Patent ID: 7699725

Claim:
A bat comprising: a hollow barrel having a first wall and a concentric second wall, wherein the first wall comprises a first group of layers and the second wall comprises a second group of layers; a first wall innermost layer having unidirectional fibers positioned at a first low angle with respect to the longitudinal axis of the bat; a first wall outer layer having unidirectional fibers positioned at a first high angle with respect to the longitudinal axis of the bat, wherein the first wall outer layer is positioned concentrically outward of the first wall innermost layer so that the first wall outer layer surrounds the first wall innermost layer; a first wall series of layers including at least three layers positioned between the first wall innermost layer and the first wall outer layer, wherein each layer in the first wall series of layers includes unidirectional fibers at angles different from the first low angle and the first high angle, and wherein the angles of the unidirectional fibers in any two successive layers of the first wall series progress by about 15 degrees; a second wall innermost layer having unidirectional fibers positioned at a second low angle with respect to the longitudinal axis of the bat, wherein the second wall innermost layer is positioned concentrically outward of the first wall so that the second wall innermost layer surrounds all of the layers of the first wall, and wherein the second wall innermost layer is separate from the first wall so that the second wall is able to move with respect to the first wall; a second wall outer layer having unidirectional fibers positioned at a second high angle with respect to the longitudinal axis of the bat, wherein the second wall outer layer is positioned concentrically outward of the second wall innermost layer so that the second wall outer layer surrounds the second wall innermost layer; and a second wall series of layers positioned between the second wall innermost layer and the second wall outer layer, wherein each layer in the second wall series of layers includes unidirectional fibers at angles different from the second low angle and the second high angle, and wherein the angles of the unidirectional fibers in two successive layers of the second wall series progress by about 15 degrees.