A system for recovering compressed air released by air suspensions of at least one rail vehicle or train

Abstract

A recovery system of compressed air released by an air suspension of at least one rail vehicle or train is described, comprising a first compressor (102), a compressed air drying device (103), a first pipe (106), a first tank (104), a check valve (107), a limiting valve (108), a second tank (109), a second pipe (220), at least one pneumatic spring (111), and a first control device (212). The recovery system further comprises a third pipe (201) arranged to be connected to the pneumatic discharge port (112) of the at least one leveling valve (110) to receive compressed air discharged by the pneumatic spring (111), and a third tank (202) arranged to be connected to the third pipe (201) and supplied by compressed air provided by the third pipe (201).

Description

TECHNICAL FIELD

[0001] The present invention generally belongs to the field of rail vehicles; in particular, the present invention relates to a system for the recovery of compressed air released by air suspensions of at least one rail vehicle or train. BACKGROUND

[0002] The air suspension system for a bogie of a rail vehicle manufactured according to the prior art is shown in Figure 1.

[0003] The compressed air source 101 comprises a compressor 102 followed by a compressed air drying device 103 and supplies a tank 104, called main tank, through a pipe 106, called main pipe.

[0004] The control device 105 monitors the pressure present in the main tank 104 and controls the compressor 102 through at least one signal 106, starting the compressor 102 when the pressure in the main tank 104 reaches a minimum pressure value and stopping the compressor 102 when the pressure in the main tank 104 reaches a maximum pressure value.

[0005] It is known to those skilled in the art of the rail industry that the minimum pressure value is generally between the nominal values of 6 bar and 7 bar, while the maximum pressure value is generally between the nominal values of 9 bar and 10 bar.

[0006] It is also known to those skilled in the art of the rail industry that the energy efficiency of a compressor for rails is approximately 30%, i.e. the energy component included in the compressed air at the outlet of the compressor corresponds to approximately 30% of the electrical energy used by the compressor to produce the compressed air. The remaining approximately 70% is converted into heat during the compression process and then dispersed into the environment.

[0007] The control device 105 can take various embodiments, for example, as non-exclusive examples, an electromechanical pressure switch, or again as non-exclusive examples, an electronic control system.

[0008] Downstream of the compressor 102, the compressed air drying device 103 is used to remove the liquid components and water vapour present in the compressed air produced by the compressor 102.

[0009] It is known to those skilled in the art that the drying process uses a portion of the compressed air produced by the compressor 102 and disperses it into the atmosphere, the amount of this portion corresponding to approximately 15% of the compressed air to be dried.

[0010] Taking into account the various efficiencies described earlier, the mechanical energy of the compressed air stored in the tank 104 corresponds to approximately 25% of the electrical energy used by the compressor 102 to bring the air in the main tank 104 to a pressure value between 9 bar and 10 bar.

[0011] Through the main conduit 106, compressed air is brought to at least one first utility system 203, for example, by way of non-exclusive example, a braking system, a pantograph lifting system, other user. It is not the purpose of the present invention to discuss in detail the implementation regarding each user system 203.

[0012] Another system using compressed air is the air suspension system described below.

[0013] Downstream of the check valve 107, a limiting valve 108 supplies the tank 109.

[0014] The purpose of the limiting valve 108 is to limit the pressure to a maximum value allowed by the suspension system. An example value is between 6 bar and 7 bar. The maximum allowed design pressure value of the suspension system determines the minimum design pressure value at which the control device 105 activates the compressor 102.

[0015] The levelling valve 110 is supplied by the tank 109 and supplies the pneumatic spring 111 which is physically constrained between the bogie 115 and the vehicle carriage 113.

[0016] The operation of the levelling valve 110, as illustrated below, is known in the art.

[0017] The levelling valve 110 is arranged to assume three states imposed by the lever 114.

[0018] In a first position, the lever 114 forces the levelling valve 110 to connect the tank 109 with the pneumatic spring 111, increasing the pressure in the pneumatic spring 111, raising the vertical position of the carriage 113 with respect to the rail level.

[0019] In a second central position, the lever 114 forces the levelling valve 110 to close the outlet of the tank 109 and the inlet of the pneumatic spring 111, respectively, keeping the pressure in the pneumatic spring 111 constant, thus maintaining a constant vertical position of the carriage 113 with respect to the rail level.

[0020] In a third position, the lever 114 forces the levelling valve 110 to close the outlet of the tank 109 and to make the pneumatic spring 111 communicate with the atmosphere through the pneumatic discharge port 112 of the levelling valve 110, lowering the vertical position of the carriage 113 with respect to the rail level.

[0021] It is known in the art how the levelling valve 110 is mechanically connected to the vehicle carriage 113 and how the apex 114 of the lever 113 is mechanically connected to the bogie 115.

[0022] Therefore, when the weight of the car 113 varies as a result of an increase or decrease in the number of passengers, the relative vertical movement between the car 113 and the bogie 115 acts on the lever 113 in such a way as to constantly bring the distance between the car 113 and the bogie 115 to a value predetermined during the design phase, corresponding to the second central position of the levelling valve 110.

[0023] For the sake of completeness of information, the predetermined value of the vertical distance between the car 113 and the bogie 115 corresponds to the height of the passenger boarding platforms of the stations, which must regularly coincide with the level of the horizontal plane of the internal floor of the vehicle, in order to avoid the presence of an unsuitable step between the vehicle and the platform during the transfer of passengers in both directions.

[0024] As is known, in general, the operating range of air suspension systems is between 4 bar and 6 bar, i.e. the range of pressure of the compressed air discharged by the levelling valve 110 to the atmosphere is generally between 4 bar and 6 bar during the phase of discharge to the atmosphere.

[0025] As is known, vibrations during travel of the vehicle cause variations in the relative height between the car 113 and the bogie 115, which cause the levelling valve 110 to be activated, with consequent unsuitable consumption of air.

[0026] As is known, the air consumption of the suspension system of a railway vehicle is such as to correspond, on average, to 60% of the air produced by the compressed air generation system 101.

[0027] Disadvantageously, this consumption of compressed air by the suspension system has a considerable value. SUMMARY

[0028] It is therefore an object of the present application to recover some of the compressed air used by the suspension system, thus recovering energy.

[0029] The above and other objects and advantages are achieved, according to one aspect of the present application, by a recovery system of compressed air released by an air suspension of at least one railway vehicle or train. Preferred embodiments of the present application are defined in the dependent claims, the content of which is to be understood as being an integral part of the present description. BRIEF DESCRIPTION OF DRAWINGS

[0030] The functional and structural characteristics of some preferred embodiments of a recovery system of compressed air released by an air suspension of at least one railway vehicle or train according to the present application will now be described. Reference is made to the attached drawings, in which:

[0031] - Figure 1 shows an air suspension system for a bogie of a railway vehicle, manufactured according to the prior art; and

[0032] - Figure 2An embodiment of a recovery system of compressed air released by air suspensions of at least one rail vehicle or train is shown. DETAILED DESCRIPTION

[0033] Before explaining the multiple embodiments of the application in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The application is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.

[0034] As Figure 2 shown, in a first embodiment, the recovery system of compressed air released by air suspensions of at least one rail vehicle or train comprises a first compressor 102 arranged to be supplied by atmospheric pressure and to produce compressed air, a compressed air drying device 103 arranged to be supplied by the compressed air provided by the first compressor 102, a first pipe 106 arranged to be supplied by the compressed air provided by the compressed air drying device 103, and a first tank 104 arranged to be supplied by the compressed air provided by the first pipe 106. In other words, the compressed air source 211 comprises the first compressor 102 followed by the compressed air drying device 103, and supplies the first tank 104 through the first pipe 106. The first tank 104 is referred to by those skilled in the art as a main tank, and the first pipe 106 is referred to by those skilled in the art as a main pipe. Downstream of the first compressor 102, the compressed air drying device 103 is used to remove the liquid components and water vapour present in the compressed air produced by the first compressor 102.

[0035] The recovery system further comprises a first control device 212 comprising a first pneumatic inlet 221 connected to the first pipe 106, wherein the first control device 212 is arranged to start the first compressor 102 by means of a first control signal 217 when the pressure present in the first pipe 106 is equal to or less than a predetermined first minimum pressure value, and the first control device 212 is arranged to stop the first compressor 102 by means of the first control signal 217 when the pressure present in the first pipe 106 is equal to or greater than a predetermined first maximum pressure value.

[0036] In other words, the first control device 212 monitors the pressure present in the first tank 104 through the first pneumatic inlet 221 connected to the first pipe 106 and controls the first compressor 102 through at least one first control signal 217, starting the first compressor 102 when the pressure in the first tank 104 reaches a first minimum pressure value and stopping the first compressor 102 when the pressure in the first tank 104 reaches a first maximum pressure value. It is known to those skilled in the art of the railway sector that the first minimum pressure value can be, but is not limited to, between the nominal values of 6 bar and 7 bar, and the first maximum pressure value can be, but is not limited to, between the nominal values of 9 bar and 10 bar.

[0037] Further, the recovery system comprises a non-return valve 107 arranged to be supplied by the compressed air provided by the first pipe 106, a limiting valve 108 arranged to be supplied by the compressed air provided by the non-return valve 107, a second tank 109 arranged to be supplied by the compressed air provided by the limiting valve 108, and a second pipe 220 arranged to be supplied by the compressed air provided by the second tank 109.

[0038] In other words, the non-return valve 107 connected to the first pipe 106 supplies the pressure limiting valve 108. The pressure limiting valve 108 in turn supplies the second tank 109 and the second pipe 220.

[0039] Still further, the recovery system comprises at least one levelling valve 110 arranged to be supplied by the compressed air provided by the second pipe 220 and at least one pneumatic spring 111 arranged to be supplied by the compressed air provided by the levelling valve 110. The pneumatic spring 111 is arranged between a bogie 115 and a car 113 of said at least one railway vehicle or of said train. The at least one levelling valve 110 comprises a pneumatic discharge port 112 arranged to discharge the compressed air stored in the pneumatic spring 111.

[0040] In other words, the at least one first levelling valve 110, the operation of which has been described above, is supplied by the second pipe 220, i.e. by the second tank 109, and supplies the first pneumatic spring 111 located between the associated bogie 115 and the associated vehicle car 113, which are not shown in Figure 2

[0041] The additional levelling valves 110 can be supplied by the second pipe 220 and supply the respective pneumatic springs 111.

[0042] ​Finally, the recovery system further comprises a third duct 201 arranged to be connected to the pneumatic discharge port 112 of the at least one levelling valve 110 to receive the compressed air discharged by the pneumatic spring 111, and a third tank 202 arranged to be connected to the third duct 201 and supplied by the compressed air provided by the third duct 201.

[0043] In other words, with respect to the conventional prior art system described so far, in which the at least one levelling valve 110 discharges air to the atmosphere through the pneumatic discharge port 112, in the present application the pneumatic discharge port 112 of the at least one first levelling valve 110 is connected to the third tank 202 through the third duct 201.

[0044] Therefore, the air discharged by the at least one levelling valve 110 is not discharged into the atmosphere, but is collected in the third tank 202 through the third duct 201.

[0045] In the case of more than one levelling valve 110, all the pneumatic discharge ports 112 associated with each levelling valve 110 are connected to the second duct 201.

[0046] With each pressure release action of the at least one levelling valve 110, the pressure in the third volume 202 increases.

[0047] The third tank 202 can comprise a pneumatic outlet 222 arranged to supply at least partially the compressed air of the third tank 202 to at least one pneumatic user system 203 of the at least one rail vehicle.

[0048] The pneumatic outlet 222 can be arranged to supply the compressed air provided by the third tank 202 directly to the at least one pneumatic user system 203, or, if the pressure present in the third tank 202 is less than a predetermined value that would be insufficient to properly supply the pneumatic user system 203, the pneumatic outlet 222 can be arranged to supply the compressed air provided by the third tank 202 to the at least one pneumatic user system 203 through a pneumatic control device 204 arranged to connect the pneumatic user system 203 to the first duct 106.

[0049] In other words, the at least one pneumatic user system 203 can be connected directly to the third tank 202 or through the pneumatic control device 204, the pneumatic user system 203 drawing compressed air from the third tank 202 for its own operation, reducing the pressure in the third tank 202. The pneumatic control device 204 is intended to connect the pneumatic user system 203 to the first duct 106, or to the atmosphere, when the pressure present in the third tank 202 is lower than a value that would be insufficient to properly supply the system 203. Figure 2An additional intermediate compressed air tank is shown and interposed between the first conduit 106 and the pneumatic user system 203.

[0050] Advantageously, the compressed air discharged by the at least one levelling valve 110 is not dispersed into the atmosphere by immediate expansion, but is recovered and used by the pneumatic user system 203. Moreover, the compressed air does not need to be dried, since it is already dry from the drying process present at the source 101. All this increases the overall efficiency of the entire compressed air generation and use system.

[0051] The recovery system can comprise a safety device 205 calibrated to a safety pressure value less than or equal to the minimum nominal working pressure value of the at least one pneumatic spring 111. The safety device 205 can then be arranged to discharge the air accumulated in the third tank 202 into the atmosphere when the pressure in the third tank 202 exceeds the safety pressure value.

[0052] In other words, in the event that the at least one pneumatic user system 203 does not promptly use the compressed air stored in the at least one pneumatic tank 202, the safety device 205 calibrated to a safety pressure value less than or equal to the minimum nominal working pressure value of the at least one pneumatic spring 111 discharges the air stored in the third tank 202 into the atmosphere when the pressure in the third tank 202 exceeds the safety pressure value, preventing the increase in pressure that exceeds said safety pressure value from preventing the correct operation of the at least one pneumatic spring 111.

[0053] Said safety device 205 can be, without limitation, a pneumatic safety valve.

[0054] In another embodiment, the recovery system can comprise a second compressor 206 comprising a suction inlet 207 arranged to be supplied with compressed air provided by the third tank 202 and an outlet port 208 arranged to supply compressed air to the second tank 109. The recovery system can thus comprise a second control device 209 and comprise a pneumatic inlet 223 arranged to be connected to the third tank 202. The second control device 209 can then be arranged to activate the second compressor 206 by means of a second control signal 210 when the pressure present in said third tank 202 is equal to or greater than a predetermined second maximum pressure value and to deactivate the second compressor 206 by means of said second control signal 210 when the pressure present in said third tank 202 is equal to or less than a predetermined second minimum pressure value.

[0055] In other words, the second compressor 206 can have an inlet port 207 connected to the third tank 202, and its outlet port 208 connected to the second tank 109. A second control device 209 can be connected to the third tank 202 through a second pneumatic inlet 223, and can monitor the pressure present in the third tank 202, and can control the compressor 206 through at least one second control signal 210, activating the second compressor 206 when the pressure in the third tank 202 reaches a second maximum pressure value, equal to or less than the minimum nominal operating value of the at least one pneumatic spring 111, and deactivating the second compressor 206 when the pressure in the third tank 202 reaches a second minimum pressure value predetermined in the design phase, less than the minimum nominal operating value of the at least one pneumatic spring 111.

[0056] Advantageously, the compressed air discharged by the at least one levelling valve 110 is not dissipated into the atmosphere through immediate expansion, but is recovered through recirculation through a pressure drop significantly less than the initial pressure drop.

[0057] Purely by way of example, in a system such as that described in the present embodiment, in which the pneumatic suspension system operates between 4 bar and 6 bar, after the first cycle performed by the first compressor 102, which brings the air through a first jump from 0 bar to 10 bar into the first tank 104, a normal operating cycle will be established, performed by the second compressor 206, to bring the air from the pressure present in the third tank 202 to the pressure of 6 bar of the second tank 109.

[0058] Furthermore, the compressed air does not need to be dried, since it is already dry from the drying process present at the source 101.

[0059] In another embodiment, the recovery system can comprise a pneumatic switching device 213.

[0060] The pneumatic switching device 213 can comprise a first suction port 215 arranged to suck air from the atmosphere, and a second suction port 216 arranged to be connected to the third duct 201 and to suck air from the third duct 201.

[0061] The pneumatic switching device 213 can comprise an outlet 219 connected to the suction inlet of the first compressor 102. The pneumatic switching device 213 can be arranged to be controlled by a third control signal 214 generated by the first control device 212. The third control signal can be arranged to assume a first value and a second value, the third control signal controlling the pneumatic switching device 213 through the first value to connect the suction inlet of the first compressor 102 to the first suction port 215 to suck air from the atmosphere, the third control signal controlling the pneumatic switching device 213 through the second value to connect the suction inlet of the first compressor 102 to the second suction port 216 to suck air from the third duct 201.

[0062] The first control device 212 can comprise a second pneumatic inlet 225 arranged to be connected to the third conduit 201.

[0063] The first compressor 102 can be in an initial operating state. That is, it can initially be in an open state or in a closed state. Thus, the first control device 212 can be arranged to:

[0064] a) when the pressure in the third conduit 201 or in the third tank 202 is equal to or greater than said second maximum pressure value, cause the third control signal 214 to assume its second value to control the pneumatic switching device 213 so as to connect the inlet of the first compressor 102 to the third conduit 201 through the second suction port 216, and, if said initial operating state of the first compressor 102 is that said first compressor 102 is in a closed state, cause the first compressor 102 to enter said current operating state in which the first compressor is in an open state, or, if said initial operating state of the first compressor 102 is that said first compressor 102 is already in an open state, cause the first compressor 102 to be in said current operating state in which the first compressor is in an open state;

[0065] b) when the pressure in the third conduit 201 or in the third tank 202 is equal to or less than said second minimum pressure value, cause the third control signal 214 to assume its first value to control the pneumatic switching device 213 so as to connect the inlet of the first compressor 102 to the atmosphere through the first suction port 215, and, if said initial operating state of the first compressor 102 is that said first compressor 102 is in an open state, cause the first compressor 102 to return to said current operating state in which the first compressor is in an open state, or, if said initial operating state of the first compressor 102 is that said first compressor 102 is in a closed state, cause the first compressor 102 to return to said current operating state in which the first compressor is in a closed state (i.e. cause the compressor to return to its previous state).

[0066] In other words, normally, the first compressor 102 can perform its usual function of filling the first tank 104 through the first suction port 215, for example, opening at 6 bar and closing at 10 bar (typical values).

[0067] Regardless of what the first compressor 102 is doing, if the pressure in the third conduit 201 (i.e. the pressure in the third tank 202) has reached its maximum value, indicating that air has been recovered from the pneumatic springs 111 (i.e. from the suspension) to a level beyond which the pneumatic springs 111 can no longer emit, it can be prioritized to return the air recovered from the third tank 202 to the first tank 104 104, switching the outlet 219 (connected to the suction inlet of said first compressor 102) to the second suction port 216 and restarting the first compressor 102 if it has not already been started.

[0068] When the third tank 202 reaches its predetermined minimum pressure, the first compressor 102 can return to doing what it was originally doing, i.e. if it was originally off, it will be turned back on, and if it was originally actively pumping air from the first suction port 215 to the first tank 104, it will return to actively pumping air from the first suction port 215 to the first tank 104 until the pressure in the first tank 104 reaches its maximum pressure.

[0069] Thus, the first compressor 102 can compress air from the pneumatic switching device 213, which is arranged to receive the third control signal 214. By way of example, the pneumatic switching device 213 can be a pneumatic valve, the capacity of which is adapted to the suction inlet of the first compressor 102. The third control signal 214 can assume a first state in which it controls the pneumatic switching device 213 to connect the inlet of the compressor 102 to the atmosphere via the first suction port 215, and can assume a second state in which it controls the pneumatic switching device 213 to connect the inlet of the first compressor 102 to the third conduit 201 via the second suction port 216.

[0070] The first control device 212, via the second pneumatic inlet 225, can further monitor the pressure present in the third tank 202 or in the third conduit 201 (the pressure in the third conduit 201 is substantially the same as the pressure in the third tank 202), i.e. the first control device 212 controls the pneumatic switching device 213 via the third control signal 214. When the pressure in the third tank 202 reaches a second minimum pressure value, regardless of the current state of the first control signal 217 and of the third control signal 214, the first control device 212 controls the third control signal 214 in a second state in which it controls the pneumatic switching device 213 to connect the inlet of the first compressor 102 to the third conduit 201 via the second suction port 216, and, if the first compressor 102 has not already been started, to start the compressor 102.

[0071] When the pressure in the third tank 202 reaches a second maximum pressure value, it restores the first control signal 217 and the third control signal 214 to their previous state.

[0072] Advantageously, the compressed air discharged by the at least one levelling valve 110 is not dispersed into the atmosphere by immediate expansion, but is recovered by recirculation through a pressure drop lower than the initial pressure drop. Moreover, said compressed air does not need to be dried, since it is already dry from the drying process present at the source 101.

[0073] It is obvious to the person skilled in the art that the above described reference to the first compressor 102, to the compressed air drying device 103, to the first duct 106, to the first tank 104, to the non-return valve 107, to the limiting valve 108, to the second tank 109, to the second duct 220, to the levelling valve 110, to the pneumatic spring 111 and to the control device 212 of the recovery system can be considered equivalent to a recovery system associated with an air suspension system, i.e. an air suspension, comprising a third duct 201 and a third tank 202, without thereby departing from the scope of the present application. Obviously, the recovery system comprising a third duct 201 and a third tank 202 can also be associated with a pneumatic suspension system which is structurally different but equally compatible, since they provide at least one levelling valve suitable for being connected to the duct 201 of the recovery system, to receive the compressed air discharged by at least one pneumatic spring, without thereby departing from the scope of the present application.

[0074] In the case of applicability, the above described with reference to the railway vehicle industry can also find application in other industries, such as, for example, the general vehicle, rubber-tired vehicle or rubber-tired vehicle fleet industry.

[0075] The various aspects and embodiments of the recovery system of the compressed air released by the air suspension of at least one railway vehicle or train according to the present application have been described. It is understood that each embodiment can be combined with any other embodiment. Moreover, the present application is not limited to the described embodiments, but can vary within the scope defined by the claims hereafter.

Claims

1. A recovery system of compressed air released by air suspensions of at least one railway vehicle, comprising: - a first compressor (102) arranged to be supplied by atmospheric pressure and to produce compressed air; - a compressed air drying device (103) arranged to be supplied by the compressed air provided by the first compressor (102); - a first pipe (106) arranged to be supplied by the compressed air provided by the compressed air drying device (103); - a first tank (104) arranged to be supplied by the compressed air provided by the first pipe (106); - a check valve (107) arranged to be supplied by the compressed air provided by the first pipe (106); - a limiting valve (108) arranged to be supplied by the compressed air provided by the check valve (107); - a second tank (109) arranged to be supplied by the compressed air provided by the limiting valve (108); - a second pipe (220) arranged to be supplied by the compressed air provided by the second tank (109); - at least one levelling valve (110) arranged to be supplied by the compressed air provided by the second pipe (220); - at least one pneumatic spring (111) arranged to be supplied by the compressed air provided by the levelling valve (110), wherein the pneumatic spring (111) is arranged between a bogie (115) of the at least one railway vehicle and a car body (113) of the at least one railway vehicle, wherein the at least one levelling valve (110) comprises a pneumatic discharge port (112) arranged to discharge compressed air accumulated in the pneumatic spring (111); - a first control device (212) comprising a first pneumatic inlet (221) connected to the first pipe (106), wherein the first control device (212) is arranged to activate the first compressor (102) by means of a first control signal (217) when the pressure present in the first pipe (106) is equal to or lower than a predetermined first minimum pressure value, and the first control device (212) is arranged to deactivate the first compressor (102) by means of the first control signal (217) when the pressure present in the first pipe (106) is equal to or greater than a predetermined first maximum pressure value; characterized in that it comprises: - a third pipe (201) arranged to be connected to the pneumatic discharge port (112) of the at least one levelling valve (110) to receive the compressed air discharged by the pneumatic spring (111); - a third tank (202) arranged to be connected to the third pipe (201) and to be supplied by the compressed air provided by the third pipe (201), wherein the third tank (202) comprises a pneumatic outlet (222) arranged to at least partially supply the compressed air present in the third tank (202) to at least one pneumatic user system (203) of the at least one railway vehicle.

2. The compressed air recovery system according to claim 1, wherein said pneumatic outlet (222) of said third tank is arranged to provide compressed air in said third tank (202) directly to said at least one pneumatic user system (203); or, said pneumatic outlet (222) of said third tank is arranged to provide compressed air in said third tank (202) to said at least one pneumatic user system (203) through a pneumatic control device (204) when the pressure present in said third tank (202) is lower than a predetermined value insufficient to properly supply said pneumatic user system (203), said pneumatic control device (204) being arranged to connect said pneumatic user system (203) to said first duct (106).

3. A compressed air recovery system of the compressed air released by the air suspensions of at least one railway vehicle, comprising: - a first compressor (102) arranged to be supplied by atmospheric pressure and to generate compressed air; - a compressed air drying device (103) arranged to be supplied by the compressed air provided by said first compressor (102); - a first duct (106) arranged to be supplied by the compressed air provided by said compressed air drying device (103); - a first tank (104) arranged to be supplied by the compressed air provided by said first duct (106); - a check valve (107) arranged to be supplied by the compressed air provided by said first duct (106); - a limiting valve (108) arranged to be supplied by the compressed air provided by said check valve (107); - a second tank (109) arranged to be supplied by the compressed air provided by said limiting valve (108); - a second duct (220) arranged to be supplied by the compressed air provided by said second tank (109); - at least one levelling valve (110) arranged to be supplied by the compressed air provided by said second duct (220); - at least one pneumatic spring (111) arranged to be supplied by the compressed air provided by said levelling valve (110), wherein said pneumatic spring (111) is arranged between a bogie (115) of at least one railway vehicle and a car (113) of said at least one railway vehicle, wherein said at least one levelling valve (110) comprises a pneumatic discharge port (112) arranged to discharge compressed air accumulated in said pneumatic spring (111); - a first control device (212) comprising a first pneumatic inlet (221) connected to said first duct (106), wherein said first control device (212) is arranged to activate said first compressor (102) through a first control signal (217) when the pressure present in said first duct (106) is equal to or lower than a predetermined first minimum pressure value, and said first control device (212) is arranged to deactivate said first compressor (102) through said first control signal (217) when the pressure present in said first duct (106) is equal to or greater than a predetermined first maximum pressure value; characterized in that said recovery system comprises: - a third duct (201) arranged to be connected to said pneumatic discharge port (112) of said at least one levelling valve (110) to receive compressed air discharged by said pneumatic spring (111); - a third tank (202) arranged to be connected to said third duct (201) and supplied by compressed air provided by said third duct (201), and - a second compressor (206) comprising: - a suction inlet (207) arranged to be supplied by compressed air provided by said third tank (202); and - an outlet port (208) arranged to supply compressed air to said second tank (109); wherein said recovery system of compressed air comprises a second control device (209) comprising a pneumatic inlet (223) arranged to be connected to said third tank (202); wherein said second control device (209) is arranged to activate said second compressor (206) by means of a second control signal (210) when the pressure present in said third tank (202) is equal to or greater than a predetermined second maximum pressure value and to deactivate said second compressor (206) by means of said second control signal (210) when the pressure present in said third tank (202) is equal to or lower than a predetermined second minimum pressure value.

4. Recovery system of compressed air according to claim 3, comprising a pneumatic switching device (213) comprising: - a first suction port (215) arranged to suck air from the atmosphere; and - a second suction port (216) arranged to be connected to said third duct (201) and to suck air from said third duct (201); wherein said pneumatic switching device (213) comprises an outlet (219) connected to the suction inlet of said first compressor (102); wherein said pneumatic switching device (213) is arranged to be controlled by a third control signal (214) generated by said first control device (212); wherein said third control signal (214) is arranged to assume: - a first value by means of which said third control signal (214) controls said pneumatic switching device (213) to connect said suction inlet of said first compressor (102) to said first suction port (215) to suck air from the atmosphere; - a second value by means of which said third control signal (214) controls said pneumatic switching device (213) to connect said suction inlet of said first compressor (102) to said second suction port (216) to suck air from said third duct (201); wherein said first control device (212) comprises a second pneumatic inlet (225) arranged to be connected to said third duct (201); wherein said first compressor (102) has a predetermined initial operating condition, said first control device (212) is arranged to: - activate said first compressor (102) by means of said first control signal (211) when said third duct (201) is connected to said first suction port (215) and said first compressor (102) is in said initial operating condition; and - deactivate said first compressor (102) by means of said first control signal (211) when said third duct (201) is connected to said second suction port (216) and said first compressor (102) is in said initial operating condition. a) when the pressure in the third conduit (201) or in the third tank (202) is equal to or greater than the second maximum pressure value, causing the third control signal (214) to assume the second value to control the pneumatic switching device (213) so as to connect the suction inlet of the first compressor (102) to the third conduit (201) through the second suction port (216) and, when the initial operating condition of the first compressor (102) is the off condition, causing the first compressor (102) to pass to the on current operating condition, or, when the initial operating condition of the first compressor (102) is already on, causing the first compressor (102) to remain in the on current operating condition; b) when the pressure in the third conduit (201) or in the third tank (202) is equal to or lower than the second minimum pressure value, causing the third control signal (214) to assume the first value to control the pneumatic switching device (213) so as to connect the suction inlet of the first compressor (102) to the atmosphere through the first suction port (215) and, when the initial operating condition of the first compressor (102) is the on condition, causing the first compressor (102) to return to the on current operating condition, or, when the initial operating condition of the first compressor (102) is the off condition, causing the first compressor (102) to return to the off current operating condition.

5. The compressed air recovery system according to claim 4, comprising a safety device (205) calibrated at a safety pressure value lower than or equal to the nominal minimum working pressure value of the at least one pneumatic spring (111); said safety device (205) being arranged to discharge the air accumulated in the third tank (202) to the atmosphere when the pressure in the third tank (202) exceeds the safety pressure value.

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