Патент USA US2135499код для вставки
Nov. 8, 1938. o. s. FIELD 2,135,499 RAILWAY TRACK CIRCUIT Filed June 21, 1935 ATTORNEY 2,135,499 Patented Nov. 8, 1938 ‘ STATES PATENT. OFFICE RAILWAY TRACK CIRCUIT Oscar S. Field, Rochester; N'. Y., assignor to General Railway Signal Company, Rochester, NY. A Application June 21, 1935," Serial No. 27,737 13 Claims. (Cl. 246-41) ‘ This invention relates in general to railway signallingtrack circuits, and more particularly to. improvements. intrack circuit voltage regulat ingmeansg eti ‘ , j A normally energized track circuit includes a track relay energized su?iciently when the asso ciated track section is unoccupied to attract its varmature by current flowing from a track bat “ terythrough the track rails in series, but when a train" shuntj is applied to the track rails, the increase .in'current at the battery end of the circuit flowing through the included resistance must reduce the voltage at the relay end suffi ‘ciently torelease thetra‘ck relay armature. The ballast between the rails of the track section however varies considerably in resistance accord ing ‘to weather conditions, thereby forming an interrail'shuntwhich may vary the interrail volt age sufficiently to at times prevent proper track circuit, operation. In other words, when the track circuit current is adjusted to provide proper operation under any one condition of the track ballast,‘ a'decrease in ballast resistance may de crease the interrail voltage sufficiently to prevent 25 the attraction of the track relay, armature upon the removal of a train ‘shunt, or an increase in ballast resistance may increase the interrail volt age su?icientlyto producea dangerous condition 30 by preventing the release of the‘armature when the train shuntis applied. a‘ 7 It then becomes desirable to employ a means for maintaining ‘a constant interrail voltage when thetrack section is unoccupied regardless of f ballast resistance , changes, but to allow changes in interrail voltage caused by the appli cation or removal of a train shunt. In my prior applicationnse'r. No.’ 25,472 ?led June '7, 1935, I have provided such a regulating me'anscompris ing a motor means for actuating a variable re sistorin ‘series with the track battery, which motor means is controlled by a relay connected across the track rails, the control relay being . more sensitive than the track relay thereby re sponding to interrail voltage changes which occur 45 in increments or decrements too small to op erate' the track relay, and being caused by changes in ballast resistance which occur slowly, these increments or decrements are compensated for before they can cumulatively amount to a change suiiiciently to cause operation of the track relay. The application of a train shunt in this arrangement causes a reduction in interrail volt age which abruptly amounts to a much greater change than is permitted to occur in response 55 to ballast resistance changes, and consequently the motor driven‘ variable resistor does not start to compensate for this abrupt decrease in volt age before the armature of the control relay has been operatedrb‘eyond its position taken in re sponse to decrements in ballast resistance, and the armature of the control relay in this ex treme position is ‘arranged to prevent operation of the _motor driven variable resistor while a train shunt exists across the track rails. The increased reliability of detecting a train 10' shunt provided by, the above regulating means however is dependent upon the proper operation of certain apparatus employed. In other words, theoperation of the motor driven variable re sistor to prevent an increase in ballast resist ance, from increasing the interrail voltage to a value preventing reliable release of the track relay armature ‘is dependent upon the proper response of thelcontrol relay to this increased voltage, which response may be prevented by an open Winding, loose connection or the like. Likewise, the, compensation for an increase in interrail voltage caused by an increase in ballast resistance even when properly detected by the control relay is dependent on the proper opera tion of the motordriven variable resistor which operation may be prevented by a failure of the motor windings, mechanical driving means or the like. Consequently, it will be clear that when a track circuit regulating means is relied upon to provide proper track circuit operation by auto matically changing the characteristics of a track circuit in response to ballast resistance changes, a failure of the apparatus employed in this regu lating means may under certain conditions result 35 in an unsafe condition. This application is an improvement upon the invention disclosed in my prior application Ser. No. 25,472 ?led June 7,1935, and no claim is made in this application to subject matter shown and claimed in said prior application. ' In view of the ‘above and other considerations, , it is proposed in accordance with the present invention 'to' provide‘ an improved means for maintaining a constant voltage between the rails of a track section when unoccupied by a train regardless of changes in interrail ballast resist ance, and for allowing changes in interrail volt age caused by the application or removal of a train shunt. It is further proposed to provide 50 means in such a track-circuit voltage regulat ing means operating in response to the failure of any of the apparatusemployed to effect regu lation to provide and to retain a condition in the track circuit which results in restricted but 55 2 2,135,499 safe train operation until the cause of such fail ure has been corrected. Other objects, purposes and characteristic fea tures of the present invention will be apparent as the description thereof progresses, during which reference will be made to the single ?gure 16 is provided on one leg of the, magnetic core of relay C which is connected in series with a winding [1 on one leg of the magnetic core of re lay K, and windings l6 and I‘! thus arranged in series are connected across the track rails l as shown. A second winding I8 is provided around of drawing which shows in a diagrammatic and the other leg of the core of relay C and con conventional manner the present invention ap nected in series with a second winding l3 wound around'the other leg of thecore of relay K, and . plied to a typical form of a railway track circuit. In the accompanying drawing, a section of track rails I is shown as electrically insulated likewise windings l8 and I!) are connected across the track rails I. The windings I 6 and I8 are from the adjacent track by insulating joints 12/ "s01 arranged on the core of relay C that‘ the in-, to form a conventional insulated track’ section.~ A terrail potential causes current to ?ow there center-tapped track battery B is connected'acros's 15 the right hand end of this track section, that is, the extreme (+) terminal of battery B is con nected through a variable resistor R to the right through which produces cumulative ?ux values which normally provide an upward tractive 15' force on a pivoted armature 20 associated there with, but the windings Hand [9 on relay K are hand end of the lower track rail (I, while the so arranged that vthis same current normally pro~ extreme (—) terminal is connected through a‘ duces opposing ?ux values in the core thus pro 20 manually variable resistor 3, such as usually ducing substantially no tractive force on a simi employed in track circuits, to. the right hand end lar, pivoted armature 22 associatedtherewith, of the upper rail 1. A primary+secondary track relay combination such asshown in my. prior ap A lower compression spring 24 isj'arranged to exert'an upward biasing force on armature 20 plication Ser. No.‘ 711,397, ‘filed Feb. ,15, 1934, which is adjusted by a screw 25 to substantially 25 is shown associated with the left hand end I of oppose the normal gravitational bias on arma-‘ this track section, this arrangement being illus trated as a means forprovidlng improved track circuit operation although it" is =under'stoodthat a single track relay .mayof course'be employed 30 in the usual manner." ‘ r ' In this primary-secondary relay combination, the magnetomotive" force required to attract the armature of a primary track relay PTfrom its re leased position issupplied by the normal track 35 circuit current ?owing through all of its wind ings, but after thearmature of relay PT has been 25 ture 20, and an upper spring 26 is also provided to exert a downward biasing force on armature 20 which is adjustable by a screw 21‘ toequally oppose a predetermined upward magnetic at traction of the armature 20. The track circuit 30 is adjusted by positioning the manually variable’ ‘ resistor 3 so that an interrail voltage exists when the track section is unoccupied which is found to provide reliable track circuit operation, and this interrail voltage provides a de?nite upward 35 attracted, a secondary relay'ST (which ‘controls attraction of the armature 20 of the control re lay C, which upward attraction obviously has a , signal circuits and the like by contacts such as l) is picked up through a front contact 4, there energization of the track relay combination at 40 by substituting a substantially equivalent re sistor 5 for a portion of the winding of relay PT by a make-before-break contact 6, thus reducing the magnetomotive force'o'ifrelayv PT to a value just su?icient to reliably retain its armature in 45 an' attracted position. '.In this manner,v a track relay combination may be arranged to drop away at nearly the same interrailvolta'ge that is suf ?cient to cause its picking up, and consequently it will be clear that when the interrail voltage 50 of the track section is maintained at a'valueper mitting proper picking up of the combination, a rather slight reduction in interrailvoltage can cause its release in response to a, train shunt. A means for operating the variable resistor R 55 at the right hand end of the track, section has herein been illustrated as a conventional perma nent magnet direct current motor including an armature A‘ and a'permanent magnet III, or of course any other suitable motor means could be 60 employed, such, as a series or shunt ?eld direct current motor, the permanent magnet ?eld- being considered preferably inview- of saving, the en ergy required to magnetize an ‘electro-magnetic ?eld. The armature A of , this'motor' is illus substantially constant relation to the degree of the other end of the track section. ‘ The downward biasing force of, spring 26 is then adjusted by screw 21 so that the upward magnetic attraction of armature 20 produced by this ‘normal interrail voltage is balanced by the biasing. force of spring 26 so that amovable con 45 tact 28 attached to the armature 20 by an insu lating block 29 is positioned midway between a pivoted front contact 30 and a pivoted back con tact..3l. The pivoted contactsv 30 and 3| are each biased inwardly ‘by compression springs 32 and 50 33 respectively to contact with inner ?xed con tacts 34 and 35 respectively, this contacting force being adjustable by screws 36 for varyingthe biasing‘ force of springs 32 and 33. A movable contact ?nger 39 is attached to the armature 22 55 of relay K by insulating connectingy'meansllo, and the armature 22, being normally released as previoulydescribed, engages the movable con tactj39 with a back ?xed contact 4|. ' In describing .the op'erationof the present in vention, it will ?rst be considered that the resist ance of the ballast between therails l increases s'othat the interrail leakage current decreases. This decreases the current ?owing through resist 65 trated as connected through a suitable reduction gearing means comprising a worm. gear H at ances>3 and R and slightly reduces the voltage tached to the shaft of armature A and driving terrail voltage of: the track circuit and likewise the energization of windings l6 and I8 of relay a sector gear l2 attached to theshaft of an arm I43 arranged to contact in a suitable manner with 70 various portions of the resistance-wire R. A means for controlling the energization and the direction of current'in the armature A is 40 drop therethrough which obviously raises the in C. ' The relay C is adjusted to respond to a much smaller change in interrail voltage than can pos sibly causeoperation of the primary-secondary track relay combination; and consequently this provided by a control relay C, and a check relay gradual decrease in interrail leakage current soon K is also provided to check the continuity of causes a su?icient increase in interrail voltage to 75 the windings of the control‘relay C. A winding upset the rather delicate balance on the armature 65 2,135,499 20' and operate ‘the movable contact 28'into en gagement with the’ pivoted front contact 30. The biasing, forcei on‘the pivoted ‘contact 30 exerted by spring? 32 however is adjusted so that the en gagement of the movable contact 28 therewith caused by this slight increase in interrail voltage - does not havesu?icient force to disengage front contact‘30 from the fixed? contact 34. ‘ A circuit is now completed for applying one polarityfof energization to the armature A which maybe (traced from the‘ (+) or extreme right hand terminal of battery B, through the pivoted front contact 30 engaged by the movable contact 28',‘ and upwardly through armature A to the cen 15 ter terminal of battery B. This upward direction of current through armature A is in a‘ proper direction to cause rotation of the resistor arm I4 in a clockwise direction which shunts out a small er portion of the resistance wire R through a cir 20 cuit including the movable contact 39 of relay K engaging the ?xed back contact 4| and the ?xed restore thenormally adjusted interrail voltage, thereby restoring the balance of the forces acting on armature 20 of-the control relay C and again positioning the movable contact 28 midway be tween the front and back contacts 30 and 3|. This operation of the control relay C and the motor driven variable resistor also continues in~ termittently as long as the ballast resistance con tinues to decrease, thereby maintaining the inter rail voltage substantially constant except for the small changes necessary to cause release of the armature 20 of the control relay,vwhich as de scribed is much smaller than can possibly cause the release of the track relay means. It is of course understood that a regulating 15 means of the present type should not operate when a 'train is occupying the associated track section, as such operation might compensate for the reduction in interrail voltage effected by the train shunt and prevent the release of the track relay, thereby defeating the purpose of the track back‘ contact 34 engaged by the pivoted front circuit. In thepresent arrangement, the entrance contact 30' of relay C. In this manner, the resist ance in series with the track battery to the track rails is increased by one direction of operation of the armature A, which continues until the inter rail voltage has been reduced to its normally ad of a train into the associated track section shunts the track rails I to cause an abnormal increase in justed value, thereby restoring the energization of the control relay C to a value which balances the 30 forces on armature 20 and positions the movable contact 278 midway between ‘the front and back contacts 30 and'3l. 35 3 ' ' ~ "The above operation of the control relay C and the motor driven variable resistor obviously con tinues in an intermittent manner as long as the ballast resistance continues? to increase, ‘thereby maintaining a substantially constant interrail voltage,-the only change in the interrail voltage beingthat which 'is required to cause an unbal 40 ance of theiforces on armature 20, which as pre viously described is'much smaller than the change required‘ to cause operation of the track relay means; ‘ - Now considering that the resistance of the com 45 paratively dry ballast decreases, it will be clear that an increased ballast leakage current occurs which ?ows'through the increased resistance in serted into the track circuit by the variable resis~ tor R. 3A slight reduction in the interrail poten 50 tial thenv occurs which reduces the energization of windings I6 and I8 of relay C to again upset the rather delicate balance of forces acting on arma ture 29 and in this case cause the movable con tact 28 to engage the pivoted back contact 3|. Likewise, the movable contact 28 does not engage ‘the pivoted back contact 3I with sufficient force to overcome the biasing. force of spring 33 so that the pivoted back contact 3| is not disengaged from the ?xed contact 35. This completes a cir cuit for applying a different polarity of energiza tion to armature A which may be traced from the center tap of battery B, downwardly through ar mature .A, through movable contact 28 of relay C engaging the pivoted back contact 3|, and 65 through ?xed contact 35 to the (—) or extreme left hand terminal of battery B. y‘ In this‘ case, current flows downwardly through‘ armature'A thereby causing a reverse direction of rotation which moves" the variable resistor arm I 4 in a counter-clockwise direction to shunt out a greater portion of the resistance wire R. This ‘rotation of the armature A continues until the variable ‘resistor arm I4 is moved in a counter clockwise direction to‘a position which decreases 75 the resistance of the track circuit su??ciently to the current ?owing through resistances R and 3, 25 thereby providing an abnormal voltage drop which reduces the energization of windings I6 and I8 of the control relay C to a much greater degree than the rather slight reduction in ener gization permitted by the regulator in response to 30 an increase in ballast leakage current. This greater degree of reduction in the ener gization of windings I6 and I8 caused by the train shunt greatly reduces the normal magnetic attraction of armature 20, thus allowing the 35 force of spring 26 to exert a downward force on the pivoted back contact 3I through the movable contact 28 which overcomes the force of spring 33 and disengages the pivoted back contact 3| from the ?xed contact 35. The en 40 er'gizing circuit for armature A is thus opened at contacts 3I—-35 which prevents operation of the motor driven variable‘resistor to restore the nor mal interrail voltage, and consequently the ar mature 20 of relay C remains in its extreme 45 lower position and the interrail voltage remains at a reduced value which releases the track re lay combination as long as the train shunt exists on the track section. The present system then differentiates be 50 tween a reduction in interrail voltage due to in creased ballast leakage current from a reduction due to a train shunt in a manner to prevent the operation of the motor driven variable resistor as long as the train shunt exists on the track cir 55 cuit. In other words, the application of a train shunt causes a reduction in interrail voltage which abruptly amounts to a much greater change than is permitted to occur in response to ballast'resistance changes, and consequently 60 the motor driven variable resistor does not start to'compensate for this abrupt decrease in volt age before the armature of the control relay C has been operated downwardly with a force suf ?cient to disengage contact 3| from contact 35 65 and prevent energization of the armature A. It will now be clear that when the apparatus of the present system thus far described is op erating properly, a constant voltage is main tained between the rails of the track section 70 whenunoccupied by a train regardless of changes in interrail ballast’ resistance, but a reduction in interrail voltage is permitted which occurs ab ruptly such as caused by the application of a train shunt. The present system also maintains 75 2,135,499 .the interrail voltage at the proper adjusted value regardless of gradual changes in the terminal voltage of the track battery B such as may be caused by improper charging, abnormal loads or the like. In other words, the adjustment of the biasing forcesof springs 24 and 26 on the arma ture 20 provides a de?nite standard unaffected by variable conditions of the track circuit, to ' which standard the interrail voltage or the en -10 ergizationof .vvindings l6 and I8 is related, there by permitting any gradual change in interrail voltage regardless of vits cause to effect opera tionof the regulating means. It‘ is further ob vious that this ‘de?nite standard to which the interrail voltage is related also determines a ?xed point at which the action of the regulating means is ‘stopped, thereby preventing the “hunting” or overrunning operation which is inherent to some regulator-operation. . ' > ' t " In the present system, any change in interrail voltage results in a corresponding change in cur rent in windings l1 and I 9 of the check relay K,.but such current changes do not affect the normal released position of armature 22. In 25 other words, the windings I‘! and I9 being in parallel circuits will receive equal‘current values, and being oppositely arranged will produce neu tralizing flux values regardless of the interrail voltage as long as these parallel circuits which 30 include windings .l6 and I8 of relay C are in tact. However, considering now that either winding IE or winding I8 of relay C becomes open cir cuited, such as by a broken wire or loose con 35 nection, thereby reducing the flux value in the control relay C to such an extent that the arma ture 2B is released in the same manner as dur ing the application of a train shunt, that is, the movable contact 28 is operated downwardly and 40 may be operated with suflicient force to disen gage contact M from contact 35. Under this condition, either winding l8 or l6 alone could notiproperly detect a change in ballast resist ance in a manner to cause operation of the mo 45 tor driven variable resistor and compensate therefor. Consequently, a continued increase in ballast resistance might cumulatively amount to an increase in interrail voltage which would'be suf?cient to prevent reliable detection'of a train 50, shunt by the track relay'combination. ~In~the present'arrangement, however, the fail ure-of‘ either winding IE or l8 of the control relay C at the same time de-energizes ‘the asso ciated winding‘ I‘! or 19 of the check relay K so that the flux produced by the Winding remain ing energized is no longer opposed by the ?ux of the other winding, thereby picking up arma ture 22 of relay K. The picking up'of arma ture 22 opens the circuit shunting out a portion 60 of the resistance wire Rjby disengaging the mov able contact 39 from the ?xed back contact 4|, thereby inserting the total value of resistance B into the track'circuit which reduces the track circuit current to a value precluding the possi 65 bility of a failure of the track relay combination to respond to-a train shunt. ' . I normally‘: increasing, the ‘interrail. voltage. ~ In otherwords, the check relay K prevents any dan gerous condition from obtaining in the track cir cuit due to a, failure ,ofyeither- winding I6 or winding l8 of the controlrelay C by causing’ the insertion of a maximumvresistance value which may result in a_.condition~r>providing more re stricted train: movements, but which obviates the possibility of afailure’of the-track relay combi nation tov detect the presence of ‘a train in a track section. In this connectionit should be'noted that the windings [Be-l1; and l8—|9‘ are indi vidually connectedto the track circuit lead-in Wires, so that a single break cannot open both pairs of windings unless the break occurs in the 15 track circuit itself. > I, > - g ' ' a g It may now be seen that although the arma ture of- relay K is attractedin'response to the de-energization of one or the other of the wind ings l6 and I8 of relay C, it will not be ‘at 20 tracted, in response to the’ de-energization of both windings. The two windings l6 and I8 however~havei~ no portion of their energizing circuits'in common which is not a part. of the track circuit, and consequently it is very re-,» mote that both ofthese windings could become de-energized simultaneously and leave the track circuit intact. However, if one of ‘the windings of relayC fails‘ andpicks up relay K, it may be advisable to mechanically retain the armature 22 in its picked up position in order to guard against its subsequent release by the‘ failure of the remaining winding of relay C before the‘ de fective one hasbeen replaced. ' - . A manually'releasable latch 44 may be pro vided for this purposeiwhich is biased by a spring 45 to retain the armature 22 in an attracted position thereby holding contacts 39,-“ open.‘ In usingthis vlatch arrangement in the ‘present system, it, is assumedthat-incaseiof a failure 40 of a windingof relayC, the ‘track relay com bination will either,be“ immediately released or will not pick up upon the departure of'a train from the track section,_and consequently, at tentionvwill be called to. thefact that an abnor mal condition exists at this track section, there by allowing vthe defective circuit to bev corrected andv the system restored to itsproper operating condition by manually releasing the latch 44. A meanscis also provided in the present sys tem for preventinga dangerous condition from erly reduce theinterrail voltage. in; response to I a decrease in ballast leakage current or the like. For example, considering that-an‘ increase in the interrail voltage occurs, due for example to an increase in ballast resistance, the armature 20 of the control relay C is moved upwardly into engagement with ‘the pivoted front contact '30 60 thereby normally operating'the motor driven re sistance to -a position compensating for this voltage .increase, but however, if the variable resistor does not respond forsome reasons such as a failure of a. motor Winding or the like, the 65 increase in interrail voltage might cumulatively It will likewise be clear that in the event- the failure of either winding "5 or l8 of the con amount to a value which would prevent proper trol relay C does not result in‘the disengage However, before the interrail voltage has reachedgsuch a value, the armature 20 of the control relay C is attracted upwardly, with suffi ment of the pivoted back contact 3| from the ?xed contact 35 to prevent operation of the ar mature A, a dangerous condition would result from the following operation of the motor driven variable resistor to decrease the resistance in sertedinto the track circuitfthereby also ab 50 obtaining in thetrack circuit due to a'failure of the'motorl drivenvariable resistance to prop tracrk circuit operation. , cient force to overcome the force of spring .32 and disengage the pivoted front contact 30'from the ?xed contact 34, thereby. opening the circuit shunting out a portion of the resistance wire R. 5 2,135,499 In: this manner, the total value of resistance R is inserted into the track circuit in the same in voltage before the armature of the control re manner as during the attraction of armature 22 of the check relay K, thus resulting in an response to a decrease in ballast resistance. ‘ abnormally low interrail voltage which may pro lay has been operated beyond its position taken in The control relay in this position is arranged to open the control circuit for the motor driven variable resistor, thereby preventing compensation for the reduction in interrail voltage caused by the train vide a restricted traf?c condition by releasing the track relay combination, but which prevents an abnormally high interrail voltage from ob shunt, and of course the armature remains in this 10, taining which would. prevent the detection of a ' position until the train departs from the track train shunt. I section to restore the system to its normal condi . It is also considered expedient to provide a means for mechanically retaining this circuit open at contacts 30-—-34 when a failure of the motor driven variable resistor occurs, as other 15 wise a subsequent train shunt would reduce the tion. 10 . . The control relay in the present system is also provided with a check contact means which is operated and mechanically retained in response to the occurrence of an abnormally high interrail 15 energization of the control relay 0 to a degree ‘ voltage, and in the present system, this contact is allowing contact 30 to again engage contact 34, arranged to remove a shunt around a portion of thereby defeating the purpose of this check con tact arrangement. Consequently, a similar man ually releasable latch 48 has been provided which is biased by a spring 49 to retain the pivoted front contact 30 inits upper position, thereby mechanically holding contacts 30-34 open. Likewise it is considered that this abnormally 25 low track circuit current will either immediately release the track relay combination or prevent its picking up when the track section becomes unoccupied,‘thereby calling attention to the fact that an abnormal. condition exists and allowing the cause of the failure of the motor driven variable resistorto be corrected and the system restored to normal by the manual release of the latch 48. , ~ A track circuit regulating means has thus been ‘provided wherein a simple and e?icient perma nent magnet motor means has been employed the variable resistor, but obviously a separate re sistor could be provided in the track circuit for this purpose. In other words, a check means is 20 provided which responds to an excessive interrail voltage such as may be caused by a failure of the motor driven variable resistor to properly increase the track circuit resistance, and this check means is arranged to prevent an unsafe track circuit 25 condition by inserting an increased resistance value. - ‘ vThe check relay is provided to likewise prevent an unsafe track circuit condition from arising due to a failure of a winding of the control relay, that 30 is this check relay as previously mentioned does not normally attract its armature, but in the event one of the windings of the control relay fails or becomes open, the armature of the check relay is attracted and mechanically retained 35 which also removes a shunt around a portion of to operate a variable resistor included in the ‘ the variable resistor, but likewise a separate re - track circuit, the operation of this motor being normally governed by a control relay which is 40 provided with two windings, each winding being energized by separate parallel circuits connected across the rails of , the track section and each circuit including a winding of a check relay. A change in current in the windings of the con sistor could also be provided in the track circuit for this purpose. The check relay thereby pre vents an abnormally high interrail voltage from being applied to the track circuit either by un warranted operation of the motor operated vari able resistor caused by the reduced magnetism of the control relay or by an increased ballast re .trol relay causes a corresponding operation of sistance which cannot be detected by the im the control relay armature while the windings paired sensitivity of the control relay. of the check relay are so arranged that a change in current does not affect the check relay arma ture as long as both the windings of the control and check relays are intact. In this manner, the control relay which is more The above rather speci?c description of one form of the present invention is given solely by the way of example, and is not intended, in any sensitive than the track relay is able to detect changes in interrail voltage which are too small to cause operation of the track relay, and the con trol relay is arranged to accordingly cause opera tion of the motor driven variable resistor to com pensate for these small changes in interrail voltage. Inasmuch as changes in interrail volt age caused by ballast resistance changes occur slowly, the motor, driven variable resistor is able to compensate for the ballast resistance changes in increments or decrements of interrail voltage detected by the control relay before they can cumulatively amount to a change su?‘icient to I a?ect the track relay. , I The present system thereby maintains a sub stantially constant interrail voltage while the track section is unoccupied regardless of ballast resistance changes, but upon'the entrance of a 70 train into the track section, a reduction in inter rail voltage occurs which abruptly amounts to a much greater change than is permitted to occur in response to ballast resistance changes, and con—' sequently the motor driven variable resistor does not start to compensate for this abrupt decrease manner whatsoever, in a limiting sense. 415 It is to 50 be understood that various modi?cations, adapta tions and alterations may be applied to meet the requirements of practice without in vany manner departing from the spirit or scope of the present invention except as limited by the appended 55 claims. What I claim is:— 1. In a track circuit, an insulated track section, a source of energy for the track section, a re sistor in series with the source of energy to the 60 track section, a motor driven arm contacting with various portions of the resistor, a control relay having two windings connected in multiple across the track section, a check relay having two oppos ing windings one in series with one of the wind 65 ings of the control relay and the other in series with the other winding of said control relay, said check relay acting to attract its armature when— ever its two windings are not equally energized, a circuit connecting the motor driven arm to one 70 extreme end of the resistor through a back con-. tact'of the check relay and a contact on the con trol relay, said contact being opened only in re sponse to current in the windings of the control relay above a predetermined value, contacts on 75 2,135,499: 6V thecontrol relay forcontrolling operation of'the. aiicontrolrelay' responsive to~theitrack circuit motor driven arm in accordance with relatively ' relay preventing operation of the motor driven‘ voltage, a variable resistance in series with the source supplying voltage across the track rails of‘ the track circuit and operated to different positionsbyrth‘e control relay to maintain a sub arm in responseto current in the windings of, the control relay below a predetermined value. stantially constant voltage acrosslthe track rails, contact means on the control relay operated in slight changes in current in the windings: of the control relay, and contact means on the control 2. In a track circuit including a track relay response to an excessive, track circuit voltage, energized by current flowing from a track battery a‘ manually releasablelatch means'for holdingv the contact means in its operated position, and resistor in series with the track circuit, a power operated arm contacting with various portions‘ of the resistor, a control relay having two windings‘ connected in multiple across the track section and, governing operation of the power operatedarm in accordance with relatively slight changes in inter rail voltage, a check relay responsive to the integrity of the windings of said .control' relay, and a shunt circuit connecting the power-oper means controlled by said contact means for in cluding all of said variable resistance intthe track 10" through the' rails of a track section in series, a 20v ated arm with one end of the resistor through a contact ofthe checkwrelay and a: contact of the control ‘relay operated by an‘excessiverinterrail voltage. , 1 3. In'a track circuit, insulated track sec 255 tion, a source of, energy fOI'IthGQtI‘aCK circuit, a power operated variable resistor in the track cir cuit, a control relay having windings energized in accordance with the interrail potentialof the track circuit and, governing operation of the 3,01 power operated variable resistor, a, check relay responsive to, the‘ integrity of the control relay windings, means controlled: by thezcheck relay for increasing the resistance of the track" circuit upona failure of the windings of thecontrol 35 relay, and means controlled by thecontrol relay for increasing the resistance of'the track circuit upon an excessive interrail potential. 4. In a track circuit: includinga track relay; means energized by currentlfrom, ajtrack bat-, tery ?owing through? therails of a track section in series, a power-actuated variable: resistor in the track circuit," a control‘ relay controlling the actuation of the variable resistor-‘in accordance: with an increase or a decrease, in interrail'ivoltage‘ 45 between predetermined limitsof variation, means on the control relay forlpreventin'g actuation" of’ the variable resistor iniresp‘onse to;a1decrease in interrail potential, beyond saidzpredetermined" limits of variation, andmeans .onith'e controli 50 relay for causin'g'a. maximum resistance, to be inserted into thev track circuit in responseto an increase in interrail potential beyond's'aid pre-' determined limits of variation. 5.. Ina track circuitfvoltage regulating means, 5.5 a‘, control relay having an energizing circuit-re sponsive to the track circuit voltage, a power, operated regulator means controlled by the con ~ circuit, a power-operated regulator governed by‘ sai'dcontrol relayi soi asito maintain aisubstan tially constant‘ inter-rail voltage upon vgradual changes in the resistance of the-track; circuit, a‘ check @relay included in series with said control relay in such a manner astoYbe actuated upon a' break in the energizing vcircuit/30f said control: relay and rendered e?ectiveupon such actuation for inserting apredetermined resistance insai'd‘ track- circuit, and ‘meansvincludi'ng, a contact of ' ' 251' said control relay which‘is actuated upon the? ' presence of an excessive voltage across the track‘ circuit‘ for causing said predetermined resistance torbe inserted in said track circuit, whereby the failure ofveithe‘r‘said control relay'ci'rcuit or‘ an» excessive voltage across the track circuit ‘results 301 in" the insertion of a predetermined“resistance in said track circuit. ~ ’ ' 9; In» a‘ track'circuit forrailroads, an insulated track ‘section having > afsource" of energy cone nected across the rails at one end of the section and a tracklrelay connected acrossthe rails'ate the‘ other end of‘v the ‘section; a’ power-operated 40'. variable- resistor included in" series with, the source of energy at‘th’e' end-of said track section at'which said source is located,la<control relay’ having'windings energized-in accordance with the interirail potential of the’ track» circuit and effective to govern the‘ power-operation of said variable resistor so as to; maintain a substan tially constant inter-rail potential‘ upon gradual changes in the ballast resistance of the track circuit, and a check relay‘ arranged to attract itsv 5,0: armature upon a failure of the- energizing circuit fo'rr‘th‘e control relay, ‘said check‘ relay being ef-" fective upon the" attraction of’its armature for inserting a predeterminedresistance in the track circuit; ' 55: 1'0'.>I'n a track eircuitfor railroads in 'combin'a? tionwith an insulated section of track and'a source of' energy for supplying currentto the appliedto said track circuit, and means respon track at one end ‘of the section foren'ergiz'ing a track relay connected to the track at the oppo 60; control relay for reducing the voltageapplied to said track circuit independently of said regulator. 6. In a track circuit voltage regulatingv means, a control relay responsive to the track circuit 65 voltage, a variable resistor in series, with. the source supplying: voltage to thetrackcircuit con trolled by the control relay, a ‘check relay ar ranged to attract itsarmature upon a ‘failure’ of the energizing circuitior the. control relay, said’ check relay upon attraction of its armature: in serting the maximum resistance of said resistor inythe track circuit, and-a manually releasable latch means for holding thearmature of-the check relay in its attracted‘position. 75 7 8. In atrack circuit voltage regulating means, 155 a control relay having an energizing ci'rcuit‘ree sponsive to the. inter-rail voltage of the track: trol relay for gradually regulating the voltage 60 sive to a break in the energizing circuit of said 70 circuit feed independently of the'voperated posi-v tion. of said variable resistance; , '7. In a track circuit voltage regulating means, site end of said section, a‘ variable resistor in series with said source ofenergy, electrically op erable ‘means for actuating said resistor to vary‘ 7 its resistance, a control relay having windings ' ' connected across the track rail'sand-having‘an armature cooperating with the windings‘ of-said relay, s'pringmeans for biasing‘ said armature away from its-attracted position, a frontcontact closed when the’ windings are energized above a predetermined value, an operating circuit for said electrically operable means closed by said front contact for- actuating’ said variable resistor to in crease the resistance insaid'track circuit and ' reducethe potentialiacross the ‘windings of said' control relay so as to returntheir energization, 2,135,499 7 to said predetermined value, another contact op erated by excessive current in said control relay by the shunting of the track circuit by a train for preventing operation of said power means, such as would occur if the variable resistor fails and other contact means responsive to a rela tively quick and large movement of said arma ture as may be caused by the failure of said to insert added resistance in the track circuit, said another contact when operated under such conditions causing a predetermined resistance to be inserted in said track circuit independently of power operating means to insert added resist ances in said track circuit for permanently pre said electrically operable means for actuating venting operation of said power operating means said variable resistor. 11. In a track circuit for railroads having the usual track‘relay connected across the rails of an until such other contact means is manually re stored. 10 13. In a track circuit for railroads having the usual track relay and source of current, a var iable resistor connected in series with the source of current at the end of the track circuit at which said source is located, power-operated 15 means for actuating said variable resistor and having an operating circuit for increasing its re sistance and another operating circuit for de insulated track section at one end and having a source of current connected across the track rails at the other end of such section, a power-operated variable resistor included in series with said source of energy connected to the track rails, control means responsive to gradual changes in the inter-rail‘ voltage for governing the power operation of the variable resistor to increase or 20 decrease the resistance in the track circuit to ob~ tain a substantially uniform inter-rail voltage creasing its. resistance for regulating the voltage impressed across the track rails, a control relay 20 having its windings responsive to the voltage ap with varying ballast leakage conditions, and plied to the track rails and having an armature means operated upon the energization of said control means by an excessive inter-rail voltage 25 such as may exist in the event that the power as to assume an intermediate neutral position erated condition until manually restored. when its windings are energized with a prede 25 termined value of current, two front contacts on said control relay one of which is opened by a small movement of said armature fromv a neutral position and the other of which is opened by a relatively larger movement of said armature 30 from a neutral position with said one front con 12. In a track circuit for railroads having the usual track relay and source of current connected power operating means to cause an increase in operated resistor fails to respond to said control means, for including a predetermined resistance in series with said source of energy independent ly of the existing condition of said variable re 30 sistor, said means being maintained in its op across the track rails of an insulated track sec tion, a variable resistor in series“ with said source of current at the end of the track circuit at which said source is located, power operating means for actuating said resistor to increase or decrease its resistance, a control relay responsive to variations in the inter-rail voltage of said track circuit and having a movable armature, spring means for biasing said armature towards its retracted position with such force that such armature assumes a neutral position for a pre 45 determined inter-rail voltage, means rendered effective upon the movement of said armature from its neutral position by an increase or de crease in inter-rail voltage above or below said predetermined inter-rail voltage for governing 50 biased to a retracted position with such a force the operation of said power operating means to cause either an increase or a decrease in the re sistance of said resistor as the case may be until said armature is restored to its neutral position, contact means responsive to a relatively quick and large movement of said armature as caused 55 tact governing the operating circuit for said the resistance of said resistor and said other front contact eifective when operated for pre 35 venting the operation of said power operating means, and two back contacts on said control relay one of which is closed by a small movement of said armature towards its retracted position and the other of which is opened by a relatively 40 larger movement of said armature towards a re tracted position with said one back contact gov: erning the operating circuit of said power-op erated means to cause a decrease in the resist ance of said resistor and the other back contact 45 eifective when operated to prevent the opera tion of said power-operated means, ‘whereby gradual changes in the inter-rail potential are governed by the operation of said variable re sistor to maintain the inter-rail potential sub 50 stantially constant, and whereby relatively sud den and large changes in inter-rail potential are effective to prevent the operation of said vari able resistor from its last operated position. OSCAR S. FIELD.