U.S. patent application number 11/004393 was filed with the patent office on 2006-06-08 for damper positioner for a rotor blade folding system.
This patent application is currently assigned to Sikorsky Aircraft Corporation. Invention is credited to Frank Paul D'Anna.
Application Number | 20060120873 11/004393 |
Document ID | / |
Family ID | 36574420 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060120873 |
Kind Code |
A1 |
D'Anna; Frank Paul |
June 8, 2006 |
Damper positioner for a rotor blade folding system
Abstract
A rotor blade folding system includes a damper assembly which is
selectively lockable. The damper assembly is locked to position
each blade yoke in a predetermined lead/lag position to minimize
strain upon elastomeric bearings between the blade yoke and the
rotor hub and contained in the damper. The rotor blade is then
folded relative to the blade yoke to a predetermined blade fold
angle.
Inventors: |
D'Anna; Frank Paul;
(Seymour, CT) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD
SUITE 350
BIRMINGHAM
MI
48009
US
|
Assignee: |
Sikorsky Aircraft
Corporation
|
Family ID: |
36574420 |
Appl. No.: |
11/004393 |
Filed: |
December 3, 2004 |
Current U.S.
Class: |
416/221 |
Current CPC
Class: |
B64C 27/51 20130101;
B64C 27/50 20130101 |
Class at
Publication: |
416/221 |
International
Class: |
F01D 5/30 20060101
F01D005/30 |
Claims
1. A damper assembly including a damper rod for rotor blade
assembly comprising: an actuator; a plunger driven by said actuator
to limit movement of a damper rod from a first direction; and a
puller driven by said actuator to limit movement of said damper rod
from a second direction such that the damper rod is selectively
axially locked in a blade fold position along a damper axis.
2. The damper assembly as recited in claim 1, further comprising a
sleeve drivable about the damper axis by said actuator, said sleeve
defines an outer circumferential jackscrew and an inner
circumferential jackscrew.
3. The damper assembly as recited in claim 2, wherein said outer
circumferential jackscrew drives said plunger.
4. The damper assembly as recited in claim 3, further comprising an
anti-rotation feature extending form said plunger.
5. The damper assembly as recited in claim 2, wherein said inner
circumferential jackscrew drives said puller.
6. The damper assembly as recited in claim 5, further comprising an
anti-rotation feature extending form said puller.
7. The damper assembly as recited in claim 6, wherein said puller
slides at least partially within a hollow cavity formed within the
damper rod.
8. The damper assembly as recited in claim 7, wherein said puller
includes a puller bushing slidable within said hollow cavity to
selectively contact a damper rod puller stop.
9. A rotor blade assembly comprising: a rotor hub; a yoke mounted
to said rotor hub with an elastomeric bearing; a damper assembly
mounted to said rotor hub and said yoke, said damper assembly
including a damper housing and a damper rod slidable along a damper
axis relative to said damper housing; an electric motor; a gear
train in meshing engagement with said electric motor; a plunger
driven by said gear train to limit movement of said damper rod from
a first direction; and a puller driven by said gear train to limit
movement of said damper rod from a second direction such that said
damper rod is selectively axially locked in a blade fold position
along a damper axis.
10. The rotor blade assembly as recited in claim 9, further
comprising a sleeve drivable about the damper axis by said gear
train, said sleeve defines an outer circumferential jackscrew and
an inner circumferential jackscrew, said outer circumferential
jackscrew drives said plunger, and said inner circumferential
jackscrew drives said puller.
11. The rotor blade assembly as recited in claim 9, wherein said
puller slides at least partially within a hollow cavity formed
within the damper rod.
12. The rotor blade assembly as recited in claim 11, wherein said
puller includes a puller bushing slidable within said damper cavity
to selectively contact a damper rod puller stop.
13. A method of folding a rotor blade comprising the steps of: (1)
sliding a plunger along a damper axis and limit movement of a
damper rod of a damper assembly from a first direction; (2) sliding
a puller along the damper axis to limit movement of the damper rod
from a second direction such that said damper rod is selectively
axially locked between the plunger and the puller in a blade fold
position along the damper axis; and (3) folding a rotor blade to a
predetermined blade fold angle about a blade fold pivot axis.
14. A method as recited in claim 13, wherein said step (1) further
comprises rotating a sleeve with the electric motor and sliding the
plunger with said sleeve.
15. A method as recited in claim 14, wherein said step (2) further
comprises rotating a sleeve with the electric motor and sliding the
puller with said sleeve.
16. A method as recited in claim 13, including performing said step
(1) and said step (2) simultaneously.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a blade fold system for a
helicopter, and more particularly to a rotor blade positioning
system which positions each rotor blade prior to blade folding
while minimizing applied strain to elastomeric bearings within the
rotor head.
[0002] While the flight capabilities of helicopters makes them
effective vehicles for a wide variety of missions, operation of
helicopters in certain circumstances may be limited by the overall
structural envelopes thereof. The large radial dimensions of
helicopter rotor assemblies results in helicopters having
relatively large structural envelopes, which may limit their
utility in some circumstances.
[0003] Helicopters, particularly military helicopters utilized for
maritime flight operations, may be required to conduct operations
from ships for extended periods of time. Shipboard space is
generally at a premium, and the large structural envelopes of
helicopters means that stowage during periods of non-use requires a
relatively significant allocation of such limited space.
Furthermore, strategic and tactical considerations in the military
utilization of helicopters has led to a requirement for helicopters
having main rotor assemblies that may be readily reconfigured for
rapid deployment, routine transport, and/or stowage through
reduction in structural envelopes.
[0004] Several options are available to reduce the structural
envelopes of helicopters to facilitate rapid deployment, routine
transport, stowage, and/or to reduce the vulnerability thereof to
environmental conditions. One option is to design the main rotor
assemblies thereof so that the main rotor blades may be folded
about the main rotor hub assembly. Main rotor blade folding
operations are typically implemented automatically.
[0005] One helicopter with an automatic blade folding system is the
CH-53E. The CH-53E is currently the world's largest shipboard
compatible helicopter. A significant consideration in the design of
the CH-53E is shipboard compatibility. The CH-53E in a stored
configuration effectively defines the maximum structural envelope
which will fit on the elevators and in the hangar deck of United
States Marine Corps Amphibious Assault Ships.
[0006] Prior to folding blades on any helicopter, the blades must
be located and locked in a pre-set blade fold position such that a
blade hinge axis is oriented to allow folding of each blade to its
proper folded position. On aircraft such as CH-53E, blade
positioning is accomplished using a series of hydraulic actuators
and stops. The current CH-53E rotor head utilizes a hydraulic
actuated piston incorporated into the damper as a pitch lock.
Accumulator pressure drives the damper to hold the blade in the
pre-set blade fold position in which the yoke is driven to full lag
or lead position. The swashplate is then located in a pre-set
position such that each blade is at the correct pitch angle for the
blade pitch locks to engage. Since pitch motion occurs between the
sleeve and the spindle, a hydraulic actuated pin on the sleeve
engages a lug on the spindle to lock the spindle and sleeve
together to prevent pitch motion. These components function
independently as the current CH-53E rotor head employs separate
conventional bearings for pitch, flap, and lead/lag blade
motions.
[0007] Elastomeric rotor heads with elastomeric bearings provide
numerous advantages over conventional rotor head assemblies which
utilize separate bearings for pitch, flap, and lead/lag blade
motions. Elastomeric rotor heads provide such significant
advantages, that current aircraft such as the CH-53E may be
modernized to include an elastomeric rotor head.
[0008] Current blade folding systems are not transferable to an
elastomeric rotor head as the elastomeric bearings and
visco-elastic damper are essentially springs which are always
biased toward a predetermined position. Deflection away from the
predetermined position strains the elastomeric bearings and
visco-elastic damper. Significant deflection over prolonged time
periods, such as during a blade fold position, may eventually
damage the elastomeric rotor head system.
[0009] Accordingly, it is desirable to provide a blade folding
system for an elastomeric rotor head system which positions each
rotor blade prior to blade folding while minimizing applied strain
to elastomeric bearings within the rotor head.
SUMMARY OF THE INVENTION
[0010] The rotor blade folding system according to the present
invention generally includes an electric motor mounted to a damper
housing of the damper assembly to drive a damper gear train and
selectively lock a damper rod relative the damper housing in a
blade fold position to minimize strain on an elastomeric
bearing.
[0011] In operation, a blade fold controller operates the electric
motor to rotate a sleeve about the damper axis such that an outer
circumferential jackscrew drives a plunger along the damper axis
toward the damper rod. Concurrently therewith, an inner
circumferential jackscrew of the sleeve drives a puller along the
damper axis until a puller bushing contacts a damper rod puller
stop. The plunger and the puller trap the damper rod in a
predetermined blade fold position. The damper assembly is locked at
a predetermined length such that the elastomeric bearing is
isolated when the rotor blade is folded. Once each yoke is locked
by the damper assembly in the blade fold position, the blade fold
controller drives the rotary actuator to rotate each rotor blade to
a predetermined blade fold angle.
[0012] To unfold the blades, the blade fold controller reverses the
rotary actuator to return the rotor blade to a flight position and
reverses the electric motor to release the damper rod such that the
yoke and damper assembly returns to a flight configuration.
[0013] The present invention therefore provides a blade folding
system for an elastomeric rotor head system which positions each
rotor blade prior to blade folding while minimizing applied stress
to elastomeric bearings within the rotor head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The various features and advantages of this invention will
become apparent to those skilled in the art from the following
detailed description of the currently preferred embodiment. The
drawings that accompany the detailed description can be briefly
described as follows:
[0015] FIG. 1 is a general perspective view an exemplary rotary
wing aircraft embodiment for use with the present invention with a
main rotor assembly in a flight position;
[0016] FIG. 2 is a top plan view of a main rotor assembly
illustrating a single blade and blade fold system;
[0017] FIG. 3 is a general perspective view of an exemplary rotary
wing aircraft embodiment for use with the present invention with a
main rotor assembly in a folded position;
[0018] FIG. 4A is a sectional view of a damper assembly in flight
condition;
[0019] FIG. 4B is an expanded sectional view of a damper assembly
in flight condition;
[0020] FIG. 4C is a sectional view of a damper assembly in a blade
fold condition;
[0021] FIG. 5 is a top plan view of a main rotor assembly
illustrating the rotor blades in a folded position;
[0022] FIG. 6 is an expanded top view of a main rotor assembly
illustrating the rotor blades in a folded position.
[0023] FIG. 7 is an expanded side perspective view of a main rotor
assembly illustrating the rotor blades folded relative a blade
yoke.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] FIG. 1 schematically illustrates a rotary-wing aircraft 10
having a main rotor assembly 12. The aircraft 10 includes an
airframe 14 having an extending tail 16 which mounts an anti-torque
rotor 18. The main rotor assembly 12 is driven through a
transmission (illustrated schematically at 20) by one or more
engines 22. This description includes the particular structural
features of the main rotor assembly 12 of a Sikorsky CH-53
helicopter configuration as illustrated in the disclosed embodiment
for discussion purposes. The present invention may be embodied for
use with rotor assemblies of other helicopters, turbo-props,
tilt-rotor aircraft and other elastomeric bearing based rotor
assemblies.
[0025] Referring to FIG. 2, the rotor assembly 12 includes seven
rotor blade assemblies 24 (one shown) each mounted to a rotor hub
26 which rotates about an axis of rotation R. Each rotor blade
assembly 24 includes a rotor blade 28, a hinge assembly 30, a
rotary actuator 32, a sleeve 34, a yoke 36 an elastomeric bearing
38, a damper assembly 40 and a blade pitch lock assembly 42.
[0026] The yoke 36 is mounted to the rotor hub 26 through the
elastomeric bearing 38 such that the blade assembly 24 may be moved
in flapping, pitch and lead/lag motions as generally understood.
The damper assembly 40 reacts with the yoke 36 to dampen lead/lag
motions and vibration of the blade assembly 24.
[0027] A rotor blade folding system 44 generally includes the blade
pitch lock assembly 42, the rotary actuator 32, a retractable blade
retaining pin 33, the damper assembly 40 and a blade fold
controller 47 (illustrated schematically) to selectively position
each rotor blade assembly 24 in a particular folded position to
minimize the aircraft structural envelope (FIG. 3).
[0028] Referring to FIG. 4A, an example damper assembly 40 includes
a damper rod 46 that is movable relative to a damper housing 50 by
two axial elastomeric bearings 48. The damper housing 50 includes a
fluid which damps movement of the damper rod 46 along a damper axis
D to react against lead/lag motions of the blade assembly 24 (FIG.
2) and to dampen vibration. The lead/lag and vibration damping
operation of the damper assembly 40 is generally understood.
[0029] A rod mount 52 extends from near an end of the damper rod 46
and a housing mount 54 extends from the damper housing 50. The
mount 52 and 54, which are ball mounts, other links or a
combination of them, mount the damper assembly 40 between the rotor
hub 26 and the yoke 36 of each blade assembly 24 (FIG. 2).
[0030] Referring to FIG. 4B, an actuator such as an electric motor
56 is mounted to the damper housing 50 to drive a damper gear train
57 to selectively lock the damper rod 46 relative to the damper
housing 50 in a predetermined blade fold position to minimize
strain on the elastomeric bearings 38 and 48. With the damper rod
46 locked, the damper assembly 40 locks the yoke 36 in a
corresponding position relative to the rotor hub 26 (FIGS. 2, 5).
The blade fold position in one example is a mid-position of the
damper assembly 40, however, other locked positions will be useful
to suit the needs of a particular embodiment.
[0031] The electric motor 56 includes an output shaft 58 which
drives an output gear 60. The output gear 60 is in meshing
engagement with a sleeve 62 at gear teeth 64. The sleeve 62 is
rotationally mounted upon a sleeve bearing 66 which is mounted
about an inner damper housing 68 such that the sleeve 62 rotates
about the damper axis D in response to operation of the electric
motor 46.
[0032] The sleeve 62 includes an outer circumferential jackscrew 70
and an inner circumferential jackscrew 72. The outer
circumferential jackscrew 70 and the inner circumferential
jackscrew 72 are preferably oppositely directed screw threads. That
is, the outer circumferential jackscrew 70 is right hand and the
inner circumferential jackscrew 72 is left hand or vice-versa. It
should be understood that other threaded members or gears other
than a jackscrew or in combination therewith may also be used with
the present invention.
[0033] The outer circumferential jackscrew 70 engages a plunger
screw thread 74 which is located within the inner diameter of a
plunger 76. The plunger 76 includes an anti-rotation feature 78
which includes a radial pin 80 which extends into a housing slot 82
such that the plunger 76 slides along the axis D but does not
rotate.
[0034] The inner circumferential jackscrew 72 engages a puller
screw thread 84 located along a length of a puller 86. The puller
86 includes an anti-rotation feature 88 such that the puller 86
slides along the axis D but does not rotate. In one example, the
puller 86 is splined at 90 and the inner damper housing 68 is
splinted at 92.
[0035] The puller 86 slides within a tubular hollow cavity 93
formed within the damper rod 46. Preferably, a puller bushing 94
moves with the puller 86 and is slidable within the damper rod 46
to selectively contact a damper rod puller stop 96 (in the position
illustrated in FIG. 4C).
[0036] A blade fold controller 47 (illustrated schematically)
operates the electric motor 56 to drive the output gear 60 which is
in meshing engagement with the sleeve 62. The sleeve 62 rotates
about the damper axis D such that the outer circumferential
jackscrew 70 cooperates with the plunger screw thread 74 to drive
the plunger 76 along axis D toward the damper rod 46. Eventually,
the plunger 76 moves into the position shown in FIG. 4C.
Concurrently therewith, the inner circumferential jackscrew 72 of
the sleeve 62 cooperates with the puller screw thread 84 to drive
the puller 86 along the damper axis D in an opposite direction
until the puller bushing 94 contacts the damper rod puller stop 96
as shown in (FIG. 4C). In this position, the plunger 76 and the
puller 86 trap the damper rod 46 in the blade fold position. That
is, the damper assembly 40 is locked at a predetermined length such
that the yoke 36 cannot pivot relative to the hub 26. This locked
condition isolates the elastomeric bearing 38 from strain when the
rotor blade is folded (FIGS. 3, 5).
[0037] Once the plunger 76 and the puller 86 trap the damper rod 46
and the damper assembly 40 is locked, each rotor blade assembly 24
may be positioned in pitch by articulating the swashplate prior to
engaging the blade pitch lock assembly 42 (FIG. 2). That is, the
blade pitch lock assembly 42 locks the yoke 36 once the yoke 36 has
previously been articulated by the swashplate. When the swashplate
is positioned properly, all the blades 28 are at a predetermined
pitch angle for each blade pitch lock assembly 42 to engage.
Separately, the blade fold pivot axis B (FIGS. 3 and 6) for each
blade 28 is typically at a different angle, pitch-wise, from a
fixed point on the yoke 36, such that each blade 28 will fold to
its own predetermined blade fold position (FIG. 7). That is, the
angle between the blade fold pivot axis B and the yoke 36 center
plane is different for each blade assembly 24. This is typically
accomplished by creating different sleeves and hinges for each
blade assembly 28 such that the more forward blades will fold
generally under the rearward blades (FIG. 3). Referring to FIG. 5,
once the damper assembly 40 is locked and the blade pitch lock
assembly 42 engaged, the blade fold controller 47 stops the
electric motor 56 through communication with a sensor such as a
limit switch or the like. The blade pitch lock assembly 42 (FIG. 2)
is then engaged such that each yoke 36 is positioned for folding of
each rotor blade 28. Once each yoke 36 is positioned for blade 28
fold, the controller 47 drives the rotary actuator 32 to rotate
each rotor blade 28 to a predetermined blade fold angle about the
blade fold pivot axis B (FIGS. 3 and 6).
[0038] Referring to FIG. 6, the rotary actuator 32 rotates each
rotor blade 28 to a predetermined blade fold angle
.alpha..sub.1-.alpha..sub.7 about a blade fold pivot axis B.sub.1-
B.sub.7 (also illustrated in FIG. 7). Notably, minimal strain is
placed on the elastomeric bearing 38 as the damper assembly 40
locks each yoke 36 relative to the rotor hub 26.
[0039] To unfold the blades, the blade fold controller 47 reverses
the rotary actuator 32 to unfold the rotor blades 28 (.alpha. to
zero) then retracts the plunger 76 and the puller 86 to release the
damper rod 46 such that damper assembly 40 (FIG. 4A) and the yoke
36 return to a flight configuration.
[0040] It should be understood that relative positional terms such
as "forward," "aft," "upper," "lower," "above," "below," and the
like are with reference to the normal operational attitude of the
vehicle and should not be considered otherwise limiting.
[0041] Although particular step sequences are shown, described, and
claimed, it should be understood that steps may be performed in any
order, separated or combined unless otherwise indicated and will
still benefit from the present invention.
[0042] The foregoing description is exemplary rather than defined
by the limitations within. Many modifications and variations of the
present invention are possible in light of the above teachings. The
preferred embodiments of this invention have been disclosed,
however, one of ordinary skill in the art would recognize that
certain modifications would come within the scope of this
invention. It is, therefore, to be understood that within the scope
of the appended claims, the invention may be practiced otherwise
than as specifically described. For that reason the following
claims should be studied to determine the true scope and content of
this invention.
* * * * *