US2357240A - Railway traffic controlling apparatus - Google Patents

Description

J. J. VAN HORN 2,357,240

RAILWAY TRAFFIC CONTROLLING APPARATUS Fi1ed sept. 1e, 1941 f Yf. sheets-snm 1 Aug. 29, 1944:

'J. J. VAN HORN Aug. 29, 1944. RAILWAY TRAFFIC CQNTROLLING APPARTUS Firledrsept. 1e, 1941 2 sheets-sheet 2 Patented Aug. 29, 1944 RAILWAY TRAFFIC CONTROLLING APPARATUS James J. Van Horn, Pittsburgh, Pa., assigner tol The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application September 16, 1941, Serial No. 410,987

(c1. 24e- 3i 14 Claims;

My invention relates to railway traffic controlling apparatus and more specifically, to the control of traiic in a stretch of single track, twodirection railway wherein centralized traic control or some other suitable form of manual control is employed in establishing the direction. Some of the distinguishing features of my system are that it is of the normally deenergized track circuit type, employs neutral track circuits, and dispenses with all control line wires except for the C. T. C. coded line circuit, if C. T. C. is used. The present invention is an improvement on the inventions disclosed in my copending applications Serial Nos. 410,504 and 410,717 led on September 12, 1941, and September 13, 1941, respectively, for Railway traffic controlling apparatus, the former of which 'became' Patent No. 2,344,573 dated March 21, 1944.

One object of my invention is to provide a normally deenergized track circuit system `of signaling which employs non-polarized orneutral track circuits for controlling traiiic moving in either direction on a single track and which employs no control line wires for the usual signaling functions. Another object of my invention is to providel means ,for retaining the established traiiic direction as long as a train is approaching or occupying the single track stretch, solely by means of the track circuit apparatus, without depending on any circuits or apparatus located at the C. 'I'. C. oflice. Other objects, purposes and characteristic features of my invention will be apparent from the description which follows.

I accomplish the foregoing objects as follows: I transmit a C. T. C. code to the new exit end of the single track stretch which causes a normal or master track circuit code to be applied at the exit end for setting up traic'in the desired direction over the stretch. This normal track circuit code is cascaded over the `track circuits to the new entrance end where it initiatesthe supply of a reverse or feed back code duringoff intervals of the master code. The feed back code is cascaded back to the exit end and when there received indicates that the entrance signal is at stop and that the stretch of track is unoccupied, The absence of this "feed back code at the eXit end is used to prevent cutting off of the'master code for the lpurpose of retaining the new traic direction as long as a trainv is approaching or occupying the single track stretch. I make no distinction as to the relative polarity'of the master and feed back codes, these codes being either of the same or of opposite polarity. I depend, instead, on lthe order in which these codes are received at a signallocation or other point of the track circuit for determining proper response of the direction establishing and direction maintaining apparatus. Code is retained on the track circuits ahead of the train through the absence of the feed back code so thatno intercontrcls need be provided on the C. T. C. machine for retaining a route which has been established and for ypreventing conflicting routes 'from being established.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

Figs, 1a and 1b of the accompanying drawings when placed end toend with Fig. la at the left, area diagrammatic view showing one form of apparatus embodying kmy inventio-n.

Similar reference characters refer to similar parts in each of the two figures.`

Referring to the drawings, the stretchof single ltrack between the two passing sidings PSI and PS2 is divided into track circuit sections by means of the usual insulated rail joints at locations D, E, F, and G. E is a cut section location and F is an intermediate signal'location. Extending from one end of the single track stretch to the other is a C. T. C. control line over the two wires of which control codes originating in` the C. T. C. machine at the control point or ofiice can be transmitted to the one or the other of the two field vstations corresponding with the two ends cf the stretch, Vfor setting up traflic in one or the other direction. Indication codes can likewise be received at the oice over the C. T. C. line from these stations or from suitable intermediate points. Since the C. T'. C. apparatus, of itself, forms no part of my present invention, it will be sufficient for an understanding of my system to point out that when the traffic lever 8 (which forms a part of the C. T. C. machine) is moved to its right-hand or R position, the eastbound traic relay BRFSR will be picked up (due to the transmission of a control code over the line), whereas when this lever is moved to the left-hand or L position, the kwestbound traic relay BLFSR will be picked up. Normally, this lever will occupy its neutral or N position in which neither traffic relay is energized, the headblock signals are at stop, and the track circuits of the single track stretch are deenergized. One form of C. T.A C.' control and indication apparatus which may conveniently be used with apparatus embodying my invention is that shown in United States Patent No. 2,229,249 granted to to send out a code which will energize the traffic direction relay 8LFSR at the field station which is associated with location D. The pick-up of relay BLFSR causes relay GRTCTM to follow 75 or 180 code depending on the position of contact II of the home relay GLAH for signal 6L. If the signal is at clear or caution, relay GLAH will be Y energized so that the front point of contact II will apply 180 code to relay GRI'CTM. If the signal is at stop, however, as shown, then the back point of contact I I will be closed and 75 code will be supplied to relay GRTCTM. The coding operation of relay SRTCTM will apply 75 code from the track battery 'I'B to the track section BRT over a circuit which includes the front point of contact I2 of relay GRTCTM, and front contacts I3 and I4 of relays BRKM and STR. Relay BRKM repeats the deenergized position of signals BRA and ERB, and is energized when and only when these signals are at stop, thus providing a check on the stop position of these signals before. code can be applied to the stretch for a westbound move. The functions and control of relays BLAH and SRKM are well known and it is deemed sufficient to indicate the control of these relays from signals 6L and GRA and GRB, respectively, by means of theV broken line connections which join these relays with the signals. The inclusion of front contact I4 of relay STR in the code feed circuit is for the purpose ofinsuring that no train is occupying the approach section 5T.

The 75 code which issupplied to section STR is detected at location E by the code following track relay BWTR which energizes the decoding transformer DT and causes pick-up of the 75 and 180 code decoding relay BWHR over the rectifying contact I5 of relay BWTR and the back point of contact I6 of relay SEHR. The track relay GWTR as well as all of the remaining track relays associated with the single track stretch may be of the neutral or non-polarized type since no dependence is placed upon the polarity of the track circuit current. Of course, it is obvious that biased polar two-position relays may also be used, and a certain amount of additional foreign current protection will result from such use. However, such polar relays are not at all necessary from the standpoint of operativeness of my system. .Relay SEHR will be .deenergized under the assumed condition, as will relay SEF'B. Ac-

cordingly, relay BECTM will now be Aenergized and will follow 75 code over a circuit which includes the coding contact II of relay GWTR, front contact I8 of relay SWHR, and the back points of contacts I9 and 20 of relay GEFB. Relay GECTM will repeat the 75 code into the cut section BART over the front point of its contact 2l. The 75 code in section BART is decoded by track relay 'IWTR at location F which results in the energization of relay IWHR in substantially the same manner as at location E. The circuit for relay 'IWI-IR includes the rectifying contact 22 of relay 'IWTR, and the back points of contacts 23 and 24 of relay 1EHR and of the eastbound directional stick relay ESR, respectively:

The track section IOLT will now receive 180 code by virtue of the energization of code following relay 1ECTM on 180 code over a circuit which includes the code terminal I B which supplies code, front point of contact 44 of relay 'IWHR, and the back points of contacts 26 and 21 of relay 'IEFB. Relay IULTR at location G will follow this code, energizing the decoding transformer DT and thus causing the code detecting relay BLFR to pick up over a circuit which includes the rectifying contact 28 of relay IGLTR and the back point of contact 29 of the eastbound traflic direction relay RFSR. Relay BRFSR will, of course, be deenergized at all times except when lever 8 is moved to its R position and conditions are then proper for establishing eastbound traffic over the stretch.

With relay IULTR following code and relay BRFSR deenergized, an impulse circuit is provided for causing relay IULTCTM to follow code also, and thus to apply impulses of a 189 feed back code to section IDLT during the off intervals of the master code being received by relay IDLTR. The manner in which the feed back code is supplied to the section during off inter vals in the master code is well known and is described in the United States ReissuePatent No. 21,783 granted to Herman G. Blosser on April 29, 1941, so that this description need not be repeated. The impulse circuit for relay IULTCTM includes the front'contact 30 of relay SLFR. The feed back code circuit will be established only if signals IULA and IULB are at stop (front contact 3I of relay IULKM closed) and if section 9T is unoccupied (front contact 32 of relay STR closed).

The feed back code is now detected at location F by relay 'IETR, and since relay 1WHR is picked up due to energization on master code, relay 'IWFB will be picked up over a circuit which includes the rectifying contact 33 of relay TETR, wire 34, front point of contact 35 of relay 'IWHR, and wires 36 and 3'I.y Relay 1WFB, when picked up, closes an obvious energizing circuit for relay 1WCTM from transformer DT so that feed back code (which is 75 code in this cut section) is supplied to the section BART during the off intervals of the 75 master code to which relay 'IWTR is now responding.

The feed back code in section BART is detected at location E by relay BE'IR which causes relay SWFB to pick up and to close the impulse coding circuit for relay BWCTM, as at location F. Relay GWCTM applies feed back code to section BRT for operating relay'GRTR at location D to thereby energize relay WFB. This relay wil1 become energized becausel the front point of contact 38 of relay BLFSR remains closed, due to lever 8 having been moved to the L position, The pickup of relay WFB indicates that the single track stretch is unoccupied and that signal IOL is at stop since master code has been cascaded to the entrance end and feed back code has been cascaded from the entrance end to the eXit end. Relay WFB controls the transmission of a suitable indication code to the ofce and also enters into the control of relay 8LFSR by closing a stick circuit for the Ilatter relay over its back contact 48 and the front contact 49 of relay 8LFSR. Ac cordingly, once relay WFB is released due either to the clearing of signal IBLA or occupancy of the stretch, Vrelay SLFSR is retained energized so that the traflic direction cannot be changed. Once the block indication transmitted by relay WFBis received at the ofiice, the operator may send out a suitable code to clearthe entrance 'signal IDLA or IULB. These signals can be cleared only if master code has been received at the entrance end G, as indicated by the prior energization of relay 8LFR at this location, A Westbound train may now be permitted to pass signal IOL and enter the single track stretch.

The block indication circuits, control of relay BLFSR by relay WFB (or control of relay BRFSR by relay EFB) and control of electric switch locks, shown and claimed in my copending application Serial No. 410,717 referred to hereinbefore, may be readily incorporated into the system embodying my present invention to extend the application thereof, but these added complications have not been shown in order to simplify the disclosure as much as possible.

Referring to contact 39 of relay BRFR at location D, the inclusion of this contact in the circuit ofy relay BRTCTM, in addition to establishing the feed back code circuit for eastbound traflic, prevents the possibility of certain undesired cyclic action occurring in the apparatus when relay 8LFSR is deenergized, following movement of lever 8 to the R position for a reversal of traffic from westbound to eastbound. Contact 30 of relay 8LFR (location G) is similarly included in the circuit for relay IBLTCTM to prevent the cyclic action occurring following a traffic reversal from eastbound to westbound, as well as to yestablish the westbound feed back code circuit.

With traffic established in the westbound direction, when a train passes signal IDL and enters section IULT, relay IBLTR will be shunted so that relay I QLTCTM will cease operating and Will discontinue the supply of feed back code to section IULT. Relay IETR at location F will accordingly cease operating and will discontinue the energization of relay 'IWFB so that relay 'IWCI'M will also cease operating. Accordingly, feed back code will be removed from sections BART and GRT, causing relay GRTR at location D to release and to deenergize relay WFB thus providing a block occupied indication. Master code will, however, continue to be supplied in the eastbound direction toward the train becauserelay BRTCTM will continue its coding action since relay SLFSR remains energized until the traffic movement is completed and the operator restores or reverses the lever 8.

Returning to the intermediate signal location F, as the westbound train passes this location, the westbound directional stick relay WSR will become energized. The pick-up circuit for this relay includes the front contact 48 of the westbound approach relay WAR (which picks up when the train approaches within a certain distance of location F, in the usual manner), and the front point of contact 4l of relay lWHR (already deenergized but not yet released because of its slow acting characteristic). When relay WSR picks up, it closes a stick circuit for itself over its front contact 42 and the back point of `contact 4| of relay 'IWI-IR. Relay WSR will remain picked up during the time that the train occupies any part of the block D-F since relay 'IWI-IR will remain deenergized during this whole time. Relay WSR will apply '75 code for operating relay IECIM, over its front contact 43 and the back point of contact 44 of relay IWI-IR. Accordingly, as soon as the train vaoates section IULT, 15 code supplied over the front point of contact 45 of relay 'IECTM will be effective in the rear section for permitting a following Westbound train to. enter the stretch.

Whenthe train clears" section BRT `(and 5'I )3,

, relay 1WHR will pick up, releasing the westbound stick relay WSR in the usual manner and trans-- ferring the coding circuit for relay 'IECTM to the front point of conta-ct 44 of relay 1WHR. The

vcode fed to section I DLT will now be 180, since the block ahead is clear. Exit of the westbound train frornthe stretch will cause receipt of the feed back code by'relay BRTR, as before, and re'- energization of relay WFB. The operator may now either leave the lever 8 in its L position to permit radditional Westbound traic to pass over the stretch, or he may place the lever in its N position so as to remove energy from the track circuits.

When establishing traic in the eastbound direction, the operator will move lever 8 to the R position in order to transmit a code which Will cause pick-up of the eastbound traiic direction relay BRFSR so as to initiate the supply of mas; ter code in the westbound direction from location G to location D. The sequence of operations tak; ing place in setting up the eastbound traine direction is identical with that described in detail above for the westbound move and will be understood without further explanation.

It will be noted that in my system, the HR relays for the two directions at an intermediate lol cation or cut section are so inter-controlled that only the westbound HR relay (or only the eastbound HR relay) and its corresponding FB relay can be energized at any one time. The master code picks up either the westbound or the eastbound HR relay, depending upon the traic-di rection being established at the time. When the master code gets through to the entrance endand feed back code returns, the feed back code then picks up the corresponding FB relay (WFB if traliic is to be westbound; EFB if traflic is to be eastbound). Accordingly, each track circuit junction Within the single track stretch in my system has associated therewith an eastbound anda westbound track relay and an eastbound and a Westbound code transmitting relay. A'I'he systemk being normally deenergized, the track relays at a given junction will pick up in a prede# termined order, depending upon the direction from which the master code reaches the junction. If the master code is cascadedin the westbound direction, then the eastbound track relay will be first to pick up and will lock out the Westbound track relay at that location from .being operated on master code, thus causing eastbound traffic conditions to be established at that location. The

` westboundvr track relay will respond only to feed back code under the assumedv condition. In'this manner, 'the system insures satisfactory traffic di.` rection selectionV and proper maintenance ofI the direction when once established. It will be ap- ,parent also that I provide a pair of 'track circuits, an eastbound and a westbound one, over the same rails between each pair of consecutive junctions referredV to above. Application of master code at one end of the stretch causes one track circuit of each such track circuit pair to respond only to Under certain conditions, some difficulty may be experienced in obtaining fully satisfactory response of certain track relays to the feed back code. It will be understood that an impulse of feed back code must be supplied during an olf interval in the master code and under certain conitions the time characteristics of the apparatus may be such that the feed back impulse is of relatively short duration. To insure that the track relays will respond properly even to very short feed back impulses, these relays can be provided With an auxiliary stick winding energized overa front contact of the associated FB relayV and a front contact of the track relay itself. This manner of improving the operation of a relay on feed back code is shown and described in United States YPatent No 2,172,893 granted to E. U. Thomas on September 12, 1939, so that details of this operation need not be repeated here.

It will be apparent that the system embodying my invention will operate properly when the intermediate locations E and F are eliminated and the stretch D-G includes but one track circuit section. This section will include the track circuit pair described above and the track circuits of the pair Will be selectively effective for master code or for feed back code, according as the master code is applied at one lor the other end of the stretch, as pointed out above.

From the foregoing, it will be apparent that I have provided a normally deenergized coded track circuit system of signaling for traffic moving in either direction on a stretch of single track, in which a master track circuit code provides controls for the signals such that these will display aspects in conformity with the block conditions, and a feed back code which checks that the stretch is unoccupied and that the entrance signals are at stop. A reversal of the traic direction is permitted only if the stretch is unoccupied and the entrance signals are at stop, the established traflic direction being retained during occupancy and during the time that the entrance signal is cleared. The master and feed back codes may be of either polarity, and neutral track circuits may be used. The selective response of the Westbound or eastbound HR (code detecting) relay at a given locationY to master code-depends on Whether the traffic direction being established is Westbound or eastbound. If the traffic direction is Westbound, then relay WHR will respond to the master code and relay WFB will respond to feed back code. If the traffic direction is east: bound, the same thing Will be true for relays EHR and EFB. Accordingly, polarized track circuits are not required in my system, and master code is retained on the track ahead of a train through theV absence of the feed back code rather than by means of inter-controls on the C. T. C. machine.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications 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 with a stretch of track over which traic may move in either direction, said stretch being divided into a plurality of track circuit sections, a traffic direction control relay adjacent the exit end of said stretch for a given direction of traffic movement, manually controlled means for operating said control relay, a stick circuit for said control relay effective when said relay is operated, means effective when said control relay is operated for cascading track circuit current impulses of a master code of a given relative polarity from said exit end over said sections to the entrance end `of the stretch for checking unoccupancy, whereby if said stretch is occupied said master code will be shunted out arid so will not reach said entrance end, traffic governing means operated in response tothe receipt of master code at said entrance end,'a signal for governing the entry of traffic moving in said given direction into said stretch, means controlled by said traffic governing means when operated effective if said signal is at stop for cascading track circuit current impulses of a feed back code of the same relative polarity from said entrance end over said sections to said exit end during off intervals in said master code, and means responsive to the receipt of feed back code at said exitend for rendering said stick circuit ineffective, whereby if said signal is cleared and a train occupies said stretch so that said feed back code is shunted and is not received at said exit end said stick circuit will cause sadgiven traffic direction to'be retained.

2. In combination with a stretch of track over which traflic may move in either direction, said stretch being divided into a plurality of track circuit sections, a traffic direction control relay adjacent the eXit end of said stretch for a given direction of traine movement, manually controlled means for operating said control relay, a stick circuit for said control relay effective when said relay is operated, means effective when said control relay is operated for cascading track circuit current impulsesof a master code of a given relative polarity from said exit end over said sections to the entrance end of the stretch for checking unoccupancy, whereby if said stretch is occupied` Said master code will be shunted out and so will not reach said entrance end, a signal for governing the entry of traic moving in said given direction into said stretch, means effective When and only when said'master code is received at said entrance end and `said signal is at stop for cascading rail current impulses of a feed back code of the same relative polarity from said entrance end over said sections to said exit end during oif intervals in said master code, and means responsive to the receipt of feed back code at said exit end for rendering said stick circuit ineffective, whereby if said signal is cleared and a train occupies said stretch so that said feed back code is shunted and is not received at said exit end said stick circuit will cause said given trafc direction to be retained.

3. In combination with a stretch of track over Which traiiic may move in either direction, said stretch being divided into a plurality of track circuit sections, manuallycontroiled means for supplying track circuit current impulses of a master code to the rails at the exit end of said stretch for a given direction of traffic movement, means including neutral track relays for cascading said master code from said exit end over said sections to the entrance end of the stretch for checking unoccupancy, whereby if said stretch is occupied said master code will be shunted out and so will not reach said entrance end, traffic governing means operated in response to the receipt of master code at said entrance end, a signal for governing the entry of traflic moving in said given direction into said stretch, means controlled by said traffic governing means When operated effective if said signal is at stop for 'cascading rail current impulses of a feed back code during off intervals in said master code from said entrance end over said acenc/io sections to said exit end, and means responsive to the receipt of f eed back code at Said exit end for governingv said manually controlled means., whereby if said signal is cleared and a train occupies said stretch said feed back. code will be shunted and will not be received at said exit end.

4-111 combination with a stretch of track over which trame may move in either direction, said Stretch being divided into a plurality of track circuit sections, manually controlled means for Supplying track circuit current impulses of a master code to the rails at the exit end of said stretch for westbound traffic, means including a neutral westbound track relay for each of said sections for cascading said master code from said exit end over said sections to the entrance end of the stretch for checking unoccupancy, whereby if said stretch is occupied said master code will be shunted out and so will not reach said entrance end, traffic governing means op. erated in response to the receipt of master code at said entrance end, a signal for governing the entry of westbound traffic into said stretch, means controlled by said tramo governing means When Operated effective if said signal is at stop for supplying track circuit current impulses oi' a feed back code during off intervals in said master code to the rails at said entrance end, means including a neutral eastbound track relay for each of Said sections for cascading said feed back Code from said entrance end over said sections to said exit end, and means responsive to the receiptof feed back code at said exit end for governing said manually controlled means, whereby if said signalis cleared and a train oc cupies V said stretch said feedback code will be shunted and will not be received at said exit end.

5. In combination with a stretch of track over which traliic may move in either direction, said stretch being divided inta trackll `circuit sections, an eastbound and a westbound entrance signal for said stretch, an eastbound and a westbound track relay for each of said sections, said track relays being neutral with respect to polare ity, a westbound tramo direction selector adjacent the westbound exit end of said stretch, an east* bound traic direction selector adjacent the westbound entrance end of said stretch, means eiTective when said westbound selector is operated and including Said westbound track relays for cas.1 cading track circuit current impulses of a master code from said westbound exit end over s'ald sections to said westbound entrance end, whereby if said stretch is occupied said master code will be shunted out and will not reachsaid entrance end, means including said Leastbound track relays effective when said master code is received at said entrance end and ysaid westbound signal is at stop for cascading track circuit current impulses of a feed back code during off intervals in said master code from said entrance end over said sections to said exit end, means eiective when said eastbound selector is operated during unoccupancy. of said stretch and including said eastbound track relays kfor cascading track cir.- cuit current impulses of said master code from Said westbound entrance end over saidl sections to said westbound exit end, means including said westbound track relays effective when said mas,- ter code is received at said westbound exit end andsaid eastbound signal is at stop for cascading track circuit current impulses of a feed back code during oi intervals in -said master .code

from said exit end over Said. sections to seid er1.- trance end, whereby if either of said signals is cleared and` a train occupies said stretch said feed back cede will be shunted out2 and means at each end of the stretch responsive to the re.-v

- vCeipt of said feed back code vat that end forcontrolling the associated traiic direction selector.

6. In combination with a stretch of track over which traic may move in either direction,r an eastbound and a westbound track circuit for said stretchl each including the same track rails, a westbound..Y neutral track relay adjacent one end of said track circuit and a westbound source of rail current adjacent the other endl an east. bound neutral track relay adjacent said other end and an eastbound source of rail current adjcent said one ende manually controlled means Afor supplying rail current impulses of a master cede trom said westbound source to operatesaid westbound track relay and so to check unoccupancy, whereby if said track circuit is occu-V pied said master code will be shunted out, a westbound entrance signal for said stretch, means controlled by said westbound track relay when operating on said master code, effective if said westbound signal is at stop for supplying rail current impulses of a feed back code from said eastbound source during off intervals in said master code to thereby operate said eastbound t track relay, whereby if said signal is cleared for a westbound train which enters said stretch and shunts said feed back code said eastbound track relay will not be operated, and means re,- sponsive to operation of said eastbound track re,- lay on said feed back code for governing said manually controlled means.

7. In combination with a stretch of track over which tramo may movein either direction, an eastbound and a westbound track circuit for said 40 stretch each including the same trackrails, a

westbound neutral track relay adjacent one end of said track circuit and a westbound source ot rail current adjacent the other end, an eastbound neutral track relay adjacent said other end and an eastbound source of rail current adjacent said one end, manually controlled vmeans for selecfr tively supplying rail current impulses of a I nas.- ter code from one said source or the other in accordance with the tramo direction being established to thereby operate the associated track relay on said master code and so to check un-v occupancy, whereby if said track circuit is occu. pied said master code will be shunted out, an entrance signal for each end of the stretch,

l means controlled by said track relay when opere ating on said master code elective if the asso.-v ciated entrance signal is at stopior supplying rail current impulses of a feed back codeA from the remaining one of said two sources during off intervals in said master code to thereby operate the remaining one of said track relays, whereby if said associated signal is cleared for a train which enters said stretch and shunts said feed back code said last-named relay will not be op.-v erated, and means responsive `to operation lot said last-named relay on said feed back cede forgoverning said manually controlled means.

8. 4In combination with a normally deenergiaed stretch of track over which traiic may move either direction, an eastbound and westbound track circuit for said stretch each including the Same track rails, a normally connected westbound neutral track relay adjacent onepend lof said track circuit and a normally disconnected westbound source ofrrail current adjacent the lother end, a normally connected eastbound neutral track relay adjacent Vsaid other end and a normally disconnected eastbound source of rail current adjacent said one end, manually controlled means for periodically connecting said westbound source across the rails so as to supply rail current'impulses of a master code to operate said westbound track relay and so to check unoccupancy, whereby if said track circuit is occupied said master code will be shunted out, a westbound entrance signal for said stretch, means controlled by said westbound track relay when operated effective if said signal is at stop for periodically connecting ysaid eastbound source across the rails during off intervals in said master code so as to supply rail current impulses oi a feed back code during 01T intervals in said master code to thereby operate said eastbound track relay, whereby if said signal is cleared for a westbound train which'enters said stretch and shunts said feed back code said eastbound track relay will not be operated, and means responsive yto operation of said eastbound track relay on said feed back code for governing said man ually controlled means.

9. In combination with a stretch of track over which tranic may move in either direction, a first and a second track circuit for said stretch each including the saine track rails, a first neutral track relay adjacent one end of said track .i

circuit and a first source of rail current adjacent the other end, a second neutral track relay adjacent said other end and a second source of rail current adjacent said one end, manually controlled traffic direction means effective when operated for supplying-rail current impulses of a master code from said rst source to operate said rst track relay and so to check unoccupancy, whereby if said track Acircuit is occupied said master code will be shunted out, an entrance signal for each end of the stretch, means controlled by said rst trackV relay when operated 'effective if the associated entrance signal is at stop for supplying rail current impluses of a feed back code from said second source during off intervals in said master code to thereby operatesaid second track relay, whereby if said associated signal is cleared for a train which enters said stretch and shunts said feed back code said second track relay will not be operated, and means responsive to operation of said second track relay on said feed back code for governing said manually controlled means.

l0. In combination with a stretch of railway track over which traffic may move in either direction, a nrst and a second track circuit for said stretch each including the same track rails, a first neutral track relay adjacent one end of said track circuitl and a rst source of rail current adjacent the other end, a second neutral track relay adjacent saidother endV and Va second source of rail current adjacent said one end,

a first traffic direction relay effective when operated for supplying rail current impulses of a master code from said first source to operate said first track relay, a second traific direction relay effective when operated for supplying rail current impulses of the master code from"said second source to operate said second track relay, means eiective for selectively operating said first or said second traffic'direction relay to thereby check unoccupancy, whereby if either track circuit is occupied said master code will be shunted out, an entrance signal rfor each end of the stretch, means effective when either of said track relays is operating on said master code eif fective if the associated entrance signal is at stop for supplying rail current impulses of a feed back code during off intervals of the master code from Athe source of rail current which is associated with the other of said track relays for operating said other track relay, whereby if said associated signal is cleared for a train which enters said stretch and shunts said feed back fcode said other track relay will not be operated, ,and means responsive to operation of said other track relay on said feed back code for governing the associated traffic direction relay.

l1. In combination with a normally deenergized stretch of railway track over which traffic may move in either direction, a track circuit junction within said stretch defining lthe ends of a first and a second adjoining trackcsection, a westbound track relay for said rst section adjacent said junction, an eastbound track relay for said second section also adjacent said junction, westbound and eastbound traffic direction control means, means for selectively operating said westbound or said easbound traffic direction means, means controlled by said traffic direction means for supplying rail current impulses of a master code first to said first section and then to said second section or rst to said second section and then to said first section according as said westbound or said eastbound means is operated respectively, said master code operating said westbound or said eastbound track relay respectively to'check unoccupancy, whereby if either of said sections is occupied said master code will be shunted away from the track relay associated therewith, an entrance sisna1 for each end of the stretch, means controlled by one of said track relays which is first operated on master code effective if the associated entrance signal is at stop for causing rail current impulses of a feed back code to be supplied to the/other section during off intervals in the master code for operating the track relay associated with said other section, whereby if said associated signal is cleared for a train which enters said stretch and shunts said feed back code said last-named track relay will not be operated, and means controlled by said last-named track relay for governing the associated traic direction control means.

12. In combination with a normally deenergized stretch of railway track over which traffic may move in either direction, a track circuit junction within said stretch defining the ends of a rst and a second adjoining track section, a westbound track relay for said first section adjacent said junction, an eastbound track relay for said second section also adjacent said junction, traffic direction control means for causing rail current impulses of a `master code to be supplied first to said first section or rst to said section to thereby operate said westbound or said eastbound track relay respectively to check unoccupancy, whereby if either of said sections is occupied said master code will be shunted away from the track relay associated therewith, means controlled by the first of said two track relays which is operated on master code for preventing operation of the remaining track relay on master code until the order in which said sections receive said master code is reversed by said trafc direction control means, an entrance signal for each end of the stretch, means controlled by said rst track relay effective if the associated entrance signal is at stop for supplying rail current im- 4pulses of a feed back code during olf intervals in said master code to thereby operate said remaining track relay, whereby if said associated signal is cleared for a train which enters said stretch and shunts said feed back code said remaining track relay will not be operated, and means controlled by said remaining track relay for governing said trafiic direction control means.

13. In a normally deenergized coded track circuit signaling syste-m, in combination, adjacent rst and second track sections through which traic may move in either direction, means for at times supplying master code energy and at other times for supplying feed-back energy to the rails of the rst section at the end thereof remote from the second section, means for at times supplying master code energy and at other times supplying feed-back energy to the rails of the second section at the end thereof remote from the first section, a code following track relay for each of said sections at the end thereof adjacent the other section and operated by either master code or feedback energy supplied over the rails of the section with which the relay is associated, each of said track relays having associated therewith normally deenergized electroresponsive means which becomes energized upon operation of the track relay when and only when the electroresponsive means associated with the other track relay is deenergized and. which when energized remains energized during subsequent code following operation of the track relay and also during occupation of the associated track section by a train leaving the other section, means for each of said sections for supplyingmaster code energy to the section rails at the end of the section adjacent the other section when and only when the electroresponsive means associated with the track relay for the other section is energized, and means responsive to operation of each of said track relays when the electroresponsive means associated with the other track'relay is energized.

14. In a normally deenergized codedtrack circuit signaling system, in combination, adjacent first and second track sections through which traflic may move in either direction, means for at times supplying master code energy and at other times for supplying feed-back energy to the rails of the rst section at the end thereof remote from the second section, means for atrtimes supplying master code energy and at other times supplying feed-back energy to the rails of the second -section at the end thereof remote from the rst section, a code following track relay for each of said sections at the end thereof adjacent the other section and operated by either master code or feed-back energy supplied over the rails of the section with which the relay is associated, each of said track relays having associated therewith normally deenergized electroresponsive means which becomes energized upon operation of the track relay when and only when the electroresponsive means associated with the other track relay is deenergized and which when energized remains energized during subsequent code following operation of the track relay and also during occupation of the associated track section by a train leaving the other section, means for each of said sections for supplying master code energy'to the section rails at the end of the section adjacent the other section when and only when the electroresponsive means associated with the track relay for the other section is energized, means for each of said sections responsive to operation of the track relay for the section for supplying feed-back energy to the section rails at the end of the section adjacent the other section when and only when the electroresponsive means associated with the said track relay is energized, and means responsive to operation of each of said track relays when the electroresponsive means associated with the other track relay is energized.

JAMES J. VAN HORN.

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