Demarini Sports v. Worth

Bat Developer “Strikes Out” on Infringement Claim


February 13, 2001


Last Month at the Federal Circuit - March 2001

Judges: Linn (author), Schall, and Bryson

In DeMarini Sports, Inc. v. Worth, Inc., No. 99- 1561 (Fed. Cir. Feb. 13, 2001), the Federal Circuit affirmed a district court’s grant of SJ of noninfringement of U.S. Patent No. 5,415,398 (“the ‘398 patent”), which claims a double-walled aluminum softball bat with increased hitting capacity.

DeMarini Sports, Inc. (“DeMarini”) charged Worth, Inc. (“Worth”) with infringement of the ‘398 patent. Specifically, the ‘398 patent claims a bat comprising a hollow tubular “bat frame” with an “insert” positioned within the frame. A preferred embodiment disclosed in the ‘398 patent, and the embodiment marketed by DeMarini, includes a bat with a large-diameter hitting end, an intermediate tapering portion, and a small-diameter handle end. A smaller cross-sectioned “insert” is disposed within a large-diameter hitting end.

The accused Worth “EST” bat uses an external shell over the hitting end of the bat instead of an insert disposed within the hitting end. In asserting infringement, DeMarini argued that the claimed “bat frame” is a hollow tube covering the end of the bat while the “insert” was a structure with both a hitting end and a handle portion.

On appeal, the Federal Circuit affirmed the district court’s construction of the claim terms “bat frame,” “large-diameter impact portion,” and “insert.” The district court had construed the claim term “bat frame” to be a “single piece with the large portion for hitting the ball at one end, tapering to the handle with a knob at the other end.”

Looking beyond the ordinary dictionary definition, the Federal Circuit noted first that the specification of the ‘398 patent distinguished prior art that used inserts within bats to improve their impact response and discussed various ways of placing an insert within a bat frame to achieve greater hitting capacity. Moreover, the preferred embodiments of the invention each used an insert within a structure having both a hitting end and a handle end. According to the Federal Circuit, the prosecution history did not compel a construction of the term “frame” other than a “tubular structure having a large diameter impact portion, a tapered portion, and a small diameter handle.”

Turning to the district court’s construction of the term “insert,” the Federal Circuit agreed with the district court that all three relevant claims make clear that the bat frame, which includes the impact portion and the handle, completely surrounds and is separate from the insert.

Having affirmed the district court’s claim construction, the Federal Circuit affirmed the district court’s literal infringement analysis. The district court had held, and the Federal Circuit agreed, that the Worth EST bat could not literally infringe the ‘398 patent because it lacked a structural insert internal to the frame. Instead, the EST bat included an external shell over the hitting end of the bat.

The Federal Circuit then affirmed the district court’s finding of noninfringement under the DOE. Distinguishing this case from earlier cases regarding equivalence by devices that merely transpose two elements of the asserted claims, the Federal Circuit agreed that the insert limitation was absent from the Worth EST bat. Specifically, the claims of the ‘398 patent require an insert contained within a bat frame that further comprises a handle portion, a tapered portion, and an impact portion.

The Federal Circuit noted that the EST bat did not have such a configuration, instead having an exterior shell in which the insert that is positioned within the shell has a handle portion and a tapered portion. The Court rejected DeMarini’s argument as an improper attempt to direct the district court’s attention away from the language of the claims and toward a more general comparison of the overall attributes of the accused device with those of the claimed device. Since the accused Worth EST bat lacked the required insert limitation, the Federal Circuit refused to reverse the district court’s finding of noninfringement under the DOE.