US1553291A - Automatic train-control system - Google Patents

Description

sept. 8, 1925. 1,553,291

w. K. HowE AUTOMATIC TRAIN CONTROL SYSTEM Filed'May 26, 1919 ssneets-Sneet 2 FIGA Sept. 8, 1925. w. K. HowE AUTOMATIC TRAIN CONTROL SYSTEM Filed May 26, 1919 5 Sheets-Sheet 5 ATTORNEY.

Patented Sept. 8, 1925*.

'UNITED STATES PATENT OFFICE.

WINTHROP K. HOWE, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL'RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK, A` CORPORATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Application lled May 26, 1919.

To all whom it may concern: 1

Be it known that I, WINTHROP K. Howe, a citizen of the United States, and resident of the city of Rochester, in the county of Monroe and State of New York, have invented a new and useful Automatic Train- Control System, of which the following 1s a specification.

This invention relates to automatic train control systems for railroads, and more particularly to means for establishing communication from the trackway to moving trains inductively, that, is, without physical contact between any parts on the track and train. A

One feature of this invention is the provision for producing a series or succession of electro-magnetic impulses or influences on a moving train, s0 as to permit the operation of those types of relays, or similar .electro-responsive devices, which require a short time to operate.

v Another feature .ofthe invention is the use of a trackway element which produces by a simple and direct action, due to its magnetic properties, a peculiar combination of impulses on passing trains of such a nature that the various magnetic bodies along the track, such as track rails a-nd the like, cannot produce the same action, thus rendering the car equipment immune to the influences of the various foreign magnetic CAD object-s ordinarilyv encountered along a railway track.

Other objects and advantages of the invention will appear hereinafter as the description progresses, and the novel features of the invention will be pointed out in the vappended claims.

In order to explain the nature and characteristics of a system of `train control em; bodyingmy invention, ll have selected some of the forms which the apparatus may take, and have illustrated such apparatus in a simplified and diagrammatic manner in the accompanying drawings, more with the idea of making it easy to understand the nature and characteristic features of the invention, than with the view of illustrating the exact construction and arrangement of parts which Y would be preferably employed in practice.

In describing the invention in detail reference will be made t9 the accompanying comprises serial No. 299,877.

drawings, in which like reference charac- Fig. 3 illustrates a modied form of construction of the trackway element;

Fig. 4 illustrates another arrangement of trackway elements and controlling circuits for providing for impulses or indications of distinctive characters, such as caution and Stop,

Fig 5 illustrates the car equipment prefeiably used in connection with the trackway apparatus and circuits shown in Fig. 4;

Figs. 6 and 7 illustrate still another modiied construction of the trackway elements and car equipment in which .certain circuits are checked; and

Figs. 8 and 9 illustrate a still further modification of the trackway element and car equipment.

Referring to the embodiment of the invention illustrated in Figs. 1 and Q, the

track rails 1 of the railway track are divided ters with distinctive exponents as a matter of convenience. Each of these blocks is provided'with the well known normally closed vtrack circuit including a track battery 3 and a track relay 4. Associated with each block, and preferably located at the entrance thereto, is the trackway element of my impulse transmitting means, which is designated ai a whole T.

The trackway element T, a-s llustrated, a middle magnetic bar or member 5, which is positioned between the ,track rails 1 and extends parallel therewith. Un

4each side of the bar 5 are a number of in- '.sociated with the several blocks are the same. Y V they will be'given thesame reference characv verted U-shaped side extensions 6 and 7 of magnetic material, which are connected at one end to said middle bar 5 and are provided with pole pieces at the other end. The upper faces of the middle bar 5 and the pole pieces of the side extensions 6 and 7 are preferably carried as high as practical clearances will permit. As shown in Fig. 2, these parts are located below the plane of the tread of the track rails, but in some instances they may be carried up to the level of the track rails, and even slightly above. The side extensions 6 and 7 are arranged in staggered relation so as to be encountered successively by passing trains. For example, in the arrangement shown in Fig. 1,.

a train traveling in the normal direction of traffic (from left to right as indicated by the arrow) will encounter first the side` extensio-n`7 of the trackway element T, and then the side extension 6, and so on. One group of the side extensions, as 7, are each provided with Va winding or coil 8; and these.

coils are connected in series in a normally closed circuit controlled by a line relay 9, or equivalent device, in accordance with traffic conditions ahead.

In the particular arrangement of trackway circuits illustrated, the controlling cir-l cuit for the line relay 9 of each block includes front contacts of the track relays of the corresponding block and the block next in advance. so that this line relay is energized or picked up when neither the corresponding block nor the next block in advance is occupied, and is deenergized or dropped when either of these blocks is occupied. Obviously, other arrangements of relays and `circuits may be employed to attain the same result.

My system of automatic train control may be used in connection with the/ordinary fixed signals employed in block signaling systems: and ysuch signals are indicated conventionally in Fig. l, the controlling circuits and devices for such signals'being omitted to avoid co-m}; lication.`

Referring to 2, the car equipment comprises a receiving element L, which consists of a yoke Y of magnetic material. having three legs 10, 11 and 12, each provided with a pole piece and having thereon a coil 13, 14l and 15, respectively. This car-carried element L is positioned on the locomo- .tive or other railway vehicle so that its pole pieces pass directly over the middle bar 5 and the pole pieces of the extensions 6 and 7, and is also preferably disposed so as to pass as close to the trackway element T as the trackway clearances will permit. so as to have as short an air-gap as practicable between the pole pieces of the car-carried element L and the trackway element T. This air-gap, however, does not/have to be so extremely short as to be impractical, and

may be three or four inches, or so, depending on the size of the parts, the energy used, and the like.

The coil 14 on the middle leg 11 of' the yokeY is continually energized by a. circuit including a battery 16 and a check relay 17. The coils 13 and 15 on the other. legs 10 and l2 of said yoke Y are connected in circuit with the field windings 18 and 19, respectively, of a two-element alternating current control relay R. This control relay R is illustrated conventionally as being of the well known rotor type. This relay is provided with the usual Contact finger 20. v The operatio-n of such a relay will be readily understood by those skilled in the art and need not be discussed in detail, other than to point out that upon energization of the two field windings of such a relay by alternating currents displaced in phase, the contact finger 20 will be moved in one direction or the other depending upon the time phase relation of the currents in the two field wind` ings, and that such movement is not produced when only Aone of the field windings of said relay is energized. In short the operation of such a two element alternating current rela-y is much the same as the well known induction motor.

Any suitable form of traincontrol apparatus may be employed in connection with my invention, either a device for automatically applying the brakes, or for setting any other suitable train governingor speed restricting means into operation; and since various forms of such train control apparatus are well known in the art, a conventional device K has been shown. The train control de-A vice K is normally energized by a circuit including a. battery 21, contact finger 22 of the check relay 17, and the contact finger 20 of the -control relay R.

The operation of the system illustrated in Figs. 1 and 2 is as followsz-Assume. a train, carrying the equipment illustrated in Fig. 2, is approaching the trackway element T at the entrance to the block B, and assume that neither the block B nor the block C is occupied by another train. Under such clear traffic conditions, the line relay 9 is picked up and short-circuits the coils 8 of the trackway element T. As the yoke Y of the car-carried element L passes overv the trackway .element T, the side extensions 6 present a magnetic loop .or bridge for onehalf of the yoke consisting of legs 10 and 11. This greatly reduces the reluctance of the magnetic circuit through the coils 13 and 14, and since the coil 14 is energized, a change of flux` takes place through the coil 13, inducing a current therein which passes through the field winding 18 of the control relay R. The coils 8 of the trackway element T, however, being short-circuited, oppose the passage of fiux through the Side extension 7, so that there is little, if any,

change in the flux through the coil 15, at least, not sufi'icient to energize theI field winding 19 of the control relay R and causey operation thereof. For efficient and 4reliable performance it is desirable, of course, that the opposing or bucking action of the coils 8, when short-circuited, Should beeffective to prevent operation of the control relay R With sufficient margin to satisfy practical working conditions; andin some instances, depending upon the size and proportion of parts, together with their electrical and magnet-ic characteristics, itmay be desirable to short-circuit the several coils 8 separately, rather than in series as shown, this being done by providing separate circuits and contacts on the track or line relay for the several coils, in a manner which will be readily apparent to those skilled in the art.

If the block C is occupied at the time the train in question passes the trackway element T at the entrance to the block B, the line relay 9 is deenergized,'and the coils 8 of said trackway element are open-circuited. As the train passes the trackway element T in this controlling condition, current is induced in both.coils 13 and 15 and Hows through both field windings 18 and 19 of the control relay R. The current induced in the coils 13 and 15 is substantially alternating in character; and on account of the staggered arrangement of the side extensions 6 and 7, these currents in the field windings 18 and 19 are displaced in phase, and thus cause movement of the contact finger 20 to open the circuit for the train control device K. The side extensions 6 and 7 are preferably spaced along thev track 'at suitable distances, with due regard to the proportioning of the parts and theiry electrical and magnetic characteristics, so as to produce currents in the control relay R with a maximum p'hase displacement, that is, so that the current in one phase is zero when it is a maximum in the other phase. Tn this connection it may be explained that the current in the winding 18, for example, may be assumed to be zero when the pair of legs 10-11 of the car element are directly over the corresponding side extensions 6, and also at some intermediate point between each two adjacentside extensions 6. Putting it another Way, as the car element approaches a given side extension 6, and comes directly over it, a half wave ofcurrent in one direction is produced in the winding 18, and as the car element recedes from this particular side extension 6, another Ihalf wave of currentl in the opposite direction is produced inthe winding 18. Thus, it may Ybe assumed that there is a maximum cur 4rent in the relay winding 18 in one direction just before the'car element passes over a side extension 6, and a maximum 1n the opposite direction just after the car element passes over said side extension; and it is contemplated that the relative positioning of the side extensions 6 and 7 will be preferably selected so that, when there is a maximum current in one Winding of the relay, there will be approximately zero curvrent in the other winding.l One relative ar- Irangement of the side extensions which, .under certain conditions, produces the desired maximum phase displacement, is where each side extension 6, for instance, is located opposite a point either about l@ or about 9%; of the space between the adjacent opposing side extensions 7. Obviously, however, the particular relative spacing of the side extensions will vary somewhat in practice dependent upon the air-gaps, the selflinduction of the coils, and similar variable factors. The check relay 17 detects breaking of the circuit for energizing coil 14, o`r depreciation of the battery 16, since this would permit the armature or Contact finger 22 of said check relay to diop and open the circuit for the train'control device K, thus protecting the train, in case such failures should occur.

In the modified construction of the trackway element shown in Fig. 3, a battery 23 is included in circuit for thecoils 8.; and the extensions 7 with a polarity opposing that ofthe legs 11 and 12 of the car-carried element. Thus, when the coil 8 is energized under clear traffic conditions, the passage of flux through the extension 7 is opposed by the counter magneto-motive force of said coils 8.

Tn the modified construction shown in Figs. 4 and 5, the principles of operation exemplified in thefconstruction illustrated in Figs. 1 and 2, are employed to provide for the transmission of two different kinds of controlling impulses, suitable for governing the train in accordance with caution conditions, or stop conditions. In this modifi` cation, the car-carried equipment is the same as that shown in Fig. 2, with the exception of the devices and circuits governed by a control relay R1. Two train control devices F and G are employed. One of these devices F is contemplated as being of a type suitable for governing the movement of the train in accordance with the kind of' the control desired `under cautionary conditions, thatfis, when a train enters a caution block next in the rear of a block occupied by another train. The other train control device G is contemplated as being of any suitable type capable of exerting the control desired when the train passes a stop signal and is about to enter a block occupied by another train. Various' devices -are well known in the art for performing these desired functions; and since they form no part of the present invention, suchdevices have been illustrated in a conventional manner. The

lContact finger 201 of the control relay R1 is controlling circuit for one train control deopens the second.

vice F, while maintaining the controlling circuit for the other train control device Gr,-

but a reversed movement of said contact finger maintains 'closed the first circuit and The train control devices F and G are thus selectively controlled by the movements of the control relay R1.

In this modification 'two trackway elements X and Y are employed. These trackway elements are substantially the same in construction as already described and differ from each other by the relative arrangement of the side extensions 6 and 7. The relation of the side extensions 6 and 7 in case of the track element X is reversed from that inthe case of the track element Y, so that the phase relation of the currents produced in the windings of the relay by the side extensions of the track element X is reversed with respect to the' phase relation of the currents produced by the track element Y, for the purpose hereinafter explained. For example, in the trackway element X the side extension 7 is irst encountered by a passing train; whereas in the trackway element Y the side extension 6 is first encountered by such train.

The operation of this modification shown in Figs. 4 and 5 will be readily apparent from analogy to that already described in connection with Figs. 1 and 2. By virtue of the different arrangement of side extenl sions of the trackway elements X and Y, the

phase relation of the induced currents in the field windings of the relay R1 is reversed, so that whenthe train passes over the trackway element X, having its coils 8 open-circuited, the contact finger 201 of said control relay will be operated in the direction to set the train control device G into operation, while the passage of the train over the other trackway element Y, having its coils 8 opencircuited, will cause the contact linger 201, of said control relayto1be operated in the opposite direction to set the other traincontrol device F into operation. In the arrangement shown -in Fig. 4,'the coils 8 of the trackway element X are controlled by the track relay of the corresponding block, whereas the'similarcoils of the other trackway element Y are controlled by a line relay 26 governed by the track relayO of the block next in advance.

Thus, at the entrance to each caution p block, the trackwayelement Y operates the cautionary train control device F; and at the entrance to each occupied block, the trackway element X sets the stop train control device G into operation. In Fig. 4 the trackway element X is shown as located in the rear of the trackway element Y, but this relative arrangement may be reversed. Likewise, while the trackway element Y is shown as located in advance of the joints 2 and as controlled only by the track relay of the next block in advance, it may be located as shown in Fig. 1 and controlled by the track relays of both the corresponding block and the block next in advance. The trackway element X, of course, must beso 1ocated with reference to the entrance of its controlling track circuit that the train will not stop itself.

It will be observed that this modified construction provides for the transmission of two different kinds of controlling impulses or influences to a passing train, which may the same train control apparatus in lin difigerent ways.

Figs. 6 and 7 illustrate a modified construction in which provision is made for checking the circuits of the coils 13 and 15, as well as the coil 14. This is .accomplished by connecting a check relay 27 and a source 'of current 28 in the circuit in each of the coils 13 and 15. This check relay 27 is preferably of a type which will detect any improper or abnormal change in the circuit, due either to an interruption of the circuit, or to a cross or ground; and in the construction illustrated, this check relay is provided with an armature 29 which is normally balanced by a spring 30, and which, if displaced in either direction from its balanced position, moves one or the other of two fixed contact springs 31 awayv from fixed contact points '32, so as' to interrupt the circuit carried lthrough said springs and contact points.

Thus, if the circuit is broken, or the battery voltage drops, the spring 30 overcomes the attractionof the'winding of the relay upon its armature, and moves the upper contact spring 3-1 away from the fixed contact points 32 to open the circuit. If the coil 13 or 15 is shunted by a cross. the current through the check relay 27 is increased, and the-attraction of its armature 29 overbalances the spring 30 and likewise opens the circuit. In

this way, .any break or improper connection changing the current normally iowing through the check relay and for which it is adjusted, results in the opening of the control device of the relay. This type of check relayv is also shownI as employed with coil 14; and the controlling circuit for the train control device K is taken in series through the contact devices of the several control relays 27 associated with the'several coils 13, 14 and 15, as Well as through the cont-act finger 201 of the control relay Rl. With such a checking arrangement, it isA found preferable to provide bothl of the extensions 6 and 7 of the trackway element T with neutralizing coils, as shown in Fig. 6. This expedient is desirable in order to obviate the possibility of the checkrelay 27 in the circuit for the coil 13 being opened each time the trainpasses a trackway element, regardless of traiiic conditions. To illustrate, it

. will be note-d that the side extension 6 in Fig.

1 always induces a current in the coil 13, and in many instances, depending upon the types of construction employed, this induced current would operate the check relay included in circuit with said coil 13, thereby producing an -unnecessary `and improper actuation of the train control device K.

In the modified construction shown in Figs. 8 and 9, the track equipment comprises a plurality of inverted U-shaped magnetic yokes 33, each provided with pole pieces and a coil 34, said coils being arranged to be short-circuited or open-circuited by the operation of the line relay 9 in the manner already described. The car equipment lcomprises a yoke 35 having two legs each carrying a coil designated 36 and 37 respectively. by a circuit including a battery 38 and a check relay 39, this check relay being shown of the type illustrated in Fig. 7 and hereinbefore described., The other coil 37 is ineluded in circuit with a battery 40,'another check relay 41 and the primary of a transformer 42. The secondary of the transformer 42 is connected in circuit with windings of a suitable single element alternating current control relay 43, 'the relay illustrated being of the well known vane type. The normally closed circuit of the train control device Kv is controlled by the contacts 44 of the control relay and the contact devices of the two check relays 39 and 41. The manner in which current is induced in the coil 37 of the car-carried element under dangerous traiic conditions will'be readily apparent in view of the previous explanation. This alternating current inthe primary of the transformer 42 induces current in the secondary of the transformer, and causes operation of the relay 43. Any number of the trackway yokes 33 may be used, 'as desired, or as found expedient to produce an ample and reliable operation of the control relay 43.

The various constructions shown and described are merely illustrative of my invention and are susceptible to modification, ad-

One coil 36 is normally energized,

ditions and adaptation Without departing from my invention'.

What I claim as new and desireto secure by Letters Patent of the United States, is

1. Inductive impulse transmitting means for automatic train control systems comprising, a two-element alternating current relay of the induction type on a vehicle adapted to operate its contacts only after energization thereof by a plurality of cycles of alternating current, a circuit on the vehicle governing said relay, a track element, and means on the vehicle adapted to cooperate with said track element, said track element when in the active stopping condition producing by its cooperation with the vehicle carried means periodical changes of magnetic fluX due to the magnetic qualities ofthe track element and thereby generating in said circuit a plurality of cycles of alternating current to operate said relay as the vehicle passes the track element.

2. Inductive impulse transmitting means for automatic train control systems comprising a two-element alternating current relay on a railway vehicle, a coil connected in circuit with each field winding of said relay, and a trackway element consisting of a plurality of magneticA members arranged in staggered relation along the track and adapted to produce alternating currents of different phase relation in said coils. Y

3. A car-carried impulse receiving element for automatic train control systems, comprising a magnetic yoke, a coil and source of energy for magnetizing said yoke, two inducing coils associated with said yoke, and a two-element alternating current relay having its field windings connected in circuit with said inducing coils.

4. A trackway impulse transmitting `ele'.- ment for automatic train control-systems, comprising a plurality of magnetic cores arranged relatively close together in sta gered relation along the track, and tra c controlled .means for opposing the passage of magnetic flux through said cores.

5. In an automatic train control system, a car-carried magnetic yoke provided with ,a `magnetizing coil and two inducing coils, a two-element alternating current relay having its field windings connected in circuit with said inducing coils, and traffic controlled trackway elements aty different points along the track and'havin magnetic cores arranged in relatively di erent staggered relation, said trackway elements acting to induce currents of reversed phase relation in said inducing coils.

6. In an automatic train control system for railroads having tracks divided into blocks each provided with a normally closed track circuit, a trackway yimpulse device. associated with each block and comprismg a plurality, of magnetic members disposed relatively close together crosswise of thel vided with a normally closed track circuit, y car 'equipment comprising a two-element alternating current relay, a coil connected in circuit with each eld winding of said relay, and trackway means associated with each block under the control of the track circuits of the corresponding block and next block in advance respectively for inducing currents of different phase relation in said coils and thereby causing the relay to operate in one direction or the other.

8. An impulse receiving element for automatic train control systems comprising a core, a coil thereon, a circuit for energizing said coil, a relay in said circuit, another relay responsive only to alternating current and controlled by said circuit, and train control means governed by either of said relays independently of the other.

9. In an automatic train control system, car equipment comprising a magnetized core, two coils thereon, a two element alternating current relay having its iield windings connected separately to said coils, and trackway means for changing the reluctance of the magnetic circuits through said coils alternately and thereby producing therein a plurality of cycles lof alternating current displaced in phase. i

10. In an automatic train control system, car equipment comprising a core of magnetic material, a constantly energized primary coil on said core tending to send flux through said corea secondary coil on the core having voltage induced therein by a change of flux in said core, electro-responsive means connected to said secondary coil, brake control apparatus governed by said electro-responsive means, and trackway means for successively changing the reluc- .tance of the magnetic circuit through said core at a predetermined control point along the track and thereby producing in said secondary coil a plurality of cycles of alternating current. f

11. In an automatic train control system, train control apparatus on a vehicle, a lthreeosition two element alternating current reay controlling said apparatus, and imulse transmitting means partly on the veliicle and partly along the track intermittently eiective at predetermined control points along the track and acting by electromagnetic induction through an intervening air gap to control the energization of said relay in accordance with traiic conditions.

12. In an automatic train control system,

train control apparatus o`n a vehicle, a control relay for governing said apparatus and responsive only to alternating current, an energizing circuit for said relay normally having no alternating current flowing therein, trackway means adapted to produce alternating current in said circuit, and automatic means for detecting failure of said circuit.

13. In an automatic train control system, train control apparatus on a vehicle, a relay on the vehicle controlling said apparatus and responsive only to alternating current, a circuit for said relay, and impulse transmitting means partlyon the vehicle and partly along the track for producing a plurality of cycles of alternating current in said circuit at control points along the track,

respectively by opening and closing a cirlcuit on the track.

15. Inductive impulse transmitting means for automatic train control systems, comprising a polyphase alternating current relay on a railway vehicle, circuits for said relay, coils in said circuits, and a trackway element to produce currents in said coils capable of operating said relay.

16. Inductive impulse transmitting means for automatic train control systems, comprising a two-element alternating current relay on a railway vehicle, energizing circuits forsaid relay, and an unenergized trackway element adapted to produce in said circuits a plurality of cycles of alternating current having a predetermined phase relation.A

17. In an automatic train control system, a car-carried magnetized yoke, inducing coils on said yoke, a polyphase alternating current relay connected to said coils, and means located along the trackway to produce current in said coils and changeable to turn the relay in one direction or the other.

18. Inductive impulse transmitting means for train control systems comprising, a polyphase rela on a railway vehicle, trackway means, an means on the vehicle adapted to cooperate with said trackway means and generating by `such cooperation while said trackway means is in the active stopping condition alternating currents in the field windings of said relay to cause operation thereof.

19. In an automatic train control system, a permanentlyclosed circuit containing an electro-responsive device adapted to respond to current of one character, a source `of energy in said circuit of a character ineffectual to operate said electro-responsive device, and means in said circuit responsive to said source for detecting failure "of, said circuit.

20. Inductive impulse transmitting means for automatic train control systems coniprising, netized car-carried element, a coil on said element connected to said relay, an unmagnetized trackway element for producing a plurality of cycles of alternating current in said coil, and automatic means for detecting failure of the circuit including said coil.

21. In an automatic train control system, a yoke, a circuit for magnetizing said yoke including an electro-responsive device, an inducing lcoil on said yoke, means along the trackway for producing a plurality of cycles of alternating current in said inducing coil, an alternating current relay governed by said inducing coil, and train control means operated when either said electro-responsive device or said relay is actuated.

22. A trackway elementfor train control systems of the type in which control in fluences are communicated inductively from the trackway to moving vehicles without physical contact through an intervening air gap, said trackway element constituting a plurality of pairs of magnetic circuits on opposite sides of a center line of the track element, said pairs of magnetic circuits being spaced in staggered relation longitudinally of the trackway and the direction of movement of the vehicles.

23. In a train control system, means for communicating control influences from the trackway to moving cars inductively through an intervening air gap comprising, a car carried three-legged' core constituting two partial magnetic circuits, a source of current on the car, a winding on the middle leg of said core connected to said source and continuously energized thereby, said windfiux in both of said partial ymagnetic circuits of said core, another winding on said core, electro-responsive means governed by current in said another windin'g,fa track element cooperating with said car carriedcore and affording two partial magnetic circuits completing respectively dthe partial magnetic circuits of said core, a coil magnetically associated with the track element, and traffic controlled means for opening and'closing a non-energized circuit including said coil.

24. In an automatic train control system, a car-carried three-legged magnetic core constituting two partial magnetic circuits, a source of current on the car, a winding on cally associated an alternating current relay, a mag-- said core connected to said source and ener-- gized thereby to produce flux in both of said magnetic circuits, a secondary coil magnetiwith each of said magnetic circuits, electro-responsive means on the cail having two windings separately connected to said secondary coils, a track element affording two partial magnetic circuits rc spectively completing the partial magnetic circuits of the car-carried core, a winding magnetically associated with one of the partial magnetic circuits of the track element, and means for including said winding of the track element in a closed deenergized circuit under clear traiiic' conditions and for putting that winding on open circuit under dangerous traffic conditions.

25. An automatic train control system comprising, a three-legged car element shaped to form two partially closed lmagnetic circuits, means including a car-carried source of current tending to produce flux in said magnetic circuits of the car element, a winding magnetically associated with each of said partially closed magnetic circuits, independent electrical circuitsfor said windings, electro-responsive means confnected to said electrical circuits, and a trafficcontrolled trackway device larranged for cooperation with said three-legged ,'element having one partial magnetic circuit adapted to cooperate with one of the partially closed magnetic circuits of the car element and having another partial magnetic circuit adaptedto cooperate with the other of said partially closed magnetic circuits.

26. comprising, a three-legged car element shaped to form two partially closed magnetic circuits, a coil on said element, a carcarried source of current constantly energizing said coil and .tending to produce linx in said magnetic circuits, a winding magnetically associated with each of said partially closed magnetic circuits, independent electrical circuits for said'windings, electroresponsive meansconnected to said electrical circuits, and` a trackway device having a plurality of partial magnetic circuits, one of said partial magnetic circuitshaving a winding thereon closed in a deenergized circuit under clear trallicconditions and open circui-ted under danger traflic conditions.

27. In an automatic train control system,

the combination with a trackway having a plurality of control points, of a car carried element having a plurality of partially closed magnetic circuits; a winding on each of said partially closed magnetic circuits,

An automatic train control vsystem I 28. In an automatic train control system, the combination with a trackway having a plurality of control points, of a car carried element having a plurality v, of partially closed magnetic circuits, a. winding on each of said partially closed magnetic circuits, independent circuits for said windings, and a traffic controlled trackway device localized at a point along the track for first completing one and immediately thereafter the other of'said partially closed magnetic circuits at each controlv point.

29. In an automatic train control system, comprising a trackwa y divided into blocks, a car-carried magnetized yoke having two partially closed magnetic circuits, a winding on each of said partially closed magnetic circuits, electroresponsive means adapted to be actuated by alternating current iowing in said windings, and trackway apparatus located at the entrance of each block governed by traffic conditions of that block and the next block in advance thereof and adapted to affect the electro responsive means dif- `ferently when the block 'to be entered, the next block in advance thereof or neither of said blocks is occupied.l

30.- In an automatic train control system for railroads divided into blocks eac-h porvided with a normally closed track circuit, of car carried apparatus comprising, a car element having a plurality of lpartially closed magnetic circuits, a winding on each of said magnetic circuits, independent circuits for said windings, alternating current responsive means governed by said independent circuits, and trackway means for affecting said windings differently when an occupied block is entered than when a block in the rear of an occupied block is entered.

31. An automatic train control system, comprising a three-legged car element, a source. of magneto-motive-force associated with said car element, a secondary coil on said element, electro-responsive means on the car connected to said secondary coil and operable only by alternatingcurrent and trackway means adapted to influence said car element to cause said source of magnetomotive-force to produce a plurality of cycle of alternating current in said secondary co1 WINTHROP K. HOWE.

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