Abstract:
A hearing aid includes at least two components joined together via an injection molding process. The injection molding process mitigates the need for a separate fastening means to join the components.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a division of application Ser. No. 09/656,805 filed on Sep. 7, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to hearing aids and more specifically to hearing aids manufactured by multi-component injection molding. 
     BACKGROUND OF THE INVENTION 
     Two-component or multi-component injection molding procedures are known from the art of plastic processing. Illustratively reference is made to Ch. Jaroschek, “Das Mehrkomponenten-Spritzgiessverfahren&#39; [Multi-component injection molding”] in Swiss Plastics 19 [1997] #12 or to U. Stenglin “Hart/Weich-Verbindungen und anwendungsbezogene Modizifierbarkeit von TPE-S (SEBS/SEPS)” [Hard/soft compounds and application-specific modification of TPE-S (SEBS/SEPS), Swiss Plastic 20 [1998] #3. These sources elucidate the advantages of two- or multi-component injection molding with respect to costs of tools, personnel, machinery and materials. These methods basically are categorized into sandwich molding injection and overmolding procedures. If not exclusively but primarily, the interest herein is the cited overmolding method. In this procedure a part is manufactured from a first material component and it is then overfilled at least segment-wise with a second, different material component, the second part of a different material being built-up on the said first part. All sprayable thermoplastics can be used, in particular also for overmolding, and furthermore, even if in very special applications, also further materials which cannot be joined. 
     The above cited costs obviously also represent substantive production factors in the manufacture of hearing aids. But with respect to the manufacture of hearing aids, there is additionally the problem of space because a permanent requirement of this field is always the most compact possible design. 
     BRIEF SUMMARY OF THE INVENTION 
     The objective of the present invention is a manufacturing method and a hearing aid made thereby to attain a significant increase in the compactness of hearing aids. 
     Consequently the method proposes manufacturing at least two of the parts to be assembled at the hearing aid by two-component or multi-component injection molding and to assemble them jointly. Obviously the advantage of cost reduction accompanying such a procedure is highly welcome, however more significantly, the said method of the present invention attains the essential criterion in hearing-aid design, namely increasing the component density per cm3 of the available space. 
     When, according to a preferred implementation of the method of the invention, one of the parts shall be at least a portion of the hearing-aid housing, namely and illustratively one shell of a two-shell housing, then it will be possible to appose directly—by means of two-component or multi-component injection molding—further elements, in particular seals for instance to set up a tight union with the second housing shell and/or impact-damping recesses for delicate hearing-aid elements and/or further active hearing-aid elements such as acoustic conductors. Basically this feature makes it possible eliminating junction means between said cited parts and elements that are required in conventional designs, or such means may be made precisely as compact as required functionally without the need for junction means such as grooves and tabs. 
     As already mentioned, basically the preferred implementation of the method of the invention builds up at least one design seal by means of two- or multi-component injection molding, in general jointly with a further part directly abutting the seal, for instance and preferably a housing part or an operational element passing through the housing or a further hearing-aid part which must be sealed per se very accurately. 
     In another preferred implementation of the manufacturing method and in particular regarding behind the ear hearing aids, the invention proposes manufacturing the acoustic conductor at the output of the electro-mechanical transducer, said conductor typically being made of plastic, using said injection molding, whether jointly directly with a housing part or for instance with a resiliently and topographically sealing assembly part that shall be received in a housing seat. 
     In a further preferred embodiment of the method, an acoustic conductor is manufactured at the input of the acousto-electric hearing-aid transducer by means of the said injection molding, whether for instance this be jointly with a portion of the hearing aid housing or with a specifically designed elastic assembly part. In further modes implementing the invention, where said modes obviously may be used individually or in combination with other preferred embodiments, seats for hearing aid elements are manufactured by said injection molding, whether jointly with housing portions and/or jointly with other elements directly abutting them 
     In another preferred implementation of the invention, predetermined surface zones made of another material are jointly manufactured on the housing outside by means of said injection molding, for instance for reasons of design and/or to facilitate touching, with the fingers alone, certain control elements mounted on the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The invention is elucidated below in illustrative manner and in relation to the drawings. 
         FIG. 1  schematically shows a perspective of a portion of a hearing aid housing with a seal apposed in the manner of the invention, 
         FIG. 2  is a cross-section of a part of the housing of  FIG. 1  with the apposed seal of the invention, 
         FIG. 3  is a cross-section of the housing wall of a hearing aid of conventional manufacture with assembled seal, 
         FIG. 4  schematically shows a cross-section of a portion of the hearing-aid housing with an acoustic conductor apposed in the manner of the invention and/or with a seat for a module, 
         FIG. 5  schematically shows a cross-section of a housing wall portion with control element and with a feedthrough of the invention and a unit support, and 
         FIG. 6  schematically and in functional manner shows the connection of the invention of two hearing-aid functional units. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The discussion already given above in the introduction to the specification provide the expert with a large number of designs, depending on the hearing aid or its configuration, to jointly manufacture two or more pertinent elements by two- or multi-component injection molding, in particular also by overmolding and then to assemble them jointly into an integral part. Nevertheless preferred procedures of the cited injection molding method shall be provided below by means of several schematic examples. The actual two-component or multi-component molding procedures will not be discussed because being well known in the general manufacture of components, in particular in plastic molding and injection molding. 
       FIG. 1  schematically and in perspective shows the shell  1  of a hearing aid housing, for instance of behind-the-ear hearing aid. This shell will be assembled along its edges  3  to further housing portions in such manner that its inside space shall be tightly sealed along these edges  3 . This problem is conventionally solved in that—as shown in FIG.  3 —positioning and fastening means are integrated in this shell as shown, for instance grooves in the wall of the housing part  1  into which, and again manually, is inserted a seal  7 . 
     As regards the invention, a seal  7   a  is sprayed by two-component injection overmolding directly on the cited housing shell  1 , ie the edge  3 . In this implementation the material of the housing wall per se meets the dimensional-stability requirements placed on the housing, while the material of the second part sprayed by overmolding meets the requirements placed on the seal  7   a . In this process the seal  7   a  can be sized exactly as needed by sealing and the wall of the housing part  1  also may be dimensioned and shaped exclusively in the light of criteria set on the wall of the housing part  1 . The housing wall no longer need be designed to meet the requirements of assembling a separate seal  7  of  FIG. 3 . 
       FIG. 4  schematically shows illustratively how, on one hand regarding a hearing aid housing  10 , the invention apposes an acoustical conductor  13 , for instance at the output of an electromechanical transducer mounted in the hearing aid, or, similarly, at the input of an acoustic/electrical transducer (omitted) present at the hearing aid. In addition a resilient bush  15  seating the transducer  12  may be integrated into the housing  10 . The housing  10  and the acoustic conductor  13  and/or the housing  10  and the seating bush  15 , or all three, namely the housing  10 , seating bush  15  and acoustic conductor  13  are manufactured as one part by two- or three-component injection molding. The material of the housing  10  or of its wall is selected in a conventional manner to meet the requirements set on said housing, and as regards the material of the acoustic conductor  13  is selected for instance to be bio-compatible with the behind-the-ear hearing aid, and as regards the material for the seating bush  15 , it will be one that meets the requirements of impact damping and holding in place the transducer  12  under such conditions. The material of the bush  15  may be readily selected to be electrically conducting if for instance the transducer  12  should be electrically screened. 
       FIG. 5  again shown in schematic manner a first part, again illustratively a wall of a housing part  10  comprising a feedthrough aperture  17  passing a control element  19  such as a switch which passes through an operating means  25  of the hearing aid. Because resilient and optionally sealing parts  21  are sprayed jointly with the housing  10  by two- or multi-component injection molding in the rim zone of the feedthrough  17  for the control element  19  and because where called for additionally also a seat  23  to resiliently affix the unit  25  in flush manner, the unit  25  can be integrated in optimally compact manner. 
       FIG. 6  shows how a seat  32  to appropriately position and hold a further system  34 , for instance a hearing-aid electronic module, can be apposed—using the said two- or multi-component injection molding—at the housing  30  so a system  34  such as a hearing aid electronic module, as a result of which optimally compact assembly of high packing density is again attained. 
     Large savings are realized in the manufacturing method of the invention: Assembly steps are eliminated by integral two- or multi-component manufacture. Moreover an advantage particularly applying to hearing aids is achieved that functionally different elements which following assembly anyway come to be abutting each other can be fitted in controlled manner with the particular needed material properties. In this manner volume-wasting steps for retrofitting such parts are eliminated. As shown for instance by the embodiment of  FIGS. 1 through 3 , it is clear that a seal  7   a  which need meeting only the sealing requirements can be made much smaller and thinner if integrated into the part  1  than if manufactured separately as a seal  7  and subsequently requiring mounting—for instance manually—to the corresponding edges of the part  1 , whether by bonding, insertion or the like. When assembling separate elements, the accuracy with which the sealing element  7   a  can be apposed to the edge  3  constituted by the wall of the part  1  is hardly possible, given the same dimensions, or if so, only at high cost.