US2550860A - Coded track circuit signaling system - Google Patents

Description

May 1, 1951 N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM Filed March 6, 19 47 3nnentor Patented May 1, 1951 Neil D'. Preston, Rochester',jN. Y.) as'si'g'no'r-to' General Railway Signal Company; Rochester,

Application March e,194'z, serialnmszflcs (claus -34 2 Claims;-

The presentinvention relates to block signallin'g systems on railroads using "coded track circuits, and more' particularly pertains to the-improvement of the code receiving apparatus em p'loy'ed'in such signalling systems.

The various blocks of a signalling system employing coded track circuits usually comprise a single track circuit for each bl'ock,-eachjtrack circuitbeing provided with suitable code transmitting'apparatus at one end of'thetrack circuit and suitablecode responsive means at the other end of "the track" circuit; The code'transmitting In such a system, as-abovebriefiy' mentioned, a

code followingtrackrelay is' usually provided with contacts for governing the code receivingapparatus, and it is desirable to havea minimum number of contactson this relay in order to have the'relay' as sensitive as possible to th'e cod'e pulses of the associated-track circuiti These contacts' on -th'e-code following track relay in controlling the decoding apparatus may under certainadverse conditions-become misplaced; or fused'and it is desirable tohave the decoding apparatus so organized that under such circumstances any *failure'is'on the side "of safety.

Generally speaking and withoutattempting to define the exact nature and scope of the present invention; it is proposed to providetwo slowacting relays; one of which is energized when the code following track relayisupicked up,and" the other of which is energized when the code-following trackrelayis released providing-the other slow actingrelayis then picked up. If these two relays were provided in 1 this particular relationship without further modification, it might ha'ppen-'5 ifthecontacts of the code :followingJ-track relay" should become misplaced orfused together orthelike, that both of the slow acting relays would become steadily energized even-though the code following track relay had ceased its "operation." Thiswould give an erroneous: signal indicatio'ni However, the present invention provides that I the" slow acting repeater relay i governed in accordance with theop'erated condition of the code front contact repeating relay' which must be pickedup in order'ior sjuch' slow acting relay to be energized; and in addition;- the controlfor the slow acting back con-tact repeating relay includes aback contact of the} quick acting repeater relay. In'this'way, the quick actingrepeater relay-must respond *to codingoperation of the code following track relay in -'order-to pick-up-either of the slow acting repeater relays'. lf -the contacts become fused or misplaced with this organization, the-most that can happen is --tliat=thequick acting repeater relay and the slow acting front contact repeater relay maylee" picked up steadily, but under such a condition theslow acting back contact repeater relay can notice energized due to the picked 'upcond-ition of the quick acting" repeater relay 7 lt is a further'object-of the invention to provide that th'e decoding apparatus which is distinctively responsive to the-different code rates shall be governed -fromcontacts of the quick acting repeater relay so'as to minimize the number of contacts on' the code following track relay andalso to prevent-operation of the decoding means if 1 the code following track relay ceases operation.

Other objects; purposes-and" characteristic f eatu res of the present invention will be in part obvious from the accompanying drawingsyand in part pointed out as the-description progresses.

In-desoiribin'g the invention inxdetail, reference will be made to the accompanying drawing; in which 'thoseparts having similar features and functions are" designated by like letter" reference characters which are gen'erally'made distinctive by reason of distinctivepreceding' numerals representative of theirlocation or association with other devices having reference characters with like numerals, and" in whi'ch't The single figure of theld'rawing illustrates one section of a coded track"circuitsignalling'jsysmore with the pur'pb'se of' making it easy to uriderstand the": principles an'd mo'de of operation than with messes-or illustrating the specific construction and arrangement of p'arts" that wqulube empioyeci iii-practice; Thusftlie 'val'io'iis relays and theircontactsare illustratedin a; conventional manner, and symbols are used to indicate the connection of terminals to batteries or other suitable sources of electric current instead of showing all of the wire connections to these terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current; and the circuits with which these symbols are employed are assumed to always have current flowing in the same direction, although it is to be understood that in some cases alternating current might be substituted for the direct current, and in such cases the and are to be used as indicating the relative instantaneous polarities of the alternating current.

With reference to the single figure of the drawing, a stretch of track has been shown divided into track sections by suitable insulated joints of which the track section 2T has been shown completely and the track sections IT and 31 in part only. Color light type signals 2 and S-are shown at the entrance ends of the track sections 2T and ST respectively, assuming a normal direction of traffic from left to right as indicated by the trafflc direction arrow. These signals can of course be of any suitable type desired.

At the exit end of each track section (such as section 2T) suitable code transmitting apparatus is located to transmit driven codes of different distinctive rates in accordance with traffic conditions in advance as governed by the code receiving means for the entrance end of the next adjoining track section.

At the entrance end of each track section (such as section 2T), a suitable decoding apparatus is located for receiving the different driven codes and decoding them so as to properly control the associated signal (such as color light signal 2).

Although this typical track section might in some cases have code transmitting and receiving apparatus for inverse codes, such apparatus has not been shown for the sake of simplicity in the illustration, but it should be understood that the decoding apparatus illustrated as employed in connection with driven codes may also be employed in connection with the decoding of inverse codes.

As typical of all such track sections above briefly described, reference may be made to the track section 2T in which coding contacts ISGC and 15C are illustrated as associated with the signal location 3. For convenience it is assumed that these contacts will continuously operate, and when the decoding relay, conveniently termed slow acting back contact repeating relay 3B? and governed in accordance with the codes in track section ST, is picked up closing front contact l4, a code of the I80 code rate is applied to the track section 2T with the energy for such pulses being supplied from the battery B. When the relay 3BP is deenergized closing its back contact Id, code pulses of the 15 code rate are applied to the track section 2T from the battery B. It is to be understood that the relay 3BP is picked up whenever a code is received over the track section 3T, but is deenergized whenever the track section 3T is occupied by a train or the reception of code ceases for some other reason. The usual clear and caution code rates .of 75 and 180 pulses per minute have been selected for the coders 15C and I880 for the purposes of this disclosure, but it should be understood that other suitable code rates might be employed if desired. Also, this simplified illustration of the application of different codes is employed merely for the purposes of simplifying the present disclosure, it being understood that various organizations for transmitting code pulses of different code rates may be employed as desired.

At the entering end of the track section 2'1, and associated with the signal 2, is a track relay ZTR which is connected across the track rails of the track section so as to follow the code pulses transmitted over the rails. This relay 2TR picks up its contact 23 for each code pulse and releases its contact 23 between successive code pulses. This code following track relay 2TB, may be of the neutral type as assumed for the purposes of this disclosure, or it may be of the polarized type, that is, its contacts may be biased to one position by gravity or suitable resilient means, and operated to a picked up or actuated position in response to energization by only a particular polarity.

A quick acting repeater relay ZTP is provided with an energizing circuit including a front contact 23 of the code following track relay 2TB. Also a slow acting front contact repeating relay ZFP is provided with an obvious energizing circuit including the front contact of the quick acting repeater relay Z'IP.

A slow acting back contact repeating relay ZBP is provided with an energizing circuit closed from and including back contact 23 of the 'code following track relay 2TB, back contact 5 of quick acting repeater relay ZTP, front contact 6 of slow acting front contact repeater relay 2FP, and windings of relay 2BP, to

With this organization, it can be seen that each time the code following track relay is initiated into operation for any particular code rate, it will close its front contact 23 on the first code pulse which will be repeated by the quick acting repeater relay 2TP, and the closure of its front contact l will energize the front contact repeater relay ZFP. If the slow acting front contact repeater relay ZFP is too slow acting to be picked up on its first energization, it will pick up on some subsequent energization such as the second or third, and after it has once been picked up, it will remain picked up between successive code pulses.

As soon as the front contact repeating relay ZFP has picked up and closed its front contact 6,

the next following deenergization of the code following track relay 2TB will close its back contact 23 followed by the closure of back contact 5 so that the relay ZBP will be energized for that space between two successive code pulses. If the relay 2BP does not pick up on the first such energization, it will upon a subsequent energization such as the second or third.

Once the relays ZFP and ZBP have both been picked up in response to the reception of a code, they remain picked up so long as that code rate or any other code rate is continuously received; but if the operation of the code following track relay 2TB. ceases, these relays will successively drop awayin accordance with their slow releasing characteristics. 7

Under conditionsof no code in the track section ET, the relays 2FP and 2BP are both dropped away closing back contact [2, so that the red lamp R, of signal 2 is energized causing such signal to. display a stop indication. On the other hand, when the relay ZBP is picked up during the reception of a code, regardless of its particular rate, the front contact I2 is closed so that the yellow or green lamps of signal 2 are ener- -open condition of back contact 5.

gized depending upon the particular rate of the code being received. This is determined bysuitrepeater relay 2TP is operated to its opposite positions. The secondary winding of the transformer 8 is connected to the primary of the transformer I0 through a condenser 9 in such a manner as to be tuned for the 180 code rate but to pass substantially no energy or a very small amount of energy in response to the 75 code rate. This energy induced in the secondary of the transformer 8 and caused to flow in the tuned circuit including the primary of the transformer Ill, is supplied through the secondary of the transformer In through a suitable rectifier II to convert the alternating current to direct current which is supplied to the slow acting distant relay 2D.

In brief, the relay 2D is caused to pick up only when the code received by the code following track relay ZTR and repeated by its quick acting repeater relay ZTP is of the 180 code rate. It should of course be understood that other code rates might be employed either separately or in addition to the ones shown, and that decoding means distinctively tuned for these other rates may be employed as desired for additional signal indications.

In the particular embodiment of the invention, the reception of a 75 code rate means that the relay 2D is released so that the yellow signal Y is energized through front contact l2 and back contact I3; but the reception of a 180 code rate results in the energization of the relay 2]) so that the green signal G is energized through front contacts l2 and I3.

While the section 2T is occupied by a train it will be apparent that no code will be repeated by the code following track relay 2TB because the track rails are shunted. But when the train passes into the track section 3T and out of the track section 2T, the relay 3BP is deenergized and a 75 code rate is applied to the track section 2T and to the relay 2TH. When the train passes from the track section 3T into the track section 4T (not shown), then a 75 code rate will beapplied to the track section 3T causing the relay 3BP to be picked up so that a 180 code is applied to the track section 2T.

Although the apparatus employed with coded track circuits for signalling systems is usually very reliable, and will operate over long periods of time without failure, it may happen that a static charge or some other condition may occur such that the front and back points of the contact 23 become fused. In such a circumstance, the relay 2T? would be steadily energized, and in turn would cause the steady energization of the relay 2FP. However, even though energy is supplied through the back point of contact 23, this energy cannot energize the relay 2BP because of the Thus, it is obvious that such a failure does not result in the erroneous control of the signal but rather causes such signal to indicate danger or stop regardless of whether a code is being received or not.

Should it happen that the circuit for the relay ZTP fails to close, then it is apparent that the relay ZFP would not be energized and the continued open condition of front contact 6 would likewise cause the slow acting back contact ZBP to be steadily deenergized. It can be seen that under such a condition the signal 2 would be held 6 at Stop for two reasons, i. e.,-the relay 25BPrwo111d be deenergized closing back contactlL and Ethe failure of oper-ation of contact 1 to a 180 code would cause the relay 2D to be deenergized. For these reasons, it is believed that the present inuention provides -a reliable (and safe decoding organization for codes used in ,acodedtrackcircuit signalling system.

Having described one form of coded track circuit block signalling system employing novel decoding apparatus to give a safe and reliable decoding organization as one embodiment of the present invention, it is desired to be understood that the invention is shown in this connection for the purpose of facilitating its disclosure, and that it can be applied to systems of various other types; and it is to be further understood that other specific embodiments and modifications of the invention may be made, and that various adaptations and alterations may be required to meet the problems of practice without in any manner departing from the spirit or scope of the present invention.

What I claim is:

1. In a decoding organization for checking the opening and closing of the contacts of a code following relay, a quick acting relay energized each time the code following relay is operated to one position and deenergized each time it is operated to its opposite position, a slow acting repeater relay energized each time said quick acting relay is energized only after its contacts have been picked up, said repeater relay being sufficiently slow acting to maintain its contacts picked up if said quick acting relay is energized and deenergized at relatively frequent intervals, and another slow acting relay energized each time the code following relay is operated to its said opposite position only providing said quick acting relay is deenergized with its contacts released and. said slow acting repeater relay has its contacts picked up, whereby the cessation .of the operation of said quick acting relay either because of the cessation of the operation of said code following relay or the failure of its contacts to open and close results in the continued deenergization of said another slow acting relay.

2. In a coded track circuit signalling system, a section of track having coded pulses applied thereto at different code rates dependent upon traffic conditions, a signal for governing trafiic over said section, a code following track relay adjacent said signal and responsive to the code pulses in said section, a quick acting repeater relay for said code following relay, a slow acting signal repeater relay for said quick acting relay, a slow acting control relay controlled through a front contact of said slow acting repeater relay and back contacts of said code following track relay and said quick acting repeater relay, whereby said signal control relay is energized whenever said code following track relay is responsive to different codes but is deenergized whenever said code following track relay ceases operation, other signal control means governed by the operation of said quick acting repeater relay only in response to a particular one of said different code rates, and circuit control means for said signal governed by said slow acting signal control relay and said other signal control means so as to govern said signal distinctively in accordance with the different codes and to clear said signal only providing said quick acting repeater relay is actually following the response of said code 7 following track relay to the difierent codes on UNITED STATES PATENTS said track section. 7 Number Name Date NEIL PRESTON; 2,353,930 Rees July 18, 1944 7 2,366,988 Rees Jan. 9, 1945 REFERENCES CITED 5 2,465,794 Fereday Mar, 29, 1949 The following references are of record in the file of this patent:

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