US Patent 6949038 Ball bat having an insert with variable wall thickness

A bat, configured for impacting a ball, includes a substantially tubular frame and a substantially tubular body. The frame extends along a longitudinal axis and has a handle portion and a primary hitting portion. The body is coaxially aligned with the hitting portion of the frame. The body includes a proximal end, a distal end, and first and second tubular wall transition regions. The wall thickness of the first tubular wall transition region generally increases along the longitudinal axis from a first position, generally near the proximal end, toward the distal end. The wall thickness of the second tubular wall transition region generally increases along the longitudinal axis from a second position, generally near the distal end, toward the proximal end. The body is configured to move independently with respect to the hitting portion of the frame upon impact with the ball.