US1942134A

US1942134A - Interlocking system for railroads

Info

Publication number: US1942134A
Application number: US412767A
Authority: US
Inventors: Charles S Bushnell
Original assignee: General Railway Signal Co
Current assignee: SPX Corp
Priority date: 1929-12-09
Filing date: 1929-12-09
Publication date: 1934-01-02
Anticipated expiration: 1951-01-02

Description

c. s. BUSHNELL 199429134 INTERLOCKING SYSTEM FOR RAILROADS Filed Dec. 9, 1929 2 Sheets-Sheet 1 ain, 2, W334 68 w WFQ mm .3 mm

INVE OR BY ATTORNEY Jan. 2, 1934.

C. S. BUSHNELL INTERLOCKING SYSTEM FOR RAILROADS Filed Dec. 9, 1929 2 Sheets-Sheet 2 MTTORNEY Patented Jan. 2, 1934 r UiTED STATES Charles S. Bushnell, Rochester, N. Y., to General Railway Signal Company,

ter, N. Y.

assignor Roches- Application December ,9, 1929. Serial No. 412,757

19 Claims.

This invention relates to interlocking systems for railroads, and more particularly pertains to indication means and devices for use in such systems.

levers are in extreme positions.

Then, the eX- treme position of each lever is given the significance that the traiiic controlling function,

lever governs, is in a correspondlocked. This is done by cmthe particular ing position and which ploying an indication latch mechanism to prevent the operation of extreme position except the control lever to a full when actuated bysuitable indication means, which indication means is such as to assure the dition of the associated tion.

position and lockedcontrafiic controlling func- In one type of indication system employed to indicate the position and locked condition of railroad track switches and associated switch machines, a called an SS relay, ing tower to indicate three position relay, commonly is employed in the interlockthe position and locked condition of its associated switch machine: {This SS relay is controlled over a; polarized line circuit receiving energy fro potential local to the switch machine and governed by contacts associated therewith. The contacts of the SS relay assume normal or reverse positions in correspondence with the normal or reverse locked position of the associated track switch, and assume m a source ofelectrical deenergized positions when the track switch is in operation orat any time that it is unlocked.

In the type of indication system above described, sometirnescalled aconstant current or battery type of indication, it may happen in the case of the control of a switch machine, that-an improper or false release of the indication latch mechanism can occur under a certain combination of circumstances.

For example, should the operator move a particular control lever to a new governing position and then quickly return it to the former governing position before the switch machine has operated sufficiently to' unlock the track switch, the contacts of the SS relay located in the interlocking tow that track swi ch, are still .in normal energized er I and associated with positions which allows the control lever to be returned to its former full extreme position. Such a condition is not dangerous if the switch machine follows the move'mentof the control lever, but if for one reason or another'aiuse or other overload device should operate upon such quick reversal of current, the momentum of the switch machine would operate it tofan unlocked condition out of correspondence "with its co'ntrol'lever which is then in a full position. The mechanical interlocking associated with that lever is thus released in accordancewith thehfull position assumed thereby, although the track switch is out of correspondence and unlocked. Such circumstances are extremely undesirable and are effectually prevented by the present invention.

With the above and other considerations in mind, it'is proposed in accordance with the present invention to provide means in the interlock- 7 ing tower which will actuate the indication latch mechanism' associated therewith, only whenthe indication means inthe tower has given a new indication. More specifically, in the case of an SSrelay indicating the position of a track switch as above described, means is to be provided which will release a particular indicationjlatch mechanism only when the contacts of' the SS relay'associated therewith have been allowed to assume deenergized positions and thenreturned to new extreme positions or the iormer extreme positions-in accordance with the operation of the track switch to such an extreme locked posi tion as to be in correspondence therewith.

A further object of the invention is to provide that once the SS relay has assumed ,a'd ener gized positiomthe indication, whichis togbe given afterit has again assumed a particular energized position, shall be maintained until-such indication has heen actively received bythe operation of theassociated controllever to a corresponding full position.

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

In describing the invention in detail, reference will be made to the accompanying drawings, in which like reference characters designate corresponding parts throughout theseveral views, and in .whichzs Fig. .1 represents in a diagrammatic, manner one specific embodiment of the present invention as applied to a control typical track switch;

Fig. 2 represents in a diagrammatic manner one modification of Fig. 1 included within the present invention as applied to a control lever associated with a typical track switch.

Withreference to Fig. 1 of the accompanying drawings, a track switch TS is shown as operated by a suitable switch machine SM which may be of the type, for example, such as shown in the patent to W. K. Howe No. 1,466,903 dated September 4, 1923. This switch machine is merely indicated, as its construction is no part of the present invention, and is shown as controlled in the usual conventionalmanner by a lever L in the interlocking tower which lever governs the application of electrical potential from a suitable source of current such as battery ET by movable contacts 5 and 6. It is to be understood that the switch machine SM may be any other suitable type of switch machine controlled by lever L to either of two extreme positions by any other suitable contact'arrangement.

Associated with the switch machine SM and track switch TS are the usual point detector contacts PD, which may be operated by any suitable type mechanism, such for example, as shown in my PatentNo. 1,517,236, dated November 25, 1924. These point detector contacts PD include movable contacts 7 and 8 which assume normal or reverse extreme positionsin correspondence with the track switch TS when it is locked, and assume intermediate positions during the operation of the track switch TS or at such other times that it is unlocked. These contacts 7 and 8 make contact between respective pairs of fixed contacts when in normal extreme positions and make contact between certain other pairs of fixed contacts when in reverse extreme positions. The point detector contacts PD also include a shunt contact 9 which is actuated to a non-contacting position when the track switch is in a normal locked position, and which assumes a biased contacting position at any such time that said track switch is not in a normal locked position; and also, a shunt contact 10 which is actuated to a non-contacting position when the track switch is in a reverse locked position, and which assumes a biased contacting position at any such time that said track switch is not in a reverse locked position.

Associated with the point detector contacts PD is a local transformer 15 which receives its energy from an alternating current transmission line of suitable potential extending from the interlocking tower.

In the interlocking tower an SS relay is provided with a line phase winding 16 which is supplied with suitable energy from the local transformer 15 at the switch as controlled by the point detector contacts PD. The SS relay also has a local phase winding 17 which is continuously energized from the secondary of a local transformer 18 in the interlocking tower. The primary of the transformer 18 is supplied with electrical potential from the same transmission line which supplies potential for the local transformer 15 at the switch. This two phase winding type SS relay operates its contacts to normal extreme positions with the line phase winding supplied with current of one instantaneous relative polarity which is sufiiciently out of phase in respect to the instantaneous relative polarity of the current in the local phase winding 1'? to produce a suitable rotating field flux, and operates its conlever associated with a tacts to opposite reverse extreme positions when the instantaneous relative polarity of the current in the line phase winding is reversed one hundred and eighty degrees. The contacts of the SS relay are so biased that they are caused to assume central deenergized positions when either or both the line phase and local phase windings l6 and 1'? respectively, are deenergized. Thus, as the point detector contacts PD are so connected as to apply potential of respectively opposite relative polarities to the line phase winding 16 from the local transformer 15 when the track switch TS is in one extreme position or the other and to deenergize said winding 16 when the track switch is unlocked, the contacts of the SS relay are caused to indicate the position and locked condition of the associated track switch TS.

The lever L is conventionally shown as being prevented from operating its movable contactsto full normal or full reverse positions N and R respectively by an indication latch mechanism including detent 20 which rides in a slot 21. This detent 2c is actuated by an armature 22 controlled by indication magnet coils 23. If the indication magnet coils 23 are deenergized, the armature 22 assumes a deenergized position so that when the lever L is moved from a normal position to a half normal position HN, detent 2G is allowed to assume a lower locking position. When the detent 20 is in a lower locking position, the lever L is prevented from movement to the full normal or full reverse positions N and R re spectively by the projections 24 and 25 until the indication magnet coils 23 are energized actuating the detent 20 to an upper unlocking position. However, should the indication magnet coils 23 be energized when the lever L is moved to a half normal position the lever cannot be moved to a new governing position such as the half reverse position HR due to the shoulder 26 which projects into the path of the detent 20.

A tappet bar 27, for operating the mechanical interlocking associated with lever L, is operated by a cam slot 28 to extreme normal or reverse positions with the lever L in corresponding normal and reverse positions N and R respectively; and is operated to an intermediate position with the lever L in either a half normal or half reverse position HN or HR respectively.

The lever L operates movable contacts 29 and 30 at the same time that the control contacts 5 and 6 are operated to their respective positions. The movable'contact 29 makes contact between a pair of fixed contacts when in the normal and half normal positions N and EN respectively, and makes contact between another pair of fixed contacts when in the reverse and half reverse positions R and HR respectively. The movable contact 30 makes contact between a pair or" fixed contacts when in the half normal position HN and makes contact between another pair of fixed contacts when in the half reverse position HR.

Associated with the lever L and the SS relay is a stick relay ST which is energized when the contacts of the SS relay assume deenergized positions; which is maintained energized after energization, if the control lever L remains in either the half normal or the half reverse positions I-IN or HR respectively although the SS relay is energized; and which is deenergized if the SS relay is again energized and the control lever is moved to either the full normal position N or the full reverse position It in accordance with the indication given by the SS relay.

The system shown in Fig. 1 of theac'companying drawings is in the full normal condition in which the contacts of the SS relay are energized to normal positions due to the positions assumed by the point detector contacts PD in accordance with the normal locked position of the track switch'TS. The local phase winding 17 of the SS relay is continuously energized from the local transformer 18 as is obvious from the drawings. The normal energizing circuit for the line phase winding 16 of the SS relay is traced as fo1lows:- from the right-hand terminal of the secondaryto the left-hand terminal of the secondary of;

local transformer 15.

Let us assume that the operator desires to operate the track switch TS to a reverse locked position. He may accomplish this by operating the control lever L to a half reverse position HR which supplies energy to the switch machine SM for the reverse operation. The switch machine SM operates in the usual manner as set forth in the above mentioned Patent No. 1,466,903. After the track switch has been operated to its reverse locked position'such indication will be received as to allow the control lever L to be moved to the full reverse position R.

In considering the operation in detail taking more particular notice of the operation of the indication system as embodying the present invention, let us assume that the operator moves the control lever L to the half reverse position HR.

As the indication magnet coils 23 are normally deenergized after the lever L has once been moved to an extreme normal or reverse position, for

reasons hereinafter pointed out, the detent 20' assumes a lower locking position in the slot 21 avoiding the shoulder 26 when the lever reaches the half normal position EN. The lever L is then moved to the half reverse position HR'in which position the switch machine SM receives reverse operating current.

As soon as the track switch TS is unlocked, the contacts 7 and 8 are caused to assume their intermediate positions deenergizing the line phase winding 16 of relay SS and allowing the shunt contact 9 to assume a biased contacting position in which the line phase winding 16 is shunted. The shunting circuit for the line phase winding 16 is traced as follows:from the right-hand terminal of the line phase winding 16 of the relay SS, through

wires

37 and 38, shunt contact 10 in a contacting position,

wires

39, 46 and'47, shunt contact 9 in a contacting position, wires 4'8 and 36, to the left-hand terminal of the line phase winding 16 of relay SS. The

contacts

49 and 50 thus assume deenergized positions.

With the contact 49 in a deenergized position, a pick-up circuit for the stick relay ST is closed, which is traced as follows:from the positive terminal of a suitable source of electrical potential indicated as B+, deenergized contact 49 V of relay wire 51, winding of relay ST, to the negative terminal of the suitable source indicated as 13-.

As soon as the relay ST becomes energized, it closes a stick circuit because the movable contact 36, operated by the lever L, is in a half reverse position HR. This stick circuit for the stick relay ST is traced as follows:from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 52 ofrel'ay ST, wires 53,- 54 and 55, contacts 3056,- wires 57,- 58 and 51, winding of relay ST, to the negative terminal of the suitable source indicated as B-.

The switch-machine SM continues to-operate the track switch TS until it is in a reversed a locked position, at which time the contacts '7 and 8 are. operated to reverse extreme positions and the shunt contact '10 isactuatedto a noncontacting position.

Thus, the point detector 7 contacts PDclose the reverse energizing circuit for the line phase winding 16, which circuit traced as foll'owst-from the right-hand terminal of the secondary of the local transformer 15,-through wire 32,'con'tacts 8-60, wires 61 and 37, line phase winding 16 of relay SS,- wir'es- 36 and 48, shuntcontact 9 in a contacting position, wires 4'? and 62, contacts 'l-'63,' wire 43,to the left-hand: terminal of -.the. secondary of local transformer 15. The contacts'49f and.50 of the SS" relay are nowioperated toreverseextreme positions.

With. the contactBO in a reverse. position the indication magnet coils 23. arev energized as the stick .relay ST still has its stick circuit closed;

This reverse energizing circuit for :the. indication magnet coils 23 is. tracedaas followsifrom:-

the positive terminal of a suitable source of electrical potential indicated: as B+, through front contact 52 of relayST, wire 53,- reverse contact. 50 of relay SS, wire 66, contacts 29-:67;,

wire 68, indicationmagnet coils 23, to the negative terminal of the suitable source indicated as B'. The detent 20 is actuated to an un-' locked position which allows the control *lever L to be operated to. the full reverse position Rh As soon as the lever L reaches itsfull reverse position R, the stick'circuit for the relay ST is broken at contacts 30-56 which deenergizes the relay ST and causes its contact 52 to assumeits deenergized position which inturn deenergizes the indication magnet coils 23. The lever 'L isnow in its fullrever'seposition R and the track switch TS is in correspondence therewith. The tappet bar 27 isin a reverse positionwhich controls the mechanical. interlocking in a:manner to release certain other control levers and lock certain others in the usual well knownmannen It is obvious from the above description,- that the energizing circuit for the indication mag-net coils 23 includes the front "contact 52' of relay ST. Should the operatormove the control lever to the half reverse position HR and quickly return it to the half normalposition HN; before the switch machine SM unlocks the track switch TS causing the line phase winding-16- of the relay SS to be deenergized, the indication magnet coils-23'could not be energized as the stick relay ST- has not yet received energy to'close its front contact 52. Thus, any quick juggling of i the lever L is effectually prevented by the circuits and devices arranged and constructed-according to the present invention. Such a -sys-- 'tem so enforces the significance placed upon the full'position of the control lever as to make it impossible that itmay ever bemoved-to a'fulh position except after the operation of its associated function to a corresponding extreme locked position.

With reference to Fig. 2 of'the accompanyingdrawings, a

trol lever having an indication latchmechanism of the 'usualtype which is employed with the modification included within; the present invention isshown as applied to, acon dynamic type indication system. This system shown in Fig. 2 differs in the respect that the indication is required onlymomentarily to release the indication latch mechanism IL, in contrast to the type of system represented in Fig.

l where it is necessary to have the indication latch mechanism continuously energized until it is accepted by movement of the control lever to a full position. The indication latch mechanism IL may be any suitable type of mechanism where a momentary actuation releases the locking means, and a continued actuation prevents movement of the associated lever to a new governing position, such for example, as shown in an application by W. K. Howe Ser. No. 388,437 filed August 26, 1929, or as shown in a patent to J. D. Taylor, Patent No 752,127 dated February 16, 1904 The parts and devices in Fig. 2 which are similar to those in Fig. 1' have been designated with like reference characters having the distinctive exponent a. The control lever L in this case, is provided with the indication latch mechanism IL which includes a dog 80 adapted to release a lock dog 81. The lock dog 81 is biased to an unlocking position by a spring 82. The lock dog 81 engages a locking shoulder 83. when the lever L is moved to a half reverse position HR as a shoulder 84 depresses the left-hand end of the.

lock dog 81 allowing the dog 80 to slip beneath the right-hand end in a manner to lock it in an engaging position with respect to the locking shoulder 83. The dog 80 is caused to assume its proper locking position by the movement of a cam 92 that is partially rotated by movement of the lever L When the coils 85 of the indication magnet I'M are energized, an armature 86 is V attracted which causes the dog 80 to release the lock dog 81 allowing the lever L to be moved to a full reverse position R. In a similar manner the lever L is prevented from being moved to a full normal position N from the half normal position HN until the indication magnet coils 85 have actuated the dog 80, as the lock dog 81 engages another locking shoulder 87. It is obvious from the description that once the dog has been actuated to an unlocking position, the lock dog 81 automatically assumes an unlocking or nonengaging position due to the spring biasing means 82, and remains in such a position until again depressed by shoulder 84. A safety dog 89 engages a shoulder 101 whenever the armature 86 isin an energized position, which prevents the control lever L from movement to a new governing position at such times.

Safety coils 88 are provided to prevent actuation of the dog 80 during the time that the switch machine SM is receiving operating current.

The control circuits for the relay SS will not be traced as they are identical to those pointed out in Fig. 1. Also, the relay ST in this case, does not require a stick circuit as the actuation 'of the coils of the indication magnet IlVl is required only momentarily. In other words, the stick feature has been transferred from the electrical stick circuit embodiment of Fig. 1 to the mechanical embodiment of Fig. 2. This relay ST is of the slow acting type and requires a period of time to reach its deenergized position, which is greater than the period of time consumed by the contacts of relay SS in operating from their deenergized positions to their energiz'ed positions, with the excess time of a sufficient value to allow for the momentary .energization of the coils 85 of indication magnet IM.

Let us assume that the operator niovesthe con trol lever L from the normal position N to the half reverse position HR. The track switch TS is unlocked and operated towards a reverse locked position. The point detector contacts PD are thus operated causing the line phase Winding 16 to be deenergized and shunted in a manner as explained for Fig. 1.

With the relay SS deenergized, a pick-up circuit for the relay ST is closed, which circuit is traced as follows: from the positive terminal of a suitable source of electrical potential indicated as B+, through deenergized contact 90 of relay SS wire 91, winding of relay ST to the negative terminal of the suitable source indicated as B When the switch machine SM has operated the track switch TS to its reverse locked position and the point detector contacts PD have energized the line phase winding 16 of the SS relay through its reverse energizing circuit, deenergized contact 90 is opened which deenergizes the relay ST Also, the polar contact 93 assumes its reverse position. These contacts 90 and 93 of the relay SS assume their positions before the contact 94 of relay ST opens. This completes a temporary or momentary reverse energizing circuit for the coils 85 of the indication magnet IM. which is traced as follows:-from the positive terminal of a suitable source of electrical potential indicated as B, through front contact 94 of relay ST wire 95, reverse contact 93 of relay SS, wire 97, contacts 98-99, wire 100, coils 85 of indication magnet IM, to the negative terminal of the suitable source indicated as 13-. The dog 80 is actuated to releaselock dog 81 which assumes its unlocked position and remains in such a position until control lever L is moved to the opposite governing position HN as above explained.

The control lever L may now be moved to the reverse full position It at th convenience of the operator controlling the mechanical interlocking in accordance therewith.

It is obvious from the above description that the modification shown in Fig. 2 also accomplishes the results of the present invention in that it prevents any false releasing of the indication latch mechanism.

It is considered unnecessary to describe the operation of the system in either Fig. 1 or Fig. 2 from its reverse condition to its normal condition as such operation is merely an inverse function of the operation already described and the circuits involved may be traced by analogy.

Thus, an interlocking system has been shown and described which is constructed and arranged according to the present invention in two of its possible embodiments. According to the present invention, it is impossible for a control lever to have its indication latch mechanism falsely released, as it is necessary that, before any releasing of such indication latch mechanism may be accomplished, the indication means in the interlocking tower which gives indication of the position and locked condition of the associated tramc controlling function, must have given a new indication before such releasing may be accomplished, although the indication means gives indication of the correspondence of the function with a full position of the lever.

The present invention may assume many forms to adapt itself to the various conditions to be met in practice. Although it has been specifically shown as associated with the control lever of a switch machine, it is to be understood that it may be associated with the control lever of a signal, the control lever of a derail or other traffic controlling function which employs a similar type of indication latch mechanism.

Having described one specific embodiment of the present invention as adapted to one type of interlocking system, it is to be understood that the circuits and devices are selected to facilitate in the disclosure of the invention rather than to limit the invention to one or two specific forms which it may assume; and it is to be understood that various modifications, adaptations and alterations may be applied to the embodiment of the present invention as shown to meet the requirements of practice without departing from the spirit or scope of the invention as set forth in the appended claims.

Having described my invention, I now claim:-

1. In an interlocking system for railroads, a remotely controlled function, means indicating in the tower the condition of said function, a controllever for governing said function, locking means both preventing final movement of said lever except when actuated, and preventing movement of said lever to a new governing position when actuated, and means for actuating said locking means only after said indicating means has displayed a new indication.

2. In an interlocking system for railroads, a remotely controlled function, means indicating in the tower the condition of said function, a control lever for governing said function, locking means preventing final movement of said lever except when actuated, and means for actuating said locking means rendered effective, only after said indication means gives a new indication and only until said control lever is operated in accordance therewith. I

3. In an interlocking system for railroads, a track switch, a switch machine, a control lever, indication means giving one indication with said track switch in a, normal position and locked, giving another indication with saidtrack switch ina reverse position .and lockedhandlgivinga third indication whenever said track sw'itchis unlocked or being operated by saidswitch machine, an indication latch mechanism means rendered eiiective, only after said indication means has given said third indication, for momentarily actuating said indication latch mechanism when saidindication means gives said one or said other indication.

4. In an interlocking system for railroads, a track switch, a switchmachine, a control lever, indicationmeans giving one indication with said track switch in a normal position and locked, givng another indication with said track switch in areverse position and locked, and giving a third indication whenever said track switch is .unlocked or being operated by said switch machine, an indication latch mechanism, means rendered. effective, only after said indication means has given said third indication, for actuating said indication latch mechanism when said indication means gives said one or said other indication, and means rendering continuously effective said actuating means to actuate said indication latch "mechanism only untilsaid control lever is operated in accordance with the actuation.

5. In an interlocking system for railroads, a

track switch, a switch machine, a control lever,

indication means giving one indication with said track switch in a normal position and locked, giving another indication with said track switch in a reverse position and locked, and giving a third indication when said track switch is unlocked or when said track switch is operated by said switch machine, an indication latch mechanism preventing operation of said control lever to a full position except when actuated and preventing movement to a new governing position when actuated, means for actuating said indication latch mechanism when said indication means gives said one or said other indication, conditioning means rendering said actuating means effective, said means being actively conditioned when said indication means gives the third indication, and means maintaining said conditioning means active only until said control lever has been operated in accordance with the actuation of said indication latch mechanism.

6. In an interlocking system for railroads, a track switch, a switch machine, a control lever, indication means giving one indication with said track switch in a normal position and locked, giving another indication with said track switch in a reverse position and locked, and giving a third indication when said track switch is unlocked or when said track switch is operated by said switch machine, an indication latch mechanism preventing operation of said controlleverto a full position except when actuated and preventing movement to a new governing position when actuated, means for actuating said indication latch mechanism when said indication means gives said one or said other indication, conditioning means rendering said actuating means effective, said means being activelyconditioned when said indication means gives saidthird indication and said means remaining actively conditioned for a predetermined time after said third indication ceases, and means maintaining the actuation of said indication latch mechanism effective for governing the control of said control lever until said lever hasbeenoperated I v,

, 7, In (an interlocking syst 'm forjrailroadsif a track switch,a switch machinefa control lever, indication means giving fone, indication withsaid track, with .i i l ibr i i jno tiiin. an la ed,

giving 'aiioth' 'r i di tit an with said track switch ina reverse positionandlocked, and giving a third indication when said track switch is unlocked or when said track switchis operatedby said switch machine, an indication latch mechasaid control lever is in a position in correspondence therewith and if said slow releasing relay has been energized within said predetermined time before said indication means gives said one or said other indication.

8. In an interlocking system for railroads, a track. switch, a switch machine, a control lever having normal and reverse governing positions, and normal and reverse full positions, an indication latch mechanism preventing operation .of said control lever to a particular full position except after being actuated when said control lever is in a corresponding governing position, and preventing operation of said control lever a) a new governing position when actuated, indication means giving one indication with said track switch in a normal position and locked; giving another indication with said track switch in a reverse position and locked, and giving a third indication when said track is being operated by said'switch machine or any other time when said track is unlocked, a slow release relay energized when said indication means gives said third indication, said relay maintaining its energized condition a predetermined period of time after en- 10 ergy is removed, and means for actuating said -indication latch mechanism when said indication 'means gives said one or said other indication if said control lever is in a corresponding governing i position and saidslow release relay has been lenergized within said predetermined period of time. r a

9. In an interlocking system for railroads, a

, track switch capable of being operated to either ii 'a normal or a reverse extreme locked position,

2 1 control means, including a control lever, for operating said track switch through a cycle of operation, said cycle of operation including either operation from one extreme locked position to C1; the other, or operation from one extreme locked position to an unlocked condition and returned from mid-stroke to its former locked position, an

,, indication latch mechanism, indication means giving one indication with said track switch in a normal locked position, giving another indication with said track switch in a reverse locked position, and giving athird indication with said track switch unlocked or in operation, and means rendered effective for actuating said indication latch mechanism wh n said indication means gives said 5' one or said other indication if said control lever is in correspondence therewith, and if said indication means has given said third indication in that cycle of operation.

' a 10. In an interlocking system for railroads, a

40 track switch capable of being operated to either .a normal or a reverse extreme locked position, .control means, including a control lever, for operating said track switch through a cycle of operation, said cycle of operation including either operation from one extreme locked position to the other, or operation from one extreme locked position to an unlocked condition and returned irom mid-stroke to its former locked position,

an indication latch mechanism,

N switch in a normal locked position, giving another indication with said track switch in a rea verse locked position, and giving a third indication with said track switch unlocked or in oper- 5 control lever for governing said function, locking 7 means preventing final movement of said control lever except when actuated, and means for actuating said locking means only during a predetermined time after said indicating means has 1 f been caused to display a new indication.

' 1 12. In an interlocking system for railroads, a

. remotely controlled function, means indicating in the tower the condition of said function, a controllever for governing said function, locking 75, means preventing final movement O sa d 90 .1-

- indication I 5 means giving one indication with said track trol lever except when actuated and preventing movement of said lever to a new governing position when actuated, and means for actuating said locking means only during a predetermined time, after said indicating means has been caused to display a new indication.

13. In an interlocking system for railroads, a track switch, a switch machine for operating said track switch, a control lever for governing said switch machine and having normal and reverse governing positions and corresponding normal and reverse extreme positions, indication means giving one indication with said track switch in a normal position and locked, giving another indication with said track switch in a reverse position and locked, and giving a third indication when said track switch is unlocked or when said track switch is being operated by said switch machine, an indication latch mechanism preventing operation of said control lever to an extreme position Q5 except after being actuated and preventing movement to a new governing position while actuated, conditioning means being actively conditioned when said indication means gives said third indiv1 cation, said conditioning means remaining active- "n30" 1y conditioned only for a predetermined time after said third indication ceases, means for momentarily actuating said'indication latch mechanism when said indication means gives said one or said other indication with said control lever in a corresponding governing position and with said conditioning means being actively conditioned, and means maintaining the actuation of said indication latch mechanism effective for allowing said control lever to be operated to a correspond- 1'19 ing extreme position.

14:. In an interlocking system for railroads, a track switch, a switch machine for operating said track switch, a control lever for governing said switch machine, said control lever being operable' ng to normal and reverse governing positions and corresponding normal and reverse extreme positions, an indication latch mechanism preventing operation of said control lever to a particular 6X1 treme position from a corresponding governing 'zo position except after being actuated and preventing operation of said control lever to a new governing position while actuated, indication means giving one indication with said track switch in a normal position and locked, giving another indi--i*25 cation with said track switch in a reverse position and locked, and giving a third indication when said track switch is being operated by said switch machine or any other time when said track switch is unlocked, a slow release relay energized when said indication means gives said third indication, said relay maintaining its energized position a predetermined period of time after energy is removed, and means including in part said slow release relay for momentarily actuating said indication latch mechanism when said indication means is caused to give either said one or said other indication by said track switch being operated to a corresponding position from an unlocked position if said control lever is in a corresponding governing position.

15. In an interlocking system for railroads, a track switch capable of being operated to either a normal or a reverse locked position, a switch machine for operating said track switch, a control lever for governing said switch machine whereby said track switch may be operated through a cycle of operation includng either operation from one extreme locked position to the other, or operation from one extreme locked position to an unlocked condition and return to its former locked position, said lever having normal and reverse governing positions and corresponding normal and reverse extreme positions, an indication latch mechanism preventing operation of said control lever to a particular extreme position from its corresponding governing position except after being actuated and preventing movement to a new governing position while actuated, indication means giving one indication with said track switch in a normal locked position, giving another indication with said track switch in a reverse locked position and giving a third indication with said track switch unlocked or in operation, and means rendered eifective for actuating said indication latch mechanism only if said indication means gives said one or said other indication and only provided said indication means has given said third indication in that cycle of operation and if said control lever is in a corresponding governing position.

16. In an interlocking system for railroads, a track switch, a switch machine for operating said track switch, a control lever governing the operation of said switch machine and operable from either of two governing positions to corresponding extreme positions, an indication latch mechanism preventing operation of said control lever from a particular governing position to a corresponding extreme position except when actuated and preventing operation of said control lever to a new governing position while actuated, a three position relay indicating the position and locked condition of said track switch, a stick relay, a pick-up circuit for said stick relay closed only when said three-position relay indicates said track switch as being unlocked, a stick circuit for said stick relay completed if said stick relay is once picked up with said control lever in a governing position, means opening said stick circuit whenever said lever is moved out of a governing position if said pick-up circuit is not closed, and means actuating said indication latch mechanism when said three-position relay indicates said track switch to be in a particular locked position in correspondence with the particular governing position of said control lever if said stick relay is picked up.

1'7. In an interlocking system for railroads, a remotely controlled function, means indicating in the tower the condition of said function, a control lever for governing said function, locking means preventing final movement of said control lever except when actuated, and slow acting means conditioned upon the indicating means changing from one indicating condition to another, for allowing actuation of the locking means only during a predetermined time after having been conditioned.

18. In an interlocking system for railroads, a remotely controlled function, means indicating in the tower the condition of said function, a control lever for governing said function, locking means preventing final movement of said control lever except when actuated, a slow release relay energized upon the indicating means moving to display a new indication, and a circuit for actuating the locking means which includes a front contact of the slow release relay.

19. In an interlocking system for railroads, a remotely controlled function, means indicating in the tower the condition of said function, a control lever for governing said function, locking means preventing final movement of said control lever except when actuated, a slow release relay energized upon the indicating means moving to display a new indication, and a circuit for actuating the locking means which includes a front contact of the slow release relay, and a contact of the indicating means in its new indication position.

CHARLES S. BUSHNELL.