US2286002A - Railway signaling system - Google Patents

Description

June 9, 1942. F. H. NICHOLSON 2 286,002

RAILWAY S IGNALING SYSTEM INVENTOR' Fra'nkllzl" U012.

HIS ATTORNEY Patented June 9, 1942 RAILWAY SIGNALING SYSTEM Frank H. Nicholson, PennTownship, Allegheny County, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application March 2'7, 1941, Serial No. 385,400

15 Claims.

My invention relates to approach control apparatus for use in railway signaling systems of the coded track circuit class, and it has special reference to the provision of improved apparatus for approach controlling various signaling functions without the use of line wires.

It is an object of my invention to provide an improved system of the type described which is arranged so that energy stored in the track circuit cannot produce improper operation of the relays employed in the system.

A further object of the invention is to provide an improved system of the type described which is arranged in such manner that the detector relay employed therein cannot be improperly energized from the track battery in the event the coding device contacts which control the circuits of the detector relay Winding and of the track battery fail to interrupt one of these circuits before establishing the circuit of the other.

Another object of the invention is to provide an improved system of the type described which is arranged in such manner that the track relay employed therein cannot be improperly energized from the impulse or feed-back battery in the event the impulse relay contacts which control the circuits of the track relay and of the battery fail to interrupt one of these circuits before establishing the other.

Other objects of my invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings.

I shall describe one embodiment of my invention together with several modifications thereof which I may employ and shall then point out the novel features thereof in claims.

In the drawings,

Fig. 1 is a diagram of a section of railway track equipped with apparatus embodying my invention,

Fig. 2 is a diagram of a modified form of apparatus which may be employed at the entrance end of the track section,

Figs. 3, 4, 5 and 6 are diagrams showing modified forms of apparatus which may be employed at the exit end of the track section,

In the drawingssimilar reference characters refer to similar parts in each of the several views.

Referring to the drawings, there is shown therein a section of railway track having track rails l and 2 over which traflic normally moves in the direction indicated by the arrow, that is from left to right. The track rails of each section are separated from the rails of the adjoining sections by insulated joints 3 in the usual manner.

The track section has at the entrance end thereof a track relay TR having a winding receiving energy over the section rails. This relay is of a type the contacts of which become picked up on the supply of energy of one polarity only to the relay Winding. The track relay TR has associated therewith a decoding transformer DT, an impulse relay IR, a battery IB from which impulses of feed-back energy are supplied to the rails of the track section, and an auxiliary relay H. The relay H may be employed in the manner well known in the art to control the supply of energy to the adjacent section in the rear and to control the signal, not shown, at the entrance end of the section.

The equipment at the exit end of the section includes a detector relay KR, a track battery TB, a coding device CR, an approach relay AR, and a transformer KT.

The detector relay KR is of the polarized type and has movable contacts which are shifted to their left-hand or normal position when the relay Winding is supplied with energy of the polarity of the impulses of master code, while these contacts are shifted to their reverse or right-hand position when the relay winding is supplied with energy of the other polarity, that is energy of the polarity of the impulses of feed-back energy. In addition, the relay KR if of a type the contacts of which when moved to either position will remain in that position until the relay winding is energized with current of the polarity effective to move the relay contacts to their other position.

The relay CR is provided with contacts which are continuously picked up and released at one or another of a plurality of different rates depending upon traffic conditions in advance. One means for controlling the relay OR is shown in Fig 5 of United States Patent No. 2,174,255 to Herman G. Blosser.

The approach relay AR may be employed to control circuits for energizing the lamps of the signal, not shown, for the adjacent section in advance, or to control circuits for any other appropriate purpose.

The equipment is shown in the condition which it assumes when the track section is vacant. At this time the contact ID of the coding relay. CR is continuously moved between its picked-up and its released positions. When this contact is in its picked-upposition, the track battery TB is connected across the rails l and 2 by a circuit which includes in series therewith the relay KR.

The contacts of the impulse relay IR are released at this time so that contact 52 connects the track relay TR across the rails l and 2. Accordingly, energy from the track battery TB flows through a circuit which is traced from the positive terminal of the battery through front contact ill of coding relay CR, winding of detector relay KR, track rail l, winding of track relay TR, back contact E2 of impulse relay IR, track rail 2, and resistance M to the negative terminal of the track battery. As a result of this fiow of energy, the relays KR and TR are energized in series. The polarity of this energy is such that it is effective to pick up the contacts of the track relay TR, while it is also such that the contacts of the detector relay KR are shifted. to their lefthand or normal position as shown.

On picking up of the track relay contacts contact l5 establishes connection from terminal B of a local source of direct current, not shown, to one terminal of the primary winding of the decoding transformer DT, while contact l6 establishes a circuit to supply energy from the transformer secondary winding to relay H. The center terminal of this winding is connected to terminal C of the source so that one-half of the transformer primary winding is energized and an impulse of energy is induced in each of the transformer secondary windings.

The impulse of energy induced in secondary winding ll of the transformer is supplied to the impulse relay IR. However, the relay IR is of a type the contacts of which become picked up only when energy of one polarity is supplied to the relay winding and the various parts of the equipment are arranged so that the energy supplied to the relay IR on movement of the track relay contacts to their picked-up positions is of such polarity as to be ineffective to pick up the contacts of relay IR.

Similarly, on movement of contact E3 of relay KR to its left-hand position a circuit is estalb lished to energize one portion of the primary winding of transformer KT from a local source of direct current, not shown, while contact 19 of the relay KR establishes a circuit to supply energy from the secondary winding of transformer KT to the approach relay AR.

After a brief time interval, the contact ll] of coding relay CR moves to its released position, thereby interrupting the supply of energy from the track battery TB over the circuit traced above, while contact lfl connects the winding of the relay KR across the track rails l and 2. On this interruption in the supply of energy from the battery TB the contacts of track relay TR release and contact l5 establishes a circuit to energize the other portion of the primary winding of transformer DT, As a. result, an impulse of energy is induced in each of the transformer secondary windings. These impulses are of the polarity opposite to that of the impulses present on movement of the track relay contacts to their pickedup positions, and accordingly the energy supplied to the relay IR is effective to pick up the contacts of this relay.

.On picking up of the contacts of relay IR contact l2 interrupts the circuit traced above for connecting the Winding of the track relay TR across the track rails and establishes a circuit to supply energy from the battery IE to the relay KR over the rails l and 2. This circuit is traced from the positive terminal of the battery IB through front contact E2 of relay IR, winding of relay TR, track rail I, winding of relay KR, back contact if) of KR to their reverse or right-hand positions.

relay CR, track rail 2 and resistance 21 to the other terminal of the battery IB. At this time, therefore, the relay KR is energized by current supplied fromjthe battery IB. The direction of flow of this energy through the winding of the relay KR is opposite to that of the energy supplied to the relay KR from the track battery TB and accordingly the contacts of the relay KR are shifted to their right-hand or reverse positions so that contact 58 establishes a circuit to energize the other portion of the primary winding of transformer KT. while contact is establishes a circuit to supply energy from the transformer secondary winding to the approach relay AR.

In addition, at this time the track relay TR is energized by current supplied from the impulse battery IR. However, the direction of flow of energy through the relay winding is such that the energy is ineffective to pick up the relay contacts, but on the contrary serves to hold these contacts more firmly in their released positions.

After a brief time interval, the contacts of relay IR release and interrupt the supply of energy from the battery IE to the section rails, while contact 52 reconnects the track relay TR across the section rails. On this interruption of the supply of energy from the battery 13 energy ceases to be supplied to the relay KR, but because of the characteristics of the relay the contacts of this relay remain in the position to which they have just been moved.

Subsequently, the contact Ill of relay CR picks up and interrupts the circuit connecting the relay KR across the section rails and again establishes the circuit for supplying energy from the battery TB to the relays KR and TR in series.

As long as the track section is vacant, the equipment continues to operate in this manner. The track relay contacts pick up on the supply of impulses of master code energy, While these energy impulses effect movement of the contacts of the detector relay KR to their left-hand or normal positions. During the off intervals between the impulses of master code the track relay contacts release, while the impulse relay contacts pick up and disconnect the track relay from the track rails and establish the circuit to supply an impulse of feed-back energy from the battery IE to the relay KR. These impulses of feed-back energy effect movement of the contacts of relay As a result of picking up and releasing of the track relay contacts, energy is supplied through the transformer DT to the relay I-I, while as a result of movement of the contacts of the detector relay KR between their normal and reverse positions, energy is supplied through the transformer KT to the relay AR. The relays AR and H are of a type a which are somewhat slow in releasing so that their contacts remain picked up during the intervals between the supply of impulses of energy thereto. As long as the track section is vacant, therefore, the relays H and AR are picked up.

When a train moving in the normal direction of trafhc, that is from left to right, enters the section, the wheels and axles of the vehicles of the train shunt the track relay TR so that its Eontacts thereafter remain released, Accordingly, impulses of energy are not supplied through the transformer DT to the'impulses relay IR and the contacts of relay IR remain released and do not supply impulses of feedback energy to the section rails and to the relay KR. In addition, energy is not supplied through the transformer DT to the relay H and the contacts of relay H release.

At this time the coding relay CR continues to operate and to supply impulses of master code energy to the sectionrails. These impulses of energy cause the contacts of relay KT to move to their left-hand or normal positions. However, at this time, as impulses of feed-back energy are not supplied to the relay KR, the contacts of this relay remain in their left-hand or normal positions and no energy is supplied from the transformer KT to the approach relay AR. Accordingly, the contacts of the relay AR release and interrupt or establish the approach control circuits.

When the train advances far enough to vacate the section, the impulses of master code energy feed to the track relay TR and produce code following operation of this relay so that energy is supplied through the transformer DT to the relays H and IR, while the relay IR operates to supply impulses of feed-back energy to the relay KR over the section rails so that energy is again supplied through the transformer KT to the relay AR. Accordingly, the relays H and AR are picked up when the track section is vacated.

In this system the polarity of the master code and feed-back energy is such that there is no possibility of improper operation of the detector reiay by energy stored in the track circuit when the track section is occupied.

When contact it of coding relay CR is picked up, energy flows from the positive terminal of the battery TB through the contact i9 and the winding of detector relay KR to track rail l, thence through the wheels and axles of a train present in the track section to track rail 2 and to the negative terminal of the battery,

When contact iii of the coding relay CR moves out of engagement with its front contact, this circuit is interrupted, but because of the inductance of the track circuit and the conductance of the ballast toward the exit end of the track circuit, current continues to flow in this circuit for a period of time so that under most ballast conditions, when the contact Ill reengages its back contact, energy stored in the track circuit will flow for a short period of time through the winding of the detector relay KR. The direction of flow of this energy is the same as that supplied from the track battery so that the only effect of the energy is to maintain the detector relay contacts in the position to which they have already been moved. Accordingly, no change in energization of the primary winding of transformer KT occurs and energy will not be supplied to the relay AR.

This circuit is also arranged so that, if the contacts of the relay CR are incorrectly adjusted or build up and the movable contact it! engages its front and back contacts at the same time, improper operation of the relay KR cannot occur.

Referring to the drawings, it will be seen that, if the front and back contacts of relay CR overlap, the track battery TB will be short circuited through the resistance l4, while no circuit will be established to improperly energize the relay KR.

Similarly, the circuit provided by my invention is arranged so that, if contact l2 of relay IR is incorrectly adjusted or builds up so that it engages its front and back contacts at the same time, the track relay TR cannot be energized from the battery IR. The only result of this conditions is to short circuit the battery 13 through the resistance 2!.

The entrance end equipment provided by this invention isarranged so that energy stored in the track circuit cannot cause undesired operation of the track relay. This problem is not present when a train enters the entrance end of the track section in the usual manner since the track relay is shunted and the impulse of feed-back energy supplied to the track rails does not flow far enough in the track rails to cause an appreciable amount of energy to be stored in the track circuit, As the track relay is shunted it remains released and no further impulses of energy are supplied to the impulse relay so the impulse relay contactsremain released and do not supply additional impulses of feed-back energy to the section.

However, if a train backs into a section, or if a section includes a switch at an intermediate point and a train enters the section through the switch, the track relay contacts will release and energy will be supplied to the impulse relay so that its contacts pick up and cause an impulse of feed-back energy to be supplied to the section rails. Thi impulse of feed-back energy will be prevented from reaching the detector relay due to the presence of the train in the track section. However, as the train is some distance removed from the entrance end of the section the feedback energy flows through a substantial part of the track circuit and considerable energy may be stored in the track circuit.

On sub-sequent release of the impulse relay contacts the supply of energy from the impulse battery to the track rails is cut off while the track relay winding is connected across the section rails. As explained in connection with the equipment at the exit end of the section, the energy stored in the track circuit flows in the same direction as the energy supplied from the battery to the section rails. Accordingly, the energy in the track circuit will flow through the track relay winding in the wrong direction to pick up the relay contacts. The track relay contacts, therefore, remain released and no energy is supplied to the impulse relay so the contacts of the impulse relay remain released and no more impulses of feed-back energy are supplied to the section rails.

In Fig. 2 of the drawings there is shown a modified form of apparatus which I may employ at the entrance end of the track section. This apparatus is substantially the same as that shown in Fig. 1, but difiers therefrom in that the impulse relay IR has a contact [3, which when picked up short circuits the winding of the track relay TR. Accordingly, the impulses of feedback energy need not flow through the track relay winding, but may flow through the circuit established by contact I3. The circuit established by contact I3 is of much lower resistance than the circuit of the track relay winding so that the impulses of energy supplied from the battery IE to the track rails are stronger when the circuit shunting the track relay Winding is employed than when this circuit is not provided. Accordingly, the circuit provided by contact i3 makes it possible to employ the equipment on longer track circuits than would be possible without this circuit.

In Fig. 3 of the drawings there is shown a modified form of equipment which may be employed at the exit end of the track section. This equipment is similar to that shown in Fig. 1, but differs therefrom in that the contact l8 of detector relay KR'directly'controls the supply of energy to the approach relay instead of controlling the supply of energy thereto through a transformer.

In this modification the circuit of the relay AR is arranged so that it is complete when contact I8 of detector relay KR is in the position to which it is moved by the impulses of feed-back energy. Accordingly, as long as the track section is vacant and impulses of feed-back energy reach the detector relay KR, impulses of energy will be supplied to the approach relay AR and the contacts of this relay will be maintained picked up. During the periods in which the detector relay contact i8 is in its left-hand or normal position as a result of the supply of impulses of master code energy to the relay winding, en-

ergy is not supplied to the relay AB. The relay AB is of a type the contacts of which are slow in releasing, however, and remain picked up during these periods.

When a train enters the section the supply of impulses of feed-back energy to the detector relay is out off, and the relay contact is moved to its left-hand or normal position by the impulses of master code energy to thereby cut off" the supply of energy to the approach relay. As the detector relay contact remains in its normal position the approach relay is deenergized and its contacts release.

In Fig. 4 of the drawings there is shown a different form of apparatus which may be employed at the exit end of the section. This equipment differs from that shown in Figs. 1 and 3 in that a different type of detector relay is employed. In the system shown in Fig. 4 the detector relay KRA is similar to the track relay and is of a type the contacts of which when released become picked up only when energy flows in one direction through the relay winding, and which when picked up become released on interruption of the supply of energy to the relay winding or on the supply of energy of the opposite polarity to the relay Winding.

The exit end equipment shown in Figs. l, 5 and 6 is intended to be used with entrance end equipment of the type shown in Figs. 1 and 2, while it is contemplated that the positive terminal of the impulse battery associated with the entrance end equipment will be connected to the same track rail as the positive terminal of the track battery associated with the exit end facilities.

In operation when the coding relay contacts are picked up contact ill establishes a circuit to supply an impulse of master code energy from the battery TB to the section rails through the winding of the detector relay KRA. The direction of flow of energy in this circuit is such that the energy is ineffective to pick up the contacts of the detector relay, but instead tends to maintain them more firmly in their released position.

On movement of the coding relay contact ii] to its released position the supply of master code energy is interrupted, while the coding relay contact iii connects the detector relay winding across the section rails so that on the supply of an impulse of feed-back energy by the equipment at the entrance end of the section this energy may feed to the detector relay winding and pick up the contacts of this relay. On picking up of the contacts of relay KRA contact 25 establishes the circuit of the approach relay AR.

On subsequent picking up of the contacts of the coding relay CR contact til interrupts the circuit connecting the detector relay KRA across the section rails and establishes the circuit connecting the track battery across the section rails in series with the detector relay winding so that another impulse of master code energy is supplied to the section rails, while the contacts of the detector relay KRA release.

As long as the track section is vacant the equipment continues to operate in this manner, that is, during the picked-up periods of the coding relay contacts impulses of master code energy are supplied to the section rails while the detector relay contacts release, and when the coding relay contacts are released the detector relay winding is connected across the section rails so that the relay contacts are picked up by impulses of feed-back energy.

If desired, the modification shown in Fig. 4 may include a contact I I on the coding relay CR and. effective when picked up to short circuit the winding of the detector relay KRA so that the impulses of master code energy need not be supplied through the detector relay winding. As explained in connection with the entrance end equipment of Fig. 2, this circuit increases the value of the master code impulses so that the length of the track circuit may be increased.

The modification shown in Fig. 4, like those shown in Figs. 1 and 3, operates so that energy stored in the track circuit cannot improperly energize the detector relay when the section is occupied, and so that overlapping contacts on the coding relay cannot produce false operation of the detector relay.

As explained in connection with the apparatus shown in Fig. 1, the energy stored in the track circuit when the section is occupied continues to flow in the same direction as the master code energy so that when coding relay contact H] is moved to its released position any flow of energy in the detector relay winding as a result of stored energy in the track circuit will flow in the wrong direction to pick up the contacts of this relay. In addition, it will be seen from the drawings that if the front and back contacts of the coding relay contact lt overlap a circuit will be established to short circuit the track battery, while no circuit will be established to supply energy to the detector relay which will result in picking up of the contacts of this relay.

The detector relay shown in Fig. 4 is provided only with a pick-up winding, and the contacts of this relay remain picked up only as long as the impulse of feed-back energy is maintained. These impulses may be of very brief duration with the result that the relay contacts will be picked up for only short periods. It may be desired to prolong the picked-up periods of the detector relay contacts as much as possible, and the modification shown in Fig. 5 provides means to do so.

Referring to Fig. 5, the detector relay KRA employed therein is provided with a pick-up winding which is connected with the track rails in the same manner as the relay shown in Fig. 4. This relay has, in addition, a holding winding, while a circuit controlled by contact 25 of the detector relay and by contact 26 of the coding relay is provided for energizing the detector relay holding winding and the winding of the approach relay AR.

In operation, on release of the coding relay contacts and the supply of an impulse of feedback energy to the pick-up winding of the detector relay KRA contact 25 of this relay picks up and establishes the circuit of the holding Winding of the detector relay and of the approach relay winding. This circuit is traced from terminal B of a local source of direct current, which may be the track battery, through the holding Winding of the detector relay KRA, back contact 26 of coding relay CR, winding of approach relay AR, and front contact 25 of the detector relay KRA to terminal C of the source. Accordingly, the holding winding of the detector relay and the winding of the approach relay are energized in series. The holding winding of the detector relay when energized assists in maintaining the relay contact picked up so that if the impulse of feed-back energy terminates before the coding relay contacts pick up the detector relay contact will be maintained picked up by the relay holding winding and energy will continue to be supplied to the approach relay winding.

On picking up of the coding relay contacts contact 26 interrupts the circuit of the detector relay holding winding and of the approach relay winding, while contact it interrupts the circuit of the detector relay pick-up winding so that the contact 25 releases and additionally interrupts the circuit of the holding winding and of the approach relay.

It will be seen that the provision of the holding winding on the detector relay insures that the detector relay contact will remain picked up as long as the coding relay contacts remain released. This prolongs the time of energization of the approach relay and correspondingly reduces the period during which the approach relay contacts must remain picked up in order to bridge the intervals between the impulses of energy supplied thereto.

The modification shown in Fig. employs a detector relay having a single contact to control the circuit of both the detector-relay holding winding and the approach relay winding. It may be preferred to employ separate contacts to control the circuits of these windings and Fig. 6 shows means to control these circuits in this manner.

This modification is substantially the same as that shown in Fig. 5 and employs a detector relay having a pick-up and a holding winding. The circuit of the holding winding is controlled by contact 26 of the coding relay CR and by contact 21 of the detector relay so that on picking up of the detector relay contacts the holding winding of the relay is energized and maintains the relay contacts picked up as long as the coding relay contacts are released. In addition, on picking up of the detector relay contacts contact 25 establishes the circuit of the approach relay AR so that this relay is energized as long as the detector relay contacts are picked up.

On picking up of the coding relay contacts the circuit of the detector relay holding winding is interrupted and contacts 25 and 2! release and interrupt the circuit of the approach relay and additionally interrupt the circuit of the detector relay holding winding.

The modifications shown in Figs. 4, 5 and 6 make it possible to supply alternating current energy to the track circuit for cab signal purposes, and the manner in which this is done is shown in Fig. 6 of the drawings. It should be understood. however, that this means is equally applicable to the modifications shown in Figs. 4 and 5;

Referring to Fig. 6, it will be seen that a track transformer TT is provided and that the secondary winding of this transformer is included in series with the track battery. The primary winding. of this transformer is connected to a source of alternating current of suitable frequency, the terminals of which are designated BX and CK.

In operation when the coding relay contacts are picked up the track battery TB and the track transformer TT are connected cross the section rails by contact 10 of the coding relay, while contact ll of the coding relay short circuits the detector relay winding to provide a low resistance.

circuit for the supply of energy to the track circuit and to prevent the impulses of alternating current from effecting picking up of the detector relay contacts.

When the coding relay contacts are released the supply of direct and alternating current energy to the track rails is cut off, while contact l0 connects the pickup winding of the detector relay across the section rails.

In the drawings of this application there are shown in Figs. 1 and 2 two forms of equipment which may be employed at the entrance end of a track section, while Figs. 1, 3, 4, 5 and 6: show various forms of equipment which. may be employed at the exit end of a section. It should be understood that either form of exit end equipment may be employed with either form of entrance and equipment.

The exit end equipment shown in Figs. 1 and 3 employs a detector relay of the polarized type the contacts of which are moved to one position.

on flow of energy in the direction through the relay winding and are moved to a second position on flow of energy in the other direction through the relay winding, while on deenergization of the relay winding these contacts remain in the position to which they have last been moved.

The modifications shown in Figs. 4, 5 and 6 employ a biased polar relay the contacts of which are normally released and become picked up only on how of energy in one direction through the relay winding, while the relay contacts when picked up become released on deenergization of the relay or on flow of energy in the relay winding in the direction opposite to that effective to pick up the relay contacts.

It will be seen that the two types of detector relays are diiferent in some respects, but that they have one characteristic in common, that is that each is uniquely responsive to flow of energy in one direction through the winding thereof, The contacts of the polar type detector relay KR when in their normal position are shifted to their reverse position on the supply of an impulse of feed-back energy to the relay winding. Similarly, the contacts of the biased polar type detector relay KRA when released become picked up on the supply of an impulse of feed-back energy to the relay winding.

Although I have herein shown and described several forms of railway signaling system 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 a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which trafiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a code following detector relay and a track battery located at the exit end of the section, continuously operating coding means having a contact effective in one position to connect the detector relay winding across the section rails and effective in another position to connect the track battery across the section rails in series with the detector relay winding, an impulse relay associated with the track relay, means effective on release of the track relay contacts to supply energy to the impulse relay, said impulse relay having a contact effective when released to connect the track relay winding across the section rails and effective when picked up to connect the impulse battery across the section rails in series with the track relay winding, the track relay and detector relay each being of a type which is uniquely responsive to flow of energy in one direction through the winding thereof and each being connected with the track rails in such manner that when energy flows from the first to the second track rail through the winding energy flows through the winding in said one direction, the track battery and impulse battery each being arranged so that when the battery is connected across the track rails the positive terminal thereof is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for supplying energy to said approach relay.

2. In a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which trafiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a code following detector relay and a track battery located at the exit end of the section, continuously operating coding means having contacts movable between a first and a second position, said means having a contact effective in its first position to connect the detector relay winding across the section rails and being effective in its second position to connect the track battery across the section rails in series with the detector relay winding, said coding means having another contact effective in said second position to short circuit the detector relay winding, an mpulse relay associated with the track relay, means effective on release of the track relay contacts to supply energy to the impulse relay, said impulse relay having a contact effective when released to connect the track relay winding across the section rails and effective when picked up to connect the impulse battery across the section rails in series with the track relay winding, the track relay and-detector relay each being of a type the contacts of which become picked up only on flow of energy in one direction through the relay winding and each being connected with the track rails in such manner that when energy flows from the first to the second track rail through the relay winding energy fiows through the winding in said one direction, the track battery and impulse battery each being arranged so that when the battery is connected across the track rails the positive terminal thereof is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for energizing said approach relay.

3. In a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a code following detector relay and a track battery located at the exit end of the section, continuously operating coding means having a contact effective in one position to connect the detector relay winding across the section rails and effective in another position to connect the track battery across the section rails in series with the detector relay winding, an impulse relay having normally released contacts, means effective on release of the track relay contacts to supply energy to the impulse relay, a contact of said impulse relay being effective when released to connect the track relay winding across the section rails and being effective when picked up to connect the impulse battery across the section rails in series with the track relay winding, said impulse relay having another contact effective when picked up to short circuit the track relay winding, the track relay and the detector relay each being of a type which is uniquely responsive to flow of energy in one direction through the winding thereof and each being connected with the track rails in such manner that when energy flows from the first to the second track rail through the relay winding energy flows through the winding in said one direction, the track battery and impulse battery each being arranged so that when it is connected across the section rails the positive terminal thereof is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for energizing said approach relay.

4. In a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which trafiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a code following detector relay and a track battery located at the exit end of the section, continuously operating coding means having contacts movable between a first and a second position, said means having a contact effective in its first position to connect the detector relay winding across the section rails and effective in its second position to connect the track battery across the section rails in series with the detector relay winding, said means having another contact eifective in said second position to short circuit the detector relay winding, an impulse relay having normally released contacts, means effective on release of the track relay contacts to supply energy to said impulse relay, a contact of said impulse relay being effective when released to connect the track relay winding across the section rails and being eifective when picked up to connect the impulse battery across the section rails in series with the track relay winding, said impulse relay having another contact effective when picked up to short circuit the track relay winding, the track relay and detector relay each being of a type the contacts of which become picked up only on flow of energy in one direction through the relay winding and each being connected with the track rails in such manner that when energy flows from the first to the second, track rail through the relay winding energy flows through the winding in said one direction, the track battery and impulse battery each being arranged so that when it is connected across the section rails the positive terminal thereof is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for supplying energy to said approach relay.

5. In a' coded railway signaling system, in combination, a section of railway track over which traflic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a polarized code following detector relay and a track battery located at the exit end of the section, said detector relay having a contact movable to one position on flow of energy in one direction through the relay winding and movable to its other position on flow of energy in the other direction through the relay winding, continuously operating coding means operative at one time to connect the track battery across the section rails in series with the detector relay winding to thereby energize the detector relay and to supply energy over the track rails to the track relay, said coding means being operative at other times to connect the detector relay winding across the track rails, means operative on release of the track relay contacts to establish a circuit to supply energy from the impulse battery over the track rails to the detector relay winding, the equipment being arranged so that the energy supplied to the detector relay from the impulse battery is of the polarity effective to move the detector relay contact to its one position and so that the energy supplied to the detector relay from the track battery is of the polarity effective to move the detector relay contact to its other position, an approach relay,

and means governed by a contact of said detector relay for supplying energy to said approach relay.

6. In a coded railway signaling system, in combination, a section of railway track over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a polarized code following relay and a track battery located at the exit end of the section,

said detector relay having a contact movable to one position on flow of energy in one direction through the relay Winding and movable to its other position on flow of energy in the other direction through the relay winding, continuously operating coding means operative at one time to supply energy from the track battery to the detector relay and to also establish a circuit to supply energy from the track battery over the track rails to the track relay, said coding means being operative at other times to connect the detector relay winding across the track rails, means operative on release of the track relay contacts to establish a circuit to supply energy from the impulse battery over the track rails to the detector relay winding, the equipment being arranged so that the energy supplied to the detector relay from the impulse battery is of the polarity effective to move the detector relay contact to its one position and so that the energy supplied to the detector relay from the track battery is of the polarity effective to move the detector relay contact to its other position, an approach relay, and means governed by a contact of said detector relay for supplying energy to said approach relay.

'7. In a coded railway signaling system, in combination, a section of railway track having a first and a second track rail over which traiiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the track section, a polar ized code following detector relay and a track battery located at the exit end of the section, said detector relay having a contact which is moved to one position when energy flows through the relay winding in one direction and which is moved to its other position when energy flows through the relay winding in the other direction, continuously operating coding means effective at one time to connect the track battery across the section rails with the detector relay winding in series with the connection from one terminal of the battery to one track rail and with the positive terminal of the battery connected to said first rail, said coding means being operative at other times to connect the detector relay winding across the section rails, means effective on release of the track'relay contacts to connect the impulse battery across the section rails with the track relay winding in series with the connection from one terminal of the battery to one track rail and with the positive terminal of said track battery connected to said first rail, said means being effective at other times to connect the track relay winding across the section rails, an approach relay, and means governed by a contact of said detector relay for supplying energy to said approach relay.

8. In a coded railway signaling system, in combination, a section of railway track having a first and a second track rail over which trafiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a polarized code following detector relay and a track battery located at the exit end of the section, said detector relay having a contact which is moved to one position when energy flows through the relay winding in one direction and which is moved to its other position when energy flows through the relay winding in the other direction, the track relay having one terminal of its winding connected to one track rail of said section and the detector relay having one terminal of its winding connected to one track rail of said section, continuously operating coding means effective at one time to connect the other terminal of the detector relay winding to the other track rail in series with the track battery so that the positive terminal of the track battery is connected to said first track rail to thereby energize the detector relay with current of one polarity and to supply energy over the track rails to the track relay, said coding means being effective at other times to connect said other terminal of said detector relay winding directly to said other track rail, means effective on release of the track relay contacts to connect the other terminal of the track relay winding to the other track rail in series with said impulse battery so that the positive terminal of said battery is connected to said first track rail to thereby supply energy of the other polarity from said impulse battery over the track rails to the detector relay winding, said means being effective at other times to connect said other terminal of the track relay winding directly to said other track rail, an approach relay, and means governed by a contact of said detector relay for energizing said approach relay.

9. In a coded railway signaling system, in combination, a section of railway track over which traffic normally moves in one direction, a code following track rela and an impulse battery located at the entrance end of the section, a polarized code following detector relay and a track battery located at the exit end of the section, said detector relay having a contact movable to one position when the relay winding is energized with current of one polarity and movable to its other position when the relay'winding is energized with current of the other polarity, means for connecting the track relay winding across the section rails, means for connecting the detector relay winding across the section rails, continuously operating coding means effective at times to connect the track battery across the section rails and to supply to the detector relay winding energy of one relative polarity, means effective on release of the track relay contacts to supply from the impulse battery over the track rails to the winding of the detector relay energy of the other polarity, an approach relay, and means governed by a contact of said detector relay for supplying energy to said approach relay.

10. In a coded. railway signaling system, in combination, a section of railway track over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a polarized code following detector relay and a track battery located at the exit end of the. section, said detector relay having a contact movable to one position when the relay winding is energized with current of one polarity and movable to its other position when the relay winding is energized with current of the other polarity, means for connecting the track relay winding across the section rails, means for connecting the detector relay winding across the section rails, continuously operating coding means effective at times to connect the track battery across the section rails and to supply to the detector relay winding energy of one relative polarity, means effective on release of the track relay contacts to supply from the impulse battery over the track rails to the winding of the detector relay energy of the other polarity, an approach relay, a transformer, a'circuit complete in one position of said detector relay contact for supplying energy from a source of direct current to the primary winding of said transformer, and means for supplying energy from the secondary winding of said transformer to said approach relay.

11. In a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of said section, a code following detector relay and a track, battery at the exit end of the section, said track relay and said detector relay each being of a type which is uniquely responsive to flow of energy in one direction through the winding thereof, means forv connecting the winding of each of said relays across the section rails in such manner that when energy flows from said first track .rail through the relay winding to said second track rail energy fiows through the relay winding in said one direction, continuously operating coding means effective at times to interrupt the connection from one terminal of the detector relay winding to one of the track rails and to establish connection from said terminal to said track rail including in series therewith the track battery, said connection being arranged so that the positive terminal of said battery is connected to said first track rail, means effective on release of the track relay contacts to interrupt the connection from one terminal of the track relay winding to one of the track rails and to establish connection from said terminal to said track rail including in series therewith the impulse battery, said connection being arranged so that the positive terminal of said battery is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for supplying energy to the approach relay.

12. In a coded railway signaling system, in combination, a section of railroad track over which trafiic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, means for connecting the track relay winding across the section rails, means effective on release of the track relay contacts to connect the impulse battery across the section rails with the positive terminal of the battery connected to said first track rail, a code following detector relay, a track battery and a continuously operating coding device located at the exit end of the section, said detector relay being of a type which is uniquely responsive to fiow of energy in one direction through the winding thereof, said detector relay having one terminal of its winding connected to one of said track rails, said coding device having contacts which are moved between a first and a second position, a contact of said coding. device being effective when in its first position to connect the other terminal of said relay winding directly to the other track rail to thereby connect said detector relay winding across the track rails so that when energy flows from the first rail through the relay winding to the second rail energy flows through the relay winding in said one direction, said coding device contact being effective when in its second position to connect said other terminal of said relay winding to said other track rail in series with said track battery, said track battery being included in said circuit in such manner that the positive terminal thereof is connected to said first track rail, an approach relay, and means governed by a contact of said detector relay for energizing said approach relay.

13. In a coded railway signaling system, in combination, a section of railroad track having a first and a second track rail over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, a code following detector relay and a track battery located at the exit end of the track section, one terminal of the detector relay winding being connected to one track rail, one terminal of the track battery being connected to the other track rail, a continuously operating coding device having a contact movable between a first and a second position, said coding device contact being effective when in its first position to connect the other terminal of said detector relay to said other track rail and being effective when in its second position to connect the other terminal of said relay winding to the other terminal of the track battery to thereby connect the battery across the section rails in series with said detector relay winding, the track battery being connected across the section rails in such manner that the positive terminal thereof is connected to said first track rail, one terminal of the track relay winding being connected to one track rail, one terminal of the impulse battery being connected to the other track rail, an impulse relay having a contact normally occupying a first position,

means efiective on release of the track'relay for moving the impulse relay contact to asecond position, said impulse relay contact being-effective when in said first position to connect the other terminal of the track relay winding to the other track rail and being effective when in said second position to connect said other terminal of the track relay winding to the other terminal of said impulse battery to thereby connect the impulse battery across the section rails in series with the track relay winding, the track battery being connected across the section rails in such manner that the positive terminal of the battery is connected to said first track-rail, the track and detector relays each being of a type uniquely responsive to flow of energy in one direction through the winding thereof and each being connected to the track rails in such manner that when energy flows from said first rail through the relay winding to the second rail energy flows through the winding in said one direction, an approach relay, and means governed by a con tact of said detector relay for supplying energy to said approach relay.

14. In a coded railway signaling system, in combination, a section of railway track over which traffic normally moves in one direction, a code following track relay and an impulse battery located at the entrance end of the section, means for connecting the track relay winding across the section rails, means efiective on release of the track relay contacts to connect the impulse battery across the section rails with the positive terminal of the battery connected to said first track rail, a code following detector relay, a track battery and a continuously operating coding device located at the exit end of the section, said detector relay having a contact movable between a first and a second position, said detector relay being of a type the contact of which when in its first position is moved to its second position when and only when energy flows through the relay winding from its first to its second terminal, the first terminal of said detector relay winding being connected to said first track rail, the negative terminal of said track battery being connected to said second track rail, said coding device having a contact which is moved between two positions, said coding device contact being effective when in one of its positions to connect the second terminal of said detector relay winding to the positive terminal of said track battery and being efiective when in its other position to connect the second terminal of said detector relay winding to said second track rail, an approach relay, and means governed by said detector relay contact for energizing said approach relay.

15. In a coded railway signaling system, in combination, a section of railway track over which traffic normally moves in one direction, a code following track relay, an impulse relay and an impulse battery located at the entrance end of said track section, said track relay being of a type the contacts of which pick up when and only when energy flows through the relay winding from its first to its second terminal, the first terminal of said track relay winding being connected to the first track rail, the negative terminal of said impulse battery being connected to the second track rail, a contact of said impulse relay be" ing effective when released to connect the second terminal of the track relay winding to the second track rail and being effective when picked up to connect the second terminal of said track relay winding to the positive terminal of said impulse battery, means effective on release of the track relay contacts to supply an impulse of en ergy to said impulse relay, a code following detector relay, a track battery and a continuously op erating coding device located at the exit end of said track section, said detector relay having a contact movable between a first and a second position, said detector relay being of a type the contact of which when in its first position is moved to its second position when and only when energy flows through the relay winding from its first to its second terminal, the first terminal of said detector relay winding being connected to the first track rail, the negative terminal of said track battery being connected to said second track rail, said coding device having a contact which is moved between two positions, said coding device contact being efiective when in one of its positions to connect the second terminal of said detector relay winding to the positive terminal of said track battery and being effective when in its other position to connect the second terminal of said detector relay winding to said second track rail, an approach relay, and means governed by said detector relay contact for energizing said approach relay.

FRANK H. NICHOLSON.

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