WO1995009515A1

WO1995009515A1 - Acoustical speaker cover

Info

Publication number: WO1995009515A1
Application number: PCT/US1994/001472
Authority: WO
Inventors: Teresa R. Czerwinski
Original assignee: W.L. Gore & Associates, Inc.
Priority date: 1993-09-30
Filing date: 1994-02-09
Publication date: 1995-04-06
Also published as: AU6548894A

Abstract

A covering for an acoustical speaker is described in which the cover is made of a substrate that passes sound waves, said substrate being coated with an organic polymer having recurring pendant fluorinated organic side chains.

Description

TITLE OF THE INVENTION

ACOUSTICAL SPEAKER COVER

FIELD OF THE INVENTION

This invention relates to a new acoustical speaker cover and to speakers utilizing the cover.

BACKGROUND OF THE INVENTION

With the increasing popularity of portable telephones, radios, and the like, it has become increasingly important to protect the interiors from water. One region of vulnerability to rainwater or to attack in underground or underwater speakers is the openings through which sound is emitted. This opening is commonly covered with a fabric, membrane, or plastic through which sound waves pass. It has proven difficult to find such a cover that has a desired combination of properties. Plastic or metal materials tend to have distorted sound. Fabrics, such as knits, wovens, or nonwovens, tend to be pervious to water which can cause a change in acoustical tone and which allows water to reach the interior of the speaker.

It is a purpose of this invention to provide an acoustical cover for speakers which has good acoustical transmission and good water repellancy.

SUMMARY OF THE INVENTION

In acoustical speakers comprising a speaker housing having an opening, an acoustical transmission device within said housing, and an acoustical cover covering said opening, this invention is an improvement wherein the acoustical cover comprises a substrate such as a fabric, coated with a coating composition that is an aqueous dispersion of an organic polymer having recurring pendant fluorinated organic side chains. BRIEF DESCRIPTION OF THE DRAWINGS

The figure depicts an acoustical speaker 10 with an acoustical filter 11 covering the opening where sound waves are transmitted.

DETAILED DESCRIPTION OF THE INVENTION

The cover can be used with any device for receiving or transmitting audible signals to another acoustical device. Examples include such devices as speakers, microphones, horns, beepers, and the like. The cover is a protective cover that protects the opening through which sound waves pass. The substrate can be made of any material that permits transmission of sound waves. Fabric material is preferred although plastic membranes are acceptable. Fabric materials include knits, wovens, nonwovens and the like. The material can be made of synthetic or natural materials. Fabrics of synthetic fibers such as polyester, polyamide, polypropylene and the like are used. A preferred material is Sontara^® polyester nonwoven fabric. The substrate, in addition to fabrics, can be a scrim, paper, or porous polymeric membranes of any form including sheets or.tubes. The coating compositions are prepared by dispersing the organic polymer having perfluoroalkyl-containing side chains in water. Such polymers include those made from monomers such as: fluoroalkyl acrylates and fluoroalkyl ethacrylates of the formula 0

wherein n is a cardinal number of 3-13 and R is H or CH3; fluoroalkyl aryl urethanes, for example

fluoroalkyl allyl urethanes, for example

0 CF₃(CF₂)n-CH2CH2-0-C-N-CH2-CH=CH2;

H fluoroalkyl maleic acid esters, for example

0 CH3(CF₂)_n-CH2CH2-0-C-CH=CH-C00H; fluoroalkyl urethane acrylates; fluoroalkyl acrylamides; fluoroalkyl sulfonamide acrylates and the like. Preferably the fluorinated alkyl moieties will have 6-16 carbon atoms and most preferably 6-12 carbon atoms.

Aqueous dispersions of some of these perfluorinated polymers are available commercially. For example, Milease F-95 from ICI Americas, Inc. is a particularly useful polymer. It is a perfluoroacrylate resin mixed with water and with a small amount of dipropylene glycol .

The polymer so produced can be applied directly from the colloidal dispersion by immersing the substrate material into the dispersion, or by painting the substrate with the dispersion, or by spraying the dispersion onto the substrate.

Once the coating is applied to the substrate, any water, or other component can be drawn off by any convenient means, such as heating, steam stripping, vacuum evaporation or the like. The substrate may contain various other additive ingredients to impart specific properties to the product or to act as process aids. For example, it may contain ultraviolet light stabilizers, bacteriostats, and the like.

The resulting coated products exhibit good hydrophobic and oleophobic properties while having good gas or air flow through the material.

The coated material permits transmission of good quality audio signals through it, while preventing water or other materials from entering. Generally, the fabric thickness will range from 0.005 inch (0.127mm) to 0.030 inch (0.76mm).

EXAMPLE

Example 1

In this example a polyester fabric, was used. It was a nonwoven dark grey Sontara 8005 obtained from Precision Fabrics, Inc. It was 2.0 oz. per square yard and was 25 mils thick. The coating composition was a perfluoroacrylate resin in water (Milease F-95), along with small amounts of stabilizers and surfactants.

Sheets of the Sontara polyester were pad coated for a time sufficient to produce a desired "add-on" amount of coating. The coated samples were heated at 150°C for a minimum of 20 seconds.

In this coated material, the water repellancy was determined by placing the coated material under 3 inches of water over it and observing water penetration on the other side. After 48 hours, no penetration was observed.

Claims

I CLAIM:

1. An acoustical speaker cover for covering the opening of an acoustical speaker, in which the speaker cover comprises a substrate that passes sound waves, said substrate being coated with an organic polymer having recurring pendant fluorinated organic side chains.

2. The speaker cover of Claim 1 in which the substrate is a fabric.

3. The speaker cover of Claim 2 in which the fabric is made of a polyester.

4. The speaker cover of Claim 2 in which the fabric is a nonwoven fabric made of a polyester.

5. The speaker cover of Claims 1, 2, 3, or 4 wherein the organic polymer is a perfluoroacrylate.

6. In an acoustical speaker having an opening for the transmission of sound, the improvement in which the opening is covered by a cover that is comprised of a substrate that passes sound waves, said substrate being coated with an organic polymer having recurring pendant fluorinated organic side chains.

7. In the speaker of Claim 6, the improvement in which the cover is a polyester fabric coated with a perfluoroacrylate.