ing the damper 15 the rate and friction of the incoming air and its tendency to raise and close the ball-valve 10 may be regulated as circumstances require. At suitable places along the line of tubing are despatching-inlets 20 20 for the insertion of the carriers and discharging-outlets 22 22, into which the carriers are shunted from the main line 1 and from which they are discharged in the usual manner. Said despatching-inlets are each closed normally air-tight by valves or flaps 24 which are normally held closed by the external air pressure, or by the usual springs or other devices, and said discharge-outlets 22 are each also normally closed air-tight by valves or flaps 26, which are normally held closed by the external air-pressure or by the usual springs or other suitable devices of such character that the impact of the cash-carriers when arriving at them will momentarily open the said valves 26 to permit said carriers to drop out, said valves immediately clos ing again automatically. Normally-that is, when no cash-carrier is in the line the ball-valve 10 will be on its seat and all the valves 24, 26 will be closed, and all the duty the exhauster 2 need then do is to maintain the normal small vacuum in the line, thereby reducing its necessary duty to a minimum. Now suppose the valve 24 of any despatching-inlet 20 is opened to insert a carrier. This opening momentarily reduces the vacuum by allowing some air to enter the line, and the valve 10 drops from its seat, opening the terminal air-inlet, which, as will be apparent, is at the remotest point of the line, measuring through the tubing, from the exhauster, and therefore beyond any despatching-inlet, and any carrier that may be inserted into the line. There is now a movement of air through the line toward the exhauster, which when the cash-carrier is inserted moves said carrier toward the exhauster, and the valve 24 at that inlet where the carrier was inserted immediately closes. The pressure of the carrier introduces, as we have hereinbefore stated, additional resistance to the motion of the air, and valve 10 remains more or less open, allowing air to enter at the terminal airinlet 3, to maintain the requisite current in the line to move the carrier through the line until it is discharged at the proper outlet. Immediately after the valve at the outlet closes the ball-valve 10 also closes and the exhauster again performs only its minimum duty. Suppose that while one carrier is traveling through another is inserted into the line. It may be either behind-that is, farther from the exhauster-or in front of-that is, between the first carrier and the exhauster. In the first case the insertion of the second carrier will not even momentarily have any practical effect on the first carrier; but the valve 10 may open a little more in accordance with the increased resistance in the line. In the second case, the motion of the first carrier will be momentarily arrested or checked, and then when the valve of the despatching-inlet at which the second carrier was inserted closes the first carrier will again proceed toward the discharge-outlet, in both cases, of course, the second carrier also moving through the line and valve 10 opening according to the resistance in the line. When the first carrier drops out of its discharge-outlet, the second carrier will be momentarily arrested or checked and then as the valve of the discharge-outlet closes will continue on its journey, the valve 10 adjusting itself to the reduced resistance in the line. Thus under all conditions the valve at the terminal air-inlet 3 adjusts itself to the conditions of service in the line and reduces the duty of the exhauster to minimum required for that service. Referring to Fig. 4, the depending tube 30 is preferably closed at its lower end, which has a small hole 40 and is provided with circumferential ports 31. A sleeve 34, provided with circumferential ports which in the open position register with the aforesaid ports 31, is preferably closed at the bottom and works with an easy approximately-tight fit on said tube 30, being stopped at its openport position by a pin 36, which works in a slot 37. The ports and the weight of the sleeve are so adjusted that when no carrier is in the line the sleeve will be drawn up by the partial vacuum in the line and close the ports 31, but that when a carrier is in the line the sleeve will descend to more or less open the ports, according to the resistance in the line, the operation of this form of closure being the substantial equivalent of the ball shown in Fig.

3. Any suitable device may, of course, be used to automatically control the exhauster according to the varying needs of the line. A suitable governor is shown in Fig. 3 (5), consisting of a diaphragm 47 of the well-known type in communication by tube 45 with the line-tube 1. Said diaphragm 47 controls the valve 48 on the steam-pipe 51 by the lever 50, and said valve controls the speed of the engine 52, which drives the exhauster 2, so that when the terminal inlet-valve is opened, as when a carrier is in the line, the diaphragm 47 being raised by the spring 49, the valve 48 is opened and the engine and exhauster run at relatively-high speed, but that when the terminal inlet-valve and tube-line are closed, as when no carrier is in the line, the vacuum developed in tube 1 will draw down the said diaphragm, closing said valve 48 and slowing down the engine and exhauster."

There can be no question as to the utility of the apparatus of the patent in suit. Aside from its convenience, it is highly economical in reducing to a minimum the power necessary for the operation of a pneumatic despatch system within the limits of distance for which such patented apparatus is adapted. But the defendants deny the validity. of the patent in suit on the ground of prior patents or other matter of an anticipatory character, and also deny that, on the assumption that the patent in suit is valid, they have infringed its claims or either of them. We shall first consider the question of the validity of the pat

ent.

The combination of claim 1 relates to a vacuo despatch system, and consists of (1) a line of tubing, (2) an exhauster operatively connected therewith, and (3) a terminal air-inlet having a closure which automatically shuts the air-inlet when no carrier is being despatched, and automatically opens the same when a carrier is being despatched, substantially as described. The combination of claim 2 also relates to a vacuo despatch system, and consists of (1) a line of tubing, (2) an exhauster operatively connected therewith, (3) despatch-inlets and discharge-outlets normally closed, and (4) a terminal air-inlet on said line. remote from said exhauster, provided with a closure which is arranged to automatically shut the said terminal air-inlet when no carrier is being despatched, and automatically open it when a carrier is being despatched, substantially as described. The meritorious and distinguishing feature of the apparatus of the patent in suit is its capacity to transmit carriers, not by means of air in the tubing compressed beyond its normal condition or density, nor by means of air in any portion or portions of the tubing so compressed in connection with air so rarified in other parts of the tubing as to constitute a partial vacuum. For such compression of air would involve waste of power and consequently unnecessary expense. It is the capacity of the apparatus to transmit carriers by means of air in the tubing so rarified between the carrier and its point of discharge as to constitute a partial vacuum, without any use of air in the tubing behind the carrier compressed beyond its normal external condition and thereby to reduce the expendiWhen the apparatus is in a normal conture of power to a minimum. dition of rest, that is to say, not transmitting a carrier, the exhauster causes only a slight vacuum or rarification of the air in the tubing just sufficient to keep the valves shut. It is known as a closed system, for such it is in its normal condition. If any of the despatch inlets

were inadvertently or otherwise opened without the insertion of a carrier, the closure or valve 10 will automatically open, and then automatically shut the terminal air-inlet 3. By arranging the tubing in a loop as shown in Fig. 1, carriers may at the same time be despatched in opposite directions. The terminal air-inlet is remote from the exhauster, not necessarily in point of distance on a straight line between the two, but with respect to the length of the tubing between them.

In the brief for the defendants many patents are referred to in support of their contention that the patent in suit is invalid by reason of direct anticipation or the prior art. Among these are U. S. patents Nos. 570,161, and 624,201, to Fordyce; No. 367,386 to Given; No. 411,333 to Given and Kelly; Nos. 551,602, 582,829 and 640,020 to Pearsall; No. 648,137 to Woodman; and No. 338,138 to Buell; in all of which a pressure and not a vacuum despatch system is disclosed. It is urged that it did not involve inventive genius to make such changes in the apparatus of the above patents as to adapt them to the transmission of carriers under a vacuum system such as that of the patent in suit that such alterations were within the competency of any one skilled in the art. Doubtless had the apparatus in question been seen and examined by those skilled in the art, as disclosed by the above patents, and they had been asked to make such changes, they might have done so. But this circumstance fails to overcome the presumption of validity arising from the granting of the patent, coupled with the nature of the changes necessary to be made to convert pressure despatch system into vacuum despatch systems.

In addition to the above patents, the defendants rely upon U. S. patents No. 652,960 to Foyer; No. 489,932 to Clay; the second certificate of addition to the French patent No. 97,158 to Crespin & Lapergue; British patent No. 5,536 to Blakeney; and U. S. patents No. 431,699 to Leake, and No. 566,575 to Hazard. No one of the last named patents discloses the combination of either of the claims of the patent in suit. Patent No. 652,960 to Foyer, discloses a combined vacuum and compressed air system, unlike the system of the patent in suit in that no vacuum is produced throughout the length of the system for forwarding and returning carriers wherever inserted in the tubing, but, on the contrary, contains two independent transmission tubes in one of which a partial vacuum is created to send carriers from the salesman's station to the cashier's station, and in the other compressed air is employed to return them from the cashier's station to the salesman's station. The apparatus also lacks a closure for a terminal air-inlet having the operation and results of the closure of the terminal air-inlet of the patent in suit; nor does it disclose a terminal air-inlet remote from the exhauster allowing carriers to be despatched in opposite directions in a loop line of tubing. Patent No. 489,932 to Clay also discloses a combined vacuum and compressed air system. The carriers are sent from subscribers' stations by means of a vacuum to a central station, and are transmitted from the central station to the subscribers' stations by compressed air in the tubing. In this system only one carrier can be sent from one of the subscribers' stations at a

time. For if several carriers were inserted in the tubing, the delivery of the first would cause the introduction of compressed air which would return the other carriers to the outer or terminal station; whereas, in the apparatus of the patent in suit, although several carriers are inserted in quick succession in the tubing at any salesman's station, the terminal air-inlet valve will automatically open and remain open until all the carriers are delivered, when it will automatically shut: the direction of the air current not being reversed but always in a direction toward the exhauster. The apparatus of the Clay patent lacks a terminal air-inlet having the operation and producing the results of the terminal air-inlet of the apparatus of the patent in suit.

The apparatus of the above-mentioned French patent No. 97,158 to Crespin & Lapergue, with the exception of that shown in Fig. 2 of the second certificate of addition, discloses a purely pressure system for the transmission of carriers, termed "trains," through a long line of pneumatic tubing divided into a number of small sections; the carriers being moved successively through the sections by the pressure of air in excess of its normal external condition. A carrier propelled by compressed air will pass through and to the end of the first section; "thence it will pass into the second section, where, by its passage, it will close a door behind it, and will instantly open a valve," thereby admitting compressed air for its transmission through the second section, and so on until the carrier reaches the discharge-outlet. But in the second certificate of addition, the patentees refer to Fig. 2, as showing a good "vacuum relay," and say that "its operation consists in maintaining the line closed and emptying it of air as completely as possible in the intervals between the trains, opening the passage only at the moment the trains pass." Under this vacuum system, a carrier cannot be despatched whenever desired, as is practicable in the apparatus of the patent in suit, nor, as far as appears, can there be intermediate despatch-inlets. We do not find in the above mentioned apparatus a terminal air-inlet with a closure automatically shutting and opening such inlet, and having the operation or producing the results of either of the combinations of the patent in suit.

The British patent No. 5,536 to Blakeney clearly is not an anticipation of the patent in suit. There is a terminal air-inlet and an exhauster at each end of the line. Not more than one carrier can be sent from either end of the line at one time. After the insertion of a carrier in the sector, the latter has to be moved manually from an inclined to a vertical position, and finally if a sector accidentally or inadvertently is placed in a position proper for the despatching of a carrier, and the latter should not be inserted, the exhauster would cause the air to move through the tubing until such sector was manually replaced in its normal position of closure. The apparatus of the British patent also lacks despatch-inlets and discharge-outlets having the operation and producing the results of either of the combinations of the patent in suit. Patent No. 431,699 to Leake relates to tubular switches for transferring carriers from one to another line of tubing.

It is confined to switching mechanism. It does not disclose either of the combinations of the patent in suit.

Patent No. 566,575 to Hazard shows an apparatus under which air continues for a period of time to flow through the tubing when no carriers are being transmitted, and such flow will continue until a carrier is inserted in the tubing to be returned from the cashier's station to the salesman's station, thereby wasting power during that interval. The closure does not automatically operate upon the discharge of the carrier at the cashier's station, nor, as stated, until it is again inserted in the line of tubing. This apparatus thus lacks the terminal air-inlet with a closure automatically shutting such inlet when no carrier is being despatched, and automatically opening the same when any carrier is being despatched, and keeping it open until such carrier or other carriers in transit is or are despatched, when the closure again operates.

No one of the foregoing patents discloses a combination containing elements the same as or equivalent to all those of the combinations of the patent in suit, co-operating upon the same principle and performing the same function in substantially the same manner and producing substantially the same results. It appears from the file wrapper and contents put in evidence by the defendants that no reference was made in the patent office to any of the foregoing patents or any others as anticipating or otherwise affecting the validity of the application for the patent in suit. The only objection encountered in the patent office by the inventors was alleged want of utility; but this objection was properly withdrawn and the patent granted. We have no doubt of its validity. We further think that within a limited field it covers what may fairly be deemed a pioneer invention, and its claims are entitled to a somewhat liberal application of the doctrine of equivalents. Paper Bag Patent Case, 210 U. S. 405, 28 Sup. Ct. 748, 52 L. Ed. 1122. We are therefore brought to the question of infringement with which the court below solely dealt in deciding the case.

The parties agreed by stipulation made part of the record that the defendants December 10, 1906, "installed in their store in Newark, New Jersey," a pneumatic despatch tube apparatus identical with that shown and described in "complainants' exhibit, description and drawings of defendants' pneumatic despatch tube apparatus," and have continued the use of such apparatus up to the present time. The drawing which illustrates the defendants' apparatus sufficiently for all practical purposes in considering the question of infringement is Fig. 1, as follows: