Patent Publication Number: US-7221772-B2

Title: Electronic device comprising a loudspeaker unit

Description:
FIELD OF THE INVENTION 
   The present invention relates to an electronic device such as a TV set, a radio etc. having a casing in which a loudspeaker unit is mounted. 
   BACKGROUND OF THE INVENTION 
   When assembling such an electronic device, mounting the loudspeakers is more problematic than mounting of most other components of the device, because the way the loudspeaker is mounted has a critical influence on the quality of sound generated by the device. This quality is seriously impaired if the loudspeaker can excite audible resonances of the casing. In TV sets a further problem is that color reproduction at a CRT tube may be degraded if sound waves from a loudspeaker can excite the mask of the tube to vibrate with respect to the electron beam. 
   Conventionally, therefore, loudspeakers have been mounted in such devices by screwing them to a support region of the casing with a body of vibration absorbing material being placed as a spacer between the casing and the loudspeaker. 
   Mounting a loudspeaker in this way is not completely satisfying for a number of reasons. One is that assembly by screws is either time consuming, when the screws are placed one by one, or expensive, if a special tool is required for mounting several screws at a time. Another reason is that it is difficult to find the optimum tightness of the screws. If they are not tight enough, the speaker as a whole may tremble within the casing, causing unpleasant noise; if the screws are too tight, the vibration absorbing body may be compressed to such an extent that it looses its vibration dampening efficiency. 
   It is therefore an object of the present invention to provide an electronic device in which a loudspeaker is reliably prevented from exciting vibrations of the casing and for which manufacturing costs, in particular for mounting one or more loudspeakers, can be kept low. Patent application GB-A-2 312 130 proposes to mount a loudspeaker into a video display apparatus with interposition of an elastic gasket using a snap-fit arrangement. First, an elastic gasket may create resonances because of its flexibility. Furthermore, the proposed gasket surrounds the loudspeaker and this solution therefore needs a lot of space to be implemented. 
   SUMMARY OF THE INVENTION 
   The invention proposes an improved solution, according to which an electronic device comprises a loudspeaker unit, a casing with a first support for receiving the loudspeaker unit in a mounting direction and with a wall perpendicular to the mounting direction, at least one vibration absorbing body forming a spacer between the loudspeaker unit and the first support, wherein that at least one abutment protruding from the wall in the mounting direction contacts the vibration absorbing body. 
   The abutment allows usage of a vibration absorbing body of reduced size. 
   According to other features of the invention: 
   the vibration absorbing body is made of foamed plastic material: 
   the vibration absorbing body is shorter than the loudspeaker unit in the mounting direction; 
   the support has lateral ridges so as to form rails adapted to guide a displacement of the loudspeaker unit in the mounting direction; 
   a second vibration absorbing body forms a spacer between the loudspeaker unit and a second support of the casing; 
   the loudspeaker unit as a rectangular projection carrying the vibration absorbing body; 
   the rectangular projection is provided with at least one pin contacting the vibration absorbing body; 
   a plate is mounted to the first support in the mounting direction and stops the vibration absorbing body; 
   the plate is adhesively bonded to the vibration absorbing body; 
   a protrusion of the plate engages a recess in the vibration absorbing body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features, details and advantages of the invention will become apparent from the subsequent description of preferred embodiments given with reference to the drawings. In the drawings: 
       FIGS. 1 and 2  are exploded perspective views of first and second walls, vibration absorbing bodies and a loudspeaker unit according to a first embodiment of the invention; 
       FIG. 3  is a perspective view of a TV set as an example of the device according to this first embodiment; 
       FIG. 4  is a simplified sectional drawing of the TV set of  FIG. 3  taken along the plane defined by lines IV—IV of  FIG. 3 ; and 
       FIGS. 5 and 6  are sectional views analogous to that of  FIG. 4 , of second and third embodiments of the invention; 
       FIG. 7  is an exploded perspective view of a loudspeaker unit and vibration absorbing bodies according to a fifth embodiment of the invention; 
       FIG. 8  is an exploded perspective of a fifth embodiment of the invention. 
   

   DETAILED DESCRIPTION OF PREFERED EMBODIMENTS 
     FIGS. 1 ,  2  show part of a front wall  1  of a casing of a TV set, part of its rear wall  2 , and a loudspeaker unit  3  to be mounted between walls  1 ,  2  by means of annular-shaped vibration absorbing bodies  4 . The front wall  1  is a part of the cabinet of the TV set whereas the rear wall  2  is a part of the back cover. 
   The loudspeaker unit  3  is a loudspeaker enclosure, i.e. a preassembled unit formed of front and rear housing elements  5 ,  6  held together by means of screws or bolts. A front surface  7  of front housing element  5  has a number of openings  8  behind which individual loudspeakers are installed. 
   At top and bottom surfaces  10 ,  11  of loudspeaker unit  3 , rectangular projections  12  are provided. These projections correspond in shape to through holes  13  of vibration absorbing bodies  4 . The height of the projections  12  is less than the thickness of the vibration absorbing bodies  4 , so that when the vibration absorbing bodies are placed at top and bottom surfaces  10  and  11 , the projections  12  are concealed within through holes  13 . 
   The vibration absorbing bodies  4  are formed of a conventional foamed plastics material which can be resiliently compressed. 
   Two support arms  14  project from the inside of front wall  1 . These support arms  14  are parallel to each other, and their distance is a bit less than the overall height of the loudspeaker unit  3  with both vibration absorbing bodies  4  mounted to it, but more than the height of the loudspeaker unit  3  alone, so that by softly compressing the vibration absorbing bodies  4 , these and the unit  3  can be inserted between the support arms  14  without any of the projections  12  touching a support arm  14 . In the present embodiment each support arm  14  has two lateral ridges  15  at a distance corresponding to the width of the vibration absorbing bodies  4 , so that the loudspeaker unit  3  can be inserted between the support arms  14  from the rear but cannot move left or right. I.e. the support arms  14  and their ridges  15  form rails that guide the displacement of the loudspeaker unit during assembly. The insertion movement of the loudspeaker unit  3  comes to an end when the vibration absorbing bodies  4 , and specifically their front lateral face, come into contact with abutments  16  formed in the front wall  1  at the base of support arms  14 . The height of the abutments  16  is less than the thickness of the vibration absorbing bodies  4  in their compressed state, so that the abutments  16  can never come into direct contact with the housing of the loudspeaker unit  3 . 
   These abutments might for example be formed as solid walls extending perpendicularly to the insertion direction of the loudspeaker unit  3 . In the present embodiment, however, the abutments  16  are short ribs parallel to the lateral ridges  15 , which provide only for a very small area of contact with the vibration absorbing bodies  4 . The advantage of such an arrangement is twofold. On the one hand, such ribs are easily formed by injection molding in one piece with the front wall  1  and the support arms  14 , the other is that if the space between front and rear walls available for the loudspeaker unit varies due to manufacturing tolerances, this can be easily absorbed by the ribs  16  intruding more or less deeply into the flexible material of the vibration absorbing bodies without compressing these too strongly, so that the dampening properties remain essentially unaffected by such variations. 
   The rear wall  2  has no support arms  14 , but it has upper and lower inwardly projecting bosses  17 , the shape of which is similar to the abutments  16  of front wall  1  and which are located at the same level as these, so that when the device is assembled, the vibration absorbing bodies  4  will be immobilized in forward and rearward directions by the abutments  16  and bosses  17 . 
   The loudspeaker unit  3  is thus held in every direction through the vibration absorbing bodies  4 . In this way, the loudspeaker unit  3  is totally suspended which gives very good acoustic and mechanical results. 
     FIG. 3  is a perspective view of a TV set  20  as an example of an electronic device according to the present invention. The housing of the TV set  20  is essentially constituted of two injection-molded elements, a front element  21  (cabinet) of which the front wall  1  is part, and a rear element  22  (back cover) of which the rear wall  2  is part. The loudspeaker openings  9  show at both sides of CRT tube  23 . 
     FIG. 4  is a cross section of the TV set  20  in the plane defined by lines IV—IV, showing the components described with respect to  FIGS. 1 and 2 , already, in an assembled state. The loudspeaker unit  3  is immobilized exclusively by its top and bottom projections  12  engaging the through holes  13  of vibration absorbing bodies  4 . These, in turn, are held in vertical directions by support arms  14 , in left and right directions (perpendicular to the plane of  FIG. 4 ) by ridges  15  and in front and rear directions (to the left and right in  FIG. 4 ) by abutments  16  and bosses  17  of front and rear walls  1 ,  2 . 
   The length of the abutments  16  and bosses  17  is chosen such that the loudspeaker unit  3  will not come into direct contact with either wall  1  or  2  and can thus not transmit any vibrations directly to it. 
     FIG. 5  is a sectional view analogous to  FIG. 4  of a second embodiment of the invention. In this embodiment, the loudspeaker unit  3  and the vibration absorbing bodies  4  are the same as in  FIG. 3 , but the roles of front and rear walls  1 ,  2  have been exchanged. Here, it is the rear wall  2  that bears the support arms  14  and abutments  16 , whereas the front wall  1  has bosses  17  for pushing the loudspeaker unit  3  and the vibration absorbing bodies  4  against the abutments  16  of the rear wall  2 . 
   A third embodiment of the invention is shown in the sectional view of  FIG. 6 . This embodiment differs from that of  FIGS. 1 to 4  in that the support arms  14  are no longer parallel but converge towards their distal ends  25  over a major part of their length. The result of this feature is that when the vibration absorbing bodies  4  are in contact with the abutments  16 , as shown in  FIG. 6 , the compression is less than it would be if the loudspeaker unit  3  was displaced to the right in  FIG. 6 . Accordingly, the loudspeaker unit  3  is firmly held in this position without the need for projections  17  of the rear wall  2  (not shown) to keep it there. This embodiment is particularly suited if the distance between front and rear walls of the device casing is much greater than the depth of the loudspeaker unit  3 , and bosses  17  of the rear wall, if provided, would have to be inconveniently long. 
   Another peculiarity of this embodiment is that in proximity of their distal ends  25 , the support arms  14  are divergent. Preferably, the distance between the free ends  25  is more than the overall height of the loudspeaker unit  3  and the vibration absorbing bodies  4  in their uncompressed state. Due to this feature, the loudspeaker unit  3  can be easily inserted between the support arms  14  without having to compress the vibration absorbing bodies  4  before. 
   Of course, the peculiar features of this embodiment can be combined with those of the second embodiment. 
     FIG. 7  is a perspective view of a loudspeaker unit  3  according to a fourth embodiment of the invention. This embodiment has several peculiar features which can be used alone or in combination with any of the embodiments described before. 
   A first peculiar feature is that the loudspeaker unit does not have a closed housing but only a frame  27  having top, bottom and front surfaces  10 ,  11 ,  7  but no left, right or rear surface. It is stabilized by ribs  28 , extending at its left and right hand sides (only the right hand side rib is shown in the  FIG. 7 ), so that it can withstand compression of the vibration absorbing bodies  4  without being bent. 
   In order to facilitate molding of the frame  27 , there is not one solid projection at top and bottom surfaces  10 ,  11 , but a plurality of narrow walls  29 , that can be easily shaped by simple molding tools moveable only in front and rear directions. 
   Another peculiarity of this embodiment is a third vibration absorbing body  30 , which is, in  FIG. 7 , shown separate from the frame  27  but which, in the assembled device, is adhered to the edges of front surface  7 . 
   A fifth embodiment of the invention is represented on the partial perspective view of  FIG. 8 . According to this embodiment, a support arm  14  (only partially represented) of the front wall  1  has a cylindrical protrusion  31 , preferably with a small-diameter hollowing-out  36 . The axis of the cylindrical protrusion  31  corresponds to the mounting direction of the loudspeaker unit  3 . 
   A plate  32  is affixed to the free end of the support arm  14  by screwing; for this purpose, the plate  32  has a through-hole  37  through which a screw can be screwed to the cylindrical protrusion  31  at the hollowing-out  36 . The plate  32  is meant to retain the vibration absorbing body  4  in the rearward direction (In this regard, the plate has the function of the bosses  17  of the first embodiment.) 
   The fifth embodiment is thus particularly suited when the rear wall  2  is too distant from the front wall  1  to be used as an abutment in the rearward direction. 
   In order to further enhance retention of the various parts, a pin or pins  35  are provided on the rectangular projections  12  to contact the vibration absorbing body  4  and a protrusion  33  on the plate  32  is provided in correspondence with a recess  34  in the vibration absorbing body  4 . 
   In the fifth embodiment, the mounting operations can consequently be the following ones : first the vibration absorbing body  4  is mounted to the loudspeaker unit  3  ; then the loudspeaker unit  3  is mounted to the front wall  1  at the level of the support arm  14 . Lastly, the plate  32  is screwed to the support arm  14  whereby complete retention of the loudspeaker unit  3  is obtained. 
   Another solution to mount the loudspeaker unit  3  to the electronic device is the following one : the plate  32  can be adhesively bonded to the vibration absorbing body  4  beforehand, at the level of the protrusion  33  and recess  34 . The final assembly is then simplified : by mounting the vibration absorbing body  4  with plate  32  onto the loudspeaker unit  3  and by engaging the loudspeaker unit  3  between the support arms  14 , the trough-hole  37  comes to facing the cylindrical protrusion  31 . 
   The loudspeaker unit  3  can thus be retained by screwing the plate  32  to the front wall  1 . 
   The above description of the fifth embodiment refers to only one of the vibration absorbing body  4  but naturally it also applies to the other vibration absorbing body  4 . 
   Another possible solution to improve the retention of the vibration absorbing body  4  on the corresponding projection  12  of the loudspeaker unit  3  is to provide that the projection  12  is thicker and wider than the through hole  13  in a cross-section, for instance in the direction of mounting of the loudspeaker unit  3 . The support arm  14  must then have a corresponding opening to receive the thick part of the projection  12 . The vibration absorbing body  4  is thus mechanically held between the top or bottom surface  10 , 11  of the loudspeaker unit and the wider section of the projection  12 . 
   In the embodiments described above, the loudspeaker unit  3  has always been shown to be supported by support arms  14  projecting in a cantilever manner from one of the walls  1  or  2 . Of course, the loudspeaker unit might just as well be supported by a bottom wall of the device casing and an upper support arm or a top wall of the casing, or by a lower support arm and a top wall of the casing. Ridges analogous to above-described ridges  15  may be provided on top and/or bottom walls as required to form guide rails for the loudspeaker unit thereon, or other means for preventing a displacement of the loudspeaker unit to the left or right may be provided instead. 
   In the above description, the loudspeaker unit  3  receives two absorbing bodies  4 . However, the invention is not limited to this possibility. It also applies to solutions with one absorbing bodies and to solutions with more than two absorbing bodies.