FR3052417A1 - DUAL-EFFECT PISTON BRAKE SYSTEM BLEEDING IN PARTICULAR BY COMPRESSED AIR AND ITS APPLICATIONS - Google Patents

Abstract

The brake system bleed valve according to the invention comprises a so-called double-acting engine cylinder VM, whose PM piston is mechanically secured to the piston PP, a second jack said pump VP, the engine cylinder VM having two chambers said left (300) and right (400) containing a driving fluid, the pump jack VP having two chambers said left (100) and right (200) containing the brake fluid called "new" LDF or other liquid for purging the circuit, a source of AC motor fluid, causing the displacement of the motor piston VM which alternately leads to the right and then to the left, which drives the integral piston pump VP in the same movement

Description

Double-acting piston brake system vent driven by compressed air and its applications.

TECHNICAL SECTOR

The present invention relates to the technical sector of the automobile, in particular the purge of a braking system or "brake bleeders" on a motor vehicle of any type, light vehicle, truck, agricultural or industrial rolling stock or military. The main function of the brake bleeders is to remove the air present in the braking circuit of the vehicle circuit and / or to replace the brake fluid (or "brake fluid") in the braking circuit of a vehicle . The most used technique is to send or "pump" new brake fluid under pressure to the reservoir of the vehicle brake fluid, the operator then opens the bleed screws on the vehicle to evacuate the used liquid (with at the same time the air bubbles) and bring new brake fluid.

The present invention relates to the new brake fluid pumping system and more precisely the device for pressurizing the new brake fluid, which can work in "continuous" mode and under high pressures in accordance with the recent recommendations of the manufacturers, particularly in the the generalization of brake assist systems.

The technical sector also includes the renewal of any gas or liquid in enclosed facilities generally under pressure, a container, tank or tank, particularly if the liquid is corrosive or presents other hazards. Applications of this type, in the automotive sector, are for example the change of the coolant, or the gearbox oil, engine oil and the like.

PRIOR ART

There are generally two main types of traps among the existing ones, so-called electric and pneumatic braking traps.

Pneumatic brake bleeders: These traps consist of a new brake fluid reservoir (approx. 10 L) separated into two hemispheres by an airtight membrane.

The principle is as follows: one hemisphere is filled with new brake fluid and the other with compressed air. When the air is pressurized, the hermetic membrane deforms and causes a decrease in volume in the chamber where the brake fluid is. This action causes the brake fluid to be put under pressure, which can then be released into the hose connected to the jar of the vehicle. The main disadvantage of this type of system is the life of the membrane. In addition, the system does not allow to have a fluid flow continuously. When the hemisphere containing the brake fluid is empty, it must be filled.

The electric brake bleeders: here we distinguish two types, the electric traps operating under 12V or 230V.

These traps have a pumping system which is realized by means of an electric pump.

Several pump technologies are used:

Peristaltic pumps (12VDC or 230VAC): the main disadvantage of these pumps is that they put the liquid in pressure by deforming a pipe. The problem is that the brake fluid is very corrosive and tends to "dry" (chemical attack or chemical aging) the rubbery materials and make them brittle or porous. The action of deforming a pipe accelerates this phenomenon of aggression of the brake fluid on the pipe which wears out quickly. This effect is called stress corrosion or stress aging.

Diaphragm pumps (12V DC or 230V AC alternating current): the diaphragm is in direct contact with the brake fluid. The deformation of the membrane makes it possible to pressurize and circulate the new brake fluid.

The service life of the traps of the prior art is restricted by the corrosive properties of the brake fluids. The elements in contact with the liquid degrade in time, leaks and malfunctions occur. A brake fluid discharge on a painted part causes a disapproval of the paint and therefore a degraded aesthetic appearance.

The pressure to be applied during a purge or replacement of the brake fluid depends on the vehicle and its equipment (presence of ABS - electronic anti-lock system, ESP - Electronic Stability Program, other assistance systems braking, characteristics of the braking circuit, etc ...). Today, car manufacturers recommend bleed pressures that are too high compared to the capacities of "traditional" traps. On the other hand, the recommendation of high pressures causes aggravation of the above defects, because the mechanical fatigue is higher and factors accelerate the aging of certain sensitive parts, such as pressure, or temperature.

The adjustment of the purge pressure is usually done by the use of a pressure regulator located on the new brake fluid circuit, this component is also also subject to degradation in time.

TECHNICAL PROBLEM

The present invention aims at designing a reliable braking system trap over time, the main technical problem being to limit the sensitive elements (seals, membranes, pressure regulating elements, flow) in contact with the brake fluid in order to maximize the service life of the components, and minimize leakage from the fittings and the like, and minimize the cost of changing the elements in contact with the brake fluid (the O-ring change being customary for a person skilled in the art, the change can be made by him without serious problem).

The purge pressure must be adjustable and the system must be able to operate without inconvenience under higher pressures than currently, to adapt to the recommendations of car manufacturers on recent vehicles. The operator (for example a car mechanic and the like) must be able to use the trap autonomously with the sources of power or energy (power source) available in the environment concerned: car repair environment of any size.

Limiting the elements in contact with the brake fluid causes significant problems: - the system of pressurizing and circulation of the new brake fluid is completely to be reviewed with technical and economic constraints (power source, service life, etc.). The pumps commonly used in "classic" traps do not allow to respond to this constraint, - allow purge pressure regulation without using a pressure regulator on the brake fluid circuit.

Finally, the existing market for vehicle traps imposes strong economic constraints. Indeed, users are used to a tariff range and the new system must be economically acceptable, especially in terms of investment and operating costs.

TECHNICAL SOLUTION

The solution adopted uses two double-acting cylinders interconnected by one or more push rods (or any other mechanical element transmitting the movement of the piston from one of the cylinders to the other piston of the other cylinder, as connecting rod, cam , etc ... and which are known to those skilled in the art, they are grouped here under the overall term "push rods").

A first VM "double-acting" motor cylinder serves as a motor part (the one that transmits the power to put the system according to the invention in motion) and is supplied with compressed air AC at controlled pressure.

A second double-acting jack VP serves as part "pump", is actuated in movement by the first, preferably by joining the PM motor pistons and PP pump via the push rod or rods, and serves for pressurizing and to the circulation of new brake fluid LDF.

Knowing the chamber section of the two cylinders VM and VP the regulation of the brake fluid pressure P sent to the braking system to be purged can directly be done by regulating the supply air pressure AC of the engine cylinder VM. The supply of the trap according to the invention AC compressed air is directly by connection to the pneumatic networks available and used by operators in the automotive repair environment. The skilled person will generally be a garage in the broad sense, and it should be that the solution is not too expensive because the Customer is accustomed to tariff traps already existing in the trade. The most used products work with 12 VDC systems, and with these products it is simply the battery of the vehicle on which the operation is carried out which serves directly for the supply of the trap. This is obviously very simple, very "direct" and very practical. The skilled person could think that the use of an external source of power such as compressed air supply could only create additional costs and disadvantages and practical complications, the user then having to connect his trap on the external supply, that is to say in this case the compressed air network of his local. The invention makes it possible to work under the higher pressures recommended by car manufacturers for recent models; to respect these "manufacturer's recommendations" is obviously an essential factor of road safety. However, current systems do not allow it.

Finally, a person skilled in the art would have feared to carry out blowdowns at too high a pressure and to fault the seal of the brake fluid reservoir of the vehicle; the present invention has the merit of lifting this prejudice.

The chosen technical solution uses standard pneumatic elements.

For the "pump" cylinder, the seals are replaced by suitable materials made of EPDM polymer ("ethylene-propylene-dienomonomer"), elastomeric material used for the manufacture of flexible lines of automotive brake fluid.

Unlike other current pump technologies, the joints of a cylinder work in quasi-static and therefore have a better resistance over time unlike other systems that have significant mechanical stresses associated with conventional corrosion known plastics: stress corrosion .

The choice of a cylinder system means that the life of the system is already intrinsically superior to that of a traditional trap. However, an actuator requires an external power source, except to consider complex and "heavy" solutions such as battery-hydraulic vehicle-cylinder, or a motor with a crank-rod system, and the choice was not easy to consider.

The technical solution envisaged makes it possible to reach higher purge pressures than with traditional traps. This allows for more efficient purges on including new brake assist technologies. This is an important factor concerning "road safety", and concerning the legal security of mechanics who would serve without respecting the pressures advocated by the manufacturer.

On recent vehicles, the batteries are fairly regularly deported in the trunk or in the cabin to optimize the space available in the engine compartment. Access to the battery terminals can be difficult and require additional connection operations. The double-acting cylinder bleed valve connected to the available air system eliminates this inconvenience as it does not require an electrical connection to the vehicle.

The fact of using a cylinder makes it possible to obtain efficiencies close to 100% on the pneumatic circuit. The air consumption is very limited: around 11 L / min.

If the two double-acting cylinders have the same section and are mounted in phase opposition, the brake fluid flow at the outlet of the trap is equal to the compressed air intake at the inlet of the trap.

The actual bleed time (time with bleed screw open on the vehicle) is directly related to the amount of brake fluid drained or drained. To drain / purge 1 liter (average volume of brake fluid present in a light vehicle) it takes 2 minutes of operation of the trap because the approximate flow rate of brake fluid is 0.5 L / min at the outlet of the trap. The purge pressure does not influence the actual purge time. On the other hand, the air is compressible, the consumption of compressed air at the inlet of the trap is proportional to the purge pressure applied. At 1 bar, the compressed air consumption is equal to the brake fluid consumption or 1 liter of air to purge 1 liter of brake fluid. At 2 bar, to drain / purge 1 liter of brake fluid, 2 liters of air are needed. At 3 bar to drain / bleed 1 liter of brake fluid, it takes 3 liters of compressed air, etc.

The choice of pressure is particularly related to the age of the vehicle. Newer vehicles can withstand higher pressures than older vehicles (where 2.5 bars is the maximum). It is likely that in the near future pressures above 5 bar will be used.

The system can be autonomous and, for example, associated with a compressed air cylinder having an autonomy of several tens of hours for a conventional 2 liter bottle under 300 bar, allowing several hundred purges.

In a 2-liter bottle, inflated to 300 bar, there are 540 liters of air accumulated with a 90% compressibility rate at 300 bar. If we consider that the bottle is usable in discharge up to 20 bar there is 500 liters of usable compressed air. Knowing that at 3 bars, the air consumption is 3 liters to drain / purge 1 liter of LDF, the autonomy in these conditions is 166 purges.

This can allow on-site intervention for an instant purge just as easy as the on-site change of a wheel. The double-jack solution (or double-acting) has been developed for use in particular with automotive brake fluids such as DOT. Due to the dissociation of the "pump" part and the "motor" part, the system can easily adapt to other applications of pressurizing or circulating corrosive or flammable fluids. In these other cases, it will suffice to use the appropriate materials for the joints, connections, pipes and elements present on the "pump" part of the system. This solution can for example be envisaged for fuel tank emptying operations (since no electrical element is present in the system), replacement or purge requiring an overpressure of specific liquids in the automotive or other medium (aeronautics, etc. ...). This type of product can also be envisaged for uses in explosive environment without expensive modification of the system.

Such adaptations will easily be within the abilities of those skilled in the art, and the invention relates to such adaptations.

DETAILED DESCRIPTION OF THE INVENTION The invention has been presented above in its general form.

A particular embodiment is presented below.

Figure 1 shows the schematic diagram (in automatic stop before the start of purging).

Note:

In all figures, the same alphanumeric references designate the same elements or functions or kinematic movements.

The same symbols represent the same mechanical or electrical or electronic elements, such as the symbol identified by CAR for a non-return valve. It is known that a non-return valve allows the passage of a fluid in one direction and prohibits its return in the opposite direction. The symbols are known to those skilled in the art and when several identical elements are present, they are not all necessarily identified by a reference.

By convention, and in order to clarify the text, an arrow indicates the direction "right" or "to the right", and another "left" or "to the left".

The braking system bleeder according to the invention is characterized in that it comprises: a jack said double-acting motor VM, whose piston PM is mechanically secured to the piston PP, a second jack said pump VP, the motor cylinder VM having two chambers said left (300) and right (400) containing a driving fluid, the pump jack VP having two chambers said left (100) and right (200) containing the brake fluid said " nine "LDF or other liquid for purging the circuit, - a source of pressurized AC working fluid alternately supplying, by the action of a distributor D arranged on the inlet circuit of said driving fluid, the left chamber (300) then the right chamber (400) in motor fluid, or an electric motor acting in translation on at least one of the pistons VM and VP to cause a reciprocal movement of said pistons. - Which causes the displacement alternately to the right and then to the left of the VM motor piston which drives the integral piston pump VP in the same movement, - said piston pump VP suction on the one hand, by its movement to the right and via the circuit (40, 340 140), the LDF in its left chamber (100) from the reservoir (600) of LDF and secondly simultaneously forcing the LDF of the right chamber (200) to the braking system SFR to be purged via the circuit (240, 30, 60), then, in its reciprocal movement to the left, forcing the LDF sucked into the left chamber (100) out of said chamber (100) and towards the braking system SFR to be purged, via the circuit (140, 50, 60), while simultaneously the movement of the piston VP sucks to the right chamber (200) of the LDF from the tank (600) of LDF via the circuit (40, 340, 240), - said connected circuits to the pump jack VP being provided with devices adapted to allow the circulation of L DF as described, - and in that the movement of the pistons PM and PP integral is made reciprocal by said distributor D motor fluid, itself activated by two detectors stop (700) on the left and (800) on the right of one of the two pistons PM or PP detecting the stop on the left then respectively the stop on the right of said piston PM or PP, these two detectors being disposed on a secondary circuit (2) continuously supplied with AC motor fluid and alternately sending said fluid motor of the circuit (2) to the control inputs of said distributor by alternately opening the circuit (25) when the detector (800) detects the stop on the right of said piston or the circuit (15) when the detector (700) detects the stop on the left of said piston, the assembly forming a continuous purge cycle with an opening valve V of the supply circuit (1) for driving fluid, and which valve is closed again when a predefined purge volume has passed in the SFR.

By "predefined purge volume" denotes the LDF volume that is recommended by the manufacturer of the vehicle, or deemed necessary by the operator; it can be measured indirectly by a flowmeter on the compressed air supply circuit which closes the inlet valve V when said volume is reached, or directly a flowmeter placed at the output LDF (60), with in this case the disadvantage of a contact with the corrosive LDF, or more simply a visible graduation on the LDF tank, and one can then use an adjustable low level detector, which one adjusts to the volume to be discharged, this detector then becoming a "Predefined bleed volume detection detector".

LDF can also be used as a bottle or can of LDF of a given volume.

These adaptations will be obvious to those skilled in the art and are presented only for the sake of remembrance, but they form part of the invention, with the other obvious adaptations not modifying the schematic diagram of the system described and claimed here.

By "reciprocal movement" is meant the fact that the pistons move alternately to the right and then to the left (in the chosen convention) then to the right, etc. until the end of the purge cycle, in a continuous movement that is to say not involving any interruption, except for the very brief moment of the abutment on the left or on the right, as will be understood by everyone skilled in the art.

By "stop detector" is meant devices known to those skilled in the art that is also referred to as "limit sensors".

By "control inputs" of the 5/2 distributor (5 orifices, 2 positions) D, it is meant the fluid inlets in the distributor which, depending on whether the fluid enters from one side, circuit (15), or from the other, circuit (25), the distributor changes state and toggles one side or the other and sends the fluid AC either in the circuit (3) to the chamber (300) or in the circuit (4) to the room (400).

The two detectors were placed on one of the pistons VM or VP, that is to say on the same piston. Those skilled in the art will understand that the detector (700) can also be placed on the stop on the left of the piston VM and the detector (800) on the stop on the right of the piston VP, since the two pistons are integral.

According to the best embodiment, the driving fluid is compressed air AC and said source of driving fluid is the compressed air circuit used by the user, including a garage. The minimum operating value of the trap is defined by the small operating pressure of the components used. By generalization, we will take a minimum operating pressure of 1 bar. The maximum operating pressure is defined by the pressure of the power source within a limit of 11 bar (maximum operating pressure of the system). The compressed air supply pressure in garages is usually 6.5 bar.

Other fluids, such as hydraulic fluid, can be thought of, but besides the fact that compressed air is clean and easy to use, it is usually the only pressurized fluid present in all automotive garages and on which it is very easy to connect.

One can also think of using an electric motor acting in translation (directly or indirectly via a known system of rods, cams, etc ...) on at least one of the pistons VM and VP to cause a reciprocal movement of said pistons, but the use of compressed air is obviously simpler.

Similarly, one could think of using an electric pump that would send a motor fluid, such as a hydraulic fluid, to the cylinders as described above, to produce said reciprocal movement of the pistons, but the use of compressed air is obviously more simple. The skilled person will easily think of other options, but the most elegant because the simplest is the use of compressed air.

In the claims, the term "source of motor fluid" or "AC" covers all of these obvious options, including by convention the use of an electric motor (although it acts mechanically and not via a fluid ). It will be easily understood that one does not wish to weigh down the claims by mentioning these various options.

Likewise, the term "braking system bleeder" also covers, throughout the present application, including the claims, applications such as the renewal of a gas or liquid in a pressure tank or the replacement of coolant. of a vehicle, or gearbox oil, engine oil etc.

It is possible to use the trap for all liquids by adapting the type of seal to the liquid that will be encountered.

Preferably, the supply circuit (1) in AC comprises a pressure regulator R and a pressure limiter L, which allows, being known the geometry of the chambers of the cylinders and circulation ducts of the LDF, to adjust the pressure P purge in the circuit (60) of LDF at a preset pressure, "preset" having the same meaning as above for the purge volume.

Also preferably, the tank (600) of LDF comprises low level detection means of LDF disposed on the supply duct (1) of compressed air with a stop function of said supply if the level of LDF in the tank (600) becomes too low.

Indeed, one can of course rely on a manual monitoring of the level, as well as for the pressure, but an automatic system is absolutely preferable. Indeed, dropping the level of LDF to near zero without stopping the arrival of engine fluid would mean that the cylinders VM and VP would cause traffic to the braking system either LDF (60) but the air content above LDF fluid in the reservoir (600); So we would send air into the SFR, which would obviously mean either restarting the operation or, worse, if the level is "limit" towards the end of the purge, to send a little air at the end of purge and therefore to deliver to the Customer, without noticing it, a SFR in a worse condition than that of the reception in garage.

A simple and effective system is as follows:

The "new" LDF brake fluid reservoir (600) comprises a float f provided with a magnetic effect chip, such as a magnet, and outside the reservoir (600), and facing the level judged " low ", a low level detector which comprises a receiver capable of reacting to said magnetic effect and of closing or triggering the closure of the fluid inlet AC, generally compressed air, in the circuit (1) (of which one recalls that it is upstream of the distributor D).

According to the preferred embodiment, the low level detector comprises a float equipped with a magnet and a pneumatic proximity detector: when the magnet descends to the vicinity of the proximity detector, said detector pneumatically triggers the closure of the circuit ( 1) (thus stops the arrival of the fluid AC) which is made possible because the detector is disposed on said circuit (1).

In a less preferred embodiment, the brake fluid reservoir can be directly a bottle or can or analog of new brake fluid. This solution may be useful for garage owners who do not regularly use the trap according to the present invention. Indeed, the liquid in the tank can absorb the ambient humidity and thus degrade the quality of the brake fluid. Ideally, it is necessary to work with the necessary amount of brake fluid in the tank.

In the case of the direct use of a container of brake fluid as a reservoir, the trap will use a conical plug system that will fit on the neck of the can. This plug will include a suction strainer a return system for depressurization (not shown in the diagrams) and may optionally be equipped with a float that allows detection of the low level.

According to the simplest embodiment, the attachment of the PM motor pistons and PP pump is obtained via the push rods or T.

Figure 2 shows the purge system according to the invention in its state "rightward movement of the pistons end of stroke" that is to say purge by sending LDF by the circuit (30, 60).

Figure 3 shows the purge system according to the invention in its state "leftward movement of the pistons end of stroke" that is to say purge by sending LDF by the circuit (50, 60).

In Figures 2 and 3, the solid black arrows indicate the movement of the LDF, while white arrows indicate the displacement of the compressed air AC.

Figure 4 shows the purge system according to the invention when the level of LDF in the tank (600) becomes too low for purging to be completed. An audible signal (1200) signals the operator of this state. Naturally, the purge system is shut down.

It is noted that on the LDF brake fluid circuit few elements are present. A double-acting VP cylinder, non-return valves that allow one-way flow from the bleed tank to the vehicle brake fluid reservoir, a pressure gauge M that serves as an indication of the purge pressure P, and finally a valve V, which allows in a first time to turn on the trap and at the end of the purge operation to drop the purge pressure imposed on the vehicle before disconnecting the product.

The manometer can be positioned on the air inlet because if the sections of the cylinders are identical and mounted in opposition of phase: air pressure equal brake fluid pressure.

The compressed air circuit consists of a double-acting cylinder VM, a distributor D for the change of direction when reaching the stop, a pressure regulator R which allows to indirectly adjust the pressure purge and to finish a pressure limiter L which makes it possible not to apply a too high supply pressure.

The SFR system for braking the vehicle has not been shown because it is known: it behaves, generally and essentially, a brake fluid reservoir, contaminated by air before the purge, a circuit of braking which comprises various known elements, more and more often brake assist systems (the braking circuit being designed by the manufacturer to be fully bleed during the purging operation in the garage), and the caliper of brake. It also includes a bleed screw that is open prior to bleeding, and an LDF inlet line ("new" brake fluid) that is connected to the outlet of the conduit (60).

The present invention also relates to the applications of the new brake fluid pumping system and more precisely the device for pressurizing the new brake fluid, as described above, to bleed a braking system of any vehicle, as well as for the renewal of any gas or liquid in closed facilities, including, in the automotive sector, the change of coolant and the like. EXAMPLES Light vehicles:

Renault space 4 (Type: JKOB, JKOD, JKOG, JKOH, JKOJ, JKOK, JKOF) Brake fluid; SAE J1703 DOT 4 Normal capacity: 0.7 liter, ABS; 1 liter Purge pressures: 2 bar to 2.5 bar

Either an actual purge time (purger operation) for complete emptying with the proposed system of 2 min for an ABS circuit and 1 min 24 seconds for a non-ABS circuit. This time does not include previous manipulations, and is given for an ideal case where the mechanic replaces the exact amount of brake fluid.

Renault Meaane 2 (Type: XM0F, XMOB, XMOH, XMOJ, XMOC, XMOG, XMOU, XM08)

Brake Fluid: SAE J1703 DOT 4 ABS Capacity: 1 liter

Purging pressures: 2 bar

Either an effective purge time for complete emptying with the proposed system 2 min. This time does not include previous manipulations, and is given for an ideal case where the mechanic replaces the exact amount of brake fluid. VUL:

Renault Trafic 3 (Type: XLOB, XLOC)

Brake Fluid: SAE J1703 DOT 4 Capacity: Normal: 0.7 liter, ABS: 1 liter Drain pressures: 2 bar to 2.5 bar

Either an effective purge time for complete emptying with the proposed system 2 min. This time does not understand the previous manipulations, and is given for an ideal case where the mechanic replaces the exact quantity of brake fluid. PL: As soon as one passes on heavy vehicles, the braking system becomes pneumatic and the vehicles are no longer concerned by the bleeding of brake fluid.

Claims (11)

1. Braking system vent characterized in that it comprises: a cylinder said double-acting engine VM ^ whose piston PM is mechanically secured to the piston PP, a second jack said pump VP, the engine cylinder VM comprising two chambers said left (300) and right (400) containing a fiuid motor ^ ie pump jack VP having two chambers said left (100) and right (200) containing the brake fluid said "new" LDF or other liquid for purging of the circuit, a source of AC fluid under pressure alternately supplying, by the action of a distributor D disposed on the inlet circuit of said driving fluid, the left chamber (300) and the right chamber (400) in fluid , or an electric motor acting in translation on at least one of the pistons VM and VP to cause a reciprocal movement of said pistons, which causes the displacement alternately to the right and to the left of the motor piston VM which drives e the self-pump piston VP in the same movement said pump piston VP sucking on the one hand, by its movement to the right and via the circuit (40, 140), the LDF in its left chamber (100) from the reservoir (600 ) of LDF and secondly simultaneously forcing the LDF of the right chamber (200) to the braking system SFR to be purged via the circuit (240, 30, 60), then, in its reciprocal movement to the left, forcing the LDF sucked into the left chamber (100) out of said chamber (100) and to the SFR brake system to be purged, via the circuit (140, 50, 60), while simultaneously the movement of the piston VP sucks towards the right chamber (200) of the LDF from the tank (600) of LDF via the circuit (40, 340, 240), said circuits connected to the pump jack VP being provided with devices adapted to allow the circulation of LDF as described, and in that the movement of the pistons PM and PP integral is rendered reciprocal by said distributor D of motor fluid, which itself is activated by two limit detectors (700) on the left and then (800) on the right of one of the two pistons PM or PP detecting the stop on the left and then the stop on the right of the said piston PM or PP, these two detectors being arranged on a secondary circuit (2) continuously supplied with AC motor fluid and alternately sending said driving fluid of the circuit (2) to the control inputs of said distributor by alternately opening the circuit (25) when the detector (800 ) detects the stop on the right of said piston or the circuit (15) when the detector (700) detects the stop on the left of said piston, the assembly forming a continuous purge cycle with an opening valve V of the supply circuit ( 1), and which valve is closed when a predefined purge volume is passed through the SFR. 2. Trap according to claim 1, characterized in that the driving fluid is compressed air AC and said source of fluid is the compressed air circuit used by the user, including a garage. 3. Trap according to claim 1 or 2, characterized in that the pressure used for the purge is between 1 bar and 11 bar. 4. Trap according to any one of claims 1 to 3, characterized in that the AC supply circuit (1) comprises a pressure regulator R and a pressure limiter L, which allows, being known the geometry of the Cylinder chambers and LDF circulation ducts, set the purge pressure P in the LDF circuit (60) to a predefined, "preset" pressure having the same meaning as above for the purge volume. 5. Trap according to any one of claims 1 to 4, characterized in that the tank (600) of LDF comprises a low level detection means LDF disposed on the supply duct (1) of compressed air with a function of stopping said supply if the level of LDF in the tank (600) becomes too low. 6. Trap according to any one of claims 1 to 5, characterized in that the tank (600) of "new" brake fluid LDF comprises a float f provided with a magnetic effect pad, such as a magnet, and has on the outside of the tank (600), and opposite the level considered "low", a low level detector which comprises a receiver capable of reacting to said magnetic effect and closing or triggering the closing of the fluid inlet AC, generally compressed air, in the circuit (1), which is recalled that it is upstream of the distributor D. 7. Trap according to any one of claims 1 to 6, characterized in that the low level detector comprises a float provided with a magnet and a pneumatic proximity sensor: when raimant down to the vicinity of the proximity detector, said detector pneumatically triggers the closing of the circuit (1) (thus stops the arrival of the fluid AC) which is made possible because the detector is disposed on said circuit 1. 8. Trap according to any one of claims 1 to 7, characterized in that the fastening of the PM motor pistons and PP pump is obtained via the push rods or T. 9. Trap according to any one of claims 1 to 4, characterized in that the brake fluid reservoir may be directly a bottle or can or analog of new brake fluid. 10. Trap according to claim 9, characterized in that one will use a conical plug system which will fit on the neck of the canister; this cap will include a suction strainer, a return system for depressurization and may optionally be equipped with a float that will allow the detection of the low level. 11. Applications of the new brake fluid pumping system and more precisely the device for pressurizing the new brake fluid, according to any one of claims 1 to 10, for bleeding a braking system of any vehicle, as well as for the renewal of any gas or liquid in closed facilities, including, in the automotive sector, the change of coolant and the like.