Law School Case Brief
Westinghouse v. Boyden Power Brake Co. - 170 U.S. 537, 18 S. Ct. 707 (1898)
A charge of infringement is sometimes made out, though the letter of the claims be avoided. The converse is equally true. The patentee may bring defendant within the letter of his claims, but if the latter has so far changed the principle of the device that the claims of the patent, literally construed, have ceased to represent his actual invention, he is as little subject to be adjudged an infringer as one who has violated the letter of a statute has to be convicted, when he has done nothing in conflict with its spirit and intent. An infringement involves substantial identity, whether that identity be described by the terms, "same principle," same "modus operandi," or any other.
Plaintiff Westinghouse brought an action against corporate defendant Boyden Brake Company and other individual defendants alleging infringement of a patent for railway train brakes, which increased the rapidity of brake action. The patent in suit, which was issued to Westinghouse is for a fluid-pressure automatic-brake mechanism, the object of which is said in the specification to be "to enable the application of brake-shoes to car-wheels by fluid pressure to be effected with greater rapidity and effectiveness than heretofore, more particularly in trains of considerable length, as well as to economize compressed air in the operation of braking, by utilizing in the brake-cylinders the greater portion of the volume of air which in former practice was directly discharged into the atmosphere." Defendant Boyden Brake Company and the individual defendants admitted that the company was engaged in manufacturing and selling a fluid-pressure brake, but denied that the same was an infringement upon plaintiffs' patent, and also denied that Westinghouse was the original inventor of the mechanism covered by the patent. The Circuit Court for the District of Maryland entered a judgment in part in favor of Westinghouse, but the Court of Appeals for the Fourth Circuit reversed. Westinghouse petitioned for a writ of certiorari to the United States Supreme Court.
Was defendants' device an infringement of Westinghouse’s patent?
The United States Supreme Court affirmed the judgment of the appellate court, which held that defendants' device was not an infringement of Westinghouse’s patent. The Court construed the language of Westinghouse’s specification as reading an auxiliary valve into the claim and as rejecting the idea that the claim should be interpreted as one for a method or process. The Court found that there were several means by which the function of the automatic brake could be accomplished and that each means was patentable provided they were not mechanical equivalents. Although the functions of the two devices were practically the same, the means used in accomplishing the function were very different. Thus, the Court held that they were not mechanical equivalents and that defendants' device was not an infringement.
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