor;
A first boom supported at one end of the support frame in the vehicle width direction so as to be rotatable up and down;
A first link mechanism including a lift cylinder for rotating the first boom in the vertical direction;
A second boom pivotally connected to the pivot end side of the first boom and having a mowing working part attached to the tip;
In the mower having the second link mechanism including the mowing working part rotating cylinder for rotating the mowing working part in the vertical direction with respect to the second boom,
In the hydraulic circuit for extending / contracting the lift cylinder of the first boom, an operation valve for extending / contracting the lift cylinder;
A switching valve for switching the expansion and contraction of the lift cylinder to a free state,
The switching valve can be switched only when the operation valve is in a neutral state and the pressure in the hydraulic piping on the side of the lift cylinder for raising the first boom is equal to or lower than an arbitrary pressure. It is a mowing machine that features it.

Further, the mower according to claim 2 is:
2. The switching valve according to claim 1, wherein the switching valve is provided so as to operate electrically, and the expansion and contraction of the lift cylinder is switched to a free state only when the operation valve is pushing the operation switch in a neutral state . It is a mower.

  According to the present invention, the hydraulic operation valve for extending / contracting the lift cylinder and the switching valve for switching the expansion / contraction of the lift cylinder to the free state are provided, so that the mowing working unit is in contact with the field scene while being in contact with the field. When the expansion and contraction is switched to the free state, the first boom automatically moves up and down even if there is unevenness in the field, and the mowing operation unit automatically follows the uneven surface and can perform mowing work without requiring skill. In addition, only when the pressure in the hydraulic piping on the side of the lift cylinder that raises the first boom is equal to or lower than the desired pressure, the lift cylinder can be freely extended and retracted so that the mowing operation unit can It is possible to provide a mower capable of performing safe work by preventing it from falling inadvertently in a raised state where it is not in contact with the ground and falling.

  Furthermore, the switching valve is provided to operate electrically, and only when the operation switch is pressed, the expansion and contraction of the lift cylinder is switched to the free state, so that the switching valve can be easily returned to the normal operation state. A good mowing machine can be provided.

It is a rear view of the working state of the mower which implemented this invention. It is a top view of the working state of the mower which implemented this invention. 1 is a hydraulic circuit diagram of a mower according to the present invention. It is a perspective view of the operation lever part which operates the hydraulic valve of the mower implements the present invention.

An example according to an embodiment of the present invention will be described with reference to the drawings.
A is a mower according to an embodiment of the present invention. Reference numeral 1 denotes an agricultural tractor that drives the mower A. In the description of this example, the upper side shown in FIG. 2 will be described as the front side in the traveling direction, and the lower side will be described as the rear side.

  The mower A shown in this example is attached to a tractor three-point link mechanism 12 provided behind the tractor 1 and is driven and used by power from the tractor 1. 10 is a tractor top link, and 11 and 11 are tractor lower links. Each is provided at the rear part of the agricultural tractor 1, and the top link 10 and the lower links 11, 11 constitute a three-point link mechanism of the tractor, and the attached mower A is connected to be lifted and pulled.

  In the mower A of this example, an arm part 3 is provided at one end in the vehicle width direction of a support frame 2 provided with a mounting part to be attached to the tractor 1, and a mowing work part 4 is provided at the tip of the arm part 3. The arm portion 3 has a first boom 30 provided with one end pivotably on the support frame 2 side in a direction orthogonal to the traveling direction, and one end pivotally connected to the pivot end side of the first boom 30. It consists of the second boom 32, and the mowing operation part 4 is positioned on the side of the tractor 1 to perform the mowing work.

  The support frame 2 is connected to the rear portion of the agricultural tractor 1, and the hydraulic oil tank 50 is placed on one end of the mower A in the vehicle width direction. 22 at the other end is a mast. The mast 22 is fixed to one end portion of the support frame 2 in the vehicle width direction, that is, in this embodiment, to the left end in the rear view of the mower A as shown in FIG. Reference numeral 300 denotes a lift cylinder. The lift cylinder 300 is attached to the support frame 2 at the end opposite to the attachment end of the mast 22 so that the base portion can be rotated by the lift cylinder shaft 301. Reference numeral 302 denotes a lift cylinder tip shaft, which is provided at the tip of the lift cylinder 300. The tip of the lift cylinder 300 and the first boom 30 are connected via a first link mechanism 31.

  The first link mechanism 31 includes a first link arm 310 having one end rotatably connected to the support frame 2 and a second link arm 312 having one end rotatably connected to the first boom 30. The first boom 30 is connected by a lift cylinder front end shaft 302 that is a connecting portion so that the end portion can freely rotate, is spanned between the lift cylinder front end shaft 302 and the support frame 2, is rotatably connected, and expands and contracts. It is comprised with the lift cylinder 300 which rotates this to an up-down direction. The first link arm 310 has a generally inverted character shape as a whole, and is connected to the mast 22 provided on the support frame 2 so that one end of the first link arm 310 is rotatable about the first link arm rotation shaft 311 as a rotation center. . The other end of the first link arm 310 is attached to the lift cylinder 300 so as to be rotatable about the same axis as the rotation center of the lift cylinder tip shaft 302.

  One end of the second link arm 312 is connected to the first boom 30 so as to be rotatable about the second link arm rotation shaft 313 as a rotation center. The other end of the second link arm 312 is attached to the lift cylinder 300 so as to be rotatable about the same axis as the center of rotation of the lift cylinder tip shaft 302 serving as a connecting portion. The first link arm 310 and the second link arm 312 are rotatably connected by a lift cylinder tip shaft 302.

  The first boom 30 is connected to the mast 22 so as to be rotatable up and down and rotatable about the first boom rotation shaft 303 as a rotation center. At the same time, the first boom 30 is supported on the mast 22 that is one end in the vehicle width direction of the support frame 2 via the first link arm 310, the second link arm 312, and the lift cylinder 300.

  In this example, the second boom 32 is connected to the first boom 30 and pivoted in the lateral direction of the traveling direction. The second pivot 32 is connected to the lateral pivoting arm 320 and one end is connected to the lateral pivoting arm 320 in the longitudinal direction of the traveling direction. The front-rear direction pivot arm 321 is configured to be rotated, and the mowing work unit holding arm 326 is coupled to the pivot end side of the front-rear direction pivot arm 321 so as to be pivotable in the front-rear direction. The mowing working unit 4 can be moved back and forth with respect to the tractor 1 by rotating the.

The side turning arm 320 and the end of the first boom 30 are connected by a second boom turning shaft 324 provided in the front-rear direction. In response to the expansion and contraction of the second boom rotation cylinder 322, the side rotation arm 320 rotates in the vertical direction, that is, in the vehicle width direction, with the second boom rotation shaft 324 as the rotation center.
The base of the second boom rotation cylinder 322 is attached closer to the second link arm rotation shaft 313 of the first boom 30. The tip end portion of the second boom turning cylinder 322 is a tip end shaft of the second boom turning cylinder provided at a position extending from the side turning arm 320 to the first boom 30 side with respect to the second boom turning shaft 324. 327. The first boom 30 and the side pivot arm 320 are pivotable in the vertical direction.

  The front / rear direction rotating arm 321 is formed of a hollow cylindrical metal square pipe. Reference numeral 323 denotes a second boom front-rear direction rotating cylinder. The base of the second boom front-rear direction rotation cylinder 323 is attached to the side rotation arm 320. The distal end of the second boom front / rear direction rotating cylinder 323 is attached to the substantially central portion of the front / rear direction rotating arm 321. The front / rear direction pivot arm 321 is pivotable with respect to the side pivot arm 320 in the front / rear direction, that is, in the forward or backward direction.

  The side pivot arm 320 rotates in the front-rear direction with respect to the first boom 30 so that the front-rear direction pivot arm 321 rotates in the up-down direction and the front-rear direction different from each other by 90 degrees. The moving arm 321 is connected. The front / rear direction rotation arm 321 connects the mowing work part 4 to the tip via a mowing work part holding arm 326 connected to one end opposite to the side rotation arm 320. In accordance with the expansion and contraction of the second boom rotation cylinder 322 and the second boom front / rear direction rotation cylinder 323, the front / rear direction rotation arm 321 is a rotation fulcrum provided on the second boom rotation shaft 324 and the side rotation arm 320. The shaft 325 is pivoted in the vertical direction and the front-rear direction, that is, the vehicle width direction and the traveling direction or the backward direction.

The mowing work unit holding arm 326 connects the front-rear direction rotating arm 321 and the mowing work unit 4. The front / rear direction rotation arm 321 and the mowing work unit holding arm 326 are rotatable about the rotation fulcrum 328 in the front / rear direction, that is, in the traveling direction or the backward direction.
Reference numeral 334 denotes a mowing operation part rotating cylinder. The mowing work part rotating cylinder 334 rotates the mowing work part 4 in the vertical direction with the mowing work part rotating shaft 337 in the front-rear direction as the center of rotation with respect to the mowing work part holding arm 326.

  Reference numeral 33 denotes a second link mechanism. The second link mechanism 33 includes a work unit side first link arm 330 whose one end is rotatably connected to the mowing work unit holding arm 326 side, and an operation whose one end is rotatably connected to the mowing work unit 4 side. The mowing working part rotating cylinder is connected to the part side second link arm 331 so as to be rotatable, and is spanably connected to the working part side second link arm 331 and the mowing work part holding arm 326 side. 334.

  The working unit side first link arm 330 has a ring shape that is approximately semicircular, and the working unit side second link arm 331 also has a ring shape that is approximately semicircular as a whole. The side second link arm 331 is connected by a mounting shaft 332. The working unit side first link arm 330 is connected to the mowing working unit holding arm 326 by a mounting shaft 333. The working part side second link arm 331 and the mowing work part 4 are connected to the mowing work part 4 by an attachment shaft 335. The mowing working unit 4 is pivotably connected around the pivoting shaft 337 in the front-rear direction. Therefore, the mowing operation unit 4 is rotatable in the vertical direction with respect to the mowing operation unit holding arm 326.

The working part side second link arm 331 and the mowing work part rotating cylinder 334 are closer to the mowing work part 4 side than the connecting shaft 332 between the working part side first link arm 330 and the working part side second link arm 331. The mounting shaft 336 at a position away from the mounting shaft 335 is rotatably connected.
The working unit side first link arm 330 and the working unit side second link arm 331 are formed in a substantially circular ring shape. Therefore, the amount of movement becomes large, and the amount of folding as a whole can be increased.

  A rod (not shown) that rotatably connects the side rotation arm 320 and the mowing work unit holding arm 326 is provided in the hollow cylindrical metal square pipe of the front / rear direction rotation arm 321. Thus, a parallel link is configured with the front-rear direction rotating arm 321. For this reason, even when the front-rear direction rotation arm 321 rotates in the front-rear direction, the mowing work unit holding arm 326 is configured to maintain a state orthogonal to the traveling direction. Therefore, the mowing working unit 4 also maintains the orthogonal state.

  The mowing operation unit 4 is attached to a mowing operation unit rotating shaft 40 in a direction orthogonal to the traveling direction with a large number of mowing blades 41 protruding therefrom. A protective cover for preventing scattering from the rotating mowing blade 41 is provided above the mowing working unit 4. Reference numeral 42 denotes a gauge roller, which is positioned behind the mowing working unit rotating shaft 40 and has a horizontal rotating shaft, and grounds the farm scene during operation to stabilize the cutting height. 43 is a hydraulic motor. The hydraulic motor 43 is rotated by the hydraulic pressure generated by the hydraulic pump 51 to rotationally drive the mowing working unit rotating shaft 40 to which the mowing blade 41 is attached.

  Each hydraulic operating part of the mower A is provided in the center of the front part of the support frame 2 and is operated by hydraulic pressure generated from a hydraulic pump 51 that is rotationally driven by power from the tractor 1. The power from the tractor 1 is input by connecting an input shaft (not shown) provided to protrude in front of the hydraulic pump 51 and a PTO shaft (not shown) of the tractor 1 by a universal joint or the like. A hydraulic oil tank 50 is provided on the right side of the support frame 2 shown in FIG. 1, and oil used by being piped to each hydraulic operating portion is stored. In addition, a hydraulic operation valve 52 for switching the piping to each hydraulic operating portion is provided in a cover on the side portion on the center side of the hydraulic oil tank 50. The hydraulic operation valve 52 is an electrically operated valve that is electrically operated and is electrically operated by an operation lever 6 provided in the vicinity of the driver's seat in the tractor 1. Each hydraulic operating part is piped by a hydraulic hose or the like (not shown).

  FIG. 3 is a hydraulic circuit diagram of the mower A of the present invention. A hydraulic pump 51 that is a source of hydraulic pressure is rotated by the power from the tractor 1 to generate hydraulic pressure. In this example, the hydraulic pump 51 is divided into two systems, a hydraulic system for rotating the mowing working unit 4 and a hydraulic system for operating each hydraulic cylinder. The hydraulic motor 43 for rotating the mowing operation unit 4 is piped from the hydraulic pump 51 through the mowing blade rotation operation valve 524. The grass cutting blade rotation operation valve 524 is an electromagnetic valve that is electrically operated, and is provided with a port for switching the rotation direction of the hydraulic motor 43 forward and reverse and a neutral port. At the neutral time, the forward / reverse rotation circuit of the hydraulic motor 43 and the drain circuit connected to the hydraulic oil tank 50 are in communication with each other, preventing reverse hydraulic pressure from being generated by inertial rotation from the hydraulic motor 43 during forward / reverse rotation switching or stop operation. To do. In addition, a relief valve 54 is provided in the circuit on the pressurization side so that when the inside of the circuit becomes a certain pressure or more, the oil escapes to the hydraulic oil tank 50 and the pressure does not rise above a certain value. .

  In the hydraulic system for operating each hydraulic cylinder, a hydraulic operation valve 52 is provided between the hydraulic pump 51 and each cylinder, and switches the expansion / contraction operation of each cylinder. The hydraulic operation valve 52 is integrally provided with a lift cylinder operation valve 520, a second boom rotation cylinder operation valve 521, a second boom front / rear direction rotation cylinder operation valve 522, and a mowing operation unit rotation cylinder operation valve 523. ing. A relief valve 54 is provided in the pressure side circuit of each operation valve so that when the pressure in the circuit exceeds a certain level, oil escapes to the hydraulic oil tank 50 and the pressure does not rise above a certain level. It has become. Each valve is an electromagnetic valve that operates electrically, and is electrically operated by an operation lever 6 provided in the vicinity of the tractor 1 driver's seat.

  The lift cylinder operation valve 520 is a valve for operating expansion and contraction of the lift cylinder 300 that raises and lowers the first boom 30. A switching valve 53 is provided between a port on the lift cylinder 300 on the side where the first boom 30 is lifted and the lift cylinder operation valve 520. The switching valve 53 includes a check valve 530 side in which the lowering direction of the first boom 30 is blocked and the rising direction is in a free state, and a side in which the circuit is released and the first boom 30 is in a free state. Can be switched to.

  When the lift cylinder operation valve 520 is switched in the direction in which the first boom 30 is lifted while the switching valve 53 is switched to the check valve 530 side, the oil passes through the check valve 530 of the switching valve 53 and this example of the lift cylinder 300. The oil flows into the port on the contracting side, and the oil in the other port flows into the circuit on the return side to the hydraulic oil tank 50. When the lift cylinder operation valve 520 is switched in the direction in which the first boom 30 is lowered, the switching valve 53 is switched to the circuit released side. The switching is electrically controlled and is set to automatically switch when the lift cylinder operation valve 520 is switched. For this reason, oil flows into the port in the direction in which the lift cylinder 300 extends in this example, and from the other port, the oil flows through the switching valve 53 to the circuit on the return side to the hydraulic oil tank 50.

  When the lift cylinder operation valve 520 is in the neutral state, the circuit in the direction in which the first boom 30 descends, that is, the direction in which the lift cylinder 300 in this example extends is blocked by the check valve 530 of the switching valve 53, and the first The lowering of the boom 30 is locked. At this time, when an external force is applied in the direction in which the first boom 30 is raised, the check valve 530 is opened, and the first boom 30 can freely move in the upward direction. For this reason, when the mowing operation part 4 is lifted carelessly by an obstacle or the like, an excessive load is prevented from acting on the arm part 3 to protect the mower A.

  Further, when the mowing operation unit 4 is in contact with the field during mowing, the lift cylinder operation valve 520 is set to the neutral state, and the switching valve 53 is switched to the side where the circuit is released, the first boom 30 is lifted and lowered. Since it becomes a free state, the mowing work unit 4 can automatically follow the unevenness of the mowing field scene by the own weight of the mowing work unit 4 to make the cutting height constant. For this reason, since the operator does not need to frequently operate the operation lever 6 according to the unevenness of the harvested farm scene, the operator can easily work. In order to switch the switching valve 53 to the side where the circuit is released, the switching valve 53 is switched by pressing the switching valve switching switch 62 of the operating lever 6 provided near the driver's seat of the tractor 1. The selector valve selector switch 62 is switched only when it is pressed. The circuit of the port of the lift cylinder 300 on the side where the first boom 30 is raised is provided with a pressure sensor 55, which is electrically controlled so that the switching valve 53 can be switched only when the pressure is equal to or lower than the set pressure. ing. For this reason, since the switching valve 53 cannot be switched in a state where the pressure is applied to the lift cylinder 300 in a state in which the mowing working unit 4 is lifted from the farm scene, the mowing working unit 4 is not accidentally dropped, which is safe. Thus, the mowing working unit 4 can be prevented from being damaged.

  The second boom rotation cylinder operation valve 521, the second boom front / rear direction rotation cylinder operation valve 522, and the mowing operation portion rotation cylinder operation valve 523 have the same circuit configuration, and the second boom rotation cylinder 322 is provided. The second boom front-rear direction rotation cylinder 323 and the mowing operation part rotation cylinder 334 are respectively piped. In the neutral state, each operation valve is closed in a state where expansion and contraction of each cylinder is prevented. When each operation valve is switched in the expansion / contraction direction, each cylinder expands / contracts and the arm portion 3 can be moved to operate the tilting posture and position of the mowing working portion 4.

  The operation of each operation valve is electrically operated by an operation lever 6 installed near the driver seat of the tractor 1. FIG. 4 shows the operation lever 6. The operation lever 6 has a rod-like grip shape that can be grasped with one hand, and operates each cylinder by tilting back and forth and left and right. The operation lever 6 is provided above the rectangular box, and a rotation direction changeover switch 60 for changing the rotation direction of the mowing operation unit 4 is provided at the front part. When the rotation direction changeover switch 60 is tilted in the front-rear direction, the rotation direction of the mowing operation unit 4 is changed, and when the rotation direction change-over switch 60 is positioned at the center, the hydraulic circuit is in a free state and stops rotating. In the rectangular box, a control unit for operating each operation valve by a signal from the operation lever 6 is incorporated.

  A cylinder changeover switch 61 and a changeover valve changeover switch 62 are provided on the upper surface of the operation lever 6 side by side. Each switch is a switch that operates only when it is pressed, and is operated with the thumb while holding the operation lever 6. When the selector valve selector switch 62 is pressed, the selector valve 53 can be switched to the circuit release side. In this example, when the operation lever 6 is tilted forward in FIG. 4, the lift cylinder 300 extends to rotate the first boom 30 downward, and when tilted backward, the lift cylinder 300 contracts and the first boom 30 is lifted upward. Rotate. Moreover, if it falls to the left, the 2nd boom rotation cylinder 322 will shrink | contract and the 2nd boom 32 will rotate to the side outside, and if it falls to the right, the 2nd boom rotation cylinder 322 will extend and the 2nd boom 32 will be lateral. Rotate inward. Further, when the cylinder changeover switch 61 is pushed down and tilted to the left, the mowing working part rotating cylinder 334 extends to rotate the mowing working part 4 downward, and when tilted to the right, the mowing working part rotating cylinder 334 contracts. The mowing working unit 4 is rotated upward. Furthermore, when the operating lever 6 is tilted forward while pressing the cylinder changeover switch 61, the second boom front / rear direction rotating cylinder 323 extends, the front / rear direction rotating arm 321 of the second boom 32 rotates forward, and the rear When tilted, the second boom front / rear direction rotating cylinder 323 contracts and the front / rear direction rotating arm 321 of the second boom 32 rotates rearward.

  Next, a case where mowing work is performed using the mower A of the present invention will be described. A lower link pin of a mounting portion provided in front of the support frame 2 of the mower is attached to a tractor three-point link mechanism 12 including a pair of left and right lower links 11 provided at the rear of the tractor 1 and a top link 10 provided at the upper center thereof. 21 is the lower link 11 and the top link pin 20 provided on the top of the mast frame formed in a gate shape upward from the left and right lower link pin 21 portions connects the top link 10 and mowing the tractor 1 respectively. Install the machine. Also, the hydraulic pump 51 can be driven by connecting the input shaft of the hydraulic pump 51 provided at the front center portion of the mower and the PTO shaft of the tractor 1 by a universal joint or the like.

  In the mowing field, the PTO shaft of the tractor 1 is rotated to drive the hydraulic pump 51, the operation lever 6 is operated to operate the arm unit 3, and the mowing work unit 4 is positioned in the mowing field. The rotation direction changeover switch 60 is tilted in the desired rotation direction to drive the mowing working unit 4 to rotate. Then, when the tractor 1 is driven, the mowing work is performed. During the operation, when the selector valve selector switch 62 is pressed, the first boom 30 can be raised and lowered freely, and the gauge roller 42 of the mowing work unit 4 abuts against the unevenness of the field scene by its own weight to keep the cutting height constant. To.

  The present invention is used in an arm-coupled mower for performing mowing work that is mounted and used behind a traveling machine such as a tractor.

DESCRIPTION OF SYMBOLS 1 Tractor 10 Top link 11 Lower link 12 Three-point link mechanism 2 Support frame 20 Top link pin 21 Lower link pin 22 Mast 3 Arm part 30 1st boom 300 Lift cylinder 301 Lift cylinder axis 302 Lift cylinder tip axis 303 First boom rotation Moving shaft 31 First link mechanism 310 First link arm 311 First link arm pivot shaft 312 Second link arm 313 Second link arm pivot shaft 32 Second boom 320 Side pivot arm 321 Front / back pivot arm 322 Second boom pivoting cylinder 323 Second boom longitudinal pivoting cylinder 324 Second boom pivoting shaft 325 Rotating fulcrum shaft 326 Mowing working part holding arm 327 Second boom pivoting cylinder tip shaft 328 Rotating fulcrum shaft 33 2nd Link mechanism 330 Working part side first Link arm 331 Working unit side second link arm 332 Mounting shaft 333 Mounting shaft 334 Mowing working unit rotating cylinder 335 Mounting shaft 336 Mounting shaft 337 Mowing working unit rotating shaft 4 Mowing working unit 40 Mowing working unit rotating shaft 41 Mowing blade 42 Gauge roller 43 Hydraulic motor 50 Hydraulic oil tank 51 Hydraulic pump 52 Hydraulic operation valve 520 Lift cylinder operation valve 521 Second boom rotation cylinder operation valve 522 Second boom front / rear direction rotation cylinder operation valve 523 Mowing working unit rotation cylinder operation valve 524 Mowing blade rotation operation valve 53 Switching valve 530 Check valve 54 Relief valve 55 Pressure sensor 6 Operation lever 60 Rotation direction switching switch 61 Cylinder switching switch 62 Switching valve switching switch

Claims (2)

A support frame attached to an agricultural tractor;
A first boom supported at one end of the support frame in the vehicle width direction so as to be rotatable up and down;
A first link mechanism including a lift cylinder for rotating the first boom in the vertical direction;
A second boom pivotally connected to the pivot end side of the first boom and having a mowing working part attached to the tip;
In the mower having the second link mechanism including the mowing working part rotating cylinder for rotating the mowing working part in the vertical direction with respect to the second boom,
In the hydraulic circuit for extending / contracting the lift cylinder of the first boom, an operation valve for extending / contracting the lift cylinder;
A switching valve for switching the expansion and contraction of the lift cylinder to a free state,
The switching valve can be switched only when the operation valve is in a neutral state and the pressure in the hydraulic piping on the side of the lift cylinder for raising the first boom is equal to or lower than an arbitrary pressure. Characteristic mower. 2. The switching valve according to claim 1, wherein the switching valve is provided so as to operate electrically, and the expansion and contraction of the lift cylinder is switched to a free state only when the operation valve is pushing the operation switch in a neutral state . Mower.

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