JPS6147671B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention includes, for example, an electric hammer, a hammer drill,
This invention relates to impact power tool structures such as chipping hammers. FIG. 1 shows the structure of a conventional single-cylinder reciprocating electric hammer. A motor 2 is built into the electric hammer body 1, and the rotation of this motor 2 is controlled by a gear 4 fixed to a crankshaft 3. It is transmitted to the crank pin 5 via the crank pin 5, and the crank pin 5 rotates. The rotation of this crank pin 5 is the cone rod 6
is transmitted to a piston 8 attached via a piston pin 7, and the piston 8 reciprocates within the cylinder case 9. A water squirrel 10 is interposed between the piston 8 and the cylinder case 9, and when the piston 8 moves in the direction of the arrow, the air between the striker 10 and the piston 8 is compressed, thereby pushing the striker 10. and hit the end face of bull point 11. The bull point 11 hits, for example, concrete 12, breaks the concrete 12, and then rebounds. Reference numeral 13 indicates a handle for supporting the electric hammer main body 1. On the other hand, the striker 10 returns to its original position with the rebound from the end face of the bull point 11 and suction due to the return stroke of the piston 8, and the same movement is repeated thereafter. The conventional electric hammer shown in Figure 1 is a striker 1.
The sound produced when the 0 and the bull points 11 collide directly through the cylinder case 9. Further, the vibration of the bull point 11 caused by the impact becomes a sound wave and is emitted as it is into the atmosphere. Impact power tools such as electric hammers
When struck, it generates noise ranging from several hundred to several thousand hertz, and the noise level is extremely high. In view of the above points, it is an object of the present invention to reduce sound energy and noise by interfering with and absorbing sound waves generated by impact. The present invention is characterized by an impact power tool that crushes concrete, etc. by striking a bull point with a striker pushed out by air pressure compressed by the reciprocating motion of a piston.
It has a hollow chamber around the striking part with a sound-absorbing material pasted on the inner wall, and the bull point is further covered with a hollow chamber whose inner wall is pasted with a sound-absorbing material. Hereinafter, one embodiment of the impact power tool assembly of the present invention will be described with reference to FIG. The same reference numerals as in FIG. 2 and FIG. 1 indicate the same parts. A hollow chamber 14 is formed in the portion where the striker 10 contacts the end surface of the bull point 11, that is, the striking portion, and a sound absorbing material 15 is pasted on the inner periphery of the hollow chamber 14. In the middle of bull point 11,
The hollow chamber 16 surrounding the bull point 11 is the hollow chamber 14.
A sound absorbing material 17 is also pasted on this cavity 16. The cross-sectional shapes of the hollow chambers 14 and 16 are circular, square,
Although it may be a rectangle or any other arbitrary shape, the attenuation amount according to the present invention is approximately as shown in the following formula (per one cavity chamber). NR=KP/S・L (dB) where NR: Reduced volume (dB) L: Pipe length (m) S: Cross-sectional area (m ² ) P: Perimeter (m) K: Value shown in the table below, where α =Sound absorption coefficient

[Table] For example, when the cavities 14 and 16 have a circular cross section, the reduced sound level is NR = 4KL/D (dB). Here, D: diameter of the circle (m). When L/D=2 and α=0.9, the volume reduction is about 7dB.
becomes. FIG. 3 shows a comparison of noise between an electric hammer according to the present invention and a conventional electric hammer. Thick solid line A
In the case of the present invention, the thin solid line B shows the case of the conventional system. Comparing the two, it can be seen that the noise at high frequencies (2 to 5 kHz), which are harsh to the ear, is reduced in the case of the present invention. According to the present invention, the sound generated by the impact can be reduced by the sound reduction effect of the hollow chamber, and it is possible to prevent the worker from suffering hearing loss. Furthermore, the noise around the workplace will be reduced, and will no longer cause discomfort to residents in the surrounding area.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional front view of a conventional electric hammer; Fig. 2 is a partially sectional front view of an implementation of the impact power tool assembly of the present invention; and Fig. 3 is a partially sectional front view of a conventional electric hammer. FIG. 3 is a diagram comparing the noise of a conventional electric hammer with that of a conventional electric hammer. 10... Striker, 11... Bull point,
14, 16... Cavity chamber, 15, 17... Sound absorbing material.

Claims (1)

[Claims] 1 In an impact power tool that crushes concrete, etc. by striking a bull point with a striker pushed out by air pressure compressed by the reciprocating motion of a piston, a cavity with sound-absorbing material pasted on the inner wall around the striking part. An impact power tool structure having a chamber, and further having a bull point part covered with a hollow chamber whose inner wall is covered with a sound absorbing material.