Abstract:
The invention is a suspension element having an outer edge and an inner edge. The suspension element, such as a spider or surround, varies in shape along at least a portion of the suspension element to help relieve both the radial and tangential stress placed on the suspension element when it is stretched. The shape employed in the suspension element allows the suspension element to stretch more easily, creating a higher performance speaker of the same size by increasing the diaphragm excursion and voice coil movement.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. application Ser. No. 10/113,627 filed on Mar. 27, 2002, which claims priority to U.S. provisional patent application Ser. No. 60/279,314, filed Mar. 27, 2001, both application of which are incorporated by reference is incorporated into this application in their entirety by reference.  
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to the reduction of tangential and radial stress in a suspension element of a loudspeaker transducer. In this invention, the suspension element, such as a surround or spider, is designed to increase its ability to expand in both the radial and tangential directions.  
         [0004]     2. Related Art  
         [0005]     Sound reproduction devices such as loudspeakers are utilized in a broad range of applications in many distinct fields of technology, including both the consumer and industrial fields. Sound reproduction devices utilize a combination of mechanical and electrical components to convert electrical signals, representative of the sound, into mechanical energy that produces sound waves in an ambient sound field corresponding to the electrical signal. Thus, variations of electric energy are converted into corresponding variations of acoustic energy, i.e., sound.  
         [0006]     Traditional speakers convert the electric energy to sound with one or more drivers that produce sound waves by rapidly vibrating a flexible cone or diaphragm. A diaphragm is usually circular with a central cone-shaped and/or dome-shaped portion that is coupled to a cylindrical former having a coil wire wrapped around the cylinder. Generally, the coil or wire is wrapped around the exterior side of the cylindrical former. The combination former and coil shall be referred to as the “voice coil.” The voice coil is typically suspended by a “spider,” which is attached to the frame of the speaker. The spider holds the voice coil in position while allowing it to move freely back and forth. The exterior edge of the diaphragm is attached to the frame of the speaker via a surround. Both the spider and the surround generally act as a rim, made of flexible material that spans between the voice coil and the frame and the diaphragm and the frame, respectively.  
         [0007]     The surround and the spider act to form the suspension system that positions the voice coil and allows the voice coil to move relative to a transducer magnet(s) when electrical current is directed to the voice coil. The suspension allows the voice coil to rapidly move up and down along the longitudinal axis and vibrate the diaphragm. The suspension needs to be flexible enough to allow for the movement of the voice coil and diaphragm while at the same time keep the diaphragm from wobbling or becoming “de-centered.” 
         [0008]     Generally, suspension designs are concerned with minimizing the radial stress of the surround caused by the movement of the voice coil and diaphragm. The surround generally has a uniform half circular cross-sectional shape that extends the entire perimeter or circumference of the surround, when the surround is generally circular. Thus, the radius of the half circular cross-section of the surround remains constant along the perimeter of the surround, creating an arched or dome shaped rim about the speaker. Similarly, the spider has a uniform cross-section that extends the entire perimeter of the spider. The cross-section of the spider generally forms uniform corrugations, where the peaks and valleys, i.e., ridges and grooves, typically are of the same radius. For purposes of this application, the terms perimeter and circumference shall be synonymous and may be used interchangeably to define the perimeter of the suspension elements, regardless of their shape.  
         [0009]     When the diagram of the speaker is vibrated, the external edge of the diaphragm moves up and down along the longitudinal axis of the speaker. During both the up-stroke and down-stroke of the voice coil, the surround is extended from its resting position to accommodate the movement of the diaphragm and the spider is extended to accommodate the movement of the voice coil. Thus, as the voice coil moves up and down, the cross-sectional shapes of the surround and spider elongate. As the voice coil moves up and down, both radial and tangential stress is placed upon the suspension elements, i.e., the spider and the surround. The radial stress is caused by the extending of the suspension elements in a direction parallel to the outer and inner edges of the suspension elements. The tangential stress, also referred to as “hoop stress”, is the stress placed on the suspension elements in a direction perpendicular to the outer and inner edges of the suspension elements. It is the tangential and radial stress on the suspension elements that limits the excursion and stiffness of the diaphragm and movement of the voice coil.  
         [0010]     The extent to which the suspension elements limit the amount of excursion of the diaphragm and the movement of the voice coil is dependent upon the size of the suspension elements. The bigger the suspension elements, the more the suspension elements can stretch and allow the diaphragm and voice coil to move more freely. Employing bigger suspension elements, is not, however, a viable solution in a smaller speaker design since the size of the diaphragm must be significantly reduced to accommodate a larger suspension. When a small surround is utilized the excursion of the diaphragm is reduced, limiting the performance of the speakers. Thus, a trade off is made between performance and size when utilizing small speakers, such as those speakers found in laptop computers or small electronic devices. A need therefore exists to design suspension elements that increase the excursion of the diaphragm and to allow more movement of the voice coil by reducing the radial and tangential stress placed on the suspension elements. While addressing this need would help to increase the performance of small speakers, any size speaker could experience increased performance capabilities from such a design.  
       SUMMARY  
       [0011]     The invention provides designs for suspension elements that, in the case of the surround, increases the amount of excursion and linearity of the diaphragm and thereby improves the performance of the speaker. The design of the suspension elements minimizes the stress on the suspension elements by incorporating various geometric designs into the suspension elements that allow the suspension elements to stretch more easily. The design is incorporated in to the suspension elements without modifying the perimeter size of the elements, allowing for greater excursion of the diaphragm and movement of the voice coil in the same size speaker. In addition to improving the excursion, a significant reduction in the stiffness of the suspension elements is also achieved. This allows for greater bass reproduction in the same size speaker. Further, the modifications to the stiffness also allow for a greater range of operation with constant stiffness, which assists in reducing distortion by allowing the force vs. deflection characteristics to be tailored.  
         [0012]     Any geometric design that increases the suspension element&#39;s ability to stretch without altering the length of its perimeter or without changing its circumference may be utilized. For example, peaks may be incorporated into the suspension element at various points along the suspension element. At the points where the peaks are not incorporated, the suspension element could maintain its generally half-circular or uniformly corrugated cross-sectional shape, as the case may be. Alternatively, on certain areas of the surround, the design of the peaks could be modified to create more of a parabolic cross-section, rather than a half-circular cross-section. The parabolic cross-section may also vary in shape along the surround. By varying the slope of the parabolic cross-section or shifting the parabolic shape from side to side, the surround, when viewed from the top, may have an appearance of sinusoidal wave face, among other things. Similarly, the ridges and grooves of the spider could take on a parabolic shape, or other varying shape along portions of the spider.  
         [0013]     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0014]     The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0015]      FIG. 1  is a cut away perspective view illustrating the general construction of a speaker system.  
         [0016]      FIG. 2  is a top view of a speaker system having a surround with peaks along the circumference of the surround.  
         [0017]      FIG. 3  is a cross-sectional view of the surround in  FIG. 2  taken along the line A-A′.  
         [0018]      FIG. 4  is a cross-sectional view of the surround in  FIG. 2  taken along the line B-B′.  
         [0019]      FIG. 5  is a cross-sectional view of the surround in  FIG. 2  taken along the line C-C′.  
         [0020]      FIG. 6  is a perspective view of a speaker system having a surround varying in shape along the circumference of the surround.  
         [0021]      FIG. 7  is a top view of the surround in  FIG. 6 .  
         [0022]      FIG. 8  is a perspective cross-sectional view of the surround in  FIG. 6  taken along the line D-D′.  
         [0023]      FIG. 9  is a perspective cross-sectional view of the surround in  FIG. 6  taken along the line E-E′.  
         [0024]      FIG. 10  is a cross-sectional view of the surround in  FIG. 6 , taken along the line F-F′.  
         [0025]      FIG. 11  is a side view of the surround in  FIG. 6 .  
         [0026]      FIG. 12  is a top view of a spider having a parabolic shape along the ridges and grooves of the spider.  
         [0027]      FIG. 13  is a cross-sectional view of the spider in  FIG. 12  taken along line F-F′.  
         [0028]      FIG. 14  is a cross-sectional view of the spider in  FIG. 12  taken along line G-G′.  
         [0029]      FIG. 15  is a perspective cross-sectional view of a segment of the spider in  FIG. 12  taken between line G-G′ and line F-F′.  
         [0030]      FIG. 16  is a top view of a spider having ridges and grooves that are both generally concave and convex in cross-sectional shape at various points along the spider.  
         [0031]      FIG. 17  is a cross-sectional view of the spider in  FIG. 16  taken along line H-H′.  
         [0032]      FIG. 18  is a cross-sectional view of the spider in  FIG. 16  taken along line I-I′.  
         [0033]      FIG. 19  is a cross-sectional view of the spider in  FIG. 16  take along line J-J′.  
         [0034]      FIG. 20  is a perspective cross-sectional view of a segment of the spider in  FIG. 16  taken between line H-H′ and line J-J′.  
     
    
     DETAILED DESCRIPTION  
       [0035]      FIG. 1  is a cut away perspective view of a speaker  20 , which illustrates the general construction of a traditional speaker  20 . A speaker  20  generally includes, among other things, a frame  22 , a diaphragm  24 , a voice coil  26 , a magnet  28 , a spider  30  and a surround  32 .  
         [0036]     The voice coil  26  is attached to the underside of the diaphragm  24 . The voice coil  26  and diaphragm  24  are attached to the frame  22  via a suspension system, which generally comprises two suspension elements, the spider  30  and the surround  32 . The spider  30  is attached to both the frame  22  and the voice coil  26 . The spider  30  is attached to the voice coil  26  in manner that holds the voice coil  28  in position, yet allows the voice coil  26  to freely move up and down. Similarly, the diaphragm  24  is attached to the frame  22  via a surround  32 . Alternatively, the surround  32  may be attached to a cylinder (not shown) that is in turn attached to the diaphragm  24 . In this regard, U.S. patent application Ser. No. 09/346,954, filed Jul. 1, 1999, titled Miniature Full Range Loudspeaker is incorporated by reference. In either instance, the surround  32  is made of a flexible material, generally circular in shape that allows the diaphragm  24  to freely move up and down.  
         [0037]     The diaphragm  24  and the voice coil  26  move when electric current is run through the voice coil  26 . When the electric current is run through the voice coil  26 , a magnetic field is created around the coil  26 . The polarity of the magnetic field is continuously reversed, causing the voice coil  26  to alternatively move toward and away from the permanent magnet  28  in the speaker  20 . The movement of the voice coil  26  vibrates the diaphragm  24 , creating sound. For this reason, both the spider  30  and the surround  32  must be made of flexible material that allows for the movement of the voice coil  26  and vibration of the diaphragm  24 .  
         [0038]     As, the voice coil  26  moves and the diaphragm  24  is vibrated, the voice coil  26  and the diaphragm  24  move up and down, causing the suspension elements  30  and  32  to expand from their resting position, which is the position of the suspension elements  30  and  32  when the diaphragm  24  and voice coil  26  are not moving. The expansion of the suspension elements  30  and  32  causes the cross-section of the elements  30  and  32 , taken across the inner edges  36  and  37  and outer edges  34  and  35  of the elements  30  and  32 , to elongate. This causes both tangential stress and radial stress on the suspension elements  30  and  32 . Again, radial stress is caused by the extending of the suspension elements  30  and  32  in a direction parallel to the outer edges  34  and  35  and inner edge  36  and  37  of the suspension elements  30  and  32 , as shown by reference number  38  in  FIG. 2 . The tangential stress is the stress placed on the suspension elements  30  and  32  in a direction perpendicular to the outer edges  34  and  35  and inner edge  36  and  37  of the suspension elements  30  and  32 , as shown by reference number  40  in  FIG. 2 . This stress can be minimized by employing different geometric design in the suspension elements  30  and  32  as shown in  FIGS. 2-17 .  
         [0039]     The surround  32  shown in  FIGS. 2-5  is one example of a geometric design that may be employed in either suspension element  30  or  32  to minimize the stress on the suspension element  30  and  32 . As can be seen in  FIG. 2 , the surround  32  is designed to include peaks  42 , or raised areas, about the perimeter of the surround  32 . Although  FIG. 2  shows a plurality of peaks  42  placed at predetermined distances about the surround  32 , any number of peaks  42  may be utilized. Those areas that do not include peaks  42  may follow the traditional design of a half-circle cross-section having a uniform radius  44 , which is illustrated by  FIG. 3 .  FIG. 3  is a cross-section taken along the portion of the surround  32  absent any peaks  42 .  
         [0040]      FIG. 4  is a cross-sectional view of the surround  32  taken along a peak  42 . This cross-section illustrates that in the areas of the surround  32  that include the peaks  42 , the surround  32  extends higher than the traditional design of a half-circle cross-section  44 , which is illustrated by  FIG. 3  and represented in  FIG. 4  by dashed lines. Thus, the radius of the cross-section along a peak  42  is not uniform. In fact, the radius increases toward the center of the cross-section, between the inner and outer edges  36  and  34 . This creates a peak  42 , which gives that portion of the surround  32  a higher amplitude if the cross-sections were viewed as waves, Rather than taking the form of a half circle, the cross-section of the peaks  42  may be generally formed as a parabola, having slopes on each side of the parabola that generally mirror one another. Other shapes that may also be employed in a suspension element  30  or  32  include, among other things, ellipses, other polynomials, a combination of straight lines and any polynomial shape, shapes with opposing varying slopes, i.e. unsymmetrical shapes, and shapes having cross-sections such that the sides of the rim between the inner edge  36  and  37  and outer edge  34  and  35  appear convex or concave. These shapes and other geometric shapes that assist in reducing the stress in the suspension elements  30  and  32  may be employed alone or in conjunction with one another. For purposes of this application, a “dome” can be taken to mean any of the above shapes, or any other geometric configuration that could be used to minimize the stress on a suspension element.  
         [0041]     As seen in  FIG. 5 , which is a cross-sectional view taken along the center circumference of the surround  32 , which is centered between the inner edge  36  and outer edge  34  of the surround  32 , the peak  42  design is graduated in that the height of the peak  42  gradually increases until it reaches the desired height, and then begins to taper back downward, eventually blending into the traditional half-circular cross-sectional portions  44  of the surround  32 . Thus, when taking cross-sections of the peaks  38 , the height of the parabolic cross-sections will vary.  
         [0042]     Another implementation of a geometric design that could be used in a suspension element  30  or  32  of a speaker  20  is illustrated in  FIG. 6  in connection with a surround  32 . In this implementation, the height of the surround  32  does not vary, although it could be designed to do so. Rather, the highest point  46  of each cross-section is varied from center, moving toward the inner edge  36 , crossing center, and then back toward the outer edge  34 , creating a wave effect about the center circumference of the surround. When viewed from the top, as illustrated by  FIG. 7 , this movement of the highest point along the surround appears as a sinusoidal wave face  48 , relative to the center circumference of the surround  32 .  
         [0043]      FIG. 8  is a perspective cross-sectional view of the surround, which is taken when the highest point  46  of the dome, or parabola  50 , is closer to the outer edge  34 , such that the slope of the dome  50  on the side of the outer edge  34  is greater than the slope of the dome  50  on the side of the inner edge  36 . On the other hand, the highest point  46  of the dome  50  in  FIG. 9  is closer to the inner edge  36 , such that the slope of the dome  50  on the side of the outer edge  34  is less than the slope of the dome on the side of the inner edge  36 .  FIG. 10  shows the highest point  46  of the dome  50  as it crosses center, creating the traditional half-circular shaped cross-section  44 .  
         [0044]      FIG. 11  is a side view of the surround  32  showing that the height of the dome  50  is uniform along the circumference of the surround, unlike the surround in  FIGS. 1-5 . Alternatively, variable or constant peaks, or variable arced sections, may also be implemented, alone or in conjunction with other geometric configurations, extending all the way around the perimeter of the surround or only across portions of the surround.  
         [0045]      FIG. 12  is a top view of a spider  30  employing the same geometric configurations of the surround  32  of  FIG. 6 . Like the implementation of this configuration in the surround  32 , the height of the grooves  52  and ridges  54  of the spider  30  does not vary, although they could be designed to do so. Rather, the highest point  56  of the ridges  54  and the lowest point  58  of the grooves  52  are varied from center, moving toward the inner edge  37  of the spider  30 , crossing the center of the ridge or groove, and then back toward the outer edge  35  of the spider, creating a wave effect about the center circumference of each groove  52  and ridge  54 . When viewed from the top, as illustrated by  FIG. 12 , this movement along the circumference of the spider  30  appears as a sinusoidal wave, along each ridge  54  of the spider  30 , the same wave shape would appear on the underside of the spider  30  along each groove  52 .  
         [0046]      FIG. 13  is a perspective cross-sectional view of the suspension system, which is taken when the highest point  56  of the ridge  54  is closer to the outer edge  35  and the lowest point  58  of the groove  52  is closer to the inner edge  37 . In contrast, the highest point  56  of the ridge  54  in  FIG. 14  is closer to the inner edge  37  and the lowest point  58  of the groove  52  is closer to the outer edge.  FIG. 15  is a perspective view of a segment of the spider  30 , which illustrates that the shifting of the highest points  56  of the ridge  54  and lowest points  58  of the groove  52  creates a wave about the circumference of each ridge  54  and groove  52  of the spider  30 .  
         [0047]     Yet another implementation of a geometric design that could be used in a suspension element  30  or  32  of a speaker  20  is illustrated in  FIG. 16  in connection with a spider  30 . As best illustrated by  FIGS. 17-19 , both the ridges  54  and the grooves  52  vary in cross-section from a parabola  62 , as illustrated by  FIG. 17 , to a configuration having a generally flat top  64  and sides at only slight angles  66 , as illustrated in  FIG. 18 , to a configuration having convex sides  68 , as illustrated by  FIG. 19 . Along the circumference of the grooves  56  and ridges  54  of the spider  30 , these configurations blend into one another, as illustrated by  FIG. 20 .  
         [0048]     In operation, the implementation of the different geometric design decreases the stress on the suspension elements  30  and/or  32 . For example, when the surround  32  employs peaks  42 , as the diaphragm  24  moves upward expanding the surround  32 , the peaks  42  will flatten, giving the surround  32  greater ability to expand in both the tangential  40  and radial direction  38 . When the surround  32  employs the sinusoidal wave face  48  design, the sinusoidal wave face  48 , as the surround  32  expands, will become more linear or simply circular without the sinusoidal curve relative to the center circumference of the surround. This gives the surround  24  greater ability to expand in the radial direction  38 . Similarly, the expansion of the spider  30  would have the same effect. The same designs employed in the surround  32  may be employed in the spider  30 . Variation of these designs discussed above may also be employed either suspension element  30  or  32 . Varying peaks  42  may be included in the sinusoidal wave face implementation  48 , such that the height of the dome  50  or ridge  54 , as the case may be, would no longer be uniform. Additionally, waves may be implemented in segments in either the spider  30  or the surround  32  similar to the implementation of the peaks  42  in the surround  32  as shown in  FIG. 2 , and may either vary in height or be uniform. Any other geometric design that functions to relieve radial and/or tangential stress when the surround  32  or spider  30  is expands, can also be employed.  
         [0049]     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.