US Patent 7033291 Polymer shell bat

A metal baseball or softball bat may be improved both for durability and performance by selectively placing a layer of polymer material around portions of the bat. In one embodiment, the barrel portion of the bat may have a polymer layer directly laid up upon the metal bat frame. In a second embodiment, the barrel portion of the bat may include an outer metal sleeve placed about the metal bat frame, with an exterior polymer shell being formed on the outer metal sleeve. In a third embodiment, an intermediate portion of the bat adjacent a zone of maximum bending stress may be reinforced by the placement of a polymer outer layer on the metal frame of the bat adjacent the area of maximum bending stress.