US 20210094676A1

INI
( 19 ) United States
( 12 ) BOSWORTH
Patent Application
et al .
Publication ((4310)) Pub
Pub.. Date
No .: :US 2021/0094676 A1
Apr. 1 , 2021
( 54 ) DYNAMICALLY ISOLATED PYLON ( 52) U.S. CI.
CPC B64C 27/001 (2013.01 ) ; B64C 2027/002
( 71 ) Applicant: Bell Textron Inc. , Fort Worth , TX (US ) ( 2013.01 ) ; B64C 29/0033 ( 2013.01 )
( 72 ) Inventors: Jeffrey BOSWORTH , Argyle, TX
(US ) ; Robert VELTRE , Irving, TX ( 57 ) ABSTRACT
(US )
( 73 ) Assignee : Bell Textron Inc. , Fort Worth , TX (US )
( 21 ) Appl. No .: 16 /588,097 An exemplary tiltrotor aircraft includes a fuselage carrying
a wing, a pylon assembly coupled to the wing such that the
(22 ) Filed : Sep. 30 , 2019 pylon assembly is rotatable to selectively operate the tiltro
Publication Classification
tor aircraft between a helicopter mode and an airplane mode ,
a vibration isolator assembly connected to the pylon assem
(51 ) Int. Cl. bly and the wing including a first vibration isolator config
B64C 27/00 ( 2006.01 ) ured to isolate vibration in a vertical plane a second vibration
B64C 29/00 ( 2006.01 ) isolator configured to isolate vibration in a lateral plane.
210
238

230

234 236
232

212 222

-216
218

228

224 . 220

214

226
Patent Application Publication Apr. 1 , 2021 Sheet 1 of 10 US 2021/0094676 A1

20a
22a
16a
16b
24a
26a

10
14

18
FIG
.
1

20b
24b
22b

26b Y

X
Patent Application Publication Apr. 1 , 2021 Sheet 2 of 10 US 2021/0094676 A1

20a
26a
16 22a
16a
-16b

10 24a
12

14

18 FIG
2
.

22b *20b
26b

24b
Patent Application Publication Apr. 1 , 2021 Sheet 3 of 10 US 2021/0094676 A1

16b
20b 16

22b
16a
24b 12
14
26b
3
.
FIG

18

22a
10
24a
20a
26a
Patent Application Publication Apr. 1 , 2021 Sheet 4 of 10 US 2021/0094676 A1

66

26a
60
58 18
64
62
46 242
44
56 82

80

34

36
32

30
20a

FIG . 4
Patent Application Publication Apr. 1 , 2021 Sheet 5 of 10 US 2021/0094676 A1

86
78
79
50?
44

2000
74
88

72
46

42
70
40
5
.
FIG

60
Patent Application Publication Apr. 1 , 2021 Sheet 6 of 10 US 2021/0094676 A1

?
52
100
FIG
7
.
6
.
FIG
18 54
ho
50
82 38
44
46 48 48
84
? 7
T ?

36

€TTO 46
38

60

?? 36

34
Patent Application Publication Apr. 1 , 2021 Sheet 7 of 10 US 2021/0094676 A1

8
.
FIG

48

38

54
18

50
82
150 90
84
92
100
Patent Application Publication Apr. 1 , 2021 Sheet 8 of 10 US 2021/0094676 A1

210
238

230

234 236
232

212 222

216
218

228

220
224

214

226 FIG . 9
Patent Application Publication Apr. 1 , 2021 Sheet 9 of 10 US 2021/0094676 A1

240
V
244
248
252 246
A? 250
242

FIG . 10

150 152 Z
172 156
170 Y

174
178
1547 182 176
166
1622 -160 -164

180
172

170

174
176 158
FIG . 11
Patent Application Publication Apr. 1 , 2021 Sheet 10 of 10 US 2021/0094676 A1

150 152
172 156 '
156 ' Z
-170 ·Y

174
178
1542
162
182
? 176

-164
-160
V 1666 166'
160 '
168 IZ
2
162 ' -164
172 Z 180
168
I
170

174
176 158 158 '
FIG . 12
US 2021/0094676 A1 Apr. 1 , 2021
1

DYNAMICALLY ISOLATED PYLON hydraulic advantage resulting from a piston arrangement,

could harness the out -of-phase acceleration to generate
TECHNICAL FIELD counter - balancing forces to attenuate or cancel vibration.
[ 0001 ] This specification relates in general to the field of SUMMARY
vibration isolation and in particular to a vibration isolator
incorporating fluid and elastomeric elements to effectively [ 0009 ] An exemplary vibration isolator assembly for con
eliminate the transmission of certain vibration frequencies necting a first body and a second body includes a first
into structural components . vibration isolator configured to isolate vibration in a first
plane and a second vibration isolator configured to isolate
BACKGROUND vibration in a second plane. Exemplary first and second
[ 0002 ] This section provides background information to vibration isolators are liquid inertial vibration eliminators. In
facilitate a better understanding of the various aspects of the an exemplary embodiment, the first vibration isolator is
disclosure. It should be understood that the statements in this tuned to eliminate a first frequency and the second vibration
section of this document are to be read in this light, and not isolator is tuned to eliminate a second frequency.
as admissions of prior art . [ 0010 ] An exemplary tiltrotor aircraft includes a fuselage
[ 0003 ] For many years , effort has been directed toward the carrying a wing, a pylon assembly coupled to the wing such
design of an apparatus for preventing the transmission of that the pylon assembly is rotatable to selectively operate the
vibration from one vibrating body to another body. Such tiltrotor aircraft between a helicopter mode and an airplane
devices are useful in a variety of technical fields in which it mode, a vibration isolator assembly connected to the pylon
is desirable to isolate the vibration of an oscillating or assembly and the wing including a first vibration isolator
vibrating device , such as an engine, from the remainder of configured to isolate vibration in a vertical plane a second
the structure. Typical vibration isolation and attenuation vibration
plane .
isolator configured to isolate vibration in a lateral
devices (“ isolators ” ) employ various combinations of the [ 0011 ] This summary is provided to introduce a selection
mechanical system elements to adjust the frequency of concepts that are further described below in the detailed
response characteristics of the overall system to achieve description . This summary is not intended to identify key or
acceptable levels of vibration in the structures of interest in essential features of the claimed subject matter, nor is it
the system . One field in which these isolators find a great
deal of use is in aircraft, wherein vibration isolation systems intended to be used as an aid in limiting the scope of claimed
are utilized to isolate the fuselage or other portions of an subject matter.
aircraft from mechanical vibrations which are associated
with the propulsion system and which are generated by the BRIEF DESCRIPTION OF THE DRAWINGS
engine, transmission , propellers , rotors , or proprotors of the [ 0012 ] The disclosure is best understood from the follow
aircraft. ing detailed description when read with the accompanying
[ 0004 ] Vibration isolators are distinguishable from damp figures. It is emphasized that, in accordance with standard
ing devices although damping devices are often erroneously practice in the industry, various features are not drawn to
referred to as isolators . As an illustration, a simple force scale . In fact, the dimensions of various features may be
equation for vibration is set forth as follows më + c8 + kx = F . arbitrarily increased or reduced for clarity of discussion .
[ 0005 ] A true vibration isolator utilizes acceleration of a [ 0013 ] FIGS . 1 and 3 illustrate an exemplary tiltrotor
fluid body (må ) to cancel the displacement of vibration (kx ). aircraft in airplane mode .
In contrast, a damping device is concerned with restricting [ 0014 ] FIG . 2 illustrates an exemplary tiltrotor aircraft in
flow of a fluid or other body and thus velocity (cë ) , and does helicopter mode .
not cancel vibration, but merely absorbs its energy. [ 0015 ] FIG . 4 illustrates an exemplary propulsion system
[ 0006 ] Minimization of the length, weight and overall size of a tiltrotor aircraft.
of the isolation device is an important consideration in the [ 0016 ] FIG . 5 illustrates an exemplary pylon assembly a
design of an aircraft vibration isolation system . This mini tiltrotor aircraft .
mization is particularly important in the design and manu [ 0017] FIG . 6 illustrates an aft view of an exemplary
facture of helicopters, which are required to hover against propulsion system and wing section of a tiltrotor aircraft.
the dead weight of the craft and which are in many ways [ 0018 ] FIG . 7 illustrates a top view of an exemplary
more constrained in their payload than fixed wing aircraft. propulsion system and wing section of a tiltrotor aircraft.
[ 0007] A marked improvement in the field of vibration [ 0019 ] FIG . 8 illustrates an exemplary wing section of a
isolation , particularly as applied to aircraft and helicopters , tiltrotor aircraft.
was disclosed in commonly assigned U.S. Pat. No. 4,236 ,
607 , entitled “ Vibration Suppression System , ” issued Dec. 2 , [ 0020 ] FIG . 9 illustrates an exemplary vibration isolator
1980 to Halwes , et al . , and which is incorporated herein by for isolating a frequency in a single direction .
reference . This patent discloses a vibration isolator in which [ 0021 ] FIG . 10 is a schematic illustration of a spring -mass
a dense, low - viscosity fluid is used as the “ tuning” mass to system representative of the operation of a vibration isolator.
counterbalance and cancel oscillating forces transmitted [ 0022 ] FIG . 11 is a schematic illustration of an exemplary
through the isolator. This isolator employs the principle that vibration isolation assembly having a vertical plane isolator
the acceleration of an oscillating mass is 180 degrees out of and a lateral plane isolator.
phase with its displacement to cancel the transmission of [ 0023 ] FIG . 12 is a schematic illustration of an exemplary
undesirable motion . vibration isolation assembly having a vertical plane isolator
[ 0008 ] Halwes , et al . recognized that the inertial charac and a lateral plane isolator and multiple harmonic isolation
teristics of a dense, low -viscosity fluid , combined with a capabilities.
US 2021/0094676 A1 Apr. 1 , 2021
2

DETAILED DESCRIPTION addition , propulsion assembly 20b includes a pylon assem

[ 0024 ] It is to be understood that the following disclosure bly 24b that is positioned inboard of fixed nacelle 22b and
provides many different embodiments, or examples , for above wing 18. Pylon assembly 24b is rotatable relative to
implementing different features of various illustrative fixed nacelle 22b and wing 18 between a generally horizon
embodiments. Specific examples of components and tal orientation , as best seen in FIG . 1 , a generally vertical
arrangements are described below to simplify the disclosure . orientation , as best seen in FIG . 2. Pylon assembly 24b
These are , of course , merely examples and are not intended includes a rotatable portion of the drive system and a
to be limiting . For example, a figure may illustrate an proprotor assembly 26b that is rotatable responsive to torque
exemplary embodiment with multiple features or combina and rotational energy provided via the engine and drive
system .
tions of features that are not required in one or more other [ 0028 ] FIGS . 1 and 3 illustrate aircraft 10 in airplane or
embodiments and thus a figure may disclose one or more forward flight mode , in which proprotor assemblies 26a , 26b
embodiments that have fewer features or a different combi
nation of features than the illustrated embodiment. Embodi are rotating in a substantially vertical plane to provide a
ments may include some but not all the features illustrated forward thrust enabling wing 18 to provide a lifting force
in a figure and some embodiments may combine features responsive to forward airspeed , such that aircraft 10 flies
illustrated in one figure with features illustrated in another much like a conventional propeller driven aircraft. FIG . 2
figure. Therefore , combinations of features disclosed in the illustrates aircraft 10 in helicopter or VTOL flight mode , in
following detailed description may not be necessary to which proprotor assemblies 260 , 26b are rotating in a
practice the teachings in the broadest sense and are instead substantially horizontal plane to provide a lifting thrust, such
merely to describe particularly representative examples. In that aircraft 10 flies much like a conventional helicopter. It
addition , the disclosure may repeat reference numerals and / should be appreciated that aircraft 10 can be operated such
or letters in the various examples . This repetition is for the that proprotor assemblies 260 , 26b are selectively positioned
purpose of simplicity and clarity and does not itself dictate between airplane mode and helicopter mode , which can be
a relationship between the various embodiments and / or referred to as a conversion flight mode . Even though aircraft
configurations discussed . 10 has been described as having one engine in each fixed
[ 0025 ] FIG . 1 depicts three mutually orthogonal directions nacelle 22a , 22b , it should be understood by those having
X , Y, and Z forming a three - dimensional frame of reference ordinary skill in the art that other propulsion system arrange
XYZ . Longitudinal axis X corresponds to the roll axis that ments are possible and are considered to be within the scope
extends through the center of aircraft 10 in the fore and after of the present disclosure including, for example, having a
directions . Transverse axis Y is perpendicular to longitudinal single engine which may be housed within one of the fixed
axis X and corresponds to the pitch axis (also known as a nacelles or within the fuselage that provides torque and
control pitch axis or “ CPA ” ). The X - Y plane is considered rotational energy to both proprotor assemblies 26a , 26b.
to be “ horizontal . ” Vertical axis Z is the yaw axis and is [ 0029 ] During all flight modes, proprotor assemblies 26a ,
oriented perpendicularly with respect to the X - Y plane . The 26b rotate in opposite directions to provide torque balancing
X - Z plane and Y - Z plane are considered to be " vertical.” to aircraft 10. For example, when viewed from the front of
[ 0026 ] Referring to FIGS . 1-3 in the drawings, a tiltrotor aircraft 10 in forward flight mode , proprotor assembly 26a
aircraft is schematically illustrated and generally designated rotates clockwise and proprotor assembly 26b rotates coun
10. Aircraft 10 includes a fuselage 12 , a wing mount terclockwise. In the illustrated embodiment, proprotor
assembly 14 that is rotatable relative to fuselage 12 and a tail assemblies 26a , 26b each include three twisted proprotor
assembly 16 including rotatable mounted tail members 16a , blades that are equally spaced apart circumferentially at
16b having control surfaces operable for horizontal and / or approximately 120 degree intervals. It should be understood
vertical stabilization during forward flight. A wing 18 is by those having ordinary skill in the art, however, that the
supported by wing mount assembly 14 and rotates with wing proprotor assemblies of the present disclosure could have
mount assembly 14 relative to fuselage 12 to enable tiltrotor proprotor blades with other designs and other configurations
aircraft 10 convert to a storage configuration . Together, including proprotor assemblies having four, five or more
fuselage 12 , tail assembly 16 and wing 18 as well as their proprotor blades . Further, it should be understood by those
various frames, longerons, stringers, bulkheads, spars , ribs, having ordinary skill in the art that even though propulsion
skins and the like may be considered to be the airframe of systems 20a , 20b are illustrated in the context of tiltrotor
tiltrotor aircraft 10 . aircraft 10 , the propulsion systems of the present disclosure
[ 0027] Located proximate the outboard ends of wing 18 can be implemented on other types of tiltrotor aircraft
are propulsion assemblies 20a , 206. Propulsion assembly including, for example, quad tiltrotor aircraft and unmanned
20a includes a fixed nacelle 22a that houses an engine and tiltrotor aircraft, to name a few .
a fixed portion of the drive system . In addition , propulsion [ 0030 ] Referring now to FIGS . 4-8 , propulsion assembly
assembly 20a includes a pylon assembly 24a that is posi 20a is disclosed in further detail. Propulsion assembly 20a
tioned inboard of fixed nacelle 22a and above wing 18 . is substantially similar to propulsion assembly 20b there
Pylon assembly 24a is rotatable relative to fixed nacelle 22a fore, for sake of efficiency, certain features will be disclosed
and wing 18 between a generally horizontal orientation , as only with regard to propulsion assembly 20a . One having
best seen in FIG . 1 , and a generally vertical orientation , as ordinary skill in the art, however, will fully appreciate an
best seen in FIG . 2. Pylon assembly 24a includes a rotatable understanding of propulsion assembly 20b based upon the
portion of the drive system and a proprotor assembly 26a disclosure herein of propulsion assembly 20a . Propulsion
that is rotatable responsive to torque and rotational energy system 20a includes an engine 30 that is fixed relative to
provided via the engine and drive system . Likewise, pro wing 18. An engine output shaft 32 transfers power from
pulsion assembly 20b includes a fixed nacelle 22b that engine 30 to a spiral bevel gearbox 34 that includes spiral
houses an engine and a fixed portion of the drive system . In bevel gears to change torque direction by 90 degrees from
US 2021/0094676 A1 Apr. 1 , 2021
3

engine 30 to a fixed gearbox 36. Fixed gearbox 36 includes [ 0035 ] Inboard pillow block 82 is structurally coupled to
a plurality of gears , such as helical gears, in a gear train that an inboard tip rib 90. Similarly, outboard pillow block 84 is
are coupled to an interconnect drive shaft 38 and a common structurally coupled to an outboard tip rib 92. Inboard tip rib
shaft depicted as quill shaft 40. Torque is transferred to an 90 and outboard tip rib 92 are structural members of the
input gear 42 in spindle gearbox 44 of proprotor gearbox 46 airframe of tiltrotor aircraft 10. In the illustrated embodi
through quill shaft 40 . ment, the inboard pedestal includes an inboard intermediate
[ 0031 ] Interconnect drive shaft 38 provides a torque path support 94 that is utilized as a structural element between
that enables a single engine to provide torque to both inboard pillow block 82 and inboard tip rib 90. Likewise , the
proprotors assemblies 26a , 26b in the event of a failure of outboard pedestal includes an outboard intermediate support
the other engine . In the illustrated embodiment, interconnect 96 that is utilized as a structural element between outboard
drive shaft 38 has a rotational axis 48 that is vertically lower pillow block 84 and outboard tip rib 92. It should be
and horizontally aft of a longitudinal axis of the spindle appreciated that the exact structural configuration is imple
gearbox 44 referred to herein as a conversion axis 50 . mentation specific , and that structural components can be
Conversion axis 50 is parallel to a lengthwise axis 52 of combined and / or separated to meet implementation specific
wing 18. Referring in particular to FIG . 8 , interconnect drive requirements. For example , in certain implementations, air
shaft 38 includes a plurality of segments that share rotational frame structures such as tip ribs 90 , 92 may extend above
axis 48. Locating interconnect drive shaft 38 aft of wing spar wing 18 and form a portion the inboard and outboard
54 , which is a structural member of the airframe of tiltrotor pedestals .
aircraft 10 , provides for optimal integration with fixed [ 0036 ] Pylon assembly 24a is generally centered between
gearbox 36 without interfering with the primary torque inboard tip rib 90 and outboard tip rib 92. One advantage of
transfer of quill shaft 40 between fixed gearbox 36 and locating pylon assembly 24a above the surface of upper
spindle gearbox 44. Conversion axis 50 of spindle gearbox wing skin 98 is that the fore / aft location of pylon assembly
44 is parallel to rotational axis 48 of interconnect drive shaft 24a can be easily tailored to align the aircraft center of
38 but located forward and above rotational axis 48 . gravity (CG) with conversion axis 50 while pylon assembly
[ 0032 ] As best seen in FIG . 4 , proprotor assembly 26a of 24a is in helicopter mode , while also aligning the aircraft
propulsion system 20a includes a plurality of proprotor center of gravity ( CG) with the wing aerodynamic center of
blades 56 coupled to a yoke 58 that is coupled to a mast 60 . lift while pylon assembly 24a is in airplane mode . It is noted
Mast 60 is coupled to proprotor gearbox 46. The collective that the aircraft center of gravity (CG) shifts as pylon
and / or cyclic pitch of proprotor blades 56 may be controlled assembly 24a rotates between helicopter mode and airplane
responsive to pilot input via actuators 62 , swashplate 64 and mode . As such , locating pylon assembly 24a above the wing
pitch links 66 . allows the exact fore /aft location to be optimized , while also
[ 0033 ] Referring in particular to FIG . 5 , proprotor gearbox structurally attaching pylon assembly 24a to a portion of the
46 is configured to transfer power and reduce speed to mast airframe in the form of a torque box defined by forward wing
60. Proprotor gearbox 46 includes a top case portion 70 and spar 100 , aft wing spar 54 , inboard tip rib 90 and outboard
spindle gearbox 44. Speed reduction is accomplished by a tip rib 92 .
low speed planetary gear assembly 72 and a high speed [ 0037] The location of the spindle gearbox 44 provides an
planetary gear assembly 74. A spiral bevel gear assembly
includes spiral bevel input gear 42 and a spiral bevel output efficient structural support for enduring operational loads by
gear 76. The spiral bevel gear assembly changes power being mounted within the structural torque box . For
direction from along longitudinal axis 50 of spiral bevel example, when aircraft 10 is in helicopter mode , torque
input gear 42 to a centerline axis 78 of spiral bevel output about mast axis 78 is reacted by the torque box . It should be
gear 76. An accessory drive 79 can be coupled to spiral bevel noted that location of spindle gearbox 44 positions mast axis
output gear 76. It should be appreciated that proprotor 78 , while in helicopter mode, inboard of outboard tip rib 92 ,
gearbox 46 can include additional or different components outboard of inboard tip rib 90 , forward of aft spar 54 and aft
including bearing systems , lubrication systems and other of forward spar 100 , which allows the axis of the torque to
gearbox related systems that may be beneficial for operation . be inside of the torque box structure, rather than cantilevered
[ 0034 ] During operation, a conversion actuator 80 , as best outside of the torque box structure. In contrast, a spindle
seen in FIG . 4 , can be actuated so as to selectively rotate gearbox location outside ( such as outboard, forward or aft )
proprotor gearbox 46 and thus pylon assembly 24a about would cause a moment that would increase operational
conversion axis 50 , which in turn selectively positions loading, thus requiring heavier and less efficient structural
proprotor assembly 26a between helicopter mode , as best support.
seen in FIG . 2 , and airplane mode, as best seen in FIGS . 1 [ 0038 ] Aircraft 10 includes a vibration isolator assembly
and 3. The operational loads , such as thrust loads , are 150 connecting the pylon assembly 24a to wing 18 and
transmitted through mast 60 and into spindle gearbox 44 of fuselage 12. For example, vibration isolator assembly 150
proprotor gearbox 46 and thus the structural support of may be positioned at one or both of ribs 90 , 92. As further
spindle gearbox 44 is critical . In the illustrated embodiment, described below , for example with reference to FIG . 11 ,
spindle gearbox 44 is rotatably coupled to the airframe of vibration isolator assembly 150 includes a vertical isolator
tiltrotor aircraft 10 by mounting spindle gearbox 44 to an 152 to isolate fuselage 12 from a harmonic frequency
inboard pedestal depicted as inboard pillow block 82 having produced for example when aircraft 10 is in helicopter mode
an inboard bearing assembly 86 and an outboard pedestal and a lateral isolator 154 to isolate fuselage 12 from a
depicted as outboard pillow block 84 with an outboard harmonic frequency produced for example when aircraft 10
bearing assembly 88. Thus, spindle gearbox 44 is structur is in airplane mode. In addition to isolating frequencies in
ally supported and is operable to be rotated about conversion two planes, isolator assembly 150 may isolate two or more
axis 50 by conversion actuator 80 . harmonic frequencies.
US 2021/0094676 A1 Apr. 1 , 2021
4

[ 0039 ] FIG . 9 illustrates an example of a single vibration 232 filled with a gas such as nitrogen . In this design , the
isolator 210 known as a liquid inertia vibration eliminator compensator does not require a barrier between gas 232 and
( LIVE ) . Vibration isolator 210 is configured to isolate vibra fluid 234 .
tion along a single axis . Vibration isolator 210 comprises an [ 0046 ] Isolator 210 communicates fluid pressure to the
upper housing 212 and a lower outer housing 214. In this volume compensator 230 via a small diameter orifice 236 .
embodiment, upper housing 212 and lower housing 214 are The size of orifice 236 is such that the pressure pulses caused
not directly mechanically connected , but are connected by oscillation of inner cylinder 216 do not pass into volume
indirectly via the other components of the device . compensator 230 in any significant degree. With this design ,
[ 0040 ] In addition to upper and lower housings 212 and orifice 236 acts as a fluid pressure filter, transmitting static
214 , isolator 210 further comprises an inner cylinder 216 pressure changes into volume compensator 230 while at the
disposed within the volume defined by the concave portions same time blocking pressure oscillations . The ideal diameter
of housings 212 and 214. In operation, inner cylinder 16 for orifice 236 will vary with the viscosity of the fluid . One
translates within this volume in reaction to motion imposed embodiment incorporates an orifice having a diameter of
by a vibrating body . approximately 0.050" .
[ 0041] Upper housing 212 is concentrically bonded to [ 0047] Damping within isolator 210 is minimized through
inner cylinder 216 by an elastomer tubeform bearing 218 . the use of elastomer bearings 218 and 220 having low
Lower housing 214 is concentrically bonded to inner cyl damping characteristics and through the use of an inviscid
inder 216 by an elastomer tubeform bearing 220. The fluid 234 within the device . Damping is additionally mini
elastomer tubeform bearings 218 and 220 serve as compliant mized through the use of a tuning port 224 having a
spring members for isolator 210. The length of the tubeform relatively large value . A large diameter tuning port 224
bearings can vary according to the demands of a particular reduces damping in isolator 210 by minimizing the velocity
application, but the length must be sufficient to minimize of fluid 234 within tuning port 224 .
elastomer bulging caused by oscillatory pressure in the [ 0048 ] Fluid 234 used may vary from one embodiment to
device. another, but it is desirable that the fluid 234 have a low
[ 0042 ] The concave inner surface of upper housing 212 viscosity and be noncorrosive. Other embodiments may
and the upper surfaces of inner cylinder 216 and tubeform incorporate mercury or hydraulic fluid having dense par
bearing 218 together define an upper fluid chamber 222 . ticulate matter suspended therein . Additionally, the mass of
Upper fluid chamber 222 is connected to the lower portions the fluid may in some embodiments be supplemented by the
of isolator 210 via a tuning port 224 passing through inner use of a solid slug disposed in tuning port 224 .
cylinder 216. The concave inner surface of lower housing [ 0049 ] FIG . 10 depicts a schematic illustration of an
214 and the lower surfaces of inner cylinder 216 and isolator system 240. System 240 comprises a fuselage mass
tubeform bearing 220 together define a lower fluid chamber 242 , a pylon mass 244 , and a tuning mass 246 connected by
226 , which is in fluid communication with the lower end of a lever arm 248 and a spring 252. Pylon mass 244 moves in
tuning port 224. In addition to serving as compliant spring response to an imposed oscillation and must be connected to
members for isolator 210 , elastomer tubeform bearings 218 fuselage mass 242 , but it is desirable to isolate fuselage mass
and 220 serve as the fluid seals for fluid chambers 222 and 242 from the vibration of pylon mass 244 .
226 . [ 0050 ] Tuning mass 246 and spring 252 have been added
[ 0043 ] Fluid chambers 222 and 226 and tuning port 224 to the system to provide isolation . The displacement of
are filled with an inviscid fluid 234 and pressurized to spring 252 is a direct function of the difference in displace
prevent cavitation . Isolator 210 incorporates a central elas ment between fuselage mass 242 and pylon mass 244. The
tomeric spherical bearing 228 in addition to the two elasto displacement of tuning mass 246 is a function of the
meric tubeform bearings 218 and 220 . displacement of fuselage mass 242 , the displacement of
[ 0044 ] In operation, upper and lower housings 212 and pylon mass 244 , the length of lever arm 248 , and the position
214 are mounted to the body (e.g. , wing rib , fuselage) to be of fulcrum 250. It can be seen in FIG . 9 that a small
isolated from vibration . Spherical bearing 228 is connected displacement of pylon mass 244 will result in a relatively
to the vibrating body ( e.g. , pylon assembly ). As inner large displacement of tuning mass 246 .
cylinder 216 moves within isolator 210 , the volume of one [ 0051 ] In isolator 210 of FIG . 9 , tuning mass 246 takes the
of chambers 222 and 226 will increase as the other form of inviscid fluid 234 filling isolator 210 , which is
decreases . This change in volume creates a pressure differ moved by actuation of inner cylinder 216. The function
ential between chambers 222 and 226 and a corresponding represented by lever arm 248 is embodied in isolator 210 in
flow of inviscid fluid 234 from one chamber to another, in the form of the difference between the area of the ends of
the opposite direction of movement of inner cylinder 216 . cylinder 216 and the area of tuning port 224. It can be seen
This movement of fluid 234 causes an inertial force to be in FIG . 9 that, owing to the relatively large cross - sectional
generated . Within a selected range of frequencies, this area of inner cylinder 216 as compared to tuning port 224 ,
inertial force substantially or completely cancels out the a small displacement of inner cylinder 216 will result in the
elastomeric spring force in isolator 210 . movement of a relatively large volume of tuning fluid . The
[ 0045 ] In order to stabilize internal fluid pressures, fluid function of spring 252 takes the form of elastomeric tube
and elastomer thermal expansion is accommodated through form bearings 218 and 220 in isolator 210 .
the use of an integral volume compensator 230. Volume [ 0052 ] FIG . 11 schematically illustrates an exemplary
compensator 230 alleviates the accumulation of excessive vibration isolator assembly 150 , which is described with
pressure and the risk of cavitation that would otherwise exist additional reference to FIGS . 1-10 . Vibration isolator assem
due to volume changes caused by operation of the isolator bly 150 comprises a pair of vibration isolators 152 , 154
across a broad range of temperatures . In the isolator shown arranged to isolate vibrations in two planes for effective
in FIG . 9 , compensator 230 takes the form of an air spring utilization in airplane mode and helicopter mode . Vibration
US 2021/0094676 A1 Apr. 1 , 2021
5

isolator 152 is oriented along the vertical Z - axis ( roll axis) include an actuator 168 to allow selective operation of the
for example to isolate the fuselage from the harmonic respective port and connected fluid chambers.
vibrations produced when the tiltrotor aircraft is in helicop [ 0056 ] Conditional language used herein , such as , among
ter mode . Isolator 154 is oriented along the lateral Y - axis others, “ can , ” “ might , ” “ may , " " e.g. , " and the like , unless
(pitch axis ) for example to isolate the fuselage from the specifically stated otherwise, or otherwise understood within
harmonic vibrations produced when the tiltrotor aircraft is in the context as used , is generally intended to convey that
airplane mode . Isolators 15 , 154 are liquid inertia vibration certain embodiments include, while other embodiments do
eliminators. Vertical vibration isolator 152 and lateral vibra not include , certain features, elements and / or states . Thus,
tion isolator may be tuned to isolate the same frequency or such conditional language is not generally intended to imply
different frequencies. that features , elements and /or states are in any way required
[ 0053 ] Isolator 152 includes a first housing 170 having a for one or more embodiments or that one or more embodi
fluid chamber 156 and an elastomer 172 and a second ments necessarily include such elements or features .
housing 174 having a fluid chamber 158 and an elastomer [ 0057] In the specification , reference may be made to the
176. Fluid chambers 156 , 158 are fluidically connected by spatial relationships between various components and to the
tuning port 160 extending through a cylinder 178. Tuning spatial orientation of various aspects of components as the
port 160 extends through a cylinder 178. Isolator 154 devices are depicted in the attached drawings. However, as
similarly includes a first housing 170 having a fluid chamber will be recognized by those skilled in the art after a complete
162 and an elastomer 172 and a second housing 174 having reading of the present application , the devices, members ,
a fluid chamber 164 and an elastomer 176. Fluid chambers apparatuses, etc. described herein may be positioned in any
162 , 164 are fluidically connected by tuning port 166 desired orientation . Thus, the use of terms such as “ inboard ,”
extending through a cylinder 180. In the illustrated embodi “ outboard , ” “ above , ” “ below ," " upper,” “ lower ,” or other
ment, isolator 152 and isolator 154 incorporate a common like terms to describe a spatial relationship between various
spherical bearing 182. Spherical bearing 182 is connected to components or to describe the spatial orientation of aspects
the vibrating pylon assembly 24a and the housings 170 , 174 of such components should be understood to describe a
of the respective isolators 152 , 154 are connected to isolated relative relationship between the components or a spatial
body, e.g. , fuselage 12 . orientation of aspects of such components, respectively, as
the device described herein may be oriented in any desired
[ 0054 ] In accordance to an embodiment, the isolated fre direction . As used herein , the terms " connect," " connec
quency for isolator 152 and isolator 154 are different to ? ?
tion , ” “ connected , ” “ in connection with ,” and “ connecting ”
address the different harmonic frequencies of concern when may be used to mean in direct connection with or in
operating in helicopter mode and airplane mode . For connection with via one or more elements. Similarly, the
example , the proprotors are operated at higher revolutions terms “ couple , " " coupling, ” and “ coupled ” may be used to
per minute ( RPM) when in helicopter mode than when mean directly coupled or coupled via one or more elements.
operated in airplane mode . For example, in helicopter mode [ 0058 ] The term “ substantially , ” “ approximately ,” and
the aircraft may operate at 100% RPM and in airplane mode “ about” is defined as largely but not necessarily wholly what
the aircraft may operate at 80 % RPM , thus the harmonics is specified (and includes what is specified ; e.g. , substan
shift by 20 % . For example , in a 3 - bladed proprotor assem tially 90 degrees includes 90 degrees and substantially
bly, a relatively strong vibration occurs three times per parallel includes parallel ), as understood by a person of
revolution ( 3 / rev ) of the proprotor. In helicopter mode a ordinary skill in the art. The extent to which the description
vertical vibration occurs and in airplane mode a lateral may vary will depend on how great a change car be
vibration occurs . The aircraft operates at a substantially instituted and still have a person of ordinary skill in the art
constant rotor speed in each of the flight modes , so the recognized the modified feature as still having the required
frequency of the dominant harmonic can be accurately characteristics and capabilities of the unmodified feature. In
predicted and suppressed for helicopter mode by vertical general, but subject to the preceding, a numerical value
isolator 152 and for airplane mode by lateral isolator 154 . herein that is modified by a word of approximation such as
[ 0055 ] FIG . 12 schematically illustrates another exem “ substantially ," " approximately ," and " about" may vary
plary vibration isolator assembly 150 , which is described from the stated value , for example, by 0.1 , 0.5 , 1 , 2 , 3 , 4 , 5 ,
with additional reference to FIGS . 1-11 . In this example, 10, or 15 percent.
each of vibration isolators 152 , 154 have dual fluid cham [ 0059 ] The foregoing outlines features of several embodi
bers, for example with an actuated port, to change the tuning ments so that those skilled in the art may better understand
from a single frequency isolated to having dual frequency the aspects of the disclosure. Those skilled in the art should
isolation capabilities . Vertical isolator 152 includes first appreciate that they may readily use the disclosure as a basis
chambers 156 , 158 connected by first port 160 and second for designing or modifying other processes and structures
chambers 156 , 158 ' connected by second port 160 ' . First for carrying out the same purposes and / or achieving the
chambers 156 , 158 may be sized and actuated to isolate a same advantages of the embodiments introduced herein .
first frequency and second chambers 156 ' , 158 ' may be sized Those skilled in the art should also realize that such equiva
and actuated to isolate a second frequency different from the lent constructions do not depart from the spirit and scope of
first frequency. Lateral isolator 154 includes first chambers the disclosure and that they may make various changes,
162 , 164 connected by first port 166 and second chambers substitutions, and alterations without departing from the
162 ' , 164 ' connected by second port 166 ' . First chambers spirit and scope of the disclosure. The scope of the invention
162 , 164 may be sized and actuated to isolate a first should be determined only by the language of the claims that
frequency and second chambers 162 ' , 164 ' may be sized and follow . The term “ comprising” within the claims is intended
actuated to isolate a second frequency different from the first to mean “ including at least ” such that the recited listing of
frequency. Tuning ports 160 , 160 ' , 166 , and 166 ' may each elements in a claim are an open group . The terms “ a , ” “ an ”
US 2021/0094676 A1 Apr. 1 , 2021
6

and other singular terms are intended to include the plural 11. The vibration isolator assembly of claim 10 , wherein
forms thereof unless specifically excluded . the first frequency and the third frequency are substantially
What is claimed is : equivalent.
1. A vibration isolator assembly for connecting a first 12. The vibration isolator assembly of claim 10 , wherein
body and a second body, the vibration isolator assembly the first vibration isolator and the second vibration isolator
comprising : are connected to the first body at outer housings and to the
a first vibration isolator configured to isolate vibration in second body at a spherical bearing .
a first plane; and 13. The vibration isolator assembly of claim 12 , wherein
a second vibration isolator configured to isolate vibration the spherical bearing is shared by the first vibration isolator
in a second plane. and the second vibration isolator.
2. The vibration isolator assembly of claim 1 , wherein the 14. A tiltrotor aircraft comprising:
first vibration isolator and the second vibration isolator are a fuselage carrying a wing;
liquid inertial vibration eliminators . a pylon assembly coupled to the wing such that the pylon
3. The vibration isolator assembly of claim 1 , wherein the assembly is rotatable to selectively operate the tiltrotor
first vibration isolator and the second vibration isolator are aircraft between a helicopter mode and an airplane
connected to the first body at outer housings and to the mode ;
second body at a spherical bearing. a vibration isolator assembly connected to the pylon
4. The vibration isolator assembly of claim 3 , wherein the assembly and the wing , the vibration isolator assembly
spherical bearing is shared by the first vibration isolator and comprising:
the second vibration isolator. a first vibration isolator configured to isolate vibration in
5. The vibration isolator assembly of claim 1 , wherein the a vertical plane; and
first vibration isolator is tuned to eliminate a first frequency ;
and
a second vibration isolator configured to isolate vibration
in a lateral plane.
the second vibration isolator is tuned to eliminate a 15. The tiltrotor aircraft of claim 14 , wherein the first
second frequency. vibration isolator and the second vibration isolator are liquid
6. The vibration isolator assembly of claim 1 , wherein the inertial vibration eliminators.
first vibration isolator and the second vibration isolator are 16. The tiltrotor aircraft of claim 14 , wherein the first
connected to the first body at outer housings and to the vibration isolator and the second vibration isolator are
second body at a spherical bearing; connected to the wing at outer housings and to the pylon
the first vibration isolator is tuned to eliminate a first assembly at a spherical bearing.
frequency; and 17. The tiltrotor aircraft of claim 16 , wherein the spherical
the second vibration isolator is tuned to eliminate a bearing is shared by the first vibration isolator and the
second frequency . second vibration isolator.
7. The vibration isolator assembly of claim 6 , wherein the 18. The tiltrotor aircraft of claim 14 , wherein the first
first vibration isolator and the second vibration isolator are vibration isolator and the second vibration isolator are
liquid inertial vibration eliminators . connected to the wing at outer housings and to the pylon
8. The vibration isolator assembly of claim 6 , wherein the assembly at a spherical bearing;
spherical bearing is shared by the first vibration isolator and the first vibration isolator is tuned to eliminate a first
the second vibration isolator. frequency; and
9. The vibration isolator assembly of claim 8 , wherein the the second vibration isolator is tuned eliminate a
first vibration isolator and the second vibration isolator are second frequency.
liquid inertial vibration eliminators. 19. The tiltrotor aircraft of claim 18 , wherein the spherical
10. The vibration isolator assembly of claim 1 , wherein bearing is shared by the first vibration isolator and the
the first vibration isolator is selectively tuned to eliminate a second vibration isolator.
first frequency and a second frequency different from the 20. The tiltrotor aircraft of claim 19 , wherein the first
first frequency ; and vibration isolator and the second vibration isolator are liquid
the second vibration isolator is selectively tuned to elimi inertial vibration eliminators .
nate a third frequency and a fourth frequency different
from the third frequency.