Patent Publication Number: US-2022226157-A1

Title: Inflatable earplug system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/138,433, filed Jan. 16, 2021, which is fully incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates generally to hearing protection devices and, more particularly, to an inflatable earplug system and device that is comfortable and easy for an untrained user to fit and remove, and which produces a high-attenuation acoustic seal deep in the ear canal. 
     BACKGROUND 
     Hearing protection is needed by those engaged in occupations or activities involving loud intermittent or sustained noise. Insufficient protection in loud noise environments can lead to permanent hearing damage with related hearing loss or tinnitus. Hearing damage negatively affects communication, job performance, and quality of life, and results in increased health care costs. 
     There are many earplugs and earmuffs on the market that attempt to reduce or eliminate the potential damage noisy environments can have on the human ear. Conventionally, high levels of noise attenuation require large earmuffs, which are bulky, and can be uncomfortable to wear, or deeply inserted earplugs, which can be difficult and painful to insert properly. Poorly fitted devices that do not seal to the head or in the ear canal at sufficient depth provides low levels of attenuation, leaving the user at risk of hearing damage. If a hearing protection device is not easy to fit correctly and comfortable, it will not be used or, if used, it will not be effective. 
     As a result, there is a need for a new and improved earplug system and device that solves the innate functional and design flaws of conventional configurations, designs, and approaches. 
     SUMMARY 
     Embodiments of the present invention include an earplug system and device that forms a high-attenuating acoustic seal deep in the ear canal, is comfortable, easy for an untrained user to fit and use, intrinsically adaptable to the broad variety of human ear canal anatomies, and secure for long term wear in active environments, while still being easily removable when desired. The earplug device provides a reliable acoustic seal past the second bend of the ear canal, which will ensure high attenuation. 
     The earplug comprises a soft elastomer shell that forms a sealed volume filled with an inert fluid. The earplug can comprise a slender, flexible stem that is easily insertable into the ear canal when deflated. The proximal end of the earplug can be situated outside the ear canal, within the concha of the ear, and incorporates a bulb with a hemispherical, bistable cap. After inserting the stem of the earplug into the ear canal, the wearer applies force with a finger to invert the cap, which transitions elastically from a convex to a concave external geometry, displacing a fixed volume of fluid to inflate a sheath that forms the outer covering of the stem, filling and sealing the ear canal. The sheath can be deflated by pulling on or otherwise engaging a release tab or other feature attached to the cap. 
     Another object of the invention is to provide such an acoustic seal that optionally incorporates an internal air channel for desirable pass-through acoustics. Various filters may be inserted in this channel to affect the frequency-dependent and level-dependent attenuation of the earplug. 
     Another object of the invention is to provide an earplug device that creates such a seal but is readily manufacturable and durable for many uses over extended periods of time, leading to low overall costs. 
     The slender stem with a soft, fluid-filled, elastic sheath enables a user to easily insert deep into the ear canal and then inflate manually. The sheath expands, conforming to the inner profile of the ear canal, and produces an acoustic seal with large surface area at uniform pressure. The constant-pressure conformability of the sheath provides a comfortable and uniform seal deep in the ear canal without pressure points that can cause discomfort. Further, the large contact surface of the area securely anchors the earplug within the ear. 
     The high acoustic impedance of the fluid that fills the sheath relative to air results in low transmission of ambient sound. The central stabilizing core constrains the inflation of the sheath in the axial direction, ensuring radial inflation, and damps axial oscillation of the fluid volume that might otherwise allow transmission of low frequency sound. The core also provides for the possibility to incorporate the internal pass-through acoustic channel. 
     Attached to the distal end of the sheath, the bistable hemispherical bulb forms a sealed volume filled with fluid. The bulb provides a reservoir for the fluid when the sheath is deflated. The bulb is an elastomeric hemisphere that is mechanically stable in either a concave or convex topology. When the bulb is inverted by force from the user&#39;s finger, a fixed volume of fluid is displaced and forced into the sheath. The geometry and material of the bulb are selected to provide the appropriate displaced volume for inflation of the sheath, and to retain the required inflation pressure without inadvertent inversion. The bulb can also incorporate a tab as an integrally molded component. To remove the earplug, the user grasps the tab and pulls, first inverting the bulb to release the inflation pressure, then continuing to extract the deflated earplug from the ear. 
     The geometry of the sheath is tailored to provide advantageous inflation behavior. The sheath is thinnest near its tip, ensuring that the onset of inflation and sealing occurs deep in the ear. The wall thickness of the sheath is tapered, increasing toward the bulb and outer ear. Inflation initiated at the tip will progress gradually outward toward the bulb with steadily increasing pressure as fluid is transferred from the bulb into the sheath. This allows ear canals of various sizes to be accommodated with a single earplug design. Large diameter ear canals will seal with greater radial expansion at the tip of the sheath and a shorter inflated region and seal in the axial direction. Small diameter ear canals will seal with less radial expansion and a longer or larger inflated region progressing axially along the stem toward the outer ear. The sheath is sufficiently thick, or very thick, in the concave region adjacent to the bulb to ensure that this portion does not inflate. 
     The above summary is not intended to describe each illustrated embodiment, claimed embodiment or implementation of the invention. The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. It is understood that the features mentioned hereinbefore and those to be commented on hereinafter may be used not only in the specified combinations, but also in other combinations or in isolation, without departing from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
         FIG. 1  shows an isometric view of an inflatable earplug system or device in a nominal state prior to insertion, in accordance with embodiments of the present invention. 
         FIG. 2A  shows an isometric view of a core of an inflatable earplug system or device, in accordance with embodiments of the present invention. 
         FIG. 2B  shows an isometric view of a sheath of an inflatable earplug system or device, in accordance with embodiments of the present invention. 
         FIG. 2C  shows an isometric view of a bi-stable cap of an inflatable earplug system or device, in accordance with embodiments of the present invention. 
         FIG. 3A  shows an orthographic view of an inflatable earplug system or device in the same nominal state as  FIG. 1 , in accordance with embodiments of the present invention. 
         FIG. 3B  shows a detail section view of the inflatable earplug system or device along cross-section A-A of  FIG. 3A , in accordance with embodiments of the present invention. 
         FIG. 4A  shows an orthographic view of an inflatable earplug system or device in an inflated state, in accordance with embodiments of the present invention. 
         FIG. 4B  shows a detail section view of the inflatable earplug system or device along cross-section A-A of  FIG. 4A , in accordance with embodiments of the present invention. 
         FIG. 5  shows a detail section view of a cap of an inflatable earplug system or device, in accordance with embodiments of the present invention. 
     
    
    
     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings, are not intended to be to scale, and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     The system and device of the present invention, shown in  FIG. 1 , is an inflatable hearing protection earplug  100  comprising a stem  102  that is inserted into a user&#39;s ear canal and a bulb  101  that protrudes from their ear canal. The length of the stem  102  should be commensurate with the typical depth of the human ear canal, typically in the range of 0.5-1.0 inches. It may be advantageous to provide multiple (e.g., two or three) different standard sizes of earplugs with different stem lengths to accommodate different ear sizes. 
     In various preferred embodiments, the earplug  100  components or parts are made of molded silicone materials. Silicones are chemically inert, bio-compatible, durable, elastic, resilient, easily molded to intricate shapes by several different processes, readily bonded together permanently with silicone adhesives, and available in a variety of formulations with a large range of durometer hardness, elongation, and other critical mechanical properties. Particular silicone formulations are selected with mechanical properties beneficial to the function of each specific component or part. It should be understood that alternative embodiments might employ other elastomeric materials, including but not limited to urethanes, nitriles, or latex rubber. 
     Referring to  FIGS. 2A-2C , the earplug  100  is assembled from three primary components or parts: a core  103 , a sheath  104 , and a bi-stable cap  105 . 
     The method by which these components are assembled to form the stem  102  and the bulb  101  is evident in the section views of  FIGS. 3A-3B —e.g., showing the earplug  100  in a deflated state with a fluid  111  stored in the volume of the bulb  101 . The sheath  104  is in operative fluid communication with the fluid volume  111  in the bulb  101  via one or more channels, transmission paths or like features between the sheath  104  and the core  103  at the interface  103   a , as shown in  FIG. 3B . The stem  102  is formed by overmolding or otherwise assembling the sheath  104  onto the core  103 . During use, the sheath  104  inflates to seal the ear canal. The functions of the core  103  are: to give the stem  102  stiffness while deflated and being inserted into the ear canal; to constrain the axial extension of the sheath  104  into the ear canal as it is inflated, preventing pain or damage to the eardrum; to damp axial motion of the inflated sheath that otherwise might transmit low frequency sound; and, optionally, to provide the isolated air channel  106  for pass-through sound. 
     The sheath  104  is fixed to the core  103  at either end using adhesive and possibly anchoring features such as those shown at the tip or end portion  107  of the core  103  to prevent leakage, and at the base  108  to prevent axial elongation. The sheath  104  is free to separate from the core surface  109  between these features when inflated. The core  103  includes an o-ring type groove  107   a  to improve adhesion at the tip  107 . The anchors  108  include a ridge or groove for the same reason. In preferred embodiments, this adhesion is achieved through silicone-on-silicone bonding while overmolding the sheath  104  onto the core  103  or through adhesive if otherwise assembled. 
     The core  103  is made of a silicone with intermediate durometer hardness, giving it flexibility for insertion, but enough stiffness to resist extension under inflation and dynamic pressures and to resist collapse of the acoustic channel when the earplug is inflated. In various preferred embodiments, the core  103  is constructed of a silicone rubber with durometer hardness of 40 on the Shore A scale. 
     The material of the sheath  104  should have very low durometer hardness and high elongation, allowing it to inflate like a balloon and strain several hundred percent at low pressure, preferably below 2 pounds per square inch (PSI). In a preferred embodiment, the sheath  104  is constructed of a silicone rubber with durometer hardness of 10 on the Shore A scale and elongation at break in excess of 400%. 
     The bulb  101  serves to seal the predefined fluid volume and provide a mechanism for displacing fluid to inflate the sheath  104 . In various preferred embodiments, the bulb  101  incorporates a bistable hemispherical cap  105  for the latter function and assumes a convex shape before inflation of the earplug  100 . The bulb  101  is formed by adhering the bi-stable cap  105  to the outer face of the sheath&#39;s flange  110 . The sealed volume within the bulb  101  formed by the cap  105  and the sheath  104  is filled with unpressurized fluid  111 , which may be air, water, oil, or other fluids. It will be understood by one skilled in the art that various other designs, materials, and constructions could achieve the same objectives consistent with the disclosure provided herein. The bulb  101  or cap  105  can include a diaphragm, one or more bellows, a valve, or a pump to facilitate fluid displacement. 
     In use, the narrow stem  102  of the deflated earplug is inserted into a user&#39;s ear until the flange  110  is seated against the ear canal opening, providing a fixed and repeatable insertion depth. The user then presses the bi-stable cap  105 , forcing fluid  111  from the bulb  101  into the sheath  104  until the cap  105  is inverted or otherwise defines a concave shape (or approaches an inverted or concave shape) and the sheath  104  is inflated. 
     Referring to  FIGS. 4A-4B , section views of the earplug  100  in an inflated state are shown. The thickness of the sheath  104  varies from thinnest at the earplug tip or end portion  112  to thickest at the flange  110 . Pressurized fluid  111  squeezed from the bulb  101  will pass through channels or unsealed transmission paths between the sheath  104  and the core  103  or will otherwise separate the sheath  104  from the core  103 , creating an interstitial space  113  through which the fluid  111  will flow until it reaches the tip  112 , where the sheath  104  is thinnest and where it will first inflate. This important aspect of the design ensures the earplug  100  will first create a seal at the tip  112 , which is located in the deepest portion of the ear canal. 
     As the sheath  104  at the tip  112  expands in the radial direction, the increased pressure required for further expansion will begin to inflate the increasingly thicker sheath  104  away from the tip  112 , and the inflated region will grow in the axial direction toward the flange  110 . As a result, air is forced out of the ear canal, rather than inward, as the earplug sheath  104  inflates. This action prevents pressurization of the sealed portion of the ear canal, which could otherwise create an unbalanced pressure force against the ear drum, causing pain. 
     When the earplug  100  is inflated in an ear canal, radial expansion at the tip  112  is constrained by the canal walls and a seal is formed. Further inflation will then increase the seal contact area. Thus, tapering of the sheath  104  thickness ensures the earplug  100  will create an effective seal in ear canals of varying diameter. In wide ear canals, the radius of the inflated sheath  104  at the tip  112  will be larger and the axial length of the inflated region will be less than in narrow ear canals, which will have a smaller inflation radius and longer axial region of inflation to accommodate the same volume of inflation fluid. To keep inflation pressure low and provide good conformability to the ear canal, the wall thickness of the sheath  104  near the tip  112  must be very thin, preferably in the range of 0.002-0.006 inches. The thickness of the sheath  104  at the flange  110  should be greater, preferably in the range of 0.010-0.050 inches. 
     An acoustic channel  106  through the core  103  and the flange  110  provides a pass-through by which sounds may be introduced past the earplug seal. Various filters may be inserted in this channel to affect the frequency-dependent and level-dependent attenuation of the earplug. 
     To withdraw the earplug  100 , the user pulls on the release tab  114  to pop the cap  105  into its original convex or non-inverted form. This action will suck fluid  111  back into the bulb  101  and deflate the sheath  104 . The earplug  100  may then be pulled from the user&#39;s ear canal. 
     Referring to  FIG. 5 , the bi-stable cap  105  provides a simple and easy-to-use mechanism and methodology for the user to inflate the sheath  104  and ensure that it remains inflated during use. The cap  105  is defined by geometric features for various preferred embodiments, including a flat land  115  for adhering to the flange  110 , a thin elastic hinge region  116  to enable inversion, and a hemispherical region  117  of uniform thickness. The cap  105  is preferably molded as a single component in its externally convex configuration and including the release tab  114 . The angle T between the tab  114  and an end portion of the hemispherical region  117  is important to the bistable function and operation of the cap  105  and is predefined appropriately, with a preferred value in the range of 20-30 degrees. 
     The cap  105  geometry is carefully tuned to achieve elastic stability in both concave and convex topologies, preferably with maximal stability in the concave case in order to resist the inflation pressure and avoid inadvertent release during use. In the preferred embodiment, the cap  105  resists between 2 and 3 PSI in that position. To achieve this performance, the cap  105  is preferably constructed of a relatively stiff silicone with durometer hardness of 60 on the Shore A scale. This silicone should also have high elongation capability to enable resilience and durability in the elastic hinge region  116 . The inversion displacement of the cap  105  is matched to the sheath inflation volume required to achieve a good seal in the ear canal. In various preferred embodiments, the inversion displacement of the cap  105  is in the range of 0.025-0.050 cubic inches. In certain embodiments, it may be advantageous to provide multiple (e.g., two or three) different standard sizes of earplugs  100  with different displacement volumes to accommodate various ear sizes. 
     For a highly attenuating earplug  100 , it is desirable for the earplug inflation fluid  111  to have acoustic impedance (the product of density and sound speed) which differs significantly from that of air. Most common liquids meet this requirement. 
     It is also beneficial to select a liquid with low vapor pressure. All silicones have high permeability, and the liquid tends to diffuse through the silicone sheath  104 . A liquid with higher vapor pressure (such as water) tends to evaporate from the outer surface of the sheath  104 . This evaporation maintains a concentration gradient across the sheath  104 , driving further diffusion and ultimately depleting the volume of liquid contained in the earplug  100  over time. A liquid with low vapor pressure will still diffuse through the sheath  104  but will not evaporate when reaching the outer surface. This brings diffusion to a halt and prevents significant depletion of the liquid volume. This diffusive process also maintains a thin layer of liquid on the exterior of the sheath  104 , providing a slight lubrication effect which can be beneficial to the function and comfort of the earplug. 
     Further, it is important for the fluid  111  to be inert and biocompatible. It should be safe for contact with the ear canal as a result of diffusion, or in the case of a leak or rupture of the sheath  104 . In certain preferred embodiments, these requirements are met with liquids such as glycerol, mineral oil, or silicone oil. In alternative embodiments, other liquids might also be used. 
     In another embodiment, the earplug fluid  111  may be a gas instead of a liquid. Experimental data show that such a gas-filled earplug provides modest sound attenuation, but a very flat frequency response. This may be beneficial for some applications. For example, musicians are chronically exposed to high sound levels during performance and would benefit from some level of hearing protection, without sacrificing acoustic fidelity. 
     In the various preferred embodiments of the invention, the three elastomer components of the earplug  100 , e.g., the core  103 , the sheath  104 , and the bi-stable cap  105 , are fabricated efficiently by molding using two-part liquid silicone, heat cured liquid silicone, or heat cured high consistency silicone rubber. The core  103  is molded first, then the sheath  104  is over-molded onto the core  103 . This overmolding process naturally forms the required mechanical attachment and seal at the tip  107  of the sheath  104  and the anchor points  108 . The required release between the sheath  104  and the core  103  at the tapered interface  109  is achieved by applying a mold release agent to that surface of the stem  102  prior to the overmolding process. These steps will be readily understood by one skilled in the art of molding. 
     Alternatively, the sheath  104  may be formed separately from the core  103  by a process such as injection molding or dip molding and may then be assembled onto the core with adhesive being applied to seal the tip  107  and anchor the base  108 . 
     The cap  105  can be formed separately by simple injection molding. It is then permanently adhered to the open end of the sheath  104  with an appropriate adhesive. 
     The fluid  111  can be introduced into the sealed volume after the cap  105  is adhered by injection with a hypodermic needle through the thick, spherical portion of the sheath  104 . Any gas bubbles remaining in the sealed volume can be extracted with the same hypodermic needle after the correct volume of liquid has been injected. When the sheath  104  is made of a soft silicone material and the hypodermic needle is small gauge and sharp, and the injection site is substantially self-sealing and does not result in a leak after the needle is removed. Alternatively, the fluid  111  may be introduced before the cap  105  is adhered by using an external vacuum to inflate the sheath  104  at the stem  102 . The fluid  111  will fill the inflated region  104  and the cap  105  may be adhered in its concave form. Other methods are also possible. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is, therefore, desired that the present embodiment be considered in all respects as illustrative and not restrictive. Similarly, the above-described methods and techniques for providing and using the present invention are illustrative processes and are not intended to limit the methods of manufacturing the present invention to those specifically defined herein. Further, features and aspects of the various embodiments described herein can be combined to form additional embodiments within the scope of the invention even if such combination is not specifically described herein.