Detailed Description
Fig. 1 is a cross-sectional view of an earplug 10 of the invention, the earplug 10 including a stem 12 extending in a forward direction F and a rearward direction R along a stem and earplug axis 14. The handle 12 has a forward portion 16 and a rearward portion 18. The front portion carries 3 flanges 21-23 for sealing against the wall of the ear canal of a person. The handle rear portion 18 serves as a handle for pushing the flanges into the ear canal and subsequently pulling them out. The flanges are thin, having a radially inner end 30 joined to the shank (on their front faces) and a free radially outer end 32.
The flange and stem are integrally molded and are generally made of the same elastomeric material, such as a material having a durometer of 30Shore a. The elastomeric material is a material having a Young's modulus of elasticity of no greater than 50,000 psi. It is desirable to mold the stem from a harder material (harder) to facilitate insertion of the stem into the ear canal and to mold the flanges from a softer material (less hard) so that the flanges are pressed against the ear canal with less force to increase comfort. However, the above-described effects have not been obtained at low cost heretofore.
In accordance with the present invention, applicants molded earplugs from a resilient material that varied in hardness between the time the earplug was initially inserted into the ear canal and perhaps 1 minute later. Applicants have used materials that have a significant decrease in stiffness as the temperature of the material increases from room temperature, such as 72F, to body temperature, such as 100F, present in a human ear canal. If the earplug is in a room at room temperature (e.g., 72F.), it has a predetermined hardness, such as 30Shore A, providing sufficient hardness to the stem to insert the flange into the ear canal without compression of the stem. The flange is initially uncomfortable. However, after about 1 minute of attachment of the flange to the ear canal, the temperature of the flange will increase to near body temperature (about 100F.) and the hardness of the earplug material will decrease to perhaps 26Shore A, so that the flange is pressed against the ear canal with less force and the earplug will be more comfortable. In industrial applications, the earplug may be worn for 110 minutes at a time, and some discomfort around the first minute may be easily tolerated.
The particular earplug 10 shown in FIG. 1 is formed of a Styrene Block Copolymer (SBC) elastomer using a mixture of a low glass transition temperature SBC (e.g., -60 ℃ to-75 ℃) and a high glass transition temperature SBC (e.g., -25 ℃ to-10 ℃). Applicants have fabricated earplugs having the structure shown in fig. 1-3 and have found that this material results in an earplug that is relatively easy to insert into the ear canal and results in (on the order of about 1 minute) less pressure being applied to the ear canal and thus is very comfortable. After inserting the earplug into the ear canal and waiting about 30 minutes, applicant pulled the earplug out, and found that the outer diameter of the flanges (or at least the flanges that had been inserted into the ear canal and deflected to a smaller diameter) was slightly reduced. However, in much less than 30 minutes, when the earplug has cooled to room temperature, the flange returns to its original size and shape. Mixing of SBC elastomer materials of different transition temperatures will result in such continued compression at 100 ° F (e.g., the diameter of the largest flange 23 drops from 12.5 mm to 12 mm) and provide further comfort.
Further testing of the earplug showed that the stiffness of the earplug material decreased as the material was heated in the ear from about 72 ° F to about 100 ° F. The hardness drop (from 30Shore A at 72F) was more than a factor of 30 (i.e., greater than 3.3%), with the hardness at 100F actually being 26Shore A. Thus, when the earplug is inserted (72F), the stem is relatively stiff, allowing the stem to be inserted without compression of the stem, however, once the earplug is inserted, the stiffness decreases, resulting in a softer flange that presses with less pressure against the ear canal, resulting in greater comfort. As the temperature is increased from 72F to 100F, the hardness should decrease by at least 1Shore A or at least 4%, preferably by at least 2Shore A or at least 8%, and most preferably by at least 3Shore A or at least 10%.
Not only does the material become less stiff, the material appears to temporarily deform as the outer diameter of the flange is found to have decreased as measured immediately after removal of the earplug from the ear canal. This results in the flange pressing against the ear canal wall with less pressure. However, the material appears to have memory because when the earplug is removed from the ear canal, the earplug cools slowly to room temperature and the flange outer diameter returns to the original diameter that existed prior to the first insertion.
Thus, the above-described styrene block copolymer elastomer apparently reduces the pressure exerted by the flange on the ear canal in two ways. One way is by decreasing in hardness as the temperature increases from room temperature to body temperature. A second way in which the material increases comfort is that when flexed and heated, the outside diameter of the flanges do not flex but temporarily decrease, and the material appears to have memory because the flanges return to their original diameter when the earplug is removed from the ear canal and cooled to room temperature. The applicant has also found the advantage that SBC materials are more noise insulating than previously used materials for flanged earplugs such as polybutadiene rubber, polyurethane elastomers or ethylene vinyl acetate elastomers.
Fig. 3 is an enlarged view of the earplug showing the original shape 10 of the outer surface of the flange 23, the deformed shape 10A after being positioned in the ear canal, and the partially recovered shape 10B after the earplug is removed from the ear canal and has not yet cooled from the ear temperature to room temperature. Fig. 3 also shows a cord 40 (capable of being detected by a metal detector) with a metal ferrule 42 at the end, the cord 40 being inserted into the back end of the earplug. The cord 40 is very long and extends loosely behind the head of the person while holding the two earplugs together.
The earplug 23 of fig. 1 has radially inner and outer flange ends 30, 32, and a central portion 50 located approximately radially midway between the opposite ends 30, 32, the radial direction being a direction perpendicular to the axis 14. The radial distances E and 2E of the flange front surface are shown from the shank to the radial midpoint 50 and from the shank to the outer end 32A of the outer surface. The flange 23 also has an inner portion 52 and an outer portion 54. The inner flange portion 52 extends from the inner flange portion inner end 30 at least 40% of the flange radial distance 2E, preferably to the flange middle 50, and the outer flange portion 54 extends from the flange middle 50 to the flange free outer end 32A. The flange front face 60 has an inner front face portion 60i along the inner flange portion 52 which extends along a majority of the radial length of the inner flange portion 52 at an angle B of 15 deg. to the direction 62, the direction 62 being directly radial to the axis 14. The included angle B is preferably no greater than 10 deg., and in practice the included angle B of the earplug is manufactured to be about 5 deg.. The outer flange portion 54 extends straight rearwardly R and radially outwardly O, i.e., along a sloping line C that is within 20 ° of an imaginary line 66, the imaginary line 66 extending between points 68 and 32A in a direction parallel to the axis 14. For ease of description, points in the cross-section are used instead of circles around the axis, although each flange and stem are 360 ° symmetrical around the axis 14.
By applicant extending the radially inner portion 52 of the flange generally radially, applicant is able to position the flange outer portion 54 proximate the ear canal. Thus, the outer portion 54 can extend a considerable axial length D of the flange, which is at least half the axial length of the flange outer portion 54, preferably at least two thirds the axial length of the flange outer portion 54, mainly linearly and at a small angle C to the axial direction. The actual length D of fig. 1 is 77% of the entire flange axial length 23 a. The larger axially extending outer portion 54 forms a good sound tight seal with the ear canal. The design of the other flanges, in particular flange 22, is preferably the same as the design of flange 23 (but with a slightly smaller diameter). The axial length of the three flanges is about 15 mm, which is approximately the length of the earplug that enters the ear canal. Applicant's outer flange portion 54 can extend at least two-thirds (67%) of the length within about 20% of the axial direction.
The three flanges 21-23 have outer flange surfaces 21s, 22s, 23s that each extend along a single imaginary line 70 at an angle C of 17 (no greater than 20) to the axis for ease of manufacture. The straight outer flange surfaces 21s, 22s, 23s preferably do not include angles of more than 25 deg. to the axis, each preferably occupying at least two-thirds of the axial length 21a, 22a, 23a of each flange. All outer flange surfaces of the 3 flanges are on the same imaginary cone with the line 70 on the imaginary cone.
The present invention thus provides an earplug of the type having a stem and having at least one flange 23, and preferably a plurality of flanges extending from the front of the stem, thereby providing a stiffer handle for ease of flange insertion and providing a flange with reduced stiffness (after about 1 minute) for increased comfort. This is accomplished by making the earplug from a material that exhibits a significant decrease in stiffness as the temperature increases from about 72 ° F room temperature to about 100 ° F body temperature. A more effective flange is obtained by configuring each flange such that its radially inner portion or radially inner half measured outwardly from the shank extends at a small angle (e.g. less than 15 °) to the radial direction, and by configuring each flange such that its radially outer portion extends straight at a small angle (e.g. 25 °) to the axial direction and such that the flange portion, which does not exceed an angle of 25 ° to the axis, extends for at least two thirds of the axial length of the flange.
The invention has been described in considerable detail, so that various alterations and modifications will become apparent to others skilled in the art upon the reading and understanding of this specification. All such changes and modifications are intended to be included herein within the scope of the present invention and protected by the following claims.