US2053889A

US2053889A - Railway traffic controlling apparatus

Info

Publication number: US2053889A
Application number: US11808A
Authority: US
Inventors: Earl M Allen
Original assignee: Union Switch and Signal Inc
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1935-03-19
Filing date: 1935-03-19
Publication date: 1936-09-08
Anticipated expiration: 1953-09-08

Description

I Sept. 8, 1936.

Filed March 19, 1935 4 INVIYNZ'OR Earl M.Alle12 BY 6L1 B B B CWWJ W m M \L T S a Z i J 3% M w 3+ m WQE M C I 53 L 2% I R 5 5 Z L H M m 7 a T m .l 4 4H 3 z 1 If g m H Mi L a n 5 I: u m H A. m; w H 1 J A s W e 5 1 m m w H 2 C6 C "4/ 7 w m U% w c m6 mm 5 P 6 4 2 0d mfi 7M 3 WW mm? 5 mg 25 I m L m m5 H M2 Z .T 1 B m C H 24 T 2 H B N N M a H M. C CFV, 9 finmlnnflw CM HIS A TTORNE Y Patented Sept. 8, 1936 uNiTlEo STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application March 19, 1935, Serial No. 11,808

23 Claims.

My invention relates to railway traflic controlling apparatus, and has particular reference to approach locking apparatus for looking a track switch against operation when a signal governing the movementof traflic over the switch has been cleared and also under certain trafiic conditions for a selected time interval after the signal is manually restored to stop. More specifically, my invention relates to the group release of approach locking, in which a single time releasing device is employed with different groups of signals, and in respect to this feature my invention is an improvement upon that disclosed and claimed. in a copending application Serial No; 11,807, filed this day by Charles W. Bell, for Interlocking control apparatus.

One object of my invention is to provide an arrangement in which a single time releasing device or group of devices is employed to release the looking for all of the signals of an interlocking plant, the time interval imposed upon the release of the locking being relatively long or relatively short, depending upon whether the signal put to stop is one for governing high speed or slow speed trafiic. v I

Another object of my invention is to arrange the time releasing device so that it is self-checking, by the provision of selecting apparatus which prevents the control of the time releasing device by a signal to release the locking associated therewith except when the time releasing device is in its normal inactive condition.

A further object of my invention resides in the provision of a thermal time releasing device which is so arranged that it can beset into operation only when in its normal'cooled condition, and which has contacts closed respectively at the be ginning and at the end of a measured time interval, these contacts being included in circuits so controlled that the time delay will not be defeated if they become connected together.

Other objects, purposes and features of my invention will appear as the description progresses. 1

I will describe one form of apparatus embodying my invention, and will then point out the novel features thereof in claims. I Referring to the accompanying drawing, the track plan at the-top represents a stretch of double track railroad comprising the territory controlled by an interlocking plant; each track being indicated by a single line. The movement of traffic over the lowertrack is normally from left to right and over the upper track is from right to left, the two tracks being connected by a crossover comprising switches I and IA, which are controlledby power operated switch machines ISM and IASM, respectively, of-the usual type. The lower track includes a switch section IT containing switch I and two

approach sections AIT

5 and 2T, while the upper track includes a switch section 3T containing switch IA and two'corresponding approach sections A3T and 4T. Each track section is provided with the usual closed track circuit including a normally energized track relay. The track relays for the upper track, being duplicates of those for the lower track, have been omitted, while the track circuits for the relays for the lower track, which are relays AI TR, I'IR and ZTR, have been indicated diagrammatically by dotted line connections from the relays to the respective track sections of the track plan.

The movement of traffic into section IT in the normal direction is governed by a signal R2 comprising a high speed arm a which may be cleared to indicate caution or proceed in accordance with traffic conditions in advance when section IT is unoccupied and switch I is normal; and an auxiliary slow speed arm, or call-on signal a, which may be cleared to permit a train to enter section IT at low speed when switch I is reversed or section IT is occupied by a preceding train. The movement of trafiic into section IT in the opposite direction is governed by the slow speed signal L2. A distant signal RZD for governing traffic approaching section IT is located a suitable distance in the rear of signal R2, and it is to be understood that in accordance with the usual practice signal 32D is cleared to indicate proceed only when arm a of signal R2 has been 35 cleared to indicate caution or proceed, and section AIT is unoccupied.

The arms a and c of signal R2 are controlled by the signal relays RA2H and RCZI-I, respectively, and signal L2 is controlled by a signal relay L2H. The local signal circuits are not shown in detail, but it is to be understood that each signal arm will be cleared when the corresponding signal relay is energized, and will indicate Stop when its signal relay is deenergized. Relays RAZH and RCZH are selectively controlled, through the medium of a lever repeating relay RZVR and a stick relay C2VS by a manually operable signal lever R2V, which is shown in the drawing in its normal position, that is, in the position to which it is moved to cause signal R2 to indicate stop. Lever R2V is a three-position lever and may be moved to the right to clear arm a; or to the left to cleararm c of signal R2.

Signal relay L2H is controlled by the lever L2V through the medium of a lever repeating relay LZVR, lever LZV being a two-position lever which may be moved to the left to clear signal L2 or to the normal position, as shown, to cause signal L2 to indicate stop.

The movement of traffic over the upper track is governed by the signals R4, L4 and LAD, which are similar to and are controlled in the same manner as the corresponding signals for the lower track. To simplify the drawing, the control circuits for these signals have been omitted, only the relays L4VR and C4VS being shown, these relays controlling the signal L4 in the same way as relays RZVR and C2VS and control signal R2.

The switch machines ISM and IASM for operating switches I and IA have the usual circuit controllers for controlling indication relays, such as INKR and IRKR, for selecting the signals in accordance with the positions of the switches. It is to be understood that relay INKR is energized only when switches l and IA are both closed and locked normal, so as to permit parallel train movements on the two main tracks, and that relay IRKR is energized only when the switches are both closed and locked reverse to permit train movements from one main track to the other.

The switch machines ISM and IASM are controlled by polarized switch control relays IWR and IAWR, respectively, by circuits not shown in detail, but which are of the usual type as illustrated for example in the Willard Patent No. 1,380,452, issued June '7, 1921. Relays IWR and IAWR are controlled over a polarized switch control circuit by a manually operable switch lever IV. This circuit, shown at the bottom of the drawing, includes contacts 24 to 29, inclusive, of approach locking relays and of the track relays for the switch sections. The purpose of these contacts is to at times lock the switch against operation by lever IV. It is obvious that the operation of the switch is prevented when any of these contacts is open, that is, when any approach locking relay is deenergized or when either switch section is occupied.

An approach locking relay is provided for each signal governing the movement of traflic into a switch section, these relays being identified by the reference MR with a prefix corresponding to the designation of the associated signal. Each approach locking relay is a stick relay, and is released to lock the switch when the associated signal is cleared, but becomes energized when the signal is restored to stop only if certain conditions are fulfilled. Thus for example, considering relay RZMR, if signal R2 is put to stop by a train entering section IT, a pickup circuit for relay RZMR will be closed over back contact 5 of track relay ITR when the train passes the signal. If signal R2 is put to stop manually, and there is no train approaching so that section AIT is unoccupied, a pickup circuit for relay RZMR will be closed over front contact 6 of relay AlTR, but if this contact is open, relay RZMR will remain deenergized and a circuit will be closed over its back contact 1 to pick up a selector relay R2S to set certain time measuring apparatus into operation, as hereinafter described, to pick up relay RZMR at the end of a measured time interval, this time interval being controlled by a stick relay C2VS in the manner disclosed and claimed in a copending application of Earl M. Allen and Henry S. Young, Serial'No. 2,076, filed Jan. 16, 1935, for Railway traffic controlling apparatus,

so that the time will be relatively long or short, depending on whether arm a or arm 0 has been put to stop. Relay RZMR when picked up is held by a stick circuit including its front contact 1 until signal R2 is again cleared. Relay LZMR is similarly controlled by signal L2 and by the track relays for sections IT and 2T, except that since signal L2 is a slow speed signal only the short time element is imposed when selector relay LZS becomes energized. The circuits for the approach locking relays LZMR and RMR associated with signals L4 and R4, respectively, are exactly like those for relays RZMR and LZMR, and are therefore omitted from the drawing, and it'is to be understood that the selector relays U38 and R48 are associated with the locking relays for the upper track in the same way relays R2S and L2S are associated with those of the lower track.

The selector relays S associated with the approach locking relays MIR. control time measuring means including a time element relay TE for providing a long time element, and a thermal relay TH for providing a short time element for at times delaying the release of the locking. The time element relay TE may be of any suitable type, and as herein disclosed is to be understood to be arranged to open a checking contact II when it becomes energized, and to then close a contact, such as contact 8 included in one of the circuits for relay RZMR, after an adjustable time interval which in practice is usually from one to four minutes. One form of relay which may be employed in this connection is disclosed in a patent for Electrical relays, No. 1,966,965, issued July 17, 1934, to B. Lazich and H. E. Ashworth. The thermal relay TH may be of the usual type comprising a contact member 9 formed of a bimetallic or thermostat strip forming a heat responsive member with a coil of resistance wire wound thereon or adjacent thereto, and the contact 9 occupies the position shown in the drawing in which it connects with a fixed back contact only when the heat responsive member is in its normal cooled condition. When the coil is energized, contact 9 becomes deflected, and connects with a fixed front contact to pick up a stick relay THS at the end of a measured time interval, whereupon the coil of the relay TH will become deenergized allowing the heat responsive member to cool for a measured time interval, when a checking relay NT becomes energized. Each approach locking relay MR associated with a slow speed signal has a pickup circuit including front contacts of the stick relay THS and of the checking relay NT, and also including a front contact of its respective selector relay, such as relay RZS, which circuit becomes closed when the selector relay has been energized and the thermal relay TH has been operated through a cycle of heating and cooling and has returned to its normal condition. Each relay MR associated with a high speed signal also has a pickup circuit including front contacts of the time element relay TE and of its selector relay such as relay RZS.

The circuits for controlling the selector relays also include contacts of a slow acting checking relay NTP, which is energized only when all selector relays S are deenergized and relays TE, NT and THS are in their normal condition, these circuits being so arranged that no selector relay can become energized unless relay NTP is energized.

In order to simplify the drawing, I have shown relay contacts which 'in some instances are not adjacent the respective "relays which operate them, but in each case such contacts bear the reference characters identifying .the respective relayas'well as a number identifying the contact. Thus,'for'example, one 'branchof the pickup circuit for 'relay RZMR includes back contact 5 of track relay ITR. The corresponding circuit for relay L2MR also includes aback contact III of the ITR relay, contact In bearing the reference I'I'R to indicate the relay which operates it. I have also, in the accompanying drawing, not shown the source of current for energizing the various relays but have shown in lieu thereof only the terminals of the source which I have identified by the references B and C to designate the supply and common terminals of the source, respectively.

I will now describe the operation of my apparatus in connection with an assumed train movement from left to right over the lower track. Considering the apparatus to be in its normal condition as shown in the drawing, a circu'it'may be traced from terminal B, contact I I, which is closed when signal R2D indicates caution or stop, back contacts I2 and I3 of signal relays RCZH and RAZH, front contact 6 of relay A'ITR, relay R2MR to the other terminal C of the source of current. Relay R2MR becomes energized over this circuit and closes its stick contact I bridging contact 6, so that relay R2MR will remain energized as long as signal R2 remains at stop.

To clear arm a of signal R2 for an approaching high speed train, the operator moves lever R2V to the right, closing a circuit which may be traced from terminal B, lever contact I4, relay R2VR to terminal C. Since switches I and IA are normal the normal-indication circuit, which may be traced from terminal B, contacts I5 and ISA of the switch circuit controllers, relay INKR to terminal C is closed, so that relay INKR is energized. Assuming that signal L2 is at stop and that its approach locking relay L2MR is energized, the circuit for relay RAZH will be closed, and may be traced from terminal B, front contact N of relay LZMR, back contact I! of relay LZVR, front contact I8 of relay INKR, front contact I9 of relay RZVR, back contact 20 of relay C2VS, front contacts 2| and 22 of relays I TR and INKR, relay RAZH to terminal C. Relay RAZI-I thus becomes energized to clear arm a of signal R2 and to open its back contact I3 to deenergize relay RZMR which relay, upon releasing, opens contact 24 in the control circuit for relays IWR and IAWR to lock switches I and IA against operation.

When the approaching train passes signal R2, relay ITR releases, opening contact 2I to deenergize relay RAZH to put the signal to stop and to close back contact I3 in the pickup circuit of relay RZMR, which circuit is completed over back contact 5 of relay ITR so thatrelay RZMR becomes energized. The switch, however, remains locked because contact 26 of relay ITR in the switch control circuit is now open. When the train leaves section IT, relay ITR again picks up to complete the switch control circuit, which may be traced from terminal B, contacts 23 to 29, inclusive, relays IWR, IAWR, contact 30 to terminal C. Contacts 23 and 30 constitute a polechanger whereby relays I WR and IAWR may be energized in the direction corresponding to the position of the lever IV to control the circuits for the switch machines ISM and IASM to operate the switches to normal when lever IV is moved to its left-hand position as shown and'to reverse the-switches when lever IV- is moved to the right.

Assume now that switches I and IA have been reversed, a circuit will be closed from terminal B,'-conta'cts 3| and BIA of the switch icircuit controllerarelay I'RKR to terminal C so that relay IRKR becomes energized. The operator may now clear. "a of signal R2 topermit a slow speed movcmeritover the switches by moving lever RZV to the left to close a circuit which may be'traced from terminal B, contact '32 of lever REV, front contact 33 of relay RZMR, relayCZVS to terminal C. Relay "CZVS therefore becomes energized and "since -'contact I 4 is also closed when lever RZV is moved to the left, relay RZVR is energized and a circuit is closed which may be traced from terminal B, back contact '34 of relay C sVS, fron t contact 35 of relay LAMR, back contact -36 of relay L4VR, contact 31 of relay 'IRKR,

front-contacts I9 andlil 'of relays RZVR and.

C2VS, relay RCZH to terminal C. Relay RC2H therefore becomes energized to clear arm 0 of signal RL-and to open contact I2 to release relay RZMR' to lock "the switches. The latter relay, upon releasing, opens the pickup circuit of relay C'ZVS, which however, does not release, being new energized 'over its stick "circuit which may be traced from terminal B, from contact 38 of relay CZVS, contact 39 0f lever RZV, back contact 33 of relay RZMR, relay CZVS to terminal C. Relay RCEH is controlled independently of track relay iTR so that arm 0 will notgo to stop when the approaching train enters'section IT and therefore to release the locking in this instance, lever REV must be restored to itsnormal position while section "IT is occupied.

Assume now that arm 21 of signal R2 has been cleared but that it is restored to stop by returning lever RZV to normal when a train is approaching and is occupying section AIT. Relays R2VR and will then release but relay R2MR will not pick up because contact 6 in its pickup circuit is open, due to the presence of the approaching train. Assuming the time element devices are in their normal condition a circuit is closed which may be traced from terminal B, back contacts 40 to 43, inclusive, of relays L45, R43, L2S and R28, back contact II of time element relay TE, front c n't-act 44 of relay NT, back contact 45 of relay checking relay NTP to terminal C. A circuit is now also closed from terminal B, contacts II, I2 and l3,b'ack contact I, front'contact 46 of relay NTP, relay R25 to terminal C. Relay R28 picks up and establishes its stick circuit including contact 41 and opens contact 43 to release relay NTP, which relay now opens contact 46 and also the similar contacts 48, 49 and 50 in the pickup circuits of the other selector relays. A circuit is now closed from terminal B, contact SI of relay R ZS, back contact 52 of relay CZVS, time element relay TE to terminal 0. Relay TE upon becoming energized, opens contact II and at the end of a measured time interval closes its contact 8 to complete the branch of the pickup circuit for relay RZMR which includes that contact and front contact 53 of relay RES so that relay RZMR picks closing its stick circuit over front contact I. Back contact I in the stick circuit of relay RESnow being open, this relay releases and deenergiz'es relay TE and upon the return of relay to its normal condition, contact II closes so that relay N'IP again picks up. The time measuring apparatus is now in its normal condition and if any of the other signals has been put to stop during the time in which relay NTP was released, their selector relays may now become energized to effect the pick up of the associated locking relays.

I will now assume that arm of signal R2 has been cleared instead of arm a, and that arm 0 is then put to stop, by manually returning lever RZV to normal while the approach section AIT is cocupied. When the signal returns to stop, back contact l2 of relay RC2H closes to complete the circuit over back contact I of relay R2MIR. and front contact 46 0f relay NTP to pick up relay R2S as already described, but in this instance, since the stick relay CZVS is energized, a circuit is closed from terminal B, front contacts and 52 of relays R28 and C2VS, back contact 54 of the stick relay THS, through the heating element of the thermal relay TH to terminal C. In a short period of time back contact 9 of relay TH will become deflected toopen the circuit from terminal B, through contact 9 and the fixed back contact of relay TH, relay NT to terminal C, thereby releasing relay NT to'open contact 44 and to close contact 56. After relay TH has been heated for a measured time interval, a circuit is closed from terminal B, front contact 9, back contact 56 of relay NT, relay THS to terminal C. Relay THS picks up, completing its stick circuit from terminal B front contacts 5!, 52 and 54, relay THS to terminal C. The opening of back contact 54 deenergizes relay TH, and after a predetermined cooling period contact 9 will assume its original position and relay NT will again pick up to complete the branch of the pickup circuit for relay R2MR which includes

contacts

51, 58 and 59 of relays NT, THS and CZVS, respectively, and contact 53 of relay R2S. Relay RZMR thereupon picks up, relays R28 and THS release in turn, and relay NTP picks up when back contact 45 of relay THS closes. Relay CZVS becomes deenergized by the opening of back contact 33 of relay RZMR and releases.

If, now the operator desires to reverse the direction of traffic and to clear signal L2, he will move lever L2V to the left, completing a circuit from terminalB, contact 60 of lever L2V, relay LZVR to terminal C, and if relay RZMR has been picked up and relay C2VS released, as described in the preceding paragraph, a circuit is closed from terminal B, back contact El of relay C2VS, front contact 62 of relay R2MR, back contact l9 of relay RZVR, front contact l8 of relay INKR, front contact I! of relay L2V'R, relay L2H to terminal C, so that relay L2H becomes energized to clear signal L2 and opens its back contact 62 to release relay LZMR. If, now signal L2H is restored manually to stop while approach section 2T is occupied and front contact 63 of relay 2TR in the pickup circuit of relay LZMR is open, a circuit will be completed from terminal 13. back contacts 62 and 64 of relays L2H and LZMR, front contact 48 of relay NTP, relay LZS to terminal C. Relay L2S picks up, closing contact 65 to complete its stick circuit, opening contact 42 to release relay NTP and closing contact 66 to energize thermal relay TH, and also closing contact 61 in the branch of pickup circuit for relay L2MR which includes contacts 68 and 69 of relays THS and NT. These relays function in the same manner as when controlled by relay R2S as already described, and relay L2MR becomes energized when relay NT picks up to close contact 69 at the end of the short time interval.

As hereinbefore pointed out, the control apparatus for the upper track is similar to that for the lower track. Relays R45 and Us together 12 in the same manner as relays R28 and L2S. It

will be clear from the drawing that any desired number of additional selector relays may be included in the circuits provided and that each such relay may have a back contact such as contact 40 in the circuit of relay NTP and a front contact such as contact for energizing the time element device or devices and that but one time element relay and but one thermal relay are required, irrespective of the size of the interlocking plant. It is also evident that the time element devices are self-checking and that since the circuit for relay NTP controlling the pickup of the selector relays includes

contacts

44, 45 and II, it is impossible for any selector relay to become energized after either time element device has started to measure a time interval until the device has again returned to its normal condition. Furthermore, if the front and back contact 9 of the thermal relay TH should stick together, relay NT would not release and therefore relay THS would not pick up and the nullification of the time element which would otherwise occur will not take place.

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

Having thus described my invention, what I claim is: 1

1. In combination, a selector relay, an electro-responsive device controlled by the selector relay, a thermal relay operable through a cycle comprising a heating period and a cooling period, a checking relay energized only when the thermal relay is in its normal condition, means preventing the selector relay from becoming energized unless the checking relay is energized, means effective when the selector relay is energized to operate the thermal relay through its cycle, and means controlling said electro-responsive device upon the return of the thermal relay to its normal condition.

2. In combination, a selector rela an electroresponsive device controlled by the selector relay, a. thermal relay operable through a cycle comprising a heating period and a cooling period, a checking relay energized only when the thermal relay is in its normal condition, means effective when the selector relay is energized to operate the thermal relay through its cycle, means preventing the return of the thermal relay to its normal condition unless the checking relay becomes deenergized, and means controlled by the selector relay for controlling said electro-responsive device when the checking relay again becomes energized.

3. In combination, a selector relay, an electro-responsive device controlled by the selector relay, a thermal relay operable through a cycle comprising a heating period and a cooling period, a checking relay energized only when the thermal relay is in its normal condition, a stick relay which becomes energized at the end of the heating period of the thermal relay, and means effective when the selector relay is energized to operate the thermal relay through its cycle and to control said electro-responsive device when both the checking relay and the stick relay are energized.

4. In combination, a selector contact, an electro-responsive device, a-thermal relay, a checkingrelay, a stick relay, an energizing circuit for the thermal relay including the selector contact and a back contact of the stick relay, a pickup circuit for the stick relay including a back contact of the checking relay and a contact closed when the thermal relay is-in its heated condition, a stick circuit for the stick relay including its own front contact and the selector contact, a circuit for the checking relay closed only when the thermal relay isin its normal cooledcondition, and an energizing circuit for said electro-responsive device including front contacts of the checking relay and of the stick relay.

5. In combination, a control contact, a selector relay controlled by said contact, an electro-responsive device, a thermal relay, a check. ing relay, a stick relay, a circuit for the thermal relay including a front contact of the selector relay and a back contact of the stick relay, a pickup circuit for the selector relay including said control contact anda front contact of the checking relay, aholding circuit for the selector relay including said control contact and a contact closed only whenthe electro-responsive device is deenergized, a pickup circuit for the stick relay including a contact-closed only when the thermal relay is in its heated-condition, a stick circuit for the stick relay including a front contact of the selector relay, a-circuit for the checking relay closed only when the thermal relay is .in its normal cooledcondition, a pickup circuit for the electro-responsive device including front contacts of the stickrelay and of the checking relay, and-a holding circuit for the electroresponsive device including said control contact and a contact closed when the electr c-responsive device is energized.

6. In combination, an electro-responsive de-' vice, a heat responsive element, aheater for heating. said element, a firstandazsecond stick relay, achecking relay, a control contact, pickup and stick circuits for the first stick relay each including said'control contact, the pickup circuit also including a contact closed only when the checke ing relay energized, an energizing circuit for the heater closedonly when the firststick relay is picked up and the secondstick relayisxreleased, a circuit for the'checking relay closed .only when the heater is in its. normal cooled condition, a pickupcircuit for the secondistickrelay closed only when the heater is in its heated condition, a stick circuit for the second stick relay controlled by afront contactiof the first stick relay, and a circuit for. energizing vsaid electro-responsive device including. front contactsv of the checking relay .and of both said stick relays. I V

'7. In combination, an electroeresponsive def vice, a stick relay, a heat responsive element, .a heater for heating said element, .a checking relay, v.a control contact, anenergizing circuitlfor said heater closed in response to the .closing of the. control contactlprovided the electro-responsive device and the stick relay are deenergized, a pickup circuit for the stick relay closed only when the checking relay is deenergized and the heat responsive element is in its heated condition, a stick circuit for the stick relaycontrolled'by the control contact and closed only whenth'e electro-responsive device is deenergized, a circuit forthe checking relay closed only when the heat responsive elementis in its normal cooled condition, a pickup circuit forthe electro-responsive device closed only-when-the stick relay and the checking relay are energized, and a holding circuit for the electro-responsive device including the control contact.

8. In combination, a selector relay, an electroresponsive device, time element means, a checking relay energized only when the time element device is in its normal condition, means preventing the energization of the selector relay unless the checking relay is energized, means efiective when the selector relay is energized to operate the time element means for a measured time intervaland to then return it to its normal condition, and a circuit controlled by front contacts of the selector relay and of the checking relay for controlling said electro-responsive .device upon the return of said time element means to its normal condition.

9. In combination, a selector relay, an electroresponsive device, time element means, a checking relay, means energizing said checking relay only when the time element device is-in its normal condition, astick relay, means effective'when the selector relay is energized to operate said time element device, means controlled by said time element device when operated to pick up said stick relay at the end of a measured time interval only if said checking relay releases, means retaining said stick relay energized until the selector relay releases, means effective when the stick relay becomes energized for restoring the time element device to its normal condition, means effective when both the stick relay and the checking relay are energized for operating said electro-responsive device, and means responsiveto the operation of the electro-responsive device for releasing the selector relay.

10'. In combination, an electr c-responsive device, a time element device, a stick relay, a check.- ing relay, a manuallycontrollable contact, an energizing circuit for said time element device including said manually controllable contact and a back contact of the stick relay, a-pickup circuit for the stick relay including a back contact of the checking relay and a contact closed-When the time element device has been energized for a measured time interval, a stick circuit for the stick relay including said manuallycontrollable contact, a circuit for the checking relay'closed only when the time element device hasbeen deenergized for a measured time interval, and an energizing circuit for the electro-responsive device including front contacts of the stick relay and of the checking relay. 7

' l1. Incombination, an electro-responsive device, a time element device, a stick relay, a checking relay, a manually controllable contact, an energizing circuit for said time element device including 'sa-id'manually controllable contact and a back contact of the stick relay, means preventing the closing of said circuit unless the checking relay is energized, apickup circuit for the stick relay closed only when the time element device has been energized for a measured time interval, a stick circuit for the stick relay including'said manually controllable contact, a circuit forthe checking relay closed only when the time element device has been deenergized for a-measured time interval, and .an energizing circuit for said elect-ro-respon-sive device including front'contacts of the stick relay and of the checking relay.

12. In combination, a plurality of selector relays, an *electro-respohsivedevice for each selector relay, a 'ncrmallydeenergized time element device, means preventing the energizaticrr of any selector relay except when said time element device is in its normal condition, means effective when any selector relay is energized to operate the time element device, means retaining such relay energized while the time element device is in operation, means controlled by the time element device for operating the electro-responsive device associated with the energized selector relay when it has operated for a measured time interval, and means controlled by the electroresponsive device when operated for restoring the time element device to normal.

13. In combination, a plurality of selector relays, an electro-responsive device for each selector relay, a normally deenergized time element device, means preventing the energization of any selector relay except when said time element device is in its normal condition, means effective when any selector relay is energized to operate the time element device through a cycle, said time element device returning to its normal condition at the end of a measured time interval, and means controlled by the energized selector relay for operating the associated electro-responsive device upon the return of the time element device to its normal condition.

14. In combination, a plurality of selector relays, an electro-responsive device for each selector relay, a time element device, a checking relay, a circuit for energizing said checking relay closed only when all of the selector relays are deenergized and the time element device is in its normal condition, means preventing the energization of any selector relay except when the checking relay is energized, means effective when any selector relay is energized to operate the time element device, and means controlled by the energized selector relay for operating the corresponding electro-responsive device at the end of a predetermined time interval measured by said time element device.

15. In combination, a plurality of selector relays, an electro-responsive device for each selector relay, a thermal relay operable through a cycle comprising a heating period and a cooling period, means preventing the energization of any selector relay except when said thermal relay is in its normal cooled condition, means effective when any selector relay is energized to operate the thermal relay through said cycle, and means controlled by the energized selector relay for operating the associated electro-responsive device upon the return of said thermal relay to its normal condition.

16. In an interlocking system for railroads, a railway track switch, a plurality of signals for governing the movement of trafiic over said switch, a locking relay for each signal which when deenergized prevents operation of the switch, a selector relay for each signal, a thermal relay operable through a cycle comprising a heating period and a cooling period, means effective when a signal is manually put to stop under certain trafiic conditions to energize the corresponding selector relay provided said thermal relay is in its normal cooled condition, means efiective when a selector relay is energized to operate said thermal relay through said cycle, and means controlled by the energized selector relay for energizing the corresponding locking relay upon the return of said thermal relay to its normal condition.

1'7. In an interlocking system for railroads, a railway track switch, a plurality of signals for governing the movement of traflic over said switch, a locking relay for each signal which when deenergized prevents operation of the switch, a selector relay for each signal, a time element device, a checking relay, a circuit for energizing said checking relay closed only when all of the selector relays are deenergized and the time element device is in its normal condition, means effective when a signal is manually put to stop under certain traific conditions to energize the corresponding selector relay provided said checking relay is energized, means effective when any selector relay is energized to operate the time element device, and means controlled by the energized selector relay for energizing the corresponding locking relay at the end of a measured time interval.

18. In an interlocking system for railroads, a railway track switch, a plurality of signals for governing the movement of trafiic over said switch, a locking relay for each signal which when deenergized prevents operation of the switch, a selector relay for each signal, a time element device, means eiiective when a signal is manually put to stop under certain traffic conditions to energize the corresponding selector relay provided said time element device is in its normal deenergized condition, means effective when any selector relay is energized to operate the time element device, means retaining such selector relay energized while the time element device is in operation, means controlled by the time element device for energizing the locking relay associated with the energized selector relay when it has been operated for a measured time interval, means effective when such locking relay becomes energized to release the selector relay, and means effective when the selector relay releases to restore the time element device to its normal condition.

19. In an interlocking system for railroads, a railway track switch, a plurality of signals for governing the movement of trafiic over said switch, locking means for each signal effective when such signal has been cleared to prevent operation of the switch, means for delaying the release of the locking when a signal is put to stop under certain trafiic conditions comprising a thermal relay operable through a cycle comprising a heating period and a cooling period, means operating said thermal relay, provided it is in its normal cooled condition, when a signal is put to stop under said certain traflic conditions, and means efiective to release the locking associated with said signal only upon the return of said thermal relay to its normal condition.

20. In an interlocking system for railroads, a railway track switch, a signal for governing the movement of trafilc over the switch, a locking relay which when deenergized prevents operation of the switch, a time element device which becomes energized when the signal is put to stop provided said locking relay is deenergized and said time element device is in its normal condition, a stick relay, means for energizing said stick relay when the time element device has been energized for a measured time interval, means controlled by the stick relay when energized for deenergizing said time element device and for then energizing said locking relay upon the return of said element device to its normal condition, and means maintaining said locking relay energized until said signal is again cleared.

21. In an interlocking system for railroads, a railway track switch, a signal for governing the movement of traflic over the switch, a locking relay which becomes deenergized when the signal is cleared and which when deenergized prevents operation of the switch, a time measuring device, means operating the time measuring device when the signal is put to stop provided the locking relay remains deenergized, a stick relay, means energizing the stick relay at the end of a measured time interval after the time measuring device is operated, means controlled by the stick relay when energized to return the time measuring device to its normal condition, means effective when the time measuring device returns to its normal condition to energize the locking relay, and means for maintaining the locking relay energized until the signal is again cleared.

22. In an interlocking system for railroads, a railway track switch, a plurality of signals for governing the movement of trafiic over the switch, a locking relay for each signal deenergized when the signal is cleared and efiective when deenergized to prevent operation of the switch, a selector relay for each locking relay, a time measuring device, means efiective when any signal is put to stop to energize the corresponding selector relay as long as the associated locking relay remains deenergized, means controlled by each selector relay when energized for operating said time element device, means controlled by the time element device when operated to energize the locking relay corresponding to the energized selector relay at the end of a measured time interval, thereby releasing such selector relay, means maintaining such locking relay energized until the corresponding signal is again cleared, and means preventing the energization of any selector relay except when all selector relays are deenergized and said time element device is in its normal condition. 23. In an interlocking system for railroads, a plurality of railway track switches, a high speed signal and a slow speed signal for governing the movement of trail-1c over each switch, locking means for each signal rendered efiective When the signal has been cleared to prevent operation of the switch, a time measuring device, means effective when a signal is put to stop under certain trafiic conditions to energize the time measuring device provided said device is in its normal condition, means controlled by the time measuring device for selectively releasing at the end of a measured time interval the locking means associated with such signal, and selecting means for causing said time interval to be relatively long when a, high speed signal has been put to stop and relatively short when a slow speed signal has been put to stop.

EARL M. ALLEN.