Endress + Hauser, Inc. v. Hawk Measurement Systems Pty. Ltd.

• Decision Date: 21 August 1997
• Docket Number: No. 96-1245,96-1245
• Citation: 122 F.3d 1040
• Parties: Page 1040 122 F.3d 1040 43 U.S.P.Q.2d 1849 ENDRESS + HAUSER, INC., and Endress + Hauser GMBH & Co., Plaintiffs-Appellees, v. HAWK MEASUREMENT SYSTEMS PTY. LIMITED, and Hawk American, Inc., Defendants-Appellants. United States Court of Appeals, Federal Circuit
• Court: U.S. Court of Appeals — District of Columbia Circuit

Page 1040

122 F.3d 1040

43 U.S.P.Q.2d 1849

ENDRESS + HAUSER, INC., and Endress + Hauser GMBH & Co. Plaintiffs-Appellees v HAWK MEASUREMENT SYSTEMS PTY. LIMITED, and Hawk American Inc., Defendants-Appellants.

No. 96-1245.

United States Court of Appeals, Federal Circuit.

Aug. 21, 1997.

Donald E. Knebel, Barnes & Thornburg, Indianapolis, IN, argued, for Plaintiffs-Appellees. With him on the brief was Dwight D. Lueck.

Thomas G. Watkins, III, Cahill, Sutton & Thomas P.L.C., Phoenix, AZ, argued, for Defendants-Appellants.

Before RICH, PLAGER and CLEVENGER, Circuit Judges.

PLAGER, Circuit Judge.

This is an appeal from a district court judgment that Hawk Measurement Systems Pty. Limited (individually "Hawk Australia") and Hawk America, Inc., (collectively "defendants" or "Hawk") infringed U.S. Patent No. 4,000,650 ("the '650 patent"). The patent, now expired, was the property of Endress + Hauser GmbH & Co. ("E + H Germany"). Endress + Hauser, Inc. ("E + H U.S."), the exclusive distributor for E + H Germany in the United States, is also a party to the suit. The plaintiffs will be referred to collectively as "plaintiffs" or "E + H". After conducting a bench trial and having heard and considered the evidence, the District Court for the Southern District of Indiana found that defendants infringed plaintiffs' patent, and awarded damages. Because the district court correctly construed the means-plus-function claims, correctly determined that they were infringed by the defendants' accused device, and properly awarded damages, we affirm.

BACKGROUND

At issue in this case are devices that measure the height or level of a material enclosed in a bin or tank by using ultrasonic pulses to determine the distance from their source, the transducer, to the material enclosed in the bin or tank. After the transducer emits an ultrasonic pulse, the device calculates the time it takes the pulse to travel to the enclosed material and reflect back to the transducer. The device then converts this time measurement to a distance measurement. A particular problem with devices of this type lies in distinguishing the true return pulse from false echoes emanating from sources other than the enclosed material, sources such as ladders or other structures within the enclosure, and echoes from the walls or dust.

Beginning in about 1988, Hawk Australia began manufacturing ultrasonic level-measuring equipment. This equipment was subsequently sold to U.S. distributors. In mid-1991, Hawk America began selling the accused Hawk Australia products in the U.S. At least as early as 1990, Hawk Australia learned of the '650 patent when plaintiffs notified Delavan, another U.S. distributor of Hawk Australia's products, of their belief that the Hawk device infringed the '650 patent.

After Hawk Australia learned of the '650 patent, it modified its device, the prior "comparator device," and instead incorporated an analog-to-digital converter. It modified its software accordingly to make it compatible with the new converter. The record indicates that the majority of the sales made in the U.S. were of the Hawk device as modified.

DISCUSSION

The claims at issue in this appeal, claims 43 and 44, are means-plus-function claims and come within 35 U.S.C. § 112 p 6 (1994). Claims so written "shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof." Id. Claim 43 is an independent claim, from which claim 44 depends. Claim 43 states:

In a control system for use in monitoring the level of material in a storage tank including a transducer directing ultrasonic pulses toward and receiving echo response pulses reflected from the upper surface of said material, and a control circuit operatively connected to said transducer to provide an indication of material level on the basis of the round-trip transit time of an ultrasonic pulse from said transducer to said material surface and back again, the improvement wherein said control circuit comprises means converting said echo response pulses to digital signals having a numerical value indicative of the intensity of each of said echo pulses relative to one another, and level indicating means responsive to said converting means to provide said indication of material level on the basis of the relative numerical value of said digitized response pulses. (emphasis added).

The claim thus recites two improvements over the prior art, the converting means and the level indicating means responsive to the converting means. Much of the argument in the district court and again on appeal centered on the question of exactly what was encompassed in the limitation regarding the level indicating means, the limitation italicized above.

The parties do not dispute that the accused Hawk device contains structure (material or acts not being applicable) that differs in certain respects from that described in the specification. Thus, as the district court correctly stated, "the only question is whether the Hawk device employs means that are the equivalent of the structures described in the ['650] patent's specification." Endress + Hauser, Inc. v. Hawk Measurement Sys., 32 USPQ2d 1768, 1776, 1994 WL 736442 (S.D.Ind.1994) (emphasis added).

In arriving at her conclusion that the answer is "yes," the district judge, in a detailed and thorough opinion, first construed the claims and their specific means-plus-function limitations, including the scope of equivalent structures those limitations encompassed, and then determined whether the accused devices infringed the claims so construed.

Defendants vigorously attack the district judge's crediting of the testimony of Dr. Silva, a professor of electrical engineering at Purdue University, who testified as an expert on behalf of the plaintiffs. Defendants point out that the district judge arrived at many of the same conclusions as did Dr. Silva, and complain that had the district judge instead agreed with their expert witness, the interpretation issues would have been decided quite differently. Defendants attack Dr. Silva on the grounds that he is not "a person of ordinary skill in the art," and that he at one point in the proceedings acknowledged that much. Of course that objection is meritless. The "person of ordinary skill in the art" is a theoretical construct used in determining...