Controlling the stiffness of a hollow metal bat by providing helical internal ribs

Abstract

A hollow metal bat comprising an elongated tubular structure having a barrel portion, a handle portion and a tapered portion connecting the barrel portion to the handle portion, and further comprising at least one helical internal rib formed along at least a portion of the elongated tubular structure.

1 . A hollow metal bat comprising an elongated tubular structure having a barrel portion, a handle portion and a tapered portion connecting the barrel portion to the handle portion, and further comprising at least one helical internal rib formed along at least a portion of the elongated tubular structure. 
     
     
         2 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib is formed along at least a portion of the barrel portion. 
     
     
         3 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib is formed along the entire barrel portion. 
     
     
         4 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib is formed along the entire elongated tubular structure. 
     
     
         5 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib has a clockwise orientation as the helical internal rib extends distally down the bat. 
     
     
         6 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib has a counter-clockwise orientation as the helical internal rib extends distally down the bat. 
     
     
         7 . A hollow metal bat according to  claim 1  wherein the bat is formed by flowforming. 
     
     
         8 . A hollow metal bat according to  claim 1  wherein the bat is formed by at least one from the group consisting of swaging, impact extruding, drawing over a mandrel (DOM), machining, and casting. 
     
     
         9 . A hollow metal bat according to  claim 1  wherein the at least one helical internal rib has its pitch, height and width profile tailored to provide the desired characteristics for the bat. 
     
     
         10 . A hollow metal bat according to  claim 9  wherein the pitch, height and width of the at least one helical internal rib is selected so that the bat has a BBCOR of 0.500 or less. 
     
     
         11 . A hollow metal bat according to  claim 1  wherein the bat comprises a plurality of helical internal ribs. 
     
     
         12 . A hollow metal bat according to  claim 11  wherein the plurality of helical internal ribs have their number, pitch, height and width profile tailored so as to provide the desired characteristics for the bat. 
     
     
         13 . A hollow metal bat according to  claim 12  wherein the number, pitch, height and width of the plurality of helical internal ribs is selected so that the bat has a BBCOR of 0.500 or less. 
     
     
         14 . A hollow metal bat according to  claim 1  wherein the bat comprises a multi-wall construction. 
     
     
         15 . A hollow metal bat according to  claim 14  wherein the multi-wall construction comprises a sleeve disposed coaxial with the barrel portion, and further wherein the at least one helical internal rib is formed on the interior of the sleeve. 
     
     
         16 . A hollow metal bat according to  claim 14  wherein the multi-wall construction comprises a sleeve disposed coaxial with the barrel portion, and further wherein the at least one helical internal rib is formed on the exterior of the sleeve. 
     
     
         17 . A method for forming a hollow metal bat, the method comprising:
 positioning a preform on a mandrel, wherein the mandrel comprises at least one helical groove; and   applying compression to the outside diameter of the preform so as to form an elongated tubular structure having a barrel portion, a handle portion and a tapered portion connecting the barrel portion to the handle portion, and further comprising at least one helical internal rib formed along at least a portion of the elongated tubular structure.