AU660864B1 - An acoustic barrier - Google Patents

Description

660864

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Winstone Specialty Products Limited ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

S. INVENTION TITLE: An acoustic barrier The following statement is a full description of this invention, including the best method of performing it known to me/us:-

S

The present invention relates to an acoustic barrier. More particularly, but not exclusively, the present invention relates to an acoustic barrier construction suitable for use in soundproof doors.

The invention is an improvement to or modification of the invention described in New Zealand patent specification No.

231784 (the parent specification).

To the present time various types of soundproof doors have been commercially available but to varying degrees have suffered from the disadvantages of being expensive, bulky, heavy and/or ineffective.

A standard hollow core door when sealed with neoprene gaskets has a sound transmission coefficient of about dB. A solid wood core door has a coefficient of about 27dB in the same circumstances. To achieve coefficiencs greater than 36dB manufacturers have generally provided multiple edge seals, very heavy door leaves, very thick door leaves using expensive or imported materials with the door thickness typically being between 70-100mm. These factors have increased cost and prevented the use of acoustic doors with hardware and in standard architectural applications.

-2- NZ 231784 discloses a form of soundproof door construction using readily available, non-toxic, inexpensive materials, which are easily machined. The doors can be made thick and faced with timber for use in normal applications.

According to NZ 231784 there is provided an acoustic barrier comprising: a frame to support covering layers; (ii) an inner rigid sheet on each side of the frame supported by ths frame and defining a cavity between the inner rigid sheets and the frame; and (iii) outer sheets of greater elasticity than the inner rigid sheets, separated from and secured S""to the inner rigid sheets by spots of adhesive.

According to a further aspect of NZ 231784 there is provided a method of manufacturing a soundproof door "i comprising the steps of: providing a door frame; (ii) applying a plurality of dots of adhesive to two sheets of medium density fibre board or plywood; (iv) pressing both pairs of sheets of medium density fibre board or plywood together to -3- 1 1 achieve the desired spacing between the sheets; affixing the pairs of sheets of medium density fibre board or plywood to steel sheets; and (vi) affixing the bonded sheets of step to either side of the frame so that a cavity is defined between the steel sheets.

A feature of the acoustic barrier of NZ 231784 is that the spots of adhesive securing the outer sheets to the inner rigid sheets can cause very slight undulations in the outer surfaces of the barrier. Although these very slight undulations do not affect the operation of the barrier, some situations require the barrier to have very flat e" ~surfaces. For example, Australian Standard No. 2688-1984 may require an acoustic barrier in the form of a door to have a flatness of -2 mm.

O o It is envisaged that in some circumstances, the spots of adhesive in the acoustic barrier of NZ 231784 may result in S" the barrier having a flatness which exceeds this standard.

9999 It is an object of the present invention, therefore, to provide an acoustic barrier which provides effective sound proofing while having conventional door -4dimensions, and which has an improved surface flatness over the acoustic barrier of NZ 231784, or which at least provides the public with a usefrl alternative.

Further objects of the present invention will become apparent from the following description.

According to one aspect of the present invention, there is provided an acoustic barrier comprising: a frame to support covering layers; (ii) an inner rigid sheet o- each side of the frame supported by the frax,e and defining a cavity between the inner rigid sheets and the frame; and (iii) outer sheets of greater elasticity than the inner rigid sheets, separated from and secured to the inner rigid sheets by a layer of foam material.

According to a further aspect of the invention, there is provided a method of manufacturing an acoustic barrier, comprising the steps of: S. providing a frame; (ii) adhering a layer of foam material to two sheets of medium density fibre board, or plywood; (iii) applying a further sheet of medium density fibre board or plywood to each sheets of step (ii) over the layer of foam material; (iv) pressing both pairs of sheets of medium density fibre board or plywood together to achieve a predetermined spacing between the sheets; affixing the pairs of sheets of medium density fibre board or plywood to steel sheets; and (vi) affixing the bonded sheets of step to either side of the frame so that a cavity is defined between the steel sheets.

Further aspects of this invention will become apparent from the following description given by way of example of a possible embodiment thereof and with reference to the accompanying drawings, in which: a. Figure i: shows a cross-sectional view of a soundproof barrier constructed according to the present invention.

S Figure 2: shows a cross-sectional view of a barrier :..according to the present invention including a transparent panel section.

The present invention relates to an acoustic barrier which in one embodiment is particularly suitable for soundproof doors. It is to be appreciated that the present invention may have application in other soundproof barrier applications.

Unlike prior art soundproof doors, neither the present invention (nor that of NZ 231784) relies upon heavy soundproofing-materials or a limp septum within the cavity.

In the present invention the acoustics rely almost entirely upon the construction of the facings. The facings consist of rigid layers, preferably steel, separated from a further layer by a layer of foam material. The facing construction provides an elastic layer which disperses sound energy, a low proportion of which is propagated by the stiff layers.

S Referring now to Figure i, a cross-sectional view of a ee** barrier constructed according to the present invention is shown. The barrier consists of framing members 1 forming a

S.

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rectangular frame and supporting a plurality of laminate layers. Clashings 2 may be provided around the edge of the S. door. Rebates la and lb are provided in framing members 1 S to accommodate layers 3 and 4 and ensure the correct spacing between layers.

The preferred method of construction of a barrier according to the invention will now be described.

-7- A first fibre board layer 4 or 5 is provided and a layer of foam material 6 is adhered to one side. A further fibre board layer 4 or 5 is placed on top of and adhered to layer 6. The boards are pressed together until the required gap between the boards is achieved. Preferably the gap will be 2mm In one preferred form of the invention, the layer of foam material 6 is a 3mm layer of polyurethane open cell foam. During manufacture of the barrier according to the invention, the layer 6 is compressed to approximately 2mm, between the layers 4 and Rectangular framing 1 is then provided having suitable rebates la and Ib to support the layers. Steel layers 3 are then secured in rebates Ib by adhesive or mechanical fasteners. Layers 4 and 5 (now bonded together via the layer of foam material 6) are then secured to framing 1 by adhesive or mechanical fasteners. Layer 4 will be secured to layer 3 by adhesive.

Layers 4 and 5 will preferably be protected with a sealant as recommended in "Guide to MDF surface coatings" published by Fletcher Wood Panels in March 1988. The sealant acts as a moisture barrier.

o• -8- Although the barrier has good soundproofing if cavity 7 remains hollow, improved sound performance may be obtained if cavity 7 is filled with mineral or glass fibre wool. The cavity is preferably not less than 32mm thick.

According to the preferred form of the present invention the steel plates 3 will be a minimum of 2mm thick and the wood laminate layers 4 and 5 will be medium density fibre board of 3mm thickness. The framing members 1 will preferably be 67mm x 44mm pine framing.

The construction shown in Figure 1 has the advantage that the stiff steel layers 3 absorb the low frequency components of the spectrum whereas the outer wooden layers 5 spaced by the layer of foam material 6 absorb the high frequency components. Layer 5 is floppy, allowing sound to be absorbed efficiently. The o• relatively elastic layer 6 transmits little force to the rigid steel layer 3.

S° If wooden layer 4 is omitted the desirable .:characteristics of the present construction could still be obtained. However, in the referred embodiment a wooden layer 4 is provided.

S. wooden layer 4 is provided.

ee -9- It is to be appreciated that the dimensions hereinbefore mentioned are those considered to be the optimum dimensions, but these may be varied within manufacturing tolerances with the likelihood that significant degradation of soundproofing performance would not occur.

Referring now to Figure 2, a barrier according to the present invention is shown including a transparent panel therein. The transparent panel 10 may be useful when the barrier comprises a door, for example.

Due to the cavity 7 and layer 6 in the construction of e Figure 1, framing members 12 and imm foam tape strips 13 o•go are provided for structural support. Beading 14 is secured to door sections 11 by nails and adhesive. Preferably the adhesive is brittle so that the beading may be easily removed.

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Between the beading and transparent panel 10 are provided foam strips 15 which serve to decouple the transparent panel from the beading. A gap 16 is also provided to ensure that vibrations from the transparent panel 10 are S not transmitted through the framing members 12.

AIIC1I11111~ The layer of foam material 6 may be adhered to each of layers 4 and 5 by use of a suitable adhesive. For example, ethylene vinyl acetate polymer or polyurethane contact adhesives may be used.

It is seen that the invention provides soundproof barriers, such as doors, of conventional dimensions having good soundproofing characteristics whilst not being unduly heiry, and having improved surface flatness.

Where in the aforegoing description reference has been made to specific components or integers of the invention having known rquivalents then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and with reference to possible embodiments thereof it is to be understood that modifications or improvements *a* may be made thereto without departing from the scope of the invention as defined in the appended claims.

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Claims (12)

1. An acoustic barrier comprising: a frame to support covering layers; (ii) an inner rigid sheet on each side of the frame supported by the frame and defining a cavity between the inner rigid sheets and the frame; and (iii) outer sheets of greater elasticity than the inner rigid sheets, separated from and secured to the inner rigid sheets by a layer of foam material.

2. An acoustic barrier as claimed in claim 1 wherein each inner rigid sheet consists of a metal sheet whi 'i is bonded to one of the outer sheets.

3. An acoustic barrier as claimed in claim 2 whe 'i n the metal sheet is a steel sheet at least 2mm thick and the further sheet is about 3mm thick and formed of .medium density fibre board or plywood.

4. An acoustic barrier as claimed in any one of the preceding claims wherein the outer sheets are *o 1 II -12- medium density fibre board or plywood of about 3mm thickness.

An acoustic barrier as claimed in any one of the preceding claims wherein the cavity is filled with fibreglass batts.

6. An acoustic barrier as claimed in any one of the preceding claims 2 to 5 wherein the frame has rebates to support the metal sheet and the further sheet.

7. An acoustic barrier as claimed in any one of the preceding claims wherein the layer of foam material is about 2mm.

8. An acoustic barrier as claimed in any one of the preceding claims wherein the layer of foam material is relatively elastic.

9. A method of manufacturing a soundproof door comprising the steps of: providing a door frame; (ii) applying a layer of foam material to :two sheets of medium density fibre board or plywood; (iii) applying a further sheet of medium density fibre board, or plywood to each sheet of step (ii) over the layer of foam material; I -13- (iv) pressing both pairs of sheets of medium density fibre board or plywood together to achieve the desired spacing between the sheets; and affixing the pairs of sheets of medium density fibre board or plywood to steel sheets; (vi) affixing the bonded sheets of step to either side of the frame so that a cavity is defined between the steel sheets.

An acoustic barrier substantially as hereinbefore described with reference to the accompanying drawings.

11. A method of manufacturing a soundprc Jf barrier substantially as hereinbefore described with reference to the accompanying drawings. S S S S SO S S -14-

12- ~-Gt1GrGf~pStOl n u~uuS disclosed herein or referred to or inaica the specification and/or claims s application, individually o ectively, and any and all combinations -G9 y two o more of gsaip- ftp orfaturcs. ge ess, egs. 0S es S. S S S DATED this TWENTY FOURTH day of DECEMBER 1993 Winstone Specialty Products Limited by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s) OS S 0 S 55 SS S. S S S S. S S S 5* S. ABSTRACT The invention relates to an acoustic barrier comprising: a frame to support covering layers; (ii) an inner rigid sheet on each side of the frame supported by the frame and defining a cavity between the inner rigid sheets and the frame; and (iii) outer sheets of greater elasticity than the inner rigid sheets, separated from and secured to the inner rigid sheets by a layer of foam material. *oo