A connection assembly allowing a pipe ( 12 ) extending from the seabed ( 14 ) to be connected to a flexible pipe ( 26 ) leading to the sea surface ( 22 ). The assembly includes a turret ( 32 ) having an upper end ( 42 ) connected to a float ( 20 ) and a lower end ( 40 ) connected to the pipe ( 12 ). The turret ( 32 ) has a duct ( 50 ) extending towards the upper end ( 42 ) and having a free end ( 66 ) provided with an end fitting ( 68 ). The turret includes retaining members ( 70, 72, 74, 76 ) that keep the connector ( 30 ) between the turret and the end fitting, facing the end fitting ( 68 ). The connector ( 30 ) is in a fixed position in relation to the retaining members ( 70, 72, 74, 76 ) and a drive device ( 112 ) drives the end fitting ( 68 ) toward the connector ( 30 ).

CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §§371 national phase conversion of PCT/FR2014/050138, filed Jan. 24, 2014, which claims priority of French Application No. 1350661, filed Jan. 25, 2013, the contents of which are incorporated by reference herein. The PCT International Application was published in the French language. 
     The present invention relates to the field of underwater installations enabling hydrocarbons to be conveyed between a seabed and a surface. 
     One field of application envisaged is notably that of petroleum exploitation at great depths. 
     TECHNICAL BACKGROUND 
     Such well-known underwater installations include a riser pipe that extends from the seabed as far as an intermediate area overlying the seabed and situated below the surface and a flexible pipe connected to extend the riser pipe and that extends catenary fashion from the intermediate area to the surface. The riser pipe is kept substantially vertical by means of a float submerged in the intermediate area. This type of installation makes it possible to raise hydrocarbons from the seabed to the surface without being constrained by disturbances of the surface linked to swell, currents or winds. 
     The document WO2009/112 687 describes an underwater installation of this type. The underwater installation usually includes a frame or a turret enabling the end of the riser pipe and the float to be connected together, and the frame is equipped with a swan-neck pipe that extends the riser. The pipe has a free end provided with an end fitting. In a first installation phase, the frame and the float hold the riser pipe in vertical equilibrium. In a second installation phase the flexible pipe terminated by a connector is connected to the end fitting, from the surface, so as to establish the connection between the riser pipe and the flexible pipe. To this end, the connector is specifically equipped with a flange and is installed at the end of the flexible pipe. It approaches the frame as the flexible pipe is paid out from the surface. As for the frame, it includes retaining members and the flange is then engaged in the retaining members. More of the flexible pipe is paid out and the connector then tilts around the retaining means so that it faces the end fitting on the pipe. The connector is then driven toward the end fitting to connect them together. 
     Difficulties arise in connecting the connector to the end fitting at greater depths of water. In fact, the riser pipes are longer and consequently heavier. The same goes for the flexible pipes and the forces to be exerted on the connector are consequently higher. Now the latter connectors are fragile and costly. Moreover, during the phase of moving the connector and the frame closer to each other, and given the masses involved, the slightest impacts can have an impact on the integrity of the connector. 
     SUMMARY OF THE INVENTION 
     Also, a problem that arises and that the present invention aims to solve is to provide an underwater connection assembly that precisely makes it possible to protect the connector, notably during connection. 
     To this end, in accordance with a first object, the present invention proposes an underwater connection assembly intended to be suspended from a float installed between a seabed and a surface of the sea to be able to connect a riser pipe extending from said seabed toward said surface to a flexible pipe extending to said surface. The assembly comprises a turret having an upper end adapted to be connected to said float and a lower end adapted to be connected to said riser pipe. The turret comprises a deformable swan-neck pipe fastened to said lower end and extending freely toward said upper end. The pipe has a free end fitted with an end fitting, while the flexible pipe includes a connector. The turret further comprises retaining members so as to be able to retain said connector facing said end fitting. The assembly further comprises a driving device for driving said end fitting and said connector toward each other so as to connect them to each other. In accordance with the invention, said connector is held in a fixed position relative to said retaining members and said driving device causes said end fitting to be driven towards said connector whereas said pipe is deformed. 
     One feature of the invention therefore resides in the use of a deformable pipe passing through the turret so as to be able to drive the end fitting toward the connector as soon as the latter has been pressed onto the retaining members. Then the deformable pipe is deformed when the end fitting is driven in movement. As a result, the movements of the connector are extremely limited and likewise the possibilities of it being damaged are limited. Moreover, the forces necessary to move the two flanges toward each other remain low compared to the weight of the flexible pipe. 
     Moreover, and in accordance with one particularly advantageous embodiment of the invention, said retaining members are mounted in the vicinity of said lower end, which makes it possible to press the connector substantially into its connection position, in which it is oriented toward the surface, whereas the flexible pipe extends toward the seabed. There is consequently no requirement to cause it to tilt around the retaining members, which limits the possibilities of movement of the connector relative to the frame and consequently the possibilities of impact and damage. 
     Moreover, said turret is advantageously equipped with guide ramps oriented from said upper end toward said retaining members so as to be able to guide the end fitting of the deformable pipe in translation when the latter is driven toward the connector. These ramps are installed laterally on each side of the end fitting, for example. Also, the end fitting preferably includes guide fingers adapted to cooperate with said guide ramps. Two guide fingers are mounted opposite each other on the end fitting, for example, so as to be able to cooperate with the respective lateral ramps. 
     In accordance with one particular embodiment of the invention, said retaining members include two V-shaped arms extending parallel to each other from said turret to form two spaced bearing surfaces. Also, the connector is equipped with two diametrically opposite journals, which come to bear in the respective bearing surfaces, when it is engaged between the two V-shaped arms. The connector then extends vertically, oriented toward the surface, whereas the flexible pipe hangs down. The method of installation is explained in more detail hereinafter. 
     Moreover, said driving device preferably comprises a retractable member, for example a hydraulic cylinder, adapted to connect said end fitting and said connector. Also, said retaining members include members for locking said connector. As a result, the connector is held in a fixed position relative to the turret and when the retractable member is retracted it is the end fitting of the deformable pipe that is driven toward the connector, whereas the latter remains immobile relative to the turret. 
     Moreover, said deformable pipe advantageously includes a first part extending outside said turret opposite said retaining members and a second part passing completely through said turret and ending at said free end. The pipe is made from a rigid material, for example steel, and is sufficiently long compared to its diameter to be able to deform elastically. The deformable pipe therefore substantially forms a loop and when the end fitting is driven in translation toward the connector the loop formed by the pipe tightens. Moreover, said deformable pipe further includes a fixing part extending axially inside said turret and connected to said first part. The pipe is therefore fastened to the lower end of the turret and is connected to the riser pipe, which it extends. 
     Said turret advantageously comprises a hollow cylindrical part having on the one hand a lower opening and a first upper opening spaced from each other along the same generatrix and on the other hand a second upper opening diametrically opposite said first upper opening. The openings therefore allow the free passage of the deformable pipe, said first part through the first lower opening and said second part through the two diametrically opposite upper openings. The openings are oblong and extend in the axial direction of the turret so as to allow the movement of the deformable pipe. 
     Said retaining members are preferably mounted on said hollow cylindrical part in a position diametrically opposite said lower opening. 
     In accordance with another object, the present invention proposes an underwater connection method for connecting, between a seabed and a surface, a riser pipe extending from said seabed toward said surface to a flexible pipe extending to said surface, said method being of the type comprising the following steps: procuring a flexible pipe including a connector; procuring a turret including an upper end and a lower end, said turret comprising on the one hand retaining members and on the other hand a deformable swan-neck pipe fastened to said lower end and extending freely toward said upper end, said pipe including a free end provided with an end fitting and facing said retaining members; installing a float between said surface and said seabed and connecting on the one hand said upper end of said turret to said float and on the other hand said riser pipe to said lower end of said turret; causing said connector to press on said retaining means to retain said connector facing said end fitting; and driving said end fitting and said connector toward each other so as to connect them to each other. According to the invention, said connector is retained in a fixed position relative to said retaining members and said end fitting is driven toward said connector, whereas said pipe is deformed. The connection method in accordance with the invention is explained in more detail hereinafter. 
     Other features and advantages of the invention will emerge on reading the description of one particular embodiment of the invention given hereinafter by way of nonlimiting illustration and with reference to the appended drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view showing an underwater connection method according to the invention; 
         FIG. 2  is a diagrammatic side view of the underwater connection assembly according to the invention in a first step of its use; 
         FIG. 3  is a diagrammatic cutaway view of a detail of the underwater connection assembly shown in  FIG. 2 ; 
         FIG. 4  is a diagrammatic side view of the connection assembly shown in  FIG. 2  in a first state; 
         FIG. 5  is a diagrammatic three-quarter front view of the connection assembly shown in  FIG. 4 ; 
         FIG. 6  is a diagrammatic view of a detail of the connection assembly shown in  FIG. 5 ; 
         FIG. 7  is a diagrammatic view of a detail of the connection assembly shown in  FIG. 6 , in a second state; 
         FIG. 8  is a diagrammatic general view of the connection assembly in said second state; and 
         FIG. 9  is a diagrammatic view showing the elements represented in  FIG. 1  in a final step of its use. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows diagrammatically a tower  10  including a rigid riser pipe  12  fixed to a seabed  14  by means of an anchor system  16 . Moreover, the rigid pipe  12  includes an upper part  18 , suspended from a float  20 , or a buoy, in which is trapped a sufficient quantity of air to maintain the rigid pipe in a vertical position. The float  20  is situated in an area between the seabed  14  and a surface  22 , and to be more precise, toward the surface  22 . This area is nevertheless chosen at a distance from the surface  22  so as to be less dependent on surface movements. 
       FIG. 1  also shows a laying ship  24  sailing on the surface  22  in line with the tower  10 . A flexible pipe  26  is suspended from the laying ship  24  by means of a cable  28 . The flexible pipe  26  includes a connector  30  to which the cable  28  is connected. The flexible pipe  26  is therefore supported by the laying ship  24  in the vicinity of the upper part  18  of the rigid pipe  12  in order to be connected thereto as explained hereinafter. To this end, the upper part  18  of the rigid pipe  12  includes a turret  32  described with reference to  FIG. 2 . 
       FIG. 2  shows partially the float  20  and the rigid pipe  12  connected together by way of the turret  32 . Also shown is the flexible pipe  26  suspended from the cable  28  by means of the connector  30 . The latter includes a sleeve  34  on the upstream side of a connecting free end  36 . The sleeve  34  includes two diametrically opposite and projecting journals  38  while the connector  30  includes an attachment member  39  forming a shoulder and that extends around the connecting free end  36 . 
     The turret  32  has a lower end  40  opposite an upper end  42 . The lower end  40  is connected to the rigid pipe  12  while the upper end  42  is attached to the float  20 . The turret  32  includes a hollow longitudinal cylindrical part  44  and a conical part  46  at the lower end  40  and a flange  48  at the upper end  42 . Moreover, the turret  32  includes a deformable swan-neck pipe  50  extending from the lower end  40  of the turret  32 . It will be noted that the deformable pipe  50  is made from a rigid metal, for example steel. In accordance with another embodiment, a deformable pipe is used made from a conventional flexible pipe of bonded or other construction. 
       FIG. 3  is also referred to in order to describe the arrangement of the deformable pipe  50  through the turret  32 .  FIG. 3  shows part of the turret  32  and in its conical part  46  an axial portion  52  of a deformable pipe  50 . Also shown is the rigid pipe  12  and the turret  32  is connected to its end at the level of the tip of the conical part  46 . The axial portion  52  of the deformable pipe  50  is therefore in line with the rigid pipe  12 . The cylindrical part  44  includes a lower oblong opening  54  that extends along a generatrix and through which a first radial portion  56  of the deformable pipe  50  extends. The first radial portion  56  extends from the axial portion  52 , which is curved at the level of the lower oblong opening  54  so as to extend out of the turret  32 . 
     As shown in  FIG. 2 , the first radial portion  56  is curved with an opposite curvature toward the upper end  42  and in an axial plane of the turret  32 . The deformable pipe  50  then has a transverse portion  58  passing completely through the cylindrical part  44  via two opposite upper oblong openings  60 ,  62 . One of the upper oblong openings  60  extends along the same generatrix as the lower oblong opening  54 . 
     The deformable pipe  50  includes a second radial portion  64  curved toward the lower end  40  and extending from the transverse portion  58  in the direction away from the first radial portion  56 . The second radial portion  64  has a free end  66  provided with an end fitting  68 . 
     Moreover, opposite the lower oblong opening  54 , near the lower end  40  of the turret  32 , are two parallel V-shaped arms  70 ,  72 . The two V-shaped arms  70 ,  72  are retained by two respective parallel uprights  74 ,  76  that extend toward the upper end  42  at the level of the other upper oblong opening  62 . The two V-shaped arms  70 ,  72  have a respective first part  78 ,  80  that extends in a direction substantially perpendicular to the turret  32  and an inclined second part  82 ,  84  that extends freely away from the lower end  40 . The two V-shaped arms  70 ,  72  therefore have a respective joint  86 ,  88  at the level of which the uprights  74 ,  76  are connected. As a result, the uprights  74 ,  76  and the V-shaped arms  70 ,  72  in two parts respectively form at the level of the joints  86 ,  88  U-shaped spaces forming spaced bearing surfaces. 
     In accordance with another embodiment that is not shown, the turret is constituted of a longitudinal frame including two parallel uprights and an upper crossmember opposite a lower crossmember. Moreover, the frame includes pairs of intermediate crossmembers situated between the opposite upper and lower crossmembers. Also, the two V-shaped arms  70 ,  72  and the corresponding uprights  74 ,  76  are respectively installed on two superposed intermediate crossmembers of the same pair. The first parts  78 ,  80  of the two V-shaped arms  70 ,  72  are advantageously respectively connected to the two uprights  74 ,  76  to form two opposite flanges. These two flanges are then respectively fastened to two superposed intermediate crossmembers. Such an arrangement makes it possible to have the bearing surfaces close to the axis of the rigid riser pipe  12 . Moreover, this makes it possible to reduce the overall volume of the turret  32  and the retaining members ( 70 ,  72 ,  74 ,  76 ). 
     Moreover, the first parts  78 ,  80  of the two V-shaped arms  70 ,  72  are mounted and articulated at the level of the joints  86 ,  88  so that they can be retracted, notably during transportation and installation. 
     Also, thanks to the pairs of intermediate crossmembers, in accordance with another embodiment, other sets of retaining members of the aforementioned type may be installed so as to be able to connect other pipes in an analogous manner. 
     As  FIG. 2  shows, the connector  30  is engaged between the second inclined parts  82 ,  84  of the two V-shaped arms  70 ,  72  by paying out the cable  28 . Also, the two journals  38  installed on the sleeve  34  of the connector  30  respectively come to bear against the inclined second parts  82 ,  84 . As the lowering of the connector  30  continues, the second inclined parts  82 ,  84  then form a ramp and guide the journals  38  toward the joints  86 ,  88  forming bearing surfaces. The connector  30  is then suspended from the two V-shaped arms  70 ,  72 . 
     It will moreover be noted that the uprights  74 ,  76  are respectively equipped with two parallel plates  90 ,  92  between which lie the free end  66  and the end fitting  68 . These plates  90 ,  92  include a respective guide groove  94  extending substantially from said other upper oblong opening  62  toward the V-shaped arms  70 ,  72  and form a lower abutment  96  also oriented toward the V-shaped arms  70 ,  72 . The functions of the guide grooves  84  and the lower abutment  96  are explained hereinafter. 
     Moreover, it will be noted that the connector includes between the journals  38  and the connecting free end  36  two opposite lugs  98 ,  100  while the uprights  74 ,  76  are equipped with clamping devices  102 ,  104 . 
     Accordingly, after the connector  30  has been suspended from the two V-shaped arms  70 ,  72 , the journals  38  respectively bear in the bearing surfaces, the cable  28  is then released, whereas the flexible pipe  26  hangs down. The other end of the flexible pipe  26 , not shown, is then taken up by another cable to be raised toward the laying ship. The connector  30  is then driven to pivot anticlockwise as the flexible pipe  26  is raised. The attachment member  39  is then pressed to the rear of the lower abutments  96  of the plates  90 ,  92  while the connecting free end  36  comes to face the end fitting  68 . 
     The situation is therefore that of  FIG. 4 , with the connector  30  pivoted in this way and its attachment member  39  to the rear of the lower abutments  96 . Moreover, the two lugs  98 ,  100  are engaged in the clamping tools  102 ,  104  so as to lock the connector  30  against the uprights  74 ,  76  and bearing on the V-shaped arms  70 ,  72 . Its connecting free end  36  therefore then comes to face the end fitting  68  at the free end  66  of the deformable pipe  50 . As a result, the connector  30  is fastened to the turret  32 . It will be noted that until this point movements of the connector  30  relative to the turret  32  and its elements have been accompanied and limited. The risks of damage by impact or by contact have therefore been reduced. 
       FIG. 5  is a three-quarter view of the connector  30  installed in this way. Moreover, there is seen in this figure, around the end fitting  68 , a guide support block  110  and a hydraulic cylinder  112  connecting the attachment member  39  and the guide support block  110 . The hydraulic cylinder  112  has been installed by an underwater robot that is not shown. 
     Refer now to  FIG. 6  showing in detail the guide support block  110  and the attachment member  39 . This figure shows the two opposite plates  90 ,  92  respectively equipped with their guide groove  94 . The guide support block  110  is engaged between the two opposite plates  90 ,  92  and is equipped on each side with two guide fingers  114 ,  116  engaged in the guide grooves  94 . The guide fingers  114 ,  116  are seen on only one side, while the other two are concealed and lie to the rear of the figure. 
     Moreover, the attachment member  39  is to the rear of the lower abutments  96  formed by the opposite plates  90 ,  92 . 
     Moreover, the hydraulic cylinder  112 , which is seen more clearly in  FIG. 6 , includes a body  118  and a rod  120  mounted inside the body  118 . The body  118  includes a body groove  122  while the guide support block  110  includes a block notch  124  adapted to receive the body  118  of the cylinder  112 . The rod  120  includes at its end a rod groove  126  while the attachment member  39  includes an attachment notch  128  adapted to receive the end of the rod  120 . 
     Moreover, the connecting free end  36  faces the end fitting  68  substantially coaxially, which end fitting  68  has an inside diameter substantially greater than the outside diameter of the connecting free end  36 . Moreover, the end fitting  68  includes sealing lips, not shown, and a spring-loaded automatic locking mechanism, for example, or a manually controlled mechanism, for locking thereto the connecting free end  36  when they are driven one into the other. The connection is therefore sealed. 
     In this situation, and by means of an underwater robot that is not shown, the hydraulic cylinder  112  is activated so as to retract the rod  120  into the body  118 . Also, the retraction of the rod  120  of the cylinder into the body  118  causes the guide support block  110  to be driven toward the attachment member  39  since the latter is immobilized against movement in translation by the lower abutments  96  and the guide support block  110  is guided in translation by means of the guide fingers  114 ,  116  in the grooves  94 . 
       FIG. 7  shows the guide support block  110  at the end of its stroke against the attachment member  39  while the rod  120  of the cylinder is entirely retracted inside the body  118 . Thanks to the aforementioned automatic locking mechanism, the connecting free end  36  is locked inside the end fitting  68  and they are therefore fastened to each other in a sealed manner. 
       FIG. 8  shows to a larger scale the turret  32  and the guide support  110  pressed against the attachment member  39 . It will be noted that the deformable pipe  50  has then been deformed during the movement of the guide support  110  toward the attachment member  39 . In fact, the deformable pipe  50  has been stretched freely through the two opposite upper oblong openings  60 ,  62  and to a lesser degree through the lower oblong opening  54 . 
     As a result, the connecting free end  36  and the end fitting  68  are locked exclusively by the movement of the guide support  110  and the deformable pipe  50  relative to the turret  32 . Thanks to this, the connector  30  has not been subjected to any impact during connection that might have damaged it. 
       FIG. 9  therefore shows the rigid pipe  12  and the flexible pipe  26  connected together at the level of the float  20  by means of the turret  32 ; the other end of the flexible pipe  26  having been entirely raised onto the laying ship  24 .