Патент USA US2123966код для вставки
July 19, 1938. ` F_ X, REES TRACK CIRCUIT Original Filed Aug. 21, 1955 . 2,123,966 Patented July 19, 1938 ’ 2,123,955 UNITED STA’FES PARENT QFFICE 2,123,966 TRACK CIRCUIT Frank X. Rees, Albany, N. EY., assignor to Genera-1 Railway Signal Company, Rochester, N. Y. Original application August 21, 1936, Serial No. 97,2011. Divided and this application Gctober 27, 1937, Serial No. 171,379 5 Ciaims. 10 (Cl. 246-34) This invention relates to improvements in the Well-known track circuits for railroads, and more the average or eifective relay energizing current, thereby serving to break down or ionize the film particularly to rectified alternating current track circuits. The primary object of the present invention is to improve the shunting operation of the usual tractive soft iron armature track relay of direct current track circuits under varying conditions or coating on the rail surface and render more of rail surface and ballast resistance. This invention is in the nature of a variation or modification for carrying out the principles and mode of operation characteristic of the track circuit organization disclosed and claimed in my effective the shunting action of the Wheels and axles of a train or trains Without increasing the average current. Various characteristic features, attributes, and advantages of the invention will be in part ap parent, and in part pointed out, as the descrip tion progresses. 10 tion disclosed in said prior application. The present application is also a division of my prior The accompanying drawing illustrates in a sim pliñed and dragrammatic manner certain specific embodiments of the invention, the parts and circuits being shown more With the View of facilitating an explanation and understanding of 15 the invention than for the purpose of showing in detail the structural organizations to be employed application Ser. No. 97,204 filed August 21, 1936 in practice. prior application Ser. No. 24,074, ñled May 29, 15 1935, and no claim is made herein to the inven and no claim is made herein to the invention 20 disclosed in the parent application as noW amended. The reliable operation of the usual track cir cuit depends upon establishing a conducting path of low resistance through the axles and Wheels of a car or train; and the Weight of the equipment and condition of the rail surface are important factors affecting the resistance of a Wheel shunt. For example, Where the track rails of sidings, Crossovers, and the like are infrequently used, a coating of rust, usually an iron oxide, accumu lates on the rail surface, and makes any Wheel shunt of high resistance for the relatively small inter-rail voltages commonly employed; and even Where train movement is frequent and the rail surface appears clean, a coating or film in the form of an oxide of silicon, or some other stable compound, is present on the rail surface, and offers a relatively high effective resistance for low voltages. It is found that these various coatings 40 or films on the rail surface, apparently because they are in the nature of a stable chemical com pound or composition, will break down and be come a low resistance conducting path upon the application of sufficient voltage, Which may be 45 termed an ionization voltage. Generally speaking, and Without attempting to denne the exact nature and scope of the inven tion, it is proposed to provide a transformer of special construction, conveniently termed a peaker- voltage transformer for supplying rectified current from an alternating current source to the ordinary direct current track circuit, so that rela In the drawing, Fig. 1 illustrates one form of the invention, and 1Eig. 2 is an explanatory dia gram illustrating how the negative Waves of the current are blocked out by the rectifier shownin Fig. 1. One important characteristic of this invention is that it assures reliable shunting of the ordi nary track circuit under unfavorable conditions of rail surface, Weight of equipment, and ballast conditions. This desirable characteristic is due to the application of high peaked voltages to break down the ñlm or coating on the track rails, thereby assuring a shunting effect of the Wheels and axles of a car or train under conditions Where a lower voltage would be insuiiicient. In accordance with the invention illustrate-d in Fig. l., it is proposed to employ a track relay 35 of the usual direct current tractive armature type but having a substantial value of inductive react ance, and to supply the track circuit with time spaced unidirectional voltage pulses, instead of voltage pulses in opposite directions as shown in 40 Fig. l. These unidirectional voltage pulses are preferably derived from alternating current but preferably have their peaks materially in excess of that of the usual sine Wave of alternating cur rent, these peak voltages also being in excess of the steady operating voltage that Would be neces sary for operating the track relay, thus tending to more easily overcome the resistance of the Wheel contact and establish a better ratio be tween maximum voltage and wheel shunt resist 50 ance. In this construction the ballast resistance between the track rails, together with an addi tively high peak voltages of short duration are tional shunt or bleeder resistance as may be rc obtained, as compared With a rectified Wave of quired, constituting a conducting path into which the relay may discharge current during the time 55 55 the usual sine Wave shape of voltage required for 2 2,123,966 intervals between the impressed voltage pulses; Fig. 2. and the voltages and resistances being so propor tioned that the rate of decay of current through the relay varies with the ballast resistance in such a way as to compensate for the change in the Wel1~known copper-oxide dry plate type, have the inter-rail impressed voltage with changes in ballast resistance, thereby maintaining a substan tially constant average operating current through the track relay throughout a wide range of varia 10 tions in ballast resistance. Referring to Fig. 1 of the drawing, it is con templated that the track rails H wil be joined together in the usual way, with insulated joints l2 designating the ends of the track sections, one of which only is illustrated. At one end of the track circuit, preferably at the entering end, the direction of traffic being in the direction of the arrow, the direct current track relay T4 of the usual tractive armature type construction is con 20 nected across the track rails Il, the resistance property or characteristic that the resistance to the ñow of current in the direction in which the rectifier is conducting, varies invariably with the current induced, such forward resistance of the rectifier increasing as the conducted current de creases. This characteristic or property of the rectiñer I5 is a factor in connection with other features of this form of the invention to compen sate for variations in ballast resistance. Considering now the operation of the track circuit organization of the construction shown in Fig. l, and the theory believed to underlie the re sults obtained, the impressed Voltage applied to the track rails at the feed end comprises uni directional time spaced pulses or waves. These voltage pulses supply current to the ballast re sistance and to the track relay through the limit» ing resistance I9; and each wave causes a cor and/or inductance of this track relay T4» being responding temporary increase in the current dependent. upon the nature of the ballast resist ñowing in the track relay. As an impressed volt age wave is applied to the relay current through this relay increases, with a time lag due to the inductive reactance of the relay; and as this ance and a number of other factors, as will pres 251 Certain types of rectifiers, such as the ently appear. It is contemplated that the impedance of track relay T4 and its connections to the track rails will be some two or six times greater than ordinarily used, as for example, where ordinarily aV 4 ohm track relay7 would be used, a track relay The pur 30 of about 25 ohms would be employed. pose for'such relatively large impedance of the track relay and its connections is to permit the use of a greater inter-rail potential for overcom ing the resistance of the wheel contact, and fur 35 Vther to supply sufficient energy to the track relay by smaller average current than would be neces sary for the'usual 4 ohm relay. In accordance with the invention the track re lay is supplied with current of unidirectional time kspaced pulses, the direction of the pulses and space between them, as well as the peak voltage, being chosen with due regard to the other char acteristics of the circuit., so as. to obtain the de sired operating characteristics of the track cir In the embodiment shown in Fig. 1, a 45 cuit. source of alternating current of an ordinary frequency, such as 60 cycles, is employed. Such source of current is shown conventionally by the generator G4. This source of alternating current 50 G4 is supplied directly to the primary winding 'i4 of a peaking transformer PT4. The secondary winding 84 of this peaking transformer PT4 is connected to the track rails through an adjusta ble resistance IQ and a rectifier l5 connected in 55 series. This adjustable resistance I9 constitutes the usual limiting resistance. In certain appli cations of the invention, for reasons hereinafter explained, it is also desirable to employ a bleeder or regulating shunt resistance 2|, preferably ad 60 justable, which is connected across the track rails, as shown, preferably at the feed end of the track circuit'. In the arrangements shown in Fig. 1, the rectiñer i5 serves to impress across the track rails waves 65 or half-cycles of peaked alternating current Volt age supplied by the secondary winding 84 of the peaking transformer PT4, thereby providing a single unidirectional impulse for each cycle of al ternating current as shown by the Waves C5 of 70 Fig_ 2. It may be pointed out that the curves shown in Fig. 2 are substantiallx7 the same as those shown in Fig, 3 of the parent application except that the negative voltage waves shown in Fig. 3 of the- parent application have been blocked out 75 "by the rectifier l5 and are therefore not shown in 20 impressed voltage wave falls, the current through the relay decreases. As thc relay current de creases, the collapse or decay of flux in the relay induces a voltage in its winding in a direction to sustain current flow in the relay, and in accord 30 ance With established principles, the rate of decrease or decay of current is dependent upon the inductance of the relay and the resistance of the multiple path which in the present instance is the ballast resistance of the track circuit. It is found that the rate at which the relay current will flow between two successive waves of uni directional potential, depends upon the. joint effect of the ballast resistance and the bleeder resistance 2l (which bleeder resistance in track circuits may be omitted). 4 (i It is thus seen that the decay of current ñowing in the relay T‘1 during the time interval between voltage pulses is at a slower rate with a lower ballast resistance, and that the greater rate of decay of current will take place for higher ballast resistance. The pick-up and drop-away current value of the track relay T4 Adepends upon what may be termed the average current through it; and it can be seen that the magnitude of this average current depends upon the rate at which the relay current decreases or decays during the half-cycles where the impressed voltage is cut oí, as well as upon the value of the voltage pulses. In other 50 Words, the higher the pulses of impressed voltage, the greater the instantaneous current; and also the slower the rate of decay of relay current, the greater will be the average current through the relay; and vice versa. In the ordinary track circuit, when the battery 60 voltage and limiting resistance has been selected or adjusted to provide sufficient current for the track relay under wet ballast conditions, that is, low ballast resistance, if the ballast dries out and its resistance increases, less current flows through the ballast and the limiting resistance, the volt age drop through the limiting resistance then becomes smaller, and a greater voltage is im pressed across the track rails to increase the cur rent through the relay. It can thus be seen that, if once the ordinary track circuit has been ad justed to hold up the relay under wet ballast con~ ditions, there will be excessive current through the relay under dry ballast conditions, which mate rially interferes with the shunting of the track 3 2,123,966 relay. For this reason, it is desirable to provide something Which will act automatically to main tain a uniform normal current through the track relay under varying ballast conditions, so that the energization of the relay is substantially the same at all times, and so that the relay can be shunted quickly and reliably under both wet and dry bal last conditions. An important feature of the invention shown in Fig. l is the automatic corn pensation provided to maintain the relay current substantially uniform for various ballast resist ances throughout a wide range at the higher ballast resistances and above what may be termed the zone of Wheel shunt resistance. Explaining the theory apparently underlying the operation accomplishing this result, it appears that changes in the voltage applied to the relay with variation in ballast resistance are accom plished by compensating change in the rate of 20 decay of the relay current between the voltage pulses, in such a way that, with suitable propor tioned parts, the average operating current through the relay is maintained substantially uni form throughout a Wide range of ballast resist 25 ances above the lower values, around 2 ohms per thousand feet of track. In practicing this invention, the parts are selected and proportioned to provide adequate operating current for the track relay T"z under the 30 most unfavorable or Wet ballast conditions to be encountered; but as the ballast dries out, less current is supplied to the track circuit as a whole, and the voltage drop through the limiting resist ance is decreases to raise the voltage impressed 35 upon the relay T4, such increase in ballast resist ance is accomplished by a more rapid decay of relay current between the pulses of impressed voltage, so that the average current iiowing in the track relay T4 remains substantially constant, 40 rather than to increase steadily with. an increase in 1ballast resistance as is the case in the ordinary track circuit. Consequently, the track relay T4 is not overenergized under dry ballast conditions and may be shunted as surely as quickly 45 under dry as under wet ballast conditions. In some applications of the invention, it is found that there is what may be termed over compensation, such that the average current through the relay of an unoccupied track circuit 50 decreases at the higher ballast resistances to the point where it will fail to hold up its armature. This appears to be due to a relatively greater change in relay current between the voltage pulses for higher ballast resistances, than changes 55 in the impressed voltage, with the result that the average current actually decreases for higher values of ballast resistances. In such cases, the shunt or bleeder resistance 2l across the track relay is employed to provide what may be consid 60 ered to be an artiiicial ballast resistance or leak age path for the purpose of maintaining a suñ'i ciently low resistance for the discharge circuit for the track relay T4 under very dry ballast condi tions to avoid too quick a decay in the relay cur 65 rent between the voltage pulses and thereby main tain the average current. This shunt or bleeder resistance 2i is preferably adjustable, and with the proper selection or adjustment thereof, to gether with the adjustment aiiîorded by the usual 70 limiting resistance i9, it appears that the desired regulation of relay current may be obtained for track circuits for various lengths and ballast materials throughout the full operating range encountered in practice. The maintenance of substantially constant 75 average current through the relay for different ballast resistances seems to be helped also by the current-resistance characteristics of the copper oxide rectifier l5 in the arrangement shown in Fig. l, the eifect of the rectifier in this respect, however, being apparently dependent upon a number of related factors and diñìcult to explain and evaluate. A source of alternating current derived from a peaker transformer when used in combination with a half-wave rectifier l5, affords 10 a convenient way of obtaining the time spaced impulses of impressed Voltage, and with such an arrangement the operating characteristics of the rectifier may also be taken advantage of to modify the current regulating characteristics of the track circuit. For example, assuming a setting for Wet ballast conditions, when the ballast dries out and less current is supplied to the track, the forward resistance of the rectiñer, i. e. the resistance in the direction in which it is conducting, increases and 20 in effect adds to the limiting resistance i9 to maintain a voltage drop wth a smaller current to give nearly the same impressed voltage across the track rails. For this reason, and in this way, the characteristics of the rectifier are helpful in 25 obtaining the desired current regulation. Another important feature of this invention is that the peak voltage of the half-cycles of peaked alternating current are much in excess of the steady direct current voltage that would be re 30 quired to produce the same general operating cur rent through the relay. In other words, the peak voltages applied across the track rails in accord ance with the form of invention shown in Fig. 1 are much greater than the steady voltage that would be used with the same type of track relay in a continuous direct current track circuit. Such peak voltages very materially assist in reducing or breaking down the resistance of the wheel con tacts and establish an effective low resistance wheel shunt, this being true more particularly with dirty or rusty track rails, or with light weight equipment, such as gas-electric cars. ' 'I‘he resistance of the Wheel Contact is found to vary greatly with the conditions of the rail surface and the weight of the equipment; and it appears that in many cases voltages much higher than the relatively small voltages, of about 2 volts normally employed for track circuits, are necessary to break down the resistance of the Wheel contact to a point where ionization and actual shunting of the track relay takes place. 'I‘he peak voltages provided by this in vention, which are many times those commonly used in track circuits, apparently break down 554 the resistance at the wheel contact by an ioniza tion eifect, and enable effective shunting with dirty or rusty track rails and light-weight equip ment in a manner not obtainable with the ordi nary track circuit arrangement. In this connection, it will be noted that the peak voltages are periodically applied at fre quent intervals and are available to break down the resistance of the Wheel contact, as the car or train moves along the track and its Wheels contact with successive points on the rails, and with the resistance once broken down it will remain of low value until the train has left and an opportunity for soiling and oxidization of the rail surface has been presented. Further, the use of a pulsating current ob taining from a peaked alternating current source through the medium of a half-wave rectifier, as distinctive from a steady current for energiz- ' ing the track relay, acts to improve the pick-up 60 4 2,123,966 and drop-away characteristics of the high im section, a peaking transformer having an in-put pedance soft iron armature track relay T4. In other Words, a direct current „tractive arma ture type relay of the usual construction will current connected to the in-put Winding of said peaking transformer, means including a half and an out-put Winding, a source of alternating pick up on less current and drop away on a Wave rectifier and a limiting resistance in series greater current When energized with half-cycles for connecting the out-put Winding of said peak of rectified alternating current or equivalent time spaced current impulses, than When ener gized With an ordinary unidirectional voltage ing transformer to the track rails at the other end of said track section to impress peak volt from a battery or the like, and this effect is still more pronounced When these half-cycles are of extremely peaked Wave form. This is attributed to the fluctuating nature of the ener gizing current which tends to initiate armature movement at critical current values in a man ner that does not occur with steady energiza tion. Also, the movement of the armature of the relay is accompanied by a flux change Which appears to be a contributing factor to the su perior ratio of drop-away current to pick-up current obtained by the use of pulsating ener gization of the track relay in accordance with this invention. From the foregoing it will be appreciated 25, that this invention involves certain selection and proportioning of parts in the complete organi zation; and the various voltages, resistances, and inductive reactances are so completely inter related that a variation in the change in one 30"; factor tends to modify one or more of the other factors. Generally speaking, the underlying principles and advantages of the invention shown in Fig. l may be obtained when the limiting resistance 35.'. I9 and the shunt or bleeder resistance 2l, if used, are selected to conform With the length of the track circuit, condition of the ballast, range of variation in ballast resistance, and the like; the inductive reactance of the relay T4 40 is preferably so chosen as to require peak volt ages suitable for reducing the resistance of the wheel contact by breaking doWn the resistance by ionization; and these various factors are rel atively proportioned to provide the necessary 45. average current through the track relay of an unoccupied track circuit under Wet ballast con ditions, and to maintain such average current substantially constant throughout the range of variation of ballast resistance encountered with changing weather conditions. The particular embodiments of the invention shown and described are merely illustrative; and various adaptations, modifications, and additions may be employed, Without departing from the 55 principles and mode of operation of the inven tion. What I claim isz 1. A track circuit for railroads comprising a half-Wave rectifier, a limiting resistance, a peak ages substantially greater than the steady op erating voltage for said relay, a shunt bleeder 10 resistance connected across the track rails, the magnitude of said peak voltages and their time spacing being selected With respect to the self induction of said track relay and the resistance of said bleeder to provide an approximately uni 15 form operating current for said track relay throughout a Wide variation in ballast resistance. 3. A track circuit for railroads comprising, a direct current track relay of the usual tractive armature type connected across the track rails 20 at one end of the track section, a source of alternating current, a transformer having a high leakage reactance, an adjustable limiting re sistance, a half-Wave rectifier, and means con necting said source of alternating current to the 25 in-put side of said transformer and connecting the out-put side of said transformer across the track rails at the other end of said track sec tion through said limiting resistance and said half-Wave rectifier, a bleeder resistance con 30. nected across the track rails of said section, the self-induction of said track relay and the re sistance of said bleeder being such as to tend to maintain current of a value in its Winding to keep its armature attracted between the half 35; cycles of impressed voltage, and the peak voltages of the half cycles of impressed voltage being such as to provide an average current through said track relay comparable with its steady operat ing current and being materially greater than 40 the voltage for such steady operating current, whereby peak voltages across the track rails suit able for breaking down anycontact resistance of the Wheel shunt are available Without a corre spondingly greater average energization of the track relay which Would interfere with its shunt ing. Ll. A track circuit for railroads comprising, a direct current track relay of the usual tractive armature type having its winding connected across 50 the track rails at one end of a track section, a limiting resistance, and means including a trans former having high leakage reactance and a rectifier included in its secondary Winding for supplying time spaced uni-directional voltage 55 pulses through said limiting resistance across the track rails at the other end of said section, a bleeder resistance connected across the track rails of said track section, the self-induction of ing transformer energized from a source of al said relay maintaining current through its -wind ternating current for impressing voltage across ing between such Voltage pulses by discharging the track rails at one end of the track section path through which the track relay having con into the ballast resistance and bleeder resistance, the rate of decay of said current of self-induc tion between the voltage pulses varying with changes in ballast resistance to compensate for 65 the variations in current supplied to said track relay by the voltage pulses for different ballast re siderable inductive reactance may discharge cur sistance so as to cause approximately the same rent during the half cycles when the impressed `voltage is blocked by the rectifier. 2. A track circuit for railroads having the relay of the tractive armature type connected average current through the track relay for a Wide variation in ballast resistance. 70 5. A track circuit for railroads having the usual variation in ballast resistance and compris ing, a direct current track relay of the usual trac tive armature type having its Winding con yacross the track rails at one end of the track nected across the track rails at one end of a track in series with said rectifier and said limiting resistance, and a shunt bleeder resistance con 65 nected across the track rails to cooperate with the ballast resistance to provide a conducting usual variation in ballast resistance between the track rails and comprising, a direct current track 60 2,123,966 section, an adjustable limiting resistance, a source of alternating current, a transformer having a. high leakage reactance and a rectifier included in series in its secondary Winding for impressing time spaced uni-directional Voltage pulses through said limiting resistance across the track rails at the other end of said track section, a bleeder resistance connected across the track rails 5 of said track section, the time spacing and mag nitude of said voltage pulses, the self-induction of said track relay, and said limiting resistance and bleeder resistance having such relation that approximately the same average current flows through said track relay for a Wide range of variation in ballast resistance. FRANK X. BEES.