U.S. patent application number 17/188785 was filed with the patent office on 2022-09-01 for spherical bearing centrifugal force retention link.
This patent application is currently assigned to Bell Textron Inc.. The applicant listed for this patent is Bell Textron Inc.. Invention is credited to Andrew Paul HALDEMAN, Timothy McClellan MOSIG, George Matthew THOMPSON, Paul Wayne WOOLBRIGHT.
Application Number | 20220274692 17/188785 |
Document ID | / |
Family ID | 1000005445048 |
Filed Date | 2022-09-01 |
United States Patent
Application |
20220274692 |
Kind Code |
A1 |
HALDEMAN; Andrew Paul ; et
al. |
September 1, 2022 |
SPHERICAL BEARING CENTRIFUGAL FORCE RETENTION LINK
Abstract
A spherical bearing centrifugal force retention link includes an
inboard spherical bearing to attach to a rotor hub and an outboard
spherical bearing to attach to a rotor blade. In use, the inboard
spherical bearing and the outboard spherical bearing react
centrifugal force radially and a torsional moment of the
centrifugal force link is substantially constant throughout the
rotor blade pitch range.
Inventors: |
HALDEMAN; Andrew Paul; (Fort
Worth, TX) ; WOOLBRIGHT; Paul Wayne; (Euless, TX)
; MOSIG; Timothy McClellan; (Richland Hills, TX) ;
THOMPSON; George Matthew; (Lewisville, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bell Textron Inc. |
Fort Worth |
TX |
US |
|
|
Assignee: |
Bell Textron Inc.
Fort Worth
TX
|
Family ID: |
1000005445048 |
Appl. No.: |
17/188785 |
Filed: |
March 1, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64C 27/35 20130101;
B64C 27/48 20130101; B64C 27/82 20130101; B64C 2027/8254
20130101 |
International
Class: |
B64C 27/35 20060101
B64C027/35; B64C 27/82 20060101 B64C027/82; B64C 27/48 20060101
B64C027/48 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with government support under
Agreement No. W911W6-19-9-0002, awarded by the U.S. Army
Contracting Command-Redstone Arsenal. The government has certain
rights in the invention.
Claims
1. A rotor blade assembly, comprising: a hub rotatable about a
rotational axis; a rotor blade extending radially from the hub
along a pitch axis and having a rotor blade pitch range; and a
centrifugal force (CF) link having an inboard spherical bearing
attached to the hub and an outboard spherical bearing attached to
the rotor blade and a torsional moment of the CF link is constant
throughout the rotor blade pitch range.
2. The rotor blade assembly of claim 1, wherein the CF link
comprises a beam between the inboard spherical bearing and the
outboard spherical bearing.
3. The rotor blade assembly of claim 1, wherein the rotor blade
pitch range is between 70 and 85 degrees.
4. The rotor blade assembly of claim 1, wherein the rotor blade
pitch range is 50 to 85 degrees.
5.-6. (canceled)
7. The rotor blade assembly of claim 10, wherein the rotor blade
pitch range is 50 to 85 degrees.
8. The rotor blade assembly of claim 1, wherein the inboard
spherical bearing and the outboard spherical bearing react a
centrifugal force radially.
9. The rotor blade assembly of claim 1, further comprising a blade
grip having an inboard end connected to the outboard spherical
bearing and a first blade grip portion rotationally coupled to the
hub outboard of the inboard end.
10. The rotor blade assembly of claim 9, wherein the inboard
spherical bearing and the outboard spherical bearing react a
centrifugal force radially.
11. The rotor blade assembly of claim 10, wherein the rotor blade
pitch range is between 70 and 85 degrees.
12. A rotorcraft, comprising: a rotor comprising a hub rotatable
about a rotational axis; a rotor blade extending radially from the
hub along a pitch axis and having a rotor blade pitch range; and a
centrifugal force (CF) link having an inboard spherical bearing
attached to the hub and an outboard spherical bearing attached to
the rotor blade, wherein the inboard spherical bearing and the
outboard spherical bearing react centrifugal force radially, and a
torsional moment of the CF link is constant throughout the rotor
blade pitch range.
13. The rotorcraft of claim 12, wherein the rotor is located in a
duct.
14. The rotorcraft of claim 12, wherein the rotor is an anti-torque
rotor.
15. The rotorcraft of claim 12, wherein the rotor blade pitch range
is between 70 and 85 degrees.
16. The rotorcraft of claim 12, wherein the rotor is a ducted
anti-torque rotor; and the rotor blade pitch range is between 70
and 85 degrees.
17. A ducted fan, comprising: a duct having a central axis; a rotor
assembly located in the duct, the rotor assembly comprising: a hub
rotatable about a rotational axis coaxial with the central axis; a
rotor blade extending radially from the hub along a pitch axis and
having a rotor blade pitch range; and a centrifugal force (CF) link
having an inboard spherical bearing attached to the hub and an
outboard spherical bearing attached to the rotor blade, wherein the
inboard spherical bearing and the outboard spherical bearing react
centrifugal force radially, and a torsional moment of the CF link
is constant throughout the rotor blade pitch range.
18. The ducted fan of claim 17, further comprising a blade grip
having an inboard end connected to the outboard spherical bearing
and a first blade grip portion rotationally coupled to the hub
outboard of the inboard end.
19. The ducted fan of claim 17, wherein the rotor blade pitch range
is between 70 and 85 degrees.
20. The ducted fan of claim 19, further comprising a blade grip
having an inboard end connected to the outboard spherical bearing
and a first blade grip portion rotationally coupled to the hub
outboard of the inboard end.
21. The ducted fan of claim 17, wherein the rotor blade pitch range
is between 50 to 85 degrees.
22. The rotorcraft of claim 12, wherein the rotor blade pitch range
is between 50 to 85 degrees.
Description
TECHNICAL FIELD
[0002] This disclosure relates in general to the field of aircraft,
and more particularly, but not by way of limitation, to a
centrifugal force link between a rotor blade and a rotor hub.
BACKGROUND
[0003] This section provides background information to facilitate a
better understanding of the various aspects of the disclosure. It
should be understood that the statements in this section of this
document are to be read in this light, and not as admissions of
prior art.
[0004] Rotors or fans implementing tension-torsion straps can be
subjected to comparatively high control loads due to the torsional
spring rate of the tension-torsion strap when centrifugal force is
applied. As blade pitch increases, so does the torsional moment
that is exerted by the tension-torsion strap. At maximum blade
pitch angle a tension-torsion strap moment can account for about 45
percent of the total pitching moment. Increased control loads drive
weight into the control system.
SUMMARY
[0005] An exemplary rotor blade assembly includes a hub rotatable
about a rotational axis, a rotor blade extending radially from the
hub along a pitch axis and having a rotor blade pitch range, and a
centrifugal force link having an inboard spherical bearing attached
to the hub and an outboard spherical bearing attached to the rotor
blade.
[0006] An exemplary rotorcraft includes a rotor comprising a hub
rotatable about a rotational axis, a rotor blade extending radially
from the hub along a pitch axis and having a rotor blade pitch
range, and a centrifugal force link having an inboard spherical
bearing attached to the hub and an outboard spherical bearing
attached to the rotor blade, wherein the inboard spherical bearing
and the outboard spherical bearing react centrifugal force
radially, and a torsional moment of the centrifugal force link is
substantially constant throughout the rotor blade pitch range.
[0007] An exemplary ducted fan includes a duct having a central
axis, a rotor assembly located in the duct, the rotor assembly
comprising a hub rotatable about a rotational axis coaxial with the
central axis, a rotor blade extending radially from the hub along a
pitch axis and having a rotor blade pitch range, and a centrifugal
force link having an inboard spherical bearing attached to the hub
and an outboard spherical bearing attached to the rotor blade,
wherein the inboard spherical bearing and the outboard spherical
bearing react centrifugal force radially, and a torsional moment of
the centrifugal force link is substantially constant throughout the
rotor blade pitch range.
[0008] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of claimed
subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The disclosure is best understood from the following
detailed description when read with the accompanying figures. It is
emphasized that, in accordance with standard practice in the
industry, various features are not drawn to scale. In fact, the
dimensions of various features may be arbitrarily increased or
reduced for clarity of discussion.
[0010] FIG. 1 illustrates an exemplary rotorcraft implementing a
spherical bearing centrifugal force retention link in a rotor
system.
[0011] FIG. 2 illustrates an exemplary anti-torque rotor
implementing a spherical bearing centrifugal force retention
link.
[0012] FIG. 3 illustrates an exemplary ducted fan implementing
spherical bearing centrifugal force retention link.
[0013] FIG. 4 illustrates an exemplary rotor blade assembly
implementing a spherical bearing centrifugal force retention
link.
[0014] FIG. 5 illustrates an exemplary spherical bearing
centrifugal force retention link with a rotor blade.
[0015] FIG. 6A illustrates an exemplary spherical bearing
centrifugal force retention link in a rotor blade assembly.
[0016] FIG. 6B is an expanded view of a portion of FIG. 6A.
[0017] FIG. 7 illustrates a rotor blade implementing a spherical
bearing centrifugal force retention link at a 0-degree pitch
angle.
[0018] FIG. 8 illustrates a rotor blade implementing a spherical
bearing centrifugal force retention link at a 50-degree pitch
angle.
[0019] FIG. 9 illustrates a rotor blade implementing a spherical
bearing centrifugal force retention link at a negative 25-degree
pitch angle.
[0020] FIG. 10 graphically illustrates a spherical bearing
centrifugal force retention link having a substantially constant
torsional moment throughout a rotor blade pitch range.
DETAILED DESCRIPTION
[0021] It is to be understood that the following disclosure
provides many different embodiments, or examples, for implementing
different features of various illustrative embodiments. Specific
examples of components and arrangements are described below to
simplify the disclosure. These are, of course, merely examples and
are not intended to be limiting. For example, a figure may
illustrate an exemplary embodiment with multiple features or
combinations of features that are not required in one or more other
embodiments and thus a figure may disclose one or more embodiments
that have fewer features or a different combination of features
than the illustrated embodiment. Embodiments may include some but
not all the features illustrated in a figure and some embodiments
may combine features illustrated in one figure with features
illustrated in another figure. Therefore, combinations of features
disclosed in the following detailed description may not be
necessary to practice the teachings in the broadest sense and are
instead merely to describe particularly representative examples. In
addition, the disclosure may repeat reference numerals and/or
letters in the various examples. This repetition is for the purpose
of simplicity and clarity and does not itself dictate a
relationship between the various embodiments and/or configurations
discussed.
[0022] In the specification, reference may be made to the spatial
relationships between various components and to the spatial
orientation of various aspects of components as the devices are
depicted in the attached drawings. However, as will be recognized
by those skilled in the art after a complete reading of the present
application, the devices, members, apparatuses, etc. described
herein may be positioned in any desired orientation. Thus, the use
of terms such as "inboard," "outboard," "above," "below," "upper,"
"lower," or other like terms to describe a spatial relationship
between various components or to describe the spatial orientation
of aspects of such components should be understood to describe a
relative relationship between the components or a spatial
orientation of aspects of such components, respectively, as the
device described herein may be oriented in any desired direction.
As used herein, the terms "connect," "connection," "connected," "in
connection with," and "connecting" may be used to mean in direct
connection with or in connection with via one or more elements.
Similarly, the terms "couple," "coupling," and "coupled" may be
used to mean directly coupled or coupled via one or more elements.
Conditional language used herein, such as, among others, "can,"
"might," "may," "e.g.," and the like, unless specifically stated
otherwise, or otherwise understood within the context as used, is
generally intended to convey that certain embodiments include,
while other embodiments do not include, certain features, elements
and/or states. Thus, such conditional language is not generally
intended to imply that features, elements and/or states are in any
way required for one or more embodiments or that one or more
embodiments necessarily include such elements or features.
[0023] Referring to FIG. 1, a rotorcraft in the form of a
helicopter is schematically illustrated and generally designated
10. The primary propulsion assembly of helicopter 10 is a main
rotor assembly 12. Main rotor assembly 12 includes a plurality of
rotor blades 14 extending radially outward from a main rotor hub
16. Main rotor assembly 12 is coupled to a fuselage 18 and is
rotatable relative thereto. The pitch of rotor blades 14 can be
collectively and/or cyclically manipulated to selectively control
direction, thrust, and lift of helicopter 10. A tailboom 20 is
coupled to fuselage 18 and extends from fuselage 18 in the aft
direction. An anti-torque system 22 includes a tail rotor assembly
24 coupled to an aft end of tailboom 20. Anti-torque system 22
controls the yaw of helicopter 10 by counteracting the torque
exerted on fuselage 18 by main rotor assembly 12. In the
illustrated embodiment, helicopter 10 includes a vertical tail fin
26 that provides stabilization to helicopter 10 during high-speed
forward flight. In addition, helicopter 10 includes wing members 28
that extend laterally from fuselage 18 and wing members 30 that
extend laterally from tailboom 20. Wing members 28, 30 provide lift
to helicopter 10 responsive to the forward airspeed of helicopter
10, thereby reducing the lift requirement on main rotor assembly 12
and increasing the top speed of helicopter 10.
[0024] Main rotor assembly 12 and tail rotor assembly 24 receive
torque and rotational energy from a main engine 32. Main engine 32
is coupled to a main rotor gearbox 34 by suitable clutching and
shafting. Main rotor gearbox 34 is coupled to main rotor assembly
12 by a mast 36 and is coupled to tail rotor assembly 24 by tail
rotor drive shaft 38. In the illustrated embodiment, a supplemental
engine 40, or supplemental power unit, is coupled to tail rotor
drive shaft 38 by a supplemental engine gearbox 42 that provides
suitable clutching therebetween.
[0025] Rotorcraft 10 is merely illustrative of a variety of
aircraft that can implement the embodiments disclosed herein. Other
aircraft implementations can include hybrid aircraft, tiltwing
aircraft, tiltrotor aircraft, quad tiltrotor aircraft, unmanned
aircraft, gyrocopters, propeller-driven airplanes, compound
helicopters, drones, and the like. As such, those skilled in the
art will recognize that the spherical bearing centrifugal force
retention link of the present disclosure can be integrated into a
variety of aircraft configurations. It should be appreciated that
even though aircraft are particularly well-suited to implement the
embodiments of the present disclosure, non-aircraft vehicles and
devices can also implement the embodiments.
[0026] FIG. 2 illustrates an exemplary anti-torque tail rotor
assembly 24 implementing a spherical centrifugal force retention
link 500 (FIG. 5). In this embodiment, tail rotor assembly 24 is a
ducted fan. The ducted fan 24 includes a rotor 44 mounted within a
duct 46 that extends through a shroud 48 of a tail portion of
rotorcraft 10. Rotor 44 is rotatably mounted within duct 46 and
includes a hub 50 and a plurality of blades 52. Rotor 44 may
include any suitable number of blades 52, e.g., nine blades, as
illustrated in FIG. 2. Hub 50 is rotatable about a rotational axis
54 that is coaxial with a central axis 56 of duct 46. Blades 52
extend radially from hub along a pitch change axis. Blades 52 are
coupled to hub 50 with a spherical bearing centrifugal link, see,
e.g., FIGS. 5-9. The spherical bearings of the centrifugal force
link react the centrifugal force radially and allow a total blade
pitch range, for example of about 50 to 85 degrees. In an
embodiment, the total blade pitch range is about 80 degrees.
[0027] FIG. 3 illustrates another exemplary rotor 302 in the form
of a ducted fan. In this example, ducted fan 302 is pivotably
coupled to a rotorcraft 300. Ducted fan 302 has a duct 304 with a
central axis 306 and a rotor assembly 310 coupled to a shaft 308 to
rotate about central axis 306. Rotor assembly 310 includes a rotor
hub 312 with a central hub fitting 314 attached to shaft 308. Rotor
blades 316 are attached to rotor hub 312 with a double spherical
bearing centrifugal force link 500 (FIG. 5) and extend radially
from rotor hub 312 along a pitch change axis 318. A control rod 320
for changing the pitch angle of blades 316 extends through shaft
308 and engages for example a spider 322 (FIG. 4) attached to pitch
horns of the blades 316.
[0028] FIG. 4 illustrates another view of exemplary rotor assembly
310. Rotor blades 316 are attached at their root ends to rotor hub
312. A spider 322 is connected to pitch horns 530 (FIG. 5) on each
of the blades 316. Control rod 320 (FIG. 3) engages spider 322 to
change the pitch angle of blades 316.
[0029] FIG. 5 illustrates an exemplary spherical bearing
centrifugal force (CF) retention link 500 with a rotor blade 516.
CF retention link 500 has dual spherical bearings 502, 504.
Spherical bearings 502, 504 may be rod ends. With reference to a
rotor assembly, the spherical bearings are identified as an inboard
spherical bearing 502 and an outboard spherical bearing 504
relative to the rotational axis of the rotor hub. Inboard and
outboard spherical bearings 502, 504 are attached to each other by
a beam 506. Beam 506 is constructed of a material sufficient to
restrict tension movement along blade pitch axis 518 caused by
blade centrifugal force. Additionally, beam 506 has a high
torsional stiffness to resist torsional (twisting) movement 508.
Conventionally, rotor blades are connected to the rotor hub by a
tension-torsion strap or bar that allows for torsional movement. In
an exemplary embodiment, CF retention link 500 has a substantially
constant torsional moment throughout the rotor blade pitch range,
see, e.g., FIG. 10. The torsional moment exerted by a traditional
tension-torsion strap increases, thereby increasing the control
loads, as the blade pitch increases. CF retention link 500, with a
substantially constant torsional moment throughout the pitch range,
may significantly reduce peak moment and peak control loads
compared to a rotor assembly using a tension-torsion strap.
[0030] Beam 506 may be constructed of various materials, including
metal. In an embodiment, beam 506 is a solid member, e.g., metal
member, as opposed to a member constructed of layers that allows
torsional movement. Beam 506 may be constructed in various
geometries and lengths to accommodate a particular rotor
assembly.
[0031] With reference in particular to FIGS. 5, 6A, and 6B, rotor
assembly 510 includes rotor blade 516 is connected to a rotor hub
512. Blade 516 extends radially from rotor hub 512 along pitch axis
518. Spherical bearing CF link 500 extends coaxially with pitch
axis 518.
[0032] A blade grip 522 and pitch horn 530 are attached to root end
520 of blade 516 for example via bolted joint. Blade grip 522 has
an inboard end 524, shown as a clevis, and two hub connection
portions 526a, 526b outboard of the inboard end. Outboard spherical
bearing 504 attaches to inboard end 524 and inboard spherical
bearing 502 attaches to central hub fitting 514, e.g., drive hub.
Spherical bearings 504 and 502 can be connected to the blade and
the hub for example by bolts. Link rotations stops 528 may be
located with each of the spherical bearings to protect the beam 506
from rotating beyond the maximum allowed bearing misalignment
angle, e.g., 20 degrees. In an embodiment, the rotor blade pitch
range is between about 50 to 85 degrees. In an embodiment, the
rotor blade pitch range is between about 70 and 85 degrees. In an
embodiment, the rotor blade pitch range is about 80 degrees. Blade
grip portions 526a, 526b are rotationally coupled, e.g., torsion
bearings, to hub 512 at locations 512a, 512b. The rotational
connections at 512a, 512b allow the rotor blade pitch to be
changed. Blade pitch input motion is transmitted for example from
spider 322 (FIG. 4) to pitch horn 530 which is connected to blade
grip 522 and blade 516.
[0033] FIGS. 7-9 schematically illustrate rotor blade 516 coupled
to central hub fitting 514 via spherical bearing CF link 500 and
positioned at different pitch angles. Rotor blade 516 has a pitch
axis 518 that defines a rotor plane, the pitch angle may be the
angle between rotor plane and the chord of the blade. FIG. 7
illustrates blade 516 at a 0-degree pitch angle, FIG. 8 illustrates
blade 516 at a positive 50-degree pitch angle, and FIG. 9
illustrates blade 516 at a negative 25-degree pitch angle.
[0034] FIG. 10 graphically illustrates an exemplary spherical
bearing CF link having substantially constant torsional moment 1010
throughout a pitch angle range 1012 of about 80 degrees. Line 1010
represents pitching moment when increasing blade pitch absolute
value. The pitching moment when increasing blade pitch absolute
value and the pitching moment when decreasing blade pitch absolute
value (not shown) are symmetric about the zero (0) pitch
moment.
[0035] The term "substantially," "approximately," and "about" is
defined as largely but not necessarily wholly what is specified
(and includes what is specified; e.g., substantially 90 degrees
includes 90 degrees and substantially parallel includes parallel),
as understood by a person of ordinary skill in the art. The extent
to which the description may vary will depend on how great a change
can be instituted and still have a person of ordinary skill in the
art recognized the modified feature as still having the required
characteristics and capabilities of the unmodified feature. In
general, but subject to the preceding, a numerical value herein
that is modified by a word of approximation such as
"substantially," "approximately," and "about" may vary from the
stated value, for example, by 0.1, 0.5, 1, 2, 3, 4, 5, 10, or 15
percent.
[0036] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the disclosure. Those skilled in the art should appreciate that
they may readily use the disclosure as a basis for designing or
modifying other processes and structures for carrying out the same
purposes and/or achieving the same advantages of the embodiments
introduced herein. Those skilled in the art should also realize
that such equivalent constructions do not depart from the spirit
and scope of the disclosure and that they may make various changes,
substitutions, and alterations without departing from the spirit
and scope of the disclosure. The scope of the invention should be
determined only by the language of the claims that follow. The term
"comprising" within the claims is intended to mean "including at
least" such that the recited listing of elements in a claim are an
open group. The terms "a," "an" and other singular terms are
intended to include the plural forms thereof unless specifically
excluded.
* * * * *