JPS5850834B2 - Air pressure adjustment device in the striking cylinder of a pneumatically driven striking tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a striking cylinder/piston mechanism incorporated in a pneumatically driven striking tool, in which the air pressure in the lower chamber of the striking piston of the striking cylinder is maintained at a desired value in a timely manner. This invention relates to an air pressure adjustment device within a striking cylinder that improves the work efficiency of the striking cylinder and prevents rebound at the top dead center of the striking piston.

2. Description of the Related Art A pneumatic nail gun has been known as an example of a pneumatically driven impact tool incorporating a percussion cylinder/piston mechanism.

The return drive of the percussion piston of this nailing machine is performed by causing pressurized air in the blowback air chamber to flow out into the lower chamber of the percussion piston of the percussion cylinder.

The lower end of the cylinder is provided with an opening communicating with the atmosphere.

Therefore, the pressurized air flowing into the lower piston chamber when the piston returns is gradually discharged to the atmosphere through the opening.

For this reason, it is necessary to ensure reliable return drive of the piston by increasing the volume of the blowback air chamber, resulting in an increase in air consumption.

Therefore, it is possible to efficiently return drive the piston by eliminating or narrowing the opening to limit the amount of pressurized air in the lower chamber of the piston that is discharged into the atmosphere. There is a drawback that this piston back pressure sometimes increases, resulting in a decrease in driving force.

In other words, the air pressure in the lower chamber of the striking piston is maintained at atmospheric pressure when the striking piston is located at the top dead center, but it is compressed during the process of pulling the trigger and lowering the striking piston. This creates back pressure, which reduces the driving force of the striking piston.

This air pressure compression phenomenon in the lower chamber of the striking piston does not become a problem when the nail driving work is performed at relatively long intervals (i.e., single nail driving), but especially when nail driving is performed repeatedly within a short period of time. In this case, the pressure builds up and increases rapidly, significantly reducing the driving force of the nail gun and having an adverse effect.

Furthermore, when the striking piston returns to the top dead center after completing the driving operation, the air pressure in the lower chamber of the striking piston drops almost to atmospheric pressure, and the striking piston is not completely held at the top dead center. This caused the nails to rebound and drive out the nails with their bottoms completely intact, causing nail jams.

In order to prevent this rebound, a rebound prevention mechanism must be provided as special mechanical means near the top dead center of the striking piston.

As a means for releasing the back pressure in the lower chamber of the striking piston, the nailer is configured to open a back pressure release valve provided in the blowback air chamber when the air pressure in the blowback air chamber reaches a certain value. It has been known.

However, with this means, the air pressure in the lower chamber of the striking piston drops to atmospheric pressure before the striking piston returns and reaches the top dead center, and the rebound prevention effect does not occur.

The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to enable efficient use of compressed air.

Another object of the present invention is to completely release the back pressure of the striking piston so that a strong striking force can be obtained.

Furthermore, the present invention provides that after the return of the striking piston,
It is an object of the present invention to prevent the rebound of the striking piston by the residual air pressure in the lower chamber of the striking piston.

In order to achieve the above-mentioned object distantly, the present invention provides a striking cylinder, a striking piston slidably and tightly fitted into the cylinder, a main air chamber formed on the outer periphery of one end of the cylinder, and the other end of the cylinder. A blowback air chamber formed on the side outer periphery, a first air communication hole opened in the cylinder and communicating between the inside of the cylinder and the blowback air chamber, and a first air communication hole on one end side of the cylinder from this communication hole. a second air communication hole opened at a position to communicate between the cylinder and the blowback air chamber, and when the trigger valve is turned on, the pressurized air in the main air chamber is transferred to the blowback piston of the cylinder. By supplying the air to the upper chamber, the piston is moved forward toward the bottom dead center, and the pressurized air from the main air chamber, which is supplied into the upper chamber of the striking piston, is transferred to the air through the second air communication hole. The pressurized air is supplied into the blowback air chamber, and by turning off the trigger valve, the supply of pressurized air to the main air chamber is cut off, and the pressurized air stored in the blowback air chamber is transferred to the second air chamber. In the pneumatically driven impact tool, the piston is returned toward the top dead center by flowing air into the lower chamber of the impact piston of the cylinder through the air communication hole, and the second air communication hole allows air to flow into the cylinder other than the cylinder. An exhaust passage opened at an end position and connecting between the inside of the cylinder and the atmosphere, a back pressure release valve provided in this passage for opening and closing the passage, and the trigger valve interposed between the exhaust passage and the main air. The air passage has an air passage provided between the chamber and the back pressure release valve, and the air passage communicates with the atmosphere when the trigger valve is turned ON, and communicates with the main air chamber when the trigger valve is turned OFF. The release valve receives air pressure acting on the exhaust passage from the lower chamber side of the striking piston when the piston moves from the top dead center to the bottom dead center in response to the ON operation of the trigger valve, and opens the exhaust passage. At the same time, when the piston returns from the bottom dead center to the top dead center due to the OFF operation of the trigger valve, the air pressure in the main air chamber supplied to the air passage is received and the exhaust passage is closed. Intimidation 1. The present invention is characterized in that the air pressure in the lower chamber of the striking piston is adjusted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 4 shows another embodiment of the invention.

In FIGS. 1 and 2, a pneumatically driven nailing machine 1 has a housing 2 that includes a striking cylinder 3, which is a type of cylinder, and a striking piston 4, which is a type of piston.

A main air chamber 5 is formed around this striking cylinder 3, and this main chamber 5 is also formed continuously toward a grip portion (not shown) of the nailing machine 1.

A blowback air chamber 6 is formed at the lower part of the impact cylinder 3 and around its outer periphery.

Two types of communication holes 7.8 are provided between the blowback air chamber 6 and the striking cylinder 3 in the peripheral wall 9 of the striking cylinder 3.
is interposed.

The communication hole 7 is located at a slightly higher position than in conventional nailers.

The communication hole 8 is provided at the lowest end of the blowback air chamber 6 and has a diameter larger than the diameter of the communication hole 7.

An 01J ring 10 is fitted at the lower side of the communication hole 8 and inside the peripheral wall 9.

Furthermore, a communication hole 12 is provided between the bottom 11 of the impact cylinder 3 and the lower end of the peripheral wall 9.

The bottom portion 11 of the striking cylinder 3 and a nail driving nose 13 (not shown) are integrally formed.

The bottom part 11 has an annular shape and a flange 1 at the lower end.
A bumper holder 15 formed with 4 is placed and fixed.

The outer peripheral surface of this bumper holder 15 is formed with a slight taper, and a slight gap 18 is formed between it and the inner surface of the peripheral wall 9.

A substantially cylindrical driver guide 16 is disposed in the center of the bumper holder 15, and the outer diameter of the lower end 16a of this driver guide 16 is enlarged to form the bottom 11 of the impact cylinder 3.
is attached to.

A bumper member 1 made of a rubber-like elastic body is placed in an annular space formed between the bumper holder 15 and the driver guide 16.
7 is inserted.

The inner diameter of the driver guide 16 is almost the same as the driver 23.
These driver guides 16 are formed equal to the outer diameter of
There is no gap between the driver 23 and the driver 23, so that there is almost no air leakage.

As shown in FIG. 2, the striking piston 4, which is slidably and tightly fitted into the striking cylinder 3, has an upper enlarged diameter part 19 and a flange part 20 on the lower side of the upper enlarged diameter part 19. There is.

An 01J ring 21 is fitted onto the outer periphery of the upper enlarged diameter portion 19.

A piston head 22 is provided in the center of the striking piston 4 to protrude upward.

A retaining ring 23, 24 made of a rubber-like elastic body is fitted onto the outer periphery of the piston head 22.

These retaining rings 23, 24 are fitted into the inner surface of the cylinder head (not shown) disposed above the percussion cylinder 3 when the percussion piston 4 returns to the top dead center. This creates a frictional force between the two and strengthens the effect of holding the striking piston.

A stud bolt portion 24a protruding from the upper end of the driver 23a is screwed onto the piston head 22,
The driver 23a is integrally fixed to the striking piston 4 by this stud portion 24a.

The outer diameter of the flange portion 20 is smaller than the outer diameter of the upper enlarged diameter portion 19, and the inner diameter of the flange portion 20 is so large that there is some margin relative to the outer diameter of the upper portion of the bumper holder 15. It is set to

The inside of the flange portion 20 is formed in a hollow shape, and an annular projection 25 is provided on the ceiling portion to protrude downward.

When the striking piston 4 reaches the bottom dead center, the annular protrusion 25 strikes the upper surface of the bumper member 17 and strikes the upper surface of the bumper holder 15 or driver guide 16 located near the bumper member 17. There isn't.

Moreover, when the striking piston 4 is stationary at the bottom dead center,
The upper enlarged diameter part 19 and a part of the flange part 20 of this striking piston 4 both face the communication hole 12. Compressed air from the flowback air chamber 6 is transmitted between the upper enlarged diameter part 19 and the flange part 20. The impact piston 4 acts on the stepped portion 20a to push the striking piston 4 upward.

On the other hand, when the striking piston 4 is stationary at the bottom dead center, the outer circumferential surface of the collar 20 is attached to the lower part of the striking cylinder 3.
1J ring 10, and communication hole 8 and communication hole 12 are cut off by this 01J ring 10.

A back pressure release valve 26 is provided below the blowback air chamber 6 in the form of an annular ring formed by a single winding of the blow cylinder 3.

The valve cylinder 27 of this backpressure release valve 26 is formed by the peripheral wall 9 of the percussion cylinder 3 , the housing 2 and the bottom 11 of the percussion cylinder 3 .

A seal ring 28 is fitted to the bottom of the pulp cylinder 27.

A valve piston 29 that moves up and down while sliding within a valve cylinder 27 is separated from a large diameter portion 30 and a small diameter portion 31.

An 01J ring 32 is fitted on the first circumference side of this large diameter portion 30, and an 01J ring 33 is fitted on the outer circumference side.

A chamfered portion 34 is provided at the lower end of the small diameter portion 31 and on the inner circumferential side, and this chamfered portion 34 allows the valve piston 29 to rest at the bottom dead center and the lower end surface of the valve piston 29 to be attached to the seal ring 28. Even while in contact, air pressure within the striking piston lower chamber 35 can be applied.

A chamfered portion 35a is formed on the upper end surface of the large diameter portion 30 and on the outer peripheral side.

A valve piston upper chamber 36 formed above the valve piston 29 in the valve cylinder 27 has an air passage 3.
7, and a valve piston lower chamber 38 formed in the lower portion of the valve piston 29 communicates with the communication hole 12 and also communicates with an exhaust hole 39 which is bored through the housing 2 and opens to the atmosphere.

A compression coil spring 40 is disposed between the bottom of the valve cylinder 27 and the valve piston 29, and constantly pushes the valve piston 29 upward.

The air passage 37 communicates with a trigger valve 41 and also with an air passage 42 which communicates with a head valve (not shown).

The trigger valve 41 is separated from a trigger valve cylinder 43 and a trigger valve stem 44, and the trigger valve cylinder 4
3 is fitted into the housing 2.

The trigger valve cylinder upper part 70 of this trigger valve cylinder 43 communicates with the main air chamber 5 through the communication hole 45, and the trigger valve cylinder lower part 46 communicates with the atmosphere.

A trigger valve chamber 47 is formed between the trigger valve cylinder upper part 44 and the trigger valve cylinder lower part 46, and this trigger valve chamber 47 communicates with the air passages 37 and 42 through a lateral hole 48.

A trigger valve stem 44 is built into the trigger valve cylinder 43 so as to be able to freely reciprocate in the longitudinal direction of the trigger valve cylinder 43.

This trigger valve stem 44 has a spring receiver projection 49, a small diameter portion 50, a large diameter portion 51, and a trigger valve stem operating end portion 52 in order from the upper end portion.

In the spring receiver, a compression spring 53 is disposed between the protrusion 49 and the upper part 70 of the trigger valve cylinder.

An 01J ring 54 is fitted into the small diameter portion 50, and an 01J ring 55 is fitted into a portion of the trigger valve stem operating end 52 that is a little distance away from the large diameter portion 51.

The distance from the lower surface 56 of the large diameter portion 51 to the O-ring 55 corresponds to the idle stroke portion 57.

An exhaust groove 58 is formed extending further downward from the fitting position of the 01J ring 55.

The trigger valve stem operation end 52 protrudes further downward from the trigger valve cylinder lower part 46 and faces the trigger lever 59 .

A contact lever 60 is provided inside this trigger lever 59.
is provided to be able to pivot freely, and one end 60a of this contact lever 60 is in contact with a base end 61a of a contact arm 61.

Hereinafter, the operation of the cylinder air pressure adjusting device according to the present invention will be explained.

First, when the trigger lever 59 is pulled and the contact arm 61 is pressed against the workpiece at the same time, the contact arm 61 moves, and the contact lever 60 presses the trigger valve stem operating end 52 to release the trigger valve stem 4.
Move 4 up.

During this upward movement, the 01J ring 54 is first pressed against the trigger valve cylinder upper part 70, and the main air chamber 5
and air passages 37 and 42.

Next, when the idle stroke part 57 enters into the trigger valve chamber 47 and the 01J ring 55 leaves the trigger valve cylinder lower part 46, this trigger valve chamber 47 is opened to the atmosphere through the exhaust groove 58, and the air passage 37
The control air in and 42 is discharged to the atmosphere.

As a result, the air pressure in the valve piston upper chamber 36 of the back pressure release valve 26 becomes atmospheric pressure.

On the other hand, as the control air in the air passage 42 is released into the atmosphere, the head valve piston upper chamber becomes atmospheric pressure, the head valve piston rises, and the working air in the main air chamber 5 flows into the striking piston upper chamber. Inflow.

Therefore, the striking piston 4 begins to descend due to the working air pressure, as shown in FIG.

Along with this descent, a compression phenomenon of air begins to occur in the striking piston lower chamber 35, and the valve piston 29 of the back pressure release valve 26 is pushed up by the upward force of the compressed air and the spring force of the compression coil spring 40. .

As a result, an air passage is formed between the communication hole 12, the valve cylinder 27 and the exhaust hole 39, and the striking piston lower chamber 3
The air inside 5 continues to flow out into the atmosphere.

During this time, since the valve piston 29 is held stationary at the top dead center, almost no back pressure acts on the striking piston 3.

Therefore, the driving force of the striking piston 3 is not diminished (it is significantly stronger than before).

During the descent of the striking piston 3, air is also blown into the blowback air chamber 6, particularly through the communication hole 8, as shown in FIG.

As shown in FIG. 3, the striking piston 4 reaches the bottom dead center and comes to rest while impacting the bumper member 17.

Thereafter, working air is introduced into the blowback air chamber 6 via the communication puller 7, and the air necessary for the return of the striking piston 4 is accumulated.

The communication hole 8 connects the upper enlarged diameter portion 19 of the striking piston 4 and the collar portion 2.
There is an opening between 0 and 0.

The striking piston lower chamber 35 is closed off from the blowback air chamber 6 by an O-ring 10.

Next, when the trigger lever 59 is released and the contact arm 61 is detached from the workpiece, the contact arm 61 is lowered, and the contact lever 60 loses its pressing force against the trigger valve stem operating end 52, and this operation is terminated. The end portion 52 is pressed down by the spring force of the compression spring 53 and descends.

During this downward movement, the 01J ring 55 is first pressed against the trigger valve cylinder lower part 46, and the trigger valve chamber 47 is closed off from the atmosphere.

At this time, the 01J ring 54 has not yet separated from the trigger valve cylinder upper part 44.

Then, when the idle stroke portion 57 enters the trigger valve cylinder lower part 46, the 01J ring 54 separates from the trigger valve cylinder upper part 44, and the air passages 37 and 42
and the main air chamber 5 are communicated with each other.

As a result, working air is first introduced into the valve piston upper chamber 36 of the back pressure release valve 26 through the air passage 37,
The valve piston 29 is pushed down to close off the communication hole 12 and the exhaust hole 39.

As a result, the striking piston lower chamber 35 is closed.

On the other hand, the air passage 42 is filled with control air again, operating air is introduced into the head valve piston upper chamber, the head valve piston is lowered, and the space between the main air chamber 5 and the striking piston upper chamber is closed. At the same time, the upper chamber of this striking piston is communicated with the atmosphere.

As a result, the air pressure in the blowback air chamber 6 becomes relatively higher than the air pressure in the upper chamber of the striking piston, and the striking piston 4 is blown up from the communication hole 8 and returned to the top dead center.

Since the air in the striking piston lower chamber 35 is completely confined, the air pressure in the striking piston lower chamber 35 is maintained higher than atmospheric pressure, which has the effect of preventing the striking piston 4 from rebounding.

FIG. 4 shows a back pressure release valve 64 of a cylinder air pressure regulating device according to another embodiment of the present invention.

The valve piston 65 of the back pressure release valve 64 is an annular body having a diameter from the upper end to the lower end, and an 01J ring 62 is fitted on the lower end surface.

Therefore, unlike the previously shown embodiment, the valve cylinder 6
No seal ring is fitted to the bottom portion 63a of No. 3.

This valve piston 65 is pushed up by the compressed working air in the lower chamber 35 of the striking piston when the striking piston 4 suddenly descends during nail driving work, since the air passage 37 is at atmospheric pressure. As a result, the space between the communication hole 12 and the exhaust hole 39 is opened.

During this time, the valve piston 65 is held at the top dead center by the pressure of the air flowing out from the striking piston lower chamber 35 toward the exhaust hole 39.

In this way, the back pressure on the striking piston 4 is released.

When the trigger lever 59 is released, the air passage 37 is filled with compressed working air from the main air chamber 5, so the valve piston 65 is pushed down to the bottom dead center, and the communication hole 12 is closed to the exhaust hole 39. Continuously against.

Therefore, the striking piston 4 is connected to the blowback air chamber 6.
Even after the blowback air from the piston returns and the piston stops at the top dead center, high pressure air remains in the lower chamber 35 of the striking piston 4 to prevent the striking piston 4 from rebounding.

As described above, according to the present invention, the pressurized air used for lowering the striking piston can be used for returning the striking piston without being released into the atmosphere, so that the pressurized air can be used efficiently.

In addition, a nail or the like can be driven into the lower chamber of the striking piston without any air compression occurring, so a strong driving force can be obtained.

Further, after the striking piston returns, the rebound of the striking piston can be prevented by the residual pressure of the air in the lower chamber of the striking piston.

[Brief explanation of the drawing]

1 to 3 are longitudinal sectional views showing the cylinder air pressure regulating device according to the present invention, in which FIG. 1 shows a state in which the trigger has not been pulled yet, and FIG. 2 shows a state in which the trigger has been pulled. Fig. 3 shows a state in which the striking piston is moving toward the bottom dead center during operation, and Fig. 3 shows a state in which the striking piston is stationary at the dead center. FIG. 4 is a partially omitted vertical cross-sectional view showing a back pressure release valve portion of a cylinder air pressure regulating device according to another embodiment of the present invention. 3...Blow cylinder, 4...Blow piston, 5...Main air chamber, 6...
...Blowback air chamber, 7...First communication hole, 8...Second communication hole, 12...
・Communication L26...Back pressure release valve, 35...
...Blow piston lower chamber, 37... Air M.

Claims (1)

[Claims] 1. A blow cylinder, a blow piston that is slidably and tightly fitted into the cylinder, a main air chamber formed on the outer periphery of one end of the cylinder, and a blowback air formed on the outer periphery of the other end of the cylinder. a first communication hole opened in the cylinder and communicating between the inside of the cylinder and the blowback air chamber; and a second communication hole that communicates with the air chamber, and when a trigger valve is turned on, pressurized air in the main air chamber is supplied to the upper chamber of the striking piston of the cylinder, thereby lowering the piston. While moving forward toward the dead center, pressurized air from the main air chamber supplied into the upper chamber of the striking piston is supplied into the blowback air chamber through the second air communication hole, and the trigger is moved forward toward the dead center. By turning off the valve, the supply of pressurized air to the main air chamber is cut off, and the pressurized air stored in the blowback air chamber is passed through the second air communication hole to the striking piston of the cylinder. In the pneumatically driven impact tool, the piston is returned to the dead center by air flowing into the lower chamber. an exhaust passageway connecting the main air chamber and the backpressure release valve, a backpressure release valve provided in the passageway for opening and closing the passageway, and a backpressure release valve provided between the main air chamber and the backpressure release valve with the trigger valve interposed therebetween; The air passage communicates with the atmosphere when the trigger valve is turned on, and communicates with the main air chamber when the trigger valve is turned off, and the release valve communicates with the atmosphere when the trigger valve is turned on. When the piston moves from the top dead center to the bottom dead center, it receives air pressure acting on the exhaust passage from the lower chamber side of the striking piston, and listens to the exhaust passage, and when the trigger valve is turned OFF, the air pressure is applied to the exhaust passage. When the piston returns from the bottom dead center to the top dead center, the air pressure in the main air chamber supplied to the air passage closes the exhaust passage and reduces the air pressure in the lower chamber of the striking piston. 1. An air pressure adjustment device in a striking cylinder of a pneumatically driven striking tool, characterized in that the air pressure is adjusted.