EP0375532B1 - 2-Way valve to be installed downstream in a fluid distribution pig pipe-line - Google Patents

Abstract

2-way valve for fluid distribution pig pipe-line, comprising a plunger tube (2; 2' + 30; 2" + 30") in which is engaged an abutment part (3, 3', 3") adapted to receive a scraper (4) in abutment, an annular slot (6, 6', 6") formed through this plunger tube upstream of this abutment part and an obturating sliding sleeve (7, 7', 7"), movable longitudinally under the action of a control device (15, 16; 37, 38; 38") between a closed configuration in which the sleeve obturates the annular slot and an open configuration in which the sleeve leaves the annular slot at least partly clear, characterised in that the abutment part (3, 3', 3") is movable and is integral with the said sleeve, a feed pressure injection orifice (18, 18', 18") opening into this abutment part. <IMAGE>

Description

The invention relates to a two-way valve intended to be mounted downstream of a liquid distribution pipe, at the free end of a dip tube, in particular for the discharge of a liquid such as oil or petroleum product in a tank or cistern.

When the same pipe is used for the successive distribution of several liquids, it is known, when one wants to change the liquid after having stopped the supply of the first liquid upstream of this pipe, before opening, also upstream of this pipe, the supply of the next liquid, to circulate in this pipe, from upstream to downstream and vice versa, a "captive" scraper adapted to sweep the inner wall of this pipe, to push downstream the residues of the first liquid that adhere to this inner wall and return to its starting point. This avoids partial mixing between successive liquids.

The captive nature of the sensors means that they are prevented from leaving the pipe freely; it is therefore necessary to provide in the downstream valves of this pipe, a stop for such a scraper capable of allowing a flow of liquid while avoiding the dragging of the scraper by said liquid.

An example of such a two-way valve intended to be mounted downstream of a liquid distribution pipe is described in the document FR-2.222.587 which provides for a peripheral bypass by the fluid of a stopper disposed on the path scraper; a cylindrical sleeve coaxial with the flow of the liquid is slidably mounted around the stop thanks to which, depending on the axial position of this sleeve, the section bypassing the stop by the liquid is either closed or released.

In addition, in this document FR-2.222.587, the injection of the pressure necessary for the upstream delivery a scraper abutting against the stop, is done in the liquid flow section near said stop. Finally, this known solution is hardly suitable for allowing a flow of fluid in the presence of a scraper against the stop.

Also known, according to a prospectus "IST Loading Lance" bearing the date of 02/13/87, a valve of a similar type in which is further provided, through the abutment piece, an orifice for the application of a discharge pressure to the scraper.

In known solutions, the control (or retention) in position of this sliding sleeve is ensured independently of the presence of a liquid pressure upstream of this valve.

The invention aims to overcome the aforementioned drawbacks by making the abutment mobile, which hitherto was fixed, and by subjecting the sliding shutter sleeve to this movable abutment: this makes it possible to establish a security which, as required, tends automatically keep the valve open or closed in the presence of a liquid pressure applying against the movable stop.

To this end, the invention proposes a two-way valve for a scrapable liquid distribution pipe, comprising a dip tube in which is engaged an abutment piece adapted to receive a scraper in abutment and into which opens an injection orifice for discharge pressure, an annular slot formed through this dip tube upstream of this stop piece and a sliding shutter sleeve movable longitudinally under the action of a control device between a closed configuration in which the sleeve closes the annular slot and an opening configuration in which the sleeve leaves at least partially clear the annular slot, characterized in that the abutment piece is axially movable and is integral with said sleeve in this abutment piece.

• la pièce de butée est, en configuration d'ouverture de la fente annulaire par le manchon coulissant, plus en amont qu'en configuration de fermeture, à une distance suffisante de la fente annulaire pour permettre la venue en butée d'un racleur sans pour autant que celui-ci obture ladite fente,
• le manchon coulissant coulisse extérieurement le long du tube plongeur en étant solidaire d'une pièce cylindrique de confinement elle-même solidaire de la pièce de butée.
• le manchon coulissant est fixe le long de la paroi interne de la pièce cylindrique de confinement, tandis que celle-ci est reliée, plus en aval, à la pièce de butée au moyen de doigts radiaux traversant le tube plongeur à la faveur de lumières longitudinales,
• la pièce cylindrique de confinement comporte en amont du manchon coulissant une bride annulaire coulissant de façon étanche autour du tube plongeur, tandis que celui-ci porte extérieurement une collerette annulaire définissant, radialement entre la pièce cylindrique de confinement et le tube-plongeur, axialement entre cette bride et ce manchon coulissant deux chambres étanches de volumes variables en sens inverse, ledit dispositif de commande comportant des orifices d'injection/évacuation de fluide sous pression débouchant respectivement dans chacune desdites chambres
• lesdits orifices d'injection de fluide sous pression traversent respectivement la bride et le manchon coulissant,
• la pièce de butée est conformée en cuvette adaptée à recevoir une portion terminale du racleur, au fond de laquelle débouche ledit orifice d'injection de pression de refoulement,
• le manchon coulissant coulisse intérieurement dans un tronçon tubulaire aval du tube plongeur, en étant formée par un prolongement vers l'amont de cette pièce de butée, ce manchon coulissant ayant un diamètre intérieur égal au diamètre intérieur du tronçon amont du tube plongeur en sorte de permettre la venue en butée d'un racleur contre la pièce de butée,
• la pièce de butée est, en configuration d'ouverture de la fente annulaire par le manchon coulissant, plus en aval qu'en configuration de fermeture,
• la pièce de butée se prolonge vers l'aval par une portion tubulaire, définissant un canal débouchant dans le fond de cette pièce de butée, et coulissant de façon étanche dans un logement cylindrique d'une pièce solidaire du tronçon tubulaire aval du tube plongeur et communiquant avec ledit orifice d'injection de pression de refoulement, ledit dispositif de commande du manchon coulissant comportant un orifice d'injection de fluide sous pression débouchant dans une chambre juste en aval de la pièce de butée,
• ladite pièce solidaire du tube plongeur comporte autour du logemenbt cylindrique un cylindre présentant en son extrémité amont une collerette en saillie radiale et le long duquel est montée coulissante de façon étanche une couronne s'étendant radialement jusqu'au tronçon tubulaire aval du tube plongeur en sorte de définir avec ladite pièce solidaire de cedit tronçon une seconde chambre dans laquelle débouche un second orifice d'injection de fluide sous pression.

According to preferred arrangements of the invention

• the abutment piece is, in the opening configuration of the annular slot by the sliding sleeve, more upstream than in the closing configuration, at a sufficient distance from the annular slot to allow the abutment of a scraper without for as far as this closes said slot,
• the sliding sleeve slides outwardly along the dip tube while being integral with a cylindrical confinement piece itself integral with the abutment piece.
• the sliding sleeve is fixed along the internal wall of the cylindrical confinement part, while the latter is connected, further downstream, to the abutment part by means of radial fingers passing through the dip tube in favor of longitudinal lights ,
• the cylindrical confinement piece comprises, upstream of the sliding sleeve, an annular flange sliding in leaktight manner around the dip tube, while the latter carries an annular collar externally defining, radially between the cylindrical confinement piece and the dip tube, axially between this flange and this sleeve sliding two sealed chambers of variable volumes in opposite directions, said control device comprising injection / evacuation orifices of pressurized fluid opening respectively in each of said chambers
• said pressurized fluid injection orifices respectively pass through the flange and the sliding sleeve,
• the abutment piece is shaped like a bowl adapted to receive an end portion of the scraper, at the bottom of which opens said discharge pressure injection orifice,
• the sliding sleeve slides internally in a downstream tubular section of the dip tube, being formed by an upstream extension of this stop piece, this sliding sleeve having an inside diameter equal to the inside diameter of the upstream section of the dip tube so allow a scraper to come into abutment against the abutment piece,
• the abutment piece is, in the opening configuration of the annular slot by the sliding sleeve, more downstream than in the closing configuration,
• the stopper piece extends downstream by a portion tubular, defining a channel opening into the bottom of this abutment piece, and sliding in leaktight manner in a cylindrical housing of a piece integral with the downstream tubular section of the dip tube and communicating with said discharge pressure injection orifice, said sliding sleeve control device comprising a pressure fluid injection orifice opening into a chamber just downstream of the abutment piece,
• said part integral with the dip tube comprises around the cylindrical housing a cylinder having at its upstream end a radially projecting collar and along which is slidably mounted a ring extending radially to the downstream tubular section of the dip tube so define with said piece integral with said section a second chamber into which opens a second orifice for injecting pressurized fluid.

• la figure 1, est une vue en coupe axiale d'une vanne de réception de racleursà deux voies conforme à l'invention, en configuration ouverte ;
• la figure 2, en est une vue partielle en coupe transversale selon la ligne de coupe 2-2 de la figure 1 ;
• la figure 3 en est une vue partielle en coupe axiale selon la ligne III-III de la figure 1 ;
• la figure 4, est une vue similaire de la figure 1, en configuration d'obturation intermédiaire ;
• la figure 5, est une vue similaire à celles des figures 1 et 4, en configuration fermée ;
• la figure 6, est une vue en coupe axiale d'une variante de réalisation de la vanne selon l'invention, en configuration fermée ;
• la figure 7, est une vue axiale de la vanne de la figure 6, en configuration ouverte ;
• la figure 8, est une vue axiale de la vanne des figures 6 et 7, en configuration d'obturation intermédiaire,
• la figure 9, est une vue axiale, en configuration fermée, d'encore une autre variante de réalisation d'une vanne selon l'invention, et
• les figures 10 à 14 sont des vues schématiques d'une conduite reliant un réservoir à une citerne, correspondant à cinq phases successives dans la distribution de liquide depuis la réservoir jusqu'à la citerne, et le raclage subséquent

   Les figures 1 à 5 représentent une première variante de réalisation d'une vanne 1 à deux voies, destinée à être montée en aval d'une conduite de distribution de liquides dans laquelle on a prévu de faire circuler au moins un racleur, d'amont en aval et d'aval en amont, entre les écoulements des liquides successifs différents.Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which:

• Figure 1 is an axial sectional view of a two-way pigs receiving valve according to the invention, in the open configuration;
• Figure 2 is a partial view in cross section along the section line 2-2 of Figure 1;
• Figure 3 is a partial view in axial section along the line III-III of Figure 1;
• Figure 4 is a similar view of Figure 1, in the intermediate shutter configuration;
• Figure 5 is a view similar to those of Figures 1 and 4, in the closed configuration;
• Figure 6 is an axial sectional view of an alternative embodiment of the valve according to the invention, in the closed configuration;
• Figure 7 is an axial view of the valve of Figure 6, in the open configuration;
• FIG. 8 is an axial view of the valve of FIGS. 6 and 7, in the intermediate closure configuration,
• FIG. 9 is an axial view, in the closed configuration, of yet another variant embodiment of a valve according to the invention, and
• Figures 10 to 14 are schematic views of a pipe connecting a tank to a tank, corresponding to five successive phases in the distribution of liquid from the tank to the tank, and the subsequent scraping

Figures 1 to 5 show a first alternative embodiment of a two-way valve 1, intended to be mounted downstream of a liquid distribution pipe in which it is planned to circulate at least one scraper, from upstream downstream and downstream upstream, between the flows of different successive liquids.

This valve comprises a dip tube 2 in which is disposed a stop piece 3, which completely seals the passage section of this dip tube 2, and which is adapted to receive a scraper 4 in stop. This stop piece 3 advantageously comprises a bowl 5 shaped so as to marry, in a complementary manner, an end portion 4A of the scraper.

Upstream of this stop piece 3 is formed an annular slot 6, here discontinuous, intended to allow a crossing by peripheral bypass of the stop piece 3 by a liquid flowing in the dip tube. A cylindrical sleeve 7 is slidably mounted along the dip tube so as to be able, as desired, to close off (FIG. 5) or, on the contrary, disengage (FIG. 1) the discontinuous annular slot 6.

This sliding cylindrical sleeve is here integral with a cylindrical confinement piece 8 which extends from the sleeve to beyond axially from the stop piece 3 so as to ensure a radial confinement of the liquid passing through peripheral bypass the stop piece 3.

Downstream of the discontinuous circular slot 6 are provided longitudinal slots 9 into which radial fingers 10 penetrate ensuring the attachment of the abutment piece 3 to this cylindrical confinement piece 8, and therefore to the sliding sleeve 7.

The cylindrical confinement piece 8 extends upstream around the dip tube 2 beyond a flange 11 secured to the outer wall of the dip tube, and adapted to constitute a stop for the sliding cylindrical sleeve 7. This cylindrical piece has at its upstream end an annular flange 12 suitable for sealingly confining, with the collar 11 and the walls of the dip tube 2 and of this cylindrical part 8, an annular space 13 of variable volume. Likewise, the sliding sleeve 7 determines downstream of this flange 11 an annular space 14 whose axial dimension varies in opposite direction to the axial dimension of the annular space 13.

Injection nozzles 15 and 16, formed respectively in the annular flange 12 and in the sliding sleeve 7, are adapted to be connected to a pressure source, alternately, so as to, as in a double-acting cylinder, enlarge at choice either annular space 13 or annular space 14.

Similarly, an injection orifice 17 also suitable for being connected to a pressure source, not shown, is provided to allow injection of pressurized fluid through the bottom of the bowl 5 of the stop piece 3.

As can be seen from FIG. 3, one 10A of the radial fingers ensuring the connection of the stop piece 3 to the cylindrical confinement piece 8, is hollow so as to allow the injection orifice 17 to be placed in communication with an orifice 18, here axially disposed, which opens into the bowl 5 of said abutment part 3.

A non-return valve 19 is provided between the injection orifice 17 and the bowl 5 of said abutment piece 3 so as to prevent any flow of liquid towards the injection orifice 17.

As can be seen from FIG. 1, the stop piece 3 is arranged downstream of the discontinuous annular slot 6 by a sufficient distance to allow a scraper 4 to come into abutment against this stop piece without hampering the penetration of the flow into the discontinuous annular slot. It will be appreciated that the scraper 4 here has a rear end piece 4B which, like the front end piece 4A, has a frustoconical shape, which ensures very good deflection of the flow towards this discontinuous annular slot.

In operation, in the configuration of FIG. 1, a fluid pressure exists in the upstream annular space 13, brought through the injection orifice 15, whereby the assembly constituted by the stop piece 3, the cylindrical confinement piece 8 and the cylindrical shutter sleeve 7 are and remain in the high configuration: in this way the liquid capable of descending along the dip tube 2 can easily cross the discontinuous annular slot 6.

If, from the configuration of this FIG. 1, a fluid pressure is injected through the orifice 16 into the annular space 14, on the other hand, an overall downward movement of the stop piece 3 is caused, by the cylindrical confinement piece 8 and of the sliding shutter sleeve 7: the discontinuous annular slot 6 is then closed and the crossing of the stop piece 3, by a possible flow of liquid, is prevented. Valve 1 is then closed (Figure 5).

In each of configurations 1 and 5, one, 13 or 14, annular spaces is maximum while the other is minimum, that is to say of zero axial dimension. The relative movement between the dip tube 2 and the mobile assembly 3 + 8 + 7 assumes that the air or the fluid contained in that of the annular spaces 13 or 14 which decreases can escape: in the configuration of FIG. 1, free exhaust is allowed through port 16, while in the configuration of Figure 5, free exhaust is allowed through port 15. Here we find a principle of operation similar to that of a double-acting cylinder.

Figure 4 corresponds to an intermediate configuration between those of Figures 1 and 5, that is to say that none of the annular spaces 13 or 14 is reduced to a zero axial dimension. To do this, a pressurized fluid, such as compressed air, is applied both to each of the annular spaces 13 and 14 (see the blackened triangles shown in FIG. 4 near the orifices 15 and 16).

As a variant, it may be sufficient to inject a single fluid under pressure, for example into the annular space 13, by preventing any reflux of fluid towards the outside of the annular space 14. In this intermediate configuration of FIG. 4 , the cylindrical shutter sleeve 7 partially seals the discontinuous annular slot 6 which allows the abutment part 3 to be crossed by bypassing with a flow rate lower than the maximum flow rate authorized by this valve 1.

It will be appreciated that the valve 1, shown in Figures 1 to 5, is of the type with automatic closing safety. Indeed, in the absence of any pressure applied in any of the annular spaces 13 and 14, without it being useful to involve any elastic return, a flow rate from top to bottom in the dip tube 2 exerts a lowering pressure on the stop piece 3 which will spontaneously induce, by the mere fact of the presence of a liquid pressure upstream of this stop piece, an overall downward movement of parts 3 and 8, and therefore of the sliding sleeve d obturation 7. A flow of the fluid is therefore only possible provided that an appropriate pressure actually reaches the annular space 13; any failure occurring in the supply circuit of this annular space 13 results in closing of the valve.

In the configurations of FIGS. 1 and 4, a scraper 4 is in abutment against the abutment piece 3. At the end of a flow of liquid through the dip tube 2, and before circulating a different liquid, circulate in the entire pipe the scraper 4 or a second scraper marked 4 ′ in FIG. 5. To return the scraper 4 to the upstream configuration, possibly at the same time as the scraper 4 ′, a fluid under pressure is injected by l orifice 17, in channel 18, which has the effect of propelling the scraper (s) upstream.

As a preference, an injection orifice 20 is formed in the cylindrical shutter sleeve 7 thanks to which it is possible to control a delivery upstream of the only scraper 4 ′.

FIGS. 6 to 8 represent a valve 1 ′ which differs from that of FIGS. 1 to 5 in that the existence of a liquid pressure upstream of the stop piece 3 ′ spontaneously tends to clear the annular slot 6 ′ ( here continues) and thus allow a crossing by bypassing this stop piece (safety in automatic opening)
In this valve 1 ′, where elements homologous to those of the valve 1 bear the same reference signs with, however, the addition of a “prime” index, the sliding shutter sleeve 7 ′ slides internally in a downstream tubular section 30 in which slides the stop piece 3 ′; this sleeve 7 ′ constitutes an axial extension of the abutment piece around the bowl 5 ′, the internal diameter of which is equal to the internal diameter of the dip tube 2 ′ (the internal diameter of the tubular portion is therefore greater than that of this dip tube).

The cylindrical confinement wall 8 ′ is fixed relative to the dip tube and is kept apart from the tubular portion 30 by radial fingers 10 ′ fixed.

The abutment piece 3 ′ is extended axially opposite the closure sleeve 7 ′ by a tubular portion 31 of smaller diameter defining a channel 18 ′ opening into the bowl 5 ′. This tubular portion slides in leaktight fashion in a cylindrical housing 32 formed in a fixed part 33 integral with the tubular section 30. This cylindrical housing 32 communicates with an orifice 17 ′ for injecting pressurized fluid suitable for being connected to a pressure source not shown. A non-return valve 19 ′ is provided to prevent any backflow of liquid from the channel 18 ′ towards the orifice 17 ′.

The fixed part 33 comprises a cylinder 34 bordering the cylindrical housing 32 and along which a crown 35 is slidably mounted in a radially sealed manner between this cylinder and the cylindrical section 30. A retaining flange 36 is formed in radial projection at the end upstream of the cylinder 34 whereby the crown 35 does not risk escaping beyond the cylinder.

An injection orifice 37 adapted to be connected to a pressure source, is formed through the tubular section 30 in the transverse plane of confrontation of the fixed part 33 and the crown 35 while a second injection orifice 38, also suitable for being connected to a pressure source, is formed in this tubular section 30 more upstream of the orifice 36, so as to open upstream of this ring. A groove 35A is provided at the periphery of this ring so as to maintain this orifice 38 in communication with the annular space 39 formed between this ring and the piece of stop regardless of the position of this crown.

In the configuration of Figure 6, a fluid pressure is injected into the annular space 39 so as to push upstream the abutment piece and thus close the annular slot 6 ′ by the sleeve 7 ′. As long as the resulting upward pushing force is greater than a possible downstream push exerted by a liquid in the dip tube 2 ′, the valve 1 ′ remains closed.

If, on the other hand, this pressure is annulled voluntarily or involuntarily in the annular space 39, the abutment piece 3 ′ slides downstream, thus releasing the sleeve 7 ′ with respect to the annular slot 6 ′. Valve 1 ′ is open (Figure 7).

If fluid pressure is now injected through the orifice 37 between the fixed part 33 and the crown 35, this crown is raised up to the stop against the flange 36, with the formation of an annular space 40 and a predetermined intermediate filling of the slot 6 ′ (FIG. 8).

In a variant not shown, the sleeve 7 'extends further upstream while lights are formed in this sleeve so as to come opposite the slot 6' in the configuration of Figure 6 and below that -ci in the configuration of Figure 7: we find the same type of security with the valve 1, that is to say that the pressure of a possible liquid in the dip tube 2 'normally tends to close the 6 ′ annular slot.

FIG. 9 illustrates a simplified variant of the valve 1 ′. It represents a valve 1˝ which differs from this valve 1 ′ by the elimination of the crown 35 (the other elements being assigned a "second" index). A possible intermediate position of the type of FIG. 8 is obtained by the appropriate choice of a quantity of fluid introduced into the annular space 39˝ (this fluid is then advantageously a liquid with little or no compressibility such as oil).

Figures 10 to 14 show an example of application of any of the valves of Figures 1 to 9. For the rest we will refer to valve 1, but it will be understood that it can be replaced if necessary one of the 1 ′ or 1˝ valves.

This valve 1 is mounted downstream of a scrapable distribution pipe 50 and is engaged in the supply orifice 52 of a tank 51. This pipe 50 comes for example from a tank (not shown) and includes a valve upstream 53 three-way ball valve (of the type described in a parallel request of the same day) in which, at rest, two scrapers 4 and 4 ′ are normally stored. This pipe comprises an articulated section 54 adapted, as necessary, to connect the downstream section of the pipe 50, to another upstream section connected to another tank through another three-way valve (not shown).

In FIG. 10, no circulation of liquid takes place in the pipe 50 and the two scrapers 4 and 4 ′ are stored in the valve 53 which is closed.

In FIG. 11, the valve 53 has been opened, and the liquid flows towards the valve 1, by propelling the scraper 4 which expels the air downstream and prevents its mixing with the liquid.

In FIG. 12, the scraper 4 is in abutment in the valve 1, which is in the open configuration of FIG. 1, so that the liquid flows from the valve into the tank which begins to fill.

When the desired quantity of liquid has passed through the valve 53, a pressure P is applied through the sealing flange thereof (FIG. 13) so as to propel the second scraper 4 ′ which thus scrapes the residues of this liquid . This movement continues until this second scraper abuts against the first scraper 4.

A discharge pressure is then injected, through the orifice 17 in FIG. 1, so as to bring the scrapers 4 and 4 ′ back into the valve 53.

Line 50 is then ready for dispensing a new liquid.

It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention.

Claims (11)

1. Two-way valve for a liquid distribution pipe adapted to be cleaned by scraping comprising a vertical tube (2; 2' + 30; 2'' + 30'') containing an abutment member (3, 3', 3'') adapted to receive a scraper (4) in abutting relationship against it and into which discharges a reverse flow pressure injection orifice (18, 18', 18''), an annular slot (6, 6', 6'') in the vertical tube on the upstream side of the abutment member and a sliding obturator sleeve (7, 7', 7'') movable longitudinally by a control device (15, 16; 37, 38; 38'') between a closed configuration in which the sleeve shuts off the annular slot and an open configuration in which the sleeve exposes at least part of the annular slot, characterised in that the abutment member (3, 3', 3'') is mobile in the axial direction and is fastened to said sleeve in said abutment member.
2. Valve according to claim 1 characterised in that when the sliding sleeve is in the configuration with the annular slot open the abutment member is farther upstream than in the closed configuration at a sufficient distance from the annular slot to enable a scraper to come into abutting relationship with it without closing off said slot.
3. Valve according to claim 2 characterised in that the sliding sleeve (7) slides along the outside of the vertical tube (2) and is fastened to a cylindrical confinement member (8) surrounding and fastened to the abutment member (3).
4. Valve according to claim 3 characterised in that the sliding sleeve is fixed along the internal wall of the cylindrical confinement member which is joined farther downstream to the abutment member by radial fingers (10) passing through longitudinal slots (9) in the vertical tube.
5. Valve according to claim 3 or claim 4 characterised in that the cylindrical confinement member (8) comprises upstream of the sliding sleeve (7) an annular flange (12) sliding in a liquid-tight way on the vertical tube which carries externally an annular collar (11) defining in the radial direction between the cylindrical confinement member (8) and the vertical tube and in the axial direction between the flange (12) and the sliding tube (7) two liquid-tight chambers (13, 14) adapted to have their volumes varied in opposite senses, said control device comprising respective pressurised fluid inlet/outlet orifices (15, 16) discharging into said chambers.
6. Valve according to claim 5 characterised in that said pressurised fluid inlet orifices (15, 16) pass through the flange (12) and the sliding sleeve (7).
7. Valve according to any one of claims 2 through 6 characterised in that the abutment member (3) is cup-shaped and adapted to receive an end portion of the scraper, said reverse flow pressure injection orifice (18) being in the bottom of said cup-shape.
8. Valve according to claim 1 characterised in that the sliding sleeve (7', 7'') slides inside a tubular downstream section (30) of the vertical tube and is formed by an extension in the upstream direction of the abutment member, the sliding sleeve having an inside diameter equal to the inside diameter of the upstream section of the vertical tube so as to enable a scraper to abut against the abutment member.
9. Valve according to claim 8 characterised in that in the configuration in which the annular slot is opened by the sliding sleeve the abutment member (3', 3'') is farther downstream than in the closed configuration.
10. Valve according to claim 9 characterised in that the abutment member is extended in the downstream direction by a tubular portion (31, 31'') defining a channel discharging into the bottom of the abutment member and slides in a liquid-tight way in a cylindrical housing (32, 32'') in a member (33, 33'') fastened to the downstream tubular section of the vertical tube and communicating with said reverse flow pressure injection orifice, said control device of the sliding sleeve comprising a pressurised fluid injection orifice (38, 38'') discharging into a chamber (39, 39'') just downstream of the abutment member.
11. Valve according to claim 10 characterised in that said member (33) fastened to the vertical tube comprises around the cylindrical housing (32) a cylinder (34) having at its upstream end a radially projecting flange (36) and along which is mounted to slide in a liquid-tight way a ring (35) extending in the radial direction as far as the downstream tubular section of the vertical tube so as to define with said member fastened to said section a second chamber (40) into which discharges a second pressurised fluid injection orifice (37).

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