JPS6131823Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention uses compressed air as a driving source to move a striking piston that is slidably and tightly fitted into a striking cylinder, and is driven by a driver that is integrally connected to the striking piston. Regarding a pneumatic impact tool for driving a striking member into an object, particularly between the upper chamber of the piston of the impact cylinder and the main air chamber in which compressed air for forward movement of the impact piston is stored, or the upper chamber of the piston. This invention relates to a sealing device for a head valve that switches between the exhaust passage and the exhaust passage.

Conventionally, an example of a pneumatic impact tool includes a hitting piston to which a driver is rigidly connected, a hitting cylinder to which the hitting piston is slidably and tightly fitted, and a blowing cylinder formed around the upper end side of the hitting cylinder, and a blowing piston having a driver attached thereto. a main air chamber that stores compressed air for forward movement; a return air chamber that is formed around the lower end of the percussion cylinder and stores compressed air for backward movement of the percussion piston; a chamber above the piston of the percussion cylinder; Some devices are known that are equipped with a head valve that switches between the main air chamber and the above-mentioned piston upper chamber and the exhaust passage.

As an example of the above-mentioned head valve, the first
The one shown in the figure is known. This head valve 50 has an annular head valve cylinder 51.
and a head valve piston 52 that is slidably and tightly fitted into the cylinder 51. The head valve piston 52 acts directly related to the opening/closing operation between the main air chamber 53 and the piston upper chamber 55 of the striking cylinder 54, an operational large diameter piston section (not shown) that receives an opening/closing signal from a trigger valve (not shown). Opening/closing thick-walled piston part 5
It consists of 6. Furthermore, the opening/closing thick-walled piston portion 5
6 has a medium-diameter piston portion 57 that protrudes deeply into the interior of the striking cylinder 54. A first O-ring 59 is fitted into the outer peripheral corner portion 58 of the opening/closing thick-walled piston portion 56 and the medium-diameter piston portion 57. Further, a second O-ring 60 having a slightly smaller diameter than the first O-ring 59 is fitted into the outer peripheral portion 57a of the medium-diameter piston portion 57.

The first O-ring 59 is connected to the head valve piston opposing portion 61 of the striking cylinder 54 when the head valve piston 52 closes off the space between the main air chamber 53 and the striking piston upper chamber 55. 56, and the second O-ring 60 is for sealing between the inner peripheral part 54a of the striking cylinder 54 and the opening/closing thick-walled piston part 5.
This is for sealing between the 6 and 6.

By the way, the head valve 50 having the above configuration
, the structure requires two O-rings 59 and 60 to close off the main air chamber 53 and the piston upper chamber 55, so these O-rings 59 and 60 are assembled together. This also requires two annular grooves for attachment, which has the disadvantage of requiring time and effort to process. Furthermore, the O-rings 59 and 60 are likely to come off due to resistance caused by the sliding movement of the head valve piston 52.

Therefore, in order to eliminate each of the above-mentioned drawbacks,
An annular sealing member is assembled to the upper end of the striking cylinder, and the lower end of the head valve piston comes into contact with the upper end of the striking cylinder via the sealing member to shut off the space between the main air chamber and the upper chamber of the piston. structure has been proposed.

However, in the structure described above, in order to position and fix the seal member to the upper end of the impact cylinder, a flange portion that wraps around the outer periphery of the upper end of the impact cylinder is required.

By the way, generally, an annular rib for positioning the impact cylinder is provided inside the tool body. The inner diameter of this rib is formed to be approximately the same diameter as the outer diameter of the above-mentioned impact cylinder.

Therefore, if the flange is located on the outer periphery of the striking cylinder as described above, if the sealing member is assembled to the upper end of the striking cylinder and inserted from the lower end of the tool body, Since the flange portion is caught on the rib, the impact cylinder must first be inserted from the lower end of the tool body and positioned, and then the seal member must be inserted and assembled from the upper end of the tool body. The work was complicated.

Therefore, the present invention was proposed in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a sealing device that is easy to process and in which the assembled state of the sealing member is stable.

Another object of the present invention is to provide a tool in which the impact cylinder is assembled from the lower end of the tool body, so that the impact cylinder and seal member can be easily assembled.

To this end, the present invention includes a striking cylinder housed in a striking tool body, a striking piston that is slidably and tightly fitted into the striking cylinder, and a nose that is rigidly connected to the striking piston and protrudes from the tool body. A main air chamber formed around the upper end of the striking cylinder and storing compressed air for forward movement of the striking piston, a head valve piston, and a head valve cylinder. A pneumatic impact tool equipped with a head valve that switches between the piston upper chamber of the impact cylinder and the main air chamber or between the piston upper chamber and the exhaust passage by reciprocating movement of the head valve piston. A ring-shaped recess is formed at the lower end of the outer periphery of the head valve piston, and an annular seal member is fitted into the recess, so that the head valve piston closes off the space between the main air chamber and the upper chamber of the piston. When the head valve piston is in contact with the upper end of the striking cylinder through the seal member, an air communication passage is provided that communicates with the outside between the circular recess and the seal member, and the head valve piston When the space between the main air chamber and the piston upper chamber is opened, compressed air in the main air chamber flows between the upper wall surface in the recess and the upper end surface of the seal member. It is characterized in that compressed air can be discharged to the outside through the air communication path.

Below, preferred embodiments of the present invention are shown in Figures 2 to 5.
This will be explained in detail according to the diagram.

FIG. 2 is a longitudinal sectional side view of the vicinity of the head valve of a pneumatic nail gun, which is an example of the pneumatic impact tool according to the present invention. A percussion cylinder 3 is disposed inside the main body 2 of the nailing machine 1, and a percussion piston 4 is slidably and tightly fitted inside the percussion cylinder 3. This striking piston 4 has a cylindrical protrusion 63 formed on the upper surface 4a. The driver 5, which serves as a nail driving member, is firmly screwed onto the protrusion 63 and rigidly connected to the striking piston 4. A main air chamber 6 for storing compressed air for forward movement of the striking piston 4 is formed around the upper end of the percussion cylinder 3 (the upper peripheral part in FIG. 2). The compressed air is supplied into the main air chamber 6 from the distal end side of the grip portion 7 (right side in FIG. 2) by a compressor such as a compressor.
On the other hand, although not shown in the drawings, there is a return air chamber in the lower end periphery of the striking cylinder 3 (lower end periphery in FIG. 2) that stores compressed air for returning the striking piston 4 to the top dead center. is formed. A striking piston 4 moves forward in this return air chamber, and an upper surface 4a of the striking piston 4
When the air passes through a plurality of return air supply holes consisting of small holes opened in the blow cylinder 3, a part of the compressed air supplied into the piston upper chamber 3A of the blow cylinder 3 is transferred to the return air. Air is supplied from the air supply hole. After the striking piston 4 reaches the bottom dead center, the compressed air for double movement of the striking piston in the return air chamber is supplied to a return air passage provided below the return air supply hole of the striking cylinder 3. The force acts on the lower chamber 3B of the striking piston of the striking cylinder 3, and the striking piston 4 returns toward the top dead center.

On the other hand, a cylindrical piston stop 8 made of an elastic member is disposed on the upper end side of the striking cylinder 3, which reliably prevents rebound when the striking piston 4 returns to the top dead center. The striking piston 4 is held in this state. Further, an air passage 13 that communicates the upper chamber 3A of the striking piston with the atmosphere is formed so as to surround a head valve 10, which will be described later.

The upper end of the striking cylinder 3 includes an upper chamber 3A of the striking piston and the main air chamber 6.
or between the piston upper chamber 3A and the exhaust passage 13.
is installed. The head valve 10 is composed of a head valve cylinder 1 which is formed in an annular shape at the upper end of the nailer main body 2 in the figure, and a head valve piston 11 which is slidably and tightly fitted into the cylinder 12. The head valve piston 11 includes an opening/closing thick-walled piston portion 11a that acts in direct relation to the opening operation of the main air chamber 6 and the upper chamber 3A of the striking piston, and an operating large-diameter piston that receives an opening/closing signal from a trigger valve (not shown). A groove is formed by a portion 11b and a small-diameter joint stem portion 11c that joins each of these piston portions 11a, 11b. Note that a communication hole 64 communicating with the exhaust passage 13 is provided in the joint stem portion 11c. Further, an annular flange portion 6 formed at the lower end portion in the figure of the opening/closing thick-walled piston portion 11a.
A compression coil spring 14 is disposed between the nail gun 2 and the inner wall 2a of the nailer main body 2, which always urges the head valve piston 11 downward in the figure. This compression coil spring 14 has the role of assisting the return (downward movement in the figure) of the head valve piston 11. Further, the piston upper chamber 15 of the head valve cylinder 12 is connected to a trigger valve (not shown) disposed at the base end of the grip portion 7 via an air communication passage 16.

In the head valve piston 11, an annular recess 20 is formed at the lower end of the outer periphery of the opening/closing thick-walled piston portion 11a. And this recess 20
For example, an annular sealing member 21 made of a rubber material is provided.
is fitted.

As shown in FIGS. 3 and 4, the sealing member 21 is arranged so that an annular gap 22 is formed at the upper end of the inner periphery when the sealing member 21 is fitted into the recess 20. It has an annular inclined surface 21C that slopes upward toward 21B. In addition, the inner circumferential surface 21A of the sealing member 21 has grooved portions 23, 23, 2 formed with notches at equal intervals in the circumferential direction.
3, 23, and air communication vertical holes 24, 24, 24, 24 formed by these grooves 23.
The cavity 22 is placed in communication with the piston upper chamber 3A of the impact cylinder 3 through the piston.

Further, on the lower end side of the outer periphery of the seal member 21,
When the head valve piston 11 closes off the space between the main air chamber 6 and the piston upper chamber 3A,
It has a first annular step 25 that closely engages the upper end 3a of the striking cylinder 3. The circumferential wall 25A of the annular stepped portion 25 is formed in the shape of a pointed peak, and the top portion 26 of the circumferential wall 25A is placed in pressure engagement with the inner circumferential surface 3C of the striking cylinder 3. Further, the upper wall 25B of the annular step portion 25 is placed in a state of pressure contact engagement with the upper end surface 3D of the impact cylinder 3. Note that the peripheral side wall 2 of the annular step portion 25
5A is in line contact with the inner circumferential surface 3C of the striking cylinder 3, so that the sliding resistance when the sealing member 21 and the striking cylinder 3 are engaged is small.

Further, on the upper end side of the outer periphery of the seal member 21,
An annular flange 27 is formed to prevent compressed air from flowing into the recess 20. The upper end surface 2 of the seal member 21 is provided on the inner periphery of the flange portion 27.
It has an annular inclined surface 28 that slopes downward toward 1B. It is placed in a suitable condition.

The sealing member 21 is positioned and held within the recess 25 by the relative engagement between the second annular step 30 formed at the lower end of the inner circumference and the lower end flange 31 of the annular recess 20. It is in a state of

Note that the outer diameter of the inner peripheral portion 20A of the annular recess 20 and the inner diameter of the seal member 21 are formed to be approximately the same diameter in consideration of the misalignment of the axes. Further, the amount of engagement between the second annular step portion 30 of the seal member 21 and the lower end flange portion 31 of the annular recess 20 is as follows:
The sealing member 21 is set to be small enough to prevent it from coming off at high temperatures and high pressures. Further, the area of the upper end surface 21B of the sealing member 21 is set smaller than the area of the upper wall surface 25B of the first annular step portion 25.

According to the seal member 21 having the above configuration, the head valve piston 11 moves upward in the figure,
When the main air chamber 6 and the piston upper chamber 3A are opened, the seal member 21 is closed due to the sliding resistance between the striking cylinder 3 and the seal member 21.
is pulled downward, and the compressed air in the main air chamber 6 flows between the upper end surface 21B of the seal member 21 and the upper wall surface 20B of the annular recess 20, and moves the seal member 21 out of the annular recess 20. Even if air pressure is applied in the removal direction (downward in the figure), this compressed air can be guided into the piston upper chamber 3A through the cavity 22 and each vertical hole 24, so that the Falling off from the annular recess 20 can be prevented.

Note that the annular flange portion 2 of the seal member 21
7 is pressed into engagement with the outer circumferential surface 11A of the thick-walled piston portion 11a by the compressed air in the main air chamber 6, so that the upper end surface 21B of the sealing member 21 and the annular recess are pressed against each other. 20 and the upper wall surface 20B can be substantially prevented from flowing into the space between the compressed air and the upper wall surface 20B. Further, since the area of the upper end surface 21B of the sealing member 21 is set smaller than the area of the upper wall surface 25B of the first annular step 25 of the sealing member 21, the cavity 22 and each vertical hole 24 Even if the flow velocity of the compressed air guided into the piston upper chamber 3A through the above is slow, the difference in area between the upper end surface 21B and the upper wall surface 20B prevents the seal member 21 from falling out of the recess 20. It can be prevented.

In addition, as shown in FIG. 5, the seal member 21
If the annular flange portion 4 formed on the upper end side of the outer circumference is formed in a vertically rising shape, when the head valve piston 11 moves forward, the circumferential side wall of the first annular stepped portion 25 of the seal member 21 Even if the seal member 21 is pulled downward in the figure due to the sliding resistance between the inner peripheral surface 3C of the impact cylinder 3 and the inner peripheral surface 3C of the impact cylinder 3, compressed air will not flow between the upper end surface 21B and the upper wall surface 20B. It is possible to more reliably prevent the inflow of.

Furthermore, the vertical holes 24, 24, 24, 24
Instead of the above, an air communication hole may be formed in the opening/closing thick piston portion 11a of the head valve piston 11 to connect between the gap portion 22 and the exhaust passage 13, and the compressed air in the main air chamber 6 may be guided to the annular recess 2 so that the compressed air does not act on the upper end surface 21B of the seal member 21.
As long as the structure is such that the discharge is performed from within the tank, various modifications are possible.

As described above, according to the present invention, one sealing member can provide the same sealing function as the conventional sealing function using two sealing members. Therefore, the structure is simple and processing is easy.

Further, according to the present invention, it is possible to maintain a stable assembled state of the seal member that can reliably prevent the seal member from falling off when the head valve is operated.

Furthermore, according to the present invention, in a type in which the impact cylinder is assembled from the lower end of the tool body,
The above-mentioned impact cylinder and seal member can be easily assembled. Further, the sealing member can be easily attached to and detached from the head valve.

[Brief explanation of drawings]

Fig. 1 is an enlarged sectional view of main parts showing a conventional example, Fig. 2 is a longitudinal sectional side view of the vicinity of the head valve of a pneumatic nailer showing an embodiment of the present invention, and Fig. 3A is an external perspective view of a sealing member. , FIG. 3B is a plan view thereof, FIG. 3C is a sectional view taken along the line A-A in FIG. 3B, FIG. FIG. 7 is an enlarged sectional view of a main part showing a modification of the sealing member. DESCRIPTION OF SYMBOLS 1...Pneumatic nailer, 2...Nailer main body, 3...Blow cylinder, 3A...Piston upper chamber, 4...Blow piston, 5...Driver, 6...Main air chamber,
DESCRIPTION OF SYMBOLS 10... Head valve, 11... Head valve piston, 12... Head valve cylinder, 13... Exhaust passage, 20... Annular recess, 20B... Top wall surface, 21... Annular sealing member, 21B... Top end surface, 24... Vertical hole for air communication .

Claims (1)

[Scope of utility model registration request] A striking cylinder built into the striking tool body, a striking piston slidably and tightly fitted into the striking cylinder, and a driver which is rigidly connected to the striking piston and is operated to move forward within a nose protruding from the tool body. a main air chamber formed around the upper end of the striking cylinder and storing compressed air for the reciprocating movement of the striking piston, and a head valve piston and a head valve cylinder. Therefore, in a pneumatic impact tool equipped with a head valve that switches between the piston upper chamber of the impact cylinder and the main air chamber or between the piston upper chamber and the exhaust passage, the outer periphery of the head valve piston An annular recess is formed at the lower end, and an annular seal member is fitted into the recess, so that when the head valve piston closes off the space between the main air chamber and the piston upper chamber, the head valve piston passes through the seal member. and an air communication path communicating with the outside between the annular recess and the sealing member;
When the head valve piston opens between the main air chamber and the upper chamber of the piston, compressed air in the main air chamber flows between the upper wall surface in the recess and the upper end surface of the seal member. A sealing device for a head valve in a pneumatic impact tool, characterized in that when the compressed air flows in, the compressed air can be discharged to the outside through the air communication path.