US2280878A - Railway track circuit apparatus - Google Patents

Description

p i ,1 E. M. ALLEN 2,280,878

RAILWAY TRACK CIRCUIT APPARATUS Filed Sept. 20, 1940 lNVENTOR 16' AfToR EY Patented Apr. 28, 1942 UN ITE-D STATES SPAT E NT F F I CE RAILWAY TRACK CIRCUIT APPARATUS -Application September 20, 1940, Serial No. 357,548

19 Claims.

My invention relates to railway track circuit apparatus, and it has particular reference to the organization of such apparatus into control systerns of the class involving two adjoining track circuits which are arranged to be particularly effective to control the operation of highway crossing signals guarding the intersection of a highway and a stretch of railway track over which trains operate in either direction, and which systems maintain operation of such signals until each train completelyclears the intersection.

This application is a continuation-in-part of my copending application, Serial No. 250,961 filed on January 14, 1939 for Apparatus for the control of highway crossing signals.

It has been proposed heretofore to control the operation of a highway crossing signal through the medium of two adjoining track circuits, one on either side of the intersection and each nor mally terminated by aninsulated joint short of the intersection so as to be normally ineffective at the intersectiom-andby shunting around the one insulated joint first to be encountered by a train approaching the intersection, provide for the track circuit'first entered by the train an extended shunt whereinthe added length of track rail is connected in the track circuit in multiple with the winding of the track relay. In such proposed systems, the extended shunt is of course incorporated into the track circuit on the open circuit principle, in that if there is an increase in the resistance of any added element of the extended shunt, or if an open circuit condition exists in any of such added elements, the

multiple path around the track relay winding becomes ineffective to enable a train on the extended shunt to shunt the track relay, and causes such relay to become controlled by its normal track circuit which is ineffective short of the intersection.

An object of my invention is to provide control systems involving two adjoining track circuits and incorporating novel and improved means for providing an extended shunt for the one of the two track circuits first entered by a train, wherein the added elements of the extended shunt are incorporated on the closed circuit principle into such first entered track circuit.

Another object of my invention is to provide control systems wherein operation of a signal is established through the medium of two adjoining track circuits and wherein means is provided for extending the effective s m ible g h O track rails connected in series across the track relay of .the track circuit first entered by a train.

A further object of my invention is to provide novel and improved crossing signal control systems of the class utilizing two adjoining track circuits each normally terminated short of the crossing, and which systems employ for governing the crossing signal, directional means controlled by the two track circuits and in turn controlling means for incorporating an additional length of track rail at the crossing in series across the terminals of the track relay included in the track circuit first entered by the train, whereby there is provided an extended shunt arranged on the closed circuit principle.

Another object of my invention is to provide control systems involving two adjoining track circuits and incorporating novel and improved means for providing an extended shunt for the track relay incorporated into the one of the two track circuits first entered by the train and a preliminary release of the track relay of the other track circuit.

A further object of my invention is to provide novel and improved crossing signal control systems of the class wherein operation of a highway crossing signal is established by directional means controlled by two track circuits each normally terminated short of the crossing, and whichsysterns incorporate means governed by the direct1 onal means for not only incorporating an additional length of track rail at the crossing in series across the terminals of the track relay included in the track circuit first entered by the train whereby the effective shuntable length of such track circuit is extended on the closed circuit principle, but also for causing the other track relay to be released prior to the entrance of a train on the other track circuit.

Another object of my invention is to provide control systems of the class described and incorporating novel and improved means for automatically restoring the system to normal in the event that both of its two track circuits become shunted simultaneously.

A further object of my invention is the organization of railway track circuit apparatus into novel and improved control systems.

The above-mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description, are attained in accordance with my invention by dividing an insulated section of railway track into two adjoining subsections through the medium of two insulated rail joints disposed one in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection. Each subsection is provided with a track circuit includin a track relay connected to the rails of the associated subsection adjacent the two insulated joints, and means is provided controlled by the one of the two track relays first to be released by a train in the section for establishing a shunt path around the one of the two insulated joints first to be encountered by the train moving through the section, and also for transferring the connection of such relay from the rail adjacent the shunted insulated joint to a point of that rail substantially opposite the other insulated joint. Additionally, my invention provides means for releasing the other of the two track relays prior to the entrance of a train on its associated subsection, and additional means may be employed to insure the restoration of the system to its normal condition in theevent that both track circuits become occupied simultaneously.

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

In the accompanying drawing, Fig. l is a diagrammatic view showing a preferred form of apparatus embodying my invention represented as applied to the control of a highway crossing signal. Fig. 2 is a diagrammatic View illustrating a modified arrangement of the apparatus of Fig. 1, and also embodying my invention. In each of the two views, similar reference characters have been employed to designate corresponding parts.

Referring to Fig. 1, the reference characters I and la designate the track rails of a stretch of railway track over which traflic moves in either direction, and which stretch is provided with an insulated section of track DG defined at its left-hand end D and its right-hand end G by the usual insulated rail joints 2. A highway H intersects track section DG at grade, and located at such intersection is highway crossing apparatus, designated by the reference character S, for warning highway users of the approach of a train to the intersection. The highway crossing apparatus may be of any suitable type, and as here shown is an audible signal in the form of an electric bell.

Section DG is divided into two adjoining subsections by means of two insulated rail joints 2 disposed, one joint in one rail and the other joint in the other rail, intermediate the ends of the section at points selected so that a portion of one rail of one subsection overlaps a portion of the other rail of the other subsection. Specifically, track rail I of section D-G, as shown, is divided by means of insulated joint 2 located at E on the left-hand side of the highway, into a left-hand section DE and a right-hand section 1 E-G, and track rail Ia of section DG is divided by means of an insulated joint 2 located at F on the right-hand side of the highway, into a left-hand section D-F and a right-hand section F-G.

The reference characters 3 each designate suitable sources of current, such as track batteries, one source of which is connected across left-hand sections D-E and DF of rails I and Ia, respectively, at the left-hand end of section DG,

and the other source of which is connected across right-hand sections E-G and FG of rails I and Ia, respectively, at the right-hand end of section DG.

The reference characters ITR and ZTR desi nate track relays normally connected across the left-hand sections and the right-hand sections, respectively, of rails I and Ia adjacent the insulated joints 2 at E and F. A track circuit whereby relay ITR normally is energized may be traced from one terminal of battery 3, connected across the left-hand sections of rails I and Is, through left-hand section DE' of rail I, wire 4, resistor 5, then through two branch paths to the winding of relay ITR, a first or stick circuit path of which comprises wire 6, front contact I of relay ITR, and wire 8, the other or holding circuit path of which comprises wire 9, front flagman contact ID of an associated or first magnet MI of an interlocking relay XR, to be referred to later, Wire I I, then the winding of relay ITR, wire I2, front fiagman contact 38 of another or second magnet M2 of relay XR, wire 34, and lefthand section DF of rail Ia to the other terminal of battery 3. A track circuit whereby relay 2TB. normally is energized may be traced from one terminal of battery 3 connected across the right-hand sections of rails I and Id, through right-hand section F-G of rail Ia, wire I3, resistor I4, then through two branch paths to the winding of relay 2TB, a first or stick circuit path of which comprises wire I5, front contact I6 of relay 2TB, and wire I1, the other or holding circuit path of which comprises wire IB, front flagman contact I9 of the associated second magnet M2 of relay XR, and wire 20', then the winding of relay 2TH, wire 2i, front flagman contact 39 of the first magnet MI of relay XR, wire 29 and right-hand section EG of rail I to the other terminal of battery 3. It should be noted that in the track circuits of relays ITR and 2TB, each track circuit normally includes but one section of track rail which extends through .the intersection and terminates on the far side of the highway, the other track rail of each track circuit normally being terminated on the near side of the intersection, so that a portion of one rail of one of the track circuits overlaps a portion of the other rail of the other track circuit. As will be pointed out in detail presently, when an eastbound train, that is, a train operating from left to right in the drawing, enters section DG at its left-hand end, left-hand section DE is then connected in series with right-hand section E-G of rail I, and relay ITR is then connected across right-hand section EG of rail l at a selected point on the far side of the highway, and left-hand section D--F of rail Ia, with the result that the track rails included in the track circuit of relay ITR both extend across the highway. Likewise, as will be pointed out hereinafter, when a westbound train enters section DG at its right-hand end, then right-hand section FG is connected in series with left-hand section DF of rail Ia, and relay ZTR is connected across left-hand section DF of rail Ia at a selected point on the far side of the inter section, and right-hand section E--G of rail .I,

with the result that the track rails included in g the track circuit of relay 2TRboth extend across to, comprises a first magnet .Ml ancla second magnet M2, and may take any one of several well-known types such as for example, the relay shown in United States Letters Patent No. 1,799,629, granted to W. K. Lockhart and T. J. OMeara on April '7, 193 1. This type of relay is well known and. is characterized by the fact that the first magnet only of the two magnets to be successively deenergized is permitted to respectively open and close its front and back contacts. That is to say, if magnet Ml is first deenergized, the downward movement of the armature associated therewith opens and closes respectively the front and back contacts controlled thereby and also actuates a mechanical locking device which holds the armature associated with magnet M2 locked up in approximately its mid position, wherein the front and. back contacts controlled thereby are prevented from opening and closing when magnet M2 is subsequently deenergized. Likewise, if magnet M2 is first deenergized, its front and back contacts are respectively opened and closed, and the mechanical locking device is actuated to lock up the armature of magnet Ml when the latter magnet subsequently becomes deenergized. In accordance with the usual practice, I have termed such front contacts of magnets MI and M2 flagman front contacts inasmuch as such contacts remain closed in the locked up" position of the armature associated therewith, and are opened only when the associated arma ture is in its full released position. Magnet Ml of relay XR normally is energized over a simple circuit passing from one terminal B of a suitable source of current, such as a battery not shown, through front contact 22 of relay lTR and the winding of magnet Ml to the other terminal C of the source of current. Magnet M2 normally is energized over a circuit which may be traced from terminal 13 through front contact 23 of relay ZTR and the winding of magnet M2 to terminal C.

The reference characteruCR designates a control relay for controlling the operation of signal S. Relay CR normally is energized over a simple circuit extending from terminal B through front fiagman contact 24 of magnet M2, front flagman contact 25 of magnet Ml, and the winding of relay CR to terminal (3. The immediate operating circuit of signal S passes from terminal B through back contact 26' of relay CR and the winding of signal S to terminal C.

When section D--G is unoccupied, the apparatus is in its normal condition as shown in the drawing. In this condition of the apparatus, relays I'IR, 2TB, XR and CR are energized, and signal S is deenergized.

When an eastbound train enters section D--G, relay lTR. is shunted and releases to open its front contacts 7 and Z2 interposed respectively in the stick circuit path of the track circuit of relay lTR, and in the energizing circuit of magnet Ml of relay XE. With the circuit of magnet Ml open at front contact 22 of relay lTR, magnet Ml becomes deenergized and releases its armature to open front flagman contacts Ill, 25 and 39, and to close back'contacts 21 and 30. The opening of front contact 25 of magnet Ml opens the previously traced circuit of relay CR, with the result that relay CR releases to close back contact 26 and thereby complete the operating circuit of signal S to initiate operation of that signal. The closing of back contact 2? of magnet Ml completes a shunt path around insulated Joint! interposed in rail l at E located at the left-handside of ,the intersection, so that lefthand section D-E is connected in series with right-hand section E-G of rail l, the circuit connection passing from left-hand section D-E of rail I through wire 4, wire 28, back contact 21 of magnet Ml and wire 29 to right-hand section E-G of rail l. The closing of back contact 38 of magnet Ml connects relay lTR across righthand sectionE-G of rail l and left-hand section DF of rail la, the circuit connection passing from right-hand section E-G of rail l at a selected point on the right-hand side of the highway, through wire 3|, back contact 30 of magnet Ml, wire H, the winding of relay lTR, wire l2, front flagm'an contact 38 of magnet ME and wire 34 to left-hand section DF of rail la. It is readily apparent that since sections D-E and E--Gr of rail I. are connected in series, the track circuit connected across the terminals of relay l TR includes in series both rails at the intersection. It follows that as long as the train operates over the intersection the train shunt is established across the track circuit connected with the terminals'of track relay 'lTR, and relay lTR is released to control signal S to its operating condition.

Relay 2TH, also releases when the eastbound train enters-section D-G at its left-hand end D. This preliminary release of relay 2TB is effected prior .to the train entering the track circuit of such relay, due to the connection of the lefthand terminal, as viewed. in the drawing, of relay 2TB. to rail I being openeda't front fiagman contact38of magnet Ml of relay KB. The releasing of relay 2TB of course causes its front contacts 16 and 23 to open, and the latter contact. in turn causes the control circuit of M2 of relay XR. to be opened whereupon magnet M2 releases its armature to its locked up position wherein its front contacts are held. closed and its back contacts are held open. It is apparent, therefore, that with relay 2TB released and its associated magnet M2 locked up, when the eastbound train enters the track circuit of relay 2TB and establishes a train shunt across'the rails l and la.

incorporated into such track circuit, the appaits previously traced track circuit including both track rails l and to at the highway, to close front contacts I and 22. The closing. of front contact 22 of relay lTR completes the energizing circuit of magnet Ml whereupon magnet Ml becomes reenergized, while the closing of front contact I of relay ITR completes the stick circuit path in the normal track circuit of relay ITR, which path holds relay ITR energized during the interval that the movable contact member of magnet Ml common to both contacts [0 and 3ll, is moving between its back contact 30 and its' front contact l8. When front contact ll) of magnet Ml closes, relay ITR is held energized over both its stick circuit path including front contact 1 of relay ITR and its holding circuit path including front contact ll) of magnet Ml. The energization of magnet Ml also disconnects right-hand section E-G from left-hand section D-E of rail I when back contact 2? of magnet M I' opens; completes the circuit of relay CR, when front contact 25 closes, to cause that relay to pick up and open its back contact 26 and thus terminate operation of signal S; and reconnects relay ZTR incircuit with rail 1 when front contact39 closes. Relay ZTR, of course, is maintained released due to the train shunt in its track. circuit.

Then, when the train vacates section D-G at its right-hand end, relay 2TB picks up over its holding circuit path including front contact I9 of magnet M2 and front contact 39 of magnet Ml. Relay 2TR in picking up closes its front contact 23 to thereby complete the energizing circuit of magnet M2 whereupon that magnet becomes energized to restore the apparatus to its normal condition.

The operation of the apparatus for a westbound train is substantially similar to the operation just described for an eastbound train, as can readily be understood from an inspection oi the drawing, and it is deemed suflicient to point out that when relay 2TB is released by a westbound train entering track section DG, magnet M2 is released to complete a shunt path around insulated joint 2 interposed in rail I a at F located on the right-hand side of the intersection, so that left-hand section D-F is connected in series with right-hand section F-G of rail la, the connection passing from right-hand section F-G of rail la through wire 13, Wire 33, back contact 32 of magnet M2, and wire 34 to left-hand section DF of rail la. Relay ZTR is now connected across left-hand section D-F of rail la and right-hand section E-G of rail I, the connection passing from left-hand section DF of rail Ia at a selected point on the left-hand side of the highway through wire 35, back contact 36 of magnet M2, wire 20, the winding of relay 2TB, wire 2i, front contact 39 of magnet MI, and wire 29 to righthand section Iii-G of rail i. cluded in the track circuit connected across the terminals of relay 2TR. now extend across the highway H, so that relay 2TB is released to control signal S to its operating condition until the train completely clears the highway. Also, relay ITR. is released since the connection of its righthand terminal to rail la is now open at front fiagman contact 38 of magnet M2, and with relay l TR released, magnet MI is deenergized and its armature drops to its locked up position.

It should be noted that when relay ITR or ZTR is energized over its normal track circuit, the associated resistor 5 or M is interposed in such circuit, but that whenever the track circuit of either relay is extended to include both track rails at the highway, the associated resistor is then excluded from the extended track circuit. It is readily apparent that the resistances of the circuit wires, control contacts, and the highway section of track rail added when the track circuit is extended, cause the resistance of the track circuit when extended to be increased over the resistance of the normal track circuit. The resistance 5 or M interposed in the normal track circuit of relay ITR or 2TB, may be so adjusted as to compensate for the added increment in resistance of the extended track circuit and cause the current energizing the track relay to be substantially the same magnitude in each instance,

thereby preventing any tendency toward over-1' energizing the track relay when included in its normal track circuit.

It should further be noted that my invention provides a control system involving two adjoining track sections, wherein the apparatus is so arranged that the efiective shuntable length of the first of the two circuits to beentered by a train is increased by an extended shunt arranged on the closed circuit principle so that in each instance when atrack circuit is extend d, the

Both track rails incircuit wires, control contacts and highway sec-' tion of track added are all connected. in series with the winding of the associated track relay;

' It is readily apparent, therefore, that in the event the resistance of any added element increases, or if an open circuit condition exists in any added element, the energization of the track relay controlled by that track circuit will be reduced. It is obvious that the abnormal condition just referred to will contribute toward effecting the release of the trackrelay, thereby insuring a safe condition of the apparatus under all conditions of operation.

From the foregoing description of the operation of the apparatus embodying my invention, it is readily apparent that when apparatus embodying my invention is utilized to control a highway crossing signal, it provides means governed by a train approaching the intersection'for extending the track circuit of the track relay on the approach side of the intersection to include both track rails at the highway, thus insuring that the track relay on the approach side of the intersec tion will pick up to interrupt the operation of the highway crossing apparatus only after the train has completely cleared the intersection. It follows that with track rails at the intersection incorporated into the track circuit of the relay on the approach side of the intersection, operation of the signal for trains operating in either direction over the intersection is maintained until the trains completely cross the highway.

In addition, it is readily apparent that my invention also incorporates means not only for providing an extended shunt for the track relay of the track circuit first entered by a train, but also for providing a preliminary release of the other track relay prior to the entrance of a train on its associated track circuit. This preliminary release of the second track relay is, of course, effective to insure that when a light, fast train passes rapidly from one track circuit to the next, the first track relay cannot pick up prior to the second track relay releasing, hence the directional set-up or route established by the train in the first track circuit will be maintained when the train occupies the second circuit.

It is, of course, to be understood that if the apparatus of Fig. 1 is desired to be employed to provide an extended shunt for the track circuit first entered by the train without providing a preliminary release of the track relay of the other track circuit, such system readily is provided merely by omittingfrom the track circuits of relays I'IR and 2TB. front contacts 38 and 39, respectively, of magnets M2 and MI of relay XR. In the event that such contacts are omitted, the release of the track relay incorporated into the track circuit first entered by a train would not effect the connection of the other track relay to the rails of its associated circuit, hence there would be provided no preliminary release of such other relay.

Fig. 2 represents the apparatus of Fig. l modifled to incorporate an auxiliary relay XZPR arranged to be energized if and only if both magnets MI and M2 of relay XR are simultaneously deenergized and permit their armatures to drop to their full released positions. Referring now to Fig. 2, relay XZPR preferably is provided with slow releasing characteristics, and as shown is provided with an energizing circuit passing from terminal B through back contact 48 of magnet M2 of the relay XR, the winding of relay XZPR, and back contact 49 of magnet Ml of relay XR to ter inal C." The en gizing cir uit of operating relay OR is slightly modified in Fig. 2 and passes from terminal B through front flagman contact 24 of magnet M2, the winding of relay CR and front flagman contact 25 of magnet MI to terminal C. Relay CR accordingly is normally energized and is deenergized if either magnet MI or M2 drops to its full-released position, While relay XZPR is normally deenergized and is energized only if both magnets MI and M2 drop to their full released positions.

In order to simplify the drawing, certain contacts controlled by relay XZPR have been represented in Fig. 2 located at points remote from the location of the relay itself, but in each case such contacts have been identified not only by placing i nection with the apparatus of Fig. 1, in that front contact 4|] of relay XZPR when closed completes an obvious shunt path around front contact 39 of magnet MI of relay XR; another front contact 4| of relay XZPR when closed completes a readily traced shunt path around front contact 38 of :3

magnet M2 of relay XR; a back contact 42 of re- I lay XZPR is interposed in Fig. 2 in the connection of wire 4 to wire 28; front contact 43 of relay XZPR when closed connects wire 4 to wire I I by shunting resistor 5 and front contact It of 1:,

magnet MI over wire 46; back contact 44 of relay XZPR is interposed in Fig. 2 between wire I3 and wire 33; while front contact 45 of relay XZPR when closed connects wire I 3 to wire by shuntlng around resistor I6 and front contact 21 of magnet M2 over wire 41.

Under normal conditions of operation of the apparatus of Fig. 2, only one of the two magnets of relay XR drops to its full released position as pointed out previously in connection with the description of the operation of the apparatus of Fig. 1, so that relay XZPR remains deenergized and the apparatus of Fig. 2 functions in the same manner as that pointed out in detail in connection with Fig. 1, to extend the effective shuntable length of the track circuit first entered by a train andto release the relay of the other track circuit prior to the entrance of a train on the latter circuit. 1

If, however, a train enters section D--G at one end at substantially the same instant that another train enters the section at the other end, and both track circuits are simultaneously shunted so that relays I TR and 2TR release to open the energizing circuits of magnets MI and.

M2 simultaneously, then the armatures associated with magnets MI and M2 drop to their full released positions. Under such assumed conditions, relay CR of course releases to close its back contact 26 and initiate the operation of signal S, l

and relays ITR and HR are both disconnected from their respective track circuits since magnet MI in dropping to its full released position opens front contact 39 to disconnect relay 2TR from rail I, and magnet M2 drops to its full released position to open its front contact 38 and thus disconnect relay I'IR from rail Ia.

Relay XZPR becomes energized when both magnets MI and M2 are in-their respective full released position, and relay XZPR accordingly opens its back contacts 42 and 44 interposed in the shunt circuits established around insulated joints 2 at E and F, respectively, to limit the effective length of thetrack circuits of relays ITR and 2'IR to their respective normal lengths; closes its frontcontacts43 and 4| to establish for relay ITR an auxiliary pick-up circuit path which may be traced from left-hand section D-E of rail I through wire 4, front contact 43 of relay XZPR, wire 46, wire II, the winding of relay ITR, wire I2, front contact 4| of relay XZPR, andwire 34 to the left-hand section D-F of rail Ia; closes its front contacts 45 and to complete for relay 2-TR anauxiliary pick-up circuit path which extends from right-hand section F-G of rail I'a, through wire I3, front contact of relay XZPR, wire 41, wire 20, the winding of relay 2TB, wire 2I, front contact 40 of relay XZPR and wire 29 to right-hand section D-G of rail I. Under the latter assumed conditions, relays ITR and Z'IRof course remain released as long as the one train occupies the one end of section D--G and the other train occupies the other end of the section. When, however, either of the trains vacate section D-G, then the relay connected in the track circuit provided for that end picks up over its just traced auxiliary pick-up circuit path to reenergize its associated magnet of relay XR. For example, if the train in the right-hand end of section D-G reverses and vacates the section, then relay ZTR picks up over its previously traced auxiliary circuit path, and when relay 2TB, picks up, magnet M2 becomes reenergized and also picks up. Relay XZPR thereupon releases at the end of its slow release period, to open the auxiliary pick -up circuit paths previously traced for relays I'IR and 2TH, respectively, and to reestablish a shunt path around insulated joint 2 at E when back contact 42 of relay XZPR closes. The dropping of relay XZPR and consequent opening of the auxiliary pick-up circuit path ofrelay 2'I'R of course causes relay ZTR to become released since its normal track circuit is open circuited at front contact 39 of magnet MI, and relay 2TB thereupon again releases to deenergize magnet M2. The armature of magnet M2, however, drops only to its locked up position since when magnet M2 picks up and magnet MI remains released, the interlocking mechanism of relay XR becomes active to condition the armature of magnet M2 to be held in its locked up position if such armature again drops.

The apparatus of Fig. 2 is now in the same condition as if section D--G had been entered only by the train at the left-hand end D, and accordingly the apparatus of Fig. 2 Will function in substantially the same manner as that previously pointed out in detail in connection with the apparatus of Fig. l, to extend the effective shuntable length of the track circuit of relay ITR and thus maintain operation of signal S until the train completely clears the intersection, and to prevent operation of the signal when the train recedes from the intersection through the righthand portion of section D-G.

The apparatus of Fig, 2 of course functions in substantially the same manner as that previously described in detail to cause relay ITR to pick up and again release if the train in the left-hand end of section DG vacates the section while the other train occupies the other end of the section. It follows, therefore, that relay XZPR provides means for automatically restoring the apparatus of Fig, 2 to its normal condition in the event that both track circuits become occupied simultaneously. 7

Although I have herein shown and described only two forms of railway track circuit 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:

1. In combination with an insulated section of railway track divided into two adjoining subsections by two insulated joints disposed. one in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection, two track circuits one for each of said subsections and each including a track relay connected to the rails of its associated subsections adjacent said two insulated joints, means controlled by the one of said track relays first released by a train in said section for establishing a shunt path around the one of said two insulated joints first to be encountered by the train moving through said section, and means controlled by said first released track relay for transferring the connection of such relay with the rail adjacent said one insulated joint to a point of that rail substantially opposite the other insulated joint.

2. In combination with an insulated section of railway track divided into two adjoining subsections by two insulated joints disposed one in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection, two track circuits one for each of said subsections and each including a track relay connected to the rails of its associated subsection adjacent said two insulated joints, directional means controlled by said track relays,

means controlled by said directional means in response to the releasing of either of said track relays by a train entering said section for establishing a shunt path around the one of said two insulated joints first to be encountered by the train, and means also controlled by said directional means when either of said track relays is released by the entrance of the train in said section for disconnecting such released track relay from the rail adjacent said shunted insulated joint and for connecting that relay to a point of that rail substantially opposite the other of said two insulated joints.

3. In combination with an insulated section of railway track intersected by a highway and divided into two adjoining subsections by two insulated joints disposed one in each rail on opposite sides of said highway, two track circuits one for each of said subsections and each including a track relay connected across the rails of its associated subsection adjacent said insulated joints, means controlled by the one of said track relays first released by a train in said section for establishing a shunt path around the one of said two insulated joints first to be encountered by the train approaching said highway, and means controlled by said first released track relay for transferring the connection of such relay with the rail adjacent said one insulated joint to a point of that rail on the opposite side of the highway.

4. In combination with an insulated section of railway track intersected by a highway and divided into two adjoining subsections by two insulated joints disposed one in each rail on opposite'sides of said highway, two track circuits one for each of said subsections and each includ ing a track relay connected across the rails of its associated subsection adjacent said insulated joints, a highway crossing signal located at the railway-highway intersection, an interlocking relay having two magnets one controlled by each of said track relays, means for operating said signal controlled by the one of said two magnets of the interlocking relay associated with the track relay first to be released in response to a train entering said section, means controlled by such one magnet for establishing a shunt path around the one of said two insulated joints first to be encountered by the train approaching said highway, and means controlled by such one magnet for transferring the connection of the associated released track relay from the point of a rail adjacent said one insulated joint to a point of that rail on the opposite side of said highway.

5. In combination with an insulated section of railway track divided into two adjoining subsections by two insulated joints disposed one in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection, two track circuits one for each of said subsections and each including a track relay connectedto the rails of its associated subsection adjacent said two insulated joints, means controlled by the one of said track relays first released by a train in said section for establish ing a shunt path around the one of said two insulated joints first to be encountered by the train moving through said section and for releasing the other of said two track relays, and means controlled by said first released track relay for transferring the connection of such relay with the rail adjacent said one insulated joint to a point of that rail substantially opposite the other insulated joint.

6. In combination with an insulated section of railway track divided into two adjoining subsecsaid subsections and each including a track relay connected to the rails of its associated subsection adjacent said two insulated joints, means controlled by the one of said track relays first released by a train in said section for establishing a shunt path around the one of said two insulated joints first to be encountered by the train moving through said section and for disconnecting the other of said two track relays from the rail adjacent the shunted insulated joint, and means controlled by said first released track relay for transferring the connection of such relay with the rail adjacent said one insulated joint to a point of that rail substantially opposite the other insulated joint.

7. In combination with an insulated section of railway track divided into two adjoining subsections by two insulated joints disposed one in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection, two track circuits one for each of said subsections and each including a track relay connected to the rails of its associated subsection adjacent said two insulated joints, direc tional means controlled by said track relays, means controlled by said directional means in response to the releasing of either one of said track relays by a train entering said section for establishing a shunt path around the one of said two insulated joints first to be encountered by 2,280,878 the train and for releasing the other of. said two' track relays, and means also controlled-by said directional means for disconnecting suchreleased one track relay from the rail adjacent said shunted'insulated joint and for connecting that relay to a point of that rail substantially opposite the other of said two insulated joints.

8. In combination with aninsulated section of railway track divided into two adjoining subsectionsHby two insulated joints disposedone in each rail in such manner that a rail portion of one subsection overlaps a rail portion of the other subsection, two track circuits one for each of said subsections and each including atrack relay connected to the rails of its associatedsubsection adjacent said two insulated joints, directional means controlled by said track relays, means controlled by said directional means in respose to the releasing of either one of said track relays by a train entering said section for establishing a shunt path. around the one of said'two insulated joints first to be encountered by the train and for disconnecting the other of said two relays from the I rail adjacent the shunted insulated joint, and means also controlled'by said directional means for disconnecting such released one track relay from the rail adjacent said shunted insulated joint and for connecting that relay to a point of that rail substantially opposite the other of said two insulated joints.

9. In combination with an insulated section of railway track intersected by a highway and divided into two adjoining subsections by two insulatedjoints disposed one in each rail on opposite sides of said highway, two track circuits one for each of said subsections and each including a track relay connected across the rails of its associated subsection adjacent said insulated joints, a'highway crossing signal located at the railway-highway intersection, an interlocking relay having two magnets one controlled by each of said track relays, means for operating said signal controlled by the one of said two magnets of the interlocking relay associated with the track relay first to be released in responseto a train entering said section, means controlled by such one magnet for establishing a shunt path around the one of said two insulated joints first to be encountered by the train approaching said highway and'for releasing the other magnet prior to the entrance of the train on the other track circuit whereby to insure directional control of the signal, and means controlled by such one magnet for transferring the connection of the associated released track relay from the point of a rail adjacentsaid one insulated joint to a point of that rail on the opposite side of said highway.

10. In combination with a section of railway track intersected by a highway, two track circuits for said section, one on either side of the highway and each normally terminated by a rail joint at the near side of thehighway but including a diiIerent rail at the highway, two track relays one for each of said two track circuits, an interlocking relay having its two magnets selectively controlled by said two trackrelays, circuit means controlled by each of said magnets and effective when the associated track circuit is occupied for completing a shunt path around the particular one of said rail joints located at the near side of said highway, and other means also controlled by that magnet for connecting both track rails at the intersection in series cir.- ,cuitwith said associated trackrelay;

11, In; combination with a section of railway track intersected by a highway, two track cir cuits for said section, oneon either side of the highway and each normally terminated by an insulated joint at the near side of the highway but including a differenttrack rail at the intersection, two track relays each having its winding connected in series withthe track'rails of a different one of said track circuits, means governed by that track relay'which becomes deenergized when a train approaching the intersection enters its associated track circuit for completing a shunt path around the particular one of said insulated joints located at thenear side of the highway, and meansalso' controlledby said one track relay to connect both track rails at the intersection in said associated track circuit in series with the winding of said one track relay.

12. In combination with a stretch of railway track intersected by a highway, an insulated joint in one trackrail at one side of the highway, an insulated joint in the other track rail at the other. side of the highway, said two insulated joints each defining a. left-hand and a right-hand section for its associated track rail, a first source of current connected across the left-handsections of said two track rails at the left-hand end of said stretch, a second source of current connectedacross the right-hand sections, of said two'traek rails at the right-hand end of said stretch, a first track relay, asecond track relay, an interlockingrelay having a first magnet and asecond magnet, circuit means for controlling said first magnet and said second i magnet of said interlocking relay governed respectively by said first track relay and said second track relay, circuit means governed by a front contact of said first magnet of said interlocking relay. for normally connecting said first track relay across the left-hand sections of said two track rails adjacent said two insulated joints, means governed by a back contact of said first magnet of said interlocking relay for connecting in series the left-hand and the right-hand sections of said one track rail, other circuit means governed by a back contact of said first magnet of said interlocking relay for connecting said first track relay across the. right-hand section of said one track rail at a selected point on the right-hand side of the highway and the left-hand section of the other track rail, circuit-means governed by a front contact of said second magnet of said interlocking relay for normally connecting said second trackrelay across the right-hand sections of said two track rails adjacent said two insulated joints, means governed by a back contact of said secondmagnet of said interlocking relay for: connecting in-series the. right-hand and the left-hand section of said other track rail, other circuit means governed by a back contact ofsaid second magnet of said interlocking relay for connecting said second track relay across the lefthand section of said other track rail at a selectedv point on the left-hand side of the highway and the right-hand section of the one track rail, and highway crossing apparatus governed by each of said magnets of said interlocking relay.

13. In combination with a stretch of railway track intersected by a highway, an insulated joint in one track rail at one side of the highway, an insulated joint in the other track rail at the other side of the highway, said two insulated joints each defininga left-hand and a right-hand section for itsiassociated track rail, a first source of current" connecteduacross the left-hand sections of said two track rails at the left-hand end of said stretch, a second source of current connected across the right-hand sections of said two track rails at the right-hand end of said stretch, a first track relay, a second track relay, an in terlocking relay having a first magnet and a second magnet, circuit means for controlling said first magnet and said second magnet of said interlocking relay governed respectively by said first track relay and said second track relay, a first and a second resistor, circuit means governed by a front contact of said first magnet of said interlocking relay and including said first resistor for normally connecting said first track relay across the left-hand sections of said two track rails adjacent said two insulated joints, means governed by a back contact of said first magnet of said interlocking relay for connecting in series the left-hand and the right-hand sections of said one track rail, other circuit means governed by a back contact of said first magnet of said interlocking relay and excluding said first resistor for connecting said first track relay across the right-hand section of said one track rail at a selected p int on the right-hand side of the highway and the left-hand section of said other track rail, circuit means governed by a front contact of said second magnet of said interlocking relay and including said second resistor for normally connecting said second track relay across the right-hand sections of said two track rails adjacent said two insulated joints, means governed by a back contact of said second magnet of said interlocking relay for connecting in series the right-hand and the left-hand sections of said other track rail, other circuit means govened by a back contact of said second magnet of said interlocking relay and excluding said second resistor for connecting said second track relay across the left-hand section of said other track rail at a selected point on the left-hand side of the highway and the right-hand section of said one track rail, and a highway crossing signal located at the intersection of the highway with said stretch of railway track governed by each of said magnets of said interlocking relay.

14. In combination with a stretch of railway track intersected by a highway, an insulated joint in one track rail at one side of the highway, an

insulated joint in the other track rail at the other side of the highway, said two insulated joints each defining a left-hand and a right-hand section for its associated track rail, a first source of current connected across the left-hand sections of said two track rails at the left-hand end of said stretch, a second source of current connected across the right-hand sections of said two track rails at the right-hand end of said stretch, a first track relay, circuit means including a front contact of said first track relay for normally connecting said first track relay across the left-hand sections of said two track rails adjacent said two insulated joints, a second track relay, circuit means including a front contact of said second track relay for normally connecting said second track relay across the right-hand sections of said two track rails adjacent said two insulated joints, an interlocking relay having a first magnet and a second magnet, circuit means for controlling said first and said second magnet of said interlocking relay governed respectively by said first track relay and said second track relay, means governed by a back contact of said first magnet of said interlocking relay for connecting in series the left-hand and the righthand sections of said one track rail, other circuit means governed by a back contact of said first magnet of said interlocking relay for connecting said first track relay across the right-hand section of said one track rail at a selected point on the right-hand side of the highway and the left-hand section of said other track rail, means governed by a back contact of said second magnet of said interlocking relay for connecting in series the right-hand and the left-hand sections of said other track rail, other circuit means governed by a, back contact of said second magnet of said interlocking relay for connecting said second track relay across the left-hand section of said other track rail at a selected point on the left-hand side of the highway and the,right-hand section of said one track rail, and highway crossing apparatus governed by said first and by said second magnet of said interlocking relay,

15. In combination with a stretch of railway track intersected by a highway, two track circuits one on either side of said highway and each terminated in shunting effectiveness short of the highway, a track relay; for each track circuit, an interlocking relay having two magnets one controlled by each of said; track relays, means controlled by the one of said two magnets associated with the track relay first shunted when a train enters either track circuit in approaching said highway for extending'the shunting effectiveness of such entered track circuit to the opposite side of the highway and for releasing the track relay of the other track circuit prior to the entrance of a train on such other circuit, a restoring relay controlled by both of said magnets and energized only when both track relays are shunted simultaneously, and means controlled by said restoring relay and effective after one of said simultaneously shunted track circuits becomes vacated for restoring such vacated circuit to its normal condition.

16. In combination with a stretch of railway track intersected by a highway, two track circuits one on either side of said highway and each terminated in shunting efiectiveness short of said highway, a track relay for each of said track circuits, an interlocking relay having two magnets one governed by each of said track relays, said interlocking relay being characterized by the fact that each magnet is rendered operative to effect a control only if such magnet is deenergized when the other magnet is energized but both magnets are rendered operative when the magnets are simultaneously deenergized, means controlled by the one magnet associated with the track relay first caused to be released in response to the entrance of a train approaching the highway in either one of said track circuits for extending the shunting effectiveness of such entered one track circuit to the opposite side of the highway, other means controlled by such one magnet for releasing the track relay of the other track circuit prior to the entrance of the train on such other track circuit, a restoring relay, a circuit for energizing said restoring relay only when both magnets of said interlocking relay are caused to be operative due to the simultaneous shunting of both of the said two track circuits, and means controlled by said restoring relay and efiective after one of said simultaneously shunted track circuits becomes vacated for restoring such vacated track circuit to its normal condition.

1'7. In combination with a stretch of railway track intersected by a highway, a highway crossing signal at such intersection, two track circuits one on either side of said intersection and each terminated in shunting effectiveness short of the intersection, an interlocking relay having two magnets one governed by each of said track circuits, said interlocking relay being characterized by the fact that each magnet is rendered operative to effect a control only if such magnet is deenergized when the other magnet is energized but both magnets are rendered operative when the magnets are simultaneously deenergized, circuit means controlled by each magnet when rendered operative for causing operation of said signal and for extending the shunting effectiveness of the associated track circuit to the opposite side of the intersection, whereby when a train approaching the intersection enters either track circuit the shunting effectiveness of such entered track circuit is extended and operation of said signal is maintained until the train completely clears the intersection, a restoring relay, a circuit for energizing said restoring relay controlled by both said magnets and efiective only when both magnets are caused to be operative due to a simultaneous shunting of both of said two track circuits, and means governed by said restoring relay when energized for rendering each of said circuit means ineffective to extend the shunting effectiveness of its associated track circuit.

18. In combination with a stretch of railway track intersected by a highway, two track circuits one on either side of said highway and each terminated in shunting effectiveness short of said highway, a track relay for each track circuit, means controlled by the track relay associated with the one of said two track circuits first entered by a train approaching the intersection for extending the shunting effectiveness of such one track circuit to the opposite side of the highway, means controlled by said track relay for causing the release of the track relay of the other track circuit, restoring means responsive to a simultaneouis shunting of both track circuits, and means controlled by said restoring means and efiective after one of said simultaneously shunted track circuits becomes vacated for restoring such vacated circuit to its normal condition.

19. In combination, two adjoining track circuits the adjoining ends of which are defined by insulated joints arranged in such manner that one rail of one track circuit overlaps the other rail of the other track circuit, two track relays one for each track circuit, an interlocking relay having two normally energized magnets one governed by each of said track relays, said interlocking relay being characterized by the fact that each magnet is rendered operative to effect a control only if such magnet is deenergized while the other magnet is energized but both magnets are rendered operative when the magnets are simultaneously deenergized, circuit means controlled by each magnet when rendered operative for extending the shunting effectiveness of its associated track circuit up to the limits of its overlapping track rail and also for opening the other track circuit, a restoring relay provided with an energizing circuit controlled by both of said magnets and completed only when both magnets are operative, and means governed by said restoring relay when energized for rendering each of said circuit means ineffective to extend the shunting effectiveness of its associated track circuit and also ineffective to open the other track circuit.

EARL M. ALLEN.

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