US 2990553 A
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July 4, 1961 R. E. ULRICH ETAL 2,9 0,553
EAR PADS Filed July 20, 1959 INVENTORS RUBERI E. ULRICH Emma Alanna United States Patent 2,990,553 EAR PADS Robert E. Ulrich, Riverton, and George A. Taylor, Gloucester, N.J., assignors to Radio Corporation of America, a corporation of Delaware Filed July 20, 1959, Ser. No. 828,310 9 Claims. (Cl. 2-209) This invention relates generally to devices for protecting the ears of a person from noise, and more particularly to improved, noise attenuating ear pads adapted to be disposed between the rigid ear cups of a noise protective device and the head of a person. The ear pads of the present invention are especially useful for personnel located in the vicinity of loud, ambient noises.
Discomfort and even loss of hearing have been induced in people by ambient noise levels approching 100 decibels and higher. Thus, the possibility of damaging their hearing presents a serious problem to all personnel who must work near high level noise operations. It has been proposed to attenuate ambient noises by providing personnel with ear cups having ear pads of soft rubber or of a plastic sheath containing a liquid. While these prior art devices have been useful in attenuating ambient noises appreciably and in relieving discomfort, they have not been altogether satisfactory. Moreover, it is desired to attenuate ambient noise still further than the attenuation afforded by the prior art pads.
In cases where liquid-filled ear pads of a plasticized material are used, it is found that the hair and body oils of a user removes the plasticizer from the plastic, liquid containing sheath. The plastic pads then readily deteriorate, so that their usefulness is relatively short lived. In many cases, especially where water has been used as part of the liquid filler within the ear pads, it is found that the liquid eventually evaporates through the plastic sheath walls.
Accordingly, it is an object of the present invention to provide improved ear pads for use with noise protective devices to efficiently attenuate ambient noise, and also which are relatively free from the aforementioned and other disadvantages of previously known pads.
It is a further object of the present invention to provide improved ear pads that have superior noise attenuating properties over ear pads of the prior art, and that resist deterioration with prolonged use.
Still a further object of the present invention is to provide improved ear pads having a filler that will remain operable to attenuate noise over a relatively wide range of temperatures.
It is another object of the present invention to provide improved, detachable, noise attenuating, ear pads that are relatively simple in structure, are easy to manufacture, and are highly efiicient in use.
In accordance with the present invention, the improved ear pads comprise tube-like sheaths of a plasticized plastic, each sheath preferably being partially collapsed and completely filled with a mixture of paste-like consistency. This mixture comprises a suspension of an inert powder suspended in a suitable medium, and which may comprise a colloidal suspension. The mixture may also contain, in addition to the suspending medium and the inert powder, a plasticizer for the plastic sheath. The plasticizer in the mixture serves to replace any plasticizer that may be removed from the plastic sheath by the hair and body oils of a person wearing the ear protective device. Deterioration of the ear pads is thus greatly retarded. Ear pads filled with the paste-like mixtures of the present invention have excellent noise attenuating properties, remain operable over a wide range of temperatures, and are more durable than prior art pads.
The novel features of the present invention, both as Patented July 4., 1961 to its organization and method of operation, as well as additional objects and advantages thereof, will be understood more readily from the following description, when read in connection with the accompanying drawings in which similar reference characters designate similar parts, and in which:
. FIG. 1 is a perspective view of an ear protective device employing improved ear pads according to the present invention; and
FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. I, viewed in the direction indicated by the arrows, and showing the internal structure of one of the ear pads of FIG. 1.
Referring, now, to FIG. 1, there is shown a noise protective device 10 having a pair of similar, rigid, circumaural ear cups 12 and 14 of plastic or other suitable material. Each of the ear cups 12 and 14 is mounted on a separate one of the two respective ends of a headband 16. The headband 16 comprises two generally parallelly disposed, resilient wires 18 and 20 held in substantially parallel alignment by a strip 22 of flexible material, such as rubber or a plastic.
The ear cups 12 and 14 are both formed, on the front portions thereof, with two, laterally extending apertured ears 24 and 26. The wire 18 extends at both ends thereof through the apertures of the respective pairs of ears 24 and 26. A bead 28 is fixed to each end of the wire 18 below the ear 26, and two beads 30 are fixed to the wire 18, each above a different one of the ears 24. A bead 32 is slidably and frictionally mounted on the wire 18 between each pair of the cars 24 and 26. The wire 20 is slidably connected to the rear portions of the ear cups 12 and 14 in the same manner as described for the wire 18. It will now be understood that the ear cups 12 and 14 may be slidably adjusted with respect to the headband 16 so as to dispose them around the ears and resiliently against the head of a wearer. Since the ear cups 12 and 14 and the ear pads therefor are similar, only the ear cup 12 and its associated ear pad 36 will be described hereinafter in greater detail.
The ear cup 12 is generally cup-shaped and large enough to fit around the ear of a person. The rim of the cup 12 is formed with a relatively wide, marginal flange 34 for the purpose hereinafter appearing. A liner 35 of sound absorbing material, such as isocyanate foam, may be disposed within the ear cup 12, as shown.
An improved ear pad 36 according to the present invention is mounted on the flange 34 of the ear cup 12 for disposition between the flange 34 and the head of a wearer. The ear pad 36 comprises a tube-like sheath 40 of pliable material having the general shape of the flange 34 forming the rim of the ear cup 12. The ear pad 36 is formed with a peripheral inwardly extending flap 38 which embraces the flange 34 for attaching the ear pad 36 to the ear cup 12. With this arrangement, the ear pad 36 may be easily removed from the ear cup 12, if necessary. The flange 34 fits between the flap 38 and the ear' pad 36. The sheath 40 of the ear pad 36 should be made from a material that has the property of remaining pliable over a long period of time. A polyvinylchloride plastic plasticized with a plasticizer of di Z-ethyl hexyl phthalate, hereinafter referred to as DOP, a trade name commonly used in the plastics industry for this plasticizer, has been found to be satisfactory. It will be understood, however, that other materials, and suitable softeners therefor, may be used within the purview of this invention.
The sheath 40 preferably is filled while in a somewhat collapsed condition, with a filler, such as a mixture 42, comprising a suitable colloid suspending medium, a plasticizer for the sheath, and a sufficient quantity of very finely divided, powder in aquantity sufficient to give the mixture a paste-like consistency.
Examples of suitable mixtures for filling and sealing within a sheath of polyvinylchloride plastic (Formula 2951 of the Bakelite Corporation, for example), 0.012 thick, containing about 38.26% DOP as a plasticizer, by weight, are:
Example 1 A mixture of aliphatic monoethers of polyoxyalkylene glycols and DOP in the proportion of 66-64% and 34- 36%, by weight, respectively, when the viscosity of said glycols is 5100 Saybolt seconds at 100 F., and suificient inert powder to give, the mixture a paste-like consistency. The aforementioned glycols are polyoxyalkylene monohydroxy compounds. A fluid known as Ucon SO-HB- 5100, a trademark of the Carbide and Carbon Chemicals Company, comprises a mixture of gylcols suitable for mixtures according to this example of the present invention. A description of these gylcols and methods of making them are described in US. Patent 2,425,755, issued on August 19, 1947, for mixtures of Polyoxyalkylene Monohydroxy Compoundsand Methods of Making Such Mixtures.
Example 2 A mixture of Coolanol 45 and DOP in the proportion of 4951% and 5149%, by weight, respectively, and a sufiicient quantity of inert powder to give the mixture a paste-like consistency. Coolanol 45 is a trademark of Monsanto Chemical Company for silicate esters of the orthosilicate type having a viscosity of about 12.2 centistokes at 100 F.
Example 3 A mixture of B01? and propylene glycol in the proportion of 1.8-2.2% and 98.297.8%, by weight, respectively, and a sufiicient quantity of inert powder to give the mixture a paste-like consistency.
An excellent powder for the mixtures forming fillers according to the present invention has been found to be a finely divided powder of calcium silicate known as Microcell E, a trademark of the Johns Manville Company. Microcell E is a synthetic calcium silicate produced by a hydrothermal reaction of diatomaceous earth with a source of calcium. An analysis of Microcell B shows it to be substantially:
Microcell E pours very easily because it does notordinarily cake. Inert powders of diatomaceous earth, talc, or powdered limestone also are suitable for mixing with suspending media such, for example, as described above to obtain a mixture of paste-like consistency. For the purpose of the present invention, paste-like mixtures having a viscosity within the range of 500 to 10,000 centipoises may be used as the mixture 42. For example, a mixture comprising 18 grams of Microcell E added to 100 grams of Ucon 50-HB-5100 mixed with DOP in the proportion of 65% and 35% respectively, by weight has been found suitable. The inert powder should preferably be ground fine enough to form a colloidal solution with the suspending medium.
In use, the resilient headband, 16 urges the ear pad 36 against the side of the head around the ear. Since the filler 42 of the ear pad 36 is of a paste-like consistency over a wide range of temperatures, the pad 36 quickly conforms to the contour of the wearers head. Body and hair oils of the wearer, however, have a tendency to remove some of the plasticizer from the plastic sheath 40. Unless this plasticizer, or some other suitable softener, is replaced in the plastic sheath 40, the sheath will deteriorate. The plasticizer in the mixture 42 serves to replace the plasticizer removed from the sheath 40 by the wearer. By the use of proper quantities, such as in the examples given, supra, an equilibrium may be maintained between the amount of plasticizer extracted from the plastic sheath 40 by the wearer and the amount of plasticizer donated to the plastic sheath 40 by the plasticizer from the paste-like mixture. Under these conditions, the ear pad 36 may be considered to be equalized.
A mixture of paste-like consistency for the plastic sheath 40, as described above, has been found to be superior to liquid fillers of the prior art from the standpoint of attenuating ambient noise, and also from the standpoint of prolonging the active life of the sheath container. For the purpose of the present invention, a mixture of paste-like consistency having a viscosity within the range of 500 to 10,000 centipoises may be used in the mixture 42.
From the foregoing description, it will be apparent that there has been described improved, circumaural, ear pads for a device for protecting personnel from noise. The mixtures of paste-like consistency described herein will retain their pliant, flexible state over a relatively wide range of temperatures, therefore being suitable for ear pads for plane and helicopter personnel. The ear pads of the present invention may also be used, in a smaller size, as direct-aural noise attenuators, that is, directily in contact with the human ear. While only a few specific examples of improved, equalized ear pads have been described, other equalized ear pads will, no doubt readily suggest themselves to those skilled in the art. Hence, it is desired that the foregoing shall be considered merely as illustrative and not in a limiting sense.
What is claimed is:
l. A pad comprising a sheath of plasticized plastic having a filler therein, said filler comprising a liquid, a powder substantially insoluble in said liquid and a plasticizer for said plastic sheath.
2. A pad comprising an endless, tube-like sheath of a plastic plasticized with di 2-ethyl hexyl phthalate, said sheath being filled with a mixture comprising a colloid suspending medium, an inert powder suspended in said medium, and di Z-ethyl hexyl phthalate.
3. A pad as defined in claim 2 wherein said medium comprises mixtures of polyoxyalkylene monohydroxy compounds.
4. A pad as defined in claim 2 wherein said medium comprises aliphatic monoethers of polyoxyalkylene glycols having a viscosity of substantially 5100 Saybolt seconds at F.
5. In an ear protective device of the type comprising a cup adapted to fit over an ear of a person and said cup being formed with a relatively wide pad receiving surface, an ear pad mounted on said surface and comprising an endless, tube-like sheath of a plasticized plastic having the general shape of said surface, said sheath being partially collapsed and filled with a mixture comprising a liquid, a powder and a plasticizer for said plastic sheath.
6. An ear pad as defined in claim 5 wherein said plasticizer is di Z-ethyl hexyl phthalate and said mixture comprises silicate esters having a viscosity of about 12.2 centistokes at 100 F., and wherein the proportions of said di 2-ethyl hexyl phthalate and said esters are 49-51% to 51-49%, by weight, respectively.
7. An ear pad as defined in claim 5 wherein said plasticizer is di 2-ethyl hexyl phthalate and said liquid is propylene glycol, and wherein the proportions of said di 2-ethyl hexyl phthalate and said propylene glycol are 1.8-2.2% to 98.2-97.8%, by weight, respectively.
8. In an ear protective device of the type comprising a cup adapted to fit around an ear of a person, and said cup being formed with a relatively wide pad receiving surface, an ear pad mounted on said surface and comprising an endless, tube-like sheath of plasticized polyvinylchloride plastic and having the general shape of said surface, and said sheath being partially collapsed and filled with a mixture comprising aliphatic monoethers of polyoxyalkylene glycols, an inert powder, and a plasticizer for said plastic.
9. An ear pad as defined in claim 8 wherein said plasticizer is di 2-ethy1 hexyl phthalate, and wherein the proportions of said aliphatic monoethers of polyoxyalkylene References Cited in the file of this patent UNITED STATES PATENTS 2,425,755 Roberts et a1. Apr. 19, 1947 2,666,208 Funk July 25, 1950 2,786,776 Allen Mar. 26, 1957 2,801,423 Shaw et a1. Aug. 6, 1957