Abstract:
A loudspeaker mounting frame ( 1 ) for an electronic appliance has a central opening for receiving a loudspeaker membrane ( 24 ), and a plurality of through holes ( 11 ) surrounding said central opening for receiving fixing means ( 25 ). The through holes ( 11 ) are tapered so as to accommodate the fixing means ( 25 ) in varying orientations. Spherical bosses ( 6 ) surrounding said through holes ( 11 ) are formed at a rear side ( 5 ) of the mounting frame ( 1 ).

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a loudspeaker mounting frame for mounting a loudspeaker in a cabinet of an electronic device such as a radio, a television set or any other type of audio or audio/video appliance. It further relates to a loudspeaker and to a cabinet comprising such a mounting frame. 
   Conventionally, electromagnetic loudspeakers have a sound-radiating membrane of roughly frusto-conical shape, the outer rim of which is fixed to a rigid support ring. Webs extending from this support ring hold an electromagnet for driving the vibrations of the membrane in position at the small base of the frusto-conical membrane. In this support ring, a plurality of holes is formed. Such a loudspeaker is usually installed by placing its rear side on a carrier and driving screws through the holes into the carrier. 
   In order to protect the loudspeaker membrane from damage, it should be covered by a sound-transmission hood such as a stretched fabric or a perforated shell that will let the sound from the loudspeaker pass to the outside but will prevent outside objects from reaching the membrane and damaging it. The distance between the membrane and the hood should be kept small in order to prevent an unwanted dampening of trebles. 
   A loudspeaker assembly comprising a carrier and a hood as described above is complicated and expensive to produce. 
   It might therefore be contemplated to simplify such an assembly by using a stiff perforated shell as the protective hood and to provide receiving portions in this shell for receiving the shafts of screws by which the loudspeaker is screwed to the shell. 
   Such a solution is unsatisfying for various reasons. One reason is that the shaft receiving portions must be located between the shell and the support ring of the loudspeaker, whereby the distance between the shell and the loudspeaker is increased by the length of the shafts, at minimum, and reproduction of trebles is impaired. Another reason is that modern electronic appliances frequently have a freely curved shape. If such a shape is formed by moulding, bores of the shaft receiving portions must be parallel to the direction of displacement of the mould elements in the moulding process, because otherwise moulds having a high number of movable elements are required. However, this direction of displacement is not necessarily perpendicular to a mounting plane of the loudspeaker. If it is not, fixing screws will extend through the holes of the support ring at non-perpendicular angles, making the assembly awkward and irreproducible. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention aims at providing a technique for mounting a loudspeaker in an electronic appliance cabinet in which at least some of the problems of the prior art are avoided. 
   In a first instance, the invention proposes a loudspeaker mounting frame having a central opening for receiving a loudspeaker membrane and a plurality of through holes surrounding said central opening for receiving a fixing means for fixing the mounting frame to a cabinet, wherein said through holes are tapered. The tapered shape allows for fixing means such as pins or screws to extend through the through holes in various directions without risk of interference, so that the frame may be easily and reproducibly mounted in a variety of oblique orientations that may be required by a convex shape of the cabinet in which the loudspeaker is installed. 
   A tapering angle of the through holes of 5° to 15° has proved suitable. 
   In a second instance, the invention proposes a loudspeaker mounting frame, preferably a frame as defined above, having a central opening for receiving a loudspeaker membrane and a plurality of through holes that extend between front and rear main surfaces surrounding said central opening for receiving fixing means, wherein said mounting frame has a number of bosses formed on at least one of said main surfaces, and said through holes extend through said bosses. Conventionally, if a workpiece is fixed to a support using a screw extending through a bore of the workpiece, and the screw is not perpendicular to the surface surrounding the bore, the screw head will not lie flat on the surface surrounding the bore, but instead, only a point contact will arise. This point contact can exercise considerable torque on the screw, so that in order to achieve a solid mount, a long thread of the screw is necessary. According to the invention by providing a boss surrounding each through hole, a contact between the surface of the boss and the head of the screw will be close to the screw shaft, so that torque is small and a solid mount can be achieved using a short thread. 
   Preferably, the bosses have the shape of sphere segments. 
   In order to achieve a contact between a screw head and the boss close to the shaft of the screw, it is preferable that the narrow side of a tapered through hole through which the screw extends is formed at the same surface of the mounting frame as the bosses. 
   The invention also proposes a loudspeaker comprising a mounting frame as defined above and a sound-emitting membrane mounted in the central opening of said mounting frame. In that case, the mounting frame may be integrally combined with the loudspeaker support ring as defined above, i.e., the loudspeaker membrane may be connected directly to an edge of the central opening of the mounting frame. On the other hand, the loudspeaker support ring and the mounting frame might be two different parts, the membrane being directly connected to the support ring and the support ring being mounted in the central opening of the mounting frame. 
   The invention also proposes a loudspeaker cabinet having a support structure to which a loudspeaker mounting frame as defined above or a loudspeaker as defined above is mounted, and a perforated shell facing the sound-emitting membrane of such a loudspeaker. 
   For a quick and easy assembly of the loudspeaker cabinet, it is preferred that the support structure has at least one pin matingly engaging one of said through holes of the mounting frame and at least one bore aligned with another one of said through holes for receiving a fixing bolt inserted through said through hole. With such a design, it is possible first to engage the mounting frame with said at least one pin, so that it is temporarily held, and then to finish the assembly by fixing said at least one bolt. 
   As already indicated above, the head of the bolt should come into contact with the surface of one of said bosses. 
   In order to keep the design of the cabinet simple, the support structure and perforated shell may be the same part. Since the bolts must not emerge at the front side of the perforated shell, the shell is preferably provided with a number of stubs formed on it, the stubs having resting surfaces which are in contact with the mounting frame, and the at least one mating pin and the at least one bore are formed at one of said resting surfaces, respectively. Since the head of the bolt is in contact with the surface of the boss surrounding the through hole in which it is inserted, the torque acting on the bolt is small, so that a short shaft of the bolt is sufficient for a solid fixation. Accordingly, the stubs may also be kept short, thus keeping the distance between the loudspeaker membrane and the perforated shell short, which, in turn, is favourable for reproduction of trebles. 
   A further possible feature for decreasing the distance between the loudspeaker membrane and the perforated shell is that a mounting surface portion of the mounting frame—to which a loudspeaker membrane may be fixed directly or via a support ring, as indicated above—surrounding the central opening is located between a plane defined by the tips of the stubs protruding from the perforated shell and the perforated shell itself. 

   
     DESCRIPTION OF THE DRAWINGS 
     Further objects, features and advantages of the present invention will become apparent from the subsequent description of specific embodiments referring to the drawings. 
       FIG. 1  is a perspective front view of a loudspeaker mounting frame according to a first embodiment of the invention; 
       FIG. 2  is a perspective rear view of the mounting frame of  FIG. 1 ; 
       FIG. 3  shows part of a cabinet element for an electronic appliance; 
       FIG. 4  is a section of the cabinet element of  FIG. 3  with a loudspeaker and a mounting frame mounted to it; and 
       FIG. 5  is a perspective view of the cabinet element of  FIG. 3  with a loudspeaker mounted to it, according to a second embodiment of the invention. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  show front and rear sides of a loudspeaker mounting frame  1  according to a first embodiment of the invention. The frame  1  is integrally formed by injection moulding of plastic material. It has four webs  2 ,  2 ,  3 ,  3  defining the sides of a rectangle with rounded corners and surrounding a central opening  4 . Its rear side  5  is essentially flat, except for spherical bosses  6  at four corners. 
   At the front side of the frame  1 , a flat rim  7  extends around the central opening  4 . 
   The rim  7 , in turn, is surrounded by ribs  8 . The ribs  8  are shaped so that a support ring of a loudspeaker, not shown, may be placed on the rim  7  and held in place by the ribs  8 . 
   In the corners of the front side of the mounting frame  1 , there are four recesses  9 , each of which has a flat base surface  10 . The base surfaces  10  of all recesses are in one plane, parallel to the two planes defined by the rim  7  and the rear side  5 , respectively. A tapered hole  11  extends from the base surface  10  of each recess to the bosses  6  at the rear side  5 . The tapering angle of the holes  11  is 5° to 15°, preferably about 10°. The narrow side of the holes  11  is at rear side  5 . 
   The purpose of the mounting frame  1  is to facilitate mounting a loudspeaker to a cabinet element of an electronic appliance.  FIG. 3  is a perspective view of part of such a cabinet element  12 , seen from inside. In the Figure, part of a main surface  13  and lateral flanks  14  of the cabinet element  12  are shown. The main surface  13  has a convex curvature. An oval rib  15  delimits a perforated surface portion  16  of the main surface  13 . Behind this perforated surface portion  16 , a loudspeaker is to be installed. The outline of rib  15  is adapted to that of ribs  8  so that the ribs  8  can matingly engage inside the rib  15 , whereby a support ring of a loudspeaker is held fixed between rim  7  and the perforated surface portion  16  facing it. 
   For fixing the mounting frame  1  to the cabinet element  12 , four stubs  17 ,  18  are formed at the inside of main surface  13 , surrounding rib  15 . Two of these stubs  17  are cylinders having flat end faces  19 . In these, a blind bore  20  is formed coaxially to the stub  17 . 
   The other two stubs  18  have a cross-shaped cross section with resting shoulders  21  formed therein between base portions  33  and tip portions  32  thereof. The resting shoulders  21  and the end faces  19  are located in the same plane. 
     FIG. 4  is a section of cabinet element  12  in a plane extending through the two stubs  17 , and of the mounting frame  1  and a loudspeaker  22  mounted to the cabinet element  12 . An angular support ring  23  of the loudspeaker is held tight between the cabinet element  12  and the mounting frame  1 . It supports the outer rim of a loudspeaker membrane  24 . The mounting frame  1  is held in place by two screws  25  extending through two of the tapered holes  11  and engaging the blind bores  20  of stubs  17 . The other two tapered holes  11  (not shown in  FIG. 4 ) are engaged by the tip portions  32  of stubs  18 . It is readily apparent that the stubs  17  (and  18 , too) are not perpendicular to the perforated surface portion  16 , but extend at an oblique angle. The reason for this is that the cabinet element  12  is formed by injection moulding in a two part mould, and that the direction of the stubs  17 ,  18  is defined by the direction in which the parts of the mould move with respect to each other when disengaging and releasing the cabinet element  12 . Accordingly, the rear side  5  of frame  1  is not perpendicular to the stubs  17 ,  18  and to the engaging direction of the screws  25 , either. Due to the tapered shape of the holes  11 , it is not difficult to insert the screws  25 , although the diameter of the narrow ends of the holes need not be much larger than that of the screw shaft. Due to the tilted orientation of the screw  25 , not all of the rear side of the screw head can come into contact with the frame  1 . If the rear side  5  of the mounting frame  1  were flat, only a point at the circumference of the screw head would be able to touch the frame  1 , and the screw  25  would be subject to a torque tending to rotate it clockwise in  FIG. 4 . By providing the bosses  6 , the point of contact between the screw head and the frame  1  is moved close to the shaft of the screw  25 , so that the torque acting on the screw  25  is reduced. Accordingly, a shorter thread of the screw  25  is sufficient for a solid fixation. In consequence, the screws  25  and the stubs  17 ,  18  may be made short, and space inside the cabinet may be saved. 
   Space is also saved by the fact that the holes  11  are formed at the bottom of recesses  9 . The depth of these recesses  9  is equal to the length of the stubs  17  and of the base portions  33 , so that these may be accommodated within the recesses  9 , and the support ring of the loudspeaker is held in direct contact with the perforated surface portion  16 . 
     FIG. 5  is a perspective view of the cabinet element  12  of  FIG. 3 , with a loudspeaker  30  according to a second embodiment of the invention mounted to it. In this embodiment, the mounting frame and the support ring supporting the loudspeaker membrane are the same thing and will be referred to as mounting frame  31 . 
   The mounting frame  31  is fixed to the cabinet element  12  in the same way as mounting frame  1  of  FIGS. 1 ,  2 . Two of its holes  11  are brought into engagement with tip portions  32  of stubs  18  that extend beyond the resting shoulders  21 . When the base surfaces  10  surrounding these two holes come into contact with the resting shoulders  21  of the stubs  18 , the other base surfaces come into contact with the end faces  19  of stubs  17 . In this position, the screws  25  are inserted through the remaining holes  11  and brought into engagement with the bores  20  of stubs  17 . When the screw heads come into contact with bosses  6 , the loudspeaker is solidly held.