AIRCRAFT ENGINE ANNULAR SHROUD COMPRISING AN
OPENING FOR THE INSERTION OF BLADES
TECHNIQUE OF THE INVENTION
The present invention relates to an annular
5 shroud comprising an opening for the insertion of
blades. The technical field of the invention is,
generally speaking, that of aircraft engines and, more
particularly, that of downstream guide vanes
comprising shrouds.
10 TECHNOLOGICAL BACKGROUND OF THE INVENTION
An aircraft engine comprises a series of
compressors. In order for compression to be optimal,
the air entering into said compressors has to be
oriented. The parts serving to orient the air are
15 downstream guide vanes. As represented in figure 1, a
downstream guide vane 10 comprises an internal shroud
11, an external shroud 12 or casing shroud, as well as
a plurality of blades 13. Each blade 13 comprises an
external root 14 and an internal root 15.
20 Conventionally, the external root 14 of a blade 13 is
fixed by welding in the external shroud, and the
internal root 15 is maintained in the internal shroud
11 by moulding of RTV silicone.
Such an assembly is not however viable at high
25 temperatures, the RTV silicone then degrading rapidly.
There are thus risks of uncoupling of the blades 13
with the internal shroud 11.
To overcome such a drawback, another attachment
system of blades, represented in figures 2 and 3, has
been proposed. The system comprises in particular a
first external half-shroud 20, a second external half-
5 shroud, an upstream internal shroud 30, a downstream
internal shroud 31, and a plurality of blades 23.
Half-shroud is taken to mean a shroud having the shape
of a half-ring. Each blade 23 comprises an external
root 24 and an internal root 25. The first external
10 half-shroud 20 comprises a peripheral annular groove
21 forming a guiding rail for the external roots 24 of
the blades 23. The external root 24 of each blade 23
is able to be inserted into the annular groove 21 via
an end 22 of the first external half-shroud 20. Each
15 external root 24 is then positioned by displacement in
the annular groove 21. Similarly, the second external
half-shroud comprises a peripheral annular groove able
to accept external roots of blades. The external roots
of blades are inserted into the grooves at the level
20 of the ends of the external half-shrouds.
After insertion of a certain number of blades 23
into the two external half-shrouds, the first external
half-shroud 20 and the second external half-shroud are
assembled by means of flanges, not represented. The
25 blades 23 are then maintained blocked in the external
half-shrouds. The upstream internal shroud 30 and the
downstream internal shroud 31 are then assembled
together to +maintain the internal roots 25 of the
blades 23 by a system of hooks and screws, known to
3030 those skilled in the art.
This attachment system does not enable the use of
annular external shrouds, in other words external
shrouds forming a complete closed ring, due to the
system of inserting the blades 23 into the annular
5 groove 21 that takes place at the ends of the external
half-shrouds. Yet, using one annular external shroud
instead of two external half-shrouds is advantageous,
because the step of assembling two half-shrouds is
avoided.
GENERAL DESCRIPTION OF THE INVENTION
The subject matter of the invention offers a
solution to the drawback that has been described, by
proposing a system making it possible to use annular
external shrouds.
15 According to a first aspect, the invention thus
essentially relates to an aircraft, engine annular
shroud comprising:
-on its internal surface, a peripheral annular
groove able to accept a plurality of blade roots;
-an insertion opening for inserting blade
roots into the annular groove;
- closure means for closing off the insertion
opening.
25 The annular shroud according to the invention
having an annular groove and an insertion opening,, it
30
replaces the assembly comprising two half-shrouds of
the prior art.
Apart from the main characteristics that have
been mentioned in the preceding paragraph, the annular
5 shroud according to the invention may have one or more
complementary characteristics among the following,
considered individually or in any technical possible
combinations thereof:
- the insertion opening is situated on the
10 annular groove;
- the insertion opening does not pass through the
annular shroud and it comprises two notches situated on
either side of the annular groove;
- the closure means comprise:
15 a lock blade, said lock blade
comprising a projecting part able to pass through an
opening formed in the insertion opening;
maintaining means able to fix
themselves on the projecting part of the lock blade.
20
- the projecting part is formed by a screw,
and the maintaining means are formed by a nut;
-the insertion opening is an opening passing
25 through a wall of the annular shroud;
30
-the closure means comprise:
a cover able to cover the insertion
opening;
maintaining means able to maintain
the cover on the insertion opening.
According to a second aspect, the invention
relates to a downstream guide vane comprising an
annular shroud according to the invention.
10 According to a third aspect, the invention
relates to a method of mounting blades on an annular
shroud, said annular shroud comprising:
- on its internal surface, a peripheral annular
15 groove able to accept a plurality of blade roots;
- an insert-ion opening intended for inserting
blade roots into the annular groove;
- closure means for closing off the insertion
opening;
20 said method comprising the following steps:
- introduction of a blade root into the insertion
opening;
- sliding of the blade root in the annular
groove ;
302 5 - closure of the insertion opening.
Apart from the main characteristics that have
been mentioned in the preceding paragraph, the method
of mounting blades on an annular shroud according to
5 the invention may have the following complementary
characteristic:
the method is carried out by means of the
insertion opening, said insertion opening coming in
the form:
10 - either of two notches situated on either side
of the annular groove;
- or of an opening passing through a wall of
the annular shroud.
The invention and its different applications
15 will be better understood on reading the description
that follows and by examining the figures that
accompany it.
BRIEF DESCRIPTION OF DRAWINGS
2 0 The figures are presented by way of indication
and in no way limit the invention.
The figures show:
- in figure 1, already described, a threedimensional
view of a section of a
downstream guide vane according to a first
embodiment of the prior art;
- in figure 2, already described, a semiexploded
view of a part of a downstream guide
vane according to a second embodiment of the
prior art;
- in figure 3, already described, a sectional
view of the downstream guide vane of figure
2;
- in figure 4, a first schematic
representation of a section of an annular
shroud according to a first embodiment of the
invention;
- in figure 5, a second schematic
representation of a section of the annular
shroud of figure 4;
- in figure 6, a third schematic
representation of a section of the annular
shroud of figure 4;
- in figure 7, a fourth schematic
representation of a section of the annular
shroud of figure 4;
- in figure 8, a fifth schematic
representation of a section of the annular
shroud of figure 4;
- in figure 9, a synoptic of the steps of a
method of assembling blades on the annular
shroud of figures 4 to 8, according to an
example of implementation of the method
according to the invention;
- in figure 10, a schematic representation of
a section of an annular shroud according to a
second embodiment of the invention;
PCT/FR2012/050980
- in figure 11, a second schematic
representation of a section of the annular
shroud of figure 10;
- in figure 12, a third schematic
representation of a section of the annular
shroud of figure 10;
- in figure 13, a fourth schematic
representation of a section of the annular
shroud of figure 10;
- in figure 14, a synoptic of the steps of a
method of assembling blades on the annular
shroud of figures 10 to 13, according to an
example of implementation of the method
according to the invention.
DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE
INVENTION
Figures 4 and 8 are schematic representations of
a section of an annular shroud 40 according to a first
embodiment of the invention, said annular shroud 40
comprising:
-an internal surface 41;
-a peripheral annular groove 42;
-an insertion opening 43;
- an opening 44 ;
The annular shroud 40 is able to cooperate with a
plurality of blades 45, and with a lock blade 60
represented in figures 6 to 8. Each blade 45 comprises
an external root 46 and an internal root 47. The
annular groove 42 is positioned on the internal
surface 41 of the shroud 40, and is able to accept the
external roots 46 of the blades 45. The insertion
opening 43 is positioned on the annular groove 42 and
comprises two notches 48 and 49 situated on either
side of the annular groove 42. The insertion opening
43 is intended for inserting the external roots 46 of
the blades 45 into the annular groove 42. In fact,
each external root 46 is inserted into the insertion
opening 43, as represented in figure 5, then slid in
the annular groove 42 to be maintained there. To this
end, the annular groove 42 has a complementary shape
to that of the external roots 46 of the blades 45,
such that each external root 46 is maintained in the
annular groove 42 by simple shape cooperation.
Furthermore, the opening 44 is formed in the
centre of the insertion opening 43, and passes through
the shroud 40. In addition, the lock blade 60
comprises an external root 61 surmounted by a
projecting part 62, said projecting part 62 being able
to be inserted into the opening 44, as represented in
figure 8. The size of the external root 61 of the lock
blade 60 is equal to the size of the insertion opening
43. Thus, when the lock blade 60 is inserted into the
insertion window, the projecting part 62 is inserted
into the opening 44, and the blades 45 are maintained
blocked in the annular groove 42, as represented in
figure 7.
Moreover, as represented in figure 9, the
assembly of the blades 45 and the lock blade 60 on the
annular shroud 40 according to the first embodiment of
the invention is carried out according to a method 90
5 comprising the following steps:
- a first step 91 of inserting an external
root 46 of a blade 45 into the insertion
opening 43. The first step 91 is
represented in figure 5.
a second step 92 of sliding in the
annular groove 42 the external root 46, so
as to free the insertion opening 43;
- the first step 91 and the second step 92
being reiterated a number of times equal to
the number of external roots 46 of blades
45 to be positioned in the annular groove
42;
a third , step 93 of inserting the
external root 61 of the lock blade 60 into
the loading opening 43. The projecting part
62 is also inserted into the opening 44.
The third step 93 is represented in figures
7 and 8.
a fourth step 94 of fixing the external
root 61 of the lock blade 60 via fixation
means, not represented, for example a nut
able to screw onto the projecting part 62.
Figures 10 to 13 are schematic
30 representations of a section of an annular shroud
30
100 according to a second embodiment of the
invention. The annular shroud 100 comprises:
- an internal surface 110;
- an external surface 111;
- a peripheral annular groove 101;
- an insertion opening 102;
The annular shroud 100 is able to cooperate with
a plurality of blades 103. Each blade 103 comprises an
external root 104 and an internal root 105. The
10 annular groove 101 is positioned on the internal
surface 110 of the shroud 100, and is able to accept
the external roots 104 of the blades 103. The
insertion opening 102 is an opening formed on the
annular shroud 100 and passing through the wall of the
15 annular shroud 100. The insertion opening 102 is
intended for inserting the external roots 104 of the
blades 103 into the annular groove 101. In fact, each
blade 103 is inserted into the insertion opening 102
on the side of the external wall 111, as represented
20 in figure 12, then the external root 104 of the blade
103 is slid into the annular groove 102 to be
maintained there. In figure 13, a cover 106 closes the
insertion opening 102, preventing the insertion of new
blades and preventing the blades 103 from disengaging
25 from the annular groove 103. The cover 106 is fixed to
the insertion opening 102 via screws 107. The blades
103 are then maintained blocked in the annular groove
101.
Moreover, as represented in figure 14, the
30 assembly of the blades 103 and on the annular shroud
30
100 according to the second embodiment of the
WO 2012/153037 PCT/FR2012/050980
invention, is carried out according to a method 140
comprising the following steps:
- a first step 101 of insertion of a blade
103 into the insertion opening 102. The
first step 101 is represented'in figure 12.
- a second step 102 of sliding in the annular
groove 102 the external root 104, so as to
free the insertion opening 102;
- the first step 101 and the second step 102
being reiterated a number of times equal to
the number of external roots 104 of blades
103 to be positioned in the annular groove
102;
- a third step 103 of fixing the cover 106 on
the insertion opening, by means of screws
107.

CLAIMS
1 - Aircraft engine annular shroud (40, loo),
characterised in that it comprises:
5 - on its internal surface (41, 110), a
peripheral annular groove (42,101) able to accept a
plurality of blade roots (46, 104);
- an insertion opening (43, 102) for inserting
the blade roots (46, 104) into the annular groove (42,
- closure means (60, 106, 107) for closing off
the insertion opening (43,102) .
2 - Annular shroud (40, 100) according to the
preceding claim, characterised in that the insertion
15 opening (43, 102) is situated on the annular groove
(42, 101).
3 - Annular shroud (40) according to one of the
preceding claims, characterised in that the insertion
opening (43) does not pass through the annular shroud
20 (40) and in that it comprises two notches (48, 49)
situated on either side of the annular groove (42).
4 - Annular shroud (40) according to one of the
preceding claims, characterised in that the closure
means (60) comprise:
- a lock blade (60), said lock blade (60)
comprising a projecting part (62) able to pass
through an opening (44) formed in the insertion
opening (43);
5 - maintaining means able to fix themselves on
the projecting part (62) of the lock blade (60).
5 - Annular shroud (40) according to the
preceding claim, characterised in that the projecting
part (62) is formed by a screw (62), and in that the
10 maintaining means are formed by a nut.
6 - Annular shroud (100) according to one of
claims 1 or 2, characterised in that the insertion
opening (102) is an opening passing through a wall of
the annular shroud (100) .
15
7 - Annular shroud (100) according to the
preceding claim, characterised in that the closure
means (106, 107) comprise:
- a cover (106) able to cover the insertion
20 opening ( 102) ;
- maintaining means (107) able to maintain the
cover (106) on the insertion opening (102) .
8 - Aircraft engine downstream guide vane
25 characterised in that it comprises an annular shroud
(40, 100) according to one of the preceding claims.
30 9 - Method of mounting blades (45, 103) on an
aircraft engine annular shroud (40, 100) according to
one of the preceding claims, said annular shroud (40,
100) comprising:
-on its internal surface (41, llO), a
peripheral annular groove (42, 101) able to accept
5 a plurality of blade roots (46, 104) ;
-an insertion opening (43, 102) intended for
the insertion of blade roots (46, 104) into the
annular groove (42, 101) ;
-closure means (60, 106, 107) for closing off
10 the insertion opening (43, 102);
said method being characterised in that it
comprises the following steps:
- introduction of a blade root (46, 104) into
the insertion opening (43,102) ;
-sliding of the blade root (46, 104) in the
annular groove (42, 101) ;
- closure of the insertion opening (43, 102) .
10 - Method of mounting blades (45, 103) on an
aircraft engine annular shroud (40, 100) according to
20 the preceding claim, characterised in that the meth,od
is carried out by means of the insertion opening (43,
102), said insertion opening (43, 102) coming in the
form:
30
- either of two notches (48, 49) situated on
either side of the annular groove (42);
- or of an opening passing through a wall of the
annular shroud (100) .