JPH09103974A - Trigger valve structure of air-operated nailing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an impact piston to automatically return to its top dead center when a nail is driven by providing a pilot valve which is moved down by compressed air from a return air chamber when the impact piston comes near its bottom dead center. SOLUTION: A variable pressure chamber 40 is vented to the atmosphere by pulling of a trigger 20 and pushing of a contact arm 3, and a nail is driven with an impact piston 7 coming to its bottom dead center. Thus even while the trigger 20 and the contact arm 3 are being operated, compressed air in a return air chamber 10 is supplied to the upper chamber of a pilot valve to move a pilot valve 32 downward so as to shut the variable pressure chamber 40 from the atmosphere and also to communicate it to an accumulator 9. Therefore, the impact piston 7 is automatically returned to its top dead center, at which time a nailing machine main body 1 is restored to its initial nonoperating state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trigger valve structure for opening and closing a head valve in an air nailer.

[0002]

2. Description of the Related Art Generally, in an air nailing machine, when compressed air is supplied to the upper chamber of a striking piston, the striking piston moves downward to drive a nail, and the return air accumulated during the downward movement of the striking piston. The compressed air in the chamber is supplied to the lower chamber of the striking piston, and the upper chamber of the striking piston is opened to the atmosphere, so that the striking piston that has reached the bottom dead center is returned to the top dead center, and a single nailing operation is performed. It is configured to be completed.

The supply of compressed air to the upper chamber of the striking piston and the switching to the atmosphere are switched by opening / closing the head valve, and the opening / closing operation of the head valve is controlled by a trigger valve. That is, in the state where the trigger arm is not operated and the contact arm provided at the tip of the driver guide is not pushed,
The variable pressure chamber of the trigger valve communicates with the accumulator to supply compressed air to the variable pressure chamber, whereby compressed air is supplied to the head valve upper chamber communicated with the variable pressure chamber and the head valve is kept closed. . When the head valve is kept closed, the upper chamber of the striking piston is cut off from the accumulator and kept open to the atmosphere, so that the striking piston is kept at the top dead center.

When the trigger valve is pushed and the contact arm is pushed to push the stem of the trigger valve to a predetermined position from the non-operating state, the variable pressure chamber is shut off from the accumulator and is opened to the atmosphere. The head valve upper chamber is opened to the atmosphere. When the head valve upper chamber is opened to the atmosphere, the head valve is moved upward by the compressed air force of the accumulator and opened, whereby the striking piston upper chamber communicates with the accumulator and compressed air is supplied to the striking piston upper chamber. It is also shut off from the atmosphere. When compressed air is supplied to the upper chamber of the striking piston, the striking piston moves downward and the nail is driven as described above.

When the pushing operation of the contact arm is canceled after the striking piston reaches the bottom dead center and the nail is driven (in the case of a single shot, the pulling operation of the trigger is further released), the stem of the trigger valve sticks out. When the variable pressure chamber is shut off from the atmosphere and communicated with the accumulator, compressed air is supplied to the head valve upper chamber, which closes the head valve and shuts off the striking piston upper chamber from the accumulator. Open to the public. When the striking piston upper chamber is opened to the atmosphere,
As described above, the striking piston is moved upward by the air pressure in the return air chamber and returned to the top dead center, and the one nailing operation is completed as described above.

[0006]

As described above, in the conventional air nailer, the pushing operation of the contact arm is canceled or the trigger of the trigger is released after the impact piston reaches the bottom dead center and the nail is driven. Since the striking piston was returned to top dead center by releasing the pulling operation (both in the case of single shot driving), if these releasing operations are delayed after nailing, the head valve is held at top dead center during that time. As a result, the striking piston is held at the bottom dead center, so that there is a problem that useless compressed air is supplied to the striking piston upper chamber during that time.

The present invention has been made in view of this problem.
An object of the present invention is to provide a trigger valve structure in which, when the impact piston reaches the bottom dead center and a nail is driven, the impact piston is automatically returned to the top dead center irrespective of the trigger or contact arm release operation. .

[0008]

Therefore, according to the first aspect of the invention, when the head valve upper chamber is opened to the atmosphere and the head valve is opened, compressed air is supplied to the striking piston upper chamber to lower the striking piston. When the nail is driven by moving, compressed air is supplied to the head valve upper chamber and the head valve is closed, the impact piston upper chamber is opened to the atmosphere and the impact piston compresses the return air chamber. A structure of a trigger valve for opening and closing the head valve in an air nailing machine that moves upward by air, wherein when the striking piston reaches the vicinity of bottom dead center, it is lowered by compressed air in the return air chamber. A moving pilot valve, and when the pilot valve moves downward, compressed air is supplied to the upper chamber of the head valve to close the head valve. And said that the content was.

According to the above construction, after the nail is driven, the striking piston automatically turns up when the contact arm reaches the bottom dead center regardless of whether the contact arm is pushed or the trigger is pulled. Since it is returned to the dead center, even if the releasing operation of the contact arm etc. is delayed, the striking piston will not be held at the bottom dead center during that time unlike the conventional case, and therefore no wasted air is consumed during that time. .

According to the second aspect of the present invention, when the upper chamber of the head valve is opened to the atmosphere and the head valve is opened, compressed air is supplied to the upper chamber of the striking piston and the striking piston moves downward to drive the nail. On the other hand, when compressed air is supplied to the head valve upper chamber and the head valve is closed, the striking piston upper chamber is opened to the atmosphere and the striking piston is moved upward by the compressed air in the return air chamber. In the structure of a trigger valve for opening and closing the head valve, the striking piston at a stage earlier than the compressed air in the striking piston upper chamber being supplied to the return air chamber in the downward movement process of the striking piston. Pilot valve that moves downward when the striking piston reaches near bottom dead center by the compressed air in the auxiliary air chamber to which the compressed air in the upper chamber is supplied. The provided, characterized in that said pilot valve is supplied with compressed air to the head top valve chamber and moves downward in the configuration wherein the head valve is closed.

According to the above construction, in addition to the same operation as the construction according to the first aspect, the pilot valve is operated by the compressed air in the auxiliary air chamber to which the compressed air is supplied at an earlier stage than the return air chamber. Since the striking piston is moved downward, after the striking piston reaches the bottom dead center, the striking piston rises and returns to the top dead center more quickly than in the configuration according to the first aspect.

[0012]

According to the present invention, when the striking piston reaches the bottom dead center and the nail is driven, the striking piston is automatically returned to the top dead center regardless of the releasing operation of the contact arm or the trigger. It is possible to eliminate the conventional useless air consumption.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a main body 1 of an air nailing machine to which a trigger valve 30 of this embodiment is applied. A driver guide 2 is provided at the lower end of the main body 1.
Is provided so as to protrude, and the contact arm 3 is provided at the tip of the driver guide 2 so as to be capable of being pushed, but in the figure, only the base of the driver guide 2 is shown, and the upper end of the contact arm 3 is shown. Only the parts are shown. Further, from the side of the main body 1, the handle 4
Are provided so as to project in a substantially T shape, but only the base is shown in the figure.

Now, the main body 1 does not need to be particularly changed, but in the following, the main body 1 has a cylinder 6 inside a case 5 and a striking piston inside the cylinder 6. 7 is arranged so that it can move up and down. A driver 8 is attached to the lower surface of the striking piston 7 so as to project in a T-shape.
It reciprocates in a. When the driver 8 moves down in the guide hole 2a, the nail supplied into the guide hole 2a is driven out from the tip of the driver guide 2.

The space between the outer periphery of the cylinder 6 and the case 5 is hermetically closed in two chambers, which are approximately half of the upper and lower sides, and the upper chamber is an accumulator 9. The accumulator 9 communicates with the inside of the handle portion 4, and compressed air is supplied through an air hose (not shown) connected to the tip of the handle portion 4. On the other hand, the lower chamber is a return air chamber 10. The return air chamber 10 is communicated with the inside of the cylinder 6 by a check valve 11 and a communication hole 12. The check valve 11 allows the flow of compressed air from the inside of the cylinder 6 to the inside of the return air chamber 10. When the striking piston 7 passes through the check valve 11 during the downward movement process, the compressed air in the striking piston upper chamber is compressed. Flows into the return air chamber 10 through the check valve 11 and acts on the lower surface of the striking piston 7 through the communication hole 12.

A head valve 13 is arranged above the cylinder 6. This head valve 13 has a compression spring 14
As shown in the drawing, when reaching the bottom dead center, the inside of the cylinder 6 is closed and cut off from the accumulator 9, and the inside of the cylinder 6 is opened to the atmosphere through the ventilation hole 13a. Also, this head valve 1
Since the lower surface peripheral edge 13b of 3 is always facing the accumulator 9, compressed air acts, and when the head valve upper chamber 15 is opened to the atmosphere, the head valve 13 moves upward against the compression spring 14. To do. When the head valve 13 moves upward, the inside of the cylinder 6 is opened to communicate with the accumulator 9, and the inside of the cylinder 6 is shut off from the atmosphere by the seal ring 13c. When the inside of the cylinder 6 communicates with the accumulator 9, the striking piston upper chamber 16
Compressed air flows in, and thereby the striking piston 7 moves downward and the nail is driven.

The head valve upper chamber 15 is communicated with a variable pressure chamber 40 of a trigger valve 30 described below through a communication passage 15a. When compressed air is supplied to the variable pressure chamber 40, the head valve upper chamber 15 is also connected. Because compressed air is supplied,
The head valve 13 moves downward due to the difference in pressure receiving area and the urging force of the compression spring 14, whereby the inside of the cylinder 6 is closed and cut off from the accumulator 9 and opened to the atmosphere. When the variable pressure chamber 40 is opened to the atmosphere, the head valve upper chamber 15 is also opened to the atmosphere, so that the compressed air force acting on the lower surface peripheral edge 13b exceeds the biasing force of the compression spring 14 and the head valve 13 moves upward. When the head valve 13 moves upward, the cylinder 6 is opened and the striking piston 7 moves downward as described above.

In the figure, 17 is a shock absorbing damper for the top dead center of the striking piston, and 18 is a shock absorbing damper for the bottom dead center. The return air chamber 10 is passed through the inner peripheral side of the bottom dead center damper 18 and the inner peripheral hole 2a of the driver guide 2.
The compressed air inside is exhausted so that the return air chamber 10 is open to the atmosphere except when the striking piston 7 reaches the bottom dead center.

Next, the trigger valve 30 is arranged on the lower surface side of the base portion of the handle portion 4. Details of the trigger valve 30 are shown in FIG. Below the trigger valve 30, the trigger 20 is arranged rotatably around the support shaft 20a. The back of the trigger 20 (the upper surface in the figure)
An idler 21 is rotatably attached to the shaft 21a about a support shaft 21a. The upper end of the contact arm 3 reaches below the idler 21, and when the contact arm 3 is pushed, the idler 21 is rotated upward.

The trigger valve 30 is mainly composed of a stem 31, a pilot valve 32 and a plate 33. The plate 33 is fixed to the mouth of a stepped valve hole 34a formed in a valve block 34, and the pilot valve 32 is fixed. Is accommodated inside the valve hole so as to be movable in the axial direction. The stem 31 is supported via a pilot valve 32 and a plate 33 so as to be movable in the axial direction.

The stem 31 has two seal rings 31
a, 31b are attached, and three seal rings 32a, 32b, 32c are attached to the outer peripheral surface of the pilot valve 32. A communication hole 32d is formed in the side portion of the pilot valve 32, and the inner peripheral side of the pilot valve 32 is communicated with the accumulator 9 through the communication hole 32d and a communication hole 37 described later. Further, since the compression spring 35 is interposed between the rear end of the stem 31 and the bottom portion of the pilot valve 32, the stem 3
1 is urged downward with respect to the pilot valve 32.

The valve block 34 is formed with three communication passages 36, 37 and 38 which communicate with the valve hole 34a. The communication passage 36 on the lower side of the drawing is the communication passage 15
a is communicated with the head valve upper chamber 15. The communication passage 37 on the middle side of the drawing communicates with the accumulator 9. The communication passage 38 on the upper side in the drawing communicates with the return air chamber 10. Hereinafter, the operation of the trigger valve 30 will be sequentially described with reference to FIGS.

FIG. 2 shows the trigger 2 in the continuous firing mode.
It shows a state in which the nailing machine is in a non-use state in which 0 is pulled but the contact arm 3 is not pushed. In the continuous shot mode, the nail can be continuously driven by repeatedly pushing the contact arm 3 while pulling the trigger 20. Therefore, the trigger 20 is pulled as shown in the drawing. Even in the state as it is, if the contact arm 3 is pushed and operated, the nail is driven out.

In this state, the stem 31 moves the compression spring 35.
And the compressed air force of the accumulator 9 acting through the communication hole 32d of the pilot valve 32, and is held at the lower end position. When the stem 31 is held at the lower end position, the lower seal ring 31 of the stem 31 is
While a is fitted in the inner peripheral hole 33a on the small diameter side of the plate 33 to shield the variable pressure chamber 40 from the atmosphere, the upper seal ring 31b is disengaged from the inner peripheral hole 32e of the pilot valve 32 so that the variable pressure chamber 40 is a communication hole. 32d and communication passage 37
And is communicated with the accumulator 9.

In this way, the variable pressure chamber 40 has the accumulator 9
Since compressed air is supplied to the head valve upper chamber 15 through the communication passages 36 and 15a, the head valve 13 is closed and the striking piston 7 is held at the top dead center.

Since the return air chamber 10 is open to the atmosphere during the non-operation, the pilot valve upper chamber 32f formed between the rear end face of the pilot valve 32 and the bottom of the valve hole 34a is connected to the return valve chamber 32f. Atmospheric pressure is acting through the passage 38. On the other hand, since the lower surface of the pilot valve 32 faces the variable pressure chamber 40, compressed air acts. From this, the pilot valve 32 has the compression spring 3
It is located at the deepest part (top dead center) of the valve hole 34a in combination with the urging force of 5.

Next, as shown in FIG. 3, by pushing the contact arm 3 to rotate the idler 21 upward, the stem 31 is pushed upward against the compression spring 35. In this ascending process, first, the upper seal ring 3
Since 1b is fitted in the inner peripheral hole 32e of the pilot valve 32, the variable pressure chamber 40 is shut off from the accumulator 9.
When the stem 31 further rises and reaches the upper end position as shown in FIG. 4, the lower seal ring 31a is disengaged from the inner peripheral hole 33a on the small diameter side of the plate 33, so that the variable pressure chamber 40 is separated from the inner peripheral hole 33a of the plate 33. And it is opened to the atmosphere through the atmosphere opening hole 33b.

Since the variable pressure chamber 40 is opened to the atmosphere, the head valve upper chamber 15 is opened to the atmosphere through the communication passages 36 and 15a, whereby the head valve 13 is opened and the striking piston upper chamber 16 is compressed from the accumulator 9 to the compressed air. Is supplied, so that the striking piston 7 reaches the bottom dead center and the nail is driven.

When the striking piston 7 passes through the check valve 11 in the downward movement process of the striking piston 7, compressed air in the striking piston upper chamber 16 is supplied to the return air chamber 10 via the check valve 11. When the compressed air is supplied to the return air chamber 10, the compressed air is also supplied to the pilot valve upper chamber 32f through the communication passage 38. Pilot valve upper chamber 3
Since compressed air is supplied to 2f and the variable pressure chamber 40 is open to the atmosphere as described above at this time point, the pilot valve 32 moves downward as shown in FIG.

When the pilot valve 32 moves downward, the lower seal ring 32a is fitted into the inner diameter hole 33c on the large diameter side of the plate 33 to shut off the variable pressure chamber 40 from the atmosphere. At the same time, since the inner seal ring 32b is disengaged from the valve hole 34a, the variable pressure chamber 40 is communicated with the accumulator 9 through the gap between the outer periphery of the pilot valve 32 and the valve hole 34a, and thus the variable pressure chamber 40 receives compressed air. Is supplied. Since the upper seal ring 32c is still fitted in the valve hole 34a, the pilot valve upper chamber 32f is cut off from the accumulator 9. Further, even if the pilot valve 32 moves downward, the seal ring 31b on the upper side of the stem 31 is still fitted into the inner peripheral hole 32e of the pilot valve 32 and sealed, and the stem upper chamber on the rear surface side of the stem 31 is 31
By extension, the accumulator 9 and the inner peripheral hole 3 of the plate 33
3c and 33a are shut off, so there is no air leakage.

Since the variable pressure chamber 40 is communicated with the accumulator 9 and compressed air is supplied, the compressed air is supplied to the head valve upper chamber 15 through the communication passages 36 and 15a, so that the head valve 13 moves downward and strikes. The piston upper chamber 16 is closed and opened to the atmosphere. Impact piston upper chamber 1
When 6 is opened to the atmosphere, compressed air in the return air chamber 10 acts on the lower surface of the striking piston 7 through the communication hole 12, so that the striking piston 7 moves upward.

In this way, by pulling the trigger 20 and pushing the contact arm 3, the variable pressure chamber 40 is opened to the atmosphere and a nail is driven, and the striking piston 7 reaches the bottom dead center and the nail is pushed. When the driving is made, even if the trigger 20 and the contact arm 3 are operated, the compressed air in the return air chamber 10 is supplied to the pilot valve upper chamber 32f and the pilot valve 32 moves downward, so that the variable pressure chamber 40 is opened. Since the impact piston 7 is automatically returned to the top dead center because it is cut off from the atmosphere and communicated with the accumulator 9, the nailing machine body 1 returns to the initial non-operation state at this point.

The striking piston 7 is returned to the top dead center and the compressed air in the return air chamber 10 is moved to the inner peripheral hole 2 of the driver guide 2.
By being exhausted via a, the impact piston lower chamber and the return air chamber 10 are opened to the atmosphere,
The pilot valve upper chamber 32f is opened to the atmosphere through the communication passage 38. However, at this time point, the pilot valve 32 moves downward and the compressed air of the variable pressure chamber 40 acts on the upper surface of the flange portion 32g that is formed to project at the lower end of the pilot valve 32. Retained.

Next, when the pushing operation of the contact arm 3 is released as shown in FIG.
It is returned to the bottom dead center by the action of the compressed air acting on 1c and the action of the compression spring 35. When the stem 31 is returned to the bottom dead center, the lower seal ring 31a is fitted into the inner diameter hole 33a on the small diameter side of the plate 33, whereby the overhanging lower surface 32h side of the pilot valve 32 is shielded from the atmosphere and the upper side. The seal ring 31b of the pilot valve 3
By being disengaged from the inner peripheral hole 32e of No. 2, it is communicated with the accumulator 9 through the communication hole 32d and the communication passage 37, whereby compressed air acts on the side of the same projecting lower surface 32h.

Overhanging lower surface 32h of pilot valve 32
When the compressed air acts on the side, the pilot valve upper chamber 32f has already been opened to the atmosphere, so that the pilot valve 32 is returned to the top dead center due to the pressure receiving area difference from the overhanging upper surface 32g and the action of the compression spring 35. This causes the trigger valve 30 to return to the initial non-operating state.

According to the trigger valve 30 constructed as described above, when the striking piston 7 is moved downward and a nail is driven, the compressed air in the return air chamber 10 is supplied to the pilot valve upper chamber 32f so as to be piloted. Since the valve 32 moves downward, the variable pressure chamber 40 is switched from the atmospheric open state to the compressed air supply state without releasing the operation of the trigger 20 and the contact arm 3 after driving the nail, and the impact piston 7 is driven.
Is automatically returned to top dead center. From this, even if the release operation of the trigger 20 and the contact arm 3 is delayed after nailing, the impact piston 7 is returned to the top dead center and the main body 1 is returned to the non-operation state regardless of this. It is possible to eliminate unnecessary air consumption during that time. Conventionally, unless the operation of the trigger or contact arm is released,
Since the variable pressure chamber was not switched to the compressed air state, the striking piston was not returned, and during this time, wasted compressed air was supplied to the striking piston upper chamber.

Next, the trigger valve structure described above is effective not only in the continuous shot mode but also in the single shot mode. FIG. 7 shows the operating state of the trigger valve 30 when the single shot mode is set. The single shot mode is set by projecting the regulation pin 22 provided on the trigger 20 below the idler 21, and when the regulation pin 22 is projected, the return position of the idler 21 when pulling the trigger 20 is changed. It is regulated higher than in the continuous firing mode.

After nailing, the pilot valve 32 is moved downward by the compressed air in the return air chamber 10, whereby the striking piston 7 is returned to the top dead center (see FIG. 5), and the contact arm 3 is pushed. When the release is released, the stem 31 moves downward by the compression spring 35. However, as described above, the idler 21 is not returned to the bottom dead center in the single shot mode, so the stem 31 is not returned to the bottom dead center.

At the position where the stem 31 is before the bottom dead center, as shown in the figure, the seal ring 3 below the stem 31 is provided.
1a is fitted in the inner peripheral hole 33a on the small diameter side of the plate 33, but since the upper seal ring 31b does not come off from the inner peripheral hole 32e of the pilot valve 32, compressed air is applied to the overhanging lower surface 32h side of the pilot valve 32. Does not work, so that the pilot valve 32 is not moved upward and is held at the bottom dead center, and therefore the trigger valve 30 is not returned to the non-operating state.

Since the trigger valve 30 is not returned to the non-operated state, even if the contact arm 3 is pushed again to move the stem 31 upward, the variable pressure chamber 40 is exposed to the atmosphere by the seal ring 32a below the pilot valve 32. Since the head valve 13 does not move upward due to the fact that the head piston 13 does not move upward because it remains blocked from the atmosphere, the striking piston 7 does not move downward, and therefore the nail is not driven.

In this single shot mode, the pilot valve 32 is moved upward by releasing the pushing operation of the contact arm 3 and releasing the pulling operation of the trigger 20. If the pulling operation of the trigger 20 is released, the idler 21 moves down together with the trigger 20,
This is because the stem 31 is returned to the bottom dead center.

Next, FIG. 8 shows a trigger valve structure different from the embodiment described above. In the embodiment described above, the pilot valve upper chamber 32f is communicated with the return air chamber 10 via the communication passage 38, and the pilot valve 32 is utilized by using the compressed air in the return air chamber 10.
However, in the trigger valve structure shown in FIG. 8, compressed air in the return air chamber 10 is not used but compressed air in the auxiliary air chamber 50 provided separately from the return air chamber 10 is used. Then, the pilot valve 32 is moved downward. The trigger valve 30 itself does not need to be changed.

The auxiliary air chamber 50 is around the cylinder 6 and the return air chamber 10 in the downward direction of the striking piston 7.
Before this, the return air chamber 10 is provided so as to be airtightly divided, and the auxiliary air chamber 50 and the pilot valve upper chamber 32f of the trigger valve 30 are connected to each other by the communication passage 5.
It is connected by 1. The auxiliary air chamber 50 and the inside of the cylinder are communicated with each other through a communication hole 50a.

According to this structure, in the downward movement process of the striking piston 7, the striking piston 7 moves toward the return air chamber 10.
Communication hole 50a at an earlier stage than when the check valve 11 passes through
Since the compressed air in the striking piston upper chamber 16 is supplied to the return air chamber 10, the auxiliary air chamber 5
Compressed air is supplied to 0. From this fact, the lower movement of the striking piston 7 can be detected more quickly in the present embodiment as compared with the configuration using the compressed air in the return air chamber 10, and therefore, the striking piston 7 can be detected more quickly after reaching the bottom dead center. In addition, the pilot valve 32 can be moved downward to move the striking piston 7 upward, and wasteful air consumption can be further suppressed.

Although compressed air can be supplied to the pilot valve upper chamber 32f at an earlier stage by setting the position of the check valve 11 to the upper side, the check valve 11 has The position is limited because it is necessary to surely move the striking piston 7 to the bottom dead center. Therefore, the means for providing the auxiliary air chamber 50 illustrated above is effective.

Here, the trigger valve structure disclosed in Japanese Utility Model Laid-Open No. 2-39887 is known as a technique having the same effect as the above. This conventionally known trigger valve structure is also provided with a plunger (stem) and a valve piston (pilot valve), and the valve piston is moved by compressed air in the return air chamber (return air chamber) after the nail is driven. This is similar to the trigger valve structure according to the present invention in that the striking piston is returned to the top dead center by closing the main valve (head valve).

However, in this conventionally known trigger valve structure, since the compressed air in the return air chamber is supplied to the lower chamber of the valve piston, the plunger can be operated without releasing the pulling operation of the trigger after driving the nail. If it is pushed upwards, the compressed air in the return air chamber will be released to the atmosphere through the valve piston lower chamber, so the valve piston will not return to top dead center and therefore the main valve will not close. Therefore, the striking piston is not returned to the top dead center, and when the striking piston reaches the bottom dead center after nailing, the return air chamber is communicated with the forward air chamber through the striking piston upper chamber. This causes serious air leakage, which is exactly the problem that the present invention has mentioned as a problem to be solved.

Moreover, according to this known structure, so-called single shot cannot be performed. Because the single shot is realized by restricting the return of the stem when only the contact arm is released and holding the striking piston at the bottom dead center, this is realized by this conventionally known configuration. If this is done, it is impossible to actually perform a single shot because the air leakage occurs as described above.

In this respect, according to the trigger valve structure of the present invention, firstly, the return air chamber 10 or the auxiliary air chamber 50 is communicated with the pilot valve upper chamber 32f, and the pilot valve 32 is utilized by utilizing these compressed air. When the valve is moved downward, the head valve 13 is closed and the striking piston 7 is returned to the top dead center. Second, the pilot valve upper chamber 32f is separated from other chambers by the upper seal ring 32c. Thirdly, the structure is such that it is always shut off. Thirdly, when the pilot valve 32 moves downward, the lower seal ring 32a is the inner peripheral hole 33c on the large diameter side of the plate 33.
Since the variable pressure chamber 40 side is shielded from the atmosphere opening hole 33b side by fitting into, the air leakage is prevented even when the trigger 20 is pulled and the contact arm 3 is pushed. It never happens.

As shown in FIG. 7, when the pilot valve 32 is moved downward and the stem 31 is returned to the middle, the seal ring 31a on the lower side of the stem 31 causes an inner peripheral hole of the plate 33 on the small diameter side. Is sealed, and the inner peripheral hole 32e of the pilot valve 32 is sealed by the upper seal ring 31b, so that an intermediate stage where the overhanging lower surface 32h side of the pilot valve 32 is not opened to the atmosphere and compressed air does not act can be achieved. Due to the configuration, single shot is possible.

[Brief description of the drawings]

1 is a longitudinal sectional view of an air nailing machine main body and a trigger valve according to an embodiment of the invention as set forth in claim 1;

FIG. 2 is a vertical cross-sectional view of the trigger valve at a stage in which only the trigger is pulled and the contact arm is not pushed.

FIG. 3 is a vertical cross-sectional view of the trigger valve at a stage in which the contact arm is started to be pushed while the trigger is pulled and the seal ring on the upper side of the stem is fitted in the inner peripheral hole of the pilot valve. Is.

FIG. 4 is a stage in which the contact arm is completely pushed while the trigger is pulled, and the seal ring on the lower side of the stem is disengaged from the inner diameter hole on the small diameter side of the plate to open the variable pressure chamber to the atmosphere. FIG. 6 is a vertical cross-sectional view of the trigger valve at the stage of being pressed.

FIG. 5 is a vertical cross-sectional view of the trigger valve at a stage where the pilot valve has moved downward.

6 is returned from the state of FIG. 5, the seal ring on the upper side of the stem is disengaged from the inner peripheral hole of the pilot valve, and the lower seal ring is fitted into the inner peripheral hole on the small diameter side of the plate. It is a longitudinal cross-sectional view of the trigger valve in the second stage.

FIG. 7 is a vertical cross-sectional view of the trigger valve at a stage when the pushing operation of the contact arm is released in the single shot mode.

FIG. 8 is a longitudinal sectional view of an air nailing machine main body and a trigger valve according to the second embodiment of the present invention.

[Explanation of symbols]

1 ... Air nailer main body part, 2 ... Driver guide, 3 ... Contact arm 4 ... Handle part, 6 ... Cylinder, 7 ... Impact piston, 8
... driver 9 ... accumulator, 10 ... return air chamber, 13 ... head valve 15 ... head valve upper chamber, 16 ... striking piston upper chamber 20 ... trigger, 21 ... idler 30 ... trigger valve 31 ... stem, 32 ... pilot valve, 32f ... Pilot valve upper chamber 33 ... Plate, 34 ... Valve block, 34a ... Valve hole, 35 ... Compression spring 36 ... Communication passage (head valve upper chamber side) 37 ... Communication passage (accumulator side) 38 ... Communication passage (return air chamber) Side) 40 ... Transformer room 50 ... Auxiliary air room

Claims (2)

[Claims] 1. When the head valve upper chamber is opened to the atmosphere and the head valve is opened, compressed air is supplied to the striking piston upper chamber and the striking piston moves downward to drive a nail, while the head valve is actuated. When compressed air is supplied to the upper chamber and the head valve is closed, the striking piston upper chamber is opened to the atmosphere, and the striking piston is moved up and down by the compressed air in the return air chamber to open and close the head valve in the air nailer. A structure of a trigger valve for operating, comprising a pilot valve that is moved downward by compressed air in the return air chamber when the striking piston reaches the vicinity of bottom dead center, and when the pilot valve moves downward, A trigger valve structure characterized in that compressed air is supplied to the head valve upper chamber to close the head valve. 2. When the head valve upper chamber is opened to the atmosphere and the head valve is opened, compressed air is supplied to the striking piston upper chamber and the striking piston moves downward to drive a nail, while the head valve is actuated. When compressed air is supplied to the upper chamber and the head valve is closed, the striking piston upper chamber is opened to the atmosphere, and the striking piston is moved up and down by the compressed air in the return air chamber to open and close the head valve in the air nailer. A structure of a trigger valve for operating, wherein the compressed air in the striking piston upper chamber is earlier than the compressed air in the striking piston upper chamber is supplied to the return air chamber in the downward movement process of the striking piston. A pilot valve that moves downward when the striking piston reaches the vicinity of the bottom dead center by the compressed air supplied from the auxiliary air chamber is provided. Trigger valve structure of the air nailer, characterized in that the valve has a configuration in which the head and the head valve compressed air is supplied to the upper chamber the valve is closed and moves downward.