JP2876982B2 - Shock absorber for pneumatic impact tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer for stopping a driving piston at a bottom dead center position of an impact stroke in a pneumatic impact tool for driving a driving piston by compressed air pressure to perform nail driving or the like. Related to the device.

[0002]

2. Description of the Related Art In general, a pneumatic type such as a nail driving machine in which a driving piston housed in a driving cylinder is driven by a compressed air pressure in a shocking manner and a driver connected to the driving piston hits and strikes a nail. The impact tool is provided with a shock absorber for absorbing the impact of the driving piston at the bottom dead center of the impact stroke and stopping the impact. This type of shock absorber is usually constituted by a hollow cylinder type bumper. Further, recently, the regulation of the air pressure used has been relaxed, so that compressed air having a higher pressure than before can be used, and accordingly, it has become possible to design a small and higher-powered nailing machine.

Since the outer diameter of the driving piston and the inner diameter of the driving cylinder are designed to be small in order to reduce the size of the nailing machine, and the outer diameter of the bumper for receiving the lower surface of the driving piston is necessarily designed to be small, the volume of the bumper is reduced. Tends to be smaller than before. However, since the high-pressure compressed air is used, the impact force of the drive piston increases, so that the amount of deformation of the drive piston due to the impact of the drive piston on the bumper increases, and the load on the bumper increases.

Further, a normal bumper is set so that it can be deformed to the outer peripheral side and the inner peripheral side of the hollow cylindrical shape. However, when the outer peripheral side swells due to the deformation, a pulling force acts on the structure of the bumper. Cracks are likely to occur, and there is a phenomenon that the outer peripheral surface is damaged earlier than the inner peripheral side. For this reason, when a large shock is received by a small-volume bumper and the amount of deformation is increased, there is a problem that the durability is extremely reduced.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks. In particular, the deformation direction of the bumper is suppressed as much as possible to the outside and the bumper is deformed toward the inside so that the durability of the bumper is impaired. An object of the present invention is to provide a shock absorber for an impact tool that can prevent the shock.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a drive cylinder, wherein an upper portion is formed on a guide surface having an inner diameter substantially the same as the inner diameter of a striking cylinder, and a lower portion is provided with a lower inner diameter than an upper inner diameter. A bumper accommodating portion having a large diameter is formed, and a hollow cylindrical bumper having an outer shape substantially the same as the inner wall surface of the bumper accommodating portion is accommodated in the bumper accommodating portion. The inner diameter is larger than the upper inner diameter to form a gap.

[0007]

According to the above configuration, when the bumper is compressed and deformed by receiving the impact load of the driving piston, the outer peripheral portion of the bumper is guided by the inner wall surface of the bumper guide, so that it can be deformed outward. Instead of trying to deform inward and downward. Since the inside diameter of the hollow lower part of the bumper is set to be large to form a gap, and the deformation of the compressed bumper is escaped, the deformation of the upper part of the bumper is transmitted downward and the gap is transmitted to the gap. The deformation in the compression direction is caused in the bumper tissue by releasing the deformation. As described above, since the deformation in the compression direction mainly acts on the bumper, the impact of the driving piston is effectively absorbed without increasing the volume of the bumper, and the impact of the driving piston driven at high pressure is effectively absorbed. And the durability is not impaired.

[0008]

FIG. 1 shows a part of a nailing machine as an example of a pneumatically driven impact tool. This nailing machine comprises a driving cylinder 2 having a driving piston 3 slidably housed in a housing 1. A driver 4 that slides in an ejection portion (not shown) formed at the tip of a nose portion 5 disposed at a lower portion of the housing is integrally connected to a lower surface of the drive piston 3. ing. The compressed air supplied from the upper end of the driving cylinder 2 to the upper surface of the driving piston 3 drives the driving piston 3 from the top dead center to the bottom dead center in a shocking manner, and the nail supplied to the injection section is injected by the driver 4. It is configured to be launched from the part. When the drive piston 3 is driven downward, the air below the drive piston 3 in the drive cylinder 2 is compressed, so that the air from the communication hole 6 ′ formed in the lower part of the drive cylinder 2 to the outer periphery of the drive cylinder 2 It is pressure-fed and stored in the formed blow-back chamber 6.
When the drive piston 3 reaches the bottom dead center, the compressed air on the upper surface of the drive piston 3 is exhausted to the atmosphere and decompressed.
The compressed air in the blowback chamber 6 is supplied to the communication hole 6 '.
From above, acts on the lower surface of the driving piston 3, and the differential pressure between the upper and lower surfaces causes the driving piston 3 to move upward and return to the top dead center.

Between the lower end of the drive cylinder 2 and the nose portion 5 is disposed a cylindrical bumper guide 7 having an inner diameter equal to the inner diameter of the drive cylinder 2. The nose part 5 forms a bumper housing part 8. A bumper 9 having a hollow center for inserting the driver 4 is formed in the bumper housing 8.
And receives the lower surface of the drive piston 3 to absorb the impact force of the drive piston 3 and stop the drive piston 3.

The bumper housing 8 is formed to be slightly longer in the vertical direction along the operating direction of the drive piston 3, and the upper part is driven and formed to have the same diameter as the inner diameter of the cylinder 2, but the lower part bulges outward. The inner diameter is formed large. A through hole for the driver 4 is formed on the lower surface of the housing portion 8 and communicates with the emission portion of the nose portion 5.

The bumper 9 has a vertically long and substantially cylindrical shape in accordance with the shape of the bumper accommodating portion 8, and has an insertion hole 10 formed therein for inserting the driver 4 of the driving piston 3. The outer shape of the bumper 9 is formed so that the outer diameter of the upper portion is smaller and the outer diameter of the lower portion is larger so that the outer shape of the bumper 9 is substantially the same as the inner shape of the housing portion 8. It is set so that the gap between the bumper 9 and the outer peripheral surface of the bumper 9 does not become large. Also, the insertion hole 10 of the bumper 9
The upper portion has an inner diameter such that a sufficient gap is formed between the outer peripheral surface of the driver 4 and the lower portion has an inner diameter larger than that of the upper portion. A cavity 9b for accommodating the amount of deformation is formed. The bumper 9 may be made of low nitrile rubber, NBR resin or the like.

According to the above configuration, the lower surface of the drive piston 3 operated by the compressed air pressure impacts on the upper surface of the bumper 9. The bumper 9 is compressed and deformed under the impact load of the driving piston 3. At this time, since the outer peripheral surface of the bumper 9 is guided by the inner surface of the wall of the accommodating portion 8, the bumper 9 cannot be sufficiently deformed in the outward direction, and thus tends to bend and deform inward and downward. Since a sufficiently large gap 9b is formed inside the lower part of the bumper 9, the upper portion of the bumper 9 is deformed and moved inward and downward, and the deformed portion escapes into the gap 9b.

As described above, the deformation of the bumper 9 in the outward direction is limited by the bumper housing 8 formed by the bumper guide 7 and the nose portion 5, while the bumper 9 is arranged so as to be easily deformed in the inner diameter direction. Therefore, as shown in FIG. 2, the deformation of the bumper 9 mainly deforms inward. Therefore, since there is no large deformation in the outward direction of the bumper as in the prior art, a large tensile force does not act on the bumper tissue, so that the outer surface portion is effectively prevented from cracking, and the bumper is used with high-pressure compressed air. Even if it bends greatly,
There is no loss of durability.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing an embodiment of an impact buffer according to the present invention, showing a state before an impact piston collides with a bumper.

FIG. 2 shows the same embodiment as FIG. 1 in which an impact piston is in contact with a bumper to absorb an impact.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Drive cylinder 3 Drive piston 4 Driver 5 Nose part 6 Blowback chamber 7 Bumper guide 8 Bumper accommodating part 9 Bumper 9a Void part 10 Insertion hole

Claims (1)

(57) [Claims] 1. A pneumatic impact tool in which a drive piston is slidably accommodated in a drive cylinder and the drive piston is driven by compressed air introduced into the drive cylinder. The upper portion is formed on a guide surface having substantially the same inner diameter as the inner diameter of the drive cylinder, and the lower portion forms a bumper housing portion formed to have a larger diameter than the upper inner diameter, and the inner wall surface of the bumper housing portion substantially corresponds to the inner wall surface of the bumper housing portion. While accommodating a hollow cylindrical bumper having the same external shape,
A shock absorber for a pneumatic impact tool, wherein a gap is formed by making the inner diameter of the lower part of the hollow part of the bumper larger than the inner diameter of the upper part.