Pneumatic braking system for a railway vehicle with a solenoid brake release valve

Abstract

The pneumatic braking system comprises a pneumatic circuit for supplying a pneumatic braking pressure to at least one brake cylinder, and includes a pneumatic solenoid charging valve and a pneumatic solenoid discharge valve adapted to cause an increase and a reduction, respectively, of the pneumatic pressure acting upon the at least one brake cylinder, the solenoid valves being controlled by an electronic braking control unit; a solenoid brake release valve adapted to cause, when energized, a complete discharge of the pneumatic pressure applied to the at least one brake cylinder, independently of the conditions of the solenoid charging and discharge valves; and an electric emergency line on which in normal operation there is a voltage which drops when emergency braking is activated.

Claims

1. Pneumatic braking system for a railway vehicle, comprising a pneumatic circuit for supplying a pneumatic braking pressure to at least one brake cylinder, including a pneumatic solenoid charging valve and a pneumatic solenoid discharge valve adapted to cause an increase and a reduction, respectively, of the pneumatic pressure acting upon said at least one brake cylinder, said solenoid valves being controlled by an electronic braking control unit; a solenoid brake release valve adapted to cause, when energized, a complete discharge of the pneumatic pressure applied to said at least one brake cylinder, independently of the conditions of said solenoid charging and discharge valves; and the system comprising further an electric emergency line on which in normal operation there is a voltage which drops when emergency braking is activated; the system being characterized in that: said solenoid brake release valve is coupled to said electric emergency line through at least one controlled electric switch that is a normally closed type and is connected to control means designed to supply thereto a disabling signal, capable of keeping said switch open in a normal operating condition of the system and switching said disabling signal off and allowing the opening of said switch in a condition of malfunction or failure, so that the solenoid brake release valve can be energized by a controlled closure of said switch when a voltage is present on said electric emergency line; and the solenoid brake release valve is de-energized when said switch is opened, as well as when the voltage on the electric emergency line drops, independently of the condition of said switch.

2. Pneumatic braking system according to claim 1, wherein there is connected, in parallel with said at least one switch, at least one second controlled electric switch of a normally open type, adapted to be closed to cause the energization of said solenoid brake release valve as a consequence of the closure of an associated switch that can be controlled by a train driver and/or an electronic control system.

3. Pneumatic braking system for a railway vehicle, comprising a pneumatic circuit for supplying a pneumatic braking pressure to at least one brake cylinder, including a pneumatic solenoid charging valve and a pneumatic solenoid discharge valve adapted to cause an increase and a reduction, respectively, of the pneumatic pressure acting upon said at least one brake cylinder, said solenoid valves being controlled by an electronic braking control unit; a solenoid brake release valve adapted to cause, when energized, a complete discharge of the pneumatic pressure applied to said at least one brake cylinder, independently of the conditions of said solenoid charging and discharge valves; and the system comprising further an electric emergency line on which in normal operation there is a voltage which drops when emergency braking is activated; the system being characterized in that: said solenoid brake release valve is coupled to said electric emergency line through at least one controlled electric switch, so that the solenoid brake release valve can be energized by a controlled closure of said switch when a voltage is present on said electric emergency line; and the solenoid brake release valve is de-energized when said switch is opened, as well as when the voltage on the electric emergency line drops, independently of the condition of said switch, wherein there is connected, in parallel with said at least one switch, at least one second controlled electric switch of a normally open type, adapted to be closed to cause the energization of said solenoid brake release valve as a consequence of the closure of an associated switch that can be controlled by a train driver and/or an electronic control system.

Description

(1) Further characteristics and advantages of the present invention will be apparent from the following detailed description, provided purely by way of non-limiting example, with reference to the attached drawings, in which:

(2) FIGS. 1 and 2, described above, are diagrams partially illustrating pneumatic braking systems according to the prior art;

(3) FIG. 3 is an electrical diagram, partially in block form, showing a first solution according to the present invention; and

(4) FIG. 4 is an electrical diagram, partially in block form, showing a second solution according to the present invention.

(5) In FIG. 3, the number 18a indicates the control winding or solenoid of the solenoid brake release valve 18 of one of the diagrams shown in FIGS. 1 and 2.

(6) In the solution according to FIG. 3, the winding or solenoid 18a has one terminal connected to an earth conductor GND and the other terminal connected to an electric emergency line or loop 20 on which, in a known way, during normal operation of the braking system of the railway vehicle, there is a voltage V.sub.S, which drops when emergency braking is activated.

(7) The winding or solenoid 18a of the solenoid brake release valve is coupled to the line or loop 20 through a controlled electric switch, indicated as a whole by 21.

(8) The switch 21 is of the normally closed type, and in the embodiment shown by way of example in FIG. 3 it is an electromechanical switch, comprising a normally closed contact 21a controlled by a winding or solenoid 21b, the latter being connected between the outlet of a driver circuit 22 and the earth conductor GND. Evidently, the controlled switch 21 could alternatively be of a static type, for example a solid state electronic switch, controlled through a galvanic decoupling device such as an optical isolator.

(9) When the braking system operates normally, a control unit 113 (which may or may not be the unit 13 described above) applies a vital signal to the input of the drive circuit or driver 22 such that said drive circuit 22 keeps the solenoid 21b energized, so that the latter holds the associated movable contact 21a in the open position, thereby keeping the winding or solenoid 18a of the solenoid brake release valve 18 de-energized. In this condition, with reference to the diagrams of FIGS. 1 and 2, the brake release valve 18 does not interfere with the normal operation of the braking system.

(10) If an operating anomaly or a failure occurs, as detected by the control unit 113, it interrupts the application of the vital signal to the input of the drive circuit 22, which consequently deenergizes the winding or solenoid 21b of the controlled switch 21, whose movable contact 21a returns to the normal closed condition. The winding or solenoid 18a of the solenoid brake release valve 18 is then energized, and this solenoid valve 18 causes the immediate emptying of the control or drive chamber of the relay valve 15, thus fully releasing the brake and preventing any risk of locking.

(11) The system remains in this state unless the emergency line or loop 20 is de-energized, in which case the solenoid 18a of the brake release valve 18 is then de-energized, returning the pneumatic braking system to the original condition.

(12) This is found to be particularly favourable in the case of an inverse pneumatic configuration, since it restores the full braking force to the vehicle, including the portion relating to the electronic control unit in an anomalous or failed condition.

(13) FIG. 4 shows a variant embodiment. In this drawing, parts and elements described previously have again been given the alphanumeric references used previously.

(14) In the solution according to FIG. 4, the brake release valve 18 can be energized either as a result of the disappearance of the vital signal at the input of the drive circuit 22, or in consequence of a request activated by the driver or by a control logic of the vehicle, through a normally open switch 30, connected in a circuit which controls the energization of a second controlled switch device 121.

(15) In the illustrated embodiment, the switch 121 is also of the electromechanical type, and comprises a normally open movable contact 121a connected in parallel to the normally closed contact 21a of the switch 21.

(16) The switch 121 further comprises a winding or solenoid 121b which controls the position of the movable contact 121a, and which can be coupled via the switch 30 to a source 31 of an energizing voltage V.sub.E.

(17) The closure of the normally open switch 30, caused directly by the driver or by a control logic of the railway vehicle, causes the activation of the solenoid brake release valve 18: when the switch 30 closes, the winding or solenoid 121b of the switch 121 is energized and causes the closure of the movable contact 121a and the consequent energizing of the winding or solenoid 18a of the solenoid release valve 18.

(18) In this case also, the control chamber 14 of the relay valve 15 is emptied virtually immediately, and the brake is released, preventing any risk of locking.

(19) The system remains in this state unless the emergency line or loop 20 is de-energized, in which case the solenoid 18a of the brake release valve 18 is then de-energized, returning the pneumatic braking system to the original condition.

(20) In other respects, the solution shown in FIG. 4 operates as described above in relation to the solution according to FIG. 3.

(21) Naturally, the principle of the invention remaining the same, the forms of embodiment and the details of construction may be varied widely from what has been described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined by the attached claims.