Patent Publication Number: US-6698847-B2

Title: Safety system for continuously checking the integrity of a railway train

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a safety system for continuously checking the integrity of a railway train which comprises a head locomotive followed by a plurality of entrained vehicles, and which is provided with a pneumatic braking system including a general duct which extends along the entire train. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide an improved system which allows continuous testing of the integrity of a railway train, in particular a very long railway train. A further object of the invention is to provide a system which further allows the emergency safety braking of two or more parts into which the train may possibly become separated. 
     This and other objects are achieved according to the invention with a system having the characteristics defined in the following claims. 
     According to a first aspect of the invention, the system comprises: 
     an electrical supply line which extends along the entire train from the locomotive at the head to the vehicle at the tail; and 
     head apparatus and tail apparatus installed on the head locomotive and the tail vehicle respectively, and connected to the ends of the said electrical supply line; and in which 
     the head apparatus comprises a first DC voltage supply operable to apply to the said line a first DC voltage having a predetermined value; 
     a detector connected to the said line and operable to detect the presence on the line of a signal having predetermined characteristics, and to generate an alarm upon loss of the said signal on the line; 
     the tail apparatus comprising: 
     a signal generator having the said predetermined characteristics, coupled to the electrical supply line, and 
     a DC/DC converter the input of which is connected to the said line and the output of which is connected to the said signal generator to provide to this latter a supply voltage derived from that generated by the first supply source of the head apparatus; 
     the system being such that an interruption of the train capable of causing an interruption of the said line is able to cause a deactivation of the signal generator of the tail apparatus which can be detected and signalled by the detector of the head apparatus. 
     Further characteristics and advantages of the invention will become apparent from the following detailed description given purely by way of non-limitative example with reference to the attached drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram partially in block diagram form, of one embodiment of a system according to the invention; and 
     FIG. 2 is a diagram of an alternative embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, the reference numeral  1  generally indicates a safety system according to the invention for continuously testing the integrity of a railway train. 
     The system  1  essentially comprises an electrical supply line L which extends along the entire train from the locomotive at the head to the vehicle at the tail. In the embodiment illustrated the line L is a twin filament line. This line L can be utilised for the electrical supply of the apparatus and various devices of the train. 
     The system  1  further comprises head apparatus HA installed on the locomotive at the head (not illustrated) of the train, as well as tail apparatus EA associated with the end vehicle or tail (not illustrated) of the train. 
     The head apparatus HA and tail apparatus EA are connected to the ends of the electrical supply line L. 
     The system  1  further comprises a plurality of wagon apparatus WA of which only one is illustrated in the drawing. Such wagon apparatus WA is installed on each wagon drawn by the head locomotive including the tail wagon or vehicle. 
     The head apparatus HA comprises a first DC voltage supply  10  operable to apply to the line L a DC current having for example a value of 48 V. This first supply is of relatively low power and is floating with respect to ground or earth and is moreover insensitive to unbalancing of the line L with respect to ground or earth. 
     The head apparatus further includes a second voltage supply  11  of relatively high power, operable to apply to the line L a DC current of for example 230 V. This supply is of balanced type and is sensitive to possible unbalancing of the line L with respect to ground or earth. The output of the voltage supply  11  is coupled to the input of the line L through a switching device  12  and an AC/DC separator device generally indicated  13  and comprising, for example, and in a manner known per se, a plurality of inductors and at least one capacitor. 
     The output of the voltage supply  11  is coupled to the output of the voltage supply  10  by a controlled isolator switch  14  connected upstream of the emergency switch  12 . 
     The reference numeral  15  in the drawing indicates a switch interposed between ground GND and one of the conductors of the line L. The functions of such switch will be explained hereinafter. 
     The tail apparatus EA comprises a signal generator  19 , operable to generate an AC signal having a predetermined characteristic, such as a frequency, for example equal to 10 KHz, or a modulation or numerical code. This generator  19  has its output coupled to the line L through a coupling device  20  operable to pass AC signals and to block DC signals. This device, known per se, comprises a transformer and a pair of capacitors in the indicative example illustrated. 
     The tail apparatus EA further includes a DC/DC converter  21  the input of which is connected to the line L through an AC/DC separator  22  similar to the separator  13  previously described. The output of the converter  21  is connected to a supply input  19   a  of the signal generator  19 . 
     Now, referring again to the head apparatus HA, this further includes a detector  16  the input of which is connected to the line L downstream from the separator  13  by means of a coupling device  17  similar to the device  20  previously described. 
     The detector  16  is intended to detect the presence on the line L of the signal produced by the generator  19 . Upon loss of the said signal on the line L the detector  16  activates an alarm device  18  and causes opening of the (normally closed) switch  14  thus causing uncoupling of the supply  11  from the line L. 
     Each wagon apparatus WA includes a DC/DC converter  23  the input of which is coupled to the line L via an AC/DC separator  24  similar to the separators  13  and  22  just described. 
     The output of the converter  23  is connected to a monostable circuit  25  of the type which can be activated by a falling edge. The output of this monostable circuit is coupled, via an amplifier  26  and a solenoid valve EV of the wagon which, in a manner known per se, is connected to the general duct BP of the pneumatic braking installation of the train. This duct extends along the entire train. The solenoid valve EV is for example of the type described in U.S. Pat. No. 6250723. 
     The excitation of the solenoid valve EV causes a controlled discharge of the pressure in the local section of the general duct or brake pipe BP. 
     The reference numerals  27  and  28  indicated two diodes having their respective anodes connected to two input terminals of the converter  23  and the respective cathodes of which are interconnected together to form overall a kind of OR circuit. Between the cathodes of these diodes  27 , 28  and ground GND is disposed a pressure sensor  29  of the threshold switch type, associated with the local section of the general braking duct BP. A current limiting resistor  33  is connected in series with the switch  29 . 
     The switch  29  is normally open when the pressure in the general duct BP exceeds a predetermined threshold value, and closes when this pressure falls below a value close to or equal to this threshold value. 
     Between the cathodes of the diodes  27 ,  28  and the switch  29  is interposed a photo coupler generally indicated  30 , comprising an emitter diode  31  coupled to a phototransistor  32 . This photo coupler  30  makes it possible to generate a signal indicative of the state of the pressure threshold switch  29  and therefore the pressure level in the general duct BP. 
     The diodes  27 ,  28  make the polarity of the coupling of the input of the converter  23  to the line L of no significance. 
     The system described above functions essentially in the following manner. 
     Switches  12  and  14  of the head apparatus HA are normally closed, whilst the switch  15  thereof is normally open. 
     The voltage supply source  10  applies to the line L a DC voltage with sufficient power that the converter  21  can apply the intended supply voltage to the generator  19 . This generator emits on the line L the appropriate signal, for example an AC signal at the predetermined frequency of 10 KHz. 
     At the other end of the line L, in the head apparatus, the signal produced by the generator  19  of the tail apparatus is detected by the detector device  16 , which continues to maintain the switch  14  closed so that the supply device  11  remains coupled to the line L. 
     In normal conditions, in particular in conditions of complete integrity of the railway train, the respective DC/DC converter  23  of each wagon apparatus WA, by means of the line L, receives at its input a DC voltage coming from the supply device  11  of the head apparatus. The output of this converter  23  applies to the associated monostable circuit  25  a DC voltage so that this monostable device remains deactivated. 
     In normal conditions the pressure in the general duct BP exceeds the minimum threshold value associated with the sensor  29  so that the switch  29  of each wagon apparatus WA is open. 
     The safety system  1  is able to react to a number of emergency situations in the modes which will now be described. 
     If emergency switch  12  in the head locomotive is opened, both the voltage supply devices  10  and  11  are decoupled from the line L. Consequently the converters  23  of all the wagon apparatus WA, upon loss of the voltage on the line L applied by the voltage supply device  11 , cease to provide an output DC voltage to the associated monostable  25 . The falling edge of the output voltage of the converter  23  causes activation of the monostable circuit  25 , which for a predetermined time causes excitation of the associated solenoid valve EV causing a controlled discharged of the pressure in the local section of the general duct BP. The almost simultaneous discharge of pressure in the local sections of the general duct involves, in a manner known per se, activation of the brakes of the entire train, which is therefore braked in an extremely rapid and uniform manner, even before possible intervention of the so called automatic continuous brake UIC the intervention of which, typically sequential, can be dangerous in the case of very long trains. 
     A further emergency situation is represented by an interruption of the line L, due for example to an interruption in the integrity of the railway train itself. In this case the detector  16  of the head apparatus HA no longer detects the signal produced by the generator  19  of the tail apparatus EA, and therefore causes opening of the switch  14  and decoupling of the voltage supply device  11  from the section of the line L which is still connected to the head apparatus HA. Consequently, both in the wagons upstream and in the wagons downstream of the interruption in the line L, the input voltage to the respective DC/DC converters  23  falls and this involves excitation of the associated solenoid valves EV and controlled discharge of pressure in the local section of the general duct. In this case also, therefore, an effective, rapid, uniform, braking takes place simultaneously in the two, or possibly more, parts of the train. 
     As well as the situations described above, an emergency situation can also occur in which the general braking duct BP is interrupted along with the train, without this involving an interruption in the line L. In this case, the pressure switch  29  associated with the wagon or wagons closest to the point of interruption or rupture of the duct close causing an unbalancing of the line L with respect to ground or earth. This unbalancing is conveniently detected by a suitable circuit  11   a , known per se, associated with the voltage supply device  11 . This unbalancing detector  11   a  causes the deactivation of the voltage supply device  11  and this in turn causes excitation of the various solenoid valves EV and the controlled discharge of the pressure in the general duct BP with an almost simultaneous braking operation in all the wagons, also in this case more rapidly than the possible intervention of the automatic continuous brake UIC. 
     The switch  15  of the head apparatus HA on the other hand makes it possible to effect a test or diagnosis of the efficacy of the pressure threshold switches  29  of the wagon apparatus WA. Such diagnosis is conveniently effected when the general braking duct BP is charged, or rather operating at normal functioning pressure. 
     Upon commencement of the charging of the duct BP the pressure threshold switch  29  of each wagon apparatus is closed. If now the switch  15  is closed the supply device  10  is connected to ground or earth and a current now flows through the photo diode  31  of the associated photo couplers  30  the photo transistors of which make it possible to verify and signal the effective closure condition of the pressure threshold switches  29 . 
     During charging of the duct BP, as soon as the pressure of this duct exceeds a predetermined value, the switches  29  open and this condition can be again detected by means of the associated photo couplers  30 . Once the diagnosis is completed the switch  15  of the head apparatus HA can be opened again. 
     In a manner not illustrated, at the output of the converter  23  of each wagon apparatus WA there can be connected control devices (such as relays or solenoid valves) for safety functions such as, for example, inhibition of traction of possible intermediate locomotives in the train or inhibition of local re-supply of pressure to the general duct BP by intermediate locomotives. 
     FIG. 2 shows a system essentially duplicated for safety redundancy purposes. It is noted in particular that this system includes duplicated identical head apparatus HA and duplicated identical tail apparatus EA coupled by two lines L. Each wagon is equipped with duplicated wagon apparatus WA and WA′ each appertaining to one of the two lines L. The apparatus WA′ does not include its own monostable circuit  25  and its own solenoid valve EV but rather the output from the converter is coupled to the input of the monostable circuit of the other wagon apparatus WA. Coupling of the outputs of the converters  23  of the apparatus WA and the apparatus WA′ to the monostable circuit  25  shared between them is achieved by means of two diodes  34  and  35  the cathodes of which are connected together. The overall duplicated arrangement makes it possible to avoid undue braking in the case of breakdown of one of the two systems belonging to the common monostable circuit. 
     Naturally, the principle of the invention remaining the same, the embodiments and details of construction can be widely varied with respect to what has been described and illustrated purely by way of non-limitative example, without by this departing from the ambit of the invention as defined in the attached claims.