CH616116A5 - Pneumatic directional control valve for railway braking - Google Patents

Abstract

The pneumatic directional control valve comprises a main device (6) for controlling a brake control pressure and a correction device for this pressure as a function of a parameter (26) depending on the weight of the vehicle. The equipment (14, 28) comprises an auxiliary reaction surface (23) capable of producing a reaction force which adds to that of the main surface (18). The main surface (18) and auxiliary surface (23) of the equipment (14, 28) are stressed by the output pressure of the pressure relief device (13) regardless of the value of the parameter (26). They act on the pressure relief device (13) in the direction of closure of the latter, whilst the surface (23) is subjected, in the direction of action, to a correction pressure which is a function of the parameter (26), but without this surface (23) being able to act on the pressure relief device (13) in the direction for opening it. <IMAGE>

Description

The present invention relates to a pneumatic distributor for controlling the braking of a railway vehicle, comprising in a body a main device for controlling a braking control pressure and a device for correcting this pressure as a function of a parameter, the main control device comprising a pressure regulator and a piston and / or diaphragm assembly which acts on the regulator in the opening direction thereof in response to an action force produced on an action surface of said crew and in the opposite direction for closing and purging, in response to a reaction force produced on a main reaction surface of the crew by the outlet pressure of the regulator, the crew of the main device comprising an auxiliary surface reaction capable of producing a reaction force adding to that of the main surface.

In most current pneumatic distributors of this type, the main control device comprises a regulator and a piston and / or diaphragm unit which acts on the regulator in one direction in response to an action force produced on a surface d action of said crew, for example by stressing this surface by means of a differential pressure between a general pipe and a pressure tank and, in the opposite direction, in response to a reaction force produced on a main reaction surface of the crew by the outlet pressure of the regulator.

The object of the invention is to improve the operation of a pneumatic brake distributor of a rail vehicle - of the autocontinuous type or at several speeds depending on the variation of a parameter such as the load or the speed of the vehicle - with regard to the brake application and release times, the progressiveness of application and release, the quality of the first action and the regularity of behavior, whatever the supply pressure.

This object is achieved in accordance with the invention because it is characterized in that the main and auxiliary surfaces of the equi2

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page are requested by the output pressure whatever the value of the parameter to act on the regulator in the direction of closing it, while one of the reaction surfaces is subjected in the direction of action to a correction pressure which is a function of the parameter, but without this reaction surface being able to act on the regulator in the direction of opening.

The auxiliary reaction surface may include a plate or piston capable of sliding or of moving axially in a sealed manner on the pusher without coming to bear on the latter when, under the action of the pressure as a function of the parameter, it moves in the direction of opening of the regulator, while when, under the action of the outlet pressure delivered by the main device, it moves in the direction of closing the regulator and purging of the outlet pressure, said plate is likely to come to bear on the pusher and the crew, in particular when the outlet pressure exerts on it an effort capable of overcoming the effort caused on it by the pressure as a function of the parameter.

On the assumption that the corrective pressure varies continuously as a function of the parameter, one thus obtains an inflection of the curve of variation of the pressure delivered as a function of time and this at a point which depends directly on the corrective pressure. The tightening times and progressiveness are therefore satisfactory.

Advantageously, the sliding plate is associated with two stroke limiting stops constituted, one by a shoulder of the crew and the other by the body of the distributor, so that said plate can be pressed against said shoulder in the direction of closing of the distributor supply valve, and it is disconnected from the crew as soon as it is no longer supported on said shoulder.

In the case where the corrective pressure is a discontinuous function of the parameter - this is for example the case when the distributor operates in two regimes (vacuum-charged or high and low powers) - the auxiliary reaction diaphragm is switched off in regime charge. This result is obtained without interposing a special valve between the outlet of the regulator and the auxiliary reaction chamber delimited by the reaction face of the auxiliary reaction membrane. This avoids introducing, by the use of this special valve, a pressure drop and a complication of production.

The main control device may include a pressure limiter, for example with two concentric plates, making it possible to communicate to the crew an action force which remains constant as soon as the pressure of the general pipe becomes less than or equal to a predetermined value, for example 3.5 bars; in this way, the pressure delivered by the regulator cannot exceed a determined maximum value.

Orifices - or chokes - calibrated clamping are advantageously placed downstream of the main control device, that is to say between this device and the brake cylinders. The number of these calibrated orifices, in principle equal to four in an empty-loaded goods-passenger distributor, can be reduced to two by a judicious choice of passage diameters.

In combination with this downstream arrangement of the calibrated clamping orifices which makes it possible to rapidly supply the two reaction chambers, a first stage device can be arranged downstream of the main control device in order to control a valve to which a orifice is annexed in parallel. calibrated goods; the first stage device typically has a valve opening surface subjected to the pressure directly delivered by the main device while in a known manner comprising a valve closing surface subjected to the pressure prevailing downstream of the calibrated orifice merchandise.

This gives a first step independent of the pressure of the auxiliary tank and usable even in passenger mode.

A device for adapting the exhaust times can be arranged between the main control device and the atmosphere in order to correct these times for the different regimes imposed. The adaptation device comprises for example at least one pusher controlled by the correction pressure in order to open a valve controlling an additional calibrated connection with the atmosphere when the correction pressure exceeds a certain value.

The push-button of the adaptation device can be returned to the closed position of the valve by the pressure delivered by the main control device. Furthermore, this pusher can be pushed back to the valve open position by a spring, so that on release the additional calibrated connections with the atmosphere are opened as soon as the pressure of the brake cylinders reaches a certain threshold, this in view to achieve a more frank re-entry of the pistons in the cylinders even in low speed (vacuum or low power).

The characteristics and advantages of the invention will be better understood on reading the description which follows of several exemplary embodiments and with reference to the appended drawings in which:

- fig. 1 schematically represents a pneumatic rail brake distributor according to the invention with a main control device in the empty position;

- fig. 2 shows in isolation the main control device in the loaded position;

- figs. 3 and 4 respectively represent the first-time device and the device for adapting the exhaust times, and

- fig. 5 shows a variant supplying the reaction chambers of the main device.

The distributor shown is connected in the usual way to a general supply and control pipe 1, to an auxiliary tank 2, to a control tank 3 and to brake cylinders 4 of which only one is shown.

In the body 5 of the distributor are provided: a main control device 6, a device for accelerating the application of the brake 7, a filling valve 8 for the auxiliary tank 2 and for the control tank 3, a first-time valve 9, a member 10 for manual and automatic draining of the tanks, a non-return valve 11 protecting the auxiliary tank 2 and a goods-passenger or GP two-way valve 12a, 12b).

The main control device 6 (FIGS. 1 and 2) comprises a double-valve regulator 13 and a crew comprising an axially movable hollow rod 14. This crew has the role of opening the supply valve of the regulator 13 when it is produces a reduction in the pressure of the general pipe 1, pressure acting, in a chamber 15, on a main action membrane 16 against the fixed pressure of the control tank 3 transmitted to a chamber 17 opposite the chamber 15. The crew further comprises a main reaction membrane 18 whose surface is smaller than that of the membrane 16. The membrane 18 is stressed in the direction directed from top to bottom in FIGS. 1 and 2 by the pressure prevailing in a chamber 19 and delivered directly by the regulator 13, the chamber 20 opposite to the chamber 19 being vented through the pipe 21. A plate 22 connected in leaktight manner to the body by a membrane reaction auxiliary 23 is subjected from bottom to top to the pressure of a chamber 24. This pressure is of the order of 5 bars under loaded conditions and 0 bars under empty conditions and is determined by a regime change valve 25 as a function of a weighing pressure supplied by a weighing or suspension member 26 (fig. 1); it can also be a continuous function of the load (fig. 2).

In the chamber 27 opposite the chamber 24, the pressure delivered by the regulator 13 reigns. The plate 22 slides axially and sealingly on an external tube 28 surrounding the rod 14 and

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mounted axially movable in the body 1. The stroke of the plate 22 relative to the tube 28 is limited downwards by a shoulder 29 of the said tube 28, so that the membrane 23 and the plate 22 constitute an additional reaction member only under operating conditions empty in the case of fig. 1 or, in the case of FIG. 2, for all the final tightening phases.

The membrane assembly comprises at its lower part a pressure relief valve constituted by a plate 30 of large section concentric with a smaller disk 31. The plate 30 is axially sliding in leaktight manner on the tube 28, while the disk 31 is axially sliding and sealingly in the body. The tube 14 is crimped coaxially by its lower end into the central bore 31a of said disc 31. The chamber 32, delimited between the plate 30 and the disc 31, is permanently vented through the annular space 33 remaining between the tubes 14 and 28, of the chamber 20 and of the pipe 21. The plate 30 is biased in abutment against the disc 31 by a spring 34; in this way, for a certain threshold of the difference between the pressures of the general line 1 and of the control tank 3, the plate 30 comes into high abutment against the body after having compressed the spring 34; the only effective action surface therefore becomes that of the disc 31 and therefore produces a constant force whatever the value of said pressure difference beyond the threshold considered.

It can be noted that no calibrated orifice is disposed on the pipe 35 which connects the auxiliary tank 2 to the regulator 13. On the other hand, on the pipe 36 connecting the regulator 13 to the brake cylinders 4, there is a first calibrated constriction 37 and, in parallel to the latter and to the valve of the first-time valve 9, a second calibrated throttle 38. The operation of these throttles 37, 38 and of the first-time valve 9 will be explained later, but it is possible to now observe that the throttle 38 is only active in goods mode (fig. 2) after the first stage phase because, for this regime, element 12a of the valve GP located downstream of the throttle 37 (or comprising this throttle 37) is closed, while in passenger mode the element 12a is open as shown in FIG. 1, so that the pressure is delivered to the brake cylinders 4 during a tightening, by means of the two throttles 37 and 38 in parallel.

An exhaust time adaptation device 39 (FIGS. 1 and 4) is arranged on an exhaust pipe 40 of the main control device 6 and has the role of controlling the exhaust speed of this pipe.

The pipe 40 is permanently connected to the atmosphere by a calibrated orifice 41. The adaptation device 39 comprises a double valve 42, 43 secured to a piston 44 which is biased in the direction of the opening of the double valve 42 , 43 by a spring 45 and by the pressure as a function of the load of the vehicle that the speed change valve 25 delivers in a chamber 46; in the direction of closing the double valve 42, 43, the piston 44 is subjected to the pressure delivered in the chamber 47 opposite the chamber 46 by the regulator 13, pressure taken upstream of the calibrated throttle 37. The spring 45 is calculated to reopen the double valve 42, 43 for a pressure of approximately 0.2 bar at the brake cylinders. It is thus possible in particular to perform in empty or low power conditions a rapid emptying of the brake cylinders upon release.

In loaded conditions, the pipe 40 is vented to the goods position only through the orifice 41 and through an orifice 48 implemented through the opening of the valve 43, and in the passenger position (fig. 4) by the orifices 41, 48 and 49, the latter being implemented by the opening of the double valve 42, 43 and of the element 12b of the valve GP.

The first-time valve 9 (FIGS. 1 and 3) controls a valve 50 controlling a passage of large section 51 located in parallel with the calibrated throttle 38. The valve 9 comprises an assembly 52 having, on the one hand, a membrane 53 subjected in the direction of closing of the valve 50 to the pressure prevailing downstream of the throttle 38 and, on the other hand, a second membrane 54 subjected in the direction of opening of the valve 50 to the pressure prevailing upstream throttle 38 and delivered by the regulator 13. A spring 55 biases the equipment 52 of the valve 9 downward, that is to say in the direction of opening of the valve 50; the latter is finally subjected to a return spring 56 in the direction of its closure.

The dispenser of fig. 1 operates as the case may be in a manner which will be explained below.

I - Vehicle loaded, goods regime:

It is first assumed that the vehicle is loaded, that is to say that the weighing member 26 provides sufficient pneumatic pressure to cause the opening of the double valve 57 of the speed change valve 25 to 1 against the prestressed spring 57a. The air under pressure from the auxiliary tank 2 therefore reaches via the duct 35 and the bypass 58 at the open valve 25 and therefore at the device for adapting the exhaust times 39 and at the chamber 24 associated with the plate 22 and the membrane. 23 of the main control device 6.

The goods regime results in the positioning of the valve GP so as to close the channel 59 comprising the calibrated throttle 37 by means of the valve element 12a and to close the channel 60 opening to the atmosphere through the orifice. calibrated 49 by means of the valve element 12b.

At rest or in normal operation, the plate 22 of the main control device 6 is therefore applied upwards against the body by the pressure of the auxiliary reservoir 2 which prevails in the chamber 24.

1. Tightening:

When the mechanic commands a gradual application of the brake, the pressure of the general pipe 1 falls to a value between 5 and 3.5 bars, so that the plates 30, 31 transmit an upward force to the tube 14 of the crew which , therefore, opens the regulator supply valve 13.

The pressurized air flows from the auxiliary tank 2 via the conduit 35 and it is transmitted via the regulator 13:

a) to the brake cylinders 4 via the large-section passage 51 released by the valve 50 of the first-time valve 9 and in parallel through the calibrated orifice 38,

b) to the main 19 and auxiliary reaction chambers 27. It may be noted that the admission of pressure into these chambers is not delayed by any constriction.

Simultaneously, the pressure delivered by the regulator 13 is transmitted:

c) to the opening chamber 61 of the valve 50 associated with the first-time valve 9 and d) to the closing chamber 47 of the valves 42, 43 of the valve for adapting the exhaust times 39.

The control of the opening of the valve 50 by pressurizing the chamber 61 - in cooperation with the action of the spring 55 - makes it possible to guarantee a first step independent of the pressure of the auxiliary tank 2.

By first time is meant the duration of a first phase during which the brake cylinders are filled with air at a higher flow rate than during the following phase.

The pressure brought to the chamber 47 remains inoperative both when the brakes are applied and when the brakes are released, since it is exerted on a surface smaller than that of the chamber 46 where the pressure from the auxiliary reservoir 2 arrives.

As soon as the mechanic commands a full or emergency tightening, the pressure limiter 30 to 34 of the main control device 6 intervenes and limits the ascending force exerted on the crew 14 to a given value. It follows that the pressure delivered by the main control device 6, while being a function of the vehicle load, is practically independent of the pressure prevailing in the auxiliary tank 2.

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2. Loosening:

To produce the release of the brake, the mechanic causes a rise in pressure in the general line 1. It follows that the crew 14, 28 descends and causes the closing of the supply valve and then the opening of the valve. exhaust of the regulator 13. The pressurized air which was trapped in the brake cylinders 4 thus reaches via the conduit 36, the regulator 13 and the central channel 62 from the tube 14 to the conduit 40 and, from there, to the atmosphere by the calibrated orifice 41 and, in parallel, by means of the opening of the double valve 42, 43 of the adaptation valve 39, by the calibrated orifice 48.

II - Vehicle loaded, passenger regime:

The modification compared to the previous case consists in the position of the valve GP, now such that the elements 12a, 12b open, respectively, the conduit 59 having the calibrated throat 37 and the conduit 60 opening to the atmosphere through the calibrated orifice 49 (fig. 4).

1. Tightening:

The pressure delivered by the regulator 13 is transmitted by the passage with large section 51 which releases the valve 50 and, in parallel, by the orifice 38, this until a pressure value determining the lifting of the crew 52 and the closing the valve 50; this pressure is also transmitted, whatever its value, through the constriction 37 of the conduit 59. It can be observed that the calibrated constriction 37 can be placed anywhere in the conduit 59, in particular in the valve element 12a.

2. Loosening:

The pressurized air contained in the brake cylinders 4 escapes as previously through the calibrated orifices 41 and 48 as well as through the calibrated orifice 49 now released to allow faster emptying.

III - Empty vehicle, goods regime:

The pneumatic pressure delivered by the weighing member 26 is too low to cause the opening of the double valve 57 of the valve 25. The chamber 24 adjacent to the movable plate 22 and the opening chamber 46 of the adaptation valve 39 are therefore vented through the conduit 63 and an inner channel 64a to the tube 64 of the speed change valve 25.

1. Tightening:

The pressure delivered by the regulator 13 as soon as the crew 14, 28 of the main control device has detected a sufficient differential pressure between the general line 1 and the tank 3, now stresses both the main reaction membrane 18 and the membrane reaction auxiliary 23. In fact, the plate 22 now biases the crew 14, 28 by its support against the shoulder 29. In this way, for the same pressure drop in the general line 1, the pressure delivered by the regulator 13 stabilizes at a value much lower than in loaded mode.

2. Loosening:

Since the atmospheric pressure prevails in the chamber 46, as soon as the pressure delivered by the regulator 13 exceeds a value determined by the spring 45, the piston 44 is raised and the double valve 42, 43 is called in the closed position by its return springs. In this way, the pressurized air accumulated in the brake cylinders 4 escapes, for release, through the only calibrated orifice 41.

IV - Empty vehicle, passenger regime:

I. Tightening:

The pressure delivered by the regulator 13 is exerted as in the previous case on the main 18 and auxiliary 23 membranes

of reaction. The throttles 37 and 38 are chosen to determine, after the first stage, a filling of the brake cylinders within the required times.

2. Loosening:

The double valve 42, 43 being here again closed, but the element 12b of the valve GP being open, the exhaust of the brake cylinders 4 takes place simultaneously through the orifice 41 and by a calibrated throttle 65, placed in parallel.

Placed in series with the constriction 65 and having a larger opening than that of said constriction 65, the orifice 49 no longer intervenes for the determination of the exhaust flow rate.

The distributor described operates in two modes depending on the vehicle load. The variable determining the speed could of course be the speed or the deceleration of the vehicle, in which case the speed change valve would for example be replaced by an electrovalve receiving an electrical signal for example as a function of the speed.

The discontinuous operation which is described above is not limiting and one could, without difficulty, obtain continuous operation by the addition of a weighing pressure varying continuously with the load. The characteristic of the pressure delivered as a function of time is then bent; it in fact comprises a steep initial part corresponding to the regime loaded with the fact that the plate 22 is inactive in the abutment position against the body then, from a point corresponding substantially to the equality of the pressure delivered and the pressure of weighed, a part with a less steep slope due to the fact that the plate 22 becomes active by pressing against the shoulder 29 of the crew 14, 28.

Fig. 5 schematically shows a variant of the pneumatic brake distributor according to the invention. In this distributor, the exhaust time adaptation device 39 comprises a piston 90 controlling a valve 91 which controls an exhaust pipe having the orifice 49, the valve 91 for its part comprising the throttle 65. The member 39 also includes a piston 92 which controls a valve 93 controlling an exhaust pipe which has the calibrated orifice 48.

It is understood that the elements 90 to 93 replace the piston 44 and the double valve 42, 43 previously described.

The upper faces of the two pistons 90, 92 are subjected:

a) when the vehicle is empty: at atmospheric pressure,

b) when the vehicle is loaded: upon the action of the pressure of the auxiliary tank 2, this pressure being transmitted by the line 63 from the valve 25 switchable by the pressure of the weighing member 26. The underside of the pistons 90, 92 delimits the downstream chamber of the valves 91 and 93.

The auxiliary reaction chamber 27 remains supplied directly by the pressure from the pressure reducer 13 and this by means of a line 94. The line 59 provided with the calibrated orifice 37 and the valve element 12a is connected to this line 94 to connect to line 36 downstream of valve 9 in the direction of supply of cylinders 4.

To the line 94 (or to the line 59 upstream from 37) is connected a line 95 connected to a line 96 or isolated from this line by means of a switching valve 97. The line 96 opens into the main chamber of reaction 19, while the valve 97 has a piston 98 controlling a valve 99 and provided with a tubular extension for controlling said valve. The tubular extension comprises a lateral passage 100 and an axial channel 101 and the lateral passage cooperates with a seal 102 so as to open the connection 95-96 in the low position and to close this connection in the high position.

A return spring returns the piston 98 to its low rest position. It should be added that the valve 99 controls the connection between the pipe 96 and a pipe 103 connected to the pipe 36 downstream of the first-time valve 9.

When empty, the valve 97 allows the non-delayed supply of the chamber 19 from the line 95, the compressed air delivered by

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the regulator using route 94, 95, 100, 101, 96 for this purpose.

Under load, the valve 25 is engaged under the effect of the weighing pressure supplied by the weighing member 26 and it transmits the pressure from the auxiliary reservoir to the pipe 63. In this way, the piston 98 is pushed upwards. , which cuts the connection 95-96 while the opening of the valve 99 opens the connection 103-96.

As a result, the air delivered by the regulator of the main device reaches the main reaction chamber 19 using the following path: throttle 37 and / or 38, line 103, valve 99 open, line 96. The reaction manifests itself by Therefore more slowly loaded on the main device, which allows to obtain the desired feeding times with only two calibrated tightening throttles.

Many variants of the present invention readily accessible to those skilled in the art can be imagined. Thus, the brake distributor can supply the brake control pressure to a small volume capacity which controls a high flow relay valve and the pressure delivered by the distributor or by this relay valve can supply pneumatic pressure transformers. -hydraulics to deliver very high hydraulic braking pressures.

When the weighing pressure acts continuously on the piston 22, 23 (see fig. 2), the braking control pressures delivered by the regulator 13 are not proportional to the load of the vehicle but the empty speed (pressure more low as a function of the general driving vacuum 1) begins to be applied for braking control pressures the lower the load. The braking application and release times could be strictly observed in this case by controlling the variations in the pressure in chamber 15.

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2 sheets of drawings

Claims (11)

616,116 CLAIMS 1. Penumatic distributor for controlling the braking of a railway vehicle, comprising in a body (5) a main device (6) for controlling a braking control pressure and a device for correcting this pressure as a function of a parameter (26), the main control device (6) comprising a pressure-reducing valve (13) and an assembly (14, 28) with pistons and / or membranes (16, 18, 23) which acts on the pressure-reducing valve (13 ) in the direction of opening of the latter in response to an action force produced on an action surface (16) of said equipment (14, 28) and in the opposite direction for closing and purging, in response to a reaction force produced on a main reaction surface (18) of the crew (14, 28) by the outlet pressure of the regulator (13), the crew (14, 28) of the main device (6) comprising an auxiliary reaction surface (23) capable of producing a reaction force in addition to that of the main surface (18), characterized in that that the main (18) and auxiliary (23) surfaces of the crew (14, 28) are stressed by the outlet pressure whatever the value of the parameter (26) to act on the pressure reducer (13) in the direction of the closure thereof, while one of the reaction surfaces (18, 23) is subjected in the direction of the action to a correction pressure which is a function of the parameter (26), but without this surface of reaction (18, 23) can act on the pressure reducer (13) in the opening direction. 2. Pneumatic distributor according to claim 1, characterized in that the auxiliary reaction surface (23) comprises a plate (22) or piston capable of sliding or of moving axially in leaktight manner on the pusher (28) without coming to bear on the latter, when under the action of the pressure as a function of the parameter (26) it moves in the direction of opening of the regulator (13), while when under the action of the outlet pressure delivered by the device main (6), it moves in the direction of closing the regulator (13) and purging the outlet pressure, the plate (22) is likely to come to bear on the pusher (28) and the crew , in particular when the outlet pressure exerts on it a force capable of overcoming the force caused on it by the pressure as a function of the parameter (26). 3. Pneumatic distributor according to claim 2, characterized in that the pusher (28) of the regulator (13) has a shoulder (29) on which the plate (22) of the auxiliary reaction surface (23) is capable of coming in support, so that the plate (22) can be pressed against the shoulder (29) in the closing direction of the regulator (13), and that it is detached from the pusher (28) of the crew (14, 28) as soon as it is no longer supported on the shoulder (29). 4. Pneumatic distributor according to any one of claims 1 to 3, characterized in that at least one calibrated supply throttle is placed between the pressure reducer (13) and the capacity or capacities (4) receiving the control pressure of the braking. 5. Pneumatic distributor according to any one of claims 1 to 4, characterized in that, in the case where the control force on the pusher (28) of the regulator (13) is constituted by a pressure difference between a pipe general (1) and a control tank (3), the main control device comprises a force limiting member (30, 31) making it possible to communicate to the crew (14, 28) a control force which remains constant, as soon as the pressure of the general line (1) is lower than a predetermined value. 6. Pneumatic distributor according to any one of claims 1 to 5, characterized in that it further comprises a first-time device (9) controlling a valve (50) which is placed in parallel with a calibrated orifice ( 38) between the main control device (6) and the brake cylinders (4), this first-time device (9) having an opening surface (54) of the valve (50) subjected to the pressure directly delivered by said main device (6) and a closing surface (53) of the valve subjected to the pressure prevailing downstream of the calibrated orifice (38). 7. Pneumatic distributor according to any one of claims 2 or 3, characterized in that an exhaust time adaptation device (39) is disposed between the main control device (6) and the atmosphere (48 , 49). 8. Pneumatic distributor according to claim 7, characterized in that the device for adapting the exhaust times (39) comprises at least one pusher connected to a piston (44) controlled by the correction pressure so as to open a valve. (42,43) controlling an additional calibrated connection (48) with the atmosphere of the exhaust (21) of the main device as soon as the correction pressure exceeds a certain value. 9. Pneumatic distributor according to any one of claims 7 or 8, characterized in that the pusher connected to the piston (44) of the adaptation device (39) is returned to the closed position of the valve (42, 43) by the pressure delivered by the main control device (6). 10. Pneumatic distributor according to any one of claims 7 to 9, characterized in that the pusher connected to the piston (44) of the adaptation device (39) is pushed back into the valve open position (42,43) by a spring (45). 11. Pneumatic distributor according to any one of claims 4 to 10, characterized in that a calibrated additional supply orifice (37) is placed in a bypass channel (59) connecting the main control device (6) to brake cylinders (4), and in that a closing valve (12a) is placed on this bypass channel (59).