Device for folding a rotorcraft rotor blade

The folding device comprises a fitting pivoting on a cuff about a folding axis which is offset laterally thanks to two lateral bearings of the fitting journal-mounted about bushings retained in lateral devises of the cuff and which are coaxial about the axis by pegs for centering a maneuvering actuator for maneuvering the fitting and the blade about the folding axis.

The invention relates to a device for folding a rotorcraft rotor blade, for 
a rotor of the type comprising a hub mounted so that it can rotate about 
an axis of the rotor, and to which each blade is connected by a linking 
member which is substantially radial with respect to the axis of the rotor 
and is itself connected to the hub by retaining and articulating means, 
each blade being secured by its root to a folding fitting mounted so that 
it can pivot about a folding axis on said linking member, between two 
positions, one of which is a flight position in which the fitting is fixed 
to said linking member in such a way that the blade has its longitudinal 
axis aligned with that of said linking member and is in the substantially 
radial extension of said linking member, and the other of which is a 
folded position, in which the fitting and the blade are pivoted about the 
folding axis substantially on one side of said linking member. 
Rotors of this type, with a device for folding each blade which includes a 
fitting which holds the blade by its root and, on the one hand, allows the 
blade to be rotated with the fitting about an axis which is stationary 
with respect to the linking member, which is the folding axis constituting 
a minimum link between the linking member and the fitting and, on the 
other hand allows active and reactive forces generated by folding or 
deploying (pivoting into its flight position) the blade to be transmitted, 
have already been used, especially as main rotors for helicopters on board 
ships, to allow automatic and non-manual folding and deployment of each 
blade using a maneuvering and locking actuator. Each actuator is mounted 
on a corresponding linking member and controls the locking of the blade in 
the deployed (flight configuration) position and in the folded position, 
as well as pivotings of the blade from one of its two limiting positions 
to the other about a pivot axis passing through the fitting and the 
linking member substantially at right angles to their longitudinal axis 
and retained by a nut itself retained by safety means which are mandatory 
for a vital link. 
The drawback of these known embodiments is that their pivoting link does 
not remain non-dismantleable during the operations of folding or of 
unfolding the blades and/or that the means of retaining the nut which 
provide a double safety feature are means whose mass and bulk, especially 
on each side of the linking member, are far from being negligible, and 
that their presence may hamper the blade-folding kinematics. 
The problem upon which the invention is based is that of overcoming at 
least one of the aforementioned drawbacks, and that of proposing a device 
for folding a blade which allows fixing with a double safety feature which 
remains non-dismantleable during the operations of folding and of 
unfolding the blades, and which furthermore has minimum bulk around the 
corresponding linking member and gives an important saving in weight for 
the flapping weight which each blade with its folding fitting and linking 
member and various components mounted on these elements constitute. 
Another object of the invention is to propose a blade-folding device which 
affords all the required safety without hampering the kinematics of 
folding or of unfolding the blades. 
To this end, the folding device of the invention is one which comprises a 
pivoting articulation which is offset laterally with respect to the 
longitudinal axis of the linking member, and by means of which the fitting 
is mounted so that it can pivot on the linking member about the folding 
axis, the articulation comprising, on the linking member just as on the 
fitting, two lateral bearings, secured respectively to one and the same 
side of the linking member and of the fitting and which are coaxial about 
the folding axis while at the same time being axially offset from one 
another along this folding axis, and two stepped bushings are mounted 
coaxially about the folding axis, each in respectively one of the two 
lateral bearings of the linking member and in respectively one of the two 
lateral bearings of the fitting, the two bushings also being mounted in 
opposition, each having a radially external step at its end pointing 
toward the other bushing, and facing a body retained on the linking member 
between the two bearings thereof and between the two bearings of the 
fitting, and a centering peg being mounted coaxially and retained axially 
in each of the two bushings in such a way that an end part of the peg 
projects axially out of the bushing beyond its step and is engaged and 
centered in respectively one of two corresponding centering housings of 
said body. 
The use of a pivoting articulation of this type, with two stepped bushings 
and two centering pegs effectively gives a fixing which is 
non-dismantleable during pivotings of the blade about the folding axis, 
without requiring the presence of a nut and of means of retaining the nut 
to provide a double safety feature, as was the case with the embodiments 
of the state of the art. 
Advantageously, each of the two lateral and coaxial bearings of the linking 
member is a double bearing formed by respectively one of two radially 
external and lateral pivot devises arranged on said linking member on each 
side of a plane at right angles to the folding axis and passing through 
the longitudinal axis of said linking member, and each of the two lateral 
and coaxial bearings of the fitting is journal-mounted between the two 
arms of respectively one of the two pivot devises and about respectively 
one of the two bushings which passes through coaxial passages formed in 
said arms of the corresponding pivot clevis, which improves safety and the 
balance of the folding device using a structure which is substantially 
symmetric on each side of the plane of rotation of the rotor. 
In an advantageously simple and economical way, each peg is retained 
axially in the corresponding bushing by a step of the peg in abutment 
against an internal step of said bushing under the thrust of a threaded 
plug screwed into a tapped bore formed in the end of the bushing on the 
opposite side to its step for bearing on the body. To guarantee that the 
peg is kept in the bushing, opposing the working-loose of the plug, the 
latter advantageously has passing through it substantially at right angles 
to the axis of the bushing and of the peg, a safety pin retained in 
cutouts formed at the periphery of the tapped bore of the bushing. Such a 
pin also makes it possible to check the presence of the peg in the 
bushing, because this peg is not visible when the assembly is mounted. 
Now, in the absence of the peg, the plug can be screwed further into the 
bore of the bushing so that the pin cannot be put in place in the cutouts 
of the bushing and passed through the plug. In order to make it easier to 
withdraw the peg, when dismantling the device, the end of each peg on the 
same side as the corresponding threaded plug exhibits a tapped blind axial 
bore intended to accommodate, by screwing, tooling for extracting the peg 
from the corresponding bushing. 
If sealing is required between the bushing and the peg, then at least one 
sealing ring may be mounted in the tapped bore of the bushing, around the 
threaded plug or, as an alternative, at least one annular seal is mounted 
between the bushing and part of the corresponding peg inside this bushing, 
and at least one other annular seal may be mounted, around the peg, in the 
bearing face of the radially external step of the bushing. 
In order favorably to fix the fitting to the linking member in the flight 
configuration, the fitting advantageously has, on the opposite side to its 
two lateral bearings at least one lateral lug which, in the flight 
position, points toward said linking member and is housed in a cavity open 
radially toward the outside on said linking member and is retained in said 
cavity by a catch of an actuator for locking the fitting on the linking 
member in the flight position. In order to obtain reliable operation using 
simple means, said cavity of the linking member is advantageously 
delimited between the two arms of a radially external locking clevis 
arranged laterally on said linking member and the two arms of which have 
passing through them coaxial passages of axis substantially at right 
angles to the folding axis and to the longitudinal axis of said linking 
member, said corresponding lug of the fitting extending in a plane 
substantially parallel to the common longitudinal axis of the fitting and 
of the blade and to the folding axis, and being pierced with a transverse 
passage of axis substantially at right angles to said longitudinal axis 
common to the blade and to the fitting and to said folding axis, said lug 
being retained in said locking clevis of the linking member by a locking 
rod which can be retracted axially by the locking actuator and is intended 
to pass through the coaxially-aligned passages of the locking clevis and 
of the lug, in the flight position. 
Furthermore, good dynamic balance of each flapping mass is ensured if the 
device advantageously comprises two locking lugs on the fitting, two 
locking devises on the linking member, as well as two locking rods of at 
least one electromechanical locking actuator arranged on the linking 
member between the two lateral bearings on one side and the two lateral 
locking devises on the other side of the longitudinal axis of said linking 
member, said lugs, devises and locking rods being arranged on each side of 
the plane at right angles to the folding axis and passing through the 
longitudinal axis respectively of the linking member and of the fitting 
and the blade. 
In the event of a mounting without maneuvering actuator, the body between 
the stepped bushings is tooling mounted on the linking member in such a 
way as to center it on the two pegs of the stepped bushings and possibly 
take up the forces acting upon the locking actuators. 
By contrast, in the event of mounting with maneuvering actuator, for a 
rotor in which the blades are folded and unfolded automatically, the body 
between the two stepped bushings is advantageously and specifically the 
body of the maneuvering actuator driving the fitting and the blade in 
pivoting about the folding axis, and at least partially housed in a part 
shaped as a cuff of the linking member, said maneuvering actuator 
comprising a moving output member mounted so that it can rotate about the 
folding axis and driving in coaxial rotation a driven member integral with 
the fitting. 
This moving output member of the maneuvering actuator may comprise a 
two-pronged fork, for example, maneuvered about the folding axis and 
between the two tines of which is driven a receiving finger integral with 
the fitting which is thus pivoted in folding and in unfolding. However, it 
is advantageous for this moving output member of the actuator to comprise 
a driving finger which is substantially radial with respect to the folding 
axis and for said driven member to be an aperture in the fitting, through 
which the driving finger passes. In a simple way, this finger may be a 
driving bushing equipped with at least one axial stop for retaining the 
bushing in the aperture of the fitting and which is fixed on a radial boss 
of an output rotary member of the drive actuator by a threaded central rod 
passing through the bushing partially fitted into said boss and screwed 
into said boss. In this case it is advantageous for the fitting to include 
a radially external clevis, the clevis bottom of which has said aperture, 
and in which the blade root is retained by two spindles which are 
substantially mutually parallel and parallel to the folding axis, one of 
which spindles is advantageously removable to give access to the aperture 
in the fitting and to the threaded rod for fixing the driving bushing by 
pivoting the blade on the fitting about the other spindle. 
In addition, if the blade is equipped with a device for discharging 
electrostatic charge and allowing lightning current to pass, which 
comprises an electrically conducting element visible on the radially 
internal end of the blade root facing the bottom of the outer clevis of 
the fitting, it is advantageous for the rod for fixing the driving bushing 
to have a head clamped against the bushing with the interposition of an 
electrically conducting washer equipped with a curved leaf spring kept in 
elastic contact with said electrically conducting element of the blade 
root, thus placed in electrical continuity with the linking member via the 
washer and the leaf spring, the fixing rod and/or the drive bushing, the 
boss and the output rotary member of the maneuvering actuator. 
In addition, to make it easier to mount and control the maneuvering and 
locking actuators on the linking member it is advantageous for these 
actuators to have a common body mounted on said linking member. 
Such a folding device has the attraction of combining the articulation of 
the folding fitting on the linking member and the linking of the fitting 
to the single actuator associated with the linking member for operating 
and locking the folding fitting.

FIG. 1 partially represents the head of a helicopter four-bladed main 
rotor, the tubular rotor mast 1 of which is integral, via its upper part, 
with a hub 2 rotating with it about the axis of rotation A--A of the 
rotor. The hub 2 is arranged as a radial (with respect to the axis A--A) 
plate with cavities having, for each of the four blades 3 of the rotor, 
one cavity 2a passing axially through a radially external part of the 
plate of the hub 2 in order to partially accommodate the means 4 for 
retaining and articulating to the hub 2 a member 5 for linking the hub 2 
to the corresponding blade 3, via a folding fitting 6 which retains the 
blade 3 and is mounted so that it can pivot about a folding axis B--B 
which is stationary on the member 5. 
As represented also in FIGS. 2a, 3a and 3b, the linking member 5, called a 
cuff in the rest of the description, because its central part 5a is 
tubular, is a member arranged substantially radially with respect to the 
axis A--A of the rotor, and the radially internal end part of which is 
arranged as an internal clevis 5b, the two parallel arms of which provide 
the link to the retaining and articulating means 4. 
In a known way, these means 4 (represented only in FIG. 1) consist of a 
laminated spherical stop comprising a central part 4a consisting of an 
alternating stack of layers of an elastically deformable material and of 
cups made of a rigid material in the shape of portions of spheres between, 
on the one hand, a radially internal armature 4b passing through the 
cavity 2a and fixed as a spacer piece between the arms of the internal 
clevis 5b by three bolted rods represented diagrammatically as 7 and, on 
the other hand, a radially external armature 4c straddling the radially 
external edge 2b of the corresponding cavity 2a of the hub 2 and fixed to 
this edge 2b of the hub by bolted rods (not represented). 
The blade root 3a is retained between the two parallel arms of a radially 
external clevis 6a of the fitting 6 by two spindles 8 which are mutually 
parallel and substantially parallel to the axis A--A of the rotor and are 
symmetric on each side of the common longitudinal axis X'--X' of the 
fitting 6 and of the blade 3, being substantially at right angles to this 
longitudinal axis X'--X', one of the spindles 8 being removable so that 
the blade 3 can be folded manually after the rotor has come to rest, by 
pivoting with respect to the fitting 6 about the other spindle 8 in order, 
as described herein below with reference to FIGS. 3a, 3b and 5, to access 
the members for coupling a maneuvering actuator to the fitting 6 for 
driving the latter in rotation about the folding axis B--B. 
For its pivoting connection to the cuff 5, and as may be seen in FIGS. 2a, 
3a, 3b and 4, the fitting 6 has, on the opposite side to the radially 
external clevis 6a along its longitudinal axis X'--X', two lateral 
bearings 9 and 10 which are offset laterally on one and the same side of 
the axis X'--X' on the fitting 6 and project axially on the opposite side 
to the clevis 6a. The bearings 9 and 10 each consist of respectively one 
of two generally cylinder-shaped lugs which are mutually parallel and 
parallel to the plane at right angles to the folding axis B--B and passing 
through the longitudinal axis X'--X', called the plane of rotation of the 
blade 3, the two cylindrical lugs being substantially symmetric on each 
side of this plane of rotation, spaced apart along the folding axis B--B 
and having passing through them cylindrical bores of the same diameter and 
coaxial about the axis B--B so as to form an upper bearing 9 and a lower 
bearing 10. 
The cuff 5 also has two bearings 11, 12 which are coaxial about the folding 
axis B--B and are offset laterally on the cuff 5 on the same side of its 
longitudinal axis X--X. The two bearings 11, 12 of the cuff 5 are spaced 
apart along the axis B--B and substantially symmetrical with one another 
on each side of the plane at right angles to the axis B--B and passing 
through the longitudinal axis X--X of the cuff 5 and which is the plane of 
rotation of the blade 3 when the latter and the fitting 6 are locked in 
the flight configuration on the cuff 5 and occupy the position of FIG. 1. 
Each of the bearings 11 and 12 of the cuff 5 is a double bearing formed by 
one respectively of two radially external and lateral pivot devises each 
consisting of an upper arm 11a or 12a and of a lower arm 11b or 12b which 
projects substantially radially outward on the radially external part of 
the cuff 5 (with respect to the rotor axis A--A), spaced apart along the 
axis B--B and parallel to one another and to the plane of rotation of the 
blade, the four arms 11a, 11b, 12a and 12b of the devises having passing 
through them cylindrical bores which are coaxial about the axis B--B and 
have substantially the same diameter as the bores of the bearings 9 and 10 
of the fitting 6 (see FIG. 4). 
The cuff 5 thus has two lateral and coaxial double bearings of which one 
11a, 11b is an upper one and the other, 12a, 12b is a lower one on its 
radially external part. 
As may be seen in FIGS. 3b and 4, each upper lateral bearing 9 or lower 
lateral bearing 10 of the fitting 6 is journal-mounted between the two 
arms 11a and 11b or 12a and 12b of the lateral and radially external upper 
pivot clevis 11 or lower pivot clevis 12, about a bushing 14 retained 
coaxially around the folding axis B--B in the bores of the corresponding 
two arms 11a and 11b or 12a and 12b and belonging respectively to the 
upper subassembly 13a or lower subassembly 13b which assemblies together 
constitute the folding pivot, as represented in FIG. 6. 
In this example, the two subassemblies 13a and 13b are identical and 
mounted in opposition, each of them essentially comprising the bushing 14 
and a centering peg 15. Each of the bushings 14 is a cylindrical tubular 
bushing of circular section, the inside and outside diameters of which are 
calibrated, over most of its length, from an end pointing toward the other 
bushing 14 and surrounded by a radially external step 14a, as far as the 
opposite end 14b of frustoconical external shape converging in the 
direction away from the step 14a. Each peg 15 is also calibrated and has a 
cylindrical end part 15a allowing the peg 15 to be mounted coaxially 
inside the bushing 14, and each peg 15 is retained axially in the 
corresponding bushing 14 by a radially external step 15b at its opposite 
end to the cylindrical end piece 15a, and by means of which step the peg 
15 is pressed into abutment against a radially internal step 14c by means 
of which a tapped bore formed coaxially in the frustoconical end part 14b 
connects with the smaller-diameter central bore of the bushing 14. The peg 
15 is held pressed by its step 15b against step 14c of the bushing 14 by a 
threaded plug 16 screwed into the tapped bore of the bushing 14 and in 
such a way that an end part of the cylindrical end piece 15a of the peg 15 
is visible projecting axially out of the bushing 14 beyond its step 14a to 
act as a centering end piece engaged in one respectively of two 
corresponding centering houses formed on the opposing faces of a body 
opposite which the two bushings 14 exhibit their radially external 
shoulder 14a and which, as represented in FIGS. 2a, 3a, 3b and 4, is the 
lateral part 18a of the body 18 of a combined actuator for maneuvering the 
fitting 6 and the blade 3 in pivoting about the folding axis B--B and for 
locking the fitting 6 on the cuff 5 in the flight configuration. As may be 
seen in FIGS. 3b and 4, this lateral part 18a of the actuator body 18 is 
retained on the cuff 5 between the pivot devises 11 and 12 of the cuff 5 
and between the bearings 9 and 10 of the fitting 6, by being centered with 
respect to the folding axis B--B by the two subassemblies 13a and 13b 
forming the folding pivot. In these pivot sub-assemblies 13a and 13b 
mounted in opposition, the stepped bushings 14 by means of their outside 
diameter provide relative centering of the cuff 5 and of the fitting 6, 
and their radially external step 14a is preferably spaced a small axial 
clearance 49 away from the body 18a after the actuator body 18 has been 
mounted on the cuff 5 in order to avoid a statically-redundant mounting of 
the actuator body 18 which would be obtained if there were contact between 
the bushings 14 and the body 18a because the actuator body 18 is already 
positioned by the latches described herein below. For greater clarity, 
this clearance 49 between the steps 14a and the body part 18a is 
exaggerated in FIG. 4. Inside the bushings 14, the concentric pegs 15, 
after their centering end piece 15a has been inserted into the 
corresponding housing of the part 18a of the actuator body 18, provide 
centering of this body 18 with respect to the folding axis B--B, and 
positioning of this body in the plane between the steps 14a of the two 
bushings 14, the remaining angular freedom of the actuator body 18 being 
taken up and blocked by two steps 18b of the central part 18c of the 
actuator against locking devises of the cuff 5, as well as by a lateral 
blocking finger 18e of the actuator on the opposite side to its part 18a 
with respect to the axis X--X and which is housed between these locking 
devises as described herein below. 
In order to counter any working-loose of the threaded plugs 16 which, in 
the example of FIG. 6, have a tightening head with a male and hexagonal 
shape 16a, a pin 17 is introduced into a bore which passes through the 
plug 16 substantially at right angles to the axis of the bushing 14 and of 
the peg 15 and is retained in stop cutouts 14d formed in the frustoconical 
part 14b of the bushing 14, at the periphery of its tapped bore. This 
safety pin 17 guarantees that the peg 15 is held in the bushing 14 and 
makes it possible to check the presence of the peg 15 which is invisible 
when each subassembly 13a or 13b is mounted (see FIG. 3b and 4). In the 
absence of the peg 15, if the plug 16 is screwed in until it comes into 
contact with the step 14c of the bushing 14, then the pin 17 can no longer 
be fitted in the plug 16. 
In order to extract the peg 15 from the bushing 14, if need be, the end of 
the peg 15 on the same side as its step 15b has a tapped blind axial bore 
15c intended to have extraction tooling (not represented) screwed into it. 
The alternative form of pivot subassembly in FIG. 7 is intended to provide 
sealing on the one hand, between the peg 15 and the bushing 14 and, on the 
other hand, between the folding pivot and the actuator body 18. This 
alternative form therefore differs from each subassembly 13a or 13b of 
FIG. 6 only in the presence of a first 0-ring seal 19 in an annular groove 
of the cylindrical end piece part 15a of the peg 15 which remains inside 
the bushing 14 to provide sealing between the latter and the end piece 
15a, and by the presence of a second 0-ring seal 20 in a groove formed in 
the bearing face of the radially external step 14a of the bushing 14 
around the centering end piece 15a to provide sealing between the bushing 
14 and the part 18a of the actuator body 18. Each of these 0-rings 19 and 
20 may or may not be bonded into the annular groove which accommodates it. 
In the alternative form of pivot subassembly in FIG. 8, sealing on the 
inside of the bushing 14 is provided by an annular ring 21, for example of 
the type marketed under the trade name "NYLSTOP" mounted in the tapped 
bore of the bushing 14 around the threaded plug 16' which, in this 
alternative form, has a tightening head 16' a with a hexagonal female 
socket. 
In order to lock the fitting 6 in the flight position (FIG. 1), the cuff 5 
also exhibits, on the opposite side to the pivot clevises 11 and 12 with 
respect to its longitudinal axis X--X, and as may be seen in FIGS. 2a, 3a, 
3b and 4, two locking devises 22 and 23 which are also lateral devises 
projecting substantially radially outward on the radially external end 
part of the cuff 5, but the two internal arms 22a or 23a and external arms 
22b or 23b of which extend substantially along planes which are at right 
angles to those of the arms 11a, 11b, 12a, 12b of the pivot devises 11 and 
12 on the other side of the cuff 5. The arms 22a and 22b or 23a and 23b 
have passing through them coaxial bores 24 or 25 the axis of which is at 
right angles both to the folding axis B--B and to the longitudinal axis 
X--X of the cuff 5. 
Likewise, the fitting 6 has, on the opposite side to its lateral bearings 9 
and 10 with respect to its longitudinal axis X'--X', two lateral lugs 26 
and 27 which project parallel to the axis X'--X', on the opposite side to 
the clevis 6a and extend in planes substantially at right angles to those 
of the bearings 9 and 10, that is to say parallel both to the axis B--B 
and to the axis X'--X'. Each of the lugs 26 and 27 is pierced with a 
transverse bore 28 or 29 of axis substantially at right angles to the axis 
X'--X' and to the axis B--B, and the locking lugs 26 and 27 and devises 22 
and 23 are arranged substantially symmetrically on each side of the plane 
of rotation of the blade 3, so that in the unfolded position (FIGS. 1 and 
4), each lug 26 or 27 points toward the cuff 5 and is housed in the 
cavity, which is open substantially radially toward the outside, of the 
cuff 5 and delimited between the two arms 22a and 22b or 23a and 23b of 
the corresponding locking clevis 22 or 23 and so that when the ends of the 
internal arms 22a and 23a come into abutment against the bottom of the 
clevis 6a of the fitting 6, the transverse bores 28 and 29 are aligned 
respectively with the transverse bores 24 and 25 respectively of the 
devises 22 and 23 (see FIG. 1). in this position, each lug 26 or 27 can be 
retained in the corresponding locking clevis 22 or 23 by a cylindrical 
locking rod 30 or 31 (FIG. 4) passing through the aligned bores 24 and 28 
or 25 and 29 and which can be retracted axially into an upper stage 32 or 
lower stage 33 of a locking actuator which is, for example, an 
electromechanical actuator, housed in the actuator body 18. Each locking 
rod 30 or 31 is integral with a slide 34 or 35 driven in translation into 
the upper stage 32 or lower stage 33 of the locking actuator from one of 
two limiting positions to the other, one of which positions is the locked 
position of FIG. 4 for flight and the other the unlocked position 
releasing the lug 26 or 27 and in which the locking rod 30 or 31 is 
retracted into the corresponding locking clevis internal arm 22a or 23a, 
whereas for mounting the actuator in the cuff 5, the rod 30 or 31 is 
completely retracted into the actuator body 18, the locking actuator 
simultaneously shifting the two locking rods 30 and 31. As may also be 
seen in FIG. 2b, the locking actuator, which may be an electromechanical 
actuator of any suitable type known for causing translational motion of 
the rods 30 and 31 with their slide 34 and 35 is housed in a central part 
18c of the actuator body 18 which central part is housed between the pivot 
devises 11 and 12 on one side of the cuff 5 and between the locking 
devises 22 and 23 on the other side of this cuff 5 (see FIGS. 3a, 3b and 
4). This central part 18c of the actuator body 18 exhibits the two steps 
18b mentioned herein above, bearing against the internal arms 22a and 23a 
of the locking devises 22 and 23 in order to block in terms of rotation on 
the cuff 5 the actuator body 18 which also comprises, on the opposite side 
to its lateral part 18a which interacts with the bushings 14 and centering 
pegs 15 as described herein above, a parallelepipedal blocking finger 18e 
between the two devises 22 and 23 and a substantially cylindrical radially 
internal part 18b which is housed in the tubular part 5a of the cuff 5. 
The maneuvering actuator also housed in the body 18 makes it possible, when 
the locking actuator has unlocked the lugs 26 and 27 of the fitting 6 by 
retracting the latch rods 30 and 31, to pivot the fitting 6 and the blade 
3 by a maximum angle of, for example, 135.degree. about the axis B--B of 
the pivot articulation which is offset laterally with respect to the 
longitudinal axis X--X of the cuff 5 between the flight position (FIG. 1) 
in which the common longitudinal axis X'--X' of the fitting 6 and the 
blade 3 is aligned with that X--X of the cuff 5, and the blade 3 and the 
fitting 6 are in the radial extension of the cuff 5, and the folded 
position in which the blade 3 and the fitting 6 are folded back by 
pivoting on that side of the cuff 5 toward which the folding articulation 
is offset (see FIG. 3b). 
The maneuvering actuator is, for example, an electromechanical actuator 
including a geared motor unit, the electric motor of which is housed in 
the cylindrical internal part 18d of the actuator body 18 which part is 
housed in the tubular central part 5a of the cuff 5, the reduction stage 
on the output side of the electric motor of the maneuvering actuator being 
a mechanical stage with two pinions, for example, and housed in the 
central part 18c of the body 18 between the two locking stages 32 and 33 
and in the lateral part 18a of this actuator body 18. 
As represented diagrammatically in FIGS. 4 and 5, this mechanical stage 
comprises a driving pinion 36 mounted so that it can rotate in the central 
part 18c of the actuator body 18 and driven by the electric motor, and in 
mesh with a driven pinion 37 which constitutes the rotary output member of 
the maneuvering actuator and is mounted so that it can rotate in the 
lateral body part 18a. By virtue of the fact that this part 18a is 
centered by the pegs 15 of the bushings 14 of the pivot, this output 
pinion 37 is driven in rotation about the folding axis B--B. The output 
pinion 37 has a radial boss 38 which projects through an opening made in 
the body part 18a (see FIGS. 3a and 3b) revealing part of the radially 
external periphery of the pinion 37. This boss 38 supports a driving 
finger 39 which is radial with respect to the folding axis B--B and by 
means of which the pinion 37 and the boss 38 drive in coaxial rotation an 
aperture 40 carried by the bottom of the clevis 6a of the fitting 6 and 
projecting on the side of the cuff 5. The driving finger 39 comprises a 
bushing 41 which passes through the aperture 40 of the fitting 6 and is 
fitted snugly inside a radial bore of the boss 38, against which it bears 
via a radially external step, and the bushing 41 is fixed to the boss 38 
by a central rod 42 which passes through it and is screwed into the boss 
38. At its end which is not engaged in the boss 38, the bushing 41 has a 
second radially external step 43 forming a stop for axially retaining the 
bushing 41 in the aperture 40 of the fitting 6 so as to obtain permanent 
coupling between the fitting 6 and the output pinion 37 of the actuator in 
order to guarantee the rotational driving of the fitting 6 and therefore 
of the blade 3 by this pinion 37. 
To mount and dismantle the driving finger 39 in order to couple or uncouple 
the fitting 6 and the pinion 37, the fitting 6 is locked on the cuff 5 by 
its lugs 26 and 27, then the spindle 8 for retaining the blade root 3a in 
the fitting 6 on the same side as the locking lugs 26 and 27 is withdrawn 
and the blade 3 is pivoted about the other spindle 8 on the fitting 6, 
which makes it possible to access the bottom of the clevis 6a and the 
aperture 40 of the fitting 6 in order to fit the driving bushing 41 in the 
aperture 40 and in the boss 38 then screw the threaded fixing rod 42 in 
or, conversely, to withdraw this rod 42 and extract the bushing 41, 
possibly using a threaded tool screwed into an extraction tapping in the 
end of the central bore of the bushing 41 on the same side as its step 43. 
In addition, screwing in the rod 42 makes it possible to clamp down against 
the bushing 41 an electrically conducting metal washer 44 which is 
equipped laterally with a spring leaf 45 bent into the shape of a crook 
held in elastic contact against part 46a of a tape 46 made of copper or 
some other electrically conducting metal which runs around the lateral 
face of the blade root 3a and extends along the span of the blade 3 for 
removing electrostatic charge and allowing lightning currents to pass, the 
part 46a of this tape 46 known as metallization tape being visible on the 
radially internal end of the blade root 3a, directly facing the bottom of 
the clevis 6a in which this blade root 3a is retained by the spindles 8. 
Thus electrical continuity between the metallization tape 46 of the blade 3 
and the cuff 5 is ensured by means of the spring leaf 45, the washer 44, 
the bushing 41 and the rod 42, the boss 38 and the pinion 37 and the 
actuator body 18 fixed to the cuff 5, which are electrically conducting 
metallic elements, the electrical continuity between the cuff 5 and the 
hub 2 being provided by other means which are known for this purpose. 
As regards mounting the assembly it is necessary, first of all, to offer up 
the bearings 9 and 10 of the fitting 6 into the pivot devises 11 and 12 of 
the cuff 5 (see FIG. 2a) then to slip the two bushings 14 in opposition 
into the aligned bores of the bearings 9 and 10 and of the arms of the 
devises 11 and 12, the pegs 15 of the bushings 14 being retracted or 
absent. Spacer tooling is then mounted between the steps 14a of the two 
bushings 14 in order to hold them in position and prevent the upper 
bushing 14 from dropping out. As an alternative, and instead of the spacer 
tooling, a circlip 47 (see Figure 10a) may be mounted in an external 
peripheral annual groove 48 around the base of the frustoconical end part 
14b of at least the upper bushing 14 or of each bushing 14 and bearing 
against the axially external face respectively of the upper arm 11a of the 
upper clevis 11 or of the lower arm 12b of the lower clevis 12 in order 
axially to retain the corresponding bushing 14 in an appropriate position 
for mounting the actuator body part 18a between the bushings 14 with axial 
clearance 49 between the steps 14a of the bushings 14 and this body part 
18a. 
Axial retention at least of the upper bushing 14 to prevent it from 
dropping out and allowing the actuator body to be mounted by giving the 
same clearance 49 between the step 14a and the body part 18a may be 
provided according to the alternative form of Figure 10b using a plug 50 
which is used as tooling, screwed via its central part 50a which projects 
axially and is externally threaded, into the tapped bore provided in the 
frustoconical end part 14b of the bushing 14 for the threaded plug 16, and 
bearing via its annular peripheral part 50b which also projects axially 
against the external face of the upper arm 11a of the upper clevis 11 of 
the cuff 5, the internal face of the lower arm 11b of this same clevis 11 
bearing axially against the corresponding step 14a, in all the examples of 
mounting. The maneuvering and locking actuators housed in their body 18 
(FIG. 2b) are offered up to the cuff 5 in such a way as to insert the 
cylindrical part 18d of the body 18 into the tubular part 5a of the cuff 
5, the lateral part 18a of the body 18 between the two bushings 14, 
possibly in place of the spacer tooling, the central part 18c of the body 
18 between the pivot devises 11 and 12 and the locking devises 22 and 23 
of the cuff 5, and the finger 18e between the devises 22 and 23 as 
mentioned herein above (see FIG. 3a). The centering pegs 15 are then 
pushed into the bushings 14 in order to introduce the centering end pieces 
15a into the receiving housings of the lateral part 18a of the body 18 in 
order to center this body 18 in such a way that the output pinion 37 is 
indeed driven in rotation about the folding axis B--B. The plugs 16 are 
then screwed with the given tightening torque and the pins 17 put in 
place. The locking rods 30 and 31 in the bores 24, 25 and 28, 29 of the 
locking devises 22 and 23 and of the lateral lugs 26 and 27 act as 
centering in the direction of the folding axis (axial direction), and this 
is allowed because of the clearances 49 between the steps 14a of the 
bushings 14 and the part 18a of the actuator body, in order to avoid a 
statically-redundant mounting of this body. 
Next, as described above, the blade 3 is pivoted with respect to the 
fitting 6, by removing a spindle 8 in order to couple the fitting 6 to the 
boss 38 of output pinion 37 by virtue of the driving finger 39, bushing 41 
and threaded rod 42, as described herein above (FIG. 3b). 
The folding device thus produced allows safety fastening of the fitting 6 
to the cuff 5, this fastening remaining non-dismantleable during maneuvers 
about the folding axis B--B. What is more, this device is compact, 
relatively lightweight, and does not in any way hamper the kinematics of 
folding and unfolding the blade. 
If it is assumed that the front of the helicopter is to the front in FIG. 
1, the folding device of FIGS. 2a, 3a, 3b, 4 and 5 equipped with the 
actuator of FIG. 2b makes it possible to fold the blade 3 to the left 
(with respect to the longitudinal axis of the helicopter) and toward the 
rear of the helicopter. 
This may be necessary in respect of two of the four blades of a four-bladed 
main rotor at rest on a helicopter loaded on board a ship, the other two 
blades of which have also to be folded toward the rear of the helicopter, 
but on the right-hand side thereof. 
To maneuver and lock each of these two blades 3' to be folded back on the 
right-hand side, the device of FIG. 9a equipped with the actuator 18' of 
FIG. 9b is used, this device and this actuator 18' differing from those of 
FIGS. 2a and 2b only in the way that they are symmetric with respect to 
the plane passing through the longitudinal axis X--X of the cuff or X'--X' 
of the fitting and of the blade and parallel to the folding axis B--B, 
which means that the analogous components are denoted in FIGS. 9a and 9b 
by the same numerical references as respectively in FIGS. 2a and 2b, but 
with a prime symbol added. 
In FIG. 9a, it may thus be seen that the two lateral pivot devises 11' and 
12' and the two lateral locking clevises 22' and 23' of the cuff 5' occupy 
lateral positions which are the reverse of those of the pivot devises 11 
and 12 and locking devises 22 and 23 of the cuff 5 of FIG. 2a. Likewise, 
on the fitting 6', the lateral positions of the bearings 9' and 10' and of 
the locking lugs 26' and 27' are the reverse of those of the bearings 9 
and 10 and of the lugs 26 and 27 of the fitting 6 of FIG. 2a, but their 
interaction with the corresponding devises of the cuff 5' takes place in 
the same way, particularly with the aid of identical pivot subassemblies 
with bushings 14. In consequence, the combined actuator 18' of FIG. 9b has 
a symmetric structure capable, with its internal cylindrical part 18'd 
which is housed in the tubular part 5'a of the cuff 5', and the two 
locking stages 32' and 33' of its central part 18'c, of blocking the lugs 
26' and 27' of the fitting 6' in the locking devises 22' and 23' of the 
cuff 5', its lateral blocking finger 18'e being housed between the two 
devises 22' and 23' of the cuff 5', and its lateral part 18'a in which the 
output pinion 37' turns driving, in rotation about the folding axis, the 
boss 38' intended to support a finger for driving the fitting 6' and the 
blade 3' held by its root 3'a in the clevis 6'a of this fitting 6' for the 
maneuvers of folding and unfolding the blade 3' as described hereinabove 
with respect to the blade 3'. Indeed, the driving link between the boss 
38' of the pinion 37' and the fitting 6' may be achieved in an identical 
way, using a bushing fitted snugly and fixed by a threaded central rod 
inside the boss 38', this bushing passing through an aperture in the 
bottom of the clevis 6'a of the fitting 6' and being retained axially in 
this aperture in order to drive the fitting 6' and the blade 3' in 
rotation.