US1733976A - Automatic train-control system - Google Patents

Description

Oct. 29,1929. N. D. PRESTON AUTOMATIC TRAIN CONTROL SYSTEM Filed Sept. 10, 1924 2 Sheets-Sheet Oct. 29, 1929. N. D. PRESTON AUTOMATIC TRAIN CONTROL SYSTEM 2 Sheets-Sheet 2 HIIIIP HI I I Filed Sept. 10, 1924 Patented Get. 29, 1929 NEI :0. rennsron, or nocnnsrnfa, NEW YORK,'ASSIG1\TOR 'ro GENERAL RAILWAY SIGNAL COMPANY, or nocnns'rnn, NEW roan p AUTOMATIC TRAIN-CONTROL SYSTEM This invention relates to automatic train control systems for railroads, and more particularly to systems of the intermittent inductive type in'which continuing speed restrictions are enforced under unsafe trafiic conditions.

In accordance with this invention, it is proposed to automatically apply the brakes and stop the train, unless the engineer takes an appropriate action, conveniently termed acknowledgement, at each caution signal or corresponding control point, and also at each stop or'danger signal. It is considered that the enforcement of such acknowledgement on the part of the engineer will serve to stimulate and maintain his vigilance, thereby assuring greater safety of train movement, inasmuch as failure of both the train control system and the engineer must occur before an accident can result. According to this invention, such acknowledgement is required at each successive stop signal.

' According to this invention, the engineer- 7 is obliged to reduce the speed of his train, if

necessary, after passing each caution signal, so as to be prepared to stop at the'next signal or block entrance, otherwise an automatic application of the brakes occurs; and this requisite is satisfied in a simple and direct manner 39 by requiring the engineer to initiate a brake application or have the brakesacting, if the speed is above some selected minimum speed.

Various other characteristic features, advantages, and specific objects of this inven tion will appear hereinafter as'the description progresses. f 1

In describing the invention in detail, reference will be made to the accompanying drawings, in which Fig. 1 shows in a simplif 40 fied and diagrammatic manner the trackway equipment and locomotive equipment constituting one embodiment of the invention and adaptable for train movement on double track railroads, the parts and circuits being shown more with the purpose of facilitating explanation and understanding of the nature and character of the invention than with the idea ofillustrating the'construction and arrangement of parts that would probably be employedinpractice; and Fig. shows dia- .phore signals "7 are shown conventionally,

grammatically and in accordance with'estab lished invention the trackway equipment for an intermediate signal location on a single track railroad equipped with an automatic block signal system of the type commonly known as the absolute-permissive-block sys- Referring to Fig. 1 of the accompanying drawings, the track rails 1 are divided into track sections or blocks by insulated joints 6] 2 in the usual way, one complete block E, with the adjacent ends of two other blocks D and F being shown. It is assumed forthe purposes of explanation that each blockwill be at least as long as braking distance forthe normal running speed on the railroad, and will include only one track circuit. The parts and circuits associated with each of. these blocks will ordinarily be the same; but for simplicity in illustration there, is shown in Fig. 1 only the equipment for the-block E. Each block is provided with the well known normally closed track circuit, including a track relay 3 and a track battery 4:. As shown, a relay 5 is included in. series with the track battery 4;, this relay being of suitablecone struction and serving its well known purpose of attracting its armature and closinga normally open front contact 6 upon the entrance of a train into the'corresponding block.

This system oftrain control is preferably used in conjunction with trackway block signals. The particular type of block signal and its-form of control circuits may be any one of the kinds well known'inthe art; Semawithout attempting to illustrate any particu; lar form of control circuits, it being assumed that these signals will be ofthe usual three position type and controlled accordingly.

The controllmg lnfluences or impulses {for the automatic train control systemare com;

'municatedor transmitted according to this. 7

invention by magnetic induction between trackway devices and receivers, the action taking place through an intervening air gap and without physical contact. These control ling impulses are transmitted onlyat prede termined points along the trackway where the track devices are located, and the system of this invention is accordingly of the intermittent inductive type.

The track device for bringing about automatic control, conveniently termed the initiating track device, is designated a whole T and comprises a permanent magnet 8, made up of a suitable number of sections of a general U-shape, in this instance shown disosed horizontally between the track rails 1.

ecured to the ends of this permanent mag-- net are vertically disposed soft iron cores 9, which have lateral extensions 10 projected toward each other and affording a leakage path for the magnetic fiux of said permanent magnet, said leakage path being of relatively higher reluctance than the flux path through the receiver later to be described. The cores 7 V netic field above the track device; whereas with these coils on open circuit and deenergized, said permanent magnet produces an active magnetic field above the track device thru which the receiver on the passing locomotive or other vehicle must pass.

- The initiating track devices T may be located at different points in the several blocks as desired; but the preferred arrangement consists in locating one such track device in each block at braking distance for the selected minimum speed in the rear of the insulated 'oints defining the exit end of that block. uch a track device T is shown in the block E.- In the case of long blocks, or under other circumstances as desired, in addition to the initiating track device near the exit end of each block, as just described, there may also be another initiating track device in that block at braking distance from the exit end thereof for the normal running s eed of trains. Such a track device T is s own in the block E. Theinitiating track device near the exit end thereof is employed to stop a train short of the end of the block, if the next signal in advance is in the danger position, unless the engineer takes appro- 'priate action. In other words, this track device, such as T is employed to enforce acknowledgement of each stop signal. The same track device may be used, if desired, to enforce acknowledgement of a caution signal and control the car equipment so as to compel a reduction in speed in obedience to the caution signal; or a separate initiating track device, such as T, may be employed in each block as the cautionary device.

Associated with each block is a reset or restoring track device, which is located near the exit end of each block. This reset track device TR comprises a soft iron core, preferably in the form of the general U-shape and provided with enlarged pole pieces. On the legs or back yoke of this core is wound a coil 12, and when this coil is energized, a magnetic field exists above the reset track device. For reasons which will appear hereinafter, in the particular form of the invention shown, the reset track device is located outside of one of the track rails and is disgoverned in various ways, by line relays,

track relays, or circuit controllers on the associated block signals. In order to economize in battery consumption, arrangements are shown such that the coils 11 and 12 of these track devices are normally deenergized and are automatically energized upon-the approach of the train.

The energizing circuit for the reset track device TR may be traced as follows :-co1nmencing at the coil 12, wire 13, armature 6 of relay 5 and its front contact, wire 14, front contact 15 of the track relay 3 of the block next in advance, wire 16, battery 17 and wire 18.

The energizing circuit for the neutralizing coils 11 of the caution track device T may be readily traced on the drawings and includes a battery 19 and the front contact 20 of a relay 21. The energizing circuit for the relay 21 includes a back contact 22 of the track relay 3 of block in which said track device is located and a front contact 23 of the track relay 3 of the next block in advance.

The other or stop signal initiating track device -T has an energizing circuit forits neutralizing coils 11 which may be traced as follows :commencing at coil 11, wire 24, front contact 6 of relay 5, wire 25,.front contact 26 of track relay of block next in advance, wire 27, battery'28, and wire 29 back to the coils 11.

The locomotive or other railroad vehicle is shown diagrammatically as two pairs of wheels and axles 30. Operated by one of these axles is an automatic reversing switch X, which in the simplified form shown comprises a pivoted switch arm 31coupled by a link 32 to the outer end of a swinging arm 33 mounted to turn freely on the axle 30. A friction shoe 34 is carried by said arm 33 and is pressed against the axle 30, or a collar thereon, by a compression spring 35, thereby forming a frictional connection between the arm 33 and the axle. In Fig. 1 the normal direction of traffic is from left to right as CD I indicated by the'arrow; and assuming a train movement in this direction, it will be evident that the arm 33 is moved by friction,as the axle turns, to the upper position shown. If the locomotive should back up, or should run in the, normal direction of trailic with the other-end ahead, the reversing switch X wouldbe operated to the other position, shiftin the switch arm 31 to its lower position.

. buitably supported on the locomotive is a receiver-R disposed in position to cooperate with the initiating track devices T and T The receiver R, in the simplified construction shown, comprises two enlarged pole pieces or collector plates 36, with extensions separated by an air-gap; and a pivoted armature 37 spans this air-gap, said armature being held in a retracted position by a suitable spring 38. This armature 37 carries a suitahis contact arranged to engage an insulated stationary contact, shown conventionally as an arrow, when said armature is in its retracted position. It will be evident that, when the receiver R passes thru the magnetic field of an active track magnet T or T the magnetic field of this track magnet will be collected by the pole pieces 36 and concentrated across the air-gap of the armature 37, thereby attracting this armature in opposition to the spring 38 and opening its contacts.

In the particular form of the invention shown two receivers RR are employed, one on each side of the locomotive in position to pass over the reset track device or magnet TR. These reset receivers RR are constructed alike, substantially the same as the receiver R, having a normally spring retracted armature 39. The contacts of the armature 39 of the reset receivers, however, are normally open and are closed by the attract-ion of this armature.

The locomotive or car equipment includes a plurality of relays P, S and Q of suitable construction, which are preferably quick acting, protected by spring supports against operation by vibration, and otherwise constructed in accordance with recognized practice so ast-o be adapted for their respective duties. The car equipment also includes a suitable speed responsive device or governor G, connected to and driven from the car wheels and acting to open contacts 40 whenever the speed of the car is above-some selected minimum speed, such as fifteen or twenty miles per hour. This speed responsive device G may be of any suitable construction and is shown in'a simplified manner as being of the well known centrifugal type.

It isassumed that the automatic application of the brakes will be produced by a suitable application valve or equivalent means, presumably controlled by an electro-pneumaticvalve. The particular type of brake applying means is not material to the present invention and has not been illustrated. A

conventional form of electro-pneumatic'valve I EPV has been shown to illustrate the manner 'of control for the brake applying means.

It is assumed that this system of train control will be applied to a locomotive or other railway vehicle equipped with the usualair brakesystem', including an engineers brake a simplified and diagrammatic manner and comprises two diaphragms 42 and 43 closing the ends of enclosed chambers 44 and 45. In the chamber 44 and actingagainst the diaphragm-42 is aspring 46 having a strength corresponding to about 20 pounds per square inch on the diaphragm 43, a 20 pound reduction being assumed as constituting the desired brake application. The diaphragms 42 and 43 are connected by member 47 which, by

the action of an insulated projection or equivalent means, acts to close contacts 48 when these-diaphragms are shifted; to the left in opposition to the spring 46. The chamber 44 is in communication with the regular equalizing reservoir of the air brake system;

whereas the chamber45 is in communication with the lowpressure side of the feed valve, so that the pressure in this chamber 45 cor responds with the normal running brake pipe pressure. t ermined reduction inthe equalizing reservoir pressure, assumed to be 20 pounds in this instance, the pressure in the chamber 45 overcomes the reduced pressure in chamber 44 lus that of the spring 46, and shifts the diaphragms and their connecting member 47 to the left, thereby closing the contacts 48. The engineer may make the reduction in one or more stages. The contacts 48 do not close until a reduction has been made in'equalizing After the engineer makes a predereservoir pressure which in time will bring out a brake application of th d i d f; fectiveness. v i

The act of acknowledgement hereinbefore mentioned has been taken to consist in manual operation of a suitable push. button or contactor. This acknowledging contactor AC is located at a convenient point inthe cab and readily accessible to the engineer; In;

the form shown, this acknowledging con- .tactor comprises a plunger 49 and two contacts or switch arms 50 and51. The plunger 49 is urged toits upper position by a spring 52. When this plunger is depressed by the engineer in opposition to the spring 52, the

contact arm 50 is moved at lonceinto engagement with a stationary'contact, shownas an I equipment in the normal position shown, with arrow. The other contact arm 51 is released by such downward movement of the plunger 49, but its downward movement, brought about by an auxiliary springv53, is retarded by a suitable dash-pot device 54, so that the resilient finger 55 of said contact arm 51 is not moved far enough to be disengaged from its cooperating contact (shown as an arrow) until after the plunger 49 has been held in the depressed position for a short interval of time, such as five or six seconds. The arm 51 returns quickly to its upper position.

In case the engineer fails to take appropriate action at each caution signal, or corresponding control point, or at each stop signal, it is desired to inflict some form of penalty'in order that the engineer may be obliged to remain alert. Such penalty'may take various forms, but in the arrangement shown, the train must be brought to a stop and the apparatus restored by operation of a reset switch BS which is accessible only from the ground. The reset switch RS comprises a push button or plunger 56 with normally closed contacts 57 and normally open contacts 58.

Opemzfion.The parts and circuits of the car equipment are shown in Fig. 1 in the normal position. The circuits have been shown. in simplified manner, embodying the symbols B and C to indicate the terminals of a car battery, turbo-generator, or other suitable source of current; and the circuits will be traced from B to C. The primary relay P is maintained energized by a stick circuit as follows :-commencing at B, front contact 60 of relay P, wires 61 and 62, relay P, wire 63, armature 37, and its contact to C.

The relay S is maintained energized by a stick circuit which may be traced as follows ;commencing at B, front contact 64 of relay S, wires 65 and 66, relay S, wire 67 and front contact 68 of relay P to C.

' The relay Q is energized by a stick circuit which may be traced as follows :-commencing at B, front contact 69 of relay P, wires 7 Oand 71, timed contacts 5551of acknowledging contactor AC, wires 72, 7 3, front con tact 74 of relay S, wires 75, 76, relay Q, wires 77 and 78, and front contact 79 of relay Q to C.

With the relay Q energized, theelectropneumatic valve EPV is maintained enr gizcd by circuit commencing through front Contact 80 of relay Q, wire 81, valve EPV, wire 8:2 and normally closed contacts 57 of the reset switch RS to C.

Entering caution block.-Assimiing the car the relays P, S and Q. energized as just oescribed, suppose that the car passe into a caution block, that is, a block next in the rear of an occupied block. For instance, assume a train 1n the block F, making the block E a caution block. As the following car or train enters the block E, the track relay 3 is shunted and closes its back contact 22, but the relay 21 cannot be energized, because the front contact 23 of the track relay 3 of the block F is open. Consequently, the deflecting or neutralizing coils 11 of the track magnet T are on open circuit, and an active magnetic field exists over this track magnet. -As the receiver R passes through this magnetic field, its armature S7 is attracted, interrupting the stick circuit for the relay and causing its armature to be retracted and open its front contacts. The opening of the front contact 68 of the relay P breaks the stick circuit for the relay S, which is thereby deenergized and remains deenergized until restored by passing an active reset magnet. Upon deenergization of the relay S, the closure of its back contact 64 together with wire 83, establishes a connection to B in multiple with that through the front contact 60 of the relay P; and since the opening of the contacts of the armature 37 of the receiver R is only momentary, the relay is (prickly reenergized.

The opening of front contact 69 of the relay although only temporary, interrupts the k circuit for the relay Q, heretofore traced would cause deenergization of this relay, as at tne time of the opening of said front co react 69, the engineer has the plunger 49 of his acknowledgingcont actor depressed so asto close the contacts 50 and establish a connection to B throi these contacts and wire 84, in c with the connection to B through contact 69. In other words, unless ..eer takes the appropriate action by manuari operating the acknowledging conmanipulation, the contacts 55 open after a .ime and interrupt the circuit for the relay Q, thereby applying the brakes. In short, the engineer must restore the acknowledging contactor AC to normal after each manipulation, otherwise the brakes are applied. The time interval provided for thecontacts 51 is selected so as to afford the engineer reason able latitude in the manipulation of this cont actor, but is short enough to prevent the engineer from acknowledging by one act two successive signals or control points.

Unless the speed of the train at the'time the relay S is deenergized is below the'minimum speed, so that the contacts 40 are closed and together with wires and 86 establish a shunt around the front contact-74L of the relay S, the engineer must either have his brake valve in the service position, or must have made the required reduction in equalizing reservoir pressure, otherwise the stick circuit for the relay Q is'interrupted, the brakes are applied and the reset switch RS must be operated from the, ground before the train can proceed. If the engineer has his brake valve in the service position, a multiple path or shunt around the front contact 74 of the relay S is established by wire 87, con tacts 41, and wire 88; and similarly, if a pre determined reduction has been made in the equalizing reservoir pressure, closing cont-acts 48, a like multiple path or shunt is established through wire 89 contacts 48 and wire 90.

By reason ofthe construction and arrangement just described, the engineer iscompolled to reduce the speed of his train, unless below the minimum speed, after passing the caution track magnet, with the result that the train is safely controlled. It will be observed that if the engineer should move his brake valve outof'the service position before making sutficient reduction in equalizing reservoir pressure to close'contacts 4,8, or should attemptto release the brakes after closure of these contacts, which would im-. mediately open upon movement of theengineers brake valve to the release 'or running positions, the relay Q, would be deenergized, since the front contact 741 01? the relay S remains open thruout the caution-block.

Ac/mmliedgment at a stop signaZ.'For reasons already explained, it is considered important to require the engineer to acknowledge each stop signal. This is done by automatically applying the brakes unless the engineer takes appropriate action. Since such acknowledgement is required to assure safe control of the train in case the engineer is incapacitated,- it is considered essential that the point where such acknowledgment is required should be so located that, if no acknowledgment is made and an automatic brake application occurs, the train will be stopped short of the point of danger. For this reason, the track device or magnet T is located braking distance for the minimum speed from the exitend oftheblock.

As the locomotive or car passes the track magnet T, which is in the danger condition with the block F occupied, due to the opening of the front contact 26 of thetrack relay 8 the armature 37 of the receiver R is attracted again and the relay P is again mo.- mentarily deenergized, such "deenergization occurring even though the relay S is deenergized, because the armature 37 breaks the connection to C through the relay P. If at the time of such momentary deenergization ofthe relay P, and the accompanying opening of its front contact 69, the engineer does not have the'plunger of the acknowledging contactor AC depressed, the quick acting relay Qis deenergized and the brakes applied. T his automatic brake application occurs even thoughthc running speed is below the low speed limit, and the contacts 40 are closed.

The relay Q, is, of course, made quick acting .so as to open in the interval of time that the armature 37 of the receiver is in the retracted position, it being noted that this time is longer because the speed of the train is low. The same acknowledgment 1s required at each successive stop signal, since the relay P 1s deenergized at each actlvetrack magnet,

Also, if two track magnets are used in a comotive is traveling in thenormal direction of traflic. It will be observed that the coil 12 of the reset track magnet TB is energized if the next block in advance is not occupied.

Assume that a train has passed thru a cau tion block and that in the meantime the block in advance has cleared up. As thetrain approaches-the entrance to the unoccupied block and passes over the reset trackmagnet TR which is energized under these conditions,

35 track device requ res ac the armature 39 of the correspondingreset receiver is attracted, establishing api'ck-up circuit for the relay S, as follows :-commencing at B, armature 39, wire 91 or 92, as the case may be, reset switch 31, wires 93 and 66, relay S, wire 67 and front contact 68 of relayP to C. Upon reenergization of the relay S the normal stick circuit for the relay Qis reestablished, and the train may proceed at its normal runningspeed without interference. In this connection it will be obvious that, if desired, speed contacts, opening abovea selected maximum speed, maybe inserted in series with the front contact 74k of the relay S, thereby providing a maximum speed limit. As shown, there is no maximum speed limit enforced under clear traflic conditions.

In case the engineer fails tov acknowledge an active initiatingtrack magnet, or fails to make timely initiating of a manual brake application whileexceeding thelow speed limit for other than clear traffic conditions, and the relay Q; becomes deenergized, it is necessary for the engineer to operate the refore, protect the reset switch RS against countered in practice.

abuse and prevent it from being carelessly or maliciously left in the operated position. Briefly summarizing the operation of the system of this invention, it will be observed that acknowledgement is required for each caution signal and for each stop signal, or corresponding control point. In the preferred. arrangement of track devices, such as shown in the block E, the acknowledgment of the caution signal takes place at the device T in advance of the signal and at least braking distance for the normal running speed from the exit end of the block; and the acknowledgement of the stop signal occurs at the device T located braking distance for the minimum speed from the exit end of the block. This arrangement requires two initiating track devices for each block, but is consideredto be the preferable arrangement for'the conditions ordinarily en- In the interests of safety, as herein before pointed out, the track device T forcing acknowledgement for the stop signal, should be located in the rear of the signal, and must be effective if the signal is at stop, though not necessarily if the signal is at caution. This same track device T could be used as the cautionary track device, but such an arrangement would have the objection that acknowledgement would be required at a distance in the rear of a caution signal and at a'point where the signal might not be readily visible, and also that a speed reduction would be compelled before reaching the caution signal. Regarding the reset magnet, in View of the foregoing explanation of operation it can be seen that this magnet should be located close to the exit end of each block, so that a train will not receive a resetting impulse if there are any cars between the reset magnet and the end of the block. Also, the reset magnet should be in the rear of the cautionary initiating track device, assuming that the reset magnet will be used to clear up the car apparatus at a caution signal as well as at a clear signal, otherwise the initiating impulse received at the cautionary track mag- Ilet might be improperly nullified by the reset track magnet. So long as the fundamental principles mentioned and other retrack magnet being of course located and' controlled accordingly.

Single track 0perat2'oa.-On single track railroads, trains normally move past signals and conrol pointsin both directions, and

since the train control system must be capable of safely regulatlng tram movement in either direction, special problems are presented in applying train control systems to single track railroads. Fig. 2 shows one arrangement of track devices and control circuits applied to an intermediate signal location of a single track block signalling sys tem of the Well known type commonly termed an A. P. B. system. The circuit arrangements and devices constituting an A. P. B. system are now generally known and recognized in the art, so that detail illus-' tration and description is unnecessary. One specific form of an A. P. B. system is shown and described in detail in the patent to Wight No. 1,294,736, dated February 18, 1919, to which reference may be made for a disclosure of the specific means utilized to obtain the operations and results herein generally explained.

Referring to Fig. 2, the adjacent ends of two blocks K and'L are illustrated, these blocks being provided with track relays 98 and 99, respectively. The signal 100, which is of the usual three-position type, governs traffic from left to right, from the block K into the block L; and a similar signal 101 governs traffic in the opposite direction from the block L into the block K. In the A. P. B.

its

system, when a train enters a stretch of single track, all of the opposing signals governing trafiic in theopposite position assume the danger or stop position. A train approaching from the left in Fig. 2 and passing from the block K into the block L will, therefore, find the signal 101 at stop, irrespective of the presence of other trains. The signals, such as in the case just assumed, governing traffic in the direction in which the train is running are automatically controlled to the clear, caution, or danger position by the presence of other trains ahead in the same way as on a double track. Associated with each of the signals in an A. P. B. system is a directional stick relay which is normally deenergized and which is automatically energized upon passage of a train by the corresponding signal in the direction of traflic governed thereby. Referring to the signal 100, the stick relay ST 100 is energized when a train, traveling from left to right, passes the signal 100, and this relay is maintained energized until the rear end of this trainhas advanced beyond the next signal ahead governing traffic in the same direction. The other stick relay ST 101 for the signal 101 is controlled in the same way. The particular circuits and devices for thus controlling these stick relays ST 100 and ST 101 are not material to the present invention and have not been illustrated, one arrangement of such control circuits and devices being shown and described in the patent to Wight above mentioned. ,F or simplicity in illustration and explanation, the controls for the track devices have been shown in Fig. 2 as accomplished by the opening and closing of circuit controllers operated in the usual way in accordance with the position of the signal. These circuit controllersare shown in accordance with established convention. There are three circuit controllers for each signal, those for the signal 100 being designated 102, 103 and 104, the corresponding circuit controllers for the other signal 101 being given the same refer- 'ence numbers with an exponent. Circuit controller 102 is closed only if the signal is inits 90or clear position. Circuit control ler 103 is closed'with thesignal in the 90 or clear position, or in the 45 or caution position, or'any intermediate position between these two. The circuit controller 104 is closed from 90 to 45, the same as the circuit controller 103. 7 i

' The cautionary initiating track device T is located at the signals substantially opposite the insulated joints defining the block ends. This track device is disposed midway between the track rails and influences a re-;

ceiver R on a car passingthereby in either dlrection. There are two. energizing circuits for theneutralizing coils 11 of the.

track magnet T, these circuits beingsimilar, so that the tracing of one will make both clear. One of these energizing circuits, controlled by the signal 100 may be traced as follows: commencing at lower coil 11, wire 105, battery 106, wires 107 and108, back contact 109 of track relay 98 of block K, wire 110, circuit controller 102, wires 111 and 112'back to the other coil 11.

7 Assuming a train approaching from the left, the opposing signal 101 will be at stop. hen the approaching train enters the track section K, the track relay 98 drops and closes its back contact 109; and if the signal 100 is then in the clear position, the neutralizing coils 11 of the track device T are energized and said track device is rendered inactive. If the signal 100 is in the caution or stop position, the circuit controller'102 interrupts the energizing circuit for the coils 11, render- 'ing the track device T active. The same eX- planation applies for train operation in the other direction, the circuit controller 102 of the coils 11 in this instance.

The initiating track device enforcing acknowledgement of a stop signal, as previouslyexplained, is located braking distance for the minimum speed in the rear of the corresponding signal. The track device T for the signal 100 has two energizing cir cuits for its neutralizing coils 11, one through the back contact 113 of the track relay 98 and through the circuit controller 104 of the signal 100, the other circuit including a front contact 114 ofthe opposing stick relay ST 101. Assuming a train traveling from left to right, the stick relay ST 101 is deenergized; and when this train enters the track section K and drops the track relay 98, closing its back contact 113, the coils 11 of the track device T are energized, providing the signal 100 is in either the clear or caution position. 7 If the signal 100 is in the stop position, the coils 11 of the track device T; are on open circuit, and the engineer must acknowledge. The stick relay ST 101 picks up for a train traveling in the other direction, from right to left, closing its front contact 114 to'energize the coils 11 of the track device T irrespective of the position of the signallOO. Consequently, the track device'T for the. signal 100 is always inactive fora train traveling in the opposite direction, due to the control of the stick relay ST 101. .The same explanation applies to the control of the track device T for signal 101.

The reset magnets for both directions are controlled in the same way as on double track, except that a back contact 115 of the adjacentt'rack relay isused instead of the front contact of a relay in series with the track battery, and a circuit controller on the signal instead of a front contact of the track relay next in advance, For-example,

the energizing circuit for the reset magnet TR fortraflic' moving from left to right'in" the direction governed by the signal may be traced as follows :-starting at the reset magnet TR, wire 24, back contact of the track relay 98 of the block K, wire 25,

circuit controller 103 of the signal 100., wire 27, battery 28 and wire 29 back to the'reset magnet. The automatic reversing switch X renders the proper receiver on the locomotive effective "to cooperate with the correct reset track device.

' The invention has been disclosed in a simple term, divested of many features of constructi-on' and operation that might be desirable in practice and it should be understood that various eXpedients may be employed in connection with the specific means of cab si -nals and automatic control with the giving of a distinctive signal, While in unequipped territory, and the like. Moreover, the invention is not restricted to the particular construction, combination or arrangements of parts and circuits herein disclosed, but is susceptible of wide variation in the particular form of means employed. Various chan es, adaptations, additions, and modifications may be made in the particular embodiment of the invention disclosed, without departing from the invention or deviating from the fundamental concept of means underlying the invention.

What I claim is 1. In an automatic train control system, the combination with a traffic controlled track device providing a local ma netic field when in the active stoppin condition, an armature on a car attracted by the magnetic field of said active track device, means on the car controlled by said armature and tending to cause an automatic application of brakes on the car, and manually operable means eii ective only ii actuated prior to the attraction of said armature for preventing such application of the brakes.

2. In an automatic train control system, the combination with a track magnet producing an external local magnetic field when in the active stopping condition, of automatic brake control apparatus on a vehicle, control means on the vehicle, operated by magnetic attraction while passing through the magnetic field 01" said trackmagnet and tending to cause operation of said apparatus, and manually operable means on the vehicle effective for a limited time only after each manual operation and capable of preventing operation of said apparatus only it manually operated prior to the operation of said control means.

3. In an automatic train control system, means on a vehicle including an electro-magnetic valve and acting upon the regular air brake equipmentof the vehicle to produce an automatic brake application upon de-energization of said valve, a stick relay on the vehicle controlling said valve and having a stick circuit including contacts of the relay closed only it said relay is energized, a traitfic controlled track magnet producing a local magnetic field under dangerous trafiic con ditions, an armature on the vehicle attracted by the magnetic field of said track magnet and when attracted interrupting said stick circuit, and manually operable means for main taining said stick relay energized independently of the break in its stick circuit made by the action of said armature, said manually operable means having a limited time of effective action and being effective only if actuated prior to the attraction of said armature.

4. An automatic train control system for railroads comprising, a track device producing'a local] magnetic field when in its active stopping conditon, brake control apparatus on a vehicle, impulse receiving means on the vehicle including relay temporarily de-energized by the influence of the magnetic field of said track device, said relay when thus deenergized tending to cause operation of said brake control apparatus, and manually controllable means including a stick relay for preventing such operation of said brake control apparatus, said manually controllable means being effective only if actuated prior to operation of said apparatus and only for a limited time after each manual operation.

5. In an automatic train control system, the combination with a brake control device ef fective when active to automatically apply the brakes of a vehicle and maintain such brake application until the vehicle has been brought to a stop, of intermittent inductive impulse transmitting means acting at predetermined control points along the track to produce initiating and restoring influences on the vehicle in accordance with the presence or absence of other trains ahead, speed con rol apparatus including a speed responsive device driven from the wheels of the vehicle and rendered effective by said initiating influences to actuate said brake control device if the running speed of the vehicle thereafter any time exceeds a predetermined low speed limit, said speed control apparatus being restored to normal by said restoring influences, control means temporarily influenced by said initiating influences for tending to actuate said brake control device, manually operable means effective for a limited time for each operation and only it operated prior to the actuation of said brake control device for maintaining it inactive in spite of its control by said control means, and other manually controllable means for maintaining said brake control device inactive in spite of said speed control apparatus only so long as the engineer is initiating a manual brake application or is maintainng a completed brake application.

6. In an automatic train control system for railroads having tracks divided into blocks, a track magnet near the exit end of each block at braking distance for a predetermined low speed from the eXit end of said block, each track magnet comprising a permanent magnet and neutralizing coils and producing a local magnetic field it the next block in advance is occupied, brake control apparatus on the vehicle tending to produce an automatic brake application at the time of movement of the vehicle past an active track magnet, and manually operable means effective only if actuated prior to the operation of said apparatus for preventing such brake application, said manually operable means being eilective for a limited time only after each manual operation thereof.

7 thereof, impulse receiving means on the ve 7. In an automatic train control system for I railroadshaving tracks divided into blocks, a track device associated with each block and assuming an active stopping condition if the next block in advance is occupied, brake control apparatus on a vehicle including a speed responsive device driven from the wheels apply the brakes automatically whenever the" speed of the vehicle exceeds a predetermined low speed limit, sa1d apparatus including a stick relay which if ale-energized produces a,

brake application that cannot bereleased until the vehicle has been brought to a stop, a normally open energizing circuit for said stick relay, and manually operable means for closing said circuit for a limited time only, said manually operable means being effective only if actuated prior to the reception of an impulse by said impulse receiving means.

8. Car apparatus for train control systems comprising, brake control apparatus including an electro-pneumatic valve for automatically applying the brakes on de-energization of said valve, a normally energized stick relay maintaining said valve energized, a stick circuit for said relay, separate circuit controlling devices for interrupting said stick circuit, one of sa1d circuit controlllng devices being temporarily opened in response to control influences from the trackway, the other of said circuit control devices being maintained open so long as dangerous tralfic conditions exist, manually operable means for establishing a shunt around the first circuit controlling device for a limited time, and other manually operable means for maintaining a shunt around the other of said circuit controlling devices only so long as the engineer is initiating or maintaining a manual brake application.

9. In a train control system for single track railroads, equipped with an absolute-permissive-block system ofthe character described, the combination with a signal governing traliic in one direction, of a track device opposite said signal and located symmetrically on the center line of the track, a control circuit for said track device acting when closed to render it inactive, means operated in accordance with the direction and movement of trains by said signal for opening sa1d control circuit when a train approaches sa1d signal in the direction of traffic governed thereby and there is another train in advance, a reset track element located on one side ofthe center line of the track and in the rear of said signal, and means for rendering said second track element active irrespective of the direction of train movement it the track in advance of said signal and protected thereby is unoccupied. v

absolute-permissive-block signal system, the

combination with an intermediate signal, of

a track element for governing traflic in both directions, and a reset track elementcapable of cooperating with trains moving in the direction of trafiic governed by said signal only, and automatic means for governing and controlling the condition of track elements in, accordance with trafiic conditions.

11. A train control system for single track railroads comprising, in combination with the intermediate signals of an absolute-permissive-block "system, of a reset traclr magnet for each signal located one side of the center and automatic means operated troni the run-,

ning gear of the vehicle for connecting said train control apparatus to the receiving device on that side or" the vehicle on which are located the reset magnets associated with the signals that govern traflic inthe direction the v vehicle is then running.

12. In a train control for single track railroads equipped with an absolute-permissiveblock signal system, thecombinatio-n with the intermediate signals of said block signalsystem, of a reset track element for each signal, active it the portion of track in advance thereof and protected thereby is vunoccupied, initiating track elements adjacent said signals, means responsive to the direction of the train movement for governing the controlling condition of each initiating track element in accordance with the presence or absence of trains in advance of the associated signal when a train approaches said signal in the direction of traflic governed thereby, a vehicle equipped with brake control apparatus having its operation dependent upon the running speed of the train, a receiver carried by said vehicle inposition to cooperate with the initiating track element irrespective of the direction in which said vehicle moves set receivers, to the brake control apparatus of braking distance for a predetermined low speed from said exit end, brake control apparatus on a vehicle including a speed responsive device driven from the wheels thereof and acting when rendered active to automatically apply the brakes if the running speed of the vehicle at any time exceeds said predetermined low speed, an impulse receiver on the car cooperating with said t-rackway impulse device for rendering said apparatus active, means governed by said impulse re ceiver intending to automatically apply the brakes independently of speed for a limited time at each active trackway impulse device, a manually operable acknowledging device on the vehicle effective for a limited time and only if operated prior to the reception of said impulses for preventing the brake application by said means, and means for automatically restorin said apparatus to normal and remove the low speed limit at the entrance to each unoccupied block. i

g 14. A train control system of the intermittent inductive type comprising, trackway and car-carried apparatus cooperating to apply the brakes irrespective of the speed of the car at a predetermined control point at braking distance for a loW speed limit in the rear of each stop signal, a manually operable acknowledging device effective to forestall such brake application, provided it is operated prior to such brake application, said acknowledging device being effective for a limited interval only when maintained in its operated condition, and brake control means including a speed-responsive device driven from the wheels of the car and governed by said trackway and car-carried apparatus to establish a restricted speed limit which the car cannot exceed without an automatic application of the brakes, said manually operable device being inefiective to prevent such brake application due to excessive speed.

15. A controlling element for train control systems comprising a circuit controller, and means for operating said circuit controller including two diaphragms, one of said diaphragms being exposed to the action of a spring and the pressure in the equalizing reservoir of the usual air brake system, and the other diaphragm being exposed to a feed valve pressure corresponding to the normal running brake pipe pressure.

16. In an automatic train control system for railroads having track divided into blocks, a track magnet near the exit end of each block braking distance for a predetermined low speed from the exit end of said block, each track magnet producing a local magnetic field if the next block in advance is occupied, a normally'energized relay on the vehicle temporarily tie-energized by the influence of the magnetic field of a track magnet in its active condition, brake control apparatus upon the vehicle, said relay upon de-energization thereof tending to actuate said apparatus, said apparatus when once actuated to apply the brakes being maintined in that condition and preventing release of the brakes until restored, means for restoring said apparatus after the vehicle has been brought to a stop, and manually operable means effective only if actuated prior to the operation of said apparatus for preventing such brake application, said manually operable means being effective for a limited time only after each manual operation thereof.

17. In an automatic train control system for railroads having tracks divided into blocks, an impulse transmitting device on the track near the entrance end of each block, a second impulse transmitting device near the exit end of each block at braking distance for a low speed from said exit end, a control circuit for rendering each of said trackway devices ineffective and closed only if the block in advance of the block in which said device is located is then unoccupied, receiv ing means on the car including a relay temporarily de-energized by the influence of said trackway device in its active condition, brake control apparatus on the car, said relay when de-energized tending to cause operation of said apparatus and apply the brakes, manually operable means efi'ective for a limited time only after each operation thereof and also only if operated prior to the actuation of said apparatus by said relay, for preventing such operation of said apparatus, another relay on the carde-energized by said first men tioned relay, and maintained de-energized until restored, mechanism on the car including a speed-responsive device driven from the wheels thereof and rendered effective upon de-energization of said another relay for tending to cause operation of said brake control apparatus if the car exceeds said low speed, and impulse transmitting means partly on the car and partly along the track effective near the exit end of each block for restoring said another relay to its normal energized condition provided the next block in advance is then unoccupied.

18. In an automatic train control system for railroads having tracks divided into blocks, a tripping impulse device on the track near the entrance to each block and automatically controlled to assume its active stopping condition if that block or the next block in advance is then occupied, a reset impulse device near the exit end of each block and automatically controlled to assume its active condition only if the next block in advance is not occupied, impulse receiving means on a vehicle including a relay momentarily deenergized by said tripping impulse device in its active stopping condition, a second relay on the vehicle also de-energized by said tripping impulse device in its active stopping condition, said second relay when de-energized remaining in that condition until restored by an active reset impulse device on the track, brake control apparatus on the vehicle governed jointly by said relays and including a speed-responsive device driven from the wheels of the vehicle, said apparatus acting while said second relay is de-energized to permit movement of the vehicle Without an automatic brake application only at speeds less than a predetermined low speed limit, said first mentioned relay when ole-energized tending to actuate said apparatus independent of the running speed of the vehicle, and manually operable means on the vehicle effective only for a limited time after each operation and only if actuated prior to the operation of said brake control apparatus for temporarily preventing operation of said apparatus by de-energization of the first relay, said manually operable means being inefiective to prevent operation of said apparatus upon de-energization of the second relay.

19. Car-carried apparatus for automatic train control systems comprising, an air brake system including an engineers brake valve, an equalizing reservoir, and a source of fixed pressure; a normally energized'brake control device adapted when de-energized to act on said air brake system and cause an automatic brake application which cannot be released until the car has been brought to a stop, an energizing circuit for said device including three branches in multiple, contacts in one branch automatically opened and closed by controlling impulses from the trackway in accordance with traflic conditions, speed-responsive means driven from the wheels of the car for opening a second branch of said circuit if the running speed of the car at any time exceeds a predetermined speed limit, and means for closing the third branch of said circuit provided said engineers brake valve is in a brake applying position or the pressure in the equalizing reservoir has been reduced a predetermined amount less than said fixed pressure.

20. Gar-carried apparatus for automatic train control systems comprising, an air brake system including an engineers brake valve, a fluid pressure operated circuit controller coupled to said air brake system and closed only if a brake application of a predeter mined intensity is acting, a normally energized electro-pneurnatic valve adapted when de-energized to act upon said air brake system and cause an automatic brake application, a normally energized stick relay controlling said valve, means etfective only after the car has been brought to a stop for restoring said stick relay after de-energization thereof, a stick circuit for said relay including two branches in multiple, a speed-responsive device driven from the car wheels having contacts for closing one of said branches only so long as the car is running at a speed less than a predetermined speed limit, means controlled from the trackway in accordance with traffic conditions for opening and closing a vshunt circuit around said contacts of the

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