Abstract:
An apparatus includes a suspension element coupling a first rigid element to a second rigid element such that the first rigid element is movable in a reciprocating manner relative to the second rigid element. The suspension element includes radial features, some of which may have radial segments of opposite concavity. The segments with opposite concavity provide added stiffness in the primary axis of vibration and may contribute to a more symmetrical force-deflection relationship.

Description:
BACKGROUND 
     This disclosure relates generally to an acoustic source, and more particularly to a suspension element associated with an acoustic source. 
     SUMMARY 
     In accordance with an aspect, an apparatus comprises first and second rigid elements and a suspension element which couples the first rigid element to the second rigid element such that the first rigid element is movable in a reciprocating manner relative to the second rigid element. The suspension element comprises a concave surface, a convex surface, and at least first and second radial segments of opposite concavity, the first segment extending away from the concave surface and the second segment extending away from the convex surface. 
     In some implementations the first and second radial segments are oriented such that lines which bisect the segments lengthwise are tangential to a circle with a radius less than an inner radius of the suspension element. 
     In some implementations the apparatus further comprises a first radial feature comprising the first and second radial segments of opposite concavity. 
     In some implementations the apparatus further comprises a second radial feature which extends away from the concave surface. 
     In some implementations the first and second radial features traverse a semi-circular roll of the suspension element. 
     In some implementations the first and second radial features are presented in alternation. 
     In some implementations the second radial segment extends from an apex of the roll to an outer edge of the roll. 
     In some implementations the second radial segment is characterized by a curved cross-section with a minimum height proximate to the apex of the roll and a maximum height proximate to the outer edge of the roll. 
     In some implementations the first radial segment extends from an inner edge of the roll to the apex of the roll. 
     In some implementations the first radial segment is characterized by a curved cross-section with a maximum depth proximate to a midpoint between the apex of the roll and an inner edge of the roll. 
     In some implementations the second radial feature is characterized by a curved cross-section with a maximum depth proximate to the apex of the roll. 
     In some implementations the first and second radial features span only a portion of the distance between an inner edge and outer edge of the roll. 
     In some implementations the suspension element comprises a rolled shape. 
     In some implementations the rolled shape comprises two or more rolls. 
     In some implementations the first and second radial features are spaced regularly along the suspension element. 
     In some implementations the second radial feature has a depth that varies along a length of the second radial feature. 
     In some implementations the suspension element comprises a surround. 
     In some implementations the suspension element comprises a spider. 
     In some implementations a material thickness of the second radial segment varies along a length of the second radial segment. 
     In some implementations the thickness of the second radial segment is greatest at the portion of the second radial segment proximate to an outer edge of the roll. 
     In accordance with an aspect, an apparatus comprises a diaphragm, a frame, and a suspension element which couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame. The suspension element comprises a roll which defines a concave surface and a convex surface. The roll comprises at least one feature having inner and outer ends proximate to an inner edge of the roll and an outer edge of the roll, respectively, and first and second segments of opposite concavity, the first segment extending away from the concave surface and the second segment extending away from the convex surface. 
     In some implementations the first feature comprises the first and second segments of opposite concavity. 
     In some implementations the roll further comprises a second feature which extends away from the concave surface. 
     In some implementations the first and second features are oriented such that lines which bisect the features lengthwise are tangential to a circle with a radius less than an inner radius of the suspension element. 
     In some implementations the second segment extends from an apex of the roll to an outer edge of the roll. 
     In some implementations the second segment is characterized by a curved cross-section with a minimum height proximate to the apex of the roll and a maximum height proximate to the outer edge of the roll. 
     In some implementations the first segment is characterized by a curved cross-section with a maximum depth proximate to a midpoint between the apex of the roll and an inner edge of the roll, and minimum depths proximate to the apex of the roll and the inner edge of the roll. 
     In some implementations the second feature is characterized by a curved cross-section with a maximum depth proximate to the apex of the roll, and minimum depths proximate to the inner edge of the roll and the outer edge of the roll. 
     In some implementations the first and second features are presented in alternation. 
     In accordance with an aspect, a loudspeaker suspension comprises a loudspeaker suspension structure having an inner circumferential border and an outer circumferential border, and a first feature extending from the inner circumferential border to the outer circumferential border, wherein the first feature comprises a first segment having a first concavity and a second segment having a second concavity, the second concavity being an inverse of the first concavity. 
     In some implementations the loudspeaker suspension further comprises a second feature extending from the inner circumferential border to the outer circumferential border and having the first concavity. 
     In some implementations, the first and second features are oriented such that lines which bisect the features lengthwise are tangential to a circle with a radius less than an inner radius of the suspension structure. 
     In some implementations the first and second features are presented in alternation. 
     In some implementations the suspension structure comprises a roll. 
     In some implementations the first feature transitions from the first concavity to the second concavity proximate to an apex of the roll. 
     In some implementations the first and second features span only a portion of the distance between the inner circumferential border and the outer circumferential border. 
     In accordance with another aspect an apparatus comprises: means for coupling a first rigid element to a second rigid element such that the first rigid element is movable in a reciprocating manner relative to the second rigid element, the coupling means comprising first and second radially oriented features of opposite concavity. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       For purposes of illustration some elements are omitted and some dimensions are exaggerated. 
         FIG. 1  is a perspective view of an acoustic device with a suspension element characterized by radial features with variations of concavity. 
         FIG. 2  is a top view of the suspension element of  FIG. 1 . 
         FIG. 3  illustrates a groove feature of the suspension element of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a groove feature of the suspension element of  FIG. 2  along section A-A. 
         FIG. 5  is an expanded view of the groove feature of  FIG. 3  including a series of cross-sections. 
         FIG. 6A  illustrates a groove portion of a rib-and-groove feature of the suspension element of  FIG. 1 . 
         FIG. 6B  illustrates a rib portion of a rib-and-groove feature of the suspension element of  FIG. 1 . 
         FIG. 6C  illustrates a rib-and-groove feature of the suspension element of  FIG. 1 . 
         FIG. 7  is a cross-sectional view of a rib-and-groove feature of the suspension element of  FIG. 2  along section B-B. 
         FIG. 8  is an expanded view of the rib-and-groove feature of  FIG. 6C  including a series of cross-sections. 
         FIG. 9  illustrates an exemplary force versus displacement curve for a suspension element of similar dimensions and materials to the suspension element of  FIG. 1 , but without the rib-and-groove features. 
         FIG. 10  illustrates an exemplary force versus displacement curve for the suspension element of  FIG. 1 . 
         FIGS. 11A and 11B  illustrate a portion of a rib-and-groove feature of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an acoustic device such as a loudspeaker, driver or transducer. The acoustic device includes a diaphragm  100  (sometimes referred to as a cone, plate, cup or dome) coupled to a frame  102  via a suspension element  104  sometimes referred to as a surround. However, the features described herein could be utilized in a spider or other suspension element. The diaphragm may be circular or non-circular in shape. For example, and without limitation, the diaphragm could be an ellipse, square, rectangle, oblong, or racetrack. The frame may be coupled to an enclosure (not illustrated). The suspension element  104  allows the diaphragm  100  to move in a reciprocating manner relative to the frame  102  and enclosure in response to an excitation signal provided to a motor that outputs a force to diaphragm  100 . Movement of the diaphragm causes changes in air pressure which result in production of sound. 
     In some examples, as shown in  FIGS. 1 and 2 , the suspension element  104  is a circular half roll having an inner edge  306  and an outer edge  308 , separated by a radial width or span. The suspension element  104  can include an inner landing  310  extending radially inward from the inner edge  306  and an outer landing  312  extending radially outward from the outer edge  308  for connection to the diaphragm  100  and frame  102 , respectively. The half roll may have a convex surface  300  facing away from the interior of the enclosure, and a concave surface  302  (shown in  FIGS. 3 and 4 ) facing toward the interior of the enclosure. Although the suspension element  104  is shown as a half roll having a single convolution, the suspension element  104  could be, without limitation, a full roll, an inverted half roll (i.e., flipped over 180 degrees), or a roll having multiple convolutions, and could include variations of concavity and other features. A convolution as used herein comprises one cycle of a possibly repeating structure, where the structure typically comprises concatenated sections of arcs. The arcs are generally circular, but can have any curvature. Although the suspension element  104  is shown as circular in shape, the suspension element  104  could also be non-circular in shape. For example, without limitation, the suspension element  104  could be an ellipse, toroid, square, rectangle, oblong, racetrack, or other non-circular shapes. In places where the terms circumferential, radial, or other circle-specific terminology is mentioned, it should be understood that we also mean to encompass non-circular geometries. 
     The suspension element  104  includes rib and groove features which may enhance axial stiffness, free length, force-deflection relationships, and buckling resistance, and may reduce the overall mass of the suspension element. For example, the suspension element  104  may include one or more radial rib features, groove features, and rib-and-groove features. Examples of these features are described below. 
     Referring to  FIG. 2 , suspension element  104  includes radial groove (or trench) features  304  and radial rib-and-groove features  500 . The groove features  304  and rib-and-groove features  500  generally extend from an inner edge  306  to an outer edge  308  of the roll. In other examples, the groove features  304  and rib-and-groove features  500  need not extend over the entire span from the inner edge  306  to the outer edge  308 . 
     In some examples, the groove features  304  and rib-and-groove features  500  generally extend at an angle to the radial direction, or more generally, at an angle to the normal of the inner edge  306  of the suspension element  104 , at the point of the groove or rib-and-groove closest to the inner edge  306 . In other words, the groove features  304  may be radially oriented such that line  202  which bisects the groove features  304  lengthwise is tangential to a circle with a radius less than the inner radius (R i ) of the suspension element  104 . Similarly, the rib-and-groove features  500  may be radially oriented such that line  204  which bisects the rib-and-groove features  500  lengthwise is tangential to a circle with a radius less than the inner radius (R i ) of the suspension element  104 . 
     As shown in  FIG. 2 , each groove feature  304  and rib-and-groove feature  500  may be skewed by an angle alpha (a) relative to radius lines R 1 , R 2  which are normal to the inner edge of the suspension element  104 . For example, alpha represents the angle between line  202  and radius line R 1  in  FIG. 2 . Alpha can vary over a wide range, and need not be the same for the groove features  304  and the rib-and-groove features  500 . Where the path of the groove feature  304  or rib-and-groove feature  500  traverses a substantially straight line from inner edge to outer edge, the angle alpha is preferably between 30 and 60 degrees (or −30 to −60 degrees), although useful behavior is obtained with an angle between 10 and 80 degrees (or −10 to −80 degrees). Negative angles of alpha refer to groove features  304  or rib-and-groove feature  500  that incline in the opposite direction from the radial (or normal) to that shown in  FIG. 2 . Groove features  304  and rib-and-groove features  500  can be straight or curved. The radius of curvature along the length of the groove or rib-and-groove can be infinite (i.e. a straight line), a finite constant, or smoothly or otherwise varying. For examples with constant, smoothly or otherwise varying curvature, alpha can vary between 0 and 90 degrees. 
     Referring to  FIGS. 3 and 4 , the groove features  304  are further described. Groove features  304  extend outward from the concave surface  302  of the roll toward the interior of the enclosure. Groove features  304  may traverse the roll from approximately an inner edge  306  to an outer edge  308  of the roll. In other words, inner end  314  and outer end  316  of the groove feature  304  may be proximate to the inner landing  310  and outer landing  312  of the suspension element  104 , respectively. Alternatively, groove features  304  may traverse the roll from a point offset from the inner edge  306  to a point offset from the outer edge  308 , or onto the inner and/or outer landings  310 ,  312 . 
       FIG. 5  is an expanded view of a groove feature  304  including a series of cross-sections  400 ,  402 ,  404 ,  406 ,  408 ,  410 ,  412 . As shown in the cross-sections, the groove feature  304  may include a curved trough or a generally V-shaped notch  416  with a rounded tip  414  that extends downward from the concave surface  302  of the roll toward the interior of the enclosure. Various geometries are possible for the notch, including without limitation a square-shaped notch with rounded edges. Other geometric aspects of the notch, including the curvature and angle of the notch and the radius of the rounded tip, may be constant or may vary along the length of the groove feature  304 . The depth of the groove feature  304  relative to the roll may vary as the notch traverses from the inner edge  306  to the outer edge  308  of the roll. For example, the depth of the groove feature  304  may range from zero depth at ends  314 ,  316  to a maximum depth somewhere between the ends  314 ,  316 . In one example, the maximum depth may be located at radius R m  (as shown in  FIG. 2 ), which is the midpoint between the inner and outer edges  306 ,  308  of the roll. In other words, the groove defined by groove feature  304  may be deepest proximate to the apex of the roll. A transition radius may be provided at the boundary between the groove feature  304  and the roll, in lieu of sharp edges. It should be understood that a wide variety of variations could be implemented and symmetry need not be maintained. For example, the point where the groove is deepest may vary. Moreover, in some examples, the groove depth may remain constant over a large portion of the length of the groove. In other examples, the groove depth may have a plurality of local maxima and minima along the groove path, forming undulations in the bottom of the groove, which could help minimize the impact of “pull up” due to stiffening of the suspension element at the extremes of the excursion path. 
     Referring to  FIGS. 6 and 7 , the rib-and-groove features  500  are further described. Rib-and-groove features may include an inner segment  502  and an outer segment  504 . As shown in  FIG. 6A , the inner segment  502  may extend outward from the concave surface  302  of the suspension element toward the interior of the enclosure, thereby presenting a groove in the convex surface of the suspension element  104 . The outer segment  504  defines an inflexion of concavity relative to the inner segment  502 . In other words, if the inner segment  502  is concave when facing the interior of the enclosure, the outer segment  504  is convex when facing the interior of the enclosure. As shown in  FIG. 6B , the outer segment  504  extends outward from the convex surface  300  of the suspension element toward the exterior of the enclosure, thereby presenting a rib in the convex surface of the suspension element  104 .  FIG. 6C  shows the inner segment  502  of  FIG. 6A  (the groove portion) combined with the outer segment  504  of  FIG. 6B  (the rib portion) which together form a rib-and-groove feature  500 . Although the examples shown in  FIGS. 6A-6C  show a groove for the inner segment  502  and a rib for the outer segment  504 , other examples may include a rib for the inner segment  502  and a groove for the outer segment  504 . 
     The rib-and-groove features  500  may traverse the roll from approximately the inner edge  306  to the outer edge  308  of the roll. In other words, inner end  510  and outer end  516  of the rib-and-groove feature  500  may be proximate to the inner landing  310  and outer landing  312  of the suspension element. Alternatively, rib-and-groove features  500  may traverse the roll from a point offset from an inner edge  306  to a point offset from an outer edge  308 , or onto the inner and/or outer landings  310 ,  312 . In some examples, inner and outer ends  510 ,  512  of the inner segment  502  (the groove portion) may be proximate to the inner edge  306  of the roll and the apex of the roll (R m ), respectively, while inner and outer ends  514 ,  516  of the outer segment  504  (the rib portion) may be proximate to the apex of the roll (R m ) and the outer edge  308  of the roll, respectively. However, other locations are contemplated for inner and outer ends  510 ,  512 ,  514 ,  516 . For example, for the inner segment  502  (the groove portion), inner end  510  may be at a point offset from an inner edge  306  of the roll and outer end  512  may be at a point offset from the apex of the roll. Similarly, for the outer segment  504  (the rib portion) outer end  516  may be at a point offset from an outer edge  308  of the roll, and inner end  514  may be at a point offset from the apex of the roll. 
     In some examples, the rib-and-groove feature  500  transitions from the inner segment  502  (the groove portion) to the outer segment  504  (the rib portion) approximately at the apex (R m ) of the roll. However, this transition could occur at other locations on the roll. Moreover, in some examples, the outer end  512  of the inner segment  502  transitions directly into the inner end  514  of the outer segment  504 . In other words, the groove transitions directly into a rib, so there is no overlap of, or gap between, the ends  512 ,  514  of the inner and outer segments. In other implementations, however, there could be a gap between the ends  512 ,  514  of the inner and outer segments. 
       FIG. 8  is an expanded view of a rib-and-groove feature  500  including a series of cross-sections  600 ,  602 ,  604 ,  606 ,  608 ,  610 ,  612 . As shown in the cross-sections, the rib-and-groove feature  500  may include a curved trough or a generally V-shaped notch  616  with a rounded tip  614  that extends downward from the concave surface  302  of the roll toward the interior of the enclosure in the inner segment  502  (groove portion) and upward from the convex surface  300  of the roll away from the interior of the enclosure in the outer segment  504  (rib portion). Various geometries are possible for the notch, including without limitation a square-shaped notch with rounded edges. Other geometric aspects of the notch, including the curvature and angle of the notch and the radius of the rounded tip, may be constant or may vary along the length of the rib-and-groove feature  500 . The depth and height of the rib-and-groove feature  500  relative to the roll may vary as the notch traverses from the inner edge  306  to the outer edge  308  of the roll. For example, the maximum depth of the inner segment  502  (the groove portion) may be at the midpoint between the inner edge  306  and the apex of the roll. In other words, the groove presented by the inner segment  502  may be deepest halfway between the apex and the inner edge  306 . The maximum height of the outer segment  504  (the rib portion) may be at the outer edge  308  of the roll, and the minimum height may be at the inner end  514  (the end proximate to the apex of the roll). In other words, the rib presented by the outer segment  504  may be tallest at the outer edge  308  of the roll. A transition radius may be provided at the boundary between the rib-and-groove feature  500  and the roll, in lieu of sharp edges. It should be understood that a wide variety of variations could be implemented and symmetry need not be maintained. For example, the extent to which the inner and outer segments  502 ,  504  protrude from the concave and convex surfaces of the suspension element may vary. Further, the cross-sections of maximum and minimum height and depth between the inner segments and outer segments are not necessarily equal in magnitude, and the point where the inner segment  502  and outer segment  504  are deepest and tallest, respectively, may vary. Moreover, in some examples, the depth of the inner segment  502  and the height of the outer segment  504  may remain constant over a large portion of their length. In other examples, the inner and outer segments  502 ,  504  may have a plurality of local maxima and minima along their path. 
     The different types of radial features may be presented alone or in any combination, and in any suitable number, spacing, pattern and ratio.  FIGS. 1 and 2 , for example, illustrate a suspension element with radial groove features in alternation with radial rib-and-groove features. But a wide variety of modifications and variations of the radial features are possible. For example, a suspension element may have radial rib features in alternation with radial rib-and-groove features, or may have all three radial features (ribs, grooves and rib-and-groove features). Moreover, the radial features need not be presented in alternation, but could be presented in any proportion, e.g., rib-and-groove features  500  could be presented every third, fourth, fifth (or any suitable number) radial feature. 
     Adjacent ribs, grooves and/or rib-and-groove features are separated by a pitch distance, which can be defined as a circumferential distance taken at a specified radial distance from the origin. For convenience, the distance will be defined at the midpoint between the inner and outer edges of the suspension element. The pitch distance between adjacent ribs, grooves and/or rib-and-groove features may vary. In some examples, the pitch distance is uniform for all of the successive pairs of ribs, grooves and/or rib-and-groove features around the circumference of the suspension element, so that the features are regularly spaced. In other examples, the pitch distance could vary between successive pairs. 
     The path of the grooves, ribs and rib-and-groove features may be straight or may comprise a plurality of sections and a plurality of transition regions. The angle of orientation of each section, where angle of orientation is defined as the angle of the section at the point along the section closest to the inner edge, to a normal to the inner edge that intersects the closest point, as well as the radius of curvature of the path section, can vary. The radius of curvature of the path section can vary over the section. Transition regions can smoothly join the ends of adjacent path sections. For the case where the radius of curvature at the end of one section and the beginning of the section to which it is joined have opposite sign, the transition region may include an inflection point. The number of inflection points in a groove, rib, or rib-and-groove feature path may vary. 
     The rib, groove and rib-and-groove features described above provide added stiffness in the primary axis of vibration (Z-axis). More particularly, the outer segments  504  (the rib portions) of the rib-and-groove feature  500  provide additional axial stiffness in the direction of the interior of the enclosure. In general, a suspension element having only radial grooves can undergo greater excursion without non-circumferential distortion in comparison with a suspension element of similar dimensions and materials, but without radial grooves.  FIG. 9  illustrates an exemplary force versus displacement curve for such a suspension element. Note the asymmetry of the curve in different directions of excursion, e.g., +2.9 N of force at +6.0 mm excursion and −1.4 N of force at −6.0 mm of excursion. Suspension element  104  can undergo similar excursion without non-circumferential distortion, and also exhibits more symmetrical force versus displacement in comparison with a suspension element with only radial grooves.  FIG. 10  illustrates an exemplary force versus displacement curve for the suspension element  104 . Note the enhanced symmetry of the curve in different directions of excursion, e.g., +3.2 N of force at +6.0 mm excursion and −3.4 N of force at −6.0 mm of excursion. 
     Among the wide variety of variations that are contemplated are variations of placement of the radial features. For example, the number of radial features, spacing between radial features and all dimensions of radial feature geometry could be varied. Further, the radial features are not limited to grooves and rib-and-groove features, but may also include ribs, and more than two different types might be utilized. Further, all of the radial features could be characterized by inflexions of concavity, e.g., in a manner similar to that of the rib-and-groove features  500 . The ends of the radial features could be in any of various locations. In one example, the rib-and-groove features  500  traverse the roll from approximately the inner edge  306  to the outer edge  308  whereas the groove features  304  traverse the roll from a point offset from the inner edge  306  to the outer edge  308 . Moreover, the maximum extent of the radial features could be varied, and transitions from zero protrusion to the maximum extent could be defined by any of various mathematical functions. Further, material thickness could be varied at the radial features and within individual radial features. For example, referring to  FIG. 11A , in examples where the rib-and-groove feature  500  has a substantially uniform thickness, the outer segment  504  of the rib-and-groove features  500  may extend onto the outer landing  312  (as shown in  FIG. 6B ). Consequently, a perimeter defined by the outer edge  308  of the suspension element  104  may be non-circular, including V-shaped protrusions (as shown in  FIG. 2 ). These V-shaped protrusions may be undesirable from the standpoint of manufacturability. Thus, in some implementations, as shown in  FIG. 11B , the material used to create the suspension element  104  is under-compressed at least at the portion  702  where the outer segment  504  meets the outer landing  312  of the suspension element  104 , thereby eliminating the V-shaped portions. Accordingly, the rib-and-groove feature  500  has varying material thickness along the length of the outer segment  504  (the rib portion). More particularly, the rib-and-groove feature  500  has increased material thickness in at least a portion  702  of the outer segment  504  proximate to the outer landing  312 . 
     A number of implementations have been described in the above examples, but it will be understood by those of ordinary skill in the art that a wide variety of modifications and variations are possible without departing from the concepts herein disclosed. Moreover, all examples, features and aspects can be combined in any technically possible way. Accordingly, other implementations are within the scope of the following claims.