A control system for railroad colour light signalling devices

Abstract: A control system wherein a central control station (4) is connected, by means of a bipolar cable (9), to at least one peripheral station (7), coupled with at least one railroad signal (11), provided with three light sources (13r, 13y, 13g), respectively, red, yellow and green, obtained from incandescence lamps. Each incandescence lamp (13r, 13y, 13g) is capable of being supplied by a respective band-pass filter (31, 32, 33), receiving, at its input, the signal sent from cable (9). Central station (4) is fitted with a signal generator (18), capable of supplying on cable (9) a periodic alternating signal, whose frequency (Fl, F2, F3) can be chosen among three different frequencies (Fl, F2, F3), each whereof corresponds to the central frequency of a respective band-pass filter (31, 32, 33) of peripheral station (7).

Description: The invention relates to a control system for railroad colour light signalling devices. Control systems are known wherein a central station is capable of controlling at least one signalling device, provided with at least a first and a second light source (generally of different colours, for instance, green and red), capable of conveying, when on, free/engaged track signals, respectively. In the known systems, each light source is generally obtained from an incandescent lamp, powered by a respective duplex cable, carrying the supply voltage for the said light source. This is why each signalling device is supplied by a multipolar cable extending from the central station to the signalling device. Each multipolar cable comprises a number of duplex cables, which is twofold the number of the light sources contained in the railroad signalling device. The main drawback of the known systems consists in the use of multipolar cables, in that the latter are very expensive, rather bulky and difficult to install. Furthermore, current leakages may occur between duplex cables belonging to the same cable, consequently leading to the erroneous turning on of light sources, which are not supplied by the central station. German patent application DE 32 23779 describes a control system for railroad colour light signalling devices as described in the preamble of claim 1. Aim of this invention is the embodiment of a control system for railroad colour light signalling devices, which may overcome the drawbacks of the known systems. This aim is achieved by the present invention as described in Claim 1. The present invention will be better described by way of a non-limiting example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic view of a control system for railroad light signalling devices according to this invention; Fig. 2 shows a graph of some quantities of the system according to the invention; Fig. 3 shows an alternative embodiment of the system in Fig. 1; and Fig. 4 shows a detail of the control system in Figs. 1 and 3. With reference to Fig. 1, there is indicated with number 1, in its whole, a control system for railroad signalling devices. System 1 comprises at least one central control station 4 communicating with at least one peripheral station 7 through a bipolar cable 9, which can extend for as long as some kilometres. Each peripheral station 7 is further coupled with a respective railroad signalling device 11 (railroad signal). In the embodiment described herein, peripheral station 7 is shown, for sake of simplicity, as a separate unit, with respect to signalling device 11; obviously, the components of station 7 can also be housed in the outer casing of railroad signal 11. In the embodiment shown in Fig 1, railroad signal 11 is fitted with three light sources (conveniently comprising incandescent lamps) 13g, 13y and 13r. Light sources 13g, 13y and 13r are housed inside a sealed casing 15 (schematically shown) and are coupled with respective coloured filters (not shown) to generate respective green, yellow and red light beams. For the sake of simplicity, in the description contained hereinafter by the expressions green, yellow or red light source reference will be made to light sources 13g, 13y and 13r, respectively. To the emission of a red light beam there corresponds a signal of a first advance condition for a railroad vehicle, for example, engaged track and vehicle stop, to a green light beam there corresponds a second advance condition for the railroad vehicle, for example, free track and go ahead. A yellow light beam can correspond to a slow-down signal (for example, because the next signalling device is red). Central station 4 is capable of being housed inside a control building (not shown) of a railway station (not shown) and peripheral station 7 is capable of being located in the service area (not shown) of the railway station, cable 9 extending along the service area. Central station 4 comprises a signal generator 18, capable of outputting a square wave periodic alternating signal S. In particular, signal S can have three different frequencies F1, F2, F3, for example, equal to 250 Hz, 364 Hz and 556 Hz respectively. Signal S output frequency is selected on the basis of the digital value of a word D at a control input 20 of signal generator 18. For example, in connection with a first digital word D1, there can be generated a signal with frequency F1 = 250 Hz, in connection with a second digital word D2 there can be generated a signal with frequency F2 = 364 Hz, and in connection with a third digital word D3 there can be generated a signal with frequency F3= 556 Hz. Central station 4 further comprises a power amplifier 22, which receives, at its input, signal S, generated by signal generator 18, and sends an output signal to a voltage elevator, conveniently obtained from a primary winding of a transformer 25. The secondary winding of transformer 25 communicates with an input terminal 9a of bipolar cable 9. Transformer 25 has a 1:3 voltage ratio and is capable of increasing the alternating signal at output of amplifier 22 (approximately 50 volts) sending on cable 9 a square wave control signal having a voltage of approximately 150 volts. Amplifier 22 has an enabling input 27 (ENABLE) whose function will be expounded later on. Peripheral station 7 comprises a voltage reduction device, conveniently comprising a transformer 29, the primary winding whereof communicates with an output terminal 9b of bipolar cable 9. Transformer 29 has a 10:1 voltage ratio. Peripheral station 7 further comprises three band-pass filters 31, 32 and 33, fitted with respective inputs 31a, 32a, 33a, communicating with a first output terminal 34 of the secondary winding of transformer 29. Outputs 31b, 32b and 33b of band-pass filters 31, 32 and 33 communicate with first terminals 13r', 13y', 13g', respectively, of incandescence lamps 13r, 13y, 13g (respectively red, yellow and green). Incandescence lamps 13r, 13y, 13g have second terminals 13r", 13y", 13g", communicating, through a power line 35, with a second output terminal 40 of the secondary winding of transformer 29. Filter 31 comprises a coil 37, whereof a first terminal communicates with input 31a and a second terminal communicates with a first terminal of a capacitor 38. Capacitor 38 is further provided with a second terminal, connected to a first terminal of a resistor 39, a second terminal whereof communicates with output 31b. In the embodiment described herein, coil 37 has an inductance value of 33 mH and capacitor 38 has a capacitance of approximately 12 microfarads. Filter 32 comprises a coil 41, whereof a first terminal communicates with input 32a and a second terminal communicates with a first terminal of a capacitor 42. A second terminal of capacitor 42 is connected to a first terminal of a resistor 43, a second terminal whereof communicates with output 32b. In the embodiment described herein, coil 41 has an inductance value of 33 mH and capacitor 42 has a capacitance of approximately 6 microfarads. Filter 33 comprises a coil 45, whereof a first terminal communicates with input 33a and a second terminal communicates with a first terminal of a capacitor 46. A second terminal of capacitor 46 is connected to a first terminal of a resistor 47, a second terminal whereof communicates with output 33b. In the embodiment described herein, coil 45 has an inductance value of 33 mH and capacitor 46 has a capacitance of approximately 2 microfarads. Resistors 39, 43 and 47 have a resistance of a few ohms and are introduced to calibrate filters 31, 32, 33, as a function of the resistance of lamps 13r, 13y and 13g. Filter 31 (supplying the red light source) has a central frequency equal to approximately 250 Hz, filter 33 (supplying the yellow light source) has a central frequency equal to approximately 364 Hz and filter 32 (supplying the green light source) has a central frequency equal to approximately 556 Hz. In Fig. 2 there are shown (approximately) transfer functions H 1 , H 2 and H 3 of filters 31, 32 and 33. Central control station 4 cooperates with a control and monitor circuit 50 (described in detail hereinafter), which controls signal generator 18 and power amplifier 22 and receives, through a line 52, amplified standards of input signal S, taken at output of the amplifier 22. In use, when an engaged-track signal is to be generated, circuit 50 supplies digital word D1 (remote control) to signal generator 18. Signal generator 18 therefore generates a square wave signal with a 250 Hz frequency F1 which, further to its amplification by amplifier 22 and a voltage boost by transformer 25, is sent out on cable 9. The control signal undergoes a voltage drop by transformer 29 and a square wave signal S1 is sent to filters 31, 32 and 33 with a 250 Hz frequency and a voltage value of approximately 15 volts. Signal S1 travels through filter 31, which is tuned with the frequency value (250 Hz) of said signal S1; in this manner, through incandescence lamp 13r there flows a current ir (in the embodiment described equal to approximately 1.63 amperes), which causes lamp 13r to turn on (red light source on). Filters 32 and 33 have high impedance values for signal S1, and currents iy and ig (in the embodiment described equal to approximately 0.31 and 0.11 amperes, respectively), flowing through lamps 13y and 13g, are not sufficient to turn on their respective yellow and green light sources. When a slow-down signal is to be generated, circuit 50 supplies digital word D2 to signal generator 18, which generates a square wave signal with a 364 Hz frequency F2. A square wave signal S2 is therefore conveyed to filters 31, 32 and 33, with a 364 Hz frequency and a voltage value of approximately 15 volts. Signal S2 travels through filter 32, which is tuned with the frequency value (364 Hz) of said signal S2 and through the filament (not shown) of incandescence lamp 13g there flows a current iy (in the embodiment described equal to approximately 1.63 amperes), which causes lamp 13y to turn on (yellow light source on). Filters 31 and 33 have high impedance values for 364 Hz signal S2, and currents ir and ig (in the embodiment described equal to approximately 0.4 and 0.16 amperes, respectively), flowing through lamps 13r and 13g, are not sufficient to turn on their respective red and green light sources. When a free-track signal is to be generated, circuit 50 supplies digital word D3 to signal generator 18, which generates a square wave signal with a 556 Hz frequency F3. A square wave signal S3 is therefore conveyed to filters 31, 32 and 33, with a 556 Hz frequency and a voltage value of approximately 15 volts. Signal S3 travels through filter 33, which is tuned with the frequency value (556 Hz) of said signal S3 and through the filament (not shown) of incandescence lamp 13g there flows a current ig (in the embodiment described equal to approximately 1.62 amperes), which causes lamp 13g to turn on (green light source on). Filters 31 and 32 have high impedance values for signal S3, and currents ir and iy (in the embodiment described equal to approximately 0.17 and 0.24 amperes, respectively), flowing through lamps 13r and 13y, are not sufficient to turn on their respective red and yellow light sources. On the grounds of the foregoing, the advantages of the present invention stand out clearly, in that the system according to the invention is of the safety type, i.e., in the event of failure, the system generates such signals, as are capable of preventing vehicles from travelling along the railroad tracks. A possible failure of system 1 can consist in the deterioration of capacitors 38, 42, 46 of filters 31, 32, 33, consequently leading to a reduction in the capacitance of said capacitors 38, 42, 46 (on well-known physical grounds, no increase in the capacitance of capacitors can take place further to deterioration of the relevant component). The decrease in capacitance corresponds to an increase in the central frequency of the respective filter; in this way, transfer functions H 1 , H 2 , H 3 (Fig. 2) of filters 31, 32, 33 can be shifted (positions indicated by numbers H d1 , H d2 , H d3 ) towards higher frequencies. This is the reason why, should the transfer function of a filter shift to the frequency range of the transfer function adjacent thereto and pertaining to another filter, there is turned on the light source which is representative of the more restrictive condition, with relation to travelling along the track. For example, in the presence of both 364 Hz signal (yellow light source on) and strong deterioration of the capacitors of filter 31, transfer function H 1 shifts to the neighbourhood of transfer function H 2 and the red light source is activated (engaged track). In the presence of both 556 Hz signal (green light source on) and strong deterioration of the capacitors of filter 32, transfer function H 2 shifts to the neighbourhood of transfer function H 3 and the yellow light source is activated (slow down). In the presence of both 556 Hz signal (green light source on) and strong deterioration of the capacitors of filter 33, transfer function H 3 shifts towards higher frequencies and the green light source is turned off. In the event of a short circuit of a capacitor 38, 42, 46, respective band-pass filter 31, 32, 33 is no longer capable of resounding and coil 37, 41, 45 is inserted directly between the secondary winding of transformer 29 and incandescence lamp 13r, 13y, 13g. In such conditions, coil 37, 41, 45 allows for a current ir, iy, ig to flow through, which is not sufficient to turn on respective incandescence lamp 13r, 13y, 13g. For example, in the presence of both 250 Hz signal (red light source on), and short circuit of capacitor 46, coil 45 is inserted directly between the secondary winding of transformer 29 and incandescence lamp 13g. At the 250 Hz frequency, coil 45 has such an impedance value, that the current flowing through said coil 45 (and, consequently, also through lamp 15g) is lower than the starting current (approximately 0.6 amperes) of lamp 13g. Should capacitor 38, 42, 46 break (open), the secondary winding of transformer 29 and incandescence lamp 13r, 13y, 13g are uncoupled, with respect to each other. Being this the case, incandescence lamp 13r, 13y, 13g is forthwith turned off. In the presence of a short circuit of a coil 37, 41, 45, respective band-pass filter 31, 32, 33 is no longer capable of resounding and capacitor 38, 42, 46 is inserted directly between the secondary winding of transformer 29 and incandescence lamp 13r, 13y, 13g. In such conditions, capacitor 38, 42, 46 allows for a current ir, iy, ig to flow through, such current being insufficient to turn on respective incandescence lamp 13r, 13y, 13g. For example, in the presence of both 250 Hz signal (red light source on), and short circuit of coil 45, capacitor 46 is inserted directly between the secondary winding of transformer 29 and incandescence lamp 13g. Capacitor 46 allows for a current ig to flow through, such current being insufficient to turn on the green light source. Coil 37, 41, 45 is obtained by winding on a magnetic core (not shown) a number of turns of insulated wire (not shown) and by separating each subsequent turn by means of high insulation foils (rigidity higher than 4 kV); given the foregoing, a short circuit of coil 37, 41, 45 is statistically highly unlikely. Therefore, the green light source can be turned on, in connection with the output of the 250 Hz signal (capable of activating the red light source), only in the event of a short circuit of both capacitor 46 and coil 45 (which, statistically, is a highly unlikely event). Being this the case, incandescence lamps 13g and 13r are turned on simultaneously, and the supply current flowing along cable 9 from station 4 to station 7 is twice the current supplied to turn on one single light source. Doubling of supply current is detected by circuit 50, which in turn generates a malfunction signal. Moreover, the control of railroad signal 11 is carried out by means of one single bipolar cable 9, which is neither expensive nor bulky or difficult to install. Furthermore, no signalling errors are possible owing to leakages along cable 9, which is of the bipolar type. Moreover, the system described hereinabove may undergo both changes and alterations falling within the scope of protection of the invention. Fig. 3 shows an alternative embodiment 1a of the system shown in Fig. 1. According to such an alternative embodiment 1a, the structure of central station is identical to the one shown in Fig. 1, its components being therefore referred to by the same numbers as in Fig. 1, accompanied by subscript a. Signal generator 18a is capable of generating a square-wave periodic alternating signal S, which can have two different output frequencies F1, F2, for example, equal to 250 Hz and 364 Hz. Signal S output frequency is selected on the basis of the digital value of a word D on control input 20a of signal generator 18a. For example, in connection with a first digital word D1, there can be generated a signal with frequency F1 = 250 Hz, and in connection with a second digital word D2 there can be generated a signal with frequency F2 = 364 Hz. Central station 4a is connected through a bipolar cable 57 to a peripheral station 7a. Peripheral station 7a comprises a transformer 58, the primary winding whereof communicates with one output of bipolar cable 57. Peripheral station 7a further comprises two band-pass filters 61 and 62, fitted with respective inputs 61a, 62a, communicating with a first output terminal 64 of a first secondary winding 58a of transformer 58. Outputs 61b, 62b of band-pass filters 61, 62 communicate with first terminals of incandescence lamps 67s and 67g, respectively, of a railroad signal 69. Incandescence lamps 67s, 67g have second terminals, communicating, through a power line 71, with a second output terminal 73 of the first secondary winding of transformer 58. Transformer 58 is further provided with a second secondary winding 58b, which is connected, through the insertion of a resistor 76, to the terminals of an incandescence lamp 67k of railroad signal 69. In particular, railroad signal 69 is of the so-called "da binario" (in the track) type, and comprises an outer casing, in the shape of a parallelepiped, a front wall 78 whereof is substantially trapezoidal/rectangular and is fitted with three openings, through which the light given out by incandescence lamps 67s, 67g and 67k is let out. In particular, lamp 67k is located near the right angle of wall 78 and lamps 67s and 67g are located near the respective oblique angles of wall 78. When on, lamp 67g is capable of conveying a free-track signal, whereas lamp 67s is capable of conveying, when on, an engaged track signal. Filter 61 comprises a coil 80, whereof a first terminal communicates with input 61a and a second terminal communicates with a first terminal of a capacitor 81. A second terminal of capacitor 81 is connected to a first terminal of a resistor 82, a second terminal whereof communicates with output 61b. Filter 62 comprises a coil 84, whereof a first terminal communicates with input 62a and a second terminal communicates with a first terminal of a capacitor 85. A second terminal of capacitor 85 is connected to a first terminal of a resistor 86, a second terminal whereof communicates with output 62b. Filter 61 supplying lamp 67s has a central frequency which is equal to 250 Hz and filter 62 supplying lamp 67g has a central frequency which is equal to 364 Hz. Operation of the system shown in Fig. 3 is similar to that of system 1, previously described, in that, according to the frequency value of signal S, generated by generator 18a, namely, whether 250 Hz or 364 Hz, incandescence lamps 67s or 67g (engaged track - free track), respectively, are supplied and caused to turn on. Lamp 67k, instead, is directly connected to secondary winding 58b of transformer 58, so that it is constantly supplied (and on), both when generator 18a generates a 250 Hz signal and when it generates a 336 Hz signal. Fig. 4 shows a schematic view of an example of a control and monitoring circuit, capable of being used in system 1, 1a. Circuit 50 comprises an interface circuit 90, the input whereof is connected to line 52, and which is fitted with two outputs 90a, 90b, communicating with a first microcontroller 92 and a second microcontroller 93, respectively. Interface circuit 90 is capable of reducing the voltage signal at its input, supplying to microcontrollers 92, 93 a square wave signal with reduced voltage and a frequency, which is equivalent to that of the signal generated by generator 18. Microcontrollers 92, 93 further receive, at their input, digital word D and are capable of calculating the frequency value corresponding to such a word D. Each microcontroller 92, 93 has a control output, connected to a respective first and second input 96a, 96b of an AND gate 96. AND gate 96 is further fitted with a third input 96c, communicating with a monitoring circuit 97 (WATCHDOG), operating with microcontrollers 92, 93. Moreover, AND gate 96 has an output 96u, communicating with enabling input 27 of amplifier 22. Microcontroller circuits 92, 93 are capable of calculating both period and frequency of the signal generated by generator 18, and are capable of comparing such a frequency value with that, which is actually required and corresponds to input word D. In the event a microcontroller 92, 93 (or both thereof) detected a significant difference between the input frequency value and the actual value, a logic zero is supplied at input 96a, 96b of AND gate 96 and amplifier 22 is turned off. Amplifier 22 is further turned off whenever WATCHDOG circuit 97 detects a failure in either of microcontrollers 92, 93.

Claims: A control system for railroad colour light signalling devices comprising: at least one central control station (4); at least one peripheral station (7); at least one electric cable (9) extending from said central control station (4) to said peripheral station (7); at least one signalling device (11), cooperating with said peripheral station (11); said signalling device (11) being provided with at least a first light source (13r), capable of indicating, when on, a first condition for the advance of a railroad vehicle, and a second light source (13g), capable of indicating, when on, a second condition for the advance of a railroad vehicle, said central control station (4) comprising signal generating means (18), capable of generating a periodic alternating signal, delivered to said electric cable (9); said signal generating means (18) being capable of alternatively generating, on the basis of information delivered to at least one control input, said periodic alternating signal with at least a first output frequency (F1), or with a second output frequency (F3); said peripheral station (7) comprising at least a first band-pass filter (31, 61), capable of receiving the periodic alternating signal from said cable (9), and supplying said first light source (13r); said first band-pass filter (31, 61) having a central frequency, which is substantially equivalent to said first frequency (F1); said peripheral station (7) further comprising a second band-pass filter (33, 62), capable of receiving the periodic alternating signal from said cable (9), and supplying said second light source (13g); said second band-pass filter (33, 62) having a central frequency, which is substantially equivalent to said second frequency (F3); said first light source (13r) is capable of signalling, when on, a restrictive condition for the advance of a railroad vehicle, in particular, a stop condition for the railroad vehicle; and said second light source (13g) being capable of signalling, when on, a non-restrictive condition for the advance of a railroad vehicle, in particular, a go-ahead free-track signal, characterized in that said first frequency (F1) is lower than said second frequency (F3). A control system according to Claim 1, characterized in that each band pass filter (31, 61, 33, 63) includes a reactance and comprises at least one coil (37, 80, 45, 84), connected in series, with respect to at least one capacitor (38, 81, 46, 85). A control system according to either Claim 1 or 2, characterized in that each light source comprises at least one incandescence lamp. A control system according to any one of the previous Claims, characterized in that said central control station (4) comprises voltage elevating means (22, 25), inserted between said signal generating means (18) and an input terminal (9a) of said cable (9). A control system according to Claim 4, characterized in that said voltage elevating means (22, 25) comprise a transformer. A control system according to either Claim 4 or 5, characterized in that said peripheral station (7) comprises voltage reduction means (29), inserted between an output terminal (9a) of said cable (9) and inputs (31a, 33a) of said first filter (31) and of said second filter (33). A control system according to Claim 6, characterized in that said voltage reduction means (22, 25) comprise a transformer. A control system according to any one of the previous Claims, characterized in that said peripheral station (7) comprises transmission coupling means (58), capable of receiving the periodic alternating signal from said cable (9) and of delivering the said periodic alternating signal to an auxiliary light source (67k), which is capable of being on both with first output frequency (F1) and with second output frequency (F3). A control system according to Claim 8, characterized in that said transmission coupling means (58) comprise a transformer (58), a primary winding whereof communicates with said cable (9a); a first secondary winding (58a) of said transformer (58) communicating with said first and said second band-pass filter (61, 62), and a second secondary winding (58b) being capable of supplying said auxiliary light source (67k). A control system according to any one of the previous Claims, characterized in that said cable is of the bipolar type.

Inventors: ELENA DOMENICO, RINALDI GIOVANNI, ELENA, DOMENICO, RINALDI, GIOVANNI
Applicants: ANSALDOBREDA S P A, ANSALDOBREDA S.P.A.
Application year: 1996
Main classification: B61L7
IPC codes: B61L7, G05B9, G05B19