Technical Field The present invention relates to an apparatus for converting a sound signal into vibration so as to stimulate the human hearing organs through the human bones. More particularly, this invention relates to an apparatus using an ironcore and an inertial mass so as to exert high power output.

Background Art Conventionally, a bone-conducting loudspeaker has been developed for persons who have difficulty in hearing. This loudspeaker is a kind of acoustic transducer that enables an auditory 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 matters, 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 diaphragm 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 waving the surrounding atmosphere.

Meanwhile, in order to expand the purpose of hearing aid for auditory 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 tools, theatre seats, etc.

However, in the conventional body-sensible loudspeaker, high power output cannot be obtained because it directly uses a structure of the conventional acoustic loudspeaker (see FIG. 1). In the conventional acoustic loudspeaker, vibrating diaphragm is made of soft materials, such as paper or PVC. Thus, it has a disadvantage that: A coil becomes short-lived because of heat generated by the amount of current increasing 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, thereby, the frequency over a certain frequency value being blocked.

Disclosure of Invention To solve the above disadvantages in conventional body-sensible loudspeakers, it is an object of the present invention to provide a new-organized loudspeaker for increasing vibration energy by using an electromagnet having an ironcore and an inertial mass.

To achieve the above object, there is provided a sound-to-vibration conversion

apparatus comprising a housing ; a plurality of magnet means, each of which has N-and S- pole being formed on the same plane and is fixed to the housing; a plurality of electromagnet, each of which is located adjacent to the plane where N-and S-pole of the magnet means are formed; and a rotating shaft for pivotally fixing one end part of the respective electromagnet, whereby the electromagnet reciprocatively pivots to get close to or away from N-or S-pole of the magnet means in accordance with the interaction between the polarities formed at the electromagnet by an acoustic signal applied to the electromagnet and N-and S-pole of the magnet means.

In the above, the respective electromagnet comprises an inertial mass for increasing inertial force of the electromagnet's reciprocal rotary motion, such that the housing including the magnet means can vibrate against the electromagnet.

It is desirable that the magnet means is a permanent magnet. It is also desirable that the electromagnet includes an E-shaped iron core having three protrusions; and a coil wound around a central protrusion.

A sound-to-vibration conversion apparatus according to the present invention may further comprises elastic means for giving the respective electromagnet a resisting power in the opposite directions of the electromagnet's motion, and for neutralizing the electromagnet, when no acoustic signal is applied to the coil.

Brief Description of Drawings The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which : FIG. 1 is a structural diagram roughly showing the conventional acoustic loudspeaker,

FIG. 2 is a typical diagram showing the principle of an apparatus of this invention, and FIG. 3 shows a preferred embodiment for carrying out the present invention.

Preferred Embodiment for Carrying out the Invention Preferred embodiment will be described herein below with reference to the accompanying drawings.

FIG. 2 shows the principle of a sound-to-vibration converter according to the present invention. A magnet means 11 having N-pole and S-pole, both of which form on the same plane, is fixed to a rigid body, such as a metal frame or housing (not shown in FIG. 2, but shown in FIG. 3 denoting"12"and"14"). The frame 12 or housing 14 may be a car seat, a bed, a chair, or any other things that 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.

An electromagnet 13 is located adjacent to the plane where N-and S-pole of the permanent magnet 11 are formed. Because an end part of the electromagnet 13 is pivotally fixed to a rotating shaft 15, the electromagnet 13 reciprocatively pivots to get close to or away from N-or S-pole of the magnet 11 in accordance with the interaction between the polarity formed at the electromagnet 13 by the acoustic signal applied to the electromagnet 13 and N-and S-pole of the magnet 11 (compare a dotted line"A"with a solid line"B").

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 an iron-cored electromagnet that a coil is wound around an iron core. Because the iron-cored electromagnet is relatively heavy, it acts as an inertial mass against the fixed magnet, so that the interaction between the fixed magnet and the electromagnet can produce much more vivid vibration. Additionally, because an iron-cored electromagnet provides higher efficiency than a non-iron-cored electromagnet, the loss of magnetic force becomes lesser in this invention.

In the mean time, the above-described concept with reference to FIG. 2 just shows the principle spirit of this invention. It still has some unsettled problems: Since the electromagnet 13 is facing the permanent magnet 11 at narrow intervals, the attractive force of the permanent magnet 11 disturbs the neutral state of the electromagnet 13. The neutral state here means the state that the electromagnet 13 is situated in the middle portion between N-and S-pole of the permanent magnet 11 (see a dotted line"A"in FIG. 2). In addition, even though inertial force of the present invention is stronger than that of the conventional body-sensible loudspeaker owing to the heavy iron-cored electromagnet 13, it is desirable to more increase the inertial force or vibration energy of the electromagnet 13 so as to maximize the advantages of the present invention.

The preferred embodiment to solve the above problems is shown in FIG. 3. As shown, it can be noted that the conceptual configuration of the present invention in FIG. 2 is arranged symmetrically on either side. Either of the electromagnets 13,13'includes an E-shaped iron core having three protrusions 13a, b, c and 13a', b', c' ; and a coil 17,17' wound around a central protrusion 13a, 13a'.

In operation, when an alternate current (acoustic signal from an audio system) is applied to the coil 17, 17', the polarity and the magnetic force of the electromagnet 13, 13' varies according to the applied signal's amplitude or phase. Thereby, the attractive force

and repulsive force between the electromagnet 13,13'and the permanent magnet 11, II' causes the electromagnet 13,13'to reciprocatively pivot centering on the rotating shaft 15, 15'. Here, the reciprocating distance of the electromagnet 13,13'traces a waveform of the applied acoustic signals.

In this embodiment, it is essential that the polarities of the respective electromagnet 13, 13'should be opposed each other, because either of the electromagnets 13,13'must move symmetrically with respect to a central vertical line of a housing frame 14.

Meanwhile, the electromagnet 13, 13'includes the inertial mass 23,23'to increase the inertial force of the electromagnet's reciprocal rotary motion. Therefore, even though the electromagnet 13,13'is movably fixed in the housing 14, because the electromagnet 13, 13'including the inertial mass is heavier than the housing 14, the housing 14 including the permanent magnet 11,11'will vibrate instead of the electromagnet 13, 13'. Accordingly, the vibration energy of a sound-to-vibration conversion apparatus of the present invention can be much more augmented. When the housing 12 vibrates, this vibration energy is transferred to a seat, a bed, a chair, etc. (not shown) to which the housing 12 is attached, and finally the vibration energy will be transmitted to stimulate the human tactile organs.

Returning to FIG. 3, the reference numerals"25a","25b","25a"', and"25b"'denote elastic members for neutralizing the electromagnet 13,13'. The elastic members 25a, b, a', b' give the respective electromagnet 13, 13'the resisting force in the opposite directions of the electromagnet's motion. Of course, when no acoustic signal is applied, the elastic members 25a, b, a', b' play a role in positioning the electromagnet 13, 13'to its neutral point between N-and S-pole of the permanent magnet 11,11'. The elastic member 25a, b, a', b' also acts as a kind of braking means for limiting the uppermost and lowest points of the electromagnet's reciprocal motion.

In FIG. 3, springs are used as the elastic member 25a, b, a', b'. Four springs are respectively installed between each the lateral face of the electromagnet 13, 13'and the housing 14. In addition to a spring, a rubber may be used as the elastic member 25a, b, a', b', or both also. If both of the spring and the rubber are used, the electromagnet's braking performance will be improved. The braking force of the elastic member 25a, b, a', b' is set in proportion to the attractive force of the permanent magnet 11,11'. That is to say, when manually moving the electromagnet 13, 13', it is desirable that the pressure of the elastic members 25a, b, a', b' is to be adjusted at the point where an adjuster feels no attractive force of the permanent magnet 11, 11'.

Among unexplained elements, reference numerals"19"and"19"'stand for bearings for supporting the rotating shaft 15. In addition, it is desirable to include a frequency trap in an amplifier for providing 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 aim is well known to an ordinary person who is skilled in the art to which this invention pertains.

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 with chief cost. This apparatus can be used for seats of vehicles to satisfy the audio or car maniacs'desire. If it is used for a computer, a game machine, a theater chair, a floor, a ceiling, a wall, etc., a user can enjoy vivid and intense sound as if he were in the spot. If it is used for a mattress or bed, it is helpful to antenatal training of pregnant women, curing insomnia, and promoting a dramatic married life.

If the sound-to-vibration conversion apparatus of the present invention is adapted to keyboards of an electronic piano, since fingers can feet 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 it attached to a conference room or window, eavesdrop can be prevented. Besides, 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.