Abstract:
The invention relates to a valve ( 24 ) comprising: a body ( 40 ) defining a cavity and provided with a first opening ( 60 ) that makes it possible to feed water into the cavity, a second opening that makes it possible to discharge water from the cavity, and a third opening that makes it possible to connect the cavity ( 41 ) with a chamber; a stopper ( 49 ) that is rotatable inside the cavity, the stopper comprising a depression ( 77 ) on the outer surface ( 90 ) thereof that contributes to the definition of a passage enabling the flow of water between the first and third openings in first angular positions of the stopper and moreover enabling the flow of water between the second and third openings in second angular positions of the stopper, a sealing device that makes it possible to ensure a sealed stopping of the first opening ( 60 ) by means of the stopper in said second angular positions of the stopper; and a second sealing device that makes it possible to ensure a sealed stopping of the second opening by means of a stopper in said first angular positions of the stopper.

Description:
This application is a 371 of PCT/FR2010/000758 filed on Nov. 15, 2010, published on May 19, 2011 under publication number WO 2011/058249 A, which claims priority benefits to French Patent Application 09/05487 filed Nov. 16, 2009, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a valve with a rotary stopper and a water-treatment plant comprising such a valve. 
     The invention relates notably to motorized three-way valves (i.e. with three connection interfaces) and to water-treatment plants for seawater or brackish water by reverse osmosis which incorporate such valves. 
     In the present application, unless explicitly or implicitly indicated to the contrary, the terms “cylinder” and “cylindrical” refer to a body delimited by—or a shape or a surface engendered by—parallel straight lines resting on a closed contour which may be circular. 
     DESCRIPTION OF THE PRIOR ART 
     In plants for desalinating seawater by reverse osmosis, the water to be treated is delivered to the inlet of a filtration device at an inlet pressure that is higher than the osmotic pressure of the water; usually, since the osmotic pressure of salt water is 25 bar, the water supply pressure at the inlet of the filter is at least equal to 25 bar, for example of the order of 30 to 100 bar, in particular of the order of 60 to 80 bar; recovered at the outlet of the filter is a concentrate of water called “brine” on the one hand, and an ultrafiltrate of desalinated water (which is at a pressure close to atmospheric pressure) on the other hand; the pressure of the concentrate at the outlet of the filter is usually not much less than the supply pressure of water to be desalinated, for example less than the supply pressure by a value of the order of 1 to 5 bar, since the pressure drop in the filter is slight. 
     Patents FR 2342252 and U.S. Pat. No. 4,124,488 describe a plant for purifying water by reverse osmosis comprising a piston pump delivering the pressurized water to the inlet of a reverse osmosis module (ROM) and receiving the pressurized brine leaving the module ROM via a controlled valve, in order to use the energy of the pressurized brine to compress/pressurize the water to be desalinated. 
     The piston of the pump is driven in an alternating translation movement by an electric motor. 
     According to one embodiment, a rear portion of the piston has two peripheral longitudinal grooves such that, the piston also being driven in an angular oscillation movement, the piston forms a stopper placing a chamber of the pump extending behind the piston in communication either with a duct for conveying brine originating from the ROM or with a discharge duct. 
     One drawback of this plant is that causing the piston to oscillate angularly requires causing the pump body to oscillate angularly, which causes an unnecessary consumption of energy. This causing of the pump body to oscillate angularly requires the pump to be connected to the circuits of the plant via flexible connectors, which has implementation problems notably because of the pressure of the water circulating in the plant. 
     Patents EP 1194691 and U.S. Pat. No. 6,652,741 describe a seawater treatment plant in which several piston pumps are driven by means of a hydraulic actuator and are controlled to ensure a stoppage time of each piston, at each end of stroke of the piston in question, and to ensure a constant total flow rate. 
     The intake of brine into a chamber of each pump for the recovery of energy from the “concentrate”; and the subsequent discharge of this concentrate, are carried out by a three-way valve or directional-flow valve. 
     This device, the valve or directional-flow valve, must satisfy several requirements: it must allow the passage of a high flow rate of water without causing considerable pressure losses; it must be designed to withstand the high pressure (of the order of 60 to 80 bar for example) of the brine leaving the osmotic filters; moreover, when no provision is made to stop the pistons of the pumps at the end of the stroke for a sufficient period, this device must then switch from a configuration for taking water into the pump to a configuration for discharging water from the pump, substantially instantaneously, at the precise moment when the pump piston in question stops at the end of the stroke. 
     The known valves and directional-flow valves do not satisfy these requirements simple and reliably. 
     SUMMARY OF THE INVENTION 
     One object of the invention is to propose a valve or directional-flow valve that is simple to manufacture and install, having a long service life and high reliability, causing little pressure loss, making it possible to close in a substantially sealed manner a duct for conveying brine connecting a filtration module to a piston pump and being able to change—“switchover”—, substantially instantaneously, from a configuration of supply in which the valve is traversed by a current of pressurized brine supplying the pump, to a configuration of discharging/emptying in which the valve is traversed by a current of brine discharged from the pump. 
     One object of the invention is to propose a valve or directional-flow valve that is improved and/or that remedies, at least in part, the shortcomings or drawbacks of the known valves and directional-flow valves. 
     One object of the invention is to propose a plant for treating seawater or brackish water comprising a pump and a three-way valve for supplying the pump with brine and for discharging the brine, that is improved and/or that remedies, at least in part, the shortcomings or drawbacks of the known water-treatment plants. 
     According to one aspect, the invention proposes a valve comprising:
         a valve body delimiting a cavity, the body being provided/pierced with a first orifice allowing water to enter the cavity, with a second orifice allowing water to be discharged from the cavity, and a third orifice making it possible to place the cavity and a chamber of a pump in communication;   a stopper mounted so as to be able to rotate inside the cavity, the stopper comprising a recess on its outer face, this recess helping, with the body to form/delimit a passageway—which rotates with the stopper—allowing water to travel between the first and third orifices in first angular positions of the stopper—corresponding to a configuration of the valve allowing the pump to be supplied—, said passageway also allowing water to travel between the second and third orifices in second angular positions of the stopper—corresponding to a configuration of the valve allowing the pump to be emptied;   a first sealing device making it possible to stop in a substantially watertight manner the first orifice by the stopper in said second angular positions of the stopper; and   a second sealing device making it possible to stop in a substantially watertight manner the second orifice by the stopper in said first angular positions of the stopper.       

     Notably when the outer face of the stopper is cylindrical, the recess may take the shape of a groove or flat extending along an axis orthogonal to the axis of revolution/rotation of the stopper, and have a width that is substantially/not much smaller than the diameter of the first and second orifices. 
     Preferably, in addition to said recess—first recess—said passageway comprises a second recess on the periphery/surface of the stopper, in particular a second recess of substantially annular shape which extends—at least in part—facing the third orifice, and a channel hollowed out in the stopper and connecting said first and second recesses. 
     The cross section of this channel may be not much smaller, equal or greater, than that of the first and second orifices in order to limit the pressure losses caused by the passage of the water in this channel and consequently in the valve. 
     In other words, and according to another aspect of the invention, what is proposed is a valve comprising a body delimiting a cavity and pierced with three orifices, and a stopper—or plug—mounted so as to rotate inside the body; the body comprises two housings leading into the cavity and surrounding respectively two of the three orifices; the valve also comprises two sealing members respectively placed slidingly in the two housings, and two pressing devices making it possible respectively to press the two sealing members against the stopper, in order to provide a substantially watertight stopping of a first of the three orifices, by the stopper, in second angular positions of the stopper and in order to provide a substantially watertight stopping of a second of the three orifices, by the stopper, in first angular positions of the stopper—distinct from the second angular positions. 
     According to a preferred embodiment, the housings take the shape of annular slots and the sealing members have an annular—or tubular—shape adapted to the shape of the portion of the stopper against which they are pressed, in particular a shape cut away like a bevel on a radius corresponding to the radius of a cylindrical portion of the stopper. 
     Preferably, each of the pressing devices comprises a channel, in particular several channels, which connect(s) one end of the housing in question that is opposite to the end (of the housing in question) that opens into the cavity: the pressing device associated with the sealing member surrounding a first of the orifices comprises at least one channel connecting the non-open end of the housing in question to a sleeve for connecting the valve to a duct conveying the water coming from a filtration module, while the pressing device associated with the sealing member surrounding a second of the orifices comprises at least one channel connecting the non-open end of the housing in question to the cavity. 
     These channels make it possible to place at equal pressure the non-open end of the housing in question and the duct conveying the water coming from the filtration module, respectively the cavity, and consequently make it possible to press against the stopper the “profiled” end of each of the sliding sealing members, notably when these members have a reduced thickness in their annular portion flush with the surface delimiting the cavity. 
     Moreover, accordingly, each of the pressing devices may comprise an elastically deformable member, such as a spring, placed in the corresponding housing, between the non-open end of the housing and the end of the corresponding sealing member, in order to keep the stopper and the sealing member in mutual contact when the valve is not operated and when no water current passes through it. 
     According to other preferred features:
         the first and second orifices are facing one another, aligned along an axis that is (substantially) orthogonal to the axis of revolution of the cavity—which corresponds to the axis of rotation of the stopper—, these two axes being (substantially) coplanar;   the valve body is pierced with two other orifices—fourth and fifth orifices—which face one another, aligned along an axis that is (substantially) indistinguishable from the axis of revolution of the cavity, and the stopper is secured in rotation to a drive shaft extending through these two orifices.       

     According to another aspect of the invention, a water-treatment plant is proposed comprising a water-filtration module, a pump with a piston, a motor, a mechanism for the driving of the pump by the motor, and a three-way valve with a rotary plug as described in the present application, the valve being fitted to a duct connecting the pump to the filtration module, the stopper of the valve being rotated substantially continuously by the motor, in synchronism with the pump. 
     According one embodiment, the stopper is driven so as to rotate one rotation when the piston of the pump makes a complete cycle, i.e. one stroke in one direction and one return stroke. 
     The continuous rotation of the stopper, usually with a substantially constant rotation speed, and the features of the stopper allowing the valve to switch substantially instantaneously from a supply configuration—for supplying the pump—with pressurized brine to a configuration for discharging the brine, in particular when the respective diameters of the first and second orifices are equal and that the depth of the first recess is equal to the difference between the radius of the stopper—in line with this recess—and the radius of the orifices. 
     According to one embodiment, the stopper provides a “total” closure of the valve for only two determined angular positions of the stopper: in each of these positions, the stopper closes the passageway between the first and third orifices and the passageway between the second and third orifices—and also the passageway between the first and second orifices. 
     In other words, according to this embodiment, the first angular positions of the stopper are adjacent so as to form a first continuous angular range of first angular positions of the stopper, which extends substantially over 180° (angle degrees), and the second angular positions of the stopper are also adjacent so as to form a second continuous angular range of second angular positions of the stopper, which also extends over 180°. 
     Other aspects, features and advantages of the invention will appear in the following description which refers to the appended figures and illustrates, without being in any way limiting, preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a water-treatment plant according to one embodiment of the invention. 
         FIG. 2  is a schematic view in perspective of a valve according to one embodiment of the invention, of which the stopper is in the closed position of the valve, with partial cutaway: in this figure, as in  FIGS. 4 to 6 , all that appears is the portion of the valve body extending under the plane containing the longitudinal axis of the body—and of the rotor—and the axis passing through the centers of the first and second orifices, the other portion of the body extending above this plane being “cut away” (not shown) in order to make it possible to view the rotor of the valve. 
         FIG. 3  is a schematic view in perspective of the rotor—including the stopper—of the valve illustrated in  FIGS. 2 and 4 to 11 . 
         FIGS. 4 to 6  are schematic views in perspective similar to  FIG. 2 , which show the rotor of the valve in other angular positions. 
         FIG. 7  is a view in longitudinal section of the valve along a first sectional plane containing the axis of two sleeves for connecting the valve to a filtration module—for one of the sleeves—and to a discharge circuit—for the second sleeve. 
         FIG. 8  is a view in longitudinal section of the valve along a second sectional plane perpendicular to the first and containing the axis of a third sleeve for connecting the valve to a piston pump. 
         FIG. 9  is a view in cross section of the valve along a third sectional plane perpendicular to the first two and containing the axis of the third connecting sleeve: this figure is a view along IX-IX of  FIG. 7 . 
         FIG. 10  is a view in longitudinal section along the first sectional plane illustrating, on an enlarged scale, the sleeve for connecting the valve of  FIGS. 2 and 4 to 11  to the discharge circuit. 
         FIG. 11  is a view in longitudinal section along the first sectional plane illustrating, on a larger scale, the sleeve for connecting the valve of  FIGS. 2 and 4 to 11  to the filtration module. 
         FIG. 12  is a view in section along the first sectional plane illustrating, on a larger scale, another embodiment of the sealing device fitted to the sleeve for connecting the valve to a filtration module. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Unless explicitly or implicitly indicated to the contrary, elements or members that are—structurally or functionally—identical or similar are indicated by identical references on the various figures. 
     With reference to  FIG. 1 , the water-treatment plant comprises a water-filtration module  15 , a piston pump  27 , an electric motor  10 , a mechanism  11  for driving the pump via the output shaft  30  of the motor, and a three-way valve  24  with rotary plug. 
     The pump  27  comprises a body  13  delimiting a cylindrical cavity  16 ,  17  inside which the piston  14  of the pump is driven in alternating translation  28 , the piston separating the cavity into two chambers: a first chamber  16  receiving the brine discharged from the module  15 , and a second chamber  17  receiving the water to be pumped and to be delivered under pressure to the module  15 . 
     The piston  14  is connected by a rod  12  to the mechanism  11 . 
     The pump  27  receives the water to be pumped delivered by a water-conveying duct  18  fitted with an inlet valve element  19  (nonreturn valve element). 
     The water pressurized by the pump  27  is conveyed to the module  15  by a duct  20  fitted with a delivery valve element  21  (nonreturn valve element). 
     The water (fresh water) filtered by the module  15  leaves the latter through a duct  22 , while the brine is conveyed by a duct  23  fitted with the valve  24 , from the module  15  to the “energy recovery” chamber  16  of the pump  27 . 
     The valve  24  is also connected to a duct  25  through which the brine is discharged from the chamber  16  at the end of each compression stroke of the piston  14  of the pump  27  during the stroke—in the reverse direction—of the piston  14  allowing the chamber  17  to be filled by the water to be pumped. 
     The transition from one configuration of the valve  24  allowing the passage of the brine originating from the module  15  to the chamber  16 , to a configuration of the valve allowing the discharge of the brine from the chamber  16 , results from the rotation  29  of the plug—i.e. of the stopper—of the valve. 
     The substantially continuous rotation of the stopper of the valve results from the driving of the stopper by the motor, in synchronism with the pump, by means of a shaft  26  for driving the stopper, this shaft  26  being connected for this purpose to the mechanism  11 . 
     With reference to  FIGS. 2 and 4 to 9 , the valve  24  comprises a body  40  delimiting a cavity  41 . 
     The body  40  comprises a tubular central part  42  extending along an axis  43 , two circular flanges  44  and  45  placed and attached—by welding for example—at the two longitudinal ends of the central part  42 , and two parts  46  and  47  respectively attached to the flanges  44 ,  45  by screws (not shown) for example. 
     Each part  46 ,  47  is in the form of a thick disk and has a circular central orifice; a shaft  48  with an axis  43  extends through these two bored orifices, this shaft being secured in rotation to the stopper or plug  49  of the valve. 
     The body  40  also comprises two parts  50  and  51  respectively attached to the parts  46 ,  47  by screws (not shown), each part  50 ,  51  being in the form of a thick disk, with an external diameter smaller than that of the parts  46 ,  47  and having a central circular orifice aligned with those of the parts  46 ,  47  and through which the shaft  48  extends. 
     The tubular collar  42  of the body is pierced with three circular orifices: a first orifice  60  allowing water to be inserted into the cavity  41 , a second orifice  61  allowing water to be discharged from the cavity, and a third orifice  62  making it possible to place the cavity  41  and the chamber (reference  16 ,  FIG. 1 ) of the pump in communication. 
     For the connection of the valve to the duct (reference  23 ,  FIG. 1 ) conveying the brine originating from the filter  15 , the body comprises a first tubular sleeve  63  extending in line with the orifice  60 . 
     For the connection of the valve to the duct (reference  25 ,  FIG. 1 ) for discharging the brine, the body comprises a second tubular sleeve  64  extending in line with the orifice  61 . 
     For the connection of the valve to the duct (reference  23 ,  FIG. 1 ) for conveying the brine between the valve and the pump, the body comprises a third tubular sleeve  65  extending in line with the orifice  62 . 
     It can be seen in  FIGS. 7 to 9  that each of these three sleeves is attached to the tubular part  42  by a first of its ends, for example by welding, and is furnished with a connecting flange  66  close to its second end. 
     The sleeves  63  and  64  are coaxial: they extend along an axis  67  perpendicular to the axis  43  and intersecting the latter; the sleeve  65  extends along an axis  68  which is also perpendicular to the axis  43  and intersects the latter, the axes  67  and  68  being orthogonal without being secant. 
     With reference to  FIGS. 2 to 6  in particular, the rotor  70  of the valve comprises a central portion forming the plug  49  and two end portions extending on either side of the plug and forming two shaft ends  48 ; these three coaxial portions, with an axis  43 , can form a single part obtained by machining of a metal blank, for example, or else may consist of several parts fixed together. 
     It can be seen in  FIGS. 2 and 4 to 8  that the stopper  49  is mounted so as to be able to rotate inside the cavity  41  of the valve body; accordingly, the rotor  70  is mounted in the bearings formed in the parts  46 ,  47 ,  50 ,  51  by means of two rolling bearings  71 ,  72  (ball bearings for example) fitted onto bearing surfaces formed by the shaft  48 . 
     With reference to  FIGS. 2 to 6  in particular, the stopper consists essentially of a first portion  73  delimited by a cylindrical casing with an axis  43  and a radius  75  (see  FIG. 9 ), and of a second cylindrical portion  74  with an axis  43  and radius  76  (see  FIG. 8 ) which extends from the first portion  73 . 
     The radius  75  of the portion  73  is chosen to be slightly less than the radius  80  (see  FIG. 8 ) of the cavity  41 , for example smaller than the latter by the order of 0.1 millimeter (mm) when the radius  80  is of the order of 100 mm, so as to define a very slight clearance between the peripheral surface of the portion  73  of the stopper and the wall  42  delimiting the cavity  41 . 
     The radius  76  of the portion  74  is chosen to be smaller than the radius  80  of the cavity  41 , for example close to the radius common to the orifices  60  to  62 , so that the portion  74  delimits with the wall  42  an annular space  79 —or second recess—allowing water to enter the valve—or leave the latter—through the orifice  62 ; for this purpose, the portion  74  of the stopper—and the volume  79 —preferably extend over a length at least equal to the diameter of the orifice  62  which opens into the volume  79 . 
     As illustrated notably in  FIGS. 2 to 4, 7 and 9 , the portion  73  of the stopper  49  comprises a recess  77  on its outer cylindrical face  90 . 
     This recess in the form of a groove or flat extends along an axis  91  orthogonal to the axis  43  of revolution/rotation of the stopper, and has a width  92  slightly smaller than the diameter of the first and second orifices  60 ,  61 . 
     The depth  81  of the first recess  77  is substantially equal to the difference between the radius  75  of the stopper—in line with this recess—and the common (identical) radius of the orifices  60 ,  61 . 
     The recess  77  helps—with the body—to delimit a passageway—which rotates with the stopper—allowing water to travel between the first and third orifices in the first angular positions of the stopper, which corresponds to a configuration of the valve illustrated in  FIG. 4  and allowing the pump to be supplied. 
     Accordingly, a channel  78  is formed in the stopper and connects the recesses  77  and  79  as illustrated in  FIGS. 2 to 4 and 7  in particular. 
     The cross section of this channel  78  is preferably at least close to that of the first and second orifices  60 ,  61  and/or of that of the groove  77 , in order to limit the pressure losses caused by the water entering the valve. 
     The passageway formed by the recesses  77 ,  79  and by the channel  78  also allows water to travel between the second and third orifices  61 ,  62  in second angular positions of the stopper—corresponding to a configuration of the valve allowing the pump to be discharged—which are illustrated in  FIGS. 6 and 9  in particular. 
     The valve also comprises two sealing devices making it possible respectively to achieve a substantially water-tight stopping of the first orifice  60  by the stopper in said second angular positions of the stopper, i.e. in the discharge position, and to ensure a substantially watertight stopping of the second orifice  61  by the stopper in said first angular positions of the stopper, i.e. in the position of supplying the pump with water. 
     Accordingly, as illustrated in  FIGS. 10 and 11 , the body comprises two housings opening into the cavity  41  and surrounding respectively the two orifices  60 ,  61 , and two sealing members respectively placed slidingly in the two housings. 
     A bush  93 ,  94  is fitted respectively into each of the sleeves  63 ,  64  with the axis  67 . 
     With respect to the sleeve  63 , in  FIG. 11 , an outer cylindrical face  95  of the bush  93  extends coaxially to an inner cylindrical face  96  of the sleeve  63 , facing the latter, so as to delimit a housing  97  receiving a sliding sealing ring  98  and a seal  99 . 
     With respect to the sleeve  64 , in  FIG. 10 , an outer cylindrical face  101  of the bush  94  extends coaxially to an inner cylindrical face  102  of the sleeve  64 , facing the latter, so as to delimit a housing  103  receiving a sliding sealing ring  104  and a seal  105 . 
     The housings  97 ,  103  take the form of annular slots and the sealing members  98 ,  104  have an annular—or tubular—shape adapted to the dimensions of the housings and to the shape of the portion of the stopper against which they are pressed: each sealing ring  98 ,  104  has, at its end  110 ,  111  being flush in the cavity  41 , a shape that is cut away according to a radius corresponding to the radius of the cylindrical portion  73  of the stopper. 
     A pressing device makes it possible to press the sealing ring  98  against the stopper, in order to ensure a substantially watertight stopping of the first orifice  60 , by the stopper, in angular positions of the stopper in which no portion of the groove  77  is facing this orifice. 
     A similar pressing device makes it possible to press the sealing ring  104  against the stopper, in order to ensure a substantially watertight stopping of the second orifice  61 , by the stopper, in angular positions of the stopper in which no portion of the groove  77  is facing this orifice. 
     Each of the pressing devices comprises several channels which connect one end (of the housing in question) that is opposite to the end of the housing in question that opens into the cavity, upstream—with reference to the direction of flow of the water in the valve—of the orifice in question: the pressing device associated with the sealing member  98  surrounding the first orifice  60  comprises four channels  100  distributed angularly about the axis  67 , each connecting the non-open end of the housing  97  to the inner face of the bush  93  of the sleeve  63 . 
     Similarly, the pressing device associated with the sealing member  104  surrounding the second orifice  61  comprises four channels  106  distributed angularly about the axis  67  and parallel with the latter, which are formed inside the sleeve  64  and each link the non-open end of the housing  103  to the cavity  41 . 
     The channels  100  make it possible to place the non-open end of the housing  97  and the duct conveying the water coming from the filtration module at equal pressure. 
     The channels  100  consequently make it possible to press against the stopper  49  the “profiled” end of each of the sliding sealing member  98 , because of the difference between the water pressures that are applied to the two opposite ends of the member  98 . 
     Similarly, the channels  106  make it possible to place the non-open end of the housing  103  and the cavity  41  at equal pressure and consequently make it possible to press the “profiled” end of each of the sliding sealing member  104  against the stopper, because of the difference between the pressures that are applied to the two opposite ends of the member  104 . 
     In the embodiment illustrated in  FIG. 12 , the sealing member  98  comprises a first annular portion  980  having a first thickness  981  and of which one end is flush with the surface of the body delimiting the cavity  41 . 
     The member  98  comprises a second annular portion  982  coaxial with—and extending—the first annular portion  980 . 
     This second portion, which extends facing—and in the vicinity of—the non-open end of the housing  97  and of the channels  100 , has a thickness  983  greater than the thickness  981  so that the ring  98  is pushed back toward the stopper when its two longitudinal ends are subjected to the same pressure. 
     In order to prevent (or limit) water getting into the interstices extending between the ring  98  and the housing  97  in which the ring can slide, each of the annular portions  980 ,  982  of the ring is furnished with an annular housing—like that referenced  984 —receiving a sealing-ring member (not shown). 
     Moreover, an elastically deformable member  120 , in the form of a ring forming a spring, is placed in the housing  97  receiving the ring  98 , between the non-open end of the housing  97  and the end of the portion  982  of the ring  98 . 
     The elastic ring  120  is arranged to keep in mutual contact the stopper  49  and the end  110  of the sealing ring  98  when the valve is not operated and/or when no water current passes through it.