US2324964A - Coded track circuit for railway train detection - Google Patents

Description

July 20, 1943. H. A. THOMPSON 2,324,964

CODED TRACK CIRCUITS FOR RAILWAY TRAIN DETECTION Filed Dec. 6, 1941 mv moR HowardAjhompyan FYQZW HIS ATTORNEY Patented July 20, 1943 CODED TRACK CIRCUIT FOR EAILW'AY TRAIN DETECTION Howard A. Thompson, Edgewood, Pa, assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application December 6, 1941, Serial No. 421,880

5. Claims.

My invention relates to coded track circuits for detecting the presence of railway trains and it has special reference to the employment by such track circuits of coded energy pulses that have positive and negative polarities in alternating sequence andthat are of relatively short individual duration.

Generally stated, the object of my invention is to improve the design and broaden the utility of coded track. circuits of the polar impulse ype just described.

A more specific object is to provide improved energy supply facilities. for polar impulse track circuits. of the single code. type. 3

Another object is to derive the polar impulse energy from non-track battery sources and to supplythe pulses of that energy atcode frequencies which are much higher than those of customary direct current codes.

A further object is, to provide code generating facilities which are of new and simplified character and which incorporate self-starting and other'desirable features.

In practicing my invention I attain the above and other objects and advantages by deriving the trackway energy from a. direct current source of twelve volt or other conventional control potentim; by interposing an impulse transformer between this source and the track rails; and by providing code generating apparatus which causes this transformer to receive from the source relatively short pulses of exciting current that recur several times each second and that have positive and negative polarities in. al-

ternating sequence- I shall describe representative forms of polar impulse coded track circuits which embody my invention and shall then point out the novel features thereof in claims. These illustrative embodiments are disclosed by the accompanying drawing in which:

Fig. l is a diagrammatic representation of a single code track circuit that incorporates the improvements of my invention and that is of the detection only type;

Fig. 2' shows the Trackway code for the circult of Fig. 1 and indicates the manner in which thatcode is produced;

. Fig. 3 illustrates a modified form of code generating'apparatus which may be employed at the exit end of the Fig. 1- track section; and

Fig. 4 shows. a modified form of code detectins; apparatus which may be employed at the entrance end: of the. Fig. I track section.

In the several views of the drawing, like ref erence characters designate corresponding parts. Referring first to m. 1, characters I and 2- designate the conductors of a control. circuit which normally is capable. of transmitting energy between its two ends but; which at times is rendered incapable oisuch transmission. As shown in Fig. 1', these control circuit. conductors take the form of the two rails of a sectionof railway trash. II-III which is separated from adjoining sections the customary insulated joints 3 and through which it will be assumed that tra'flic moves in the singledirection indicated by the arrow. Suchv movement, of course, makes location II the'section entrance end. and location III the section exit end.

At this exit end 111 there is provided an impulse transformer T1 having an output winding that is continuously connected with the section rails and an: input winding that has one center and two end terminals; a source of direct current exciting. energy for this: transformer which has first and second terminals B and: C and which may take the form of a twelve volt. control battery (not shown) or the like; any impedance 5 which continuously connects source terminal C with the center terminal of transformer 'I'IFs' input winding; and coder relays. CTt and GT2 which. repeatedly connect source terminal B first with. one and; then with the other of that input windingstwo end terminails and which'thereby cause the. transformer T1 to supply the section rails with recurring pulsesoi outputpotential that have positive and negative polarities. in alternating sequence.

At the section entrance end II there is provided a. track relay TR of? the code following type which has its winding connected across the rails and which holds contacts 8.--9 to the 1eit during each positive polarity pulse of winding received energy and to the right during each negative pulse of received energy; a decoding transformer DI' which. receives primary current under the control otthe pole changing. contact 8 of'the track. relay; and a code detecting. relay H. which is 01 thedirect current delayed. release type and which is energized. from the decodin transformer secondary over a rectifying contact 5 or the track relay.

Two-relay coderappdratus of Fig. I

The exit end or location III apparatus just described forthe' Fig. 1 track section will first be examined in greater detail. Each of the coder relays CT! and GT2- is of'the magnetically toggled code following type having a delayed response of the short character later described. Looking; at device CTI, when the leitportion or its winding is energized the relay holds it contacts I t- L2- 3 in the left or normal position; when, however, the right portion-or the relay winding is energized contacts I ll2|3 then are shifted to the right or reverse position.

011cc, moreover,- eitherof these positions is established, the contacts there remain continuously until therela winding is energized in the opposing direction. Relay GT2 performs in exactly the same manner. When the left portion of its winding is energized it holdscontacts l'| 6 inthe left or normal position; when, however,

the right portion of the relay winding is ener gized these contacts -16 are shifted to the right or reverse position. r

In the illustrative organization shown, current for operating the first coder relay CT! is supplied over contact N5 of the companion relay. GT2 while the current for operating that com-- panion coder device GT2 is supplied over contact [3 of the first coder relay GTl. As will be seen:

(1) relay CT2s energizing circuits cause CTZs contacts I5l6 to go to their left or normal posi tion following eachnormal positioning of relay GTI s control contact l3 and to their right or reversed-position following each reverse positioning of thatcontrol contact; and (2) relayGTis energizing circuits cause GTls contacts I |l2.l3 to go'to their right or reversed position following each normal positioning of GT2s control contact l6 and to their left or normal position following In the complete organization of Fig. 1, each one Of those four periods defines the completion of a circuit through which the input winding of impulse transformer TT is supplied with a pulse of exciting current from direct current source BG. The first of these circuits extends from sourceterminal B'throughnormal contact 55 of deviceGTZ, conductor it, normal contact ll of device GTE, conductor 19, the eft half of transformer TTs input winding, and impedance 5 back. tosource terminal C. By it, transformer 7 interval c--d of Fig. 2.

each reversed positioning of that control con- 7' tact.

By these uniquely arranged energizing'circuits, the two coder relays GTl and GT2 are caused rev peatedly to shift the positioning of their contacts in the cyclic manner which Fig. 2 represents. In the diagram of that figure, the elevated portions of the CTI pattern designate a normal or left closure of contacts H'l 2i3, while the depressed portions of that pattern designate a reverse? or right closure of the same contacts; Similarly,.the elevated'portions of the :2

GT2 pattern designate a normal or left closure of contacts l5:-l6, while-the depressed portions of the pattern designate a reverseior right closure of the same contacts.

From this Fig. 2 diagram, it will be seen that: (1) if the contacts of coding device GT2 reach theirleft or normal position at point a, then the contacts of device GTI will begin movement from will begin movement from their reverse 'to their normal positions at the later point 1; (4). if those CTI contacts reach their normal position at point .0, then the GT2 contacts will begin movement from their reverse to theirnormal positions at point h; and (5) if the GT2 contacts again'reach their normal position at point al; then theGTl contacts will start to move from their normalto their reverse position at the later point bl.

The just stated periods ab, 'cd, e-f, g--h and aI-bl of contact positionfoverlap result from the earlier mentioned delayed response characteristics of the two coder relay CTI and GT2. .As" long. as proper potential continues to be .appliedto the operating circuit terminals plus'and minusv the sequence of actions diagrammed by Fig. 2 continues to repeat itself on the .four periodbasis already indicated. The various time intervals in the sequence... are, of

course, dependent upon the response speeds of coder devices GT|--GT2. v i

For reasons to be madehclearrpresently, .it is preferable to arrange that these periods a. b,

c-d, e -f and g,h of contact register recur at the rate of severaltimes each second;

The third exciting circuit for the transformer extends from source terminal B through reverse contact #5 of device GT2, conductor 23,.reverse contact if of device GT5, conductor 19, the'left half oftransformer TT input winding and impedance5 back to source terminal C. By this third circuit, the transformer TT is supplied with positive polarity exciting current during time interval cf of Fig.2.

The fourth exciting circuit for transformer TT extends from source terminal B through reverse contact of device GT2, conductors 23 and 28,

normal contact #2 of device GT1, conductor 24,

the right half of'the transformer input winding and impedance 5 back to source terminal C. By that fourth circuit, the transformer is supplied with negative polarity exciting current during time. interval gh of Fig. 2. k

Through their earlier described cyclic operations, therefore, the two coder relays CTI and thus cause the impulse transformer TT to be suppliedwith recurring pulses of exciting current which have positive and negative polarities in alternating sequence and which produce in the transformer core magnetic fluxes having the general character designated by the .TT flux D tion of Fig. 2. The alternate reversals of flux polarity are, of course, effected by the relatively reversed directions of current flow through the left and right halves of the transformer input winding.

By those recurrently reversing core fluxes there is generated in the output winding of transformer TT a secondary potential having the general character indicated. by the Trackway code portion of Fig. 2. As that figure shows, this track- Way potential is alternating in polarity; it takes the form of positive and negative voltage pulses which follow one another inregularly recurring sequence; each of those pulses has a high peak 01' impulse value; and each pair of pulses constitutes a code cycle consisting of a positive period followed by a negative period.

Preferably, these polar impulse cycles recur at a code frequency which is much higher than that of customary direct current codes. Typically such customary codes have an upper limit of the order of cycles per minute, or three cycles per second. In the polar impulse code of Figs. 1 and 2, frequencies of the order of six or more cycles per second are to be preferred and such ar readily obtainable by means of coder relays arranged in the novel manner shown at CT!- GT2 in Fig. l. 7

Looking next at the entrance end or location II apparatus earlier described for the Fig. 1 track section, it will first of all beobserved that track relay TR also is a code following device of the magnetically toggled or polar stick type. Such a relay is capable of transferring its contacts from one position to the other rather rapidly and in response'to only a short application of winding energy. A positive polarity pulse of the short character indicated in Fig. 2 is. therefore efiective to shift the track relay contacts 8-9 to their normal or left position while a negative'polarity Pulse otcorrespondingly short. duration is efiective to shift the contactsto their right or reversed position. I

Operation of the track relay is, therefore, exactly the same as were each of the positive pulses to be prolonged for the: full duration of the positive. codeperiod; and each of the negative pulses to be prolonged for the full duration of the "negative code period. Even with code frequencies of the elevated. order of six. or more cycles per second such desired operation of the track relay continues to he achieved;

As earlier indicated, the track relay TR controls a code detector relay H in such manner that the latter relay holds its contact 2.1. picked. up

when and only when the track'relay'is following 51" with those pulses, this code detector relay H receives the code frequency pulses; of unidirectional current which hold: contact. 21 continuously picked up. In the event, however, that contacts 8-3 stay in one position. continuously, no secondary voltage is generated by transformer TT and relay H then allowed to releaseccntact 21.

From the foregoing description. of the appas ratus at exit and entrance. locations III and II. the functioning of the complete polar impulse track circuit combination of Fig. 1 will have become apparent. Coder relays CTI and GT2 operate continuously and cause exit end elements BC and TT to supply the section rails with trackway energy having the polar impulse character represented. by the lower portion. of Fig. 2. Under vacant conditions ofthe section this energy is transmitted to entrance end track relay TR..

In responding, that relay repeatedly shifts contacts 8-9 between their normal and reverse positions and thereby causes code detecting relay H to hold contact 21- continucusly. picked up. This picked up condition peisists, quite. obviously, as long as track section IIII-I remains vacant. Entry of a train into the section by-passcs rails .l- 2 in the usual manner and thereby cuts 03ft all energy reception; by relay TR. Such cut-0E causes contacts 39to remain continuously in the position to whichthey. were last energized ay'IR serves to pole change the itis responsive to each pulse ofoutput voltage and thereby deenergizes code detecting relay H. As a result of that deenergization, contact 21 now releases.

'As .the train passes out of section IIIII, transmission. of: the -polar' impulse energy through entrance end trackrelay TB is once more resumed; contacts 8-4! thereof again iollow code, transformer. DT once more supplies energizing current to the winding of relay I-l, andcontact [8 of that relay again picks Any suitable use of the code detector rclays contact 21. may,.of course, be made and because of the diversity of such possible uses there has been no attemptto represent any particular one of them; Typically, however, they will be of the detection. only'variety wherein relay H performs the single function of distinguishing between vacant and occupied conditions of the associated track section. Such a function is, of course, required in many signaling system applications of commercially well-known character..

,Single relay coder apparatus of Fig. 3

Referring to Fig. 3, I have there shown an alternative arrangement for generating polar impulse code of the general character indi-- cated by Fig; 2. In this arrangement only one polarized code following relay is used the exit location III and it is shown in the form of a device GT3.

In these modified exit end facilities of Fig. 3, use is made of an impulse transformer TTl which corresponds to device T1 of Fig. l but which differs therefrom in being equipped with a. second output winding. 39 by which operating energy is. supplied to relay GT3. That relay is provided with a single contact 32 over which direct current sourceB-C supplies exciting current to the input Winding of transformer TTI.

when contact 32 occupies left hernia? position shown, the flow of exciting current is upwardly through the lower half of the trans-- former and the efiect of. a negative or: citing pulse (see the Flux of Fig. 2) is had; Whcmhowcver, contact 3.. in the right or reverse position, the fl0WOf.QXCll;ll1Z current isdownwardly through the upper half of he transformer primary and the eifect or" a no u to pulse of exciting-current (again see Fig. 2) then is'had.

Interposed between output winding of; transformer T1! and the track rails is a current limiting impedance 33 which performs the samefunction as does elementfi of the Fig. 1 combination, but which permits the eneration or substantially fullv transformer even during shunted. conditions of the suppne track. rails l.-2..

Thesingle coder relay GT3 of Fig. 3 has response characteristics which are generally similar to those earlier described for I C'I'i--CH2 of Fig, It. That is, flow of one: ing current through the relay winding in the direction of from left to right causes contact 32 to go to the left or normal position; likewise, flow of relay winding current in the opposite or right toleft direction causes contact 32 to go to the right orreverse position. Like coder relay devices CTICT2, moreover, this relay (3T3 is of the delayed responding type.

In the code generating combination of Fig.

Prop

that results from; each establishment of an exciting. connection. In the particular organization illustrated, relay GT3 thus is caused to'shift contact 32 to the opposing position a short time 'following each such establishment.

Looking more closely at Fig. 3, assume that contact 32 has just moved to the illustrated normal position wherein negative polarity current is supplied to the primary of transformer 'ITl and positive polarity potential is asa result ofsuch application being generated in'each of the transformerstwo output windings. Such generation in winding 35}. fio'ws' current from the right to the left through relay GT3 and thus causes contransfer contact 32. between thenormal and the reverse positions. 7

By such transfer, tr'ansformerTTl iscaused to impress upon rails l-Z coded trackway energy of the polar impulse characterrepresented in Fig. 2. By choosing the responsecharacteristics of relay GT3 the frequency of such code pulse application may, quite obviously, be selected within wide limits. I Preferably, however, a frequency of'the order of six or more cycles; per second is to be desired. 1 Single-relay detector appa mfus oj Fig, 4 Entrance end code detecting facilities of the character represented at location II'in Fig. 1 are usable with code generating apparatus not only of the two relay type shown at Fig.'1s location 111 but also of the single relaytype which Fig. 3

illustrates.

Such facilities utilize, as had been seen, a code following track relay TB of conventional polar stick character plus a code detecting relay H and an energizing transformer DT therefor. "i 1 In Fig. 4, I have represented a simplified form of code detecting equipment wherein only a single relay TR! is utilized. This relay isa non-code following track device which'receives energy from the rails through a relaytransform'er RT and a full wave rectifier 35. It has a contact 2Twhich performs the same function as does the similarly designated element of Fig. 1, and which has slow releasing characteristics. f Reception at Fig. 4s location II of polar impulse trackway energy, such as the code generating apparatus of either Fig. 1 or 3 produces, causes transformer RT and rectifier 35 to impress upon relay TRI pulses of unidirectional energizing current which recur at code pulse frequency and which are effective to hold contact 21 continuously picked up. Entry of a train into the section of which Fig. 4s location 11 marks the entrance cuts off all of these energy pulses and thereby allows contact 2! to release. As the train passes out of the section, transmission of the coded polar impulse energy through transformer RT is once more resumed and relay TR is caused again to pick up contact 21. p f

This Fig. 4 arrangement is best suited for use with code frequencies of comparatively, high character, such as the six or more cycles per second earlier: named. With such frequencies therelease period for relay 'I'Rls contact Zlmay be reduced sufficiently to provide a very quick shunting response. a

Summary The polar impulse coded track circuits herein shown are alternative to a detector only organization which is disclosed and claimed by my copending application Serial No. 412,624 filed on September 27, 1941, forfCoded track circuits for railway trafiic control. For the track circuits of the present application, therefore, the same, broad advantages may be claimed as are enumerated by my copending application just identified.

These broad advantages flow from the use of the polar impulse principle and include a lowering of power requirements, a raising of immunity to false operation by foreign currents, an elimination of operating difficulties due to storage energy persistence, a lowering of code distortion effect, and an improvement in shunting sensitivity.

In addition, the novel code generating apparatus of this appliction broadens the utility of coded track circuits of the -polar impulse type by: (1) improving the design of energy supply facilities for "single code track circuits; (2) deriving the polar impulse energy from nontrack battery sources and supplying the pulses of that energy at. code frequencies which are much higher than those of customary direct current codes and which approximate the characteristics of an alternating current track circuit;

and (3) permitting allof the code generating devices to be of similar design.

In each of the organizations moreover, the code generating apparatus is inherently self-starting and automatically begins to function when energy of a proper character is impressed upon the terminals of its'driving circuits. I .1

From the foregoing it will accordingly 'be seen that the improved polar impulse coded track circuits of my invention are of broad utility and that their application is by no means restricted to the detector only forms which are herein shown by way of illustration.

Although I have herein shown and described only representative forms of coded track cirmy invention, what I 1. In track circuit energy supply means, in

, combination, a transformer having an output gizedin one direction and which occupy a reversed position when and after the relay is energized in the opposing direction, an energizing circiut for said second relay which'is controlled by a contact of said first relay and which causes the second relay contacts to go to their normal of Figs. 1 and 3,

position following each normal positioning of the first relay contacts and to their reversed -posi-- tion following each reversed positioning of the first relay contacts, an energizing circuit for said first relay which is controlled by a contact of said second relay and which causes the first re lay contacts to go to their reversed position following each normal positioning of the second rel-- lay contacts and to their normal position following each reversed positioning of the second relay contacts, and circuits including contacts of said first and second relays over which said first terminal of said direct current energy source is repeatedly connected first with one and then with the other of said two end terminals of said transformer input winding and by which said transformer output winding is caused to supply recurring pulses of output potential that have positive and negative polarities in alternating sequence.

2. In combination, a pair of conductors, a transformer connected in energy supplying relation with said conductors, a source of direct current exciting energy for said transformer, first and second coder relays each having contacts which occupy a normal position when and after the relay is energized in one direction and which occupy a reversed position when and after the relay is energized in the opposing direction, an

energizing circuit for said second relay which is controlled by a contact of said first relay and which causes the secondrelay contacts to go to their normal position following each normal positioning of the first relay contacts and to their reversed position following each reversed posiposition following each normal positioning of the second relay contacts and to their normal position following each reversed positioning of the second relay contacts, and circuits including contacts of said first and second coder relays over which said transformer primary is from said source supplied with exciting current of a character that causes the transformer to supply said conductors with recurring pulses of positive polarity energy which are separated by intervening pulses of negative polarity energy.

3. In combination, current-receiving apparatus, a source of energy therefor, first and second coder relays each having contacts which occupy a normal position when and after the relay is energized in one direction and which occupy a reversed position when and after the relay is energized in the opposing direction, an energizing circuit for said second relay which is controlled by a contact of said first relay and which causes the second relay contacts to go to their normal position following each normal positioning of the first relay contacts and to their reversed position following each reversed positioning of the first relay contacts, an energizing circuit for said first relay which is controlled by a contact of said second relay and which causes the first relay contacts to go to their reversed position following each normal positioning of the second relay contacts and to their normal position following each reversed positioning of the second relay contacts, and circuits governed by contacts of said first and second coder relays over which said apparatus is from said source supplied with recurring pulses of positive polarity energy that are separated by intervening pulses of negative polarity energy.

4. In combination, current-receiving I apparatus, a source of energy therefor, first and second coder relays each having contacts which occupy a normal position when and after the relay is energized in one direction and which occupy a reversed position when and after the relay i energized in the opposing direction, an energizing circuit for said second relay which is controlled by a contact of said first relay and which causes the second relay contacts to go to their normal position following each normal positioning of the first relay contacts and to their reversed position following each reversed positioning of the first relay contacts, an energizing circuit for said first relay which is controlled by a contact of said second relay and which causes the first relay contacts to go to their reversedposition following each normal positioning of the second relay contacts and to their normal position following each reversed positioning of the second relay contacts, a first circuit which connects said source in positive energy supplying relation with said apparatus when the contacts of both of said relays are in their normal position, a second circuit which connects said source in negative energy supplying relation with said apparatus when the contacts of said second'relay are in their normal position and the contacts of said first relay are in their reversed position, a third circuit which connects said source in positive energy supplying relation with said apparatus when the contacts of both of said relays are in their reversed position, and a fourth circuit which connects said source in negative energy supplying relation with said apparatus when the contacts of said second relay are in their reversed position and the contacts of said first relay ar in their normal position.

5. In combination, current-receiving apparatus, a source of energy therefor, first and second coder relays each having contacts which occupy a normal position when and after the relay is energized in one direction and which occupy a reversed position when and after the relay is energized in the opposing direction, an energizing circuit for said second relay which is controlled by a contact of said first relay and which causes the second relay contacts to go to their normal position following each normal positioning of the first relay contacts and to their reversed position following each reversed positioning of the first relay contacts, an energizing circuit for said first, relay which is controlled by a contact of said second relay and which causes the first relay contacts to go to their reversed position following each normal positioning of the second relay contacts and to their normal position following each reversed positioning of the second relay contacts, a first circuit completed over a normal contact of said second relay and a normal contact of said first relay for connecting said source in positive energy supplying relation with said apparatus, a second circuit completed over a normal contact of said second relay and a reversed contact of said first relay for connecting said source in negative energy supplying re lation with said apparatus, a third circuit completed over a reversed contact of said second relay and a reversed contact of said first relay for connecting said source in positive energy supplying relation with said apparatus, and a fourth circuit completed over a reversed contact of said second relay and a normal contact of said first relay for connecting said source in negative en ergy supplying relation with said apparatus.

HOWARD A. THOMPSON.

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