JP2003071744A - Impact dynamic tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight impact dynamic tool compact in the axial direction capable of preventing the occurrence of cavitation effectively. SOLUTION: A piston 5 having a large diameter part 5a is slidably assembled into the inside of a cylinder 1. A spool 17 which moves vertically in the interlocking relationship with lifting and lowering movements of the piston 5, communicates an oil supply port 14 with a lower chamber 6 provided on a lower face side of the large diameter part 5a at a descent position, and communicates an intermediate chamber 7 formed on an upper face side of the large diameter part 5a with an oil discharge port 15 is assembled into a valve chest 16 of a valve casing 13 attached to outer periphery of the cylinder 1. After shutting off the communication of the intermediate chamber 7 with the oil discharge port 15 in an ascent process of the spool 17, a lower end opening of a through hole 19 formed in the spool 17 is communicated with the oil supply port 14 and the lower chamber 6 to prevent pressure oil in the lower chamber 6 from being discharged from the oil discharge port 15 in the ascent process of the spool 17, hit a chisel 2 due to the descent of the piston 5 in a high pressure condition in which the lower chamber 6 is communicated with the intermediate chamber 7, and suppress abrupt pressure reduction in the lower chamber 6 when the piston 5 rises due to repulsion by the hitting in order to prevent the occurrence of cavitation.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulically operated impact power tool for demolition of concrete structures, crushing of rock, and the like. 2. Description of the Related Art As this kind of impact power tool, a piston is slidably incorporated in a cylinder, the piston is raised by hydraulic pressure, and the gas sealed in the upper chamber is compressed by the rising stroke of the piston. By accumulating energy, the energy of the gas lowers the piston instantaneously,
There is known one that hits a chisel attached to the lower end of a cylinder. In the above-mentioned impact power tool, the lower chamber is in communication with the oil discharge port at the time of impact, so that when the piston strikes the chisel and the piston instantaneously rises due to the reaction, the pressure in the lower piston chamber increases. Sharply drops, and the pressure drop causes a phenomenon in which air bubbles precipitate from the hydraulic oil in the lower piston chamber, a so-called cavitation phenomenon. [0004] Here, when air bubbles are precipitated from the hydraulic oil in the lower piston chamber, the air bubbles are destroyed by the hydraulic oil supplied from the oil supply port to the lower piston chamber, generating a very high pressure and a shock wave. In the case of an impact power tool, the above phenomenon is repeated several hundred times per minute. Therefore, when the impact power tool is used for a long time, erosion occurs on a sliding surface between a cylinder and a piston. In order to prevent the occurrence of such inconvenience,
In the impact moving tool described in Japanese Patent Publication No. 7-63939, pressurized oil flows into a lower chamber formed on the lower surface side of the large diameter portion of the piston to raise the piston, and the piston is almost moved to the upper limit position. When it reaches, the spool of the switching valve is raised, and when the spool rises to some extent, the lower chamber is communicated with the oil drain, and the pressure oil in the lower chamber flows out to the oil drain to lower the pressure in the lower chamber. Then, the piston is lowered by the gas pressure. During the lowering stroke of the piston, the spool further moves up to shut off the inner chamber from the oil drain port. When the piston descends to some extent, pressure oil is supplied to the inner chamber, and the piston is further lowered while the pressure in the lower chamber communicating with the inner chamber is increased, thereby hitting the chisel. As described above, by increasing the pressure in the lower chamber immediately before the piston hits the chisel, even if the piston rebounds immediately after hitting, there is no significant drop in pressure in the lower chamber, and cavitation is prevented. Can be prevented. By the way, in the impact power tool described in the above publication, the lower chamber and the oil discharge port are communicated with each other before the lower chamber and the middle chamber communicate with each other to increase the pressure of the lower chamber. , The piston starts lowering after the pressure is once lowered, so that the pressure in the lower chamber cannot be sufficiently increased immediately before the piston hits the chisel. For this reason, it is not possible to effectively prevent the occurrence of cavitation,
There are still points to be improved. Japanese Utility Model Publication No. Hei 6-39904 discloses a hydraulic breaker in which a piston is lowered while a lower chamber is maintained at a high pressure to strike a chisel. In the hydraulic breaker described in the above publication, a pair of upper and lower large-diameter portions are formed on the piston when the switching valve for controlling the flow of the pressure oil is switched, and between the pair of large-diameter portions. It is necessary to always form a low-pressure chamber, and the length of the piston in the axial direction becomes longer, and the total length of the hydraulic breaker becomes longer. SUMMARY OF THE INVENTION It is an object of the present invention to effectively prevent cavitation by allowing a piston to strike a chisel while maintaining a lower chamber pressure at a high pressure. The present invention provides a compact and lightweight impact power tool having an axial length that can be used. In order to solve the above problems, according to the present invention, a chisel is mounted on a lower end of a cylinder so as to be able to move forward and backward, and a piston for chisel striking is provided inside the cylinder. A large diameter portion is provided in the middle of the piston, and a lower chamber is provided on the lower surface side of the large diameter portion, a middle chamber is provided on the upper surface side of the large diameter portion, and a piston is provided inside the cylinder. An upper chamber filled with gas is formed on the upper end surface side, and a valve box having an oil supply port and an oil discharge port is provided outside the cylinder, and the valve box communicates with the oil supply port and the oil discharge port in the valve box. A large-diameter portion of a spool having an upper portion is slidably incorporated in the valve chamber, and an actuating chamber is formed on a lower surface side of the large-diameter portion. The first oil passage for introducing pressure oil from the mouth into the lower chamber, and the lowering of the spool A second oil passage that communicates the middle chamber and the oil discharge port at a position, and a third oil passage that communicates the lower chamber and the actuate chamber at the position where the piston is raised. The piston is lowered by the pressure of the gas in the upper chamber in a state where the middle chamber and the lower chamber communicate with each other through the through hole at the ascending position where the first oil path and the second oil path communicate with each other. In the impact power tool configured to hit the chisel, the first oil passage communicating with the lower chamber is always in communication with the oil supply port, and the large-diameter portion is drained during the upward stroke of the spool. After blocking the communication between the mouth and the inner chamber,
The configuration is such that the through hole of the spool communicates with the first oil passage. [0013] With the above construction, the piston rises to the upper limit position, and during the upward stroke of the spool in which the pressure oil is supplied from the oil supply port to the actuating chamber, the spool is connected to the oil discharge port and the second oil passage. After the communication is cut off, since the lower end opening of the through hole is connected to the first oil passage communicating with the oil supply port, the pressure oil in the lower chamber is not discharged from the oil discharge port, and the lower chamber is maintained at a high pressure. The chisel can be hit by the piston in the state. Therefore, even if the piston rebounds immediately after the impact, the pressure drop in the lower chamber is extremely small, and the occurrence of cavitation can be effectively prevented. Also,
The spool can be raised and lowered in conjunction with the lifting and lowering of a piston having a single large-diameter part, so it is compared with an impact power tool in which a pair of upper and lower large-diameter parts are provided on the piston to switch the switching valve. Thus, the axial length of the piston can be reduced in size and weight. Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG.
The upper end of the chisel 2 is slidably inserted into the lower end of. A notch 3 long in the axial direction is formed on the outer periphery of the upper part of the chisel 2, and a pin 4 provided at the lower end of the cylinder 1 is inserted into the notch 3. For this reason,
The chisel 2 can be moved up and down within a range where the upper and lower ends of the notch 3 abut on the pin 4. A striking piston 5 of the chisel 2 is slidably incorporated in the cylinder 1. The piston 5 has a large-diameter portion 5a that is slidably guided on the inner peripheral surface of the cylinder 1, a lower chamber 6 is formed on the lower surface side of the large-diameter portion 5a, and a middle chamber is formed on the upper surface side of the large-diameter portion 5a. 7 are provided. In the cylinder 1, an upper chamber 8 is formed on the upper end side of the piston 5, and gas is sealed in the upper chamber 8. The large-diameter portion 5a is provided on the inner peripheral surface of the cylinder 1.
Three annular grooves 9, 10, 11 are formed within the range in which. When the piston 5 is in the lowered position, the upper annular groove 9 and the middle annular groove 10 communicate with each other, and the middle annular groove 10 and the lower annular groove 1
When the piston 1 is in the raised position, the upper annular groove 9 and the middle annular groove 10 are shut off, and the middle annular groove 10 and the lower annular groove 11 communicate with each other. A switching valve 12 is provided on the upper part of the outer periphery of the cylinder 1.
Is provided. As shown in FIG.
The valve box 13 is connected to the cylinder 1, and an oil supply port 14 and an oil discharge port 15 are formed in the valve box 13. A valve chamber 16 is formed inside the valve box 13 so that the oil supply port 14 and the oil discharge port 15 communicate with each other. A spool 17 is slidably incorporated in the valve chamber 16. The spool 17 has a large diameter portion 17a at the upper part, and the actuating chamber 1 is located below the large diameter portion 17a.
8 are formed. The spool 17 is formed with an axial through hole 19 which is open at the upper and lower ends. A first ring groove 21 is formed in the inner periphery of the valve chamber 16 at a position corresponding to the oil supply port 14, and the oil discharge port 15 is formed.
The second ring groove 22 is provided at a position corresponding to.
Further, a third ring groove 23 and a fourth ring groove 24 are provided close to each other between the first ring groove 21 and the second ring groove 22. On the other hand, on the outer periphery of the large diameter portion 17a of the spool 17, an annular groove 25 is formed for communicating the third ring groove 23 and the fourth ring groove 24 when the spool 17 is lowered. As shown in FIG. 1, the cylinder 1 and the valve box 13 are provided with a first oil passage 31 communicating the lower annular groove 11 and the first ring groove 21, and an upper annular groove 9 when the spool 17 is lowered. A second oil passage 32 that communicates with the second ring groove 22; and a third oil passage that communicates the middle annular groove 10 with the actuating chamber 18 via the third ring groove 23, the fourth ring groove 24, and the annular groove 25. 33 are formed. The communication between the second ring groove 22 and the second oil passage 32 is interrupted by the large-diameter portion 17a of the spool 17 when the spool 17 rises from the lowered position by a predetermined amount. When the spool 17 further rises, the lower end opening of the through hole 19 corresponds to the first ring groove 21, and the through hole 19 becomes the oil supply port 14 and the first oil passage 31.
It is designed to communicate with A plunger insertion hole 40 is provided in the top wall of the valve chamber 16.
Is formed. The upper part of the plunger insertion hole 40 and the fuel supply port 14 communicate with each other through a passage 41 formed in the valve box 13. A plunger 42 is slidably incorporated in the plunger insertion hole 40, and the lower end thereof is in contact with the upper end surface of the spool 17. The area of the upper end surface of the plunger 42 is smaller than the area of the lower surface of the large diameter portion 17a formed on the spool 17. FIG. 1 shows a state in which the piston 5 and the spool 17 of the switching valve 12 are at the lowered position. In this state, when pressure oil is supplied to the oil supply port 14, the pressure oil flows from the first ring groove 21 to the first oil passage 31 and flows into the lower chamber 6. 5 rises. The gas in the upper chamber 8 is compressed by the rise of the piston 5. At this time, since the middle chamber 7 communicates with the oil discharge port 15 through the second oil passage 32 and the second ring groove 22 formed in the upper part of the inner periphery of the valve chamber 16, the piston 5 rises. As a result, the oil in the middle chamber 7 flows to the oil discharge port 15 and is returned to the tank (not shown). Since the pressure oil supplied to the oil supply port 14 is supplied from the passage 41 to the upper portion of the plunger insertion hole 40, the plunger 42 is pushed down, and the plunger 4 is pressed.
2, the spool 17 is pressed and held in a lowered state. The piston 5 further rises, and the lower end of the large-diameter portion 5a provided on the piston 5, as shown in FIG.
When it rises to a position corresponding to the middle annular groove 10 and the middle annular groove 10 communicates with the lower chamber 6, the pressure oil in the lower chamber 6 flows from the middle annular groove 10 to the third oil passage 33, and the actuating chamber Flow into 18. Since the area of the lower surface of the large diameter portion 17a of the spool 17 is larger than the area of the upper end surface of the plunger 42, when the pressurized oil is supplied to the actuating chamber 18, the spool 17 starts to rise. When the spool 17 rises by a predetermined amount, the large-diameter portion 17 a is connected to the second ring groove 22 connected to the oil discharge port 15 by the second ring groove 22.
The communication of the oil passage 32 is cut off. After the interruption, the spool 17
Keeps rising further, and the through hole 19 is connected to the fuel supply port 14. When the through hole 19 communicates with the oil supply port 14, the middle chamber 7 and the lower chamber 6 communicate with each other via the first oil passage 31, the lower part of the valve chamber 16, the through hole 19 and the second oil passage 32, and And the middle chamber 7 are maintained at the same pressure, and pressurized oil is supplied from the oil supply port 14 to the two chambers 6 and 7 to increase the pressure in the two chambers 6 and 7. FIG.
As shown in FIG. 7, when the spool 17 rises to near the upper limit position, the piston 5 is pressed by the pressure of the gas in the upper chamber 8 and falls rapidly. In the downward stroke of the piston 5, the large-diameter portion 5a of the piston 5, as shown in FIG.
And the middle annular groove 10 are cut off from each other. After the interruption, the piston 5 hits the chisel 2 and moves upward due to the repulsion at the time of hitting. Due to the movement, the pressure in the middle chamber 7 is instantaneously increased, so that the spool 17 is lowered by the pressure increase of the middle chamber 7 and the pressing force of the plunger 42 pressing the spool 17 to return to the state shown in FIG. Thereafter, the above operation is repeatedly performed. As described above, the piston 5 rises and the pressure oil in the lower chamber 6 is supplied from the third oil passage 33 to the actuating chamber 18, and during the upward stroke of the spool 17 due to the supply of the pressure oil, the spool 17 After cutting off the communication between the second ring groove 22 communicating with the oil discharge port 15 and the second oil passage 32, the middle chamber 7 and the lower chamber 6 are communicated with each other through the through hole 19, and the pressure oil in the lower chamber 6 is It does not flow to the drain port 15. The lower chamber 6 is always kept in communication with the fuel supply port 14. For this reason, the pressure of the lower chamber 6 does not drop, and the piston 5 descends and hits the chisel 2 while being connected to the high-pressure oil supply port 14, and the piston rebounds immediately after hitting. Also, the pressure drop in the lower chamber is small, and the occurrence of cavitation can be effectively prevented. As described above, according to the present invention, when the spool is raised, the communication between the oil discharge port and the second oil passage is interrupted by the large diameter portion of the spool, and then the spool is formed. The lower end opening of the through hole communicates with the oil supply port and the first oil passage, so that the lower chamber does not communicate with the oil discharge port during the descending stroke of the piston, and there is no pressure drop in the lower chamber. The chisel can be struck by the piston while maintaining a high pressure. Therefore, even if the piston rebounds immediately after the impact, the pressure drop in the lower chamber is small and cavitation can be effectively prevented. Further, since the spool can be moved up and down in conjunction with the up and down movement of the piston having a single large diameter portion, the piston is provided with a pair of upper and lower large diameter portions to switch the switching valve. Compared to a power tool, the axial length of the piston can be reduced in size, and a compact and lightweight impact power tool having an axial length can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional front view showing an embodiment of an impact moving tool according to the present invention; FIG. 2 is an enlarged longitudinal sectional front view showing a switching valve of the impact moving tool shown in FIG. 1; FIG. 3 is a longitudinal sectional front view showing a rising stroke of a piston of the impact moving tool shown in FIG. 1; FIG. 4 is a longitudinal sectional front view showing a state where a spool of a switching valve in the impact moving tool shown in FIG. 1 is raised; 1 is a longitudinal sectional front view showing a state in which the piston of the impact power tool shown in FIG. 1 hits the chisel. Drain port 16 Valve chamber 17 Spool 18 Actuate chamber 19 Through hole 31 First oil passage 32 Second oil passage 33 Third oil passage

Claims (1)

Claims: 1. A chisel is mounted on a lower end portion of a cylinder so as to be able to advance and retreat, and a piston for chisel striking is slidably incorporated in the cylinder, and a large diameter portion is formed in the middle of the piston. Inside the cylinder, a lower chamber on the lower surface side of the large diameter portion, a middle chamber on the upper surface side of the large diameter portion, and an upper chamber in which gas is sealed on the upper end surface side of the piston. A valve box having an oil supply port and an oil discharge port is provided outside the cylinder, a valve chamber communicating with the oil supply port and the oil discharge port is formed in the valve box, and a large-diameter portion is provided in the valve chamber. A first oil passage that slidably incorporates a spool provided at an upper portion, forms an actuate chamber on the lower surface side of the large diameter portion, and allows the cylinder and the valve box to introduce pressure oil of an oil filler port into a lower chamber; A second oil passage for communicating the middle chamber with the oil discharge port at a lowered position of the spool, and the piston A third oil passage that communicates the lower chamber and the actuate chamber at the ascending position is formed, and the spool has an axial through hole that communicates the first oil passage and the second oil passage at the ascending position of the spool. In an impact power tool in which the piston is lowered by the pressure of the gas in the upper chamber and the chisel is hit in a state where the middle chamber and the lower chamber communicate with each other through the through hole, the communication with the lower chamber is performed. The first oil passage is always in communication with the oil supply port, and during the ascending stroke of the spool, the large-diameter portion cuts off the communication between the oil discharge port and the inner chamber, and then the spool has a first oil passage. An impact power tool characterized by communicating with