US2045892A - Centralized traffic controlling system for railroads - Google Patents

Description

s N. W1GHT 2,045,892

' Filed Jan. 25, '1955 2 Sheets-Sheet 1 June 30, 1936.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS ATTORNEY S. N. WIGHT June 30, 1936,

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Jan. 25, 2 sheets-sheet 2 m .0 g L :0 K m xL 0. mm B 3 W J61 E Q.\ e b.\ q L 1 5 :H am w Patented June 30, 1936 PATENT CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Sedgwick N. Wight, Rochester, Y., assignor to General Railway Signal Company, Rochester,

Application January'25, 1935, Serial No. 3,476

13 Claims.

This invention relates to centralized trafiic controlling systems for railroads, and more par-- ticularly pertains to a system of the type employing direct line wire control for the switches 5 and signals of such a system.

The'present invention proposes to govern the operation of a railroad track switch over one polarized control circuit, and to govern the operation of the signals associated therewith over lo another polarized control circuit. The polarized control circuit for the control of the signals is contemplated as having superimposed thereon the indication of the trackswitch correspondence with its switch controlling means and also the i5 indication of whether the signals are at stop or clear.

One object of the present invention is to provide means associated in a simple manner'to accomplish the above mentioned purposes, while -30 another object of the invention is to provide such signal control and superimposed indications in a manner that the signal control can be transmitted only when the switch is in correspondence with its control means.

.23 Another object of the invention is to provide for the indication of the condition of the signals by the use of high and low currents on the signal control circuit, to thereby increase the capacity of the signal control circuit. I

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out, as the description of the invention progresses. I

In describing the invention in detail, reference will be made to the accompanying drawings, inwhich like reference characters designate corresponding parts throughout the several views, and in which: I

Fig. 1 illustrates in a diagrammatic manner one embodiment of the present invention as applied to the control of traffic over a single railroad track switch;

Fig. 2 illustrates in a diagrammatic manner a simplified form of the signal control and indication illustrated in Fig. .1; I I

Fig. .3 illustrates in a diagrammatic manner a modified form of signal control and indication; I

and

Fig. 4 illustrates in a diagrammatic manner, a modified form of control for the signal control circuit at the field station to superimpose the signal indication, which modified 'form may be employed in connection with either Fig. 2 or Fig. 3. Although the traffic controlling system of the present invention may be applied to various track layouts involving conflicting routes and non-confiictin'g routes as well as various other conditions encountered in signalling practice, it has been specifically illustrated in the present embodiment as applied to a single track switch with "its signals, which switch and signals are preferably associated with suitable automatic signalling either of the automatic block signal type as shown, for example, in my pending application, Ser; No. 120,423, filed July 3, 1926, or in connection with interlocking type of signalling as shown, for example, in my pending application, Ser. No. 540,596, filed May 28, 1931.

With reference to the accompanying Fig. 1 of the drawings, a railroad track switch TS is illustrated as connecting the rails of a main track to the rails of a diverging or turnout track. This track switch TS is operated by a power driven switch machine SM which may be of any suitable type, such, for example, as disclosed in the patent to W. K. Howe, Patent No. 1,466,903, dated September 4, 1923. This switch machine may also -be provided with a dual control selector to permit hand operation of the track switch, as shown, for example, in the patent to W. K. Howe,

Patent No. 1,852,573 dated April '5, 1932.

The main track adjacent the track switch TS and a portion of the divergingtrack to the fouling point comprises the usual detector track circult of the closed circuit type, the specific details of which have been omitted for the sake of simplicity in the disclosure. However, the opposite ends of the detector track section are provided with suitable signals for governing trailic over such track section including the track switch, as well as the subsequent track sections usually governed by such signals.

'Trafi'ic over the track switch TS in an east bound direction is governed by the signals IA and IE on the main track and onto the diverging "track respectively; while signals 2A and 2B are provided for governing trafiic in a west bound direction on the main track and off the diverging track respectively These signals lA-lB and 2A'-2B preferably have suitable automatic signalling associated therewitmbut for the sake of simplicity in the present disclosure, the signals have only been indicated as controlled by suitable signal controlling relays.

More specifically, the signal EA is indicated as controlled by the signal controllingrelay [AG to display stop while back contact 53 is closed and to display clear while front contact 43'is closed. r

Similarly, the signal I B is controlled by relay IBG to display stop while back contact 42 is closed and to display clear while front contact 42 is closed. The signals 2A and 2B for the opposite direction are similarly controlled by relays 2AG and ZBG having controlling contacts 44 and 45 respectively.

When all of the signals are at stop by reason of the deenergization of their respective signal control relays G (with suitable preceding designations) a signal at stop relay RP is energized by a circuit closed from through a circuitincluding back contact 38 of relay IBG, back contact 39 of relay iAG, back contact 45 of relay 2AG, back" contact 4| of relay 213G, winding of relay RP, to

(). The relay RP has a contact 3i! which is employed to govern the signal control circuit in a manner to transmit the signal indication, as hereinafter described in detail.

The track switch TS and the switch machine SM are preferably provided with point detector contacts (not shown) of some suitable type, as disclosed, for example, in the patent to C. S. Bushnell, Patent No. 1,517,236, dated November 25, 1924. These point detector contacts are employed to energize with current of one polarity a switch position repeating relay WP of the usual polar neutral type when the track switch is in an extreme normal locked position, and to energize it with current of the opposite polarity when the track switch is in an extreme reverse locked position, or to deenergize this relay WP Whenever the track switch TS is unlocked or the switch machine SM is in operation. Such control of the relay WP is well understood and is merely indicated by a dotted line extending from the relay WP to the track switch TS and switch machine SM.

A polar neutral relay WZ, preferably of the magnetic stick type, is governed from the control oiiice over a suitable polarized line circuit by a switch machine control lever SML in accordance with the position of its contact I0. Such control has been merely indicated by a dotted line, but any suitable type control may be employed such, for example, as shown in my pending application Ser. No. 737,780, filed July 31, 1934.

The polar neutral relay W2 is provided with a contact l3 which is indicated as controlling the switch machine SM, which control has been merely indicated by a dotted line, but this control may be of any suitable type, it being understood that suitable approach locking and time releasing therefor and other adjuncts of a signalling system are preferably employed in connection therewith so that the track switch TS cannot be operated while such operation is unsafe.

Neutral relays NWP and RWP are associated with the relays WP and WZ to indicate when the switch control relay and track switch are in corresponding positions. More specifically, the relay NWP is energized whenever the relays W2 and WP are in corresponding normal positions by a circuit closed from through a circuit including front contact 24 of relay WZ, front contact 25 of relay WP, polar contact 26 of relay WP in a right hand position, winding of relay NWP, polar contact 21 of relay WZ in a right hand position, to On the other hand, when the relays W2 and WP are in corresponding reverse positions, the relay RWP is energized by a circuit closed from through a circuit including front contact 24 of relay WZ, front contact 25 of relay WP, polar contact 25 of relay WP in a left hand position, winding of relay RWP, polar contact 21 of relay WZ in a left hand position, to

lever SML is provided with a contact I l which is employed to control a correspondence stick relay CS which in turn governs a correspondence indicator l5 suitably located on the control panel adjacent the switch machine control lever SML.

A signal control lever SL is suitably located upon the control panel in the central ofiice; and, through its contact l2 supplies positive or negative potential to the signal control line circuit, or deenergizes such circuit so as to suitably control the polar neutral signal control relay SZ at the field station.

A marginal neutral relay SK is employed in connection with a signal lever repeating relay SLP to provide the correspondence and signal indications as transmitted from the field station over the signal line circuit. These two relays in combination are employed to control the indicators l5 and I5 which are suitably located on the control panel. I

A suitable source of energy is indicated by battery 4'! at the field station for supplying potential to the signal control and indicating circuit and is shown as having a center or mid-tap connected to the common return line wire 9. v In the control oifice, a battery 45 supplies positive and negative potential to bus wires Sand! respectively, and a mid tap isiconnected to a common bus wire 5 and thecommon return line wire 9.

Various circuits not connected with the line circuit are indicated as being supplied with energy froma suitable source indicated by and for the opposite terminals of such source. It is to be understood in this connection that various circuits may be supplied with energy from the same source or different sources than those shown in accordanceiwith the practicalapplication of the system of the present invention. Also, those sources which have been indicated as direct current may be changed to alternating current as desired, by suitably substituting alternating cur- Operation With the system in its normal condition, the signals IAIB and 2A.-2B are at stop by reason of the deenergization of the signal control re ys G (with suitable preceding numerals and 161351613). Also, the track switch TS'is shown as being in a normal main track position.

Assuming that the switch machine control lever SML has not been operated since the last operation of the track switch TS, then the correspondence stick relay CS is energized by a circuit closed from through a circuit including its front contact I4, lowerwinding of relay CS, contact 5 l of lever SML in a normal position, to

The switch position repeating correspondence relays NWP and RWP have energizing circuits previously pointed out, andunder normal conditions only the relay NWP is energized.

Let us assume that the operator moves the switch machine control lever SML to a reverse position operating the contacts l and I I to their dotted line positions. With traflic conditions proper, all automatic control in accordance with traffic being omitted for the sake of simplicity, the relay W2 is energized so as to operate its polar contacts l3 and 2'! to reverse dotted line positions and its neutral contact 24 may or may not be momentarily caused to assume a deenergized position depending upon whether the relay W2 is of the usual polar neutral type relay, or whether its neutral armature is of the retained type. The contact IS in a reverse position causes the switch machine SM to unlock the track switch TS and operate it to a reverse position in which it is again locked up. While the track switch TS is in an unlocked condition, the relay WP is deenergized opening its neutral contact 25.

As soon as the contact I l oi lever SML is operated to its dotted line reverse position, the lower winding of the relay CS is deenergized and a. circuit is closed through its upper winding which is differentially connected with respect to its lower winding. This circuit includes front contact I4, so that the magnetic flux in the relay CS is quickly reduced to zero and the contact l4 immediately drops away opening such energizing circuit and causing the relay CS to remain deenerg-ized until its pick-41p circuit is closed. The correspondence indicator I5 is now energized through back contact M, thereby indicating to the operator that the control lever SML has been moved out of correspondence with the track switch TS.

As soon as the contact 21 of relay WZ assumes a position out of correspondence with the polar contact 26' of relay WP, the switch position repeating correspondence relay NWP is deenergized which closes back contact 29. This causes the relay SK in the central cffice to be energized by a circuit closed from the positive terminal of the battery 41, through a circuit including back contact 29 of relay back contact 28 of relay RWP, line wire 8, upper and lower windings of relay SK in multiple, contacts 22 and 2-3 of relay SLP in multiple, common bus 5, common return line 9, to the mid-tap or battery 41.

The relay SK has its windings so designed that when both the upper and lower windings are energized by half potential supplied by the battery 41, its contacts are picked up, but, if only one of its windings is energized with such a potential then its contacts drop away. Likewise, if only one of its windings, such as the upper winding,

is energized from half potential from the battery 46, its contacts do not pick up;- but, when half potential from the battery 66 and half potential from the battery 4'! are connected inseries through its upper winding, then its neutral contacts pick up. 7

Thus, as the circuit above traced for the relay SK includes both of its windings in multiple, its neutral contacts. pick p. closes a. pick p circuit for the relay CS from 6+), through a circuit including front contact IQ of relay SK, upper winding of relay CS, contact ll. of lever SML in a reverse dotted line position, to

A circuit is also closed. from (-1 through a circuit includin iron con ac ll of r lay SK, back contact is or relay SLP, indicator l5, to So, long as the track switch, TS is unlocked or out, of; correspondence with the lever S-ML, the out of correspondence indicator l5 will be illuminatcd.

When the track switch TS is completely operated to its reverse looked position, then the relay WP is energized with the reverse polarity closing front contact and operating contact 2% to its dotted line position which then energizes the relay RAMP by a circuit previously pointed out. Upon energization of relay RWP' and the opening of back contact 28, the relay SK is deenergized which opens front contact IT. This deenergization of the indicator l 5 advises the operator that the track switch TS is in correspondence with its control lever SML.

The operation of the system upon controlling the track switchTS to its normal position from its reverseposition is merely an inverse function of the operation already described, and thus will not be set forth in detail.

I Let us assume that the system is in its normal condition, and that the track switch TS is unlocked and'operated by hand to its reverse position, which may be accomplished by a suitable dual "control selector, as above mentioned. As soon as the track switch TS is unlocked, relay WP is deenergized opening front contact 25 which in'turn deenergizes the relay NWR' Theclosure of back contact 29 energizes the relay SK by the circuit above pointed out, so that the out of correspondence indicator I5 is illuminated. Such condition will be maintained even when the track switch TS is in its reverse locked position energizing the relay WP with the opposite polarity by freason of the fact that polar contacts 25 and 21 are out of correspondence and neither of the relays NWP and RWl? can be energized.

Assuming that the system is in its normal posi tion, we may now consider how the signal control lever SL controls the signals and its interrelation with the switch correspondence indication above described.

Let us assume that the operator moves the lever SL to a right hand position to clear the signal IA .1

for trafiic in an east bound direction over the track switch TS in a normal position. This closes an energizing circuit for the signal lever repeating 'rclay SLP from the positive bus 5 through acircuit including contact l2 in a right hand position, back contact 20 of relay SK, winding of relay SLPgto'the common bus 6. This causesthe relay SLP to pick up. and close front contact 2! so that the relay SLP will remain energized so long as the lever SLremains in an operated signal clearing position, irrespective of whetherthe relay SK opens back contact 20 or not.

In thisconnection, it may be well to note, that, if the track switch TS is unlocked thus energizing the relay SK,'a's previously pointed out, the open back contactZfl prevents the energization of relay S'LP. Thisarrangement prevents any interference between the switch out of correspondence indication and the signal control, which sequence is perfectly permissible inasmuch as it would be undesirable to transmit signal control if the track switch were not in an extreme locked position in correspondence with its control lever.

Assuming, however,'that the track switch TS is in a normal locked position and that the relay SLP can be properly energized, then the picking up of the contacts of relay SLP closes an ener gi-zing circuit for the relay SZ from the positive bus 5-, through a circuit. including contact I2 of lever SL in a right hand position, front contact 2| ofrelay SLP, front contact 2-2 of relay SLP, upper winding of relay SK, line wire 8, back contact 28 of relay RWP, front contact 29 of relay NWP,

relay RP, upper winding of relay SZ, common return line wire 9, to the mid-tap of battery 46.

The energy which flows in this circuit is insuflicient to actuate the contacts of the relay SK, as previously mentioned. However, the current is sufiicient to cause the actuation of the contacts of the relay SZ, as the windings of relay SZ are so connected that the magnetic fluxes in these windings are additive.

The energization of the relay SZ with current flowing in the circuit just traced, causes its polar contacts 3| and 33 to be actuated to right hand positions and its neutral contacts to be picked up. Thus, an energizing circuit is closed for the signal control relay [AG by a circuit closed from through a circuit including front contact 32 of relay SZ, polar contact 33 of relay SZ in a right hand position, front contact 35 of relay NWP, windings of relay IAG, to The energization of relay lAG causes the red or stop indicator of the signal IA to be deenergized and the green or proceed indicator to be energized by reason of its contact 42.

The energization of the relay IAG opens back contact 39 deenergizing the signal repeating relay RP. The opening of front contact 30 of relay RP disconnects the upper winding of the'relay SZ from the signal control circuit above traced, and includes the right hand portion of battery 41 in such circuit by reason of the closure of back contact 3!! with polar contact 3| in a right hand position. This circuit may now be traced from the positive terminal of battery 46, positive bus 5, lever contact l2 in a right hand position, front contact 2| of relay SLP, front contact 22 of relay SLP, upper winding of relay SK, line wire 8, back contact 28 of relay RWP, front contact 29 of relay NWP, lower winding of relay SZ, back contact 30 of relay RP, polar contact 3| of relay S2 in a right hand position, negative terminal of battery 47, mid-tap of battery 41, return line wire 9, to the mid-tap of battery 46.

Thus, with half potential from each of the batteries 46 and 41 connected in series upon the deenergization of the signal repeating relay RP, sufficient current flows through the lower winding of relay SZ to maintain it in an energized condition, while the current value flowing through the upper winding of relay SK causes its'neutral contacts to be picked up. Such picking up of contact is immaterial to the energization of relay SLP for reasons previously mentioned; but the picking up of contact I I with relay SLP energized closes a circuit from through a circuit including front contact l1, front contact l8 of relay SLP, indicator [6, to This energization of the indicator l6 advises the operator that a signal is cleared in accordance with the positions of the control levers SML and SL.

The removal of the upper winding of relay SZ upon the inclusion of the battery 41 in the signal control circuit is for the purpose of preventing the relay $2 from becoming overenergized and also for the purpose of causing a greater increase of current in the control circuit. In other words, the added current which fiows, due to the increase of potential and the decrease in resistance in the circuit upon the insertion of battery 41, merely compensates for the removal of the upper Winding of relay SZ, thereby causing the ampere turns of the relay to remain substantially constant.

The relay S2 is sufiiciently slow acting to remain picked up during the shift from the upper winding to the battery 41.

It is apparent that if the lever SL were operated to its opposite position that opposite potential would be applied to relay SZ operating its polar contacts to opposite positions, so that the-opposite portion of battery 41 would be includedin series with the opposite portion of battery 46 upon-the deenergization of relay RP, thereby accomplishing the energization of indicator 16 in the control ofiice, as above pointed out in connection with the signal IA.

It is believed unnecessary to pointout the operation necessary to clear the various signals in further detail than to state that the signal lever SL in a right position clears east bound signals IA or IE depending upon the position of the track switch TS, while in a left hand position it clears the signals 2A and 23 depending upon the position of the track switch TS. V

The restoration of a signal-to a stop condition is accomplished, as is readily apparent, by the return of the signal lever SL to a central stop position which in turn deenergizes the relay SZ and the particular signal relayG which isenergized. When all of the signals are at stop the relay RP is energized and the system is thereby restored to its normal condition.

Fig. 2. (Simplification 0 Fig. 1).- -This figure illustrates the principles of the signal control and signal indication shown in Fig. 1 but disassociated from the switch out of correspondence indication. Similar parts in the system are given the same reference characters as in Fig. 1. The relay SK issimilar to the relay SK of Fig. 1 but is shown as having but a single winding. The armature of relay SK requires a' predetermined number of ampere turns topick it up. The current supplied by either part of battery 46 is insufiicient to energize the relay SK to such a degree, but when the proper part of battery'4! is added in series, sufiicient current flows to give the required ampere turns to pick its armature ,up. This is the same relation between the signal control and indication currents as exists for Fig. 1.

When the relay SK is picked up, it closes front contact 50 to energize the signal indicator Hi to advise the operator that, a signal is clear. When the signal control circuit is closed and'is energized with half potential from the battery 46, the relay 3K does not respond, but the relay SZ responds, as described inconnection with Fig. 1.

Upon the clearing of the selected signal the relay RP is deenergized inserting the proper section of ,battery 41. Thus, with half potential from battery 41 and half potential from battery 46 connected in series, sufiicient current is supplied to the relay SK so that it is picked up giving the signal clear indication. Contact of relay RP controls the exclusion of the upper winding of relay SZ and the insertion of the battery 41 in the signal control circuit, while the polar contact3| of relay SZ selects the particular section of battery 41 to be included.

The specific control of the signals will readily be understood by reference to Fig. 1 and its description.

Modification of Fig. 3.-Similar parts in this Fig. 3 are given the same reference characters as in Fig. 1, but as the relays SK and S2 have slightly different control, they have been given distinctive exponents. This modified system also disassociates the signal control and indication from the out of correspondence switch indication disclosed in Fig. 1. The detail signal control is the same as in Fig. 1 which is indicated by relay 8Z being provided with thesame contacts 32 and 3.3 for such signal control purposes.

The degree of energiza'tion of 'sign'al control and indication" circuit is'th'e same irrespective of whether the lever SL is operated to theright or to the left, the only difference being the energiz'ation of the control circuit with the opposite polarity to cause the polar contacts of the relay 8Z to be operatedto the desired positions. Thus, a description 'oi the operation of the, lever SL to'a particular position will give an adequate un derstanding of the principles of thisfOrm of the present invention.

Let us assume that the leverSLis operated to the right. This closes. an energizing circuit for the reIays SK and S2 in series from the positive terminal of battery'l46, positive bus 5, .contact H2 in a right hand position, upper winding of relay 8K line wire 8, upper winding of 8Z lower winding of' relay SZ common'return line wire 9, to the mid-tap of battery 46. g 'f At the same instant that current flow is established in the controlcircuitaboveftraced, a local energizing circuit for the lower'wihding of relay 8K is closed from the positive bus 5, contact i2 in a right hand position, lower winding oi relay SK to the common'bus 6. V The current'which flows in the signal control line circuit is o f'sufficient value to cause the actuation of the neutral andp'olar contacts of the relay 3Z to their proper positions, as thefluxes produced by the current the two coils of the relay S2 are additive asindicat'edjby the'arrows. The fluxes produced by'the. current in thetwo coils of the'relay SK buck each other to zero, as indicated by the arrows in the windings of relay SK so that the contact'5l ofrelay 8K does not respond- V The closure of'iront' contact 32 bf relay SZ causes a signal control relay'tdbe. energized, which in turn clears a signal and deenergizes the signal repeating relay fRP. The closure of back contact 520i relayRP short ,circ'uits'the lower winding'of the rela'yTSZ and reduces the value of resistance in the signal control circuit to such a value that the current therein is increased to a value substantially double,. for example. This, increasedcurrent I in the signal control circuit causes the upper winding of the relay SK to providaa greater amount of flux than the'current m" a lower winding so that the difference in flux value'is sufficient to. actuate the contact 5! of relay SK- .,to a pickedup position, thereby energizing the'indicator l6 andadvising the operator that a signal is clean f The increase in current'in the 'upper winding of relay S2 causes a corresponding increasein the ampere turns provided by such winding which compensates for the shuntingof the lower windmg. I l I It is apparent that the .returnpf' the signal lever SL to a mid-positioni'willrestore the signals to stop andreturn thesysternto its normal .condition as shown.

This modified form shown gin Fig. 3 has several distinct advantages in the control of; relay SK over the relay SK of Fig. l ,fo'r'example, insofar as the operating characteristics of the relay are concerned. g j

More specifically, the relay 8K is'immune'to variations in, the voltage of battery 46,'as itis readily apparent'that any change in the voltage "of'this battery'is equally effective in both windings of the relay SK Inother words, the relative changeinthe resistance of the' line circuiti'is'the armature so long asrelay contact 52 is open, but 7 upon the closureof such contact the flux in the upper winding increases so that the difference in flux between the upper and lower windings is the amount of flux which passes through, the armature of the relay 8K This difference in flux even though it may be of a small value may be made sufficient to operate. a relay armature by making the relay of a very sensitive type.

- The relay 8K is quicker in dropping away upon the picking up of contact 52 because its operating value, of flux in the armature is reduced to sub stantially zero. In other Words, the usual relation between the drop away flux and the operating flux is maintained, that is, there is the usual margin of difference between the value of flux at which the relay armature will drop away and the actual value of flux supplied to the armature at the time it is desired that it drop away, which actual value of flux in this case is substantially zero. This can be best understood by contrasting such operation with the operation of the relay in 4 Fig. 2, where it will'be seen that in certain cases when the signals are put to stop automatically (by means undisclosed in Fig. 1), the current value of the relay SK will be reduced to a value not below the operating valuefor relay SZ. This operating value for relay S2 is below the drop away value of the relay 8K but the margin of difference is not as great as is the corresponding margin in the case of relay 8K I Modification of Fig. 4.This figure illustrates a single winding signal control relay 82 associated with the signal repeating relay RP with suitable resistors 55 and 56 in a manner that the marginal relays SK or 8K of Figs. 2 and 3 respectively may be suitably controlled by such an arcloses back contact 5 3 to shunt out the resistor 56 to thereby increase the current value in the signal control circuit to a sufficient amount to cause the actuation of the signal indication marginal relay SK (with suitable exponent) Back contact 53 of relay RP includes the resistor 55 in multiple with the relay 8Z so that such relay will not become overenergized;

In brief, the resistor 55 placed in multiple with relaySZ and the resistor 56 shunted from the in series connection with relay S2 reduces the resistance value of the signal control circuit to a surficient value so as to cause the energization of the signal indication relay SK (with suitable exponent) without efiecting the overenergization ofthe relay S2 The resistors 55 and 56 must of course be designed to fit each particular situation with each provided with proper relative resistance to give the desired control or the SK relay. The

resistors 55 and 56 may be made variable resistors to. thereby furnish a ready means of adapting standard'apparatus to all practical conditions.

. As'the' relay 8Z controls the signals by co ntacts 32 and 33 the same as in Fig. 1; as the relay RP is contemplated as being controlled the same as in Fig. l; and as the signal control circuit and indication relays are located in the central ofiice the same as in Fig. 2 or in Fig. 3, it is believed that further description relative to Fig. 4 is unnecessary.

Summary The present invention provides, as above described, a system of signal control and indication wherein the control is accomplished by the transmission of current of one polarity or the other to a polar neutral signal control relay to cause the clearing of signals in one direction or another. The deenergization of such signal control relay holds such signals at stop. By including in such signal control circuit a relay which requires a greater current for its pick up than the initial signal controlling current, the amount of current in such signal control circuit may be increased at the field station either by the inclusion of an additional battery source in series with the one in the control ofiice or by the reduction of the amount of resistance in the signal control line circuit, to cause the marginal relay to pick up, and thereby indicate to the operator that the signal is clear.

The present invention also provides a suitable manner in which to associate such signal control and indication with the switch control lever and the switch indication relays to transmit an out of correspondence indication to the central ofilce without conflict. Such out of correspondence indication is transmitted by the inclusion of a suitable battery source at the field station in the signal control line circuit while it is deenergized with the signals at stop.

Having thus described a traffic controlling system arranged and organized in accordance with the present invention as one specific embodiment thereof, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of formswhichit may assume; and, it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims.

What I claim is:

1. In a centralized traflic controlling system for railroads, a stretch of track, a signal for governing traffic over said stretch, a line circuit extending from said signal to a central ofiice, means at the central office for causing current to flow in said circuit, means at said signal responsive to said current in said circuit for clearing said signal, means for increasing the current flow in said circuit throughout the time that said signal is cleared, and means at the central ofiice responsive to said increased current in said circuit for indicating the cleared condition of said signal.

2. In a centralized traflic controlling system for railroads, a stretch of track, a signal for governing taffic over said stretch of track, a line circuit extending from said signal to a central oflice, a source of energy at the central office, a signal control lever for controlling the application of energy to said line circuit from said source at the central oifice, a relay in said line circuit responsive to current therein and eflective to "clear said signal, a source of energy at said signal, means inserting said source at said signal into said line circuit in series with said source at the central ofiice when said signal is cleared thereby increasing the current flow in said circuit, and a relay at the central ofiice included in said line circuit and responsive only to said increased'current flow in said line circuit.

3. In a centralized traflic controlling system for railroads, a stretch of track, a signal for governing trafiic over said stretch of track in each direction, a line circuit extending from said signal to a central oflice, manually governable means at the central oifice including a signal control lever for applying current of one polarity or the other to said line circuit depending upon which of said signals is to be cleared, a polar relay included in'said line circuit and responsive to one polarity or the other for clearing one or the other of said signals, means for increasing the current in said line circuit when either of said signals is cleared only provided the polar contacts of said polar relay have properly responded to the polarity of current in said line circuit as applied by said lever, and means at the central ofiice responsive only to said increased current fiow in said line circuit.

4. In a centralized traflic controlling system for railroads, a line circuit connecting a central ofiice and a field station, a track switch at the field station, signals for governing tramc over said track switch, means at the field station for energizing said line circuit when said switch is unlocked, means at the'central ofiice for energizing said line circuit when a signal is to be cleared, means at said field station responsive to the energization of said line circuit at the control ofiice for clearing one of said signals, means operative upon the clearing of one of said signals to increase the current flow due to the energization 'of said line circuit at the central ofiice, and

means at the central ofiice responsive to current flow in said line circuit due to its energization at said field station for indicating the unlocked condition of said track switch and efiective when thus responding to prevent the energization of said line circuit at the central oflice, said means also being responsive to said increased current flow when said line circuit is energized at said control oflice and one of said signals is cleared to thereby indicate that such signal is cleared.

5. In a centralized trafilc controlling system for railroads, a line circuit connecting a central ofiice and a field station, a railroad track switch at the field station, a signal for governing traffic over said track switch, a signal control lever at the central oflice, a signal lever repeating relay at the central office, a double winding indication relay at the central ofiice having both windings included in said line circuit when said signal lever repeating relay is deenergized but having only one winding included in said line circuit when said lever repeating relay is picked up, a pick-up circuit for said lever repeating relay in- .cluding a contact of said lever and a back contact of said indication relay, 2. stick circuit for said lever repeatingrelay including a contact of said lever and its own front contact, means supplying energy to said line circuit at the centra1 oflice when and only when said lever repeating relay is picked up, means for supplying energy to said line circuit at the field station when said track switch is unlocked, a signal control relay at the field station connected in said line circuit only when said track switch is locked and 7 responsive to the current flow in said line circuit for controlling said signal, and means increasing the current flow in said line circuit when said signal is cleared whereby said signal indicating relay is picked up even though it has only one winding included in said line circuit.

6. In combination, a line circuit connecting a central ofiice and a field station, a double winding indication relay in said central ofiice, a control lever for supplying energy to said line circuit through one winding of said indication relay with current flowing in one direction and for supplying current flow in the other winding of said indication relay in the opposite direction whereby the contacts of said indication relay remain dropped away until otherwise acted upon, a control relay at the field station responsive to current flow in said line circuit, traflic controlling means controlled by said control relay, means rendered effective by said traffic controlling means to at times increase the current flow in said line circuit whereby said indication relay is caused to be picked up, and an indicator controlled by said indication relay.

7. In combination, a line circuit connecting a control office and a field station, a source of energy in said control office, a control lever forat times supplying energy to said line circuit from said source, a control relay at the field station always responsive to current flow in said line circuit for governing a traffice controlling device, means efiective to reduce the resistance of said line circuit when the traflic controlling device is governed by said control relay whereby the current in said line circuit is increased, indication relay means at the control office responsive to said increased current to thereby pick its contacts up, and other means controlled by said indication relay means.

8. In combination, a control lever for controlling a railroad track switch, a stick relay having a stick circuit which is broken each time said lever is operated to a new position, a relay controlled by the track switch for indicating its unlocked condition, a pick-up circuit for said stick relay closed when said indication relay indicates the unlocked condition of the track switch, and an indicator energized whenever said stick relay is deenergized and when said indication relay indicates the unlocked condition of the track switch.

9. In combination, a control lever for controlling the operation of a railroad track switch, an indication relay caused to assume one position when the track switch is locked in correspondence with said control lever and caused to assume another position when the track switch is out of correspondence with its control by said lever or the switch is unlocked, a stick relay, a stick circuit means for said stick relay including a contact of said lever and its own front contact, a pick-up circuit for said stick relay including a contact of said indication relay in its said other position, and an indicator jointly controlled by said indication relay and said stick relay.

10. In combination, a line circuit connecting a control oflice and a field station, a source of energy in said control office, a control lever for at times supplying energy to said line circuit from said source, a trafiic controlling device at the field station capable of assuming either of two conditions, means effective when said trafiic controlling device assumes one of said conditions to reduce the resistance of said line circuit whereby the current in said line circuit is increased, a 5 control line relay having a winding included in said line circuit and responsive to current flow therein under both said two conditions of said trafiic controlling device, indication relay means at the control office responsive to said increased 10 current in said line circuit to thereby pick its contacts up, and other means controlled by said indication means.

11. In combination, a line circuit connecting a control ofiice and a field station, a source of en- 15 orgy in said control office, a control lever for at times connecting said source of energy in series in said line circuit, a trafiic controlling device at the field station capable of assuming at least two different conditions, means at the field sta- 20 tion controlled by said trafiic controlling device in one of its said conditions to increase the current flow in said line circuit, a control relay at the field station for governing the conditions of said trafiic controlling device and responsive to 25 the current flow in said line circuit at all times, an indication relay included in series in said line circuit at all times and responsive to said increased current flow to thereby pick its contacts up, and indicator means controlled by said 30 indication relay, whereby said traffic controlling device is directly and continuously controllable by said control lever, and whereby said indication relay is directly and continuously controllable in accordance with the condition of said trafiic controlling device.

12. In a centralized trafiic controlling system for railroads, a stretch of railway track, a signal for governing traffic over said stretch and capable of assuming clear or stop conditions, a line 40 circuit extending from said signal to a central office, manually governable'means at the central office for at times causing currentfiow in said line circuit, electro-responsive means at said signal responsive to the current flow in said line circuit both when signal is cleared and when said signal is'at stop, said electro-responsive means being effective to determine the clear or stop condition of said signal, means for increasingthe current flow in said line circuit whenever said signal is cleared, and means at the central ofiic'e responsive to said increased current in said line circuit for indicating the cleared condition of said signal.

13. In a centralized traffic controlling system for railroads, a stretch of track, a signal for governing traffic' over saidstretch, a line circuit extending from said signal to a central office, means at the central ofiice for causing current to flow in said circuit, a relay at said signal having two windings connected in series in said circuit and responsive to said current for clearing said signal, means for shunting one of said windings throughout the time that said signal is cleared, and means at the central ofiice responsive to the increased current in said circuit due to such shunting for indicating the cleared condition of said signal.

SEDGWICK N. WIGHT.

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