Patent Publication Number: US-9895588-B2

Title: Ball bat including a stiffening element in the barrel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/251,181, filed Apr. 11, 2014 and now pending, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Baseball and softball governing bodies have imposed various bat performance limits over the years with the goal of regulating batted ball speeds. Each association generally independently develops various standards and methods to achieve a desired level of play. Bat designers typically comply with these performance standards by adjusting the performance, or bat-ball coefficient of restitution (“BBCOR”), of their bat barrels. Typical methods of controlling BBCOR include thickening the barrel wall of a hollow metal bat, or increasing the radial stiffness of a composite bat via the selection of specific materials and fiber angles. A composite bat&#39;s radial stiffness and fiber orientations are limited, however, by a given material thickness. The barrel walls in composite bats, therefore, are also often thickened to provide additional stiffness, which in turn limits BBCOR and barrel performance. 
     Thickening a barrel wall generally increases the bat&#39;s weight and, more importantly, it&#39;s “swing weight” or moment of inertia (“MOI”). MOI is the product of: (a) a mass, and (b) the square of the distance between the center of the mass and the point from which the mass is pivoted. Mathematically, this is expressed as follows:
 
MOI=ΣMass×(Distance) 2  
 
     Accordingly, the MOI dictates that it becomes increasingly difficult to swing a bat as the bat&#39;s mass increases or as the center of the bat&#39;s mass moves farther from the pivot point of the swing (i.e., farther from the batter&#39;s hands). Because thickening the barrel wall increases the bat&#39;s weight at a region relatively distal from the batter&#39;s hands, doing so also increases the bat&#39;s MOI. Thus, while thickening a barrel wall effectively stiffens the barrel and reduces its performance, the consequent increase in MOI is generally undesirable for batters. 
     SUMMARY 
     A ball bat includes a barrel in which one or more stiffening elements are located. The stiffening element may be positioned at a variety of locations, and may have a variety of configurations, for selectively limiting the barrel&#39;s performance without appreciably increasing the bat&#39;s moment of inertia. In one configuration, the stiffening element includes two radially outer flanges, a radially inner flange, and two web members connecting the outer flanges to the inner flange. The radially outer surfaces of the radially outer flanges contact, and may be affixed to, the inner surface of the barrel wall. Other features and advantages will appear hereinafter. The features described above can be used separately or together, or in various combinations of one or more of them. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side-sectional view of a ball bat, according to one embodiment. 
         FIG. 2  illustrates a stiffening element in a ball bat, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these embodiments. One skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or functions may not be shown or described in detail so as to avoid unnecessarily obscuring the relevant description of the various embodiments. 
     The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this detailed description section. 
     Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of items in the list. Further, unless otherwise specified, terms such as “attached” or “connected” are intended to include integral connections, as well as connections between physically separate components. 
     The embodiments described herein are directed to a ball bat having a limited bat-ball coefficient of restitution (“BBCOR”), or limited barrel performance, allowing the bat to perform within regulatory association performance limits. The National Collegiate Athletic Association (“NCAA”), for example, has proposed limiting a barrel&#39;s BBCOR to below 0.510 or below 0.500. Limiting of the BBCOR is preferably accomplished without appreciably increasing (or by decreasing) the ball bat&#39;s moment of inertia (“MOI”). 
     Turning now in detail to the drawings, as shown in  FIG. 1 , a baseball or softball bat  10 , hereinafter collectively referred to as a “ball bat” or “bat,” includes a handle  12 , a barrel  14 , and a tapered section  16  joining the handle  12  to the barrel  14 . The free end of the handle  12  includes a knob  18  or similar structure. The barrel  14  is preferably closed off by a suitable cap  20  or plug. The interior of the bat  10  is optionally hollow, allowing the bat  10  to be relatively lightweight so that ball players may generate substantial bat speed when swinging the bat  10 . The ball bat  10  may be a one-piece construction or may include two or more separate attached pieces (e.g., a separate handle and barrel), as described, for example, in U.S. Pat. No. 5,593,158, which is incorporated herein by reference. 
     The ball bat  10  is preferably constructed from one or more composite or metallic materials. Some examples of suitable composite materials include fiber-reinforced glass, graphite, boron, carbon, aramid, ceramic, Kevlar, or Astroquartz®. Aluminum or another suitable metallic material may also be used to construct the ball bat  10 . A ball bat including a combination of metallic and composite materials may also be constructed. For example, a ball bat having a metal barrel and a composite handle, or a composite barrel and a metal handle, may be used in the embodiments described herein. 
     The bat barrel  14  may include a single-wall or multi-wall construction. A multi-wall barrel may include, for example, barrel walls that are separated from one another by one or more interface shear control zones (“ISCZs”), as described in detail in U.S. Pat. No. 7,115,054, which is incorporated herein by reference. An ISCZ may include, for example, a disbonding layer or other element, mechanism, or space suitable for preventing transfer of shear stresses between neighboring barrel walls. A disbonding layer or other ISCZ preferably further prevents neighboring barrel walls from bonding to each other during curing of, and throughout the life of, the ball bat  10 . 
     The ball bat  10  may have any suitable dimensions. The ball bat  10  may have an overall length of 20 to 40 inches, or 26 to 34 inches. The overall barrel diameter may be 2.0 to 3.0 inches, or 2.25 to 2.75 inches. Typical ball bats have diameters of 2.25, 2.625, or 2.75 inches. Bats having various combinations of these overall lengths and barrel diameters, or any other suitable dimensions, are contemplated herein. The specific preferred combination of bat dimensions is generally dictated by the user of the bat  10 , and may vary greatly between users. 
     The ball striking area of the bat  10  typically extends throughout the length of the barrel  14 , and may extend partially into the tapered section  16  of the bat  10 . For ease of description, this striking area will generally be referred to as the “barrel” throughout the remainder of the description. A bat barrel  14  generally includes a maximum performance location or “sweet spot,” which is the impact location where the transfer of energy from the bat  10  to a ball is maximal (in the absence of a stiffening element or other performance-reducing feature located at or near the sweet spot), while the transfer of energy to a player&#39;s hands is minimal. The sweet spot is generally located at the intersection, i.e., average location, of the bat&#39;s center of percussion (COP) and its first three fundamental nodes of vibration. This location, which is typically about 4 to 8 inches from the free end of the barrel  14 , does not move appreciably when the bat is vibrating. While the sweet spot is not typically located precisely at the COP of the bat, for ease of description, and for ease in locating the “sweet spot” in a given ball bat, the COP will be considered the location of the sweet spot throughout this description. The COP of a ball bat may be measured using ASTM F2398-11. 
     The barrel regions between the sweet spot and the free end of the barrel  14 , and between the sweet spot and the tapered section  16  of the bat  10 , do not provide the maximum performance that occurs at the sweet spot of the barrel  14 . Indeed, in a typical ball bat, the barrel&#39;s performance, or trampoline effect, decreases as the impact location moves away from the sweet spot. Accordingly, the sweet spot generally requires the greatest limitation or reduction of BBCOR to bring the bat within regulatory association limits. 
     One approach to reducing BBCOR without significantly increasing MOI is to include one or more stiffening elements in the bat barrel, as described, for example, in U.S. Pat. No. 8,298,102, which is incorporated herein by reference. In one embodiment, a stiffening element  22  is positioned in the bat barrel  14 , at or near the sweet spot of the barrel  14 , to limit or reduce the BBCOR of the barrel  14  (such that the sweet spot is no longer the maximum performance location in the barrel). The stiffening element  22  may be co-molded with the inner surface of a composite bat barrel, or may be adhesively bonded, welded, or otherwise affixed to the inner surface of a composite or metallic bat barrel. In some embodiments, the stiffening element  22  may optionally be spaced from, and affixed to, the inner surface of the bat barrel  14 . In other embodiments, the stiffening element  22  may alternatively be held in place in the barrel via an interference fit. Further, in some embodiments, more than one stiffening element may be positioned in the bat barrel  14 . 
     Any of the stiffening elements described herein, unless otherwise specified, may be made of any suitable stiffening materials. A stiffening element may be made of, for example, aluminum, titanium, or steel; composites of polyester, epoxy, or urethane resins with fibers of carbon, glass, boron, Spectra®, Kevlar®, Vectran®, and so forth, including sheet molding compound or bulk molding compound; or thermoplastics such as ABS, nylon, polycarbonate, acrylic, PVC, Delrin®, and so forth, with or without additive fibers, platelets, and particulates, such as nano-clay, nano-particulates, platelets, or short or long fibers of glass, carbon, and so forth. 
     While the dimensions and weight of the stiffening elements may vary greatly depending on the requirements of a particular regulatory association or batter, it is generally preferred that they weigh less than one ounce so as to minimize the effect on the bat&#39;s MOI. In some applications, however, heavier stiffening elements may be used. 
     Further, while it is generally preferred that the stiffening elements be positioned at or near the sweet spot of the barrel  14 , it may be preferable in some embodiments to locate a stiffening element in other bat regions, such as closer to the handle  12  to limit the increase in MOI resulting from inclusion of the stiffening element. While doing so may necessitate an “over-reduction” in BBCOR at the location of the stiffening element (since the sweet spot will still need to be brought within association performance limits, and a lesser reduction in BBCOR generally occurs at locations spaced from the stiffening element), the tradeoff in substantially reduced MOI may be preferred for certain bats or batters. Thus, depending on the design goals for a particular bat, stiffening elements may be utilized at one or more locations of the ball bat  10 . 
     The inclusion of one or more stiffening elements  22  in the barrel  14 , as opposed to significantly thickening a substantial portion of the barrel  14 , provides a significant reduction in BBCOR without a substantial increase in the bat&#39;s MOI. Surprisingly, inclusion of a single stiffening element  22  can appreciably reduce BBCOR along a substantial length of the bat barrel  14 . 
       FIG. 2  illustrates a ball bat including one embodiment of a stiffening element  84  that increases barrel stiffness over a substantial length of the barrel. The bat includes a barrel wall  82  that may be of uniform or varying thickness, depending on local stiffness goals. The stiffening element  84  includes two annular base members or radially outer flanges  86   a  and  86   b , an annular radially inner flange  88 , and two web members or webs  90   a  and  90   b  connecting the outer flanges  86   a  and  86   b  to the inner flange  88 . The radially outer surfaces of the radially outer flanges  86   a  and  86   b  contact the inner surface of the barrel wall  82 . In some embodiments, they may be affixed or otherwise connected to the inner surface of the barrel wall  82 . 
     This “double-web” stiffening element  84  with an elongated inner flange  88  includes more material located toward a centerline  98  of the bat barrel  82  than does a typical single-web design, resulting in a stiffening element  84  with a higher cross-sectional moment of inertia. Further, the centroid of the stiffening element  84  may be located closer to the centerline  98  of the barrel if the radially inner flange  88  is of sufficient length, resulting in increased barrel stiffness relative to a single-web design. 
     This configuration also increases stiffness over a greater length of the barrel  82  because the radially inner flange  88  is connected at both of its ends by stiffening webs  90   a  and  90   b . Additionally, smaller diameter pipes or flanges have a higher hoop stiffness than larger diameter pipes or flanges of like material, and the longer the flange  88 , the greater the stiffness effect on the barrel. As a result, the double-web stiffening element  84  may be relatively lightweight, which minimizes the overall bat weight and MOI in a manner that is generally not possible with single-web designs. Indeed, a limitation of single-web stiffening elements is that they increase barrel stiffness where the web is located but the overall length of the stiffness zone may be somewhat limited. 
     The stiffening element  84  may have any suitable dimensions to meet desired stiffness and performance goals. In one embodiment, the radially outer flanges  86   a  and  86   b  are each approximately 0.375 inches long and run parallel to the bat axis  104 . The outside diameter of each of the radially outer flanges  86   a  and  86   b  may be designed to fit tightly within a bat barrel. For example, the outer flanges  86   a  and  86   b  may each have an outside diameter of approximately 2.400 inches to fit tightly inside of a typical baseball bat barrel. The connecting webs  90   a  and  90   b  may be angled at approximately 10-45 degrees from a line running perpendicular to the bat&#39;s centerline or axis  98 . In one embodiment, the connecting webs  90   a  and  90   b  are angled at approximately 15 degrees from such a line (i.e., 105 degrees from the longitudinal axes of the outer flanges  86   a  and  86   b ). 
     The radially inner flange  88  runs between the radially inner ends of the webs  90   a  and  90   b . The inner flange  88  may be oriented in the same direction or in substantially the same direction as the outer flanges  86   a  and  86   b  (i.e., parallel or substantially parallel to the centerline  98  of the barrel  82 ). The inner flange  88  may have a length of approximately 0.10 inches to 0.60 inches. In one embodiment, the inner flange  88  has a length of approximately 0.13 inches. 
     The radially outer surface of the inner flange  88  may be spaced from the radially outer surface of each outer flange  86   a  and  86   b  (in a direction perpendicular to the barrel&#39;s centerline  98 ) by approximately 0.10-0.40 inches. In one embodiment, this spacing is approximately 0.32 inches. The thickness of the inner flange  88  may be approximately 0.03 inches to 0.150 inches. In one embodiment, the inner flange has a thickness of approximately 0.08 inches. The overall length of the stiffening element  84  in the direction of the barrel&#39;s centerline  98  (i.e., the distance between the extreme ends of the outer flanges  86   a  and  86   b ) may be approximately 1.0-2.0 inches. In one embodiment, the stiffening element  84  has a length of approximately 1.25 inches. 
     As described above, the stiffening element  84  may be made of one or more suitable materials. For example, it may be made of a metal or composite material. Some suitable metals include aluminum and aluminum alloys, as well as light weight metals such as titanium and magnesium. A metal stiffening element  84  may be made via machining, forging, casting, or welding. Some suitable composite materials include fibers of carbon, glass, aramid, flax, boron, ceramic, or nano-based materials. Suitable resins for the composite material may include thermoset resins of epoxy, polyester, phenolic, or vinylester, or thermoplastic resins of polyamide, polyurethane, polypropylene, polyphenylsulfide, or polyehteretherketone. 
     In one embodiment, a carbon-fiber-reinforced epoxy material, or other fiber-reinforced epoxy material, is used to form the stiffening element  84 . The stiffening element  84  may be formed, for example, using carbon-fiber strips preimpregnated with epoxy resin. The strips may have any suitable dimensions and fiber angles. Fiber angles of 90 degrees relative to the centerline  98  or axis of the bat produce the highest effective modulus of the stiffening element. Due to shear loads resulting from barrel compression, however, plies oriented at approximately +/−60 degrees relative to the barrel axis may be desired to adequately transfer stress. 
     The preimpregnated strips may be rolled into a tubular preform to conform to the dimensions of a mold used to form the stiffening element  84 . A typical mold may include two halves with annular protrusions that shape the stiffening element  84 . Once formed, the tubular preform is placed in the mold and a bladder is positioned inside the preform. The bladder may be made of silicone rubber or of another material that restricts shifting of the preimpregnated strips. The mold is then closed and heat is applied. As the preform warms up, air pressure is applied inside the bladder. The preform expands to conform to the mold cavity. After the mold cycle is completed, the air pressure is released and the mold is cooled. Once the stiffening element  84  cools, it may be removed from the mold. 
     Features of the above-described embodiments may be used alone or in combination with one another. Furthermore, the ball bats may include additional features not described herein. While several embodiments have been shown and described, various changes and substitutions may of course be made, without departing from the spirit and scope of the invention. The invention, therefore, should not be limited, except by the following claims and their equivalents.