US2311034A - Railway track circuit apparatus - Google Patents

Description

' Feb. 16, 1943. A. E. DODD RAILWAY TRACK CIRCUIT APPARATUS Filed May 31, 1941 3 3 i i m 9 56 11 $56 F :35 32.: F cr r; 1 W I j m Fig. 4.

A BY

lNV TOR 1 0044 HIS ATTORNEY Patented Feb. 16, 1943 BAIPWAY TRACK CIRCUIT APPARATUS Arthur E. Dodd, Edgewood, Pa., assignor to The Union Switch 8; Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application May 31, 1941, Serial No. 395,925

7 Claims.

My invention relates to railway track circuit apparatus, and it has particular reference to the organization of apparatus into railway track circuits of the class wherein improved operating characteristics are obtained by varying the en- Railway track circuits are arranged in such manner that the track relay is controlled by an application of a shunt which decreases the energy available at the relay to hold it picked up. This factor of controlling a relay by the application of a shunt rather than by opening or interrupting the circuit, generally results in providing the relay with characteristics that make it slow to release and quick to pick up, inasmuch as the pickup energy level of a relay ordinarily is much higher than the drop-away level at which the relay releases. In order, therefore, for a train shunt to be effective to release the relay, the shunt must be sufficiently low in resistance to shunt away from the relay winding the increment of energy above the drop-away energy level of the relay. This shunt, however, provides a low resistance or short circuit path across the relay winding which maintains the flux in the relay for an appreciable interval of time, so that a correspondingly long time interval is required for even a low resistance train shunt to lower the energy level of the relay below its drop-away value. Hence, if the train shunt varies intermittently in effectiveness, the release period of the relay might be materially increased and after the relay releases due to a shunt, there is a possibility that these variations in shunt might cause the relay to be picked up and released and thus follow the fluctuations in the applied shunt. of ordinary relays to follow varying train shunts, and the slow releasing characteristics possessed by such relays when shunted, are undesirable in track relays since such relays often are incorporated into signaling or control systems not only for controlling signal indications, but also, for establishing directional control in accordance with the sequence in which the relays of two or more successive sections are released. It is apparent, therefore, that if a relay is improperly picked up in response to a momentary loss of train shunt, or if the relay of a section vacated by a, train picks up prior to the train causing the release of the relay of the section in advance, an improper directional set-up might be established as well as causing flashing signal indications,

etc. Furthermore, such relays are oftenemployed for electrically locking signals and ergization of the track relay after it has picked The tendency switches against operation, and if a track relay is intermittently released and picked up due to a varying train shunt in its section, the effectiveness of such locking is materially decreased.

I am aware that schemes have been proposed heretofore to condition a track relay to create its pick-up energy level when it is released, and to reduce the energy level in the relay after it has picked up, thereby obtaining a track circuit having high shunting characteristics. One of the most effective of such schemes is to employ a secondary relay, which ordinarily is slow to pick up, controlled by the track or primary relay and in turn controlling the release sensitivity of the track relay. Such systems commonly are termed primary-secondary track relay combinations, and although they materially improve the operation of track relays and track circuits, the use of two independent relays increases the initial and maintenance cost of such track circuit arrangement to a considerable extent.

In view of the foregoing and other important considerations, it is an object of my invention to provide a track relay having means for c0ntrol ling its own release sensitivity in such manner that the relay is conditioned to create its proper pick-up energy level when released, and when picked up the energy level in the relay is reduced to a value only slightly above that required to hold its armature in its attracted position.

Another object of my invention is to provide a railway track circuit incorporating a track relay having means for incorporating into a single relay structure the functions of the two relays of a primary-secondary relay combination.

A further object of my invention is the provision of railway track circuit apparatus incorporating relays having means for delaying the pickup of the armatures of such relays.

An additional object of my invention is the provision of safe, reliable, and relatively inexpensive means for obtaining in a single relay the benefits and advantages of a primary-secondary relay combination.

Another object of my invention is the provision of novel and improved forms of electrical relays arranged to be slow to pick up and having quick release characteristics when shunted.

The above-mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description, are attained in accordance with my invention by incorporating into a track relay a retaining winding coupled to a track circuit and arranged to oppose the attractive action of the operating winding of the relay on its armature, and by utilizing a make-before-break contact combination operated by such armature to control the energy level created by the operating winding. The coupling of the retaining winding of the relay to the track circuit is effected in accordance with my invention in such manner that the decay of flux due to current in the operating winding is not effected, but the growth of flux is prolonged to provide the relay with slow pick-up characteristics.

I shah describe four forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fi 1 is 2. diagrammatic view showing a preferred form of apparatus embodying my invention. Figs. 2, 3 and 4 are diagrammatic views each illustrating a modified form of the apparatus shown in Fig. 1, and each also embodying my invention.

In each of the several views of the drawing, similar reference characters have been employed to designate corresponding parts.

Referring first to Fig. 1, the reference characters I and la designate the track rails of a stretch of railway track divided by insulated joints 2 into an insulated section DE. Section DE is provided with a track circuit comprising a suitable source of current, such as a battery TB, connected in series with the usual current limiting resistor 3, across the rails I and la at one end D of the section, and at times only a portion and at other times the entire operating winding of a relay TR connected across the track rails at the other end E of the section.

Relay TR comprises a magnetizable core 5pmvided with an operating winding 8, another magnetizable core I provided with a retaining winding II, and armature means comprising two armatures I and 8 disposed in magnetic relation to cores and II), respectively. and connected together by means of a rigid non-magnetic member 9. The armature means are biased, as by gravity, into a released or back position wherein armature 8 engages core III, and are operated to a front or picked-up position in response to the attractive action on armature I of the flux due to current in winding 6. This operation of the armature means is at times opposed by the attractive action on armature 8 of flux due to current in retaining winding II. Armature I is pivoted at 4 in the usual manner and has associated therewith a plurality of contact members I2, I3 and I4 which cooperate with the usual front and back contact points to form front and back contacts according as armature I is in its picked-up or released position, respectively. One of the contact members I2 is bifurcated and functions as the common or bridging member of a make-before-break contact arrangement. When armature I is in its attracted position, a portion only of winding 6 is connected across the track rails I and la at E over an obvious circuit including front contact I2-I5 and a resistor I1, and when armature I is released, the entire operating winding 6 is connected to the track rails over an obvious circuit including back contact I2I6.

The retaining winding II is coupled with the track circuit in such manner as to provide the relay with slow pick-up characteristics. Various means are provided to eifect this coupling. In Fig. 1, for example, the retaining winding is coupled to the track circuit through the medium of a secondary winding I8 disposed on core 5 and connected to retaining winding l I through a back contact I3-I9 of armature I; in Fig. 2 the coupling is effected through a condenser 20 (see Fig. 2) which may, for example, be of the electrolytic type, connected in series with retaining winding II across the track rails I and Ia in multiple with winding 5 of relay TR; in Fig. 3 the coupling is effected through the medium of an auxiliary transformer 22 (see Fig. 3) having a primary winding 23 interposed in series in the connection of winding Ii of relay TR to the track rails and having a secondary winding 24 connected over back contact I3I9 of armature I to retaining winding I I; and in Fig. 4 the coupling is also effected by means of auxiliary transformer 22.

The operation of the apparatus illustrated in Fig. 1 is as follows: When section DE is unoccupied, armature I of relay TR is in its attracted or upper position as shown in the drawing, and in this position of armature 1 front contact I2--I5 of relay TR is closed to complete the obvious circuit path which connects resistor I! and a portion of coil 6 of relay TR across the rails I and la. The parts of relay TR preferably are designed and proportioned in such manner that with only a portion of coil 6 energized, an energy level only sufficiently above the release value of the relay to assure reliable operation of such relay under the various ballast conditions, is created in the relay due to current supplied to the portion of coil 6 of the operating winding from the rails I and 1a.

When a train enters section D--E, the current supplied from the battery 'I'B to the rails I and I a. is shunted away from the operating winding 6 of relay TR. Since the relay armature is held attracted by an energy level only slightly in excess of its release value, the shunt applied to the relay causes the energy level in the relay to decrease and as a result armature I quickly drops to its released position, wherein contact members I2, I3 and I4 engage their respective back contact points. During the travel of armature I from its attracted to its released position, contact member I2 makes engagement with back contact point I6 prior to breaking engagement with front contact point I5, thereby avoiding opening of the relay circuits.

In the released position of armature I of relay TR, back contact I3--I9 is closed to connect; retaining winding II to secondary winding Midisposed on core 5. Also, resistor I is placed on open circuit and the entire operating winding ii of relay TR is connected across the track rails I and la over back contact I2-IB, thereby conditioning the relay to create its pick-up energy level. When the train shunt is removed from relay TR, as for example, when the train vacates section DE or when the shunt is momentarily lost due to rail film conditions or other poor shunting conditions, current from battery TB is supplied through rails I and la to the entire operating winding 6 of relay TR. During the building up of flux in core 5 dueto such current, an electromotive force is induced in the secondary winding I8 disposed on core 5 and is applied through back contact I3-I9 to retaining winding II. The flux set up due to current in winding Ii threads armature 8 to hold that armature down and thus opposes the action on armature 1 of the flux due to current in winding 6. If the energization of the relay operating winding is caused b'y'the train vacating the section, the action of winding II in opposing the pick-up eifect of the flux due to current in winding 6 i lnotions to maintain armature 1 released until the flux condition in core reaches substantially a constant state condition so that no electromotive forces are induced in secondary winding I8. This steady state flux condition in core 5 substantially corresponds to the pick-up energy level of the relay, and since under the condition of flux equilibrium in core 5 no current is induced in winding I8, the attractive effect of the flux due to current in winding 6 on armature I is no longer opposed by the attractive effect on armature 8 of flux due to current in winding II, with the result that armature I is operated to its picked-up position wherein back contact I3--I9 is opened to disconnect retainingwinding I I from secondary winding I8, and contact member I2 is operated from its released to its attracted position to form front contact I2--I5 prior t breaking engagement with back contact point IS. The closing of front contact I2--I5 connects resistor I! in circuit with a portion of operating winding 5 of relay TR across the track rails I and Ia, hence armature I of relay TR is held in its attracted position by virtue of the energization of only a portion of the operating winding 8 of relay TR and the energy level of the relay accordingly is reduced to a value only slightly greater than the release value of the relay, as was pointed out heretofore. Resistor I1 is selected to have a resistance substantially equal to the resistance of the portion of winding 6 that is cut out when the relay is picked up, hence the resistance of the relay is substantially the same in both its released and picked-up positions, and the percentage reduction of flux, effected when the relay is picked up, iscaused to be independent of the track circuit length and adjustment. Relay TR accordingly is caused to be slow to pick up, and when the train vacates its associated section, the pickup of the associate. relay is delayed for an interval suflicient to enable the train to shunt the relay of the section in advance and cause such advance track relay to be released to establish the proper directional set-up, signal control, locking, or other function wherein it is required for proper operation that the advance relay be released prior to the rear relay picking up.

In the event that armature I of relay TB. is released so that its entire operating winding 8 is connected in circuit with the track rails, and

current is supplied from the rails to such winding due to a loss of shunt in section D-E, then retaining winding II is energized by current supplied from secondary winding I8 during the building up of flux in core 5 and armature I is held down due to the attractive effect on armature 8 of flux due to current in retaining winding I I. This hold-down effect of winding I I prevents armature I of relay TR from picking up immediately on a loss of shunt, and provides a delayed pick-up period for relay TR sufiicient under normal conditions to enable the train shunt to be restored and the winding 6 again to be shunted prior to armature 'I being attracted from its released to its picked-up position. It can be-seen, therefore, that the delayed response characteristics of a relay of the class illustrated in Fig. l prevents improper operation of the relay due to a momentary loss of train shunt in its associated section.

It should be noted that the contacts operated I2 of relay TR function as contacts during the travel of from its released to its by contact member make-before-break the relay armature picked-up position, that is, front contact I2--I5 is closed prior to back contact I2--I6 being opened. In addition, the operation of these contacts is effected by the travel of armature I from its released to its picked-up position only after the pick-up energy level is created in the relay, hence armature I is attracted in response to a relatively high energy level available in the relay and moves rapidly due to the magnetic force present in the relay. The momentum developed due to the rapid movement of armature I is, therefore, sufficient to carry the armature to its fully attracted position even though the energy level in the relay is reduced when back contact I2-I6 opens. With armature I in its fully attracted position, the reduced energy level available in the relay after front contact I2-I5 closes is effective to maintain the armature in its,

picked-up position.

In addition, it should be noted that secondary winding I8 disposed on relay core 5 is open circuited at all timesexcept when back contact I3l9 of the relay is closed and it follows that when armature I is picked up, winding I8 cannot operate to delay the decay of relay flux such as might happen if winding I8 were connected at all times in circuit with retaining winding Ii.

I have represented in Fig. 2 a modified arrangement of the relay shown in Fig. 1, wherein retaining winding II is coupled to the track circuit through a condenser 20 which is charged when the section becomes unoccupied, and which discharges through retaining winding I I and the train shunt when the section becomes occupied. During the interval that condenser 20 becomes charged, winding II is energized and functions to hold down armature 8 and thus oppose operation of armature I. For example, when relay TR is shunted, armatures 1 and 8 are released and condenser 20 is discharged. When the shunt is removed, the charging current of the condenser flows through retaining winding II and of course is effective to energize winding II to create flux which tends to hold armature B in its released position against the attractive effect on armature I of flux due to current in winding 6, thereby rendering the relay slow to pick up. When the section becomes occupied, the condenser discharges through winding II and the low resistance train shunt, but this action has little or no effect upon operation of the relay at this time other than to condition the condenser to become charged again when the section becomes vacated. It is, of course, readily apparent that by properly proportioning condenser 20, the relay shown in Fig. 2 may be provided with slow pick-up characteristics substantially similar to those pointed out in connection with relay TR of Fig. 1. It is further apparent that the relay shown in Fig. 2 functions to vary the energy level in the relay after it picks up in substantially the same manner that such energy level is varied by the apparatus represented in Fig. 1.

The apparatus represented in Fig. 3 illustrates a further modification of the apparatus of Fig. 1

wherein retaining winding II is coupled to the track circuit by means of a transformer 22 having its primary winding 23 interposed in the connection of winding 8 to the track rails. Secondary winding 24 of transformer 22 is connected to retaining winding II when back contact I3-I9 is closed, and it is readily apparent that the apparatus shown in Fig. 3 will operate in substantially the same manner as that illustrated in Fig. 1 to provide slow pick-up characteristics and vary the energy level of the relay after it picks up.

A still further modification of the apparatus illustrated in Fig. 1 is represented in Fig. 4, wherein a polarized relay TRI is interposed in a polarized track circuit supplied with unidi-' rectional current of one relative polarity or another from battery TB according as pole changing contacts 26 and 21 are in their picked-up or released positions, respectively. Relay TRI is ance with the polarity of current energizing opcrating winding 8 of th relay.

Relay 'I'Rl, as shown, is provided with an auxiliary magnetic structure 30 carrying retaining winding II and provided with a core extension I 0 arranged to hold down armature 8 when winding H is energized. Core extension I0 of relay 'IRI therefore corresponds to auxiliary cores l0 shown in Figs. 1, 2 and 3. When armature I of relay TRI is in its upper attracted position, armature .8 is operated into magnetic relation to core 30 so that when winding H is energized, armature 8 is attracted to core 30 and functions to hold armature 'l in its upper position. Winding II is connected to secondary winding 24 of transformer 22 which has its primary winding 23 interposed in the connection of operating winding 6 of relay 'I'Rl to the track rails. Relay 'I'RI also incorporates the make-betore-break contact arrangement hereinbei'ore described and by means of which the energy level in the relay is varied according as the relay is released and picked up.

When section DE is unoccupied and pole changing contacts 28 and 21 are in their upper positions as shown in the drawing, current of one relative polarity which I shall term positive polarity is supplied through the track rails l and la to a portion of operating winding 6 of relay TRI. The parts of relay TRI are so proportioned that with only a portion of winding 8 energized, the energy level created in the relay is sufiicient to hold neutral armature l in its upper attracted position, and with relay 'I'Rl energized with current of normal polarity, polar contact member 28 is operated to its normal oi. left-hand position, as viewed in the drawing.

If, now, pole changing contacts 26 and 21 operate to their released positions, current of the opposite or reverse polarity is applied through transformer 22 to operating winding 8 of relay TRI. During the interval of flux reversal in transformer 22, an electromotive force is induced in secondary winding 24 of the transformer and is applied to retaining winding II to energize that winding and attract auxiliary armature 8. The parts of relay 'IRl are so proportioned that the energization of retaining winding ll efiected due to a reversal of current in winding 23 ottransformer 22 is effective to hold armature 8 in its upper position until the flux in core 5 builds up to its value sufllcient to hold armature I in its attracted position. It follows, therefore, that neutral armature 1 of relay TB! is held in its upper attracted position during the intervals of current reversals in the track circuit. Under the assumed conditions, polar contact member 29 will of course be caused to operate to its reverse or right-hand position, as viewed in Fig. 1.

When section D-E becomes occupied by a train, the current supplied from battery TB is shunted away from operating winding 5 of relay TRI and neutral armature l releases to open front contact I2l5 and close back contact lZ-lB, the closing of this latter contact conmeeting the entire operating winding 6 of relay 'IRI in circuit with the track rails. When the section becomes vacated, therefore, the entire operating winding of relay TRI is available to create flux and pick up neutral armature 1. However, the energizatlon of operating winding -6 of relay TR! causes the induction in secondary winding 24 or transformer 22 of an electromotive force which energizes winding H and causes flux to thread core extension l0 and armature 8 to hold armature 7 down against the attractive effect of flux due to current in winding 5. After the current in winding 6 attains substantially a constant state condition, winding It becomes deenergized and no longer opposes the attractive effect of flux due to current in winding 6 on armature 1, so that the armature moves rapidly from its released to its attracted position, thereby opening back contact l2-l6 and closing front contact i2l5. The closing of front contact l2-l5 of course results in the energization of only a portion of operating winding 6 of relay TRI, and the energy level created in the relay is therefore reduced to a value only slightly greater than the releasevalue or the relay. It follows, therefore, that relay ml is made slow to pick up, is held in its attracted position during inter vals of reversals of current polarity in the oper ating winding of the relay, and the energy level in the relay is varied according as the relay is released or picked up in order to attain more satisfactory shunting characteristics for the relay.

Although I have herein shown and described only four forms 01' track circuit apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a magnetizable core, armature means disposed in magnetic relation to said core and provided with contacts including a make-before-break contact combination comprising a front contact and a back contact with a bridging member which causes both said contacts to become closed momentarily during the movement of said armature means from its released to its attracted position, an operating winding disposed on said core and effective when energized to actuate said armature means from its released to its picked-up position, a control circuit connected to a portion only of said operating winding over said front contact and to the entire operating winding over said back contact, a retainingwinding disposed to be efiective when energized to oppose the attractive action of said operating winding on said armature means, and a condenser connected in series with said retaining winding across said control circuit in multiple with said operating winding.

2. In combination, a magnetizable core, armature means disposed in magnetic relation to said core and provided with contacts including a make-before-break contact combination comprising a front contact and a back contact with a bridging member which causes both said contacts disposed on said core and efiective when energized to actuate said armature means from its released to its picked-up position, a control circuit connected to a portion only of said operating winding over said front contact and to the entire operating winding over said back contact, a retaining winding disposed to be effective when energized to oppose the attractive action of said operating winding on said armature means, and a transformer having a primary winding interposed in the connection of said operating winding to said control circuit and having a secondary winding connected to said retaining winding over a back contact operated by said armature means.

3. In combination, a magnetizable core, an armature disposed in magnetic relation to said core, an operating winding on said core for actuating said armature, contacts operatively connected to said armature and operated from one position to another in response to energization of said operating winding, 3. control circuit connected to a portion only of said operating winding over a contact of said armature closed in its said other position and connected to the entire operating winding over a contact of said armature closed in its said one position; and a retaining winding supplied with current during a growth of flux in said core due to current in said entire operating winding, said retaining winding being disposed so as to be effective when energized to retain said armature in its said one position in opposition to the attractive action of said operating winding on said armature.

4. In combination with a control circuit, a niagnetizable core, an armature disposed in magnetic relation to said core, an operating winding connected to said control circuit and disposed on said core for actuating said armature, contacts operatively connected to said armature and including a front contact operated from an open to a closed condition in response to operation of said armature from its released to its attracted position caused by energization of said operating winding, a retaining winding inductively coupled to said control circuit when said armature is released and disposed to oppose the attractive action 01' said operating winding on said armature, and means controlled by said front contact for decreasing the energization of said operating winding by said control circuit, whereby said op-- erating winding is conditioned to create a high or a low energy level in the core according as said armature is released or is picked up.

5. In combination, a magnetizablc core, an op crating winding disposed on said core, an arma ture disposed in magnetic relation to said core and provided with contacts including a makebefore-break contact combination comprising a front contact and a back contact with a, bridging member which causes both said contacts to become closed momentarily during the movement of said armature from its released to its attracted position, a control circuit connected over said front contact to a portion only or said operating winding and connected over said back contact to the entire operating winding, 2. retaining winding disposed to oppose the attractive action of said operating winding on said armature, and a secondary winding disposed on said core and connected to said retaining winding over a back contact operated by said armature.

6. In a relay, in combination, two magnetizable cores, an armature biased away from one toward the other 01' said cores, an operating winding on said onecore for actuating said armature to said one core, contact members controlled by said armature from one position to another in response to the energization of said operating winding, a retaining winding disposed on said other core and eil'ective when energized to delay the response 0! said armature to energize.- tion of said operating winding, and means including a secondary winding disposed on said one core and a contact closed in said one position of said contact members for energizing said retaining winding.

7. In combination, two magnetizable cores, an armature biased away from one toward the other of said cores, an operating winding on said one core for actuating said armature against its bias to said one core, contacts operatively connected with said armature and operated from one position to another when said armature is actuated to said one core, a control circuit, means controlled by contacts of said armature for connecting only a portion of said operating winding with said control circuit when said other position and for connecting the entire operating winding with said control circuit when said contacts occupy their said one posi tion, a retaining winding disposed on said other core, and means for supplying energy to said re taining winding during the growth of flux in said one core due to cm nt in said entire operating winding, whereby energy in said retaining wind ing creates firm actin on said armature in opposition to the flux created by energy in said entire operating winding for delaying actuation of said armature from said other core to said one core.

ARTHUR E. DODD.

said contacts are in

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