The above drawings are somewhat clearer than those annexed to the patent, and exhibit the triple valve and its connections in three positions, viz., No. 13, Released or "Brakes Off;" No. 14, Ordinary Service Application, and No. 16, "Quick Action" Position.

The only claims of the patent alleged to have been infringed are the first, second and fourth, which read as follows:

1. In a brake mechanism, the combination of a main air-pipe, an auxiliary reservoir, a brake-cylinder, a triple valve, and an auxiliary-valve device, actuated by the piston of the triple valve and independent of the main valve thereof, for admitting air in the application of the brake directly from the main air-pipe to the brakecylinder, substantially as set forth.

2. In a brake mechanism, the combination of a main air-pipe, an auxiliary reservoir, a brake-cylinder, and a triple valve having a piston whose preliminary traverse admits air from the auxiliary reservoir to the brake-cylinder, and which by a further traverse admits air directly from the main air-pipe to the brake-cylinder, substantially as set forth.

4. The combination, in a triple-valve device, of a case or chest, a piston fixed upon a stem and working in a chamber therein, a valve moving with the piston-stem and governing ports and passages in the case leading to connections with an auxiliary

reservoir and a brake-cylinder and to the atmosphere, respectively, and an auxiliary valve actuated by the piston-stem and controlling communication between passages leading to connections with a main air-pipe and with the brake-cylinder, respectively, substantially as set forth.

The joint and several answer of the Boyden Brake Company and the individual defendants admitted that such company was engaged in manufacturing and selling a fluid-pressure brake, but denied that the same was an infringement upon complainants' patent, and also denied that Westinghouse was the original inventor of the mechanism covered by the patent, and alleged that an apparatus, substantially identical in character, had been previously granted Westinghouse, March 5, 1872, (No. 124,404,) and that a like apparatus was previously described in the following patents issued to Westinghouse, viz: No. 138,827, May 13, 1873; No. 144,006, October 28, 1873; No. 168,359, October 5, 1875; No. 172,064, January 11, 1876; No. 220,556, October 14, 1879, and also in three patents to other parties, not necessary here to be specifically mentioned.

The answer further denied any infringement of the first, fourth and fifth claims of the patent sued upon, (No. 360,070,) and, with respect to the second claim, averred the same to be invalid because the combination of parts therein named is inoperative to perform and incapable of performing the function set forth in said claim; and that, if the said claim be considered merely as the combination of parts therein set forth, and without reference to the function described as performed by it, it is invalid for the reason that the same combination of parts is shown in most of the prior patents above cited, and has been publicly used by the complainants for a long time prior to the date of the said Letters Patent No. 360,070.

The answer further averred the claim to be uncertain and ambiguous, and if the functions recited by it are construed as amplifying the description of the combination to distinguish this combination from that shown in the prior patents

then the defendants say that the said claim is anticipated by the prior Letters Patent issued to George A. Boyden on June 26, 1883, No. 280, 285, for the reason that air-brake valves made in accordance with the last-mentioned patent embody the same combination of parts, and will perform the same functions, and operate in substantially the same manner as stated in said second claim.

Upon a hearing in the Circuit Court upon the pleadings and proofs, that Court was of opinion that the second claim was valid, and had been infringed, but that defendants had not infringed claims 1 and 4, and as to those the bill was dismissed. (C. D., 1895, 283; 71 O. G., 298; 66 Fed. Rep., 997.) From the decree entered in pursuance of this opinion both parties appealed to the Court of Appeals for the Fourth Circuit, which affirmed the action of the Circuit Court with respect to the first and fourth claims, but reversed it with respect to the second claim, and dismissed the bill. (C. D., 1895, 735; 73 O. G., 1857; 25 U. S. App., 12782- -29

475.) Whereupon complainants applied for and were granted a writ of certiorari.

Full copies of the principal Westinghouse patents are printed in Westinghouse Brake Co. v. N. Y. Brake Co., (C. D., 1894, 594; 69 O. G., 945; 26 U. S. App., 248,) and of the Boyden patents in the report of this case in 25 U. S. App., 475.

Mr. Justice BROWN delivered the opinion of the Court.

The history of arresting the speed of railway trains by the application of compressed air is one, to which the records of the Patent Office bear frequent witness, of a gradual progress from rude and imperfect beginnings, step by step, to a final consummation, which, in respect to this invention, had not been reached when the patent in suit was taken out, and which, it is quite possible, has not been reached to this day. It is not disputed that the most important steps in this direction have been taken by Westinghouse himself.

The original substitution of the air-brake for the old hand-brake was itself almost a revolution, but the main difficulty seems to have arisen in the subsequent extension of that system to long trains of freightcars, in securing a simultaneous application of brakes to each of perhaps forty or fifty cars in such a train, and finally in bringing about the instantaneous as well as simultaneous application of such brakes in cases of emergency, when the speediest possible stoppage of the train is desired to avoid a catastrophe.

Patent No. 88,929, issued April 13, 1869, appears to have been the earliest of the Westinghouse series. This brake, known as the straight air-brake, consisted of an air-compressing pump, operated by steam from the locomotive-boiler, by which air was compressed into a reservoir, located under the locomotive, to a pressure of about eighty pounds to the square inch. This reservoir, being still in use, is now known as the main reservoir. From this reservoir an air-pipe, usually called the trainpipe, led into the cab, where the supply of air was regulated by an "engineer's valve," thence down and back under the tender and cars, being united between the cars by a flexible hose with metal couplings, rendering the train-pipe continuous. These couplings were automatically detachable; that is, while they kept their grip upon each other under the ordinary strains incident to the running of the train, they would readily pull apart under unusual strains, as when the car-coupling broke and the train pulled in two.

From the train-pipe of each car, a branch pipe connected with the forward end of a cylinder, called the "brake-cylinder," which containeda piston, the stem of which was connected with the brake-levers of the car. This piston was moved and the brakes applied, by means of compressed air admitted through the train-pipe and its branches, into the forward end of the brake cylinder. When the brakes were to be applied, the engineer opened his valve, admitted the compressed air into

the train-pipes and brake-cylinders, whereby the levers were operated and the brakes applied. To release the brakes, he reversed the valve, whereby the compressed air escaped from the brake-cylinders, flowed forward along the train-pipe to the escape-port of the engineer's valve, thence into the atmosphere. Upon the release of the compressed air, the pistons of the brake-cylinders were forced forward again by means of springs, and the brake-shoes removed from the wheels. By means of this apparatus, the train might be wholly stopped or slowed down by a full or partial application of the brakes. As between a full stop and a partial stop, or slow speed, there was only a question of the amount of air to be released from the main reservoir. The validity of this patent was sustained by the Circuit Court for the Northern District of Ohio, Mr. Justice Swayne and Judge Welker sitting, in Westinghouse v. The Air Brake Company, (C. D., 1876, 317; 9 O. G., 538.) The Court said, in its opinion, that while Westinghouse was not the first to conceive the idea of operating railway-brakes by air-pressure, such fact did not detract at all from his merits or rights as a successful inventor; that the new elements introduced by him

fully substantiated his pretensions as an original and meritorious inventor, and entitled him as such to the amplest protection of the law.

and that it appeared from the record and briefs that he was the first to put an air-brake into successful actual use.

While the application of this brake to short trains was reasonably successful, the time required for the air to pass from the locomotive to the rear cars of a long train (about one second per car) rendered it impossible to stop the train with the requisite celerity, since in a train of ten cars it would be ten seconds before the brakes could be applied to the rear car, and to a freight-train of fifty cars nearly a minute. While the speed of the foremost car would be checked at once, those in the rear would proceed at unabated speed, and in their sudden contact with the forward cars would produce such shocks as to often cause damage. As a train moving at the rate of fifty miles an hour makes over seventy feet per second, a train of fifty cars would run half a mile before the brakes could be applied to the rear car. So, too, if the rear end of the train became detached from the forward end by the rupture of the train-pipe or couplings, the brakes could not be applied at all, since the compressed air admitted to the train-pipe by opening the engineer's valve would escape into the atmosphere without operating the brakes, or if the brakes were already applied, they would be instantly released when such rupture occurred.

The first step taken toward the removal of these defects resulted in what is known as "the automatic brake," described first in Patent No. 124,404 in a crude form, and, after several improvements, finally culminating in Patent No. 220,556 of 1880. The salient features of this brake were an auxiliary reservoir beneath each car for the reception and storage of

compressed air from the main reservoir, and a triple valve, so called, automatically controlling the flow of compressed air in three directions, by opening and closing, at the proper times, three ports or valve-openings, viz: first, a port or valve known as the "feeding-in valve" from the train-pipe to the auxiliary reservoir, allowing the auxiliary reservoir to fill so as to be ready when the brakes were applied; second, a port or valve from the auxiliary reservoir to the brake-cylinder, which allowed a flow of compressed air to apply the brakes, and was called the "main valve;" third, a port or valve from the brake-cylinder to the open air, denominated the "release-valve," to be opened when it was desired to release the brakes.

The operation of these valves was as follows: Before the train starts, compressed air from the main reservoir is permitted to flow back through the train-pipe, and through valve No. 1, for the purpose of charging the auxiliary reservoir beneath each car with a full working pressure of air. When it is desired to apply the brakes, the engineer's valve is shifted, and the air in the train-pipe is allowed to escape into the atmosphere at the engine. Thereupon the compressed air in the auxiliary reservoir closes valve No. 1, leading to the train-pipe, and opens the main valve No. 2, from the auxiliary reservoir to the brake cylinder, whereby the piston of that cylinder operates upon the brake-levers and applies the brakes. By this use of the auxiliary reservoirs a practically simultaneous application of the brakes is secured for each car. This application of the brakes is secured, not by direct application of compressed air from the engine through the train-pipe, but by a reverse action, whereby the air is allowed to escape from the train-pipe toward the engine, the pres sure being applied by the air escaping from the auxiliary reservoirs. It also results that, if a train should pull in two, or a car become detached, the same escape of air occurs, the same action takes place automatically at the broken part, and the same result follows by the escape of the compressed air through the separated couplings. When it is desired to release the brakes, the engineer's valve is again shifted, and the compressed air not only opens valve No. 1 from the train-pipe to the auxiliary reservoir, but valve No. 3 from the brake-cylinder to the open air, which allows the air from the brake cylinder to escape and thus release the brake.

From this description it will be seen that the action of the automatic brake was, in fact, the converse of that of the straight air-brake, and that the result was to obviate the most serious defects which had attended the employment of the former.

This automatic brake appears, in its perfected form, in Patent No. 220,556, although this patent was but the culmination of a series of experiments, each successive step in which appears in the prior patents. Thus in Patent No. 124,404, (1872,) is introduced the auxiliary reservoir beneath each car in connection with a double line of brake-pipes and a single cock with suitable ports for charging the reservoir and for oper