Abstract:
A case of the information equipment is provided for setting various parts in. A speaker and receiver are provided in the frame. A first back chamber is formed in the speaker and a second back chamber is formed in the receiver. A baffle is formed on a part of the frame for dividing the inner space of the case so as to separate the first and second back chambers from each other.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a compound sound generator for an information equipment such as a portable telephone. 
     The compound sound generator has a speaker for converting a call signal into a sound and a receiver for converting a sound signal into a sound. The sound emitted from the receiver is heard with user&#39;s ear close to the telephone and the sound emitted from the speaker is heard even when the telephone is away. Thus the speaker generates sounds of larger volume than the receiver. 
       FIG. 6  is a sectional view of a conventional compound sound generator set in a case  20  of an information equipment. 
     The compound sound generator has a flat circular or ellipse shape and is set in a case  20  having substantially a shape of a box. In the case  20 , there is provided an annular frame  1  made of synthetic resin on which various parts of the compound sound generator are mounted, and a common yoke  2  made of a magnetic material is mounted in the frame  1 . 
     The yoke  2  comprises a flange  2   a  formed on an upper periphery of a cylindrical portion  2   b  having a bottom  2   c.  An annular first magnet  3  for the speaker is secured to the underside of the flange  2   a,  and a second magnet  8  for the receiver having disc shape is secured to the bottom  2   c  of the yoke  2 . An annular first top plate  4  made of a magnetic material is secured to the underside of the first magnet  3 , and a second top plate  9  having a disc shape is secured to the upper surface of the second magnet  8 . 
     A first diaphragm  6  is secured to the underside of the frame  1 , thereby forming a relatively small back chamber  22   a  between the diaphragm  6  and the yoke  2 . A second diaphragm  11  is secured to the upper surface of the frame  1 , thereby forming a relatively small back chamber  22   b  between the diaphragm  11  and the yoke  2 . A first voice coil  5  and a second voice coil  10  are secured to inside surfaces of the first and second diaphragms  6  and  11 , respectively. The first diaphragm  6  and the first voice coil  5  compose a first sound production device as a speaker, and the second diaphragm  11  and the second voice coil  10  compose a second sound production device as a receiver. Protectors  7  and  12  each having a dish shape and made of a thin metal plate are secured to the underside and upper surface of the frame  1  for protecting the diaphragms  6  and  11 . 
     There is formed sound discharge holes  7   a  formed in the protector  7 , sound discharge holes  12   a  in the protector  12 . 
     The outer peripheries of the protector  7  and the diaphragm  6  are inserted and press fitted in an annular recess formed in a lower projection  1   a  of the frame  1 . The outer peripheries of the protector  12  and the diaphragm  11  are inserted and press fitted in an annular recess formed in an upper projection  1   b  of the frame  1 . 
     The compound sound generator is assembled into the case  20  with other parts. Cushioned annular spacers  21  are disposed between each of the protectors  7  and  12  at outer portions of the sound discharge holes  7   a  and  12   a  and the inner surface of the case  20 . 
     The external case  20  has a plurality of sound discharge holes  20   a  formed in the bottom thereof and a sound discharge hole  20   b  formed in the upper surface thereof. 
     Sound produced by the diaphragm  11  is discharged through the sound discharge holes  12   a  and further outside through the sound discharge hole  20   b  as shown by an arrow a. Similarly, sound produced by the diaphragm  6  is discharged through the sound discharge holes  7   a  and further outside through the sound discharge holes  20   a  as shown by an arrow b. Mixing of sounds emitted from the back chambers  22   a  and  22   b  with the sounds emitted through the sound discharge holes  7   a  and  12   a  are prevented. The spacers  21  are provided to enhance the air-tightness, thereby separating the sounds from one another. 
     In order to allow the vibration of the diaphragms and to improve the acoustic characteristics such as volume and sound quality, the back chambers  22   a  and  22   b  are communicated with atmosphere. Namely, as shown by arrows c and d, air in the back chamber  22   b  flows through openings  1   d  partially formed in the projection  1   b  into the inner space of the case  20 . Air in the back chamber  22   a  flows into the inner space of the case  20  through air passages  1   c  formed in the shoulder of the frame  1  as shown by arrows e and f. 
     In the conventional compound sound generator, the back chambers  22   a  and  22   b  are thus communicated with the entire inner space of the case  20 . Therefor, a part of the airflow from one of the hack chambers  22   b  and  22   a  may flow into the other back chamber through the openings  1   d  or the passages  1   c  as shown by arrows g and h. Hence, when the diaphragm  6  for the speaker is vibrated, the produced sound causes the air pressure to change, thereby vibrating the diaphragm  11  for the receiver so that sound is also emitted from the receiver. If a large sound is emitted from the receiver with user&#39;s ear close to the telephone, user&#39;s ear may be hurt. In another case, telephone conversation may leak out and be heard by others through the receiver. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a compound sound generator which prevents sound leaking and causing vibration of the other diaphragm. 
     According to the present invention, there is provided a sound generator for an information equipment comprising a case of the equipment, a frame set in the case, a speaker and receiver provided in the frame, the speaker having a first diaphragm and the receiver having a second diaphragm, a first back chamber behind the first diaphragm of the speaker and a second back chamber behind the second diaphragm of the receiver, and a baffle formed on a part of the frame for dividing the inner space of the case so as to separate the first and second back chambers of the compound sound generator from each other. 
     One of the first and second back chambers of the speaker and the receiver is opened to the outside of the case, the other chamber is opened to the inner space of the case. 
     The first back chamber of the speaker is opened to the outside of the case. 
     The second back chamber of the receiver is opened to the outside of the case at a same surface as a surface where a sound discharge opening of the speaker is formed. 
     The first back chamber of the receiver is opened to the outside of the case at a surface different from a surface where a sound discharge opening of the speaker is formed. 
     These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view showing a compound sound generator according to a first embodiment of the present invention, set in a case of a portable telephone; 
         FIG. 2  is a plan view showing an upper part of the compound sound generator of the first embodiment; 
         FIG. 3  is a sectional view taken along a line III—III of  FIG. 2 ; 
         FIG. 4  is a plan view showing an underside of the compound sound generator; 
         FIG. 5  is a sectional view showing a second embodiment of the present invention; and 
         FIG. 6  is a sectional side view showing a conventional compound sound generator set in a case of a portable telephone. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a sectional view of a compound sound generator of a first embodiment according to the present invention, set in a case of a portable telephone,  FIG. 2  is a plan view of the sound generator,  FIG. 3  is a sectional view taken along a line III—III of  FIG. 2 , and  FIG. 4  is an underside view. 
     The compound sound generator of the present invention is set in an ellipse shaped case  50 . In the case  50 , there is provided a frame  31  made of synthetic resin, on which various parts of the sound generator are mounted, and a common yoke  32  made of a magnetic material is mounted in the frame  31 . 
     The yoke  32  comprises a flange  32   a  formed on an upper periphery of a cylindrical portion  32   b  having a bottom  32   c.  An annular first magnet  33  is secured to the underside of the flange  32   a  with an adhesive, and a second magnet  38  having disc shape is secured to the bottom  32   c  of the yoke  32 . An annular first top plate  34  made of a magnetic material is secured to the underside of the first magnet  33 , and a second top plate  39  having a disc shape is secured to the upper surface of the second magnet  38 . 
     A first diaphragm  36  is secured to the underside of the frame  31 , thereby to form a back chamber  43   a  between the diaphragm  36  and the yoke  32 . A second diaphragm  41  is secured to the upper surface of the frame  31 , thereby to form a back chamber  43   b  between the diaphragm  41  and the yoke  32 . The first diaphragm has a larger size approximate to the protector  37 , and the second diaphragm has a smaller size approximate to the protector  42 . A first voice coil  35  and a second voice coil  40  are secured to inside surfaces of the first and second diaphragms  36  and  41 , respectively. The first diaphragm  36  and the first voice coil  35  compose a first sound production device as a speaker, and the second diaphragm  41  and the second voice coil  40  compose a second sound production device as a receiver. First and second protectors  37  and  42 , each having a dish shape and made of a thin metal plate, are secured to the underside and upper surface of the frame  31  for protecting the diaphragms  36  and  41 . 
     The first protector  37  has a sound discharge holes  37   a  so as to discharge sounds generated by the first diaphragm  36  in the downward direction. The second protector  42  has sound discharge holes  42   a  so as to discharge sounds generated by the second diaphragm  41  in the upward direction. 
     The frame  31  has a lower projection  31   a  and an upper projection  31   b.  In the lower projection  31   a,  an annular recess is formed so that the outer peripheries of the protector  37  and the diaphragm  36  are inserted and press fitted therein. In the upper projection  31   b,  an annular recess is formed so that the outer peripheries of the protector  42  and the diaphragm  41  are inserted and press fitted therein. In a shoulder  31   c  of the frame  31 , an air passage  31   d  is formed. An opening  31   e  is formed in the lower portion of the upper projection  31   b  at the opposite side of the air passage  31   d.    
     In accordance with the present invention, the frame  31  further has an integrally formed U-shaped baffle  52  so as to surround the opening  31 e as shown in  FIG. 2 . The baffle extends vertically through the entire inner height of the case  50 , thereby forming an air passage  53  as shown in  FIG. 1 . 
     The sound generator is assembled into the case  50  with other parts. Annular spacers  51  are disposed between each of the protectors  37  and  42  and the case  50  at the outer portions of the sound discharge holes  37   a  and  42   a,  Upper and lower spacers  54  are interposed between the upper and lower ends of the baffle  52  and the case  50 . 
     The case  50  has a plurality of sound discharge holes  50   a  formed in the bottom thereof at a portion inside the spacers  51  and a sound discharge hole  50   b  formed in the upper surface thereof. Another sound discharge hole  50   c  is formed in the bottom opposing the lower end of the air passage  53 . 
     Referring to  FIG. 2 , metal terminal electrodes  45  are molded in the frame  31 . Grooves  44   a  and  44   b  are formed in the frame  31  at a position lower than the protection  31   b  and at a position upper than the projection  31   a,  respectively, so as to allow the end portions of the voice coils  35  and  40  to be connected to the electrodes. 
     Sounds generated by the diaphragm  41  are discharged through the sound discharge holes  42   a  of the protector  42  and further outside of the case  50  through the sound discharge hole  50   b  as shown by the arrow a. Similarly, sounds generated by the diaphragm  36  are discharged through, the sound discharge holes  37   a  of the protector  37  and further outside the case through sound discharge holes  50   a  as shown by the arrow b. As shown by the arrow c, air in the back chamber  43   b  flows through the opening  31   e  formed in the projection  31   b  into the air passage  53  and further out of the case  50  through the opening  50   c  as shown by an arrow i. Air in the back chamber  43   a  flows into the inner space of the case  50  through air passages  31   d  formed in the shoulder  31   c  of the frame  31  as shown by the arrows e and f. Namely, the back chambers  43   a  and  43   b  are not communicated with each other so that the air in one of the chambers is prevented from entering the other chamber through the space in the case  50 . It is assumed that the vibrations of the diaphragms are not affected by the sounds outside the case. 
     Thus, in the present invention, the sound from the speaker is only emitted from the sound discharge holes  50   a  and the sound from the receiver is only emitted from the sound discharge hole  50   b.  Hence the problems of injury to the ear and leaking of conversation do not occur. 
       FIG. 5  shows a second embodiment of the present invention wherein the frame  31  has a horizontal baffle  52   a  integral thereto. In the present embodiment, a sound discharge hole  50   d  is formed in the side wall of the case  50  so that the back chamber  43   b  is communicated with the atmosphere through the opening  31   e  and the discharge hole  50   d  as shown by an arrow j. The present embodiment provides a wider range of design choice in manufacturing the compound sound generator. 
     The present invention is not limited to the embodiments described above. For example, the back chamber of the receiver may be communicated with a sealed space of a predetermined volume formed in the case instead of with the atmosphere. Alternatively, the back chamber of the speaker may be communicated with the atmosphere. Various modifications of structure of the baffle and air passage and acoustic separating method and the material thereof are further possible. 
     The present invention provides a compound sound generator where the back chambers of each of the speaker and the receiver are effectively separated from each other by a simple and inexpensive means of providing a baffle. Accordingly, injury to the ear and leaking of conversation are prevented. 
     While the invention has been described in conjunction with preferred specific embodiment thereof, it will be understood that this description is intended to illustrate and not limit the scope of the invention, which is defined by the following claims.