US1976437A - Railway signaling system - Google Patents

Description

P. H. CRAGO RAILWAY SIGNALING SYSTEM Oct. 9, 1934.

Filed Feb. 4, 1932 2 Sheets-Sheet l {I INVENTOR Paul H. Cmzyo. diam HIS A TTORNE Y.

Patented Oct. 9 1934.

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Lardner RAILWAY SIGNALING SYSTEM Paul H. Crago', Wilkinsburg, Pal, assignor to The Union Switch ;& Signal Company, Swissvale, Pa, a corporation of Pennsylvania; Application February 4, 1932, Serial No. 596,821

rs Claims. (c1. 246-41;

My invention relates to railway signaling systems of the type involving light signals.

One feature of my invention is the provision of means for preventing a signal from momentarily displaying a stop indication when the indication changes from caution to proceed or vice versa. Other features and advantages will appear from the description which follows.

I will describe three forms of signaling systems embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic View showing one form of signaling system embodying my invention. Figs. 2 and 3 are views showing modifications or" the system shown in Fig. 1, and also embodying my invention.

Similar reference characters refer to similar parts in each of the several views. 7

Referring first to Fig. 1, I have shown therein a stretch of railway track divided by insulated joints into blocks 12, 23, and 3--4 along which traflic normally moves in the direction of the arrow. Each block is provided with a track circuit comprising a battery 5 connected to the rails adjacent one end of the block through the winding of an approach lighting relay L and the pole-changing contacts of a slow-release relay P, and having a track relay T connected with the rails adjacent the other end of the block. To designate the relays L, P, and T, use is made of distinguishing exponents corresponding to the location.

Located adjacent the entrance end'of each block is a light signal designated by the reference character S with a distinguishing exponent. Each signal, as here shown, is of What is known as the searchlight type comprisinga polarized armature 6 mounted to oscillate and controlled by a winding '7. The armature 6 carries three roundels G, R, and Y arranged to cooperate with a lamp C in such manner that when the armature 6 is in its middle position to which it is biased, winding '7 being deenergized, roundel R becomes illuminated, whereas when armature 6 is swung to the right or to the left, resulting from the energization of winding '7 with current of what I shall term normal or reverse polarity, respectively, roundel G or roundel Y will become 0 illuminated. The lamp C is shown alcove the roundels for purposes of illustration, but it will be understood that in actual practice it'is placed behind theroundels. The signal will indicate proceed, caution, or stop, according as rounde'l-G,'Y, or :R occupies a position-in front of lamp C when the lamp is lighted. Operatively connected with armature 6 are two contacts 8 and B operated in such manner that when thesignal is in its stop position, both contacts are open, when the signal is in its caution position 53? contact 8 is closed and 8 is open, whereas when the signal is in its proceed position, contact 8 is closed and S is open.

Associated with each signal S is an approach lighting relay L and an auxiliary relay P which, as here shown, is a pole-changing relay. Relay P is constructed to be slow releasing so that it will not open its front contacts while the associated signal is changing from the caution to the proceedposition or vice versa.

Each track relay T in the particular embodiment shown is of the polarized type and serves to pole change the current supplied to winding '7 in response tea reversal of the current supplied to the track circuit from battery 5. Referring to signal S for example, the normal energizing circuit for winding '7 for a proceed indication is from terminal B, front contact 10 of relay T wires 1'1 and 12, polar contact -13l3 winding 7 of signal S polar contact 14-44 and wire '71 to terminalD. The reverse-energizing circuit for winding 7 for a caution indication is from terminal B, front contact 10 of relay T wires 11, 15, and 16, contact 14--14 winding '7, contact 13-13", and wire '71 to terminal 0. The polarized track relay-T is of the usual type wherein, when the track circuit becomes pole changed, the neutral contacts 10, 1'7, and '20 will openbefore the polar contacts 13 and 14 reverse, and were no other means provided, armature 6 would move to the stop position immediately after the deenergization of winding 7 at neutral contact 10 of the track relay. Since the circuit for lamp '0, with signal S in either the proceed or caution position, is made over the front neutral contact 1'7 of relay T therefore, should roundel R assume its positionin front of lamp C immediately following the opening of contact 1'7, the afterglow of the filament in lamp C might cause a momentary stop indication. To avoid this condition'and delay the movement of armature 6 of signals .until contacts13 and l4-of relay T are reversed, a holding circuit for winding '7 is provided which includes terminal B, front contact 18 of relay P wire 19, and the remaining circuit for winding 7, ,previously traced. In this manner, a-time interval sufiicient for the cooling of the filament of lamp C is providedbefore a moveme'ntnf .armatureifi takes place.

The circuit for relay P is from one terminal B, front contact 20 of relay T wire 21, either contact 8 or contact 8 in the closed position, wire 22, and winding of relay P to terminal 0. Therefore, relay P will remain energized at all times when signal S indicates proceed or caution, or is passing from one to the other energized position, whereas relay P will become deenergized when a train enters section 23, deenergizing track relay T Each signal lamp 0 is controlled by a front contact 26 of the associated approach lighting relay L. Referring to signal S there are two circuits for lamp C, one of which, effective when signal S indicates stop, is from terminal B, back contact 23 of relay P wires 24 and 25, front contact 26 of relay L wire 27, and lamp C to terminal 0. The other circuit for lamp C, effective when signal S indicates proceed or caution, is from terminal B, front contact 17 of relay T wire 30, and wire 25 over the remaining circuit traced above.

To explain the operation of the system. shown in Fig. 1, I shall assume that a train has entered section 1-2, with sections 23 and 34 unoccupied. The train shunt around the winding of relay T will result in an increase of current through relay L causing contact 26 of this relay to close the circuit for lamp C, and since winding 7 of signal S is energized with current of normal polarity, signal S will indicate proceed. When the train enters section 23, assuming approach lighting relay L to remain energized, relay I will release, opening neutral contacts 10, 20, and 17. Lamp 0 will be momentarily extinguished at contact 17, but winding 7 will remain energized until relay P releases, which will occur a short time interval after contact 20 opens. The release of relay P will open the holding circuit for winding 7 at front contact 18, whereupon roundel R will be moved to its position in front of lamp C and the lamp circuit will become closed at back contact 23 of relay P Signal S will now indicate stop.

When the train leaves section 23, assuming approach lighting relay L to remain energized, relay P will release due to the opening of contact 20 of relay T and will supply current of reverse polarity to the track circuit of section 23. Relay T will now become energized, reversing polar contacts 13 and 14 and closing neutral contacts 10, 20, and 17. r This will cause current of reverse polarity to be supplied to winding 7 of signal S whereupon armature 6 will move roundel Y into position in front of lamp C and will close contact 8' Signal S will now indicate caution. The closing of contact 3* will complete the energizing circuit for relay P, which will pick up, opening back contact 23, but lamp C will remain lighted because a second circuit for lamp C will have previously become closed at contact 17 of relay T If the train leaves section 34, relay T will pick up, energizing relay P so that current of normal polarity will be restored to the track circuit of section 23. The direction of current flow -j through relay T will reverse, and neutral contacts 10, 20, and 17 will first open, extinguishing lamp C at contact 17 with the result that when polar contacts 13 and 14 become subsequently reversed, roundel R may move past its position in j front of lamp C without producing amomentary stop indication. As soon as contacts 13 and 14 reverse, roundel G will be placed in front of lamp C and contact 17 will reclose, lighting lamp C for the proceed indication. Signal S and its j associated apparatus will now be in the condition illustrated, except for relay L which is assumed to be energized (as would be the case with a following train occupying track section 1--2) in order that signal S may display an indication.

Although approach lighting relay L has been included in the drawings and description to make the disclosure more complete, it will be understood that this relay does not form an essential element of my invention and may be eliminated as for example, by a connection from wire 25 to wire 27, and from wire 31 to wire 32. Furthermore, should it be desired to approach-light only the caution and proceed indications, and not the stop indication, this can be accomplished by removing wire 24 and connecting the back point of contact 23 of relay P with wire 27.

From the foregoing description of Fig. 1, it will be apparent that I have provided means for extinguishing lamp C during a reversal of the polar ized track relay governing the signal, which means become effective from the instant when the neutral front contacts of the track relay open. In this manner, the signal indication can be changed from caution to proceed, and vice versa, with no stop indication intervening.

Referring now to Fig. 2, which illustrates a modification of Fig. 1 for controlling a block signal by means of a polarized line relay, I have shown therein a stretch of railway track divided into blocks such as 1-2, each of which may be further sub-divided into two or more sections 11 1 -2, etc., having a source of energy 5 and a track relay T for each section. Traffic entering each block is governed by a signal S with which are associated a polarized line relay A, a pole-changing slow-release relay P, and an approach lighting relay L.

In explaining the operation of the system of Fig. 2, I shall assume that a train occupies the section next in the rear of signal S and that two blocks in advance of signal S are unoccupied. Under this condition, approach lighting relay L will be deenergized because its circuit will be open at contacts 42 and 43 of one of the track relays for the section occupied by the train. Signal S will indicate proceed, lamp C being lighted over a circuit from terminal B, contact 8 of signal S wire 33, normal polar contact 34 of relay A wires 35 and 36, front neutral contact 37 of relay A wires 38 and 39, back contact 40 of relay L wire 41, and lamp C to terminal 0. Relay A will be supplied with current of normal polarity over a circuit from one terminal B, winding of relay L wires 45 and 46, front contact 47 of relay P wire 48, front contact 49 of relay T wires 50 and 51, contacts 43 of relay T and T winding of relay A contacts 42 of relays T and T, wires 52 and 53, front contact 54 of relay T wire 55, and front contact 56 of relay P to terminal 0.

When the train enters section 11 assuming relay L to remain deenergized on account of the approach lighting feature, polarized relay A will release due to the opening of contacts 42 and 43 of relay T and lamp C will be momentarily extinguished at contact 37 of relay A The opening of contact 44 of relay A will release relay P opening contact 18 which, in turn, will open the holding circuit for winding 7 of signal S causingproundel R to move into position in front of lamp C. The release of relay P will also close back contact 23, lighting lamp C for the stop indication of signal S 1 When the train enters section 1 2, no change in the indication of signal S will occur because relay A will remain deenergized due to contacts integer 42 and 43 of relay T being open. As the train progresses into section 22 relay T will release, releasing relay A and causing relay P to become deenergized after an interval due to opening of contact 44 of relay A It should be noted that relay A will become energized with current of reverse polarity as soon as relay T releases, by virtue of a circuit'from one terminal B, winding of relay L wires 45 and 57, back contact 54 of relay T wires 53 and 52, winding of relay A wires 51 and 50, and back contact 49 of relay I to terminal 0.

As soon as relay P releases, a second circuit for supplying current of reverse polarity to relay A will become closed at back contacts 4'? and 56 of relay P which circuit includes one terminal B, winding of relay L wires 45 and 46, back contact 47 of relay P wire 52, winding of relay A wires 51 and 58, and back contact 56 of relay P to terminal 0. The advantage of energizing relay A as soon as relay T releases is that the possibility of a momentary false proceed indication at signal S which might occur when a fast-moving, light-weight rail vehicle passes i the block joints at location 2, is very much reduced, as it is unnecessary to await the relase of relay P before a possible temporary proceed circuit for signal S becomes interrupted and the caution indication is obtained.

The reverse energization of relay A will energize winding '7 of signal S with current of reverse polarity, causing armature 6 to move roundel Y into position in front of lamp C, and closing contact 8 Lamp C will now be illuminated over a circuit from one terminal B, contact 8 of signal S wire 59, reverse polar contact 3a of relay A wires 35 and 36, contact 37 of relay A wires 38 and 39, and the remaining circuit previously traced for lamp C. Signal S will now indicate caution.

When the train leaves the section which begins at 2 relay A will become energized with current of reverse polarity and will pick up relay P over a circuit from terminal B, contact B of signal S wire 59, reverse polar contact as of relay A wires 35 and 60, contact or of relay A wire 61, and winding of relay P to terminal 0. When relay P picks up, it will pole change relay A supplying this relay with current of normal polarity. During the pole-changing procedure, neutral contact 3'? of relay A will first open to extinguish lamp C, after which polar contacts 13 and 14 will move to the normal position, causing roundel G to be placed in front of the lamp, followed by re-closing of contact 37 of relay A to light the lamp. Signal S will now indicate proceed and its associated apparatus will be restored to the condition illustrated, except for approach lighting relay L which has been assumed to remain deenergized. I

Since the circuit for lamp C includes either contact 8 or 8 of signal S as well as polar contact 34 of relay A it will be apparent that a check of correspondence is obtained between the position of armature 6 of signal S and the position of polar contact 34 of relay A so that the signal cannot indicate proceed or caution until relay A has been energized with current of the proper polarity and roundel G or Y has attained its position in front of lamp C. Also, since relay P is designed to bridge the reversal of relay A as well as the reversal of armature 6 of signal S no stop indication can be given unless relay P is first released, which will occur only when the block next in advance of signal S is occupied, deenergizing relay A and will not occur when relay A is being pole-changed.

Referring to Fig. 3, the system shown therein is similar to Fig. 2 with the exception that in place of a single polarized relay A, a neutral home relay H, and a neutral pole-changing distant relay D are used. It is believed that a detailed explanation of the circuits of Fig. 3 is not necessary. To show the manner in which the system operates, I shall assume that a train occupies section 22 Relay H will be deenergized at contact .2 of relay T opening the circuit for winding 7 of signal S at contacts 62 and 63, so that roundel R will be placed in front of lamp C, and signal S will be in condition to indicate stop by virtue of the closing of back contact 64 of relay H to light lamp C.

lhe release of relay 1-1 will open contact 65, deenergizing relay D which will supply current of reverse polarity to winding '7 of signal S placing roundel Y in front of the lamp Signal S will indicate caution because the lamp circuit will be closed at contact S of signal S back contact 66 of relay D back contact ii) of relay L assuming relay L to have been deenergized.

When the train leaves the section which begins at 2, relay D will become energized, causing roundel G of signal S to move toward its position in front of lamp 0, but the lamp will not become lighted until roundel G is in position, and contact 8 has become closed, thereby preventing a momentary stop indication from being flashed when roundel R passes in front of lamp C. lhe purpose of slow-release relay P is to prevent release of relay D when relay D pole changes winding 7 of signal S Relay P is so designed that it will bridge the reversal of armature 6 of signal S and also the open circuit interval of contact 66 of relay B In order to obtain a caution or proceed indication at signal S it is, therefore, necessary that the position of armature 6 of signal S check with the position of distant relay D the stop indication being obtained only when home relay 5: is deenergized.

Although I have herein shown and described only three forms of signaling systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Havingthus described my invention, what I claim is:

1. In combination, a stretch of railway track divided into blocks, a source of energyand a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, o1 energized with current of reverse polarity respectively; means governed by the track'relay associated with said signal for deenergizing said mechanism when the first block in advance of said signal is occupied; means governed by traffic conditions in the second block in advance of said signal for energizing said mechanism with current of normal or reverse polarity according as said second clock is unoccupied or occupied respectively, provided that said first block remains unoccupied; a slowacting relay associated with each signal for supplying the block next in the rear of said signal with current of normal or reverse polarity acits cording as said slow-acting relay is energized or deenergized respectively, an energizing circuit for each slow-acting relay effective when the associated track relay and mechanism are both energized, and a circuit for each lamp comprising two branch paths one of which becomes effective when the associated slow-acting relay is deenergized and the other of which becomes effective when the associated track relay is energized.

2. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; means governed by the track relay associated with said signal for deenergizmg said mechanism when the first block in advance of said signal is occupied; means governed by trafiic conditions in the second block in advance of said signal for energizing said mechanism with current of normal or reverse polarity according as said second block is unoccupied or occupied respectively, provided that said first block remains unoccupied; a slow-acting relay associated with each signal for supplying the blocl: next in the rear of said signal with current of normal or reverse polarity according as said slow-acting relay is energized or deenergized respectively, an energizing circuit for each slow-acting relay efiective when the associated track relay and mechanism are both energized, means effective when said slow-acting relay is energized for maintaining said mechanism associated therewith in its last energized condition for a predetermined time interval which begins when the current supplied to said first block becomes pole-changed, and a circuit for each lamp comprising two branch paths one or" which becomes efiective when the associated slow-acting relay is deenergized and the other of which becomes efiective when the associated track relay is energized.

3. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; means governed by the track relay associated with said signal for deenergizing said mechanism when the first block in advance of said signal is occupied; means governed by trafiic conditions in the second block in advance of said signal for energizing said mechanism with current of normal or reverse polarity according as said second block is unoccupied or occupied respectively, provided that said first block remains unoccupied; a slow-acting relay associated with each signal for supplying the block next in the rear of said signal with current of normal or reverse polarity according as said slow-acting relay is energized or deenergized respectively, an energizing circuit for each slow-acting relay effective when the associated track relay and mechanism are both energized, an approach lighting relay for each signal which becomes energized when the block next in the rear of the associated signal is occupied, and a circuit for each lamp comprising two branch paths one of which becomes effective when the associated slow-acting relay is deenergized and the other of which becomes effective when the associated track relay and approach lighting relay are both energized.

4. In combination, a stretch of railway track divided into blocks, a source of energy and a polarized track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity or energized with current of reverse polarity respectively; a slow-acting relay associated with each signal for supplying theblock next in the rear of said signal with current of normal or reverse polarity according as said slow-acting relay is energized or deenergized respectively, a first normal energizing circuit for said mechanism including a front neutral contact and a normal polar contact of the associated track relay, a second normal energizing circuit for said mechanism including a front contact of the associated slow-acting relay and said normal polar contact, a first reverse energizing circuit for said mechanism including said front neutral contact and a reverse polar contact of the associated track relay, 2, second reverse energizing circuit for said mechanism including said front contact of the slow-acting relay and said reverse polar contact, a circuit for each slowacting relay including a second front neutral contact of the associated track relay and a contact controlled by the associated mechanism which becomes closed when said mechanism is energized with current of either normal or reverse polarity, and a circuit for each lamp comprising two branch paths one of which includes a back contact of the associated slow-acting relay and the other of which includes a third front neutral contact of the associated track relay.

5. In combination, a stretch of railway track divided into blocks, track circuits including track relays for said blocks, a light signal for each block comprising an electric lamp and a mechanism responsive to current of normal or reverse polarity for causing said signal to display an indication in accordance with said current polarity, a slowacting relay associated with each signal for polechanging the supply of current to the track circuit immediately preceding said signal, means for supplying current to said mechanism, means governed by the track relay associated with said signal for pole-changing the current supplied to said mechanism when the track circuit immediately in advance of said signal becomes polechanged, a circuit for said slow-acting relay governed by said track relay, a first circuit for energizing said lamp governed by said slow-acting relay, and a second circuit governed by said track relay and effective for energizing said lamp at such times as said track relay is energized.

6. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp, a circuit for energizing said lamp, and a mechanism for causing said signal to display one or another indication according as said mechanism is supplied with current of normal or reverse polarity respectively; means governed by traffic conditions in the two blocks next in advance of said signal for supplying said mechanism with current of normal polarity when said two blocks are both unoccupied and for supplying said mechanism with current of reverse polarity when the first of said two blocks is unoccupied and the second block is occupied,

and means governed by the track relay associated with said signal for rendering said circuit ineffective to energize said lamp during the time interval when the current supplied to said mechanism is being reversed.

7. In combination, a stretch of railway track divided into blocks, source of energy and a track relay for each block; a light signal for each block comprising an electric lamp, a circuit for energizing said lamp, and a mechanism for causing said signal to display one or another indication according as said mechanism is supplied with current of normal or reverse polarity respectively; means governed by trafic conditions in the two blocks next in advance of said signal for supplying said mechanism with current of normal polarity when said two blocks are both unoccupied and for supplying said mechanism with current or" reverse polarity when the first of said two blocks is unoccupied and the second block is occupied, and means governed by trafiic conditions in said second block for extinguishing said lamp for a redeterinined time interval following the exit of a train from said second block when said first block is unoccupied.

8. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp, a circuit for lighting said lamp, and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; means governed by the track relay associated with said signal for deenergizing said mechanism when the first block in advance of said signal is occupied; means governed by trafiic conditions in the second block in advance or" said signal for supplying said mechanism with current of normal or reverse polarity according as said second block is unoccupied or occupied respectively, provided that said first block remains unoccupied; and other means governed by traffic conditions in said second block for extinguishing said lamp while the current to said mechanism is being reversed.

9. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp, a circuit for lighting said lamp, and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; means governed by track relay associated with said signal for deenergizing said mechanism when the first block in advance of said signal is occupied; means govern d by trafiic conditions in the second block. in advance oi said signal for supplying said mechanism with current of normal or reverse polarity according as said second block is unoccupied or occupied respectively, provided that said first block remains unoccupied; an approach lighting relay for energizing said lamp circuit only when the "clock next in the rear of said signal is occupied, and other means governed by traffic condition in said second block for e) tinguishing said lamp while the current to said mechanism is being reversed and said rear clock is occupied.

1c. In combination, a stretch of railway track divided into blocks each comprising a plurality of sections, a source of energy and a track relay f r each section; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, ener ized with current of normal polarity, or energized with current of reverse polarity respectively; a polarized relay for each signal for supplying said mechanism with current of normal or reverse polarity according as said polarized relay is supplied with current of normal or reverse polarity respectively, and for deenergizing said mechanism when said polarized relay is deenergized; a circuit for each polarized relay governed by the track relay for each section comprising the first block in advance of the associated sign 1, a slow-acting relay associated with each signal for supplying said polarized relay circuit with current of normal polarity when said slowacting relay and the track relay for the first section in advance of said signal are both en rgized and for supplying said polarized relay circuit with current of reverse polarity when said slowactin relay is deenergized, means independent of said slow-acting relay for supplying said polarized relay circuit with current of reverse polarity when the track relay for said first section in advance is deenergized, a circuit for each slowacting relay efiective when and only when the mechanism and polarized relay associated therewith are both supplied with current or" the same polarity, and a circuit for each lamp comprising two branch paths one of which becomes effective when the associated slow-acting relay is deenergized and the other of which becomes eiiective when the associated mechanism and associated polarized relay are both operated by current of the same polarity.

11. In combination, a stretch of railway track divided into blocks, a source or" energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; a polarized relay for each signal for supplying said mechanism with current of normal or reverse polarity according as said polarized relay is supplied with current of normal or reverse polarity respectively, and for deenergizing said mechanism when said polarized relay is deenergized; a circuit for each polarized relay governed by the track relay for the first block in advance or" the associated signal, a slow-acting relay associated with each signal for supplying said polarized relay circuit with current of normal polarity when said slow-acting relay and the track relay for said first block are both energized and for supplying said polarized relay circuit with current of reverse polarity when said slow-acting relay is deenergized, means independent of said slow-acting relay for supplying said polarized relay circuit with current or" reverse polarity when the track relayv for said first block is deenergized, a circuit for said slovv-acting relay eiiective when and only when said mechanism and said polarized relay are both suppned with current of the same polarity, and a circuit for lighting said comprising two branch paths one of which becomes efiective when said slow-acting is deenergized and the other of which becomes effective when said mechanism and said polarized relay are both operated by current of the same polarity.

12. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; a polarized relay for each si nal for supplying said mechanism with current of normal or reverse polarity according as said polarized relay is supplied with current of normal or reverse polarity respectively, and for deenergizing said mechanism when said polarized relay is deenergized; a circuit for each polarized relay governed by the track relay for the first block in advance of the associated signal, a slowacting relay associated with each signal for supplying the polarized relay circuit for the block next in the rear of said signal with current of normal polarity when said slow-acting relay and the track relay for said first block are both energized and for supplying said polarized relay circuit with current of reverse polarity when said slow-acting relay is deenergized, means independent of said slow-acting relay for supplying said polarized relay circuit withcurrent of re- .verse polarity when the track relay for said first block is deenergized, a circuit for said slow-acting relay effective when and only when the associated mechanism and polarized relay are both supplied with current of the same polarity, means effective when said slow-acting relay is energized for maintaining said mechanism in its last energized condition until the current to said mechanism be comes interrupted at the polarized contacts of said polarized relay, an approach lighting relay for each signal having its winding included in the circuit for the polarized relay associated with the signal next in the rear, and a circuit for lighting said lamp comprising two branch paths one of which becomes effective when said slowacting relay and said approach lighting relay are both deenergized and the other of which becomes effective when said approach lighting relay is deenergized and said mechanism and said polarized relay are both operated by current of the same polarity.

13. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism for causing said signal to display a first, second, or third indication according as said mechanism is deenergized, energized with current of normal polarity, or energized with current of reverse polarity respectively; a home relay, a distant relay, and a slow-acting relay for each signal; a circuit for each home relay governed by the track relay for the first block in advance of the associated signal, a circuit for each distant relay governed jointly by the home relay and the slow-acting relay both for the next signal in advance, means for energizing said mechanism with current of normal polarity when the associated home and distant relays are both energized, means for energizing said mechanism with current of reverse polarity when the associated home relay is energized and the associated distant relay is deenergized, means for deenergizing said mechanism when the associated home relay is deenergized, a first circuit for each slow-acting relay effective when the associated home and distant relays are both energized and the associated mechanism is energized with current of normal polarity; a second circuit for each slow-acting relay effective when the associated home relay is energized, the associated distant relay is deenergized, and the associated mechanism is energized with current of reverse polarity; a first circuit for each lamp efiective when the associated home relay is deenergized, a second circuit for each lamp effective when the associated distant relay is energized and the associated mechanism is energized with current of normal polarity, and a third circuit for each lamp eiiective when the associated distant relay is deenergized and the associated mechanism is energized with current of reverse polarity.

14. In combination, a stretch of railway track divided into blocks, a source of energy and a track relay for each block; a light signal for each block comprising an electric lamp and a mechanism capable of assuming a neutral position when deenergized and a normal or a reverse position when energized with current of normal or reverse polarity respectively to cause said signal to display a first, second, or third indication in accordance with the position of said mechanism; a distant relay and a slow-acting relay for each signal, a circuit for each mechanism governed by both the track relay and distant relay associated therewith and effective for supplying said mechanism with current of normal polarity when said track relay and said distant relay are both in the energized condition and effective for supplying said mechanism with current of reverse polarity when said distant relay is in the deenergized condition and said track relay is energized, means for deenergizing said mechanism when the. track relay associated therewith is deenergized, a circuit for each distant relay governed by the track relay as well as the slow-acting relay, both for the next signal in advance; a circuit for each slow-acting relay governed by the associated track relay, associated distant relay, and associated mechanism and efiective only if the track relay is energized and the position assumed by said mechanism agrees with the condition of said distant relay; and a circuit for each lamp comprising two branch paths one of which becomes effective if the track relay associated therewith is deenergized and the other of which becomes eiiective if the posiiton assumed by the associated mechanism agrees with the condition of the associated distant relay.

15. In combination, a stretch of railway track divided into blocks; a light signal for each block comprising an electric lamp, a circuit for energizing said lamp, and a mechanism for causing said signal to display one or another indication according as said mechanism is supplied with current of normal or reverse polarity repectively; means governed by trafiic conditions in the two blocks next in advance of said signal for supplying said mechanism with current of normal polarity when said two blocks are both unoccupied and for supplying said mechanism with current of reverse polarity when the first of said two blocks is unoccupied and the second block is occupied, and means governed by traffic conditions in the first of said two blocks for rendering said circuit ineffective to energize said lamp during the time interval when the current supplied to said mechanism is being reversed.

PAUL H. CRAGO.

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