U.S. patent application number 10/375707 was filed with the patent office on 2004-02-12 for method and apparatus for folding/unfolding the blades of a rotary-wing aircraft rotor.
Invention is credited to Cayol, Marcel, Romani, Michel.
Application Number | 20040026564 10/375707 |
Document ID | / |
Family ID | 27763699 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026564 |
Kind Code |
A1 |
Romani, Michel ; et
al. |
February 12, 2004 |
METHOD AND APPARATUS FOR FOLDING/UNFOLDING THE BLADES OF A
ROTARY-WING AIRCRAFT ROTOR
Abstract
To fold/unfold blades of a rotor, at least one variable-length
linear actuator is removably attached to two blades locked in the
flight position. A first blade is unlocked, and the actuator is
actuated to vary its length and bear against the other blade which
remains locked. This causes the first blade to pivot about its
pivot axis and move to a folded position where it is again locked.
The other blade is then unlocked and the actuator once again
actuated but this time bearing against the first blade. In this way
the other blade pivots into the folded position where it is again
locked. The two locked folded blades may be connected to each other
by a link rod. Rotors with three blades, four blades, five and six
blades can be folded/unfolded with only two actuators.
Inventors: |
Romani, Michel; (Vitrolles,
FR) ; Cayol, Marcel; (Velaux, FR) |
Correspondence
Address: |
STURM & FIX LLP
206 SIXTH AVENUE
SUITE 1213
DES MOINES
IA
50309-4076
US
|
Family ID: |
27763699 |
Appl. No.: |
10/375707 |
Filed: |
February 27, 2003 |
Current U.S.
Class: |
244/17.11 |
Current CPC
Class: |
B64C 27/50 20130101 |
Class at
Publication: |
244/17.11 |
International
Class: |
B64C 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2002 |
FR |
FR 02/03013 |
Claims
1. A method of folding/unfolding at least one blade of a
multi-bladed rotor of a rotary-wing aircraft, with at least a first
blade being connected to a hub of the rotor by a coupling
comprising a pivotal connection defining a pivot axis and a
releasable connection, release of which allows its blade to be
pivoted about its pivot axis between an unfolded position and a
folded position, the method comprising steps: (a) removably
attaching at least one variable-length linear actuator to the first
blade and a second blade, each locked in a fixed position with
respect to the hub which is itself locked stationary; (b) releasing
the first blade from its fixed position with respect to the hub;
(c) actuating the linear actuator to vary its length and bear
against the second blade, thereby pivoting the first blade about
its pivot axis to a new position with respect to the hub; and (d)
locking the first blade in the new position.
2. A method according to claim 1, wherein the second blade is
connected to the hub of the rotor in an analogous way to the first
blade, and wherein the method further comprises after step (d)
steps: (e) releasing the second blade from its fixed position with
respect to the rotor; (f) actuating the linear actuator to vary its
length and bear against the first blade, thereby pivoting the
second blade about its pivot axis to a new position with respect to
the hub; and (g) locking the second blade in its new position.
3. A method according to claim 2, further comprising before step
(f): removably attaching a link rod to the first blade locked in
its new position and to a third blade whose position is fixed with
respect to the hub, whereby under subsequent actuation the linear
actuator bears against the first and third blades together when the
second blade pivots about its axis.
4. A method according to claim 2, wherein the multi-bladed rotor is
a two-bladed rotor with the blades being foldable towards a rear
part of the rotary-wing aircraft, and wherein the method further
comprises: locking the stationary rotor with the first and second
blades aligned substantially transversely to a longitudinal axis of
the rotary-wing aircraft; and attaching pivotally the linear
actuator to a forward part of one blade and a rearward part of the
other blade such that the linear actuator extends rearwardly of a
line passing through the pivot axes of the two blades, and such
that the linear actuator is disposed rearwardly of the hub of the
rotor.
5. A method according to claim 4, wherein the linear actuator is
attached to the blades via two securing brackets, one projecting
forwardly of a leading edge of one blade and another projecting
rearwardly of a trailing edge of the other blade.
6. A method according to claim 1, wherein the multi-bladed rotor is
a three-bladed rotor, with the blades being foldable towards a rear
part of the rotary-wing aircraft, and with a third blade connected
to and fixed in position with respect to the hub of the rotor in an
analogous way to the first blade, and wherein the method further
comprises: locking the stationary rotor with the second blade
aligned over the rear part of the rotary-wing aircraft; removable
attaching a variable-length linear actuator to the second and third
blades; releasing the third blade from its fixed position;
actuating the linear actuator to vary its length and pivot the
third blade about its pivot axis to a new position with respect to
the hub; and locking the third blade in its new position.
7. A method according to claim 6, wherein the linear actuator
between the first and second blades and the linear actuator between
the third and second blades are attached substantially to a common
attachment point on the second blade, the common attachment point
being substantially aligned with a longitudinal axis of the second
blade and radially outwardly of any pivot axis the second blade has
relative to an axis of rotor rotation.
8. A method according to claim 2, wherein the multi-bladed rotor
has at least four blades, with the blades being foldable towards a
rear part of the rotary wing aircraft, and with a third blade and a
fourth blade each connected to and fixed in position with respect
to the hub of the rotor in an analogous way to the first blade, and
wherein the method further comprises: locking the stationary rotor
with the first and second blades disposed on one side of the
rotary-wing aircraft and the third and fourth blades disposed on an
opposite side, with the first blade rearwardly of the second blade
and the third blade rearwardly of the fourth blade; carrying out
steps (a) to (d) so that the new position of the first blade is
over the rear part of the rotary wing aircraft; repeating steps (a)
to (d) for the third blade in place of the first blade so that the
third blade is positioned adjacent the first blade; carrying out
steps (e) to (f) for the second blade so that the second blade is
positioned adjacent the first blade; repeating steps (e) to (f) for
the fourth blade in place of the second blade so that the fourth
blade is positioned adjacent the third blade.
9. A method according to claim 8, further comprising connecting the
first blade to the third blade with a removable link when the first
blade is in the new position and the third blade is positioned
adjacent to it.
10. A method according to claim 8, wherein the stationary rotor is
locked with one blade positioned over the rear part of the rotary
wing aircraft when the multi-bladed rotor has an odd-number of
blades.
11. A method according to claim 8, wherein the multi-bladed rotor
has more than five blades, and wherein the method further
comprises: removing the linear actuator between the first and
second blades once pivoted respectively to the new position over
the rear part of the rotary wing aircraft and adjacent to the new
position; removably attaching the linear actuator between the
second and a fifth blade connected to and fixed in position with
respect to the hub of the rotor in an analogous way to the first
blade; and repeating steps (e) to (f) for the fifth blade in place
of the second blade so that the fifth blade is positioned adjacent
the second blade.
12. A method according to claim 1, wherein the first blade is
locked in the folded position by attaching said blade to a rear
part of the rotary wing aircraft by at least one attachment tool
selected from the group consisting of a pole, a folding pole,
strapping and a support.
13. Apparatus for folding/unfolding at least one blade of a
multi-bladed rotor of a rotary-wing aircraft, with at least a first
blade being connected to a hub of the rotor by a coupling
comprising a pivotal connection defining a pivot axis and a
releasable connection, release of which allows its blade to be
pivoted about its pivot axis between an unfolded position and
folded position, the apparatus comprising: at least one variable
length, removable linear actuator configured to be removably
attached to two adjacent blades of the rotor and to exert forces in
either direction along its longitudinal axis on two blades
connected by the linear actuator; and connectors for removably
attaching the linear actuator to two adjacent blades, each
connector comprising an end fitting integral with the linear
actuator and an attachment device configured for attachment to one
blade, the end fitting and the attachment device being releasably
interconnectable.
14. Apparatus according to claim 13, comprising two substantially
identical linear actuators, each having at each of its two
longitudinal ends an end fitting for attaching removably to at
least one attachment device configured for attachment to a
blade.
15. Apparatus according to claim 13, further comprising at least
one substantially rectilinear removable link rod configured for
removable attachment to two blades via releasable connectors at
opposed ends of the link rod.
16. Apparatus according to claim 13, wherein the at least one
removable linear actuator comprises at least one double-acting
linear jack comprising at least one rectilinear rod configured to
move a either direction in a jack body into which said rod is
partially inserted and drivable by a drive device housed in the
body.
17. Apparatus according to claim 16, wherein said jack is one of
mechanical and electromechanical with the body housing a mechanical
drive device which is configured to multiply forces imparted to the
rod.
18. Apparatus according to claim 17, wherein the mechanical drive
device comprises at least one stage of reduction gearing comprising
at least one input shaft configured to be driven from outside the
jack by one of a mechanical or electromechanical device.
19. Apparatus according to claim 18, wherein the at least one
reduction stage comprises gearing selected from the group
consisting of a worm screw, a rack-and-pinion combination and a
gearwheel-pinion combination.
20. Apparatus according to claim 18, wherein the mechanical drive
device comprises a worm screw engaged with the rod which is
tubular, the worm screw partially extended into the tubular rod,
with the worm screw being rotatably driven by an output gearwheel
of a pair of bevel gears, an input pinion of which is integral with
the input shaft.
21. Apparatus according to claim 17, wherein the jack further
comprises a manually operated mechanism for disengaging the rod
from the mechanical drive device and allowing rapid adjustment of
the jack to any desired length.
22. Apparatus according to claim 16, wherein the jack further
comprises a shock absorber in series with at least one of the rod,
the body and one end fitting of the jack.
23. Apparatus according to claim 13, wherein at least one connector
for removably attaching the linear actuator to adjacent blades,
comprises at least one ball joint for connecting at least one end
fitting to its respective attachment device.
24. Apparatus according to claim 23, wherein the at least one ball
joint comprises at least one swivel ball of at least one ball joint
end fitting for cooperating with an attachment pin of its
respective attachment device.
25. Apparatus according to claim 23, wherein the at least one ball
joint comprises: at least one swivel ball supported by the
attachment device so that in use the swivel ball projects above a
root portion of its blade; and at least one sleeve of an elbow end
fitting for removably attaching the linear actuator, the at least
one sleeve being configured to fit and be releasably locked onto
said swivel ball.
26. Apparatus according to claim 25, wherein the at least one
swivel ball is supported by a support retained by at least one pin
or screw in at least one insert of the attachment device which is
integrated into a root portion of its blade.
27. Apparatus according to claim 25, wherein the at least one
swivel ball is supported by a support integrated as an insert in a
root portion of its blade.
28. Apparatus according to claim 23, wherein at least one
attachment device comprises at least one attachment element fitted
by a removable attachment into at least one insert integrated into
a root portion of the blade.
29. Apparatus according to claim 23, wherein at least one
attachment device is configured to be removably fitted to its
respective blade.
30. Apparatus according to claim 29, wherein the at least one
attachment device comprises a retaining collar supporting one of a
swivel or a pin cooperating with a swivel ball, the retaining
collar being removable and configured to grip part of a root
portion of a blade and be locked thereto by snug fitting and by a
spacer keeping the retaining collar radially spaced towards the
outside of the pivot axis of the blade, about which the spacer is
pivotable with the retaining collar and the blade.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method and apparatus for
folding/unfolding the blades of a rotary-wing aircraft rotor, such
as a helicopter main rotor. More particularly but not exclusively,
the invention relates to a method and apparatus which may be
advantageously used to assist in manually folding the blades of a
helicopter main rotor towards the rear, substantially along the
fuselage and tail boom of the helicopter, in order to reduce the
space required, during periods when it is out of service and/or in
order to make it easier to stow in a hangar, especially on a ship,
or to load and stow in the hold of a transport aircraft.
BACKGROUND TO THE INVENTION
[0002] In the flight configuration, rotary wing aircraft blades are
connected to the rotor hub by connecting means which lock the
blades in this unfolded position, in which their freedom of
movement in a plane substantially perpendicular to the axis of
rotation of the rotor, or the plane of the rotor disc, is very
limited due to the stiffness of the means retaining the blades and
hinging them to the hub being added to the stiffness of the blade
drag dampers, in the case of hinged rotors, or due to the stiffness
of the flexible torsion arms of the hub to which the blades are
connected on rotors of the semi-rigid type.
[0003] To fold a blade, it is therefore necessary firstly to unlock
it in order to allow it to have large-amplitude swing-type
movement, generally towards the rear, and then to lock it in the
folded position to avoid unwanted unfolding or deployment
movements. To unfold or deploy a blade, i.e. to return it to the
flight configuration, the sequence of operations mentioned above is
carried out in reverse order, i.e. the blade in the folded position
is unlocked to allow it to have large-amplitude swing-type
movement, generally towards the front, and is then locked in the
unfolded position or flight configuration.
[0004] These operations must be carried out in compliance with
strict procedures, in order that the folding/unfolding of the
blades is carried out without damaging the blades or other parts of
the helicopter, and without danger to any personnel who may be
present, such as operators assisting in the folding/unfolding
manoeuvres.
[0005] Rotary-wing aircraft with folding/unfolding rotor blades and
in particular such main rotors of helicopters, typically have at
least two blades, each of which is connected to the rotor hub and
locked in the unfolded position in the flight configuration by
means connecting the blade to the hub comprising, as is generally
the case on state-of-the-art rotors, a connecting device forming a
pivot axis and at least one other device the movement of which
causes the blade to be unlocked, allowing it to be folded by
pivoting about said pivot axis, preferably towards the rear,
substantially along the fuselage and the tail boom of the
rotary-wing aircraft.
[0006] To fold the blades, two main types of folding procedures and
devices are currently employed, namely manual folding, involving
one or more operators, and automatic folding.
[0007] As illustrated in FIG. 2, which shows the folding of a blade
of the four-bladed main rotor 2 of the helicopter 1 in FIGS. 1, 3
and 4, by pivoting this blade relative to the hub 3 of the rotor 2,
it is frequently the case that the means connecting the blade to
the hub comprise two pins such as 9 substantially parallel with
each other, and symmetrical either side of a longitudinal axis X-X
of the blade, to retain the blade root 8 in an outer radial yoke 11
of a substantially radial connecting device 10, relative to the
axis of rotation of the rotor, and generally termed a cuff, itself
connected to the hub 3 of the rotor 2 by retaining and hinging
means (not described or shown, as they do not form part of the
invention). One of the two pins 9 is removable (it is shown
withdrawn in FIG. 2) to allow the blade to fold by pivoting its
root 8 about the other pin 9 which thus constitutes the pivot or
folding axis, as also shown in FIGS. 2 and 5 of U.S. Pat. No.
4,268,222 for respectively three-bladed and four-bladed rotors with
star-shaped hubs with flexible arms.
[0008] Conventionally, manual folding takes place after preparation
of the helicopter and its main rotor, this preparation consisting
in chocking the helicopter by means of chocks and/or a parking
brake, lining up the rotor to position the blades favourably, half
of them being on the left and the other half on the right of the
helicopter, substantially symmetrically relative to the
longitudinal axis of the helicopter running from the rear forwards,
(a blade being substantially aligned with the tail boom of the
helicopter when the number of blades of the rotor is odd), locking
the rotor in this position by means of a rotor brake or any other
equivalent means, positioning the angle of attack of the blades at
a fixed pitch value or within a certain pitch range and, where
appropriate, locking the blades in pitch, so that the blades can be
moved by pivoting without interference with each other or with
other elements of the helicopter, then folding in succession all
the blades of the rotor other than the one, if any, aligned with
the tail boom, beginning on each side by folding the rearmost blade
(when folding is towards the rear), and continuing on each side by
folding the remaining blade, in the case of a rotor with four or
five blades, or the rearmost of the remaining blades in the case of
a rotor with at least six blades.
[0009] As is known and shown in FIGS. 1 to 5, for each of the
blades 4 to 7, and where the means connecting each blade 4 to 7 to
the hub 3 comprise, as described above and shown in FIG. 2, two
blade pins 9, one of which is removable, the folding procedure
consists, where folding is towards the rear, in withdrawing the
removable pin 9 situated furthest forward in order to unlock the
blade 4 to 7 in its flight configuration, and in such a way that
the blade 4 to 7 can pivot towards the rear about the one of the
two pins 9 which is situated furthest to the rear, moving the blade
4 to 7 in rotation by means of a folding pole 12 equipped at its
upper end with a hinged hook 13 to grip the blade close to its tip,
and which is held and raised at its lower end by one or more
operators 14, in order to support the blade 4 to 7, and counteract
bending of the blade under the effect of its own weight, which
tends to prevent the insertion or extraction of the removable pin 9
and, after rotation about the pivot pin 9 and when the blade has
reached its folded position (as have the front left blade 4 and
rear left blade 5 in FIG. 1) along the tail boom 15 of the
helicopter 1, securing it to the rear structure of the fuselage 16
or the tail boom 15, and locking it in the folded position by means
of this same folding pole 12 which is hooked on by the operator or
operators 14 to supports 17 integrated in said structure (16-15),
the folding pole 12 being held by straps 18 fastened to said
structure (16-15).
[0010] Where appropriate, as described for example in U.S. Pat. No.
4,268,222, other tools to assist in folding may be used in addition
to the folding poles, pole supports and straps, for example a
support secured removably to the central parts of the hub, this
support supporting the inner radial ends of rigid arms, the outer
radial ends of which are connected removably to the upper end of
the pivot pin of each blade or a service tool pin replacing said
pivot pin, in order to limit the bending of the flexible arms of
the star-shaped hub.
[0011] To facilitate the extraction and insertion of the removable
blade pins, in order to facilitate the folding and unfolding of
such blades, it is also known practice to use, as means of
connecting the blade to the hub, expanding blade pins such as
described in particular in patent U.S. Pat. No. 3,192,820, which
are pins which in service run through bushes permanently installed
in the blade roots and in the locked position have a diameter
greater than their diameter in the unlocked position, due to the
fact that they are locked by pivoting a pin lever which compresses,
along the axis of the pin, a stack of spring washers, for example
of the conical washer type, the axial compression of which causes
radial expansion deforming the tubular pin which swells and is then
locked in the corresponding bush of the blade root.
[0012] In the case of a four-bladed rotor (see FIGS. 1 to 5),
manual folding of the four blades in succession is generally
carried out in the following order: rear left blade 5, then front
left blade 4, then rear right blade 7 and finally front right blade
6.
[0013] This manual folding procedure has a major disadvantage
resulting from the fact that each of its steps requires the
intervention of one or more operators 14, not only to withdraw the
removable blade pins 9 but also and above all to support, hold and
move the blades 4 to 7 by means of the folding poles 12, so that
any failure by an operator 14 may lead to a loss of control of the
movement of a blade. This may result in serious damage to the
blades 4 to 7 and/or to the other components of the helicopter 1,
as well as injuries to the operators 14. The risk is particularly
great when folding is carried out in high winds, ashore or at sea,
in the case of a helicopter on board ship, because of the sudden
loads caused by the gusts of wind on the blades. This risk is
greater still on a ship in heavy seas, since the operators are
subjected to the rolling and/or pitching movements of the ship, on
a deck which may be made slippery by the rain and/or the spray,
etc. Operational conditions combining high winds and a rough sea
make it impossible to execute rotor blade folding or unfolding
operations in acceptable safety conditions. Operationally, manual
folding is therefore confined to helicopters of low or medium
tonnage, the blades of which have a weight which can still be
controlled by the operators.
[0014] In other words, manual folding remains economical, as it can
be effected using simple tools, but its operational performance and
level of safety are limited.
[0015] Automatic folding procedures and devices, an example of
which is described in EP 0 057 053, employ an automated sequence of
operations executed by means constantly present on the rotor. In
general, on an automatic folding rotor of this type, each blade has
its root retained in a yoke of a folding fitting mounted so as to
pivot about a folding axis at the outer radial end of a cuff
connecting it to the hub, and this cuff supports at least one
operating actuator, causing and controlling the pivoting of the
corresponding blade and its folding fitting about its folding axis,
and at least one locking actuator, causing locking or unlocking, at
least in the flight configuration, on the cuff.
[0016] This type of automatic folding procedure and device can
provide folding and unfolding in difficult conditions, but has
major disadvantages because of the very high development and
acquisition costs, so that automatic folding can only be envisaged
for medium or large tonnage helicopters and, in addition, automatic
folding has to be taken into account from the design stage of the
rotor, and in particular of its hub, so that the installation of an
automatic folding device on an existing helicopter initially
lacking such a device involves complete redesign of at least the
hub.
[0017] In other words, automatic folding offers an excellent level
of operational and safety performance in all weathers, but its cost
is extremely high, and it requires particularly stringent
maintenance. This applies even more when the automatic folding
device has to provide locking not only in pitch but also in drag
and/or flapping of components of the hub, such as the cuffs
connecting the blades to the hub.
SUMMARY OF THE INVENTION
[0018] The problem addressed by the invention is to propose a
method and apparatus for folding/unfolding the blades which ensures
that the folding/unfolding operations proceed satisfactorily on
helicopters operating in difficult conditions, as is the case for
example with helicopters on board ship, which may be subjected to
particularly difficult wind and sea conditions.
[0019] Another aim of the invention is to propose a procedure and a
device for folding/unfolding blades which are advantageously
employed as a procedure and a device to assist manual
folding/unfolding of rotor blades of the known type presented
above, requiring the intervention of operators using folding poles
to support the blades and facilitate withdrawal of the removable
blade pins, and to move the blades in rotation and then lock them
in the folded position by securing the poles to the rear structure
of the helicopter.
[0020] According to a first aspect of the present invention, there
is provided a method of folding/unfolding at least one blade of a
multi-bladed rotor of a rotary-wing aircraft, with at least a first
blade being connected to a hub of the rotor by a coupling
comprising a pivotal connection defining a pivot axis and a
releasable connection, release of which allows its blade to be
pivoted about its pivot axis between an unfolded position and a
folded position, the method comprising steps:
[0021] (a) removably attaching at least one variable-length linear
actuator to the first blade and a second blade, each locked in a
fixed position with respect to the hub which is itself locked
stationary;
[0022] (b) releasing the first blade from its fixed position with
respect to the hub;
[0023] (c) actuating the linear actuator to vary its length and
bear against the second blade, thereby pivoting the first blade
about its pivot axis to a new position with respect to the hub;
and
[0024] (d) locking the first blade in the new position.
[0025] Folding or unfolding of any other blade to be folded or
unfolded may be performed conventionally or preferably by attaching
said linear actuator or other similar actuator to two blades, at
least one of which is to be folded or unfolded, and by employing
the procedure above, step by step, until the last blade of the
rotor is folded or unfolded. The procedure according to the
invention can therefore be employed with a single actuator,
whatever the number of blades, provided that the actuator is moved
to different positions on the rotor in the course of the folding or
unfolding operation.
[0026] This procedure according to the invention can assist and
even replace the action of the operators employing a conventional
manual folding/unfolding procedure, by means of at least one simple
removable actuator, which may economically be a simple
double-acting linear jack, to provide the energy required for
pivoting the blades, and to control this pivoting, so that although
folding poles, which may be identical to those used at present, are
attached to the blade tips and handled by operators on the ground,
the only function of these poles, after the removable blade pins
are extracted, is to prevent unwanted vertical movements due to
gusts of wind on the blades, since the folding or unfolding
manoeuvre properly so-called is performed by the removable linear
actuator, whereas in conventional manual folding, these poles are
also used to move or hold blades in rotation to fold or unfold
them.
[0027] In one embodiment, where the second blade is coupled to the
hub of the rotor in an analogous way to the first blade, the method
further comprises after step (d) steps:
[0028] (e) releasing the second blade from its fixed position with
respect to the rotor;
[0029] (f) actuating the linear actuator to vary its length and
bear against the first blade, thereby pivoting the second blade
about its pivot axis to a new position with respect to the hub;
and
[0030] (g) locking the second blade in its new position.
[0031] This procedure, combining the action of at least one
removable linear actuator with suitable steps of locking and
unlocking the blades, enables said removable linear actuator, or
each of them, to manoeuvre a first, unlocked blade, by bearing
against the second, locked blade, and then to manoeuvre the second,
unlocked blade, by bearing against the first, locked blade, which
minimises the number of linear actuators required and the number of
times they are operated, a single actuator being sufficient
whatever the number of blades, if it is moved to different
positions on the rotor, in the course of the folding or unfolding
operation.
[0032] Also advantageously, before step (f) the method may further
comprise removably attaching a link rod to the first blade locked
in its new position and to a third blade whose position is fixed
with respect to the hub, whereby under subsequent actuation the
linear actuator bears against the first and third blades together
when the second blade pivots about its axis. A link rod of this
type, in particular when it is attached to two locked blades folded
towards the rear, because of its stiffness strengthens the assembly
comprising these two folded rear blades, the hub of the rotor and
the rear part of the fuselage, to which the two folded blades are
connected by being locked in this position. However, this rod is
not essential if the dimensioning of this assembly is compatible
with the forces encountered during the complete folding procedure
and during the period of immobilisation, in particular to enable it
to withstand gusts of wind.
[0033] For implementation of the method aspect of the invention as
presented above, there is also proposed apparatus for
folding/unfolding at least one blade of a multi-bladed rotor of a
rotary-wing aircraft, with at least a first blade being connected
to a hub of the rotor by a coupling comprising a pivotal connection
defining a pivot axis and a releasable connection, release of which
allows its blade to be pivoted about its pivot axis between an
unfolded position and folded position, the apparatus
comprising:
[0034] at least one variable length, removable linear actuator
configured to be removably attached to two adjacent blades of the
rotor and to exert forces in either direction along its
longitudinal axis on two blades connected by the linear actuator;
and
[0035] connectors for removably attaching the linear actuator to
two adjacent blades, each connector comprising an end fitting
integral with the linear actuator and an attachment device
configured for attachment to one blade, the end fitting and the
attachment device being releasably interconnectable.
[0036] For rotors with at least three blades, it is sufficient for
the folding/unfolding apparatus to comprise a single actuator, but
preferably two linear actuators, preferably substantially
identical, each fitted at each of its two longitudinal ends with an
end fitting for attaching removably to at least one attachment
device fitted to a blade, so as not to have to carry out too great
a number of operations successively fitting and removing a single
actuator to fold or unfold all the blades.
[0037] Advantageously, the device comprises in addition at least
one substantially rectilinear removable link rod, designed to be
removably attached to two blades, in particular two blades locked
in the folded position towards the rear, said rod being fitted for
this purpose and at each of its two longitudinal ends with means
for connecting it removably to one respectively of the blades.
[0038] The folding/unfolding method and apparatus aspects of the
invention have the advantages that, because at least one removable
linear actuator is used, movement of the blades is caused and
controlled, thus avoiding any undesirable movement of a blade which
might have broken free from the operators, so that for a reasonable
cost of such a device, the blades can be folded safely in strong
winds and/or heavy seas. The procedure and device according to the
invention thus fill the gap which currently exists between the
procedures and devices for manual folding, of low cost but with
limited performance and safety, and automatic folding procedures
and devices, offering good performance and good safety, but at very
high cost.
[0039] Compared with an automatic folding device, the rotary-wing
aircraft rotor of which the blades are to be folded does not
permanently carry the folding/unfolding device of the invention,
which is fitted to the rotor only when the rotary-wing aircraft is
on the ground, at least during the blade folding/unfolding
operations and, where appropriate, during the period of
immobilisation of the folded blades. The saving in weight and
therefore improvement in performance is very appreciable, since for
a helicopter of the eight to ten tonne class, the weight saved is
of the order of 100 kg.
[0040] In addition, as the folding/unfolding apparatus is only a
tool used solely on rotary-wing aircraft on the ground, this tool
is not subject to the same rules and constraints as equipment used
in flight. The result is that development, acquisition and
maintenance costs are markedly lower than those of a device carried
on board the aircraft.
[0041] The invention may be applied to all types of existing
helicopter rotors, whatever the number of blades, provided that the
blades are able to pivot, substantially in the plane of the rotor
disc, about one of the means connecting them to the hub (pin, bolt
or other equivalent means). Adaptation of the invention to an
existing helicopter requires no modification of the hub, in
particular of the main rotor, and only the blades have to be
equipped with means for removably attaching the linear actuator or
actuators, and these attachment means may be at least partially
integrated into the blades or completely removable from the
latter.
[0042] For a new helicopter or more simply a new rotor, in
particular a main rotor, for which blade folding is required, the
folding/unfolding method and apparatus aspects of the invention do
not add design constraints with regard to folding, so that the
prime function of the hub, which is to control the lift of the
rotor, can be optimised.
[0043] Depending on the number of blades of the rotor, the core
method and apparatus defined above must be adapted to each rotor,
but the same basic principle still applies, using at least one
linear actuator attached to two adjacent blades of the rotor and
bearing against one locked blade, to cause the other, unlocked, to
pivot.
[0044] Two-Bladed Rotor
[0045] For a two-bladed rotor with blades which can be folded
towards the rear, the method may further comprise:
[0046] locking the stationary rotor with the first and second
blades aligned substantially transversely to a longitudinal axis of
the rotary-wing aircraft; and
[0047] attaching pivotally the linear actuator to a forward part of
one blade and a rearward part of the other blade such that the
linear actuator extends rearwardly of a line passing through the
pivot axes of the two blades, and such that the linear actuator is
disposed rearwardly of the hub of the rotor.
[0048] In this way, steps (a) to (d) may be used to bring the first
blade from its transversely aligned fixed position to the new
position towards the rear of the rotary-wing aircraft, and steps
(e) to (f) may be used to bring the second blade from its
transversely aligned fixed position to its new position. In this
case, the method may in addition comprise the step consisting in
attaching the actuator to the blades by means of two securing
brackets previously removably attached, one projecting towards the
front of the leading edge of the root portion of one blade and the
other projecting towards the rear of the trailing edge of the root
portion of the other blade.
[0049] Three-Bladed Rotor
[0050] In the case of a three-bladed rotor with blades which can be
folded towards the rear, the method may further comprise:
[0051] locking the stationary rotor with the second blade aligned
over the rear part of the rotary-wing aircraft;
[0052] removable attaching a variable-length linear actuator to the
second and third blades;
[0053] releasing the third blade from its fixed position;
[0054] actuating the linear actuator to vary its length and pivot
the third blade about its pivot axis to a new position with respect
to the hub; and
[0055] locking the third blade in its new position.
[0056] In this way, steps (a) to (d) may be used to bring the first
blade from its fixed position (unfolded configuration) to the new
position towards the rear of the rotary-wing aircraft and adjacent
the second blade, and the third blade may be likewise be moved from
its fixed position (unfolded configuration) to its new position
adjacent the second blade. As a variant, a single actuator may be
removably attached firstly to the second blade and to one of the
other two blades, to fold or unfold it, then detached and removably
attached to the second blade, and to the other of the other two
blades, to fold or unfold the latter.
[0057] In cases where two actuators are used, the method may
advantageously comprise in addition the step consisting in
attaching the two actuators substantially to the same attachment
point on the rear blade, substantially along the longitudinal axis
of said rear blade and radially towards the outside of the pivot
axis of said rear blade relative to the axis of rotation of the
rotor.
[0058] Rotor With at Least Four Blades
[0059] Finally, to fold towards the rear the blades of a rotor with
at least four blades, with a third blade and fourth blade each
connected to and fixed in position with respect to the hub of the
rotor in an analogous way to the first blade, the method further
comprises:
[0060] locking the stationary rotor with the first and second
blades disposed on one side of the rotary-wing aircraft and the
third and fourth blades disposed on an opposite side, with the
first blade rearwardly of the second blade and the third blade
rearwardly of the fourth blade,
[0061] carrying out steps (a) to (d) so that the new position of
the first blade is over the rear part of the rotary wing
aircraft;
[0062] repeating steps (a) to (d) for the third blade in place of
the first blade so that the third blade is positioned adjacent the
first blade;
[0063] carrying out steps (e) to (f) for the second blade so that
the second blade is positioned adjacent the first blade;
[0064] repeating steps (e) to (f) for the fourth blade in place of
the second blade so that the fourth blade is positioned adjacent
the third blade.
[0065] The method may further comprise connecting the first blade
to the third blade with a removable link when the first blade is in
the new position and the third blade is positioned adjacent to it.
As a variant, a single actuator may be used, but it must then be
frequently moved to different positions on the rotor in the course
of the work.
[0066] If the multi-bladed rotor has an odd number of blades, the
stationary rotor is locked with one blade positioned over the rear
part of the rotary-wing aircraft. In all cases, each blade may be
advantageously locked in the folded position by attaching said
blade to the rear structure of the rotary-wing aircraft, by means
of attachment tools such as folding poles and/or straps and/or
supports, as is already known in manual folding.
[0067] Regarding the apparatus for folding/unfolding the blades,
the removable linear actuator, or each of them, may advantageously
comprise at least one double-acting linear jack, comprising at
least one rectilinear rod moveable axially in both directions in a
jack body, into which said rod is partially inserted and driven by
a drive device housed in the body.
[0068] The jack may be a fluid-operated jack, i.e. a pneumatic or
hydraulic jack, powered either from a pneumatic or hydraulic
circuit on board the helicopter, or from the pneumatic or hydraulic
outlet of a ground power unit.
[0069] However, as this jack is a tool to be installed temporarily
on the rotor, it is advantageous for reasons of lightness, bulk and
ease of use that this jack should be a simple, lightweight and
therefore economical structure, and in particular a mechanical or
electromechanical jack, the body of which houses a mechanical drive
device with multiplication of force at the rod. In the case of an
electromechanical jack, a reduction gear unit driven by an electric
motor may be integrated in the jack body and powered from the
on-board electrical network of the helicopter or the electrical
outlet of a ground electrical generating unit.
[0070] Nevertheless, whether the jack drive is mechanical and
provided manually or assisted by an electric motor, it is
advantageously simple and practical for the mechanical drive device
with multiplication of force at the rod to comprise at least one
stage of reduction gearing engaged with the rod and using a worm
screw, driven in rotation in the body, and/or with
gearwheel-and-pinion gears, said reduction gearing stage comprising
at least one input shaft, designed to be driven from the outside of
the jack body by mechanical operating means, such as a crank, or
electromechanical means, such as a cordless screwdriver, with a
battery powered electric motor.
[0071] In a simple, economical but nevertheless effective mode of
embodiment, the drive device with multiplication of force at the
rod comprises a worm gear meshing with the tubular rod into which
the worm gear partly extends, and driven in coaxial rotation by an
output gear of bevel gearing of which an input opinion is integral
with the input shaft, accessible from the outside of the jack
body.
[0072] Advantageously, to bring together the removable attachment
end fittings of the jack and their respective attachment points on
the blades, the jack also comprises a manually operated mechanism
for disengaging the rod, allowing rapid and simple adjustment of
the jack to the desired length, for it to be attached by its end
fittings to the attachment devices on two adjacent blades.
[0073] Moreover, to reduce loads due to any impacts at the end of
the folding or unfolding movement, in particular when an unfolded
blade approaches the hub of the rotor or the means of connecting it
to this hub, the jack also comprises shock absorbing means, such as
at least one axial spring and/or at least one block of elastically
deformable material, in series with the rod and/or the body and/or
at least one of the end fittings of the jack.
[0074] In addition, to avoid the moments induced in the links
between the jack and the two blades which it connects by a
combination of the pivoting of a folded or unfolded blade and the
generally non-zero angle of attack of this blade, the connectors
for removably attaching the actuator to the blades comprise at
least one ball joint connecting at least one removable attachment
end fitting of at least one actuator to at least one corresponding
attachment device on a blade, so as to allow the actuator or jack
to swivel.
[0075] To this end, the ball joint may comprise at least one swivel
ball of at least one removable attachment ball joint end fitting of
the actuator or jack which cooperates with an attachment pin
comprised in said attachment devices fitted to a blade.
[0076] However, it is also possible for the ball joint to comprise
at least one swivel ball supported by the attachment devices fitted
to a blade, so that this swivel ball projects above a portion of
root of the blade, and at least one end sleeve of a removable
attachment elbow end fitting of an actuator or jack, said sleeve
being designed to fit and lock releasably on the swivel ball. This
swivel ball may be supported by a support retained by at least one
pin or at least one screw in at least one insert of the attachment
devices which is integrated in a root portion of the blade, but, as
a variant, the swivel ball may be supported by a support integrated
directly as an insert in this root portion of the blade.
[0077] Generally, the devices attaching an actuator or jack to a
blade may be completely integrated in this blade, or comprise at
least one attachment element fitted by a removable attachment into
at least one other attachment element such as an insert integrated
into the root portion of the blade. In both these cases, the blade
is not standard, but specific to the folding blade rotor which
comprises it.
[0078] As a variant, all the devices for attaching an actuator or
jack to a blade may be removably fitted to this blade, which is
then standard. In a preferred mode of embodiment of attachment
means of this type, these attachment means comprise a retaining
collar supporting a swivel ball or a pin cooperating with a swivel
ball, this retaining collar being removable and designed to grip a
part of the root portion of a blade by being locked to the latter
by snug fitting and also by a spacer keeping the retaining collar
spaced radially towards the outside of the pivot axis of this
blade, about which the spacer can pivot with the retaining collar
and the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
[0079] Other characteristics and advantages of the invention will
emerge from the description given below of examples, though not
limited to these, of embodiments described with reference to the
attached drawings in which:
[0080] FIG. 1 shows schematically in side elevation a helicopter
with a manually folding four-bladed main rotor according to the
state-of-the-art,
[0081] FIG. 2 is a partial plan view of a blade root pivoting on a
device connecting it to the hub, in the process of being
folded,
[0082] FIG. 3 is a schematic plan view showing the helicopter in
FIG. 1 on which the four main rotor blades are folded,
[0083] FIG. 4 is a view from the rear of the helicopter in FIGS. 1
and 3 when folding is finished,
[0084] FIG. 5 is a schematic view partly in section and partly in
rear elevation, showing the locking of two blades of the main rotor
of the helicopter in FIGS. 1, 3 and 4 locked in the folded position
by means of folding poles, straps and support arms,
[0085] FIGS. 6 to 11 are partial schematic views in plan of the
head of the four-bladed main rotor of the helicopter in FIGS. 1 to
4 on which is fitted a folding device according to the invention,
these figures showing a sequence of folding the four blades towards
the rear,
[0086] FIGS. 12 and 13 are partial schematic plan views showing the
folding of the blades of a two-bladed rotor according to the
procedure and with the device of the invention,
[0087] FIG. 14 is a schematic plan view of a variant two-bladed
rotor blade,
[0088] FIGS. 15 and 16 are partial schematic plan views showing the
folding of the blades of a three-bladed rotor by the procedure and
with the device of the invention,
[0089] FIGS. 17 and 18 are figures similar to FIGS. 15 and 16 for a
five-bladed rotor,
[0090] FIGS. 19 to 21 are also views similar to FIGS. 15 and 16 for
the folding of a six-bladed rotor,
[0091] FIGS. 22 and 23 are schematic views respectively in axial
section and side elevation of a mechanical jack which can be used
as a linear actuator in the device of the invention,
[0092] FIGS. 24 to 28 show schematically different modes of
embodiment of the means for removable attachment of the end
fittings of the jack in FIGS. 22 and 23 to the blade roots, and
[0093] FIGS. 29 and 30 show schematically and respectively in plan
and side elevation, removable attachment devices fitted to a blade
for attaching to the latter an end fitting of the jack.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0094] FIGS. 6 to 11 show a sequence of folding towards the rear,
according to the procedure and with the device of the invention, of
the blades 4 to 7 of the four-bladed main rotor 2 of the helicopter
1 in FIGS. 1 and 3 to 5 described previously, each blade being kept
locked, as is also the case in the other examples of rotors
described below, by its root 8 in the flight configuration, in the
unfolded position, on a cuff 10 connecting it to the hub 3 of the
rotor 2 by two blade pins 9, parallel to each other and
substantially symmetrical on either side of the longitudinal pitch
change axis X-X of each blade, and one of the pins 9 of which,
situated nearest the front of the helicopter, is removable to allow
the blade to be folded towards the rear by pivoting about the other
pin 9, situated nearest the rear of the helicopter, and
constituting a pivot pin or folding/unfolding pin of the blade
considered, as described above with reference to FIG. 2.
[0095] Before the folding operation is carried out, the helicopter
1 and its main rotor 2 are first prepared in the same way as for
conventional folding, i.e. by means of a parking brake and/or
chocks, the helicopter is chocked, and then the rotor 2 is lined up
so as to position blades 4 to 7 favourably by arranging them
substantially symmetrically relative to the longitudinal axis L-L
of the helicopter, on which an arrow indicates the front of the
helicopter, one half of the blades, i.e. blades 4 and 5, on the
left side and the other half, i.e. blades 6 and 7, on the right
side of the helicopter, and the rotor 2 is locked in this position
by using a rotor brake or any other equivalent means. The angle of
attack of the blades 4 to 7 is also positioned at a fixed value or
within a certain pitch range, and where appropriate locked, to
allow the blades 4 to 7 to be moved without interference between
blades or with other components of the rotor 2 and, more generally
of the helicopter 1.
[0096] Two linear actuators 19, preferably identical, of variable
length, are then removably attached to the rotor 2 by attaching one
of them to the two left-hand blades 4 and 5 so that this actuator
19 extends between the roots 8 of these two blades 4 and 5, to each
of which the actuator 19 is removably attached by one respectively
of two end fittings at the axial ends of the actuator 19, to one of
the two attachment points 20, formed by attachment devices fitted
to the blades and described below, these attachment points 20 being
situated on the roots 8 of the blades 4 and 5, substantially on the
longitudinal pitch change axis X-X of each blade 4 and 5, and
radially to the outside of the corresponding blade pins 9, relative
to the axis of rotation A-A of the rotor 2, at the centre of the
hub 3.
[0097] The other linear actuator 19 is fitted removably in the same
way to the right-hand blades 6 and 7, as shown in FIG. 6.
[0098] In a practical manner, each linear actuator 19 is a
double-acting linear jack, preferably a mechanical jack as
described below with reference to FIGS. 22 and 23, and fitted at
both of its axial or longitudinal ends with removable attachment
end fittings cooperating with removable attachment devices fitted
to the blades, and preferably such as described below with
reference to FIGS. 24 to 30.
[0099] After each of the two actuators 19 is attached to two
adjacent or consecutive blades 4, 5 or 6, 7 of the rotor 2, on the
same side of the helicopter, and locked in the flight
configuration, the rear blade for example on the left side 5 is
unlocked by withdrawing its front blade pin 9, while the front left
blade 4 remains locked in the flight configuration. The left
actuator 19 is caused to extend, which has the effect of pushing
the rear left blade 5 towards the rear, as shown in FIG. 7, by
pivoting about its pivot pin 9, which is the rear pin kept in the
initial position. The actuator or jack 19 provides the energy to
drive the blade 5 in pivoting and controls the pivoting movement,
in the course of which the blade 5 may be held at the tip by an
operator using a folding pole 12 with a hinged hook 13 at its upper
end, as described above with reference to FIGS. 1 to 5, in order to
avoid accidental vertical deflection of this blade 5 as a result of
gusts of wind. When folding of the blade 5 is finished, the latter
is locked in the folded position by attaching it to the tail boom
15 or to the rear structure 16 of the fuselage by means of a pole
12, supports 17 and straps 18 as previously described with
reference to FIGS. 4 and 5.
[0100] Then, keeping the front right blade 6 locked in the flight
configuration, the rear right blade 7 is unlocked by withdrawing
its blade pin 9 located towards the front, and the right-hand
actuator or jack 19 is caused to extend, which has the effect of
causing the rear right blade 7 to pivot towards the rear about its
pivot pin 9, the rearmost, and kept in the initial position as
shown schematically in FIG. 8. The rear right blade 7 folded
towards the rear is then locked in this position by being attached
to the tail bloom or rear structure of the helicopter fuselage, as
explained above for the rear left blade 5.
[0101] The two rear blades 5 and 7 are then locked in position
folded towards the rear.
[0102] As shown in FIG. 9, a rectilinear rigid link rod 21 may then
be removably attached between the two rear blades 5 and 7 locked
and folded, and this rod 21 is preferably removably attached by two
axial end fittings of the rod 21 at the two attachment points 20 of
the two actuators or jacks 19 to the roots 8 of these two rear
blades 5 and 7, using quick-connection means of any known suitable
type, for example of the same type as the devices for removably
attaching the jacks 19 to the blades.
[0103] The rigid link rod 21, which is optional, has the effect of
strengthening the assembly constituted by the two rear blades 5 and
7, locked folded to the fuselage, the hub 3 and the rear structure
of the fuselage 16 or of the tail boom 15.
[0104] The front left blade 4 is then unlocked by withdrawing its
front blade pin 9, and the left jack 19 is caused to retract, which
has the effect of pulling the front left blade 4 towards the rear
and causing it to pivot about its pivot pin 9, kept in the initial
rear position, and when the front left blade 4 is folded towards
the rear along the rear part of the fuselage 16 and of the tail
boom 15, this front left blade 4 is locked in position folded
towards the rear by attaching it to the tail boom 15 or rear
structure 16 of the fuselage, as for the two rear blades 5 and 7
previously folded (see FIG. 10), or to the rear left blade 5
previously folded.
[0105] The front right blade 6 is then unlocked by withdrawing its
front blade pin 9 and, by retracting the right jack 19, the front
right blade 6 is pulled and made to pivot towards the rear about
its pivot pin 9, kept in the initial rear position, and the front
right blade 6 is then locked in position folded towards the rear
(see FIG. 11) by its attachment to the tail boom 15 or rear
structure 16 of the fuselage, as for the other blades previously
folded, or to the rear right blade 6 previously folded.
[0106] In the course of these operations of extension or retraction
of the jacks 19, each of them bears against a blade kept locked to
push or pull the other blade to which this jack is connected,
moving the blade by pivoting it.
[0107] In FIG. 11, solid lines are used to represent the four
blades 4 to 7 locked folded at the end of the folding sequence and,
for unfolding, the procedure described with reference to FIGS. 6 to
11 must be carried out in reverse order, retraction of the jacks 19
being of course substituted for extension, and vice versa.
[0108] After the unfolding operation, by which the four blades 4 to
7 are returned to the flight configuration and locked in this
position (FIG. 6), the two jacks 19 are withdrawn from the rotor 2.
These two jacks 19 as well as the optional link rod 21 are
therefore tools which are fitted only temporarily to the rotor 2
for the folding and unfolding operations, and which can be kept on
this rotor 2 for as long as the blades have to be kept locked and
folded.
[0109] As a variant, a single jack 19 is used, firstly to
fold/unfold the two blades on one side, and then to fold/unfold the
two blades on the other side.
[0110] In the case of a two-bladed rotor, as shown in FIGS. 12 and
13, this rotor is locked stationary after being lined up so that
the two blades 22 and 23, diametrically opposite relative to the
axis of rotation A-A of the rotor, are positioned transversely to
the longitudinal axis L-L of the helicopter, the front of which is
indicated by the arrow on the axis L-L (upwards in FIGS. 12 and
13). The two blades 22 and 23 locked in the flight configuration in
this transverse position, are then connected to each other by a
single linear actuator or jack 24 which is removably attached to
the front of the blade 23 on the one hand and on the other to the
rear of the blade 22, so as to avoid any interference with the
rotor head, and in particular its hub 3 and the cuffs or arms 10
connecting the blades 22 and 23 to the hub 3, and so that this jack
24 can effectively exert a folding (or unfolding) force on the
blades 22 and 23, substantially in the plane of rotation of these
blades or rotor disc, the line of action of the jack 24, which
extends along its longitudinal axis, extending towards the rear
(i.e. in the direction of folding) of a virtual axis passing
through the pivoting points of the two blades 22 and 23, i.e.
through the two pivot pins 9 situated towards the rear, each of
which constitutes the folding/unfolding axis of one respectively of
the two blades 22 and 23. In the example in FIGS. 12 and 13, and as
shown in more detail in FIG. 14, the single jack 24 is removably
attached by each of its longitudinal ends at an attachment point 25
to the end of one respectively of two securing brackets 26 attached
beforehand, preferably removably, one projecting towards the front
on the leading edge of the root 8 of the blade 23, and the other
securing bracket 26 projecting towards the rear on the trailing
edge of the root 8 of the other blade 22.
[0111] The two blades are folded by first of all unlocking a first
blade, such as 22, by withdrawing its front blade pin 9, then
causing a first retraction of the jack 24 which bears against the
other blade 23 kept locked in the flight configuration, so to cause
the blade 22 to pivot towards the rear into the folded position
(see FIG. 13) by pivoting about its pivot pin 9, then locking this
blade 22 in this position by attaching it to the rear structure of
the fuselage or tail boom of the helicopter for example by means of
a folding pole, supports and straps as explained above. The second
blade 23 is then unlocked by removing its front blade pin 9, and
the jack 24 is caused to retract a second time, so as to cause this
second blade 23 to pivot towards the rear about its rear pivot pin
9 until it reaches the folded position shown in FIG. 13, in which
the second blade 23 is locked by attaching it, as for the blade 22,
to the tail boom or rear structure of the helicopter.
[0112] To change from the position in FIG. 13 to the one in FIG.
12, the blades 22 and 23 are unfolded by a sequence repeating the
operations described above in reverse order and by causing the jack
24 to extend twice in succession instead of causing them to retract
twice when folding.
[0113] As a variant, the single jack 24 may be attached directly to
the blades 22 and 23, but attaching them via the securing brackets
26 enables the blades to be standardised, which is more economical,
by equipping them all with the same point 27 for attaching a
securing bracket 26 to a corresponding blade. As shown in FIG. 14,
which shows the blade 23 equipped with a securing bracket 26
projecting towards the front of the leading edge of its root 8, the
securing bracket 26 may be formed as a stirrup straddling the
leading edge of the blade root 8, and in such a way that the jack
24 is removably attached to the attachment point 25 on the front of
the securing bracket 26, the rear of which is retained on the blade
root 8, substantially in the middle of its chord, by the attachment
point 27 formed by a transverse retaining pin. On the other blade
such as 22, the same attachment point 27 attaches to the blade a
securing bracket 26 shaped as a stirrup which straddles the
trailing edge of the blade root 8, so that the jack 24 can be
attached to the end of the stirrup 26 which projects towards the
rear of this trailing edge.
[0114] It is therefore the positioning of the securing bracket 26
on the blade 22 or 23 which differentiates the blades.
[0115] In the case of a three-bladed rotor, as shown in FIGS. 15
and 16, the rotor is locked stationary lined up so as to position
the one 28 of the three blades towards the rear and substantially
aligned with the tail boom of the helicopter and with its
longitudinal axis L-L, this rear blade 26 remaining locked by its
two blade pins 9 in the flight configuration when it is locked in
the rotor folding position, in which this rear blade 28 is
preferably also attached, as in the previous examples, to the tail
boom or structure of the rear part of the fuselage of the
helicopter by attachment means such as folding poles, supports and
straps as previously described.
[0116] To fold the other two blades 29 and 30 extending
symmetrically one to the left and the other to the right of the
helicopter, from their position locked in the flight configuration
as shown in FIG. 15, two identical linear actuators or jacks 31 are
used, each of which is removably attached to the rear blade 28
locked in this position, and to one respectively of the other two
blades 29 and 30, locked in the flight configuration. Next, one of
the two side blades, for example the blade 29, is unlocked by
withdrawing its front blade pin 9, and the jack 31 which connects
this blade 29 to the rear blade 28 is caused to retract, so that by
pulling on this unlocked side blade 29, and by bearing against the
locked rear blade 28, this jack 31 causes the blade 29 to pivot
towards the rear by rotating about its pivot pin 9 to the rear
position, until it reaches the folded position shown in FIG. 16, in
which the blade 29 is locked folded by being attached as described
above to the tail boom or structure of the rear part of the
helicopter fuselage. The other side blade 30 is then unlocked by
removing its front blade pin 9, then the other jack 31 which
connects this blade 30 to the locked rear blade 28 is caused to
retract so as to cause the blade 30 to pivot about its rear pivot
pin 9 towards the rear, by the jack 31 pulling on this blade 30 and
bearing against the locked rear blade 28, until the blade 30 is
moved into the position folded towards the rear, as shown in FIG.
16, and in which this blade 30 is locked in the same way as the
other side blade 29.
[0117] The blades are moved from the folded position (FIG. 16) to
the unfolded position or flight configuration (FIG. 15) according
to a reverse sequence in which the two jacks 31 are caused to
extend instead of being caused to retract.
[0118] On the side blades 29 and 30, the attachment points 32 of
the jacks 31 are situated, as are the attachment points 20 in the
example in FIGS. 6 to 11, on the longitudinal pitch change axes X-X
of the blades and radially on the outside of the blade pins 9
relative to the axis A-A of rotation of the rotor, and the two
jacks 31 are preferably attached to the root 8 of the rear blade 28
at the same attachment point 32 positioned in the same way as on
the other blades 29 and 30, so that the blades are standardised and
comprise only a single attachment point 32, which is favourable in
terms of weight and cost. As a variant, the two jacks 31 may be
attached to the rear blades 28 at two adjacent points, with the
disadvantage that this blade 28 is not standard and must be
specially balanced to make it compatible with the other two blades
29 and 30 on the same three-bladed rotor. As a variant, a single
jack 31 is used, firstly between the blades 28 and 29, and then
between the blades 28 and 30, or vice versa.
[0119] FIGS. 17 and 18 show a rotor with five blades respectively
locked in the flight configuration and folded towards the rear. The
procedure and the device for folding/unfolding such a five-bladed
rotor are the same as those described for the four-bladed rotor
with reference to FIGS. 6 to 11, the only difference being that the
rotor is initially locked stationary in a position in which one of
the blades 33 extends towards the rear and is substantially aligned
with the tail boom of the helicopter, in the same conditions
substantially as the rear blade 28 of the three-bladed rotor in
FIGS. 15 and 16. This rear blade 33 is therefore kept locked in the
flight configuration by its two blade pins 9 in its "folded"
position in which it is locked in addition by being attached to the
tail boom or rear structure of the helicopter as described
previously. The other four blades of the rotor are a front left
blade 34 and a rear left blade 35, corresponding respectively to
the blades 4 and 5 of the four-bladed rotor mentioned above, and on
which is installed removably one of the two jacks 19 of the folding
device, and a front right blade 36 and a rear right blade 37,
corresponding to the blades 6 and 7 of the four-bladed rotor, and
to which is removably attached the other linear jack 19 of the
device, as on the four-bladed rotor (see FIG. 6). The sequence of
folding of the four blades 34, 35, 36 and 37 is exactly the same as
that of the blades 4, 5, 6 and 7 of the four-bladed rotor, and as
has been described above, the attachment points of the jacks 19 to
the blades being the same as the attachment points 20 in FIGS. 6 to
11.
[0120] Similarly, after the two rear side blades 35 and 37 are
folded towards the rear, these two blades 35 and 37 may be
connected to each other by a rectilinear, rigid link rod, similar
to the rod 21 in FIGS. 9 to 11, and attached temporarily and
removably to the two blades which it connects, for example at the
points of attachment 20 of the two jacks 19 to these two blades 35
and 37. On the five-bladed rotor in FIGS. 17 and 18, another
rectilinear, rigid link rod, such as 21, may be removably attached
to the two front side blades 34 and 36, when these are locked
folded (FIG. 18), in order also to strengthen the assembly
constituted by these two pairs of blades folded and locked with the
fuselage and the hub of the rotor.
[0121] As a variant, a single jack 19 may be used, in a first step
to fold or unfold in succession the two blades on one side and
then, in a second step to fold or unfold the two blades on the
other side, the position of the rear blade 33 being unchanged.
[0122] FIGS. 19 to 21 show a sequence for folding the blades of a
six-bladed rotor using only two jacks which may be similar to the
jacks 19 used for folding/unfolding the four-bladed and five-bladed
rotors as described above, but these two jacks 19 have to be moved
to different positions on the rotor in the course of a folding or
unfolding operation. As a first step, the rotor is locked
stationary in a position in which the three blades 44, 45 and 48 of
a first half of the rotor blades extend on one side of the
longitudinal axis L-L of the helicopter, for example on the left
side, looking towards the front of this axis L-L, indicated by an
arrow on this axis, whereas the three blades 46, 47 and 49 of the
second half of the rotor blades extend substantially symmetrically
on the right side of the helicopter. The six blades being locked,
each by its two blade pins 9, in the flight configuration, in this
position, one of the two jacks 19 is installed, as in the examples
of the four-bladed and five-bladed rotors, between the two rearmost
blades 44 and 45 on the left side, being removably attached to each
of them at an attachment point 20, positioned on the root 8 of the
corresponding blade as explained above, and the other jack 19 is
installed between and attached to the two rearmost blades 46 and 47
on the other side of the helicopter. These four blades 44, 45, 46
and 47 are then folded towards the rear according to a sequence
which is identical to that described above for folding the blades
4, 5, 6 and 7 of the four-bladed rotor, according to FIGS. 6 to 11,
and for folding towards the rear the blades 34, 35, 36 and 37 of
the five-bladed rotor according to FIGS. 17 to 18.
[0123] The six-bladed rotor, the four rearmost blades 44, 45, 46
and 47 of which are locked folded towards the rear, is shown in
FIG. 20. It then remains to fold towards the rear the two
forwardmost blades 48 and 49. To this end, the jack 19 on the left
side is separated at least from the rearmost blade 45 on the same
side, and this left jack 19 is installed between and removably
attached to the blades 44 and 48 on the left, which are
respectively the second rearmost blade and the forwardmost blade on
that side.
[0124] Similarly, the jack 19 on the right side is separated at
least from the rearmost blade 47 on the right and locked folded,
and this right jack 19 is installed between and removably attached
to the two blades 46 and 49 on the right, which are respectively
the second rearmost blade and the forwardmost blade on that side.
One of the front blades 48 or 49 is then unlocked by removing its
blade pin 9 situated nearest to the front and, by causing the jack
19 on the corresponding side to retract, this blade 48 or 49 is
made to pivot towards the rear by rotating about its pivot pin 9,
the rearmost and kept in place, and then this blade 48 or 49 is
locked in position folded towards the rear (see FIG. 21) by
attaching it, as explained above, to the rear part of the
helicopter structure or to the tail boom or to the other blades
previously folded and locked. The same actions are then taken for
the other front blade 49 or 48, so that the six blades of the rotor
are locked folded in the position shown in FIG. 21.
[0125] As a variant, a single jack 19 may be used, but it must be
installed four times in succession on and between two adjacent
blades, twice on each side of the helicopter, for example between
the blades 44 and 45, then between the blades 44 and 48, then
between the blades 46 and 47, and finally between the blades 46 and
49; or between the blades 44 and 45, then between the blades 46 and
47, then between the blades 44 and 48 or 46 and 49, and finally
between the blades 46 and 49 or 44 and 48.
[0126] The folding procedure described above may also be applied to
any number of blades greater than six, although rotors with more
than six blades are not easily made compatible with blade
folding/unfolding capabilities.
[0127] In the figures showing the folding of four-bladed,
five-bladed and six-bladed rotors, it will be noted that on each
side of the helicopter the rearmost blade of the rotor, in the
folded position, occupies the top position in a vertical plane,
whereas the forwardmost blade, in the folded position, occupies the
bottom position in a vertical plane. However, depending on the
configuration, geometry and operating mechanisms proper to each
rotor, the relative positions of the blades in a vertical plane, in
the folded position, may be different from that shown in the
drawings.
[0128] In the course of folding the blades of the six-bladed rotor
in FIGS. 19 to 21, a rectilinear, rigid link rod, similar to the
rod 21 in FIGS. 9 to 11, may be removably attached, under the same
conditions and with the same purpose as in FIGS. 9 to 11, between
the two rearmost folded and locked blades 45 and 47, to strengthen
the bearing point of the jacks 19 for retracting the blades 44 and
46 towards the rear, and/or another link rod also similar to the
rod 21 may also be removably attached to the second rearmost blades
44 and 46 locked folded, to strengthen the bearing points of the
two jacks 19 for folding the two front blades 48 and 49 towards the
rear.
[0129] A telescopic link rod may also be used, installed firstly
between the blades 45 and 47 folded and locked, then after folding
the blades 44 and 46 towards the rear, between these latter two
blades 44 and 46, for folding the front blades 48 and 49. This
operation makes it necessary to adjust the length of the telescopic
rod to a first value, to attach it removably to the blades 45 and
47, and then to detach this rod from these blades 45 and 47, alter
its length and set it to a second value suitable for connecting it
removably to the blades 44 and 46, for example at the attachment
points 20 on these different blades. As a variant, a non-active
jack may be used as a link rod.
[0130] The variable-length linear actuator or jack 19, 24 or 31 of
the examples of rotors described above may be a double-acting
linear jack suitable for exerting on the two blades to which this
jack is removably attached forces in both directions along the
longitudinal axis of this jack. Such a jack, of simple and
lightweight structure, small in size and easy to install on the two
blades and to remove from the latter, is preferably such as shown
in FIGS. 22 and 23.
[0131] These show a mechanical jack with a tubular body 50 in which
a rectilinear rod 51 is fitted and is telescopic axially. The rod
51 is itself tubular and its part inserted axially in the body 50
encloses at least a part of a worm screw 52, preferably reversible
for the reason indicated below, with which the rod 51 is engaged.
This worm screw 52 is fitted so as to rotate coaxially and retained
in a fixed axial position in the body 50, in which the axis of the
worm screw 52, at the end opposite the rod 51, is integral in
rotation with a bevel output gearwheel 54 of bevel gears 53, a
bevel input pinion 55 of which is meshed with the gearwheel 54, so
as to constitute a reduction stage, and the input pinion 55 is
integral in rotation with an input shaft 56 extending radially
(perpendicularly to the common longitudinal axis of the body 50,
the rod 51 and the worm screw 52) and running through the wall of
the body 50, so as to be accessible from outside the body 50, into
a drive casing 57 integral with the body 50 and projecting radially
towards the outside of the latter, and in which the end of a hand
crank may be inserted to drive manually the mechanical jack thus
produced, or the end of a reversible screwdriver with an electric
motor powered from a battery and therefore self-contained and easy
to use in succession on the different jacks which may be fitted on
the same rotor to fold or unfold the blades.
[0132] It will be understood that driving the input shaft 56 in
rotation in one or other direction causes the rod 51 to move
axially in one or other direction along the longitudinal axis of
the body 50, via the mechanical drive device with multiplication of
force at the rod 51 which is constituted by the bevel gears 53 and
the worm screw 52.
[0133] The jack also comprises a manually operated mechanism to
disengage the rod 51, and this mechanism, not shown in detail in
the drawings but of known structure, allows the bevel pinion 55 to
be moved in the direction of the input shaft 56 so as to move the
pinion 55 away from the bevel gear wheel 54, which allows the
length of the jack to be adjusted quickly and easily by moving its
rod 51 relative to its body 50, for installing and attaching the
jack to the two blades which it is intended to connect, when the
worm screw 52 is reversible.
[0134] To this end, the jack is equipped at its two axial ends with
the end fittings 58 and 59 for attaching removably and quickly and
with no special tools to compatible attachment devices fitted to
the blades.
[0135] In the example in FIGS. 22 and 23, the end fittings 58 and
59 are tubular end fittings, transverse relative to the
longitudinal axis of the jack, one of which 58 is at the end of the
rod 51 which is external to the body 50 and constitutes an end
elbow of this rod 51, while the other tubular end fitting 59 is
integral with the end external to the body 50 of a small sleeve 60,
fitted so as to slide axially through the end of the body 50 at the
opposite end to the rod 51, and such that the end internal to the
body 50 of this sleeve 60 constitutes a stop limiting the movement
of the sleeve 60 and of the end fitting 59 axially towards the
outside of the body 50. A helical spring 61 is wound about the
sleeve 60 bearing at one end against the body 50 and at the other
against the end fitting 59, so that this spring 61 provides a
certain axial elasticity for the jack, being in series with the end
fitting 59 and the body 50, in order to limit abnormal loads
produced in particular by impacts during manoeuvres to bring
together the different parts in motion, and in particular when a
blade connected to one of the end fitting 58 or 59 reaches the end
of its travel in the unfolded position, by bearing against another
blade via the other end fitting 59 or 58 of the jack. Other elastic
means in series with the other end fitting 58 or with the rod 51
may also be used and embodied in a different form, for example in
the form of a block of elastically deformable material such as an
elastomer.
[0136] In the example in FIGS. 22 and 23, the transverse tubular
end fittings 58 and 59 of the jack, when they are coupled to the
corresponding attachment devices on the blades, enable the body 50
and the rod 51 of the jack to be offset in a vertical plane to
avoid any interference with the rotor components situated above the
blades. These end fittings 58 and 59 contribute to the link between
the jack and the blades which these end fittings provide in
combination with attachment devices fitted to the blades, at the
attachment points 20, 27 and 32 of the examples of rotors described
previously, and in such a way that this connection between the jack
and the blades fulfils two functions, namely transmitting the axial
forces of the jack to the two blades which it links, these forces
being substantially parallel to the plane of the blades (plane of
the rotor disc) and allowing the jack to swivel, by a joint with
three degrees of freedom, to avoid moments induced in the joint by
a combination of the pivoting of a blade and of the generally
non-zero angle of attack of this blade.
[0137] The attachment devices fitted to the blades to provide the
removable joints of the end fittings 58 and 59 of the jack to the
blades, may be either entirely fitted onto the blades, and are then
removable attachment devices not forming part of the structure of
the blade, which may still be a standard blade, or completely or
partially integrated in the structure of the blade so that the
latter is specific to the folding, and in this case the attachment
devices fitted to each blade may comprise one or more elements
inserted in the blade, in particular its root or portion of root,
and one or more removable elements, fitted onto the element or
elements inserted in the blade.
[0138] To reduce working time when connecting a jack end fitting to
a blade, or when separating them, a quick-locking ball joint is
used.
[0139] As shown in FIG. 24, the swivel ball 62 projects above a
support plate 63 which is attached to the root 8 of the
corresponding blade by two screws 64 screwed into tubular inserts
65 with a threaded internal bore sunk in the blade root 8 so that
the openings of their threaded bores are flush with the upper face
of the blade root 8.
[0140] Each tubular end fitting 58, 59 of the jack such as 19, 24
or 31, has a recess 66 (see FIG. 23) by which the corresponding end
fitting 58, 59 can fit onto the swivel ball 62 fitted to the blade.
As shown in FIG. 25, a known locking device, using a key or, as
shown in this figure, a finger 67 loaded by a calibrated spring
towards the inside of the recess 66, prevents accidental release of
the end fitting 58, 59 of the jack when this end fitting is fitted
onto the swivel ball 62. This finger 67 may be moved manually
against the spring which loads it, so as to clear the way for the
swivel ball 62 to come out of the recess 66 when the end fitting
58, 59 is withdrawn, when the jack is separated from the
corresponding blade.
[0141] In the assembly shown in FIG. 24, the support plate 63, with
which the swivel ball 62 is integral, provides proper distribution
of the forces in the blade root 8, but it is also possible, as in
the variant shown in FIGS. 26 and 27, for the swivel ball 62 to be
integral with a threaded support pin 68 which is screwed into a
tubular insert 69 with a threaded internal bore and designed to be
permanently sunk into the blade root 8. In this case, the swivel
ball 62 is removable with its support pin 68, which is screwed into
the insert 69 to allow a folding jack to be fitted. FIG. 27 shows
the assembly of the swivel ball 62, its support pin 68 and the
insert 69 fitted in a blade root 8 and being centred in a plane
midway between the sleeves 70 also sunk into the blade root 8 to
receive the blade pins 9.
[0142] As a variant, the swivel ball 62 may be integral with a
support 69' which directly constitutes an insert sunk into the
blade root 8, in which case the swivel ball 62 remains installed on
the blade even outside the operations of folding/unfolding the
blades.
[0143] The swivelling function may also be integrated into the end
fittings of the jack 19, 24 or 31. In this case, as shown in FIG.
28, the jack 19, 24 or 31 is fitted at each of its longitudinal
ends with a conventional ball joint end fitting 71, the swivel ball
72 of which is retained removably on the blade root 8 by means of a
pin 73 integrated in this blade root 8.
[0144] As a variant, the device or devices removably attaching a
jack to a blade may or may not be entirely fitted onto the blade,
without altering the structure of this blade. An example of this
variant is shown in FIGS. 29 and 30, in which the removable
attachment device is a removable retaining collar 74 which supports
a swivel ball 75 projecting from the upper face of the blade root
8. The retaining collar 74, when it is assembled, has the form of a
sleeve the inner bore of which is shaped so as to fit over the
changing cross-section portion of the blade root 8, between the
normal part of the blade and the end portion of this blade root 8
which is fitted into the outer radial end yoke 11 of the cuff or
arm 10 connecting it to the hub which has the two blade pins 9
running through it when this blade is locked in the flight
configuration. The retaining collar 74 thus fitted over the blade
root 8 is locked on this blade root 8 by form fitting, and is held
along the longitudinal axis of the corresponding blade in the
position in which it grips the changing cross-section portion of
the blade root 8 by means of a spacer 76, which keeps the retaining
collar 74 spaced radially towards the outside of the pivot pin 9
(towards the rear of this blade) about which pivot pin 9 this
spacer 76 pivots with the retaining collar 74 and the blade.
[0145] As a variant, the retaining collar 74 supports, instead of
the swivel ball 75, a pin such as the retaining pin 73 in FIG. 28,
to cooperate with the swivel 72 of a ball joint end fitting 71 of a
jack (see FIG. 28). However, as shown in FIGS. 29 and 30, the
retaining collar 74 with swivel 75 may cooperate with end fittings
such as 58, 59 with recesses 66 for removably attaching jacks as
shown in FIGS. 22, 23 and 25.
[0146] To fulfil its function, it will be understood that the
retaining collar 74 in FIGS. 29 and 30 is completely locked
relative to the blade, so that the loads from the jacks do not
cause any relative movement between the blade and the retaining
collar 74, which would result in damage to the blade or the hub, or
the arm or cuff 10 connecting it to the latter. The form fitting
between the retaining collar 74 and the changing cross-section
portion of the blade root 8 enables all the movements of rotation
of the retaining collar 74 relative to the blade to be locked, as
well as relative movements, since slippage of the retaining collar
74 towards the cuff or arm 10 of the hub is prevented by the spacer
76, constituting a pivoting connecting device between the retaining
collar 74 and the hub or its arm or cuff 10.
[0147] In the examples of rotors described above with reference to
the figures, conventional blade pins 9 are used to provide the
joint between the blades and the cuffs or arms connecting them to
the hub 3. However, to facilitate extraction and insertion of these
blade pins 9, and in particular of the front pin, which must be
removable to allow the blades to be folded by pivoting towards the
rear about the rear blade pin, it is preferable to use at least one
front blade pin of the expanding pin type, well known, such as
described in U.S. Pat. No. 3,192,820, the use of which on
rotary-wing aircraft rotors with manual folding blades is well
known, and in particular proposed in FR 00 16065. These expanding
pins are lever pins, on which the operation of the lever, by means
of an eccentric, axially compresses devices forming an elastic
bellows in a cylindrical pin barrel, which has the effect of
slightly increasing the diameter of this barrel, and therefore of
locking it in a sleeve inserted into a blade root to receive an
expanding pin of this type.
[0148] The invention has now been described in detail for the
purposes of clarity of understanding. It will, however, be
appreciated that certain changes and modifications may be practical
within the scope of the appended claims.
* * * * *