US2702851A - Arrangement and automatic control of railway signals for directing only one train tooccupy single track between consecutive passing sidings at any given time - Google Patents

Description

1955 A. R. WHITEHORN 2 7 ARRANGEMENT AND AUTOMATIC CONTROL OF RAILWAY SIGN FOR DIRECTING ONLY ONE TRAIN TO OCCUPY SINGLE TRACK BETWEEN ANY GIVEN TIME CONSECUTIVE PASSING SIDINGS AT Filed March 23,v 1948 3 Sheets-Sheet l HIS ATTORNEY Swami VX 1M mw INVENTOR. Arthur H. Wfiiteizorn' v mm mmfiw I RR m k E A a E Q a a A msw E N mm QM 4 N Nu B EN $3 5..

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' II BY E115 A1 TTQZ ZNE FOR DIRECTING ONLY ONE TRAIN TO OCCUPY SINGLE TRACK BETWEEN Feb. 22, 1955 A. R. WHITEHORN ARRANGEMENT AND AUTOMATIC CONTROL OF RAILWAY SIGNALS CONSECUTIVE PASSING SIDINGS AT ANY GIVEN TIME 3 Sheets-Sheet 5 INVENTOR.

Fflzitdzozn Filed March 23, 1948 Art/inn? BY C14 HIS ATTORNEY United States Patent ARRANGEMENT AND AUTOMATIC CONTROL OF Arthur R. Whitehorn, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application March 23, 1948, Serial N 0. 16,447

5 Claims. (Cl. 246-39) My invention relates to a railway signal control system, and particularly to a control system for signals for governing traific movements in opposite directions over a stretch of single track railway.

In a railway signaling system for a stretch of single track railway which is provided with passing sidings spaced along the single track, two pairs of head block signals, each comprising an entering and a leaving signal, are commonly employed for each passing siding for governing trafiic movements in opposite directions, and are placed one pair adjacent each end of each passing siding. For stretches of single track railway on which trafiic is relatively dense, that is, over which relatively many trains move within a given period of time, train operation is facilitated by permitting more than one train, moving in the same direction, to occupy the track between two consecutive sidings at the same time, although preventing a train which is moving in either direction from entering the stretch of track between two consecutive sidings if the same stretch of track is already-occupied by.

a train moving in the opposite direction. For such train operation, a signal arrangement and control system of the well-known absolute permissive block type may be employed.

For stretches of single track railway on which trafiic is relatively thin, that is, over which relatively few trains move within a given period of time, it is neither necessary nor important to permit more than one train moving in either direction to occupy the single track between any two consecutive passing sidings at the same time.

One feature of my invention, therefore, for stretches of single track railway on which traffic is relatively thin, but on which train speeds may be relatively high, is the provision of a signal arrangement which embodies head block signals similar to those commonly employed except that each of the head block signals displays only two indications, stop and clear. The signal arrangement also embodies an approach signal for each entering signal, each located a sufficient distance in the rear of its entering signal to provide double braking distance between each approach signal and its entering signal.

Another feature of my invention is the provision of a novel and improved arrangement of overlapping controls for the leaving head block signals for the opposite ends of a stretch of single track railway between two consecutive passing sidings.

Another feature of my invention is the provision of track circuits between the two pairs of head block signals at a passing siding in which the portion of track between the switch at each end of the passing siding and the adjacent pair of head block signals is by-passed when the switch is moved to its reverse position.

Another feature of my invention is the provision of a novel and improved arrangement for approach controlling a signal by the track circuit for the second section in the rear of the signal.

Still another feature of my invention is the provision of means for controlling an approach signal by current of normal or reverse polarity over a given pair of control conductors, and for controlling the next leaving signal in the rear of the approach signal by current of reverse polarity only over the same pair of control conductors.

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

In the accompanying drawings, Figs. la, lb, and 10, when placed end to end in that order, with Fig. 1a on the left, constitute a diagrammatic view showing one form of apparatus embodying my invention, in which a stretch of single track railway is provided with passing sidings spaced along the stretch, and in whichtwo pairs of head block signals are employed for each passing siding and are placed one pair adjacent each end of each passing siding, and an approach signal is provided for each entering signal; and in which the controls for the leaving head block signals for opposite ends of the stretch of track between any two consecutive passing sidings are overlapped so that the control for each leaving head block signal extends to the head block signal location at the remote end of the next passing siding when the switch at the remote end of the next passing siding is in its normal position, but the control for each leaving head block signal extends only to the switch at the remote end of the next passing siding, but does not include the switch, when this switch is in its reverse position; and also in which the signal mechanisms and lamps are normally deenergized, and become energized only when a train is approaching.

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

Referring further to the drawings, a stretch of single track railway is shown, which is provided with a plurality of passing sidings spaced along the single track. Two such passing sidings, designated by the reference characters X and Y, are shown in the drawings. The ends of siding X are connected with the single track railway by switches designated by the reference characters aw and bw, and the ends of siding Y are connected with the single track railway by switches cw and dw.

Rails 1 and 1a of the single track are divided by insulated joints 11 to form sections a-b, b-c, c-d,

de, and e-f. A portion of another section of the single track railway is also provided to the left of signal I clear position.

18, as shown in the drawings, and a portion of another section is also provided to the right of signal 108, as shown in the drawings. It should be understood that signals 18 and 2S correspond to signals 78 and 8S and that signals corresponding to signals 68 and 58 would be placed further to the left of signal 18. Signals 9S and 108 are counterparts of signals 38 and 48. The portion of the system shown in Figsla, lb and 1c is duplicated recurrently to the left and right beyond sidings X and Y respectively.

An auxiliary insulated joint 12 is also placed in rail 1a of the single track adjacent, and in the trailing'direction from, each'of the track switches aw, bw, cw, and dw.

Adjacent each end of each of the passing sidings X and Y is a pair of head block signals for governing trafiic movements in opposite directions. Signals 18, 48, 7S, and 108, which govern traflic movements away from the passing sidings, are known as leaving signals, whereas signals 28, 38, 8S and 98, which govern traflic movements toward the passing sidings, are known as entering signals. entering signals, such as approach signals 58 and 68 shown for entering signals 35 and 33, respectively. Signals 28, 48, 68, 8S and 10S govern traffic movements toward the right, as shown in the drawings, which I shall assume is the eastbound direction, and signals 18, 38, SS, 78 and 9S govern trafiic movements in the opposite or westbound direction.

The signals may be of any suitable design, such, for example, as the well-known searchlight type shown in the drawings, each comprising a mechanism, designated by the reference character m, and a lamp, designated by the reference character 1', each of which is preceded by a numerical prefix corresponding to that in the reference character for its signal. The mechanism of each signal is normally in the stop position, as shown by the solid line at the top of the mast for each signal.

Each of the head block signal mechanisms has only one proceed control position, shown by the dotted line as the Each of the approach signals has two An approach signal is provided for each of the proceed positions, shown by the dotted lines as a caution and a clear position.

Each of the track sections ab and e-f, at the passing sidings, is provided with two coded track circuits, one for each direction of traffic movements. The eastbound track circuit for each of these sections is supplied with current, from a suitable source such as a battery 13 at its east end, coded at a frequency of 120 times per minute by a code transmitter designated 120CT and includes, at its west end, a code following track relay, designated by the reference character 120CF, which responds to the current coded at the 120 frequency. The westbound track circuit for each of these sections is supplied with current, from a suitable source such, for example, as a battery 13, coded at a frequency of 75 times per minute by a code transmitter designated by the reference character 75CT, and includes, at its east end, a code following track relay, designated by the reference character 75CF, which responds to the current coded at the 75 frequency.

The circuit for each of the relays 120CF includes the back point of a contact of the adjacent code transmitter 75CT, so that none of the coded current of the 75 frequency from the adjacent battery 13 can pass through the windings of the relays IZOCF. Similarly, the circuit for each of the relays 75CF includes the back point of a contact of the adjacent code transmitter 120CT, so that none of the coded current of the 120 frequency from the adjacent battery 13 can pass through the windings of the relays 75CF.

The code transmitters 75CT and 120CT employed at the opposite ends of sections ab and ef have contacts which are continuously actuated between their picked-up and released positions. These devices are selected so that their contacts have substantially different rates of operation. Thus, the contacts of the device 120CT are moved to their picked-up positions 120 times per minute, while the picked-up periods of the contacts are separated by periods of equal length during which the contacts occupy their released positions. Similarly, the contacts of the device 75CT have 75 picked-up and released periods per minute. As these devices operate at substantially different speeds, the contacts do not operate in synchronism and there are frequently recurring periods during which the contacts of one of the devices are picked {up agd the contacts of the other of the devices are reease During the periods when the contacts of the code transmitter 120CT for each of the sections ((-12 and e-] are picked up while the contacts of the transmitter 75CT for the opposite end of the section are released, impulses of current are supplied for energizing the relay 120CF for the opposite end of the section. During the periods when the contacts of the code transmitter 75CT for each of the sections rz-b and ef are picked up while the contacts of the transmitter 120CT for the same section are released, impulses of current are supplied for energizing the relay 75CF for the same section.

It follows, therefore, that when either of the track sections a-b and e-f is vacant, impulses of energy are supplied from each end of the section to the track relay at the other end of the section. These impulses are of sufiicient length for controlling relays 75CF and 120CF to effect energization of decoding transformers, each of which is designated by the reference character F with a numerical prefix which is the same as that of the adjacent entering signal, for energizing decoding track repeater relays, designated by the reference character T? with a numerical prefix which is the same as that of the associated decoding transformer.

The circuit for each of the relays 75CF and 120CF includes a normal contact of the adjacent track switch, so that each of these relays becomes deenergized when the adjacent switch is moved away from its normal posilOIl.

A switch repeater relay is provided for each switch, and 1s deslgnated by the reference character P with a prefix which is the same as the prefix in the reference character for its switch. Each of these switch repeater relays is controlled in conjunction with its switch by a contact which is normally closed when its switch is in the normal position and becomes opened when its switch is moved to the reverse position, so that each switch repeater relay becomes deenergized when its switch is moved away from the normal position.

A circuit path is included in each of the track circuits for sections ab and ef, connected around each of the insulated joints 12 with the track rail 1a in which the joint 12 is located, through a front contact of the switch repeater relay for the adjacent switch. When a switch is moved away from its normal position, a bypass is completed, through a back point of a contact of the switch repeater relay, around a portion of the track rail 1a in which the adjacent insulated joint 12 is located.

The portion of the track rail thus by-passed extends between the adjacent insulated joint 12 and the adjacent end of the track section, so that the code following relay CF or IZOCF for the opposite end of the section will not be affected by a train moving over the switch in its reverse position.

Each of the track sections b-c and de, and also the first section west of signal 18 and the first section east of signal 105, is provided with a polarized coded track circuit, one end of which is supplied with current of normal or reverse polarity coded at a frequency of 75 times per minute by a code transmitter 75CT, and the opposite end of which includes two polar biased code following track relays, designated by the reference characters TRN and TRR with a distinguishing numerical prefix, connected in series opposition across the rails of the section. The relay designated by the reference character TRN responds by operating its contacts between front and back points only when the track circuit is energized by coded current of normal polarity, and similarly the relay desig nated by the reference character TRR responds by operating its contacts between front and back points only when the track circuit is energized by coded current of reverse polarity.

The relays TRN and TRR control decoding track repeater relays designated by the reference characters DP, TNP and TRP, preceded by a numerical prefix which is the same as that of the associated relays TRN and TRR. Each of the relays DP is made slow releasing by an asymmetric unit t, which may be of the well-known copper oxide rectifier type, connected with its high resistance direction in multiple with the winding of the relay DP. Each of the relays TNP and TRP is also made slow releasing by a resistor r and a condenser u connected, in series with each other, in multiple with its winding.

Section 0-11 is provided with a center-fed coded track circuit which is supplied with current coded at the frequency of 75 times per minute by a code transmitter 75CT, and which includes a code following track relay STR connected across one end of the section, and a second code following track relay, designated by the reference character 6TR, connected across the opposite end of the section. Each of the relays 5TR and 6TR controls a track repeater relay through a decoding transformer F.

The mechanism In and lamp i for each signal are normally deenergized, and become energized when a train approaches their signal in the direction of trafiie movements governed by their signal.

Having described, in general, the arrangement and control of the apparatus shown by the accompanying drawings, I shall now describe, in detail, its operation.

As shown by the drawings, all parts of the apparatus are in their normal condition, that is, switches aw, bw, cw, and dw are in their normal position; each signal mechanism m is deenergized, and each signal lamp 1' is unlighted; each of the code transmitters 75CT and CT is energized; switch repeater relays 0P, bP, 0P, and dP, track relays ITRN, 120CF, 75CF, 4TRN, STR, 6TR, 7TRN, and IOTRN, and decoding track repeater relays IDP, lTNP, 2TP, 3TP, 4DP, 4TNP, 5T1, 6TP, 7DP, 7TNP, 8TP, 9TP, 10DP, and 10TNP are in the picked-up condition; and track relays lTRR, 4TRR, 7TRR and 10TRR, and decoding track repeater relays lTRP, 4TRP, 7TRP and 10TRP are deenergized.

The circuit by which relay aP is energized passes from terminal B of a suitable source of current, through contact 15 operated in conjunction with switch aw, and the winding of relay al to terminal N of the same source of current. Each of the relays bl, cP and d? is energized by a similar circuit.

Each of the code transmitters 75CT and 120CT is constantly connected across terminals B and N, so that each of the code transmitters is constantly moving its contacts between closed and open positions at the frequency of 75 or 120 times per minute for which it is designed.

The contacts of each of the code transmitters 75CT are therefore repeatedly moved alternately to their front and back positions 75 times per minute. Similarly, the contacts of each of the code transmitters 120CT are repeatedly moved alternately to their front and back positions 120 times per minute. The circuit by which relay 120CF for section ab is periodically energized passes from a suitable source of current, such as a battery 13, through the front point of contact 16 of relay bP, rail 1a of section ab, contact 17 of relay bP, rail 1a of section ab, contact 17 of relay aP, rail 1a of section a-b, winding of relay 120CF, contact 18 operated in conjunction with switch aw, back point of contact 19 of a code transmitter 75CT, rail 1 of section a.b, and the front point of contact 20 of a code transmitter 120CT, back to battery 13. The circuit by which relay 75CF for section a--b is periodically energized passes from battery 13 at the west end of section ab, through the front point of contact 16 of relay aP, rail 1a of section a-b, front point of contact 17 of relay aP, rail 1a of section a-b, front point of contact 17 of relay bP, rail in of section a-b, contact 18 operated in conjunction with switch bw, winding of relay 75CF, back point of contact 20 of code transmitter 1'20CT, rail 1 of section ab, and the front point of contact 19 of code transmitter 75CT, back to battery 13. Relays 120CF and 75CF for section e-f are energized by circuits which are similar to the circuits just traced for relays 120CF and 75CF, respectively, for section ab.

With relay 120CF for the west end of section ab repeatedly moving its contact 21 between front and back points, primary winding y of decoding transformer 2F is repeatedly energized, alternately in opposite directions, by current passing from terminal B through the front and back points of contact21 of relay 120CF, and upper and lower portions, respectively, as shown in the drawing, of winding y, to terminal N. Alternating current is thereby generated in secondary winding n of transformer 2F, and is rectified by the front and back points of contact 22 of relay 120CF for energizing track repeater relay ZTP. Decoding transformer 3F and track repeater relay 3T? are controlled by relay 75CF at the east end of section a-b similarily to the manner described in which transformer 2F and relay 2TP are controlled by relay 12iiCF at the west end of section ab. Transformers 8F and 9F and relays 8TP and 9TP for section ef are controlled similarly to the corresponding transformers and relays for section a.b as just described.

Relay 4TRN for section b-c is energized by current of normal polarity in a circuit passing from battery 13 at the east end of section b-c, through the front point of contact 23 of relay STP, contact 24 of code transmitter 75CT, rail 1a of section b-c, windings of relays 4TRR and 4TRN in series opposition, rail 1 of section b-c, and the front point of contact 25 of relay STP back to battery 13. Relay 4TRN responds to the coded current of normal polarity, thus supplied to section b-c, by repeatedly moving its contact 26 between its front and back points, whereas contact 28 of relay 4TRR remains constantly closed at its back point.

During the periods when contact 26 of relay 4TRN is closed at its back point, relay 4DP is energized by current passing from terminal B, through the back point of contact 26 of relay 4TRN, back point of contact 28 of relay 4TRR, and the winding of relay 4DP in multiple with the high resistance direction of asymmetric unit I, to terminal N. During the periods when contact 26 of relay 4TRN is closed at its front point, relay 4TNP is energized by current passing from terminal B, through the front point of contact 26 of relay 4TRN, contact 27 of relay 4DP, and the winding of relay 4TNP in multiple with a path through a resistor r and a condenser u to terminal N. Relays lTRN, 7TRN, and IGTRN are energized similarly to relay 4TRN as previously described. Relays IDP, 7D? and DI are also energized similarly to relay 4DP, and relays lTNP, 7TNP and itlTNP are energized similarly to relay 4TNP.

Relay STR is energized by current supplied by a battery13 at an intermediate point of section b-c, through contact 54 of a code transmitter 75CT. Relay STR, being of the code following type, therefore repeatedly moves its contacts 21 and 22 between their front and back points, and thereby effects energization of relay STP from transformer 5F. Relays 6TR and 6TP are 6 energized similarly to relays 5TR and STP, respectively, as just described.

I shall assume that, with apparatus embodying my invention, as shown in the drawings, thus in the normal condition, an eastbound train approaches signal 28 and deenergizes relay ITRN, which in turn deenergizes relay iTNP. With relay ITNP deenergized, mechanism 2m of signal 28 becomes energized by current passing from a suitable source, such as a battery 14 shown adjacent the mechanism 3m for signal 38, through the front point of contact 30 of relay 4TNP, contact 31 of relay 3TP,

control conductor 32, contact 33 of relay 2TP, back point of contact 34 of relay lTNP, mechanism 2m, back point of contact 35 of relay lTNP, control conductor 35, and the front point of contact 37 of relay 4TNP, back to battery 14. At the same time, lamp 21' of signal 28 becomes lighted by current passing from terminal EB of a suitable source of lighting current, through contact 38 of relay 1TNP, and lamp 2i to terminal EN of the same source of lighting current. With mechanism 2111 thus energized and lamp 2i lighted, signal 28 displays the clear proceed indication.

The eastbound train, upon passing signal 28 into section ab, shunts both track circuits for this section, thereby deenergizing both of the track relays 75CF and 126CF for section a-b. With relay 120CF deenergized, relay 2T1 becomes deenergized, and therefore the circuit for mechanism 2m of signal 25 becomes opened at contact 33 of relay ZTP, causing signal 25 to indicate stop. Signal 23 will continue to display the stop indication as long as lamp 21' remains lighted because of the deenergization of relay ITRN by the train.

With relay 75CF deenergized, relay 3TP is also deenergized, so that mechanism 4m of signal 48 is now energized by current passing from battery 14 adjacent signal 88, through the back point of contact 40 operated in conjunction with mechanism 8m of signal 88, front point of contact 41 of relay 8TP, front point of contact 42 of relay 6TP, front point of contact 43 of relay 5TP, control conductor 44, back point of contact 45 of relay 3TP, mechanism 4m, back point of contact 46 of relay 3TP, contact 47 of relay 4TNP, control conductor 49, front point of contact 50 of relay STP, front point of contact 51 of relay 6TP, contact 47 of relay 7TNP, front point of contact 52 of relay STP, and the back point of contact 53 of mechanism 8m, back to battery 14. With relay 3T1 deenergized, lamp 4i of signal 48 is lighted by a circuit passing from terminal EB, through contact 39 of relay 3T1, and lamp 41' of signal 48 to terminal EN. With mechanism 4m energized and lamp 4i lighted, signal 45 now displays the clear proceed indication.

When the train enters section bc, deenergizing relay 4TRN, relay iTNl, in turn, becomes deenergized, and therefore its contact 47 opens the circuit traced for mechanism 4m, causing signal 45 to now display the stop indication. Signal 48 will then continue to display the stop indication as long as lamp 4i is lighted because of relay 3TP being deenergized by the train on section a-b.

When the train enters section c-d, relay STR becomes deenergized, causing relay STP in turn to also be deenergized. The train, upon entering section cd, also deenergizes relay 6TR, causing relay 6TP to in turn be deenergized. With relay 6TP deenergized, mechanism 6m of signal becomes energized by current of reverse polarity passing from battery 14 adjacent relay STP in Fig. 10, through the back point of contact 40 operated in conjunction with signal mechanism 8m, front point of contact 41 of relay STP, back point of contact 42 of relay 6TP, mechanism 6m, back point of contact 51 of relay 6TP. contact 47 of relay '7TNP, front point of. contact 52 of relay 8T5, and the back point of contact 53 operated in conjunction with signal 8m back to battery 14. At the same time, lamp 6i of signal 68 becomes lighted by a circuit which is similar to the circuit shown for lamp 5i of signal 58. Signal 65, therefore, displays the caution indication.

With relay 6TP deenergized, a circuit is completed for energizing relays 7TRN and 7TRR by current of reverse polarity, this circuit passing from battery 13 adjacent signal mechanism 6M, through the back point of contact 25 of relay 6TP, rail 1 of section d-e, windings of relays 7TRR and 7TRN in series, rail 1a of section de, contact 24 of code transmitter CT, and the back point of contact 23 of relay 6TP back to battery 13. With relays 7TRN and 7TRR now energized by current of reverse polarity, relay 7TRR responds by repeatedly moving its contact 28 between its front and back points, and contact 26 of relay 7TRN ceases to move between its front and back points and remains closed at its back point. Relay 7TNP is therefore now deenergized, and relay 7TRP becomes energized by its circuit passing from terminal B, through the back point of contact 26 of relay 7TRN, front point of contact 28 of relay 'YTRR, contact 29 of relay 7DP, and the winding of relay 7TRP in multiple with a path through a resistor r in series with a condenser 11, to terminal N.

A second circuit is now completed for mechanism 511:, which is the same as the circuit previously traced except that it includes contact 48 of relay '7TRP instead of contact 47 of relay 7TNP.

With relay 7TNP deenergized, mechanism 8m of signal SS becomes energized by its circuit passing from battery 14 adjacent signal 108, through the front point of contact 30 of relay IOTNP, contact 31 of relay 9T1 control conductor 32, contact 33 of relay STP, back point of contact 34 of relay 7TNP, mechanism 8m, back point of contact 35 of relay 7TNP, control conductor 36, and the front point of contact 37 of relay 10TNP, back to battery 14. With relay 7TNP deenergized, lamp 8:" of signal 88 is lighted by a circuit passing from terminal EB, through contact 38 of relay 7TNP, and lamp 81' to terminal EN. With mechanism 8111 thus energized and lamp 8i lighted, signal 88 will now display the clear proceed indication.

When mechanism 8112 is moved to its clear position, contacts 40 and 53 operated in conjunction with mechanism 8m become closed at their front points, so that now mechanism 6111 becomes energized by current of normal polarity in a circuit which is the same as the circuit previously traced for this mechanism except that it includes the front points of contacts 4t) and 53 of signal mechanism Sm instead of the back points of these contacts. Signal 65 therefore now changes from the caution to the clear proceed indication.

When the train enters section d-e. relay TFRR becomes deenergized, so that relay 7TRP, in turn, also becomes deenergized. Mechanism 6m of signal 65 is then deenergized by the opening of contact 48 of relay 7TRP, so that signal 65 changes from the clear proceed to the stop indication.

When the train enters section e-f, the operation of the apparatus at passing siding Y is similar to that previously described for the apparatus at siding X when the train entered section ab.

I shall now assume that all parts of the apparatus are again in the normal condition, and that an eastbound train passes signal 28 onto section nb, causing signal 48 to display the clear proceed indication, as previously described. I shall assume further that a westbound train approaches signal 98, deenergizing relay IOTRN, which in turn deenergizes relay IOTNP, so that mechanism 9m becomes energized by a circuit which is similar to the circuit previously traced for energizing mechanism 8m when an eastbound train approached signal 88. Lamp 91' for signal 98 becomes lighted by a circuit which is similar to the circuit previously traced for lamp 8: of signal 88.

I shall also assume further that the westbound train passes signal 98 before the eastbound train reaches signal 48, so that relays 75CF and 120CF for section e-J become deenergized. With this relay 75CF deenergized, relay 9TP also becomes deenergized, causing mechanism 9m in turn to also be deenergized, so that signal 98 will now indicate stop.

With relay 120CF for section deenergized, relay STP is in turn deenergized, but mechanism 7111 does not become energized because relay STP at section a-b has already been deenergized by the eastbound train on section n-b. With relay 8TP deenergized, mechanism 4/12 for signal 43 becomes deenergized. Signal 45 will therefore display the stop indication for the eastbound train, and signal 78 Will display the stop indication for the westbound train.

One of the trains will then take a passing siding allowing the other to clear on the main track in accordance with established priority.

I shall next assume that all parts of the apparatus are again returned to the normal condition, and that a westbound train approaches signal 95 while an eastbound train is approaching signal 48 on section ab. I shall 8 assume further that the westbound train stops, and that a trainman reverses switch dw at the east end of siding Y for the westbound train to move onto siding Y so that the eastbound train can pass the westbound train at this siding.

When switch dw is moved away from its normal position, contact 15, which is operated in conjunction with this switch, opens the circuit for relay (11, causing relay (1P to become deenergized. Contact 18, also operated in conjunction with switch dw, becomes opened when switch dw is moved away from its normal position, thereby causin g relay 75CF at the east end of section e-f to become deenergized which in turn causes relay 9TP to become deenergized.

With relay [1P deenergized, a portion of the rail 1a of section ef between insulated joints 12 adjacent switch dw and signal 98 is by-passed in a track circuit which includes relay 120CF for section e-f. Relay 120CF is therefore now energized by current passing from battery 13 adjacent switch a'w, through the back point of contact 16 of relay dP, rail 1a of section ef, front point of contact 17 of relay cP, rail 1a of section ef, winding of relay 120CF, contact 18 operated in conjunction with switch cw, back point of contact 19 of code transmitter 75CT, rail 1 of section ef, and the front point of contact 20 of code transmitter 120CT, back to battery 13.

Relay 8TP will therefore also be energized, and signal mechanism 4m will be energized, as previously described, because of the eastbound train on section a-b. Signal 48 will therefore display the clear proceed indication for the eastbound train.

It follows that the presence of the westbound train on section ef, moving onto siding Y over switch dw, does not cause signal 48 to indicate stop, and so the eastbound train may proceed past signal 48.

When the westbound train has moved off of section e-f onto siding Y, relay 75CF for section ef will still be deenergized while switch dw is in its reverse position causing its contact 18 to be open. With relay 75CF for section ef deenergized, relay 9TP will be deenergized, and so signal 98 cannot clear for a following train, and signal 88 cannot clear for the eastbound train. Therefore, if, while switch dw is still in its reverse position, the eastbound train enters section c--d, signal 88 cannot clear on account of relay 9T1 being deenergized, mechanism SM remains in its deenergized position, contacts 40 and 53 remain in the position as shown on Fig. 1c in which current of reverse polarity is applied to mechanism 6M and therefore signal 65 will display the caution indication for the eastbound train.

I shall now assume that all parts of the apparatus are again in the normal condition, and that an eastbound train passes signals 28 and 48 onto section b-c, and that a westbound train approaches signal 98, causing signal to clear as previously described. I shall assume further that the eastbound train enters section cd before the westbound train reaches signal 98. With the eastbound train on section cd, relay 6TP will be deenergized, so that relay 7TNP will also be deenergized and relay 7TRP will be energized as previously described.

With relay 10TNP deenergized because of the westbound train approaching signal 95, signal 88 cannot clear for the eastbound train, and therefore signal 68 will display the caution indication. With relay 7TNP deenergized because of the eastbound train, signal 98 will be controlled to indicate stop for the westbound train, while the eastbound train will receive a stop indication from signal 88.

Assuming that the westbound train had orders to take the passing siding upon meeting the eastbound train it would have been traveling in anticipation of stopping prior to reaching switch dw and could now proceed into the siding under flag protection. However, in any event, the signal indications would be such as to stop the trains before a collision would occur.

From the foregoing description, it follows that, with all switches in the normal position, the control for each leaving head block signal is overlapped to the entering signal at the remote end of the next passing siding in advance, that is, with all switches in the normal position, the control circuit for leaving head block signal 48 extends to entering signal 98 at the opposite end of siding Y, and the control circuit for leaving head block signal 78 extends to entering signal 28 at the opposite end of siding X. v I

When switch dw at the east end of siding Y is reversed, the control for signal 48 extends only to the insulated joint 12 adjacent switch dw, and similarly, when switch aw is reversed, at the west end of siding X, the control for signal 78 extends only to the insulated joint 12 adjacent switch aw.

It also follows, from the foregoing description, that the control for each entering head block signal is overlapped to the approach signal for the next entering signal in advance which governs traflic movements in the same direction, so that the control for signal 98 extends to signal 58, and the control for signal 85 extends to the approach signal for the next eastbound entering signal similarly to the arrangement shown for controlling signal 28 to signal 68.

I have described the operation of the apparatus for only a few typical traflic movements. It is believed that, in view of those descriptions, the operation of the apparatus for any other possible trafiic movement can be readily traced on the accompanying drawings.

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 in vention.

Having thus described my invention, what I claim is:

l. A signal location and control arrangement for a stretch of single track railway which is provided with passing sidings spaced along said stretch, comprising in combination, two pairs of head block signals for each passing siding each pair comprising an entering and a leaving signal located one pair adjacent each end of each passing siding, means controlled by traffic conditions for controlling each entering signal for each siding to display a stop or a proceed indication according as said stretch of track is occupied or unoccupied between that entering signal and a point beyond the opposing entering signal for the next siding, a track switch located adjacent each end of each passing siding, means controlled by trafiic conditions for controlling each leaving signal to display a stop or a proceed indication according as said stretch of track is occupied or unoccupied between each leaving signal and the opposing entering signal for the next siding if the track switch adjacent said opposing entering signal at the next siding is in its normal position, a short insulated track section for each track switch, said short insulated track section including the portions of said stretch of track and of the siding lying on each side of the associated track switch, and means for eliminating from the control of each leaving signal the traflic conditions for the short insulated track section of said stretch of track between the opposing entering signal at the next siding and said adjacent track switch during the times when said adjacent track switch is in its reverse position.

2. In combination, a section of railway track including a switch, an insulated joint in one rail of said track section, a switch repeater relay controlled in conjunction with said switch to be energized only if said switch is in its normal position, a circuit path including a front contact of said switch repeater relay connected with said one rail around said insulated joint, a track circuit including a suitable source of current connected across the rails of one end of said section through a front contact of said switch repeater relay and including a track relay connected across the rails of the opposite end of said section, means including a back contact of said switch repeater relay for connecting said source of current between the other rail of said section and said one rail on the opposite side of said insulated joint from said one end of said section, and traffic governing means controlled by said track relay.

3. In combination, a section of railway track including two switches one adjacent each end of said section, a source of current and a track relay connected across a given end of said section through contact means closed only if the adjacent switch is in its normal position, an auxiliary insulated joint in one of the rails of said section adjacent each of said switches, means including a contact which is closed only if the switch adjacent said given end of said section is in its reverse position for connecting said source of current between the opposite rail and said one rail on the opposite side of the adjacent auxiliary insulated joint from said given end of said section, a second source of current and a second track relay connected across the opposite end of said section through contact means closed only if the switch adjacent said opposite end of said section is in its normal position, means including a contact which is closed only if said second switch is in its reverse position for connecting said second source of current between the opposite rail and said one rail on the opposite side of the adjacent auxiliary insulated joint from said opposite end of said section, and traffic governing means controlled by said track relays.

4. In combination, a section of railway track including two switches one adjacent each end of said section, a track circuit including a source of current connected through a front contact of a given coding device across a given end of said section and including a track relay connected through a back contact of a second coding device across the opposite end of said section, means controlled in conjunction with the switch adjacent said given end of said section for by-passing a portion of said section in said track circuit when the switch is moved to its reverse position, a second track circuit including a second source of current connected through a front contact of said second coding device across said opposite end of said section and including a second track relay connected through a back contact of said first coding device across said given end of said section, means controlled in conjunction with the switch adjacent said opposite end of said section for by-passing a portion of said section in said second track circuit when this switch is moved to its reverse position, and signal apparatus controlled by said track relays.

5. In a signal location and control arrangement for a stretch of single track railway which is provided with passing sidings spaced along said stretch, and wherein there is provided a pair of head block signals for each end of each passing siding, each pair comprising an entering and a leaving signal and each of said entering and leaving signals controlled by trafiic conditions to display only a stop indication or a clear indication, the combination of a first entering signal for one of the passing sidings, an approach signal located a sufficient distance in the rear of said entering signal to provide double braking distance between the approach signal and the first entering signal, an approach track section in the rear of said approach signal, a track circuit for said approach track section which is normally energized but which becomes deenergized when a train approaches said approach signal through said approach track section, a track circuit for the portion of said track between said approach signal and its associated entering signal, said track circuit being normally energized by current of normal polarity but becoming energized by current of reverse polarity in response to a train entering said approach track section, a second entering signal for the next passing siding in advance, an approach signal for said second entering signal, means controlled by trafiic conditions in advance of the approach signal for the first entering signal up to the approach signal for the second entering signal and including said track circuit for said portion of said track upon becoming energized by current of reverse polarity for controlling said first entering signal to display a proceed indication or a stop indication, a pair of head block signals at the remote end of said one of the passing siding-s and means, including said track circuit for said approach track section upon becoming deenergized, for controlling the approach signal associated with said first entering signal to display a caution or a clear indication according as said first entering signal is controlled to display a stop or proceed indication, and further means to cause the approach signal associated with the first entering signal to display a stop indication in response to the presence of a train on said single track at any point between the approach signal and the pair of head block signals at the remote end of said one of the passing sidings.

References Cited in the file of this patent UNITED STATES PATENTS 531,284 Wilson Dec. 18, 1894 1,194,116 Abernethy Aug. 8, 1916 (Other references on following page) 11 Wight Feb. 18, Wight Apr. 8, Wight Apr. 8, Wight Apr. 8, Spray Jan. 27, Pfiasterer Oct. 18, Pflasterer May 13,

12 Thompson May 19, 1942 Kemmerer July 14, 1942 Young et a1 Sept. 29, 1942 Scheg Jan. 9, 1945 Langdon Jan. 1, 1946 Nicholson Feb. 8, 1949 Fereday Dec. 23, 1952

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