| 摘要 |
<p>PURPOSE:To maintain the sound deadening characteristic and vibration-proofing characteristic of a metal bat over a long period of time by providing a foaming layer on the interior wall portion of a metal bat main body, the specific gravity of the foaming layer getting smaller continuously toward the center portion of the bat main body along an inclination. CONSTITUTION:A foaming layer 2 is provided on the interior wall portion of a metal bat main body 1, the specific gravity of the foaming layer 2 getting smaller continuously toward the center portion of the bat main body 1 along an inclination. A method of manufacture of this metal bat comprises inserting a raw foaming resin supply pipe into the hollow metal bat main body 1 from the head portion or grip end of the bat main body, applying raw foaming resin to the interior wall surface of the bat while rotating the bat main body 1 and/or the supply pipe; then substituting a hot air supply pipe for the supply pipe, forming a foaming layer 2 the specific gravity of which gets smaller continuously toward the center portion of the bat main body along an inclination, while rotating the bat main body or the hot air supply pipe, and securing a head portion or a grip end to the bat main body 1.</p> |
