HEARING AID EAR PIECE HAVING DISPOSABLE, COMPRESSIBLE POLYMERIC FOAM SLEEVE

Abstract: Detachably secured to the ear piece (11) of a hearing aid is a user-disposable sleeve (13) comprising soft polymeric retarded recovery foam (14) that can be compressed to be freely insertable into a person's ear canal and then allowed to recover to become wedged in the canal. The sleeve preferably includes a flexible, elongated plastic duct (16) over which the foam fits, and the duct is formed with a screw thread of a rigid plastic which mates with a screw thread on the ear piece for each attachment and removal. The external surface of the foam preferably is substantially cylindrical and can be formed with flutes (26) to provide venting of the user's ear.

Description: The invention relates to the ear piece of a hearing aid, namely the portion which is inserted into the external ear canal. The ear piece may be the hearing aid itself, for example, a canal hearing aid or an in-the-ear hearing aid; or an attachment, such as the end of a flexible sound tube of a behind-the-ear hearing aid. The ear piece often is molded to fit an individual's ear canal and sometimes has a compressible, resilient sleeve for enhanced comfort. Such a sleeve is often employed to permit one or a few ear pieces to fit nearly everyone, as do ear pieces of the invention. The problem of providing a hearing aid with an ear piece that can be continuously worn with comfort has long been a subject of research. See, for example, US-A-1753817 (Aber). There, an impression of an individual's ear canal was used to mold an ear piece (there called an "audiphone cap"). Such a procedure is still in widespread use, even though time-consuming and expensive and requiring two visits to fit a person with a hearing aid. Moreover, the resulting ear piece is rigid, uncomfortable to wear, and prone to falling out of the ear canal. GB-A-2091063 (Blackstone) discloses the use of a layer of cushioning material, preferably one providing a high coefficient of friction, to seal a small gap between the external surface of a molded ear piece (called a "plastics molded component") and the internal surface of the ear canal, and to eliminate any whistling sound or echo effect. The molded ear piece approximates the shape of the external ear canal. Only a thin layer of the cushioning material is employed with the result that it does not provide a truly comfortable fit. Figs. 14-18 of US-A-4375016 (Harada) show a layer of cushioning material in the form of a sleeve which fits over the distal end of the ear piece and is said to provide excellent fit without the necessity of using a custom molded construction. That sleeve is "formed from a compressible foam with characteristics as shown in US-E-29487." The foam "can be compressed to a diameter less than that of the auditory canal. As the foam slowly attempts to return to its original configuration, it seals the auditory canal in a comfortable fashion as shown in FIGS. 17 and 18" (Col. 4, lines 41-56). However, the Harada patent does not indicate how the sleeve is prevented from remaining in the ear canal if the ear piece is either accidentally dislodged from the ear canal or simply pulled out. Rather than dealing with such matters, the Harada patent concentrates on the venting of excess sound pressure from the ear canal to the atmosphere. The reissue patent (Gardner, Jr.) cited in the Harada patent does not concern hearing aids but describes an "earplug ... composed of a resilient, plasticized polymeric foam containing a sufficiently high concentration of organic plasticizer to provide the foam with a rate of recovery from 60 percent compression to 40 percent compression in 1 to 60 seconds and an equilibrium pressure at 40 percent compression thereof from 0.2 to 1.3 p.s.i." (claim 1). Cylindrical plugs of this material can be coaxially bored and employed as a covering over a tubular tip portion of a lightweight headphone set. However, like the Harada patent, Gardner does not indicate how the plug is prevented from remaining in the ear canal if the tubular tip portion is accidentally dislodged or simply pulled out. EP-A-0173371 discloses a hearing aid adapted to be inserted into the external passage of the vast majority of human ears while leaving the concha unencumbered and without requiring individual impressions, the invention proposes a hearing aid which comprises a housing, a coupling element connected to the housing in communication with the sound emission opening of the hearing aid, and a sealing plug detachably connected to the coupling element and having an end remote from the housing, the sealing plug being comprised of cylindrical inner part mounted on the coupling element and an outer part turned back from the inner part at the remote end. Despite the approaches discussed above, none have been truly effective, particularly from the standpoint of providing an ear piece which is comfortable, retained during use, and readily removable when desired. Moreover, none have addressed a continuing problem in the hearing aid art, namely clogging of the sound tube by ear wax. Approximately half of professional repairs of hearing aids are either to remove ear wax or to repair damage caused by a user who tried to clean out the wax. That problem has been addressed in GB-A-2155276 (Brander et al.); DE-A-2818273 (Sommer); and EP-A-0159571 (Moser et al.). The present invention provides a sleeve adapted for use with a hearing aid, which hearing aid has an ear piece including a sound tube, wherein the sleeve is characterized by the combination of a substantially cylindrical body with an external surface, a central passage through said body, and at least one flute on the external surface of the body, and a fastening means for disposably attaching the sleeve to the hearing aid, the fastening means providing a Holding Value and Pullout Value, wherein the Holding Value is at least 1-½ times the Pullout Value, the sleeve being made from a retarded recovery foam. In one embodiment of the invention a user-disposable sleeve comprises; a flexible, elongated duct (16) which is formed with a longitudinal passage and fastening means at one end thereof for disposably attaching the duct to said ear piece with said passage connecting the sound tube of the hearing aid to the user's ear, and soft polymeric foam (14) having proximal and distal ends, the foam fitting over and being firmly secured to the duct, with the fastening means being at the proximal end of the foam, which foam has an external surface, is highly compressible, has slow, substantially complete recovery, and can be compressed to be freely insertable into a user's external ear canal and to become wedged in the canal when the foam is allowed to recover, the fastening means on the duct providing a Holding Value and a Pullout Value, wherein the Holding Value is at least 1-½ times the Pullout Value. The user-disposable attachment to a hearing aid enables the user to keep its ear piece clean with only minimal, if any, risk of damage to the hearing aid. Moreover, hearing aids utilizing this disposable sleeve enable the user to hear better, that is, hear better quality sounds. The novel user-disposable attachment comprises a sleeve which can be used with an in-the-ear hearing aid, a behind-the-ear hearing aid, or a canal hearing aid. The novel sleeve is: (1) easy to use, (2) easy to change, (3) comfortable to wear due to its conformability and yet reliably stays in place, (4) easy to manufacture, and (5) conveniently fitted by an audiologist to almost any user. Furthermore, by selecting from a set of sleeves of the invention, the audiologist will be able to provide each user with the best possible acoustical fit. In another aspect, the invention provides a hearing aid comprising an ear piece through which a sound tube extends plus a sleeve which is formed with a central longitudinal passage approximating the size of the sound tube. The sleeve comprises soft polymeric foam that has retarded recovery. That is, while being highly compressible, it has slow, substantially complete recovery, and can be compressed to be freely insertable into a user's external ear canal to become wedged in the canal when the foam is allowed to recover. These retarded recovery attributes also are possessed by the foam sleeve of the hearing aid of Figs. 14-18 of the above-cited Harada patent. Unlike that of the Harada patent, the sleeve of the present invention is user-disposable and the hearing aid of the invention includes means for disposably attaching the sleeve to the ear piece. When attached, said central longitudinal passage of the sleeve connects the sound tube to the user's ear. The attaching means should provide a Holding Value at least 1-1/2 times the Pullout Value, each of which terms is defined hereinbelow. At substantially lower ratios of Holding Value to Pullout Value, there is a danger that the polymeric foam sleeve will be left in the person's ear canal if the ear piece were accidentally dislodged or otherwise pulled out. The exterior surface of the novel sleeve preferably is substantially cylindrical, tapering slightly inwardly toward its distal end to enhance insertion into the user's ear canal. The sleeve may be formed either by molding or by cutting a section from a block. If the sleeve is molded, the exterior surface may possess a skin of higher density cell structure than that of the interior of the sleeve. This skin may minimize ear wax penetration of the foam; provide water resistance to the foam; and generally improve the cleanliness of the foam. To remove the novel hearing aid from the ear canal, the user may first wiggle the ear piece laterally to compress the foam of the sleeve, thus reducing the friction against the wall of the canal during removal. In addition to its sound tube, the ear piece of a canal or an in-the-ear hearing aid usually is formed with one or more air vents, in which event the sleeve may be formed with air vents connecting one or more of those air vents to the inner reaches of the ear canal. When used with a behind-the-ear hearing aid, the air vents may open to the atmosphere. The air vents preferably are provided by flutes formed in the exterior surface of the polymeric foam of the novel sleeve, usually two, three or four flutes symmetrically positioned around the exterior surface. When the exterior surface of the sleeve is substantially cylindrical, each flute preferably is semi-cylindrical, from 2 to 3 mm in breadth, and extends 1.0 to 1.5 mm beneath the substantially cylindrical surface. To simplify changing sleeves by the user, the means for disposably attaching the sleeve preferably includes a duct over which the retarded recovery foam fits and to which the foam is firmly secured. When the sleeve includes a duct, the central longitudinal passage of the sleeve is provided by the duct. The duct preferably comprises a moldable plastic that is flexible to allow it to conform to the user's external ear canal and to minimize any hazard of scratching or otherwise irritating the user's ear. Preferred materials from which a flexible plastic duct may be molded include a filled or unfilled semi-crystalline polymer such as plasticized poly(vinyl chloride) or crosslinked natural or synthetic elastomers such as natural rubber, chlorinated isoprene, silicone rubber, and block copolymers of styrene-dienes. The material of the duct preferably has a Shore durometer value between 40A and 40D. The foam may be secured to the duct by a layer of adhesive cement but preferably is molded onto the duct, thus serving as its own adhesive. The duct and the ear piece can be formed with mating screw threads which preferably are self-aligning, e.g., tapered to guard against cross-threading. This makes it easy for the user to detach a used sleeve and securely attach a fresh sleeve. When the duct comprises a flexible plastic, the portion of the duct which is threaded preferably is more rigid. When the screw threads of the duct extend beyond the proximal end of the foam, they do not interfere with the compression of the foam. Easy attachment and detachment can also be provided by forming the duct and the ear piece to provide bayonet or ball-and-socket attachments. A preferred retarded recovery foam for the foam sleeve is that of the "Attenutech" 6300 earplugs available from 3M. These earplugs are resilient and recover slowly from compression to provide adequate time for insertion of a compressed earplug into the external ear canal before it recovers to fill the canal. These earplugs are formed from polyurethane foam which does not contain any plasticizer. The retarded recovery foam of the Gardner patent should also be useful but less preferred because of potential problems stemming from the tendency of plasticizers to migrate and volatilize. Preferably the compressible, soft polymeric foam of the novel sleeves has a Retarded Recovery Value (as defined below) of at least 4 seconds and no more than 45 seconds, ideally from 15 to 35 seconds. If the sleeve does not include a duct, it preferably is molded to form an impervious skin covering the walls of its central passage. Whether or not the walls of the central passage are provided by an impervious skin or a duct, those walls preferably are flared out at the distal end of the sleeve, thus minimizing the danger of blockage by ear wax. In the drawing, all figures of which are schematic, Fig. 1 is a longitudinal cross-section through a portion of a preferred hearing aid of the invention with its user disposable sleeve in position to be threaded onto its ear piece, parts thereof shown in elevation; Fig. 2 is an end view of the hearing aid of Fig. 1; Fig. 3 is a longitudinal central cross-section through the ear piece and sleeve of another hearing aid of the invention, parts thereof shown in elevation; Fig. 4 is a longitudinal cross-section through the ear piece and sleeve of a third hearing aid of the invention, parts thereof shown in elevation; Fig. 5 is a longitudinal central cross-section through the ear piece and sleeve of a fourth hearing aid of the invention, parts thereof shown in elevation; Fig. 6 is a longitudinal cross-section through the ear piece and sleeve of a fifth hearing aid of the invention, parts thereof shown in elevation; and Fig. 7 is a longitudinal cross-section through the ear piece and sleeve of a sixth hearing aid of the invention, parts thereof shown in elevation. Referring to Figs. 1 and 2, the molded plastic casing 10 of a canal hearing aid has an ear piece 11, the external surface of which is formed with a male screw thread 12. A sleeve 13 consists of retarded recovery foam 14 and an internal, flexible, elongated plastic duct 16 formed with a longitudinal passage which provides a central passage for the sleeve 13. A substantially cylindrical layer of adhesive cement 18 secures the foam to the duct. The longitudinal passage through the duct 16 is formed with a female screw thread 20 which mates with the male screw thread 12 of the ear piece. When the sleeve 13 is threaded onto the ear piece 11, a flange 21 of its duct 16 comes to rest against the casing 10 of the hearing aid. At its distal end, the foam 14 has a flared opening 22 so that any wax from the user's ear which may accumulate on the foam is unlikely to block completely the portion of the sound tube that extends through the central passage of the sleeve 13 and connects to an internal passage 24 through the ear piece 11. When the foam is compressed to permit the assembly to be inserted into a person's ear canal and then allowed to recover to become seated, the compressive forces cannot substantially close its flared opening 22, because the foam extends only slightly beyond the distal end of the duct 16. The external surface 25 of the foam 14 is substantially cylindrical except for two diametrically opposed flutes 26 which, when the foam is compressed by the user's ear canal, will communicate through an annular channel 27 to a series of cylindrical air vents 28 in the casing 10 (two of which are shown), the centers of which lie substantially in a circle concentric with axis of the male screw thread 12. The substantially cylindrical surface 25 of the foam 14 tapers inwardly toward its distal end to enhance insertion into the user's external ear canal. Shown in Fig. 3 is an ear piece 31 of a behind-the-ear hearing aid, the distal end of which is formed with a self-aligning tapered male screw thread 32. Detachably secured to the ear piece 31 is a sleeve 33 that consists of retarded recovery foam 34, a flexible, elongated plastic duct 36, and a substantially cylindrical layer of adhesive cement 38 securing the foam to the duct. At the proximal end of the duct 36, its longitudinal passage is formed with a female screw thread 37 that mates with the male screw thread 32 of the ear piece 31. Shown in Fig. 4 is an ear piece 41 of a behind-the-ear hearing aid, the distal end of which has a protuberance in the form of a ball 42. Detachably secured to the ear piece 41 is a sleeve 43 that consists of retarded recovery foam 44, a flexible, elongated plastic duct 46, and a substantially cylindrical layer of adhesive cement 48 securing the foam to the duct. The longitudinal passage through the duct 46 is formed with a socket 47 into which the ball 42 fits to permit the sleeve 43 to be readily attached or detached. The distal end 49 of the longitudinal passage of the duct 46 is conical to enhance attachment. The behind-the-ear hearing aid of Fig. 5 has an ear piece 51, the external surface of the distal end of which is formed with a male screw thread 52, having a major diameter/minor diameter ratio of about 2. Disposably attached to the ear piece 51 is a sleeve 53 consisting of retarded recovery foam 54 formed with a cylindrical central passage 55. Because of the resilience of the foam, the sleeve has been self-threaded onto the male screw thread 52 of the ear piece 51 until its proximal surface 56 (which extends orthogonally to the axis of the passage 55) abuts the distal face 57 of the ear piece. By providing a high major diameter/minor diameter ratio, there should be no danger of leaving the sleeve in a user's ear upon withdrawing the ear piece from a wearer's ear, especially when the male screw thread is coarse and sharp. The behind-the-ear hearing aid of Fig. 6 has an ear piece 61 which is formed with a tapered projection 62 having a central passage 65 to provide an outlet for its sound tube. Disposably attached to the ear piece 61 is a sleeve 63 consisting of retarded recovery foam 64, a flexible, elongated plastic duct 66, and a substantially cylindrical layer of adhesive cement 68 securing the foam to the duct. The proximal internal surface of the longitudinal passage 67 through the duct is tapered to mate with the projection 62. An annular layer of pressure-sensitive adhesive 69 on the proximal surface of the sleeve 63 contacts a smooth distal surface on the ear piece around its projection 62, thus releasably securing the sleeve to the ear piece. A preferred pressure-sensitive adhesive layer 69 is "Scotch" A-60 acrylic systems No. 444 double-coated pressure-sensitive adhesive film tape from 3M. The behind-the-ear hearing aid of Fig. 7 has an ear piece 71 which is formed with a female screw thread 72. Disposably attached to the ear piece 71 is a sleeve 73 consisting of retarded recovery foam 74, a flexible, elongated plastic duct 76, a layer of adhesive cement 78 securing the foam to the duct, and a rigid plastic adapter 79. The duct 76 and adapter 79 have been bonded together at 75 with a plastic solvent. The proximal end of the adapter is formed with a male screw thread 77 which mates with the female screw thread 72 of the ear piece 71. Holding Value Drilled in aluminum block 1.6 cm in thickness are a number of holes, each 0.344 inch (8.74 mm) in diameter. After coating a hole with adhesive cement, a sleeve to be tested is compressed to permit insertion and then allowed to expand against the adhesive cement. After standing in a room temperature environment (23°C, 48% relative humidity) for at least one day to allow the adhesive cement to cure, the jaw of a tensile tester ("Instron" Model 1122) is clamped either onto a protruding duct of the sleeve or, if there is no duct, onto a portion of an ear piece onto which the sleeve has been fitted. The assembly is then warmed to 37°C, held at that temperature for 3 minutes, and then immediately tested in the room temperature environment by measuring the axial force required to pull the duct or ear piece out of the foam at a rate of about 25.4 cm/min. Pullout Value This test is carried out in the same way except as follows: The holes in the aluminum block are reamed (but not polished) to a roughness of 32 microinches (0.8 micrometers) peak-to-valley, and no adhesive is applied to the holes. After standing for at least three minutes, the tensile tester measures the axial force required to pull the sleeve out of the hole. Retarded Recovery Value A 8.0-mm cube is cut from the foam and then held for 24 hours at 23°C, 48% relative humidity and tested under those conditions. While standing on an aluminum plate, it is compressed to 1.6 mm using an aluminum piston 19 mm in diameter and immediately released. The time required for it to recover to a height of 6.4 mm is the Retarded Recovery Value of the foam. Example 1 A number of sleeves were made as illustrated in Fig. 7 using unplasticized polyurethane foam identical to that used in the aforementioned "Attenutech" 6300 earplugs. The foam had a Retarded Recovery Value of 27 seconds. When tested according to ANSI Specifications S3.19-1974, it provided a noise reduction rating of 29 dB. The flexible plastic duct 76 was molded of plasticized poly(vinyl chloride), and the foam was adhered to the duct using plastic adhesive No. 4475 from 3M. Its rigid plastic adapter 79 was polycarbonate. Significant dimensions were: Foam 74 maximum outer diameter 12.7 mm length 15.9 mm Duct 76 length 12.7 mm outer diameter 3.1 mm inner diameter 1.9 mm Using a die punch, the foam of each of the sleeves had been formed with a central passage 3.2 mm in diameter while sometimes simultaneously forming 2, 3 or 4 symmetrically arranged flutes, each 3/16 inch (4.8 mm) in diameter and centered on the maximum circumference of the foam. A set of four such sleeves including one with no flutes should permit an audiologist to fit 80-90% of potential users while also affording whatever level of venting is desired. A number of persons have worn such sleeves with their hearing aids, and a majority of them reported enhanced comfort and improved sound quality. Example 2 A number of sleeves were made substantially as illustrated in Fig. 5 using the same foam as was used in Example 1. Using a die punch, the foam was formed with a central passage 2.4 mm in diameter, and flutes were simultaneously formed in some of the sleeves as in Example 1. Each sleeve was self-threaded onto the male screw thread 52 of the ear piece 51 which had been formed of a rigid plastic ("Ultem" from G.E.) as follows: major diameter of thread 4.6 mm minor diameter of thread 2.8 mm pitch of thread 0.55 thread/mm width at crown 0.25 mm thread profile of leading (distal) face 105° of trailing (proximal) face 95° Example 3 A number of sleeves were made as illustrated in Fig. 6, except that, for purposes of testing, the duct 66 extended beyond the proximal end of the foam 64. The foam and duct were made from the same materials as were used in Example 1.

Claims: A sleeve (13) adapted for use with a hearing aid, which hearing aid has an ear piece (11) including a sound tube, wherein the sleeve is characterized by the combination of a substantially cylindrical body with an external surface, a central passage through said body, and at least one flute (26) on the external surface of said body, and a fastening means for disposably attaching said sleeve to said hearing aid, said fastening means providing a Holding Value and Pullout Value, wherein said Holding Value is at least 1-½ times said Pullout Value, said sleeve being made from a retarded recovery foam (14). A sleeve according to claim 1 wherein the ear piece is formed with a distal screw thread (12) and the sleeve is formed with a proximal screw thread (20) which mates with the screw thread of the ear piece. A sleeve according to claim 1 wherein said foam (14) is highly compressible, has slow, substantially complete recovery, and can be compressed to be freely insertable into a user's external ear canal and to become wedged in the canal when the foam is allowed to recover. A sleeve according to claim 1 further comprising a moldable, flexible plastic duct (16) secured in the central passage of the cylindrical body. A user-disposable sleeve (13) for a hearing aid, which hearing aid comprises an ear piece (11) including a sound tube, wherein the sleeve is characterized by the combination of a flexible, elongated duct (16) which is formed with a longitudinal passage and fastening means at one end thereof for disposably attaching the duct to said ear piece with said passage connecting the sound tube of the hearing aid to the user's ear, and soft polymeric foam (14) having proximal and distal ends, said foam fitting over and being firmly secured to the duct, with said fastening means being at said proximal end of said foam, which foam has an external surface, is highly compressible, has slow, substantially complete recovery, and can be compressed to be freely insertable into a user's external ear canal and to become wedged in the canal when the foam is allowed to recover, said fastening means on said duct providing a Holding Value and a Pullout Value, wherein said Holding Value is at least 1-½ times said Pullout Value. A user-disposable sleeve according to claim 5 wherein the elongated duct (16) approximates the size of the sound tube and wherein the distal end of the sound tube and the proximal end of the sleeve are each formed with screw threaded portions which mate with one another. A user-disposable sleeve according to claim 5 formed with at least one flute (26) on the external surface. A sleeve according to either claim 1 or claim 5 wherein the external surface of the sleeve (13) comprises a skin of higher density cell structure than that of the interior of said sleeve. A sleeve according to either claim 1 or claim 5 wherein the foam (14) has a Retarded Recovery Value of at least 4 seconds and no more than 45 seconds. Hearing aid having an ear piece (11) including a sound tube, wherein the hearing aid is characterized by a user-disposable sleeve (13) according to either claim 1 or claim 5 and fastening means on the sleeve and mateable fastening means on the ear piece for disposably attaching the sleeve to the ear piece, both fastening means combining to have a Holding Value of at least 1-½ times a Pullout Value. Hearing aid as defined in claim 10 wherein said fastening means comprise mating screw threads (12 and 20) formed on the duct and the ear piece. Hearing aid as defined in claim 11 wherein the external surface of the sleeve (13) is formed with at least one flute (26) for venting the user's ear. Hearing aid as defined in claim 12 wherein the distal end of the ear piece (11) is formed with an annular channel (27) extending around the sound tube and with a series of air vents (28), each opening into the annular channel, at least one flute communicating with the air vents through the annular channel.

Inventors: AHLBERG, CARL S. C/O MINNESOTA MINING AND, BUSHONG, JEROLD W. C/O MINNESOTA MINING AND, CHAMBERLIN, DAVIS W. C/O MINNESOTA MINING AND, KOLPE, VASANT V. C/O MINNESOTA MINING AND, OLIVEIRA, ROBERT J. C/O MINNESOTA MINING AND
Applicants: MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1987
Main classification: H04R25
IPC codes: H04R25