US2740040A - Railway block signalling system - Google Patents

Description

March 27, 1956 c. R. MARCUM 2,740,040

RAILWAY BLOCK SIGNALLING SYSTEM Filed April 27, 1951 s Sheets-Sheet 1 wozm 5520 N M U Em 1 R A m v @N WWII: w m n W r I |w||| ||W|--l .J W q d m 2% m N N 4 I g I:

March 27, 1956 c. R. MARCUM RAILWAY BLOCK SIGNALLING SYSTEM 3 Sheets-Sheet 2 Filed April 27, 1951 M 0 M m. R 5 M h 6 V... B INN NNXQQQQ AYTORNEY March 27, 1956 c. R. MARCUM RAILWAY BLOCK SIGNALLING SYSTEM 3 Sheets-Sheet 5 Filed April 27, 1951 JNVENTOR. Char/es R. M area/77 ATTORNEY RAILWAY BLOCK SIGNALLING SYSTEM Charles'R. Marcum, Jefiersontown, Ky., assignor to General Equipment & Mannfacturing Company, Zionist rile, Ky., a corporation of Kentucky Application April 27, 1951,5erial No. 223,397

17 Claims. (Cl. arr-as This invention relates to signal systems for railway blocks having, two or more entrance-exit stations.

One of the principal objects of the invention is to provide a relatively simple but highly flexible system which permits the optional use of two or three signals, such'as yellow, green and red, at each station and which, in either event-will not only produce a proceed signal at only one station where two or more vehicles are attempting to enter two ormore stations at the same time, but also produce a stop or red signal upon a failure in'the proceed or green circuit at any station and in the caution or yellow circuit;

Another important objectis to provide a signalling system which operates automatically to prevent a vehicle which has overrun the entrance to an occupied block, and must back out of that block, from clearing the signalling system asit backs out of the block.

Another important object is to provide means at each station for rendering the signal clearing mechanismof any one station automatically inoperative upon the en"- trance through that station of an overrunning vehicle'into an occupied block and, at the same time, isolate the signal clearing system at the overrun station from the signal clearing mechanism at the other stations so that the vehicle. which first occupied the block can clear the entire signalling system upon its exit from the block Anothcr'important object is'to enable the operator of a vehicle, which must stop immediately as it leaves one block because of tratlic conditions in the next block, to control one or more entrances of the preceding block which his vehicle has just left, so as to permit-traffic to flow through. the preceding block in one direction While preventing it in the opposite direction.

Embodiments of the invention are illustrated in the ac companying drawings wherein:

Figure '1 is a' circuit diagram illustrating thebasic cir cuitsof asimple control system made in accordance with my invention;

Figure 1A is a schematicview of the layout of a'railway block showing 'the location of the exit-entrance stations of Figure 1, this view showing the power-line 12 instead of the railway tracks;

Figure 2 is a circuit diagram illustrating'thesame basic circuits and containing two additional features, one for use with a block layout of the character shown in Figure 3 Figure 3 is a schematic view of the layout of a railway. block showing the location ofthe Figure 2'exit-entrance stations in relation to the power line 12;

Figure 4 is a schematic view of the layout of another block;

Figure 5 is another modified circuit system constructed iii-accordance with my invention for the block layout of Figure 4, this circuitsystem being similar to the arrangement shown in Figure 3;

Figure -6 is a vertical end view of an entrance-exit switch- 2,740,040 Patented Mar. 27, 1956 Figure 7 is a horizontal sectional view along line 7--7 of Figure 6.

Figure 1 be'generally designated by the same numerals, but-distinguished from each other by the letters A, B and C cor-- responding. to their respective stations.

Each unit comprises: a relay 1 at each station (or 1A, 1B, 10) having normally closed and normally open contacts 2 and? on one side with a common terminal'4 on the other side and first and second actuating means 5 and 6; a nor-mally energized electromagnet 7 controlling a normally closed switch 8 and a normally open switch 9; anda conventional vehicle-responsive mechanism'having a-nor'mally open entrance switch 10 and a normally open exit switch 11. These elements are connected together to provide: a normally open green signalling circuit at each station, extending from the common terminal 4 through the normally open relay contact 3 and the normally energized eletromagnet 7 to one side of the source of power which hereinafter is always designated as the ground side; a normally open red signalling circuit ex"- tendingfr-om a power line 12-tl1rough the normallyopen switch 9 ofelectromagnet 7 to ground; a normally open entrance circuit extending from the power line 12 through the normally open entrance switch 10, the normally closed switch 8 of electromagnet '7 and the second actuating means-or coil 6 of relay 1 to ground; and a normally open exit-circuit extending from power line 12 through the'normally open exit switch 11 and the first actuating means or coil 5 of relay 1 to ground.

The foregoing control units are integrated into a control system by: extending the power line 12to all stations; extendinga signal wire 13 and a clearing wire 14 to all stations-with the clearing wire connecting the exit circuits of all stations together at corresponding points, hetween their respective normally open exit switch 11 and their first actuating means or coil 5 of relay 1; and providingayellow circuit which is normally energized when the block is clear and which first connects the normally closed relay contacts of successive stations in series between the power line 12 and the signal wire 13 and second connects the electr'omagnet 7 at all stations in parallel between the signal wire 13 and ground. The series connection extends from power line 12 through contacts 4A and 2A ( contacts 4 and 2 at station A), interstation wire 15, contacts 4B'and 2B, interstation wire 16 and contacts 4C and 2G to signal wire 13. Since this series connection proceeds from power successively through the control units of A, then B and finally C, it establishes the order of these stations with station A being of the highest order, B next and C last.

The normally open green signalling circuit at each stat tion contains, between the normally open relay contact 3 and electromagnet 7, a green signalling means G which may b'eeither a signalling lamp or some electrically actuated mechanism for operating some other form of green or proceed signal. The normally open red signalling cir cuit similarly contains a red or stop signalling means-R, The yellow circuit contains, in each of its parallel branches between the signal wire 13 and the electromagnet 7, either nalling means Y in the form of either a yellow or-cautionlampor some electrical means for actuatingsome other form of yellow or caution signal.

In'ex'plainingthe operation of the system, we shall as suine that the yellow circuit is a signalling circuit and that all of the signalling circuits contain signalling lamps. Accordingly, when the block is clear, the yellow circuit will normally be energized, thus energizing the yellow lamp and the electromagnet 7 at each station, the latter holding the entrance circuit switch 3 closed and the red circuit switch 9 open.

As a train approaches the block, the operator will know, upon seeing the yellow lamp at that station energized, that the block is clear, but at the same time, he knows that he must extinguish the yellow lamp and illuminate the green lamp in properly entering the block. When his train does enter a clear block at any station, the entrance switch 10 of that station will be momentarily closed, energizing the entrance circuit of that station long enough to cause the second relay coil 6 of that station to actuate its relay from its normal position to its other position When the relay i thus actuated, it breaks the yellow circuit at all stations and closes the green circuit at the entering station only, leaving the green circuits open at the other or remaining stations. Since both the green and yellow circuits, at all stations other than the entering station, are now open, their respective electromagnets 7 are deenergized, additionally opening their normally open entrance circuits and closing their red circuits. In this way the red lamps, at all stations other than the entering stations, are energized. While the yellow circuit is also opened at all stations, including the entering station, the green circuit of the entering station is closed; hence the green larnpand the electromagnet 7, of the entering station, are energized, thus holding the red circuit at that station open.

When the train, which thus entered the block at station A for example, leaves the block at any other station, say station B, it will close the exit switch 113 at the exit station, thus energizing the first relay actuating means or coils of all stations, but this will normally have elfect only at the entered station A because it is only the entered station relay 1A that will now normally be out of its normal position. The vehicle exiting at the B station, in thus actuating the relay 1A at the entered A station, will open the green circuit at the entered A station but, at the same time, close the yellow circuit for all stations. Thus the green light at the entered A station is extinguished, while the electromagnets at all stations are energized to illuminate the yellow lamps at all stations and to darken the red lamps at stations other than the en'- tered station, which was of course already dark.

In the event two or more trains, approaching diiterent stations of a clear block, strike the corresponding entrance switches at slightly difierent intervals, the one closing an entrance switch first will get the green signal, whereas the others will get a red signal because the first. to close will actuate its relay to establish a green signal at its station and a red signal at all other stations.

On the other hand, if two approaching trains strike their respective entrance switches at one and the same time, then the train at the station of higher order will get the green signal, while the other will get a red. For example, if entrance switches 10A and 18C are closed simultaneously so that relays 1A and 1C are actuated simultaneously, each relay will close the normally open relay contacts of its green circuit. But relay 1A will connect its green circuit directly to power, and, at the same time, break the power line connection to the green and yellow circuits of both remaining units.

Thus relay 1A not only prevents relay 161 from connecting the green circuit of station C to power, but also deenergizes electromagnets 7B and 7C so as to produce red signals at both the B and C stations, regardless of the position of their respective relays 18B and 10C. Furthermore, when the first train, which entered station A to actuate relay 1A, leaves the block at any of the other stations, say the second or B station of the series, it will close the exit switch 1113 at that particular station and energize all of the first relay coils 5A, B and C, thus returning relays 1A and 1C to their respective normal positions. The train thus waiting at the C station will now get a yellow signal indicating that he may proceed into the block if he can change that yellow to a green signal in the normal way.

With a two-signal system, instead of the three-signal system previously described, it will be appreciated that the operation of the circuits remains exactly the same as before. The only difference is that each station will be dark when the block is clear. As before, however, the train operators must get a green signal in entering the block.

It will also be appreciated that this system, as a three light system, will produce a stop or red signal upon a failure of the yellow or green circuits, and a dark signal upon a failure of any red circuit. The same is true of this system as a two-light system, except the stations will be dark when the yellow circuit is energized. Of course it will be understood that a dark signal, or no signal at all, requires as much caution from the train operators as a red signal, if not more.

As noted previously, where two or more trains; approaching different stations of a clear block, strike the corresponding entrance switches at slightly different intervals, the one closing its entrance switch first will get the green signal and the others a red signal. If any of the said other trains actually enters the block, it must back out. Upon backing out, it will actuate the exit switch at that station and clear the entire system, reenergizing the yellow circuit despite the fact that the block is occupied. To avoid this, it has heretofore been proposed to have the operator manually jog the entrance-exit switch operating pole, of his train as it backs out, to avoid closing the exit switch, in accordance with the present invention a vehicle overrunning an entranceexit station of an occupied block is prevented auto matically from clearing the block when backing out of it by the system shown in Figure 2.

Figure 2 The control system of Figure 2 employs the same basic yellow, green and red circuits as Figure 1 and the' corresponding relays, electromagnets, switches and other connections are designated by numerals and letters as in Figure l. Since the arrangement and operation of these circuits is the same as before, it will not be repeated here. However it may be noted that, while the entrance and exit switches of Figure 2 may be of the same type as is indicated in Figs. 1 and 1A, a dilferent but conventional type of switch is indicated in Figure 2. Its operation will be more fully explained hereinafter in connection with Figures 2-3 and 45.

In accordance with my invention, to prevent 3. vehicle, which ocerruns an entrance-exit station of an occupied block, from clearing the system upon backing out of the block, each station is provided with auxiliary means operative, upon the closure of its entrance switch by a vehicle overrunning its entrance-exit station to enter the block after the deenergization of its electromagnet, to render its exit switch ineffective when the overrunning vehicle backs out of the block. Such auxiliary means includes, at each station: an auxiliary relay 20 having an actuating coil 21 and a normally closed switch 22 in the exit circuit between exit switch 11 and the clearing wire 14; and a normally open secondary entrance circuit for actuating the auxiliary relay coil 21 after the electromagnet 7 has been deenergized and upon closure of the entrance switch 10', this circuit extending from the entrance switch 10 through the aux iliary coil 21 to ground and having, between the entrance switch and the coil, a normally open switch 23 controlled by the electromagnet 7 to close upon the deenergization A the electromagnet 7 atstations B and:.C will Zbet as; energized in the normal way, closing 'theinxredi circuit switch. 9 and their secondary entrance: circuit switch 23; Thesclosure of switch 23 closes the-normally open secondary entrance circuit from groundithrough coil..21 and 'switch 23-up to the normally open entrance switch 10'. Now, if a vehicle overruns the exit-entrance sta tion B'it will momentarily closeits entrance'switch 10'. to actuate the auxiliary relay coil 21 momentarily. The momentary energization of auxiliary'relay coilJ21 opens switch22'in'the exit circuit of that station'between exit switch 11 and the clearing wire:14.

To maintain this. auxiliary relay switchz22-openrlong enough to permit the train toback out of the block without clearing the control system, the relay-'may be quick-acting in the direction in which it opens: switch 22 and slow-acting in the opposite direction over a requisite period of time. Preferably, however, to hold switch 22 open, the relay 20 is provided with. awn'ormally open switch 24 for connecting the coil' 21- directly to the-power line 12, independently ofrthe: entrance switch 10'. In. this way the exit switchll ofstation "B' issren+ dered ineffective without interferingwith theability-of the:exit switches at the other stations to operate-therexit circuits ofall stations. Consequently, whenthe-vehicle, occupying the block, exits from the block at station C, for example, it will be effective to close the exit 'switch 11' of station C, and, in doing so, energize the exit circuitszof all stations to clear the entire system.

When the system is thus cleared, the yellowcircuittfor all stations is energized, energizing the electromagnets of all stations to open their. respective;- red. circuit switches: 9' and secondary entrance circuit. switches 23 and to close their entrance-circuit switches 8; However; the. auxiliary'relaycoil21, being connectedv directly; to power, would normally remainv energized: and. thus: con.- tinue to hold theexit'switch 1d of overrun station/B ineffective; Toavoid this, the auxiliary relay 20 at eachstation is: arranged to be restored. to its -.n'ormal?po-' sition upon the reenergization of the correspondingelectromagnet 7, by short-circuiting auxiliary relay coil; 21 through? the agency of a switch. 25 controiledby said electromagnet 7 as to be normally closed when that eleetromagnet is normally energizedand open:whensthe electromagnet is deenergized.

Once the system is thus cleared, the yellow circuit willbe energized so that the operator of the overrunning vehicle at station B will receivev a yellow'signahxif the yellow circuit is a singalling circuit, and: a dark signal otherwise. Upon'receiving such. signa'hptheroperator will know that, if he can obtain a greensignal, he canzproceed safely into the block.

Figures 2 and 3 The block layout shown in Figure 3 includes a block 3-! having entrance-exit stations A, B" and C with the exitpart of stations A, B and Con side tracks. For these'stations of block 31, itwill be noted: that the entrance switches 10', on the main track power line 12', are" as shown in Figures 6 and 7 with contactll' omitted; and the exit switches 11', on the side track powerlines 12, are as shown in Figures 6 and7'with contact" I0- omitted.

The arrangement of Figures 2 and 3 is such that a train entering block 31 at station A can leave that blockon the side tracks of either station B'or C and either enter the next adjacentblock or stop on the side track between block 31 and the next adjacent block, as 'would be the case where it is stopped on the side track: by a stop signal controlling the entrance to the nextLblock; Thus'a first train leaving block 31 on the sidextrackoistationB will bestopped' on that same side track. at. the'A. station; of the nextblock 32 when the nextsblock32 is occupied by-a second train. If this secondztrainis approaching-the entrance-station B of block .3'1,.it can. enter .block' 31. onizther propervsignalrand thus CIGaITblOCkISZt Onxthe otherhand, it: willibe i held on block '32 at the: entrance station B for block 31 .if a third train. enters block. 31.: at station A before the rs'econd train. could enterv that: block a't station. B. If the third train;is. headed 'for block 32, all three: trains'will be-stymied from further movement in the. areav of station B.

To prevent such occurrence,.II.provide means onictlie side track, hetweenthe exitstation B of. block: 31 and the entrance station A of block 32.,v enabling the operator ofuthe first train .to set a redsignal at station-A .of block.31n.in.'order"to preventthe said third train from entering block. 31 at station A,. while permitting the second train Lto'enterhlo'ck. 31..a't station B or another train to enter. .block 31 at station C. In :otherw'ords, such means-will block traffic :on..block.3.1.in:the one .direction which can. effect a stymie and permitit-in the opposite direction.

Accordingly, at station B, :Iprovideaiholding relay 33rhaving a normally closed switc'h 34,.in1theyellow circuit signalwire 13 between. STEItiOI'IS 'B and A, and a holdinggcoil 35 operative, whenuenergized, to open that: line andthus break the yellowcircuit of station A alone; To energize the coil 35", a normally open trackside circuitswitch 36is'. provided on. the side'track at station.B between 'the'exit .switch 11 of block 31 and the-entrance switch .10" of: block 32;- The switch 36:is' of-vth'e type'showninsFigs'. 6'and 7 with. one con+ tact omittedl The operator oh the first train; which ist-blocked' onuthis 'sidetrack: by a: red signalat-the A stationot blockv 32,.cani either manually jog'th'e'c'ontrol system or trolley pole' of'histrain to. close the. trackside circuit 'switch:36*and thus energize the holding: coil 35101'1 maneuverixhisi traini to a .point wherethe normal switchopera'ting member will automatically. close the trackside circuit switch 36 and hold it closed sorlon g as the train stationarilymemains in. that particular; position; Insthis latter: case, a train passing. through '.'that side track will. close: trackside sircuit switch" 36/ IIIOIl'lCIH tarily, causing1thesignals to flash, but thiswillinottaf= fect the operationxof the signal. system.

In: order to. indicate to that operator that the. track switch is closed, the holding relay 33is 'providedswithi'a normally open switch 37 arranged: to'bex closed when the coil'isienergize'd and thereby energize an appropriate holding'signal circuit having:signallingr'tmeans' Hi When block 32 is cleared, the operator of the first train. can move. into block: 32 and; 'in doing so, open trackside circuit switch. 36 to-deenergize the-holding. coil 35" and thereby close switchi34.-to*restore thetyel-low'circuit for normal operation;

A similar arrangementis provided at 'station. C, but', when the signal wire'1'3 is' openat this station, it bre'aks theyellow circuit of stations A and B, thus preventing the trains, which approach either'of :these "stations; 'from enteringblock 31. without 'preventingi'o'ther. trains 1 from enteringth'at block" at the": G station;

Figures 4' and. 5"

The block layout shown imEigure 4 includes a bloek 41 having entrance exit stations A, B, C and- 11 The A and -D- stations-aremainrline stationswith .sidetracks, while the B andC stations are-branch line stations; The side( track. of. station A-provides the exit. part of that station, while-thesidetrack atstation-D- provides the entrance part, but eitherror. both. of these arrange= ments may be reversed. Sinceth'e entrance" switches for each: of the stations. A" and D-areseparatedfrom the exitswitches, each entrance switch-10* shallomiththe exit contact 11 and teach exitswitch 11. shall omit-the. entrance contact 10' from the arrangement shown- Figures 6 and 7. However, since. the-entrance and exit switches;v for each oi the branch. line stations Band-G,

are adjacent each other, as shown in Figs. 4, 6 and 7, an explanation of their operation may be desirable.

With the adjacent contact relationship shown in Figures 4, 6 and 7, the contact shoe, of a train entering block 41 at either branch line station B or C, first strikes entrance contact 10' and immediately thereafter strikes exit contact 11'. The entrance circuit is therefore completed a moment before the exit circuit is completed. During this moment, the entrance circuit, of the Figure control system for the Figure 4 layout, is operatively energized while the condenser, shown in both entrance and exit circuits near the ground connection, is charged. The operative energization of the entrance circuit is momentary only because, as the condenser charge builds up, the entrance circuit current flow falls off and quickly reaches an inoperative value. By the time the exit circuit is completed, the charge on the condenser is sufficient to prevent the flow of an operative current therethrough. This inoperative condition of both of these circuits continues so long as the contact shoe remains in engagement with either or both of the contacts and 11. Upon disengagement, the condenser rapidly discharges, quickly restoring both circuits to an operative condition. Naturally, when a train leaves the block, the exit circuit will be momentarily energized in like manner. This type of operation which also occurs in block 32 of Figure 3, is conventional in this art.

As above indicated, the Figure 4 block layout is controlled by the control system of Figure 5. The Figure 5 control system includes the basic circuits of Figure l and, since it controls four stations instead of three, the power line 12, signal wire 13, and clearing wire 14 are extended to the fourth station, which has an identical control unit, and the series connection of the yellow circuit is extended from the third to the fourth station by a wire 17 connecting relay contact 2C with relay contact 4D.

The control system of Figure 5 is also the same as the control system of Figure 2 in that it includes, at each station, an auxiliary relay 20 for overrunning purposes and a holding relay 33 at station D. This holding relay is arranged in the signal wire 13 between stations D and C in the same manner as the holding relay 33 is arranged between stations C and B of Figure 2. It enables the operator, of a train leaving block 41 through main line exit station D, to prevent any train from entering block 41 through any of the other stations A, B or C.

It will be remembered that the holding relay 33 at station D, or relay 33D, is in the yellow circuit. With this in mind, it may be noted that the series connection of the yellow circuit extends from the power line 12 successively through the various stations, in the order of stations A, B, C and D, to the signal wire 13 and that this signal wire 13 is in efiect a return connection proceeding through the stations in the reverse order, that is to say, from D through C and B to A. Consequently, a holding relay in this return'signal wire 13 between D and C will cut off the remaining stations along that return wire, namely C, B and A. In other words, a holding relay between any two stations in the return signal wire 13 will cut oif the remaining stations along that return wire.

It may also be desirable for the operator of a train leaving block 41 through the side track of station A to prevent any train from entering block 41 through any of the other stations. This, however, cannot be effected simply by breaking the signal wire 13 adjacent the A station. However, it can be effected by additionally opening the series connection of the yellow circuit between stations A and B and establishing a new power connection leading directly to the yellow circuit of station A.

Accordingly, station A is provided with a relay 33 breaking the return signal wire between stations A and B, and this relay 33 is also arranged to control a normally closed switch 42 in the series connection of the yellow circuit between stations A and B and a normally open switch 43 for connecting power to the yellow circuit of station A. Thus, when an operator on the side track of station A closes the track switch 36 to actuate relay 33, he will open the yellow circuit both on-the series side and on the parallel side between stations A and B, thus breaking the yellow circuit for stations B, C and D and, at the same time, establishing a yellow circuit leading from the power line 12 through the normally closed relay contacts 4 and 2 of station A and through switch 43 to that parallel branch of the yellow circuit which extends through station A alone.

It will of course be appreciated that other types of relays may be employed in place of the relays 1, 20 and 33. Thus, for example, latching relays of the type commonly employed in this art may be used in place of relays 1 and 20. r

I claim as my invention:

1. A signal control for the entrance-exit station of a railway section or block, comprising: a normally energized yellow circuit and a normally open green circuit, each including the same electromagnet; an armature having a normal or first position closing the yellow circuit and opening the green circuit and a second position opening the yellow circuit and closing the green circuit; first and second relay coils, operative, when temporarily energized, to actuate said armature to its first and second positions respectively; normally open entrance circuit means, operative, in response to the entrance of a vehicle into the block, to close temporarily to energize said second coil so as to move said armature to its second position, therebyopening said yellow circuit and energizing said green circuit; and normally open exit circuit means operative, in response to the exit of a vehicle from said block, to close temporarily to energize said first coil so as to move said armature to its first position, thereby opening the green circuit and energizing the yellow circuit; and a source of power for energizing said circuits.

2. The control of claim 1 including: a normally open red circuit; and means operative, in response to the deenergization of said electromagnet in said yellow and green circuits, to close and energize said red circuit.

3. A signal system for a railway block having at least two entrance-exit stations comprising: a normally energized yellow circuit containing an electromagnet at each station, the electromagnets of all stations being connected in parallel; a normally open green signalling circuit at each station contaning the electromagnet of its station; a normally open red signalling circuit at each station arranged to close upon the deenergization of the electromagnet of its station; entrance circuit means at each station responsive to the entry of a vehicle at its station to close its green signalling circuit and to open the yellow circuit so as to deenergize the electromagnets of the other stations and thereby energize the red signalling circuits of said other stations; and exit circuit means for all stations operative, in response to the exit of a vehicle at any station, to open the previously energized green signalling circuit and to close the yellow circuit so as to energize all electromagnets and open the previous energized red signalling circuits.

4. A signal system for a railway block having at least two entrance-exit stations comprising: a power line, a signal wire and a clearing wire, each extending to all stations; a relay at each station having normally closed and normally open contacts, cooperating with a common terminal to form normally closed and open switches, and first and second actuating means; an electromagnet at each station; a yellow circuit, normally energized when the block is clear, said circuit connecting the normally closed relay switches of successive stations in series between the power line and the signal wire and the electro-' :ayamoao eachstation operative, inresponse to the entry of :1 vehicleintotheblockatthat station, toenergize the sec- .ond actuating meansof therelay at that station to close its normally open switch, so as to energize :its :green :sig-

na-lling circuit including its electromagnet,z and to open itstnormally closed switch, so as to deenergize the yellow circuit including the electromagnetsot all other stations and-thereby close and energize the red signalling circuits ofisaid other stations; and anexitswitch at eachstation connected to said clearingwireand operative, inresponse to thet-exit of 1 a vehicle from the .block: at: that: station, to energize the first actuating means-of: all relays to restore the relay, at the.station where theiexiting vehicle entered the blOC'kftOlts normal position so as to energize the yellow circuit,including all electromagnets and thereby; deenergize said previously energized red signalling circuits, sand to. deenergize the greensignalling circuit'at the entering stat-ion.

5. The control of claim 4 wherein at least one station includes: auxiliary means, responsive to the closure of the entrance switch at that station by a vehicle overrunning that station to enter an occupied block after the deenergization of the electromagnet at that station, to render the exit switch at that station ineffective to energize the first actuating means of that station when said overrunning vehicle backs out of said block at that station.

6. The control of claim 4 wherein at least one station includes: auxiliary means controlled by the electromagnet of that station to be ineffective when said electromagnet is energized and conditioned for operation when said electromagnet is deenergized, said conditioned auxiliary means being operative, in response to the closure of the entrance switch at that station by a vehicle overrunning that station to enter an occupied block after the deenergization of the electromagnet at that station, to render the exit switch at that station ineffective to energize the first actuating means of that station when said overrunning vehicle backs out'of said block at that station:

7. The control of claim 6 wherein said auxiliary means at said one station includes: an auxiliary circuit at that station, serially containing an auxiliary relay and a normally open switch, which closes upon the deenergization of the said electromagnet of that station to condition said auxiliary circuit for energization, said conditioned auxiliary circuit being connected to power through the normally open entrance switch of that station so as to be energized upon the temporary closure of such entrance switch by a vehicle which overruns that station after the deenergization of said electromagnet.

8. The control of claim 7 wherein: said auxiliary relay of said one station is operative, when energized, to open one switch and close another, said one switch being operative, when open, to render the exit switch of that station inetiective, and said other switch being operative, when closed, to connect said auxiliary relay to said source of power independently of said overrun entrance switch so as to maintain said relay energized after said overrun entrance switch opens.

9. The control of claim 8 wherein: the electromagnet of said one station, when reenergized, closes a switch short-circuiting the auxiliary relay of that station to render it ineifective and thereby open said other auxiliary relay switch to break the independent connection of said auxiliary relay to power.

10. The system of claim 4 including: an exit circuit aextending,tatteachrstation, from the powerlinez'. serially topen, to "the .nclearing wireland from thezclearing wire through fiaffirst :coil, which constitutes the: first actuating zmeans of that/station, to ground; i an auxiliary ;relay at each station ehaving-sa normally deenergized :coil: for'iopcrating. a normally :closedanti-clearing switch :in the .exit

circuit ,ofrits station zbetweenthe :exit. switch and the clearing wire; and a secondary entrance circuit extending-rat eachsstation from" the-power line serially through the entrance. switch of that-station, iwhichis normally -.open,aa normally openiconditioning .switchsati thatustation: and the auxiliary-relay operating coil "of that i station to ground, said *conditioningz switch 1 being :controlled :by the ::electromagnet ofthat'stationto render the secondary entrance circuit-inoperative when said :electromagnet iswenergized andto condition vsuch circuit for operation when :said electromagnet is tleenergized, said :conditionedssecondary circuit being :operative, vupon .the :closure of its entrance switch 'byavehicle overrunningiits .StatiOnFtO :enter the block after the block has been occupied :andsthet electro- V magnet Vat thatsistationfdeenergized, to energize: :saiduauxiliary relay coil so: as to openz theexit circuit. of that'rsta- :tion at its-:anti cle'aringi switch :in orderi torender the exit switch atthat stationsineffective to energizetherexitcircuit when saidoverrunning vehicle: backs out of'said. block atthat station.

, 11. -A=s ignal--system-for.a railwaylblock hav-ingtatt-least two entrance-exit stations comprising: signal means at each station adapted to be set when the block is occupied and to be cleared when the block is cleared; vehicle re sponsive switch means at each station, each switch means having entrance and exit contacts; a signal circuit system controlled by said contacts to set the signal means for the block when the entrance contacts are actuated by the entry of a vehicle into the block and to clear said signal means when the exit contacts are actuated by the exit of the vehicle from the block; and anti-clearing means responsive to the actuation of the entrance contacts at one station, by a vehicle overrunning that station to enter the block after the signals for that block have been set by a vehicle entering at another station, to render the actuation of the exit contacts at the overrun station ineffective to clear the signal means when said overrunning vehicle backs out of said block at said overrun station.

12. The signal system of claim 11 wherein said anticlearing means comprises: a secondary entrance circuit at one station normally open at the entrance contacts of that station so as to be energized upon the actuation of the entrance contacts at that station by a vehicle overrunning that station to enter the block after the signals for that block have been set by a vehicle entering at another station; and means responsive to the energization of said secondary entrance circuit to isolate the exit contacts at that station from the said signal circuit system so as to prevent the overrunning vehicle from clearing the system when it actuates said exit contacts as it backs out of said overrun station.

13. A signal system for a railway block having at least two entrance-exit stations comprising: signal means at each station adapted to be set when the block is occupied and to be cleared when the block is cleared; vehicle responsive entrance and exit means at each station; a signal circuit system controlled by said vehicle responsive means to set the signal means for the block when the entrance means is actuated by the entry of a vehicle into the block and to clear said signals when the exit means is actuated by the exit of the vehicle from the block; and auxiliary means outside of said block but adjacent one station thereof for operating said signal circuit system to set the signals for said block at a remote station other than said adjacent station so as to prevent a vehicle from properly entering the block at said remote station and permit a vehicle to enter said block at said adjacent station.

14. The signal system of claim 13 wherein said auxr, 1 1 iliary means includes: a track switch positioned outside of said block and operative, when actuated, to operate said signal circuit system to set the signals at a remote station; and means, controlled by the operator of a vehicle, to actuate said switch from said vehicle, when the latter exits from and clears said block, said means operating to hold the switch in its actuated position over a period of time determined by the will of the operator of said vehicle.

15. A signal system for a railway block having at least two entrance-exit stations comprising: a normally energized yellow circuit containing an elcctromagnet at each station, the electromagnets of successive stations being connected in parallel between a signal wire and ground; a normally open green signalling circuit at each station containing the electromagnet of its station; a normally open red signalling circuit at each station arranged to close upon the deenergization of the electromagnet of its station; entrance circuit means at each station responsive to the entry of a vehicle at its station to close its green signalling circuit and to open the yellow circuit so as to deenergize the electromagnets of the other stations and thereby energize the red signalling circuits of said other stations; exit circuit means for all stations operative, in response to the exit of a vehicle at any station, to open the previously energized green signalling circuit and to close the yellow circuit so as to energize all electromagnets and open the previously energized red signalling circults; and auxiliary means outside of said block but adjacent one station thereof for deenergizing a parallel portion of the yellow circuit containing the electromagnet of another station so as to prevent a vehicle from properly entering said block at said other station while permitting a vehicle to enter it at said adjacent station.

16. The signal system of claim 15 wherein said auxiliary means includes: a track switch positioned outside of said block and operative, when actuated, to deenergize said portion of the yellow circuit of said other station; and means, controlled by the operator of a vehicle, to actuate said switch from said vehicle, when the latter exits from and clears said block, said means operating to hold the switch in its actuated position over a period of time determined by the will of the operator of said vehicle.

17. The signal system of claim 16 including: normally closed switch means positioned in the yellow circuit signal wire between the said adjacent station and said other station; and normally open circuit means controlled by said track switch and operative, in response to the actuation of said track switch, to open said normally closed signal wire switch means.

References Cited in the file of this patent UNITED STATES PATENTS 1,219,528 Balcom Mar. 20, 1917 2,148,005 Allen et al. Feb. 21, 1939 2,210,423 Miller Aug. 6, 1940

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