JP2017040458A - Acoustic absorption breather pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop an acoustic absorption breather pipe efficiently absorbing acoustic sound of middle to high frequency band without completely damaging a duct original function.SOLUTION: Thermoplastic resin fiber acting as a binder is mixed with thermoplastic resin fiber acting as fiber through a needle punch processing to form a needle felt and the thermoplastic resin is applied as coating to at least one surface of the needle felt. After the resin is preheated to a value higher than a melting temperature of the thermoplastic resin fiber acting as the binder, the resin is cold pressed to form it into a tubular-shaped one component or semi-split shaped two or more elements and the processed two-elements are combined to make a pipe shape and to form an acoustic absorption breather pipe.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vent pipe having a function of reducing noise.

For example, in order to transport a gas such as a low-temperature gas or air for the purpose of cooling, a ventilation pipe is disposed at a necessary place in a building, a transport machine, or the like.
In order to increase the cooling efficiency, it is desirable that the flow velocity of the gas flowing through the vent pipe is high, but along with this, the sound of the fan that blows the gas and the sound of the motor that drives the gas propagates through the vent pipe. Noise is a problem due to air column resonance generated in the vent pipe.

As a measure for reducing the noise caused by such a ventilation pipe, a so-called Helmholtz resonator equipped with a resonance silencer has been developed.
Separately from this, there has been developed a technique in which the inner wall of the ventilation pipe is replaced with a ventilation material such as a nonwoven fabric from a conventional non-breathing material to prevent occurrence of air column resonance in the ventilation pipe.
In the invention described in Patent Document 1, a hole is formed in a part of a non-breathable duct wall, and a porous material such as a non-woven fabric having appropriate breathability is attached so as to cover these holes. The outer space and the external space are ventilated by a porous material, and in the present invention, a small cylindrical portion protruding from the wall surface of the duct is provided, and the nonwoven fabric is thermally fused to the opening at the tip of the small cylindrical portion. Yes. In the invention, by adjusting the air permeability of the porous material, the occurrence of air column resonance in the duct is prevented, and the noise transmitted through the duct system is reduced.
The invention described in Patent Document 2 is an automobile engine intake pipe in which a part of the wall of the pipe is made of a nonwoven fabric molded body. This nonwoven fabric molded body is three-dimensionally formed into a half-divided shape of a duct by, for example, hot press molding, and a pair of half-broken bodies are bonded and integrated at a joint portion to constitute a ventilation duct.
The invention described in Patent Document 3 is an invention in which members constituting the ventilation duct are integrated by overmolding. In other words, the joints of a pair of synthetic resin half-cracks are overlapped, the joint surfaces are welded together, and the pair of half-cracks are integrated by secondary molding in which the outer periphery of the joint is covered with a synthetic resin material. It is to become.
The invention described in Patent Document 4 is an invention that is described in Patent Document 3 and is intended to prevent molding defects in the process of forming a ventilation duct by overmolding. That is, a thermoplastic resin fiber on the surface is formed by covering and molding the resin coating so as to wrap the end portion of the overlapping portion of the half-cracked body constituting the ventilation duct and selectively heating the surface of the nonwoven fabric molded body. Is melted to increase the rigidity.

JP 2001-323853 A JP 2000-73895 A JP-A-5-305679 JP2011-101984

The aim is to develop a sound-absorbing vent pipe that efficiently absorbs sound in the mid-high frequency band, which is not found in ducts having conventional sound-absorbing performance.
In addition, by coating the surface of the felt material with resin, we tried to develop a sound-absorbing vent pipe that prevents air leakage from the side of the duct and efficiently absorbs sound in the mid-high frequency band without impeding the duct function. To do.

  In the present invention, a thermoplastic resin fiber as a fibrous body is mixed with a thermoplastic resin fiber as a binder by a cylinder opener or the like, and the fibers are entangled by needle punching to form a needle felt. At least one of the needle felts is provided. The surface is coated or laminated with a thermoplastic resin. Preheat at or above the melting temperature of the thermoplastic resin fiber as the binder, and then cold-press to form one tube-shaped part or two or more half-cracked parts. As a sound absorption vent pipe.

Examples of the thermoplastic resin fiber that can be used as the fiber body or binder include PET (polyethylene terephthalate) fiber, low melting point PET fiber, acrylic fiber, nylon fiber, PP (polypropylene) fiber, PE (polyethylene) fiber, and PET / PE (bicycle). Component), PET / low melting point PET fiber (bicomponent), PE / PP (bicomponent) PE / PET (bicomponent), and the like.
The mixing ratio of thermoplastic resin fibers as a binder to the fiber body needs to be 20% by mass or more. If the amount is less than 20% by mass, the sound absorbing vent pipe may not be formed, and the molded sound absorbing vent pipe may have a weak strength.

  Examples of the resin to be coated or laminated on the needle felt include PP resin, PP-ethylene copolymer resin, low density PE resin, high density PE resin, linear PE resin, and latex resin.

  The sound-absorbing vent pipe of the present invention does not interfere with the original function of the vent pipe, which conveys gas, and does not disturb the rotation sound of the fan for efficiently transporting gas or the motor drive sound for driving this fan. Noise that is propagated through the inside of the ventilation pipe or caused by air column resonance generated in the ventilation pipe can be reduced and suppressed.

It is a schematic diagram of the sound absorption effect measuring device of the sound absorption vent pipe according to the present invention. It is a graph of the result of having measured with the measuring apparatus shown in FIG. 1 the sound absorption coefficient of the ventilation pipe shape | molded and processed as a raw material by the polypropylene resin as a typical example of the conventional ventilation pipe, and the sound absorption coefficient of the sound absorption ventilation pipe which becomes this invention. The vertical axis represents the sound absorption coefficient, and the horizontal axis represents the frequency.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to embodiment shown below, It is possible to change and implement the form suitably according to a use.

  The thermoplastic resin fiber as a binder to be mixed by 20% by mass or more with respect to the thermoplastic resin fiber used as the fiber body is mixed by a cylinder opener or the like and entangled with each other by a conventionally known carding process, needle punching process, or the like. It is made with felt.

A thermoplastic resin is coated or laminated on one side or both sides of the felt. The coating method is not particularly limited, and it can be exemplified that the thermoplastic resin is heated to the melting point to become liquid and then pressurized to be ejected from a nozzle having an arbitrary shape. As such a coating apparatus, a hot melt adhesive coating apparatus widely used in the field of the packaging industry can be used.
The method of laminating is not particularly limited, and the film-like thermoplastic resin is heated to soften the film surface by the thermoplastic resin, and the thermoplastic resin film is laminated on the felt surface by a suitable method such as a roller. A continuous film is formed. When the film-like thermoplastic resin is heated, unlike the coating, it is not heated up to the melting point of the thermoplastic resin. This is because if the film is heated to the melting point, holes may be formed in the film, and the continuous film may not be maintained.

A felt that is coated or laminated with a thermoplastic resin on one side or both sides is formed into a necessary shape to form a vent pipe that transports gas. Specifically, the felt heated above the melting temperature of the thermoplastic resin fiber used in the felt is placed on the lower mold, and the upper mold is lowered and cold pressed. Is processed into a substantially cylindrical shape. At that time, it is necessary to stretch the felt by cold pressing. If the felt dimensions do not stretch, when forming into a substantially cylindrical shape, a large stress is applied to the rising part of the cylinder and the edge of the cylindrical side wall and the top, so these parts break. This is because there is a risk of losing. The shape of the felt immediately before being used for a part is a rectangle having a thickness of several mm to several tens of mm, but the length of at least one side of the rectangle excluding the felt thickness portion is the same as that before heating and cold. When the stretched length after pressing is compared, it is 1.2 times to 1.8 times, preferably 1.3 times to 1.7 times, and more preferably 1.4 times to 1.6 times.
A step of obtaining a sound-absorbing vent pipe by cutting the cylindrical cross section at the top of the cylindrical part and the peripheral unnecessary part of the substantially cylindrical part thus obtained can be exemplified.
For molding with two parts, the lower part and the upper part are obtained by heat-pressing the lower part and the upper part of the half-cracked shape, which is divided into two vertically divided pipes (cylinders), with a molding die, etc. Are combined into a tube shape by bonding, heat fusion, or the like.

DESCRIPTION OF SYMBOLS 1 Sound absorption vent pipe 2 Hose 3 Blower 4 Sound pickup microphone near an inlet port 5 Sound receiver microphone

It is a schematic diagram of the sound absorption effect measuring device of the sound absorption vent pipe according to the present invention. 3: When the blower sucks air, 2: Connected by a hose 1: Air is sucked from the inlet of the sound absorption vent pipe (sample) and flows through the vent pipe. 3: Flow of air sucked into the blower create. At this time, the sound level ratio of the sound measured by the two receiving microphones of 4: intake inlet vicinity microphone / 5: exhaust outlet receiving microphone was measured by a 1/3 octave band frequency analyzer (not shown). Evaluate the sound absorption characteristics at each frequency. As a typical example of a conventional vent pipe, a vent pipe (sample A) molded into a rectangular parallelepiped (100 x 150 x 700 mm) using polypropylene resin as a raw material, and a sound-absorbing vent pipe (surface weight 1200 gsm, thickness 5 mm needle) according to the present invention The surface of the felt is coated with 150 gsm of polypropylene resin, and this coating surface is inside and molded into a rectangular parallelepiped (100 x 150 x 700 mm) (sample B). It is a graph of the result (sample A = dashed line, sample B = solid line) which measured the effect. The vertical axis represents sound absorption rate (unit = dB), and the horizontal axis represents frequency (unit = Hz).

Claims (7)

A thermoplastic resin fiber as a binder is mixed with a thermoplastic resin fiber as a binder by a cylinder opener or the like, and the fibers are entangled by needle punching to form a needle felt, and at least one surface of the needle felt is thermoplastic. Resin is coated or laminated, preheated at or above the melting temperature of the thermoplastic resin fiber as a binder, and then cold pressed to form a tube-shaped part or two or more half-cracked parts. If so, a sound-absorbing ventilation pipe characterized in that the processed parts of the two parts are combined into a pipe shape. The sound-absorbing vent pipe according to claim 1, wherein the thermoplastic resin fiber as the fibrous body is a PET (polyethylene terephthalate) resin. The thermoplastic resin fiber as a binder according to claim 1 is a PP (polypropylene) resin. The sound-absorbing vent pipe according to claim 1, wherein a thermoplastic resin composed of at least one resin selected from PP (polypropylene) resin and ethylene copolymer resin is coated or laminated. 2. The sound-absorbing vent pipe according to claim 1, wherein the sound-absorbing vent pipe is molded so that a surface on which the thermoplastic resin is coated or laminated is inside the pipe shape. 2. The sound-absorbing vent pipe according to claim 1, wherein the sound-absorbing vent pipe is molded so that a surface on which the thermoplastic resin is coated or laminated is an outer side of the pipe shape. 2. The sound-absorbing vent pipe according to claim 1, wherein the surfaces on which the thermoplastic resin is coated or laminated are both inside and outside of the tube shape.

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