Patent Publication Number: US-7899202-B2

Title: Loudspeaker with cone-coupled damper

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to acoustical transducers and manufacturing methods thereof. More particularly, the present invention relates to damper and bobbin assemblies of loudspeakers. 
     2. Related Art 
     A loudspeaker is essentially a transducer for converting electrical energy to acoustic energy, and is universally known and utilized in audio systems. There are a wide variety of designs employing various operational principles, and can be generally categorized as electrodynamic, electrostatic, piezoelectric, or discharge speakers, among others. The most common type of loudspeaker is of the electrodynamic variety, in which an electrical signal representative of the desired audio is applied to a voice coil suspended between opposite poles of a magnet and attached to a semi-rigid cone. The voice coil interacts with the magnet by the generated electromagnetic force, and causes the coil and the semi-rigid cone to vibrate and reproduce the frequencies present in the electrical signal. 
     Conventional loudspeaker designs typically include a T-yoke, which defines an annular slot or air gap for receiving a bobbin having a voice coil. As will be readily recognized, the bobbin is a hollow cylindrical member configured to enable a sliding relation with the T-yoke, particularly within the annular slot. The T-yoke is typically cylindrical in shape and holds a magnet that is positioned in alignment with the voice coil on the bobbin. Placed above the magnet is a top plate, which connects the yoke and the magnet to a basket. The basket serves as an attachment and securing point for the surround, which is an annular flexible member that holds a cone-shaped diaphragm having a central opening. The bobbin is attached to the central opening of the diaphragm, and the opening of the bobbin is covered by a dust cap to reinforce the structural integrity of the diaphragm. Lateral and axial stability of the bobbin, and thus the diaphragm, is enhanced by a damper. The damper is typically a ring-shaped member having an interior edge glued to the bobbin and an exterior edge glued to the basket. In this regard, the damper resiliently supports the diaphragm and bobbin at the respective predetermined static positions within the air gap without contacting the surrounding surfaces of the yoke or the magnet. 
     One inherent deficiency in prior loudspeaker designs was that the power output of the loudspeaker was directly related to the number of turns in the voice coil, and consequently, the size of the voice coil was related to the size of the loudspeaker. Few alterations attempting to overcome these proportion-related deficiencies have been contemplated. In order to accommodate a greater number of turns, it was necessary for the height of the bobbin to be increased for a given width of the magnet and the yoke cooperating therewith. However, by increasing the height of the bobbin, the vertical position of the voice coil which is electromagnetically driven is deviated from the vertical position of the interior edge of the damper. This destabilized the bobbin and the diaphragm, resulting in what is referred to in the art as “rolling,” thereby causing the voice coil to rub against the magnet or the yoke and resulting in distorted audio and damage to the voice coil. Therefore, under conventional loudspeaker designs, there was a ceiling of which no greater power output was possible without increases in size. Therefore, an alternative loudspeaker overcoming the aforementioned deficiencies would be desirable. 
     BRIEF SUMMARY 
     In accordance with the present invention, there is provided a loudspeaker which may include a circular damper which may define a first diameter. The damper may have a centrally disposed cone attachment protuberance and a peripherally disposed top plate attachment surface. Additionally, the loudspeaker may include a cone which may have a central inner portion and an outer portion. The central inner portion may be attached to the cone attachment protuberance of the damper. The loudspeaker may also include a cylindrical bobbin which has a second diameter, and attached to the cone. There may be a voice coil coupled to the cylindrical bobbin. 
     The second diameter of the bobbin may be greater than the first diameter of the damper. Effectively, the damper may be enclosed within the bobbin. The cone may be semi spherical and may define an interior convex surface and a corresponding exterior concave surface. In another embodiment, the cone attachment protuberance may include a concave surface corresponding to the shape of the cone, so that it may accommodate the interior convex surface thereof. As incident to the damper being enclosed within the bobbin, the bobbin may be attached to the outer portion of the cone. 
     The loudspeaker of the present invention may also include a yoke. The yoke may include a side wall member defined by an inner vertical surface and an outer vertical surface. The yoke may also include an annular base that defines a bottom base surface, a top base surface, and a first circular opening extending from the bottom base surface to the top base surface. The first opening may be centered on the annular base. 
     The loudspeaker may also include a basket that is coupled to the aforementioned yoke, as well as a surround that is attached to the basket and to the outer portion of the cone. There may also be an annular magnet disposed within the yoke. The annular magnet and the inner vertical surface of the yoke may define a section of an air gap. Additionally, a top plate may be disposed within the yoke. The yoke may define a damper attachment surface, an outer periphery, and a central opening. In one embodiment, the top plate may be attached to the annular magnet. The outer periphery of the top plate and the inner vertical surface of the yoke may define another section of the air gap, within which the voice coil may be positioned. Referring back to the damper, it may be attached to the damper attachment surface of the top plate. 
     The damper for an acoustic transducer may include a circular damper main body which defines a cone attachment protuberance. The circular damper main body may also define a peripheral corrugated section that has an inner portion which is contiguous with the cone attachment protuberance. Further, the circular damper main body may include an outer section that includes a top plate attachment surface. In another embodiment, the cone attachment protuberance may define a concave top surface. The circular damper main body may be defined by a top face and a bottom face, with the cone attachment protuberance projecting from the top face. On the other hand, the top plate attachment surface may be defined by the bottom face. 
     Further in accordance with the present invention, there is provided a method of constructing an acoustic transducer. One step may be constructing an upper assembly, including a bobbin having a voice coil, a cone, and a flexible annular surround. Another step may be constructing a transducer based including a magnet affixed to a yoke, and a top plate affixed to the magnet. This step may result in the magnet and the top plate being enclosed by the yoke and define an air gap therebetween. Next, the method may include attaching a basket to the transducer base, and affixing the upper transducer assembly to the basket such that the bobbin of the upper transducer assembly may be disposed within the air gap. The method may also include the step of removing the basket and the upper transducer assembly from the transducer base. The method may then be followed by the step of removing the basket and the upper transducer assembly from the transducer base. The method may further include the step of affixing a damper, which may have a main body defined by a central cone attachment protuberance and a peripheral corrugated section, to the top plate. The method of constructing the acoustic transducer may be concluded by affixing the basket and the upper transducer assembly to the transducer base. More particularly, the cone on the upper transducer assembly may be affixed to the central cone attachment protuberance on the damper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a perspective view of a loudspeaker constructed in accordance with the present invention; 
         FIG. 2  is a cross-sectional view of the loudspeaker shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a damper which may be incorporated in a loudspeaker constructed in accordance with the present invention; 
         FIG. 4  is a flowchart illustrating the steps necessary to assemble a loudspeaker in accordance with the present invention; 
         FIG. 5  is a perspective view of an upper assembly of the loudspeaker of the present invention with its constituent parts separated, including a bobbin, a voice coil, a cone, and a surround; 
         FIG. 6  is a perspective view of a completed upper assembly as shown in  FIG. 5 ; and 
         FIG. 7  is a perspective view of a base of the loudspeaker of the present invention with its constituent parts separated, including a yoke, a magnet, and a top plate. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the functions and the sequence of steps for developing and operating the invention in connection with the illustrated embodiment. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. It is further understood that the use of relational terms such as first and second, top and bottom, and the like are used solely to distinguish one from another entity without necessarily requiring or implying any actual such relationship or order between such entities. 
     Referring now to  FIG. 1 , a loudspeaker  10  constructed in accordance the present invention is illustrated. Loudspeaker  10  includes a basket  12 , which is attached to a yoke  14 . The yoke  14  is cylindrical, as is the portion of the basket  12  which attaches thereto. A flexible surround  18  is attached to the basket  12 , which supports a cone  16 . 
     In order to illustrate further details of the loudspeaker  10 , reference may now be had to  FIG. 2 , which is a cross-sectional view of the loudspeaker  10  taken along axis A-A of  FIG. 1 . The yoke  14 , as described above, is cylindrical in shape, and is defined by a cylinder wall portion  20  and an annular base portion  22 . While being described in terms of these portions, a person having ordinary skill in the art will recognize that the cylinder wall portion  20  and the annular base portion  22  are typically of unitary construction. The cylinder wall portion  20  is defined by an outer wall surface  24 , an opposed inner wall surface  26 , and a top rim  27 . The top rim  27  is perpendicular to the outer wall surface  24  and the inner wall surface  26 . Further, the annular base portion  22  includes an outer base surface  28  and an inner base surface  30 . The inner base surface  30  is typically perpendicular to the inner wall surface  26 , as is the outer base surface  28  to the outer wall surface  24 . Centrally disposed on the base  22  is a cylindrical port  32  that extends from the inner base surface  30  to the outer base surface  28 . Projecting from the periphery of the port  32  is a notch  33 . 
     Disposed within the interior of the yoke  14  is an annular magnet  34 , which is defined by a top surface  36 , an opposed bottom surface  38 , an outer periphery  40  and an inner periphery  42 . The annular magnet  34  is attached to the yoke  14 , where the bottom surface  38  of the annular magnet  34  abuts the inner base surface  30  of the yoke  14 . The inner periphery  42  of the annular magnet  34  defines a cylindrical opening therein, and frictionally engages the notch  33  of the yoke  14 . In this manner, the annular magnet  34  is centrally attached to the yoke  14  such that the center axis of both the annular magnet  34  and the yoke  14  remain aligned. In addition, the outer periphery  40  of the annular magnet  34  and the inner wall surface  25  of the yoke  14  defines a section of an air gap  44 . 
     Also disposed within the interior of the yoke  14  is a top plate  46 , which is attached to the annular magnet  34 . In this regard, the bottom surface  48  of the top plate  46  is in an abutting relationship with the top surface  36  of the annular magnet  34 . The top plate  46  is defined by a top plate outer periphery  50 , which is a cylindrical wall generally conforming to the shape of the inner wall surface  26  of the yoke  14 . As illustrated in  FIG. 2 , the inner wall surface  26  of the yoke  14  and the top plate outer periphery  50  defines a section of the air gap  44 . With respect to that section of the air gap  44  defined in part by the top plate outer periphery  50 , it will be understood that the size thereof is typically smaller than that section of the air gap  44  defined in part by the annular magnet  34 . In other words, the diameter of the top plate  46  is typically larger than the diameter of the magnet  34 . However, such a configuration is presented by way of example only and not of limitation, and the diameter of the top plate  46  may be equal to the diameter of the magnet  34 , in which the top plate outer periphery  50  is coplanar with the outer periphery  40  of the magnet  34 . 
     As the top plate  46  is annular, a central opening  52  is defined by the same. Between the central opening  52  and the top plate outer periphery  50  is an inner region  54 . While being illustrated as including various angles, sections, and the like in the figure, a person of ordinary skill in the art will recognize that the configuration of the inner region  54  may be of any shape. However, it is understood that the inner region  54  will include a flat arcuate damper attachment surface  56  encircling the central opening  52 . 
     With reference now to  FIG. 3 , a damper  58  for attachment to the top plate  46  on the damper attachment surface  56  is illustrated. As understood in the art, damper  58  may also be referred to as a spider. The damper  58  includes a centrally disposed cone attachment protuberance  60 , a peripheral corrugated section  62  defining a series of concentric ridges  70  and peaks  72 , and a top plate attachment section  63 . As illustrated, the damper  58  is of a circular and a generally flat shape, and it follows that the cone attachment protuberance  60 , the peripheral corrugated section  62 , the top plate attachment section  63  are likewise circular. Specifically, the peripheral corrugated section  62  is annular, with the inner periphery of the annulus defined thereby adjacent to the outer periphery of the cone attachment protuberance  60 . Additionally, the damper  58  defines a top face  64  and a bottom face  66 . The cone attachment protuberance  60  protrudes upward from the top face  64 , and includes a concave top surface  68 , which is so configured to be adapted to the convex shape of the cone  16 . The bottom face  66  of the damper  58 , particularly that part which includes the top plate attachment section  63 , defines a top plate attachment surface  65 . Referring back to  FIG. 1 , the damper  58  is shown attached to the top plate  46 . More particularly, the top plate attachment surface  65  on the damper  58  abuts the damper attachment surface  56  of the top plate  46 . 
     The damper  58  is also directly attached to the cone  16 , which is generally defined by a central inner portion  74 , a surrounding outer portion  76 , and an arcuate rim  77 . The cone  16  also has an exterior, concave surface  78  and a corresponding interior convex surface  80 . It will be understood that the central inner portion  74  refers to that area of the cone  16 , particularly that of the interior convex surface  80  which contacts the cone attachment protuberance  60  of the damper  58 . As discussed above, interior convex surface  80  of the cone  16  facilitates its attachment to the concave top surface  68  of the damper  58 . A person of ordinary skill in the art will appreciate that while the cone  16  as illustrated in the figures is semi-spherical, a cone of any configuration may be readily substituted without departing from the scope of the present invention. It will further be understood that any variety of materials, including paper, metal, carbon fiber, and the like may be utilized for the construction of the cone  16 . 
     At or in the vicinity of the rim  77  of the cone  16 , a bobbin  82  and a surround  18  are attached thereto. More particularly, the bobbin  82  is attached to the interior convex surface  80  of the cone  16 , while the surround  18  is attached the exterior concave surface  78  of the cone  16 . It is understood that the attachment plane of the bobbin  82  to the cone  16  need not be the same as that of the surround  18 . Additionally, it will be understood that neither the bobbin  82  nor the surround  18  are required to be attached exactly at the edge of rim  77 , and any variation in the attachment of the bobbin  82  and surround  18  which enables the bobbin  82  to enclose the damper  58  is deemed to be within the scope of the invention. 
     The bobbin  82  is a hollow cylindrical member having a top end  86  and a lower end  88 . Disposed at the lower end  88  is a voice coil  90 , which is a strand of wire, wrapped around the bobbin  82  such that the coil resulting therefrom is coaxial with the bobbin  82  and the annular magnet  34 . The voice coil  90  and the bobbin  82  are sized to fit within the confines of the air gap  44  and to freely move therein without contacting the top plate  46 , the annular magnet  34 , or the yoke  14 . Typically, the bobbin  82  is constructed of paper fiber, but may be constructed of any suitably lightweight and rigid material such as aluminum. Additionally, as will be readily understood, the wire used to form the voice coil  90  is typically copper, and may be electrically connected to terminals (not shown) that may be attached to the basket  12  or other location deemed appropriate by one of ordinary skill in the art. 
     With regard to the annular surround  18 , the inner periphery  92  thereof is attached to the vicinity of the rim  77  of the cone  16 , while the outer periphery  94  thereof is attached to the basket  12 . The basket  12  has an upper rim  96 , to which the outer periphery  94  of the cone  16  is attached, and a lower rim  98 , which attaches to the top rim  27  of the yoke  14 . The annular surround  18  has appropriate compliance and stiffness, and supports the cone  16 , the bobbin  82 , and the voice coil  90  wound thereto. 
     As is well understood by those having ordinary skill in the art, and as hereinbefore described, sound is reproduced by the loudspeaker  10  by the vibration of the cone  16 . An electrical signal is applied to the voice coil  90 , inducing a magnetic field concentrated in the air gap  44 . The voice coil  90  interacts with the annular magnet  34 , thereby moving the bobbin  82  a proportional distance to the electrical signal applied. As described above and as illustrated in the figures, the bobbin  82  is attached to the cone  16 , resulting in the cone  16  being vibrated according to the movement of the bobbin  82 . As the bobbin  82  moves within the air gap  44 , it is supported by the surround  18 , serving to reduce the lateral movement, or rolling, of the bobbin  82 . Furthermore, the damper  58  likewise flexibly supports the bobbin  82 , indirectly via the cone  16 . The corrugations defining the peaks  72  and the ridges  70  on the damper  58  resiliently support the cone  16  and permit the same to vibrate. However, because of its slight rigidity, excessive vibration of high amplitude is reduced, as are the effects of rolling. By constructing the loudspeaker  10  such that the bobbin  82  encloses the top plate  46  and the damper  58 , with the damper  58  being attached to the cone  16 , lateral stability of the bobbin  82  is maximized due to the increased diameter thereof and the damper  58 . Further, the larger bobbin  82  permits greater turns in the voice coil  90 , enhancing the power output of the loudspeaker  10 . 
     Turning now to the flowchart of  FIG. 4 , the steps for constructing the loudspeaker  10  in accordance with an aspect of the present invention will now be described. As per step  1   a , now referring additionally to  FIGS. 5 and 6 , an upper assembly  120  is constructed. The upper assembly  120  includes the bobbin  82  with the voice coil  90  wound thereon, and the cone  16  attached to the surround  18 . The bobbin  82  is glued or otherwise affixed to the cone  16 . Concurrently, according to step  1   b , a base  122  is constructed as illustrated in  FIG. 7 . The base  122  includes the yoke  14 , the annular magnet  34 , and the top plate  46 . As described above, the notch  33  on the yoke  14  aids in the alignment of the annular magnet  34  within the yoke  14 . Prior to the insertion of the annular magnet  34  within the yoke  14 , glue or other adhesive is applied thereon. Thereafter, the top plate  46  is glued to the magnet  34 , resulting in the base  122 . 
     Next, according to step  2 , the basket  12  is temporarily attached to the base  122 , and according to step  3 , the upper assembly  120  is attached to the basket. More particularly, the surround  18  is glued to the basket  12 . In this way, prior to finalizing the assembly, proper fitting of the bobbin  82  and the individual components of the base  122  may be verified, ensuring that the voice coil  90  does not rub against either the annular magnet  34 , the top plate  46 , or the yoke  14 . 
     As indicated in step  4 , the combined basket  12  and upper assembly  120  is removed from the base  122 , and separated. Upon separation, as per step  5 , the damper  58  is glued to the base  122 , specifically to the top plate  46 . According to step  6 , after drying the glue applied in step  5 , the upper assembly  120  and the now attached basket  12  is glued to the base  122 . Specifically, the basket  12  is glued to the yoke  14 , and the cone  16  is glued to the damper  58 , completing the assembly of loudspeaker  10 . 
     The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.