Abstract:
In a succession of rotor disks, only the end disks are connected to a main structure by bolted extensions and the intermediate disks are suspended from rigid spacer pieces by centering and anti-rotation connections. The end disks are interconnected to clamp the assembly in the axial direction. There is no bolted connection between the successive disks. Assembly is very easy. The disks and the spacer pieces are stacked together in alternately, and the assembly is torsionally very rigid because of the use of a high number of claw-coupling teeth formed by protruding ends of the blade roots forming teeth that engage in spacer piece end rims.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The subject of this invention is a turbomachine rotor arrangement.  
           [0002]    Such rotors often comprise individual disks bearing rotor-blade stages and joined by spacer pieces. The main purpose of the spacer pieces is to provide seals restricting the flow of gases between the stages. The disks normally have extensions that extend towards a central structure of the rotor to which they are fixed by bolts. They also comprise rims that extend under the spacer pieces and are joined together by bolts at their ends. Each disk is thus connected directly to adjacent disks, in addition to having an indirect connection via the central structure of the rotor. However, it is found that this arrangement is not as rigid as may have been hoped, something which is all the more disappointing since all these bolted connecting means take a long time to assemble and to disassemble and represent a significant weight.  
         SUMMARY OF THE INVENTION  
         [0003]    According to the invention there is provided a rotor arrangement comprising a succession of disks carrying blades and joined by spacer pieces, wherein two of the disks, at opposite ends of the succession, are provided with extensions, wherein the extensions are tapered to meet at joined flanges, each the disk being provided with axially spaced annular ledges, the spacer pieces comprising axially spaced annular rims, each rim engaging an associated ledge, and the disks and the rims comprising co-operating arrays of claw-coupling teeth and recesses for receiving said teeth and extending around the rims.  
           [0004]    This arrangement therefore concerns the connection between the disks and the spacer pieces: the spacer pieces are now rigid pieces tasked with holding the intermediate disks and provided with means for centering the connection about the axis of the rotor and means for preventing rotation collaborating with complementary means situated on these disks. The bolted connections between the disks can therefore disappear, as can the connections of the intermediate disks to the central structure of the rotor: the intermediate disks are therefore suspended from the spacer pieces.  
           [0005]    Although the resulting assembly may seem loose, it is rather more rigid than the known methods of assembly. One reason is undoubtedly the fact that the bolts hitherto used were relatively few in number, whereas the claw-coupling teeth may, according to an important embodiment of the invention, correspond to ends of the blade roots engaged in individual slots in the disks which pass through the disk, these ends protruding from the slots. The claw-coupling connection therefore has recourse to a great many teeth, without the arrangement being complicated thereby, since it involves no additional parts and simply requires extending the blade roots by comparison with prior practice.  
           [0006]    The arrangement according to the invention is therefore a single and compact structure which can be joined to the central structure of the rotor by a single bolted flange. In addition, the continuations of the end disks may also be joined by an array of claw-coupling teeth and of recesses for said teeth so as to give a more rigid connection directly between the end disks. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a view of a first embodiment of the invention showing a rotor of a turbomachine formed by a central structure carrying a disk assembly,  
         [0008]    [0008]FIG. 2 is a perspective view of part of the assembly of FIG. 1 showing the connection of a spacer piece of the assembly to a disk of the assembly, and  
         [0009]    [0009]FIG. 3 is a similar view to FIG. 1 but sharing an alternative form of the assembly. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]    Referring first to FIG. 1, the rotor comprises a central structure  1  of known type usually, in many known turbomachines, made of elements assembled by bolting that will not be described in detail. The disk assembly bears the overall reference  2  and extends around a portion of the central structure  1 . The main components of the disk assembly are upstream and downstream end disks  3  and  4 , two intermediate disks  5  and  6 , situated between the previous end disks  3 ,  4 , and three spacer pieces  7 ,  8  and  9  connecting the disks ( 3  and  5 ,  5  and  6  and  6  and  4 , respectively) in successive pairs. The disks  3 ,  4 ,  5  and  6  are more or less flat, parallel to one another and arranged in axially spaced succession. The disks  3 ,  4 ,  5  and  6  are all intended to carry rotor-blade stages  10  to extend into a stream of gases with each rotor blade stage  10  being arranged between respective stator-blade stages  11 . The spacer pieces  7 ,  8  and  9  carry respective wipers  12 , in the form of annular crests that engage respective rings of abradable material  13  extending around the stator-blade stages  11  to form labyrinth seals that make it difficult for gases to circumvent the stator blades  11  and produce losses of efficiency to flow. As all these details are well known, they will not be given a fuller description.  
         [0011]    The upstream and downstream end disks  3  and  4  each comprise an outer ring  14 , an inner ring  15  and a web  16  joining the two rings. An extension  17  extends from the ring  15  of the upstream end disk  3  and an extension  18  extends from the ring  15  of the downstream end disk  18 . The extensions  17 ,  18  extend radially inwardly with a tapered conical shape. The two extensions  17  and  18  converge towards one another with the extension  18  of the downstream end disk  4  comprising an end ring  19  that engages a circular bearing surface  20  provided on the extension  17  of the upstream end disk  3  and rests against an abutment face  21  of this extension  17 . A nut  22  is screwed onto a threaded face  23  of the extension  17 , with the face  23  extending beyond the bearing surface  20 , to hold the ring  19  against the abutment face  21 . In addition, the ring  19  and the extension  17  are equipped with teeth which nest into intermediate recesses to form a circular claw coupling  24 . This connection allows the disks  3  and  4  to be held firmly in an immovable position relative to one another. The extension  17  continues beyond the bearing surface  20  towards the center of the rotor and is joined to the central structure  1  via an arrangement of bolted flanges  25 .  
         [0012]    The intermediate disks  5  and  6  have no such inward extensions and are therefore connected directly neither to the other disks nor to the central structure  1  of the rotor. They are supported only by the spacer pieces  7 ,  8  and  9  by means of joints which will now be described with reference to FIG. 2.  
         [0013]    The spacer pieces  7 ,  8  and  9  are each provided with two flat rims  26  and  27  which extend radially inwardly from respective opposite ends of the associated spacer piece  8 ,  8 ,  9 . The flat rims  26 ,  27  rest on axially extending annular ledges  28  and  29  of the pair of disks  3 ,  4 ,  5  and  6  separated by the associated spacer piece  7 ,  8 ,  9  One ledge  28  being provided on one disk and the other ledge  29  on the other disk. The rims  26  and  27  are equipped with respective recesses  30  with each recess  30  receiving a respective end of a root  31  of a rotor blades  10 . The arrangement often used for assembling rotor blades to a disk consists in making slots  32  through an outer ring of the disk in an axial or oblique direction. The cross section of each slot  32  is bulbous, dovetail, Christmas tree or similar shape, opening to the outside of the disk via a narrow neck to retain a rotor blade root. In the present arrangement, the roots  31  are lengthened at part of their cross section and protrude from the slots  32  as seen in FIG. 2. It is also noted that there is no specific means for preventing the roots  31  from sliding in the slots  32 , this function being effected by the rims  26  and  27  whose outer faces butt against the lateral faces of the outer rings  14  and therefore prevent the rotor blades  10  from moving by barring a portion of the slots  32  which is occupied by non-lengthened portions of the roots  31 .  
         [0014]    Screwing the nut  22  onto the threaded face  23  maintains cohesion of the assembly in the axial direction by clamping together the disks from  3 ,  4 ,  5   6  with the intermediate spacer pieces  7 ,  8   9  via the rims  26  and  27 . They are centered by the engagement of the rims  26  and  27  against the ledges  28  and  29  in a radial direction. Finally, relative rotation is prevented by the claw couplings formed the teeth provided by the lengthened ends of the roots  31  of the rotor blades  10  and the corresponding recesses  30  of the rims  26  and  27 , which give the assembly better torsional rigidity. The claw coupling  24  formed between the extensions  17  and  18  of the upstream and downstream end disks  3  and  4  has the benefit of establishing a direct anti-rotation connection between the end disks  3  and  4  and therefore also contributes to the torsional rigidity. This claw coupling  24  is not, however, always necessary because of the claw couplings that exist at the joints between the disks  3 ,  4 ,  5   6  and the spacer pieces  7  to  9 . If it is present, then it may contribute to making the assembly statically redundant, and it may then be advisable to eliminate one of the other claw couplings, for example one of those involving the central spacer piece  8 .  
         [0015]    Returning to FIG. 1, it can be seen that the assembly is supplemented by three shell rings  33 ,  34  and  35 . Each shell ring  33 ,  34 ,  35  extends between an associated pair of disks  3 ,  4 ,  5 ,  6  and is radially inwardly of and concentric with an associated spacer piece  7 ,  8  and  9 , to define associated chambers  36 ,  37  and  38  for the passage of ventilation air that also passes through unoccupied portions of the slots  32 . The ventilation air is led in through ducts  40  formed between a flange  41  of the upstream disk  3  and an additional spacer piece  42 , associated with another labyrinth seal  43  upstream of the disk  3 . This ventilation air is led out to the gas stream after passing through the slots  32  of the downstream disk  4 . The reference  44  denotes a passage admitting ventilation air to the assembly and drillings  45  and  46  are made in the extensions  17  and  18  of the end disks  3  and  4  to allow the ventilation air to cool a chamber  47  inside the assembly  2 , particularly the intermediate disks  5  and  6 . Each shell ring  33  to  35  comprises, at one end thereof, lugs  48  which extend radially outwardly from the associated shell ring  33 ,  34 ,  35  and enter notches made in the ledge  28  of the associated disk. They are thus prevented from rotating.  
         [0016]    [0016]FIG. 3 illustrates a slightly different arrangement in which the shell rings  33  to  35  are omitted as are the separate chambers  36  to  38 . The ventilation air flow passing through the slots  32  flows directly into the gas stream. The spacer pieces  7 ,  8  and  9  of FIGS. 1 and 2 are replaced by spacer pieces  107 ,  108  and  109  which resemble them but in each of which the upstream rim is replaced by an inverted rim  126 , extending outward from the main portion of the spacer piece. The principles and the advantages of the assembly remain unchanged: in particular, the rims  126  continue to press against the ledges  28  and comprise recesses  30  for the receipt of extended ends of the roots  31  of the blades, so as to establish claw-coupling connections, and they comprise portions restraining the roots against sliding movements.  
         [0017]    It should be added that the assembly of the rotor arrangement  2  is very simple to do because it consists in stacking the disks, spacer pieces and shell rings in succession and in tightening the single nut  22  when the extensions  17  and  19  of the end disks  3  and  4  have met.