US3395274A - Movable block train speed control system - Google Patents

Description

G. w. BAUGHMAN 3,395,274

2 Sheets-Sheet l `uly 30, 1968 MOVABLE BLOCK TRAIN SPEED CONTROL SYS-TEM Filed Jan. 12, 196e July 30. 1968 G. w. BAUGHMAN MOVABLE ELOCK TRAIN SPEED CONTROL SYSTEM Filed Jan. 12, 196e 2 Sheets-Sheet 2 .lillllllllllln..

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HL; ATWOQNEY United States Patent O 3,395,274 MOVABLE BLOCK TRAIN SPEED CONTROL SYSTEM George W. Baughman, Swissvale, Pa., assignor to Westinghouse Air Brake Company, Swissvale, Pa., a corporation of Pennsylvania Filed Jan. 12, 1966, Ser. No. 520,125 4 Claims. (Cl. 246-187) ABSTRACT OF THE DISCLOSURE This invention relates to a train speed control system which includes a Wayside transmitter arrangement to deliver a speed control signal to trains approaching the wayside transmitters. A train speed command receiver and a train speed responsive transmitter are carried by each train. The train speed responsive transmitter produces a train speed control signal output at the rear of the train which is always indicative of a more restrictive train speed command than a train speed command signal received from a wayside transmitter arrangement being approached. The train speed responsive transmitter is thereby eifective to control the speed of a following train.

This invention relates to a movable block system for controlling the'speed of `one or more vehicles in such a manner that a vehicle operating within the system will automatically control the speed of a following vehicle.

More specically this invention relates to a train speed control system which includes a wayside transmitter arrangement to deliver a speed control signal to trains approaching the wayside transmitters. A train speed command receiver and a train speed responsive transmitter are carried by each train. The train speed responsive transmitter produces a train speed control signal output at the rear of the train which is always indicative of a more restrictive train speed command than a train speed command signal received from a wayside transmitter arrangement being approached. The train speed responsive transmitter is thereby elective to control the speed of a following train.

Close headway between trains has become the rule rather than the exception in modern high speed rapid transit systems. With decreasing headways being demanded to accommodate increased passenger transportation densities the problem of assuring that one train cannot overtake another slowly moving train has become manifestly critical. The prior art handled this problem by using iiagmen and some improvement has been attained by extensive use of wayside signaling. These just noted approaches have not provided a completely failsafe manner of avoiding rear end collisions. Even prior art systems that brought the following train to a halt automatically failed to provide a sutiiciently small headway which is called for in high speed rapid transit applications.

The invention to be described more fully hereafter allows significant decreases in headway under all dynamic conditions that are demanded by rapid transit systems of the present and the foreseeable future. In the system to be described, train'speed control signal information which is fed into the track at the rear of a train is always for a slower speed than that at which the train is moving. This means that the speed at which a following train would be authorized to move would always be less than the-speed of the train immediately ahead. This will tend to give a reasonable `spread of separation and thereby avoid the possible compounding of an accident in the event of sudden derailment of the lead train. Use of the invention to be described will allow control of the speed Patented July 30, 1968 of a train as it approaches an occupied station track. The greater the speed of the train leaving the station, the' greater would be the authorized speed of the following tram as it approached the station.

It should be recognized that while the invention is to be described in a railway environment, the invention is intended to include all mass transit applications where vehicle speed control is essential. Accordingly,l the references made hereafter to trains and rails are intended to refer equally to vehicles, and to electrically conductivel elements.

It is therefore an object of this invention to provide a train speed control system in which the headway between trains may be reduced to a minimum by the utilization of a train speed control signal fed to the tracks at the rear of a train.

It is another object of this invention to provide a posi tive, dynamically responsive speed control system for vehicles operating at minimum headways.

Another object of this invention is the provision of a train-carried speed control arrangement that may be readilly installed in territories that incorporate track detection sections separated by insulated joints.

In the attainment of the foregoing objects a movable block train speed control system is provided in territories characterized by the presence of a plurality of consecutive track sections defined by insulated joints. A train speed command, signal producing wayside transmitter is electrically coupled to the rails at the exit end of each track section and this transmitter provides a train speed command signal to control a trains speed entering the track section. Each wayside transmitter is controlled by a wayside receiver electrically coupled to the rails at the entrance end of the next succeeding track section. The trains that operate within the system have thereon a train speed responsive transmitter which transmitter has a signal output which is always less than the train speed command signal from the wayside transmitter of the track section entered by the train. This output from the train speed responsive transmitter is transmitted via an induction loop above the rails at the rear of the train which induces in the rails the output from the train speed responsive transmitter. This output signal induced in the rails controls the next wayside transmitter, to the rear through the wayside receiver of the track section entered to produce a train speed control signal in the next track section to the rear, which train speed control signal is dependent upon the signal produced by the train speed responsive transmitter.

In addition to the train speed responsive transmitter on each train there is also a train speed control unit which receives train speed control signals from the rails of the track section occupied. This train speed control unit responds to a train speed control signal from the wayside transmitter of the track section entered unless the track section is occupied by a train, at which instance the train speed control unit responds to and is controlled by the signal output from the train speed responsive transmitter of the train which is already occupying the track section.

Other objects and advantages of the present invention will become apparent from the ensuing description of illustrative embodiments thereof, in the course of which reference is had to the accompanying drawings in which:

FIG. 1 illustrates in block diagram form an embodiment of the movable block train speed control system of the invention.

FIG. 2 is an illustration of the typical resultant coded speed control signal .pattern that could arise in the employment of the invention.

FIG. 3 is a circuit diagram of the system set forth in FIG. 1.

A description of the above embodiment will follow and then the novel features of the invention will be presented in the appended claims.

Reference is now made to FIG. 1 in which there is illustrated in block diagram form a system which has incorporated therein the invention to be described more fully hereinafter. Specifically, there is depicted a train 11 traveling upon the rails 12 and 13. The train 11 passes through a plurality of track detection sections 1T, 2T and 3T as noted in FIG. 1. The train 11 carries thereon a train speed command receiver 61 which receives train speed command signals from the wayside. The train speed command signals received determine the speed of the train.

Each track detection section 1T, 2T and 3T is characterized, for example, with reference to track detection section 1T by the presence of insulated joints 17 and 18 at the right end of track detection section 1T and insulated joints 23 and 24 at the left-hand end of track detection section 1T. The rails 12 and 13 at the righthand end of the track detection section 1T are electrically interconnected by a winding 19 of impedance bond 20 which functions to balance the propulsion return current between the rails 12 and 13 when this system is employed in electrified territory. The exact details of the impedance bond 20 as well as the other impedance bonds 25, 39 to be noted hereafter may be had upon a study of the copending application for Letters Patent of the United States, Ser. No. 382,551, filed on July 14, 1964 by Ralph Popp, for Electric Induction Apparatus, now Patent No. 3,268,843, issued Aug. 23, 1966. The winding 22 of the impedance bond 25 at the left-hand end of the track detection section 1T electrically interconnects the rails 12 and 13 at that end. Electrically connected via the leads 57 and 58 to the rails 12 and 13 at either end of the winding 19 of the impedance bond 20 is a wayside transmitter 56. This wayside transmitter 56 delivers a train speed command signal to the rails 12 and 13 which is received by the train speed command receiver 61 through the conventional use of induction coils, not shown, but mounted on the front of the train over the rails 12 and 13. The wayside transmitter 56, in turn, is controlled by a code following receiver 53 which has its output 54 connected to the transmitter 56. This code following receiver and its precise function will be described more fully hereafter. At this point it is sutiicient to say that the code following receiver is electrically connected via the leads 51 and 52 to the rails 14 and 16 at either end of the winding 21 of the impedance bond 20. This code following receiver 53 is designed to detect the presence of coded energy in the rails 14 and 16 and produce an output over the output 54 from the code following receiver 53 which, in turn, controls and determines the output from the wayside transmitter 56 which is feeding the rails 12 and 13 of the track detection section 1T.

If track detection section 1T is unoccupied, a track circuit would be completed between the wayside transmitter 56, through electrical leads 57 and 58, the rails 12 and 13 and finally the wayside code following receiver 80 at the left-hand end of the track detection section 1T. The wayside receiver 80 is electrically connected to the rails 12 and 13 via the electrical leads 81 and 82. This wayside receiver 80, in turn, has a control output 83 which controls the wayside transmitter 95 which is electrically connected via the leads 96 and 97 to the rails 27 and 28 of the track detection section 2T. These rails 27 and 28 are electrically interconnected by winding 26 of impedance bond 25, Therefore, with the wayside transmitter 95 electrically connected to the rails 27 and 28 an additional circuit is completed which includes the wayside transmitter 95, the electrical leads 96 and 97, the rails 27 and 28, the electrical leads 85 and 86, and the wayside code following receiver 84. It will be seen that the wayside receiver 84 has an output 87 which, in turn, feeds the wayside transmitter 88 which CLD is electrically connected to the rails 33 and 34 via the the electrical leads 89 and 90. The rails 33 and 34 are electrically interconnected by a winding 36 of the impedance bond 30 at the right-hand end of the track detection section 3T, each of the track detection sections 1T, 2T and 3T being defined, respectively, by the presence of insulated joints 17, 18, 23, 24 and 31, 32. It will be noted that the windings 19, 21, 22, 26, and 29 and 36 are center tapped and are connected by electrical center tap leads 37, 38 and 39, respectively.

Returning now again to the description of the train 11 and its car-carried equipment. As has been noted, there `is located on each train to be utilized in the system a train speed command receiver 61 which receives the train speed command signals of a specific character which signal controls the train and is received inductively from the rails which the train is passing over.

The train also carries a speed responsive code producing transmitter 62 which is electrically connected via the leads 63 and 64 to a code transmitting loop 66 positioned in the rear of the train over the rails which the train is passing over. This code transmitting loop 66 inductively induces in the rails immediately beneath it, behind the train, a signal dependent upon the signal selected to be transmitted by the speed responsive code transmitter 62.

In general, it may be said that the speed responsive code transmitter detects the speed at which the train is actually traveling and is responsive to this actual speed to produce a train speed command signal to be delivered by the code transmitting loop 66 to the rails. This train speed command signal will always be of a character to effect a lower speed limit on a following train than the train .speed command signal being received by the train speed command receiver 61 from the wayside transmitter 56 which the train 11 is approaching in this figure. In other words, should the train 11 be receiving from the wayside transmitter 56 a train Speed command signal which authorizes a maximum speed, the train speed responsive code transmitter 62 would detect the actual speed of the train and produce a signal which would enforce a lower speed limit on a following train than the signal being delivered to the train 11 from the wayside transmitter 56. This signal would be impressed in the rails 12 and -13 immediately at the rear of the train 11.

It will be seen that in every situation to be described hereafter there will always be impressed in the rails immediately behind the train a train speed command signal which commands a lower train speed than the actual speed at which the train 11 is traveling. Therefore, in the track detection section or that portion of the track detection section immediately following the train there is always present a command signal indicative of a more restrictive train speed command. Therefore, a train (not shown) similar to train `11 approaching from the rear of train 11 would receive in its train speed command receiver a signal indicative of a more restrictive speed and thereby effect a slowing of the second or following train with respect to the speed of the train 11.

In the left-hand portion of track detection section 1T, the code following wayside receiverwith the train 11 occupying track detection section 1T will be shunted by the wheels and axles of the train so that the receiver will not receive current from 4the circuit which included the wayside transmitter 56. The only signal that the wayside receiver 80 will be able to detect or pick up is that signal induced in the rails by the code transmitter loop 66 at the rear of train 411. Accordingly, a signal delivered by the code transmitting loop 66 will travel along the rails 12 and 13 over the electrical leads 81 and 82 to the wayside code following receiver 80 whereupon this receiver 80 will control the wayside transmitter via the output 83 to produce in the track detection section 2T a train speed command signal which is dependent upon the speed at which train 11 is advancing. This may be better `appreciated from a study of FIG. 2 in which three distinctive situations are schematically illustrated. It is intended that FIG. 2 graphically illustrate the dynamic operation of the system. The precise cooperation of the wayside transmitters and receivers with the train speed responsive transmitter of the train will be explained in more detail with reference to FIG. 3..

Now with reference particularly to FIG. 2, it will be seen that at the u-pper portionl of FIG. 2, there is depicted a situation where train A shown at the right in this figure is standing, for example, in a station, in track detection section 1T. Since the train is standing in the station, the speed responsive transmitter located within the train would not have an output since the train only permits an output when the train is moving. Accordingly, the transmitting loop of the train A would not deliver to the rails any signal at all. Therefore, it will be seen that immediately to the left in the rear of the train A there is no signal in lthe rails behind the train in detection section 1T. Should a train somehow approach and enter this track detection section 1T, its train speed command receiver would not receive a signal and this train would immediately come to a halt. IIt will be appreciated as the description proceeds that whenever a train speed command signal is absent, asin the present instance, the track detection section 2T will then receive a command signal at a rate of 75 cycles per minute which, of course, is indicative of a restrictive speed but one which is not actually intended to bring the train to a halt. The presence of a code rate of 75 in the track detection section 2T, in turn, induces or causes to be produced in track detection section 3T a coded command rate of 120 cycles per minute and the presence of this coded command -rate of 120 in the track detection section 3T produces a coded rate in section 4T of 180 cycles per minute. This 180 code rate is indicative -of full speed ahead. Accordingly, the train B depicted in track detection section 4T will receive a signal at the 180 code rate and this train B will then operate in a full speed ahead mode.

In the second dynamic situation depicted immediately beneath .-the situation just described in which train A is standing, there is illustrated a dynamic situation where train A is moving at a speed between 40 and 75 miles per hou-r. Train A, in a manner to be described hereafter, and its associated train speed responsive transmitter will produce in its code transmitting loop at the rear of the train A a train speed command signal which is at a 75 code rate. Therefore, should a train be entering the track detection section 1T, this train would receive a command code rate of 75 and, therefore, would follow at the speed commanded by the 75 code rate. In this instance, this speed would not be suicient for the train following train A to overtake the train A; In a similar maner to that which was described with reference to the train standing in the station, the presence of a 75 code rate in track detection section 1T would produce in track detection section 2T a coded command rate of 120, andthe presence of a code rate of 120` in track detection section 2T would produce a code rate of 180 in track detection section 3T. This code rate of 180 in track detection se-ction 3T would Iproduce a code rate of 1-80 in track detection section 4T.

As this figure illustrates, the train B in track detection section 3T would receive a code rate of 180 and, therefore, train B would proceed at a full speed ahead.

There is depicted in FIG. 2 one final situation where at the bottom of this ligure .train A is moving at 75 miles per. hour or more. In this situation, the speed responsive code transmitter in train A would produce a code rate of 120. Now the train A is operating at its full speed ahead or its maximum rate and, therefore, the train A would have produced immediately behind it in the track detection section 1T a code rate of 120. This 120 code rate would be indicative of a speed less than the full speed ahead that the train A is traveling.

It will be seen that the headway permissible between train A and train B constantly decreases as the train speed of the lead train increases but at all times the command speed immediately following the lead train is less than the authorized command speed at which the lead train is traveling.

In these types of situations, it will be seen that the headway between trains may be greatly reduced and the trains following each other lare sure of the fact that at no time will there ever be a situation in which the second or following train may overtake the lead train and thereby produce a collision. The reason for this is that as a train slows down the speed responsive code transmitter located on the lead train A will produce a more restrictive code rate which will cause the following train B to slow down as it approaches the track detection section that the train A is occupying.

It will be seen, therefore, that the arrangement to be described more fully hereafter presents an inventive approach which `takes into account the dynamic nature of trains starting and stopping, entering and leaving stations, and in addition takes into account the fact that trains may be caused to slow down within .the system. At all times, the invention to be described hereafter will permit a safe headway between following trains, while simultaneously allowing the headway to be reduced to the minimum consistent with safety. The result that follows is that maxi- |mum traffic density will be permitted on any section of rail within the system.

Reference is now made to FIG. 3 which illustrates a preferred embodiment of the invention and includes all the essential elements of a complete circuit diagram setting forth the invention. In FIG. 3 wherever possible, reference symbols have been employed similar to those used with reference to FIG. 1 and, accordingly, a detailed reiteration of those elements already described with reference to FIG. l will only be mentioned again to the extent that they are essential to understand the operation of the system set forth in FIG. 3.

The train 11 is depicted in the right-hand portion of FIG. 3 in the same manner as was depicted in IFIG. 1. This train 11 is operating in track detection section 1T. The train 11 receives a coded train speed command signal from a wayside transmitter 56, via the electrical leads 57 and 58 and the `rails 12 and 13 of the track detection section 1T. This train speed command signal is received by the train speed commnad receiver 61 which inductively picks up the signals from the rails 12 and 13. It will be recognized that if the train speed command receiver 61 receives a command signal which is indicative of a maximum authorized speed the train would gradually increase its speed until the authorized speed commanded by the wayside transmitter 56 is reached. It is during this increase of speed by the train 11 that this system and the invention being described has one significant use in that there is placed in the rails 12 and 13 at the rear of a train a command signal which is indicative of a more restrictive speed than the actual speed of the train. As `a practicable matter in most instances the speed commanded by the signal being delivered to the rear of the train is less than the authorized speed being commanded by the wayside transmitter 56 at the :righthand end of the track detection section 1T. By convention, the wayside transmitter 56 is connected at the exit end of the track detection section 1T to the rails 12 and 13 by the leads 57 and 58. The entrance end of the track detection section is defined as the left-hand portion of the track detection section 1T where the wayside receiver 80 is electrically connected via leads 81 and 82 to the rails 12 and 13 immediately adjacent the insulated joints 23 and 24.

The train 11 has located thereon a speed responsive code transmitter 62 depicted in this figure removed from the train 11. It should be understood that the speed re- 7 sponsive code transmitter 62 is mounted on the train, and for purposes of illustration only is set forth beneath and away from the train 11. This transmitter 62 is electrically connected via the leads 63 and 64 to the code transmitting loop 66 positioned over the rails 12 and 13 at the rear of the train. The speed responsive code'trans-mitter has an oscillator 67 which is producing a carrier frequency of a suicient level so that this energy when placed in the rails will be effective to actuate the code following receiver 80 positioned at the entrance end of the track detection section 1T. The oscillator 67 provides as has been noted, a constant carrier frequency energy and this constant carrier frequency energy is delivered through a speed responsive switching mechanism 70. The speed responsive switching mechanism 70 is driven by a suitable connection to one of the trains axles (the connection to the axle is not shown). The speed responsive switching mechanism 70 has in this illustration two ranges of operation, one between O and 40 miles per hour and another between 40 and 75 miles per hour. The speed responsive mechanism 70 closes its front contact a at 40 miles per hour and closes its front contact b at 75 miles per hour and in so doing completes the following circuits. When the speed responsive mechanism 70 which is connected to the axle of the train is producing a rotary output to the speed responsive mechanism 70 which causes the mechanism to centrifugally advance the contact a into a closed position with the front contact a of the speed responsive mechanism 70 a circuit will then be completed from the oscillator 67, through the front contact a of the speed responsive mechanism 70, the back contact a of the 4repeater relay 75R, the contact 75 of the code transmitting relay CT, lead 63, to the transmitting loop 66, and thence over lead 64 back to the oscillator 67. In other words, the code transmitting relay CT, which receives its energy from a battery source having B and N terminals, will open and close the contact 75 at the code rate of 75 cycles per minute, thereby interrupting the energy from the oscillator 67. At this rate, this energy from the oscillator 67, as has been noted, is being delivered over the front contact 75 of the code transmitting relay CT. Coded energy is then supplied to the code transmitting loop 66 and thence to the rails 12 and 13 in the rear of the train.

When the train is operating at a speed of 75 miles per hour, the speed responsive mechanism 70 causes the contact b to complete a circuit from the battery terminal B over the .front contact b of the speed responsive mechanisrn 70 through the repeater relay 75R to the negative battery terminal N. In the completion of this circuit, the contact a of repeater relay 75R completes a circuit for the transmitting loop 66 over the front contact a of the speed responsive mechanism 70 and the front contact a f the repeater relay 75R. This allows the energy from the oscillator 67 to pass over this front contact a of the speed responsive mechanism 70, over the front contact a, the repeater relay 75R Where this energy is interrupted at a 120 code rate by the code transmitter relay 120 contact. This coded energy is delivered to the electrical lead 63, through the transmitting loop 66 and electrical lead 64 which is connected back to the oscillator 67.

It will, therefore, 4be seen that the train speed responsive transmitter 62 has various distinctive operating ranges, namely, when the speed of the train is below miles per hour there are no circuits completed between the oscillator 67 and the code transmitting loop 66. Accordingly, the absence of a signal in the rails immediately behind the train establishes the most restrictive train speed condition for any train that might enter the track section occupied by train 11. When the speed of the train reaches 40 miles per hour, a circuit is completed which permits a coded energy signal at the 75 code rate to be delivered to the code transmitting loop 66 which then places in the rails 12 and 13 immediately behind the train a signal indicative of a lmaximum permissible speed which is lll proportional to the code rate. When the train 11 reaches its maximum speed of 75 miles per hour or greater, the code rate of 120 is delivered to the code transmitting loop 66 and, therefore, there is coded signal energy in the rails 12 and 13 immediately -behind the train 11 of a 120 code rate. In the system being described, there has been presented four distinctive speed ranges for the trains of this system. They are as follows: When there is an absence of a signal or zero code rate in the rails this is the most restrictive condition and the train will brake to a stop. When there is a code rate of 75, the train may operate up to but not in excess of 40 miles per hour. When there is a code rate of 120, the train may operate between the speeds of 30 and 75 miles per hour but may not eX- ceed 75 miles per hour and should the train receive a code rate of 180, the train would be permitted to travel in excess of 75 miles per hour or atthe maximum authorized speed. When the train ahead is moving at 40 miles per hour it authorizes the following train to advance at 30 miles per hour. It will be seen, therefore, that immediately behind the train 11 there is induced in the rails 12 and 13 three distinctive conditions. These distinct conditions are a zero code rate, a 75 code rate, or a l2() code rate. The manner in which this affects the other blocks of the system being described will now be set forth.

When there is an absence of a signal in the rails 12 and 13, the receiver with its track relay TR, which receives or detects the presence of energy in the rails 12 and 13 via the leads 81 and 82, will be inactive. In other words, the relay TR will not be energized and this will result in the following circuits being completed in the wayside transmitter 95.

With the track relay TR deenergized, a circuit is completed from battery terminal B, through the back contact a of the track relay TR, the lower portion of the transformer T1, and back to the battery terminal N through the center tap 106 of the primary winding of transformer T1. The presence of a coded current in the primary winding of transformer T1 will induce in the secondary winding of the transformer T1 an alternating current which has been indicated by a solid arrow in the central iportion of the secondary Winding of the transformer T1. This current will flow from the terminal tap 103 through the secondary winding to the terminal tap 104, thence along the leads 110 through the winding of the relay H the lead 113, back contact b of the track relay TR, and the lead 109 back to the terminal 103. Relay H picks up over the circuit just traced. With non-coded or steady state direct current in the primary, there is no current induced in the secondary and, therefore, relay H remains in its released position. In other words, in the absence of any code rate, the -mere fact this circuit has been completed will not allow the relay H to pick up. Therefore, in the absence of a signal in the rails 12 and 13, with the relay TR deenergized, the relay H -wlll not `be picked up and the following circuit will be completed within the wayside transmitter 95. Current from a power source BX-NX coded at a 75 rate will be delivered over the back contact a of the relay H, thence over the lead 123a to the transformer T2 of the transmitter 95, where this 75 code rate will be delivered via this transformer T2 and the leads 96 and 97 to the rails 27 and 28. Accordingly, under the conditions just described, when the track detection section 1T immediately behind the train 11 c has a zero code rate or the absence of a signal in the rails,

there will automatically appear within the rails 27 and 28 of the track detection section 2T, a signal of 75 code rate. Accordingly, a train that would appear in the track detection section 2T would operate at the speed commanded by the 75 code rate, and upon entering the track detection section 1T the train, which has not -been shown but has been schematically set forth in FIG. 2, would `receive no signal immediately behind the stopped train 11 and the second train or following train would come to a halt. It should also be recognized that the second train would also come to a halt should the train 11 be ac celerating from a zero actual speed up to the speed of 40 miles per hour.

A second dynamic situation Will now be described. As the train speed increases, that is, the train speed of train 11 increases to and reaches 40 miles per hour, the circuit previously noted between the oscillator 67 of the train speed respon-sive transmitter will be completed and there will be delivered to the code transmitting loop 66 a coded energy signal at a 75 code rate. When the train 11 is operating at its actual speed of 40 miles per hour or greater there will be a signal in the rails 12 and 13 immediately behind the train at a 75 code rate. With a 75 code rate signal present in the rails 12 and 13, the following circuits will be caused to be completed in the wayside transmitter 95. The track relay TR of the wayside receiver 80 is a code following track relay which will open and close its contacts in accordance with the code rate received from the rails 12 and 13. Therefore, the track relay TR will open and close its contacts a and b at a code rate of 75. This code rate of 75 will cause the following circuits to come into operation in the wayside transmitter 95. As has been noted, with the track relay in its released position, a circuit is completed through the code detecting relay H, but the code detecting relay H will not respond unless the circuit is interrupted at some code rate. This code detecting relay responds when coded energy is delivered to the relay TR. When this occurs, track relay TR picks up thereby opening its back contacts and closing its front contacts. In this condition the current, shown by a dotted arrow, will flow from the battery terminal B over the front contact a of the track relay TR through the upper portion of the primary of transformer T1, and back to the battery terminal N from the center tap terminal 106. This passage of current through the primary winding of the transformer T1 which is represented by the dotted arrow in the lower portion of the secondary winding of the transformer T1. This current will tlow through the secondary winding of the transformer T1 to the terminal tap 104, thence along the lead 110 through the relay H, the lead 113, the front contact i; of the track relay TR, and finally the electrical lead 112 back to the lower end of the second winding of the transformer T1. When the circuit is interrupted by the opening and closing of the contacts a and b of the track relay TR, the code following relay H will respond by being energized and, therefore, picking up its contact a so that the 75 code rate being delivered from the terminal BX will be interrupted and a new code rate will be delivered in the following manner. As long as the 75 code rate and only the 75 code rate is being recognized by the track relay TR, there will be present in the secondary winding tof the transformer T1 a coded signal which Will be of the 75 code rate. This signal will appear simultaneously in the electrical lead 108, which Iis connected to the resonant frequency selective circuit 130D, designated by reference symbol 119. The frequency selective circuit 180D will only respond when the energy being delivered is at a 180 code rate. Therefore, in the absence of such a signal of a code rate of 180 there will be no output from the resonant frequency selective circuit 119 and the relay D will not be energized through the electrical leads 121 and 122. In a similar manner, there is connected in parallel across the electrical leads 108 and 111, which leads 108 and 111 emanate from either end of transformer T1, the electrical leads 123 and 114. Coded energy at the 75 code `rate will therefore also appear in leads 123, 114. The resonant frequency selective circuit 116, which was designated thereon 120D, will not respond to the 75 code rate but will only produce a direct current signal in the leads 118 and 117 to energize relay J when the code rate present in the leads 123 and 114 is at a 120 code rate. Therefore, the relays D and J remain inactive in the presence of a 75 code rate being delivered by the code following relay of the wayside receiver 80.

The following circuit is now completed in the wayside transmitter 95 with the code following relay H being energized by the code rate. The coded energy at the 120 code rate is delivered from the terminal BX over the back contact a of the relay D, the back contact a of the relay I and the front contact a of the relay H to the lead 123a,

where this 120 coded energy is delivered to the transform-` er T2 which induces in the leads 96 and 97 the 120 coded signal. This 120 code rate signal is impressed in the rails 27 and 28 in the track detection section 2T.

Under the situation just described, it will be recognized that when the train 11 is operating at a speed of 40 miles per hour or greater there will at least be a signal induced in the rails 12 and 13 at a code rate of 75, which, in turn, will cause to be delivered in the track detection section 2T a code rate of 120. Therefore, a train (not shown) entering the track detection section 2T would receive an authorized speed command represented by the code rate of 120. As the train proceeds from the track detection section 2T into track detection section 1T, this code rate will decrease to a code rate of 75 and the second or following train will proceed at this more restrictive speed command. There is possibe another range of operation.

When the train reaches 75 miles per hour, that is, an actual speed of 75 miles per hour, the speed responsive mechanism 70 of the train speed responsive transmitter 62 will complete the circuit as noted earlier when the contact b of the speed responsive mechanism 70 is closed. This will cause, as has been noted, the delivery of ya coded signal to the code transmitting loop 66 at the rate of 120. Therefore, there will appear in the rails 12 and 13 immediately behind the train 11 coded energy at the 120 code rate whenever the train is operating at 75 miles per hour or greater. This 120 code rate will produce the following coded energy signal in the track detection section 2T. With a 120 code rate being delivered to the wayside receiver via the leads 81 and 82 from the rails 12 and 13, track relay TR is driven at the code rate. The track relay contacts a and b will be actuated at a 120 code rate. The fact that a circuit is now being completed at a 120 code rate will be detected by the code detecting relay H in the same manner that the 75 code rate was detected and described earlier. Therefore, without regard to the code rate being delivered the code detecting relay H will remain in a picked-up position as long as any code signal is being received by the wayside receiver 80. With the code detecting relay picked up and a signal induced in the secondary winding of the transformer T1 at a 120 code rate, the resonant frequency selective circuit 116 designated 120D, which is connected via the electrical leads 123 and 114 to the leads 108 and 111 to either end of the secondary winding of the transformer T1, will cause a direct current signal to appear in the leads 118 and 117 from the resonant or frequency selective circuit 116. This will energize the relay I, and with the relay I in a picked-up condition, the following code command signals will be delivered to the track detection section 2T.

The code rate will be delivered from the terminal BX over the front contact a of the relay J, over the front contact a of the relay H to the lead 123 where this 180 code rate will fbe delivered to the transformer T2, by the leads 96 and 97 to the rails 27 and 28 of the track detection section 2T.

It will, therefore, be seen that when a code rate of 120 is delivered to tbe rails immediately behind the train 11 there will instantly appear in the track detection section 2T a code rate of 180 which is indicative of a maximum authorized speed. When the train 11 is operating at this maximum speed there is always present behind it the next most restrictive train speed, namely, that of a 120 code rate.

In order that the system have a continuity of dynamic responses to the train speed commands being delivered to the rails behind the train, there is provided in a conventional manner the additional capability within the wayside transmitter 95 of responding to the 180 code rate. In other words, since all of the wayside transmitters 88, 95 and 56 may be affected by the presence of a 120 code rate in a preceding track detection section, there is provided the resonant or frequency selective circuit 119 in the wayside transmitter 95 and this resonant or frequency selective circuit 119, which has 180D designated thereon, will respond to the situation where a 180 code rate is being received by the wayside receiver 80. Since the code following relay H is always picked up when a code is present, a circuit will be completed in the following manner. Since the presence of a 180 code rate will not be detected or produce a signal by the resonant or frequency selective circuit 116, the relay J will be deenergized but simultaneously with this deenergization the appearance of a 180 code rate in the leads 108 and 111 from the secondary of the transformer T1 will cause a direct current signal to appear in the leads 121 and 122 from the resonant or frequency selective circuit 119. This will energize the relay D and cause a 180 code rate command signal to be delivered from the terminal BX, over the front contact a of the relay D, over the back contact a of the relay I, the front contact a of the relay H to the lead 123, whereupon this 180 code rate will be delivered to the transformer T2 and thence through the leads 96 and 97 to the rails 27 and 28. This 180 code rate would then be received -by a following train and would permit the maxi-mum authorized speed by the following train. It should be recognized that this code following receiver and transmitter per se is part of the prior art and a more detailed description of the operation of this code following procedure may be had with reference to Nicholson et al. Patent No. 2,218,120 for Railway Traffic Control Apparatus.

By way of summary, it will be recognized that this system provides an inherent fail-safe arrangement in which following trains may decrease their headway between trains and always receive a train speed command signal that will allow them to approach the rear of a preceding train while safely maintaining a reasonable headway in all dynamic operations of the trains system. This system will, therefore, provide a most unique advance to the movable block concept of train speed control, and in so doing, will advance the state of the art to allow greater transportation rates and higher speeds within the systems because of the interlocking nature of the train speed control between trains operating within the system.

While the present invention has been illustrated and disclosed in connection with the details of the illustrative embodiments thereof, it should be understood that those are not intended to be limitative of the invention as set forth in the accompanying claims.

Having thus described my invention, what I claim is:

1. A movable block train speed control system for controlling the speed of one or more trains in territories characterized by the presence of a plurality of consecutive track sections defined by insulated joints and a train speed command signal producing a wayside transmitter at the exit end of each track section controlled by a wayside receiver at the entrance of the next succeeding track section, wherein said system has (a) a train speed responsive transmitter means on each train, said train speed responsive transmitter means having a signal output which is always indicative of a train speed command less than the train speed command signal from said wayside transmitter of the track section entered by said train.

5 said train speed responsive transmitter includingenergy to said signal transmitting means to there-k by induce in said rails of said track detection section at said rear of said train a train speed control signal to control the speed of a following train,

said train speed responsive transmitter output controlling the wayside receiver of the track section occupied which wayside receiver in turn controls the next wayside transmitter through said wayside receiver of the track section entered to produce a train speed control signal dependent upon the signal produced by said train speed re.- sponsive transmitter means,

(b) a train speed control means on each train controlled by said train speed wayside transmitter means, said train speed control means responsive to a train speed wayside transmitter signal of a track section entered unless said track section is occupied by a train when said train speed control means is responsive to and controlled directly by the output of said train speed responsive transmitter means of the train occupying said track section.

2. The train speed control system of claim 1 wherein said train speed command signal producing wayside transmitter is electrically coupled to the rails of said track detection section at said exit end of said track detection sec tion.

3. The train speed control system of claim 1 wherein said wayside receiver is a signal following receiver which controls said wayside transmitter to produce in the rails of said exit end of said track detection section a train speed command signal having a value dependent upon the nature of the signal received by said wayside receiver.

4. The train speed control system of claim 1 wherein said train speed responsive transmitter means includes,

(a) a code transmitting means at the rear of said train,

(b) a source of coded energy, and

(c) a train speed responsive mechanism to selectively electrically couple said source of coded energy to said signal transmitting means to thereby produce at said rear of said train a train speed control signal to control the speed of a following train.

References Cited UNITED STATES PATENTS 1,627,748 5/ 1927 Rowntree. 1,877,626 9/1932 Loughridge.

2,702,342 2/ 1955 Korman. 3,038,066 6/1962 Barry 246-182 XR ARTHUR L. LA POINT, Primary Examiner.

S. T. KRAWCZEWICZ, Assistant Examiner.

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