US2623162A

US2623162A - Railway signal control system

Info

Publication number: US2623162A
Application number: US769466A
Authority: US
Inventors: Sr Frederick T Fereday
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1947-08-19
Filing date: 1947-08-19
Publication date: 1952-12-23
Anticipated expiration: 1969-12-23

Description

Dec. 23, 1952 FQT. FEREDAY, SR

RAILWAY SIGNAL CONTROL SYSTEM 4 Sheets-Sheet 1 Filed Aug.' 19. 1947 INVEN TOR. Fred c1: 7. ieredayild BY g. qt]- His Aiioz'ney Dec. 23, 1952 F. 'r. FEREDAY, SR

RAILWAY SIGNAL CONTROL SYSTEM 4 Sheets-Sheet 2 Filed Aug. 19. 1947 INVENTOR. Zfleredzzy S1: BY C I Hvde His Attorney 4 Sheets-Sheet 3 IN VENT 0R.

W m m T r. M

His Aztbrney F :r FEREDAY SR RAILWAY srcmu. CONTROL SYSTEM Dec. 23, 1952 Flled Aug 19 1947 1952- F. "r. FEREbAY, SR 2,623,162

RAILWAY SIGNAL CONTROL SYS Filed Aug. 19, 1947 4-"Shee'ts- Sheet 4 d y f v. .4 \I fi-Y L 5- Q INVENTOR. Frederz" flleredayiz BY g 7 Patented Dec. 23, 1952 UNITED STATES PATENT OFFICE RAILWAY SIGNAL CONTROL SYSTEM Frederick T. Fereday, Sr., Louisville, Ky., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application August 19, 1947, Serial No. 769,466

My invention relates to a railway signal control system, and particularly to arailway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks, each of which is provided with a signal comprising a lamp and a mechanism,.both operated by primary battery energy, for governing trafilc movements in a given direction'through its block.

In a railway signaling system embodying signals each of which comprises a lamp and a mechanism operated by power from primary batteries, it is desirable to energize the signal lamps and mechanisms for minimum periods of time in order to conserve the primary batteries. It is also desirable to accomplish this result with -a control system which embodies a minimum number of line control conductors.

' One feature of my invention is the provision of an arrangement in which all signalv lamps and mechanisms are normally inoperative, and each lamp or mechanism becomes operated only when a train approaches its signal.

Another feature of my invention is the provision by which the continuity of each signal lamp filament is checked by including it inv the control circuit for a pole-changing relay for its signal.

Another feature of my invention is the provision of a signal lighting circuit which includes a back contact of the pole-changing relay for its signal in addition to a back contact of ..a track relay for the next block in the rear of, its signal.

The pole-changing relay is made slowreleasing by a condenser connected in multiple withits control winding, and is controlledto be energized previous to the time its signal mechanism becomes operated in response to an approaching train, and to become deenergized at the time of this operation of its signal mechanism. The pole-changing relay, on account of being slow releasing, prevents lighting of the signal lamp until its signal mechanism has been operated to its final position in response to an approaching train, and thereby prevents a red flash of the signal lamp before a yellow or a green indication is displayed.

Another feature of my invention is the provision of an approach stick relay for each signal having a pick-up and a stick circuit each of which is controlled by a front contact of a track relay for the first block in the rear of its signal, and by a front contact. of a track relay for the first block in advance of its signal, and the pickup circuit is also controlled by a second approach 16 Claims. (01. 246-53) relay for its signal, which is controlled by a front contact of a track relay for the first block in the rear of its signal and by a back contact of atrack relay for the second block in the rear of its signal. The stick circuit prevents release of the approach stick relay if the second approach relay becomes deenergized during operation of the pole-changing contacts which control the next signal in the rear.

Still another feature of my invention is the provision of a control circuit for each signal mechanism which includes the winding of an approach relay for the next signal in advance, in which the parts are so proportioned that the signal mechanism will be operated by this circuit but theapproach relay for the next signal in advance will not be operated. When a train approaches, an auxiliary path is connected in multiple with the signal mechanism so that the approach relay for the next signal in advance will then be operated.

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

In the accompanying drawings, Fig. l is a diagrammatic view showing one form of apparatus embodying my invention, in which an approach relay for each signal is controlled in series with its signal mechanism by a front contact of a track relay for the first block in the rear of its signal, and is controlled by track circuits between its signal and the next signal in advance, and in which each signal mechanism is controlled by a circuit which is the same as thatfor its approach relay except that it includes-a back contact of the track relay for the first block in the rear instead of a front contact I of the track relay for the block in the rear and the control winding of the approach relay, and also in which a pole-changing relay for each signal is controlled by a circuit which includes the filament of the signal lamp and a front con tact of its approach relay and which also includes a condenser in multiple with the control winding of the pole-changing relay, and in which a lighting circuit for each signal lamp includes a back contact of its pole-changing relay in series with a back contact of the track relay for the next block in the rear; Fig. 2 is a diagrammatic view showing a modified form of the apparatus of Fig. 1, in which an approach relay placed similarly to the approach relay shown in Fig. 1 is provided with a stick circuit as well as a pick-up circuit, so that it is here an approach stick relay, and a second approach relay is provided for each signal and its controlled by the control circuit for the next signal in the rear; Fig. 3 is a diagrammatic view showing another modified form of the apparatus of Fig. 1, in which the approach relay of Fig. 1 is omitted, but another approach relay for each signal is included in the control circuit for the mechanism for the next signal in the rear but is not operated by this circuit alone but becomes operated when an auxiliary path is connected in multiple with the mechanism of the next signal in the rear when a train approaches; and Fig. 4 is a diagrammatic view showing still another modified form of the apparatus of Fig. 1, in which the approach relay of Fig. 1 is omitted, but another approach relay for each signal is included in the control circuit for a control relay for the next signal in the rear, and in which a slow releasing relay for each signal for controlling its lamp is controlled by its approach relay and by a'front contact of a track relay for its block.

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

Referring first to Fig. 1, a stretch of railway track is shown, over which traffic movements are made in the direction indicated by the arrow, which I shall assume is the eastbound direction. Rails I and la of the stretch'of track are divided by insulated joints 2 to .form blocks b-d and d Each of these blocks is further :divided by other Jinsulated joints 2 to form sections b-c, c-d, de and e). A section ab of a block in the rear of 'blockb-d, and a section f-g.of a block in advance of block ldf are also shown in the drawing.

Signals designated by the reference characters 48, 6S and as for blocks bzi, d-f 'andrtheblock in advance of block d--f, respectively, are shown adjacent the entering ends of these blocks for governing traffic movements into the respective blocks. These signals may be of any suitable design such, for example, as the well-known Searchlight type comprising a mechanism or operative element m anda lamp 2'.

Each track section is provided with a track circuit including a suitable source of current such as a battery 3 connected across the railsadjacent one end of the section, and a track relay designated by the reference character R with a prefix including the numeral for the reference character for the signal for its block.

Approach relays, designated by the

reference characters

4A, 6A and 8A are provided for

signals

6S, 6S and 88, respectively, and a pole-changing relay is also provided for each signal such, for example, as relays SP and BP for signals 68 and BS, respectively. A condenser r is connected in multiple with the control winding of each of the pole-changing relays, as shown for relays SP and 8P, in order to make these relays slow in releasing.

Each approach relay is controlled by a circuit which includes its Winding in series with mechanism m of its signal, as shown, for example, for relay 6A, but its signal mechanism is not operated by this circuit. This circuit 'is controlled by a front contact of a track relay'for the first track section in the rear of its signal such, for example, as relay A4R, and by a front contact of one or more track relays for the block for its signal, such as relays BR and ASR, and includes pole-changing contacts of the pole-changing relay for the next signal in advance, such as contacts 4 and 8 of relay 8P. Each-signal mechanism m is controlled by a circuit which is the same as the cir- 4 cuit for its approach relay except that it includes aback contact of a track relay for the next block in the rear, such as relay A4R, instead of a front contact of this track relay and the control windingof the approach relay.

Referring next to Fig. 2, the track and signal arrangement is the same here as in Fig. l. The

approach relays

4A, 6A and 8A shown in Fig. 1 are replaced by stick approach relays designated by the reference characters 4A8, BAS and 8AS, respectively. A second or auxiliary approach relay is here provided for each signal, such as relays 4AA, 6AA and 8AA for signals 4S, 6S and 88, respectively. The control winding of each auxiliary approach relay is included in series with the mechanism of the next signal in the rear in the pick-up and stick circuits for the stick approach relay for the next signal in the rear, but the auxiliary approach relay is not operated by this circuit. Each auxiliary approach relay is also includedin a control circuit forthe 'mechanism for the next signal in the rear, and

is operated by thiscircuit. Each pole-changing relay is here controlled by a circuit which includes only a front contact of thestick approach relay for its signal.

Referring now to Fig. 3, the

approach relays

4A, 6A and 8A, shown in .Fig. 1, are here omitted. Other approach relays, designated by the reference characters 4A3, GAB and BAB, are here included in thesignal mechanism circuits similarly to relays 4AA, 6AA and 8AA, respectively, shown in Fig. 2. but are not operated by these signal mechanism circuits alone. In Fig. 3, a resistor t is connected in multiple with each signal mechanism .m through a back contact of the track re- .layfor thenextsection in the rear when a train approaches its signal, for effecting operation of the approach relay for the next signal in advance.

Eachof the Dole-changing relays 4P, GP and .BP is here controlled by a circuit which includes'a front contact of the track relay for the first section in the rear of its signal, and includes a contact closed by it signal mechanism when its signal mechanism is in the caution position only.

Each signal mechanism m becomes operated, to the position by displaying the yellow or caution indication, by a circuit which includes a front contact of its approach relay such, for example, as shown for signal 68, the mechanism m ofwhich becomes energized by a circuit including a front contact of relay GAB. Mechanism m of signal 63 is then retained energized by a circuit which includes a'frontscontact of its pole-changing relay 6P. Each signal mechanism m becomes operated'to the position for displaying the green or clear indication by a circuit which includes a back contact of the track relay for the first 'section'in the rear of its signal.

iii)

. series with the signal control relay 6H for signal 68. Each signal mechanism m is here controlled similarly to mechanism m forsi nal ES which shown controlled by its approach relay GAC and by itssignal control relay 6H. Each of the relays f4? and 8P is here controlled similarly to relay -6P which is shown controlled by a back contact of the approach relay for its signal and by a front contact of a track relay for the block for its signal, and is made slow releasing by an asymmetric unit which may, for example, be a half wave copper oxide rectifier, connected with its high resistance direction in multiple with the .winding of relay 6?.

Each signal lamp is controlled similarly to lamp 2' for signal BS for which one lighting circuit is shown including back contacts of its signal mechanism and back contacts of its signal control relay 6H and of its slow releasing relay BP, and for which a second lighting circuit is shown including operation in detail.

As shown in Figs. 1 Z and 4 of the drawings, all parts of the apparatus are in the normal condition, that is, each of the signal mechanisms -m is in the position for displaying a stop indication; each signal lamp 2' is unlighted; each track section is unoccupied, so that the track relays are energized; each of the

relays

4A, 6A, 8A, 6? and BP in Fig. 1, and relays 6A0, 8A0, 6H and 81-1 in Fig. 4 is energized; and relays AAS, SAS, 8AS, 4P, 6P, 8?, AAA, 6AA and 8AA in Fig. 2, and relay 6? in Fig. 4 are deenergized.

In Fig. 1, the circuit by which relay 6A is energized passes from terminal B of a suitable source of current, through the front point of contact a of relay 8P, front point of contact 5 of relay ASR, contact 6 of relay 6R, front point of contact I of relay A lR, winding of relay 8A, mechanism m of signal 66, and front point of contact 8 of relay 8P, to terminal N of the same source of current.

- Relays 5A and 8A are energized by similar circuits.

Relay SP is energized by a circuit passing from terminal B, through the filament of lamp i of signal 58, contact 9 of relay 5A, and the winding of relay BP in multiple with condenser r to terminal N. Relay HP is energized by a circuit which is similar to the circuit just traced for relay 6?.

I shall assume that, with apparatus arranged as shown in Fig. 1, an eastbound train enters section deenergizing relay AZR. Relay 4A becomes deenergized because of the opening of contact 1 of relay AZR at its front point, and mechanism m of signal 48 becomes energized by its operating circuit which includes the back point of contact 1 of relay AZR. This operating circuit is energized by current of normal polarity passing from terminal B, through the front point of contact 4 of relay 6?, front point of contact 5 of relay Adi-t, contact 6 of relay 4R,'back point of contact! of relay AZR, mechanism 712, of signal 48, and the front point of contact 8 of relay GP to terminal N. Mechanism m of signal 48 is operated by this circuit to the proceed position, and lamp i of signal 4S becomes lighted by a circuit which is similar to that which I shall trace for signal 68 as controlled by the arrival of the train on section c-d.

When the train enters section bc, contact 6 of relay dR. opens the circuit just traced for mechanism m of signal 46, causing the mechanism m to move to the stop position.

When the train enters section cd, relay BA becomes deenergized because of the opening of contact I of relay A4R at its front point, and mechanism m of signal (is becomes energized by current of normal polarity in a circuit which is similar to the circuit previously traced for mechanism m of signal 48. When relay BA becomes deenergized, its contact 9 opens the circuit for 6 relay 6P, causing relay GP to become deenergized. Since relay SP is slow releasing, the back point of its contact 4 does not close until after mechanism m of signal 68 has been operated to the proceed position.

Lamp i of signal 68 therefore does not become lighted until after mechanism m of signal 68 has left its stop position, and hence signal 68 does not display a red flash just before it displays a proceed or green indication. The circuit for lighting lamp i, when contact 4 of relay 6P closes at its back point, passes from terminal B, through the. filament of lamp 2' of signal 6S, back point of contact 5 of relay AAR, and the back point of contact 4 of relay GP to terminal N.

When the train enters section d--e, contact 6 of relay 6R opens the control circuit for mechanism m of signal 58, causing this mechanism m to "move to the stop position. Lamp i of signal 68 will then remain lighted while the train is in block d], as long as any portion of the train still remains in section cd, or if a following train enters section cd while the first train is in block df.

I; shall assume that, after the first train has left block df, and while it occupies section ,f-g, a second eastbound train enters section c-d. With the first train in section f-g, relay 8A will be deenergized because contact 6 of relay 8R will be open. With relay 8A deenergized, relay 8P will also be deenergized because contact 9 of relay 8A will be open. With the first train in section fg and the second train in section cd, mechanism m of signal 68 will therefore be energized by current of reverse polarity which is similar to the circuit previously traced for mechanism m of signal except that it includes the back points of contacts 4 and 8 of relay -8P. On account of being energized by current of reverse polarity, mechanism m of signal 6S will occupy the caution or yellow position. Lamp 2' of signal 68 will now be lighted as before, and hence signal 68 will display a yellow indication.

With apparatus arranged as shown in Fig. 2, I shall assume that an eastbound train enters section'ab, causing mechanism m of signal 48 and relay 6AA for signal 68 to be operated by a circuit which is similar to a circuit which I shall presently trace for mechanism m of signal 68 and relay 8AA for signal as when the train enters section cd. Lamp 2 of signal 4S will become lighted by a circuit which is similar to the circuit which I shall presently trace for lamp 2' forsignal 6S.

' 1 When relay 6AA becomes energized in the operating circuit for mechanism m of signal 4S, contact Id of relay 6AA will complete the pick-up circuit for relay BAS for signal BS, this circuit passing from terminal B, through the back point of. contact ll] of relay 8P, front point of contact ll of relay A'GR, contact I2 of relay 6R, front point of contact l3 of relay A4R, contact 14 of relayfiAA, winding of relay GAS, mechanism 112 of signal 6S, back point of contact l6 of relay 6P, and the winding of relay 8AA to terminal N. Relay GAS, upon becoming energized by its pickup circuit just traced, closes its contact l5, thereby completing its stick circuit which is the same as its pick-up circuit except that it includes contact I5 of relay BAS instead of contact M of relay 6AA.

With relay BAS energized, relay 6P becomes energized by a circuit passing from terminal B, through contact I! of relay SAS, and the wind- 7 ingiof relay BP in multiple with a condenser r to terminal N.

When the train enters section 17-0, contact 12 of relay 4R opens the circuit for mechanism m of signal GS, causing the mechanism m of signal 45 to move to the stop position. Relay 6AA also becomes deenergized by the opening of contact I2 of relay 4R, but relay GAS now remains energized by its stick circuit after contact Id of relay 6AA opens.

When the train enters section c-d, causing relay A4R to become deenergized, mechanism m of signal 66 becomes operated by current of reverse polarity in series with the winding of relay 8AA, this circuit passing from terminal B, through the back point of contact It of relay 8P, front point of contact ll of relay AER, contact l2 of relay 6R, back point of contact 13 of relay A4R, mechanism in of signal ES, back point of contact it of relay 8P, and the winding of relay 8AA to terminal N.

If, when the train enters section c-d, a preceding train occupies section f-g, relay 8A8 will not become energized by the closing of contact M of relay 8AA since contact i2 of relay 8R will now be open. When the train enters section c-d, relay GAS becomes deenergized because contact it of relay A lR opens at its front point, and therefore relay 6P will become deenergized because contact F of relay GAS will open. As soon as contact iii of relay 6P closes at its back point, lamp 2' of signal 68 becomes lighted by its circuit passing from terminal B, through the back point of contact It of relay 5P, back point of contact H of relay A lR, and the filament of lamp 1' of signal 63 to terminal N. With mechanism m of signal 6S energized by current of reverse polarity, and with lamp 2 of signal 6S lighted, this signal will now display the yellow or caution indication.

If, however, the block of signal as is clear instead of being occupied by a preceding train, relay 8A8 will become energized, upon the closing of contact M of relay 8AA, by a circuit which is similar to the circuit previously traced for relay GAS. Relay BAS, upon becoming energized, completes a circuit for energizing relay 8? which is similar to the circuit previously traced for energizing relay GP, and relay 8P then closes its contacts i0 and it at their front points. With contacts it and I6 of relay 8P closed at their front points, mechanism m of signal 63 will be operated by current of normal polarity in a circuit which is similar to the circuit previously traced for operating this mechanism by current of reverse polarity except that it includes the front points of contacts It and it of relay 8P instead of the back points of these contacts. Since relay 6P is slow releasing, its contact it] will not close at the back point, when a train enters section c--d, until after mechanism m of signal BS has been moved to the caution or the proceed position. Therefore, signal 68 will not display the stop indication before it displays the caution or the proceed indication.

When the train enters section dP-e, mecha nism m of signal as will become deenergized by the opening of contact 92 of relay 6R, causing signal ES to display the red or stop indication as long as any part of the train is in section cd orif a following train enters section c-d while the first train still occupies block df.

In Fig. 3, I have shown section ab occupied by an eastbound train W, while blocks bd and d are unoccupied. Under these conditions,

signal 48 is displaying a green or proceed indication, mechanism m of signal SS is in the cau tion position, mechanism m of signal BS is in the stop position, and lamps i of signals 68 and 88 are unlighted; mechanism m of signal 4S is energized by current of normal polarity, mechanism m of signal BS is energized by current of reverse polarity, and mechanism in of signal is deenergized; relays GAB, GP and all track relays except relay AZR are energized; relays AZR, AAB, 4P and BP are deenergized; and relay 8AB is energized by current of insufficient magnitude to operate relay BAB for closing its front contact.

The circuit by which mechanism m of signal is is energized by curernt of reverse polarity passes from terminal B, through the back point of contact E8 of relay 8P, front point of contact iii of relay AER, contact 20 of relay GR, contact 2| of relay BAB in multiple with contact 22 of relay 6P, mechanism 172 of signal 6S,- the back point of contact 25 of relay 8?, and winding of relay flAB to terminal N. The winding of relay 8A3 is so proportioned that relay 8AB does not become operated by this circuit, and hence its contact 2i is open. Mechanism m of signal 68, on account of being energized by current of reverse polarity, occupies the caution position, in which its contact 2? is closed. Relay BP is therefore energized by a circuit passing from terminal 8, through contact 26 of relay A4R, winding of relay 6P in multiple with a condenser r, and contact 2'! of mechanism m of signal 68 to terminal N.

With relay 6P thus energized,

contacts

18 and 25 of this relay are closed at their front points, and hence mechanism m of signal 4S is energized by current of normal polarity in a circuit passing from terminal B, through the front point of contact l8 of relay 6P, mechanism m of signal 4S, contact 23 of relay AZR, contact 20 of relay 4R, front point of contact IQ of relay A4R, front point of contact 25 of relay 6?, and the winding of relay SAB' to terminal N. Mechanism m of signal tS, on account of being energized by current of normal polarity, occupies the proceed position, and therefore its contact 2? is open and hence relay 4P is deenergized. With relays AZR and @P deenergized, lamp 2' of signal 48 is lighted by a circuit passing from terminal B, through the back point of contact I8 of relay 4P, back point of contact IQ of relay AZR, and the filament of lamp 2' of signal as to terminal N. Signal 4S is therefore displaying the green or proceed indication.

With relay AER deenergized, a branch path is completed around mechanism 122 of signal 4S, including contact 24 of relay A2R and a resistor t. Because of this branch path being closed inmultiple with mechanism 722 of signal 4S, the winding of relay GAB now receives sufiicient current for operating this relay and closing its contact 2|.

When the train enters section b-c, mechanism m of signal QS becomes deenergized by the opening of contact 28 of relay 4R, and therefore moves to the stop position, causing signal 48 to now display the red or stop indication. Lamp 1' of signal 48 will now remain energized as long as any part of the train occupies section ab, or if a following train enters section a-b while the first train occupies any part of block b--d. Although relay AB becomes deenergized when the train enters section bc, because of the opening of contact 26 of relay 5R, mechanism m of signal 68 Will remain energized by current of reverse'polarity in its circuit including contact 22 of relayBP.

When the train enters section c-d, however,

a branch path including contact 24 of relay A43 and a resistor t will be completed in multiple with mechanism m of signal 6S, causing relay BAB to become energized by current of suflicient magnitude for closing its front contact 2|.

If the block for signal 88 is occupied by a pre; ceding train, mechanism mv of signal 88 will not become energized although contact 2| of relay SAB is,now closed. Contact 21 of mechanismj'm of signal 8S will therefore be open, and there fore relay 81? will be deenergized, so that mechanism m of signal 6S will continue energized in the reverse direction and will therefore remain in the caution position. Signal 68 will therefore display the yellow or caution indication. I

If the block for signal 88 is clear insteadof being occupied by a preceding train, when 'a following train enters section c--d, mechanism m of signal 88 will become energized by current of reverse polarity by closing of contact 2| of relay BAB. Mechanism m of signal 83, upon reaching its caution position, closes its contact 21, thereby completing a circuit for energizing relay 8P which is similar to the circuit previously traced for relay 6P.

Relay 8P, upon becoming energized, completes a circuit for energizing mechanism m of signal (is by current of normal polarity which is similar to the circuit previously traced for energizing mechanism m of signal 48 by current of normal polarity. Relay 6P becomes deenergized by the opening of contact 26 of relay A4R when the train enters section cd, but, on account "of being slow releasing, its contact [8 does not close at its back point for lighting lamp 1 of signal 6S until mechanism m of signal 68 has been operated to the proceed position. Signal 68 therefore does not display a red flash preceding the displaying of the green indication. I

In Fig. 4, the winding of relay 6H is energized by current of normal polarity in a circuit including the winding of relay 8A0, this circuit passing from terminal B, through the winding of relay 8A0, front point of contact 28 of relay 8H, contact 29 of relay 6R, winding of relay 6H, andthe front point of contact 30 of relay 8H to terminal N.

I shall assume that, with apparatus arranged as shown in Fig. 4, an eastbound train enters the first block in the rear of signal 6S, thereby deenergizing relay BAC which has been previously energized by a circuit similar to that previously traced for relay BAC. With relay SAC deenergized, the normal operating circuit for mechanism m of signal 6S becomes closed, passing from terminal B, through contact 3| of relay 6H, contact 32 of relay 6H closed in the normal or left hand position, as shown in the drawing, contact 33 of relay SAC, mechanism m of signal 68,

and contact 34 of relay 61-1 in the normal position, to terminal N. The mechanism of signal nal B, through the back point of contact 38 of mechanism m, front point of contact 35 of mechanism m, front point of contact 38 of relay GP, and the filament of lampi for signal 63, to terminal N. Signal 68 therefore displays the green or proceed indication.

When the train enters block df, relay 6R becomes deenergized and opens its contact 29 in the circuits for relays 6H and 8A0, causing these relays to become deenergized. Mechanism m becomes deenergized by the opening of contact 3! of relay 6H, and therefore moves to the stop position. Relay 6P becomes deenergized by the opening of contact 40 of relay GR, and therefore a second lighting circuit for lamp 2' of signal GS is now completed, passing from terminal B, through the back points of

contacts

36 and 35 of mechanism 111. of signal 68, contact 31 of relay 6H, back point of contact 38 of relay GP, and lamp i to terminal N. Signal 6S therefore displays the red or stop indication as long as the train remains in block f.

When the train enters the block of signal 88, relay 8H becomes deenergized, causing signal 88 to display the stop indication.

When the train leaves block cL-f, relay 6H will become energized by current of reverse polarity because of relay 8H being deenergized and its contacts 28 and 30 now being closed at their back points. Mechanism m of signal 68 will, however, now be deenergized if relay BAC is energized because there is no train in the first block in the rear of signal 68.

If, however, a following train enters the first block in the rear of signal 6S, causing relay SAC to become deenergized while the block of signal 86 is occupied by the first train, the mechanism m of signal 68 will be energized by current of reverse polarity passing from terminal B, through contact 3| of relay 6H, contact 32 of relay 6H closed in the reverse position, mechanism m of signal 6S, contact 33 of relay 6AC, and contact 34 of relay 6H closed in the reverse position, to terminal N. Relay 6P will now be energized as before. Lamp 2 of signal BS will then be energized by a circuit passing from terminal B, through the front point of contact 36 which is closed on account of mechanism 121. being in the caution position, front point of contact 38 of relay GP, and filament of lamp i of signal 68 to terminal N. Signal 6S therefore now displays the yellow or caution indication.

Although I have herein shown and described only a few forms 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 invenion.

Having thus described my invention, what I claim is:

1. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal having an operative element for governing traffic movements in a given direction through its block, the combination comprising, a slow releasing pole-changing relay for each of said signals, an approach relay for each of said signals so proportioned that it will close a front contact if its control winding is connected in series with the operative element for its. signal but its signal operative element will not be operated, a control circuit for each of said approach relays including its control winding in series with the operative element for its signal and controlled by a front contact of a track relay for the next block in the rear of its signal and by traffic conditions between its signal and the next signal in advance of its signal, a control circuit for each of said signal operative elements controlled by a back contact of said track relay for the next block in the rear of its signal and by traific conditions between its signal and the next signal in advance and also by the pole-changing relay for the next signal in advance, and a control circuit for each of said pole-changing relays controlled by a front contact of the approach relay for its signal.

2. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided With a signal having an operative element-for governing trafific movements in a given direction through its block, the combination comprising, a slow releasing pole-changing relay for each of said signals, an approach relay for each of said signals so proportioned that it will close a front contact if its control Winding is connected in series with the operative element for its signal but its signal operative element will not-be operated, acontrol circuit for each of said approach relays including its control winding in serieswith the operative element for its signal and controlled by a front contact of a track relay for the next block in the rear of its signal and by traffic conditions between its signal and the next signal in advance and also by pole-changing contacts of the pole-changing relay for the next signal in advance of its signalfa control circuit for each of said signal operative elements which is the sameas the control circuit for the approach relay for its signal except that it includes a back contact of said track relay for the next block in the rear of its signal instead of the control Winding for the approach relay for its signal and said front contact of said track relay for the next block in the rear of its signal, and a control circuit for each of said pole-changing relays controlled by a front contact of the approach relay for its signal;

3. In a railway signal control system for a stretch of railway trackwhich is divided into a plurality of consecutive blocks each of which is provided with a signalhaving a mechanism and a lamp for governing trafiic movements in a given direction through its 'block, the combination comprising, aslow releasing pole-changing relay and an approach relay for each of said signals, a control circuit for each of said approach relays controlled by a front contact of a track relay for the next block in the rear of its signal and by a front contact of a track relay for the first track circuit in advance of its signal, a control circuit for each of said signal mechanisms controlled by a back contact of said track relay for the next block in the rear of its signal and by trafiic conditions between its signal and the next signal in advance and also" by pole-changing contacts of the pole-changing relay for the next signal in advance, a control circuit for each ofsaid polechanging relays including the filament of the lamp for its signal and controlled by a front contact of the approach relay for its signal, and a lighting circuit for each of said signal lamps controlled by a back contact of the pole-changing relay for its signal and by a back contact of said track relay for the next block in the rear of its signal. v v y '4'. In'combination, a's'tretch of railway track divided into a first section and asecond section in the rear of said first section, a signal having a mechanism and a lamp for governing traffic movements from said second section into said first section, a second signal having an operative element for governing traffic movements through said second section toward said first section, a control circuit for said mechanism for said first signal controlled by trafiic conditions in advance of said first signal, an approach relay for said first signal, a control circuit for said approach relay controlled by a front contact of a track relay for each of said sections, a pole-changing relay, a control circuit for said pole-changing relay including the filament of said lamp for said first signal and controlled by a front contact of said approach relay, a lighting circuit for said lamp controlled by a back contact of a track relay for said second section and by a back contact of said pole-changing relay, and a control circuit for said operative element for said second signal controlled by pole-changing contacts of said polechanging relay.

5. In combination, a stretch of railway track divided into a first section and a second section in the rear of said first section, a signal having alamp for governing trafiic movements from said second section into said first section, a second signal for governing traffic movements through said second section toward said first section, an

approach relay and a pole-changing relay for said first signal, a control circuit for said approach relay controlled by a front contact of a track relay for each of said sections, a control circuit for said pole-changing relay including the filament of said signal lamp and controlled by a front contact of said approach relay, a lighting circuit for said signal lamp controlled by a back contact of a track relay for said second section and by a back contact of said pole-changing relay, and control circuits for said second signal including pole-changing contacts of said polechanging relay.

6. In combination, a stretch of railway track divided into a first section and a second section in the rear of said first section, a signal having a lamp for governing traffic movements from said second section into said first section, a second signal for governing traific movements through said second section toward said first section, an approach'relay and a pole-changing relay for said first signal, a control circuit for said approach relay controlled by a front contact of a track relay for each of said sections, a control circuit for said pole-changing relay including the filament of said signal lamp and controlled by a front contact of said approachrelay, a lighting circuit for said signalilamp controlled by a back contact'of said pole-changing relay, and a control circuit for said second signal controlled by means including said pole-changing'relay.

7'. In' combination, astretch of railway track divided into a first section and a second section in the rear of said first section and also a third section in the rear of said second section, a signal adjacent the leaving end of. said first section for directing traffic movements off of said stretch, a second signal having an operative element for governing traffic movements from said second section into said first section, a. third signal having an operative element for governing trafiic movements from said third section into said second section and toward said first section, an approach relay for each of said first and-sec ond signals, an approach stick relay for said second signal so proportioned that it will close a front contact when its control winding and the operative element of its signal and the control winding of the approach relay for said first signal are included all in series in a control circuit for said approach stick relay but the approach relay for said first signal and the operative element for said second signal are not operated by this circuit, a pick-up and a stick circuit for said approach stick relay each including the winding of said approach stick relay and the operative element for its signal and also the control winding of the approach relay for said first signal all in series and controlled by a front contact of a track relay for each of said first and second sections and said pick-up circuit also controlled by a front contact of the approach relay for said second signal, pole-changing contacts controlled by said approach stick relay, and a circuit for energizing the operative element for said third signal in series with the control winding of said approach relay for said second signal controlled by said pole-changing contacts and by a front contact of a track relay for said second section and by a back contact of a track relay for said third section.

8. In combination, a stretch of railway track divided into a first section and a second section in the rear of said first section, a signal for governing trafiic movements from said second section into said first section, a second signal having an operative element for governing traffic movements into said second'section toward said first section, an approach relay and an approach stick relay for said first signal, pole-changing means controlled by said approach stick relay, a circuit for energizing said operative element for said second signal and the control winding of said approach relay in series controlled by said pole-changing means and by a front contact of a track relay for said second section, and a pickup and a stick circuit for said approach stick relay each controlled by front contacts of track relays for said first and second sections and said pick-up circuit also controlled by a front contact of said approach relay.

9. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal having a mechanism and a lamp for governing traffic movements in a given direction through its block, the combination comprising, a pole-changing relay and an approach relay for each of said signals, a control circuit for each of said approach relays controlled by a front contact of a track relay for the next block in the rear of its signal and by a front contact of a track relay for the first track circuit in advance of its signal, a control circuit for each of said signal mechanisms controlled by traffic conditions between its signal and the next signal in advance and also by pole-changing contacts of the pole-changing relay for the next signal in advance, a control circuit for each of said pole-changing relays controlled by the approach relay for its signal, and a lighting circuit for each of said signal lamps controlled by a back contact of the pole-changing relay for its signal connected in series with a back contact of said track relay for the next block in the rear of its signal.

10. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blockseach of which is provided with a signal having a mechanism and a lamp for governing trafilc movements in a given direction through its block, the combination comprising, a pole-changing relay and an approach relay for each of said signals, a control circuit for each of said approach relays controlled by a front contact of a track relay for the next block in the rear of its signal and by a front contact of a track relay for the first track circuit in advance of its signal, a control circuit for each of said signal mechanisms controlled by traffic conditions between its signal and the next signal in advance and also by pole-changing contacts of the pole-changing relay for the next signal in advance, means for energizing each of said pole-changing relays only if said track relay for the next block in the rear of its signal is energized, and a lighting circuit for each of said signal lamps controlled by a back contact of the pole-changing relay for its signal.

11. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal comprising a lamp and a mechanism for governing traffic movements in a given direction through its block, the combination comprising, an approach relay for each of said signals, a control circuit for each of said signal mechanisms controlled by traffic conditions between its signal and the next signal in advance and including the control winding of the approach relay for the next signal in advance and also including a back contact of a track relay for the next block in the rear in multiple with a front contact of the approach relay for its signal, and a resistor connected in multiple with each of said signal mechanisms through a back contact of said track relay for the next block in the rear for effecting sufiicient energization of the approach relay for the next signal in advance for closing its front contact.

12. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal comprising a lamp and a mechanism for governing tramc movements in a given direction through its block, the combination comprising, an approach relay for each of said signals, a slow release relay for each of said signals, a circuit for energizing each of said slow release relays controlled by a front contact of its signal mechanism and by a front contact of a track relay for the next block in the rear, a control circuit for each of said signal mechanisms controlled by traific conditions in its block and including the control winding of the approach relay for the next signal in advance and also including a back contact of said track relay for the next block in the rear in multiple with a front contact of its slow release relay and also with a front contact of the approach relay for its signal, and a resistor connected in multiple with each of said signal mechanisms through a back contact of said track relay for the next block in the rear for efiecting sufficient energization of the approach relay for the next signal in advance for closing its front contact.

13. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal comprising a lamp and a mechanism for governing traffic movements in a given direction through its block, the combination comprising, an approach relay for each of said signals, a slow release relay for each of said signals, a circuit for energizing each of said slow release relays controlled by a front contactof its signal mechanism and by a front contact .of a track relay for the next block in the rear, a control circuit for each of said signal mechanisms controlled by traffic conditions in its block'and including the control winding of the approach relay for the next signal in advance and polechanging front and back contacts of the slow-release relay for the next signal in advance and also including a, back contact of said track relay for the next block in the rear in multiple with a front contact of its slow release relay and also with a front contact of the approach relay for its signal, and a, resistor connected in multiple with each of said signal mechanisms through a back contact of said track relay for the next block in the rear for effecting sufficient energization of the approach relay for the next signal in advance for closin its front contact.

14. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which is provided with a signal comprising a lamp and a mechanism for governing trafiic movements in a given direction through its block, the combination comprising, an approach relay for each of said signals, a slow release relay for each of said signals, a circuit for energizing each of said slow release relays controlled by a front contact of its signal mechanism and by a front contact of a track relay for the next block in the rear, a control circuit for each of said signal mechanisms controlled by trafiic conditions in its block and including the control winding 'of the approach relay for the next signal in advance and polechanging front and back contacts of the slow release relay for the next signal in advance and also including a back contact of said track relay contact of the slow release relay for its'signal and by a back contact of said track relay for the next block in the rear.

15. In a railway signal control system for a stretch of railway track which is divided into a plurality of consecutive blocks each of which-is provided with a signal comprising a lamp and a mechanism for governing traffic movements in a given direction through its block, the combination comprising, an approach relay for each of said signals connected in series with the mechanism for the next signal in the rear and constructed so that it will not close its front contact when energized by only suflicient current for operatin the mechanism for the next signal in the rear, and an auxiliary path at times connected in multiple with the mechanism for the next signal in the rear by a train in the second block in the rear for effecting sufiicient energization of the approach relay for closing its front contact.

16, In combination, a stretch of railway track divided into a first section and a second section in the rear of said first section, a signal having a lamp for governing trailic movements from said second section into said first section, a second signal for governing traffic movements through said second section toward said first section. a pole-changing relay for said first signal, a control circuit for said pole-changing relay controlled'by traffic conditions in'advance of said first signal and including the filament of said lamp for said first signal, and a control circuit for saidsecond signal including pole-changing contacts of said pole-changing relay.

FREDERICK T. FEREDAY, SR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,790,524 Spray Jan. 27,1931 2,017,452 Young Oct. 15, 1935 2,115,459 Gilbert Apr. 26, 1938 2,241,958 Pflasterer May 13, 1941