US2623161A - Railway signal control apparatus for protecting against momentary loss of track shunt - Google Patents

Description

Patented Dec. 23, 1952 RAILWAY. SIGNAL CONTROL APPARATUS FOR PROTECTING AGAINST MOMENTARYv LOSS 0F TRACK SHUNT Otto W. Rost, Chicago, Ill., as'signor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application May 26, 1949, Serial No. 95,498

12 Claims. (Cl. 246-41) 1 My invention relates to railway signalcontrol apparatus for protecting-against a momentary loss of shunt of a track circuit for a given track section while the given tracksection is occupied by a train. More speciiically, my invention relates to an arrangement for controlling a railway signal which governs traiiic movements onto the given section sothat it will not display a false proceed indication momentarily, but will display the stop indication without interruption, in the event of a momentary reduction or loss of track shunt of the track circuit for Athe given track section while the given track section is occupied by a car or train. @It sometimes happens that a track relay becomes sufficiently energized to closeits iront contacts for a brief period of timewhile a car or train is moving over the associated track section. This is more possible when a single car or a short train moves over the track section,l and particularly if the car or train is of light weight. .Such false energization of a track relay may be due to some material such, for example, as dirt, grease, or sand between the rails of the track and the wheels oi the train. The presence of such material between the rails of the track and the wheels of the train may introduce momentarily so much resistance into the multiple shunting paths across the rails, through'the wheels and axles of a train, that track battery current of sufficient magnitude can pass throughth-e control winding of the track relayto effect closure of the front contacts of thetrack relay.

It follows that, if a signal operating circuit con trolled by a front contact of a track relay becomes closed as soon as the front contact of the track relay is closed, the signal may be operated to display a false proceed indication for a brief period of time while it should be displaying"y the stop indication. Obviously, such operation of a signal `might result in unsafe operation of a train, and `should therefore be prevented.

An object of my invention is therefore the provision of novel and improved means to insure that a false proceed indication `is not'momentarily displayed, but that the stop indication is uninterruptedly displayed, by a railway signal when a track relay by which the signal is con trolled becomes energized and closes its front contacts duringa momentary reduction, orloss, of shunt of the track circuit with which the track relay is associated. l l

A feature of my invention, for attaining this object, is the provision of an arrangement (fordelaying operation of a railway signal by retaining 2 the operating circuit for the signal in its deenergized condition during a brief period after .the front contacts of a track relay by which the signal is controlled become closed.

In my invention, means for retaining the operating circuit for a signal in its deenergized condition during such brief periods includes a directional stick relay which becomes energized when a train' passes the signal onto a given track section while the signal is displaying a proceed indication for directing traiiic movements in a given direction onto the given -track section. A stick circuit for retaining the directional stick relay energized after the signal changesfrom the proceed to the stop indication is controlled by a contact operated by a time -element device, so that it is closed while the time element device is deenergized, and becomes opened after the time element device has been energized for a measured period of time.

An operating element for the signal is controlled by a back contact of the directional stick relay, and an auxiliary relay is connected with the signal control circuit through a front contact of the directional stick relay.

An energizing circuit for the time element device is controlled by a iront contact of the stick relay and by a front contact of the auxiliary relay.

Afcontrol circuit for an opposing signalwhich directs trahie movements in the opposite direction onto the given track section is controlled in part by the contact of the time element device -and by a back contact of the stick relay.

'andthe back point of a contact of a directional stick relay; in which the directional stick relay becomes energized in responseto a train enter- `ingthe given track-section in the given direction .while the signal is controlled to display a proceed indication; inwhich an auxiliary relay is controlled over a portionof the signal-control circuit, including the track relay contact, through the front point of a contact of the directional stick relay; `in which a time element device is controlled by a circuit including front contacts of the stick and auxiliary relays; and in which a contact of the time element device opens a stick circuit for the directional stick relay upon the lapse of a measured period of time after the track relay closes its front contact, so that the contact oi the stick relay is again closed at its back point in the control circuit for the signal.

Similar reference characters refer to similar parts in the drawing.

Referring further to the drawing, a stretch of single track railway is shown connected by a track switch W with a siding Z. `The single track stretch is divided by insulated joints into sections designated by the reference characters IT, 3T, and 4T. Each of these track sections is provided with a track circuit including a suitable source of current such as a battery connected across the rails adjacent one end of the section, and a track relay, designated by the reference character TR preceded by a numeral Whioh is the-same as the numeral the reierence character for the .associated traes section, oomleoted aoioss the rails adjacent the opposite end of the section.

In order to simplify the drawing, each track, comprising two parallel series oi track rails, is represented by a `single line.

A pair of signals, designated by the reference characters IS and 2S, for governing trafc nieve.- ments in opposite directions, is located adjacent insulated joints 5 between sections iT and 3T. A second pair of signals, designated lov the .refers ence characters 3S and .4.5, .for governing traffic movements in opposite directions, is located ade jacent the insulated joints 5 between sections @T and IST. Signals iS and 2S may be referred to as head block signals, and signals 3S and 4S may be referred to as intermediate signals. Signal IS may also be referred to as an entering signal, and signal 2S may be referred to as a leaving or starting signal.

I shall assume that traffic movements toward the left, as shown in the drawing, are in the westbound direction, Whereas traflic movements toward the right, as shown in the drawing, are in the eastbound direction. Signals IS and 3S accordingly govern westbound trailic movements, and signals 2S and 4S govern eastbound traffic movements.

The signals may be of any suitable design such, for example, as the well-known searchlight type. A signal of this type comprises various parts, which have grouped together for signal 3S, for example, and designated as a signal mechanism m, preceded by a numeral which is the same as the numeral in the reference character for the associated signal.. Each of the signal. mechanisms such, for example, as signal mechanism 3m shown for Signal 3S, comprises an optical unit which has a single lamp E and an operating element comprising a member 'l mounted to rotate in both directions as controlled by a signal winding 8. Attached to member '1, for rotation therewith between a normal position to the right and a reverse position to the left, are three colored filters or roundels, designated by the reference characters G, R, and Y, which may be of the colors green, red, and yellow, respectively. Member l is biased to a mid stroke or intermediate position to which it therefore moves when the associated signal winding 8 is deenergized. When signal winding S is energized by current oi the polarity which I shall term normal polarity, member I is moved to the righthand position. and when winding 8 is energized by current of the opposite or reverse polarity, member 'I .is moved to the left-hand position.

For convenience in illustration, lamp E is shown above the roundels, but it is to be understood that lamp E lis actually located directly behind one ci the roundels according to the position of the member l. Roundel G, R, o1' Y is moved in front of lamp E according as member 1 is moved te its right-hand position, its intermediate posit-ion, or its left-hand position, respectively.

The signal displays a clear proceed indication, an approach proceed indication, or the stop indication when roundel G, Y, or R, respectively, is" placed in front of lamp E.

Operatively connected with member 1 is a circuit controller comprising two movable contact fingers il and I0. Contact nger 9 engages a fixed contact element 9a when member 1 occupies its` right-hand positionarid engages a fired eoritaot .element Se when member 1 oef euries either its intermediate or its left-hand position Contact; iinser i!! engages iixedconf tact element .lila when member l occupies its left-hand position, and engages a fixed contact element lllb when member T occupies either its intermediate oi' its richtiiaiifi position.

A signal ci the type described is disclosed and ,Claimed in Letters Patent of the United States No. 1,864,224, granted June 2l, i932, to Wesley B. Wells. iol.' Licht Signals.-

Proceed signal repeater relays designated by thereference characters ZGYPR and GGYPR are Controlled V1oy the circuit controllers for signals 2S and 4S., respectively, so that each of these relays is energized when the member l of the associated signal is in either its left-hand or its right-hand position, but is deenei'eized when the member 'l' of the associated signal is in its in.- termediate position. Each of the relays ZGYBR and AGYPR is made slow releasing 'oy an asymmetric unit I l connected in multiple with the winding of the relay. Asymmetric units I! may be of any suitable design such, for example, as the well-known copper oxide half-wave rectifier.

A clear signal repeater relay, designated by the reference character lGPR, is controlled by the circuit controller for signal iS so that this relay is energized when the member l; oi signal IS is its right-hand position, but Ais deenergizod when the member l of signal IS is in the lefthand or the intermediate position. Relay lGPR islmade slow releasing, similarly to relays QGYPR and QGYPR, by an asymmetric unit Il Connected `iacross its control winding.

Associated with. signals 2S and 4S are direc.- tional stick relays designated by the reference characters ZSR. and 45B, respectively. Relays AZSR and HSR become energized by pickup circuits controlled in part by contacts 23 and 2 of relays `2GYPR and dGYPR, respectively, and in part by ' back contacts 22 and 26 of track relays STR and KIR, respectively. It follows that each of the vdirectional stick relays, as will be described in detail, becomes energized when a train, moving lto display either of its two proceed indications.

Each of the stick relays ZSR and ISR then 11e-- mains energized by a stick circuit controlled by a contact i6 or 28 of a time element device 2TE or 4`TE, respectively.

Each of the time element devices 2TE and TE is-normally deenerglzed, and opens its contact upon the lapse of a measured period of time after its control element becomes energized.

Signal winding 8 of signal 2S is controlled by normal and reverse control circuits which include a front contact I3 of track relay 3TR for the track section 3T onto which signal 2S governs traic movements. The control circuit for winding 8 of signal 2S also includes the back point of a contact I4 of relay 2SR. 4An auxiliary relay ZSRP, associated with signal 2S, is controlled through the front point of contact I4 o relay 2SR over a portion of the control circuit for winding 8 of signal 2S.

Time element device 2TE is controlled by front contacts 24 and 25 of relays 2SRP and ZSR, respectively, and time element device 4TE is controlled by `front contacts 30 and 3I of relays 4SR and 4GYPR, respectively.

Signal control winding 8 of mechanism 3m of signal 3S is controlled by normal and reverse control circuits which include contact I6 of time element device ZTE and the back point of a contact I1 of relay 2SR. Signal winding 8 of vsignal 4S may be controlled by normal and reverse control circuits which are similar to those shown for signal 3S.

Signal control winding 8 of signal IS may be controlled by normal and reverse control circuits which are similar to the circuits shown for signal 3S in a patent application of common ownership Serial No. 53,112, led October 6 1948 by James H. Butridge and William H. Claus, now Patent No. 2,546,331, for Railway Signal Control Systems.

Having described, in general, the arrangement and control of the various parts of apparatus embodying my invention, I shall now describe the circuits and operation in detail.

As shown in4 the drawing, all parts `of the apparatus are in the normal condition, that is, track sections IT, 3T, and 4T are unoccupied, and therefore track relays ITR, STR, and 4TR are energized; each of the signal windings 8 is energized by current of normal polarity, and therefore each of the signals is controlled to display the clear proceed indication; each of the proceed signal repeater relays ZGYPR and 4GYPR and the clear signal repeater, relay IGPR is energized; and relays 2SR, 4SR, and 2SRP, and time element devices 2TE and 4TE are deenergized.

The circuit by which winding 3 of signal 2S is energized by current of normal polarity passes from terminal B of a suitable source of current, shown as a battery Q, through the back point of contact I2v of relay 4SR, contact I3 of relay 3TR, back point of contact I4 of relay ZSR, winding 8 of signal 2S, and the back point of contact l5 of relay 4SR to terminal N of the same source oi current, battery Q. The circuit by which winding 8 of signal 3S is energized by current of normal polarity passes from terminal B, through contact I5 of device ZTE, back point of contact I1 of relay 2SR, contact I8 of relay ITR, front point of contact I9 of relay IGPR, winding 8 or signal 3S, contact 20 of relay STR, and the front point of contact 2I of relay IGPR to terminal N.

Relay 2GYPR is energized by current passing from terminal B, through contacts IO-Ib and S--Sa of signal 2S, and the winding of relay ZGYPR in multiple with asymmetric unit II in the high resistance direction, to terminal N. Relay 4GYPR is energized by a similar circuit controlled by contacts I0-I0b and' .Q -9m of signal 4S. Relay IGPR is energized by a circuit 6 passing from terminal B, through contacts lil-@IUD and S-Sa of signal IS, and the winding of relay I GPR in multiple with the asymmetric unit II in the high resistance direction, to terminal N.

1 shall assume that, with apparatus embodying my invention arranged as shown in the accompanying drawing, an eastbound train approaches signals IS and 2S, causing signal IIS to display the stop indication. Contacts IB--Ib and 9-Eia of signal IS will therefore be opened, causing relay IGPR to be deenergized. With relay IGPR deenergized, its contacts I9 and 2| will now be closed at their back points, so that winding 8 of signal 3S will now be energized by current of reverse polarity in a circuit which is the same asv the circuit previously traced for this winding except that it includes the back points `of contacts I9 and 2I of relay IGPR instead of the front points of these contacts. Member 'I of signal 3S will. therefore move to its left-hand position, in which roundel Y is in front of lamp E, so that now signal 3S will display the approach proceed indication.

-When the train enters section IT, winding 3 of signal SS will be deenergized because contact I8 of relay ITR will be opened. Member 'l of signal 3S will therefore move to its intermediate position, in which roundel R is in front of lamp Eso that now signal 3S will display the stop indication.

.When the train enters section 3T, contact I3 of relay STR will open the circuit previously traced for winding 8 of signal 2S, causing this winding to be deenergized. Signal 2S will therefore now display the stop indication, and contact ch-SicI of signal 21S will be open while contact Iii-Illa will still be open, and therefore relay ZGYPR will be deenergized.

With relay STR deenergized, the circuit for winding -8 of sign-al 3S will now be open at a secon-d point on account of contact 2i! of relay STR being open. i

Relay ZGYPR, on account of being slow releasing, retains its contact 23 closed for a brief period of time, so that relay ZSR becomes energized by a pickup circuit 4passing from terminal B, through contact 22 of relay STR, contact 23 of relay ZGYPR, and the winding of relay ZSR to terminal N. Relay 2SR, upon becoming energized, completes its own stick circuit passing from terminal B, through contact I6 of time element device 2TE, front point of contact I1 of relay ZSR, andthe winding of relay ZSR to terminal N.

With contact I of relay ZSR now open at its back point, the circuit for Winding 8 of signal 3S is open at a third point. A

When the train leaves section IT, signal IS will again be operated to the clear proceed position.

Relay IGPR will therefore again be energized by its circuit previously traced.

I shall now assume further that, while the train is on section 3T, there -is a momentary loss of shunt of the track circuit for section 3T, so that relay 3TR closes its front contacts for a brief period `of time. Relay ESRP will therefore now be energized by a circuit passing from terminal B, through the back point of contact I2 of relay 4SR. contact I3 of relay 3TR, front point of contact It of relay 2SR, winding of relay ZSRP, and the back point of contact It of relay 4SR to terminal N.

Time element device ETE will then also be energized by its circuit passing from terminal B, through contacts 24 and 25 of relays ZSRP and 7 ZSR, respectively, and the control element of device 2TE to terminal N. Device ZTE is so designed and constructed that the time required for its contact I6 to open is longer than the period of a momentary loss of shunt of a track circuit.

Therefore, relay STR will again be deenergized and its contact I3 will Open before the stick circuit for relay ZSR is opened by contact I6 of relay ZTE. Relay .ZSR will therefore remain energized, and winding 8 of signal 2S therefore remainds deenergized, and so signal 2S will not momentarily display a proceed indication, but will display the stop indication uninterruptedly during the occurrence of the momentary loss of shunt.

When the train enters section 4T, signal 4S will be controlled to display the stop indication. With signal 4S indicating stop, relay GYPR will now be deenergized. However, since relay 4GYPR is slow releasing, relay ISR will become energized by its pickup circuit passing from terminal B, through contact 26 of relay 4TR, contact 27 of relay dGYPR, and the winding of relay 4SR to terminal N. A stick circuit for relay IISR will then be completed, passing from term-inal B, through conta-ct 28 of device 4TE, contact 29 of relay ASR, and the winding of relay 4SR to terminal N.

When the train leaves section 3T, relay ZSRP again becomes energized by a circuit which is the same as the circuit previously traced except that it includes the front points of contacts l2 and I5 of relay IISR instead of the 'back points of these contacts. Time element device ZTE will then again become energized by its circuit previously traced.

Upon the lapse of a measured period of time, contact I6 of device ZTE will open the stick circuit previously traced for relay 2SR, causing relay ZSR to become deenerg-ized. When relay ZSR becomes -deenergized, its -contact I4 becomes opened at the front point, thereby deenergizing -relay ZSRP, and contact opens the circuit traced for device ZTE, so that device 2TE becomes deenergized.

When contact I4 of relay ZSR becomes closed at its back point, winding 8 of signal 2S will be energized by current of reverse polarity in a, circuit which is the same as the circuit previously traced for this relay except that it includes the front points of contacts I2 and I5 of relay 4SR instead of the back points of these contacts. Signal 2S will therefore now be operated to its position in Wh-ich roundel Y is in front of lamp E. Signal 2S will therefore now display the approach proceed indication. Relay ZGYPR will therefore now be energized by a circuit passing from terminal B, through contact IU-I Ua of signal 2S, and the winding of relay ZGYPR in multiple with asymmetric unit II in the high resistance direction, to terminal N.

With relay ZSR and time element device ZTE deenergized, the normal control circuit previously traced for signal 3S will again become closed when contact I6 of device 2TE closes.

When the train has proceeded far enough so that signal 4S is again displaying a proceed indication, relay IIGYPR will again become energized, and time element device 4TE will then be energized by a circuit passing from terminal B, through Contact of relay 4SR, contact 3| of rel-ay lGYPR, `and the control element of device 4TE to terminal N. Upon the lapse of a measured period of time, contact 28 of device ATE will Cil open the stick circuit for relay 4SR, causing relay ASR to become deenergized.

Winding 8 of signal 2S will then again become energized by current of normal polarity in its circuit iirst traced, so that signal 2S will then again display the clear proceed indication.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination, a section of railway track, a railway signal for governing trai'c movements in a given direction onto said section, a track circuit for said section including a, track relay, a directional stick relay, an auxiliary relay, a control circuit for controlling said signal to display a proceed indication including a front contact of said track relay and the back point of a contact of said stick relay, a control circuit for said auxiliary relay including said front contact of said track relay and the front point of said contact of said stick relay, a pickup circuit for energizing said stick relay when a train enters said section while said signal is controlled to display a proceed indication, a time element device, a contact operated by said time element device normally closed while said time element device is deenergized but becoming opened after said time element device has been energized a measured period of time, a stick circuit for said stick relay controlled vby said Contact of said time element device1 an energizing circuit for said time element device controlled by a front contact of said stick relay and by a front contact of said auxiliary relay, a second railway signal for governing traino movements in the opposite direction onto said section, and a control circuit for controlling said second signal to display a proceed indication controlled in part by said contact of said time element device and by a back contact of said stick relay.

2. In combination, a section of railway track, a railway signal for governing traffic movements in a given direction onto said section, a track circuit for said section including a track relay, a directional stick relay, an auxiliary relay, a control circuit for controlling said signal to display a proceed indication including a front contact of said track relay and the back point of a contact voi said stick relay, a'control circuit for said auxiliary relay including said front contact of said track relay vand the iront point of said conltact of said stick relay, a pickup circuit for energizing said stick relay when a train enters said section while said signalis controlled to display a proceed indication, a time element device, a contact operated by said time element device normally closed while said time element device is deenergized but becoming opened after said time element device has been energized a measured period of time, a stick circuit for said stick relay controlled by said Contact of said time element device, and an energizing circuit for said time element device controlled by a front contact of said stick relay and by a front Contact of said auxillary relay,

3. In combination, a section of railway track, a railway signal for governing traic movements in a given direction onto said section, a track circuit for said section including a track relay, a directional stick relay, an auxiliary relay, a circuit for operati'ng said signal to display a proceed indicationcontrolled by a front contact of said track relay. =and by a, back contact of said stick relay, a circuit controlled by a front contact of said track relay and by a iront contact of said stick relay for energizing said auxiliary relay, a pickup circuit for energizing said stick relay if a train enters said section while said signal is controlled to display a proceed indication, a normallyclosed Contact, a stick circuit for said stick relay controlled by said normally closed contact, and means controlled by a iront contact of said stick relay andby a front contact of said auxiliary relay for opening said normally closed contact.

4. In combination, a section of railway track,

a railway signal for governing traffic movements in a given direction onto said section, a track circuit for said section including a track relay, a directional stick relay, means controlled by a iront contact of said track relay and by a back contact of saidstick relay for controlling said signal for displaying a proceed indication, a pick up circuit for energizing said stick relay when a tra-in enters said section while said signal is controlled for displaying a proceed indication, anormally closed contact, a stick circuit for said stick relay controlled by said normall 1 closed contact, and'ineans controlled by front contacts of said track and stick relays for opening said normally closed contact.

5. In combination, a section of railway track, a railway signal for governing` traiiic movements onto said section, a track circuit for said section including a track relay, a control circuit including a front contact oi said track relay for controlling said signal for displaying a proceed indication, and an arrangement embodying time element means controlled by means including a front contact of said track relay for delaying operation of said signal for displaying a proceed indication by retaining said control circuit in the deenergized condition for a brief period of time after said front contact of said track relay closes when said track relay becomes energized after having been deenergized.

6. In combination, a section of railway track, a railway signal for governing traiiic movements onto said section, a track circuit for said section including a track relay, control means including a front contact of said track relay for controlling said signal for displaying a proceed indication, and an arrangement for delaying operation of said signal for displaying a proceed indication including a directional stick relay which becomes energized and deenergizes said control means in response toa train entering said section while said signal is controlled to display a proceed indication and said directional stick relay is then retained in the energized condition by a stick circuit, and time element means controlled by a front contact of said track relay and by a iront contact of said stick relay for opening said stick circuit upon'the lapse of a measured period of time after said'track relay becomes energized.

7. In combination, a section of railway track, a ,railway signal for governing traffic movements onto said section, a track circuit for said section including a track relay, a control circuit including a front contact of said track relay for controlling said signal for displaying a proceed indication, a directional stick relay, a pickup circuit for energizing said stick relay when a train enters said section while said signal is controlled to display a proceed indication, a stick circuit for then retaining said stick relay in the energized condition,

, acceder 10 means controlled by said stick relay for opening said signal control circuit when said stick relay becomes energized, and time element means for opening said stick circuit upon the lapse of a measured period of time after said track relay becomes energized.

8. In combination, a section of railway track, a railway signal for governing tramo movements onto said section, a track circuit for said section including a track relay, a control circuit including a front contact of said track relay for controlling said signal to display a proceed indication, a directional stick relay, a pickup circuit controlled by a train for energizing said stick relay when said train enters said section while said signal is displaying a proceed indication, a stick circuit including a front contact ci said stick relay for then retaining said stick relay in the energized condition, means controlled by said stick relay upon Y becoming energized for opening said signal control circuit, and time element means controlled by said track relay and by said stick relay for opening said stick circuit upon the lapse of a measured period of time after said track relay becomes energized.

9. In combination, a section of railway track, a railway signal for governing traiilc movements onto said section, a track circuit for said section including a track relay, a control circuit including a front contact of said track relay for controlling said signal to display a proceed indication, a directional stick relay, a pickup circuit controlled by a train for energizing said stick relay when said train enters said section while said signal is displaying a proceed indication, a stick circuit including a front contact of said stick relay for then retaining said stick relay in the energized condition, means controlled by said stick relay upon becoming energized for opening said signal control circuit, time element means controlled by said track relay and by said stick relay for opening said stick circuit upon the lapse of a measured period of time after said track relay becomes energized, a second signal for governing traic movements in the opposite direction onto said section, and a control circuit for controlling said second signal to display a proceed indication including a contact of said time element means closed when said time element means is deenergized and also including a back contact of said stick relay.

10. In combination, a section of railway track, a railway signal for governing traffic movements onto said section, a track circuit for said section including a track relay, a control circuit including a front contact of said track relay for controlling said signal for displaying a proceed indication, time element means normally deenergized, a second contact also included in said control circuit which is normally closed but which becomes opened in response to a train entering said section while said signal is controlled to display a proceed indication, means controlled by said time element means for then retaining said second contact open while said time element means is deenergized and for again closing said second contact upon the lapse of a measured period of time after said time element means becomes energized, and means including said track relay contact for eiecting energization of said time element means when said track relay contact again becomes closed while said second contact is open.

1l. In combination, a section of railway track, a railway signal for governing traiiic movements onto said section, a track circuit for said section including a track relay, a control circuit including a iront contact of said track relay for controling said signal for displaying a proceed indication, a second contact also included in said control circuit which is normally closed but which becomes opened in response to a train entering said section while said signal is controlled to display -a proceed indication, a time element device having a contact which is normally closed but which becomes opened after said time element device has been energized a measured period of time, means for energizing said time element device if said track relay contact becomes closed while said second contact is open, and means controlled by said time element device contact for retaining said second contact open while said time element device contact is closed and for effecting the closing of said second contact when said time element device contact becomes opened.

12. YIn combination, a section of railway track, a railway signal for governing traffic movements onto said section, a track circuit for said section including a track relay, -a control circuit including a front contact of said track relay for controlling said signal for displaying a proceed indication, a second contact also included in said control cir. cuit which is normally closed but which becomes opened in responsev to a train entering said section while said signal' is controlled to display a second contact when said time element device contact becomes opened, a second signal for governing traiiic movements in the opposite direction onto said section,- and a control circuit for said second signal including said time element device contact and a third contact Which is controlled by the same means as said second contact and is closed when said second contact is closed.

OTTO W. ROST.

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

UNITED STATES PATENTS Number Name Date 1,790,526 Young Jan. 27, 1931 2,242,984 Williamson May 20, 1941

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