US2753447A

US2753447A - Railway signaling systems

Info

Publication number: US2753447A
Application number: US269475A
Authority: US
Inventors: Howard A Thompson
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1952-02-01
Filing date: 1952-02-01
Publication date: 1956-07-03
Anticipated expiration: 1973-07-03

Description

juh 3, 1956 H. A. THOMPSON RAILWAY SIGNALING SYSTEMS Filed Feb. l, 1952 INVENTOR. Howavd A. T/zomfon.

HIS'

Lu L. Saut Hmmm!) RAHWAY SKGNALENG SYSTEMS Howard A. Thompson, Edgewood, Pa., assigner to Westinghouse Air Brake Company, Willmann-ng, Pa., n corporation of Pennsylvania Application February 1, 1952, Serial No, 269,475

3 Claims. (Cl. 21mm-d6) My invention relates to railway signaling systems, and particularly to an improved form of railway signaling system in which the circuits employed for transmitting information concerning traic governing conditions in advance of a particular location may also be employed to ransmit information in the reverse direction.

in conventional railway signaling systems, a stretch of trailic to be protected is divided into sections or blocks, each of which has associated therewith at the entrance end a signal for governing movements of traffic into the block. Such signals may be governed by a combination of track circuits extending through the block to indicate the traflic conditions within the immediate block in advance of a signal, and may also include a line circuit extending to the signal location in advance which line circuit is arranged to reflect the traffic conditions in the next block in advance of a particular wayside signal. Thus when a train occupies the block immediately in advance of a wayside signal, the shunting of the track circuit or track circuits within the block causes the signal to display its most restrictive aspect, and when the train vacates the block immediately in advance of the signal, the track relays pick up to cause the signal to display a caution aspect. When the train vacates the second section in advance of a signal, the line circuit is energized by energy governed over the track relays of the second block in advance so that a relay at the rst wayside signal is picked up, to cause the signal at that location to display a clear or proceed aspect'.

It may at times be desirable to transmit information over the line circuits in the opposite direction to the usual direction of traffic` to provide information at the end of a block concerning traffic conditions at the entering end. One such application of an arrangement of this type is employed in approach lighting signals in advance, by having a series relay connected in the line circuit, so that when the tracl; relay of the block section is released the line circuit is interrupted and the series approach relay releases its contact, thereby supplyinfy energy to the lamp of the signal in advance of the approaching train. Another condition in which it is desirable to transmit traffic information from the entering end of the block section to the leaving end of the block section is the condition wherein vehicles which will not shunt the usual track circuits are operated over the stretch of railway track, and it is desirable to provide a system for registering the entry and the exit of these vehicles in any particular block section. in this connection, it is also desirable to transmit supplemental information over the line circuit from the exit end of the block to the entrance end of the block to indicate that such registration has been accomplished.

Accordingly, it is an object of my invention to provide, in a railway signaling system of the type employing line wire control for signals governing the movement of trallc in a particular' direction, means for utilizing the line circuit for transmitting additional information in the direction opposite to the direction of traffic movement.

Another object of my invention is to provide a railway uit tates Patent O signaling system arranged to provide protection for nonshunting vehicles traversing the section of track so equipped which will not interfere with the normal operation of the signal system by trains or other shunting vehicles using the stretch.

Another object of my invention is to provide, in a system of the type described, an arrangement whereby the entrance of a non-shunting vehicle into the block section may be registered by suitable circuit means, and whereby this registry will be indicated at the entrance point of the section.

Another object of my invention is to provide, in a system of the type described, a superimposed supplemental system for the protection of non-shouting vehicles, requiring the minimum of apparatus, and adapted to be used with conventional signal systems.

Still another object of my invention is to provide, in a signaling system of the type described employing a pair of line wires for the control of signal aspects in accordance with conditions in advance of the signals, means for at times recurrently interrupting the energy flowing in the line circuit, registering these interruptions at the energized end of the line circuits, and indicating the reception and registry of the impulses at the relay end of the line circuit.

@ther obiects of my invention and features of novelty thereof will be apparent from the following description taken in connection with the accompanying drawing.

in practicing my invention, I provide, in a railway signaling system of the type employing a pair of line wires for governing the wayside signals in accordance with conditions in advance of the signal, means for recurrently interrupting the line circuit at the receiving or relay end thereof, and means at the other end of the line circuit for detecting the recurrent interruptions of the line circuit, in accordance with a predetermined sequence or pattern of interruption. The reception of the proper sequence or pattern of interruption causes the energization of the line circuit to be changed in a characteristic manner, and this change in the energization is reflected at the receiving end of the line circuit, to thereby indicate that the control information transmitted from the receiving end of the line circuit has been received properly. in a preferred embodiment of my invention, l provide means, such as a push button connected in series with the: line circuit, at the entering end of a block section, for recurrently interrupting the line circuit to thereby actuate a series con nected relay at the exit end of the block section. rThe recurrent operation of the series connected relay at the exit end of the block section causes the operation of a counting chain, which counts and registers the number of impulses transmitted by the opening and closing of the line circuit. lf the line circuit is recurrently opened and closed in the proper' sequence, as determined by the arrangement of the counting chain, a relay is energized to pole change the energy supplied to the line circuit at the exit end of the block section, and thereby cause the operation of a polarity responsive relay at the entering end of the block section, to indicate that the desired conditions have been obtained.

l shall describe one form of railway signaling system embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic View of a stretch of railway track equipped with a railway signaling system constructed in accordance with my invention, and which is arranged so that the apparatus normally functions in the usual manner to govern the operation of train proceeding through the stretch, but may be also employed to aiford protection to the operators of vehicles which traverse the stretch and which are incapable of shunting the track circuit to cause the operation of the signaling system in its usual manner.

Referring to the drawing, there is shown a stretch of railway track having track rails 1 and 3 which are divided into the customary block sections by the conventional insulated joint 5. Only one complete block section, 2T, is shown in the drawing, together with portions of adjoining block sections 1T and 3T, it being understood that the apparatus for each of the sections is arranged in a manner similar to that shown for section 2T. Traic normally moves through the stretch in the direction indicated by the arrow on the drawing, that is, from left to right. At the entrance or left-hand end of each of the block sections, there is located a wayside signal, such as signal 2S, which functions to govern the entrance of traf into the section in advance of the signal. The signals may be of any of the well-known types, and as here shown are of the conventional color light type, having a green lamp G, a yellow lamp Y, and a red lamp R, which when lighted provide a proceed, caution and stop aspect, respectively. Additionally, at each of the signals there is provided an additional marker or auxiliary lamp designated by the reference character M, for purposes which will be subsequently explained. Each of the sections in the stretch, such as section 2T, is equipped with a conventional direct current neutral track circuit comprising a track battery, such as battery ZTB connected across the rails of the section at the exit end thereof, and a track relay, such as track relay ZTR, connected across the rails at the entrance end of the section. The track relays are shunted by the presence of a train in the section and operate to govern the wayside signals thereby, as will be explained in detail subsequently.

Between signal locations, such as signal 2S and signal 3S, there is provided a pair of line wires, such as the wires designated by the

reference characters

11 and 13, which are employed to additionally govern the wayside signal at the entrance end of the section, and, in accordance with my invention, to also provide means for providing protection for non-shunting Vehicles Which are 0perated through the stretch.

Energy is supplied to the line circuit at the exit end of the block section, and energizes load devices such as polarity responsive relays 2DR and ZMCR at the entrance end of the stretch, which also corresponds to the receiving end of the line circuit. The energy supplied to the line circuit at the transmitting end of the line, corresponding to the exit end of the stretch, also serves to energize a series relay such as relay SAER. The relays 2DR and ZMCR are of the biased type, in which the contacts of the relay are picked up when and only when energy is supplied through the winding of the relay in the direction indicated by the arrow thereon. The load device which is normally energized by the energy supplied over the line circuit, such as relay 2DR, functions as a signal control relay, and cooperates with the track relay, such as relay ZTR, to govern theindication of the wayside sig nal. The other line circuit load device, such as relay ZMCR, is normally supplied with energy which is ineffective to pick up the contacts of the relay, but when the polarity of the line circuit is reversed, the second relay picks up, and is used to indicate, at the receiving end of the line circuit, the conditions at the transmitting end of the circuit. The series approach relay, such as the relay SAER, is connected in series with the circuit for supplying energy to the line wires, and the circuits are arranged so that relay SAER is picked up at all times except when the line circuit is interrupted, during which time the relay will release its contacts.

In addition to the apparatus described above, there is located at each signal location, means for detecting and registering recurrent pick up and release of the series relay. This apparatus may be of any of the well-known types for counting and registering impulses, such as wellknown electron tube circuits, but as here shown comprises a group of counting chain relays, such as relays 3A1, 3A2, 3A3, and 3A4, which are arranged so that the relays operate in sequence as a result of the recurrent operation of the contacts of series relay SAER, so that upon reception of the proper number of impulses, the counting chain relays will become picked up to thereby cause the reversal of the polarity on the line circuit to indicate at the receiving end of the line circuit that a predetermined condition has been established at the transmitting end of the line circuit.

Energy for the operation of the various apparatus and the energization of the signal lamps is provided by a suitable source or" low voltage direct current, such as the battery LB, having its positive and negative terminals designated by the reference characters B and N, respectively.

i'n addition to the apparatus described above, which is located at each of the signal locations in the stretch, my invention also provides for the inclusion of apparatus in the line circuit at intermediate points in the stretch for the purpose of registering the entrance of a nonshunting vehicle into the stretch at that point. This apparatus would comprise a series push button such as the normally-closed push button ZPB- A, and an auxiliary indicator relay such as relay 2MCR-A, the push button and the relay winding being connected in series with the line circuit at a predetermined point in the stretch. Relay ZMCR-A may indicate its energized condition by any suitable means, such as the lamp ZMKE-A energized by a battery ZMCB over a front contact a of relay 2MCR-A, when the relay is picked up, as shown in the drawing.

lt is believed that the description of the operation of the apparatus embodying my invention will be enhanced by describing the manner of operation of the equipment under various trac conditions.

In the normal condition of the apparatus as shown in the drawing, with no train occupying the stretch, and with no non-shunting vehicle registered in the stretch, the line circuit extending between the signal locations 3S and 2S is energized by energy supplied from the battery at signal location 3S, by a circuit which may be traced from terminal B, through the winding of series relay SAER, back contact a of relay SAS, the line wire l1, the normally closed contact of push button 2PB-A, front Contact a of relay ZTR (the track relay ZTR being picked up at this time since the track section 2T is unoccupied), the normally-closed contact of push button ZEPB, the winding of relay 2DR from left to right, the winding of relay ZMCR from left to right, the line wire 13 including in series therewith the winding of relay 2MCR-A, back contact b of relay 3A4, back contact a of relay MCR, and front contact a of relay STR to terminal N. lt will be seen therefore, that at this time, with the apparatus in its normal condition, the energy supplied to the line circuit will cause the contact of the approach relay BAER f' to be picked up, and the direction of flow of energy will be such that the contacts of relay 2DR at signal location 2S will be picked up, while the contacts of relay ZMCR and relay 2MCR-A will be released, the tlow of current through their windings being in the opposite direction to that required to pick these relays up.

lt will now be assumed that a train proceeding through the stretch occupies section 1T in the rear of signal 2S. Accordingly, at this time the line circuit, not shown, cxtending rearwardly from signal 2S in the manner similar to that extending between signal 2S and signal 3S, will be deenergized by the shunting of the track relay associated with section 1T. Accordingly, the series relay ZAER vat signal 2S will become deenergized, audits back` Contact a will establish a circuit for lighting the green lamp G of signal 2S. This circuit may be traced from terminal B at back contact a of relay ZAER, over back contact b of relay ZMCR, front contact b of relay ZTR, front contact a of relay 2DR, and through the green lamp G of signal 2S to terminal N. Accordingly, the signal 2S will display a clear or proceed aspect for the approaching train.

acarrear When the train moves into section 2T, the Wheels and axles of the train shunt the track circuit and relay 2TH accordingly releases and remains released as long as any portion of the section is occupied by any portion of the train. When contact b of relay ZTR releases, it interrupts the circuit previously traced for supplying energy to the green lamp G of the signal and establishes a circuit, obvious on the drawing, for supplying energy to the red lamp R of the signal. Additionally, when contact a of relay ZTR releases the liow of energy in the line circuit previously described is interrupted, so that relays 2DR and 3AER are deenergized and these relays release. When contact a of relay 2DR releases, it further interrupts the circuit for supplying energy to the green lamp G of the signal, but at the present time, with contact b of relay 2TR released, the release of contact a of relay 2DR has no effect upon the signal indication, The release of relay BAER at signal 3S will cause the lighting circuit for this signal to be established in the manner described above for signal 2S, so that signal 3S will display a proceed aspect for the approaching train. Additionally, when contact a of relay SAER releases a circuit is established for supplying energy over the back contact of relay 3AER to the winding of the first counting chain relay 3Al. Accordingly, relay 3A1 picks up and its front contact a closes in a circuit for picking up the second counting chain relay 3A2. However, the pick up circuit for counting chain 3A2 is open at front contact a of approach relay `JAER, so that relay 3A2 does not pick up at this time.

When the train in question moves past signal 3S into section 3T, track relay 3T R will release and its front contact a will further interrupt the line circuit for conM tro-lling the relays 2DR and ZMCR at the entrance end of the section. 2T, relay ETR will again be energized and its contacts will pick up. When contact a of relay ZTR` picks up, it closes the line circuit at the signal location 2S, but, as previously explained, the circuit remains deenergized duc to the interruption thereof by front contact a of the track relay STR. At this time, should a second train be following, a release of the series relay ZAER at signal 2S will cause the signal to display a yellow or caution indication, since at this time front contact b of relay ZTR will be closed, but contact a of relay 2DR will be released so that a lighting circuit for the yellow lamp Y of signal 2S will be completed upon the deenergization of the series relay ZAER.

When the train vacates section 3T, track relay STR will be energized and its front contact a will again be closed, reestablishing the circuit for supplying energy over the line wires to the relays 2DR and ZMCR at signal location ZS. Since relay 3A4 remains released at this time, the polarity of the energy supplied over the line wires to relays at signal 2S is of the polarity to cause the contacts of the relay 2DR to pick up, and the contacts of the relay 2li/ICR will remain released. Accordingly, the signal lighting circuits for signal 2S are again connected in such manner that deenergization of the series relay ZAER by an approaching train will cause the signal 2S to display a green or clear aspect.

Reestablishment of the energy to the line circuit also causes the contact a of relay BAER to become picked up. When contact a of relay SAER picks up, a circuit isestablished momentarily for the pick up of relay 3A?. which circuit includes front contact a of relay SAER and front contact a of relay BA1. However, the supplyv of energy to relay 3All is cut ott when contact a of relay 3AER picks up, so that the contact a of relay 3A1 releases, after a short time interval, thereby interrupting the supply of energy to the winding of relay 3A2, which subsequently releases. At this time7 relay SAS cannot pick up since when relay 3AER picks up its contact a, the pick up cirA cuit for relay SAS, which includes front contact a of relay SAZ and back contact a of relay SAER, is broken by con- When the rear of the train vacates section 6 tact' a of relay SAER before front Contact a of relay SAE closes, so that relay 3A3 remains released.

The apparatus is now restored to its normal position as shown on the drawing. lt will be apparent from the foregoing description that the apparatus .normally functions in the usual manner of a two-block three-indication signaling system upon the passage of a train through the stretch equipped with this type of arrangement. The most restrictive indication is controlled by the track relays, to denote occupancy or unoccupancy of the stretch immediately in advance of each Wayside signal, while the line circuit described above provides an additional control for displaying a yellow or green` aspect in accordance with the occupancy or nonoccupancy of the second section ahead of the wayside signal, provided of course, that the first section is unoccupied. as determined by the track circuit of that section.

It will now be assumed that the operator ot a motor car or other vehicle which is not capable of shunting the track circuit desires to place the vehicle upon the rails at the entrance end of one of the sections and proceed therethrough. To establish the necessary protection for the motor car, it is necessary that its presence within a given stretch be registered and that a distinctive indicao tion is provided to warn the enginernen of approaching trains of the fact that a motor car has been registered into the section.

To register a motor car in the section from the entrance end thereof, such as at signal 2S, the motor car operator will operate the push button ZEPB twice in succession, with the intervals between operations rela tively short. As will be apparent from the previous dis-- cussion ot the line circuit, each operation of the push button ZEPB causes the line circuit to become deenergized and results in the release of the relay 3AER at the exit end of the section for such time as the push button ZEPB is depressed.

When the motor car operator depressies the push button ZEPB twice at the entering end of the section 2T, the contact a of relay SAER at the exit end of the section will be released, picked up, released, and then picked up again. Upon the rst release of contact a of relay SAER energy is supplied to the winding of the tirst conne ing chain relay 3Al, so that this relay picks up. When the contact a of relay SAER picks up for the first time, a circuit is established over front contact a of relay Alit and front contact a of relay 3A1 to cause the pick up of the second counting chain relay 3A2. When contact a of relay SAER releases in response to the second operation of push button ZEPB, energy is supplied to the third counting chain relay 3A3 by a circuit including back contact a of relay SAER and front contact a of relay 3A3. When the contact a of relay SAER is finally picked up after the push button ZEPB is released the second and last time, a circuit is established including front contact a of relay SAER and front Contact a of relay 3A3 to pick up the fourth counting chain relay 3A4l. When relay 3Ad picks up, a stick circuit is established for the relay` which circuit may be traced from terminal B, over a normally closed push button SXPB, back contact b ot relay SAS, back contact b of relay SMCR, front contact c of relay 3A4', and through the winding of relay 3A4 to terminal N. Accordingly, at this time relay 3A@ will have its contact picked up and will remain picked up after the previous counting chain relays have released, as a result of the closure of the stick circuit of the relay. When contacts a and b of relay 3AflV pick up, the supply of energy to the line circuit is pole changed, so that energy is now supplied to the relays at the entrance end of the section by a circuit which may be traced from terminal B through the winding of series relay 3AER, over front contact b of relay 3A4, line wire 13 including in series therewith the winding of relay 2MCR--A, the winding of relay ZMCR, the winding of relay 2DR, all from right to left, over the contact ofV push button ZEPB,

front contact a of track relay 2TR, line wire 11 including in series therewith the contact of the push button ZPB-A, and over front contact a of relay 3Ali to terminal N. The ilow of current in the circuit at this time is such as to cause the contacts of relays ZMCR and 2MCR-A to pick up, and the contacts of relay 2DR will be released and remain released.

The picking up of relay ZMCR at the entrance end of the section causes an indication lamp ZMKE to be supplied with energy by a circuit including front Contact a of relay ZMCR, to thereby indicate to the operator of the motor car that the registry of the entrance of the motor car in the section 2T has been properly accomplished. Additionally, when Contact b of relay ZMCR picks up it establishes a circuit for supplying energy to the marker lamp M of signal 2S, in the event that lthe series relayl ZAER should be released by the approach of a train. Accordingly, if the train is approaching section iT at this time, the lamp M of signal 2S will be lighted, to

thereby provide a distinctive aspect from signal 2S, in-

dicating to the engineman of the approaching train that a motor car has been registered in the section in advance, so that the engineman may govern the operation of his train accordingly.

lt will now be apparent that the purpose of the push button ZPB- A and the series relay ZMCR-A connected in the line wires in the middle of the block section is for the purpose of permitting the motor car operator to register the entry of his car in case the car is placed upon the tracks at the middle block section. Additionally, the relay ZMCR-A provides an indication at that point as to whether or not a motor car is registered in the block by controlling the indicator light MKB-A. it will be apparent that a plurality or" push buttons and indication relays may be connected in series in the line circuit at various places throughout the block section, wherever it may be desired to provide for registration and/or indication of the registration of the motor cars in the block section.

When the motor car reaches the exit end of section 2T, the counting chain relay 3A4 may be released to clear out the registration by either one of two means. First, the operator may push the cancellation button SXBP, which will break the stick circuit for the relay SAA, or, second, if the motor car is to progress into section 3T, the operation of the push button for registering the car in section 3T will cause relay SMCR to pick up, in the manner similar to that described .for relay MCR, and when relay 3MCR picks up, its back contact b Will interrupt the stick circuit for relay 3A4. ln either case, the release of relay 3A@ causes its contacts a and b to pole change the energy supplied to the line circuit, with the result that the motor car indication relays 2MCR and MCR-A will be released, and relay 2DR will be en ergized as previously described. Such operation will restore the apparatus to its normal condition as shown in the drawing and described heretofore.

It will be noted that when relay SMCR is picked up, its front contact a inserts a resistance R1 in the circuit tor supplying energy to the line circuit and the relays ZDR and ZMCR at the entrance end of the block section. This resistance is proportioned so that the current which ows through the line circuit at this time will be insufficient to pick up relay 2DR but will be suflicient to cause relay SAER to'remain energized. Accordingly, when relay SMCR is picked up by the registry of a motor car in section 3T, signal 3S will display the distinctive indication consisting of the lighted marker lamp M upon the approach of a train, and additionally, the signal in the rear of the section in which the motor car is registered, in this case signal 2S, cannot display better than a yellow aspect, thus warning the engineman of an approaching train that a restrictive condition exists in advance. However, since the relay BAER remains energized at this time it is possible for a second motor car operator 8 to register his car in section 2T, by operation of the push button ZEPB, to thereby operate relay BAER in the manner described above to pick up the counting chain relay and register the motor car in section ZT.

The system also functions to register the entry of a motor car and provide cancellation of this registry when the motor car backs out of the section at the same end Where it was originally registered into the section. For example, let it be assumed that a motor car operator has registered in section 2T by operation of push button ZEPB at signal 2S, in the manner described above. It will now be assumed that the motor car operator wishes to reverse his direction of travel and back out of section 2T, removing the car from the rails at signal location 2S. After the car is removed from the rails, the motor car operator depresses the push button ZEPB twice in succession, holding the push button depressed for a relatively long interval during the second operation thereor". When the push button is iirst depressed, relay SAER. will release and its back contact a will establish a pick up circuit for relay 3A1. When relay SAER picks up at the end of the rst operation of the push button ZEPB, the circuit for picking up relay 3A2 is established over front contact a of relay SAER and front contact a of relay 3A1. When relay 3AER is released upon the second operation of push button ZEPB, relay 3A3 is picked up over back contact a of relay SAER and front contact a of relay 3A2. The previously traced stick circuit for relay 3A4 is interrupted by the opening of back Contact b of relay 3A3, and since the pickup circuit for relay 3A4 is open at this time due to the release of relay SAER, the supply of energy is cut off from relay 3A4, and after a short time interval, relay 3A4 releases, restoring the polarity of the line circuit to normal. Since contact a of relay BAER will remain released for a considerable interval at this time, relay 3A2 will release during this interval, thereby opening the circuit for relay 3A3, which in turn releases, so that when relay SAER is finally picked up upon the second release of the push button, the circuit for picking up relay 3A4 will not be established, since relay SAS will be released and its front contact a will hold the pick up circuit for relay 3A4- open.

From the foregoing it will be seen that the arrangement of the circuits as shown in the drawing and embodying my invention provides for the operation of nonshunting vehicles through a stretch of track equipped with a signaling system which operates in the conventional manner for trains and motor vehicles which are capable of shunting the track circuits. Such operation is accomplished by providing means for recurrently interrupting a normally energized line circuit at the receiving end thereof in a predetermined sequence, registering the interruptions at the transmitting end thereof, and providing an indication at the receiving end of the line circuit that the registry has been accomplished by changing the characteristics of the energy supplied over the line circuit.

Although I have herein shown and described only one form of railway signaling system embodying my invention, it will be apparent to those skilled in the art that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination, a source of electrical energy, a load device, a pair of conductors for supplying energy from said source to said load device, said load device being connected to said pair of conductors at one end thereof and said source being connected to said conductors at the other end thereof, means connected between said load device and one of said conductors for at times recurrently interrupting the connections of said load device to said source in a predetermined sequence, detecting means connected to said conductors at the end of said conductors at which said source is located and respongrsser 9, sive to changes in the interrupted energy supplied from said source to said conductors, relay means governed by said detecting means and rendered effective when and only when said detecting means is recurrently operated in said predetermined sequence, said rel'ay means operative when rendered effective to change the character of the energy supplied from said source to said conductors, and means associated with said load device for indicating the character of the energy supplied over said conductors to said load device.

2. ln combination, a source of electrical energy, a load device, a pair ot conductors for supplying energy from said source to said load device, means associated with said load device for at times" recurrently interrupting the connection of saidload device to said conductors in a predetermined sequence, a series relay connected between said source and said conductors and having contacts which are picked up or released according as energy is or is not being supplied to said load device from said source, counting chain relay means governed by said series relay contacts and rendered effective when and only when said series relay contacts are picked up and released in said predetermined sequence, and means governed by said counting chain relay means for changing the characteristics of the energy supplied to said load device from said source when said counting chain relay means is rendered effective.

3. ln combination, a section of railway track over which traiic normally moves in a given direction from a designated entrance end of the stretch to the designated exit end of the stretch, a pair of conductors extending from the entrance end of the stretch to the exit end of the stretch, means for normally supplying direct current energy of a given polarity to said conductors at the exit end of said stretch in accordance with trai-lic conditions in advance of said stretch, a wayside signal located at the entrance end of said stretch, a signal control relay connected to said conductors at the entrance end of said stretch and responsive to energy of said given polarity for governing said wayside signal, a circuit-interrupting Contact at the entrance end of the Stretch and effective at times for interrupting said line circuit in a predetermined sequence, registry means including a relay counting chain located at the exit end of said stretch and rendered effective when said line circuit is interrupted in said predetermined sequence for reversing the polarity of the energy supplied to said line circuit from said source, and auxiliary relay means associated with said signal control relay for indicating the reversal of the polarity of energy supplied to said line circuit.

4. ln combination, a section of railway track over which traiiic normally moves in a given direction from a designated entrance end of the stretch to the designated exit end of the stretch, a pair of conductors extending from the entrance end of the stretch to the eXit end of the stretch` means for normally supplying direct current energy of a given polarity to said conductors at the exit end ot said stretch in accordance with tratlic conditions in advance ot said stretch, a wayside signal located at the entrance end ot` said stretch, a signal control relay connected to said conductors at the entrance end of said stretch and responsive to energy of said given polarity for governing said wayside signal, a circuit interrupting Contact at the entrance end of the stretch and eiective at times lor interrupting said line circuit in a predetermined sequence, registry means including a relay counting chain located at the exit end of said stretch and rendered eliective when said line circuit is interrupted in said predetermined sequence for reversing the polarity of the energy supplied to said line circuit from said source, auxiliary relay means associated with said signal control relay and responsive to reversal of the polarity oi the energy supplied to said line circuit, and circuit means governed by said auxiliary relay means ior causing said wayside signal to display a distinctive aspect,

itl"

5. A railway signal system comprising a stretch of track divided into sections, a track circuit including la track relay for each section, a pair of line conductors for each section, at least one of which includes in series therewith a front contact of the associated track relay, energy supply means for each section for supplying the pair olf conductors for the section next in the rear with energy of a given polarity in accordance with traiiic conditions in advance, a signal control relay for each section receiving energy from said conductors and responsive only to energy or" said given polarity, a signal for each section governed jointly by said track relay and said signal control` relay, circuit controlling means located at each of said signal locations for at times interrupting said line conductors in a predetermined sequence, a series relay at each signal, location and connected in series with the line conductors for the section in the rear, a group oli` counting relays governed by said series relay, said counting relays being rendered operative when and only when said line conductors are interrupted in said sequence, pole-changing means governed by said counting relays andV effective when rendered operative to reverse the polarity of the energy supplied to said line conductors, an auxiliary control relay for each section receiving energy from said conductors and responsive only to energy of reverse polarity, and indication means governed by said auxiliary relay.

6. A railway signal system comprising a stretch of track divided into sections, a track circuit including a track relay for each section, a pair of line conductors for each section, at least one of which includes in series therewith a front contact of the associated track relay, energy supply means for each section for supplying the pair of conductors for the section next in the rear with energy of a given polarity in accordance with traliic conditions in advance, a signal control relay for each section receiving energy from said conductors and responsive only to energy of said given polarity, a signal for each section governed jointly by said track relay and said signal control relay, circuit controlling means located at each of said signal locations for at times interrupting said line conductors in a predetermined sequence, a series relay at each signal location and connected in series with the line conductors for the section in the rear, a group of counting relays governed by said series relay, said counting relays being rendered operative when and only when said line conductors are interrupted in said sequence, pole-changing means governed by said counting relays and elifective when rendered operative to reverse the polarity of the energy supplied to said line conductors, an auxiliary control relay for each section receiving energy from said conductors and responsive only to energy of reverse polarity, and means governed by said auxiliary relay for causing said signal to display a distinctive aspect.

7. A railway signal system comprising a stretch of track divided into sections, a track circuit including a track relay for each section, a pair of line conductors for each section, at least one of which includes in series therewith a front contact of the associated track relay, a source of direct current energy for each section for supplying energy to the pair of conductors for the adjacent section in the rear, a pole-changing relay having contacts which govern the polarity of the energy supplied to said conductors from said source, polarized relay means receiving energy from said conductors, circuit controlling means for at times interrupting the ow of' energy in said conductors, a series relay having a winding connected in series between said source and said contacts of the polechanging relay, said series relay having contacts which are picked up or released according as energy is or is not flowing through said conductors, a signal for said section, said signal being governed jointly by said track relay and said polarized relay means energized with energy of a given polarity, a chain of counting relays governed by said series relay and arranged so that the counting relaysv are picked up sequentially when said line conductors are interrupted in said predetermined sequence, a pick-up circuit for said pole-changing relay including contacts of said series relay and the last relay in said counting chain, a stick circuit for said pole-changing relay including a normally closed circuit controller, and indication means including said polarized relay means for indicating the reversal of polarity of the energy supplied to said line conductors.

8. A railway signal system comprising a stretch of track divided into sections, a track circuit including a track relay for each section, a pair of line conductors for each section, at least one of which includes in series therewith a front contact of the associated track relay, a source of direct current energy for each section for supplying energy to the pair of conductors for the adjacent section in the rear, a pole-changing relay having contacts which govern the polarity of the energy supplied to said conductors from said source, polarized relay means receiving energy from said conductors, circuit controlling means for at times interrupting the flow of energy in said conductors, a series relay having a winding connected in series between said source and said contacts of the polechanging relay, said series relay having contacts which are picked up or released according as energy is or is not flowing through said conductors, a signal for said section, said signal being governed jointly by said track relay and said polarized relay means energized with energy of a given polarity, a chain of counting relays governed by said series relay and arranged so that the counting relays are picked up sequentially when said line conductors are interrupted in said predetermined sequence, a pick-up circuit for said pole-changing relay including contacts of said series relay and the last relay in said counting chain, a stick circuit for said pole-changing relay including a normally closed circuit controller, and means governed by said polarized relay means for causing said signal to display a disf tinctive aspect when the polarity of the energy supplied over said line circuit is reversed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,168,817 Ptlasterer Aug. 8, 1939 2,232,379 Field c Feb. 18, 1941 2,503,716 Failor Apr. 11, 1950 2,572,234 Young Oct. 25, 1951