Abstract:
A vent having a reduced cross-section or taper permits the fabrication of very small hearing instruments while providing the necessary openings for the receiver tube and the vent in the tip of the instrument. The reduced cross-section provides sufficient clearance for the full cross-section of the receiver tube, without sacrificing the performance of the vent. The modified vent may be created in a CAD environment using Boolean modeling operations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following U.S. Patent Application(s), incorporated herein by reference: Ser. No. 09/887,939 filed Jun. 22, 2001. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Hearing instruments, i.e., devices that assist the hearing impaired, designed for complete or partial insertion into the user&#39;s ear canal, have a shell or housing that holds various components. One such component is the receiver, which generates the sound heard by the hearing instrument&#39;s user. The sound is carried from the receiver by a receiver tube affixed to a port on the receiver to an opening (the receiver tube hole) in the tip of the shell, the portion of the hearing instrument positioned in the ear canal towards the eardrum. 
     Another feature of a hearing instrument is a vent, a conduit from the inner ear to the outside. When a person speaks, vibration is generated in the bone structure of their head, creating sound pressure in the inner ear. Normally, this sound pressure escapes if the ear canal is not occluded. However, if a hearing instrument is inserted into the ear, occluding the ear canal, the hearing instrument user will perceive an unpleasant, hollow sound, a phenomenon known as the occlusion effect. A hearing instrument vent will provide relief, allowing at least some of the sound pressure to escape from the inner ear. A vent also permits the pressure in the ear to equalize with respect to the outside when the hearing instrument is inserted into the ear. An opening provided in the shell tip serves as the inlet for the vent. 
     If the hearing instrument shell is small in size, there may not be sufficient room to accommodate the full diameters or cross-sections of both the receiver tube hole and the vent hole, and the underlying receiver tube and vent. (The receiver tube and the vent may have circular cross-sections or any other suitable cross-section.) Some arrangement is then required to provide room for the receiver tube and vent in the shell tip, as well as openings for the receiver tube and the vent on the surface of the shell tip, such that they do not interfere with each other. 
     A Tapered Vent 
     By reducing the cross-section of the vent tube near the tip of the shell, the vent hole can be made smaller, allowing for a receiver tube hole equal to the full cross-section of the receiver tube. A reduction in the cross-section may be achieved by introducing a taper to the vent as it reaches the end of the tip and the vent hole or otherwise providing a vent of smaller cross-section. The cross-section of the vent is reduced only in the vicinity of the tip, preserving its full cross-section elsewhere in the instrument. Computer-aided design (CAD) techniques, including Boolean operations, may be utilized to create the smaller vent and vent hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a hearing instrument positioned in the ear canal; 
         FIG. 2  is a partial cross-sectional view of a hearing instrument comprising a receiver tube and vent; 
         FIGS. 3 and 4  are partial cross-sectional views of hearing instrument shells comprising a receiver tube and a tapered vent; 
         FIGS. 5-9  illustrate processes for tapering the vent in view of the receiver tube; 
         FIG. 10  is a drawing of the tip surface; 
         FIG. 11  is a partial cross-sectional view of a hearing instrument shell comprising a receiver tube and a vent having a cylindrical section of reduced diameter; 
         FIGS. 12-15  are flow charts of processes for manufacturing the hearing instrument; and 
         FIGS. 16-20  illustrate an arrangement for accommodating a wax guard. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a hearing instrument, which has an outer shell or housing  10  positioned as least partially in the ear canal, adjacent the walls  20  of the canal of the person wearing the hearing instrument. The hearing instrument shell  10  has a tip  12 —the section of the shell  10  inserted into the ear canal—oriented towards the inner ear and a faceplate  14  oriented towards the outer ear. 
       FIG. 2  illustrates a partial cross-sectional view of the hearing instrument shell  10 . The only parts of the hearing instrument shown in this figure are the receiver tube  100 , the vent  120 , and a portion of the shell  10 . 
     The vent  120  may be fabricated as a channel on the inside wall of the shell  10 , but is shown here as a cylindrical object. One could choose to create a vent using either configuration. For example, the vent could be realized as a separate tube similar to the receiver tube  100 . 
     The receiver tube  100  exits the shell  10  at a receiver tube hole  102  and the vent  120  has a port at a vent hole  122 . As illustrated in  FIG. 2 , the tip  12  of the shell  10  has sufficient area to accommodate openings (i.e., the receiver tube hole  102  and the vent hole  122 ) for the full circumferences of the respective receiver tube  100  and the vent  120 , as well as sufficient volume within the tip  12  for the receiver tube  100  and the vent  120 . 
     In  FIG. 2 , the receiver tube  100  and the vent  120  are immediately adjacent one another. If hearing instrument tip  12 , there would not be sufficient room to position the receiver tube  100  and the vent  120  side-by-side, as well as provide openings for the full circumferences of the receiver tube and the vent, without interference. 
     An arrangement illustrating a smaller shell tip  212  is shown in  FIGS. 3 and 4 . There, the housing or shell  10  comprises a receiver tube  220  and a vent  240 , and the end region or shell tip surface  214  of the shell tip  212  comprises a receiver tube hole  222  and a vent hole  242 . The vent  240  has a reduced cross-section in the vicinity of the shell tip  212  where it is adjacent the receiver tube  220 . 
     As illustrated in  FIGS. 3 and 4 , a cutaway section or taper  250  has been applied to the vent  240  near the shell tip  212 . Given the smaller cross-section of the vent  240 , the vent hole  242  similarly requires less surface area on the shell tip surface  214  and its shape conforms to the tapered outline of the vent  240  where it intersects the shell tip  212 . However, the vent  240  is tapered only for a short distance and resumes its otherwise full circumference or cross-section below the shell tip  212  where the full cross-section of the vent  240  would no longer interfere with the receiver tube  220 . The taper  250  begins inside the shell  200  at the point  224  where the receiver tube  220  first meets the vent  240  and continues as the vent  240  narrows until the shell tip surface  214  is reached, where the receiver tube  220  terminates in the receiver tube hole  222 , and the vent  240  terminates in the vent hole  242 . 
     Utilizing depictions of the receiver tube  220  and the vent  240 ,  FIGS. 5-7  illustrate a process for creating the taper in the vent  240 . In the example shown in  FIGS. 5 and 6 , a portion of the vent  240  is removed using the surface  226  of the receiver tube  220  as a cutting tool, leaving a cutaway section or taper  250 . The receiver tube  220  is then positioned against the vent  240  at the location where the material has been removed, as illustrated in  FIG. 7 . In a rapid prototyping or direct manufacturing environment, this process could be achieved by fabricating a vent with a reduced cross-section or taper already in place and thus not requiring a machining or cutting operation. 
     If the receiver tube  220  penetrates the interior  244  of the vent  240  (see  FIGS. 5 and 7 ), the surface  246  of the vent  240  in the region of the cutaway section  250  may be reconstructed with a wall section  252 , as illustrated in  FIG. 8 . The wall section  252  may be concave and can be created using the Boolean intersection of the surface  226  of the receiver tube  220  and the surface  246  of the vent  240 . Depth (i.e., thickness) may be provided for the wall section  252  by offsetting the surface resulting from the Boolean intersection a distance equal to the desired thickness. Here again, the wall section  252  can be fabricated directly as part of the vent  240  using rapid prototyping or direct manufacturing techniques. Since the receiver tube  220  may be a tubular component physically separate from the shell  10 , the wall section  252  seals the vent  240  and prevents sound from leaking where the receiver tube  220  would otherwise adjoin the vent  240 . Instead, the receiver tube  220  and the wall section  252  sit adjacent each other as shown in  FIG. 9 . 
     As an alternative to tapering the vent in the vicinity of the tip, the receiver tube  220  could be tapered, or both the vent  240  and the receiver tube  220  could be tapered. Also, the reduction in cross section of either the receiver tube  220  or the vent  240  could be achieved without applying the taper or shape conforming to the receiver tube  220  shown in  FIGS. 3-9 . For example, as illustrated in  FIG. 11 , the vent  240  could have a cylindrical section  270  of reduced diameter in the area between the vent hole  242  and the point in space ( 224 ) where the vent  240  and the receiver tube  220  would not physically interfere. 
     In the following discussion, the hearing instrument shell  10  is modeled in virtual space, using well-known computer-aided design (CAD) tools, including Boolean modeling operations. As illustrated in  FIG. 10 , the shell tip surface  214  of the shell tip  212  may be roughly elliptical in shape. As a design choice, the centers of the receiver tube  220  and the vent  240  can be positioned on the major axis  260  of the shell tip surface  214 . If the receiver tube  220  and vent  240  do not interfere with each other, as is the case in  FIG. 2 , then no modification is required of either. However, if there is insufficient area to position both the receiver tube and the vent and their respective openings in the shell tip  212 , then a portion of either the vent hole  242  or the receiver tube hole  222  must be removed. This determination is set forth in the flow chart of  FIG. 12 . 
     As shown in  FIGS. 5-7 , the vent tube hole  242  and the vent  240  can be trimmed (or tapered) to accommodate the receiver tube hole  222  and the receiver tube  220 . Therefore, in this arrangement, the dimensions of the receiver tube  220  and the receiver tube hole  222  are protected, maintaining their full cross-sections. 
     Utilizing the steps set forth in the flow chart of  FIG. 13 , the location of the vent  240  and the vent hole  242  are fixed. Next, the location of the receiver tube hole  222  is then determined. Using the surface  226  of the virtual receiver tube  220  as a cutting tool, a Boolean subtraction operation may be performed on the vent tube  240  and the vent hole  242 , removing material from both. If desired, a wall  252  of predetermined thickness may be added to the vent  220 . A Boolean intersection operation may be used to generate the outer surface  254  of the wall  252 . By “growing” the wall  252  inwardly (i.e., towards the interior  244  of the vent  240  proper), the wall  252  is given a desired thickness. 
     Instead of first positioning the vent hole  242 , the receiver tube hole  222  and receiver tube  220  positions could be fixed, as outlined in the flow chart of  FIG. 14 . Then, the respective locations and positions of the vent hole  242  and vent  240  would be determined and moved into place using a Boolean subtraction based on the surface of the receiver tube  220 . Finally, a wall  252  can be added if desired. 
     The flow chart of  FIG. 15  offers a third method of locating the receiver tube and vent holes. In this option, the locations of both the receiver tube hole  222  and the vent hole  242  are selected at the same time, adjusting them as necessary to provide the desired size for the vent hole  242 . As in the other methods discussed here ( FIGS. 13 and 14 ), the surface of the receiver tube  220  is used to perform a Boolean subtraction of the interfering portion of the vent  240 . Finally, a wall  252  may be added based on the Boolean intersection of the receiver tube  220  and the vent  240 . 
     In some hearing instruments, wax guards are provided to keep cerumen, the waxy buildup in the ear, from entering the receiver tube.  FIGS. 16-20  illustrate an arrangement for accommodating a wax guard  300  in a recess  310  provided in the tip surface  214  of the hearing instrument shell  10 . The recess  310  is located where the receiver tube hole  222  would be positioned in the shell tip  12 . The receiver tube  220  in this instance would terminate at the recess  310 . The Boolean methods could be employed to remove material from the vent hole  242  that would be in the space occupied by the wax guard (see, e.g.,  FIGS. 17-19 ).