Abstract:
Industry regulatory organizations have created performance restrictions for ball bats. The present invention relates to a ball bat with an internal impact dampening means. More particularly, the present invention relates to a ball bat with a handle, a barrel, and a central tube positioned coaxially within the barrel. The central tube includes at least one restriction member capable of limiting the deformation experienced by the ball bat upon impact of a ball. Precisely limiting the deformation of the ball bat allows the present invention to achieve, but not exceed, performance substantially equal to the maximum performance allowed by industry regulatory organizations and maintain that level of performance over a substantial length of the ball bat.

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/284,659, entitled BALL BAT WITH INTERNAL DAMPENING MEANS, filed Dec. 22, 2009 to George W. Burger and incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     Industry regulatory organizations have created performance restrictions for ball bats. The present invention relates to a ball bat with an internal impact dampening means. More particularly, the present invention relates to a ball bat with a handle, a barrel, and a central tube positioned coaxially within the barrel. The central tube includes at least one restriction member capable of limiting the deformation experienced by the ball bat upon impact of a ball. Precisely limiting the deformation of the ball bat allows the present invention to achieve, but not exceed, performance substantially equal to the maximum performance allowed by industry regulatory organizations and maintain that level of performance over a substantial length of the ball bat. 
     (b) Description of the Prior Art 
     Baseball and softball are very popular sports in the United States, Japan, Cuba, and elsewhere. While ball bats have traditionally been made of wood, metallic and/or composite ball bats having generally cylindrical, hollow barrels have emerged in recent years. 
     The performance of a ball bat is related to the force imparted to a ball upon impact. In a collision between a ball and a bat, enormous energy is required to halt and reverse the direction of a fast moving ball in a fraction of a second. Upon impact, a portion of this kinetic energy is converted into temporary compression or deformation of the ball bat. Much of this stored energy is returned to the ball as it leaves the bat. This phenomenon is generally referred to as the “trampoline effect.” The barrel of a ball bat has an optimal hitting area where the trampoline effect is maximized, referred to as the bat&#39;s “sweet spot.” 
     One issue affecting high performance ball bats is the introduction of performance restrictions on ball bats by industry regulatory organizations governing organized play. Many of these organizations have imposed limits or restrictions on the maximum performance of ball bats. In particular, a need exists for a ball bat capable of achieving, but not exceeding, performance substantially equal to the maximum performance allowed by industry regulatory organizations and maintaining that level of performance over a substantial length of the ball bat. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a novel design for a ball bat capable of achieving, but not exceeding, performance substantially equal to the maximum performance allowed by industry regulatory organizations and maintaining that level of performance over a substantial length of the ball bat. The present invention achieves the objective by including at least one restriction member capable of limiting the deformation of the ball bat, thereby decreasing the trampoline effect. 
     The present invention relates to a ball bat including a central tube coaxially positioned within the barrel of the ball bat. The central tube is attached to the end cap of the ball bat. The central tube includes at least one restriction member capable of limiting the deformation of the ball bat upon impact. Preferably, each restriction member is a washer-shaped member positioned coaxially around the central tube with a diameter slightly less than the inner diameter of the ball bat barrel. Each restriction member is a resilient object capable of resisting deformation. When the ball bat impacts a ball, the ball bat barrel transiently deforms and the inner surface of the barrel may contact one or more of the at least one restriction member. The end cap flexes as the barrel deforms, allowing the central tube to move from a coaxial position in a direction opposite from the impact until the at least one restriction member contacts the inner surface of the barrel on a side opposite from the impact. The barrel then returns to its original, non-deformed shape, and the central tube returns to a coaxial position therein. The transient deformation of the barrel is limited by contact with one or more of the at least one non-deforming restriction member. Restricting the deformation of the barrel limits the trampoline effect, thus decreasing bat performance. 
     The present invention may be customized to conform to different performance restrictions or different play styles. For example, a comparatively large restriction member may be used in a baseball league with severe restrictions on bat performance. A comparatively small restriction member may be used in a baseball league which requires only a slight decrease in performance for high performance bats. A smaller restriction member allows for greater deformation of the ball bat before the restriction member is contacted, thereby causing a smaller effect on the performance of the ball bat. The effective diameter of a restriction member may be increased by using a larger restriction member or by disposing a resilient member about the outer diameter of the restriction member. 
     High performance bats with large sweet spots may include a plurality of restriction members. For example, a ball bat may have a large sweet spot wherein the center of the sweet spot has a performance significantly above the allowed level and the edge of the sweet spot has a performance only slightly above the allowed level. Such a bat may include a larger restriction member positioned at a longitudinal station equal to the center of the sweet spot and a smaller restriction member positioned at the edge of the sweet spot. By using a plurality of restriction members with different diameters along the barrel of a ball bat, the deformation of the ball bat may be selectively limited. The present invention provides selective control over the deformation of a ball bat, thus controlling the trampoline effect and allowing fine control over the performance of a ball bat. 
     In one embodiment, the present invention is a ball bat comprising: a hollow barrel having an inner diameter; a central tube extending along a longitudinal axis, the central tube located coaxially within the barrel; and at least one restriction member positioned transverse to the longitudinal axis, the central tube extending through the at least one restriction member; whereby deformation of the barrel can be limited by the barrel coming into contact with at least one of the at least one restriction member. 
     In another embodiment, the present invention is a ball bat comprising: a hollow composite barrel having an inner diameter; a central tube extending along a longitudinal axis, the central tube having an end and being located coaxially within the barrel; at least one restriction member positioned transverse to the longitudinal axis, the central tube extending through the at least one restriction member; a generally cylindrical support including a support central channel, whereby the central tube extends at least partially through the support central channel; and an end cap including a central ring, the end cap positioned on an end of the barrel, the end of the central tube positioned within the central ring; whereby deformation of the barrel can be limited by the barrel coming into contact with at least one of the at least one restriction member. 
     In a further embodiment, the present invention is a method for making a ball bat comprising the steps of: (a.) providing a hollow barrel; (b.) providing a central tube extending along a longitudinal axis, the central tube sized to fit within the barrel without contacting the barrel; (c.) providing at least one restriction member including a restriction member central channel; (d.) providing a support, the support including a support central channel; (e.) serially positioning the central tube within the restriction member central channel and at least partially within the support central channel; and (f.) positioning the central tube coaxially within the barrel, whereby deformation of the barrel can be limited by the barrel coming into contact with at least one of the at least one restriction member. 
     In another embodiment, the present invention is a method of impacting a ball with a ball bat with reduced performance comprising the steps of: (a.) providing a ball bat comprising: (1.) a hollow barrel with an inner surface; (2.) a central tube positioned coaxially within the hollow barrel, and sized to fit within the barrel without contacting the barrel; (3.) at least one restriction member positioned transverse to the longitudinal axis, the central tube extending through the at least one restriction member; (4.) a void located between the at least one restriction member and the inner surface; and (b.) impacting a ball with the ball bat barrel, wherein the impact causes the ball bat barrel to transiently deform, causing the central tube to move from the coaxial position in a direction opposite from the impact until at least one of the at least one restriction member contacts the inner surface of the barrel on the side opposite from the impact, the central tube then returning to the coaxial position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings, wherein: 
         FIG. 1  depicts a ball bat; 
         FIG. 2A-2B  depict a top interior view and a cross-sectional view along lines  2 - 2  of an end cap; 
         FIG. 3A-3B  depict a knob-end view and a cross-sectional view along lines  3 - 3  of a central tube with two restriction members; 
         FIG. 4  depicts a cross-sectional view of the barrel of an embodiment of the ball bat of the present invention along lines  4 - 4  of  FIG. 1 ; 
         FIG. 5  depicts a cross-sectional view of the barrel of a second embodiment of the ball bat of the present invention along lines  4 - 4  of  FIG. 1 ; 
         FIG. 6  depicts a top interior cross-sectional view of an end cap and central tube mechanically locked with a split pin along lines  6 - 6  of  FIG. 5 ; 
         FIG. 7A-B  depict a side view and a cross sectional view along lines  7 - 7  of the restriction member of a third embodiment of the ball bat of the present invention; 
         FIG. 8A-B  depict a side view and a cross sectional view along lines  8 - 8  of the resilient member of the third embodiment of the ball bat of the present invention; 
         FIG. 9A-B  depict a side view and a cross sectional view along lines  9 - 9  of the restriction member resilient member of the third embodiment of the ball bat of the present invention including the resilient member; and 
         FIG. 10  depicts a cross-sectional view of the barrel of the third embodiment of the ball bat of the present invention along lines  4 - 4  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIG. 1 , an embodiment of the ball bat  10  of the present invention is shown having an end cap  12 , a barrel  14 , a transition region  16 , a handle  18 , and a knob  20 . The barrel  14  is a hollow tube and, in one embodiment, has an inner diameter of about 2.0 inches (5.08 cm). 
     As shown in  FIGS. 2A-B , the end cap  12  includes a central ring  22  stabilized by a plurality of ribs  24 . In one embodiment, the central ring  22  has an inside diameter of about 0.625 inches (1.59 cm). The end cap  12  may be secured to the barrel  14  by any suitable method, such as, for example, bonding with an adhesive, a friction fit, or a mechanical lock where an end cap ridge and corresponding barrel channel, or vice versa, secure the end cap  12  via mechanical interference. The end cap  12  may be manufactured using common manufacturing techniques, as known in the art. 
     With reference to  FIGS. 3B ,  4 , and  6 , the ball bat includes a central tube  26  coaxially positioned within the barrel  14 . The central tube  26  extends along a longitudinal axis  40  and includes an end  28  sized to snugly fit within the central ring  22 . The end  28  may be retained within the central ring  22  by any suitable means, such as, for example by bonding with an adhesive and with a pin  44 . In one embodiment, as shown in  FIG. 6 , corresponding central tube holes  46  and central ring holes  48  are formed, such that a split pin  44  may be inserted through the holes  46 ,  48 , mechanically locking the end  28  within the central ring  22 . 
     The central tube  26  may be constant diameter or variable diameter. In one embodiment, as shown in  FIG. 3 , the end  28  has an outer diameter of about 0.625 inches (1.59 cm), remaining constant for a length of about 0.755 inches (1.92 cm). The diameter of the central tube  26  then increases over a length of about 0.47 inches (1.19 cm) to a diameter of about 0.875 inches (2.22 cm), which remains generally constant for a length of 5.9 inches (15.0 cm). The total length of the central tube  26  is about 7.125 inches (18.1 cm). The central tube  26  may be made of any suitable material, such as, for example, composite fiber. 
     The central tube  26  includes at least one restriction member  50  capable of limiting the deformation experienced by the ball bat  10  upon impact of a ball. The at least one restriction member  50  is a generally washer-shaped member with a restriction member central channel  42 . The at least one restriction member  50  is positioned coaxially around the central tube  26 , with the central tube  26  positioned within the restriction member central channel  42  of the at least one restriction member  50 . The outer diameter of the at least one restriction member  50  is less than the inner diameter of the barrel  14 , creating a void  90  between the at least one restriction member  50  and the inner surface of the barrel  14 . In the embodiments shown in  FIGS. 4 and 5 , the outer diameter of the at least one restriction member  50  may be 75-95% the inner diameter of the barrel  14  or, preferably, 85-92% the inner diameter of the barrel  14 . The at least one restriction member  50  is composed of a resilient material capable of resisting deformation, such as aluminum or pre-impregnated composite fiber (“pre-preg”). In a preferred embodiment, the at least one restriction member  50  is composed of 7075 aluminum or laminated graphite pre-preg. 
     In one embodiment, as shown in  FIG. 3 , the central tube  26  includes a first restriction member  30 . In this embodiment, the first restriction member  30  has an outer diameter  51  of about 1.75 inches (4.45 cm), 87.5% the inner diameter of the barrel  14 , and a length  53  of about 0.11 inches (2.8 mm). The first restriction member  30  is located along the length of the central tube  26  at about the same longitudinal station as the center of the optimal hitting area or “sweet spot” of the ball bat  10 . In this embodiment, the first restriction member  30  is located about 6.5 inches (16.5 cm) from the end of the ball bat  10 . 
     In this embodiment, the central tube  26  further includes a second restriction member  32 . The second restriction member  32  has an outer diameter of about 1.70 inches (4.32 cm), 85% the inner diameter of the barrel  14 , and a length of about 0.11 inches (2.8 mm). The second restriction member  32  is located along the length of the central tube  26  at a position between the first restriction member  30  and the end cap  12 . In this embodiment, the second restriction member  32  is located about 5.0 inches (12.7 cm) from the end of the ball bat  10 . 
     In other embodiments, the central tube  26  may include a single restriction member, two, three, or more restriction members. The maximum performance of a ball bat  10  may be precisely controlled by varying the number of restriction members and the diameter, length, and location of each. 
     The ball bat  10  preferably includes a support  34 , as shown in  FIG. 4 . The support  34  is generally cylindrical and sized to snugly fit within the barrel  14 . The support  34  includes a support central channel  36  sized to snugly accept the central tube  26 . In one embodiment, the support  34  has a diameter of about 2.0 inches (5.08 cm) and the support central channel  36  has a diameter of about 0.875 inches (2.22 cm) and snugly accepts the 0.875 inch (2.22 cm) diameter section of the central tube  26 . 
     The central tube  26  extends at least partially through the support central channel  36 . Preferably, the support  34  is placed coaxially around the central tube  26  at a longitudinal station where the support  34  contacts at least one restriction member  50 . In an embodiment with a first restriction member  30  and second restriction member  32 , the support  34  is preferably placed coaxially around the central tube  26  between the first restriction member  30  and second restriction member  32 , as shown in  FIG. 4 . Preferably, the support is of sufficient length to contact both the first restriction member  30  and second restriction member  32 . In an embodiment where the first restriction member  30  is located about 6.5 inches (16.5 cm) from the end of the ball bat  10  and the second restriction member is located about 5.0 inches (12.7 cm) from the end of the ball bat  10 , the support  34  has a length of about 1.39 inches (3.53 cm), which places the support  34  in contact with both the 0.11 inch (2.8 mm) long restriction members. In an embodiment with a third or more restriction members, the present invention preferably includes additional supports  34  positioned between each pair of restriction members. In an embodiment with a single restriction member, as shown in  FIG. 5 , the support is preferably placed coaxially around the central tube  26  on a side of the restriction member opposite the end cap  12 , such that the central tube  26  extends partially through the support central channel  36 . 
     The support  34  may be made of any suitable material, such as, for example, foam, or preferably, expanded polyproplyene (“EPP”) foam with a density between 1.0 and 2.0 lb/cu. ft. (16.0-32.0 g/l), ideally about 1.3 lb/cu. ft (20.8 g/l). By contacting at least one restriction member  50 , the support  34  serves to dampen any vibration of the at least one restriction member  50  and the central tube  26  that occurs as a result of an impact between the ball bat  10  and a ball. 
     For example purposes only, a central tube  26  may be made by rolling at least one flat sheet of pre-preg around an appropriately shaped mandrel, thereby making a variable diameter tube as described above. In a preferred embodiment, the sheet of pre-preg comprises six layers of graphite pre-preg with fibers angled +/−20 degrees from the longitudinal with each layer orientated at a negative angle to the previous layer. Each layer has a height of about 0.005 inches (0.127 mm), providing a central tube  26  with a thickness of about 0.03 inches (0.76 mm). 
     At least one restriction member  50  is positioned on the central tube  26  at the appropriate longitudinal station. The central tube  26  is then placed in a mold conforming to the shape of the central tube  26  including the at least one restriction member  50 . The mold includes at least one pair of hollows where excess composite fiber may be added. For each pair of hollows, one hollow is located adjacent to and on the end cap  12  side of a restriction member  50  and the other hollow is located adjacent to and on the knob  20  end side of the same restriction member  50 . Upon curing, the excess composite fiber in each hollow forms a protrusion on the central tube  26  extending perpendicular to the longitudinal axis  40  of the central tube  26 . Each protrusion has a height of about 0.11 inches (2.8 mm). Each pair of protrusions creates and defines a groove  38  extending perpendicular to the longitudinal axis  40  of the central tube  26 . Each groove  38  is sized such that it may secure and retain a restriction member  50  by mechanical interference. In one embodiment, each groove  38  has a length of about 0.11 inches (2.8 mm). In an embodiment including a plurality of restriction members, as shown in  FIGS. 3B and 4 , the central tube  26  includes a plurality of grooves  38 , whereby each groove  38  accepts and secures one restriction member  50  at the desired longitudinal station. 
     After curing, the central tube  26  is positioned within the support central channel  36 . In a preferred embodiment, a slit is introduced into the support  34 , such that the support  34  may be opened in a clamshell fashion to receive the central tube  26 . 
     The handle  18  is a mostly constant diameter hollow tube. The handle  18  may be manufactured using common manufacturing techniques. 
     For example purposes only, a composite handle  18  may be made by rolling at least one flat sheet of pre-preg around a mandrel, thereby making a tube with an outer diameter appropriately sized for a ball bat handle. In a preferred embodiment, the sheet of pre-preg comprises two layers of graphite pre-preg with fibers angled +/−15 degrees from the longitudinal with one layer orientated at a negative angle to the other layer. Two layers of pre-preg with a height of about 0.005 inches (0.127 mm) and fibers angled 90 degrees from the longitudinal are wrapped around the last 7.87 inches (20.0 cm) of the handle  18  at the end opposite the knob  22 . 
     The barrel  14  is a mostly constant diameter hollow tube that tapers through a transition region  16  to the handle  18 . In one embodiment, the barrel  14  is made of composite material. The composite barrel  14  may be manufactured using common manufacturing techniques. 
     For example purposes only, a composite barrel  14  may be manufactured by spirally rolling 24 layers of high aspect ratio parallelogram-shaped pieces of pre-preg, each layer having a height of about 0.005 inches (0.127 mm), on a rolling mandrel with the fibers oriented longitudinally, thereby making a tube with an outer diameter appropriately sized for a ball bat barrel. The parallelograms are rolled up such that each layer has a butt joint with itself and such that on one end all the layers stop at the same longitudinal station but on the other end, each layer is about 2.54 inches (1.0 cm) shorter than the previous layer, creating a tapered end. In one embodiment, the layers are angled +/−37 degrees from the longitudinal with each layer orientated at a negative angle to the previous layer. 
     After being rolled up, a tapered mandrel is added to one end of the rolling mandrel immediately after where the lay-up ends on the tapered end. Rubber bands are placed around the lay-up on this end, then the entire assembly is partially slid off the rolling mandrel and onto the tapered mandrel, forming a tapered transition region  16 . In one embodiment, the transition region  16  is about 8.0 inches (20.3 cm) in length. 
     The barrel  14  is removed from the mandrels and a portion of the handle  18  is inserted. An inflatable bladder is inserted into the ball bat  10  assembly and a standard knob  20  is applied using techniques common in the industry. The bladder is inflated, expanding the barrel  14  and handle  18 . The assembly then is placed into a ball bat-shaped mold under pressure and heated to cure the ball bat, using standard techniques known in the art. After curing, the end cap  12  and central tube  26  are inserted into the ball bat  10 . 
       FIG. 5  depicts a second embodiment of the ball bat  110  of the present invention wherein the at least one restriction member  50  is a single restriction member  130 . In this embodiment, the single restriction member  130  has a diameter of about 1.75 inches (4.45 cm) and a length of about 0.11 inches (2.8 mm). The single restriction member  130  is located along the length of the central tube  26  at about the same longitudinal station as the center of the optimal hitting area or “sweet spot” of the ball bat  10 , about 6.5 inches (16.5 cm) from the end of the ball bat  10 . In this embodiment, the central tube  126  includes a single groove  138  which secures and retains the single restriction member  130 . The support  134  is preferably positioned around the central tube  126  on a side of the single restriction member  130  opposite the end cap  12 . In this embodiment, the 1.39 inch (3.53 cm) long support  134  will extend past the central tube  26 , as shown in  FIG. 5 . In alternative embodiments, a shorter support  134  may be used such that the support  134  does not extend past the central tube  26 . 
     In a third embodiment of the present invention, as shown in  FIGS. 7A-B ,  8 A-B,  9 A-B, and  10 , a ball bat  210  may include at least one resilient member  252  disposed about at least one of the at least one restriction member  250 . As previously discussed, when the ball bat  210  impacts a ball, the barrel  214  transiently deforms until the inner surface of the barrel  214  contacts the at least one restriction member  250 . The resilient member  252  increases the effective diameter of the at least one restriction member  250 , which provides a smaller void  290  between the at least one restriction member  250  and the inner surface of the barrel  214 , which can further limit the performance of the ball bat  210 . Use of at least one resilient member  252  has also been found to affect the sound upon impact between a ball and the ball bat  210 . In one embodiment, the at least one resilient member  252  is a rubber ring encircling or otherwise disposed about the at least one restriction member  250 , as shown in  FIGS. 9A-B . In a preferred embodiment, the resilient member  252  is a rubber ring with a hardness of about 90-95 Shore A. In embodiments including a plurality of restriction members  250 , resilient members  252  may be disposed about none, less than all, or all of the plurality of restriction members  250 . 
     Referring now to  FIGS. 7A-B , the at least one restriction member  250  of the third embodiment is preferably shaped to retain the resilient member  252  about the at least one restriction member  250 . In one embodiment, where the inner diameter of the barrel  214  is 2.28 inches (5.79 cm), the at least one restriction member has a diameter of about 2.124 inches (5.38 cm) and includes a restriction member central channel  242  with a diameter of about 0.875 inches (2.22 cm). The at least one restriction member  250 , at a position adjacent of the restriction member central channel  242 , has a length of about 0.3 inches (7.6 mm) and maintains this length from a diameter 0.875 inches (2.22 cm) to about 1.148 inches (2.92 cm). The length of the at least one restriction member  250  is about 0.08 inches (2.0 mm) from a diameter of about 1.148 inches (2.92 cm) to about 1.752 inches (4.45 cm). The length of the at least one restriction member  250  increases at about a 45 degree angle from 0.08 inches (2.0 mm) to 0.3 inches (7.6 mm) as the diameter increases from about 1.752 inches (4.45 cm) to about 1.86 inches (4.72 cm). The at least one restriction member  250  maintains the length to a diameter of about 2.114 inches (5.37 cm), then, on either end of its length, decreases on a curve with a radius of 0.01 inches (0.25 mm) to a maximum diameter of 2.124 inches (5.38 cm). The diameter of the at last one restriction member  250  then decreases at about a 15 degree angle to a diameter of 2.07 inches (5.26 cm), forming a restriction member groove  254  about 0.25 inches (6.4 mm) in length bounded by a pair of projections  256 . Other designs for shaping the at least one restriction member  250  to retain the at least one resilient member will be apparent to individuals skilled in the art. 
     The resilient member  252  in this embodiment has a inner diameter  258  of about 2.07 inches (5.26 cm) and an outer diameter  260  of about 2.25 inches (5.72). The resilient member  252  is sized to fit within the restriction member groove  254  and preferably includes a length about equal to or less than the length of the restriction member groove  254 . As shown in  FIGS. 9A and 9B , the resilient member  252  encircles the at least one restriction member  250 , and is retained within the restriction member groove  254  by the projections  256 . In this embodiment, where the inner diameter of the ball bat is 2.28 inches (5.79 cm), there is a 0.03 inch (0.76 mm) void  290  between the resilient member  252 . The outer diameter  260  of the resilient member  252  may 90-99.5% the inner diameter of the barrel  214 , or preferably 94-99% the inner diameter of the barrel  214 . In this particular embodiment, the outer diameter  260  of the resilient member  252  is 98.7% the inner diameter of the barrel  214  and the length of the resilient member is about 0.236 inches (6.0 mm). 
     In the third embodiment, as shown in  FIG. 10 , the central tube  226  includes a first restriction member  230 . In this embodiment, the inner diameter of the barrel  214  is 2.28 inches (5.79 cm) and the total length of the ball bat  210  is 32 inches (81.3 cm). In this embodiment, the first restriction member  230  has a diameter of about 2.03 inches (5.16 cm) to the surface of the restriction member groove  254 , and a diameter of about 2.08 inches (5.28 cm) to the tips of the projections  256 . A first resilient member  262  is disposed about the first restriction member  230  in the restriction member groove  254 , and has an outer diameter  260  of about 2.21 inches (5.61 cm). The second restriction member  232  has a length of about 0.3 inches (7.6 mm). The first restriction member  230  is located along the length of the central tube  26  at about the same longitudinal station as the center of the optimal hitting area or “sweet spot” of the ball bat  210 . In this embodiment, the first restriction member  230  is located about 6.75 inches (17.1 cm) from the end of the ball bat  210 . 
     In this embodiment, the central tube  226  further includes a second restriction member  232 . The second restriction member  232  has a diameter of about 2.07 inches (5.26 cm) to the surface of the groove  254 , and a diameter of about 2.12 inches (5.38 cm) to the tips of the projections  256 . A second resilient member  264  is disposed about the second restriction member  232  in the restriction member groove  254 , and has an outer diameter  260  of about 2.25 inches (5.72 cm). The second restriction member  232  has a maximum length of about 0.3 inches (7.6 mm). The second restriction member  232  is located along the length of the central tube  26  at a position between the first restriction member  230  and the end cap  12 . In this embodiment, the second restriction member  232  is located about 5.25 inches (13.3 cm) from the end of the ball bat  210 . 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention.