Abstract:
An armature for a receiver comprising a first and a second leg portion each having a thickness and a width and connected to each other, and a connection portion in communication with the first and second leg portions. The connection portion has a width greater than the width of the first and second leg portions individually. The connection portion reduces the stiffness of the armature and minimizes magnetic reluctance of the connection between the first and second leg portions. According to one aspect of the invention, the first and second leg portions are integrally formed with the connection portion and the connection portion includes a least a portion having a thickness less than the thickness of the first and second leg portions individually to reduce the stiffness of the armature. According to another aspect of the invention, the first and second leg portions are separately formed and attached to the connection portion in a way that reduces the stiffness of the armature.

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 10/769,528, entitled “Armature for a Receiver,” filed Jan. 30, 2004, which is a continuation of U.S. application Ser. No. 09/850,776, filed May 8, 2001, which claims the benefit of U.S. Provisional Application No. 60/202,957, filed May 9, 2000, and U.S. Provisional Application No. 60/218,996, filed Jul. 17, 2000. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to receivers for microelectronic devices, and more particularly to armatures for use in hearing aid receiver transducers. 
     BACKGROUND OF THE INVENTION 
     Electroacoustic transducers are capable of converting electric energy to acoustic energy and vice versa. Electroacoustic receivers typically convert electric energy to acoustic energy through a motor assembly having a movable armature. Typically, the armature has one end that is free to move while the other end is fixed to a housing of the receiver. The assembly also includes a drive coil and one or more magnets, both capable of magnetically interacting with the armature. The armature is typically connected to a diaphragm near its movable end. When the drive coil is excited by an electrical signal, it magnetizes the armature. Interaction of the magnetized armature and the magnetic fields of the magnets causes the movable end of the armature to vibrate. Movement of the diaphragm connected to the armature produces sound for output to the human ear. Examples of such transducers are disclosed in U.S. Pat. Nos. 3,588,383, 4,272,654 and 5,193,116. 
     The sound pressure output of a receiver is created by the travel, or deflection, of the armature when it vibrates. Maximum deflection of the moving armature creates maximum sound pressure output for a given armature geometry. The maximum deflection of an armature is limited by the magnetic saturation of the armature, which is governed by the maximum magnetic flux that the armature geometry can allow to pass therethrough. Therefore, the magnetic flux must be increased in order to increase the sound pressure output. The magnetic flux is limited by material type and cross-sectional area of the armature. Although an increase in the cross-sectional area causes a proportional increase in the maximum magnetic flux, the relative stiffness of the armature increases as well. Thus, merely increasing the cross-sectional area of the armature geometry does not provide a significant improvement in the maximum deflection of the armature. 
     The present invention addresses these and other problems. 
     SUMMARY OF THE INVENTION 
     An armature for a receiver comprising a first and a second leg portion each having a thickness and a width and connected to each other, and a connection portion in communication with the first and second leg portions. The connection portion has a width greater than the width of the first and second leg portions individually. The connection portion reduces the stiffness of the armature and minimizes magnetic reluctance of the connection between the first and second leg portions. According to one aspect of the invention, the first and second leg portions are integrally formed with the connection portion and the connection portion includes at least a portion having a thickness less than the thickness of the first and second leg portions individually to reduce the stiffness of the armature. According to another aspect of the invention, the first and second leg portions are separately formed and attached to the connection portion in a way that reduces the stiffness of the armature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational side view of a first embodiment of a two-piece armature assembly according to the invention. 
         FIG. 2  is a top plan view of a first preform used to form a first leg of the armature assembly shown in  FIG. 1 . 
         FIG. 3  is a top plan view of a second preform used to form a second leg of the armature assembly as shown in  FIG. 1 . 
         FIG. 4  is a side elevational view of a second embodiment of a two-piece armature assembly of the invention. 
         FIG. 5  is a top plan view of a preform used to form a leg portion of the armature assembly shown in  FIG. 4 . 
         FIG. 6  is an elevational side view of a third embodiment of a two-piece armature assembly of the invention. 
         FIG. 7  is a top plan view of a first preform used to form a first leg of the armature assembly as shown in  FIG. 6 . 
         FIG. 8  is an elevational side view of a one-piece armature according to the invention. 
         FIG. 9  is a top plan view of a blank used to form the one-piece armature shown in  FIG. 8 . 
         FIG. 10  is an elevational side view of the blank shown in  FIG. 9 . 
         FIG. 11  is an elevational side view of a one-piece E-shaped armature according to the invention. 
         FIG. 12  is a top plan view of the E-shaped armature shown in  FIG. 11 . 
         FIG. 13  is a top plan view of a blank used to form the one-piece E-shaped armature shown in  FIG. 11 . 
         FIG. 14  is an elevational side view of the blank shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the invention will be described fully hereinafter with reference to the accompanying drawings, in which particular embodiments are shown, it is to be understood at the outset that persons skilled in the art may modify the invention herein described while still achieving the desired result of this invention. Accordingly, the description which follows is to be understood as a broad informative disclosure directed to persons skilled in the appropriate arts and not as limitations of the invention. 
       FIG. 1  illustrates a first embodiment of a two-piece armature assembly  10 . The armature assembly  10  comprises a first leg portion  12  and a second leg portion  14 .  FIG. 2  shows a preform  16  used to form the first leg portion  12 .  FIG. 3  shows a second preform  18  used to form the second leg portion  14 . The leg portions  12  and  14  are formed by bending the preforms  16  and  18  along bend lines A and B, respectively. The bend lines A and B are merely reference lines for purposes of illustrating the line along which the preforms  16  and  18  are bent and are not formed on the preforms  16  and  18 . However, in an alternate embodiment, the preforms  16  and  18  may be provided with a score line or other means (not shown) to aid in the bending of the preforms  16  and  18 . 
     The first leg portion  12  includes a connection region or segment  24 , as shown in  FIG. 2 . The second leg portion  14  includes a connection region or segment  25 , as shown in  FIG. 3 . The connection segment  25  includes a magnetic keeper region  26  and integrally formed connecting straps  28  and  30  disposed adjacent to the magnetic keeper region  26 , as shown in  FIG. 3 . The connecting straps  28  and  30  provide a surface for the second leg portion  14  to be attached to the first leg portion  12 , as shown in  FIG. 1 . Alternatively, the connecting straps  28  and  30  can be integrally formed with the first leg portion  12 . Furthermore, the connecting straps  28  and  30  may be fabricated as separate pieces and mechanically connected to either or both of the leg portions  12  and  14 . In a preferred embodiment, the first and second leg portions  12  and  14  are welded together. 
     When the first and second leg portions  12  and  14  are assembled, a connection portion  31  is formed, as shown in  FIG. 1 . Within the connection portion  31 , the connection segment  24  of the first leg portion  12  and the magnetic keeper region  26  of the connection segment  25  of the second leg portion  14  overlap and define a gap  32  therebetween, as shown in  FIG. 1 . The gap  32  provides clearance between the two leg portions  12  and  14  to allow adequate deflection of one of the leg portions  12  and  14  with respect to the other. Preferably, the first leg portion  12  is fixed relative to the second leg portion  14 . Preferably, the leg portions  12  and  14  are fixed by a weld C disposed between the connecting straps  28  and  30  of the connection segment  25  and the connection segment  24 , as shown in  FIG. 1 . Preferably, the weld C between the connecting straps  28  and  30  of the connection segment  25  of the second leg portion  14  and the connection segment  24  of the first leg portion  12  is a contact weld. However, any type of weld well known in the metal fabrication arts can be used. To insure that the gap  32  is formed between the connection segment  24  and the magnetic keeper region  26  of the connection segment  25 , either segment  24 , region  26  or the connecting straps  28  and  30  may be punched or swaged to form a bump or other raised portion (not shown) that acts as a standoff between the segment  24  and the region  26  of the segment  25 . 
     The overlapping connection segment  24  and the magnetic keeper region  26  of the connection segment  25  have large enough surface area to minimize the magnetic reluctance between the two leg portions  12  and  14 . This allows maximum magnetic flux to pass through the armature assembly  10 . The gap  32  can be sized to accommodate the maximum deflection of one of the leg portions  12  and  14  for a maximum flux defined by the armature assembly  10 . 
       FIG. 4  illustrates an alternate embodiment armature assembly  40 . In this embodiment, a first leg portion  42  and a second leg portion  44  are integrally formed from a single preform  46 , as shown in  FIG. 5 . The preform  46  includes a central connection portion  48  having a cutout  50  defining connection legs  52  and  54  and a magnetic keeper region  56 . The connection legs  52  and  54  are etched or machined to be thinner than the thickness of the remaining portions of the perform  46 . This reduces the stiffness of the connection legs  52  and  54  with respect to the remaining portions of the preform  46 . The preform  46  is bent along bend lines D and E to form an armature leg portion  62  of the armature assembly  40 , as shown in  FIG. 4 . In a preferred embodiment, the central connection portion  48  includes a generally flat cover portion  64  that is attached to one or more other portions  65  of the central connection portion  48  to complete the armature assembly  40 , as shown in  FIG. 4 . Preferably, the cover portion  64  is welded at a weld F. The cover portion  64  provides a large surface area that overlaps and interacts with the magnetic keeper region  56  to minimize the magnetic reluctance between the first and second leg portions  42  and  44 . As with the first embodiment, a raised portion (not shown) can be provided on the cover portion  64  of the central connection portion  48  to act as a standoff between the cover portion  64  and the other portions  65  and the magnetic keeper region  56  of the central connection portion  48 . 
       FIG. 6  illustrates an alternate embodiment two-piece armature assembly  70 . In this embodiment, the armature assembly  70  includes a first leg portion  72  and a second leg portion  74 .  FIG. 7  generically depicts a preform  82  used to form the leg portions  72  and  74  of the armature assembly  70 . Each of the leg portions  72  and  74  include a connection segment  75  having two connection flaps or tabs  76  and  78  that accommodate attachment of the leg portions  72  and  74  to each other. As can be seen in  FIG. 7 , a width of the connection segment  75  (which comprises connection flaps or tabs  76  and  78 ) is greater than a width of the remaining part of the leg portions  72  and  74 . When the leg portions  72  and  74  are attached, a connection portion  79  is formed, as shown in  FIG. 6 . In a preferred embodiment, the leg portions  72  and  74  are connected via a snap fit. The connection flaps  76  and  78  are bent along bend lines G and H and can be punched to form either holes or dimples to facilitate connection with a second set of connection tabs. One pair of connection tabs  76  and  78  can be provided with holes and the other pair can be provided with dimples or other raised portions (not shown) that snap fit within the holes at a connection point  80 , as shown in  FIG. 6 . With this snap fit of the dimples within the holes, one pair of the connection flaps  76  and  78  is pivotably fastened to the other pair at the connection point  80 . Thus, the leg portions  72  and  74  can pivot with respect to each other about the connection point  80  and the stiffness of the armature is reduced. Since this embodiment has no inherent centering as in the previously described embodiments, a spring (not shown) can be provided between the two leg portions  72  and  74  to facilitate deflection of the leg portions  72  and  74  with respect to each other. The connection tabs  76  and  78  of one of the leg portions  72  and  74  will be spaced farther apart from each other to allow the connection tabs  76  and  78  of the other of the leg portions  72  and  74  to fit therebetween, as shown in  FIG. 6 . As can be seen in  FIG. 6 , one pair of flaps  76  and  78  overlaps with the other pair flaps  76  and  78 , providing a surface area in which magnetic flux may pass between the leg portions  72  and  74 . This surface area minimizes the magnetic reluctance between the leg portions  72  and  74 . 
       FIG. 8  illustrates a one-piece armature  100  of the invention. The armature  100  is generally U-shaped and comprises a first leg portion  102  and a second leg portion  104  that are offset by a connection portion  106  disposed generally perpendicularly therebetween. The first and second leg portions  102  and  104  are generally flat and are disposed such that they are generally parallel to each other. 
     The first and second leg portions  102  and  104  and the connection portion  106  are integrally formed from a blank  108 , as shown in  FIG. 9 . The blank  108  is made of a metallic material having good magnetic permeability that can be fabricated and formed through conventional metal fabrication and forming techniques that are well known in the art. The connection portion  106  is wider than the first and second leg portions  102  and  104 , as shown in  FIG. 9 , but has a material thickness that is less than the first and second leg portions  102  and  104 , as shown in  FIG. 10 . The connection portion  106  also includes angled portions  110  integrally formed between the connection portion  106  and the first and second leg portions  102  and  104 . The angled portions  110  help to guide the magnetic flux from the wide connection portion  106  to the narrower leg portions  102  and  104 . The angled portions  110  also help reduce the material stresses that would normally be concentrated at corners  112 , during and after fabrication, if those corners  112  were positioned along bends  114  of the armature  100 , as shown in  FIG. 8 . Additionally, the connecting portion  106  includes tapered portions  116  that reduce material stresses along the bends  114  of the armature  100 , as shown in  FIG. 10 . The tapered portions  116  reduce the material stresses normally associated with sharp corner bends in metal fabrication. 
     The reduced material thickness of the connection portion  106  reduces the stiffness of the connection portion  106  while the greater width of the connecting portion  106  compensates for the increased magnetic flux density that would be associated with the decreased cross-sectional area of the connection portion  106  due to the reduced material thickness. Thus, the additional cross-sectional area associated with the wider connection portion  106  minimizes the magnetic flux density of the connection portion  106 , which allows the magnetically permeable material of the armature  100  to be able to perform at higher receiver drive levels. 
     In a preferred embodiment, the connection portion  106  is half as thick and twice as wide as the first and second leg portions  102  and  104 . This configuration keeps the cross-sectional area constant throughout the armature  100 , thereby preserving the armature&#39;s ability to carry magnetic flux. Furthermore, the increased width of the connection portion  106  in this configuration does not increase the stiffness of the connection portion  106 , since material stiffness is a function of the cube of the material thickness while only proportional to the width of the material. 
     The reduced stiffness of the connection portion  106 , combined with its increased width, allows maximum magnetic flux to pass through the connection portion  106 , as well as the first and second leg portions  102  and  104 , while allowing maximum deflection between the first and second leg portions  102  and  104  for maximum output sound pressure of a receiver incorporating the armature  100 . 
       FIG. 11  shows an alternate embodiment in the form of an E-shaped armature  130 . The armature  130  includes a generally flat first leg portion  132  and a generally flat second leg portion  134 . The second leg portion  134  has two legs  135  and  136  disposed generally transverse to the first leg portion  132 , as shown in  FIG. 12 . The first leg portion  132  is disposed between the two legs  135  and  136  as shown in  FIG. 12  and below the two legs  135  and  136  as shown in  FIG. 11 . A connection portion  138  is in communication with the first and second leg portions  132  and  134 , as shown in  FIGS. 11 and 12 . The connection portion  138  includes a portion  140  having a material thickness that is less than the other portions of the armature  130 . The reduced material thickness is best shown in  FIG. 11 . As shown in  FIG. 12 , the connection portion  138  includes angled portions  142  integrally formed between the portion  140  and the first leg portion  132 , which is narrower than the portion  140 . The angled portions  142  help to guide the magnetic flux from the portion  140  of the connection portion  138  to the narrower first leg portion  132 . 
     The E-shaped armature  130  is formed from a blank  150 , as shown in  FIG. 13  and  FIG. 14 . The blank  150  is made of a metallic material having good magnetic permeability that can be fabricated and formed through conventional metal fabrication and forming techniques that are well known in the art. 
     The reduced material thickness of the portion  140  reduces its stiffness. This allows for an increased deflection of the first leg portion  132  with respect to the legs  135  and  136  of the second leg portion  134 . The greater width of the connection portion  138  compensates for the increased magnetic flux density that would normally be associated with the decreased cross-sectional area of the portion  140  of the connection portion  138  due to the reduced material thickness without an increase in width. Thus, the additional cross-sectional area associated with the greater width minimizes the magnetic flux density associated with portion  140 , which allows the magnetically permeable material of the armature  130  to be able to perform at higher receiver drive levels. 
     While the specific embodiments have been illustrated and described, numerous modifications may come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying claims.