Abstract:
In order to improve the immunity of a hearing aid to interference caused by the penetration of high-frequency electromagnetic waves via seams and openings of the hearing aid housing, the housing is composed of at least two electrically conductive parts that are joined in electrically conductive fashion via a high-frequency seal.

Description:
This is a continuation of application Ser. No. 08/352,191, filed Dec. 01, 1994,abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a hearing aid to be worn at the head, of the type having a housing containing an amplifier circuit, the amplifier circuit including a microphone, an earphone and a battery. 
     2. Description of the Prior Art 
     Swiss Patent 664 057 discloses a hearing aid to be worn at the head having a housing wherein an amplifier circuit is arranged. The amplifier circuit has a microphone, an ear phone and a battery. Receptacle parts composed of a metallic or non-metallic material for the electromagnetic shielding of the acoustic transducer are also provided in this hearing aid. 
     Further, German utility model GM 87 13 089 and European Application 0 352 954 respectively disclose hearing aids having a shielding plate for protecting the ear phone from the magnetic field of an audio coil, and a shielded magnet arrangement for the hearing aid. 
     Hearing aids of this type can be taken by the hearing-impaired wearer of the hearing aid into the proximity of strong transmitters such as, for example, automobile telephones, mobile radio equipment or microwave irradiation devices. In the proximity of such a transmitter, the emitted electromagnetic waves often have an extremely high field strength. These high-frequency electromagnetic waves can, in particular, penetrate through openings into the hearing aid and may have a disturbing influence on the amplifier circuit. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a hearing aid of the type described above wherein the penetration of high-frequency electromagnetic waves through joints and openings is substantially suppressed. 
     The above object is achieved in accordance with the principles of the present invention in a hearing aid having a housing formed by at least two electrically conductive housing parts that are connectable in electrically conductive fashion via a high-frequency seal. As a result, joints and openings between the housing parts are closed or shielded in a high-frequency-tight manner by means of the high-frequency seal. Given the inventive fashioning of the hearing aid, high-frequency electromagnetic waves can no longer disturbingly influence the amplifier circuit of the hearing aid or, can only do so to a slight extent. Moreover, the high-frequency seal simultaneously forms a protection against the penetration of superfine foreign bodies such as, for example, dust and/or moisture or sweat into the component mounting space within the hearing aid. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a hearing aid constructed in accordance with the principles of the present invention, to be worn at the head behind the ear, or to be worn contained in the frame of a pair of eyeglasses. 
     FIG. 2 illustrates the two housing shells of the hearing aid of FIG. 1. 
     FIGS. 3-5 respectively shown sections through two electrically conductive hearing aid housing parts that adjoin one another in electrically conductive fashion via a separate high-frequency seal. 
     FIG. 6 is a section through an operating element arranged in a housing part having an allocated high-frequency seal. 
     FIG. 7 is a view from the inside of a housing onto an operating element of FIG. 6 provided with a high-frequency seal. 
     FIG. 8 illustrates a further hearing aid to be worn at the head constructed in accordance with the principles of the present invention that can be introduced into the auditory canal. 
     FIG. 9 is a section through a rotatable operating element arranged in a hearing aid housing constructed in accordance with the principles of the present invention and having an allocated high-frequency seal. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a hearing aid to be worn at the head (behind-the-ear hearing aid) having a hearing aid housing 1 formed by an upper housing shell 2 and a lower housing shell 3. A carrying hook 4 that simultaneously serves as the audio channel is secured to an ear phone output baffle 5 of the housing. An operating element 6, for example, a volume control or potentiometer rotatory knob, a switch 7 and a tab 8 for the battery compartment project from the upper housing shell 2. 
     The two housing shells 2 and 3 are separately shown in FIG. 2. A tongue 9 runs around the inside of the opening of the upper housing shell 2. This tongue 9 covers a small gap 10 (separating seam), as shown in FIG. 3. The gap 10 arises when joining the two housing shells 2 and 3 between seating points that arise due to slight irregularities of the housing shells adjoining one another. According to the invention, the two housing shells 2 and 3 are fashioned as electrically conductive parts. The tongue 9 proceeding around, for example, the upper housing shell 2 is likewise fashioned electrically conductive and is formed as one piece with the upper housing shell 2. The electrically conductive parts 2, 9 and 3 of the housing 1 can, for example, be composed of plastic that has been made conductive by admixing electrically conductive powder, for example, graphite. 
     In the embodiment of FIG. 4, the two housing shells 2 and 3 composed of plastic are respectively provided or lined with respective electrically conductive layers 11 and 12, for example, at their inside. The conductive layers 11 and 12 also cover the adjoining edges 13 and 14 of the housing shells 2 and 3. The electrically conductive layers 11 and 12 can be elastically fashioned, so that the gap 10 (separating seam) shown in FIG. 3 can be completely closed when joining the two housing shells 2 and 3 due to the elasticity of the layers 11 and 12 that cover over the edges 13 and 14. The elastic and electrically conductive layers 11 and 12 of the borders 13 and 14 thus form an elastic high-frequency seal. The layers 11 and 12 can be composed of an electrically conductive foil or of an electrically conductive lacquer layer. 
     According to FIG. 5, the two housing shells 2 and 3 are again composed of plastic having an embedded, electrically conductive material. According to this exemplary embodiment, an all-around elastic high-frequency seal 15 is arranged between the edges 13 and 14 of the housing shells 2 and 3. For example, this high-frequency seal 15 can be a hose-shaped aluminum foil cladding having an elastic core. Irregularities can thus be compensated high-frequency-tight and a disturbing gap 10 can be avoided or, bridged. Further, the high-frequency seals shown in FIGS. 3-5 can also be provided in combination embodiments. 
     FIG. 6 shows a portion of the upper housing shell 2 that contains an operating element 16. The operating element 16 is fashioned as an electrically conductive part. The adjoining housing shell 2 has an electrically conductive coat 11, for example, at the inside of the housing. The operating element 16 partially projects from the opening 17 of the housing shell 2, for example, in the form of a small wheel or drum. An annular gap 18 that can be sealed by a high-frequency seal 19 of the above-described type remains between the electrically conductive operating element 16 and the housing shell 2. As a result, the parts 2 and 16 adjoining one another are electrically conductively connected to one another for shielding an external electromagnetic radiation and disturbing housing openings are avoided. 
     FIG. 7 shows the portion of the upper housing shell shown in FIG. 6 with a direction of view onto the inside of the housing shell (as seen from below onto the coating 11 of the housing). The opening 17 is indicated by a dot-dashed line. The operating element 16 is arranged inside the opening 17. The high-frequency seal 19 closes the gap 18 proceeding around the operating element 16. The operating element 16 can be electrically conductively fashioned in various ways, for example, by manufacturing the small wheel 16 of a plastic that is conductively coated or rendered conductive or metalized. 
     In the exemplary embodiment of FIG. 8, the hearing aid to be worn at the head is shown as an in-the-ear hearing aid that has a correspondingly shaped housing 20. An amplifier circuit 19 with various electronic components as well as a microphone 21, an ear phone 22 and a battery introducible into a battery compartment 23 is arranged in the housing 20. The battery can be replaced via a battery holder 24 that can be swung out of a face plate 25. The face plate 25 forms an outer wall of the housing 20 and has an electrically conductive coating 26 for shielding external electromagnetic radiation and for protecting the amplifier circuit 19 against high-frequency electromagnetic waves. Further the housing 20 can carry an electrically conductive coating 27, for example, at its surface. Finally, it is expedient when the allocated seating surfaces 28 and 29 of the in-the-ear hearing aid housing 20, or of the face plate 25, are likewise coated in electrically conductive fashion so as to make an electrically conductive connection, or are sealed from one another and secured by means of an insertable high-frequency seal. 
     FIG. 9 shows the shielded arrangement of the volume control 30 of the in-the-ear hearing aid in the face plate 25 that is provided with an electrically conductive lining 31 at the inside of the housing. The rotational axis 32 of the volume control 30 projects through a bore 33 into the interior of the hearing aid. For sealing and shielding the annular gap 34 between the bore 33 and the rotational axis 32, an annular high-frequency seal 35 having an electrically conductive contact is provided at the lining 31 and surrounding the rotational axis 32. 
     Further, an electrical connection between the electrically conductive housing lining 31, the high-frequency seal 35 and the amplifier circuit 19 can be produced, for example, by means of the rotational axis 32 of the volume control 30. It is also possible to join the electrically conductive parts of the hearing aid housing by a contact (not shown), for example, to a pole of the battery or a battery spring contact, whereby non-inductive impedance such as capacitors, resistors or the like may be possible provided in the electrical line connection. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.