Sectored, one-piece nozzle of a turbine engine turbine stator

A nozzle of a turbine stator of a turbine engine, wherein at least two of the vanes are fixed to each inner platform and to opposite each outer platform, and a maintaining unit is configured to maintain each sector with respect to a case of the turbine stator and to connect sectors together and has a rotational maintaining element, a radial maintaining element and an axial maintaining element. The radial maintaining element is flexible so as to permit a radial expansion of each sector and is constituted by an elastic joint fixed to the case so as to surround the sectors.

BACKGROUND OF THE INVENTION 
The invention relates to the high pressure turbine of a turbine engine such 
as the turbojets used on an aircraft. It more specifically relates to the 
sectored, one-piece structure of the high pressure turbine stator nozzle. 
DISCUSSION OF THE BACKGROUND 
Existing or future turbine engines, such as the turbojets equipping civil 
and military aircraft, must have high performance characteristics, but 
must also have a light weight and only require easy, less frequent and 
therefore less costly maintenance. The taking account of these aims makes 
it necessary for aircraft manufacturers to reconsider the definition of 
certain or all the parts of such turbine engines. 
With reference to FIG. 1, concerning the high pressure turbine 1 of the 
turbine engine, the stator is in most cases formed by sectors constituted 
by several vanes 2 connected by platforms. It is consequently frequent to 
find sectors formed by two vanes 2 linked by an inner platform and an 
outer platform. These sectors are then fixed to circular ferrules. 
It is clear that approach and connecting zones create geometrical 
imperfections in this arrangement, which disturb the flow of air through 
the high pressure turbine. These imperfections allow leaks to exist, which 
are prejuducial to the efficiency of the turbine engine. 
The object of the invention is to obviate these disadvantages. 
U.S. Pat. No. 4,126,405 discloses a segmented assembly of a turbine nozzle. 
The sectors are locked in rotation by studs 46 in FIG. 1 of the U.S. 
patent. Sealing between each sector is ensured by tongues, which are 
located in the grooves of the platforms. 
SUMMARY OF THE INVENTION 
To this end, the main object of the invention is a turbine engine stator 
nozzle comprising vanes associated with one another by sectors, e.g. in 
pairs, inner platforms on each of which are fixed two vanes by a first 
end, outer platforms on which are fixed the two same vanes by their two 
other ends and means for retaining the sectors with respect to a stator 
case and in particular means for fixing in rotation, radial fixing means 
and axial fixing means. 
According to the invention, the radial nozzle fixing means are flexible and 
permit a radial expansion, being constituted by an outer elastic joint 
fixed to the stator case and surrounding the nozzle sectors and the nozzle 
comprises means for fixing together the sectors, so that the nozzle 
maintains its one-piece character. 
When peripheral studs are used as means for the fixing in rotation of the 
nozzle, the means for the mutual axial fixing of the sectors comprise 
blocks placed on the edge of the outer platforms and which are mutually 
displaced so as to permit a juxtaposing of the sectors, the blocks of two 
contiguous sectors being positioned axially against one another in order 
to lock in axial translation in one direction the two contiguous sectors 
and the studs placed outside each outer platform axially abut against 
clips of the elastic joint. 
Preferably, said elastic joint has undulations. 
In a second embodiment of the invention, the flexible, radial fixing means 
for the nozzle comprise for each sector a first half-clevis placed on the 
outer surface of each of the outer platforms, a second half-clevis fixed 
with respect to the stator case and a rod mounted so as to pivot in each 
half-clevis by a first end and fitted in pivoting manner with respect to 
the stator case by a second end. 
Preferably, the first half-clevis is constituted by two rings each joined 
to a different sector, but adjacent to one another, so as to ensure that 
each sector is retained with respect to the others.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 2 is a partial view of a first embodiment of the nozzle. It is 
possible to see the vanes 2 integral with inner 4 and outer 5 platforms. 
Thus, in this embodiment a sector 3 has two vanes 2, an inner platform 4 
and an outer platform 5. 
The sectors 3 are shown in contiguous form, but it is possible to move them 
apart, particularly when they are moving away from the centre of the 
nozzle, i.e. the turbine engine axis 6. 
They are mutually axially positioned by blocks 7, each of which is placed 
on the two edges 8 of an upper platform 5 and which face one another when 
the sectors 3 are contiguous. The blocks 7 project beyond said edges B. 
However, they are fixed in displaced manner along the edge where they are 
located, so that the sectors 3 can be contiguous, the blocks 7 then being 
adjacent and thus forming an axial abutment in one direction for two 
contiguous sectors 3. 
To prevent the axial displacement of two contiguous sectors in the other 
direction, use is made of peripheral studs 9 used for the blocking in 
rotation of the sectors 3. Thus, each peripheral stud 9 projects beyond an 
upper platform 5, so as to be able to reenter a not shown groove of the 
stator 10. Thus, all the sectors 3 are locked in rotation. The fact that 
the peripheral studs 9 project makes it possible to have a supplementary 
axial abutment. 
Reference should be made to FIGS. 3 and 4 for an understanding of how the 
peripheral studs 9 are used for forming an axial abutment. 
FIG. 3 shows a vane 2 integral with its inner platform 4 and its outer 
platform 5. The assembly is held tightly in the stator case 10 by an 
elastic joint 11 placed around said sector and in particular around the 
peripheral studs 9. Thus, when the flexible joint 11 is installed, the 
peripheral studs 9 can touch the inner face 11A of the flexible joint 11 
when each sector 3 is slightly moved away from the turbine engine axis. 
The flexible joint 11 is positioned in an annular groove 12 of the case 10. 
It also has a series of inwardly curved clips 13 in order to form axial 
abutments against which abut the peripheral studs 9. 
FIG. 4 perfectly shows this constructional detail, where it is possible to 
see the clips 13 abutting against the downstream, radial face 9R of the 
peripheral studs 9. Thus, each sector is blocked in axial translation both 
by the elastic joint 11 and one of the two adjacent sectors. 
It is possible to see in FIG. 3 that a sector can slide radially, i.e. 
perpendicular to the axis of the turbine engine with respect to the stator 
case 10. Thus, there is a clearance between the elastic joint 11 and the 
top of the peripheral studs 9. There is also a radial clearance between 
the inner end 4A of the inner platform 4 and an inner ferrule 14 of the 
stator. There is also a guide groove 15 constituted by said inner ferrule 
14 and the central hub 16 of the stator. 
Thus, as a result of the blocks 7 and the peripheral studs 9, each sector 
is held axially and in rotation and is radially positioned with a slight 
clearance. However, as the sectors are axially positioned with respect to 
one another, the complete nozzle constitutes a one-piece ring. The 
compactness of the thus formed nozzle makes it possible to maintain an 
effective sealing system, so as to bring about a performance improvement 
on the part of the turbine engine. 
The sealing of the complete nozzle is ensured by three sealing joints 19, 
whereof two are placed upstream and downstream of the upper platform 5 and 
whereof the third is positioned upstream of the inner platform 4. 
With reference to FIG. 5 showing the second embodiment of the invention, 
the sectors 3 are provided on the outer surface SE of their outer platform 
5 with a half-clevis 21, which enables a rod 20 to be fitted so as to 
pivot about an axis 24 parallel to the axis of the turbine engine by a 
first end. 
With reference to FIG. 6, by its second end the rod 20 is also mounted so 
as to pivot in another half-clevis constituted by a bush 23 and a 
positioning part 22 fixed with respect to the not shown stator case. This 
pivoting also takes place about an axis 25 parallel to the axis 24. 
Thus, each sector can have a slight freedom of movement in the radial 
direction and in rotation about the turbine engine axis. However, as the 
sectors 3 are juxtaposed, they still constitute a one-piece ring. 
The slight displacement possible for each sector is also guided, as in the 
first embodiment, by a groove 15 defined by the inner ferrule 14 and the 
central hub 16 of the stator. 
On the upstream side of each sector use is also made of sealing joints 19, 
as in the first embodiment. 
FIG. 7 is a plan view of the previously described embodiment. It is 
possible to see a rod 20 fitted in the first half-clevis 21 fixed on the 
outer platform 5 of a sector. It should be noted that each half-clevis 21 
is constituted by two rings, each fixed to a different, adjacent sector 5. 
Thus, the half-clevises 21 fix together the sectors and are driven in 
rotation together. This fixing procedure ensures the one-piece character 
of the thus formed ring-shaped nozzle, whilst permitting a slight radial 
movement of each sector. This nozzle is more particularly appropriate for 
the stator of a high pressure turbine of a turbojet.