DK165899B - EARNINGS OF ELASTIC POLYMER - Google Patents

Description

DK 165899B

The invention relates to an earplug of the kind specified in the preamble of claim 1 and which can be used as a hearing protector.

One of the best-known earplugs of this kind in the United States is 5 known by the name "V-51 R", and its construction is described in more detail in a report entitled "Development of an Extra Small and Extra Large Size for the V-51 R Earplug ", DT Blackstock and H.E. Von Gierke, April 1956,

Aero Research and Development Command, United States Air 10 Force, WADC Technical Report 56-142. This earplug was developed during World War II in order to create a better hearing protection for military personnel who were exposed to shock sound waves from e.g. cannon fire or explosions or particularly noisy work processes, such as at airports or aircraft maintenance facilities. The V-51 R earplug is made of an elastic elastomer, such as neoprene rubber, and has a single rearward collar extending from the nose end of a round rubber pin. The collar extending backwards from the nose of the round rubber pin has such a distance from it that a free annular space is formed between them. When the earplug is used, it is pressed into the ear canal, whereby the rear-facing collar is at least partially pushed into the free annular space and will form an acoustic seal against the narrow walls of the ear canal.

U.S. Patent No. 2,427,664 to J.Y. Dunbar and J.S. Knight, September 23, 1947 and U.S. Pat.

2,717,596, J.S. Knight, September 13, 1955, described a similar earplug as the V-51 R earplug described in the above-mentioned report by Blackstock et al.

In the U.S. Patent No. 2,427,664, FIG. 2 and 3, there is also shown an earplug having four plate-shaped collars whose diameters grow in sequence and extending substantially transversely from a supporting stem. As best seen in FIG. 3. all four collars of this construction are intended to be inserted into the ear

DK 165899 B

the corridor where they lie sloping backwards against their narrowing walls.

Unfortunately, earplugs of this kind described in the above-mentioned publications often have several drawbacks.

First, a lot of users will feel uncomfortable using such earplugs, even if used properly.

In general, this discomfort is experienced as a feeling of intense and unrelenting pressure against the walls of the ear canal, a pressure that can become so severe that it seems painful. A common user reaction to this discomfort is to pull the annoying earplug out of the ear canal to a point where the intense pressure being felt is relieved, and when this is done, the acoustic seal 15 between the earplug and ear canal will most often be broken or weakened, thereby destroying the desired effect of the earplug as a hearing protector or at least partially eliminating it. This is a highly detrimental deficiency, since the person in question appears to be sufficiently hearing-protected from the outside, while the real fact is that he or she may be completely unprotected. Second, because of well-known anatomical differences in size and shape among people's ear canals, including differences that occur frequently in an individual user, and naturally occurring size variations in a single ear canal, there will generally be a need for the earplugs are manufactured in a wide variety of sizes and are carefully placed by trained personnel to ensure that the earmuffs are sufficiently effective. Thus, the above-mentioned V-51 R earplug is currently manufactured in five different sizes, which according to the above-mentioned report by Blackstock et al. allows 80-85% of adult male users to use these earplugs. The need for earbuds to be manufactured in a variety of sizes will, of course, increase manufacturing costs and complicate production. The earplug according to the invention has several collars and can fit and constitute an effective hearing protection for the majority of the population with just a single size.

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DK 165899B

It is the object of the invention to provide an earplug of the kind mentioned above, which is more comfortable in use and which provides a better acoustic seal of the ear canal than hitherto known, and which with just a single size correctly and conveniently fits up to 98% of all 10 adult users.

This object is achieved in that the earplug is designed as defined in the characterizing part of claim 1.

Suitable details of the earplug of the invention are set forth in claims 2-16.

The annular free space between the inner surface of the skirt and the trunk is large enough for the skirt 20 to be pressed into it as the earplug is inserted into the ear canal.

An embodiment of the earplug according to the invention is shown schematically in longitudinal section in the drawing and will be described in more detail below with reference to it.

The earplug has a stem 1 and a row consisting of at least three rearwardly spaced and spaced apart collars 10, 20 and 30, each having a substantially circular cross-section. Each of the collars of the row has, from their attachment regions to the stem, a curved backward convex extent, which is preferably substantially hemispherical. By "substantially hemispherical" it is meant that the collars consist of not less than approx. 45% and 35 not more than 55% of a section of a hollow spherical body, the outer surface of which at all points has substantially the same distance from a single geometric center.

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DK 165899 B

The earplug of the invention can be made by any suitable polymeric material casting technique, e.g. injection molding. In order to obtain the desired benefits, the choice of the elastic polymer to be used in the preparation of at least the skirts 12, 22 and 32 of the respective collars 10 20 and 30 is of particular importance. This material must have a Durometer hardness (measured in accordance with ASTM 2240-81) of between 10 and 90 Shore A, preferably between 30 and 60 Shore A. The stem 1 may, of course, be made of an elastic polymer of the same type , which is used for collars skirts 12, 22 and 32, but it may also, if desired, be made of a resilient polymer having a somewhat higher Durometer hardness, e.g. up to about 100 Shore A. In a preferred embodiment, the stem 1 is made of a material having a Durometer hardness of between 50 and 70 Shore A. However, in another preferred embodiment, preferably the same polymer is used to facilitate the entire polymer. Mold.

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There are many known elastic polymers which are fully useful in the manufacture of the earplug of the invention. Eg. are natural rubber, neoprene rubber, SBR rubber, silicone rubber, EPDM rubber, polybutadiene, elastic polyurethane, elastic ethyl vinyl acetate, elastomers based on the acrylic acid precursor and elastic vinyl halides all fully suitable manufacturing materials which are generally marketed with D hardness, or which can be suitably composed (e.g.

30 by being internally and / or externally plasticized) to achieve the required hardness. Particularly preferred polymers are thermoplastic silicone rubber compositions such as a group of thermoplastic injection molding elastomers marketed under the trademark C-35 FLEX, Concept Polymer Technologies, Inc., Clearwater, Florida. These silicone rubber compositions are available with Shore A Durometer hardness in a wide range, the 5

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can be thermoformed in intricate shapes by ordinary thermoplastic molding processes, and the manufactured products can usually be sterilized or purified without damage. Another preferred manufacturing material 5 for the earplug of the invention is a thermoplastic SBR block copolymer which is manufactured and sold in various grades under the trademark KRATON of the Shell Chemical Company, Synthetic Rubber Division, NY, NY.

The first collar 10 extends outwardly in the rearward direction from the face 3 of the stem 1, forming a uniform, thin skirt 12, which is in its entire extent spatially separated from the underlying portion of the stem 1. The second collar 20 extends extends outwardly in a backward direction from a first intermediate region along the stem 1, forming a uniform thin skirt 22 which, throughout its extent, is spatially separated from the portion below the stem 1. Correspondingly, the third collar 30 extends outwardly in backward direction from a second intermediate region along the stem 1, forming a uniform, thin skirt 32, which is, in its entire extent, spatially separated from the underlying portion of the stem 1. As shown in the drawing, the roots 16, 26 and 36 are the respective skirts 12, 22 and 32, or in other words, the transitions between the inner sides of the skirts and the stem 1, preferably formed such that the radii between these parts is kept to a minimum of what is compatible with good casting practices, so as to minimize the thickness and the stiffness of the material at these junctions. This construction characteristic of the invention not only ensures that the skirts 12, 22 and 32 obtain the greatest possible flexibility at the root parts, but also the skirts 12, 22 and 32 can be desirably extended beyond their connecting regions with the stem, so that the skirts 35 easily can be tilted from their normally backward position to a forward position. In this forward position, the inside of the skirts and the pieces are on

DK 165899B

The 6 trunk, which usually lies beneath the skirts, is exposed, so that the user can easily inspect and / or clean areas of the earplug that are not normally visible.

As can be seen, the diameter of the hollow collars 10, 20 and 30 grows in sequence, and in a preferred embodiment of the invention, the collars are spaced along the stem 1 in such a way that it is possible to draw a straight line L , which on the finished earplug touches 10 each of the collars in the collar row. Furthermore, in this preferred embodiment, the diameters of the collars and the distance between them are selected such that the angle of intersection e between the line L and the extension of the center line CL of the stem 11 is in the range between 10 ° and 16 °, preferably between 12 °. and 14 °. By adhering to these dimensional criteria, it is ensured that the earbuds can be used and be effective for the vast majority of users.

For example, when the cutting angle Q is 130, the collars generally hemispherical and the radius of the first collar 10 20 approx. 4.19 mm, it has been found that the earplug according to the invention can form an effective acoustic seal for up to 98% of all adult users, incl. women.

In this connection, it is convenient that the distance 25 between claims 10, 20 and 30. along the stem 1 is such that the trailing edges 14 and 24 of the skirts 12 and 22 are coupled to or preferably overlap the nose end of the subsequent collar.

It will be appreciated by those skilled in the art that many of the functional advantages of the invention are at least in part due to the fact that the design collars are so designed that they can be deformed elastically as much as necessary in the practice of relatively small and substantially linear forces exerted by or against the walls of the ear canal when the earplug is inserted into it. Thus, a complicated interaction exists between the specific

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7, the specific geometry and the size of the parts of the earplug assembly and the hardness or hardness of the resilient polymer (s) used to make the earplug. In addition, it is not only important that the material used for each of the skirts 12, 22 and 32 has a Durometer hardness of between 10 and 90 Shore A, as it is equally important that the thickness of each these skirts 12, 22 and 32 are in the range of 0.20 mm to 1.27 mm. No specific design rules can be established in this regard, but generally the thickness of the skirts 12, 22 and 32 may be greater, the softer the material of manufacture. When this has a Shore Durometer hardness of between 30 and 60 Shore A, it has been found that the advantages of the invention are usually substantially 15 obtained by thicknesses of the skirts 12, 22 and 32 of between 0. 76 mm and 0.30 mm. The correct balance between the thickness of each of the skirts 12, 22 and 32 and the Shore A Durometer hardness of the elastic polymer from which the earplug is made can be easily determined experimentally. In a preferred embodiment of the invention, it has been found that a nominal thickness of approx. 0.50 mm of each of the skirts 12, 22 and 32 and use of an elastic polymer having a Durometer hardness of approx. 40 Shore A, provides an earplug that has an excellent overall combination of effective acoustic and comfortable user characteristics.

As mentioned above, the diameter of the piece of the stem 1 which lies below each of the skirts 12, 22 and 32 of their respective collars 10, 20 and 30 is selected such that annular, free spaces 11, 21 and 31 are formed below them. which the skirts can bend into when the earplug is inserted into the ear canal. The specific dimensions of the annular free compartments 11, 21 and 31 are not very critical, but of course 35 must be sufficient for the annular compartments to serve the above purpose. Generally, however, it is desirable that each of the

DK 165899B

8, free space has a size measured transversely and determined by subtracting the diameter of the underlying stem from the inner diameter of the open end of the skirt and dividing the result by two, at least twice the thickness of the skirt in question , 12, 22 and 32, which surround the room. By "annular free space" is meant that the annular space 11, 21 and 31 does not contain parts or materials that could interfere with or hinder the movement of the associated skirt into the space.

The earplug of the invention may also have a stem 1 having the same diameter throughout its length. In this case, however, having regard to the annular free space under each of the collar skirts, the diameter must be dimensioned on the basis of the annular free space under the smallest skirt, ie. skirt 12 at collar 10's nose. As a result, it has been found that the earmould thus formed, except in cases where the constant diameter stem is made of a relatively rigid elastic polymer, such as e.g. having a Durometer hardness of more than 50 Shore A, may appear quite flaccid in the stem 1, and that it does not provide sufficient support for the second and third collars 20 and 30 to be readily inserted into the ear canal by hold in the trunk. As a rule, it is therefore preferred that the diameter of the stem 1, especially when made of a material having a Durometer hardness of less than 50 Shore A, smoothly advancing or in section collar for collar, is increased in the backward direction so that that the stiffness of the pieces of the strain carrying the collars 30 is made progressively stiffer evenly or in sections.

In order that the earplug of the invention can be easily inserted and retracted from the ear canal, it is convenient that the stem 1 extends backwards from the edge 34 of the rear collar 30 to a suitable length so that this rear part of the stem forms a handle 42 , which is easy for the user to grasp with thumb and forefinger.

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DK 165899 B

It is regularly desirable to have earplugs in pairs that are linked together by a flexible piece of line.

A structure in which the earplugs are thus linked together may serve to prevent the earplugs from accidentally falling or lost. This can be of great importance, e.g. when the earplugs are used in environments where food is industrially prepared, or in environments where a lost earplug may very well be so dirty that it may be considered useless or completely lost. In order to provide such an interconnected earplug assembly, the free end 40 of the stem 1 may be provided with an axially extending hole or channel 41, the size of which is adapted to accommodate the end of a piece of flexible line (not shown). The line may be secured to the hole or opening 41 in any suitable manner, e.g. by means of melt or thermal welding, by means of suitable adhesives, or by using a line whose ends have a slightly larger diameter than the diameter of the hole or channel 41 which serves to receive the line end, so that the the resilient polymeric material surrounding the hole or channel 41 is resiliently secured in a secure manner. Further embodiments of interconnected earplugs of this kind are known from the following US Patent Nos. D-241,881, No. 4,193,396, no.

25 4 219 018 and No. D-245 202.

The earplug according to the invention is described above in an embodiment in which it is used individually, but it can also be used as an earplug in a hearing protection device consisting of a generally U-shaped spring headband to which the free ends of the earplugs are fastened inwards. In this embodiment, the earplugs of the invention are inserted into the user's ear canals where they are retained under the sustained inwardly directed lateral pressure 35 of the resilient headband. Further embodiments of hearing protectors of this kind are known from U.S. Pat.

4,461,290 and UK Patent No. 1,355,052.

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In order to illustrate the invention, a number of earplugs with three collars were made using the above-mentioned design principles and in the main proceedings in accordance with the drawing, which may only be regarded as 5 samples which do not limit the scope of the invention. These samples were prepared by injection molding a thermoplastic silicone rubber (C-FLEX elastomer) having a 40 Shore A. Durométer hardness. Referring to the drawing, the earplugs had the 10 dimensions listed below:

Total length of stem 1 30.05 mm

Diameter of stem 1 at end 40 5.15 mm

Diameter of the stem 1 under the skirt 32 5.15 mm 15 Diameter of the stem 1 under the skirt 22 4.78 mm

Diameter of stem 1 under skirt 12 3.40 mm

Radius of the hemispherical collar 10 4.19 mm

Radius of the hemispherical collar 20 5.15 mm

Radius of the hemispherical collar 30 6.48 mm 20 Axial length of the hemispherical collar 10 4.42 mm

Axial length of the hemispherical collar 20 5.23 mm

Axial length of the hemispherical collar 30 6.65 mm

Thickness of the skirts 12, 22 and 32 0.48 mm

Distance from nose 3 to edge 24 9.78 mm 25 Distance from nose 3 to edge 34 16.48 mm

Cross dimensions of the annular space 11 2.16 mm

Cross dimensions of the annular space 21 2.28 mm

Cross dimensions of the annular space 31 3.43 mm

Cutting angle ø 130 30 The earplugs were tested in accordance with the test procedure specified by ANSI S3.19-1974. In the first test series (hereafter referred to as the "maximum comfort test"), the subjects were instructed to insert only the 35 earplugs into the ear canals to the point where they felt the greatest comfort. In the second test series (hereafter referred to as the "maximum damping test"), the

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u of the earplugs individually adapted to each specimen by a trained technician to the point where maximum acoustic seal was obtained. The maximum comfort sample gave an NRR value of 22, while the maximum attenuation sample gave an NRR value of 25. During the run of the maximum comfort sample, subjects were asked to rate the relative comfort of the fitted earplugs on the following scale: -

SCALE FOR THE CONSIDERATION OF THE COMFORT OF HEARING PROTECTION

Very comfort- comfort- comfort- painful belt indefinitely full, _ 012 34567 8 9 10

15 II II

The comfort provided by the earplug of the invention was judged by the subjects to be about 3.

In comparison, a similar series of experiments were conducted with the same subjects, who in this case used a commercially known earplug with multiple collars. The maximum grain strength sample gave an NRR value of just 16. The maximum attenuation sample gave an NRR value of about 23.

The average comfort provided by these commercially traded earbuds during the maximum grain fort sample was rated to be about 4.

Another maximum comfort test was performed with the same subjects and this time with another commercially negotiated known earplug with several collars. The NRR value was approx. 13, and the earplug average comfort was rated to be around 6.

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Claims (1)

40 Shore A and their thickness is approx. 0.50 mm. Earplug according to claim 1, characterized in that the diameter of each part of the trunk (1) which lies below a respective skirt (12, 22, 32) is larger in the rearward direction collar part by collar part. Earplug according to claim 7, characterized in that the elastic polymer from which the stem (1) is made has a Durometer hardness of less than approx. 50 Shore A. 20 An earplug according to claim 1, characterized in that the elastic polymer from which the stem (1) is made has a Durometer hardness of between approx. 50 and 70 Shore A. The earplug according to claim 1, characterized in that the distance across each of the annular free spaces (11, 21, 31) is at least twice the thickness of the associated skirt (12, 22, 32). . Earplug according to claim 1, characterized in that the stem (1) extends so far backward from the last collar (30) that the length becomes sufficiently large to form a grip (42) for handling the earplug. Earplug according to claim 11, characterized in that the free end of the stem (1) has an axially extending hole (41) having a size adapted to accommodate an end of a flexible line acting as a link for 14 DK 165899B earplug. Earplug according to claim 1, characterized in that the transition (16, 26, 36) between the innermost part of the skirt (12, 22, 32) on each of the collars (10, 20, 30) in the collar row and stem (1) has such a small radius that the thickness of the material at this transition becomes of limited size so that the skirt is able to be manually tilted to a forward position, with the inner surface of the skirt and the lower portion of the stem is exposed. Earplug according to claim 1, characterized in that it is made of a thermoplastic silicone rubber. Earplug according to claim 1, characterized in that there is such a gap between the generally hemispherical collars (10, 20, 30) along the stem (1) that the trailing edge (14, 24, 34) of each collar (12) , 22, 32) 20 is at least coplanar with the nose end of the subsequent collar. Earplug according to claim 1, characterized in that there is such a gap between the generally hemispherical collars (10, 20 ^ 30) along the stem (1) that the trailing edge (14, 24, 34) of each collar skirt (12, 22, 32) slightly overlaps the nose end of the subsequent collar. 30 35