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Patent Specification Limits Claim Scope and Scope of Equivalents

April 01, 2004

Decision icon Decision

Last Month at the Federal Circuit - May 2004

Judges: Bryson (author), Rader, and Dyk

In Gaus v. Conair Corp., No. 03-1295 (Fed. Cir. Apr. 1, 2004), the Federal Circuit reversed the district court’s judgment of infringement of U.S. Patent No. 4,589,047 (“the ‘047 patent”), wiping out a jury verdict and enhanced damages totaling more than $37 million.

Dr. Harry Gaus charged Conair Corporation (“Conair”) with infringement of the ‘047 patent, which is directed to a safety mechanism that prevents fatal shocks to users of electrical appliances such as hairdryers. The patented mechanism operates by disconnecting the appliance from its power source when it comes in contact with water. More particularly, the patent describes protective circuitry that includes “a pair of spaced-apart electrically exposed conductive probe networks.” When water is present, current passes through the protective circuitry. The current melts a resistance element, which stops current flow to the voltage-carrying portions of the device so that the user of the device receives no shock.

The accused device, a Conair hairdryer, includes protective circuitry that has a single sense wire that branches throughout the housing near the voltage-carrying operating elements of the device. When water is disposed between the sense wire and the electrical operating portion of the device, current flows through the protective circuit, causing the device to be disconnected from the power supply.

The Federal Circuit interpreted the asserted claim as requiring that the pair of probe networks is a distinct component separate from an electrical operating unit. The Court noted that the specification describes several ways in which the pair of probe networks and the electrical operation unit are separate. Moreover, the specification explains that “[t]he object of the invention is to devise a protective device . . . which device will respond in an extremely short time . . . independently of the operating state of the apparatus, so as to protect the user from electric shock.”

The Federal Circuit further noted that the specification describes an advantage of the invention in a way that excludes the electrical operating unit from serving as part of the pair of probe networks. The specification indicates that the invention protects a user from the brief shock that is associated with prior art devices with protective circuits by arranging for the protective circuit to be separate from the voltage-carrying components of the device. This objective is achieved because the invention ensures that water will encounter the two probe networks before it encounters the voltagecarrying electrical operating unit.

The Federal Circuit thus determined that the specification shows that the invention requires that the user be completely protected from shock. Therefore, the Court reasoned, the invention cannot encompass a hairdryer with a protective device that relies on current passing between a probe and the electrical operating system, because such a device would be triggered only when the hairdryer was operating and voltage was being applied to the electrical operating system.

Having construed the claim language, the Federal Circuit addressed the issue of infringement and concluded that Conair’s hairdryer does not have a pair of probe netpage works that is separate from the electrical operating unit. Accordingly, the Federal Circuit found that Conair’s hairdryer does not literally infringe.

With respect to the DOE, the Federal Circuit concluded that because structure such as that in the Conair device was excluded from the scope of the claimed invention, Conair could not be infringing under the DOE. Thus, the Federal Circuit held that the Conair device does not infringe the ‘047 patent under the DOE, and the district court should have granted Conair’s motion for JMOL of noninfringement.

[Don Dunner, Kara Stoll, and Scott Herbst of our firm successfully represented Conair in this appeal.]