JPH0451992Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic impact tool such as a rock drill.

[Prior Art] Conventionally, a chisel is provided with a striking cylinder that houses a striking piston for striking a chisel, and pressurized oil is applied alternately to a front chamber and a rear chamber of this striking cylinder.
Hydraulic impact tools that drive impact pistons are well known (for example, Utility Model No. 58-160782).
(see publication).

In this type of hydraulic impact tool, an accumulator for quickly and stably supplying pressure oil is provided in communication with the pressure oil supply passage.The inside of the accumulator is partitioned by a bladder, and one chamber is
It has a structure in which it is filled with an inert gas such as _N2 , and the other chamber is communicated with a pressure oil supply passage through a number of small diameter holes.

However, even in hydraulic impact tools equipped with such an accumulator, the hydraulic oil pressure may become unstable during unsteady conditions such as during startup. In some cases, the bladder was struck by the pressure of the inert gas against the small diameter communication section, which in extreme cases caused damage.

[Purpose of the invention] The present invention focuses on the fact that in this type of hydraulic impact tool, the impact piston is driven by alternately switching the rear chamber of the impact cylinder into a pressure oil passage and a return passage. However, by adjusting the amount of pressure oil returned to the return passage, when the oil pressure of the pressure oil drops to a certain extent, the amount of return to the return passage is throttled to prevent a rapid decrease in oil pressure, and when the oil pressure is low, The purpose of this is to protect the accumulator by stopping the hydraulic impact operation itself.

[Configuration of the invention] For this reason, the present invention includes a bladder-type accumulator that communicates with a first pressure oil passage that supplies pressure oil to the front chamber of the percussion cylinder that accommodates the percussion piston, and a bladder-type accumulator that communicates with the first pressure oil passage that supplies pressure oil to the front chamber of the percussion cylinder that accommodates the percussion piston. In a hydraulic impact tool equipped with a switching valve that alternately switches a communicating second pressure oil passage between a pressure oil source and a return passage, when the switching valve is switched to the return passage side, the second pressure oil passage is switched to the return passage side.
A regulating valve having a hollow tip is fitted in the communicating passage connecting the pressure oil passage to the return passage so as to be slidable in the axial direction of the communicating passage, and the regulating valve is inserted from the second pressure oil passage side. A biasing member that biases against the acting pressure oil is provided, and a plurality of communication holes are provided at different positions in the axial direction at the tip of the regulating valve to communicate the inside and outside of the regulating valve. The feature is that the amount of return oil is adjusted according to the directional position.

[Effects of the invention] According to the invention, the hydraulic pressure is automatically adjusted to a predetermined value using only a single regulating valve, and the operation is stopped especially when the hydraulic pressure is low, so that the bladder in the accumulator is effectively protected.

In addition, in this invention, since a regulating valve is provided separately from the switching valve, the switching operation of the switching valve is independent of the switching operation.
The return oil amount can be adjusted according to the magnitude of the acting oil pressure, and the oil amount can be adjusted stably and accurately, even if the switching valve performs a switching operation when the oil pressure is unstable, such as during startup. When the oil pressure drops, the operation can be reliably stopped and the bladder can be safely protected.

[Example] Hereinafter, an example of the present invention will be specifically described.

As shown in FIG. 1, a striking piston 2 for striking a chisel (not shown) is housed in the hydraulic striking cylinder 1 so as to be able to reciprocate in the axial direction. A front chamber 3 and a rear chamber 4 are formed. Pressure oil is supplied to this cylinder front chamber 3 from a first pressure oil passage 5, and a bladder type accumulator 6 is connected in the middle of this first pressure oil passage 5. When the supply of pressure oil becomes insufficient, the pressure oil accumulated in the accumulator 6 can compensate for the shortage.

On the other hand, a second pressure oil passage 7 communicating with the cylinder rear chamber 4 is intermittently connected to a pressure oil source by a switching valve 8, so that pressure oil is supplied to the cylinder rear chamber 4. Sometimes, the striking piston 2 is driven forward to perform a single strike. The switching valve 8 is switched by the hydraulic pressure of a hydraulic switching passage 10 communicating with a chamber 9 that can communicate with the front chamber 3 of the hydraulic impact cylinder 1, and the chamber 9 is connected to the front chamber 3. When the striking piston 2 moves forward, when hydraulic pressure acts on the back side of the switching valve 8 through the hydraulic pressure switching passage 10, it is driven in the closing direction and communication with the second pressure oil passage 7 is cut off, and as a result, the cylinder front chamber The striking piston 2 is driven backward by the hydraulic pressure supplied to the piston 3 . As the impact piston 2 retreats, the hydraulic switching valve 8
When the hydraulic pressure acting on the back surface of the cylinder decreases, the hydraulic switching valve 8 is operated in the opening direction by the hydraulic pressure of the second pressure oil passage 7, and high pressure oil is supplied from the second pressure oil passage 7 to the cylinder rear chamber 4. Then, the striking piston 2 is driven forward. A part of the hydraulic pressure supplied to the cylinder rear chamber 4 when the percussion piston 2 is driven forward is directly returned to the drain from the oil return passage 11 when the percussion piston 2 is retracted.

A regulating valve 12 for regulating the return pressure is provided between the second pressure oil passage 7 and the oil return passage 11. The structure of this regulating valve 12 is shown more clearly in FIG.

As shown in FIG. 2, the block body 13 that fits on the inner periphery of the hydraulic switching valve 8 has a radial passage 14 that can communicate with the second pressure oil passage 7, and a radial passage 14 that is perpendicular to this passage and has an oil passage at the other end. An axial passage 15 communicating with the return passage 11 is provided. This axial passage 15
The passage diameter is enlarged in three stages from the passage 14 side in the radial direction, and a regulating valve 1 is installed in the middle diameter section 15b.
2 are fitted. This regulating valve 12 has a tip shaft portion formed as a hollow portion 17, in which small-diameter internal and external communication holes 18, . . . , 18 are regularly provided in both the radial direction and the axial direction. A large-diameter hollow portion 20 on the rear side communicates with this hollow portion 17 via an axial communication hole 19.
A coil spring 21 that biases the regulating valve 12 in the closing direction is supported by a bolt 22 and is interposed therein. The outer periphery of the rear end of this regulating valve 12 has an outer periphery 12a whose diameter is increased by one step, and a pilot chamber 24 is formed between it and a stopper portion 23 provided on the block body 13 side that guides the regulating valve 12. for,
Hydraulic pressure from a pressure oil source passes through the pilot passage 25 and acts as pilot pressure.

In the above configuration, the axial position of the regulating valve 12 is set to a state where communication between the second pressure oil passage 7 and the pressure oil source is cut off by the hydraulic pressure on the second pressure oil passage 7 side or by the hydraulic pressure switching valve 8. In the case, it is automatically determined by the hydraulic pressure in the cylinder rear chamber 4 and the set spring force of the built-in coil spring 21, and the intermediate diameter stepped portion 15 is automatically determined depending on the position.
The number of communication holes closed by b is increased or decreased, and accordingly the oil return passage 1 is
In other words, the return oil pressure is adjusted. That is, when the hydraulic pressure acting on the regulating valve 12 is relatively low, the spring force of the built-in coil spring 21 is overcome and the regulating valve 12 is displaced in the closing direction, and the amount of oil flowing out is reduced accordingly. This will prevent a decrease in Therefore, even if the pressure oil decreases and the oil amount becomes insufficient, a large amount of oil will not be consumed, thereby avoiding a situation where the entire amount of pressure oil accumulated in the accumulator 6 is consumed at once. This prevents the bladder 6a from being hit against the communication hole 6b of the accumulator 6.

Furthermore, when the pressure of the pressure oil that drives the percussion piston 2 is extremely reduced, the regulating valve 12 is fully closed by the coil spring 21, so the percussion piston 2 is locked and unnecessary percussion drive is avoided. be done.

As is clear from the above, in this invention,
Since the return hydraulic pressure is adjusted in accordance with the hydraulic pressure acting on the percussion piston, an extreme decrease in the hydraulic pressure is avoided, and thereby an extreme stroke of the bladder of the accumulator is also avoided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view showing the drive system of the hydraulic impact piston, and FIG. 2 is an enlarged sectional view of the hydraulic pressure adjustment device. 1...Blow cylinder, 2...Piston, 6...
Accumulator, 5, 7...First and second pressure oil passages, 8...Switching valve, 11...Oil return passage, 12...Adjustment valve, 15...Communication passage, 18,...
..., 18... Communication hole, 21... Coil spring.

Claims (1)

[Utility Model Claims] A hydraulic impact tool equipped with a bladder-type accumulator communicating with a first pressure oil passage which supplies pressure oil to a front chamber of a striking cylinder which accommodates a striking piston, and a change-over valve which alternately switches a second pressure oil passage which communicates with a rear chamber of the striking cylinder between a pressure oil source and a return passage, wherein the hydraulic impact tool further comprises: an adjusting valve having a hollow tip which is fitted axially in a communicating passage which connects the second pressure oil passage with the return passage when the change-over valve is switched to the return passage side; a biasing member which biases the adjusting valve against pressure oil acting from the second pressure oil passage side; and a plurality of communicating holes which communicate between the inside and outside of the adjusting valve are provided at the tip of the adjusting valve at different axial positions, so that the amount of return oil can be adjusted in accordance with the axial position of the adjusting valve.