JP2002138829A - Air duct with sound absorbing material and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily manufacturable air duct with a sound absorbing material with a simple structure. SOLUTION: A downstream connecting part (24) connected to a downstream air duct is formed at an end part of an inner tube (21) having a plurality of through-holes (27) in an outer-peripheral wall section, and a flange part (25) with a diameter larger than the outside diameter of the sound absorbing material (40) is formed in the vicinity of the connecting part. An annular projecting part (26) is formed at the outer periphery of the flange part (25). An upstream connecting section (32) connected to the upstream air duct is formed at one end part of an enlarged-diameter section (31) of an external pipe (30) covering the through-holes (27) in the inner pipe (21). An opened engaging part (35) for fitting the flange part (25) is formed at the other end part, and an annular groove (36) engaging with the annular projecting part (26) is formed at the inner periphery. The sound absorbing material (40) is intervened between the inner pipe (21) and the enlarged-diameter section (31).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material-provided air tube provided with a sound absorbing material in a wind tube through which air or the like passes, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, air of a blower flowing in a cylindrical tube,
Alternatively, various arrangements in which a muffler is provided in the middle of a pipe in order to reduce noise such as engine exhaust are found. As an example, Japanese Patent No. 2967390 (U.S. Pat.
Pat. No. 5718045), JP-A-10-19000
No. 5,827,473, U.S. Pat. No. 5,821,473.
S. There is one disclosed in Pat. No. 4421202.

The first example disclosed in Japanese Patent No. 2967390 aims to reduce the exhaust noise of an internal combustion engine. As shown in FIG. 6, the silencer 50 is configured by interposing a sound absorbing material 53 such as glass wool in an annular gap formed between an inner perforated tube 51 and an outer tube 52 surrounding the perforated inner tube 51. I have. Front and rear end portions 51a, 51b of the porous inner tube 51
Has a larger diameter than the middle part. The outer circumferences of the caps 55 and 56 are welded to the front and rear ends of the outer tube 52, respectively. A plurality of separator plates 54 are provided inside the perforated inner tube 51.
a, 54b, 54c, and a plurality of exhaust expansion chambers C1,
C2, C3, and C4 are formed. At the time of assembling, a sound absorbing material 53 having a predetermined thickness coated with a binder is wound around the outer periphery of the porous inner tube 51 to which the separator plates 54a, 54b, 54c are attached, and roll forming is performed using an ironing roller (not shown). The outer tube 52 is inserted.

A second example of Japanese Patent Application Laid-Open No. Hei 10-19000 discloses a silencer mounted on a blower pipe (corresponding to a wind tube according to the present invention) of a portable blower.
As shown in FIG. 7, the muffler 60 includes a blower pipe 61.
Enlarged portion 62 extending over a predetermined length L1 in the axial direction of
The inner pipe 63 having a large number of sound deadening holes 64 is inserted into the enlarged diameter portion 62, and a silence made of urethane foam is inserted into an annular gap formed between the inserted inner pipe 63 and the enlarged diameter portion 62. It has a configuration in which a material 65 is interposed. The inner pipe 63 is made of a pair of thin plate materials divided into two in the axial direction, and when assembling, a sound deadening material 65 is attached to each outer periphery, and the pair of thin plate materials are bent to be bent from the end of the blower pipe 61. Inserting and expanding part 62
It is designed to be stored inside. As another method, as shown in FIG. 8, the inner pipe 63 is formed by a strip 66 formed into a spiral shape made of a flexible material having appropriate elasticity such as polypropylene. . The band 66 is provided with a large number of sound deadening holes 64. At the time of mounting, first, the silencer 65 is inserted from one end of the blower pipe 61, and the silencer 65 is placed in the enlarged diameter portion 62. Next, the strip 66 is pulled in the axial direction to have its outer diameter d2.
Is made smaller than the inner diameter d1 of the blower pipe 61 and inserted into the blower pipe 61.
6, the outer diameter d2 is increased, and the muffling material 65 is pressed and attached to the enlarged diameter portion 62.

The U.S. Pat. S. Pat.No. 4421
As shown in the perspective view of FIG. 9, the noise reduction device 70 disclosed in No. 202 has a pair of collars 72, 7 at both ends on an outer cylinder 71.
2 is inserted, and a sound absorbing material 74 is interposed in an annular gap formed between the outer cylinder 71 and the inner cylinder 73. The pair of collars 72 are fastened to the outer cylinder 70 by screws 75. The inner cylinder 73 is
It is composed of twisted cords stitched together and hardened with resin, and has many voids.

[0006]

However, the above configuration has the following problems. 1) The one disclosed in Japanese Patent No. 2967390 has a problem that the number of components is large, the size is large, the structure is complicated, the weight is heavy, and the cost is high. 2) In the device disclosed in Japanese Patent Application Laid-Open No. 10-19000, the operation of housing the sound deadening material 65 in the enlarged diameter portion 62 is very troublesome, and the inner pipe 63 is placed inside the sound deadening material 65. Need to be inserted. Therefore, there is a problem that assembly is complicated, man-hours are required, the number of parts is large, and the cost is high. 3) See also U.S.A. S. The system disclosed in Pat. No. 4421202 has a problem that the number of parts is large, the structure is complicated, a large number of steps are required for assembly, and the cost is high.

An object of the present invention is to provide a wind tube with a sound absorbing material which is light in weight, has a simple structure, has a small number of parts, is easy to manufacture and is inexpensive, and a method for manufacturing the same. .

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, an air tube with a sound absorbing material according to the present invention has a cylindrical shape, and a plurality of outer circumferential wall portions having a predetermined length in a longitudinal direction. An inner tube having a through-hole and through which air or the like is passed, an outer tube that covers the through-hole portion, and a sound-absorbing air tube including a sound absorbing material interposed between the inner tube and the outer tube. The inner tube has a rotation-preventing projection provided at one end, a flange portion having a diameter larger than the outer diameter of the sound absorbing material, and a flange portion provided near the other end. An annular convex portion provided on an outer peripheral portion, and a plurality of through holes provided on a wall portion between the distal end portion and the flange portion, wherein the outer tube covers the through hole of the inner tube. An enlarged-diameter portion, a fitting portion provided on one side of the enlarged-diameter portion and having a groove portion for fitting the inner tube and engaging with the protrusion, and on the other side of the enlarged-diameter portion. Provided mouth, an engaging portion for fitting the flange portion, provided on the inner peripheral portion of the engaging portion, and configured to have an annular groove which engages the annular projection of the flange portion.

According to the above construction, the inner tube is inserted into the sound absorbing material, the inner tube is inserted into the outer tube, the tip of the inner tube is fitted into the fitting portion of the outer tube, and the projection and the groove are engaged. At the same time, the flange portion is fitted into the engaging portion to engage the annular groove with the annular convex portion. As a result, the inner tube and the outer tube are connected, and a wind tube with a sound absorbing material can be easily and easily formed. Therefore, a wind tube with a sound absorbing material having a small number of parts, a simple structure, and a low cost can be obtained. In addition, since there is a detent between the inner pipe and the outer pipe, they do not rotate relative to each other. Since they do not rotate with each other, assembly work is easy.

Next, in the method of manufacturing a wind tube with a sound absorbing material according to the present invention, a plurality of through holes are formed in a cylindrical outer peripheral wall portion having a predetermined length in a longitudinal direction, and air is passed through the inside. In a method for manufacturing a wind pipe with a sound absorbing material comprising a pipe, an outer pipe covering a through hole, and a sound absorbing material interposed between the inner pipe and the outer pipe, the sound absorbing material is provided near the longitudinal end. A resin-made cylindrical inner tube having a flange portion having a diameter larger than the outer diameter and having an annular convex portion on the outer peripheral portion of the flange portion is manufactured, and then this inner tube is inserted into a cylindrical soundproofing material. And then, the enlarged portion covering the soundproofing material, provided on one side of the enlarged portion, a fitting portion for fitting the distal end portion of the inner tube, and provided to be open on the other side of the enlarged portion, A resin outer tube having an engagement portion having an annular groove on the inner periphery for engaging the flange portion of the inner tube and engaging the annular protrusion of the flange portion is blown. After the molding, the inner tube with the soundproofing material is inserted within a predetermined period of time when the temperature is high, and the tip of the inner tube is fitted into the fitting portion, and the flange portion of the inner tube is fitted into the engaging portion, thereby cooling. Later, the manufacturing method is such that the annular groove of the engaging portion is engaged with the annular convex portion of the flange portion.

According to the above method, the inner tube and the outer tube are made of resin, so that they are lightweight. Also, in the assembling stage, the preformed inner pipe is inserted into the sound absorbing material, the outer pipe is blow-molded, the inner pipe is fitted within a predetermined time at a high temperature, and after cooling, the inner pipe flange and the outer pipe are fitted. Since the engagement portion is connected, assembly can be performed with a small number of parts and a small number of steps, and the cost is reduced.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a wind tube with a sound absorbing material according to an embodiment of the present invention. A portable blower will be described as an example of a machine to which the present invention is applied.

First, referring to FIG. 1, a schematic configuration of a portable blower 1 including a wind tube 20 with a sound absorbing material according to the present invention will be described.
A blower 4 driven by an engine 5 is mounted on the substantially L-shaped frame 3. Air outlet 7 of blower 4
An elbow 10 is attached to the upper end of the elbow 10, and an upstream wind pipe 12, a wind pipe 20 with a sound absorbing material, and a downstream wind pipe 13 are sequentially connected to a distal end of the elbow 10 via a flexible tube 11. The wind blows out and blows off dead leaves and the like. An operator carries the portable blower 1 and performs a cleaning operation while holding the air tubes 12 and 13.

Next, the structure of the air tube 20 with sound absorbing material will be described. FIG. 2 is a partial cross-sectional side view of the air tube 20 with a sound absorbing material. In FIG. 2, a wind pipe 20 with a sound absorbing material includes a cylindrical inner pipe 21, a cylindrical outer pipe 30 covering the inner pipe 21, and an inner pipe 21.
And a cylindrical sound absorbing member 40 interposed between the outer tube 30 and the outer tube 30. One side of the wind pipe 20 with the sound absorbing material is connected to the upstream wind pipe 12, and the other side is connected to the downstream wind pipe 13. FIG. 3 is a view on arrow AA of FIG. 2, and FIG. 4 is a view on arrow B of FIG.
FIG. 5 is an exploded perspective view showing the configuration of the wind tube 20 with a sound absorbing material. 2, 3, 4, and 5, a pair of rotation-preventing projections 23, 23 are provided at a distal end 22 on one side in the longitudinal direction of the inner tube 21, and a downstream end is provided at the other end. A downstream connection portion 24 connected to the side air duct 13 is provided. The downstream connection portion 24 is provided with a projection 24 a for connection to the downstream air tube 13. A flange portion 25 having an outer diameter D larger than the outer diameter C of the sound absorbing material 40 is integrally formed near the downstream connection portion 24, and an annular convex portion 26 is provided on an outer peripheral portion thereof. And the projection 23
A plurality of through holes 2 is formed in the cylindrical surface between the
7 are provided. At one end of the enlarged diameter portion 31 covering the sound absorbing material 40 of the outer tube 30, an upstream connection portion 32 connected to the upstream wind pipe 12 is provided, and between the enlarged diameter portion 31 and the upstream connection portion 32. A fitting portion 33 into which the distal end portion 22 of the inner tube 21 is fitted is provided. The upstream air tube 12 is connected to the upstream connection portion 32.
And a connection groove 32a for the connection. The fitting portion 33 is provided with a pair of grooves 34, 34 that engage with the projections 23, 23 provided on the distal end portion 22 of the inner tube 21, and engage with each other during assembly to prevent mutual rotation. It has become. An engaging portion 35 is provided on the other side of the enlarged diameter portion 31 so as to open and fit the flange portion 25 of the inner tube 21.
An annular groove 36 that engages with the annular convex portion 26 of the flange portion 25 is provided in the inner peripheral portion of the flange 5, and engages with each other to connect the inner tube 21 and the outer tube 30. A cylindrical sound absorbing material 40 is interposed in a space defined by the inner tube 21 and the enlarged diameter portion 31 of the outer tube 30.

In this embodiment, as an example, the annular convex portion 2
6 and the annular groove 36 are provided at three places.
It may be provided at two locations or at four or more locations.

Since the air tube 20 with the sound absorbing material of the present invention is configured as described above, the inner tube 21 and the outer tube 30 do not rotate relative to each other or expand and contract in the longitudinal direction. The noise of the air passing through the pipe is absorbed by the sound absorbing material 40, and the noise is reduced.

Next, the manufacturing method will be described. Inner tube 21
Is a resin such as ABS or polyamide, and is manufactured by injection molding. The outer tube 30 is made of a resin such as polyethylene, polypropylene, or polyamide, and is manufactured by blow molding. When assembling, first, the inner pipe 21 is manufactured,
It is inserted into the cylindrical sound absorbing material 40. Next, the outer tube 30 is blow-molded, and the inner tube 21 with the sound absorbing material 40 is inserted within a predetermined time at a high temperature (for example, within 10 minutes after molding), and the distal end portion 22 of the inner tube 21 is fitted to the outer tube 30. The projection 23 and the groove 34 are engaged with each other while being fitted into the joint 33. At the same time the inner pipe 21
Is fitted into the engaging portion 35 of the outer tube 30. Since the outer tube 30 is not hardened within a predetermined high temperature time after the blow molding and has elasticity, the annular convex portion 26 of the inner tube 21 extends and expands the annular groove 36 of the engaging portion 35 to facilitate the expansion. Can be fitted into Then, with the passage of time, the extended portion of the outer tube 30 contracts and is cooled and hardened, and the annular groove 36 of the engaging portion 35 is firmly engaged with the annular convex portion 26 of the inner tube 21, The inner tube 21 and the outer tube 30 are connected. The outer tube 30 may be cooled by natural heat radiation, or may be forcibly blown with cold air to accelerate the cooling.

Since the wind tube with sound absorbing material of the present invention and the method of manufacturing the same are as described above, the assembling work is easy, the structure is simple, the number of parts is small, the weight is small, the sound absorbing material is easy to manufacture and the cost is low. Wind tubes are obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a portable blower provided with an air tube with a sound absorbing material of the present invention.

FIG. 2 is a partial cross-sectional side view of a wind tube with a sound absorbing material of the present invention.

FIG. 3 is a view as viewed in the direction of arrows AA in FIG. 2;

FIG. 4 is a view taken in the direction of arrows BB in FIG. 2;

FIG. 5 is an exploded perspective view of the air tube with a sound absorbing material of the present invention.

FIG. 6 is a side sectional view of a muffler with a sound absorbing material according to a first example of the prior art.

FIG. 7 is a side sectional view of a wind tube with a sound absorbing material of a second example of the prior art.

FIG. 8 is a side view of an inner pipe of a wind tube with a sound absorbing material according to a second example of the related art.

FIG. 9 is an exploded perspective view of a wind tube with a sound absorbing material according to a third example of the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Portable blower, 12 ... Upstream side wind pipe, 13 ... Downstream side wind pipe, 20 ... Wind pipe with sound absorbing material, 21 ... Inner pipe, 22 ... Tip part,
23: Projection, 25: Flange, 26: Annular convex, 3
0: outer tube, 31: enlarged diameter portion, 33: fitting portion, 34: groove portion,
35: engagement portion, 36: annular groove, 40: sound absorbing material.

Claims (2)

[Claims] 1. An inner pipe having a plurality of through holes in an outer peripheral wall portion having a predetermined length in a longitudinal direction and having a plurality of through holes therein, and an outer pipe covering the through hole portions, In a wind pipe with a sound absorbing material comprising a sound absorbing material interposed between a pipe and an outer pipe, the inner pipe (21) has a rotation-preventing projection provided at one end (22). (23), a flange portion (25) having a diameter larger than the outer diameter of the sound absorbing material (40) provided near the other end, and an annular convex portion provided on the outer peripheral portion of the flange portion (25). (26), and a plurality of through holes (27) provided in a wall portion between the tip portion (22) and the flange portion (25), and the outer tube (30) is An enlarged portion (31) covering the through hole (27) of the pipe (21) and an enlarged portion (31)
A fitting portion (33) provided on one side of the inner tube (21) and having a groove (34) for fitting the inner tube (21) and engaging with the protrusion (23);
The flange portion is provided to be open on the other side of the enlarged diameter portion (31).
An engaging portion (35) into which the (25) is fitted, and an annular groove (36) provided on an inner peripheral portion of the engaging portion (35) and engaged with the annular convex portion (26) of the flange portion (25). And a wind tube with a sound absorbing material. 2. An inner pipe having a plurality of through holes formed in a cylindrical outer peripheral wall portion having a predetermined length in a longitudinal direction and allowing air to pass therethrough, an outer pipe covering the through holes, and an inner pipe. In a method for manufacturing a wind tube with a sound absorbing material comprising a sound absorbing material interposed between the outer tube and a sound absorbing material, a flange portion (25) having a diameter larger than the outer diameter of the sound absorbing material (40) is provided near an end in the longitudinal direction. To produce a resin-made cylindrical inner tube (21) having an annular convex portion (26) on the outer peripheral portion of the flange portion (25),
Next, this inner pipe (21) is inserted into the cylindrical soundproofing material (40), and then the enlarged diameter portion (31) covering the soundproofing material (40) and one side of the enlarged diameter portion (31). A fitting portion that is provided and that fits the tip portion (22) of the inner tube (21).
(33), and provided on the other side of the enlarged diameter portion (31) so as to fit the flange portion (25) of the inner pipe (21) and the annular convex portion (26) of the flange portion (25). Blow-molding a resin outer tube (30) having an engagement portion (35) having an annular groove (36) on its inner periphery to engage with the sound-insulating material ( 40)
Insert the attached inner pipe (21) and insert the tip of the inner pipe (21) into the fitting part (33).
(22) and the flange (25) of the inner pipe (21) into the engaging portion (35), and after cooling, the engaging portion (35) is inserted into the annular convex portion (26) of the flange (25). A) producing a wind tube with a sound absorbing material, wherein the annular groove (36) is engaged.