Patent Publication Number: US-6903474-B2

Title: Electro-mechanical transducer

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for converting a sound signal into vibration so as to stimulate the human hearing organs through the bones. More particularly, it has adopted an iron core and an inertial mass in order to achieve high power output. 
     2. Related Prior Art 
     Conventionally, a bone-conducting loudspeaker has been developed for persons who have difficulty hearing. This loudspeaker is a kind of acoustic transducer that enables an auditorily handicapped person who does not have the tympanic membrane to hear by stimulating the auditory nerves through the cranial bone instead of the tympanic membrane. Basically, the bone-conducting loudspeaker produces sound through the medium of liquid or solid matter, such as the human body, while the conventional loudspeaker uses the atmosphere. 
       FIG. 1  is a structural diagram roughly showing the conventional acoustic loudspeaker. As shown, a permanent magnet  3  is fixed to a conical frame  1 . One pole of the magnet  3  is inserted in a cylindrical electromagnet  7  around which a voice coil  5  is wound and which has a closed face. To the closed face of the electromagnet  7 , a conical vibrating diagram  9  is attached. This diaphragm  9  vibrates back and forth (in the direction of Y in  FIG. 1 ) along with the electromagnet  7 . More specifically speaking, when an acoustic signal V is applied to the voice coil  5 , the coil  5  produces magnetic force. The magnetic force interacts with the magnet  3  to move the electromagnet  7 . Thereby the diaphragm  9  vibrates and regenerates acoustic sound by generating pressure waves in the surrounding atmosphere. 
     Meanwhile, in order to expand the functionality of hearing aids for auditorily handicapped persons, a “body-sensible loudspeaker” has been developed, by which a user can sense the acoustic energy generated from an audio system through the tactile organs rather than the auditory organs. The body-sensible loudspeaker, which converts the acoustic signal into vibration to stimulate the human body, provides even more vivid sound in comparison with the conventional acoustic loudspeaker. It can be used for vehicle seats, game devices, theatre seats, etc. 
     However, in the conventional body-sensible loudspeaker, high power output cannot be obtained because it directly uses the same structure as the conventional acoustic loudspeaker (see FIG.  1 ). In the conventional acoustic loudspeaker, the vibrating diaphragm is made of a soft material, such as paper or PVC. Thus, it has a disadvantage that: 
     The service life of the coil is limited by the heat generated by the electric current, which must be increased when the output power is made higher. Moreover, if the fundamental oscillation frequency of the vibrating diaphragm coincides with the frequency of the amplified acoustic signal, the diaphragm may resonate. This will cause the diaphragm to abnormally oscillate, blocking the response over a certain frequency range. 
     SUMMARY OF THE INVENTION 
     To overcome the above disadvantages in conventional body-sensible loudspeaker, it is an object of the present invention to provide a redesigned loudspeaker for increasing vibration energy by using an electromagnet having an iron core and an inertial mass. 
     To achieve the above object, there is provided a sound-to-vibration conversion apparatus comprising a housing; a magnet means having an N-pole and an S-pole, only one of which is fixed to the housing; and an electromagnet movably fixed to the housing so as to face whichever pole of the magnet means (N or S) that is not fixed to the housing, whereby the electromagnet reciprocates in such a way to get close to or away from the magnet means in accordance with the interaction between the polarity formed at the electromagnet by the acoustic signal applied to the electromagnet and either the N-pole or S-pole of the magnet means. 
     In the above, the electromagnet includes an E-shaped iron core having three protrusions and a coil wound around the central protrusion. 
     It is desirable that the electromagnet comprises an inertial mass for increasing the inertial force of the electromagnet&#39;s reciprocal motion, such that the housing including the magnet means can vibrate against the electromagnet. It is also desirable that the magnet means is a permanent magnet. And it is also desirable that the apparatus according to this invention further comprises an elastic means for giving the electromagnet a force resisting the electromagnet&#39;s motion, and a spacer for keeping the electromagnet apart from the permanent magnet event when the electromagnet approaches nearest to the magnet means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will became more apparent from the following description in conjunction with the accompanying drawings, in which 
         FIG. 1  is a structural diagram roughly showing the conventional acoustic loudspeaker. 
         FIG. 2  is a cross-sectional view showing a preferred embodiment for carrying out the present invention. 
     
    
    
     DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present embodiment will be described below with reference to the accompanying drawings. 
       FIG. 2  is a cross-sectional view showing the preferred embodiment of the present invention. A sound-to-vibration conversion apparatus according to the present invention is roughly composed of a magnet means  11  having an N-pole and an S-pole and being fixed to a housing  23 , and an electromagnet  13  arranged to face the N-pole or S-pole of the magnet means  11  and movably fixed to the housing  23 . (Even though  FIG. 2  shows that the electromagnet  13  faces the N-pole of the magnet means  11 , the invention is not limited to this configuration.) 
     The housing  23  may be a car seat, a bed, a chair, or any other item to which this apparatus could be adapted. Even though the magnet means  11  can include either a permanent magnet or an electromagnet, in this description a permanent magnet will be typically referred to for convenience. 
     As shown in  FIG. 2 , the electromagnet  13  includes an E-shaped iron core having three protrusions  13   a, b,  and  c  and a coil  15  would around the central protrusion  13   a . To the coil  15 , alternating current (acoustic signal from an audio system) is applied. 
     From the above configuration, it can be noted that the electromagnet  13  reciprocates in such a way to get close to or away from the magnet means  11 , in accordance with the interaction between the polarities formed at the electromagnet  13  by the acoustic signal applied to the coil  15  and the polarity of the magnet means  11 . That is to say, when an acoustic signal is applied to the coil  15 , the polarity and the magnetic force of the electromagnet  13  varies according to the applied acoustic signal&#39;s amplitude or phase. Thereby, the attractive force and repulsive force between the electromagnet  13  and the permanent magnet  11  causes the electromagnet  13  to reciprocate. Here, the reciprocating distance of the electromagnet  13  traces a waveform of the applied acoustic signals. 
     From the foregoing, a sound-to-vibration conversion apparatus of the present invention utilizes magnetic force to convert sound into vibration, like the conventional acoustic loudspeaker. Therefore, it is necessary to adapt a magnet and a coil to this invention also. However, unlike the conventional body-sensible loudspeaker, this invention employs and iron-cored electromagnet  13  in which a coil is wound around an iron core. Because the iron-coated electromagnet  13  is relatively heavy, it acts as an inertial against the fixed magnet  11 , so that the interaction between the fixed magnet  11  and the electromagnet  13  can produce much more vivid vibration. Additionally, because an iron-cored electromagnet  13  provides higher efficiency than a non-iron-cored electromagnet, the loss of magnetic force is minimized in this invention. 
     Meanwhile, the electromagnet  13  includes an inertial mass  17  to increase the inertial force of the electromagnet&#39;s reciprocal motion. Therefore, even though the electromagnet  13  is movably fixed to the housing  23 , because the electromagnet  13  including the inertial mass  17  is heavier than housing  23 , the housing  23  including the permanent magnet  11  will vibrate instead of the electromagnet  13 . Accordingly, the vibration energy of a sound-to-vibration conversion apparatus of the present invention can be augmented. 
     When the housing  23  vibrates, this vibration energy is transferred to the seat, bed, chair, etc. (not shown) to which the housing  23  is attached, and finally the vibration energy will be transmitted to stimulate the human tactile organs. 
     Returning to  FIG. 2 , the reference numeral “ 19   a ” and “ 19   b ” denote elastic members for giving the electromagnet a resistive force in the direction opposite to the electromagnet&#39;s motion. The reference numeral “ 21 ” denotes a spacer for keeping the electromagnet  13  apart from the permanent magnet  11  and for absorbing the impact shock when the housing  23  including the permanent magnet  11  collides with the electromagnet  13 . 
     As described above, when the housing  23  vibrates or collides with the electromagnet  13 , a user can sense the strong vibration from this apparatus. This invention provides a user with a strong and vivid explosive sound and explosive vibration when used in a computer program game station or a theater seal. 
     In the mean time, it is desirable to include a frequency trap in an amplifier for providing an acoustic signal to the apparatus of this invention, because the electromagnet may abnormally oscillate in response to a particular frequency. A frequency trap for this purpose is well known to an ordinary person who is skilled in the art to which this invention pertains. 
     Unexplained element “ 25 ” denotes a frame for supporting the electromagnet  13 , the elastic members  19   a  and  b , and the inertial mass  17 , which is separated from the housing  23  on which the permanent magnet  11  is fixed and that is attached to the seat or the chair, etc. 
     From the foregoing the sound-to-vibration conversion apparatus according to the present invention has an advantage of providing high power vibration energy with lower heat consumption loss. Moreover, its simple structure makes it possible to improve the productivity at low cost. This apparatus can be used in vehicle seats to satisfy desires of audiophiles. If it is used for a computer, a game machine, a theater chain, a floor, a ceiling, a wall etc., a user can enjoy vivid and intense sound as if he were on the spot. If it is used for a mattress or bed, it is helpful for the antenatal training of pregnant women, curing insomnia, and promoting a dramatic married life. 
     If the sound-to-vibration conversion apparatus for the present invention is adapted to the keyboards of an electronic piano, since fingers can feel the vibration through the keyboards, even auditorily handicapped persons can play the piano as they are feeling the tones. This invention may be applied to an acoustic resonator apparatus. That is, this invention can reduce vehicle or toilet noise, and, if attached to a conference room wall or window, eavesdropping can be prevented. In addition, this invention is applicable to communication means using the medium of liquid or solid, and to a massage treatment machine. 
     While the invention has been shown and described with reference to a certain embodiment to carry out this invention, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.