Patent Publication Number: US-2005117772-A1

Title: Thin type speaker having a damper

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the invention  
      The present invention relates to a thin type speaker and, more particularly, to a thin type speaker having a damper.  
      2. Description of the Related Art  
      A conventional dynamic speaker  90 , as shown in  FIG. 4 , comprises a conical casing  91 , a first pole piece  92  disposed at the bottom side of the casing  91 , an annular magnet  93  disposed at the bottom side of the first pole piece  92 , a second pole piece  94  disposed at the bottom side of the annular magnet  93 , a core member  95  provided at the second pole piece  94  in the center of the annular magnet  93 , an annular vibration diaphragm  96  peripherally bonded to the top edge of the inside wall of the casing  91 , a voice coil  97  disposed in between the magnet  93  and the core member  95  and connected to the inner periphery of the vibration diaphragm  96  at the top thereof, an annular damper  98  of corrugated cross section disposed under the vibration diaphragm  96  with its outer diameter and inner diameter respectively connected to the casing  91  and the connection area between the voice coil  97  and the vibration diaphragm  96 , and a dust-proof cap  99  provided at the center area of the outer side of the vibration diaphragm  96 .  
      Upon input of electric current into the voice coil  97 , an electromagnetic effect is produced, thereby causing the vibration diaphragm  96  and the damper  96  to vibrate with the voice coil  97  and to further produce sound. When increasing input electric current, the amplitude of the resonance of the voice coil  97  and the vibration diaphragm  96  is relatively increased. The connection of the damper  98  eliminates abnormal beatings of the voice coil  97 , i.e., stabilizes the resonance of the voice coil  97  and the vibration diaphragm  96  for high power output.  
      However, the aforesaid design is simply employed to big scale speakers. For a thin type speaker to be used in a mobile electronic apparatus, the limited internal space can only accommodate the vibration diaphragm and the electromagnet set, and has no room for the above-mentioned installation of the damper. Therefore, conventional thin type speakers are not suitable for high power output.  
     SUMMARY OF THE INVENTION  
      It is the primary objective of the present invention to provide a thin type speaker, which uses the limited inside space to hold a damper for high power output.  
      To achieve this objective of the present invention, the thin type speaker comprises a casing having a top-open receiving chamber, an electromagnet set mounted in the top-open receiving chamber, and a vibration diaphragm. The electromagnet set has a yoke, a magnet, a pole piece, and a voice coil. The vibration diaphragm is peripherally connected to the periphery of the top-open receiving chamber and has a damper at the center thereof. The damper has a corrugated cross section and a center part fixedly connected to the electromagnet set. The voice coil of the electromagnet set is provided at one side of the vibration diaphragm facing the top-open receiving chamber and is connected to the periphery of the damper. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectional view of a thin type speaker according to the first preferred embodiment of the present invention.  
       FIG. 2  is a sectional view of a thin type speaker according to the second preferred embodiment of the present invention.  
       FIG. 3  is a sectional view of a thin type speaker according to the third preferred embodiment of the present invention.  
       FIG. 4  is a sectional view of a thin type speaker according to the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 1 , a thin type speaker  10  in accordance with the first preferred embodiment of the present invention is shown comprised of a casing  20 , an electromagnet set  30 , and a vibration diaphragm  40 .  
      The casing  20  has a recessed top receiving chamber  21 .  
      The electromagnet set  30  is mounted inside the recessed top receiving chamber  21 , comprising a yoke  31 , a magnet  34 , a pole piece  35 , and a voice coil  36 . The yoke  31  is mounted in the bottom side inside the recessed top receiving chamber  21 , having a circular base  32 , and an annular upright peripheral wall  33  upwardly extended from the border of the circular base  32 . The magnet  34  is a cylindrical member disposed at the center of the top surface of the circular base  32  of the yoke  31 . The pole piece  35  is bonded to the top side of the magnet  34 . The voice coil  36  is provided at an inner side of the vibration diaphragm facing the top-open receiving chamber  21  and spaced between the periphery of the magnet  34  and the annular upright peripheral wall  33  of the yoke  31 .  
      The vibration diaphragm  40  is made of flexible material, having an integrated damper  41  at the center. The damper  41  has a corrugated cross section. The periphery of the vibration diaphragm  40  is bonded to the top side of the periphery of the recessed top receiving chamber  21  of the casing  20 , keeping the center of the damper  41  fixedly fastened to the top surface of the pole piece  35  of the electromagnet set  30  by adhesion (or heat sealing, or high-frequency bonding). The top side of the voice coil  36  of the electromagnet set  30  is peripherally bonded to the periphery of the damper  41 .  
      Upon input of electric current into the electromagnet set  30 , the voice coil  36  is driven to vibrate alternatively up and down, thereby causing the vibration diaphragm  40  to produce sound. Because the damper  41  is connected to the voice coil  36 , it vibrates steadily following increase of input electric current, thereby eliminating abnormal beatings. Therefore, the invention uses the limited inside space to install a damper for high output.  
       FIG. 2  shows a thin type speaker constructed according to the second preferred embodiment of the present invention. As illustrated, the thin type speaker  50  comprises a casing  51 , an electromagnet set  52  mounted inside the casing  51 , a vibration diaphragm  53  peripherally connected to the top edge of the casing  51  and having an integrated damper  54  at the center, and a cap  55  covered over the top side of the casing  51 . The dust cap  55  has a plurality of sound holes  56 . The damper  54  of the vibration diaphragm  53  has a center area projecting vertically upwards and connected to the inner side of the cap  55 .  
      Further, a speaker according to the present invention can be of paper cone series or general ferrite type made in a circular, rectangular, or oval shape.  
       FIG. 3  shows a thin type speaker constructed according to the third preferred embodiment of the present invention. As illustrated, the thin type speaker  60  is substantially similar to the aforesaid first preferred embodiment of the present invention. According to this embodiment, the electromagnet set  62  and the vibration diaphragm  63  are mounted in the casing  61 ; the magnet  64  of the electromagnet set  62  is an annular member spaced around the voice coil  65 ; the electromagnet set  62  further comprises a core member  66  disposed inside the voice coil  65 ; the center of the damper  64  of the vibration diaphragm  63  is fixedly fastened to the top side of the core member  66 . This arrangement achieves high power output.  
      In order to provide many power output choices and to facilitate fabrication, the vibration diaphragm and the damper may be separately made from different materials and then fixedly fastened together. This fabrication method achieves the aforesaid same effects.