JPH0763939B2 - Impact tool - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulically-operated impact tool attached to the tip of a hydraulic power shovel or the like and used for dismantling a concrete structure, crushing rocks, excavating rock, etc. Is.

[Conventional technology]

Hydraulically operated impact tools can be roughly divided into an accumulator system and a gas system.

The accumulator method is a method of accumulating oil in the accumulator when the piston rises and discharging it in the striking stroke to accelerate the piston.

The gas system stores energy by compressing the gas above the piston when the piston rises due to hydraulic pressure, and accelerates the piston by utilizing the energy that expands the gas in the striking stroke. This method is shown in Japanese Patent No. 32192.

[Problems to be solved by the invention]

In the invention described in the publication shown in FIG. 7, since the middle chamber is always connected to the oil discharge port, the valve is in the raised position in the striking stroke of the piston, so the lower chamber is connected to the axial center of the valve. It communicates with the middle chamber and the low-pressure drain port through the hole and the valve chamber.

Therefore, when the piston hits the chisel and then repels violently, the pressure in the lower chamber sharply drops, and a phenomenon called a cavitation phenomenon occurs in which bubbles contained in the hydraulic oil rapidly grow.

Next, when the valve descends and pressure oil flows into the lower chamber from the oil supply port, the rapidly growing bubbles momentarily collapse, generating extremely high pressure and shock waves.

Since this phenomenon is repeated hundreds of times per minute, erosion occurs on the surfaces of the piston and the cylinder when the impact tool is used for a long time.

The present invention prevents the occurrence of this cavitation phenomenon,
The purpose is to eliminate erosion that occurs on the surface of the piston and cylinder.

[Means to solve the problem and its action]

The reason why the bubbles in the oil in the lower chamber grow immediately after the piston hits the chisel is that the lower chamber pressure at the time of striking is low because the lower chamber is in contact with the oil drain port at the time of striking, and the piston repels. It is because the pressure in the lower chamber suddenly decreases at the moment when you do. Therefore, if the pressure in the lower chamber at the time of impact is raised to the extent that bubbles do not grow, cavitation does not occur.

Therefore, according to the present invention, when the valve rises in the striking stroke (lowering stroke) of the piston and is close to the maximum raised position, the lower chamber communicates only with the middle chamber and the communication with the oil drain port is blocked, and Just before the piston hits the chisel, the pressure oil flows from the pressure oil side into the middle chamber to increase the pressure of the lower chamber communicating with the middle chamber.

Therefore, even if the piston repels immediately after the impact, the pressure in the lower chamber does not become so low that bubbles in the oil in the lower chamber grow, and cavitation does not occur. Next, even if the valve descends and the pressure oil flows into the lower chamber and the pressure in the lower chamber rises, bubble collapse does not occur, so erosion (erosion) occurs even if the impact tool is used for a long time. ) Does not occur.

[Example] First, a first example will be described.

In FIG. 1, 1 is an impact tool, 2 is a cylinder, and a piston 3 is slidably incorporated in the cylinder 2. The piston 3 has an upper small-diameter portion 4 and a lower small-diameter portion 5 having the same diameter at the top and bottom, and a large-diameter portion 6 is integrally formed at the center.

Inside the cylinder 2, a middle chamber 7 and a lower chamber 8 are formed by the upper surface and the lower surface of the large diameter portion 6 of the piston, and an upper chamber 9 containing nitrogen gas is formed above the piston upper small diameter portion 4. .
At the lower end of the cylinder 2, the chisel 10 is slidable within a certain range.
Is fitted so that the lower end of the piston 3 strikes the upper end of the chisel 10.

Inside the cylinder 2 along which the large-diameter portion 6 of the piston 3 slides, inner circumferential grooves 12, 13, 14 are provided from above. Due to the large-diameter portion 6, the inner peripheral grooves 12 and 13 communicate with each other by the large diameter portion 6, the inner peripheral grooves 13 and 14 are blocked, and when the piston is in the raised position, Inner peripheral groove 13 and 14 communicate, inner peripheral groove
Form so that 12 and 13 are blocked.

15 is a valve box fixed to one side of the cylinder 2, and this valve box 15
A valve chamber 11 is provided inside, and a valve 16 is slidably fitted therein.

A chamber 17 communicating with the oil supply port 33 is provided above the valve chamber 11 and a plunger 18 is slidably fitted in the chamber 17, and the lower end of the plunger 18 is brought into contact with the upper end of the valve 16. The valve 16 having the upper large-diameter portion 19 and the lower small-diameter portion 31 is fitted in the large-diameter portion and the small-diameter portion of the valve chamber 11 so as to be able to move forward and backward, and between the lower end surface of the large-diameter portion 19 and the valve chamber 11. Forms actuate chamber 34. The difference in cross-sectional area between the large-diameter portion and the small-diameter portion of the valve is set larger than that of the plunger 18.

An outer peripheral groove 20 is formed below the small diameter portion of the valve 16, and a communication hole 21 that passes through the upper portion and the lower portion of the valve chamber 11 is formed in the axial center. Valve chamber
Inner peripheral grooves 22, 23 are formed in the large diameter portion of 11 from above, and inner peripheral grooves 24, 25, 26 are formed in the small diameter portion.

When the valve 16 is in the lowered position, the inner peripheral grooves 25 and 26 communicate with each other by the outer peripheral groove 20, and the inner peripheral grooves 24 and 25, the inner peripheral groove 26 and the lower portion of the valve chamber 11 are blocked. When the valve 16 starts to rise, the inner circumferential grooves 25 and 26 are first blocked, and at the same time the inner circumferential grooves 24 and 2 are closed.
5. The inner circumferential groove 26 communicates with the lower portion of the valve chamber 11, and when further raised, the large diameter portion of the valve 16 blocks the inner circumferential groove 22 from the upper portion of the valve chamber 11.

The upper portion of the valve chamber 11 is connected to the inner circumferential groove 12 in the upper portion of the cylinder inner chamber 7 by the oil passage 27. Inner groove of cylinder 13,1
4 is made to communicate with the inner circumferential grooves 23, 26 of the valve chamber 11 by the oil passages 28, 29, respectively, and the small diameter oil passage 30 branched from the oil passage 28 is the inner circumferential groove 24.
Connect to.

Reference numeral 32 is a low-pressure oil discharge port that communicates with the inner circumferential groove 22 of the valve chamber, and
The oil passage 33 communicates with the inner circumferential groove 25 of the valve chamber and the chamber 17.

Next, the operation will be described.

In FIG. 1, both the piston 3 and the valve 16 are in the lowered position. When pressure oil is supplied to the oil supply port 33 in this state, the pressure oil flows through the inner peripheral groove 25, the outer peripheral groove 20, the inner peripheral groove 26, the oil passage 29, the lower chamber 8, and the lower end surface of the large diameter portion 6 of the piston 3. Add hydraulic pressure to. At this time, since the middle chamber 7 is connected to the oil passage 27 → the upper part of the valve chamber 11 → the inner circumferential groove 22 → the oil discharge port 32, the piston 3 rises while compressing the nitrogen gas sealed in the upper chamber 9. To start. At the same time, pressure oil also flows into the chamber 17 from the oil supply port 33 and pushes the plunger 18 downward, so that the valve 16 is also pushed downward.

The piston 3 further rises, and the lower end of the large diameter portion 6 has an inner circumferential groove.
When the state shown in FIG. 2 in which 13 and the lower chamber 8 are communicated is established, the lower chamber 8
Oil pressure passes from the inner peripheral groove 13 through the oil passage 28 to the actuate chamber.
Flowing to 34, hydraulic pressure acts on the lower end surface of the large diameter portion 19 of the valve 16.
Since the area of this lower end surface is larger than the cross-sectional area of the plunger 18, the valve 16 starts moving upward.

When the valve 16 rises to some extent, the inner circumferential grooves 25 and 26 are blocked, and the inner circumferential grooves 24 and 25, the inner circumferential groove 26 and the lower portion of the valve chamber 11 communicate with each other, so that the lower chamber 8 has the oil passage 29 → the inner circumferential groove 26. → The lower part of the valve chamber 11 → the communication hole 21 → the oil drain port 32 is connected, and the pressure in the lower chamber 8 drops.
Therefore, the piston starts to descend due to the pressure of the compressed nitrogen gas in the upper chamber 9.

When the valve 16 further rises to the raised position, the large-diameter portion 19 blocks the inner circumferential groove 22 from the oil discharge port 32, and the lower chamber 8 and the middle chamber 7 communicate with each other via the valve chamber. Even when the lower end of the piston large-diameter portion 6 blocks the inner peripheral groove 13 and the lower chamber 8 in the piston descending stroke, the inner peripheral grooves 25, 24 and the small-diameter oil passage 3 are formed in the actuate chamber 34.
Since the pressure oil is sent from the oil supply port through 0, the valve holds the raised position. This state is shown in FIG.

The piston 3 further descends, and the upper end of the large diameter portion 6 has an inner circumferential groove 13
4, the pressure oil from the oil supply port 33 passes through the inner peripheral grooves 25, 24 → the small diameter oil passage 30 → the oil passage 28 and the middle chamber 7
And the pressure in the middle chamber rises. With this, valve chamber 1
1, the pressure in the lower chamber 8 communicating with the middle chamber 7 through the communication hole 21 also rises to the same pressure. In this way, the lower chamber 8 and the middle chamber 7
When the pressure of the piston rises and it is connected to the filler port, the piston 3
Hits the chisel 10, so that even if the piston repels after hitting, the pressure drop in the lower chamber 8 is small, and bubbles in the oil do not grow.

When the piston repels in this way, the pressure in the middle chamber 7 is reduced to the lower chamber 8.
Since the pressure is instantaneously higher than the pressure of, the pressure in the upper part of the valve chamber 11 becomes higher than that in the lower part for a moment, and the valve 16 is pushed downward.
When the upper end of the large-diameter portion 19 of the valve 16 passes through the inner circumferential groove 22, the valve chamber 11 and the middle chamber 7 are connected to the oil discharge port 32 and the pressure is reduced. Therefore, the pressure in the actuate chamber 34 is also reduced and the plunger
The valve is pushed down by the pressing force of 18 and returns to the lowered position shown in FIG.

As long as the pressure oil is supplied from the oil supply port 33, the impact tool repeats the above operation.

Next, a second embodiment will be described.

In the first embodiment, the chamber 17 and the plunger 18 are used as means for constantly pressing the valve 16 downward.

In the second embodiment shown in FIG. 5, as an alternative means, a medium diameter portion 35 is added above the large diameter portion of the valve 16 so that the valve chamber
A chamber 36 is formed between the upper portion of 11 and the medium diameter portion 35, and this chamber is always communicated with the oil supply port 33 through an oil passage. The difference in sectional area between the large diameter portion 19 and the medium diameter portion 36 of the valve 16 is made smaller than the difference in sectional area between the large diameter portion 19 and the small diameter portion. The other structure is the same as that of the first embodiment, and the operation is exactly the same as that of the first embodiment.

Next, a third embodiment will be described.

In the first and second embodiments, as a means for holding the valve 16 in the raised position, an oil passage connected to the actuate chamber 34 is used.
A small diameter oil passage 30 branched from 28 is provided.

Instead of this, in the third embodiment shown in FIG. 6, a medium-diameter portion is added above the large-diameter portion of the valve to form a chamber 36, and at the same time the large-diameter portion of the valve 16 slides. Inner groove in chamber 11
37 is provided, and the inner peripheral groove is communicated with the oil supply port 33 by the oil passage 38 having a small diameter. In this embodiment, when the valve 16 is raised, the inner circumferential groove
25 and 26 are cut off so that the inner circumferential groove 26 and the lower portion of the valve chamber 11 are communicated with each other, and at the same time, the actuate chamber 34 and the inner circumferential groove 37 are communicated with each other. With this configuration, the pressure oil flows through the oil passage 38 having a small diameter, flows from the inner peripheral groove 37 to the actuate chamber 34, and the valve 16
Push up and hold the raised position. Other configurations and operations are similar to those of the first embodiment.

In each of the above embodiments, the upper small diameter portion 4 of the piston 3
The case where the lower small diameter portion 5 and the lower small diameter portion 5 have the same diameter has been described as an example, but the diameter of the upper portion may be made slightly smaller than the diameter of the lower portion, and all other configurations may be the same. In this case, in the striking stroke, not only the gas pressure but also the hydraulic pressure due to the difference in sectional area between the upper surface and the lower surface of the large diameter portion acts on the piston, so that the striking force can be further increased.

〔The invention's effect〕

The impact tool of the present invention, in the striking stroke of the piston,
Before the moment when the piston hits the chisel, the middle chamber is cut off from the oil discharge port to communicate with the oil supply port, pressure oil is sent to the lower chamber communicating with the middle chamber, and the pressure in the lower chamber is increased. Therefore, even if the piston repels greatly immediately after it is hit, no significant pressure drop occurs in the lower chamber. Therefore, bubbles in the oil in the lower chamber do not grow and cavitation can be prevented from occurring, so that the durability of the cylinder or piston is significantly improved. Therefore, there is an effect that the laborious repair and replacement work is reduced.

[Brief description of drawings]

1 to 4 are sectional views for explaining the operation in the first embodiment which is the impact tool of the present invention, FIG. 5 is a sectional view showing the second embodiment, and FIG. 6 is a sectional view of the third embodiment. A sectional view and FIG. 7 are sectional views of a main part of a conventional example. 1 ... Impact tool, 2 ... Cylinder 3 ... Piston, 4 ... Upper small diameter part 5 ... Lower small diameter part, 6 ... Large diameter part 7 ... Middle chamber, 8 ... Lower chamber 9 ... Upper Chamber, 10 …… Chisel 11 …… Valve chamber, 16 …… Valve 17 …… Chamber, 18 …… Plunger 19 …… Valve large diameter part, 32 …… Oil drainage port 33 …… Fluid port, 34 …… Actuate Room 36 …… Room 30,38 …… Small oil passage

Claims (1)

[Claims] 1. A tool such as a chisel (10) is attached to the lower end of the cylinder (2) so as to be able to move back and forth, and a piston (3) for striking the chisel when descending is slidably fitted inside the cylinder (2). A large diameter portion (6) is provided at a middle position, and a middle chamber (7) is provided inside the cylinder (2) on the upper surface side of the piston large diameter portion (6).
A lower chamber (8) is provided on the lower surface side, and an upper chamber (9) for applying gas pressure is provided on the upper end surface of the piston (3),
A slidable valve (16) is fitted in the valve chamber (11) provided between the lower chamber (8) and the middle chamber (7) and the oil supply port (33) and the discharge port (32) to form the middle chamber. And a lower chamber, an oil supply port, and an oil discharge port are controlled by a valve and an oil passage, and an impact tool that raises and lowers a piston by hydraulic pressure and gas pressure. The oil discharge port (32)
Communicates with the middle chamber (7) through the valve chamber when the valve (16) is in the lowered position, and when the valve (16) is in the raised position from slightly before the raised position, the valve chamber (11) A small diameter that is provided at the shut-off position to cut off communication between the middle chamber (7) and the lower chamber (8) and the oil discharge port (32) and also connects the actuate chamber (34) to the oil supply port when the valve is in the raised position. Oil passage (30), (38)
Is provided so that the valve (16) maintains the raised position during the descending stroke in which the piston strikes the chisel, the piston descends to a predetermined position, and the intermediate chamber (7) communicates with the actuate chamber (34). And an oil passage that connects the oil supply port (33) to the lower chamber (8) through the middle chamber (7) and the valve chamber (11).