Patent Publication Number: US-6334825-B1

Title: End cap assembly for thin wall metal ball bats

Description:
BACKGROUND OF THE INVENTION AND PRIOR ART 
     1. Field of the Invention 
     The present invention relates to hollow bats primarily for softball and, more particularly, to metallic and composite hard shell bats. Such bats typically include a metal outer shell which may be formed of aluminum or titanium alloy or other metals or may be made of composite construction. As referred to herein, the terms “aluminum” and “titanium” are intended to encompass the metals and alloys and mixtures of metals and alloys formulated for the manufacture of bat shells. 
     2. Prior Art 
     Various methods of affixing end caps to the tubular barrel end of baseball bats are known. Typically, the end cap includes a cylindrical plug or skirt which is which may be cast in place or force fit so as to be closely received in the end of the barrel and affixed thereto by adhesive or by a mechanical interlock or both. See, for example the Heald U.S. Pat. No. 3,729,196 issued Apr. 24, 1973; the Wilson U.S. Pat. No. 3,735,473 issued May 29, 1973 and U.S. Pat. No. 3,811,596 issued May 21, 1974; the Pouzou U.S. Pat. No. 3,834,698 issued Sep. 10, 1974; and the Souders, et al U.S. Pat. No. 5,395,108 issued Mar. 7, 1995. 
     OBJECT OF THE INVENTION 
     The primary objective of the invention is to provide an end cap assembly for thin wall tubular baseball and softball bats, particularly aluminum bats, so that the thin wall barrel need not be machined or otherwise reconfigured to facilitate attachment of an end cap thereto. 
     SUMMARY OF THE INVENTION 
     The present invention provides an end cap assembly for closing the open end of a tubular ball bat having a thin generally cylindrical barrel wall, said assembly comprising a cylindrical sleeve sized to slidably and closely fit into the barrel of the bat, said sleeve providing an annular cap seat at one end of said sleeve, and an annular groove on an exterior annular surface of said sleeve for defining an annular glue chamber with said barrel, a glue fill port extending through said sleeve from the interior of said sleeve to said annular groove, said sleeve also having an internal annular recess for receiving an annular lock collar on a depending skirt of a bat end cap, said recess being axially spaced from said annular cap seat, and a bat end cap having an axially extending annular skirt and an annular lock collar on the exterior surface of said skirt, said collar being closely received in said annular recess in said sleeve for affixing said cap to said sleeve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of the barrel end of a prior art bat having a urethane end cap affixed thereto. 
     FIG. 2 is a cross sectional view of the barrel end of a thin wall bat and an end cap assembly according to the invention affixed thereto by adhesive. 
     FIG. 3 is a substantially enlarged partial end view of the bat barrel and end cap affixation sleeve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A tubular baseball bat ordinarily includes a metal or metal alloy shell which may be of aluminum or other metals, a handle, a barrel and a tapered section interconnecting the handle and the barrel. A knob closes the handle end of the bat and an end cap is typically affixed to the barrel end of the bat as is well known. 
     Reduction of the wall thickness of the outer shell of a tubular bat desirably reduces the weight of the bat but undesirably increases the longitudinal flexibility thus absorbing a portion of the batter&#39;s energy which would otherwise be imparted to the ball and may result in permanent denting of the bat if the wall is too thin. Thinning of the wall of a metal shell bat desirably results in higher ball rebound velocity due to more significant flexing of the bat wall, commonly referred to as “trampoline effect”. Composite shell bats and metal shell bats with resilient walls are intentionally designed to permit controlled localized flexing of the outer bat wall. The present invention is directed to affixation of the end cap to the newer thinner wall bats and, while primarily designed for aluminum bats, the teachings of the invention may be easily adapted to thin wall tubular bats of other metals or materials. 
     A bat and cap  10 , which may be molded of a plastic such as urethane or formed of metal, includes a domed head  12  and an integral cylindrical skirt  14  which extends axially of the bat as seen in FIG. 1 into the end of the barrel  16  of the bat. Circumferentially spaced webs  15  radially support the skirt  14  which has an exterior taper  13  for assisting insertion of the end cap  10  into the barrel  16  of the bat. A mechanical lock between the end cap skirt  14  and barrel  16  is provided by machining or otherwise forming an annular recess  18  in the internal wall of the barrel so that an externally projecting annular lock collar  20  on the end cap skirt  14  can be snapped into the recess  18  to firmly affix the end cap to the barrel. Adhesive is typically also applied to meeting areas of the barrel  16  and end cap  10  for additional adhesion. As is seen in FIG. 1, the end  17  of a prior art bat barrel  16  is of sufficient wall thickness to provide a seat for engagement with an annular lip  19  on the underside of the head of the end cap for seating the lip  19  cap flush with the end  17  of the barrel. The axially abutting radially extending shoulders  22 ,  23  of the recess  18  and the lock collar  20  prevent axial movement of the end cap relative to the bat in a direction tending to detach the cap from the bat. Since a typical prior art aluminum bat has a barrel wall thickness in the range of 0.055″ to 0.120″, the wall of barrel  16  is of sufficient thickness to permit machining of the locking recess  18  without undue weakening of the bat. 
     With the newer thin walled bats having aluminum barrel walls in the range of 0.036-0.055 inches (for softball bats), machining of an annular groove in the internal surface of the barrel of sufficient depth to engage a locking collar on the end cap is impractical. Accordingly, a cylindrical end cap reception sleeve  30 , preferably of aluminum, has been provided as shown in FIG.  2 . The sleeve  30  has an outside diameter, at the top and bottom of the sleeve, sized to slidably and closely fit the sleeve into the barrel  16  of the bat. The upper end surface of the sleeve  30  thus is of sufficient width to provide an annular cap seat  32  of sufficient width to engage the radially extending lip  19  on the end cap  10  to prevent movement of the cap into the sleeve and into the barrel of the bat. 
     An annular groove  34  is provided on the exterior cylindrical wall of the sleeve  30  so that, when the sleeve  30  is slid into the barrel  16 , the sleeve and bat barrel together define an annular glue chamber  36  for receiving liquid adhesive to adhere the sleeve firmly to the barrel. Preferably, the sleeve is machined with O-ring grooves at the top and bottom ends of the annular glue chamber for receiving rubber O-rings  40 ,  42  to resiliently seal the glue chamber. At least one, and preferably a plurality, of circumferentially spaced glue fill ports  44  extend through the sleeve  30  from the interior of the sleeve to the annular glue chamber  36 . 
     The sleeve  30  also is provided with an annular groove  48  on its inside cylindrical surface for receiving the radially projecting annular lock collar  20  on the axially depending skirt  14  of the bat end cap, the internal groove  48  being of sufficient width and depth to closely receive and prevent the collar  20  from axially moving relative to the sleeve. 
     As is known in the art of bat manufacture, a bat end cap  10  such as one made of urethane, allows sufficient flexibility of the axially extending skirt  14  to permit insertion of the skirt into the sleeve  30 , the inherent resilience of the skirt enabling snap fitting the radially projecting collar  20  into the annular groove  48  to firmly affix the end cap to the sleeve  30  after the sleeve  30  has been inserted into and adhesively affixed to the barrel  16  by injecting glue through the fill ports  44  to substantially completely fill the annular glue chamber  36 . It will be noted that the above construction requires no machining of the barrel of a thin wall bat yet provides an efficient and easy to affix an end cap thereto. 
     Persons skilled in the art will appreciate that various modifications of the invention can be made from the above described preferred embodiment and that the scope of protection is limited only by the following claims. Also, those skilled in the art of bat manufacture will understand that the bat end cap assembly disclosed herein need not be limited to thin wall bats. Use of the cylindrical sleeve is also useful, for example, in the manufacture of other bats such as those which have inner sleeves of the same or of different materials such as carbon core bats or dual metal wall bats.