Abstract:
The invention relates to a ring ( 120 ) that is intended for being mounted tightly around a shaft of a hydraulic machine to form a portion of a hydrostatic or hydrodynamic bearing. The ring includes at least one first section ( 122 ), at least one second section ( 124 ) and means ( 132 ) for mounting the first and second sections around the shaft. Each section ( 122, 124 ) includes two edge surfaces ( 1223, 1243 ) connecting the external ( 1221, 1241 ) and internal ( 1222, 1242 ) radial surfaces thereof. The first section ( 122 ) is provided with at least one threaded hole ( 127 ) accessible via an edge surface ( 1223 ) and capable of receiving a screw ( 132 ) projecting from an edge surface ( 1243 ) of the second section ( 124 ). The screw ( 132 ) is provided, on the portion of the shank ( 134 ) thereof that projects from the second section ( 124 ), with at least one raised pattern ( 140 ) for rotatably moving the shank ( 134 ) in order to screw or unscrew the shank in the threaded hole ( 127 ). The screw ( 132 ) is provided with a piston ( 130 ) sliding in a recess ( 128 ) arranged in the second section ( 124 ), connecting to the edge surface ( 1243 ) of the second section and isolated from the outside by a bearing ( 136 ). The second section ( 124 ) is provided with means for supplying pressurized fluid to a chamber (C 1 ) with variable volume arranged between the piston ( 130 ) and the bearing ( 136 ), inside the recess ( 128 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a ring designed to be clamped around a shaft of a hydraulic machine for the purpose of forming a hydrostatic or hydrodynamic bearing. The invention also relates to a hydraulic machine including, inter alia, such a ring. Finally, the invention relates to a method of mounting such a ring on a hydraulic machine shaft for the purpose of forming a portion of a hydrostatic or hydrodynamic bearing. 
     2. Brief Description of the Related Art 
     A hydraulic machine comprises a rotary portion, such as a wheel or “runner” of a turbine or of a turbine pump, which wheel is designed to have a forced flow of water pass through it. Such a forced flow is a driving flow when the machine operates as a turbine, and a driven flow when the machine operates as a pump. In such a machine, a radial hydrostatic or hydrodynamic bearing can be provided around a shaft that supports the wheel, with the function of taking up the radial forces to which said shaft is subjected. The radially inner portion of such a bearing is sometimes constituted by a metal ring that forms an interference-fitted band in that it is clamped around the shaft. Such a ring is generally formed integrally as a single piece, i.e. it extends in one piece over 360° around the shaft, thereby ensuring continuity for its radially outer surface that constitutes the radially inner surface of the bearing. The fact that the ring is in one piece is a source of design and assembly constraints. 
     Multi-part rings made of metal could be devised, such rings being assembled around the shaft by welding or by mechanical means. In order to ensure good continuity and circularity that is as exact as possible for the radially outer surface of such a ring, rectification machining would need to be effected on the ring, once said ring has been assembled around the shaft, after the orifices for passing the assembly means such as bolts have been filled. In practice, such machining operations, to be performed on site would be lengthy and difficult, even though they would not guarantee continuity and circularity for the outside surface of the ring. 
     In addition, rings made of ceramic exist that cannot be assembled by welding and with which use of mechanical assembly means would induce discontinuities in the material of their outside surfaces. That is why such rings are always made integrally as a single piece, and must therefore be inserted over a hydraulic machine shaft via one end of that shaft which must have transverse dimensions less than the dimensions of the central bore of the ring. This can be problematic when a shaft is provided with lower and upper ends respectively of the “base” and of the “head” type that are enlarged so as to co-operate respectively with a turbine wheel and/or with the inlet shaft of an alternator. 
     SUMMARY OF THE INVENTION 
     More particularly, an object of the invention is to remedy those drawbacks by proposing a novel ring that is easier to mount around a hydraulic machine shaft, without inducing significant discontinuity on its radially outer surface, thereby enabling it to constitute the inside portion of a hydrostatic or hydrodynamic bearing without requiring rectification machining. 
     To this end, the invention provides a ring designed to be clamped around a shaft of a hydraulic machine for the purpose of forming a portion of a hydrostatic or hydrodynamic bearing, said ring being characterized in that: in a circumferential direction, it comprises at least a first segment, at least a second segment, and means for mounting first and second segments around a shaft; in that each segment comprises a radially outer surface, a radially inner surface, and two end faces interconnecting its radially outer and inside surfaces; in that the first segment is provided with at least one tapped hole accessible via one of its end faces and adapted to receive a screw projecting from an end face of the second segment; in that the or each screw is provided, on the portion of its shank that projects relative to the end face of the second segment, with at least one piece in relief for driving the shank in rotation about a longitudinal axis of the shank in order to screw the screw into the tapped hole or in order to unscrew it therefrom; in that the or each screw is provided with a piston slidably mounted in a recess that is provided in the second segment, which recess opens out in the end face of the second segment, and is isolated from the outside by a bearing through which the shank of the screw can slide; and in that the second segment is equipped with means for feeding pressurized fluid to a chamber of variable volume formed between the piston and the bearing, inside the above-mentioned recess. 
     By means of the invention, the two segments of a ring, forming an interference-fitted band to be mounted around a hydraulic machine shaft, can be assembled together by engaging the shank of each of the screws projecting from the second segment into a corresponding tapped hole in the first segment, and then by driving the screw so as to screw it into the tapped hole by means the piece(s) in relief provided on the shank of the screw. Once this first step has been implemented, it is possible to finalize the clamping of the ring/interference-fitted band around the shaft of the hydraulic machine by injecting a pressurized fluid into each chamber defined in part by the pistons of the screws, thereby exerting a traction force transmitted to the first segment. This presses the end face of the first segment firmly against the end face of the second segment. The structure of the ring is remarkable, in particular, in that the tapped hole and the recess open out in the end faces of the first and second segments so that, when said end faces bear against each other, these hollow volumes do not generate any discontinuity in the radially outer surface of the ring/interference-fitted band. This surface can thus constitute the radially inner surface of a hydrostatic or hydrodynamic bearing, without requiring rectification machining. The fact that the ring is a multi-part ring facilitates design and offers multiple possibilities of use, in particular for renovation or reconditioning work, where the geometrical shape of the turbine shaft is pre-imposed. 
     In advantageous but non-essential aspects of the invention, a ring such as the above-defined ring may incorporate one or more of the following characteristics, taken in any technically feasible combination:
         A first end face of each segment is provided with at least one tapped hole for receiving a screw projecting from a first end face of the other segment, and a second end face of each segment is provided with a projecting screw for engaging in a tapped hole accessible via the second end face of the other segment. In this aspect of the invention, each segment thus carries tapped holes and screws designed to co-operate with respective ones of the screws and of the tapped holes of the other segment.   Each first segment is provided with a plurality of tapped holes, distributed over the height of its end face, which height is a dimension parallel to a central axis of its radially inner surface, while each second segment is provided with a plurality of projecting screws, the number of which is equal to the number of tapped holes in the first segment, and which are distributed over the height of its end face, which height is a dimension parallel to a central axis of its radially inner surface.   Each piston of a screw is disposed in a dedicated recess and the feed means for feeding the chambers of the various recesses with pressurized fluid are common to at least two such chambers.   The feed means comprise at least one duct interconnecting at least two chambers in which the pistons of respective ones of two distinct screws are disposed.   When the first and second segments are in the assembled configuration, the or each chamber is at least partially filled with a solid material.   Means are provided for feeding pressurized fluid to a second chamber of variable volume that is defined by the piston inside the recess, opposite from the bearing.       

     The invention also provides a hydraulic machine comprising a rotary member supported by a shaft around which a hydrostatic or hydrodynamic bearing is disposed, said hydraulic machine being characterized in that it further comprises a ring according to any preceding claim that is mounted around the shaft and that defines a radially inner surface of the hydrostatic or hydrodynamic bearing. 
     Such a machine is easier to install and to maintain than state-of-the-art machines. 
     Finally, the invention provides a method of mounting a ring on a shaft of a hydraulic machine so as to form a portion of a hydrostatic or hydrodynamic bearing, said method being characterized in that it comprises steps consisting in: 
     a) bringing together at least one first circumferential segment and at least one second circumferential segment, each of which has a radially outer surface, a radially inner surface and two end faces interconnecting its radially outer and radially inner surfaces, by bringing at least a first end face of the first segment to face a first end face of the second segment; 
     b) engaging at least one screw projecting relative to the first end face of the second segment into a tapped hole accessible via the first end of the first segment; 
     c) screwing the screw into the tapped hole by driving it in rotation about a longitudinal axis of its shank, by acting on a piece in relief of the shank that is disposed between the end faces of the first and second segments; and 
     d) injecting a pressurized fluid into a chamber of variable volume defined by a piston integral with or secured to the screw and slidably mounted in a recess provided in the second segment. 
     By means of the method of the invention, the segments of the ring are assembled in such manner as to be clamped around the shaft of the hydraulic machine, without generating any significant surface discontinuity on the outside of said ring. 
     In an advantageous aspect of the invention, the pressurized fluid is solidified subsequently to being injected into the chamber of variable volume. The mass of solidified material then holds the piston stationary in a configuration in which the segments making up the ring are clamped around the shaft of the hydraulic machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood and other advantages of the invention appear more clearly from the following description of an embodiment of a ring of the invention, of an embodiment of a hydraulic machine of the invention, and of an implementation of a mounting method of the invention, the description being given merely by way of example and with reference to the accompanying drawings, in which: 
         FIG. 1  is an axial section view showing the principle of an installation incorporating a machine of the invention; 
         FIG. 2  is a section view on a larger scale on line II-II of  FIG. 1 ; 
         FIG. 3  is a plan view of a two-part ring used in the installation of  FIG. 1 , shown prior to assembly and partially cut away; 
         FIG. 4  is a view on a larger scale of the detail IV of  FIG. 3 ; 
         FIG. 5  is a view analogous to  FIG. 4 , during a first step of assembly of the ring; 
         FIG. 6  is a view analogous to  FIG. 4 , during a second step of assembly of the ring; 
         FIG. 7  is a section view on a smaller scale on line VII-VII of  FIG. 6 ; 
         FIG. 8  is a view on a larger scale of the detail VIII of  FIG. 7 ; and 
         FIG. 9  is a view analogous to  FIG. 4  when the ring is in a configuration in which it is clamped around the shaft of the machine shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The installation  1  shown in  FIG. 1  includes a Francis turbine  2  having its wheel or “runner”  3  fed from a casing  4  into which a forced-flow duct  5  opens out. 
     The turbine  2  also includes a shaft  6  on which the wheel  3  is mounted and that rotates with said wheel about a vertical axis X 6  that is also the longitudinal axis of the shaft  6 . The shaft  6  is constrained in rotation with another shaft  7  forming a drive member for driving an alternator  8 . 
     Between the casing  4  and the wheel  3  there is disposed a series of stationary guide vanes  9  and of wicket gates  10  having the function of guiding a flow E that is coming from the duct  5  and from the casing  4  and that is to pass through the wheel  3  towards a suction duct  11 . 
     The wheel  3  is provided with blades  31  that extend between a ceiling  32  and a belt  33 . 
     The wheel  3  is fastened to the lower end  61  of the shaft  6  or “base of the shaft”. The base  61  of the shaft may be formed integrally with the remainder of the shaft  6 , or else be mounted thereon. The wheel  3  is then mounted on the base  61  of the shaft by means that are known per se, such as screws that are not shown. 
     In order to take up the transverse forces to which the shaft  6  is subjected while the moving portions  3  and  6  of the turbine  2  are rotating about the axis X 6 , a hydrostatic bearing  100  is formed around the shaft  6 , above the base  61  of the shaft. 
     In a variant, the bearing  100  may be a hydrodynamic bearing. 
     Said bearing  100  is defined between a stationary lining  110  and a ring  120  forming an interference-fitted band, i.e. clamped around the shaft  6 . The lining  110  is stationary in that it does not rotate about the axis X 6  while the wheel  3  and the shaft  6  are rotating. The lining  110  is thus stationary relative to the structure of the turbine  2  that comprises, in particular, the elements  4  and  5 . 
     The bearing  100  is defined between the radially inner surface  111  of the lining  110  and the radially outer surface  121  of the ring  120 , both of these surfaces being cylindrical, circular, and centered on the axis X 6  when the turbine  2  is in the assembled configuration. 
     A feed line  160  makes it possible to feed clean water under pressure to the interstice corresponding to the bearing  100  between the surfaces  111  and  121 , through the lining  110 . 
     In view of the rotation movement between the surface  121  and the surface  111 , it is important for the surface  121  to be as continuous as possible and free from any roughness or unevenness. 
     In order to make it easy to mount around the shaft  6 , the ring  120  is made up of two segments  122  and  124  that are assembled together around the shaft  6  while exerting a centripetal force thereon, so that ring  120  constitutes an interference-fitted band for the shaft  6 . 
     The structure of the ring  120  appears from  FIGS. 2 to 9 . 
     The segment  122  is semi-circular and has a radially outer surface  1221 , a radially inner surface  1222  and two end faces  1223  and  1224  respectively interconnecting the surfaces  1221  and  1222 . In the same way, the segment  124  is defined between a radially outer surface  1241 , a radially inner surface  1242 , and two end faces  1243  and  1244  interconnecting the surfaces  1241  and  1242 . The surfaces  1221  and  1241  together constitute the surface  121  of the ring  120 . The segments  122  and  124  are circumferential in that their inside surfaces  1222  and  1242  are brought into abutment in order to constitute the inside circumferential surface  121  of the ring  120 . Each of the surfaces  1222  and  1242  has a radius R 1222  or R 1242  equal to, or slightly less than the radius R 6  of the shaft  6 , in its portion around which the ring  120  is mounted. 
     The ring  120  is thus clamped on the shaft  6  so as to avoid any relative movement between these elements. The clamping is preferably “light” in that it is not necessarily sufficient to take up seizure torque in the event of failure in the bearing  100 . The clamping is defined to take up the expansion effects due to the temperature gradient between the shaft  6  and the ring  120 , and the expansion effects due to centrifugal forces. Heating the parts  6 ,  122 , and  124  to a moderate extent facilitates putting the ring  120  into place around the shaft. Seizure torque, which is higher, can be taken up by a cotter pin (not shown) that is disposed between the shaft and the ring. 
     The segment  122  is provided with a bore  126  that opens out in the end face  1223  and that is extended, at its end opposite from said end face, by a tapped hole  127  that is centered on an axis X 127  perpendicular to the end face  1223 . Thus, the tapped hole  127  is accessible from the end face  1223 , through the bore  126 , and it can be considered that the tapped hole  127  opens out in the end face  1223 , via the bore  126 . 
     In addition, the segment  124  is provided with a recess  128  that opens out in the end face  1243  of said segment and that receives a head  130  in the form of a piston that is part of a screw  132 , the shank of which is referenced  134 . 
     The shank  134  of the screw  132  passes through a bearing  136  screwed into the mouth of the recess  128  that it therefore isolates from the outside. The dimensions of the bearing  136  and of the shank  134  are such that said shank can slide in said bearing, along its longitudinal axis X 132 . 
     Seals  138  seal the interface between firstly the bearing  136  and the rod  134  and secondly the bearing  136  and the segment  124 . 
     Two chambers C 1  and C 2  are defined on either side of the piston  130  of a screw  32 , inside the corresponding recess  128 . The chamber C 1  is defined between the bearing  136  and the piston  130 , while the chamber C 2  is defined between the piston  130  and the end-wall  1281  of the recess  128  that is opposite from the bearing  136 . 
     The shank  134  is threaded over a portion of its length, in the vicinity of its end opposite from the head  130 . In its intermediate portion  135 , situated between its threaded portion and its head or piston  130 , the shank  134  is provided with two flats  140  that are diametrically opposite about the axis X 132 . These flats make it possible to drive the shank  134  in rotation about the axis X 132  when the screw  132  is to be screwed into or unscrewed from the tapped hole  127 . 
     As appears more particularly from  FIG. 7 , the segment  122  is equipped with five bores  126  and with five tapped holes  127  over its height H 122 , i.e. over its dimension parallel to the axis of symmetry X 1222  of the surface  1222  that coincides with the axis X 6  when the ring  120  is in the assembled configuration. In the same way, the segment  124  is equipped with five recesses  128 , with five bearings  136  and with five screws  132  that are superposed and that serve to be engaged simultaneously in the bores and recesses  126  and  127  in the segment  122 . These recesses  128  are distributed over the height H 124  of the segment  124 , i.e. its dimension parallel to the axis of symmetry X 1242  of its surface  1242 , which axis coincides with the axis X 6  when the ring  120  is in the assembled configuration around the shaft  6 . The heights H 122  and H 124  have the same value. 
     The number of recesses  128  is adapted to the height H 122  or H 124  and to the diameter of the heads  130 . 
     A first duct  150  extends in the segment  124  parallel to the height H 124 . This duct interconnects the chambers C 1  of the various recesses  128 . 
     A second duct  152  extends over the height H 124  of the segment  124 , parallel to the segment  150 . This duct  152  is connected via tap-offs  154  to each of the chambers C 2 . 
     The ducts  150  and  152  are equipped with couplings, respectively  156  and  158 , making it possible to feed them with a pressurized fluid, in particular a polymerizable resin. Couplings  157  and  159  equip respective ones of the ends of the ducts  150  and  152  opposite from the couplings  156  and  159  and make it possible to connect these ducts to circuits for removing or recirculating excess pressurized fluid. 
     In practice, the segment  122  is also equipped, at its end face  1244 , with five recesses  128 , with five bearings  136 , and with five screws  132 , while the end face  124  is provided with five bores  126  and with five tapped holes  127 . In other words, an interface of the same type as the interface formed between the edge faces  1223  and  1243  is formed at the end faces  1224  and  1244 , the structure merely being inverted as regards what belongs to the segment  122  and what belongs to the segment  124 . 
     The segments  122  and  124  are thus identical, which is advantageous in terms of manufacturing and management of the spare parts. 
     In order to make the drawings clearer, the shaft  6  is not shown in  FIGS. 4 to 9 . 
     When the ring  120  is to be assembled around the shaft  6 , the segments  122  and  124  are brought around said shaft while putting the end faces  1223  and  1243  face-to-face with each other and while putting the end faces  1224  and  1244  face-to-face with each other. This is the configuration that is shown in  FIG. 4  and in which it is possible to move the segment  124  towards the segment  122 , in the direction indicated by the arrow F 1 , parallel to the axes X 127  and X 132  that are then aligned, thereby causing the shank to be engaged in the bore  126  and into the start of the tapped hole  127 . 
     In this configuration, shown in  FIG. 5 , the flats  140  are accessible for a tool, such as a wrench inserted in the direction indicated by the arrow F 2  between the end faces  1223  and  1243 . This tool makes it possible to drive the shank  134  in rotation about the axis X 132  in such a manner as to screw the screw  132  into the tapped hole  127 . The effect of this is to bring the end faces  1223  and  1243  closer together, until the configuration shown in  FIG. 6  is reached. 
     The same method is used for each of the screws  132  disposed at the end faces  1224 . 
     In the configuration shown in  FIG. 6 , a thermosetting resin is injected, under a pressure of about 1500 bars, into the duct  150 . This resin spreads around the screw  132 , into the various chambers C 1  of the segment  124 , and its pressure is such that it exerts a force, represented by the arrow F 3  on the various pistons  130  that is sufficient to move each piston towards the end wall  1281 , until the configuration shown in  FIG. 9  is reached in which the end faces  1223  or  1243  are bearing firmly against each other. 
     While the pistons  130  are moving towards the end faces  1281  of the recesses  128 , the air present in the chambers C 2  is removed through the tap-offs  154  and through the duct  152 . 
     The feed pressure of the resin is maintained for a length of time sufficient to enable it to polymerize, so that said resin is transformed into a solid mass  170  that locks the pistons  130  in the configuration shown in  FIG. 9  and in which the outside surfaces  1221  and  1241  join together without any apparent discontinuity, so that the surface  121  has no significant unevenness; 
     It can be understood that the chambers C 1  are fed with pressurized polymerizable resin simultaneously in the vicinity of the end face  1243  of the segment  124  and in the vicinity of the end face  1224  of the segment  122 , so that the segments  122  and  124  are clamped evenly around the shaft  6 . 
     This force is maintained so long as the chambers C 1  are filled with polymerized resin. The screws  132  are thus locked “mechanically” in the recesses  126 , in a configuration in which the end faces  1223  and  1243  bear against each other and in which the end faces  1224  and  1244  bear against each other. So long as the mass  170  of polymerized resin keeps its properties, the screws  132  cannot be released relative to the recesses  128 . 
     It can sometimes be necessary to remove the ring  120 , e.g. for a maintenance operation. In which case, the segments  122  and  124  are heated in the vicinities of the recesses  128 , which makes the resin present in the chambers C 1  fluid again. It is then possible to inject into the chambers C 2  and through the duct  152  and through the tap-offs  154  another pressurized fluid, thereby causing the various pistons  130  to be moved towards the bearings  136 , to the extent that the end faces  1223  and  1243  are spaced apart and that the end faces  1224  and  1244  are spaced apart, thereby making the flats  140  accessible again, which enables the screws  132  to be driven in an unscrewing direction relative to the tapped hole  127 . 
     It is thus possible to separate the segments  122  and  124 . 
     During this operation, the resin is removed via the duct  150  and via one of the couplings  156  or  157 . 
     Thus, the invention makes it possible to secure together effectively and lastingly two segments  122  and  124  making up a ring  120 , while the radially outer surface  121  of said ring does not have any significant discontinuity because, once the end faces  1233  and  1243  are bearing against each other and the end faces  1224  and  1244  are bearing against each other, the recesses and bores used are masked. 
     Very advantageously, the clamping force exerted by each screw  132  is exerted in the vicinity of the neutral axis of each of the segments  122  and  124 . 
     In addition, this force can be distributed over the height of the segments  122  and  124 , by means of the tapped holes  127  and the recesses  128  being distributed over the height of the segments. This offers a considerable advantage compared with clamping bolts being installed above the top edge and below the bottom edge of a multi-part ring. 
     The invention is shown for a hydrostatic bearing. However, it is also applicable to a ring forming part of a hydrodynamic bearing.