US3663809A - Detection of end zones in alternating track circuits - Google Patents

Detection of end zones in alternating track circuits Download PDF

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Publication number
US3663809A
US3663809A US34237A US3663809DA US3663809A US 3663809 A US3663809 A US 3663809A US 34237 A US34237 A US 34237A US 3663809D A US3663809D A US 3663809DA US 3663809 A US3663809 A US 3663809A
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Prior art keywords
shunt
circuit
track
rails
track circuit
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Expired - Lifetime
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US34237A
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English (en)
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Henry C Sibley
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SPX Technologies Inc
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General Signal Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L1/00—Devices along the route controlled by interaction with the vehicle or train
    • B61L1/18—Railway track circuits
    • B61L1/181—Details
    • B61L1/187—Use of alternating current

Definitions

  • ABSTRACT A continuous rail track circuit apparatus having termination shunts at each end detects the presence of a railroad vehicle shunt across the rails and indicates vehicle presence.
  • Shunt means near one end of the track circuit periodically introduces a test shunt across the track
  • U 8 Cl 246/34 CT 246/40 pled to the rails near the other end of the track circuit is sensi- [511 23/30 tive to changes in track circuit parameters occasioned by the test shunt and respondingly introduces a reply test shunt in ac- [58] Field of Search ..246/34 R, 34 CT, 36, 40 cordance with the period of the Shunt means- Means at the [56]
  • References Cited first end of the circuit sensitive to changes in track circuit parameters occasioned by the reply test shunt provides indica- FOREXGN PATENTS OR APPUCATIQNS tion of vehicle presence when the change in track circuit parameters ceases. 1,036,142 9/1953 France ..246/34 CT 9 Claims, 4 Drawing Figures T ⁇ 1 END ZONE I CENTER ZONE I END ZONE I T l PULSE
  • the train Since the train must be considered to be less than a perfect short circuit, the train close to the shorting bar will have very little effect on the track circuit and will not be detected.
  • the length of this blind spot depends on frequency and the adjustment of the receiver can easily range between 2,000 feet at 65 hertz and feet at 7 kHz.
  • the scheme herein is for a track circuit which is terminated by a shorting bar and can detect a single 0.06 ohm shunt within a foot or two of the ends.
  • a continuous rail track circuit apparatus having termination shunts at each end.
  • the track circuit detects the presence of a railroad vehicle shunt across the rails which is indicative of vehicle presence.
  • Shunt means near one end of the circuit periodically introduces a test shunt across the tracks and a receiver means coupled to the rails near the other end of the circuit is sensitive to changes in the circuit parameters occasioned by the test shunt.
  • the receiver periodically introduces a replytest shunt in accordance with the period of the shunt means and means at the first end of the circuit is sensitive to changes in circuit parameters occasioned by the reply test shunt and provides indication of vehicle presence when the change in circuit parameters ceases.
  • the track circuit parameters referred to as being changed by the shunt are an increase in track circuit current in the area of a test shunt and a resulting increase in carrier current shift frequency feeding the track circuit as a means for communicating the detection of the test shunt at one end of the track circuit to the opposite end of the track circuit.
  • a track circuit having three zone defined track circuits including a center zone track circuit and two end zone track circuits having one end coupled to an end of the center zone and terminated at the other end of the termination shunt.
  • the track circuits have characteristics such that the signals present in the rails and blocked by a vehicle shunt present in the center zone and increased by a vehicle shunt present in the end zones. Means responsive to both the blockage and increase in the signals provides indication of vehicle presence.
  • FIG. 1 is a schematic diagram showing the apparatus necessary for practice of the present invention
  • FIG. 2 is a circuit detail showing track coupling and the shunt means
  • FIG. 3 is a repeater station for extending track circuit length
  • FIG. 4 is a waveform diagram showing introduction of coded information as well as vehicle detection.
  • Receivers sense current at the ends opposite their transmitters by means of loops or small coils mounted close to the rail.
  • the train anywhere along the track, except close to the ends, will reduce the current into the receivers to the point where detection is certain.
  • the ends are the problem.
  • a train close to the end will not reduce received current appreciably, but it will increase the transmitted current.
  • Receivers tuned to the local transmitter frequencies are added to each end to detect when track current is increased by a train.
  • the system described here shows three track circuits detecting vehicles. In the center zone or circuit most of the length of the track circuit vehicles are detected in the conventional closed circuit manner. The two end zone circuits are checked by the open circuit series method and the three readings are combined in a logic scheme that provides fail-safe train detection, security against operation by false signals, and a choice of such options as a simple repeater to double the circuit length and message handling capability for traffic control and cab signals.
  • the end zone requiring special detection means is a length of track having the shorting bar at one end and having an impedance of approximately 0.6 ohm looking into the other end. If a train having a shunt value of 0.06 ohm stands at the end of this track section, the current divides sending approximately 90 percent through the train axle and leaving only 10 percent for the receiver at the far end of the track section. A train further from the end will cause a greater reduction in receiver current because the end zone has even a higher impedance.
  • the series circuits at the ends must detect a train at a distance where the track impedance is 0.6 of an ohm or more.
  • a track circuit of this type will probably work well over a mile with ballast resistances as low as 5 ohms in 1,000 feet.
  • the end zones; that is, the 0.6 ohm track sections are about 500 feet long. A short poor shunting vehicle might be lost within 500 feet of the ends unless the special end zone circuits are used.
  • the transmitting loop and its 8 foot section of track may be considered as a transformer feeding a mile long track circuit with a short at the far end.
  • This mile long track circuit will look like a load that varies between 2 and 7 ohms depending on ballast resistance if there are no trains. If a train is within 500 feet of the end, the transformer will feed a load of 0.6 ohm or less.
  • the receiver sensing transmitter current must indicate occupancy when the current is that value which fiows through 0.6 ohm or less. At lower current values it need not indicate occupancy because track current increases as the shunt moves away from the receiver and at the current value that flows into a mile of wet track, for example, 2 ohms it must not indicate occupancy.
  • the current detector is tested by simulating a train at the limit of the end zone. Since by the conventional method of track shunting it is possible to detect a train at a distance of across the track at the end of the transmission loop and will affect the circuit such that the same current in the track circuit is produced as if a train were present within the 500 foot end zone section.
  • This resistor is alternately switched in and out of the circuit continually testing the end zone circuit. This resistor affects only the end zone being tested and'has negligible effect on the signal transmitted from the end zone being tested to the other end of the circuit. If this were not true, there would be no problem detecting trains near the ends.
  • This track circuit uses track transmitters which are of the frequency shift keyed type. Receivers responsive to the transmitters can detect which way the transmitters are shifted and have the added safety feature that they will respond to both shifts simultaneously so that any interference that produces what looks like an impossible condition, will not be resolved but will result in a safe failure.
  • This carrier equipment plus cycle checked logic combine the end zone and main line signals.
  • FIG. 1 shows a railroad track circuit including a set of rails indicated by reference R terminated at end by a termination shunt S
  • the first or left end of the track circuit is fed by a track transmitter T, including an oscillator capable of generating an F, frequency and an amplifier 11 which increases the gain of the carrier frequency F, and couples it to the rails R through a loop transmitter 12.
  • a pulse generator 13 drives a track test shunt 14. Shown in FIG. 2, this consists of a relay l5 driving its contact 16 in series with a 0.6 ohm resistor 17 coupled across the track rails R.
  • This track test shunt 14 periodically is coupled across the rails R and the shunt in the rails produced by the coupling of the F, signal by loop 12 increases.
  • a receiver R1 responsive to the F, frequency is capable of detecting an increase in track current.
  • the receiver R consists of a filter l8 and a detector 19 calibrated so as to detect some threshold current.
  • the detector 19 provides a signal to the transmitter T, and in particular to the oscillator 10. This signal causes the oscillator to shift up the basic frequency F, to some preselected value F
  • This signal F,+ is thence coupled to the rails R through loop 12 and transmitted to the second or right end of the track circuit.
  • a receiver R responsive to the shifted frequency drives a return shunt relay 20.
  • the receiver R consists of a filter 21 which responds to the frequency F,+ and an amplifier 22 which is used to increase the gain of the received signal and drive a flip-flop 23 one output of which is coupled to the return shunt 20.
  • the return shunt actuates a contact 16 coupled in series with a resistor 17 across the rails R. This periodic shunting in accordance with the receiver R, causes an increase in the track current.
  • Track current for the second end is provided by a second transmitter T feeding the rails through transmitting loop 25.
  • Transmitter T consists of an oscillator 26 generating a frequency F, and an amplifier 27 for increasing the gain of the oscillator signal and coupling the second carrier F to the rails R via the transmitting loop 25.
  • the current necessarily increases and a receiver R, responsive thereto drives the transmitter T into a shifted frequency F
  • the receiver R consists of a filter 28 responsive to the carrier frequency and a detector 29 capable of detecting a preset current threshold for providing a signal to the transmitter T
  • the receiver R provides the shift signal to the transmitter T the shifted frequency signal is coupled to the rails through the loop coil and transmitted back to the left end of the track circuit.
  • a receiver R is responsive to the shifted frequency 5+ and provides an output signal to flip-flop 30.
  • the receiver R consists of a filter 31 and a driving amplifier 32 for providing an output signal to the flip-flop 30.
  • the pulse generator 13 is coupled to output logic circuitry 40, as is the R
  • the test shunt 14 is activated which causes an increase in track current and shift-up of frequency oscillator 10 with a subsequent reaction at the right end of the track circuit and a return test shunt, which is in turn received by the receiver R,'.
  • the inputs to the output logic 40 must occur with a certain predetermined phase relation one to the other. If, for any reason, the return test shunt is interrupted as by a failure of the apparatus or a vehicle shunt, the output logic 40 will provide an indication of such a condition by deenergizing the output relay 41 and dropping its associated front contact 42.
  • a train in the center section of the track circuit about 500 feet from each termination shunt S will completely interrupt communication from one end of the track circuit to the other.
  • the receiver R, or R depending upon the direction of travel of the vehicle will be activated by an increase in the current.
  • the current in the track circuit remains above that threshold and the receiver R, or R is always activated.
  • the period rate of introducing the test shunt 14 to the circuit by pulse generator 13 is therefore substantially bypassed because the transmitter R, is always in the shift-up position.
  • the output logic 40 senses a cessation of the inputs at required periodic intervals and causes the relay 41 to drop its contact 42.
  • the logic 40 as previously noted in response for holding the relay 41 energized only wne its two inputs are satisfied.
  • Diodes 48 and 49 assure that only pulses of the proper polarity actuate the associated relay.
  • the contacts 46 and 47 are coupled to AND gate 50 to alternate sets of associated inputs.
  • the second input to the output logic 40 is provided from the output of flip-flop 30 through transformer 51 for driving the relays 52 and 53 and their associated contacts 54 and 55 respectively.
  • the diodes 56 and 57 permit activation of the associated relays 52 and 53 only upon proper polarity as provided through the transformer 51 from the flip-flop 30.
  • the contacts 54 and 55 are also coupled to the AND gate 50 to alternate inputs and as can be seen from the drawing, the contacts 46, 54 and 47, 55 are associated inputs to the AND gate 50.
  • a repeater station near the mid-point of the track circuit may be installed and substantially double the length of the circuit.
  • the repeater circuit is coupled to the rails R at the mid-point as shown in FIG.
  • the second receiver R responsive to F includes a filter 63 and amplifier 64 driving frequency detector 65 which has an output which drives a second input to transmitter T
  • Frequency detectors 62 and 65 are connected to oscillators in the transmitter T one of which is a shift-up oscillator 66 and the other is a shift-down oscillator 67.
  • the receivers at opposite ends of the track circuit shown in FIG. 1 corresponding to R, and R are responsive when used in connection with the repeater station to the F and F signals respectively. The same continuity of indication is provided using the repeater station. However, an extra frequency shift transmitter T is necessary and variation in the receiver circuits necessary for receiving the particular mid-station signals are provided. This modification provides for nearly double the track length with a minimal amount of additional apparatus.
  • Code communications may be incorporated into this track circuit by utilizing an encoder 69.
  • a shift-down signal may be provided which is illustrated in the waveform diagram of FIG. 4.
  • the center frequency or carrier F, and a shift-up to the F signal provides the vehicle detection information as previously described.
  • the shift from F to F can be utilized to provide coded information during the times when the test shunt l4 and return test shunt are not activated by initiating the shift-up phase of the vehicle detection. If, for example, as is contemplated in the present invention, a test shunt is introduced every second or some short interval of time, perhaps 50 milliseconds, then the remainder of the one second interval is available for transmission of coded information. Under these conditions, therefore, it is possible to provide not only vehicle detection information but also the cab signaling and 4 other useful indications without the necessity of providing wayside line wires.
  • Decoding is accomplished by coupling decoder 68 to one input of the output logic 40 associated with flip-flop 30.
  • Information from encoder 69 may be supplied by some program or other external source such as for example a hot box detector. Decoder 68 output may be coupled to a signal on other warning devices to be actuated in accordance with the information supplied by encoder 69.
  • the above is merely an example and it is obvious that many purposes may be seen by such a communications channel.
  • a continuous rail track circuit apparatus having termination shunts at each end for detecting the presence of a railroad vehicle shunt across the rails indicative of vehicle presence comprising:
  • a. shunt means near one end of the circuit for periodically introducing a test shunt across the tracks
  • receiver means coupled to the rails near the other end of the circuit sensitive to change in circuit parameters occasioned by said test shunt for respondingly introducing a reply test shunt in accordance with the period of the shunt means;
  • c. means at the first end of the circuit sensitive to change in circuit parameters occasioned by said reply test shunt for providing indication of vehicle presence when said change in circuit parameters ceases.
  • transmitter means coupled to the rails at the first end for feeding the rails with a carrier signal
  • shift means responsive to an increase in track current occasioned by the test shunt for shifting the frequency carrier signal.
  • test shunt means comprises:
  • switch means serially connected with said impedance operative when actuated by said drive means for shunting said track with the calibrated impedance.
  • driver means includes a pulse generator for providing periodic pulses of energy for actuating said switch means.
  • a. reply test shunt means at the second end for shunting the rails in the vicinity of the termination shunt
  • second transmitter means at the second end for feeding the circuit with a second carrier signal
  • second shift means responsive to an increase in track current occasioned by the reply test shunt for shifting the frequency of the transmitted signal.
  • a capture receiver coupled to the rails responsive for generating a signal in accordance with the occurrence of the second frequency shift carrier
  • output logic means responsive to the period of the first shunt means and the capture receiver signal for providing an output signal as long as the period of the first shunt means agrees with the occurrence of the second shifted carrier signal, said output indication of a clear track circuit and ceasing the output upon occurrence of disagreement of the signals thereby providing indication of vehicle presence.
  • a switching means for changing conductance state in accordance with each state of said capture receiver and said driver means
  • gate means responsive to positive and negative conductance states of the capture receiver and driver means respectively for generating an output when said conductance states are in phase correspondence and clearing said output for indicating vehicle presence when said correspondence ceases, thereby providing synchronism of the ends of the track circuits such that spurious signals are substantially ineffective to actuate said output logic means to an unsafe condition.
  • a continuous rail track circuit apparatus having termination shunts at each end for detecting the presence of a railroad vehicle shunt across the rails indicative of vehicle presence comprising:
  • a. train simulation means near one end of the circuit for periodically introducing a fixed impedance across the rails commensurate with an ideal vehicle shunt at a selected distance from the end of the track circuit
  • tion shunt for providing indication of vehicle presence when said change in circuit parameters ceases.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
US34237A 1970-05-04 1970-05-04 Detection of end zones in alternating track circuits Expired - Lifetime US3663809A (en)

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CA (1) CA933641A (enExample)
DE (1) DE2121971A1 (enExample)
FR (1) FR2091201A5 (enExample)
GB (1) GB1341465A (enExample)
NL (1) NL7106098A (enExample)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951364A (en) * 1975-01-09 1976-04-20 General Signal Corporation Track circuit
US4467430A (en) * 1980-09-22 1984-08-21 Compagnie De Signaux Et D'entreprises Electriques Railway track circuit
EP0217297A3 (en) * 1985-09-28 1989-01-18 Ivv Ing Verkehrsplan Verkehrsicherung Track circuit with or without insulated joints for railway systems
EP1634793A1 (en) * 2004-09-09 2006-03-15 Westinghouse Brake And Signal Holdings Limited Train detection

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CS217737B1 (en) * 1980-04-04 1983-01-28 Oldrich Poupe Connection of the railway circuit with plural signalling sources
FR2486006A1 (fr) * 1980-07-07 1982-01-08 Jeumont Schneider Boucle induisant un courant dans les deux rails d'une voie ferree
MX2022004535A (es) 2019-10-14 2022-09-19 Athena Industrial Tech Inc Detector de rieles rotos.
US12459551B2 (en) 2019-10-14 2025-11-04 Athena Industrial Technologies Inc. Broken rail detector

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1036142A (fr) * 1950-04-27 1953-09-03 Materiel Telephonique Circuit de voie pour système de sécurité de transport par rails

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1036142A (fr) * 1950-04-27 1953-09-03 Materiel Telephonique Circuit de voie pour système de sécurité de transport par rails

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951364A (en) * 1975-01-09 1976-04-20 General Signal Corporation Track circuit
US4467430A (en) * 1980-09-22 1984-08-21 Compagnie De Signaux Et D'entreprises Electriques Railway track circuit
EP0217297A3 (en) * 1985-09-28 1989-01-18 Ivv Ing Verkehrsplan Verkehrsicherung Track circuit with or without insulated joints for railway systems
EP1634793A1 (en) * 2004-09-09 2006-03-15 Westinghouse Brake And Signal Holdings Limited Train detection
US20060060724A1 (en) * 2004-09-09 2006-03-23 Francis Jonathan D Train detection
US7523893B2 (en) 2004-09-09 2009-04-28 Westinghouse Brake And Signal Holdings Limited Train detection

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GB1341465A (en) 1973-12-19
NL7106098A (enExample) 1971-11-08
DE2121971A1 (de) 1971-11-25
CA933641A (en) 1973-09-11
FR2091201A5 (enExample) 1972-01-14

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