Bat and method of manufacturing the same

Abstract

A bat comprises a bat body and a foamed core member provided inside the inner space of the bat body. The foamed core member is made of pre-foamed methacryl resin beads, which have been treated with a foaming process. The pre-foamed methacryl resin is filled up in the bat body so that approximately 100% of the volume is filled up. The foamed core member is formed by heating the pre-foamed methacryl resin beads in order to perform a secondary foaming process while the inner space is sealed. The bat has an expanded sweet-spot area and enhanced impact absorbing characteristics. By leveling the thickness of the bat body, mechanical strength is enhanced, and further, the weight of the bat can be reduced and satisfactory swing balance can be obtained.

1 . A bat comprising; 
 a bat body made of metallic material or fiber-reinforced plastic material, wherein the bat body has a tip portion being closed and a grip-end portion having an opening; and    a core member provided in an inner space of the bat body;    wherein the core member made from foamed methacryl resin in which approximately 100% of a volume of the inner space is filled with the core member.    
     
     
         2 . The bat according to  claim 1 , wherein the metallic material includes aluminum, aluminum alloy, titanium, or titanium alloy.  
     
     
         3 . The bat according to  claim 1 , wherein the core member is formed by filling up pre-foamed methacryl resin in the inner space and carrying out a secondary foaming process to the pre-foamed methacryl resin in a state where the opening is closed and the inner space is tightly sealed.  
     
     
         4 . The bat according to  claim 3 , wherein the pre-foamed methacryl resin is in form of beads or beads powder.  
     
     
         5 . A method of manufacturing a bat comprising the following steps of; 
 filling up pre-foaming methacryl resin beads into an inner space of a bat body from an opening formed in part of a grip portion so that approximately 100% of a volume of the inner space is filled up with the pre-foamed methacryl resin beads;    sealing the inner space of the bat body; and    heating the pre-foamed methacryl resin beads to carry out a secondary foaming process inside the inner space by treating the bat body.    
     
     
         6 . The method of manufacturing a bat according to  claim 5 , wherein the step of sealing the inner space is carried out by inserting a plug member into the opening of the bat body; and  
     
     
         7 . The method of manufacturing a bat according to  claim 6 , further including forming a cylindrical base material from the metallic material or the fiber-reinforced plastic material.  
     
     
         8 . The method of manufacturing a bat according to  claim 7 , further including forming a bat body material by fixedly inserting a core metal member into an inner hole of the cylindrical base material.  
     
     
         9 . The method of manufacturing a bat according to  claim 8 , further including pressing a plurality of rollers located at different positions of a circumference of the cylindrical base material, and performing a spinning rolling process for shifting the rollers in an axial direction of the cylindrical base material while rotating the cylindrical base material so as to form a predetermined thickness for a local area corresponding to the grip-end portion so that a bat body material is formed.  
     
     
         10 . The method of manufacturing a bat according to  claim 9 , further including performing a cold swaging process to the bat body material so as to form the bat body having a predetermined shape having a continuous surface linking a grip portion and a sweet-spot portion via a tapered portion.  
     
     
         11 . The method of manufacturing a bat according to  claim 5 , further including foaming un-foamed methacryl resin beads so as to prepare pre-foamed methacryl resin beads.  
     
     
         12 . The method of manufacturing a bat according to  claim 11 , wherein the a volume of the un-foamed methacryl resin beads is increased by approximately 10 to 30 times as much as the un-foamed foamable methacryl resin beads in the step of foaming un-foamed methacryl resin beads.  
     
     
         13 . The method of manufacturing a bat according to  claim 12 , wherein the a volume of the un-foamed methacryl resin beads is increased by approximately 20 times as much as the un-foamed foamable methacryl resin beads in the step of foaming un-foamed methacryl resin beads.  
     
     
         14 . The bat manufactured by a method comprising the following steps of: 
 filling up pre-foaming methacryl resin beads into an inner space of a bat body from an opening so that approximately 100% of a volume of the inner space is filled up with the pre-foamed methacryl resin beads;    sealing the inner space of the bat body by inserting a plug member into the opening of the bat body; and    heating the pre-foamed methacryl resin beads to carry out a secondary foaming process inside the inner space.