AU7259300A - Fan silencer - Google Patents

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Name of Applicants: Actual Inventors Address for service is: RONALD JAMES GOUGE, DAVID JOHN WILKIE and DAVID THOMAS LAW RONALD JAMES GOUGE, DAVID JOHN WILKIE and DAVID THOMAS LAW WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: "Fan Silencer" Details of Associated Provisional Application No(s): PQ4933 The following statement is a full description of this invention, including the best method of performing it known to me:- -2- "Fan Silencer" Field of the Invention This invention relates to noise control for fans including in particular ventilation fans in underground mines. More particularly, the invention relates to a silencer for a fan, and to a method of constructing such a silencer.

Background Art Noise control is an important part of underground mining operations. Fans used in ventilation of underground mines are particularly noisy and so require silencing. Indeed, current legislation in Western Australia requires that all ventilation fans operating above a prescribed maximum decibel limit be fitted with silencers.

S Fan silencers currently available are constructed of metal, and in particular steel.

Typically, ventilation fans fitted with conventional silencers have a length of *.i approximately 8 metres and a weight of approximately 3 tonnes. Owing to its size and weight, such a fan and silencer can be costly to manufacture and install.

Indeed, in some situations it can be particularly difficult to install such a fan and o *silencer owing to space limitations.

It is against this background, and the problems and difficulties associated oeee• therewith, that the present invention has been developed.

e 20 Disclosure of the Invention The present invention provides a silencer comprising an inner wall defining a flow passage, the inner wall having perforations therein, an outer wall disposed around and in spaced apart relationship with respect to the inner wall, and sound insulation provided in the space between the inner wall and the outer wall, the inner and outer walls being formed of plastics material.

-3- A particularly suitable plastics material from which the inner and outer walls can be formed is polyethylene.

The sound insulation between the inner and outer walls may be of composite construction, comprising an inner layer of acoustic foam immediately adjacent the inner wall, an outer layer of acoustic foam adjacent the outer wall and an intermediate layer of sound barrier material interposed between the two layers of acoustic foam.

Preferably, the intermediate layer comprises a flexible high-mass noise barrier.

The acoustic foam providing the inner and outer layers may be a polyester polyurethane offering excellent hydrolysis resistance which makes it particularly suitable for use in wet and humid conditions.

More particularly, the sound insulation may comprise a known modified composite sandwich material comprising a single high-mass noise barrier laminated between two layers of flexible acoustic foam. This arrangement 15 increases transmission loss and provides sound absorption. The outer layer of acoustic foam provides a high degree of sound absorption reducing reverberant noise levels. The inner layer of acoustic foam acts as a decoupling layer. In particular, it decouples the noise barrier and spaces it from the structure.

A film facing may be positioned about the outer layer to provide mechanical 20 protection and high resistance to contaminants such as dust, oil, liquids and sprays.

The perforated construction of the inner wall assists in the performance of the noise barrier.

The perforations may comprise rectangular cut-outs in the inner wall.

Preferably, coupling portions are provided at adjacent ends of the inner and outer walls. The coupling portions facilitate coupling of the silencer to other structures -4such as a fan or a similar silencer. The coupling portions also provide end walls between the inner and outer walls, so encasing the insulation therebetween.

Preferably, the silencer is of generally cylindrical construction, whereby the inner wall is generally cylindrical and the outer wall is also generally cylindrical. The inner wall may be formed from a generally rectangular sheet rolled into a cylindrical form.

Preferably, the inner wall has a length of about 1.5 times its diameter.

The use of plastic material in the construction of the silencer provides performance benefits in comparison to conventional silencers constructed of steel. The plastics material, and in particular polyethylene, does not have the same sound attenuation as steel. This in combination with other features of the silencer allows it to be constructed of a length which is shorter overall than a corresponding silencer constructed of steel. Additionally, it is lighter in weight.

The construction also provides good impact resistance and is generally non-corrosive.

o o The present invention also provides a method of constructing a silencer comprising the steps of: forming perforations in a generally rectangular sheet of plastics material; rolling the sheet into a cylindrical shape to form an inner cylinder defining an inner wall; applying insulation about the exterior face of the 20 inner wall; applying means to retain the insulation in place; and positioning an •outer cylinder about the inner cylinder and the insulation therearound to provide an outer wall in circumferentially spaced apart relationship with respect to the inner wall with the insulation therebetween.

Preferably, the method further includes applying end walls between the inner and outer walls thereby to encase the insulation.

Preferably, the end walls are bonded to the inner and outer wall by a plastic welding process.

Preferably, the inner cylinder is formed from the generally rectangular sheet by rolling the sheet into a cylindrical form with opposed edges thereof being brought into abutting contact and bonded together by a plastic welding process.

Brief Description of the Drawings The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which: Figure 1 is a schematic sectional view of a fan silencer according to the embodiment fitted onto a fan; Figure 2 is a perspective view of the fan silencer and fan shown in Figure 1; Figure 3 is a perspective view of the fan silencer; Figures 4 to 7 illustrate various steps in the construction process of the fan silencer; Figure 8 is a side view of the fan silencer showing a mounting structure fitted thereon; and Figure 9 is a fragmentary view of a support structure for supporting a fan motor in the fan silencer.

S*°

Best Mode(s) for Carrying Out the Invention The embodiment shown in the drawings is directed to a fan silencer 10 for a fan 11 used in ventilation of underground mines.

The fan silencer 10 comprises a body 13 comprising an inner cylinder 15, and an outer cylinder 17 positioned in circumferentially spaced apart relationship with respect to the inner cylinder 15 to define a gap 19 therebetween. A coupling -6portion 21 is provided at each end of the body 13. One of the coupling portions 21 is utilised to couple the fan 11 to the body 13 (as will be explained later) and the other coupling 21 can be utilised to couple the body to some other component or structure (not shown) such as an intake bell or another silencer body. The inner cylinder 15 and the outer cylinder 17 are connected together at their adjacent ends by the coupling portions 21.

The inner cylinder 15, the outer cylinder 17 and the coupling portions 21 are all formed of polyethylene, with the flanges 21 being fixed to the inner and outer cylinders by a plastic welding process.

The inner cylinder 15 defines an inner wall 23 and the outer cylinder 17 defines an outer wall A flow passage 27 is defined within the inner cylinder 15 for air flow generated by the fan 11.

Each coupling portion 21 comprises a flange 22 mounted on the adjacent end of 15 the inner cylinder 15 to project outwardly therefrom, and an annular member 24 associated with the flange 22. The annular member 24 is of angular cross-section to provide a first web 26 and a second web 28. The annular member 24 is positioned on the inner cylinder 15 with the free end of the first web 26 in contact with the inner cylinder and the free end of the second web 28 20 in contact with the flange 22. With this arrangement, an annular cavity 29 is defined between the inner wall 15, the flange 22 and the annular member 24.

The flange 22 is provided with a plurality of bolt holes 30 for receiving bolts (not o shown) for coupling the silencer body 13 to some other component or structure, such as the fan 11. Access holes 32 are provided in the web 28 of the annular member 24 in radial alignment with the bolt holes 30 to provide access to the cavity 29. Such access is necessary in order to permit installation and tightening of bolt and nut assemblies coupling the silencer body 13 to the other structures or components.

The ends of the outer cylinder 17 are secured to the first web 26 of the coupling portions 21 by way of a plastic welding process.

The fan 11 is supported within the silencer 10 by a support structure 31 which includes a shroud 33 in which part of the body 35 of the fan motor 37 is received and supported, as best seen in Figure 1 of the drawings.

The fan 11 includes a casing 36 onto which the fan motor 37 is mounted by means of mounting arms 39. The fan motor 37 extends beyond one end of the casing 36 to permit the motor body 35 to be received in the shroud 33 when the casing is positioned at the adjacent end of the silencer body 13, as shown in Figure 1.

As alluded to earlier, the coupling portions 21 allow the silencer 10 to be mounted to other structures as necessary. For example, in the arrangement illustrated in Figure 1 of the drawings, the casing 36 of the fan 11 is fastened-to the adjacent coupling portion 21 by bolt and nut assemblies.

15 The inner wall 23 defined by the inner cylinder 15 is provided with a plurality of perforations 41 in the form of apertures. The perforations 41 extend entirely through the inner wall.

Insulation 43 is provided in the gap 19 between the inner wall 23 and the outer S: wall 25. The insulation 43 comprises a modified composite sandwich material of 20 known kind, comprising a single high-mass noise barrier laminated between two layers of flexible acoustic foam, with one layer of the acoustic foam being adjacent the inner wall 23 and the other layer of acoustic foam being adjacent the outer wall 25. The acoustic foam providing the inner and outer layers is a polyester polyurethane which offers excellent hydrolysis resistance in wet and humid conditions.

The insulation 43 is retained in position about the inner cylinder 15 by way of strapping 47, as shown in Figure 7 of the drawings.

-8- A protective film (not shown) is applied to the outer side of the insulation 43 wrapped around the inner cylinder 15. The protective film is in the form of conventional plastic film. The film provides some mechanical protection to the insulation and inhibits contamination by foreign matter such as dust, oil, liquids and sprays.

The insulation 43 is encased between the inner wall 23, the outer wall 25, and end walls defined bythe coupling portions 21.

The support structure 31 which supports the fan 11 within the silencer comprises the shroud 33 and a plurality of circumferentially spaced mounting brackets 55 extending between the shroud 33 and the inner cylinder 15. Each mounting bracket 55 comprises a radial web 56, as well as an inner mounting flange 57 and an outer mounting flange 61, as best seen in Figure 9. The inner mounting flange 57 is fixed to the shroud 33 by way of fastening means 59 such i* as bolts. Similarly, the outer mounting flange 61 is fixed to the inner cylinder S 15 by way of fastening means 63 such as bolts. The bolts 63 extend through the inner cylinder 15 and also through a mounting band 65 which surrounds the inner cylinder at the location where the mounting brackets 55 are to be positioned.

The, mounting band 65 is formed of metal so as to provide a rigid structure to which the support structure 31 can be attached.

In this embodiment, the fan silencer 10 is provided with a mounting structure .i which allows the fan structure to be suspended in an elevated condition. The .oo.°i mounting structure 70 comprises two circumferential mounting bands 71 positioned around the exterior of the outer cylinder 17. The mounting bands 71 are positioned in a spaced apart relationship and are interconnected by connecting bands 73. The mounting bands 71 are secured to the body 13 of the fan silencer 10 by way of fixing elements 75. Each mounting band 71 is provided with a hanging bracket 77 by means of which the mounting structure 70 can be connected to a suspension system.

The manner in which the silencer 10 is constructed is best illustrated in Figures 4, 5, 6 and 7 of the drawings. The inner cylinder 15 is formed from a rectangular sheet of polyethylene 51 having opposed edges 52, as shown in Figure 4 of the drawings. Rectangular cut-outs 53 are formed in the sheet 51 to provide the perforations 41, as shown in Figure 5. The rectangular sheet 51 is then rolled into a cylindrical form with edges 52 being brought into abutting contact and bonded together by a plastic welding process. The coupling portions 21 are then welded onto the ends of the inner cylinder 15 so formed, as shown in Figure 6 of the drawings. The insulation 43 is then wrapped around the inner cylinder and retained in place by the strapping 47, as illustrated in Figure 7 of the drawings. The protective plastic film is then wrapped around the insulation. The outer cylinder 25 is then positioned around the inner cylinder 15 with the insulation 43 wrapped therearound. The ends of the outer cylinder 17 are then bonded to the webs 27 of the coupling portions 21 by way of a plastic welding process.

S: The support structure 31 can be installed in the silencer at any appropriate time in the construction process.

The mounting structure 70 can be positioned on the body 13 after construction of the fan silencer Various componentary can be fitted onto the silencer 10 as necessary, such componentary including an intake bell and a mesh or other protective guard preventing an authorised entry into the silencer.

*i From the foregoing, it is evident that the present embodiment provides a simple yet highly effective silencer which is of a construction which provides benefits in comparison to conventional silencers constructed of steel.

It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described. In particular, while the embodiment has been described with the inner and outer cylinders being formed of polyethylene, it should be understood that the cylinders can be made of any suitable plastics material.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (15)

1. A silencer comprising an inner wall defining a flow passage, the inner wall having perforations therein, an outer wall disposed around and in spaced apart relationship with respect to the inner wall, and sound insulation provided in the space between the inner wall and the outer wall, the inner and outer walls being formed of plastics material.

2. A silencer according to claim 1 wherein the plastics material from which the inner and outer walls are formed comprises polyethylene.

3. A silencer according to claim 1 or 2 wherein the sound insulation between the inner and outer walls is of composite construction, comprising an inner layer of acoustic foam immediately adjacent the inner wall, an outer layer of acoustic foam adjacent the outer wall, and an intermediate layer of sound barrier material interposed between the two layers of acoustic foam.

4. A silencer according to claim 3 wherein the intermediate layer comprises a .e flexible high-mass noise barrier. A silencer according to claim 3 or 4 wherein the acoustic foam providing the inner and outer layers comprises a polyester polyurethane. A silencer according to claim 1 or 2 wherein the sound insulation comprises ee *o S• a modified composite sandwich material comprising a single high-mass noise barrier laminated between two layers of flexible acoustic foam.

7. A silencer according to any one of the preceding claims wherein a film facing is positioned about the outer layer to provide mechanical protection and resistance to contaminants.

8. A silencer according to any one of the preceding claims wherein the perforations comprise rectangular cut-outs in the inner wall. -12-

9. A silencer according to any one of the preceding claims wherein the inner wall is generally cylindrical and the outer wall is generally cylindrical. A silencer according to claim 9 wherein the inner wall is formed from a generally rectangular sheet rolled into a cylindrical form.

11. A silencer according to claim 9 or 10 wherein the inner wall has a length of about 1.5 times its diameter.

12. A silencer according to any one of the preceding claims wherein coupling portions are provided at adjacent ends of the inner and outer walls.

13. A method of constructing a silencer comprising the steps of: forming perforations in a generally rectangular sheet of plastics material; rolling the sheet into a cylindrical shape to form an inner cylinder defining an inner wall; applying insulation about the exterior face of the inner wall; applying means to retain the insulation in place; and positioning an outer cylinder about the inner cylinder and the insulation therearound to provide an outer wall in circumferentially spaced apart relationship with respect to the inner wall with .the insulation therebetween.

14. A method according to claim 13 further comprising the step of applying end walls between the inner and outer walls thereby to encase the insulation. p.

15. A method according to claim 14 wherein the end walls are bonded to the inner and outer wall by a plastic welding process.

16. A method according to claim 14 or 15 wherein the inner cylinder is formed from the generally rectangular sheet by rolling the sheet into a cylindrical form with opposed edges thereof being brought into abutting contact and bonded together by a plastic welding process. -13-

17. A silencer substantially as herein described with reference to the accompanying drawings.

18. A method of constructing a silencer substantially as herein described. Dated this twenty-ninth day of December 2000. RONALD JAMES GOUGE, DAVID WILKIE and DAVID THOMAS LAW Applicants Wray Associates Perth, Western Australia Patent Attorneys for the Applicants 5 *S