After a further reference to the drawings, he again states that, "so far as herein before described, the triple valve accords in all substantial particulars with, and is adapted to operate similarly to, those of my letters patent Nos. 168,359, 172,064, and 220,556; and, in order that it may perform the further functions requisite in the practice of my present invention, it is provided with certain additional members, which will now be described." These additional members, which are said to be for the purpose of effecting | the admission of air directly from the main air pipe to the brake cylinder when it is desired to apply the brakes with great rapidity and full force, consist of (1) a passageway through which air can be admitted directly from the main air (or train) pipe to the brake cylinder without passing through the auxiliary reservoir; and (2) an auxiliary valve in connection with such passage, that, when the triple-valve piston makes a short or preliminary movement, the passageway direct from the train pipe to brake cylinder, controlled by said valve, will not be opened, while in the event of a long or full movement of the piston, or "further traverse," as it is called, such direct passageway will be thrown wide open to the admission of trainpipe air, and the brake cylinder will be rapidly filled thereby.

After describing the auxiliary sliding valve, 41, and its connections, as well as the operation of the device in ordinary (nonemergency) cases of checking the speed of or stopping trains, already fully provided for in previous patents, he proceeds to state its operation in cases of emergency which the patent was specially designed to cover, as follows:

"In the event, however, of its becoming necessary to apply the brakes with great rapidity and with their greatest available force, the engineer, by means of the valve at his command, instantly discharges sufficient air from the front end of the main air pipe to effect a sudden reduction of pressure of about twenty pounds per square inch therein, whereupon the piston, 12, of the triple valve, is forced to the extreme limit of its stroke in the direction of the drain cup, 19, carrying with it the stem, 36, and auxiliary slide valve, 41, which instantly uncovers the port, 42. and discharges air from the main air pipe through the opening of the check valve, 49, and the passages, 46 and 48, to the brake cylinder; and, each car being provided with one of these devices, it

will be seen that they are successively moved with great rapidity,-there being, practically, on a train of fifty cars, fifty openings for discharging compressed air from the main pipe, instead of the single opening heretofore commonly used. Not only is there a passage of considerable size opened from the brake pipe on each car, whereby the pressure is more quickly reduced, but the air so discharged is utilized in the performance of preliminary work; it being found, in practice, that the air so taken from the pipe will exert a pressure of about twenty-five pounds in the brake cylinders. When the piston, 12, arrives at the extremity of its stroke as above specified, the supplemental port, 35, of the slide valve, 14, is brought into communication with the port, 33, and passages, 22 and 16, which serves to discharge the reservoir pressure into the brake cylinder, thereby augmenting the pressure already exerted in the brake cylinder by the air admitted from the main air pipe. Upon the reduction of the pressure in the main air pipe below that in the brake cylinders, as by the breaking in two of the train, the check valve, 49, closes communication between the passages, 46 and 18, thereby preventing the return of the air from the brake cylinder to the main air pipe. The feed opening for the admission of air from the auxiliary reservoir to the brake cylinder is purposely made of comparatively small diameter, it having been determined by experiment that the initial application of the brakes should not be made with maximum force, and this opening may be made of such size as to apply the brakes exactly in accord with the requirements of the most efficient work.

"In using the terms 'triple valve' and 'triplevalve device,' I refer to a valve device, however specifically constructed, having a connection with the main air or brake pipe, another with an auxiliary reservoir or chamber for the storage of power, and another with a brake cylinder, or its equivalent, for the utilization of the stored power, and with a release or discharge passage for releasing the operative power from the brake cylinder, whether the valves governing these passages or connections are arranged in one or more cases, and are moved by a piston, or its equivalent, or by a series of pistons, or their equivalents; there being numerous examples in the art of constructions varying materially in appearance, whereby these functions are performed, both in plenum and vacuum brake mechanisms."

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, 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. 66 Fed. 997. From the decree entered in pursuance of this opinlon 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. 25 U. S. App. 475, 17 C. C. A. 430, and 70 Fed. 816. Whereupon com

plainants applied for, and were granted, writ of certiorari.

Full copies of the principal Westinghouse patents are printed in Westinghouse AirBrake Co. v. New York Air-Brake Co., 26 U. S. App. 248, 11 C. C. A. 528, and 63 Fed. 962, and of the Boyden patents in the report of this case in 25 U. S. App. 475, 17 C. C. A. 430, and 70 Fed. 816.

George H. Christy and F. H. Betts, for Westinghouse. Lysander Hill, Hector T. Fenton, Philip Manro, and Melville Church, for Boyden Co.

* Mr. Justice BROWN, after stating the facts in the foregoing language, 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 freight cars, in securing a simultaneous application of brakes to each of perhaps 40 or 50 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 aircompressing 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 80 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 "train pipe," led into the cab, where the supply of air was regulated by an "engineer's valve," and 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 contained a 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, and 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, and flowed forward along the train pipe to the escape port of the engineer's valve, and 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. Air-Brake Co., 9 O. G. 538, Fed. Cas. No. 17,450. 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 10 cars it would be 10 seconds before the brakes could be applied to the rear car, and, to a freight train of 50 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 50 miles an hour makes over 70 feet per second, a train of 50 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 ap

plied, they would be instantly released when such rupture occurred.

The first step taken towards 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.: (1) 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; (2) 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"; (3) 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 towards the engine; the pressure 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 reser voir, 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 operating the brakes,-a device which was obviously the foundation of the triple valve which first made its appearance in patent No. 141,685 (1873), in which the main valve, which admitted air from the auxiliary reservoir to the brake cylinder, was of the poppet form; and, as a poppet valve can govern only one port, separate valves had to be provided for feeding in the air from the train pipe to the auxiliary reservoir, and for discharging the air from the brake cylinder to release the brakes. In subsequent patents, No. 144,006 (1873) and No. 163,242 (issued in 1875 to C. H. Perkins, and assigned to Westinghouse), Mr. Westinghouse improved upon his prior devices by substituting a sliding-piston valve for the poppet form of main valve previously used by him. This enabled the piston to perform the feedvalve function, of admitting air from the train pipe to the auxiliary reservoir; the main-valve function, of admitting air from the auxiliary reservoir to the brake cylinder to apply the brakes; and the release-valve function, of discharging the air from the cylinder to release the brakes. In patent No. 168,359 (1875) a piston actuating a slide valve was substituted for the piston valve, and, after a series of experiments, which did not seem to have been successful, he introduced into patent No. 217,838 the idea of venting the train pipe, not only at the locomotive, but also under each car, in order to quicken the application of the brakes. Prior to this time, "when the engineer desired to apply his brakes with full force he operated the valve at the engine, and opened the port wide; letting the compressed air out of the train pipe at the locomotive, then its only vent. The air, as before said, had to travel from the rear cars along the cars forward to the engine before it could lessen the pressure of the train pipe air,

and before the brake cylinder could be operated with air from the auxiliary reservoirs. In a train of fifty cars, it would have to travel nearly half a mile to get out at the engine." He embodied in patent No. 220,556 1879) the most complete form of the autonatic brake. As stated by the court below, the ordinary work of braking was performed by a partial traverse of its chamber by the triple-valve piston, graduated, ac

cording to the purpose desired, at the will of the engineer; and emergency work was done by an extreme traverse of the piston to the end of its chamber."

While the automatic brake had thus obviated the most important defects of the old or straight air brake, and came into general use upon passenger trains throughout the country, it was found, in practice, upon long freight trains, that the air from the auxiliary reservoirs did not act with suffi. cient promptness upon the brakes of the rear cars, where a particularly speedy action was required, and that it would be necessary to devise some other means for cases of special emergency. In the business of transporting freight over long distances, the tendency has been in the direction of increasing the load by using stronger and heavier cars and larger locomotives. Upon a long train of this kind, composed of 30 to 50 cars, a demand was made for quicker action in cases of emergency than had yet been contemplated, although, for ordinary work, such as checking the speed of a train while running, holding it at a slow speed on a down grade, and also for making the ordinary station stops, the automatic brake was still sufficient, and produced satisfactory results, even in the equipment of long and heavy trains. But, however effective for ordinary purposes, the automatic brake did not sufficiently provide for certain emergencies, requiring prompt action, and therefore failed in a single important particular.

Upon examination of these defects, it was found that they could only be remedied by securing (1), in cases of emergency, a more abundant discharge of compressed air into the brake cylinder; and (2) an escape of air near to each triple valve without requiring the escaping air to travel all the way back to the engine. The latter device having been already embodied in patent No. 217,838, these features Mr. Westinghouse introduced into the patent in suit, by which a passage was opened directly from the train pipe, filled from the main reservoir on the engine, to the brake cylinder, through which, in cases of emergency, the train-pipe air, instead of being discharged into the atmosphere, could pour directly from the train pipe into the brake cylinder. This operation resulted in charging the brake cylinder and applying the brakes more quickly than before; and also, by reason of the fact that the filling of the brake cylinder from the train pipe on one car made what was, in effect, a local vent for the release of pressure sufficient to operate the valve on the next car behind, each successive valve operated more quickly than when a diminution of pressure was caused by an escape of air only at the locomotive. The direct passage of the air from the train pipe to the brake cylinder was effected by a valve, 41, colored red in the above diagrams, which is never opened except in cases of emergency. In ordinary cases, when the brakes are desired to be