US 3041449 A
Description (OCR text may contain errors)
June 1952 R. BINGEN 3,041,449
AUTOMATIC BRAKING CONTROL SYSTEM Filed Nov. 1'7, 1959 3 Sheets-Sheet 1 A &
United States Patent 3,041,449 AUTOMATIC BRAKING CONTROL SYSTEM Roald Bingen, Marcinelle, Belgium, assignor to Ateliers de Constructions Electriques dc Charleroi, Brussels, Belgium, a company of Belgium Filed Nov. 17, 1959, Ser. No. 853,601 Claims priority, application France Nov. 17, 1958 2 Claims. (Cl. 246182) This invention relates generally to automatic train control and more particularly to an automatic coded braking control system for trains.
Automatic train control devices are being employed more and more in order to diminish the effect of human errors and thereby to increase the safety of railway traflic. More especially various systems have been proposed for effecting automatic braking of railway trains when the engineer does not reduce the speed sufficiently to permit stopping in a required distance.
A principal object of the present invention is to provide an automatic braking control system for trains, which comes into action when the retardation curve of the train, as a function of the distance traveled, has ordinates higher than those of a set limit curve.
In accordance with the invention, a track section or zone upon which the retardation or slowing-down of a train must be effected is provided with transmitter means at a certain number of spaced points which transmit to the comotive coded command signals which initiate thereon a signal which is combined with another signal representa tive of the square of the speed limit for the train in the vicinity of the points in question. This combined signal is a directive signal representing the limit variation of the square of the speed of the train.
The locomotive is provided with a tachometric generator which supplies a signal, continuously proportional to the speed of the train, which is transformed by an appropriate circuit into a signal proportional to the square of the speed of the train. This latter signal is compared, in a comparator, with the directive signal representing the limit variation of the square of the speed of the train, and the resultant or differential signal regulates, according to its sign, the control means of the train brakes to apply the brakes.
Other features and advantages of the automatic braking control system in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings in which:
FIG. 1 is a diagram of retardation curves illustrative of the operation of the invention;
FIG. 2 is a block diagram of equipment, of an auto matic coded braking control system installed on a railway vehicle according to the invention;
FIG. 3 is a diagram illustrative of the application of signals usable to controllably slow-down and stop railway rolling stock in a given zone or section of trackway;
FIG. 4 is a diagram illustrating the application of the system, according to the invention, to a railway system.
As indicated heretofore the automatic braking control system, according to the invention, comes into action when the retardation curve of a train, as a function of the distance traveled, has ordinates higher than those of a set limit curve.
It can be readily shown that on braking a train with constant deceleration, the curve of the square of its speed, as a function of the distance traveled, is a straight line. It has also been confirmed by practical tests that the curve of the square of the speed of a train under braking action,
as a function of the distance traveled, is practically a straight line, at least over the greater part of its length.
The actual curve obviously depends upon the type of the train and upon the grade of the track, Whether the track grade is level, uphill or downhill, but in all cases it retains its characteristic near-linearity. Such curves are represented in FIG. 1 of the accompanying drawings. Curve A relates to braking a predetermined type of train on a down grade and curve B to its braking on an up grade.
The braking system according to the invention comprises, aboard of the locomotive, a tachometric generator 1, driven by an axle of the locomotive, which supplies a signal voltage v proportional to the instantaneous speed of the train. This voltage is transformed in a known cir cuit 2 to a voltage signal v proportional to the square of the instantaneous speed of the train.
A pick up coil 27 receives coded signals emitted from determined spaced points along the track. These signals are selected by a discriminator 28 of any suitable known type which energizes successively relay coils 22, 23, 24, 25, closing successively during a short time contacts 9, 10, 11, 12 and so charging a capacitor 21 at different successive voltages supplied by a voltage divider comprising resistors 15, 16, 17, 18 connected across a DO. source 14. The capacitor 21 is connected between the input and output terminals of an amplifier 19 which receives an input voltage through a resistor 20 from the tachometric generator 1. I
The output signal c of the amplifier 19 is compared with the voltage signal v in a differential amplifier 13 which :actuates a solenoid 29 through a rectifier 28 when the voltage v is greater than the voltage 0. This solenoid 29 controls the braking equipment of the train.
Assume that the distance in which the train is to be braked is represented by a length x (see. FIG. 3), terminating at the abscissa 0 where the train comes to rest. Distance x is subdivided at x1, x2, x3, x4, at which points the coded signals are transmitted tothe locomotive FIG. 3 illustrates the curve of the squares of the speed limit for the train; the ordinates corresponding to the abscissae x1, x2, x3, x4 are designated respectively by V V V and V and the voltages applied to the capacitor 21 by means of contacts 9, 10, 11, 12 in FIG. 2 are respectively proportional to V V V and V If G denotes the gain of the amplifier 19, v its input voltage, C the capacity of the capacitor 21 and R the resistance of the resistor 20, and if the input impedance of the amplifier 19 is sufiiciently high, there are obtained;
1) d2); a a lin or, if according to (1), v is replaced by c/ G,
1) do 1 0 do I r+ atc(a+ at) As the gain G is very high, the second item can be considered as equal to zero, then a: ,fvdt+ constant The integration constant is represented by the initial charge of the condenser 21, obtained by the momentary closure of the contacts 9, 10, 11, 12. i
The voltage 0 is thus a voltage having, on passing the point x1 a value proportional to V then decreasing proportionally to the distance travelled by the train. The downward slope of this decrease depends upon the product RC.
The coded signals transmitted to the locomotive will consequently comprise information relating to the section of the track (level, up-grade or down-grade) and this information will require an appropriate variation of the resistance 20 or of the capacity of the condenser 21. It should be observed that there is a certain latitude regarding the value of the slope of the limit curve, since the amplitude of this curve is readjusted each time a transmitter point is passed. In general it will be sufficient to establish a discrimination between the case of an upgrade and that of a down-grade, by reckoning upon a mean value thereof. If it is desired to take further account of the true form of the curves in FIG. 1, it isalways possible to modify the characteristics of the circuit 2 in FIG. 2, so that it supplies an output signal which Varies according to the desired law.
In order to permit greater flexibility in the operation of the system, it is possible to envisage the automatic braking of the train not being continued until the train comes to rest, in which case the train is decelerated only to a very low speed (for example km. per hour). Thus the minimum value of the order voltage may be above zero. On approaching a fixed braking signal (for example, limiting the speed to 70 km. per hour), the system is put in action there in a manner such that when the locomotive arrives at the braking zone, the speed limit determined by the system is that imposed by the signal, and as from this point this speed limit is maintained until the signal for resumption of speed is received. To this end, a fixed speed order is superimposed upon the progressive deceleration order signal and becomes preponderant as soon as it is greater than the latter.
The transmission of the comm-and signals to the locomotive can be effected by any known system, for ex ample, by means of magnetic pick-ups, as shown. The type of signals may also be of any desired form; for example, a multiple frequency system, not shown, may be used. FIG. 4 shows some examples of the application of the invention to railway lines equipped with a signalling system such as that in use in the Belgian National Railway Co. The track signals are represented in the form of discs with indication of the corresponding color in ligh)t signalling (J, V, R, respectively for yellow, green, red
At points a, b, c, d, along the line, the command signals transmitted to the locomotive are represented by small circles; a white circle signifies the absence of the corresponding signal, a black circle the presence thereof.
The trains are presumed to be traveling from left to right.
In the case of la, the warning signal situated at a and the block signal situated at care on. These signals are separated by the normal distance. On arrival of the locomotive at a, the'corresponding transmitter provides the speed order as described above. At the following points b, c, d, the transmitters efieot the variation of this order, readjusting it if necessary to the prescribed value.
Case Ib corresponds to. the free passage of the train, all the transmitter points are in the same state or condition, no speed order is transmitted to the locomotive. The transmitter points nevertheless supply positive information, which is indispensable from the point of view of safety, and further permits suppressing the braking action when the track becomes clear when the train has already passed a warning signal which is on. Cases 11a to 0 illustrate three track signals spaced apart at normal distances; these are analogous to the previous cases. Cases H111 to d relate to three track signals, the third of which is at a reduced distance from the second. Case 1110 is a ease in which the train must halt at e; (see case Ia). a V
- In case 1111), the track is clear at a, but as the train must stop at'h, it must have a normal braking distance avail-able,
which means that the transmission of the speed order must commence at d. The transmitter point situated at e reproduces the same indication as that at d, but it is immediately followed by another point at e, which causes the continuation of the variation of the speed order, so that apart from a discontinuity of short duration at e, everything happens as if the point situated at 2 did not exist. This arrangement is necessary, however, as will appear from an examination of case IIId.
At IIIc the track is clear everywhere (see case lb). Case IIId is that of a train which has passed the point a while the track signals were in the position corresponding to case Ilia, but which, at the moment when the locomotive is situated at T, these signals assume the position corresponding to case IIIb-' The train having already slowed down with a view to stopping at e, and having at this moment the corresponding order which had been readjusted at the point 11, it must be permitted to continue its own until it, observing the speed order corresponding to the new situation. Then in this case the transmission speed order is initiated at e, with transmission immediately afterwards, at e, of the following stage of this order, as in case' 1111).
Case IV relates to a train which passes a fixed retardation indicator signal which compels deceleration to reach, at the start of deceleration, at O, a speed limit of km. per hour, for example; At point a, the appearance of the start to brake order isinitiated, at the same time as a supplementary signal is dispatched, indicated by a small square, which starts up a sumnn'ng device which is stopped by the command signal at a, of a second analogous signal. The distance between the points a and a is a function of the speed limit and is established so as to permit the summing device to impose a fixed speed order which will become preponderant at the latest as the point 0 is passed. At the point V, this order is suppressed by the transmission of the clear track signal.
Other cases can be envisaged without departing from the scope of the present invention which obviously can be applied to the control of traffic on routes other than railways.
What I claim and desire to secure by Letters Patent is:
1. In a railway system having tracks along which coded control signals are emitted at spaced points along the tracks and at least one locomotive operable thereon and having brake-operating equipment for braking the locomotive and rolling stock operating on said tracks in conjunction with said locomotive as a train, an automatic coded braking control system comprising, on said locomotive a taehometric generator operably driven by the locomotive, a transforming circuit connected to said tachometric generator for producing a voltage signal proportional to the square of the speed of the train, means comprising an integrating amplifier operatively connected to said tachometric generator and having a capacitor connected between its input and output for developing a variable reference voltage signal having an amplitude representative of the square of the limit speed of the train at the corresponding point and then decreasing proportionally to the distance travelled by the train from said corresponding point, a plurality of DC, voltage sources for providing D.C. voltages respectively representative of the square of the limit speed of the train at the diiferent points of the track where coded signals are emitted, means respectively responsive to said coded signals for causing.
said D.C. voltages to be applied during a short time interval to said capacitor so that said integrating amplifier produces said reference voltage signal having an amplitude representative of the square of the limit speed of the train at the corresponding point and then decreasing proportionally to the distance travelled by the train, means for developing a difierence signal between said difference signal and said signal proportional to the square of the speed of the train, meansfor actuating said brake-operating equipment, a difierential amplifier connected for amplifying the difference signal between said reference signal and the signal proportional to the square of the speed of the train operatively connected to said means for actuating said brake-operating equipment of the train in response to said difference signal.
2. An automatic braking system according to the claim 1, comprising, means for developing at least one constant reference voltage, means responsive to said coded signals transmitted along the track for causing said constant reference voltages to be superimposed on said variable reference voltage, and means for causing the greater of the reference voltages to be applied to said diiferential amplifier.
References Cited in the file of this patent UNITED STATES PATENTS Howe Sept. 22, Simmen Oct. 13, Snavely June 1, Sunstein Nov, 27, Ford Aug. 23,
FOREIGN PATENTS Australia Oct. 27, Great Britain July 4, Great Britain Sept. 5,