US1566901A - Electric interlocking system - Google Patents

Description

2` Sheets-Sheet l P. E. CARTER ET AL Filed August 16, 1923 VENTORS I T EY ELECTRIC INTERLOCKING SYSTEM Dec. 22, 1925.

Dec. 22, 1925- 1,566,901 P. E. CARTER ET AL ELECTRIC INTERLOCKING SYSTEM Filed August 16, 1923 2 Sheets-Sheet 2 IN V EN TORS wm 9. mm E E mw Patented Dec. 22, 1925.

UNlTE 'STATES `aterrizar Ncette PAUL E. carefree, or BnenXvrr/nnnw Yoan, ann nor eonnnnr., or Wnsrrrnnn,

`NEW JnnsnY, Ass-tenons To GENERAL narnia/'AY SIGNAL COMPANY, or nocrrns- TER, new Yoan.

ELECTRIC INTERLOCKING SYSTEM.

ilipplcaticn led August 16, 1923. Serial No. 657,715.

`interlocking systems for railroads, and more `particularly to the automatic control ot switch operating mechanisms directly by an lassociated track circuit.

`For reasons .well recognized by `those lskilled in the art, it is essential in the interests ot' safety to organize a power operated interlocking system m lsuch away that the operator can not accidentally or carelessly Vthrow a switch under a train or directly in front ot' it. The present invention deals more particularly with this problem, especially from the standpoint ot obtaining the desired automatic. control through the agencyot a detector track circuit, rather than by the use oi" detector bars or the like. It may be explained that while thisproblem is ot' course'common to all types ot' power interlocking systems, the particular embodiment of the invention herein disclosed is more especially applicable to electric interlocking systems, the various 'features ot'this particular embodiment, however, being adaptable in an obvious manner to systems ot other types.

VGenerally stated, the principal objects or functions sought to be obtained by the present invention are the. prevention ol' operation ot a switch while a train is standing over or near a switch allowing the switch operating mechanism or-switch machine to complete a cycle'ot operation startedvprior to the entrance ot a train into the controlling detector track circuit, in spite of the tact that the Vtrain has entered this track circuit; and preventing the operator trom stopping an operation or" the switch machine or reversing the switch after the track circuit has become o-cfjupied.

.l1/lore specifically, the present invention contemplates, among other features, the provision et an. electric lock controlling the Usual lever et the interlocking system, conf `electric locking of a lever, irrespective trolling this lock from the trackcircuit, and providing in addition means for assuring ot' clearances demanded by practical require- .ments, in either ot its indication positions in which operating current is supplied to a switch machine. In other words, the invcntion contemplates the lever lock ell'ective in indicating positions and having associated therewith a means assuring that the lever shall be under the cont-rol ot' the electric lock whenever operatingcurrent can be supplied to the switch machine.

Various other characteristic features of the invention, its application to practical working conditions, and advantages will be pointed out hereinafter.

In the drawings, Figure l illustrates in a simplified and diagrammatic manner the principal operating parts and circuits of a well-known type of all-ele::tric interlocking systems, together with the organization of parts and circuits embodying the invention;

Fig. 2 is an enlarged fragmentary view ol the lever and the electric lock therefor showing more particularly the relative positions of the lock dog and the lever contacts;

Fig. 3 is a side elevation ot one specii'ic term ot indication selector preferably employed in accordance with this invention; and

Fig. 4 is a vertical transverse section `through the selector ot Fig. 3, said section beingl taken on the line iwi-it in Fig. 3 and `looking in the direction indicated by the arrows.

Referring lirst to Fig. 1, there is shown in a simplitied and conventional manner the organization of the system embodying the invention. There is a` stretch ot' track C withA a switch D leading from the track C to a siding, turnout or crossoveigitbeingunderstood that this track organization is merely a typical instance ot a track layout to which the invention is applicable. The points of the switci D are connected together in the usual manner, and are operated by a switch machine or power sw'itclrariddock morement. In the particular arrangement selected to explain the nature of this invention, this switch machine SM is presumed to be of the type disclosed, for example, in the patent to lV. K. Howe, No. 1,288,595 dater ':D'ecember 14:, 1918', although it should be understood that the invention is not essentially restricted to this particular type of switch machine.

The track rails 1 and 2 of the track S and switch lead-out D are divided by insulated joints 3 and bonded in any one of the approved ways to provide a detector track circuit, having a track battery or other source of energy 4 and a track relay T with the usual contact linger or armature 5. Since the detail construction of the switch machine SM is pointed out in the prior patent above mentioned, it will sufiice to consider only those parts directly involved in making a clear explanation of the present invention. These parts, shown enclosed within the dotted rectangle 7, comprise the operating motor, shown conventionally and having an armature 8 and a field 9; a circuit controller or pole-changer O for governing the operating and indication circuits; pole-changer coils E for at times electrically operating the'circuit controller O; and a circuit controller P for governing the circuits for these pole-changer coils. The specific structure. and preferred arrangement of these various parts is shown and described in detailkin said prior patent; and for the present purposes, the primary functions and elemental structure of these parts will be described.

rlhe operating circuit controller O comprises an insulated contact block 10, to which are fastened conducting bars or strips 11 and 12, arranged to bridge pairs of conta-ct springs 13, 14, 15 and 16 in the different extreme positions in said contact block. As shown'and described in said prior patent, the contact block 10 is operated from one extreme position, such as shown in Fig. 1, to the other opposite extreme position by the final locking movement of the locking plunger of the switch machine; or, in other words, the contact block 10 .is mechanically shifted from one extreme position to the 'other upon completion of the cycle of operation of the switch machine. In addition to the mechanical operation of the contact block 10, this block may be shifted to either of its extreme positions by energization of the corresponding pair of pole-changer coils E, provided the switch machine is at an intermediate point in its cycle of o-peration.

The circuit controller P comprises a similar block of insulating material 17, shiftable back and forth, which carries two conducting bars 18 and 19 adapted to bridge and electrically connect pairs of contact springs 2O and 21, respectively. The contact block 17 is mechanically operated from an extreme position, such as shown in Fig. 1, to a middle position wherein both pairs of contact springs 2() and 21 are bridged, upon the initial unlocking movement of the switch machine, and is tiien shifted to the other exttreme position, to bridge only one pair of said Contact springs, during the final locking movement.

The principal parts of the interlocking system, located at the tower and of interest in connection with this invention, are shown in the lefthand part of F ig. 1 wit-hin a dotted rectangle 22. There is a lever L, socalled, which is essentially a flat bar 23 slidable back and forth in any suitable way. The supporting frame for the bar 23 and the other similar bars making up the machine, comprises a lever guide 24 supporting the indication mechanism 25, which being of well-known construction, need not be described in detail. It may be explained that this indication mechanism essentially consists of a latch and dog which arrest movement of the lever, or rather the bar 23, in the indication positions thereof, until the indication magnet I is energized and its yarmature 26 raised to trip off or release said indication mechanism.

n lthe bar 23 of the lever L is a cam slot 27 which drives a roller on the upper hand of the tappet bar 28, this tappet bar being connected to the usual mechanical interlocking between the particular lever illustrated and others of the complete machine in the manner and for the purpose well recognized by those familiar with this art.` The bar 23 of the lever L is fastened to a handle 29 for facilitating reciprocation of said bar; and pivotally connected to this handle in the position illustrated is an angle shaped latch lever 30, the free end of which is notched m0 `and engages a fixed lug 31 so as to hold the lever against accidental displacement.

Fastened to the lever guide 24 above the bar 23` is an electric lock EL, with its latch contacts. This electric lock EL comprises a 105 main supporting frame or cast-ing 32, which is formed to receive a coil 33 and a core 3&1-, making up an iron-clad solenoid, commonly termed the lock magnet. Fastened to the lower end of the core 34 is a lock dog 35 (see 110 also Fig. 2). This lock dog 35 extends crosswise above the lever and is guided at its ends in the lever guide 241, so that while said dog may mov(J up and down, it can not be moved by the lever. Fixed by screws or otherwise 115 in a recess in the upper edge of the bar 23 is a stop 36, kformed with shoulders as shown to engage the lock dog 35 in the indication positions of the lever. Also fastened to the bar 23 above the stop 36 is a force-down cam 37, 120 which is shaped or cut away as shown and engages the upper edge of the lock dog 35 and forces it down to the locking position, as more fully explained hereinafter.

The latch contact associated with the lock 125 magnet 33 comprises an angle shaped contact finger 33 pivotally supported from an in sulated block and spring pressed to the pesitien shown in Fig. 1. The stationary in- .Snlated contact 3.9 is supportedF b@ ,0011- se tacted by thefinger 38 and close a break in the energizing 'circuit for the lock magnet 33, whenever contact 38 is rocked. The contact 38 is shifted by a. button 40 of insulating material when the latch is pressed to release thellever.

The lever L is used for making' and breaking certain circuits in their different positions. ln the conventional arrangement shown, a rod ll isconnected to the end of the bar 23 of the lever and carries or opel'- ates insulated Contact blocks 42, fl-3 and fill,

'moving these Contact blocks into and out of engagement with pairs of contact springs to 50, inclusive.

It may be` explained here that the lever L has four significant positions,two extreme positions and two intermedia-te positions.

Vinthe extreme positions, commonly known yas full normal and fullirererse, the roller on the tappet bar 28 is at. the extreme ends of the cam `slot 27 with said tappet bar in its uppermost 01" lowermost position and t-he conflicting levers locked or unlocked by tlre mechanical locking as the case may be.

In the two intermediate positions, commonly known as the normal and reverse indication `:position-s, the roller on the tappetv bar 28 is in the intermediate portion ofithe cam slot 27, and theindication mechanism is acting to prevent further movement of the lever to the corresponding extreme position until said indication mechanism is released. The pairs of contact springs 45 to itl are of such a length as to be engaged and electrically connected by the contact hlocks l2 and lil in the corresponding indication and extreme positions; whereas the pair-s of contact Asprings t9 and 50 are shorter and are not connected by the block etat until after the corresponding pairs of lingers and l: oi'

#alti and i8 have been electrically connected by their cooperating blocks and a3, the purpose of this particular arrangement being' more conveniently explained hereinafter in connection with the operation.

-The type of all-electric interlocking system includes7 1n addition to the lever L. in-

dication magnet l and velectric lock EL. a `sniffety magnet S, a. cross protection relay Cl) and indication selector IS. The safety magnet S and cross protection relay Cl are of the usual construction, perform their well-known functions. and need not be fin'- ther discussed. The indication selector lo.

however, is of a particular construction and performs a` function peculiar and sipjnii'icant to this invention. so that it requires further One specific forni of a suitable construction of the indication selector IS is shown in detail in Figs. 3 and 4.

B-eferriiigto Figs. 3 and 1, the indication vselector IS comprises a rectangular open tween these coils is an armature which is pivotally supported near its upper end by a shaft 5G, which is jonrnaled in upstanding ears or lugs 52 integral with the franiewoizc 52, `said shaft 5G being held in the armature by a small transverse pin 5T. At the lower end of the armature is a spgiiicT holding or o\'ei'center throwing' device, which, as shown, comprises a pair of plungers 58 slidingg' in holes in a rocking' member 59 pirotally supported on the base member of the frame 52. The plungers titl hare enlarged heads pii'otally si'ipportcd upon a pin (it) in the lower end of the armature 55; and compression spifinns (31 between the rocking member 59 and the heads of said plungers act to force and hold the armature 55 in its extreme positions. lt will be readily understood that this spring device keeps the armature 55 in its extreme positions. irrespective of the de-energization of the coils 53 and 5l, and also acts to force said ari'nature to one or the other extreme position as soon as it has been shifted slightly beyond its middle position.

rihe arinatnre 55 is arranged to open and close certain contacts as it is rocked back and forth. ln the construction shown, two contact lingers (i2 and (S53 are clamped to the bifurcated upper end of the armature 5.7 by a plate G-t and screws (55, these lingers (11% and (353 heilig' insulate-il from the armature and from cach other by interposed pieces of liber or insulating' material. To the lingers G2 and (SS are riveted side contact arms (it and o?, respecti\'cl i:. which rub against the edge ol" stationary springs (3io and (S). To thc .cnil of lhe'ilrainc 5:) are 'fastened terminal l'ilocks Tl) and 'Till of suitable insulating material, one of which. Tl), supi'iorts the springs (SF-lu (if) and binding posts for the connecting' wires; and fastened to bolli ol' these contact blocks 'TO and Fill are contact picccsl Tl. ai'- ranged to he engaged by the ends of the lini312 and (ifi when the arnialui'e ti is siifted to a corresponding' estreme position lt is explained here that cnc iiiiporlaul clniracteristic o'l the indication selcctiii' iti, particularlyv of interest with this inii'cntion. is that the coils 53 and 5t are wound relatively high resistance. such as ohiiis` so that with one of these coils connected in series with the operating' niotor of thc switch machine, there is not sullicicnt current lloiv for the motor to operate the switch machine. ln addition to the parts just d 'iibed. the apparatus at the tower includes a suitable relay R controlled by the track relay rl`. rlhe relay R is essentially a repcatiimi relay for the detector track circuit, and may he the indicating' or control relay commonly located in the tower in connection with ap preach locking'` controllingi the lights of track diagrams, etc. ln the conventional circuit arrangement shown, the relay R is ener- V(il) l 72 controls the energization of the coils 53 and 54 of the indication selector in a manner more conveniently explained hereinafter in th-e description of the operation; and the armature 7 3 and its front contact determines the' energization of the lock magnet 33, the

circuit therefor being readily traced onY the drawings as including said front contact of the relay 1t, a battery or suitable source 74 (which in practice is the main battery) and the latch contacts 38-39.

O parat/ion.

The operation of the specific embodiment of this invention illustrated will be taken up in steps for the different conditions encountered in practice. A discussion of the complete operation would involve description of the interlocking system itself and the operation of its parts, but this will not be here explained in detail, reference being made to the prior patent above mentioned for further discussion of detail features or operation of the switch machine and other parts of the interlocking system.

Normal operation-Detector trac/c circuit not occipital-Assuming that the parts and circuits of the system are in the normal condition shown in Fig. 1, and suppose that the operator desires to throw the switch D to the other eXtreme or reverse position, and that the track circuit is not occupied. The operator presses the latch releasing lever 30, thereby closing the latch contacts 38-39, whereupon the lock magnet 33 is energized, since the detector track circuit is assumed to be unoccupied and the relay R is energized.

The energization of the lock magnet 33 raises the lock dog out of engagement with the shoulders of stop 36, so that the lever is free to be moved to the opposite intermediate or reverse indication position, further movement of the lever beyond this indication position being prevented by the indication mechanism. l 1n this reverse indication position, assuming that the operator moves the lever (pulls it out to the left as shown) as far as the indication mechanism will permit, all three pairs of contact springs 45, 47 and 49 are bridged by their respective blocks 42, 43 and 44. There is then established a circuit through the coil 54 of the indication selector as follows commencing at the main battery B, wire 75, safety magnet S, wires 76 and 77, finger 72 and front .contact of relay lia ,wires 78 -and 79, coil .54

Location.

of the indication selector IS, wire 80, springs 49 and block 44, wire 81, springs 47 and block 43, wires 82 and 83, springs 14 and contact strip 12, wire 84, armature 8 of the motor, wire 85, springs 13 and strip 11, wires 86 and 87, field 9 of the motor, wire 88 through the contacts 89 of the cross protection relay CR, and wire 90 back to the battery B.

On account of the resistance of the coil 54 of the indication selector IS which is included in this circuit, the current flowing through the armature 8 and field 9 of the switch machine motor is not sufficient to cause operation of the switch machine; but this current, however, causes the armature of the indication selector to be attracted and shifted to the other extreme position, rocking the Contact lingers 62 and 63 from the position shown in Fig. 1 to the opposite position indicated by dotted lines, thereby establishing a shunt around the coil 54 as follows commencing at wire 76, wire 91, finger 63, wire 92 to the springs 47. The current now iiowing through the operating motor ot' the switch machine is at the full strength and causes the switch machine to operate in the regular manner, unlocking switch points, throwing them to the reverse position, and locking them up again. At the completion of this cycle of unlocking, shifting, and locking, the contact block 10 of the operating circuit controller Ol is shifted from the position shown in Fig. 1 to the opposite extreme position, breaking at the springs 13 and 14 the operating circuit heretofore traced, and establishing through the pairs of springs 15 and 16 the reverse indication circuit, which includes the armature 8 and the field 9 of the mot-or, with their connections reversed, the indication magnet I and the contact finger 62 of the indication selector. This reverse indication circuit is conveniently traced starting at the armature S asl follows commencing at the upper brush of the armature 8, wire 93, springs 15 and strip 11, wire 87, iield 9, wire 88, contacts 89 of the cross protection relay, wire 94, winding of the cross protection relay GP, wire 95, indication magnet I, wire 96, finger 62 of the indication selector IS (now shifted -to the dotted line position), wire 97, springs occupati-ln the foregoing description of the operation, it was assumed that the relay R is energized, this being the condition existing when there is no train upon the track circuit. Jassume, however, that there is a train or car standing on some part of thedetectortrack circuit at the time the operator attempts to snift the. lever L. Under these conditions,

it isevidcnt that itA should not be possible to apply power to the switch machine and Aeither unlock' or. move the switch points.

According'- tothe particular arrangement illustrated, the application of power to the switch machine is prevented for two reasons. ln the first place, since the detector track circuit is occupied. and the relay R deener.- gizechthe lock magnet Bican not be energized and the operator can not move the leverv beyond the normal indication position. ln the second place, even thoughtlie lever could'be placed in the reverse indica-` tion position, the circuit for energizing the coil 5a; of the indication. selector would be.

interrupted at the finger 72v ofl the-relay R,

cycle of operation, a train enters the detector track circuit. After some considerationl it will be readily appreciated that, from the i standpoint of safety, it would be preferable to allow the switch machine to complete the cycle of operation it had started rather than stop such operation and leave the switch points partly open or unlocked, in spite of the fact that ordinarily aV train on the detector track circuit should prevent operation of the switch. This requisite is taken care of in the presentv invention by reason ofthe fact that, after the indication selector IS has once responded, the operating circuit is set up and remains intact until broken at the switch machine, even though the relay R may be deenergized. Consequently, after the lever has been shifted, the indication selector has responded, and the cycle of operationof the switch machine has started, then the entrance of a traininto the track circuitfi's not effectual to arrest orprevent operation of the. switch.

ln addition to allowing the switch inachine to complete the cycle of operation once started prior to the entrance of a train into the dotectorptrach circuit, it isalsodesirablc and importantlo preventvthc operator from accidently or carelessly himself stopping tliisoperal'ion and leave the switch partly openedor unlocked,- more particularly prevent the operator from reversing or attempting to reverse the switch.` Putting it another way, if itA should happen that a traint gets into thc detector track circuit while, the switch machine is operating, it is important, not only to allow the switch machine to complete the existing-cycle of opera tion, but also prevent the operator from stoppingV that cycle and: particularly from reversing switch points. The reason for this maybe best appreciated by imagining` a train approaching and about to pass over the switch, and visualizing' the operator at.V the distant tower, frequently out of view of the train entirely, shifting the lever back, perhaps because he hasijust realized that no attempt should have been made to throw the switch;` or, as has actually happened, thc operator` in ignorance of the presence of the train or perhaps excited shifts the level' first one way and thenthe other, and splitsf7 the train, part goingone way and part the other.

According to the present invention, it is not possible for the operator to stop a cycle of operationonce started, after the `detector track4 circuit has become occupied, nor is it possible for him to reverse the switch. Since the detector track circuit is occupied, the relay R` is decnergized, andl the lock magnet 33 is deenergized. rlhis holds the lever in the corresponding indication position. The operator can notpull the lever back from` that indication position far enough to cut ott1V operating current, for the reasons about to be explained, much less shift` the lever tothe other indication or operating position and cause reversal of the switch. The safeguard against reversal is also obtained by` virtue of t-he control of the indication selector by the relay R, since this indication selector can not be changed and current applied to reverse the switch, while thc track circuit is occupied.

The particular feature of this invention of prominent` importance, resides in the particular provisions made to assure locking of the lever in the indication position. Herctofore it` has been` attempted to provide a lever lock which will hold the lever in the indication positions as well as in the usual full normal or full reverse positions.. Spealc ing of the indication position as the point CII where electrical connection is first made to set up the operating circuits, that is, the pointwhere theK contact blocks 42 and 43 first engage the contact springs 45 and 47, forexample, it has been found impractical, on account of the problems of mechanical clearance, to provide an electric lock which will be effective inthe indication positions of the lever. In the irst place, it will be readily recognized that there must be some clearance between the edge of the lock dog 35 and the shoulder of the stop 36 with which it engages (see Fig. 2). Likewise, for mechanical reasons, there is necessarily some slight variation in the precise point in the movement of the lever where the contact blocks first touch their contact springs. Now, if the locking shoulder of the stop 36 and the edge of the lock dog 35 are selected so that, before engagement of the contact blocks with their springs, the lever must be moved far enough to give suihcient mechanical clearance to allow the dog 35 to drop behind the shoulder on the 'u stop 36, then the operator would be able to defeat the purposes of the invention and cut off current from the switch machine in spite of the lever lock by forcing the lever as far as the dog 35 would permit, whereupon the contacts would be broken and the circuit interrupted, because the parts have been purposely proportioned to leave clearance between said dog and its locking shoulder before the contacts were closed. On the other hand, if it is attempted tomake the parts accurately, such that the dog 35 will drop behind the shoulder on the stop 36 atthe same point in the movement of the lever where the contact blocks engage their pairs of springs, then on account of mechanical clearances required and slight variations oc curring in practical operation, the operator would be able to defeat the purpose desired by moving the lever up to the point where contact is made but the lock dog 35 has not cleared the shoulder and is not able to drop.

This problem of clearance, nicety of adjustment and variations of wear and usage have all been obviated by the adoption of the expedients characterizing this invention. Before it is possible to supply effective oper ating current to the switch machine, the indication selector IS must respond; and before this can happen, the contact block 44 must be in engagement with the short springs 49 or 50. If the lever has been moved far enough, say to the position illust-rated in Fig. 2, for the contact block 44 to just touch the short springs 49, then the blocks 42 and 43 will have been wiped a considerable distance over the pairs of springs 45 and 47. Considerable clearance, therefore, may be provided between the lock dog 35 and its shoulder, as indicated in Fig. 2, with assurance that, if the operator shifts the lever back as far as the lock dog will permit, the electrical connection through the lingers 45 and 47 will still be maintained. The latitude in the clearances afforded by the adoption of the short springs 49 and 50 and their interconnection with the indication selector IS also facilitates the application of the force-down principle, and makes it possible to provide a force-down guide cam 47 which will perform the proper function.

In view of the special provisions for assuring the engagement of the electrical lock in the indication position of the lever, the system of this invention positively prevents the operator from cutting oif current to the switch machine and arresting its cycle of operation while a track circuit is occupied, because the electric lock holds the lever at the existing end of its movement-so long as the track circuit is occupied.

Simultaneous movement of the Zever and cat/rance of miur-The control of the indication selector IS by the track circuit through the agency of the relay R and its front contacts 72 is particularly effective for the rather rare condition where the train enters the track circuit substantially simultaneously with the movement of the lever. Imagine that the operator, with the lever in the normal position shown, releases the electric lock and starts to move the lever to the reverse indication position, and assume that just after the lock has been released and such movement of the lever is started, the track circuit becomes occupied. Under this particular set of conditions, it may be considered desirable to prevent operation of the switch machine and leave the switch undisturbed in its existing position. So far as the electric lock EL is concerned, however, an operation of the switch machine will occur under the particular conditions recited, inasmuch as the lock has been released before the track circuit becomes occupied. The indication se-lector IS and its control by the track circuit, however, takes care of this particular contingency and prevents the application of defective operating current to the switch machine, since the relay R will be deenergized and its front contacts'7 2 open at the time the lever reaches its reverse indication position.

Another rare contingency exhibits advantages and the protection afforded by the indication sclector and its control by the track circuit, as compared with the protection afforded by the electric lock alone. To illustrate, it may happen for some peculiar reason that the operator has the lever in an intermediate or middle position between the indication points at the particular instant the train enters the track circuit. Although the electric lock EL is of course deenergized on account of the occupancy of the tract',

erator couldfinove the lever from the inten mediate position assumed to the indication position opposite to the existing position ot the switch, apply power to the switch machine and` shiftl the switch in spite o't the presence oil the train. The track circuit control ot the indication selector IS, however, prevents operation of the switch machine under these peculiar conditions, since with the relay R deenergized and its iront contact72 open, no current can be supplied to the switch machine.

Preferred arrmtgen'zent-hhile, for rcasons'above exnlained, it is desirable to provide track circuit control of the indication selector, in addition tofand supplementary to the track circuit controlled lever lock, the conditions under which such track circuit control of.` the indication selector is capable of aii'crding protection not provided with the lever lockalone are rather rare and en'n ceptional, so that for ordinary operating conditions it is frequently found sutiicient to provide the lever lockfEL and its associated control parts, omitting the control of theV indication selector IS bythe relay It. With this arrangement, which may be said to berthe preferred form of the invention on account of its simplicity, the r'ront contact 72 of the relay Ris omitted together with wiring connections??- and 7 8, and two coils 53 and 54 of the indication selector are directly connected on one side to the battery B, as for example, by connecting);` the wire "91 to the point Where wires T8 and'79 join. l/Vith this adaptation of the invention, the track circuit :has no direct control over the supply of power to the switch machine and servesmerelyV to determine the encrgization ofthe electric lock EL. The indication selector IS, its shunting contacts 63, and t ie short contact` springs 49 and 50 are employed in connection with the lever lock, for reasons hereinbe'tore explained, so as to assure locking` of thel lever in its indication positions, with due allowance for mechanical clearances and performinglocking in such a fashion as to prevent opening of the regular lever contacts by manipulation of the lever within the limits of movement allowed by the clearance of the electric lock.

It. may be said that the princinal characteristicvfeature of this invention resides in the organi/Zingof the high resistance indication selector, its shunting contacts, and the short Contact springs 49 and t), in conjunction with a leveijlock of the torce-down solenoid type shown. Putting it another way, the regular contact springs 45 48 may be considered as made somewhat longer than ordinarily so as to be engaged by their contact blocks 42 and43 for some distance at the indication positions of the lever, this distance being' greater than thatl through which the lever may be shifted on account ot the mechanical clearances ot the lever lock. In this connection, it is oi? course to be understood that the indication mechanism 25 arrestingl movement ot the levcr in the indication position does not stop movement ot the lover until the contact springs 45) or 5i) are bridged by the contact block 44. In other words, il the operator pulls a lcvcr as tar as the indication mck'hanism permits, then the contact springs 4) or of), as the case may be, are coniiected b v their contact block 44, and likewise the pairs ot' contact sprii 1: 4i`3t or i6-4h are cminectcd by their contact. blocksfi and 43 a considerable distance ot' wipe sutlicientto assure maintenance ot the operating circuit even thougl'i the lever is backed ott as tar as the electric lock will permit.

In the foregoing' discussion ot thc operation, particularly where certain conditions have been assumed, complication has been avoided by omitting explanation of the eltect ot signal indication, route locking ar' rangements, time element or push button releases, and various other auxiliary devices` commonly used in accordance with modern practice in connection with power interlockingi systems; and it should be understood that these auxiliary devices or features o't the complete system, ior reasons well recoin nized by those skilled in the art, may modity or make exceptionally diticult the particular combinations ot conditions or eontin gencies discussed. For example, a power interlocking system ot n modern type, through the agency of signal indications, some-times automatic train control or stops, route interlocking, and other auxiliary arrangements ot devices, makes it necessary for certain peculiar con'ibinations ot circumstances to occur betere a train may cuter a track circuit. while the switch machine is operated. Likewise, the skill and care et the operator ordinarily used has been disregard ed to a large extent in the 'foregoing discussion of the operation ano advantages ot this invention.

lVhile one specitic and particular construction and organization ot devices and circuits, and one specially designed and adapted for use in connection with a certain type ot' all-electric interlocking` svstcm has been selected and explained to give a disclosure ot this invention, it will be cvident to those skilled in the art that various and obvious moditications and adaptations ot this specific disclosure may be made in practice without altering the nature and essential characteristics ot the invention: and vfe desire to have it understood that this specitic system disclosed is merely illustrative of the invention, and that various other forms and means may be provided to constitute the invention.

That we claim is z- 1. In an electric interlocking system, the combination with a track switch, a detector track circuit, a switch machine for operating the switch, a lever for controlling the operation of the switch machine 'from a distant point, an electric lock tor the lever controlled by said track circuit and operable to prevent movement thereof beyond an indication position toward the other extreme position, the co-acting parts of said lock having a mechanical clearance permitting slight movement ot the lever at the indication position, means adaptable to prevent operation of the switch machine, and means for rendering said preventing means ineffective for each position of the lever only after the lever has been moved tar enough to allow enga-gement of the coacting parts ot the lever lock.

2. In an electric interlocking system, the ycombination with a track switch, a detector track circuit, a switch machine for operating the switch, a lever for controlling the operation of the switch machine from a distant point, an electric lock for the lever controlled by said track circuit and comprising, a lock dog and a stop secured to the lever and provided with shoulders engageable by said l-ock dog, and automatic means preventing operation of the switch machine by movement of the lever to an indication position until the lever has been moved some distance beyond the point where said lock dog may pass back of a shoulder on said stop.

3. In an electric interlocking system, the combination with a track switch, a detector track circuit, a switch machine for operating the switch, a lever for controlling' the operation of the switch machine from a dis- ,tant point, 'an electric lock controlled by 'said track circuit for holding said lever in its indication positions, contacts operated by the lever for controlling the switch machine and closed for some distance of movement of the lever at the indication positions, and automatic means preventing operation of the switch machine until said contacts have been closed for a range of movement otl the lever greater than permitted by the electric lock.

4. In an electric interlocking system of the type described, a lever, an electric lock for holding said lever in its indication positions, contacts operated by the lever and closed tor some distance of movement thereot at their indication positions, other contacts operated by the lever and closed only after the first mentioned contacts have been closed for said distance of movement, and means controlled by said other contacts tor governing the supply of current through the irst mentioned contacts.

5. An electric interlocking system of the type described, a switch machine, control circuit for said switch machine, a lever and contacts operated thereby for governing said contro'l circuits, an electric lock for holdingv said lever in its indication position but per-.

mitting slight movement thereof due to Inechanical clearances between the cooperating parts ot" said lock, said contacts governing said control circuits being closed throughout said range of movement ot' the lever at its indication positions, and automatic means preventing operation ot' the switch machine until the lever has been moved substantially through said range ot' movement at an indication position, whereby the switch machine can not be operated until the lever has been moved far enough to assure engagement of the electric lock and closure of its controlling contacts in spite ot' the lost motion attorded the mechanical clearances of the co-l operating parts of the electric lock.

6. In an electric locking arrangement for levers ot' the power interlocking systems, the combination with a lever, of an electric lock holding said lever in its indication positions but permitting slight movement thereof, operating contacts connected to the lever and closed throughout said range of movement, and other contacts closed only after said lever has been moved to the extreme ot' said range of movement.

7. In an electric interlocking system, the combination with a lever and an electric lock therefor eliective at the indication positions or' the lever, said electric l-ock on account v of mechanical clearances affording some lost motion of the lever, of long and short contact springs, and contact blocks connected to said lever and engaging said contact springs.

8. In an electric interlocking system, the combination with a switch machine and a lever for controlling the operation thereof, ot an electric lock for said lever effective in the indication positions of the lever and permitting slight movement of the lever at said indication positions, and automatic means for preventing the supply of effective operating current to the switch machine until said lever shall have been moved toward its extreme position throughout the range ot movement aliorded by said electric lock, whereby operation of the switch machine is prevented until the lever has been moved far enough to assure locking thereof by said electric lock.

9. In an interlocking system of the type described, a switch, a switch machine for operating the switch, a detector track circuit associated with said switch, a lever at a distant point for controlling the operation of the switch machine, an indication selector associated with the lever and having high resistance coils alternately included in the operating circuits for the switch machine, said coils limiting the flow of current to an amount insufiicient to permit operation of the switch by said switch machine, an electric lock for the lever controlled by said track circuit and operable near an extreme position thereof to prevent movement to the other extreme position, and means for establishing' a shunt, of low resistance for the coils of said indication selector only after said lever has been moved to its eX- treme position beyond the point where said electric lock prevents return of the lever to the other extreme position.

10. In an electric interlocking system, the combination with a lever, a track circuit controlled electric lock therefor, said lock being effective in the indication positions of said lever, an indication selector having high resistance coils, contacts operated by said selector for establishing a shunt of low resistance around t-he corresponding coil, and contacts operated by the lever for establishing a circuit through said coils of the indication selector alternately, said contacts being closed only after the lever has been moved beyond the point where said electric lock is effective.

11. An electric interlocking system of the type described comprising, a switch, a switch machine operating the switch, a detector track circuit associated with said switch, a lever controlling the operation of the switch machine, an electric lock for the lever effective in the indication positions, an indication selector having high resistance coils, and means for establishing a shunt of low resistance around each coil of the indication selector in turn as. the lever is lmoved to its indication positions, said means being eective only after the lever has been moved beyond the point where said electric lock is effective and provided said track circuit is lnot then occupied.

12. In an electric interlocking system of the type described, a movable lever, indication mechanism for said lever limiting the movement thereof to its extreme positions at a predetermined indication point, an electric lock operable to lock said lever near said indication point but permitting slight movement of the lever from said indication point toward the other extreme position, contacts operated by the lever and closed throughout the range of movement thereof between said indication point and the point where said lock prevents movement of the lever, and other contacts operated by the lever and closed only after said lever has been moved fully to said indication point.

13. In an electric interlocking system of the type described, the organization of parts operating substantially as described and comprising, al lever, an electric lock therefor effective in the indication positions, an indication selector having high resistance coils, and pairs oit' long and short contact springs, said long spring including the control circuits governed by the lever, and the short springs the energizing circuits for said coils of the indication selector.

14. In an electric interlocking system, the combination with a movable control lever, of an electric lock effective to limit movement of said lever in one direction in a predetermined position of the lever, a poweroperated device controlled by the movement of said lever, and means requiring movement of the lever to a point where said electric loc-k will become effective irrespective of mechanical clearances between its cooperating parts. before said device will bel controlled by the lever.

15. In an electric interlocking system, the combination with a movable lever, contacts closed by movement of said lever to a predetermined position, a power-operated device and a control circuit therefor including closure of said contacts unless the lever is moved far enough to force the lock dog into position to engage said shoulder.

16. In an electric interlocking system, the combination with a movable lever, contacts closed during a limited range of movement of said lever near one extreme position, locking means effective to hold mechanically said lever against movement from said position far enough to open said contacts, a power-operated device having a control circuit governed by said contacts. and automatic means preventing operation of said device irrespective of the closure of said contacts unless the lever is moved far enough to permit said locking means to be effective.

In testimony whereof we hereby affix our signatures.

PAUL E. CRTER. ROY CONNELL.

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