Patent Publication Number: US-8968125-B2

Title: Tennis racket

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority from U.S. Provisional Application No. 61/799,555, filed on Mar. 15, 2013, the entirety of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure is directed to a tennis racket and, more particularly, to a tennis racket having improved playing characteristics. 
     BACKGROUND OF THE DISCLOSURE 
     The game of tennis has changed significantly in the past several decades. Presently, tennis balls are struck with more speed and spin, and elite tennis players are physically much stronger than previous generations of players. Additionally, stroke technique and biomechanics have also evolved. As recently as the 1980&#39;s, common stroke technique involved players having a fixed wrist during ball contact. However, it is now common for players to have a loose wrist during ball contact so that the wrist acts as an additional pivot point during the stroke. Thus, as compared to several decades ago, players now generate significantly more angular velocity in a given stroke. Further, players also generally rotate the racket about the racket&#39;s longitudinal axis during a stroke in order to generate topspin. 
     Changes to the physical structure of a tennis racket (e.g., size, shape, balance, weight, weight distribution, material) can affect the playing characteristics of that racket. For example, altering the weight distribution within a given racket will affect that racket&#39;s comfort, control, and power characteristics. As a result of the changing stroke styles, there is a need for a racket with improved playing characteristics. 
     SUMMARY 
     In one aspect, the present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket may have a Power Maneuverability Ratio from about 4500 to about 7915, the Power Maneuverability Ratio governed by the equation: PMR= 
                   (     S   ⁢           ⁢   W     )     ⁢     (     R   ⁢           ⁢   W     )         (     P   ⁢           ⁢   U   ⁢           ⁢   W     )       ,         
where SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis,
 
                 R   ⁢           ⁢   W     =       S   ⁢           ⁢   W     -       (       W   ⁢           ⁢   t     1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; and wherein the head includes a composite material and the higher density portions include rubber. 
     In another aspect, the present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket may have a Stabilized Power Maneuverability Ratio from about 57,000 to about 115,000, the Stabilized Power Maneuverability Ratio governed by the equation: 
                 S   ⁢           ⁢   P   ⁢           ⁢   M   ⁢           ⁢   R     =         (     S   ⁢           ⁢   W     )     ⁢     (     R   ⁢           ⁢   W     )     ⁢     (     T   ⁢           ⁢   W     )         (     P   ⁢           ⁢   U   ⁢           ⁢   W     )         ,         
where SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis,
 
                 R   ⁢           ⁢   W     =       S   ⁢           ⁢   W     -       (       W   ⁢           ⁢   t     1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; and wherein the head includes a composite material and the higher density portions include rubber. 
     The present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket hay have a Stabilized Maneuverability Ratio from about 211 to about 318, the Stabilized Maneuverability Ratio governed by the equation: 
     
       
         
           
             
               
                 S 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 M 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 R 
               
               = 
               
                 
                   
                     ( 
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       W 
                     
                     ) 
                   
                   ⁢ 
                   
                     ( 
                     
                       T 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       W 
                     
                     ) 
                   
                 
                 
                   ( 
                   
                     P 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     U 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     W 
                   
                   ) 
                 
               
             
             , 
           
         
       
     
                 R   ⁢           ⁢   W     =       S   ⁢           ⁢   W     -       (       W   ⁢           ⁢   t     1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis, Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; and wherein the head includes a composite material and the higher density portions include rubber. 
     The present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket may have a Power Maneuverability Ratio greater than about 4500, the Power Maneuverability Ratio governed by the equation 
                 P   ⁢           ⁢   M   ⁢           ⁢   R     =         (     S   ⁢           ⁢   W     )     ⁢     (     R   ⁢           ⁢   W     )         (     P   ⁢           ⁢   U   ⁢           ⁢   W     )         ,         
where SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis,
 
                 R   ⁢           ⁢   W     =       S   ⁢           ⁢   W     -       (     Wt   1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein the Power Maneuverability Ratio is from about 4500 to about 7915; wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; and wherein the head includes a composite material and the higher density portions include rubber. 
     In yet another aspect, the present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket may have a Stabilized Power Maneuverability Ratio greater than about 57,000, the Stabilized Power Maneuverability Ratio governed by the equation: 
               SPMR   =         (   SW   )     ⁢     (   RW   )     ⁢     (   TW   )         (   PUW   )         ,         
where SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis,
 
                 R   ⁢           ⁢   W     =       S   ⁢           ⁢   W     -       (     Wt   1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein the Stabilized Power Maneuverability Ratio is from about 57,000 to about 115,000; wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; and wherein the head includes a composite material and the higher density portions include rubber. 
     In yet another aspect, the present disclosure is directed to a tennis racket. The tennis racket may include a handle with a butt end, and a head configured to support strings. The tennis racket may also include a throat connecting the handle and the head, wherein the racket may have a Stabilized Maneuverability Ratio greater than about 211, the Stabilized Maneuverability Ratio governed by the equation: 
               SMR   =         (   RW   )     ⁢     (   TW   )         (   PUW   )         ,     RW   =     SW   -       (     Wt   1000     )     ⁢       (       b   10     -   10.16     )     2           ,         
SW=the moment of inertia in kilogram-centimeters squared of the tennis racket about a swingweight axis that is perpendicular to a longitudinal axis of the tennis racket, parallel to a tennis ball hitting surface contained by the head, and intersecting a point on the handle that is four inches from the butt end along the longitudinal axis, Wt=the weight of the racket in grams, b=the distance in millimeters between a center of gravity of the racket to the butt end, TW=the moment of inertia of the tennis racket about the longitudinal axis, and PUW=(Wt)(b).
 
     Various examples of the present disclosure may include one or more of the following aspects: wherein the Stabilized Maneuverability Ratio is from about 211 to about 318; wherein a weight of the racket is from about 255 grams to about 348 grams; wherein a balance distance from the butt end to the center of gravity of the racket is from about 300 mm to about 356 mm; further including higher density portions of the head at 3, 9, and 12 o&#39;clock positions; further including a higher density portion of the racket at the butt end; wherein the head includes a composite material and the higher density portions include rubber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of an exemplary disclosed tennis racket; and 
         FIG. 2  is a table listing various physical parameters of exemplary tennis rackets in accordance with the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the present disclosure described above and illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     According to an embodiment of the present disclosure, a tennis racket  1 , shown in  FIG. 1 , includes a frame  3  having a head  5 , a throat  7 , and a handle  9 . Head  5  may be a closed, oval shape loop, or may alternatively be any other suitable shape. Handle  9  may be connected to a junction of two members of throat  7  and extend toward a butt end  11 . The two members of throat  7  may extend from the junction and connect to head  5 , and a bridge  13  may connect between the two connection points. It is understood that in certain embodiments, a bridge  13  may be excluded. Head  5  may also generally define a string area  15  that, when strung with a plurality of strings (not shown), forms a tennis ball hitting surface. The head  5  may also include one or more bumper guards and grommet strips (not shown) as is known in the art. 
     Tennis racket  1  may include a central longitudinal axis  17  that extends along the length direction of the racket from butt end  11  toward an end of head  5 . Tennis racket  1  may also include a swingweight axis  19  and a recoilweight axis  21 . Swingweight axis  19  may be substantially perpendicular to longitudinal axis  17  and parallel to the direction of the cross strings (not shown), and extend through a point G located on handle  9  about four inches from butt end  11 . Recoilweight axis  21  may also be substantially perpendicular to longitudinal axis  17  and extend through a center of gravity C g  of tennis racket  1 . Both swingweight axis  19  and recoilweight axis  21  may be parallel or coplanar to the tennis ball hitting surface (or string plane). 
     Turning to the table of  FIG. 2 , rows A-P list various physical parameters of exemplary tennis rackets in accordance with the disclosure. These physical parameters correspond to an unstrung racket  1 , but otherwise including all of the components of a playable racket, such as handle grip, grommets, and bumper strips. 
     The listed parameters are as follows: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Racket 
                 Wt = 
                 the weight of the racket in grams 
               
               
                 Weight 
                   
                   
               
               
                 Balance 
                 b = 
                 distance in millimeters from the center of 
               
               
                   
                   
                 gravity C g  to butt end 11 
               
               
                 Length 
                 I = 
                 the length in millimeters of tennis racket 1 
               
               
                 Swing- 
                 SW = 
                 the moment of inertia of tennis racket 1 about swing- 
               
               
                 weight 
                   
                 weight axis 19 in kilogram-centimeters squared, 
               
               
                   
                   
                 obtained by measuring the moment of inertia about 
               
               
                   
                   
                 swingweight axis 19 using any suitable diagnostic 
               
               
                   
                   
                 tool known in the art 
               
               
                   
               
               
                 Recoil- 
                 RW = 
                 the moment of inertia of tennis racket 1 about 
               
               
                 weight 
                   
                 recoilweight axis 21 in kilogram-centimeters 
               
               
                   
                   
                 squared calculated by the equation: 
               
               
                   
                   
                 
                   
                     
                       
                         SW 
                         - 
                         
                           
                             ( 
                             
                               Wt 
                               1000 
                             
                             ) 
                           
                           ⁢ 
                           
                             
                               ( 
                               
                                 
                                   b 
                                   10 
                                 
                                 - 
                                 10.16 
                               
                               ) 
                             
                             2 
                           
                         
                       
                     
                   
                 
               
               
                   
               
               
                 Twist- 
                 TW = 
                 the moment of inertia of tennis racket 1 about 
               
               
                 weight 
                   
                 longitudinal axis 17 in kilogram-centimeters 
               
               
                   
                   
                 squared, which may be obtained by the following 
               
               
                   
                   
                 equation: 
               
               
                   
                   
                 
                   
                     
                       
                         
                           
                             254.458 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               ( 
                               
                                 
                                   T 
                                   c 
                                 
                                 π 
                               
                               ) 
                             
                           
                           - 
                           8.357 
                         
                         , 
                       
                     
                   
                 
               
               
                   
                   
                 where T c  is a center period determined by 
               
               
                   
                   
                 hanging tennis racket 1 and using a measurement 
               
               
                   
                   
                 instrument such as a calibrated torsion pendulum 
               
               
                   
                   
                 or other suitable instrument. It should be noted 
               
               
                   
                   
                 that the moment of inertia of tennis racket 1 about 
               
               
                   
                   
                 longitudinal axis 17 may also be calculated in ounce- 
               
               
                   
                   
                 inches squared by what is known as the trifilar 
               
               
                   
                   
                 method. According to this method, the racket is 
               
               
                   
                   
                 oscillated about longitudinal axis 17 with three 
               
               
                   
                   
                 fibers, each of which has a length of approximately 
               
               
                   
                   
                 1.5 meters, are connected to tennis racket 1 from 
               
               
                   
                   
                 a fixed point above tennis racket 1. Then the 
               
               
                   
                   
                 oscillation time of the racket is measured and 
               
               
                   
                   
                 utilized in the following equation 
               
               
                   
                   
                 
                   
                     
                       
                         
                           TW 
                           = 
                           
                             ( 
                             
                               
                                 
                                   ( 
                                   Wt 
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   9.807 
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     r 
                                     ⁢ 
                                     1 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     r 
                                     ⁢ 
                                     2 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     t 
                                     2 
                                   
                                   ) 
                                 
                               
                               
                                 ( 
                                 
                                   
                                     ( 
                                     4 
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ( 
                                     
                                       l 
                                       1 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ( 
                                     
                                       π 
                                       2 
                                     
                                     ) 
                                   
                                 
                                 ) 
                               
                             
                             ) 
                           
                         
                         , 
                       
                     
                   
                 
               
               
                   
                   
                 where r1 and r2 are the radii 
               
               
                   
                   
                 of the circles formed by the three aforementioned 
               
               
                   
                   
                 fibers; (I 1 ) was the length of the fibers, and (t) was 
               
               
                   
                   
                 the time to complete one oscillation. 
               
               
                   
               
               
                 Pickup- 
                 PUW = 
                 the pickup weight of tennis racket 1 in kilogram- 
               
               
                 weight 
                   
                 centimeters governed by the equation: 
               
               
                   
                   
                 PUW = (Wt)(b) 
               
               
                   
               
               
                 Power 
                 PMR = 
                 a design factor calculated by the equation: 
               
               
                 Maneuver- ability Ratio 
                   
                 
                   
                     
                       
                         
                           
                             ( 
                             SW 
                             ) 
                           
                           ⁢ 
                           
                             ( 
                             RW 
                             ) 
                           
                         
                         
                           ( 
                           PUW 
                           ) 
                         
                       
                     
                   
                 
               
               
                   
               
               
                 Stabilized 
                 SPMR = 
                 a design factor calculated by the equation: 
               
               
                 Power Maneuver- ability 
                   
                 
                   
                     
                       
                         
                           
                             ( 
                             SW 
                             ) 
                           
                           ⁢ 
                           
                             ( 
                             RW 
                             ) 
                           
                           ⁢ 
                           
                             ( 
                             TW 
                             ) 
                           
                         
                         
                           ( 
                           PUW 
                           ) 
                         
                       
                     
                   
                 
               
               
                 Ratio 
                   
                   
               
               
                   
               
               
                 Stabilized 
                 SMR = 
                 a design factor calculated by the equation: 
               
               
                 Maneuver- ability Ratio 
                   
                 
                   
                     
                       
                         
                           
                             ( 
                             RW 
                             ) 
                           
                           ⁢ 
                           
                             ( 
                             TW 
                             ) 
                           
                         
                         
                           ( 
                           PUW 
                           ) 
                         
                       
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     A tennis racket  1  in accordance with this disclosure may be manufactured by selectively positioning weight about the racket frame  3 . According to one example, racket frame  3  may be formed in a conventional manner, such as through the use of a composite of carbon fibers, glass fibers, and epoxy resin, but with additional weight portions at the 3, 9, and 12 o&#39;clock positions, and at the butt end  11  of the racket frame  3 . This additional weight can be provided on the racket frame  3  as portions of increased density. For example, as shown in  FIG. 1 , racket  1  may include portions  27 ,  23 , and  25  of greater density (at the 3, 9, and 12 o&#39;clock positions, respectively), and at the butt end  11  of the racket  1 . These portions of greater density may be achieved by adding higher density material to the racket composite material in these areas. For example, higher density portions can be achieved by adding rubber particles to the racket material in the higher density portions  11 ,  23 ,  25 , and  27 . The use of rubber provides the benefit of greater density, and thus increased weight, but does not significantly increase detrimental stiffness in the portions  11 ,  23 ,  25 , and  27 . The varying weight at one or more of the portions  11 ,  23 ,  25 , and  27  may be achieved by alternative methods. For example, frame thickness variations and/or separate weights may be provided in one or more of the portions  11 ,  23 ,  25 , and  27 . 
     The disclosed tennis racket  1  may possess a relatively high swingweight, recoilweight, and twistweight, while also possessing a relatively low pickup weight. A high swingweight may be beneficial to a tennis player by allowing tennis racket  1  to generate more power. 
     High recoilweight and high twistweight of tennis racket  1  may contribute to increased stability of tennis racket  1 . In particular, because tennis rackets are becoming lighter, they generate less momentum and absorb more shock and vibrations. When tennis racket  1  strikes a tennis ball, its motion is altered about both recoilweight axis  21  and longitudinal axis  17 . As the magnitude of these motion forces after ball-strike about recoilweight axis  21  and longitudinal axis  17  increase, the amount of energy wasted increases. Therefore, the high swingweights and twistweights achieved by the various tennis rackets  1  of the present disclosure result in more efficient energy transfer from the player to the ball through the racket. That is, less force is wasted through vibration and deflection of tennis racket  1  as compared to rackets with lower swingweight and twistweight. 
     However, it may also be important for game play to have a racket with improved maneuverability. The pickup weight (PUW) characterizes the apparent weight of a tennis racket  1  sensed by a player while tennis racket  1  is held in a player&#39;s hand. A low pickup weight corresponds to a lower sensed weight, improving maneuverability of tennis racket  1 . On the contrary, a high pickup weight corresponds to a higher sensed weight, reducing the maneuverability of tennis racket  1 . 
     Because the tennis rackets of the present disclosure may possess a relatively high swingweight, recoilweight, and twistweight, while also possessing a relatively low pickup weight, tennis rackets  1  may exhibit improved power and stability characteristics while still maintaining desirable maneuverability. An improved tennis racket  1  of the present disclosure may have a Power Maneuverability Ratio from about 4500 to about 7915, a Stabilized Power Maneuverability Ratio from about 57,000 to about 115,000, and a Stabilized Maneuverability Ratio from about 211 to about 318. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed tennis racket without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only. The following disclosure identifies some other exemplary embodiments.