Patent Publication Number: US-7211010-B2

Title: Reinforcing member for a badminton racquet

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to a badminton racquet. In particular, the present invention relates to a reinforcing member for improving the coupling of the hoop and handle portions of the badminton racquet frame. 
   BACKGROUND OF THE INVENTION 
   Badminton racquets are well known and typically include a tubular head portion attached to a tubular handle portion. The head portion forms a hoop supporting a latticework of tensioned strings. The latticework of strings is commonly referred to as a string bed and includes a plurality of intersecting cross and main string segments, which attach to the head portion. The handle portion downwardly and outwardly extends from a lower portion of the head portion to form a generally T-shaped connection region. The handle portion typically includes a handle attached to the proximal end of the handle portion. The handle is covered by a grip. 
   There is a continuing desire to increase the performance, responsiveness and control of the racquet, and to improve the strength and durability of the connection region of head and handle portions. Badminton racquets must provide players with the ability to complete high-speed swing actions to bat a shuttlecock at short intervals in a relatively small court space compared with, for example, the game of tennis. The speed of the game necessitates that a badminton racket be constructed to be light in weight and have satisfactory resilience for easy handling. Furthermore, in order to satisfy the need for a high-speed swing action, the dimensions of the badminton racket in the swing direction must be minimized. Such configurations maintain the moment of inertia and air resistance of the badminton racquet at desirable levels. It is also necessary that the racquet possess high mechanical strength in order withstand the stress of a high-speed swing as well as various impact loads arising from the use of the racquet. It can be very difficult to reliably satisfy all of these design requirements. For example, a badminton that is light weight, highly resilient and provides minimum air resistance may also have very low mechanical strength. 
   The cross-sectional size of the handle portion of a badminton racquet is generally quite small compared to that of other racquet sport racquets such as tennis or racquetball. The cross-sectional size of the head portion of a badminton racquet is also smaller than that of other sports racquets. Also, the head portion typically connects to the handle portion at a single location as opposed to two or more locations commonly used with tennis racquets. This single connection point provides badminton racquets with a high level of flexibility. Although flexibility in some aspects of the racquet is desired, such as in the swing direction, a highly torsionally flexible racquet, or a racquet with a reduced resistance to torsional bending, is undesirable because it can lead to poor control, reduced accuracy and lower performance. Further, the relatively small size of the head and handle portions place a large amount of stress on the single connection region of the head and handle portions. As a result, it is not uncommon for badminton racquets to prematurely fail at the connection region. 
   In an effort to address the premature failure issue, some existing badminton racquets have included T-shaped joints at the connection between the head and handle portions. These joints typically include an elongate vertical joint section that extends a significant distance into the handle portion of the racquet. As a result, the length, and the cross-sectional size, of the joint section within the handle member is typically as large, or larger, than the length, and the cross-sectional size, of the joint section positioned within the head portion of such racquets. The rather large size of the existing T-shaped joints can negatively effect the weight of the racquet and, as a result, the playability of the racquet. Further, the elongate extension into the handle portion of the racquet can stiffen, and reduce the flexibility of, the racquet, particularly in the swing direction. Such stiffening is undesirable because it can decrease the responsiveness and playability of the racquet. 
   Thus, there is a continuing need for a badminton racquet that is highly durable and reliable, but also provides the desired level of performance and playability. What is needed is an improved racquet design that inhibits premature failure without negatively affecting the overall weight of the badminton racquet. What is also needed is a durable badminton racquet with desired responsiveness, particularly in the swing direction. Further, it would be advantageous to provide a durable racquet with high playability that can be efficiently and reliably produced. 
   SUMMARY OF THE INVENTION 
   The present invention provides a reinforcing member for a badminton racquet wherein the racquet extends along a longitudinal axis and includes a frame having a tubular hoop portion supporting a string bed and a tubular handle portion. The reinforcing member includes a generally T-shaped body having first and second sections. The first section has an outer surface that defines a first cross-sectional area measured about a longitudinal plane positioned generally perpendicular to the string bed. The second section longitudinally and outwardly extends from the first section. The second section has an outer surface that defines a second cross-sectional area measured about a transverse plane. The first cross-sectional area is at least 50 percent greater than the second cross-sectional area. The first and second sections are configured for placement within the hoop and handle portions of the frame, respectively. 
   According to a principal aspect of the invention, a badminton racquet includes a frame having a tubular hoop portion and a tubular handle portion, a string bed, and a generally T-shaped reinforcing member. The string bed is supported by the hoop portion. The first section has an outer surface that defines a first cross-sectional area measured about a longitudinal plane positioned generally perpendicular to the string bed. The second section longitudinally and outwardly extends from the first section. The second section has an outer surface that defines a second cross-sectional area measured about a transverse plane, the first cross-sectional area being at least 50 percent greater than the second cross-sectional area. The first and second sections are configured for placement within the hoop and handle portions of the frame, respectively. 
   According to another principal aspect of the invention, a badminton racquet extends along a longitudinal axis is configured for impacting a shuttlecock and for placement within a test support for a racquet torsional stability test. The racquet includes a frame, a string bed and a generally T-shaped reinforcing member. The frame includes a tubular hoop portion defining a hoop and a tubular handle portion. The frame has a head size of approximately 54.5 inches 2 . The handle portion has a distal end region having an outside diameter within the range of 6.75 mm to 7.25 mm. The string bed is supported by the hoop portion. The racquets has a strung weight within the range of 88.0 to 93.5 grams. The reinforcing member includes first and second sections configured for placement within the hoop and handle portions of the frame, respectively. The second section longitudinally and outwardly extends from the first section. The racquet has a torsional deflection of less than 10.5 degrees when measured in a torsional stability test wherein the handle portion is fixedly supported by the test support, and the shuttlecock travels at an incoming velocity of approximately 34 miles per hour and impacts the string bed at a location approximately 1.25 inches to the left or right of a geometric center of the hoop portion. 
   This invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings described herein below, and wherein like reference numerals refer to like parts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front perspective view of a badminton racquet in accordance with a preferred embodiment of the present invention. 
       FIG. 2  is a cross-sectional view of the head portion of the frame taken along line  2 — 2  of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the head portion of the frame taken along line  3 — 3  of  FIG. 1 . 
       FIG. 4  is a cross-sectional view of the head portion of the frame taken along line  4 — 4  of  FIG. 1 . 
       FIG. 5  is an exploded view of a portion of the badminton racquet of  FIG. 1  without racquet string. 
       FIG. 6  is a longitudinal cross-sectional view of a portion of the badminton racquet of  FIG. 1  without racquet string. 
       FIG. 7  is a top perspective view of a reinforcing member of the badminton racquet of  FIG. 1  prior to assembly. 
       FIG. 8  is a side view of the reinforcing member of  FIG. 7 . 
       FIG. 9  is a longitudinal cross-sectional view of the reinforcing member taken along line  9 — 9  of  FIG. 8 . 
       FIG. 10  is a transverse cross-sectional view of the reinforcing member taken along line  10 — 10  of  FIG. 8 . 
       FIG. 11  is a side view of a torsional stability test assembly including a shuttlecock projected toward a badminton racquet. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a badminton racquet is indicated generally at  10 . The racquet  10  includes a frame having a hoop portion  12  and a handle portion  14  outwardly extending from the hoop portion  12  along a longitudinal axis  16  of the racquet  10 . The head portion  12  is a curved tubular structure preferably defining a generally oval shaped opening  18  for supporting a substantially planar latticework of strings in tension, also referred to as a string bed  20 . In alternative preferred embodiments, the opening formed by the head portion  12  can be generally tear drop shaped or generally circular. The head portion  12  is coupled to the handle portion  14 . In one preferred embodiment, the head portion  12  is integrally formed with the handle portion  14 . 
   The head and handle portions  12  and  14  are formed of a lightweight, flexible and durable material, preferably a carbon-fiber composite material. Alternatively, the head and handle portions  12  and  14  can be formed of other materials, such as, for example, other non-carbon fiber composite materials, aluminum, metallic alloys, thermoplastic materials, thermoset materials, and combinations thereof. The racquet  10  preferably has an unstrung weight in the range of approximately 79.0–95.0 grams, and a strung weight of approximately 82.0–98.0 grams. In a particularly preferred embodiment, the strung weight of the racquet is within the range of 89.0–92.0 grams. In alternative preferred embodiments, the racquet can be formed of a weight below or above the above-listed weight ranges. 
   The head portion  12  preferably includes a plurality of string holes (not shown) for receiving and supporting the string bed  20 . The string bed  20  is formed by a plurality of main string segments  22  interwoven with a plurality of cross string segments  24 . The main string segments  22  extend across the opening  18  in a direction generally parallel to the axis  16 , and the cross string segment extend across the opening  18  in a direction generally perpendicular, or transverse, to the longitudinal axis  16 . The head portion  12  has a geometric center indicated as point A. The head size of the racquet, or the size of the string bed  20 , can be within the range of 48.0 to 60.0 in 2 . In one preferred embodiment, the head size of the racquet can be within the range of 54.0 to 56.0 in 2 , and in a particularly preferred embodiment, the head size is approximately 54.5 in 2 . Alternative head sizes can also be used, such as approximately 60.0 in 2 . 
   The handle portion  14  is an elongate tubular member having distal and proximal end regions  26  and  28 . The distal end region  26  of the handle portion  14  is preferably directly connected to the hoop portion  14 . The distal end region  26  of the handle portion  14  preferably has an outer diameter in the range of 6–10 mm. In one particularly preferred embodiment, the outer diameter of the distal end region  26  is within the range of 6.75 to 8.0 mm. In another particularly preferred embodiment, the outer diameter of the distal end region  26  is within the range of 6.75 to 7.25 mm. In yet another particularly preferred embodiment, the outer diameter of the distal end region  26  is within the range of 6.95 to 7.05 mm. In another preferred embodiment, the outer diameter of the proximal end region can be approximately 7.5 mm. 
   The handle grip assembly  30  is attached to the proximal end region  28  of the handle portion  14 . The handle portion  14  spaces apart the grip assembly from the head portion  12  providing the racquet with the desired length. The handle grip assembly is configured for grasping by a user, and preferably includes a pallet  32 , a butt cap  34 , and a grip  36 . The pallet  32  is a tubular member configured to slide over the outer surface of the proximal end region  28  of the handle portion  14 , or to attach to the proximal end region  28 . Alternatively, the pallet can be integrally formed with the handle portion. The butt cap  34  is a protective member, which generally covers the proximal end of the handle portion  14  and the pallet  32 . The grip  36  is an elongate strip of material that substantially covers the pallet  32  and at least a portion of the butt cap  34 . 
   Referring to  FIGS. 1–4 , the head portion  12  is shown in greater detail. The tubular head portion  12  preferably gradually increases in size from a mid-section of the head portion  12  (see  FIG. 2 ) toward the lower section.  FIGS. 2–4  illustrate the increase in the size and the outer cross-sectional area of the head portion at three different locations. In an alternative preferred embodiment, the size of the head portion  12  can remain generally constant along the middle and lower sections of the head portion  12 . Referring to  FIGS. 1 and 4 , in a particularly preferred embodiment, a decorative cover  38  is secured to the upper portion of the lower end of the head portion  12 . The cover  38  provides the racquet  10  with a unique aesthetic design and can also be employed to increase the structural integrity of the head portion  12 . 
   Referring to  FIGS. 5 and 6  the juncture of the head and handle portions  12  and  14  is shown in greater detail. The head and handle portions  12  and  14  are preferably integrally formed or connected to each other. A generally T-shaped reinforcing member  40  is preferably positioned within the frame at the juncture of the head and handle portions  12  and  14 . The reinforcing member  40  is formed of a strong, lightweight material, preferably a carbon-fiber composite material. Alternatively, the head and handle portions  12  and  14  can be formed of other materials, such as, for example, other non-carbon fiber composite materials, aluminum, metallic alloys, polyurethane, nylon, other thermoplastic materials, other thermoset materials, wood, and combinations thereof. 
   The reinforcing member  40  has a generally T-shaped body including first and second sections  42  and  44 . The first section  42  is configured for placement within the lower end of the head portion  12  and thus extends generally transverse to the longitudinal axis  16 . The second section  44  outwardly and downwardly extends from a lower surface of the first section  42 , and is configured for placement within the distal end region  26  of the handle portion  14 . The second section  44  extends generally parallel with the axis  16 . The reinforcing member  40  is preferably formed as a solid continuous member. Alternatively, one or both of the first and second sections  42  and  44  can be hollow. In another alternative embodiment, the reinforcing member  40  can be formed of two or more sub-members connected together to form the reinforcing member  40 . 
   The first section  42  includes left and right projecting ends  46  and  48  outwardly extending from a central segment  50 . A plurality of string holes  52  are formed into the head portion  12 , and, preferably, two spaced apart string holes  52  are also formed into the first section  42  (one in each of the left and right projecting ends  46  and  48 ). The string holes  52  enable racquet string to extend through and around the head portion  12  to form and support the string bed  22 . 
   Referring to  FIG. 6 , the head portion  12  preferably includes a recess  54  formed into an inner surface of an upper segment of the lower end of the head portion  12 . The recess  54  is advantageously sized to receive a ledge  56  upwardly and outwardly extending from the central segment  50  of the first section  42  of the reinforcing member  40 . Preferably, the ledge  56  substantially fills the recess  54 . The engagement of the ledge  56  with the lower end of the head portion  12  facilitates and helps ensure the proper centering of the reinforcing member  40  within the frame of the racquet  10 . 
   Referring to  FIGS. 6–10 , the reinforcing member  40  is shown in greater detail. The first section  42  is configured to be greater in size than the second section  44 . Each of the left and right projecting ends of the first section  42  of the reinforcing member has an outer surface  58  defining a first cross-sectional area measured about a longitudinal plane positioned generally perpendicular to a plane defined by the string bed  22  (as seen in  FIG. 9 ). The second section  44  of the reinforcing member  40  has an outer surface  60  that defines a second cross-sectional area measured along a transverse plane (as seen in  FIG. 10 ). In one preferred embodiment, the first cross-sectional area is at least 50 percent greater than the second cross-sectional area. In a particularly preferred embodiment, the first cross-sectional area is at least 100 percent greater than the second cross-sectional area, and in another particularly preferred embodiment, the first cross-sectional area is at least 150 percent greater than the second cross-sectional area. 
   Further, the length of the first section  42  measured from the left projecting end  46  to the right projecting end  48  is significantly greater than the length of the second section  44 , measured along the longitudinal axis  16 . In one preferred embodiment, the length of the first section  42  is at least 30 percent greater than the length of the second section  44 . In a particularly preferred embodiment, the length of the first section  42  is at least 50 percent greater than the length of the second section  44 , and in another particularly preferred embodiment, the length of the first section  42  is at least 80 percent greater than the length of the second section  44 . 
   In one preferred embodiment, the first cross-sectional area is within the range of 24 to 34 mm 2 , and the second cross-sectional area is within the range of 5 to 10 mm 2 . In one particularly preferred embodiment, the first cross-sectional area is in the range of 27 to 31 mm 2 , and the second cross-sectional area is in the range of 7 to 8 mm 2 . The first section  42  has a length within the range of 18 to 24 mm, and the second section  44  has a length within the range of 4 to 10 mm. In one particularly preferred embodiment, the first section  42  has a length within the range of 21 to 23 mm, and the second section  44  has a length within the range of 8 to 9 mm. In alternative preferred embodiments, other dimensions for the first and second cross-sectional areas and the length of the first and second sections can be used. 
   The reinforcing member  40  strengthens the connection between the head and handle portions  12  and  14  of the racquet  10  thereby improving the reliability and durability without negatively affecting the performance and playability of the racquet. By reducing the size and length of the second section  44  relative to the first section  42 , unnecessary weight is eliminated from the reinforcing member, and the flexibility of the racquet in the swing direction is not negatively affected. 
   The reinforcing member  40 , with the enlarged first section  42 , significantly improves the torsional stability and torsional strength of the racquet  10  over conventional badminton racquets. The increased torsional stability improves the control and playability of the racquet  10 . The torsional stability of the racquet  10  can be tested in a badminton racquet high speed video impact test. 
   Referring to  FIG. 11 , the ability of a racquet to resist torsional bending is demonstrated through a torsional stability test wherein the handle portion  14  is secured in a test stand  70  at the grip  36 . Once secured, the racquet  10  is positioned such that the longitudinal axis  16  of the racquet is vertical with the handle portion  14  positioned below the hoop portion  12 . An air cannon  72 , such as the Model No. 101 by Lobster Sports, Inc. of Toluca, Calif., is positioned to project or launch a shuttlecock  74  along a trajectory such that the shuttlecock  74  impacts the string bed from a direction that is perpendicular to the string bed, cap end forward, and at a location that is approximately 1.25 inches to the right or left of the geometric center of the string bed defined by the hoop portion of the racquet (see location B on  FIG. 1 ). The air cannon is positioned approximately two feet from the head portion of the racquet (distance d of  FIG. 11 ) and projects the shuttlecock  74  such that the shuttlecock  74  impacts the string bed at a speed of approximately 34 miles per hour. 
   A high speed video machine  76 , such as Model HS-4, from Motion Pro of San Diego, Calif., is positioned above the racquet and directed to view the top of the racquet along the longitudinal axis of the racquet. The high speed video machine collects images at a rate of 5000 frames per second and captures the shuttlecock and the racquet before, during and after the impact. The high speed video machine enables the speed of the shuttlecock to be determined as well as the amount of torsional and longitudinal bending of the racquet in response to the impact with the shuttlecock. 
   During testing, the racquet and air cannon are positioned as described above. A shuttlecock is launched from the air cannon with its cap end forward into the string bed  22  at an incoming velocity of approximately 34 miles per hour. When viewed from the direction of the air cannon, the shuttle cock is launched to impact the contact the racquet at approximately 1.25 inches to the right (or left) of the geometric center of the string bed. The high speed video camera records the amount of torsional and longitudinal deflection of the racquet in response to the impact of the shuttlecock. 
   A torsional stability test was performed on two different model badminton racquets. The first racquet, model Armortec™ 800 Offensive by Yonex Kabushiki Kaisha, is representative of a high performance badminton racquet including a generally conventional T-shaped joint support positioned within the racquet at the juncture of the head and handle portions. The first racquet has a strung weight of 90.8 grams and a head size of approximately 54.5 in 2 . The distal end region of the handle portion of the first racquet has an outer diameter of approximately 7.0 mm. The second racquet, the Wilson® nCode® 1, is built in accordance with an embodiment of the present invention with a reinforcing member formed of carbon fiber composite material. The second racquet has a strung weight of approximately 90.8 grams, and a head size of approximately 54.5 in 2 . The distal end region of the handle portion of the second racquet also has an outer diameter of approximately 7.0 mm. 
   A shuttlecock was projected from an air cannon positioned two feet from the string bed, dimension d from  FIG. 11 . The incoming velocity, longitudinal deflection and torsional deflection of the racquet were measured. Specifically, the torsional stability correlates to the degree of torsional deflection, or twisting, of the racquet in response to the impact with the shuttlecock. The torsional deflection or twisting is measured in degrees with respect to the longitudinal dimension of the racquet. The incoming velocity of the shuttlecock prior to impact with the first racquet, the Yonex Armotec 800, was 33.42 miles per hour, and the incoming velocity of the shuttlecock prior to impact with the second racquet, the Wilson® nCode® 1, was 33.82 miles per hour. The torsional deflection of the first racquet, the Yonex Armotec 800, was measured at 11.5 degrees, and the torsional deflection of the second racquet, the Wilson® nCode® 1, was measured at 9.3 degrees. 
   Accordingly, the torsional stability tests indicates that two badminton racquets having substantially the same strung weight and head size and with handle portions having substantially the same outside diameter at their distal end regions produce significantly different torsional stability results. Specifically, the torsional stability test indicates that the racquet built in accordance with an embodiment of the present invention, the Wilson® nCode® 1, is over 20 percent more torsionally stable than the racquet having a generally conventional T-shaped reinforcing member, the Yonex Armotec 800. The second racquet exhibited a torsional deflection of less than 10.5 degrees when measured in the torsional stability test. The torsional deflection of the second racquet was also less than 10.0 degrees and less than 9.5 degrees. 
   A racquet having a high level of torsional stability, such as a racquet of the present invention, will provide better control and improved accuracy over a racquet having a low level of torsional stability. A racquet having improved torsional stability will also generally provide the player with better feel and a more enjoyable playing experience. 
   The present invention provides for a racquet with improved durability and reliability without negatively affecting the performance, playability and maneuverability of the racquet. The present invention provides these benefits without negatively affecting the weight of the racquet and without negatively affecting the flexibility of the racquet in the swing direction. Further, the present invention can be readily produced without significantly increasing the complexity or cost of the racquet. 
   While the preferred embodiments of the present invention have been described and illustrated, numerous departures therefrom can be contemplated by persons skilled in the art. Therefore, the present invention is not limited to the foregoing description but only by the scope and spirit of the appended claims.