JPH0827842A - Hydraulic device of paralelly lifting loader - Google Patents

Abstract

PURPOSE:To securely hold a dump cylinder even when a large working reaction acts on the dump cylinder. CONSTITUTION:A cylinder chamber 19a for a dump of a dump cylinder 19 and a cylinder chamber 8b for a moving-down of a lift cylinder 8 are connected together by a connection path 39. A relief valve 40 is provided in the connection path 39. When a changeover valve 31 for lift is changed over to a lift position X in order to extend the lift cylinder 8, the cylinder chamber 8a for lift is connected to a hydraulic pump P and the cylinder chamber 8b for moving-down is connected to an oil tank T through the path 30. An external force contracting the cylinder 19 for damp works in the lifting control state, the hydraulic oil in the cylinder chamber 19a for the dump is conducted to the oil tank T through the relief valve 40 and hence, the contraction is allowed. On the other hand, when the changeover valve is turned to the neutral position, the path 30 is closed and hence, even if the relief valve 40 is opened, the hydraulic oil in the cylinder chamber 19a is not discharged to the oil tank T.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device for a parallel lifting type loader provided on a work vehicle such as a tractor.

[0002]

[Prior art]

(Basic Structure Premised on the Present Invention) First, the basic structure of the parallel lifting type loader premised on the present invention will be described with reference to FIG. 2 corresponding to the embodiment of the present invention. That is, the lift arm 6 that is vertically swung by the lift cylinder 8
A dump cylinder 19 that supports the attachment 12 so that it can swing up and down and swings the attachment 12 in the vertical direction is provided. While the lift arm 6 is swinging, the inclination angle of the attachment 12 is set by the parallel lifting mechanism L. It is configured such that it can be held within the range.

In the loader 3, the attachment 1
In order to prevent 2 from swinging toward the dump side by a predetermined amount or more, when the full dump stopper A is provided, the lift arm 6 may be lifted and locked. That is, the solid line diagram in FIG. 2 shows the full dump descending state in which the dump cylinder 19 is extended and the lift cylinder 8 is contracted, but in this full dump descending state, the lift arm 6 cannot be lifted. .

More specifically, in the link type parallel elevating mechanism L shown in FIG. 2, the intermediate swing arm 16 is used to switch the lift arm 6 from the full dump descending state shown by the solid line diagram to the ascending state shown by the two-dot chain line diagram. Must be swung clockwise to increase the diagonal length connecting the pins 7 and 23 of the parallel lifting mechanism L. However, the swinging of the arm 16 in the clockwise direction is prevented by the extended dump cylinder 19 and the full dump stopper A, so that the lift arm 6 cannot be raised.

(Structure of Conventional Hydraulic System) In order to avoid the above-mentioned up-lock state, the hydraulic system of the loader 2 is conventionally configured as shown in the first conventional example of FIG. 5 or the second conventional example of FIG. I was making up.

In the first conventional example of FIG. 5, the lift cylinder 8
Both the dump cylinder 19 and the dump cylinder 19 are configured as a single rod type. The lift cylinder 8 has a lifting cylinder chamber 8a.
And a lowering cylinder chamber 8b, and a lift switching valve 31
Is extended by switching to the ascending position X, and contracted by switching the switching valve 31 to the descending position Y. The dump cylinder 19 is the dump cylinder chamber 1
9a and a squeeze cylinder chamber 19b, and is extended by switching the dump switching valve 32 to the dump position U, and contracted by switching the switching valve 32 to the squeeze position V.

A discharge passage 51 is led out from the dump passage 35 connected to the dump cylinder chamber 19a to the oil tank T, and a relief valve 52 is provided in the discharge passage 51. When the lift arm 6 is lifted from the full dump lowering state shown by the solid line in FIG. 2, the dump cylinder 19 is pushed toward the contraction side by the swing of the intermediate swing arm 16 in the clockwise direction. When the pressure in the dump cylinder chamber 19a becomes equal to or higher than the relief setting pressure due to the pressing force,
The pressure increase in the cylinder chamber 19a is due to the relief valve 5 described above.
2 is released and the dump cylinder 19 is allowed to contract. As a result, the intermediate swing arm 16 is allowed to swing clockwise, and the lift arm 6 is allowed to rise.

A second conventional example shown in FIG. 6 is a dump cylinder 1.
9 is a double rod type, a relief valve 55 is provided between the dump passage 35 and the squeeze passage 36, and when the pressure of the dump cylinder chamber 19a becomes equal to or higher than a set pressure, Drain the oil and dump cylinder 1
9 is allowed to shrink.

[0009]

The first conventional example shown in FIG. 5 has the following problems. When a work reaction force acts in a direction of contracting the dump cylinder 19 during work with a loader, the work pressure is resisted by the hydraulic pressure of the dump cylinder chamber 19a, and the work force of the cylinder chamber increases as the work reaction force increases. The oil pressure of 19a increases. When the oil pressure becomes equal to or higher than the set pressure of the relief valve 52 (for example, about 120 kgf / cm ² ), the pressure oil in the cylinder chamber 19a is discharged to the oil tank T through the relief valve 52, so that the dump cylinder 19 is easily contracted. Therefore, the dump cylinder 19 cannot be reliably held against a large work reaction force, and strong work cannot be performed.

Also in the second conventional example of FIG. 6, the cylinder chamber 19a
When the oil pressure in the cylinder chamber 19a rises above the set pressure of the relief valve 55, the pressure oil in the cylinder chamber 19a passes through the relief valve 55 and passes through the squeeze passage 36.
Since it is released, the dump cylinder 19 is contracted. Therefore, the dump cylinder 19 cannot be reliably held against a large work reaction force, and strong work cannot be performed.

By the way, in the loader 3 having the above-mentioned basic structure, as shown in FIG. 3 corresponding to the embodiment of the present invention, the attachment 12 is swung toward the squeeze side by a predetermined amount or more by the full squeeze stopper B. Even in the case of blocking, the same adverse effects as those of the above-mentioned conventional examples occur. That is, FIG.
The solid line in the figure shows a full squeeze ascending state in which the dump cylinder 19 is contracted and the lift cylinder 8 is extended. In this full squeeze ascending state, the lift arm 6 is in the descending lock state.

More specifically, in the link-type parallel elevating mechanism L shown in FIG. 3, in order to switch the lift arm 6 from the full squeeze raised state shown by the solid line diagram to the lowered state shown by the chain double-dashed line diagram, the intermediate swing arm 16 is used. Must be swung counterclockwise to reduce the diagonal length connecting the pins 7 and 23 of the parallel lifting mechanism L. However, the arm 16
The counterclockwise swinging of the lift arm 6 is prevented by the contracted dump cylinder 19 and the full squeeze stopper B, so that the lift arm 6 cannot be lowered.

In order to avoid this downward lock state,
As shown by the one-dot chain line in FIG. 5, another relief valve 53 needs to be led out from the squeeze passage 36 to the oil tank T, and as shown by the one-dot chain line in FIG.
It is necessary to lead the relief valve 56 from 6 to the dump passage 35. However, in these configurations, when a large work reaction force acts in the direction in which the dump cylinder 19 is extended during work with the loader, the pressure oil in the squeeze cylinder chamber 19b is released through the relief valves 53 and 56. The dump cylinder 19 easily extends. Therefore, the dump cylinder 19 cannot be reliably held against a large work reaction force, and strong work cannot be performed.

An object of the present invention is to reliably hold the dump cylinder against the reaction force of the work.

[0015]

In order to achieve the above-mentioned object, the present invention has a hydraulic device configured as follows, for example, as shown in FIGS. 1 to 3 or 4. .

(Invention of Claim 1) The attachment 12 is supported by a lift arm 6 swingable in a vertical direction by a lift cylinder 8 so as to be swingable up and down, and the attachment 1
2 is provided with a dump cylinder 19 for vertically swinging,
While the lift arm 6 is swinging, the attachment 12 is
The parallel elevating type loader having a full dump stopper A for preventing the attachment 12 from swinging to the dump side by a predetermined amount or more by constructing the parallel elevating mechanism L so that the inclination angle thereof can be held within a predetermined range. In the above, a communication passage 39 that connects the dump cylinder chamber 19a of the dump cylinder 19 and the lowering cylinder chamber 8b of the lift cylinder 8 is provided, and the pressure of the dump cylinder chamber 19a is provided in the communication passage 39. The relief valve 40 (46) is provided to release the increased pressure when the pressure rises above the set value.

(Invention of Claim 2) The attachment 12 is supported by a lift arm 6 which is vertically swung by a lift cylinder 8 so as to be vertically swingable, and the attachment 1
2 is provided with a dump cylinder 19 for vertically swinging,
While the lift arm 6 is swinging, the attachment 12 is
A parallel lifting type loader having a full squeeze stopper B which prevents the attachment 12 from swinging to the squeeze side by a predetermined amount by the parallel lifting mechanism L. In the above, there is provided a communication passage 42 connecting the squeeze cylinder chamber 19b of the dump cylinder 19 and the ascending cylinder chamber 8a of the lift cylinder 8, and the pressure of the squeeze cylinder chamber 19b is provided in the communication passage 42. The relief valve 43 (46) is provided to release the increased pressure when the pressure rises above the set value.

[0018]

[Action]

(Invention of Claim 1) The present invention operates as follows, as shown in FIGS. 1 and 2, for example. In the full dump lowering state shown by the solid line in FIG. 2, when the lift switching valve 31 is switched to the raising position X to raise the lift arm 6, the raising cylinder chamber 8a is connected to the hydraulic pump P which is the pressure supply source. At the same time, the lowering cylinder chamber 8b is connected to the oil tank T which is a discharge port. Then, the lift cylinder 8
Is extended to try to increase the distance between the pins 7 and 23 of the parallel lifting mechanism L. As a result, the intermediate swing arm 16 swings in the clockwise direction to contract the dump cylinder 19, so that the pressure in the dump cylinder chamber 19a rises.

The pressure is a set pressure (for example, about 120 kgf / cm
² ) When the pressure rises above, the increased pressure is quickly discharged to the oil tank T through the relief valve 40 and the descending passage 30, so that the dump cylinder 19 is smoothly contracted.
As a result, the loader 3 is prevented from entering the ascending lock state, and is switched to the ascending state of the chain double-dashed line diagram in FIG.

When the work is carried out strongly by the loader 3, the lift switching valve 31 is switched to the neutral position Z and the descending passage 30 is closed. Accordingly, even if the pressure in the dump cylinder chamber 19a increases due to work resistance during work and the relief valve 40 is opened, it is possible to prevent the pressure oil in the cylinder chamber 19a from being discharged to the oil tank T. As a result, the cylinder chamber 19a can be maintained at a high pressure and work can be performed strongly.

(Invention of Claim 2) The present invention operates as follows, as shown in FIGS. 1 and 3, for example. In the fully squeezed state shown in the solid line diagram in FIG. 3, the lift arm 6
When the lift switching valve 31 is switched to the lowering position Y in order to lower the pressure, the lowering cylinder chamber 8b is connected to the hydraulic pump P that is the pressure supply source, and the rising cylinder chamber 8 is
a is connected to the oil tank T which is a discharge port. Then
When the lift cylinder 8 is contracted, the distance between the pins 7 and 23 of the parallel lifting mechanism L tends to be reduced. As a result, the intermediate swing arm 16 swings in the counterclockwise direction to try to extend the dump cylinder 19, so that the pressure in the squeeze cylinder chamber 19b increases.

When the pressure becomes equal to or higher than the set pressure, the increased pressure is quickly discharged to the oil tank T through the relief valve 43, so that the dump cylinder 19 is smoothly extended. As a result, the loader 3 is prevented from being in the descending lock state, and is switched to the descending state of the chain double-dashed line diagram in FIG.

When the loader 3 is to work strongly, the lift passage 29 is closed by switching the lift switching valve 31 to the neutral position Z. Accordingly, even if the pressure in the squeeze cylinder chamber 19b increases due to work resistance during work and the relief valve 43 is opened, the pressure oil in the cylinder chamber 19b is prevented from being discharged to the oil tank T. As a result, the cylinder chamber 19b can be maintained at a high pressure and work can be performed strongly.

[0024]

The present invention has the following effects because it is configured and operates as described above. (Invention of Claim 1) Since the relief valve is provided in the communication passage connecting the dumping cylinder chamber of the dump cylinder and the lowering cylinder chamber of the lift cylinder, the lowering cylinder chamber and the oil tank are connected during the loader work. If the communication state between the two is cut off, the communication state between the dump cylinder chamber and the oil tank can be automatically cut off. Therefore, even when the work resistance during work is large, the dump cylinder chamber can be maintained at a high pressure and can be worked strongly. In order to achieve the above effect, it is only necessary to provide the communication passage and the relief valve, and it is not necessary to provide a new switching valve or the like, so that the hydraulic device can be manufactured with a simple configuration at low cost.

(Invention of Claim 2) Since the relief valve is provided in the communication passage which connects the squeeze cylinder chamber of the dump cylinder and the lift cylinder chamber of the lift cylinder, the above-mentioned lift cylinder chamber and the oil can be operated during loader work. If the communication state with the tank is cut off, the communication state between the squeeze cylinder chamber and the oil tank can be automatically cut off. Therefore, even when the work resistance during work is large, the squeeze cylinder chamber can be maintained at a high pressure and can be worked strongly. In order to achieve the above effect, it is only necessary to provide the communication passage and the relief valve, and it is not necessary to provide a new switching valve or the like, so that the hydraulic device can be manufactured with a simple configuration at low cost.

[0026]

1 to 3 show an embodiment of the present invention. FIG. 1 is a circuit diagram of a hydraulic device provided in a loader. FIG. 2 is a diagram showing an operation when the loader is switched from the full dump descending state to the ascending state. FIG. 3 is a diagram showing an operation when the loader is switched from the full squeeze ascending state to the descending state.

As shown in FIG. 2, the vehicle body 2 of the tractor 1
The loader 3 attached to the front part of is configured as follows.
A base of a lift arm 6 is supported by a pin 7 so as to be vertically swingable on a frame 5 fixed to the vehicle body 2, and the lift arm 6 is vertically swung by a lift cylinder 8.

A bracket 10 is supported on the tip of the lift arm 6 by a pin 11 so as to be vertically swingable.
The bucket 12, which is an attachment, is detachably attached to the bracket 10. In order to prevent soil or the like that has been squeezed into the bucket 12 from spilling, the bucket 12 is swung during the swing of the lift arm 6.
The inclination angle of is held within a predetermined range by the link-type parallel elevating mechanism L.

That is, the front swing arm 14 is swingably supported by the pin 15 at the front portion of the lift arm 6, and the intermediate swing arm 1 is provided at the middle portion of the lift arm 6 as above.
The pin 6 is swingably supported by the pin 17. The front and rear swing arms 14 and 16 are connected by a dump cylinder 19, the front swing arm 14 and the bracket 10 are connected by a connecting rod 20, and the intermediate swing arm 16 and the frame 5 are connected. Are connected by the upper link 21. Both ends of the upper link 21 have pins 22.2
Pivoted by 3.

A full dump stopper A for preventing the bucket 12 from swinging toward the dump side by a predetermined amount or more is provided. The stopper A is composed of a received portion 26 provided on the front swing arm 14 and a receiving block 27 provided on the lift arm 6.

Further, as shown in FIG. 3, a full squeeze stopper B for preventing the bucket 12 from swinging toward the squeeze side by a predetermined amount or more is provided. This stopper B is the received portion 2 provided on the bracket 10.
8 and the block 27.

The hydraulic system of the loader 3 is constructed as follows, as shown in FIG. The lift cylinder 8
Is provided with an ascending cylinder chamber 8a and a descending cylinder chamber 8b, and is expanded by switching the lift switching valve 31 to the rising position X, and contracted by switching the switching valve 31 to the descending position Y. The symbol Z indicates the neutral position. Further, reference numeral 29 indicates an ascending path, and reference numeral 30
Indicates a descent path, symbol P is a hydraulic pump, and symbol T is an oil tank.

The dump cylinder 19 has a dump cylinder chamber 19a and a squeeze cylinder chamber 19b, and is extended by switching the dump switching valve 32 to the dump position U, and the switching valve 32 is switched to the squeeze position V. Be contracted by. Reference numeral W indicates a neutral position, reference numeral 35 is a dump passage, and reference numeral 36 is a squeeze passage.

A selection switching valve 33 is provided between the dump switching valve 32 and the dump cylinder 19, and the dump cylinder 19 is selected by switching the selection switching valve 33 to the first position M. The attachment cylinder 34 is selected by switching the selection switching valve 33 to the second position N. Although not shown in FIG. 2 or FIG. 3, the attachment cylinder 34 is attached to the bracket 10 so that a predetermined work can be performed.

The dump switching valve 32 and the selection switching valve 3
A dump-side relief valve 37 that communicates with the dump passage 35 is provided between the dump-side relief valve 37 and the dump valve 3. The relief valve 37 is provided to prevent an abnormally high pressure from being generated in the dump cylinder chamber 19a, and prevents the pressure in the cylinder chamber 19a from becoming an abnormally high pressure (for example, 150 kgf / cm ² or more). Note that, similarly to this, the squeeze passage 36 and the ascending passage 29
Also, each has a relief valve (not shown) for preventing abnormal high pressure.
Are in communication.

Further, the dump passage 35 and the descending passage 3
A first communication passage 39 is provided between the first and second communication passages 0.
9, the dump cylinder chamber 19a of the dump cylinder 19 and the lowering cylinder chamber 8b of the lift cylinder 8 are connected. A first relief valve 40 is provided in the communication passage 39. The relief valve 40 functions to release the increased pressure when the pressure in the dump cylinder chamber 19a increases above a set value.

Further, the squeeze passage 36 and the ascending passage 29
A second communication passage 42 is provided between
The same as above, the squeeze cylinder chamber 19b of the dump cylinder 19 and the lift cylinder chamber 8 of the lift cylinder 8 are
a is connected. A second relief valve 43 is provided in the second communication passage 42. The relief valve 43 functions to release the increased pressure when the pressure in the squeeze cylinder chamber 19b rises above a set value.

The above hydraulic system operates as follows. As shown in FIG. 2, when the loader 3 is switched to the full dump descending state of the solid line diagram, the dump cylinder 19 is extended and the received portion 26 contacts the block 27.
The bucket 12 is prevented from swinging in the clockwise direction.

When the lift arm 6 is lifted from the full dump lowering state, the lift switching valve 31 is switched to the rising position X. Then, the hydraulic pump P moves up the passage 2
9 is connected to the ascending cylinder chamber 8a via
The descending cylinder chamber 8b communicates with the oil tank T via the descending passage 30. As a result, the lift cylinder 8 extends and the distance between the pins 7 and 23 of the link-type parallel elevating mechanism L increases accordingly, so that the intermediate swing arm 16 swings in the clockwise direction. It moves to try to contract the dump cylinder 19.

Then, the pressure in the dump cylinder chamber 19a rises, and the pressure increases to a set pressure (for example, about 120 kgf /
When the pressure becomes equal to or more than cm ² ), the increased pressure is discharged to the oil tank T from the first relief valve 40 through the descending passage 30 and the lift switching valve 31 in the ascending position X in order. Therefore, the dump cylinder 19 is smoothly contracted. As a result, the loader 3 is prevented from entering the ascending lock state and is switched to the ascending state of the chain double-dashed line diagram.

As shown in FIG. 3, in the state where the loader 3 is switched to the full-squeeze raised state shown by the solid line diagram, the dump cylinder 19 is contracted and the receiving portion 28 is blocked by the block 27.
The bucket 12 is prevented from swinging in the counterclockwise direction.

When lowering the lift arm 6 from the above-described full squeeze state, the lift switching valve 31 is switched to the lowering position Y. Then, the hydraulic pump P communicates with the descending cylinder chamber 8b through the descending passage 30, and the ascending cylinder chamber 8a communicates with the oil tank T through the assembling passage 30. As a result, the lift cylinder 8 contracts, and the distance between the pins 7 and 23 of the link-type parallel elevating mechanism L decreases accordingly, so that the intermediate swing arm 16 moves in the counterclockwise direction. It swings and tries to extend the dump cylinder 19.

Then, the pressure in the squeeze cylinder chamber 19b rises, and the pressure rises to a set pressure (for example, about 120 kgf /
When the pressure becomes equal to or higher than cm ² ), the increased pressure is discharged from the second relief valve 43 to the oil tank T through the rising passage 29 and the lift switching valve 31 at the lowering position Y in order. Therefore, the dump cylinder 19 is smoothly extended. As a result, the loader 3 is prevented from entering the descending lock state, and is switched to the descending state of the chain double-dashed line diagram.

When working strongly with the bucket 12, after adjusting the lift arm 6 to a desired swing angle, the lift switching valve 31 is switched to the neutral position Z, and the tractor 1 is moved forward or dumped in this state. Cylinder 1
Bucket work is performed by expanding and contracting 9. Due to the work resistance during this bucket work, the dump cylinder chamber 1
A large pressure acts on the 9a and the cylinder chamber 19b for the squeegee, and when the pressure becomes equal to or higher than a set pressure (for example, about 120 kgf / cm ² ), the first relief valve 40 and the second relief valve 43 are opened. . However, since the lift switching valve 31 is switched to the neutral position Z, the cylinder chambers 19a and 19 are
The pressure oil b is prevented from being discharged to the oil tank T.
Therefore, the bucket work can be performed strongly while keeping the cylinder chambers 19a and 19b at a high pressure.

The pressure of the dump cylinder chamber 19a is set to the set pressure of the dump side relief valve 37 (for example, about 1
At 50 kgf / cm ² ) or more, the pressure oil in the cylinder chamber 19a is discharged to the tank T through the dump side relief valve 37, so that damage to the hydraulic equipment such as the dump cylinder 19 is prevented. The relief valves (not shown), which are in communication with the squeeze passage 36 and the ascending passage 29, are similarly operated. It is preferable to set the set pressures of the relief valve for preventing abnormally high pressure to pressures close to the pressure resistance limit of the hydraulic equipment in order to perform strong work.

(Modification) FIG. 4 shows a modification and corresponds to FIG. 1 described above. In this modified example, members having the same functions as those in the above-described embodiment are, in principle, given the same reference numerals.

In this modification, the two relief valves 4 described above are used.
This is a relief valve 46 replacing 0.43. That is, the first communication passage 39 and the second communication passage 42 are connected at an intermediate portion, and the relief valve 46 is provided at the connecting portion. Furthermore, the above-mentioned communication passages 39 and 42
A check valve 47 is provided on each of the inlet side and the outlet side of the relief valve 46. As a result, similarly to the above-described embodiment, the lift lock state and the fall lock state of the lift arm 6 are prevented.

The above-described embodiments and modifications can be modified as follows. The dump cylinder 19 may be of another type such as a double rod type instead of the single rod type. The lift cylinder 8 is also the same. When the attachment cylinder 34 is not attached, the selection switching valve 33 can be omitted. However, according to the present invention, even when the switching valve 33 for selection is attached, the relief valve 40 or 43 (or 46) can avoid the ascending lock state and the descending lock state, so that the lock state avoidance is performed. It has the advantage that no additional relief valve is required.

Only one of the above-mentioned two stoppers A and B may be provided in the loader 3. In the embodiment of FIGS. 1 to 3, when only the full dump stopper A is provided, only the corresponding communication passage 39 and the relief valve 40 are provided. When only the full squeeze stopper B is provided, only the communication passage 42 and the relief valve 43 corresponding thereto are provided. The parallel lifting mechanism L is
Instead of the link type, it may be configured as follows.
That is, a sub-cylinder is provided in parallel to the lift arm 6 in parallel with the lift cylinder 8, and the expansion / contraction operation of the sub-cylinder and the expansion / contraction operation of the dump cylinder 19 are made to cooperate with each other so that the inclination angle of the bucket 12 falls within a predetermined range. Hold it.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a hydraulic device provided in a loader, showing an embodiment of the present invention.

FIG. 2 is a diagram showing an operation when switching the loader from a full dump descending state to an ascending state.

FIG. 3 is a diagram showing an operation when switching the loader from a full squeeze ascending state to a descending state.

FIG. 4 is a diagram showing a modified example of the above hydraulic device.

FIG. 5 is a diagram showing a first conventional example and corresponding to FIG. 1 described above.

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

[Explanation of symbols]

6 ... Lift arm, 8 ... Lift cylinder, 8a ... Ascending cylinder chamber, 8b ... Descent cylinder chamber, 12 ... Attachment (bucket), 19 ... Dump cylinder, 19a ... Dump cylinder chamber, 19b ... Squeeze cylinder chamber, 39
... Communication passage (first communication passage), 40 ... Relief valve (first relief valve), 42 ... Communication passage (second communication passage), 43 ... Relief valve (second relief valve), 46 ... Relief Valve, A ... stopper for full dump, B ... stopper for full squeeze,
L ... Parallel lifting mechanism.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F15B 11/028

Claims (2)

[Claims] 1. A dump for vertically swinging the attachment (12), wherein an attachment (12) is swingably supported by a lift arm (6) vertically swingable by a lift cylinder (8). A cylinder (19) is provided to allow the attachment (12) to move while the lift arm (6) swings.
The tilting angle of the parallel lifting mechanism (L) can be held within a predetermined range, and a full dump stopper (A) is provided to prevent the attachment (12) from swinging toward the dump side by a predetermined amount or more. In the parallel lifting type loader, the dump cylinder chamber (19) of the dump cylinder (19) is
a) and the lowering cylinder chamber (8) of the lift cylinder (8)
b) is provided with a communication passage (39), and the communication passage (3
9) is provided with a relief valve (40, 46) for releasing the increased pressure when the pressure in the dump cylinder chamber (19a) rises above a set value. Hydraulic system. 2. A dump for vertically swinging the attachment (12), which supports an attachment (12) swingably up and down on a lift arm (6) swingable vertically by a lift cylinder (8). A cylinder (19) is provided to allow the attachment (12) to move while the lift arm (6) swings.
The parallel lifting mechanism (L) can be used to hold the tilt angle within a predetermined range, and a full squeeze stopper (B) that prevents the attachment (12) from swinging to the squeeze side by more than a predetermined amount is provided. In addition, in the parallel lifting type loader, the squeeze cylinder chamber (19) of the dump cylinder (19) is
b) and the lifting cylinder chamber (8) of the lift cylinder (8)
A communication passage (42) for connecting with a) is provided, and the communication passage (4
In 2), a relief valve (43, 46) is provided to release the increased pressure when the pressure in the squeeze cylinder chamber (19b) rises above a set value. Hydraulic system.