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Publication numberUS2672863 A
Publication typeGrant
Publication dateMar 23, 1954
Filing dateMay 29, 1951
Priority dateMay 29, 1951
Publication numberUS 2672863 A, US 2672863A, US-A-2672863, US2672863 A, US2672863A
InventorsCharles Leight
Original AssigneeCharles Leight
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Ear plug and sound absorbing material construction
US 2672863 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

March 23, 1954 c. LEIGHT 2,672,863

EAR PLUG AND SOUND ABSORBING MATERIAL CONSTRUCTION Filed May 29,' 1951 removal of the plug from the ear canal.


Application May 29, 1951, Serial No. 228,851

2 Claims. 1 Thisvinvention relates to sound absorbing devices, and particularly to an ear plug adapted to decrease or attenuate the amplitude of sound waves reaching the ear drum of a person.

The use of ear plugs to prevent auditory injury and noise fatigue are well-known, and plugs for attenuating the amplitude of sound waves reaching the ear have been used in different occupations. Ear plugs are also worn by aviators, in which case the plugs should be of a type which are comfortable when worn under headphones.

The construction of the present plug is of the general type disclosed and claimed in my U". S. Patent No. 2,446,707.01 August 10, 1948. This prior plug is in the form of a cylindrical body tapered at one end and having a right-angle handle section to facilitate the insertion and The present plug has two general over-all shapes.

One is of the type shown in the above mentioned patent, and the other is one whereby the external form is modified for improving the fit of the plug in the ear.

The primary feature of the present plug is a filler insert made of a special formula spongy sound absorbing material to improve the selective absorptivity of the sound waves. The insert may be in two sections, as shown in the patent, or may be a single unit. The plug is provided with pressure equalizing vents and an opening which aids the transmission of the lower frequencies to permit almost normal conversation while protecting the ear from harmful noise amplitudes and frequencies.

The principal object of the invention, therefore, is to facilitate the selective attenuation of sound amplitudes and frequencies to the ear.

Another object of the invention is to facilitate the fit of a sound absorbing ear plug in the ear.

A further object of the invention is to provide an improved ear plug which absorbs the harmful noise while permitting the plug to be worn under earphones.

A still further object of the invention is to provide an improved method of constructing an ear plug which is comfortable in the ear at all times and which is particularly efficient in the absorption of harmful sound waves while permitting almost normal conversation.

A still further object of the invention is to provide an improved method of producing a selective sound absorber for ear plugs.

A still further object of the invention is to pro- Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the appended claims, the manner of its organization and the mode of its operation will be better understood by referring to the following description, read in conjunction with the accompanying drawings, forming a part hereof, in which:

Fig. 1 is a perspective view of one form of ear plug embodying the invention.

Fig. 2 is a sectional view, partly in cross-section, of the plug shown in Fig. 1.

3 is an expanded view of the plug shown in Figs. 1 and 2 showing the selective sound absorbing insert.

Fig. 4 is a perspective view of a second modification of an ear plug embodying the invention, and

Fig. 5 is a sectional view, partly in cross-section, of the ear plug of Fig. 4.

Referring now to the drawings, in which the same numerals identify like elements, the plug is vide an improved sound absorber for ear plugs.

formed of a thin outer shell or skin 5 of flexible material, such as sheet rubber, obtained by molding, the tip of the plug having pressure equalizing vents 6. Molded to the skin section 5 and as an integral part thereof is a handle formed with a section 1 at right angles to the longitudinal axis of the plug, and a section 8 at right angles to section I and parallel to the longitudinal axis of the plug. The section 1 is tapered from opposite points on the circumference of the larger diameter section of the skin section 5 to the width of the rectangular tab section 8.

As shown in Figs. 1, 2, and 3, one end of the plug is pointed in an oval or bullet shape, while the skin section is of two diameters, the section I0 having the point formed at one end thereof.

Section in is of a smaller diameter than the section II, the variation in diameters being approximately one-sixteenth of an inch. That is, the smaller section ID for a medium sized plug is approximately six-sixteenths of an inch in. diameter, and the diameter of the larger section. II is approximately seven-sixteenths of an inch. For other sizes of plugs, these dimensions areproportional. The length of the tab section 1 for a plug having the above dimensions is oneeighth of an inch, and the length of the section 8 is three-sixteenths of an inch. A two-sectioned plug of this type has been found to be easily insertable and removable from the ear, while providing a snug fit to prevent the passage of sound waves around the plug.

Referring now to the plug shown in Figs. 4 and 5, this plug has a skin section I4 of the same type as the skin section 5 of the first modification, and also, has the same form of integral tab with sections I5 and I6; It also has equalizing vents H. Th diiference between the plugs in Fig. 1 and in Fig. 4 is in the shape of the skin section [4. It has been found that the ear canal is such that a betterfit fonmany ear canals is-generally accomplish d the. sla eer diameter s ct on" l similar to section II in Fig. 1, extends only one- That is, one-half of the plug divided lengthwise is cylindrical from th open end 0f-'- t hetskin leto the point, while the other half varies in diameter 20, and then baked at a temperature of substantially 250 degrees Fahrenheit for approximately eighteen minutes. This time has been varied between fifteen and twenty-five minutes with satisfactory results. After the inserts are cured, they are punched from the mold. Although cellulcse is preferred, finely ground cork has been usedwith satisfactory-results.

vrizf heaaboveeear plugsgitheretorei *are particu- 10 larly efficient in absorbing an adequate proporhalf way around the circumference of the plug I tion of harmful noise to reduce the noise level to a safe value. The ear plugs are safe, comfort- -,able,g; and invisible, and may be worn with com- "fortat work or during sleep. Ventilation is prosimilarly to the plug of Fig. 1. Thatis section e 5 videdtqlthe inner ear to avoid dizziness, and the IQ divided transversely is the same as section in of the plug in Fig. 1, while section-118 is onl-y onehalf of section II. This provides an improved. wedging action, inasmuch as the tab is always placed toward the backof the ear.

The primary improvement of;th ;p lugs above described is provided-by-the use of a ,newform of absorbent filler insert shown atin. both plugs; This material is molded'to-fitthe internal form of either skin 5- 0r-l4, the form-forFig. 1 being shown in perspective in Fig. 3.; Theginsert :20 has ahole 2| therein extending"axiallyofthe plug for a short distance ;therein."- Thisopening has been found'to aid-'the-passage of the lower frequencies to the ear -drum, and thus, permit almost normal conversation while 'the" plugs are being worn, the plugsattenuatingthe;higher;amplitude levels-andfrequencies of the sound waves. This opening, along Withvents 6; aids in; pressure equalization as well as permitting f-breathing" -of the plug for ventilation.

The plug- 20- is made fromdatex foamrubber impregnated with flocculated cellulose. To -produce the soundabsorbing-insert 20; the latex foam may be made in'accordance-with several standard formulas. The formula used herein consists of approximately sixty-five;-percent of dry latex by weight-to approximately "thirty flve percent of other-ingredients. These other-im ingredients are a soap solution to produceemulsi- :7 ficationand frothing, accelerators and sulfur for curing or vulcanization, a protective colloid for stabilization, an= anti-oxidantfor optimum aging, a metallic salt-to activate curing,- a-colorcarrier -=to provide the desired opacity,-a color-pigment, and a gellation material to control-coagulation of the-foam.

solution is mechanically mixed with? the 'r flocculated cellulose-at the ratio'of' on hundred parts of the dry latex rubber component-to three to twenty parts ofcelluloseby weight. After the liquid--latex foam and cellulose are thoroughly .mixed, themixture is poured into a die-of"-;the

. proper shape to form an insertsuch as shown at plugs are shaped to provide a beveled wedging -=action insuring=- one hundred percent eiiiciency ,atifillvtimes. The special type of insert material has been found to have the ability to absorb the 20 higher frequencies of sound waves, I while xpermitting' the lower frequencies f conversatiOn to I penetrate to; the ear." Therefore it is unnecesyt m ve t e uss f r normal convers tion.

e a me -m d ma. fo m. tb t t a ticular internal shape of the skin or shellportion of ,1 the plug. The: inserts generally remain fixed in their shells after insertion, buta spot 'of glue may be a plied at, the; time, Of insertion;to

36 insure their remaininginposition.

I claim:

, 1. In an ear devicehaving a shelLanjnsert j plug comprising i asolid integral member formed -;-o f a-vulcanized mixtur of liquid latex foam; and

-;-cel1ulose, said member beingshapedto'fitithe -i-nterioriof the shell.

'- 2; In a plugffor-an:eardevice, a solid'-integral member having latexfoam and cellulose mixed so as to absorb soundwaves of-relativelybh'igh 0 frequeneieswhile permitting the passage" 'jof sound waves of lower "frequencies," said member being provided with an axially extending hole for ventilating the plug.


References: Cited iinthe :file- *of this patent "U ITED STATESFATENTIfi "Name 7 Number ,135,9 2

, cgeaqov 2,498,785

.12.568366. 0sterhof,Leanne. .,m, f.

FQREIGN PATENTS Num e Cou try Date iv 1,387 1. GreatBritam b11888

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2875088 *Oct 28, 1954Feb 24, 1959DegussaMethod of improving porous films of plasticized vinyl polymers
US3736929 *Jul 9, 1970Jun 5, 1973Mills ASelf-shaping earplugs
US3872559 *Jan 11, 1973Mar 25, 1975Leight CharlesEar plug
US3881570 *Aug 6, 1973May 6, 1975Marion Health And Safety IncSelf-fitting hearing protector
US3915166 *Apr 23, 1974Oct 28, 1975Mccrink Frank PEarplug attached to an elastic band
US4160449 *Sep 28, 1977Jul 10, 1979Wade Kenneth LEarplug
US4326512 *Feb 14, 1980Apr 27, 1982Peerless Sidney AComposite ventilation tube for the middle ear
US4498469 *Sep 30, 1981Feb 12, 1985Gullfiber AbEar plug as well as a method and apparatus for the production thereof
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US4614487 *Oct 2, 1984Sep 30, 1986Gullfiber AbEar plug as well as a method and apparatus for the production thereof
US5044463 *Nov 30, 1989Sep 3, 1991Cabot CorporationMolded foam earplug and method for making same
US5799658 *Aug 15, 1996Sep 1, 1998Cabot Safety Intermediate CorporationHearing protective device comprising a foam and a porous component and method of manufacture thereof
US5904143 *Oct 21, 1996May 18, 1999Magidson; MarkFoam earplug with non-permeable elastomeric coating
US7510046 *Dec 2, 2005Mar 31, 2009Cabot Safety Intermediate CorporationLow attenuating push-in earplug with integral handle
US20040045558 *Sep 6, 2002Mar 11, 2004Duncan TaylorEarplug and method of manufacturing an earplug
US20060169291 *Feb 3, 2005Aug 3, 2006Yuichiro ShiraiEarplug
EP0050601A1 *Sep 30, 1981Apr 28, 1982Gullfiber AbEar plug as well as a method and apparatus for the production thereof
EP0836840A2Sep 5, 1997Apr 22, 1998Moldex-Metric, Inc.Foam earplug with non-permeable elastomeric coating
WO1991007914A1 *Nov 21, 1990Jun 13, 1991Cabot Safety CorpMolded foam earplug and method for making same
U.S. Classification128/867
International ClassificationA61F11/00, A61F11/08
Cooperative ClassificationA61F11/08
European ClassificationA61F11/08