JP3096922B2 - Hydraulic device for parallel lifting operation of the agricultural front loader attachment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural front loader which is detachably mounted on a tractor (for example, a bucket, a hay fork, a mania fork, etc.). The present invention relates to a hydraulic device for operating a vertical lifting operation of an attachment for an agricultural front loader.

[0002]

[Premise structure] The hydraulic device for parallel lifting operation of the attachment of the agricultural front loader of the present invention is disclosed in, for example, Japanese Patent Application No. 62-36542.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-209, and as shown in Conventional Example 1 of FIG. 6 and Conventional Example 2 of FIG.

That is, a lift arm 3 is pivotally supported by a lift cylinder 4 on a loader base frame 2 of an agricultural front loader 1 so that the lift arm 3 can be driven to swing up and down.
Further, the attachment 5 is pivotally supported by a dump cylinder 6 so as to be able to swing back and forth, and a parallel control cylinder 7 is provided in parallel with the lift cylinder 4 over the loader base frame 2 and its lift arm 3.

[0006] The lift cylinder 4, dump cylinder 6, and parallel control cylinder 7 are connected to a hydraulic pump 9 and an oil tank 10 via a direction switching valve device 8. In addition, the direction switching valve device 8 is configured to be able to selectively switch between a squeeze input state A, a dump input state B, a parallel upward input state C, and a parallel downward input state D.

The hydraulic oil pumped by the hydraulic pump 9 presses into the squeeze operating chamber 6a of the dump cylinder 6 in the squeeze input state A, and presses into the dump operating chamber 6b of the dump cylinder 6 in the dump input state B. The configuration is as follows.
In the parallel rising state C, the pressure oil of the hydraulic pump 9 is supplied to the lift-up operation chamber 4 of the lift cylinder 4.
a into the dump working chamber 6b of the dump cylinder 6, and
a from the parallel control cylinder 7
Is press-fitted into the parallel control oil chamber 7a.

Further, in the parallel lowering injection state D, the pressure oil of the hydraulic pump 9 is pressed into the lift-down operating chamber 4b of the lift cylinder 4, and the hydraulic oil is supplied from the parallel control oil chamber 7a of the parallel control cylinder 7. The discharged hydraulic oil is pressed into the squeeze operation chamber 6a of the dump cylinder 6, and the return oil discharged from the dump operation chamber 6b of the dump cylinder 6 and the lift-up operation chamber 4a of the lift cylinder 4 is discharged. , And is configured to return to the oil tank 10.

[0007]

2. Description of the Related Art In the above-mentioned premise structure, the operation states necessary for operating the agricultural front loader 1 are four operations of squeeze, dump, parallel ascent and parallel ascent. Was supposed to. ○ Conventional example 1 (see Fig. 6)

The direction switching valve device 8 includes a direction switching valve 20 for dump operation, a direction switching valve 21 for lift operation, and a direction switching valve 22 for parallel lifting / lowering operation. The dump operation direction switching valve 20 includes a squeeze position M, a neutral position N, and a dump position P. The lift operation direction switching valve 21 includes a lift-down position Q, a neutral position R, and a lift-up position S. The direction switching valve 22 for the parallel lifting / lowering operation has a communication position T and a cutoff position U.

When the directional control valve 21 for lift operation is set to the neutral position R
In a state in which the parallel up / down operation direction switching valve 22 is located at the shutoff position U and the dump operation direction switching valve 20 is operated at the squeeze position M, the squeeze-in state A is set. In the state where the user has operated the dump position P, the state is the dumping state B.

When the directional control valve 20 for dump operation is set to the neutral position N
In the state where the directional control valve 2 for lift operation is
In a state in which 1 is operated at the lift-up position S and the direction control valve 22 for parallel elevating operation is operated at the communication position T, the above-mentioned parallel ascending state C is established. When the user has operated the lift-down position Q and the communication position T, respectively, the state is the parallel-down state D.

The directional control valve 22 for parallel raising / lowering operation is resiliently pressed to a shut-off position U by a spring 22a and is opened to a communication position T by a solenoid 22b. The solenoid 22b is energized by turning on the parallel up / down operation button switch 23. The button switch 23 is attached to the upper end of the operation lever 21a of the lift operation direction switching valve 21.

Conventional Example 2 (see FIG. 7) In the above premise structure, the lift cylinder 4 is changed from a double-acting type to a single-acting type. The single-acting lift cylinder 4 is extended by hydraulic pressure to drive the lift arm 3 upward, and contracts by gravity to allow the lift arm 3 to descend.

The direction switching valve device 8 comprises a direction switching valve 20 for dump operation and a direction switching valve 22 for parallel lifting operation. The dump operation direction switching valve 20 includes a squeeze position M, a neutral position N, and a dump position P. The directional control valve 22 for parallel up / down operation includes a neutral position R, a parallel up position V, and a parallel down position W.

When the directional control valve 22 for dump operation is operated to the squeeze position M while the directional control valve 22 for parallel lifting operation is located at the neutral position R, the squeeze-in state A is set. In the state where the user has operated the dump position P, the state is the dumping state B.

When the directional control valve 20 for dump operation is set to the neutral position N
In the state where the parallel ascent / descent operation direction switching valve 22 is operated to the parallel ascending position V in the state where it is located at the position C, the state is the parallel ascending throwing state C. Further, in the state where the user has operated to the parallel lowering position W, the above-mentioned parallel lowering throwing state D is set. In this parallel lowering state D, the attachment 5 and the lift arm 3
, The lift cylinder 4 contracts.

[0016]

The above prior art has the following problems. -Conventional example 1 a. Three directional control valves, ie, a directional control valve 20 for a dump operation, a directional control valve 21 for a lift operation, and a directional control valve 22 for a parallel lifting / lowering operation, are required, which increases the manufacturing cost.

B. For each operation of parallel ascent and parallel descent,
The operation of the operation lever 21a of the lift operation direction switching valve 21 and the ON operation of the button switch 23 need to be performed in a combined manner, and the operation is complicated.

Conventional example 2 c. Since the lift cylinder 4 is a single-acting type, the lowering speed of the lift arm 3 is determined by gravity, and the working speed is reduced. d. By lifting the attachment 5 against the ground and squeezing it with the dump cylinder 6, in the work of digging a hole in the ground, the lift arm 3 descends only by its own weight,
The attachment 5 is less protruded into the ground, and the efficiency of digging work is low.

Conventional example 1, Conventional example 2 e. During the parallel lowering, when the dump cylinder 6 reaches the squeeze operation end, an abnormal pressure is about to be generated in the parallel control oil chamber 7a of the parallel control cylinder 7. When the abnormal pressure is released by the relief valve, oil deterioration and packing burning occur due to power loss and abnormal rise in oil temperature. The present invention relates to the aforementioned a. To e. It is an object to solve each of the above problems.

[0020]

According to the present invention, in order to achieve the above-mentioned object, the following characteristic structure is added to the above-described premise structure, for example, as shown in FIGS. ○ First invention That is, the direction switching valve device 8 includes the hydraulic pump 9
The oil tank 10 is configured to be able to communicate with the lift cylinder 4 and the dump cylinder 6 via the forward / reverse selection direction switching valve 11 and the cylinder selection direction switching valve 12 in order. The forward / reverse selection direction switching valve 11
Has a neutral position E, a normal feed position F, and a reverse feed position G.

The directional control valve 12 for selecting a cylinder
Are the dump cylinder selection position H and the parallel lifting / lowering selection position J
Is provided. When the cylinder selecting direction switching valve 12 is operated at the dump cylinder selecting position H and the forward / reverse selecting direction switching valve 11 is operated at the normal feed position F, the squeeze-in state A
(See FIG. 3 (X)), and when the dump cylinder selecting position H and the reverse feed position G are operated, the dumping state B is established (see FIG. 3 (Y)).

Further, in the state where the operation is performed between the parallel up / down selection position J and the forward feed position F, the parallel up / down insertion state C is obtained (see FIG. 1). Is operated in the parallel lowering state D (see FIG. 2).

In the first invention, the squeeze operation chamber 6a and the dump operation chamber 6b of the dump cylinder 6 are communicated via the lock release valve 13, and the valve 13a of the lock release valve 13
Is configured to be closed by the valve closing spring 13b and to be opened by the operating force of the piston 6c at the end of the squeeze operation of the dump cylinder 6.

[0024]

The present invention has the following effects because it is constructed and operates as described above. ○ First invention

A. Only two directional control valves, ie, the directional control valve 11 for forward / reverse selection and the directional control valve 12 for cylinder selection, are required, and one can be omitted as compared with the case of the prior art 1 in which three directional control valves are required. Become.

B. The number of operation of the directional control valve is only two, that is, parallel ascent and parallel ascent. c. Since the lift cylinder 4 is of the double-acting type, the lowering speed of the lift arm 3 can be increased and the working speed can be increased as compared with the case of the single-acting type of the second conventional example.

D. In the work of digging a hole in the ground by pushing the attachment 5 against the ground and squeezing with the dump cylinder 6, the lifting arm 3 is driven downward by the lift cylinder 4, and the speed of the attachment 5 into the ground is improved. The power can be increased, and the weight of the tractor can be applied to the attachment 5 by floating the front wheels, so that the efficiency of the digging operation can be improved.

○ Second invention e. During the parallel lowering, when the dump cylinder 6 reaches the squeeze operation end, the operation of the piston 6c of the dump cylinder 6 causes the lock release valve 13 to open, and from the parallel control oil chamber 7a of the parallel control cylinder 7 The hydraulic pressure of the oil pushed into the squeeze working chamber 6a of the dump cylinder 6 is released. As a result, it is possible to eliminate the power loss and the oil deterioration and the packing burnout caused by the abnormal rise of the oil temperature when the abnormal pressure is released by the relief valves of the first and second conventional examples.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an operating system diagram of the hydraulic device for the parallel raising / lowering operation of the attachment of the agricultural front loader at the time of parallel raising, FIG. 2 is an operating system diagram of the same device at the time of parallel lowering, and FIG. FIG. 3 (Y) is a main part operation system diagram at the time of dumping of the same device, FIG. 4 is a cross-sectional view of the lock release valve 13, and FIG. 5 shows another embodiment, and FIG. FIG.

In FIG. 1, reference numeral 1 denotes an agricultural front loader. The agricultural front loader 1 is mounted on a tractor (not shown) via a loader base frame 2 so as to be exchangeable.
A lift arm 3 is pivotally supported on the loader base frame 2 by a double-acting lift cylinder 4 so that the lift arm 3 can be vertically driven to swing.
The bottom of the hydraulic working chamber in the lift cylinder 4 is
Lift up working chamber 4a, rod side lift down
It becomes the working chamber 4b.

An attachment (bucket) 5 is pivotally supported by a double-acting dump cylinder 6 so as to be able to swing back and forth at the tip 3a of the lift arm 3. This dump serial
The rod 6R of the lifter 6 has a pin 2
1, the cylinder body 6S of which is attached to the attachment 5
To the input link 23 of the four-link mechanism 22 for driving the
24. Oil in this dump cylinder 6
In the pressure working chamber, the bottom side is the squeeze working chamber 6a,
The dump side is the dump working chamber 6b.

As shown in FIG . 1, there is no work in the dump working chamber 6b.
When hydraulic oil is injected, lift arm 3 and lock
The cylinder 6S moves forward with respect to the arm 6 (to the left in FIG. 1).
Move), pin 24, input link 23, quadruple link mechanism
Attachment 5 is dump-driven 25 via 22
You.

As shown in FIG . 2, there is no work in the squeeze working chamber 6a.
When hydraulic oil is injected, lift arm 3 and lock
The cylinder body 6S moves backward with respect to the door 6R (rightward in FIG. 2).
To 24), pin 24, input link 23, quadruple link machine
The attachment 5 is connected to the squeeze drive 26 via the structure 22.
It is.

Further, a single-acting parallel control cylinder 7 is provided in parallel with the lift cylinder 4 over the loader base frame 2 and the lift arm 3 thereof. This parallel system
The hydraulic chamber 7a for parallel control of the control cylinder 7 is shown in FIG.
The expansion operation is performed when the lift arm 3 is driven upward 27.
On the other hand, the lift arm 3 shown in FIG.
When the contraction is performed.

Hydraulic chamber for parallel control of parallel control cylinder 7
7a is a screw cylinder of the dump cylinder 6 via the oil passage 29.
It communicates with the working chamber 6a. As shown in FIG.
And the parallel control hydraulic chamber 7a is expanded.
When the tension operation is performed, part of the pressure oil in the squeeze operation chamber 6a
Flows into the parallel control hydraulic chamber 7a, and the squeeze operating chamber 6a
Is retracted, and the cylinder body 6S of the dump cylinder 6 moves forward.
Advance, pin 24, input link 23, quadruple link mechanism 22
, The attachment 5 is dump-driven 25.

On the contrary, as shown in FIG.
The arm 3 is driven downward to retract the parallel control hydraulic chamber 7a.
When the compression operation is performed, the pressure of the parallel control hydraulic chamber 7a is reduced.
Part of the oil is press-fitted into the squeeze operating chamber 6a,
6a expands, and the cylinder body 6S of the dump cylinder 6 moves rearward.
Retreat, pin 24, input link 23, quadruple link mechanism 22
The attachment 5 is driven 26 via the drive.

The lift cylinder 4, the dump cylinder 6, and the parallel control cylinder 7 are connected to a hydraulic pump 9 and an oil tank 10 via a direction switching valve device 8. The direction switching valve device 8 is configured to be able to selectively switch between a squeeze input state A, a dump input state B, a parallel upward input state C, and a parallel downward input state D. Reference numerals 16a, 16b and 16c are relief valves, and reference numeral 17 is a check valve.

In the first invention, the directional control valve device 8 connects the hydraulic pump 9 and the oil tank 10 to the directional control valve 11 for forward / reverse selection, the directional control valve 12 for cylinder selection, and the electromagnetic floating valve 14 in order. It is configured such that it can communicate with the lift cylinder 4 and the dump cylinder 6.

The forward / reverse selection direction switching valve 11
Is provided with a neutral position E, a normal feed position F, and a reverse feed position G, and is controlled so that the opening amount can be adjusted by digital control valves 15a and 15b.

The cylinder selecting direction switching valve 12
Are the dump cylinder selection position H and the parallel lifting / lowering selection position J
, And is electromagnetically controlled to be on / off. When the cylinder selection direction switching valve 12 is operated at the dump cylinder selection position H and the forward / reverse selection direction switching valve 11 is operated at the normal feed position F, the squeeze-in state A is set. On the other hand, in a state where the operation is performed between the dump cylinder selecting position H and the reverse feed position G, the dumping state B is configured.

The pressure oil pumped by the hydraulic pump 9 presses into the squeeze operation chamber 6a of the dump cylinder 6 in the squeeze input state A, and enters the dump operation chamber 6b of the dump cylinder 6 in the dump input state B. Press fit.

Further, in the state where the operation is performed between the parallel elevation selection position J and the normal feed position F, the parallel elevation insertion state C
And the pressure oil of the hydraulic pump 9 is supplied to the lift cylinder 4
The hydraulic oil discharged from the squeeze operation chamber 6a of the dump cylinder 6 is pressed into the lift-up operation chamber 4a and the dump operation chamber 6b of the dump cylinder 6, and the parallel control oil chamber of the parallel control cylinder 7 7a. Note that the cylinder cross-sectional area of the dump cylinder 6 and the rod cross-sectional area of the parallel control cylinder 7 are appropriately set so as to maintain the parallel movement of the attachment 5.

On the other hand, in the state in which the operation has been performed between the parallel lifting / lowering selection position J and the reverse feed position G, a parallel lowering / injection state D is established, and the hydraulic oil of the hydraulic pump 9 is pressed into the lift-down operation chamber 4b of the lift cylinder 4. And parallel control cylinder 7
The hydraulic oil discharged from the parallel control oil chamber 7a is pressed into the squeeze operation chamber 6a of the dump cylinder 6, and is discharged from the dump operation chamber 6b of the dump cylinder 6 and the lift-up operation chamber 4a of the lift cylinder 4. The return oil is returned to the oil tank 10.

The electromagnetic floating valve 14 normally operates at the floating stopping position L shown in FIG.
Floating operating position M by floating lever
Side, and the lift arm 3 is brought into a floating state in which the lift arm 3 can freely swing up and down.

The operation of the first invention. . Operation when the attachment 5 rises in parallel. See Figure 1
Teru. FIG. 1 is an operation system diagram when the attachment 5 is raised in parallel.
You. In the state of the parallel ascent in FIG.
The selection directional control valve 12 is operated to the parallel up / down selection position J.
And the forward / reverse selection direction switching valve 11 is moved to the normal feed position F.
By operation, the direction switching valve device 8 is thrown in parallel upward.
It becomes the input state C.

In the parallel ascent state C, the hydraulic pressure
The pressurized oil sent from the pump 9 is refilled by the lift cylinder 4.
Dump work of the lift-up working chamber 4a and the dump cylinder 6
It is press-fitted into the moving chamber 6b. Lift cylinder 4 lifter
When the working chamber 4a is expanded by pressurized oil, the lift
The arm 3 is raised 27. Dump cylinder 6
When the working chamber 6b is expanded by pressurized oil, the cylinder
The trunk 6S moves forward, and the pin 24, the input link 23, and the four-link
Attachment 5 is driven through dump mechanism 2
5

The dump drive 25 of the attachment 5
The dump speed is such that the pressure oil in the squeeze working chamber 6a to be compressed is
Depending on the amount flowing into the parallel control hydraulic chamber 7a through the passage 29.
Is controlled. That is, the lifting drive of the lift arm 3
27 is the amount by which the parallel control hydraulic chamber 7a expands.
Then, the squeeze working chamber 6a contracts. As a result,
The lifting speed of the lifting drive 27 of the
And the dump speed of the dump drive 25 of the
Attachment 5 goes up in parallel
It is.

[0048]. Work when attachment 5 is lowered in parallel
Motion. See FIG. FIG. 2 is an operation system diagram when the attachment 5 is lowered in parallel.
You. In the state at the time of parallel lowering of FIG.
The selection directional control valve 12 is operated to the parallel up / down selection position J.
And the forward / reverse selection direction switching valve 11 is moved to the reverse feed position G.
When operated, the directional control valve device 8 causes the parallel downward throw.
It becomes the ON state D.

In the parallel lowering state D, the hydraulic pressure
The pressurized oil sent from the pump 9 is refilled by the lift cylinder 4.
The lift arm 3 is press-fitted into the
Drive down 28. Accordingly, the parallel control cylinder 7
Of the parallel control hydraulic chamber 7a is contracted,
The pressure oil in the control hydraulic chamber 7a is dumped through the oil passage 29.
The cylinder body 6S
Is driven backward, and the pin 24, the input link 23, and the four-link
The attachment 5 is moved through the
6

Lowering speed of the lowering drive 28 of the lift arm 3
First, the contraction speed of the parallel control working chamber 7a is determined.
And then the expansion of the squeeze working chamber 6a of the dump cylinder 6.
The speed is determined, and the squeeze drive 2 for the attachment 5
6 is determined. Thereby, the lift arm 3
Of the attachment and the squeezing speed of the attachment 5
Is maintained, and the attachment 5 descends in parallel.
Go.

[0051]. Operation when the attachment 5 is squeezed.
See FIG. FIG. 3 (X) is an operation system diagram when the attachment 5 is squeezed.
It is. In the state at the time of squeeze of FIG. 3 (X),
Cylinder selection directional control valve 12 is in dump cylinder selection position
H, and the direction switching valve 11 for forward / reverse selection.
Is operated to the normal feed position F, so that the direction switching valve
The device 8 is in the squeeze-in state A.

In this state A, the lift
Lift-up operation chamber 4a of cylinder 4 is also lift-down
The moving chamber 4b is also provided with the damper of the directional switching valve 12 for cylinder selection.
It is closed at each of the cylinder selection positions H. others
The lift cylinder 4 is fixed to a certain length
The arm 3 is now fixed at a certain height.

The pressure oil sent from the hydraulic pump 9 is
Press-fit into the squeeze working chamber 6a of the
The cylinder body 6S is driven backward to move the pin 24
Attachment member via link 23/4 link mechanism 22
Is driven 26 by the squeeze drive.

[0054] . Operation when the attachment 5 is dumped.
See FIG. FIG. 3 (Y) is an operation system diagram when the attachment 5 is dumped.
It is. In the state at the time of dumping in FIG.
Cylinder selection directional control valve 12 is in dump cylinder selection position
H, and the direction switching valve 11 for forward / reverse selection.
Is operated to the reverse feed position G, so that the direction switching valve
The device 8 is in the dumping state B.

In the dumping state B, the lift
Lift-up operation chamber 4a of cylinder 4 is also lift-down
The moving chamber 4b is also provided with the damper of the directional switching valve 12 for cylinder selection.
It is closed respectively with phosphoric da selected position H. others
The lift cylinder 4 is fixed to a certain length
The arm 3 is now fixed at a certain height.

The pressure oil sent from the hydraulic pump 9 is
Press-fit into the dump working chamber 6b of the
The cylinder body 6S is driven forward to move the pin 24
Attachment member via link 23/4 link mechanism 22
That is, the drive 5 is driven to dump.

○ Second Invention In the first invention, as shown in FIG. 1 or FIG.
The squeeze operation chamber 6a and the dump operation chamber 6b of the dump cylinder 6 are communicated via the lock release valve 13. As shown in FIG. 4, the valve body 13a of the lock release valve 13
The valve is closed by the valve-closing spring 13b and is opened by the operating force of the piston 6c at the end of the squeeze operation of the dump cylinder 6.

With this configuration, when the dump cylinder 6 reaches the squeeze operating end while the lift arm 3 is descending in the above-mentioned parallel lowering state D, an attempt is made to generate in the parallel control oil chamber 7a of the parallel control cylinder 7. When the relief pressure is released by the relief valve, oil loss and packing burnout occur due to power loss and abnormal rise in oil temperature, but the lock release valve 13 is opened at the end of the squeeze operation of the dump cylinder 6 during parallel lowering. The valve is opened to communicate the squeeze operation chamber 6a of the dump cylinder 6 with the dump operation chamber 6b, and the squeeze operation is automatically released and the lock is released. As a result, oil deterioration and packing burnout due to power loss and abnormal rise in oil temperature do not occur.

Instead of the electromagnetic floating valve 14,
As shown in FIG. 5, a single / double switching valve 1 is provided between a lift-down operation chamber 4b of the lift cylinder 4 and the oil tank 10.
8, the same operation can be performed.

Further, the lock release valve 13 is added to the dump operation end portion of the dump cylinder 6 so as to operate in the reverse direction, or is installed inside the dump cylinder 6 instead of the dump cylinder 6. It is also possible to independently attach it outside.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is an operation system diagram of a hydraulic device for parallel lifting operation of an attachment of a front loader for agricultural use at the time of parallel lifting.

FIG. 2 shows an embodiment of the present invention, and is an operation system diagram of the same device at the time of parallel descent.

FIG. 3 shows an embodiment of the present invention. FIG. 3 (X) is a main part operation system diagram of the same device at the time of squeezing, and FIG. 3 (Y) is a main part operation system diagram of the same device at the time of dumping.

FIG. 4 is a sectional view of the lock release valve 13 according to the embodiment of the present invention.

FIG. 5 shows another embodiment of the present invention, and is an essential part operation system diagram corresponding to FIG. 1;

FIG. 6 is a view showing a conventional example 1 and corresponding to FIG. 1;

FIG. 7 is a view showing Conventional Example 2 and corresponding to FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Farm front loader, 2 ... Loader base frame, 3 ... Lift arm, 3a ... Tip part, 4 ... Lift cylinder, 4a ... Lift-up operation chamber, 4b ... Lift-down operation chamber, 5 ... Attachment, 6 ... Dump cylinder, 6a: Squeeze working chamber, 6b: Dump working chamber, 6c: Piston, 7: Parallel control cylinder, 7a: Parallel control oil chamber, 8: Direction switching valve device, 9: Hydraulic pump, 10: Oil tank, 11 ... Directional switching valve for forward / reverse selection, 12 ... Directional switching valve for cylinder selection, 1
3: unlocking valve, 13a: valve body, 13b: valve closing spring, A
... Squeeze-in state, B ... Dump-in state, C ... Parallel ascending state, D ... Parallel-down state, E ... Neutral position, F ...
Forward feed position, G: reverse feed position, H: dump cylinder selection position, J: parallel up / down selection position.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02F 3/43 E02F 9/22

Claims (2)

(57) [Claims] 1. A loader base frame of an agricultural front loader (1).
In (2), the lift arm (3) is pivotally supported by a lift cylinder (4) so as to be vertically oscillatingly driven, and a tip end of the lift arm (3) is provided.
(3a) Attachment (5) is pivotally supported by a dump cylinder (6) so that it can be driven to swing back and forth, and a parallel control cylinder (5) is provided over the loader base frame (2) and its lift arm (3). 7)
Is provided in parallel with the lift cylinder (4), and the lift cylinder (4), the dump cylinder (6), and the parallel control cylinder (7) are connected to the hydraulic pump via a directional switching valve device (8). (9) and the oil tank (10), and the direction switching valve device (8) is in a squeeze input state (A), a dump input state (B), a parallel upward input state (C), and a parallel downward input state.
(D) The hydraulic pump is configured to be switchable
The pressure oil fed in (9) is pressed into the squeeze working chamber (6a) of the dump cylinder (6) in the squeeze-in state (A), and is dumped in the dump cylinder (6) in the dumping state (B). It is configured to be press-fitted into the working chamber (6b), and in the parallel ascending charging state (C), the hydraulic oil of the hydraulic pump (9) is supplied to the lift-up working chamber (4a) of the lift cylinder (4) and the lift-up working chamber (4a). It is press-fitted into the dump working chamber (6b) of the dump cylinder (6), and the squeeze working chamber (6a) of the dump cylinder (6).
Hydraulic fluid discharged from the cylinder for parallel control (7)
The parallel control oil chamber (7a) is press-fitted. In the parallel lowering state (D), the pressure oil of the hydraulic pump (9) is supplied to the lift-down operation chamber (4) of the lift cylinder (4). 4
b), and pressurizes hydraulic oil discharged from the parallel control oil chamber (7a) of the parallel control cylinder (7) into the squeeze operation chamber (6a) of the dump cylinder (6). A farm front configured to return the return oil discharged from the dump working chamber (6b) of the dump cylinder (6) and the lift-up working chamber (4a) of the lift cylinder (4) to the oil tank (10). In the hydraulic device for parallel lifting operation of the attachment of the loader, the direction switching valve device (8) switches the hydraulic pump (9) and the oil tank (10) to the direction switching valve (11) for forward / reverse selection and the direction switching for cylinder selection. Lift cylinder (4) and dump cylinder (6) via valve (12) in sequence
The directional control valve (11) for forward / reverse selection has a neutral position (E) / forward feed position (F) and a reverse feed position (G). Switching valve
(12) has a dump cylinder selection position (H) and a parallel lifting / lowering selection position (J).
When 2) is operated to the dump cylinder selection position (H) and the forward / reverse selection direction switching valve (11) is operated to the forward feed position (F),
In the state where the squeeze input state (A) is set, and the dump cylinder selection position (H) and the reverse feed position (G) are operated, the dump input state (B) is set, and the parallel vertical selection position (J) is set. In the state where it has been operated to the forward feed position (F),
It is configured to be in the parallel ascending state (C), and to operate in the parallel ascending / descending selection position (J) and the reverse feed position (G) as the parallel ascending state (D). Hydraulic device for parallel lifting operation of the agricultural front loader attachment. 2. A squeeze working chamber of the dump cylinder (6).
(6a) and the dump working chamber (6b) are communicated via an unlocking valve (13), and the valve body (13
a) The valve is closed by the valve closing spring (13b), and the piston (6c) at the end of the squeeze operation of the dump cylinder (6).
The hydraulic apparatus for parallel lifting operation of an attachment of a front loader for agricultural use according to claim 1, wherein the valve is configured to be opened by an operating force.