FR2590348A1 - Sealing flap for a tap connecting a vessel containing a liquefied gas to means using gas in liquid phase - Google Patents

Abstract

The invention relates to a sealing flap for a tap intended to connect a vessel containing a liquefied gas to means using gas in liquid phase. The sealing flap 35 of the tap comprises an internal valve 88, 76 which is normally closed, employing an elastically compressible ball 88 housed in a cavity 86 into which there opens, in the form of a sealing seat 76, a section of pipe 68 opening moreover into a peripheral face 41 of the piston; in a zone 89 of the cavity 86 which is offset with respect to the sealing seat 76 there opens another section of pipes 69 opening moreover into a flap zone situated inside the sealing seat 14 of the tap when the sealing flap 35 interacts with this sealing seat 14. The sealing flap 35 may thus have the same dimensions as a sealing flap without a valve, while at the same time offering increased safety.

Description

 The present invention relates to a sealing valve for a tap intended for the connection of an enclosure containing a liquefied gas to means using gas in the liquid phase.

 Such valves are for example used to connect a bottle of liquefied propane gas to the carburetor of an internal combustion engine using a mixture of propane gas in liquid phase and air; naturally, this example is in no way limiting as to the possible applications of the valve concerned by the present invention.

Traditionally, such taps have
- a hollow body sealingly defining a passage having an inlet orifice and an outlet orifice,
an annular sealing seat secured to the body, inside and around the passage, between the inlet and outlet orifices, said sealing seat being turned downstream with reference to a direction going from the inlet port to the outlet port,
- a sealing valve movable relative to the body, inside the passage and facing the sealing seat, downstream of the latter with reference to said direction, to occupy a closed position in which the valve seal and the seal seat are in mutual contact to close the sealed baleen passage and an open position in which the seal valve and the seal seat are mutually spaced to open the passage,
- Means for operating the sealing valve between said positions.

 To increase the safety of such valves, provision is also made to interpose in the passage, between the sealing seat and the outlet port, an outlet valve normally closed and opening mechanically when the port is connected. outlet to user means, and to arrange in the sealing valve a conduit opening into the passage on the one hand between the sealing seat and the outlet valve, and on the other hand between the sealing seat and the inlet orifice at least in said closed position, this conduit housing a normally closed valve and opening under the action of an overpressure downstream, with reference to a direction going from the inlet orifice to the outlet.

 Thus, if the sealing valve and the outlet valve come to be closed at the same time, enclosing between them a certain quantity of gas in liquid phase whose natural tendency is to relax, the valve authorizes the return, towards the inside the enclosure, liquefied gas thus trapped when there appears in it, in comparison with the pressure prevailing inside the enclosure, an overpressure whose value exceeds a predetermined threshold for opening the valve ; this threshold can be easily defined by a person skilled in the art, by an appropriate choice of the characteristics of the valve.

 It will be noted that the fact that the conduit and the valve are arranged in the sealing valve makes it possible to keep the body of the tap the simple structure of traditional tap bodies, devoid of such safety means.

 However, in the current state of the art, the presence of the valve in the sealing valve requires an increase in the dimensions of the latter, and consequently also in the dimensions of the valve body, in comparison with valves without means. of security ; up to now, it has always been proposed to house in the sealing valve a traditional valve, comprising in particular a valve head and a spring for biasing the latter, requiring the arrangement of a receiving cavity having dimensions incompatible with the preservation of a valve size identical to that of a valve without valve.

 The object of the present invention is to remedy this drawback, that is to say to propose a design of a valve-sealing valve compatible with the preservation of a valve size identical to that of a valve. tightness without valve naturally, this goal must be achieved by keeping the body of the valve a simple structure, so that it is possible to use a standard body as well with sealing valves without valve as with sealing valves according to the present invention.

To this end, the sealing valve according to the invention, having a manner known per se
a cylindrical peripheral face of revolution about an axis and provided with annular sealing means with respect to a valve body,
- a transverse end face relative to the axis and intended to cooperate with an annular sealing seat of the valve body in a closed position,
- a sealed interior cavity,
a first section of conduit opening on the one hand into the cavity, through another sealing seat, and on the other hand into the peripheral face, between the sealing means and the end face,
- A second section of conduit opening on the one hand into the cavity, by a mouth offset with respect to said other sealing seat, and on the other hand in an area of the end face located inside the annular seat sealing the valve body in the closed position,
- Means housed in the cavity and cooperating with said other sealing seat to form a normally closed valve, is characterized in that the means housed in the cavity comprise a sealed ball, elastically compressible, sandwiched in the cavity against said other seat sealing, in a mean direction thereof, in that the cavity has a zone offset from said other sealing seat transversely to the mean direction thereof and released by the ball, and in that that the mouth of the second section of conduit is located in this zone of the cavity.

 By adopting such an embodiment, the safety advantages offered by traditional type valve seals can be obtained, without increasing the overall dimensions of the valve in comparison with valves without such valves, that is to say -b say by being able to use standard type valve bodies whether or not the sealing valve is provided with a valve; furthermore, the particularly simple structure of the valve makes the latter particularly reliable.

 According to a particularly advantageous embodiment, in which the sealing valve comprises in a known manner a sealed piston defining the peripheral face and a sealing pad integral with the piston and defining the transverse end face, the piston and the pad d 'sealing define between them the cavity, and the first and second sections of conduit are arranged respectively in the piston and in the sealing pad; this results in great simplicity and great economy in the manufacture of the valve sealing valve.

 Other characteristics and advantages of the invention will emerge from the description below, relating to a non-limiting mode of implementation, as well as from the appended drawings which form an integral part of this description.

 - Figure 1 shows a partial sectional view of a valve according to the present invention, in the state mounted on an enclosure of liquefied gas such as propane, simply shown, and in connection with user means such as the carburetor an internal combustion engine, also shown schematically.

 FIG. 2 shows an enlarged view, in a partial section similar to that of FIG. 1, of the valve sealing valve illustrated in FIG. 1.

 In the overview of Figure 1, the valve has been illustrated in its normal mounting position on a bottle of liquefied gas in use and, subsequently, this valve will be described with reference to this position.

 A vertical zone of the wall of the bottle supposed to be in use position has been shown diagrammatically at 1; this wall zone 1 thus establishes a sealed separation between the interior 2 of the bottle, containing a liquid phase 45 in a lower zone and a gas phase 46 in an upper zone, and the exterior 3 of the bottle, at the atmosphere.

 As is known per se, the wall zone 1 is pierced right through, along a horizontal axis 4, with a tapped orifice 5, of generally frustoconical shape of revolution around the axis 4, widening towards the exterior 3, and in this orifice 5 is screwed, with establishment of a conventional seal, a complementary threaded connection 6 that has for this purpose a body 7 of tap.

 This valve body 7 is sealed and has an oblong shape along the axis 4, the connector 6 defining an end for this body 7 which is essentially placed outside 3 of the bottle.

The body 7 is pierced right through, along the axis 4, with a bore 8 having a general shape of revolution around the axis 4; successively along this axis, that is to say from an annular face 10 of the end of the body 7, turned towards the inside 2 of the bottle, to an annular face 11 of the end of the body 7, placed at the outside 3 of the bottle, the bore 8 is delimited by the following faces, all of revolution around the axis 4
a cylindrical face 9 facing the axis 4 and opening into the annular face 10 through a gas inlet orifice 18,
- a flat annular face 12 facing inward 2 of the bottle,
a cylindrical face 13 facing the axis 4,
- an annular face 14 facing outwards 3 and one section of which by a plane including the semi-circular axis 4, to define a sealing seat as will appear further
a cylindrical face 15 turned in the direction of a radial distance with respect to the axis 4,
a flat annular face 16 facing outwards 3,
- a cylindrical face 17 facing the axis 4 and smooth,
a cylindrical face 19 facing the axis 4 and provided with a 2Q thread, of the same internal diameter as the face 17,
a tapered face 21 facing outwards 3,
- A cylindrical face 22 facing the axis 4 and hollowed out by an annular groove 23, of revolution around the axis 4, receiving an annular, elastic ring 24 thus secured to the body 7 by projecting towards the axis 4 relative to faces 22 and 19.

 In addition, in the immediate vicinity of the face 16, in the face 17, opens inside the bore 8 a second bore 25 arranged in the body 7, under the axis 4, along a vertical axis 26 perpendicular to the axis 4 at a level thereof corresponding substantially to the level of the face 14 and such that the bore 25 opens to the outside 3 of the bottle; in the direction of a distance from the axis 26, the bore 25 is delimited by a cylindrical-conical face, of revolution about the axis 26, of a tubular lower appendage 27 of the body 7, which tubular appendage 27 is provided with an external thread 28 by which it carries in a solid and permanent manner, after manufacture of the tap, a waterproof sleeve 47 having - for this purpose an upper thread 48 complementary to the thread 28 t the waterproof sleeve 47 extends downwards appendix 27 and internally delimits a bore 49, of revolution about the axis 26, itself extending downward the bore 25, with which it is tightly connected due to the interposition of a lining d seal 50, annular of revolution around the axis 26, between annular shoulders 51 and 52, transverse to the axis 26, that the appendage 27 and the sleeve 47 have respectively, facing each other , at their connection; downwards, the bore 49 opens outwards 3 through an outlet orifice 53, of axis 26, around which the sleeve 47 externally carries a bayonet fitting 94 allowing the removable connection of the outlet orifice 53 a pipe 55, for example flexible, for connection with means using gas in the liquid phase, such as the carburetor 54 of an internal combustion engine; in an alternative embodiment not shown, the sleeve 47 could be made in one piece with the appendage 27 of the body 7 of which it is functionally an integral part.

 Through its face 9 via the inlet orifice 18, the bore 8 integrally receives, by tight fitting with sealing, an upper end region 29, horizontal, of a sealed tube 30 for gas passage, which tube 30 abuts outwardly against the face 12 and has a bent downward shape, from its zone 29, so as to plunge inside 2 of the bottle; the tube 30 thus extends towards the interior 2 of the bottle, through an interior space 32, the bore 8 with which the space 32 communicates; at a level adjacent to the lowest zone of the interior 2 of the bottle, that is to say in the liquid phase 45 except when the bottle is practically empty of such a phase, the tube 30 has a zone lower end 31 through which its internal space 32 opens towards the inside 2 of the bottle via a filter strainer 34 which the lower end zone 31 of the tube 30 carries in a manner known per se, via suitable mounting means 33 known to a person skilled in the art.

 Thus, the interior 2 of the bottle communicates, via the strainer 34, the interior space 32 of the tube 30, the inlet orifice 18 and the bore 8, with the bore 25, the bore 49 and the orifice exit 53, and therewith user means 54.

Inside the respective passages 25 and 49 of the tubular appendage 27 and of the sleeve 47 is disposed an outlet valve 60 comprising a sealing seat 61, annular of revolution around the axis 26, having the form a shoulder which the sleeve 47 has inside the passage 49, towards the passage 25, and a valve head 62 housed in the bore 25, that is to say upstream of the sealing seat 61 if we refer to a direction 56 of gas passage from the inlet orifice 18 to the outlet orifice 53, from the interior 2 of the bottle to the user means 54, 55; the valve head 62 carries integrally, downstream with reference to direction 56, a hollow rod 63, of axis 26, engaged in relative sliding along this axis 26 in the bore 49 of the sleeve 47, which rod 63 is provided with perforations 64 on the one hand in the immediate vicinity of the valve head 62 and on the other hand towards the outlet orifice 53 (not visible); the outlet valve 60 can thus occupy two states, namely:
a state of rest illustrated in the left-hand part of FIG. 2, and in which the valve head 62 is applied against the seat 61 under the action of elastic means not shown, known to a person skilled in the art, and sealingly insulates the outlet orifice 53 from the bore 25;
a state, illustrated in the right-hand part of FIG. 1, in which the valve head 62 is moved away from the seat 61 so that the orifices 64 put the passage 25 into communication with the outlet orifice 53; unrepresented mechanical means, known to a person skilled in the art, automatically bring the outlet valve 60 in this state when the pipe 55 is connected to the sleeve 47 by the bayonet fitting 94, and letting the valve 60 return automatically matically previous state when the pipe 55 was disconnected.

 To further allow, at will, to open or close, in a sealed manner, the passage in the direction 56 going from the inlet orifice 18 to the outlet orifice 53, the bore 8 includes internally a sealing valve 35 more particularly visible in FIG. 2, from which it can be seen that this valve 35 comprises in particular a tight, rigid piston 39 delimited in particular by an outer peripheral face 41 of generally cylindrical shape of revolution around the axis 4 , with a diameter as close as possible to that of the face 17 so that there is established between the faces 17 and 41 a guide contact with relative sliding along the axis 4; a seal between the faces 17 and 41 is ensured by a suitable lining 36 received in an annular groove, continuous 40 of revolution around the axis 4, that the piston 39 has in its face 41; the piston 39 is moreover delimited by two annular faces 57 and 58, of revolution around the axis 4, respectively turned towards the inside 2 of the bottle and towards the outside 3 of the latter, and each of which is connected on the one hand to the face 41 in the direction of a radial distance with respect to the axis 4, and on the other hand to the orifice of a respective blind hole 59, 60, arranged in the piston 39 along the axis 4, in the direction of a radial approach with respect to axis 4.

 The annular face 57 is continuous and its connection 37 with the orifice of the blind hole 59 has the shape of a circular edge of axis 4, with a diameter equal to or preferably greater than that of the face 15 of the body 7 ; inside this edge 37, the blind hole 59 is closed by a flat face 65, perpendicular to the axis 4 and turned towards the face 14 of the bore 8, which has a seal 38 in the form of a rigid pellet housed in the blind hole 59 and secured to the piston 39 for example by crimping, the edge 37 then constituting a narrowing of the blind hole 59 transversely to the axis 4. By sliding the piston 39 respectively in the direction of approximation vis-à-vis the face 14 or a distance vis-à-vis the latter, it is thus possible to bring the face 65 of the seal 38, either in a position illustrated in the upper part of the figure 1, in which this face 65 is applied flat against the face 14 and thus closes any passage from the inlet orifice 18 to the bore 25 via the bore 8, or in the position illustrated in the lower part of FIG. 1 and in FIG. 2, in which the face 65 of the seal 38 is e spaced from the face 14 so as to open a passage between the inlet orifice 18 and the bore 25 via the bore 8.

 The passage of the piston 35 and of the seal 65 to either of these positions by sliding along the axis 4 inside the bore 8 of the body 7 can be easily caused by manual action on a handwheel 42 covering the upper end face 11 of the body 7 and integrally carrying, inside the bore 8, a rod 43 of axis 4, engaged in the blind hole 60 of the piston 39 and cooperating with this blind hole 60, by complementarity of shape, so that the rod 43 and the piston 39 are integral against a relative translation parallel to the axis 4 but are however free vis-à-vis relative rotation around axis 4; the rod 43 has in abutment, opposite the threaded face 19 of the bore 8, a thread 44 complementary to the thread 20 and cooperating with it, so that the rotation of the button 42 in one direction or the other, around the axis 4, with respect to the body 7, results in a joint translation of the flywheel 42, the rod 43, the piston 35 and the seal 38, in one direction or the other, according to the axis 4 relative to the body 7; towards the handwheel 42, the rod 43 has a shoulder 66 capable of coming into abutment towards the outside 3 against the rod 24 when, by such a rotation, the valve 35 is brought into a limit position defining an open position maximum between the bore 25 and the interior 32 of the tube 30 via the inlet orifice 18 (lower part of FIG. 1).

 It will be noted that it may happen that the outlet valve 60 is in the closed state, and that, simultaneously, the valve 43 is itself in the closed position, with sealed contact between the face 65 of the lining. seal 38 and the seal seat 14, so that a certain amount of liquid gas can be trapped between the outlet valve 60 and the seal valve 35.

 To avoid any risk of deterioration of the valve in the event that the gas thus trapped vaporizes, developing a considerable pressure inside the valve, means are provided for authorizing a return, towards the interior of the bottle 2, of the liquid gas thus trapped when it tends to vaporize.

 These means are provided inside the sealing valve 35, the internal structure of which will now be detailed, more particularly with reference to FIG. 2.

 it appears in particular from this figure 2 that the face 41 of the piston 39 has an annular groove, continuous 67, of revolution about the axis 4, arranged between the groove 40 for receiving the seal facing the face 17 of the bore 8, and the end face 57 so that the groove 67 is not sealed with respect to the passage 25, that the piston 39 occupies its position of opening the passage of the orifice inlet 18 to the outlet orifice 53 or on the contrary that it occupies its closed position; moreover, in this position, the groove 67 preferably has an area placed directly opposite the passage 25, as is the case in the example illustrated in FIG. 1.

 In the groove 67 opens a first section 68, arranged in the piston 39, of a duct having moreover a second section 69 arranged in the seal 38, closer to the axis 4 than the face 14 forming a seat d sealing for the face 65 of the lining 38, so that the conduit formed by the two sections 68 and 69 connects the groove 67, that is to say in fact the bore 25, with the inlet orifice 18 by the area of the bore 8 delimited by the face 13 thereof, even when the face 65 of the seal 38 is applied against the face 14 by establishing a sealed mutual contact.

 More specifically, the conduit 68 has a first rectilinear zone 70, of axis 71 concurring with axis 4, which zone 70 opens on the one hand into the groove 67 and on the other hand into a second zone 72 of the first section of conduit 68, which zone 72 constitutes a bottom zone of the blind hole 59; this zone 72 is delimited in the example illustrated by a cylindrical face 73 of revolution around the axis 4, towards which it is turned, with a diameter less than that of the edge 37 of the piston 39, the zone 70 opening precisely in this face 73, and by a conical face 74 of revolution about the axis 4, which face 74 is connected to the face 73 in the region thereof closest to the other blind hole 60 of the piston 39 for close zone 72 of blind hole 59 towards blind hole 60.

 In the direction of a distance, along the axis 4, relative to the bottom face 74, the face 73 is threaded, by a circular edge of axis 4, to a face 76 of the blind hole 59, which face 76 has a frustoconical shape of revolution around the axis 4, with a convergence in a direction going from the blind hole 59 towards the blind hole 60, with a clean surface state to allow this frustoconical face 76 to play the role of 'a sealing seat, as will appear later.

 Connecting to the face 73 in the direction of approximation with respect to the axis 4, the frustoconical face 76 is connected in the direction of a distance with respect to this axis 4 to a cylindrical face 77 of revolution around the axis 4 towards which it is turned, with a diameter intermediate between the respective diameters of the face 73 and the edge 37; the face 77 connects the face 76 to an annular, flat face 75, of revolution about the axis 4, which face 75 itself connects the face 77, in the direction of a radial distance from the axis 4, to a second frustoconical face 78, of revolution around axis 4 with a convergence identical to that of face 76; this face 78 connects the face 75, in the direction of a distance with respect to the axis 4, to a cylindrical face 79 of revolution around this axis, towards which it is turned, with a diameter greater than that of the edge 37 to which the face 79 is connected by a face 80, annular of revolution about the axis 4, turned towards the face 78 so as to retain, integrally, inside the blind hole 59 the gasket sealing 38.

 In addition, the face 65 of the latter has the general shape of a circular disc with a diameter substantially equal to that of the face 79 of the blind hole 59, and is connected in the direction of a distance from the axis. 4 to a cylindrical face 81 of revolution about the axis 4 and turned in the direction of a distance relative to the latter, with a diameter substantially identical to that of the face 79; parallel to axis 4, face 81 has a length identical to the length of face 79 measured between face 80 and face 78 and, in the direction of a distance from face 65 parallel to the axis 4, the face 81 is connected to a frustoconical face 82 of revolution about the axis 4 with a convergence identical to that of the face 78 of the hole. blind 59, so that the seal 38 is placed in close contact, respectively by the faces 81 and 82, with the faces 79 and 78 of the blind hole 59 by establishing a seal as good as possible with the piston 39.

 In the direction of approximation with respect to the axis 4, the frustoconical face 82 is connected to an annular, flat face 83, of revolution around the axis 4, which face 83 is turned in the opposite direction from the face 65 and directly complementary to the face 75 against which it is applied.

 The face 83 connects the face 82, in the direction of approximation with respect to the axis 4, to a cylindrical face 84 of revolution around this axis towards which it is turned, with a diameter identical to that of the face 77 that the face 84 extends directly inside the seal 38.

 The face 84 connects the face 83, in a direction going from the latter towards the face 65 parallel to the axis 4, to a conical face 85, of revolution around the axis 4 with a convergence going from the face 83 towards the face 65, symmetrically of face 76 with respect to a common virtual plane of faces 75 and 83 so that each generator of face 85 is parallel to a respective generator of face 76, by means of an identical mutual spacing whatever the generators thus parallel envisaged.

 It will be noted that the piston 39 and the lining 38 define, by their respective faces 76, 77 and 84, 85, a cavity 86 in which the first section of conduit 68 opens along the axis 4 through its zone 72, and more precisely by the connection of the face 73 with the face 76, and in which the second section 69 arranged in the lining 38 for example in a rectilinear direction 87 parallel to the axis 4 and merged with a generator of the face 84, opens into the faces 83, 84, 85 overlapping the face 84; for this purpose, the common diameter of the faces 84 and 77 is chosen to be less than the diameter of the face 13 delimiting the face 14 towards the axis 4.

In view of the implementation of the present invention, the spacing e between two parallel generators respectively of the face 76 and of the face 85 is less than the common diameter of the faces 77 and 84 so that one can trap in the cavity 86 a ball 88 of tight, elastically compressible material and for example of elastomer, with a diameter at rest at least equal and preferably greater than the value e but less than the value of the common diameter of the faces 77 and 84; thus, this ball 88 is clamped and, preferably, kept in compression, in the direction of the axis 4, between the faces 85 and 76, against the connection of the latter with the face 73, so as to establish a tight contact with the face 76, in. on the other hand, leaving an annular zone 89 of the cavity 86 clear; this zone 89 constitutes the zone of the cavity 86 furthest from the axis 4, defined by the faces 77, 84 and by the respective zones of the faces 76 and 85 adjacent to these faces 77 and 88, that is to say precisely the zone in which the mouth 90 of the section of conduit 69 is located in the cavity 86,
The ball 88 and the sealing seat defined by the frustoconical face 76 thus jointly define a normally closed internal valve sant any passage from the section of conduit 69 to the section of conduit 68 by authorizing on the other hand a passage from the section of conduit 68 to the section of duct 69 if the section 68 is placed under overpressure, relative to the section 69, by a value exceeding a threshold determined by the possible compression pre-stress of the ball 88, along the axis 4, inside of the cavity 86.

 Insofar as the section of conduit 68 is permanently connected to the bore 25 and the section 69 to the inlet orifice 18, it is conceivable that the valve thus formed by the ball 88 and the face 76 allows a return to the inside the bottle 2, liquid gas possibly trapped between the valves 35 and 60 as soon as this gas, tending to vaporize, is placed under overpressure relative to the inside of the bottle 2, by a value exceeding the predetermined opening threshold of this valve.

 Naturally, the embodiment of the invention which has just been described constitutes only a non-limiting example.

Claims (6)

 1. Sealing valve for a valve intended for the connection of an enclosure containing a liquefied gas to means using gas in the liquid phase, said valve having  a peripheral face (41) cylindrical of revolution about an axis (4) and provided with annular sealing means (36, 40) with respect to a body (7, 47) of the tap,  an end face (65) transverse to the axis (4) and intended to cooperate with an annular sealing seat (14) of the body (7, 47) of the valve in a closed position,  - a sealed internal cavity (86), "- a first section of conduit (68) opening on the one hand into the cavity (86), through another sealing seat (76), and on the other hand into the peripheral face (41), between the sealing means (36, 40) and the end face (65),  - A second section of conduit (69) opening on the one hand into the cavity (86), by a mouth (90) offset relative to said other sealing seat (76), and on the other hand in an area of the end face (65) situated inside the annular sealing seat (14) of the body (7, 47) of the valve in the closed position,  - means (88) housed in the cavity (86) and cooperating with said other sealing seat (76) to form a normally closed valve,  characterized in that the means (88) housed in the cavity (38) comprise a sealed ball (88), elastically compressible, clamped in the cavity (86) against said other sealing seat (76), in a medium direction ( 4) thereof, in that the cavity (86) has a zone (89) offset relative to said other sealing seat (76) transversely relative to the mean direction (4) thereof and released by the ball (88), and in that the mouth (88) of the second section of conduit (69) is located in this zone (89) of the cavity.  2. Valve according to claim 1, characterized in that the ball (88) is made of elastomeric material.  3. Valve according to any one of claims 1 and 2, characterized in that the ball (88) is compressed, in the cavity (86), against said other sealing seat (76).  4. Valve according to any one of claims 1 to 3, characterized in that said mean direction (4) coincides with said axis (4).  5. Valve according to any one of claims 1 to 4, characterized in that the first section of conduit (68) opens into the peripheral face (41) by a continuous annular groove (67), of revolution about the axis (4), arranged in this face (41).  6. Valve according to any one of claims 1 to 5, comprising a sealed piston (39) defining the peripheral face (41) and a sealing pad (38) integral with the piston (39) and defining the end face transverse (65), characterized in that the piston (39) and the sealing pad (38) delimit between them the cavity (86), and in that the first (68) and second (69) sections of conduit are arranged respectively in the piston (39) and in the sealing pad (38).