Electro-acoustic transducer

Abstract: An electro-acoustic transducer includes a housing (202) enclosing an electro-acoustic transducer device (201) and having an opening (202 a ) through which the diaphragm side of the transducer device (201) is exposed to the outside. A ring (209) is provided at and permanently fixed to the outer surface of the perimeter of the opening (202 a ). An outer part (211) of the ring (209) is much softer and more pliable than an inner member (210) and the elastic ring portion (211) has inner peripheral side edge portions and supporting portions which are engaged with peripheral edge surfaces and ribs of the base ring portion (210).

Description: The invention relates to an electro-acoustic transducer of the kind suitable for insertion in the ear. So called inner ear type headphone units have been previously proposed in which a housing enclosing an electro-acoustic transducer device is inserted into and attached within the concha of the ear of the user. Such a unit is shown in Fig. 1 of the accompanying drawings and includes a housing 102 enclosing a speaker unit which is the electro-acoustic device. The housing 102 is formed of a size such that it can be introduced into the ear's concha and has an open sound-radiating surface of the speaker unit 101. A connecting cord 103 supplying acoustic signals to the speaker unit 101 has its end 104 connected as by soldering to an input terminal 105 of the speaker unit 101. The connecting cord 103 exits the housing 102 to the outside by way of a cord extraction opening 106. An ear pad ring 107 is provided at the portion of the housing 102 facing to the ear's concha and on the perimeter of the front side of the speaker unit 101. The ear pad ring 107 is engaged with a rib 102 a provided at the perimeter of the open portion of the housing 102, and is attached to this portion by auxiliary securing means, such as adhesion. The housing 102 is formed of a relative hard material since it has to hold the speaker unit 101 in position and provide determined acoustic effects. On the other hand, the ear pad ring 107 is formed of a relatively soft material for providing good contact feel with the inner wall of the ear's concha and to permit insertion of the ring into ear conchae of different sizes. In order that the portion of the connection cord 103 extracted through the extraction opening 106 may be protected from accidents such as cord breakage caused by repeated cord flexure, a cylindrical cord bush 108 is provided on the housing 102 on a line of extension of the cord extraction opening 106. The cord bush 108 is formed of a relatively soft material, similarly to the ear pad ring 107, and provided with peripheral slots 109 to allow the bush 108 easily to be flexed. The portion of the connection cord 103 extracted through the cord extraction opening 106 may be bent smoothly as it is encased within the cord bush 108 when a stress is applied from outside to prevent accidents, such as breakage of the cord at the edge of the cord extraction opening 106. In the operation of the above described headphone unit, when the housing 102 is introduced into the ear's concha, the ear pad ring 107 is deformed under a pressure applied from the inner wall of the ear's concha. The ear pad ring 107 closes the ear's concha completely by abutting on the inner wall of the ear's concha by its own resiliency. With the ear's concha thus closed completely, the sound may be reproduced by the speaker unit 101 with optimum electro-acoustic characteristics. It will be noted that, since the size of the ear's conchae will differ from one person to another it may occur that the above described headphone unit cannot be introduced into the ear's concha, or the ear's concha cannot be closed satisfactorily by the ear pad ring 107, with the result that optimum acoustic characteristics are not obtained. That is, with the outside diameter d ₁ of the ear pad ring 107, the ear pad ring cannot be deformed to an outside diameter d ₀ of the rib 102 a . Therefore, when the ear's concha has an inside diameter less than the outside diameter d ₀ of the rib 102 a , the housing 102 cannot be introduced into the ear's concha. On the other hand, when the ear's concha has an inside diameter larger than the outside diameter d ₁ of the ear pad ring 107, a void or gap remains between the ear pad ring 107 and the inner wall of the ear's concha, so that the ear's concha is not closed completely. When the ear's concha is not closed completely in this manner, the output is lowered especially in the lower frequency range of the acoustic characteristics, as shown at C in Fig. 7, with the result that optimum electro-acoustic characteristics cannot be realized. It should be noted that the acoustic characteristics shown at B in Fig. 7 are those obtained when the ear's concha is closed as normally in the above described conventional headphone unit. For maintaining the optimum acoustic characteristics as described above, it is necessary that the ear pad ring 107 be formed of a softer material and with an increased thickness so that it may be deformed radially more easily and with a larger amount of deformation. However, when the housing 102 is mounted to or detached from the ear's concha, a stress is applied to the ear pad ring 107 tending to displace the ear pad ring 107 away from the housing 102 in the directions shown by arrow F in Fig. 1 under the force of friction with the inner wall of the ear's concha. When the ear pad ring 107 is formed of a soft and pliable material, the ear pad ring is deformed easily under such stress. When the ear pad ring 107 is deformed under stress in this manner, both the aforementioned engaging and auxiliary securing means tend to be loosened so that the ear pad ring may be detached from the rib 102 a . In short, when the material of the ear pad ring is formed of a softer material, the size range of the ear's conchae into which a given ear pad ring can be introduced is enhanced, while the contact feel of the apparatus with the ear's concha is improved. However, when the ear pad ring is formed of a softer material, the ear pad ring is more likely to be detached from the housing, so that durability of the earphone unit is not ensured. For this reason, the desired durability may only be ensured at the sacrifice to some extent of the aforementioned acoustic characteristics or contact feel. The same inconvenience as experienced with the ear pad ring arises with the cord bush 108, that is, when the cord bush is formed of a softer material, the connection cord 103 may be protected more reliably, however, the cord is more likely to be detached from the housing 102. It has been proposed, in an electro-acoustic transducer in which the housing encloses the speaker unit, for the ear pad ring and the cord bush to be moulded integrally from the same material thus facilitating the assembly operation and improving the durability. However, in this electro-acoustic transducer, since the portion contacting the ear's concha and the housing holding the speaker unit are formed of the same material, a material suitable for both the contacting portion and the housing cannot be used, such that the contacting portion and the housing need be formed of a material having only moderate hardness. Patent Specification US-A-3 671 685 discloses an audio headset with earpieces each of which comprises a projection of a rigid plastics material with a sound channel therethrough and a groove around the outer face to receive a projecting rib of a tip of soft elastic plastic in the form of a tube. A tip of suitable outside diameter is chosen to suit the size of the ear canal of the user in whose ear the tip is to be received. According to the invention an electro-acoustic transducer of the kind suitable for insertion in the ear comprises a housing enclosing an electro-acoustic transducer device, the housing being formed of a synthetic resin and including an opening through which the diaphragm side of the electro-acoustic transducer device is exposed to the outside, and a ring at and permanently fixed to the outer surface of the perimeter of the opening, the outer periphery of the ring being softer and more pliable than the housing; characterised in that the ring comprises a base ring portion and an elastic ring portion; the elastic ring portion is provided at the outer periphery of the base ring portion and is formed of a synthetic resin material softer and more flexible than the material of the base ring portion; the elastic ring portion is formed by double-shot moulding on the outer periphery of the base ring portion with the elastic ring portion formed of a material having a lower rubber hardness than the rubber hardness of the material of the housing; the base ring portion is formed to fit the outer surface side of the opening in the housing; the base ring portion is provided with a plurality of slots mating with projections on the outer surface side of the opening; and the elastic ring portion has inner peripheral side edge portions and supporting portions engaged with peripheral edge surfaces and ribs of the base ring portion. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Fig. 1 is a sectional view showing the construction of a headphone unit of previously proposed kind; Fig. 2 is a sectional view showing the construction of a headphone unit according to the invention; Fig. 3 is an exploded perspective view showing the construction of the headphone unit of Figure 2; Fig. 4 is an exploded perspective view showing a base ring portion and an elastic ring portion employed in the unit of Figures 2 and 3; Fig. 5 is a sectional view showing the base ring portion and the elastic ring shown in Fig. 4; Fig. 6 is a plan view corresponding to Fig. 5; and Fig. 7 is a diagram showing acoustic characteristics of the headphone unit of the invention and those of the conventional headphone unit. Referring to the drawings, a headphone unit comprises a housing 202 and an electro-acoustic transducer or speaker unit 201 enclosed in the housing 202. The speaker unit 201 includes a magnetic circuit composed of a magnet and a yoke, a coil bobbin driven by the magnetic circuit and a diaphragm attached to the coil bobbin. The electrical signals supplied to the coil bobbin are converted into sounds by vibration of the diaphragm, in a well-known manner. The housing 202 is of a size such that it can be introduced into the ear's concha. The side of the housing 202 corresponding to the sound radiating side of the speaker unit 201 is formed with an opening 202 a . To hold the speaker unit 201 in position, and to provide acoustic effects, the housing 202 is formed of a relatively stiff material having a rubber hardness of about 90 degrees, such as ABS resin. The speaker unit 201 is held in position with its peripheral portion fitted in a mating recess 202 b formed in the inner wall of the opening 202 a . A connecting cord 203 supplying electric signals to the speaker unit 201 has its terminal portion 204 connected as by soldering to an input terminal 205 of the speaker unit 201. The connecting cord exits the housing 202 through a cord extraction opening 206. To protect the portion of the connecting cord 203 exiting through the cord extraction opening 206 against accidents such as cord breakage caused by repeated cord flexure, a cylindrical cord bush 207 is provided on a line of extension of the cord extraction opening 206. The cord bush 207 is formed of a relatively soft and pliable material and moreover has a plurality of annular grooves 208 as shown, so that it may be flexed easily. The portion of the connecting cord 203 exiting out of the cord extraction opening 206 is supported by the cord bush 207 so that it may be flexed smoothly as it is encased in the cord bush 207 when the external force is applied thereto. In this manner, the risk of accidents such as cord breakage otherwise caused by the flexure of the cord in contact with the edge of the cord extraction opening 206, may be minimized. The housing 202 is fitted, as shown in Figs. 2 and 3, with a ring member 209 at the perimeter of the opening 202 a . The ring member 209 is formed by a base ring 210 and an elastic ring 211 provided at the perimeter of the base ring 210, as shown in Figs. 5 and 6. The rings 210, 211 are formed by double-shot moulding from respective different materials. The base ring 210 is formed of the same material as the housing 202, and with a toroidal profile with an outside diameter D₀ as shown in Figs. 2 and 5. The toroidal or ring-shaped peripheral wall of the base ring 210 is formed with a plurality of circumferentially extending slots 210 a , as shown in Fig. 3, to be engaged by mating projections 202 c provided on the outer wall of the housing 202 about the opening 202 a . Between each two neighbouring slots 210 a a rib 210 b is formed. The base ring 210 is fitted to the housing 202 in position, with the projections 202 c engaged in the recesses 210 a . The elastic ring 211 is formed of a material having a rubber hardness of, for example, 60 degrees, or of a softer material, such as so-called elastomer, having a rubber hardness of 20 to 40 degrees, and is moulded on the outer perimeter of the base ring 210 by double-shot moulding. The ring 211 has a prescribed outside diameter D₁ as shown in Fig. 2. Portions of the elastic ring 211 cooperating with the base ring 210 are recessed to accommodate the elastic ring 211, while portions of the ring 211 cooperating with the ribs 210 b are formed with tongue-like supporting portions 211 a . The elastic ring 211 has its inner peripheral side edge surfaces 211 b , 211 c and the supporting portions 211 a operatively associated with the one and the other peripheral edge surfaces 210 c , 210 d and the ribs 210 b of the base ring 210, as best shown in Fig. 4. By "double-shot moulding" is meant a method of moulding including the steps of initially forming a portion of a first material using a first metal mould, placing the portion of the first material in a predetermined position in a second metal mould and injecting and moulding a second material in the second metal mould to form a moulded article composed of the first and the second materials rigidly connected and united to each other. When a two-colour injection moulding machine is employed, after the portion of the first material is moulded, the predetermined movable portion of the metal mould may be shifted and the second material injected and moulded to form a moulded article formed of two kinds of materials. In the above described headphone unit, the outside diameter of the elastic ring 211 shown at D₁ in Fig. 2 is selected to be larger than the largest likely ear's concha of users, while the outside diameter of the base ring 210 shown at D₀ in Fig. 2 is selected to be smaller than the size of the smallest likely ear's concha of the users. When the housing 202 is introduced into an ear's concha, since the elastic ring 211 is formed of a material of low hardness and recessed, it can be easily deformed from the outside diameter in the undeformed state of the elastic ring 211 to an outside diameter approximately equal to the outside diameter of the base ring 210. In this manner, the sealing properties of the housing 202 with respect to the ear's concha when the housing is inserted into the ear's concha are improved, so that satisfactory acoustic properties are obtained in which, as shown at A in Fig. 7, the output in the low frequency range is improved compared to that of the above described previously proposed headphone unit. A soft contact feel of the portion of the housing 202 contacting with the ear's concha may also be achieved. The base ring 210 and the elastic ring 211 are formed by double-shot moulding so that the materials of the rings 210, 211 are strongly bonded together without the risk of peeling apart even after extended usage. It should be noted that the acoustic characteristics shown at P in Fig. 7 represent those in the ideal complete sealing state of the housing with respect to the ear's concha. It should be noted that the electro-acoustic transducer of the invention is not limited to the above described headphone unit, but may also be applied to the earphone or microphone units. For example, when a microphone unit is constructed in accordance with the invention and the rings are provided at the outer side of the opening of the housing exposing the sound input side of the electro-acoustic transducer unit, the effect of the noises generated by contact of the user's hands or fingers with the housing on the electro-acoustic transducer unit may be minimized. Also, since the base ring and the elastic ring are attached to the manually gripped portion of the housing, the housing may be gripped with improved hand feel and slip-proofness. Thus a base ring is provided on the outer surface of the perimeter of the opening of the housing, by which the sound radiating side or the sound input side of the electro-acoustic transducer is exposed to the outside, and an elastic ring is provided on the outer periphery of the base ring and is formed of an elastic material by double-shot moulding. The elastic ring is subject to considerable deformation and the two materials constituting the elastic ring are united together strongly by the double-shot moulding.

Claims: An electro-acoustic transducer of the kind suitable for insertion in the ear comprising a housing (202) enclosing an electro-acoustic transducer device (201), the housing (202) being formed of a synthetic resin and including an opening (202 a ) through which the diaphragm side of the electro-acoustic transducer device is exposed to the outside, and a ring (209) at and permanently fixed to the outer surface of the perimeter of the opening (202 a ), the outer periphery of the ring (209) being softer and more pliable than the housing (202); characterised in that the ring (209) comprises a base ring portion (210) and an elastic ring portion (211); the elastic ring portion (211) is provided at the outer periphery of the base ring portion (210) and is formed of a synthetic resin material softer and more flexible than the material of the base ring portion (210); the elastic ring portion (211) is formed by double-shot moulding on the outer periphery of the base ring portion (210) with the elastic ring portion (211) formed of a material having a lower rubber hardness than the rubber hardness of the material of the housing (202); the base ring portion (210) is formed to fit the outer surface side of the opening (202 a ) in the housing; the base ring portion (210) is provided with a plurality of slots (210 a ) mating with projections (202 c ) on the outer surface side of the opening (202 a ); and the elastic ring portion (211) has inner peripheral side edge portions (211 b , 211 c ) and supporting portions (211 a ) engaged with peripheral edge surfaces (210 c , 210 d ) and ribs (210 b ) of the base ring portion (210).

Inventors: ISO MASAHIKO C O PATENTS DIVIS, KAMON YOSHIYUKI C O PATENTS DI, YAMAGISHI MAKOTO C O PATENTS D, ISO, MASAHIKO, C/O PATENTS DIVISION, KAMON, YOSHIYUKI, C/O PATENTS DIVISION, YAMAGISHI, MAKOTO, C/O PATENTS DIVISION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1988
Main classification: H04R1
IPC codes: H04R1