Patent Publication Number: US-2004045558-A1

Title: Earplug and method of manufacturing an earplug

Description:
BACKGROUND OF INVENTION  
       [0001] (1) Field of Invention  
       [0002] The present invention relates generally to hearing protective devices, and more particularly to an earplug including an injection molded stem adhesively bonded to a foam.  
       [0003] (2) Description of Related Art  
       [0004] The use of hearing protective and noise attenuating devices is well known, and various types of devices are available including semi-aural devices and earplugs. Foam components are well known for use with these devices, providing both sound attenuation and enhanced comfort for the wearer.  
       [0005] Earplugs are generally utilized for continuous use over longer periods of time. Foam earplugs composed of resilient polymer foam materials such as foam rubber or polyurethane are well known in the art. Slow recovery foam earplugs, such as those disclosed in U.S. Reissue. No. 29,487 to Gardner, Jr., provide comfort and have also been shown to deliver high in-field noise protection at all frequencies. U.S. Pat. No. 5,203,352 to Gardner, Jr. also discloses a hearing protective earplug comprising a polymeric foam.  
       [0006] Such earplugs may further include a cord that attaches a pair of plugs and extends therebetween. Conventional cords are commonly designed so that the cord may be permanently attached to the earplugs and more specifically, each end of the cord may be permanently attached to ends of stem portions of the respective earplugs.  
       [0007] The sound-attenuating (acoustical) component of earplugs has been made both of foam, as described above, and of flexible, rubber-like materials. The rubber-like materials are advantageous because they allow direct and easy insertion of the earplug into the wearer&#39;s ear. However, such earplugs and devices typically become uncomfortable over long periods of use. In this respect, foam earplugs are preferred for enhanced comfort.  
       [0008] Foam earplugs of the roll-down type are known in the art. These earplugs are generally cylindrical in shape and include a body composed of a resilient foam material. In use, a wearer rolls the body to compress the earplug, thus reducing a cross-sectional area thereof. In this compressed state, one end of the earplug is inserted into the ear canal while the opposite end serves as a handle to aid insertion. Once inserted in the ear canal, the plug expands towards its original dimensions, filling a portion of the ear canal, and providing a comfortable fit and suitable attenuation properties.  
       [0009] However, foam earplugs of the roll-down type are often difficult to fully insert due to the pliable nature of such plugs. That is, even in the rolled down state, the plug still may not provide adequate rigidity to insert the body of the plug a sufficient distance into the ear canal. Insufficient insertion results in inadequate attenuation and is thus undesirable.  
       [0010] To remedy the insertion deficiencies of the roll-down type earplugs, foam earplugs have been developed to include rigid or semi-rigid stem components. Such earplugs include a resilient foam body and a rigid or semi-rigid stem portion embedded in the foam portion. The stem portion may be embedded entirely in the foam portion or may include a first end embedded in or attached to the foam portion and a second end extending from the foam portion. The stem portion is intended to provide a degree of rigidity to the earplug to aid the wearer in inserting the earplug into the ear canal. That is, the rigidity of the stem portion enables the wearer to push the earplug into the ear canal to a proper insertion depth thus allowing the earplug to provide adequate attenuation. The stem portion also often includes a degree of pliability to ensure comfort of the earplug once inserted into the ear canal.  
       [0011] A strong attachment of the stem component to the foam is critical to ensure functionality of the earplug. Typically, the stem is mechanically bonded to the foam during the earplug manufacturing process. First, the stem is manufactured and then placed in a mold as an insert. The foam portion is then formed in the mold around a portion of the stem such that the foam mechanically bonds to the stem insert. The result is an earplug including a foam bonded with a stem, the stem extending from the foam. Alternatively, the entire stem may be placed in the mold and the foam allowed to form entirely around the stem and bond thereto, thus encapsulating the stem. In this case, the resulting earplug includes a foam outer body and a stem portion embedded at an interior of the body.  
       [0012] Mechanically bonding the foam and stem as described is a difficult and often inconsistent process. For example, proper formation of the foam and proper bonding of the foam to the stem require adequate venting of the mold in which the foam is formed about the stem. Various attempts have been made at properly venting the molds. For example, a porous stem is disclosed in U.S. Pat. No. 5,799,658 to Falco. Therein, individual porous stems are mechanically bonded to the foam during manufacture by controlled penetration of the foam into the pores of the stem. Air entrapped in the mold is permitted to vent during the process through the pores. However, the individual porous stems are relatively expensive and somewhat difficult to manufacture and proper venting is often not attained. In another example, venting means may be added to the exterior of stems or to the interior of molds to create venting channels or pathways between the stem and mold which lead from an interior of the mold to an exterior. Again, such additions to stems and molds are costly and their effectiveness in properly venting the mold is often found to be insufficient.  
       [0013] Non-automated, manual gluing of the foam and stem to form the earplug has also been attempted. However, an insufficient bond is often formed between the foam and stem when utilizing this process. Further, such process is messy, labor intensive, time consuming, and costly, thus not presenting a suitable means for automated mass production of stem component foam earplugs.  
       [0014] Accordingly, there remains a need for a stemmed foam earplug that is effective in providing hearing protection, yet convenient and comfortable to use, and has a more efficient and lower cost method of manufacture.  
       SUMMARY OF INVENTION  
       [0015] The above discussed and other problems and deficiencies of the prior art are overcome or alleviated by the hearing protective device and method of manufacture of the invention.  
       [0016] In one embodiment of the invention, an earplug comprises a foam including an insertion portion for being inserted into an ear canal of a user and a skirt extending from the insertion portion. The skirt includes a receptacle formed at an interior thereof. The earplug further comprises a molded stem including a bonding portion which is received in the receptacle and a handle portion which extends from the receptacle. The handle portion facilitates handling of the earplug during manufacture and use thereof. The skirt extends around the bonding portion of the stem and the bonding portion and the foam are adhesively bonded in the receptacle.  
       [0017] In another exemplary embodiment, an earplug comprises a foam including a rounded insertion portion for being inserted into an ear canal of a user, a cylindrical skirt extending from the insertion portion, a receptacle formed at an interior of the skirt, and ribs extending from the cylindrical skirt to the rounded insertion portion. The earplug further comprises a molded stem including a bonding portion having a flattened surface, a handle portion having contouring to facilitate handling of the earplug during manufacture and use of the earplug, and a collar disposed intermediate the bonding portion and the handle portion. The skirt extends around the bonding portion. The flattened surface of the bonding portion receives a bonding agent to adhesively bond the bonding portion and the foam in the receptacle.  
       [0018] In a further embodiment of the invention, a method of manufacturing an earplug comprises molding a foam to include a rounded portion and a skirt extending from the rounded portion, forming a receptacle at an interior of the skirt, molding a stem to include a bonding portion having a flattened surface and a handle portion having contouring to facilitate gripping the stem, applying a bonding agent to the flattened surface, inserting the bonding portion into the receptacle, and curing the bonding agent to adhesively bond the bonding portion and the foam in the receptacle.  
       [0019] The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020] Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
     [0021]FIG. 1 is perspective view of an earplug according to the invention;  
     [0022]FIG. 2 is a side elevational view thereof;  
     [0023]FIG. 3 is another side elevational view thereof;  
     [0024]FIG. 4 is a top plan view thereof;  
     [0025]FIG. 5 is a bottom plan view thereof;  
     [0026]FIG. 6 is a perspective view of a foam of the earplug of FIG. 1;  
     [0027]FIG. 7 is a cross-sectional view of the foam of FIG. 6;  
     [0028]FIG. 8 is a perspective view of a stem of an earplug according to the invention;  
     [0029]FIG. 9 is side elevational view thereof;  
     [0030]FIG. 10 is another side elevational view thereof;  
     [0031]FIG. 11 is a bottom plan view thereof;  
     [0032]FIG. 12 is a top plan view thereof;  
     [0033]FIG. 13 is a cross-sectional view thereof; and  
     [0034]FIG. 14 is a perspective view of the earplug of FIG. 1 with a cord attached thereto. 
    
    
     DETAILED DESCRIPTION OF INVENTION  
     [0035] FIGS.  1 - 5  show various views of an earplug  10  in one embodiment of the invention. The earplug  10  includes a foam  12  and a stem  14 . The foam  12  includes a rounded portion  16  at a first end  18  of the foam  12  and a skirt  20  at an opposite second end  22  of the foam  12 .  
     [0036] The rounded portion  16  has a substantially semi-hemispherical shape and includes a rounded surface  24  formed proximate the first end  18  of the foam  12  and a concave surface  26  disposed opposite the rounded surface  24 . The rounded and concave surfaces  24  and  26 , respectively, give the rounded portion  16  a generally crescent shaped axial cross-section (FIG. 7). As such, an edge  30  is formed at an interface between the rounded and concave surfaces  24  and  26 , respectively. The edge  30  comprises essentially a flap of the rounded portion  16  is pivotably movable relative to a longitudinal axis of the earplug  10 . This feature provides comfort and ensures a proper fit when the earplug  10  is inserted into an ear canal of a user.  
     [0037] The skirt  20  extends from the rounded portion  16  and is generally a cylindrical element having a first skirt end  32  formed integrally with the rounded portion  16  at the concave surface  26  and a second skirt end  34  being free relative to the rounded portion  16 . The skirt  20  includes a receptacle  36 . The receptacle  36  extends the length of the skirt  20  from the first skirt end  32  to the second skirt end  34  where the receptacle  36  opens to an exterior of the foam  12 . At the first skirt end  32 , the receptacle  36  exposes a portion of the concave surface  26 .  
     [0038] A cross-sectional area of the receptacle  36  is generally circular in shape and is of a consistent dimension from the first skirt end  32  to the second skirt end  34 . That is, the receptacle  36  has a substantially cylindrical shape. Of course, the shape of the receptacle  36  may be other than cylindrical. The receptacle  36  may, for example, include a circular or rectilinear cross-sectional area which varies in dimension throughout the length of the receptacle  36 . In one such embodiment, the receptacle  36  includes a circular cross-sectional area having a larger dimension proximate the second skirt end  34  and a smaller dimension proximate the first skirt end  32  such that the receptacle  36  tapers toward the first skirt end  32 . In another embodiment, the receptacle  36  has a shape including rounded and flat portions and a cross-sectional area which tapers in a direction toward the first skirt end  32 . The receptacle  36  may extend past the concave surface  26  into the rounded portion  16  (FIG. 7).  
     [0039] The skirt  20  is generally elongated so as to include an axial length X equal to or greater than an axial length Y of the rounded portion  16 .  
     [0040] The foam  12  further includes ribs  40  extending between the rounded portion  16  and the skirt  20 . The ribs  40  are essentially flat members formed integrally with the cylindrically shaped skirt  20  and extend radially therefrom to the concave surface  26  of the rounded portion  16 . The ribs  40  are fixed to the first skirt end  32  and include a portion extending to the second skirt end  34 . In a preferred embodiment, the foam  12  includes four ribs  40  disposed equi-angularly about an outer surface of the skirt  20 .  
     [0041] The foam  12  is manufactured in a molding process, as described in more detail herein below. The molding process includes a venting step which releases air entrapped in the mold and allows the foam  12  to properly form therein. The venting step also allows for the ribs  40  to form integrally with the foam  12 .  
     [0042] Referring now particularly to FIGS.  8 - 12 , the stem  14  includes a first stem end  42  and an opposing second stem end  44 . A bonding portion  46  is formed at the first stem end  42  and a handle portion  48  is formed at the second stem end  44 .  
     [0043] The bonding portion  46  is generally a cylindrical element and, in one embodiment, includes a circular cross-sectional area which tapers in a direction toward the first stem end  42 , i.e., the circular cross-sectional area is larger proximate the second stem end  44  and gradually becomes smaller along a length of the bonding portion  46  in a direction toward the first stem end  42 .  
     [0044] The bonding portion  46  includes a first flattened surface  54  and a second flattened surface  56 . The first flattened surface  54  is a planar portion on the surface of the bonding portion  46  which is otherwise generally cylindrical in shape. The first flattened surface  54  extends from the first stem end  42  in a direction toward the second stem end  44 . The first flattened surface  54  includes a width W which gradually increases over the extension of the first flattened surface  54 , i.e., the width W proximate the first stem end  42  is smaller than the width W proximate the second stem end  44 . The second flattened surface  56  is substantially identical to the first flattened surface  54  and is disposed on the bonding portion  46  opposite the first flattened surface  54 . As a result of the first and second flattened surfaces  54  and  56 , the generally cylindrical shape of the bonding portion  46  includes two substantially flattened sides.  
     [0045] The handle portion  48  extends from the second stem end  44  in a direction toward the first stem end  42  and meets the bonding portion  46  at a point approximately midway between the first and second stem ends  42  and  44 . The handle portion  48  includes a collar  62  proximate the bonding portion  46 . The collar  62  is a cylindrical element having a cross-sectional area greater than the cross-sectional area of the bonding portion  46 . In one embodiment, the collar  62  has a cross-sectional area greater than a cross-sectional area of the remaining portion of the handle portion  48 , i.e., the collar circumferentially extends beyond a remaining section of the handle portion  48  as well as beyond the bonding portion  46  such that the stem  14  has a largest cross-sectional area at the collar  62 .  
     [0046] The handle portion  48  includes a first side  64  and an identical opposite second side  66 . The first and second sides  64  and  66  extend from the second stem end  44  to the collar  62 . The handle portion  48  further includes a third side  68  and a fourth side  70 , the fourth side  70  being identical to the third side  68  and being disposed opposite the third side  68 .  
     [0047] The first and second sides  64  and  66  are generally disposed parallel to one another and the third and fourth sides  68  and  70  are generally parallel to one another. The first and second sides  64  and  66  are generally disposed perpendicular to the third and fourth sides  68  and  70 . The third side and fourth sides  68  and  70  are disposed between and substantially connect the first and second sides creating the three-dimensional shape of the handle portion  48  as shown.  
     [0048] The first, second, third, and fourth sides,  64 ,  66 ,  68 , and  70 , are arcuate in shape. More particularly, the first and second sides  64  and  66  comprise a first arcuate surface having a first radius of curvature and the third and fourth sides  68  and  70  comprise a second arcuate surface having a second radius of curvature where the first radius of curvature is greater than second radius of curvature such that an overall width of the first and second sides  64  and  66  is greater than an overall width of the third and fourth sides  68  and  70 . The first, second, third, and fourth sides,  64 ,  66 ,  68 , and  70 , combine to form the thin rounded member of the handle portion  48 .  
     [0049] The third and fourth sides  68  and  70  each include an indent  72 . The indent  72  is a recessed portion formed in the surface of the third and fourth sides  68  and  70 . The indents  72  extend longitudinally from the collar  62  towards the second stem end  44  and terminate at a point before the second stem end  44 . The indents  72  provide a section on the handle portion  48  of a narrow cross-sectional area relative to elsewhere on the handle portion  48 . The indents  72  essentially create a recessed gripping area on the handle portion  48 . This gripping area facilitates handling of the stem  14  during molding of the stem and during assembly of the stem and foam. Additionally, the gripping area created by the indents  72  provides enhanced grip to a user when inserting, removing and generally handling the earplug  10 . Gripping elements may be integrally formed on the gripping area to provide such enhanced grip. Also, the recessed area created by indents  72  creates a display surface which may be used for displaying characters such as numbers, letters, and/or symbols to a visual observer. Brand names, logos, product information, technical specifications, advertising items, etc. may be formed on the display surface during molding of the stem  14  for visual display purposes.  
     [0050] The first and second sides  64  and  66  each include a footing  74  disposed proximate the collar  62 . The footing  74  includes a base  76  extending from the each of the first and second sides  64  and  66 . A flat surface  78  is formed atop the base  76 . In one embodiment, the footing  74  is flush on one side against the collar  62 .  
     [0051] The handle portion  48  of the stem  14  further includes a cavity  80  formed at an interior of the handle portion  48 . The cavity  80  is exposed to an exterior of the stem  14  at opening  82  formed at the second stem end  44 . The cavity  80  extends axially along a length of the handle portion  48  in a direction toward the first stem end  44 . In one embodiment, the cavity  80  terminates at a point approximately midway between the second stem end  44  and the collar  44 . The cavity  80  has a substantially circular cross-section which, in one embodiment tapers in a direction toward the collar  62 , i.e., the cross-sectional area of the cavity  80  gradually reduces over the length of the cavity in a direction from the second stem end  44  toward the collar  62 . The cavity  80  and the opening  82  are particularly designed to receive and retain an earplug cord  84  as shown, for example, in FIG. 14.  
     [0052] The stem  14  is manufactured of a plastic material in a molding process. Particularly, the stem  14  is manufactured in an injection molding process. The foam  12  is manufactured in a molding process separately from the stem  14 . In such process, the foam  12  is placed in a mold in liquid form; the foam is allowed to expand, taking the shape of the mold; the mold is properly vented during expansion of the foam  12  to allow air entrapped in the mold to escape the mold; the foam  12  is allowed to cure; and, finally, the foam  12  is ejected from the mold.  
     [0053] The stem  14  is molded into a specific shape to facilitate the molding process there of and the subsequent earplug assembly process. For example, the stem  14  and, particularly, the handle portion  48  provide various surfaces by which injection molding machines and related earplug assembly apparatuses may easily grip the stem  14 . Elements of the stem  14  which enable such gripping include, but are not limited to, the following: the collar  62 ; the first through fourth sides  64 ,  66 ,  68 , and  70 ; the indents  72 ; the footing  74 ; the flat surface  78 ; and the relative positioning of the first flattened surface  54  and the second flattened surface  56 .  
     [0054] Additionally, the center of gravity of the stem  14  may be located in a position so as to facilitate assembly of the earplug  10 . In one embodiment, the center of gravity of the stem  14  is located in a position such that if the stem  14  is dropped during a stage of the assembly process, the second stem end  44  is consistently displaced during the dropping so as to be beneath the first stem end  42 . Alternatively, of course, the center of gravity of the stem  14  may be placed such that the first stem end  42  is positioned beneath the second stem end  44  during the dropping of the stem  14 . Typically, the third and fourth handle portion sides  68  and  70  and the flat surface  78  control axially rolling of the stem  14 . The invention additionally contemplates that the center of gravity of the entire earplug  10 , including the stem  14  and foam  12 , may be selected so as to facilitate manufacture, assembly, and/or usage thereof.  
     [0055] The earplug  10  is assembled by adhesively bonding the foam  12  to the stem  14 . Particularly, an adhesive is placed on one of the first or second flattened surfaces  54 ,  56  of the bonding portion  46 . The bonding portion  46  is then inserted through the opening  38  into the receptacle  36  of the skirt  20 . The adhesive agent on the first or second flattened surface  54 ,  56  contacts the foam  12  in the receptacle  28  and allowed to cure, thus bonding the foam  12  to the stem  14 .  
     [0056] The first and second flattened surfaces  54  and  56  are particularly designed to receive and retain the adhesive agent prior to insertion of the bonding portion  46  into the receptacle  36  and, further, to distribute the adhesive agent across appropriate portions of the foam  12  in the receptacle  36  upon inserting the bonding portion  46  therein.  
     [0057] In a preferred embodiment, the stem  14  is maneuvered during or immediately after insertion of the bonding portion  46  into the receptacle  36  to distribute the adhesive agent across a desired area of the foam  12  in the receptacle  36 . For example, the stem  14  is twisted upon insertion of the bonding portion  46  into the receptacle  36  such that the bonding portion  46  is rotated in a spiral or semi-spiral manner within the receptacle  36 , thus distributing the adhesive agent across an appropriate area of the foam  12  in the receptacle  36 . In another example, the stem  14  is twisted after the bonding portion  46  is fully inserted into the receptacle  36  such that the bonding portion  46  is rotated within the receptacle  36 , thus distributing the adhesive agent as desired. Of course, the stem  14  and, accordingly, the bonding portion  46  may be maneuvered in any manner (longitudingly, rotationally, etc.) before, during, or after insertion of the bonding portion  46  into the receptacle  36  to distribute the adhesive agent across the foam  12  as desired.  
     [0058] Maneuvering the stem  14  as described enables proper and complete distribution of the adhesive agent across the foam  12  in the receptacle  36 , thus providing enhanced preparation of the respective foam and stem bonding surfaces and ensuring adequate and consistent bonding thereof.  
     [0059] The adhesive agent may be any material suitable for securely bonding the foam  12  and the stem  14 , for example, a cyano-acrylate adhesive such as the commercially available “Loctite 416” adhesive.  
     [0060] The foam  12  may be composed of any suitable foam for use with the earplug  10 . For example, the foam  12  may comprise a soft, pliable self-rising foam with instant recovery properties such as a polyurethane or acrylic blend foam. Other suitable foams include PVC, silicone, and nitrile, among others. A suitable foam is described, for example, in U.S. Pat. No. 5,792,998 to Gardner, Jr. et al., herein incorporated by reference. The earplug described therein is comprised of a dynamically stiff foam material having a low static stiffness, and a high dynamic stiffness. Another suitable foam is described, for example, in U.S. Pat. No. 4,158,087 to Wood, herein incorporated by reference.  
     [0061] While the foam  12  has been described herein as any soft, pliable self-rising foam, the invention contemplates the use of any suitable sound attenuating element for bonding with the stem  14  to form the earplug  10 . For example, a plastic or rubber material may be used instead of the described foam to provide a sound attenuating element to the earplug  10 . That is, in one embodiment of the earplug, a sound attenuating element of plastic, rubber, etc. includes the described skirt and receptacle and is adhesively bonded to the stem in the receptacle to form the earplug of the invention.  
     [0062] The stem  14  is composed of a material rigid enough to aid insertion into the wearer&#39;s ear, yet soft and pliable enough to be comfortable and safe for the wearer. The stem  14  is made of a material that is compatible with the foam  12  and which facilitates creation of a bond between the stem  14  and the foam  12 . Thus, the material is preferably of a plastic material. More specifically, the stem material may be a vinyl material such as PVC having, for example, a shore durometer of 50-90. The stem  14  may be of a solid or dense construction, or may include a hollow interior, or may include one or more cavities formed therein, such as cavity  80 .  
     [0063] The foam  12  and the stem  14  may be of identical colors. Alternatively, the stem  14  may be of a different color than the foam  12 , thus clearly distinguishing the handle portion  48  of the earplug  10  for ease in inserting, removing, and otherwise identifying the earplug  10 , and for allowing an observer to visually determine the extent and sufficiency of insertion of the earplug  10 , e.g., visibility of the color of the skirt  20  may indicate improper insertion.  
     [0064] The earplug contemplated herein provides a comfortable and effective hearing protection device which may be readily manufactured in bulk quantities at a low cost with minimal labor.  
     [0065] The sleeve extending from the foam portion of the earplug provides increased surface area to which the stem may bonded. That is, an end of the stem as well as sides of the stem may be readily bonded to the foam. The extended sleeve enables a strong and consistent bond to be formed between the stem and the foam.  
     [0066] Injection molding of the stem ensures consistent manufacturing of large quantities thereof and allows for specific contouring to be applied thereto. Such contouring may be designed to provide gripping surfaces to facilitate handling of the stem and the earplug the during molding process of the stem, assembly of the plug, and throughout use of the plug by a user. Additionally, bonding surfaces, such as the flattened surfaces of the bonding portion of the stem, may be easily formed during the stem molding process to allow formation of a strong adhesive bond between the stem and the foam. Also, a certain visual presentation, such as letters, numbers, or symbols, may be readily formed on the stem during the molding thereof.  
     [0067] While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.