Baseball bat with modified internal air pressure

Abstract

An aluminum baseball bat with plug of solid rubber or similar material at one end thereof and a knob at the other end is disclosed. The rubber end plug is sealed in place in a leak-proof junction to define a hollow interior space. By inserting a needle through the end plug, fluid communication between a source of air or other gas which is pressurized either above or below atmospheric pressure and the interior of the bat space can be provided to achieve a desired pressure therewithin. Once the desired interior pressure has been achieved, the needle is withdrawn and the natural resiliency of the rubber acts to immediately seal the puncture to thereby permanently maintain the desired interior pressure conditions.

What is claimed is: 
     
       1. A metallic bat comprising sidewalls which terminate at one end in a closed end and at the other end in an open end, the open end being closed with a resilient end plug secured to the interior surface of the sidewalls to define an interior space capable of maintaining a quantity of confined gas therewithin, the confined gas being characterized by a pressure other than atmospheric, the resilient end plug having a passage therethrough in communication with the interior space, the passage being open when a pressure introducing needle is inserted through the plug to introduce gas into the interior space and the passage being closed when the needle is withdrawn to seal the said interior space, the said pressure being appropriate to produce a natural frequency of free vibration of such frequency and amplitude in the bat that when coupled with the excitation frequency caused by the impact of the bat striking a ball, resonance results.   
     
     
       2. The bat of claim 1 wherein the said pressure is approximately 6 psi greater than atmospheric. 
     
     
       3. The bat of claim 1 wherein the pressure is less than atmospheric. 
     
     
       4. The method of modifying the initial pressure of a gas entrapped within the interior of a metallic baseball bat of the type having an interior space defined by the bat sidewalls and having one closed end and one open end, the open end being closed by a resilient plug, comprising the steps of forming an opening through the resilient plug part of the bat construction in communication with the interior space by forcing a hollow conduit therethrough until its inner end reaches the interior space and its outer end extends outwardly of the plug;   determining the critical structural frequency of the bat;   introducing a gas at a pressure other than the initial pressure to the outer end of the conduit and forcing the gas through the conduit to establish the final pressure of the gas in the interior space;   pressurizing the gas to a final pressure necessary to achieve critical structural frequency in the bat; and   removing the conduit and automatically closing the opening through the resilient plug and maintaining the final pressure of the gas in the interior space.   
     
     
       5. The method of claim 4 including the step of pressurizing the gas to a final pressure of approximately 6 psi .Iadd.greater than atmospheric pressure..Iaddend..Iadd. 
     
     
       6.  In a metallic bat construction of the type comprising sidewalls and closed first and second ends defining an interior space and capable of maintaining a quantity of confined gas therewithin, the improvement comprising gas passage means in the bat construction in fluid communication with the interior space to pass gas therethrough,   the confined gas being characterized by a pressure that is other than atmospheric, and   the said pressure being appropriate to produce a natural frequency of free vibration of such frequency and amplitude in the bat that when coupled with the excitation frequency caused by the impact of the bat striking a ball, resonance results. .Iaddend. .Iadd.7. The bat of claim 6 wherein the said pressure is approximately 6 psi greater than atmospheric..Iaddend. .Iadd.8. The bat of claim 6 wherein the pressure is less than atmospheric. .Iaddend. .Iadd.9. The method of modifying the initial pressure of a gas entrapped within the interior of a metallic baseball bat of the type having an interior space defined by the bat sidewalls and having a first closed end, a second closed end and gas passage means in fluid communication with the interior space, comprising the steps of determining the critical structural frequency of the bat;   introducing a gas at a pressure other than atmospheric pressure to the gas passage means and forcing the gas through the gas passage means to establish the final pressure of the gas in the interior space;   pressurizing the gas to a final pressure necessary to achieve critical structural frequency in the bat; and maintaining the final pressure of the gas in the interior space. .Iaddend. .Iadd.10. The method of claim 9 including the step of pressurizing the gas to a final pressure of   
     
     
        approximately 6 psi greater than atmospheric..Iaddend. .Iadd.11.  The bat of claim 6 wherein the pressure is greater than atmospheric..Iaddend. .Iadd.12. The method of claim 9 including the step of pressurizing the gas to a final pressure that is greater than atmospheric..Iaddend.