US1263603A

US1263603A - Automatic train-control system.

Info

Publication number: US1263603A
Application number: US3653515A
Authority: US
Inventors: Oscar A Ross
Original assignee: General Railway Signal Co
Current assignee: SPX Corp
Priority date: 1915-06-26
Filing date: 1915-06-26
Publication date: 1918-04-23
Anticipated expiration: 1935-04-23

Description

0. A. ROSS. AUTOMATIC TRAIN CONTROL SiSTEM.

APPLICATION FILED JUNE 26. "[5. 1,263,603. PatentedApr. 23. ma

2 SHEEIFSHEEI 1.

FIG.1.

INVENTOR BY I y xfr omn Quad-M O. A. ROSS. Auwmmc mm CONIRUI. SYSTEM.

Patented Apr. 23,1918

- 2 SHEHS-5REET 2.

INVENTOR M a. M

ATTORNEY u 4 m. s? n 3 h fi A. .H WU u ON m M m .Q n N a Q a U. 0 Q Q E A II 4A. U N. w R A w i w HI u 7 h n a a um /fi no 3 h. N E n 3 m a A Ev t UNITED STATES PATENT OFFICE.

OSCAR A. ROSS, OF ROCHESTER, NEW YORK, ABSIGNOR T0 GENERAL RAILWAY SIGNAL COMYANY, 0F GATES, NEW YORK, A CORPORATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Specification of Lctteralatent.

Patented Apr. 23,1918.

Application filed June 26, 1915. Serial 110.36.535.

To all whom it may concern:

Be it known that I, Oscan A. Ross, a citizen ot' the lTnited States, and a resident of the city of Rochester, in the county of Monroe and State of New York, have invented a new and usefulAut-omatic Train-Control Systcnnct' which the following is a Specilication.

This invention relates to automatic-train control systems, and more particularly to such systems in which the movemcut'of the train is controlled. in some appro riute manner. by an electrically operated cvice located on lhc train. as a control relay, the coutrolof said device being accomplished Ivy suitahleramps or other devices arranged along the trackway and adapted to cooper? ate with shoes or other devices carried by the train." a

One of the principal objects of the invention is to construct and arran e the parts of atrain control system of t e character specified so that a number of units, such as two or more locomotives or motor cars, may

be included in the same train without affecting the operation'of the train control system or impairing its elliciency.

A further object of the invention is to devise a simple and reliable train control apparatus and ramps, circuits and electrical connections therefor arranged along the trackway which will operate to'proporl ctmtroldhd control, r( ..hiy. or other contrl ling device on eachlocomotive or motor car .lIIClUdCtllll a train, regardless of the'numher of locomotives or motor cars, or their position in the train. or of the length of the blocks or of the train.

Other objects and advantages will appear as the description of the invention progresses, andt 0 novel features of the invention will be particularly pointed out in the up )ende'd claims? lencrallj, stated, the. invention consists in providing a shorflcoutr'ol section at the entrance to caehblock section of the trackway over whichthc train passes to which is connected and 'lry which'liscontrolled suitulilc electrical appliances "so that" the condi ileil'l of the ramp or control device adjacent to each control section'will be maintained the some while the train is passing that control section.

The invention further consists in the partsand in the arrangements and combinations of parts, more fully set forth hereinafter.

In describing the invention in detail, reference'is had to the accompanying drawing, wherein I have illustrated a preferred physical embodiment of my invention, and wherein like characters of reference designate corresponding parts throughout the several views, and in which:

Figure 1 is a diagrammatic illustration of a railway train and a track for said train, and shows the parts associated with thetrain and with the track and the circuits and electrical connections between said parts which embody the invention, the parts in said figure being shown in their normal positions and in the condition existing when a train approaches one of the ramps located the required spacing of the trains, and for convenience in description will be hereinafter termed block sections. The sections B and D are comparatively short and may he as short as desired. prmiding that they are longer than the distance between any two successive pair of wheels. In other words. the sections B and D, which will he hereinafter termed control sections, are long enough so that as the train passes over them at least. one pair of wheels of said train will at all times he. on said controlsectio'n. Although only two control sections B and 1), tho intermediate block section C and the adjacent ends of the two block sections A and E, are show-11in the drawings,

' my 1:: mthe it is to be understood that the same alternate arrangement of control sections and block sections is carried out throughout the desired length of the track, a control section being located at the entrance to each block section, as illustrated, the direction of normal trallic being indicated by the arrow X.

Across the two track rails 1 and 2 at one end of each block section A, C and E is connected a source of electric current, as a. battery 4; and at the other end of each block section a track relay 7 is connected across the track rails 1 and 2 by conductors 5 and 6. The parts and circuits are the same for the control sections B and D, and the con: doctors and parts of the control section D are given the same reference character as the corresponding parts and conductors of the control section B with a distinctive exponent 1 added thereto. These track relays 7, together with the track rails 1 and 2 and the battery 4, constitute the well known normally closed track circuit, as will be readily understood by those skilled in the art of railway signaling. The track relay for each block section is normally energized, that is, when no train occupies that block section, and their armaturcs will be normally held in their upper position, as shown in the drawing.

Associated with each control section isa relay 8,- hereimiftcr termed a ramp relay, which is connected by a conductor 9 to the track rail 2 and by conductors 10 and 11 to a local source of current, such as a battery 12, which in turn is connected by u conductrack ruill. Adjacent to each control sect ion B and D is a contact rail or ramp R, which is supported in any suitable way on the tics of the railway track, but is insulated from said tics and from the track rails. The conductors and-electrical connections between the different, operative parts of the control system alone the trackway will not be described in detail since thcsoconncctions and the different operating circuits will be fully set forth hereinafter in the description of the operation.

T no apparatus on the vehicle for controlling the mownnent tiicreof may he of any suitable constructlonfbut is llustrated as constructed and arranged sothnt it will not be all'eiitcd if a glifl'erencc of potential exists between the raihiTIi-anyl the truck rail 1, but will be set into operation to control the movement of the train in some prtrpriatc uninncr in'cnsc such difference 0 potci'itial does not exist; The railway train isshown 'diagrummatically as coinprisiug two pairs of wheels 14-14 and 16-1( connected by axles l5 and 17 respectively w'lfibh. rcprsent the wheels and axles of separate cars .or locomotives constituting a train. The, x'les 15 and 17 are illustrated as connected v a bar 18 which represents the frames of the cars or locomotives constituting the train.

A bracket 1}) of insulatin material is suitably su ported "on the trai-n,'fbeilig shown as mounte on the rear mile 17 and so orted on the bracket 19 is a vertically move e shoe or plunger 20, which is pressed downwardly by a spring 21. i The shoe 20 .is arranged to cooperate with the ramps R arranged along the trackway and is designed to make electrical contact with said ramps and also to be raised so as to interrupt a normal! closed circuit on the train. To accomplish t is pur- Jose, the shoe 20 may be provided with a utton 24 of insulatin material arranged to lift a contact spring 2 out of contact with a contact member 28, said button 24 also serving tolimit downward movement of the shoe 20. The contact sprin 22 and the contact member 23 are suita'b y secured to the bracket 19, which being of insulating material, serves to insulate said contact spring and said contact member from each other and from the frame of the vehicle.

The contact spring 22 and the contact member 23 control a normally closed circuit for maintaining a control relay 25 energized. This control relay 25 has two

armatures

27 and 28, one armature 27 being interposed in the local normal] 1 closed circuit, for saidrelily 25, and the ot er armature 28 controlling a local normally closed circuit for a-de'vice K by means of which the movement 'of the train is controlled. This device K maybe of any suitable construction, but is illustrated as set into operation .whendciinergized and restored to its normal position whencnergized. This device K may be used to apply the brakes on the tram instantancously when it is operated or after a certain interval, which may be fixed or variable according to the speed of the train and the distance it has traveled after said device K was set into operation. Various devices well known in the art will satisfy the requirements of the device K and a detail description ofsaid device will not be given here.

Having described generally the structure and arrangement of, the various parts or stituting a system for automatically controlling railway trains which embodies theinrent ion, the operation of said system will be described for diifercnt cases in which cerlain conditions,"sueh as may occur in praclice, are nssllliioil to exist along the trackway.

Referring to Fig. l, for the first condition to be considered, assume that the train under consideration is m the block section A, as shown in sniddigurc and is about to enter the'control section B; [that "the train has Found the trackway unobstructed and is running without being under, the control of the device K and that lhercis no train either in the block section the control section D. or the block section E. Since the block sections C and E ar'e not occu ied, the track relays 7 and 7f therefor wil be, energizcd by current supplied from the batteries l, as will be clearly understood by those skilled in the art; and since said track relays are cnergizcd, their

armaturcs

32, 33 and 32, 33 will. be. in their raised position, as shown. The ramp relay 8 for the ramp R at the entrance to the control section B is deencrgized and its a rmatures 30 and 3t are in their lower position, as shown. A difference of potential exists between the ramp it and the track rail 1 according to the par tial circuit as follows: from the ramp R, comlimtor 3t, arn'iature 30 of the ramp relay H in its lower position, conductor 35, armature 52 of the track relay 7 in its upper position. conductors 36, 37 and 1]. battery 12 and conductor 13 to the track rail 1.

It is noted that this first partial circuit tor maintaining a difference of potential between the ramp R and the track rail 1 Will he ilucrrupted if a train occupies the block section but this partial circuit is in no wise rlcpcndent upon whether or not the control section I) and the block section E are m-cupicd. lhis condition, which exists before the first wheels 14 and axle 15 of the train enter the control section B, may be used in cases where the construction of the device K makes it desirable thht each time a train approaches a block section the shoe of the train, should strike a ramp between which and a traclrrail a difference of potential should exist, provided the next block section, as (7, is unoccupied, and re gardlcss ot' whether or not the next succeeding block section, as E, is occupied. To obtain this result the ramp R may be made long enough and so located with reference to the insulating joint 3 at the entrance to the control section B that the first shoe 20 ot the train will make electrical contact with said ramp before the first pair of wheels hi H and their axle 15 enter the control section ll.

Another factor which determines the length and location of the ramps and which may he noted at this time, is that the front end of a ramp must be a greater. distance from the insulating joint 3 at the entrance to the next block sectionlhan the distance between the last pair of wheels and axle of the train and the last contact shoe 2t in order that the last contact shoe-2o will ha re discontinued electrical comm-r with the ramp b the time the last pair of 'whe'els'andaxlc leav'c the control section 1 When the lirst pair of"i\"hi-.cls H-'-l-l and axle ii": of the train'cnter the control s ction 1 the ramp relay 8 of'said control section is energized according-{to the lollo\\'itn circuit: battery l'2, eondnctors ll and I0, re in 8. conductor 9, track iail 2, wheels 14,

the axle 1.), track rail 1 and conductor 13 back was battery, 12. whim theti icjis conductor 4,4, contact member 23, contact cnergized its armature is. raised, t reby interrupting the first partial circuit hereinbefore traced which normally maintains a difference of potential between the ramp R and the track rail 1. However, under the conditions assumed the control section I) is unoccupied and the armatures 3t) and 31 of the relay 8 of the control section D are in their lower position, as shown; and since the block section E is unoccupied, the arniatures 32 and 33 of its track relay 7" are in their upper position, as shown. onsequently. when the armature 30 of the relay 8 ofthe control section B is raised, asecond partial circuit for maintaining a difference of potential between the ram) R and the track rail 1 is established as ollow's: from the ramp R, conductor 34, armature 30 ot the relay 8 in its up )(l' position, conductor 38. arn'iaturc 31 of the relay 8 in its lower position, conductor 35), armature 33 of the track relay 7 in its upper position, conductors 37" and 11, battery 12, conductor 13 to the track rail '1. It is noted that this lastmentionod second, partial cuit is interrupted if the control section I) or the block section E are occupied by a train. but is not affected by the presence of a train in the block section C, and the result is that, as the wheels of the train enter the block section (7 and cause the'track' relay, 7

thereof to be dciinergizial, this last-incritioned partial circuit will not be interrupted; but will be maintained untilthe last .pair of wheels and axle of the train have left the control section B.

Whenthe shoe 20 engages the ramp R the contact spring 22 and the contact m'e nbcr 23 is broken, thereby interrupting the following normally closed circuit through the control relay 25: from the battery 26,

spring 2:2, conductor 45, armature 27 of the control relay 25 in its upper position, conductors ltt and 47, control relay 25 and condoctors 48 and 49 back to the battery 26, Also, as soon as the shoe 20 makes electrical contact with the ramp R and shortl before the contact spring 22 is separated rein the contact; member 23, current will be supplied to the control relay 25 from the ramp R according to the following circuit: from the battery 12, conductors 11, 37', and 4t), armature 33 of the track relay 7 in its upper position, conductor 3!), armature It! of the ramp relay 8' in its lower position, conductor 38, armature 30 of the ramp relay 8 in'its'upper position, conductor 34, ramp R. sho'etQt), conductors titland 48. control relay 25, mnductors 4-7 and 51 to the flgime 18 iii" the trai'n, and thence throuti'hftlhc wheels; and axle to the track rail 1 and along conductor 13 back to the battery 12. In

it is raised and electrical contact between v block section E.

this way, each time the shoe 20 engages a ramp the control relay 25 will be kept energized and the vehicle may proceed safely, providing a dili'erence of potential exists between that ramp and a track rail.

For the next condition to be considered, assume that the train is in the block section A and about to enter the control section B; that said train has found the track unobstructed and is running without being under the dominance of the train control device K; and that there is no train in the block section C, but there is a train in the In this case the track relay 'i' of the block section E will be denergized by the presence of the train in said 1 block section, as will be understood by those skilled in the art, and the armature 33 of said truck relay will be in its lower position, thereby interrupting the second partial circall; for maintaining '1 difference of potential between the ramp R and the track rail 1 as the train proceeds through the control section B and into the block section C. The first partial circuit which normally maintains a difference of potential between the ramp R and the track rail 1, however, will not be affected by the presence of the train in the block section E, as pointed out hereinbefore, so that the control. relay 25 on the train will be energized if a. shoe 20 of said train strikes the. ramp R before the firstair of wheels and axle of the train enter t e control section B; and then subsequently, when said first pair of wheels and axle enter the control section B, the control relay 25 will be deenergized.

When the control relay 25 is deenergized its armature 27 drops and interrupts the normally closed circuit from the battery 26 through the control relay 25 so that after the shoe 20 leaves contact with the ramp R and the contact spring 22 makes electrical contact with the contact member 23, the control relay 25 will remain deia'nergized. Also, when the control relay 25 is deenergized, its armature 28 drops and interrupts the following normally closed circuit through the control device K: from the battery 29, con doctor 52, control device K, conductor 53, armature 28 in its upper position and conductor 54 back to the battery 29. In this way, when the train occupies the block section E, the control device K will be set into operation, and may operate to apply the brakes automatically or may be used to set any suitable train control apparatus of some other description into operation. The same result is produced in case the control section I) is occupied, as by a single locomotive or motor car, since in this case the ramp relay 8 of said control section D will be energized and its armature 31 raised to interrupt the secondpartial circuit for mamtaining a difference of potential between the ramp R and the contact ramp 1.

For the next condition to be considered, assume that the train is in the block section A and is about to enter the control section B, and that the block section C is occupied. In this case the train before it entered the block section A would have been placed under the dominance of the control device K, since the presence of a train in the block 0 would have set the control apparatus K into operation at the entrance to the block section A. in the same way as the presence of a train in the block section E causes the control device K to be set into operation when the train entered the block section C,

as hereinbefore explained. The presence of the train in the block section 0 requires that the train in the block section A must either stop before it enters the block section C or must proceed with great caution and at a low speed under the dominance of the train control apparatus; and, consequently, to acconiplish this result, no difference of potential should exist between the "ramp R and the track rail 1. in order that the following train will not be released from the dominance of its train control apparatus. This absence of any difference of potential between the ramp R and the track rail 1 is efi'ected by reason of the fact that the presence of a train on the block section 0 causes the dei nergization of the track relay 7, with the result that its armature 33 drops and interrupts the first partial circuit, hereinbefore set forth, which normally maintains a ditl'erence of potential between the ramp it and the track rail 1.

The modified arrangement of circuits shown in Fig. 2 is substantially the same as the arrangement of circuits in Fig. 1, except that the ramp relays 5-) in Figv 2 are arranged on a normally closed circuit, instead of on a normally opcn'circuit as in Fig. 1. Each control section B and D is provided with a track battery 59 connected across the track rails 1 and 2 and the ramp relay 55 is connected by wires 56, I? and it; cross the track rails 1 and without. however. a battery being included in said wires. as is the case in Fig. 1. In this arrangclnentof circuits the ramp relay 55 is normally energized from the track battery 59 and when a, pair of wheels and axle en tor the control section B the battery 59 is shunted to dci nergize the relay 55. Because of this change from a normally open to a norlnally c'loscdcircuit, the contacts o the armaturesol the ramp relay 55') are re versed, will be clearly understood by those skilled" in the art. A further dill'ercnce between Fig. 2 and Fig. 1 is tha the battery 6-1 for establishing a dill'ercnce of potential between the ramp R and the track rail 1 is interposed in the conductor between said ramp and the armature 60 of the ramp relay 55, In other respects, the parts and their electrical connections are the same in Fig. 2 as in Fig. 1.

Without entering into a detail description of the operation of the modified arrangement of circuits shown in Fig. 2, the first partial circuit for normally maintaining a difference of potential between the ramp R and the track rail 1 is traced as follows: from the ramp R. conductor 65, battery 64, conductor 66, armature 60 of the ramp 55 in its upper position, conductor 67, armature 62 of the track relay 7 in its upper position,

conductors

68, 69 and 57 to the track rail 1. When the control section D and the block section E are not occu ied and the first pair of wheels and axle o the trainv enter the control section B, the second partial circuit for maintaining a difference of potential between the ramp R and the track rail 1 is as follows: from the ramp R, conductor 65, battery 64, conductor 66, armature 60 of the ram relay 55 in its lower position, conductor 0, armature 61 of the ramp relay 55 in its upper position, conductor 71 armature 63 of the track relay 7 in its upper position, conductors 72 69 and 57 to the track rail 1. The operation of the modified arrangement of circuits shown in Fig. 2 for difierent conditions will be obvious b comparison with the similar 0 oration o the arrangement of circuits 5 own in Fig. 1; and a detail description will not be given.

Although I have particularly described the construction of one physical embodimont of my invention, and ex lained the operation and principle thereo nevertheless, I desire to have it understood that the form selected is merel illustrative, but does not cxhaust'the possible physical embodiment of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United. States, is:

1. In an automatic train control 5 stem, in combination: a railway trackway a apted for fnovin vehicles and comprising electrically iso ated block sections, a comparatively short control section at the entrance to each of said block sections and electrically isolated therefrom, an insulated ramp positioned near the entrance to each of said block sections-1 a ramp relay as ciated with each 'control section and centre led by the presence of a; train on the corresponding section for creating a difi'crencc of potential between each of said ramps and a track rail.

2. In an automatic train c itrol system, in combination: a railway tra (way adapted for moving vehicles and comprising electrically isolated block sections, a comparatively short control. sectitm at the entrance to each of said block sections and electrically isolated. therefrom, an ihsulatcal rump positioned near the entrance to each of said block sections, a ramp relay associated with each control section and controlled by the presence of a train on the corresponding control section, a source of electric current and a track relay associated with each block section and constituting a normally closed track circuit, a partial circuit controlled by the corresponding ramp relay and the track relay of the next succeeding block section for creating a difference of potential between each of said ramps and a track rail, and another partial circuit for creating a diflerenee of potential between said ramp and a track rail which is controlled by the ramp relay of the next succeeding control section and the track relay of the second succeeding block section. v

3. In an automatic train control system, in combination: a railway trackway adapted for moving vehicles and comprising electrically isolated block sections, a comparatively short control section at the entrance to each of said block sections and electrically isolated therefrom, an insulated ramp positioned near the entrance to each of said block sections, a source of electric current and a track relay for each blocksection constitutin a normally closed track circuit, each of said track relays having a pair of cooperating contacts which are closed when said re ay is energized, a relay associated with each ramp, a circuit for each ramp relay connected across the track rails of the cor responding control section and including a source of electric current, said ramp relays being energized when the wheels of a tram are on said control sections, circuit. controllers operated by said ramp relaysand two partial circuits for each ramp arranged in multiple and in series with a source ofcurrent, said partial circuits creating a difference of otential between said ramp and a track rail, one of said partial circuits being closed when the ramp relay of the correspondim ramp is deiiner'gized and the track relay or the next "succeeding block section is ener ized, and tlsfeother partial circuit bein c osed when said ramp relay is energize and the track relay of the second succeeding' block section is energized.

4. Inan automatic train control s stem, in combination: a railwaytrackway a apted for moving vehicles and comprising electricall isolated block sections, a comparative y short control section at the entrance to each of said block sections and electrically isolated therefrom, an insulated ramp ositioned near the entrance to each of said iilock sections, circuit controlling devices associated with each control section, a circuit controlling device associated with each lock section, a partial circuit associated with each ramp for creating a difl'erenoe of potential between that ramp and a track rail; said partial circuit being controlled by the responding control section and the block section next ahead and being interrupted when either said control section or said block section is occupied by a train, and another partial circuit associated with each ramp and in multiple with said first-mew tioned partial circult for creating a difl'erence of potential between said ramp and a track rail, said second partial circuit being controlled by the circuit controlling devices of the control section next ahead and the second block section ahead and being interrupted when either said control section ahead on said second block section-ahead is occu ied. p

5. n an automatic train control system, in combination: a track divided into track circuit block sections and comparatively short control section'sone at the entrance to each block section; an impulse device associated with each block section; control circuits for each impulse device governed respectively by the track circuit of the corresponding "block section and the trackcircuit of the block section next in advance; and means associated with each control section and responsive to the presence of a train thereon for selectively controlling the connection between the device and its controlling circuits.

6. In an automatic train control in combination: a track divided into track circuit block sections and comparatively short control sections one at the entrance to each block section; an impulse device associated with each block section; 'a relay and asource of current connected to each control sectionand constituting means for detecting the presence. of a train on that control section; and each im ulse device 7 relay of the corresponding control section for governing said I sively in accordance with traflic conditions in the corresponding block section and in the next blocksection in ad In an automatic train control system,"

in combination; a. track divided 'intotrack circuit block sections and comparatively short control sections, one at the entrance to each block section; an impulse device associated with each block section; arelay circuit controlling devices of the corcorresponding impulse system,

means associated with and-controlled by the trolled by the relay of, th

in: nlse device succesdevice in a controlling condition I section and a source of current connected to each control section and constituting means for detecting the presence of a train thereon; a controlling circuit for each impulse de vice governed by the track circuit of thecorrcsponding block section; a second controlling circuit for each impulse device governed by the relay of the control section next in advance and also by the track circuit of the block section next in advance; and means associated with each im ulse device and controlled by the relay of the corresponding control section for connecting the first control circuit to that impulse device prior to the entrance of a train into said corresponding control section and for connecting the second control circuit to that impulse device after a train enters said corresponding control section and so long as any part of such train remains on that control section.

8. In an automatic train control system, in combination: a track divided into track circuit block sections; a comparatively short control section at the entrance to each block section; a relay and a source of current connected to each control section and constituting means for detecting the presence of a train thereon; an insulated ramp located at the entrance to each block section; a partial circuit for normally energizing each ramp controlled by the track circuit of the corresponding block section; a second partial circuit associated. with each ramp and controlled by the track circuit of the block sec- 100 tion next in advance; and means controlled by the relay of each control section for disconnecting he corresponding ramp from its first partial circuit and connecting it to its second partial circuit when a train enters 105 that control section and so long as any part remains on that control secof such train tion. 1

9. In an automatic train control system, in combination; a track divided into track circuit, block sections; a comparatively short control section at the entrance to each'block section; a i'elay an-d a source of current connected to each control section and constituting means for rletectin the presence'of a train thereon; an impu se device at theentrance to; each block section; vand means itssociated with each impulse device and conc corresponding: control section for maintaining said impulse while-any part of a passing train occupies said'control. section in accordance with thepresence or absence of another ,trainin thelnczktrcontrol section or the next block SQClIi HIiIYE-dVaIICQ. 10. In anautomatic traitij control system, in combinationratrack; divided into track circuit block 5a comparatively short control sectionatthe entrance to each block a-ramp at the entrance to each block section; means associated with each ramp and controlled by the corrcs )onding control.

section and corresponding b ock section for establishing a difi'erence of potential between said ramp and a track rail when neither said control section or said block section is occupied; other means associated with each ramp and controlled by the control section and block section next in ad- 10 Vance for establishing a difference of potential between said ramp and a tl ack rail when neither that control section or that block section is occupied; a vehicle adapted to travel over said truck; automatic train control apparatus on the vehicle; and means on the vehicle responsive to the existence of a difference of potential between a ramp and :1 track rail for controlling said apparatus.

OSCAR A. ROSS.