JPH0124959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a side branch type underwater sound silencer that reduces the pulsating sound of water passing through a water conduit.

As shown in Fig. 1, a side branch type underwater sound silencer is a water conduit 1 in which a branch pipe 2 of a predetermined length with a closed tip is provided in the middle of a water conduit 1, and the water inside the water conduit 1 is triggered by a pump 3 or the like. This is designed to reduce the pulsating sound that is transmitted through the air. In the case of this figure, the pulsating sound is loud in area A, but it is small in area B.

In this silencer, the length l of the branch pipe 2 is set to 1/4 of the wavelength λ of the pulsating sound transmitted inside the water conduit 1.
It is known that the pulsating sound in area B can be reduced by setting the pulsating sound to
A structure in which a branch pipe 2 having a length of 1/4 of the wavelength λ of the pulsating sound is simply provided is used.

In this way, this type of silencer has a simple structure, so it can be installed in a short period of time.
Moreover, it has the advantage of being inexpensive. However, this method has the disadvantage that the length of the branch pipe 2 must be increased in response to low-frequency pulsating sounds, and it is not practical when installed in a narrow space.

This invention was made in view of the above circumstances,
By arranging an elastic tube made of rubber or other material filled with air around the inner circumference of the branch pipe, the branch pipe can be shortened and installed even in narrow spaces.
The purpose of the present invention is to provide a practical side branch type underwater sound silencer that allows construction work to be performed more easily.

This invention will be explained below with reference to FIGS. 2 and 3. In addition, in this invention as well, the provision of the branch pipe 2 in the middle of the water conduit 1 is the same as in the first embodiment.
This is similar to the conventional example shown in the figure, and the same elements are given the same reference numerals and their explanations will be omitted.

First, in this invention, when air is mixed in water, the specific weight of the mixture of water and air slightly decreases compared to water, but the compressibility increases significantly, so that the apparent Focusing on the phenomenon that the propagation speed of pressure waves in water decreases as elasticity increases,
By arranging an elastic tube 4 made of rubber or the like containing air inside the branch pipe 2, the propagation speed of pulsating sound (pressure pulsating wave) in the water inside the branch pipe 2 is significantly reduced, and the pulsating sound is reduced. The feature is that the wavelength of the wavelength is shortened, thereby shortening the length of the branch pipe 2, which should be set to 1/4 of the wavelength.

In the embodiment of the present invention shown in FIG. 2, the elastic tube 4 consists of two rod-shaped parts 4a and an annular part 4b connecting them, and each part 4a, 4b are all in communication with each other, so that the enclosed air pressure is elastic. It is made to be uniform throughout the inside of the tube 4. This elastic tube 4
An annular portion 4b is located on the end side of the inner peripheral portion of the branch pipe 2, and a rod-shaped portion 4a is disposed along the length direction of the branch pipe 2 and along the inner peripheral wall. In this way, the elastic tube 4 is disposed at the inner peripheral portion of the branch tube 2, and is not disposed at the end portion of the branch tube 2. Therefore, the end of the branch tube 2 is not covered by the elastic tube 4. The sealed air pressure is adjusted from the outside of the branch pipe 2 through the pot 5 according to the water pressure inside the branch pipe 2 and the water conduit 1, and after adjustment, the pot 5 is closed and sealed.

By the way, in a configuration including such an elastic tube 4, as is clear from the figure, a wave propagation path L is formed that extends linearly from the end of the branch tube 2 into the water conduit 1, and this wave propagation path The elastic tube 4 is located on the inner circumference of the branch tube 2 so as not to block the L. The end of the branch pipe 2 is connected to the wave propagation path L
It becomes a reflective surface R that reflects the waves that enter through it and eliminates the sound of pulsating water.

By doing the above, the apparent elasticity of the water in the branch pipe 2 increases, and the speed of sound (propagation speed of pressure waves) in the water in the branch pipe 2 decreases.
Therefore, the wavelength of the pulsating sound (pulsating wave) guided into the branch pipe 2 is shortened to about 1/2 to 1/4 of the wavelength λ when the elastic pipe 4 is not inserted. Therefore, if the length l of the branch pipe 2 is set to 1/4 of the shortened wavelength λ',
The pulsation noise can be reduced, and the length can be reduced to 1/2 to 1/4 compared to the conventional one that does not include the elastic tube 4. By the way, in order to reduce such pulsating noise, the wave propagation path L and the reflecting surface R are
It is essential that the As is clear from the figure, the wave propagation path L is a space that leads straight from the end of the branch pipe 2 into the water conduit 1 without any obstruction, and the reflective surface R is the space that extends straight from the end of the branch pipe 2 to the inside of the water conduit 1. It is a surface located at , which reflects waves entering through the wave propagation path L. Only when a reflection action occurs on this reflecting surface R through this wave propagation path L does the side branch type underwater sound silencer have its original function of reducing pulsating noise. Therefore, for example, the wave propagation path L
If the elastic tube 4 is provided so as to block the wave propagation path L, the wave propagation path L itself will not be formed, and the wave reflecting action by the reflecting surface R cannot be expected, and the original function of the side branch type underwater sound silencer will be impaired.
Naturally, the same applies to the case where the elastic tube 4 is provided so as to cover the reflective surface R.

Therefore, in this invention, it is extremely important that the deployment position of the elastic tube 4 is specified as described above. That is, in this invention, by providing the elastic tube 4 on the inner circumference of the branch pipe 2 so as not to block the wave propagation path L, the reflecting surface R is secured for the wave propagation path L. Only in this way can the intended purpose of this invention be achieved.

Regarding how to install the branch pipe 2, when installing it in the horizontally running water conduit 1, it should face upward as shown in Figure 3 a, or downward as shown in Fig. 3 b. A drain 6 is provided, and if it is provided facing downward, a mud drain 7 is provided at the bottom. In addition, when installed in a vertically running water conduit 1,
As shown in c, α is set at about 22.5° so that air bubbles inside the pipe can escape into the vertical water conduit 1, and a mud drain 7 is provided at the bottom.

As described above, there are various ways of providing the branch pipe 2, but the present invention is suitable for any case and is not limited to the method of providing the branch pipe 2.

As explained above, the side branch type underwater sound silencer of the present invention has a
Since it is equipped with an elastic tube filled with air, it increases the apparent elasticity of the water in the branch pipe without impairing the original function of the side branch type underwater sound silencer due to the action of the end of the branch pipe. The propagation speed of the pulsating sound in the water within the branch pipe can be significantly reduced, and therefore the wavelength of the pulsating sound within the branch pipe can be shortened, and the length of the branch pipe can therefore be set short. For this reason, the installation work can be performed very easily, and it can also be easily installed in a narrow space, so that effects such as practicality can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a general example of a side branch type underwater sound silencer, Fig. 2 shows the main part of an embodiment of the present invention, in which a is a vertical cross-sectional view of a branch pipe, b is a cross-sectional view, c is a perspective view of the elastic tube, Figure 3 is a,
It is a figure which shows the example of how to provide b and c branch pipes, respectively. 1... Water conduit, 2... Branch pipe, 4... Elastic tube, L... Wave propagation path, R... Reflection surface.

Claims (1)

[Scope of Claims] 1. A branch pipe of a predetermined length with a closed end is provided in the middle of the water pipe, and inside this branch pipe there is a wave wave that leads linearly from the end of the branch pipe into the water pipe. forming a propagation path, and forming a reflective surface at the end of the branch pipe to reflect waves entering through the wave propagation path and muffle the pulsating sound of water passing through the water conduit, and to block the wave propagation path. A side branch type underwater sound silencer characterized in that an elastic tube made of rubber or the like containing air is disposed on the inner circumference of the branch tube so as to prevent noise from occurring. 2. The side branch type underwater sound silencer according to claim 1, wherein the elastic tubes are arranged uniformly along the length direction of the branch tube.