Abstract:
The manufacture of a hearing instrument having a hard inner shell and a softer outer covering, for insertion into the ear canal of the user, may be accomplished using rapid manufacturing and prototyping techniques. Starting with a digital model of the ear canal, a mold for the softer outer covering may be fabricated using a process such as stereo lithography.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
       [0001]    A hearing instrument for insertion into the user&#39;s ear canal may be manufactured by fabricating a hard inner shell that contains the components of the hearing instrument, such as the receiver, battery, and electronics, and then an softer outer covering that conforms to the contour of the ear canal. The method described below utilizes rapid manufacturing and prototyping techniques for both the hard inner shell and the softer outer covering. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0002]      FIG. 1  is a cross-sectional view of a hearing instrument comprising a hard inner shell and a softer outer covering; 
           [0003]      FIG. 2  is a cross-sectional view of the inner contour of the hard inner shell, sized to hold the components of the hearing instrument of  FIG. 1 ; 
           [0004]      FIG. 3  is a cross-sectional view of the hard inner shell, utilizing the inner contour of  FIG. 2 , and the components of the hearing instrument; 
           [0005]      FIGS. 4 and 5  are cross-sectional drawings of a mold for fabricating the softer outer covering for the hearing instrument of  FIG. 1 ; 
           [0006]      FIGS. 6 ,  7 , and  8  are cross-sectional drawings of the mold of  FIGS. 4 and 5 , illustrating the placement of the hard inner shell within the mold and the fabrication of the softer outer covering for the hearing instrument of  FIG. 1 ; 
           [0007]      FIG. 9  is a flow chart of a fabrication process; and 
           [0008]      FIGS. 10 and 11  are cross-sectional drawings of a mold for fabricating the softer outer covering for an otoplastic or ear adaptor member for a behind-the-ear hearing instrument. 
       
    
    
     DESCRIPTION OF THE INVENTION  
       [0009]    A hearing instrument  10  comprising a hard inner shell  20 , a softer outer covering  30 , and a faceplate  40  are illustrated in the cross-sectional view of  FIG. 1 . The instrument  10  has an outer contour  12  that may be selected to conform to the contours of the user&#39;s ear canal  14 . A battery  50 , an electronics module  60 , a receiver  70 , and a receiver tube  72  connecting the receiver to a receiver hole  22  in the hard inner shell  20  are also shown in the figure. The faceplate  40  may be added after fabrication of the inner shell  20  and the outer covering  30 , and the components can be inserted during assembly of the hearing instrument  10 . The process described here, and outlined in the flow chart in  FIG. 9 , concerns the fabrication of the hard inner shell  20  and the softer outer covering  30 . 
         [0010]    The hearing instrument  10  may be fabricated using one of the processes mentioned in U.S. Patent Application Publication No. 2002/0196954 A1, published Dec. 26, 2002 and titled, “Modeling and fabrication of three-dimensional irregular surfaces for hearing instruments,” incorporated here by reference. As a preliminary step, a three-dimensional model of the contours of the user&#39;s ear canal  14  is obtained. This is used to define the outer contour  12  of hearing instrument&#39;s softer outer covering  30 . 
         [0011]    Fabricating the Hard Inner Shell 
         [0012]    The hard inner shell  20  contains the components of the hearing instrument  10 . The minimum inner dimensions of the hard inner shell  20  may be determined using a method such as the component location and positioning scheme described in U.S. Patent Application Publication No. 2002/0196954 A1. This will yield the inner contour  24  shown in  FIG. 2  (note the thick line to the left and right of the components; the softer outer covering  30  and the faceplate  40  are shown in phantom). 
         [0013]    The outer dimensions of the hard inner shell  20  are then determined by selecting a desired thickness (e.g., 1.5 mm). The shell  20  may then be fabricated using a process such as stereo lithography or any other desired process, yielding the shell  20  as shown in  FIG. 3 . The adherence of the softer outer covering  30  to the hard inner shell  20  may be enhanced by fabricating the shell  20  with a material having a high porosity. 
         [0014]    Fabricating the Softer Outer Covering 
         [0015]    Having fabricated the hard inner shell  20 , the next step is to apply the softer outer covering  30  to the shell  20 . The outer covering  30  may be fabricated using a material such as silicone. 
         [0016]    First, a mold  100  is created. A suitable mold  100  is shown in  FIG. 4 . The mold  100  has an inner contour  102  conforming to the outer contour  12  of the hearing instrument  10  (see  FIG. 1 ). As depicted in  FIG. 5 , the mold  100  has a channel  104  for injecting the material that forms the softer outer covering  30 . In addition, a pin  106  is positioned at the bottom of the mold  100  to locate and support the shell  20 . 
         [0017]    To facilitate removal of the outer covering  30  after fabrication, the mold  100  may be made from a material of low porosity. Additionally, the mold  100  may be fabricated as two halves or some other suitable configuration that aids in removing the now-combined softer outer covering  30  and hard inner shell  20  after fabrication. 
         [0018]    Next, as shown in  FIG. 6 , the hard inner shell  20  is placed in the mold  100  and onto the pin  106 . A top plate  110  covers and seals the mold  100 , and has a plug  112  having an outer contour conforming to the inner contour of the hard inner shell  30  where they meet (see the arrows in the figure). Referring to  FIG. 7 , the top plate  106  is then placed on top of the mold  100 , sealing the area  120  between the hard inner shell  30  and the inner contour  102  of the mold  100 . 
         [0019]    A material, such as silicone, is now introduced through the channel  104 , injecting it into the mold  100  and filling the area  120  to create the softer outer covering  30 . Once the material has cured, the top plate  110  may be removed and the combined hard inner shell  30  and the softer outer covering  30  are removed from the mold  100 . 
         [0020]    The technique described above may also be used to fabricate an otoplastic or ear adapter member for a behind-the-ear hearing instrument, such as described in U.S. Pat. No. 5,008,058, issued to Henneberger et al. on Apr. 16, 1991, incorporated here by reference. Two possible configurations are shown in  FIGS. 10 and 11 , respectively. In the first ( FIG. 10 ), a hard inner receptacle  200  receives a sound conducting tube  210 , which will be connected to the hearing instrument that sits behind the ear. A soft outer covering  220  is fabricated around the receptacle  200  in the same manner as the soft outer covering  30  of  FIG. 8 . The portion of the receptacle  200  in contact with the conducting tube  210  would conform to the outside of the tube  210 . As an alternative, the sound conducting tube  210  could be placed directly within the mold  100 , as illustrated in  FIG. 11 , and the soft outer covering  220  would be formed around the tube  210 .