Loudspeaker with closed membrane and relative assembly method

Abstract

An assembly method of a loudspeaker with closed membrane provides for preassembling a mobile unit having two centering devices fixed to a voice coil; pre-assembling a fixed unit that has a basket fixed to a magnetic unit, assembling the mobile unit in the fixed unit, by a centering device; extracting the centering device and fixing a closed membrane to the voice coil and to the basket.

Claims

1. A method of assembling a closed membrane loudspeaker, the method comprising: preassembling a mobile unit having a voice coil with a cylindrical support upon which at least one winding is wound, the step of preassembling comprising fixing a first centering device and a second centering device directly to the cylindrical support; preassembling a fixed unit having a basket and a magnetic unit, the magnetic unit having a lower polar plate with a core in which an annular magnet is disposed around the core and an annular upper polar plate disposed on the annular magnet and around the core so as to form an air gap; inserting a cylindrical temporary centering device into the cylindrical support so as to fit onto the core of the lower polar plate such that the voice coil is centered in the air gap between the core and the annular magnet and the annular upper polar plate; gluing the mobile unit to the basket of the fixed unit, the step of gluing comprising gluing the first centering device and the second centering device to the basket such that the first and second centering devices are disposed along parallel plans such that the voice coil is centered in the air gap and minimizes a first distance between an external surface of the core and an internal surface of the cylindrical support and a second distance between an external surface of the winding of the voice coil and an internal surface of the upper polar plate; extracting the cylindrical temporary centering device from the voice coil; gluing an edge of a closed membrane to the basket; and gluing a central portion of the closed membrane directly to the cylindrical support of the voice coil.

2. The method of claim 1, wherein each of the first and second centering devices has an internal ring, an external ring and a plurality of elastic elements that connect the external ring to the internal ring, the step of preassembling the mobile unit comprising: fixing the internal ring of the each of the first and second centering devices to the cylindrical support, the step of gluing the mobile unit to the basket comprising: gluing the external ring of each of the first and second centering devices to the first annular shoulder and to a second annular shoulder of the basket, wherein the first and second annular shoulder of the basket are disposed along parallel planes at different levels.

3. The method of claim 2, the step of gluing the edge of the closed membrane to the basket comprising: gluing the edge of the closed membrane to a third annular shoulder of the basket, wherein the first annular shoulder and the second annular shoulder and the third annular shoulder of the basket are disposed along parallel plans at the different levels.

4. A loudspeaker comprising: a magnetic unit having an upper polar plate with a core, the core having an annular magnet disposed therearound, the annular magnet having the annular upper polar plate disposed thereon, the annular upper polar plate being positioned around the core, wherein an air gap is formed between the core and the annular magnet and the annular upper polar plate; a basket fixed to said magnetic unit; a voice coil having a cylindrical support whereon at least one winding is wound, the cylindrical support having an axial through hole; a first centering device directly fixed to the cylindrical support of said voice coil and to the basket so that said voice coil is centered on the air gap; a single closed membrane formed as a single piece, the single closed membrane being centrally fixed directly to the cylindrical support of said voice coil and peripherally fixed to an edge of said basket such that the single closed membrane covers the axial through hole of the cylindrical support; and a second centering device directly fixed to the cylindrical support of said voice coil and to said basket such that said first centering device and said second centering device are disposed along parallel planes so as to minimize a first distance between an external surface of the core and an internal surface of the cylindrical support of said voice coil and a second distance between an external surface of the winding of said voice coil and an internal surface of the upper polar plate.

5. The loudspeaker of claim 4, wherein each of said first centering device and said second centering device has an internal ring, an external ring and a plurality of elastic elements that connect the external ring to the internal ring, wherein the internal ring is fixed to the cylindrical support, wherein the external ring is fixed to the first annular shoulder and to the second annular shoulder of said basket, the first and second annular shoulder of said basket being disposed along parallel planes at different levels.

6. The loudspeaker of claim 5, wherein said basket comprises a third annular shoulder, wherein the first annular shoulder and the second annular shoulder and the third annular shoulder are disposed along parallel planes at different levels.

7. The loudspeaker of claim 4, said voice coil having a travel less than 3 millimeters, the first distance being less than 0.2 millimeters, the second distance being less than 0.3 millimeters.

8. The loudspeaker of claim 4, said voice coil having a travel of between 3 and 8 millimeters, said first distance being less than 0.25 millimeters, the second distance being less than 0.5 millimeters.

9. The loudspeaker of claim 4, said voice coil having a travel of between 8 and 20 millimeters, said first distance being less than 0.35 millimeters, said second distance being less than 0.6 millimeters.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Additional features of the invention will appear manifest from the detailed description below, which refers to merely a illustrative, not limiting embodiment, as illustrated in the attached figures, wherein:

(2) FIGS. 1-5 are diagrammatic axial views showing an assembly method of a loudspeaker with open membrane according to the prior art;

(3) FIG. 6 is a diagrammatic axial view of a loudspeaker with open membrane, in assembled condition, according to the prior art;

(4) FIG. 6A is an enlarged view of a detail of the loudspeaker of FIG. 6;

(5) FIGS. 7-11 are diagrammatic axial views showing an assembly method of a loudspeaker with closed membrane, according to the prior art;

(6) FIG. 12 is a diagrammatic axial view of a loudspeaker with closed membrane, in assembled condition, according to the prior art;

(7) FIG. 12A is an enlarged view of a detail of the loudspeaker of FIG. 12;

(8) FIGS. 13-17 are diagrammatic axial views showing an assembly method of a loudspeaker with closed membrane, according to the invention;

(9) FIG. 18 is a diagrammatic axial view of a loudspeaker with closed membrane, in assembled condition, according to the invention;

(10) FIG. 18A is an enlarged view of a detail of the loudspeaker of FIG. 18.

DETAILED DESCRIPTION OF THE INVENTION

(11) With reference to FIG. 13, according to the invention, the mobile unit (A) comprises a first centering device (3) and a second centering device (3) that are directly fixed to the cylindrical support (20) of the voice coil (2). Such a mobile unit (A) is pre-assembled.

(12) For illustrative purposes, each centering device (3, 3) comprises an internal ring (30), an external ring (31) and a plurality of elastic elements (32) that connect the external ring to the internal ring

(13) With reference to FIG. 14, the internal ring (30) of each centering device (3, 3) is fixed to the cylindrical support (2) with glue, in such a way that the centering devices (3, 3) are arranged according to two spaced-out horizontal planes.

(14) The external ring of the first centering device (3) has a higher diameter than the external ring of the second centering device (3).

(15) The fixed unit (B) is pre-assembled. Said fixed unit (B) is substantially similar to a traditional fixed unit. The only difference is represented by the fact that the basket (5) comprises three annular shoulders (51, 52, 53) disposed at three different height levels; a first annular shoulder (51) to receive the external ring of the first centering device (3), a second annular shoulder (52) to receive the external ring of the second centering device (3), a third annular shoulder (53) to receive the edge (11) of the membrane.

(16) The three annular shoulders (51, 52, 53) are disposed on parallel horizontal planes. The third shoulder (53) is the highest and has the largest diameter. The second shoulder (52) is the lowest and has the smallest diameter.

(17) With reference to FIG. 15, the centering device (6) is inserted into the cylindrical support (20) of the voice coil and fitted on the core (41) of the lower polar plate.

(18) The external rings of the first and the second centering device (3, 3) are glued with glue, respectively on the first annular shoulder (51) and on the second annular shoulder (52) of the basket. It must be noted that the voice coil (2) is connected to the basket (5) on two spaced-out gluing planes, in such a way as to ensure a perfect centering of the voice coil (2) in the air gap (T).

(19) With reference to FIG. 16, after the polymerization of the glue, the centering device (6) is removed, extracting it from the top of the cylindrical support of the voice coil (2).

(20) With reference to FIG. 17, after extracting the centering device, the membrane (100) is fixed to the fixed unit (B), by gluing the edge (11) of the membrane to the third shoulder (53) of the basket (5) and the upper edge of the cylindrical support (20) of the voice coil to a central portion of the membrane (100). Therefore, the membrane (100) is directly fixed to the cylindrical support (20) of the voice coil and is a closed membrane because it covers the axial hole of the cylindrical support (20) of the voice coil. It must be noted that the loudspeaker comprises only one membrane (100) that is made in one piece.

(21) With reference to FIGS. 18 and 18A, in such a case of loudspeaker with closed membrane (100) according to the invention, a first distance (T5) is provided between the external surface of the core (41) and the internal surface of the cylindrical support (2) of the voice coil, and a second distance (T6) is provided between the external surface of the winding (21) of the voice coil and the internal surface of the upper polar plate (43).

(22) In such a case, the distances (T5, T6) obtained with the loudspeaker with closed membrane according to the invention are considerably lower than the distances (T3, T4) obtained with loudspeakers with closed membrane according to the prior art and are similar to the distances (T1, T2) obtained with loudspeakers with open membrane.

(23) In view of the above, the loudspeaker with closed membrane according to the invention guarantees a better performance than a loudspeaker with closed membrane according to the prior art, with the same dimensions and the same cost of the magnetic unit.

(24) Table 1 shows the values of the distances (T1, T2, 5 T3, T4, T5, T6) respectively measured in a loudspeaker with open membrane, in a loudspeaker with closed membrane according to the prior art and in a loudspeaker with closed membrane according to the invention, according to the travel of the voice coil. All numerical values in the table are expressed in millimeters.

(25) The term travel indicates the axial translation of the voice coil relative to a central fixed horizontal plane, applying a sinusoidal signal to the winding of the voice coil with power equal to the rated power of the loudspeaker.

(26) TABLE-US-00001 TABLE 1 Loudspeaker Loudspeaker with closed with closed Loudspeaker membrane membrane with open according according to membrane to prior art invention Travel T1 T2 T3 T4 T5 T6 <+3 0.1-0.2 0.15-0.3 >0.2 >0.3 0.1-0.2 0.15-0.3 3-8 0.17-0.25 0.3-0.5 >0.25 >0.5 0.17-0.25 0.3-0.5 8-20 0.25-0.35 0.4-0.6 >0.35 >0.6 0.25-0.35 0.4-0.6

(27) As shown in Table 1, the distances (T5, T6) obtained with the loudspeaker with closed membrane according to the invention are considerably lower than the distances (T3, T4) obtained with loudspeakers with closed membrane according to the prior art and equal to the distances (T1, T2) obtained with loudspeakers with open membrane.

(28) The differences between the loudspeaker with closed membrane according to the invention and the loudspeaker with closed membrane according to the prior art increase when the travel of the voice coil increases.

(29) The loudspeaker according to the invention, with a travel of the voice coil lower than 3 mm, has a first distance (T5) lower than 0.2 mm and a second distance (T6) lower than 0.3 mm.

(30) The loudspeaker according to the invention, with a travel of the voice coil comprised in the range3-8 mm, has a first distance (T5) lower than 0.25 mm and a second distance (T6) lower than 0.5 mm.

(31) The loudspeaker according to the invention, with a travel of the voice coil comprised in the range8-20 mm, has a first distance (T5) lower than 0.35 mm and a second distance (T6) lower than 0.6 mm.

(32) Numerous equivalent variations and modifications can be made to the present embodiments of the invention, which are within the reach of an expert of the field and fall in any case within the scope of the invention as disclosed by the attached claims.