US2370091A - Railway traffic controlling apparatus - Google Patents

Description

72' heb 20, 1945. H. A. THoMPsoN ET AL RAILWAY TRAFFIC GONTROLLING APPARATUS Filed Sept. 25, 1941 4 Sheets-Sheet 1 j @5:35 mmc,

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RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 25, 1941 4 sheets-sheet 2 @wbmm QLWITIMFf F..

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RAILWAY TRAFFIC CONTROLLING APPARATUS l Filed Sept. 25, 1941 4 Sheets-Sheet 4 l d n n $5@ was@ s m7@ n @QS mi m WMV@ W..4 T 7/ N i MHYAL $5@ Mw w mM.; m. @QMS MSSS www@ vw Vimmm w m m wma@ um y T Wm 5%@ mw w mw, JA m mw, 1JL l l 55 Q gmk@ www@ w E@ LM IQ www@ E v w S@ WNS@ bm w@ SNMXQ N l@ @@w) @QV Q NS Patented Feb. 20, 1945 UNITED STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application September 25, 1941, Serial No. 412,278

11 Claims.

Our invention relates to railway traic controlling apparatus and is directed to the control of traffic in a single track, two-direction system of signaling in which manual control either at the two ends of the single track stretch or at a remote control point is used for controlling traffic passing over the stretch. Our system employs no control line wires except for the C. T. C. line circuit, if remote control is used, and is normally deenergized insofar as the presence of track circuit code is concerned, the only energy normally in the track being uncoded or steady current. This is used to provide the block unoccupied indication and to provide the unlock which is necessary before a reversal of the established traffic direction can be accomplished.

One object of our invention is to provide a non-line-wire system for coded track circuit operation in a single track, two-direction system which incorporates important safety features which are comparable to those which are present in line wire systems designed for this type of service. Another object of our invention is to employ steady energy transmitted over the track to provide traffic locking. A further ob'- ject of our invention is to control such a system manually, at the two ends, or by means o-f C. T. C. control, or a combination of the two. Other objects, purposes and characteristic features of our invention will be apparent from the description which follows.

We accomplish the foregoing objects by normally transmitting steady track circuit energy in the direction in which trafc is established,

under the contr-ol of a manually operable lever at each end-of the single track stretch or at a remote control `point,which energy must be detected at the exit end for the established traffic direction before a trailic lever reversal can be made at this end. Reversal of the trailc lever at the exit end (new entrance end) causes steady energy to be transmitted to the new exit end and when there detected, permits a reversal of the tra-flic lever at that end. The steady energy is discontinued by operation of the signal lever for clearing the entrance signal and when this effect reaches the exit end, code is transmitted from that end to the new entrance end. Receipt of code at the entrance end permits the entrance signal to clear so that trame may enter the single track stretch. The steady energy is applied to the track circuits in the rear of the train so that the system is automatically restored to its normal condition upon the exit of the train from the stretch. By cutting off the steady energy at the entrance end, the signal may again be cleared for a following train movement.

Our present invention is an improvement on the invention disclosed in the copending United States applications, Serial No. 410,504, filed on September 12, 1941, by James J. Van Horn, now Patent No. 2,344,573, dated March 21, 1944, and Serial No. 411,481, led on September 19, 1941, by Crawford E. Staples, now Patent No. 2,353,421, dated July l1, 1944, both for Railway trac controlling apparatus.

We shall describe several forms of apparatus embodying our invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. la, 1b, and le when taken together, with Fig. la at the left, are a diagrammatic view showing one embodiment of our invention as applied to a stretch of single track railway extending between the passing sidings PSI and PS2 at the two ends of the stretch. Fig. 2 is a diagrammatic view, also embodying our invention, and showing a modified form of the invention shown in Fig. 1,

' in which the apparatus at one end of the stretch is controlled from a remotely located control oflice over a C. T. C. line circuit. Fig. 3 shows the direct current track circuit modification for location D of Fig. 1a,lof the apparatus embodying our invention.

Similar reference characters refer to similar parts in each of the several views.

Referring next to Figs. la, 1b, and 1c, we shall iirst describe, the general features of operation in order to make the subsequent detailed circuit description more readily understandable.

In theform of the invention .shown in Figs. y1a, 1b, and 1c, a traiiic direction control lever is used at each end of the single track stretch. With both traffic levers 8 and I8 set for westbound traic (N position) and the westbound entering signal ISL in the stop position, steady non-coded track circuit energy feeds from the east end and is repeated through all of the track circuits from location G at the east end to location D at the west end. This steady energy controls a through traffic block indicator light WB at the west end whichA informs lthe operator at that location that the entire stretch is clear. It is only when this steady energy is received throughout the entire stretch that the operator at the west end may reverse his traffic lever 8 to initiate the reversal of traiiic. When it is desired to revers-e this direction of traffic, the operator at the west end first contacts the operator at the east end (location G) and then moves his traffic lever 8 to the -this coded track circuit energy reverse position R. The operator at the east end then moves his tralilc lever I8 to the center position which cuts ofi the steady energy that has been flowing from east to west. This permits steady energy to flow from w-est to east throughout the entire stretch, and only when this steady energy is received at the east end, lighting the through traffic block indicator EB at that loca tion, will the operator at the east end be able to complete the movement of his traffic lever I8 to the reverse position. When lthis has been accomplished, the operator at the west end moves his signal lever 6 to clear the eastbound signal. The moving of the signal lever cuts off the steady energy which has been flowing from West to east and when this energy has been vre#- moved, with the trafc lever I8` at the east end set for eastbound traino, coded track circuit energy will be relayed through the entire stretch from locationG to location D, and only when this coded track circuit energy is received at the west endwill the eastbound signal BR assume the clear position.

In the rear of an eastbound train, steady energy is fed from the west end through each track section as that track section becomes vacated. The operator 'at the west end may again clear his eastbound signal by operation of the signal lever l6 which cuts off the steady energy and allows lcoded track circuit energy to feed from east to west in the-vacated track sections. This coded 4track circuit energy may originate `either at the east end or at any inter'- mediate signal location such as location F, in the rear of an eastbound train. vThe operation of changing the traiiic direction from eastbound to westbound is similar to the operation just described and requires no added description.

It will be noted that'ahigh degree of protection against the possibility of reversal of tranic with a train occupying the stretch is provided. Before a reversal of traffic can be initiated, steady venergy must be `flowing through the entire stretch in the established direction ol 'traili'c and this steady 'energy lcannot be received at the `exit end 'if there is a train within the stretch approaching that end'. Then also, steady energy must be transmitted throughout the entire stretch in the opposite direction of traffic, that is, in the new traic direction. 'Only when this is accomplished can lcoded track circuit `energy be applied at the new exit end and only when is relayed throughout the entire stretch to the new entrance end can the entrance signal for the new direction 'of traino kbe clear-ed, the presenceof coded energy again 'checking against an opposing move.

Fig. 1a shows the circuits involved lfor traiiic locking at the west end of the territory and the circuits involved at the cut section E. Fig. 1b shows the `circuit arrangement required at a double intermediate signal location F, 'and Fig. 1c shows the tranic locking circuits required 'at the east 'end of the territory.A The 'double intermediate signal location i's typicaloi all vsuch locations irrespective oi the number involved and likewise, the circuits shown for the cut section are typical for all cut sections irrespective 'of their number.

We shall now describe the circuits more in detail. With trani'c lever I8 in its norin'al 'position and signal lever I6 occupying Vany position from normal (Nv) to riglflthan'd (R), in'clusive, battery is connected to the winding 'of relay lIIiLC'AlLM through a front contact 20 oi relay ISTMS, which is a stick repeater for the approaclrtrack circuit section IST, to hold r-elay IBLCTM steadily energized. The circuit control for relay ISTMS is well known and is shown, for example, in Fig. 1c of United States Patent No. 2,141,074, granted to H. S. Young on December 20, 1938. In that patent, repeater relay ITS corresponds with relay IBTMS and is seen to have an energizing circuit which extends over a front contact of the detector track relay and the lever contactJ which is closed in the normal position of the lever, as well as a stick circuit which excludes the lever contact and includes a iront contact of the repeater relay itself. (Corresponding circuits control the relay BTMS at the other end ofthe stretch.) The energization of relay IGLC'M opens the circuit of the resonant transformer-rectier unit TRU at that location at its back Contact 2I to prevent energization of the track relay I'BLTR 'and it also` causes non-coded track circuit energy to be applied 'to the track transformer TT over its front contact 22. At the lintermediate signal location F, relay IIJECTM is deenergized so that the circuit of the resonant transformer-rechner unit for relay IDETR is closed at back contact 23, and the primary winding of its associated track transformer TT is shunted over the back point of contact 45 of relay IUECTM. This allows relay IUETR to be steadily energized. The energization of relay IDETR energiz'es relay vIUETFSA continuously. Relay IUWCTM is continuously energized over the iront point of contact 25 of relay IDETFSA and the back point of contact 2E of relay IGHR. The continuous energization of relay IUWCTM opens the resonant transformer-rectiiier circuit for relay IIIWTR and applies steady non-coded energy to the track transformer feeding westward.

At the cut section location E, this steady noncoded energy continuously energizes relay ETR which has its resonant transformer-rectifier circuit closed through a back contact 2'I of relay WTR. The energization of relay ETR closes a circuit yover the front point o'f its contact 28 so as to apply non-coded energy to the track transformer feeding westward. The `transformerrec tilier circuit of Yrelay WTR. has been opened at back contact 29 with 'the energization of relay ETR and now remains open. As shown, relay GRC'FM at location D is deenergized. Accordin'gl'y, the circuit of the resonant transformerre'cti'iler unit for -the track relay SRTR at that location is 'closed a't back 'contact 30 of relay GRCTM, and the 'primary Winding vof the track transformer is shunted over 'the back point of Contact 3| of this relay, allowing the track relay to be continuously energized. The energization of relay SRTR energizes relay 'BRTFSA over its iront contact 32, whereupon the Ienergization of relay GRTFSA closes the 'circuit to the through traffic block indicator light WB over itsfront contact 'II and the back contact 13 of relay BR'CDR, thus indicating 'that the 'stretch is clear.

For permitting a Westward train movement with the two traffic levers 8 and I8 at the two ends 'occupying lthe normal position, the operator at the east end Iwill move signal lever AII to the left. This opens the circuit of relay yILCT-M, 'deenergizing that relay which discon- `nects the steady non-coded track circuit energy from the primary of the track transformer TT at the front vpoint of lits contact 22, thus discontinuing the steady track 'circuit energy which asvdoci has been feeding westward. At the intermediate signal location F, relayl IUETR now becomes deenergized which, in turn, deenergizes relay IilETFSA at front contact 33. The deenergization of relay IEIETFSA deenergizes vrelay lWCTM at the front point of its contact 25, thus removing the noncoded energy which had been connected to the track transformer feeding westward. At the cut section location E, relay ETR is now deenergized and so disconnects noncoded energy at the front point of contact 28 from the track transformer feeding westward at that location.

At location D, relay BRTR becomes deenergized which causes relay SRTFSA to become deenergized at the front point of contact 32. The den energization of relay SRTFSA closes a coding circuit for relay BRCTM over the back contact 34 of relay GRTFSA and the normal contact N on the traffic lever 8 (closed in the N position of the lever), to battery over either the front point of contact 35 of relay GLI-IR (the home relay for signal L) and the 180 code contact of the code transmitter CT, or over the back point of the same contact of relay SLHR and the 75c0de contact of the code transmitter, and finally a front contact 36 of relay ETMS which is a stick repeater of the track relay for the detector track section 5T. The energized or deenergized position of the home relay BLHR for signal EL depends on traffic conditions to the West of location D, as will be obvious. This coding circuit causes relay GRCTM to be periodically energized and deenergized at the '75 or 180 code rate in accordance with traffic conditions in advance. When relay GRCTM is energized, energy is connected to the primary Winding of the track transformer TT over the front point of contact 3i to feed coded energy eastward. The transformerrectiiier circuit for relay SRTR is open at back contact 3i] when relay GRCTM is energized.

The coded energy which is now applied at the West end of the block will be detected by relay WTR opens the circuit of the transformer-rectiner unit controlling the track relay ETR at back contact 2 1, so that relay ETR Will not respond to energy applied to the track circuit BART east of the cut section during the time that relay- WTRl is energized. Energy is now applied to the track circuit east of the cut section during the time that relay WTR is energized, so that the code received from the West side of the cut section is transmitted to the east side Where it will be detected by relay IBWTR at the intermediate signal location F.

The absence at the intermediate signal location cf steady energy from the east end of the block resulted in the previous deenergization of relays IGETR, IBETFSA, and IDWCTM so that the circuit for the transformer-rectifier unit controlling relay IEWTR is closed at the back contact 3l of relay IUWCTM to permit relay IQWTR to respond to the coded energy. The energization of relay IUWTR causes the energization of `relay IWTFSA at front contact 38. With relay IQETFSA deenergized and relay IUWTFSA energized so that back contact 4D and front contact :lll are both closed,lbattery is applied tothe decoding transformer DT alternately through the' front and back' points of contact 39 of relay.

IDWTR, so that the decoding relay IOHR will respond to the coding action of relay IIIWTR in the usual manner.

Relay IVUECTM Will now be energized to follow code by the circuit from battery through the back Contact 40 of relay IUETFSA, wire 4I, normal polar contact 42 of the directional stick relay DS (to check that the latter relay has responded to the energization of the I BWTFSA and IHR relays so that its polar contacts are closed in the proper position for a following westbound point of contact 23 of relay IOECTM so that this relay will not respond to the code impressed on the track circuit IGLT.

The code applied to the track circuit ISLT is detected by the transformer-rectier unit at locationV G and causes the energization of relay iSLTR, since the transformer-rectifier unit has its circuit closed through the back contact 2l of relay IGLCTM. 'The latter relay has 'been in the deenergized position since lever I6 was moved to the left, opening the NR contact which is closed only when the lever I6 is in its N or its R position or is intermediate these two positions. Relay IBLTFSA will accordingly be energized over the front contact 45 of relay ISLTR and will retain its front contacts closed during the coding operation of relay IGLTR. The acti-on of relay ISLTR in alternately closing its front and back contacts applies energy to the decoding transformer DT for energizing the code detecting relay I'BLCDR in the usual manner. Relay IGLCDR is designed to have a quick pick-up characteristic so that it Will' be energized atthe same time as relay IBLTFSA, whether coded or non-coded energy is being received by relay ISLTR. Ifnoncoded energy is being received, relay IBLCDR will subsequently release and prepare the circuits for the traflic lever lock ISK over its back contact 4l, and for the eastbound indication light EB over its back contact 48. The traffic lever lock I8K for lever I8 prevents a reversal of this lever unless the lock is energized at the time. As will be apparent, the circuit for lock I8K can be completed only if steady energy is being received at location G (relay ISLTFSA energized) since when code is received, relay IBLCDR will open the lock circuit at its back contact 41. In the present case, coded energy is being received at location G so that the lock IBK is deenergized and lever I8 is locked against reversal. Relay IBLCDR will remain energized vand will complete the circuit for relay I'BLHR which when energized permits the displayy of a proceed indication 'by signal ISL. This circuit includes an L contact on the signal lever I6 and front contacts 49 and 50 of relays ISTMS and IBLCDR. As 180 code is being received, relay ISLJ which is selectively responsive to 180 code but not to 75 code will also be energized in the usual manner through the resonant rectier unit so that a clear indication will be displayed by signal IBL.

When a westbound train accepts and passes signal IBL, relay ISTMS, which is a track repeater stick relay for the approach section I-5T will be deenergized and will remain in this 'con-` dition until lever I6 is restored to its normaiposltion with the track circuit IST unoccupied. .Re lay IBLCTM will then become steadily energized over the front contact 20 of Yrelay I'STMS, the NR contact on lever- I5, and the normal contact N on lever I8. With relay ISLCTM continuously energized, non-coded energy is applied to the veast end of the track stretch to feed. Westward in the rear of the train in the same manner as previ ously described when the application lof lsteady energy throughout the stretch was traced. When the train passes the intermediate signal IIJW and before it vacates the track section ISLT, relay IUECTM will .be responding to 75 code. The circuit for this relay is battery, back contact 40 of relay IDETFSA, Wire III, normal polar contact 4-2 of relay DS, '75 code contact of the vcoder CT, and back point -of contact 44 of relay IOW'I'FSA. Thus, when the train vacates the track section IGLT, coded energy of 75 code will be impressed across the track circuit due to the operation of relay IDECTM at this code rate.

As has been pointed out before, the transformer-rectifier unit for relay Ill-ETR is open .at the time when code is applied so that this relay will not respond to the code. During the off interval of the code, relay IOECTM will be deenergized to close the circuit of the transformer-rectifier unit TRU for relay BETR. At the .same time, the primary winding 0f the track transformer TT lis shunted, so that relay IOETR may respond to the non-coded energy impressed on the .track circuit ISLT at vlocation G.

cludes the front point of contact 25 of relay IQETFSA and the back point of contact 26 of relay WHR. Relay IUHR, it will be appreciated, responds only to code and will, of course, be deenergized during the time that the westbound' train is between signals IBW and 6R. The energization of relay lIlWCTM applies non-coded energy to the track circuit BART west of the intermediate signal location as previously described. This non-coded energy will be detected by relay ETR at the cut section when the train vacates the track circuit GART between the cut section and signal IDW. Under this condition, the train be- If a following train movement is to be made `in the westbound direction, the movement of signal lever I6 -to lthe L position will cause the deenergization of relay IGLCTM with the consequent removal oi non-coded energy 'from the east end of the track circuit ISLT, as previously described. The absence of non-coded energy at the inter- .mediate .signal location will cause the deenergization of relays IOETR and IOETFSA .and will cause the energization of relay IOECTM over the same -circuit as previously traced. Accordingly, coded energy of 75 code will be applied to the track circuit vI BLT. vThis code will be detected by the track relay 'IBLTR in the same manner as described for Ithe detection of 180 code when the entire stretch was unoccupied.

The control of 75 code applied to the track circuit .IfBLT .in approach to .signal I'IlW for a -following move is determined by the position of the polar contacts of relay DS. It will be noted .that this relay is `energized so as to close .its nor-mal contact 42 when relay IDWTFSA is energized, relay IOETFSA is deenergized and when .relay .IllHR is energized. This is the condition existing when a Westbound train is approaching signal IW with the track sections SRT and BART between signal IW and signal 6R unoccupied. For an eastbound train approaching signal `I-(JE, relays IOETFSA and I UHR would be energized, thus causing the .reverse polar contact y5I .of relay DS to close.

We lshall next follow the movement of the first train through the remainder Aof the stretch. As-

suming that lever I6 is normal and that a following train movement 4is not being made, steady energy will be fed westward from signal ISR up to signal IDW, as previously described. With `the westbound train occupying section EART-.or BRT between signal yIllW and signal 6R, .relays I-:GETR .and IUETFSA at the intermediate signal location will be energized continuously. Relay IGWCTM will also be Venergized over the circuit which ining between location E and location D, relay WTR will be deenergized and the circuit for the transformer-rectifier unit oi relay ETR will accordingly be complete land will enable this relay to respond to the non-coded energy. With relay ETR energized, non-coded energy will be applied to the `west side of the insulated `joints (track ,section ERT) at the cut section. As previously noted, the transformer-rectifier unit for track relay WTR is open at the back contact of relay ETR so that .relay WTR will not respond to the noncoded yenergy impressed across the track When the rear end of the train vacates the .track circuit SRT, relay BRCTM will remain deenergized because its .control circuit is open at the iront contact SB-of relay STMS. This permits relay BR'I'R to respond to steady energy impressed on the track circuit BRT. The energization of relay GRTR permits the energization of relay :GRTFSA which, in turn, also opens the circuit of relay SRCTM, thus continuing the withholding of coded energy from the track circuit SRT when relay STMS picks up. As relay GRTFSA is now `energized and relay YGRCDR is deenergized (relay IiRCDR .is energized lonly when code is being received), the west-bound indication light WB which indicates the unoccupied condition of the block will be illuminated to inform the operator of this fact so that a reversal of traic may be effected, if desired.

Having described the relay operations involved in a westbound train movement, we shall next assume that traffic is to be reversed for an east- .bound movement. Withsteady energy being re ceived at .location .D from they east end of the block, relay BRTFSA Aat the west end will be Venergized .so that the operator may move lever .8 to its .reverse position since the lever lock 8K can now be energized over .front contact 15 of relay SRTFSA. After lever 8 has been moved, the operator may communicate with the operator vat theeast end of the block, instructing him to move tramo lever I8 `to the center position. This movement of traic lever I8 will cause the deenergization of relay IGLCTM and the removal of uncoded energy .from the track circuit IGLT at the east end of the block. When the absence of steady energy from the east end is detected at the west end of the block, relays SRTR and GR'IFSAat .location D will be deenergized whereupon relay BRCTM will .be continuously energized kover the circuit which includes the reverse contact R on` lever 8, the NL contact on lever 6 (which is `closed only when the lever 6 is in its N or its L .position or is intermediate these two positions), and front contact 36 of relay STMS. 'This non-coded energy applied at the west end of the block will be detected and transmitted through the Vcut .section and intermediate signal location inthe same manner as previously described for the application of non-coded energy when the westbound direction 'of traine was being established. The receipt of non-coded energy by relay IBLTR will pick up this relay and will cause the energization of relay IBLTFSA. Relay IGLCDR will pick up when relay IELTR closes the front point of its contact 52 but will soon release when relay IBLTR. retains this front contact closed, as there will then be no change in the direction of 'current through the decoding transformer DT to continue the energization of relay iBLCDR. When relay IGLCDR closes its back contact 18,the indication light EB at the east end of the block will be illuminated, thus informing the operator to complete the reversal of his traffic lever I8. Non-coded energy will remain applied to the track circuit at the west end of the block until the lever 6 which controls signal 5R is moved to the R position, whereupon relay SRCTM at location D will be deenergized to remove the non-coded energy. Lever 6 should not be moved to the R position until the operator at the east end informs the west end operator that trafc lever i8 has been reversed. As long as the non-coded energy is received at location G, relays IGLTR and IBLTFSA will remain energized. When the non-coded energy is removed, the circuit is completed for relay IBLCTM through a back contact 53 of relay ISLTFSA, the reverse contact R on lever IB, the front or the back point of contact l! of relay IERI-IR, and the 180 or '75 code contact, respectively, on the code transmitter CT. Coded energy is now applied to the track circuit iLT at the east end of the block. This coded energy will be detected at the intermediate signal location and coded energy of the proper code frequency will be applied to the track sections between signal lE and signal BL in the same manner as already described for-the westbound direction.

The operation involving restoration of the traiic levers to their normal position for a westbound move will be similar to that described for the change from westbound to eastbound, so that no additional description is necessary.

Referring now to Fig. 2, this gure shows an application of our trailic locking circuit wherein the apparatus at one end of the stretch is controlled from a control oice at a remote point by a system of C. T. C. control.` The operation duplicates that obtained when mechanically' locked levers are used, as was previously discussed, and the apparatus of Fig. 2 is intended to replace the apparatus at location G' of Fig. 1c.

Relays iNFSR, lRFSR and ISCFSR are C. T. C. controlled traflic direction relays and these relays repeat the N, R, and C positions, respectively, of the traihc lever i8 at the control office. The communication system by means of which the C. T. C. operator at the control oiice governs the traiic relays iSNFSR, iSRFSR and lSCF'SR may be of any suitable type, but preferably it is of the selective code type in which communication is established intermittently by means of impulse codes transmitted over a single pair of line wires from the control oce to the station. The details of such a communication system do not enter actively into our present invention and it is deemed suiiicient for an unof suitable indication codes over the C. T. C. line to the control office, for operating the westbound and eastbound indication apparatus as well as providing the unoccupied block indication. Theapparatus at the control oiiice prevents a reversal of the established traine direction except under proper trafiic conditions, as will be pointed'out hereinafter. One form of communication system suitable for use in my system is that shown in Letters Patent of the United States No. 2,229,249, granted to L. V.

Lewis on January 2l, 1941, for Remote control system. In order to simplify the disclosure as much as possible, the terminals of the eld station unit have been designated with terminal numbers which correspond with the terminal wires in the above Lewis patent which control analogous functions.

With the trafc lever i8 normal, relay ISNFSR will become energized, relays ISRFSR and lCFSR being deenergized. and if the relay which controls signal IBL (iLHSR) is deenergized, relay IGLCTM will be energized over the circuit from battery, front contacts and 55 of relays iTM and IBLKM, respectively, back contact 51 of relay iSLI-ISR, front contact 58 `of relay iSNFSR and back contact 59 of relay IBCFSR. Relay I5TM is the repeater relay for the detector track section I5T, and relay IBLKM is the appreach locking relay for signal IBL.

The receipt of steady energy at the west end of the block will permit the reversal of traic lever 8 in the usual manner. After the reversal of the traine leverv 8, the operator at the control oice vthich governs the east end of the stretch would be so advised and would thereupon transmit a code from the C. T. C. machine with trailic lever I8 on center to pick up relay IBCFSR through the code equipment, and a front contact 60 of relay IBNFSR. Relay IBNFSR will continue energized as its stick circuit is complete from battery. through back contacts 51 and 16 of relays IBLTFSA and IBRFSR, and front contact 'l1 of relay I BNFSR. Relay I8CFSR will remain energized through its own front contact Bi, a portion of the code equipment circuits not shown but which include terminals 83 and 81 of the .field station unit and the front contact 60 of relay I8NFSR, thus opening the steady energy circuit of relayIELCTM. This relay, in turn, removes steady energy from the east end of the stretch and allows steady energy to flow from the west end of the stretch to the east end. This is because relay BRCTM at the West end is continuously energized over a front contact of relay ETMS, the NL contact on lever 6 and the R contact on lever 8. The receipt of steady energy at the east end of the stretch 'will cause the energization of relay IELTFSA with the relay IGLCDR deenergized, thus completing a circuit to terminal es, to illuminate the block indication light BK on the C. T. C. machine.

derstanding of the present invention to point out that movement of the traiiic lever I8 lto the diiierent positions results in the transmission of suitable codes to the field station for selectively energizing the traffic relay corresponding with the lever position. Moreover. the operation of these traiic relays and other apparatus at the iield station location results in the transmission lmoved from that end, thus deenergizing` relay IILTFSA at the east end and. completing the coding circuit of relay ISLCTM from battery', i'ront contacts 55 and 56 of relays I5.TM and ISLKM, 180 code contact and front point of contact 64 oi relay IBRHR, or 'I5 code contact and back point of contact 64 of relay IERI-IR, iront contact B of-relayl IBRFSR' and back contact B6 of relay IGLTFSA. The coding action of relay IGLCTM impresses coded energy on the track circuit IELT which is repeated in the usual manner to thewest end o1' the block.

It will be noted that the stick circuits of relays IiBNFSR and IBRFSRv include a back contact 61 of relay IGLTFSA in multiple with a front contact 68 ofV relay IBLCDR. Thus, either of these relays when energized will be retained in that condition independently of the code equipment, unless steady energy is being received at the east end of the block.

To establish traiiic for the westbound direction with the block unoccupied and the eastbound entrance signal at stop, steady energy would be received at the east end, thus permitting a code to be sent tov energize relay IBNFSR and to deenergize relay IBRFSR. The energization of relay IBNFSR completes the. steady energy circuit of relay ISLCTM to apply' steady energyl to the stretch feeding west for the unlock of the traiilc lever at the other end so that this lever may be restored to its. normal position after iirst being moved to center to removev the, steadyl energy feeding from west to east;

Directional lights WB and EB on the C. T. C. machine are controlled in the usual manner over contacts of relays IBNFSR and IBRFSR and the coded l'ine circuit.

The modification of a portion of the apparatus at location D which is shown. in Fig. 3 `shows how this apparatus can be adapted for direct current trackl circuit operation. Obviously, although alternating current track circuits are shown in Figs. 1 and 2, the invention is not, limited to alternating current operation since. the various track transformers can be replaced by direct current sources in well-known manner.

From the foregoing description, it will be apparent that we have provideda traillc control system for a. stretch of single track railway which does not require control line wires and' which pro vides an unusually high degree of safety and freedom from interference, with the movement of traine in the established direction. comparable with that obtained in systems:- which employ line wire control for the traino locking functions. By employing' uncoded track circuit energy during the time that the track circuits are inactive, a substantial power saving is accomplished and it becomes possible. to provide the operator with a block indication which at, all times informs him whether the stretch is unoccupied or occupied, without the necessity for first transmitting curreversal can be eilective. Removal of the steady energy must then be detected at the entrance end. Second, steadyy energy vis transmitted over the track circuits of' the stretch in the new tramo direction and must 'be detected at the new exit end before the traffic reversal is completed and code can be applied atV the new exit end. Third, code is. transmitted over the track circuits of the stretch and must be detected at the new entrance end before the entrance signal can be cleared and a train permitted to enter the stretch in the reverse traiic direction.. Accordingly, clearing o! the entrance signal provides. a. guarantee that the stretch is not occupied by a train approaching from the other end and that the track circuit apparatus of the system is functioning properly. By using a C. T. C. line circuit, the traiilc direction apparatus at one or both ends, of the system can beY governed from .a control oice at a. remote location, the same, safety checks which prevent interference with authorized movement of tramc beingr as effective in the case of C. T; C. control as in the case of direct manual control at the two ends of the, stretch.

Although we have herein shown and described only a, few forms of apparatus embodying our invention, it is understood that various changes and modifications maybe made therein within the scope of thev appended claims without departing from the, spirit and. scope. of our invention.

Having thus described our invention, what we claim is:

l. In combination with a stretch of trackV over which traic may move in either direction, a irst and a second manually controlled traic direction lever adjacent one and the other end of said stretch and having a normal and a reverse position corresponding with trafllc inthe normal and reverse direction respectively over said stretch, means elective when both said levers occupy said normal position for transmitting uncoded rail current in the normal trame. direction from one to the other end of said stretch, means effective when said uncoded current is detected at said other end for permitting a reversal of said second traillc, lever, means controlled by said first traillc lever eiective when said second lever is reversed for discontinuing the supply of'said uncoded rail current at said one end. means eiiective when rent over the stretch to obtain this, information.

The presence of steady energy in the track at all times when the stretch is unoccupied provides'a constant check on the integrity of the track circuits so that track circuit failures can be detected and corrected before such time as a train approaches an entrance signal and causes the system to be set into operation. It will be noted that actually three checks are provided as to the integrity of the system before a train is permitted tok enter the stretch. AThese are as follows. First, steady energy is relayed over the track circuits of the stretch in the direction of trailic and must be detected at the exit end before a traffic lever the absence of said uncodedcurrent is detected at said other end for transmitting uncoded rail current in the reverse tramo direction from said other end to said one end of the stretch, means effective,- Whcn saiduncoded current is detected at said one end for permitting a reversal of said iirst traillc lever, an entrance signal at said other end, control means for said signal, means effec'- tive when said control means is operated for discontinuing the supply of said uncoded current at said other end, means effective when the absence of said uncoded current is detected at said one end for transmitting. coded rail current from said one end to said other end', and means effective when said coded current is detected at said other end `for clearing said entrance signal.

2. In combination with a stretch of track over which traic may move in either direction, a first A and a second manually controlled tramo direction lever adjacent one and the other end respectively of said stretch, means controlled by said first; lever for normally transmitting uncoded rail current in a given direction from one to the other end of said stretch, means responsive to the receipt of said uncoded current at said other end for permitting a reversal of said second lever,

means controlled by said rst lever for discontinuing the supply of said uncoded current at said one end, means effective after said second lever is reversed and the supply of uncoded current at said one end is discontinued for transmitting uncoded current in the reverse direction from said other to said one end of said stretch, detecting means responsive to the receipt of said uncoded current at said one end for permitting a reversal of said rst lever, means controlled by said rst lever when reversed for transmitting coded rail current from said one to said other end of the stretch, and traffic governing means responsive to the receipt of said coded current at said other end.

3. In combination with a stretch of track over which trailic may move in either direction, a rst and a second manually controlled traiilc direction lever adjacent one and the other end respectively oi said stretch, means controlled by said first lever for normally transmitting uncoded rail current in a given direction from one to the other end of said stretch, detecting means energized in response to the receipt of said uncoded current at said other end, locking means for preventing a reversal of said second lever unless said detecting means is energized, means for discontinuing the supply of said uncoded current at said one end.

means effective after said second lever is reversed and the supply oi said uncoded current at said rst lever effective after said uncoded current is detected at said one end for transmitting coded rail current in said given direction from said one end to said other end of the stretch, and means effective after said coded current is detected at said other end for clearing said entrance signal.

4. In combination with a stretch of track over which traic may move in either direction, means for normally transmitting current of a rst character in a given direction from one to the other end of said stretch to provide an unoccupied block indication for said stretch, a first and a second manually controlled traffic direction lever adjacent one and the other end respectively of said stretch, means responsive to the receipt of current of said rst character at said other end for permitting a reversal of said second lever, means including said first lever for discontinuing `the supply of said current at said one end, means controlled by said second lever when reversed effective after said current isdiscontinued for transmitting rail current of said rst character in the reverse traffic vdirection from said other to said one end, means responsive to the receipt of saidcurrent at said one end for permitting a reversal of said first lever, means at said other end for discontinuing said last-named current, means controlled by said rst lever when reversed effective after said last-named current is discontinued for transmitting rail current of a second character` in said given direction from said one to said other end, and means responsive to thefreceipt of current of said second character at said other end for governing the entry of traillc at said other end.

5. In combination with a stretch of track lover which tralic may move in either direction, means for normally transmitting uncoded rail current in a given direction from one to the other end of 1 other end respectively of said stretch, means responsive to the receipt of said uncoded current at said other end for permitting operation of said second traiic direction control means, means effective after said second trac direction control means is operated and said stretch is unoccupiedy for transmitting uncoded current in the reverse direction from said other to said one end of said stretch, means responsive to the receipt of said uncoded current at said one end for permitting operation of said iirst traiiic direction control means, means at said other end for discontinuing the supply of said uncoded current, means controlled by said first traic direction control means when operated effective after said uncoded current is discontinued for transmitting coded rail current, in said given direction from said one to said other end of the stretch, means responsive to the receipt of said coded current ab said other end for governing the entry of traffic at said other end of the stretch, and trailic lgcking means at said one end effective for preventing the supply of said coded current at said one end unless said uncoded current is first detected at said one end.

6. In combination with a stretch of track over which trallic may move in either direction, means for normally transmitting uncoded rail current in a given direction from one to the other end of said stretch provided said stretch is vacant, detect` ing apparatus adjacent said other end energized in response to receipt of said uncoded current at said other end, means at said one end for discontinuing the supply of said uncoded current to thereby deenergize said detecting apparatus, manually governed traic direction control means adjacent said other end, means controlled by said traflic direction means effective when said detecting apparatus is deenergized for transmitting coded rail current from said other to said one end o f said stretch provided said stretch/is vacant, code responsive means adjacent said one end energized in response to said coded current, traflic governing means controlled by said Code responsive means when energized, and locking means for said traiiic direction means controlled by said detecting apparatus.

'7. In combination Witn a stretch of track over which traffic may move in either direction, first current, locking means for preventing a reversal of said second tralilc direction control means, means effective when said track relay is energized for rendering said locking means ineffective, meanscontrolled by saidsecond traffic governing means when reversed andfsaid uncoded current is discontinued for operating'said code transmitting relay to thereby transmit coded rail current from said other to said one end of the stretch, a code responsive track relay at said one end operated by said coded current, and means effectiver When said last-named track relay is operated for governing the entry of traic into said stretch at said one end.'

8. In combination With a stretch of track over which traffic may move in either direction, rst

and second manually governed traffic direction control means adjacent one and the other end respectively oi said stretch, means effective when said first trafiic direction control means is reversed and said stretch is unoccupied for transmitting uncoded current from said one to said other end of the stretch, a normally inoperative code transmitting relay adjacent said other end, a track relay adjacent said other end energized on said uncoded current over a back contact of said code transmitting relay, locking means for preventing a reversal of said second traffic direction control means, mea-ns effective when said track relay is energized for rendering said locking means ineffective, a slow acting repeater relay for said track relay, means at said one end yfor discontinuing the supply of said uncoded current, means including a back contact of said repeater relay and controlled by said second traic direction control means when reversed and said uncoded current is discontinued for operating said code transmitting relay to thereby transmit coded rail current from said other to said one end of the stretch, a code responsive track relay at said one end operated by said coded current, and means effective when said last-named track relay is operated for governing the entry of traflic into said stretch at said one end.

9. In combination with a stretch of track over which traffic may move in either direction, a first manually controlled traffic direction lever adjacent one end of said stretch, a second manually controlled traftlc direction lever at a remotely located control oiiice, said second lever having a normal and a reverse position, a normal and a reverse traffic direction control relay adjacent the other end of said stretch for repeating the normal and reverse position respectively of said second lever, an energizing circuit for said normal control relay controlled by said second lever when occupying said normal position, means effective when said normal control relay is energized for transmitting uncoded rail current from sa-id other to said one end of the stretch to permit a reversal of said rst lever, means at said other end for discontinuing said uncoded current, means eiec tive when said first lever is reversed and said y uncoded current is discontinued for transmitting uncoded rail current from said one to said other end of the stretch, a detecting relay energized l,

when said uncoded current is received at said other end, an energizing circuit for said reverse control relay controlled by said second lever when occupying said reverse position and including a front Contact of said detecting relay, a stick circuit for said normal control relay including its own front contact and a back Contact of said reverse control relay, whereby said reverse control relay cannot be energized unless uncoded current is rst detected at said other end and when ener- .gized opens the stick circuit for said normal concontrolled traffic direction lever at said control location having a normal and a reverse'position corresponding with traflic in the normal and the reverse direction respectively over said stretch, means for transmitting uncoded rail current over said stretch to said one end provided said stretch is vacant, a detecting relay adjacent said one end energized in response to the receipt of said uncoded current at said one end, a normal and a. reverse traffic direction control relay adjacent said one end for controlling traffic in the normal and the reverse direction respectively over said stretch, a pick-up circuit for said normal control relay effective when said lever occupies its normal position and including a front contact of said detecting relay, a pick-up circuit for said reverse control relay effective when said lever occupies its reverse position and also including a front contact of said detecting relay, a stick circuit for each said control relay including a front contact of the relay itself and a back contact of the other control relay, means at said other end for discontinuing said uncoded current to thereby deenergize said detecting relay, and means including a front contact oi'l said reverse control relay effective when said detecting relay is deenergized for supplying coded energy to the rails of said track stretch at said one end thereof.

11. In apparatus for controlling traic movremote control location comprising, a. manually controlled tramo direction lever at said control location having a normal and a reverse position corresponding with traic in the normal and the reverse direction respectively, means for transmitting uncoded rail current over said stretch to said one end provided said stretch is vacant, a detecting relay adjacent said one end energized in response to the receipt of said uncoded current at said one end, a normal and a reverse trafic direction control relay adjacent said one end for controlling traflic in the normal and the reverse direction respectively over said stretch, a pick-up circuit for said normal control relay effective when said lever occupies its normal position and including a front contact of said detecting relay, a pick-up circuit for said reverse control relay effective when said lever occupies its reverse position and also including a front contact of said detecting relay, a stick circuit for each said control relay including a front contact of the relay itself and a back contact of the other control relay, means at said other end for discontinuing said uncoded current to thereby deenergize said detecting relay, means including a front Contact of said reverse control relay eifective when said detecting relay is deenergized for transmitting coded rail current from said one end over said stretch, means at said other end of said stretch responsive to receipt of coded current over the rails of said stretch. and governing the entryl of traffic into said stretch at the other end, and means including a front Contact of said normal control relay for transmitting uncoded rail current from said one end over said stretch-to said other end provided said stretch is vacant.

HOWARD A. THOMPSON.

JAMES J. VAN HORN.

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