Stator for directing the inlet of air inside a turbo-engine and method for mounting a vane of said stator

A stator for a turbo-engine and a method for mounting the stator serve to improve fixing of the vanes of the stator and resistance of these vanes to impact in the event foreign bodies enter the turbo-engine. The stator includes several vanes radially maintained by their external and internal pivots between an internal ferrule and an external casing. The internal ferrule includes at least one bore intended to receive one of the internal pivots and the external casing includes a mechanism for the radial positioning and locking of the vane so as to make it possible to keep the internal pivot of the vane in the bore.

FIELD OF THE INVENTION 
The present invention concerns a stator for directing the inlet of air 
inside a turbo-engine or a compressor, such as that of an airplane 
turbojet engine. The invention also concerns the method for mounting a 
vane of said stator. 
BACKGROUND OF THE INVENTION 
The general structure of a turbojet engine shall now be mentioned in brief 
with reference to FIG. 1. The turbojet engine is traversed by a current of 
axial air (symbolized by the arrow F). It successively includes a blower 
or low-pressure compressor 1, a high-pressure compressor 3, a combustion 
chamber 5, a turbine 7 and an air ejection pipe 9. The air sucked up by 
the turbojet engine successively traverses the low-pressure compressor 1 
and the high-pressure compressor 3 where it is compressed, and then the 
combustion chamber where it is heated, and finally the pipes 9 where it is 
ejected. 
The constant search for weight reduction has led motorization technicians 
to study and produce compressors fitted with hollow vanes or vanes made of 
a composite material. The use of these techniques unfortunately results in 
the production of vanes which are more fragile than those vanes used 
hitherto. 
Furthermore, increasing of the diameter of blowers is a determinant factor 
concerning the risks of foreign bodies being sucked up from the ground or 
during flight. For example, these foreign bodies may be birds which may be 
present in large numbers when airplanes fly at high speeds or at low 
altitudes. At high altitudes, these foreign bodies may be pieces of ice. 
When these foreign bodies penetrate into the blower or low-pressure 
compressor 1, they generally result in a slight movement in the axial 
direction of the vanes of the stator or the vanes of the rotor, and indeed 
may even result in breaking of these vanes as they are quite fragile. When 
a vane of a stage moves, they abut against the vanes of the next stage and 
thus break. The vane fragments then penetrate into the high-pressure 
compressor 3 resulting in secondary damage to the vanes of the stator and 
the rotor. 
It is thus important to ensure that the vanes do not move axially towards 
the front or rear of the turbojet engine as a result of an impact with a 
foreign body. 
One first solution to try to resolve the damage caused to vanes by foreign 
bodies entering is described in the patent application FR-2 326 603. The 
vane described in this document is intended to be placed in an air flow 
blowing channel and be disposed in series with an adjacent vane against 
which it is likely to abut in the event of an impact occurring. These 
vanes are conventionally orientated radially inside the blowing channel. 
Each vane is constituted in this case by one metallic main portion fitted 
at its extremities with pivots allowing for a selective rotation of the 
vane around the axis defined between the two pivots. This vane has in its 
external downstream radial portion a block made of a composite material. 
This block is generally made of a graphite-epoxy composite material and 
forms the trailing edge of the vane. It is fixed rigidly to the rest of 
the vane by means of an adhesive, for example. This block is able to break 
and separate from the metallic portion, either when it directly receives 
an impact, or when the vane moves and when the block abuts against the 
following vane. Thus, at the time of impact, only the more fragile block 
made of a composite material is split into small pieces and, when these 
pieces are sucked up by the compressor, they do not cause any secondary 
damage downstream. 
This technique, even if it does partially limit damage caused to the vanes 
of the secondary stages of the compressor, does not prevent the axial 
movement of this vane. 
The vanes of the prior art are generally fixed as shown on FIG. 2. 
The vane 11 is fixed at its two extremities between an external casing of 
the cylindrical stator (not shown in FIG. 2) and an internal ring-shaped 
ferrule 13 disposed coaxially inside the external casing. Each vane 11 has 
at its internal radial extremity a platform 14 ending in a pivot 15. This 
pivot 15 is maintained between two annular half-rings 17 and 19 fixed 
around the ferrule 13 of the compressor. An antifriction washer 20 is 
placed between the pivot 15 and the two half-rings 17 and 19. In addition, 
these two half-rings 17 and 19 are kept assembled by a set of soldered 
plates 21 which comprise a gasket 22. As can be seen in FIG. 2, the vane 
11 is not locked at its base (towards the center of the engine), and the 
platform 14 merely rests inside a housing 23 provided in the half-rings 17 
and 19. This explains the easy axial movement of the vane when a foreign 
body enters. 
SUMMARY OF THE INVENTION 
Accordingly, the aim of the invention is to overcome these drawbacks and 
concerns a stator directing the inlet of air into a turbo-engine. In the 
invention, it is preferable that this stator is situated at the entrance 
of the high-pressure compressor 3 and is indicated by reference number 30, 
as shown on FIG. 1. However, it is quite clear that a stator constituted 
in this way could be placed in front of the blower 1 and even more 
generally in all other types of gas turbines or turbines with hydraulic 
transmission. 
The invention concerns a stator directing the inlet of air inside a 
turbo-engine, said stator including a set of vanes kept radially inside an 
air intake channel between an internal ferrule and a radially external 
casing, each vane being provided with one internal pivot and one external 
pivot respectively integral with its internal and external extremities, 
these two pivots defining the radial axis of the vane, the external casing 
being provided with at least one bore intended to receive the external 
pivot. 
According to the characteristics of the invention, the internal ferrule 
includes at least one bore intended to receive and to allow for embedding 
of, one of said internal pivots, the external casing includes means for 
the radial positioning and locking of at least one vane, said means for 
the radial positioning and locking of at least one vane making it possible 
to keep the radial extremity of the internal pivot of said vane in one of 
the bores provided in the internal ferrule when the vane is mounted in the 
stator and the external casing as a housing for receiving the external 
extremity of the vane, and the bore receiving the external pivot opens 
inside this housing. Further, the distance between the external extremity 
of the vane and the radial extremity of the internal pivot is less than 
the distance between the bottom of this housing and the face of the 
internal ferrule directed towards the inside of the air intake channel. 
These vane radial positioning and locking means combined with the bore of 
the internal ferrule make it possible to firstly ensure the double 
embedding of the vane at its two extremities, and secondly facilitate the 
mounting of the vanes. 
Advantageously, the vane locking and radial positioning means include a 
bush threaded on its external surface and disposed around the external 
pivot, the bore of the external casing being threaded so as to be able to 
cooperate with said bush. An antifriction ring is provided between said 
bush and the external pivot. The radially internal extremity of the bush 
rests on the external extremity of the vane so as to prevent any radial 
movement of the vane once the latter is fixed in the stator. 
These vane locking and radial positioning means are thus easy to produce 
and install and do not involve any significant excess costs. 
Moreover, the locking and positioning means include a washer disposed 
around the external pivot of the vane between the bottom of said housing 
and the external extremity of the vane ; the radially internal extremity 
of the bush resting against at least one portion of this washer. 
Finally, according to other characteristics of the invention, the internal 
pivot of the vane is kept between two half-rings disposed around the 
internal ferrule, each half-ring having at least one housing for receiving 
one portion of the internal extremity of the vane, these two half-rings 
being kept opposite each other by at least one support pierced with an 
orifice opposite the bore of the internal ferrule and allowing for passage 
of the internal pivot. 
As the conventional mode for fixing the radially internal portion of the 
vane has been modified so as to enable it to be embedded, it has therefore 
been found necessary to embody an orifice in the support so as to allow 
for passage of the internal pivot through said orifice until it arrives 
inside the bore of the internal ferrule. 
Finally, if it is desired to vary the angle of incidence of the vane with 
respect to the current of fluid traversing the turbo-engine, the free 
extremity of the external pivot is connected to means for making the vane 
pivot around its radial axis. 
The invention also concerns a method for mounting a vane of said stator, 
this mounting seeking to ensure the double embedding of the vane inside 
the stator. This mounting method includes the following stages: 
introducing the external pivot of the vane into the bore of the external 
casing from the inside of the air intake channel so as to embody the first 
embedding of the vane, 
having this vane pivot around its radial axis so as to be able to 
completely drive in the external pivot in said bore, 
introducing from outside the external casing the vane radial positioning 
and locking means, 
installing the internal ferrule via axial movement inside the turbo-engine, 
having the vane pivot until its leading edge is brought to the entrance of 
the air intake channel, 
radially moving the vane until the extremity of the internal pivot is 
brought into the bore of the internal ferrule so as to embody the second 
embedding of the vane, 
moving the locking and radial positioning means until the latter lock the 
vane and prevent the internal pivot from leaving the bore of the internal 
ferrule. 
More specifically, this method consists of: 
disposing a washer around the external pivot of the vane, 
introducing said external pivot into the bore of the external casing from 
inside the air intake channel so as to effect the first embedding of the 
vane, 
having the vane pivot around its radial axis so as to be able to completely 
drive in the vane and have the washer come into contact with the bottom of 
the housing of the external casing, 
introducing an antifriction ring inside the bush, 
screwing the bush in the bore of the external casing from the outside of 
the air intake channel until its radially internal extremity comes into 
contact with the washer, 
installing the two half-rings on both sides of the internal pivot, 
installing the support of these two half-rings, 
introducing the internal ferrule axially, 
having the vane pivot until the leading edge is brought back to the 
direction of the entrance of the air intake channel, 
moving the vane and the washer radially inwardly until the extremity of the 
internal pivot traverses the support and penetrates into the bore of the 
internal ferrule, thus embodying the second embedding of the vane, 
screwing the bush until its radially internal extremity touches the washer 
and locks the vane radially.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIG. 3, the air penetrates inside the stator along an axial 
direction shown by the arrow F so as to be brought inside a turbo-engine, 
for example inside the high-pressure compressor of a turbojet engine. An 
air intake channel is defined by two walls constituted, at least 
partially, by one internal ferrule 31 and by one radially external casing 
32. The external casing 32 is ring-shaped and surrounds the ferrule 31. 
The vanes 34 of the stator (only one being shown on FIG. 3) direct the 
flow of air inside the intake channel. These vanes are disposed radially 
with respect to the axial direction F. In the remainder of the 
description, the word `internal` shall relate to the elements of portions 
of elements radially directed towards the inside of the stator and 
conversely for the word `external`. Each vane 34 has one leading edge 36 
directed towards the air inlet and one opposing trailing edge 38. Each 
vane 34 is provided at its external extremity with one external pivot 40 
and at its internal extremity with one internal pivot 42. These two pivots 
define the radial axis X--X of the vane. In the particular case of the 
vane shown on FIG. 3--and this is frequently the case--, the vane 34 
further includes one external platform 44 and one internal platform 46. In 
the remainder of the description, these platforms 44 or 46 shall sometimes 
be designated by the more general term `extremity`. In fact, it is 
important to note that all the vanes do not have a platform. 
As conventionally shown in FIGS. 3 and 4, the internal pivot 42 of the vane 
is maintained between two half-rings 48 and 50, the latter being annular 
and completely surrounding the internal ferrule 31. These two half-rings 
48 and 50 are in fact constituted by complementary symmetrical profiles. 
Each profile 48, 50 has one shoulder 51 (respectively 52) defining two 
internal support zones 53 and 54. In its radially internal portion, each 
half-ring 48, 50 further has one shoulder forming a projection 56. 
Moreover, each half-ring 48, 50 has in its central portion a set of 
half-countersinkings or housings 55 and when the two half-rings 48, 50 are 
assembled, these half-countersinkings 55 define an annular shoulder 57 
(see FIG. 4). These two half-rings are kept in place by a support unit 58 
constituted by soldered plates. This unit simultaneously supports the two 
shoulders 57, takes support on the contact zones 53 and 54 and on the 
internal ferrule 31 and bears a gasket 58a. Each half-ring 48, 50 further 
has several vertical radial throats which, once the two half-rings 48 and 
50 have been assembled, form orifices 59 intended to receive the pivots 
42. The shape and fixing of the two half-rings 48 and 50 and the support 
58 are extremely conventional and shall not be described further in 
detail. 
According to the characteristics of the invention and as shown on FIGS. 3 
and 5, the internal ferrule 31 has a bore 60 allowing, contrary to what 
existed in the prior art, the internal pivot 42 of the vane to be 
embedded. The support 58 also has an orifice 61. When the vane is mounted, 
as shown on FIG. 5, the internal pivot 42 penetrates inside this bore 60. 
In addition, an antifriction ring 62 and an antifriction washer 64 are 
disposed respectively between the two half-rings 48 and 50 and the 
internal pivot 42 and between these half-rings and the internal platform 
46 of the vane 34. The antifriction ring 62/antifriction washer 64 unit 
may also be a monoblock. 
Furthermore and as shown on FIGS. 3 and 5, the external casing 32 is 
provided with a housing 66 receiving the platform 44 of the vane, this 
housing 66 extending outwardly by a tapped bore 68 intended to receive the 
external pivot 40. This tapped bore 68 has an external shoulder 70. A bush 
72 threaded on its external surface (reference 74) is disposed around the 
pivot 40 and partially inside the bore 68. In its radially internal 
portion, this bush has one extremity 75 and in its radially external 
portion a shoulder 76 extending radially (with respect to the longitudinal 
axis of the bush). An antifriction ring 78 is disposed between this bush 
and the external pivot 40. This bush and a washer 80 constitute the means 
for the radial positioning and locking of the vane. This washer 80 is 
disposed between the bottom 82 of the housing 66 and the external surface 
of the platform 44. According to the invention, this washer 80 preferably 
has in its central portion a shoulder 84 forming an annular projection. An 
antifriction ring 85 is preferably provided between the washer 80 and the 
platform 44. The radially internal extremity 75 of the bush 72 rests on 
the washer 80 or more specifically on its shoulder 84. However, in another 
embodiment variant, the washer 80 and the ring 85 could be suppressed and 
would be necessary when the extremity 75 of the bush rests directly on the 
external extremity 44 of the vane so that said vane is locked. Finally, as 
shown on FIG. 5, the vanes are able to pivot around their radial axis X--X 
by means denoted under the general reference 86. As shown on FIG. 5, these 
means conventionally include a rocker bar 88 kept at the extremity of the 
external pivot 40 with the aid of a bolt cooperating with the threaded 
extremity (see FIG. 3) of the external pivot 40. 
The successive stages of mounting are now to be described in detail with 
reference to FIG. 3. 
First of all, the antifriction ring 85 and the washer 80 are disposed 
around the external pivot 40. Then the unit is introduced into the 
external casing 32 through the interior of the air intake channel until 
the external pivot 40 penetrates into the bore 68 (i.e. the operation 
shown by the arrow I). This makes it possible to carry out the first 
embedding of the vane. Then the vane 34 is made to slightly pivot around 
its radial axis X--X so as to move it from the position shown in FIG. 5 to 
the position shown in FIG. 3 where the upper portion of its trailing edge 
38 no longer abuts the external casing 32 (i.e. the operation shown by the 
arrow II). This makes it possible to drive in the vane 34 until the washer 
80 abuts against the bottom 82 of the housing 66. Then the antifriction 
ring 78 is disposed inside the bush 72 and introduced around the pivot 40 
from outside of the casing 32. This bush 72 is screwed inside the tapped 
bore 68 until its radially internal extremity 75 comes into contact with 
the projection 84 of the washer 80 (i.e. the operation shown by the arrow 
III). 
When this vane 34 and possibly the other vanes of the stator have been 
disposed in this way and after the antifriction ring 62 and the 
antifriction washer 64 have been carefully disposed, the two half-rings 48 
and 50 are placed on both sides of the internal pivot 42. Then the support 
58 (i.e. the operation shown by the arrows IV) is placed. 
Next, the internal ferrule 31 is introduced in an axial direction until the 
bore 60 is opposite the internal pivot 42 and the orifice 61 (i.e. the 
operation shown by the arrow V). As shown on FIG. 3, this operation is 
possible to the extent that the distance D1 between the radially external 
extremity 44 of the vane and the free extremity of the internal pivot 42 
is less than the distance D3 between the internal ferrule 31 and the 
bottom 82 of the housing 66. 
Then the vane 34 is radially moved (i.e. the operation shown by arrow VI) 
inwardly so as to bring the pivot 42 into the bore 60 and so that the 
platform 46 rests on the antifriction washer 64 at the bottom of the 
housing. Next, the second embedding of the vane is effected. This 
operation is completed by making the vane move inversely to that of the 
arrow II until its leading edge 36 is brought back into the direction of 
opening of the air intake channel, as shown on FIG. 5. 
Finally, the bush is fully screwed until the radially internal extremity 75 
of the bush again touches the washer 80 (more specifically the projection 
84). This makes it possible to stop any subsequent radial movement of the 
vane 34. It is important that the shoulder 76 of the bush 72 does not abut 
against the external shoulder 70 of the bore 68 before the extremity 75 of 
the bush touches the projection 84. The dimensions of these various 
elements shall thus be calculated according to these requirements. 
For the second embodiment of the invention (i.e. without the washer 80 and 
the antifriction ring 85) reference should be made to FIGS. 6 and 7. Here, 
each vane is introduced into the external casing 32 through the inside of 
the air intake channel until the external pivot 40 penetrates into the 
bore 68 (i.e. see arrow I.) The vane 34 is made to slightly pivot around 
its radial axis X--X so as to move it from the position of FIG. 5 to the 
position of FIG. 3. This makes it possible to drive in the vane 34 until 
the radially external extremity 44 of the vane abuts the bottom 82 of the 
housing 66 (see FIG. 6). The bush 72 (provided with the antifriction ring 
78) is screwed inside the tapped bore 68 until its radially internal 
extremity 75 comes into contact with the radially external extremity 44 of 
the vane (i.e. see arrow III in FIG. 6). When all of the vanes 34 have 
been disposed in this manner, the two half-rings 48 and 50 are placed on 
both sides of all of the internal pivots 42, the support 58 is placed and 
the internal ferrule 31 is introduced in an axial direction (i.e. see 
arrows IV and V in FIG. 6). Then the vane 34 is radially moved (i.e. see 
arrow VI in FIG. 6) so as to bring the pivots 42 into the bore 60. The 
vane is movable universally as indicated by arrow II. Finally, the bush 72 
is fully screwed until the radially internal extremity 75 of the bush 
again touches the radially external extremity 44 of the vane (see FIG. 7). 
This method of mounting the vane is also possible because the distance D1 
between the radially external extremity 44 of the vane and the radial 
extremity of the internal pivot 42 is less (i.e. only slightly less in 
this case) than the distance D3 between the bottom 82 of the housing 66 
and the face of the internal ferrule (around the bore 60), directed 
towards the inside of the air intake panel. In this embodiment as well as 
the first embodiment, the length of the pivot 42 must be great enough to 
allow the extremity of the pivot to penetrate inside the bore 60 when the 
platform 46 abuts against the antifriction washer 64. In the same manner, 
the length of the bush 72 must be great enough to allow its extremities 75 
to abut against the vane 44 or the washer 80, when the vane 44 is in an 
up-position (FIG. 3 or 6) and to define a small gap between the shoulder 
76 of the bush 72 and the external shoulder 70 of the tapped bore 68.