Patent Publication Number: US-10329947-B2

Title: 35Geared unison ring for multi-stage variable vane actuation

Description:
BACKGROUND 
     The present disclosure relates to a gas turbine engine and, more particularly, to a variable vane system therefor. 
     Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases. 
     Some gas turbine engines include variable vanes that can be pivoted about their individual axes to change an operational performance characteristic. Typically, the variable vanes are robustly designed to handle the stress loads that are applied to change the position of the vanes. A mechanical linkage is typically utilized to rotate the variable vanes. Because forces on the variable vanes can be relatively significant, forces transmitted through the mechanical linkage can also be relatively significant. Legacy compressor designs typically utilize fueldraulic actuation to rotate the variable vanes. 
     SUMMARY 
     A variable vane system, according to one disclosed non-limiting embodiment of the present disclosure can include an actuator; a harmonic drive driven by the actuator; a drive gear driven by the harmonic drive; an extended geared unison ring driven by the drive gear; and a first variable vane stage with a multiple of actuator gears, each of the multiple of actuator gears mounted to a respective variable vane, each of the multiple of actuator gears driven by the extended geared unison ring. 
     A further embodiment of the present disclosure may include an actuator gear mounted to each of a multiple of variable vane. 
     A further embodiment of the present disclosure may include wherein the unison ring includes a first gear rack meshed with the actuator gear. 
     A further embodiment of the present disclosure may include wherein the unison ring includes a gear rack segment meshed with the drive gear. 
     A further embodiment of the present disclosure may include wherein the harmonic drive includes a strain wave gearing mechanism. 
     A further embodiment of the present disclosure may include wherein the strain wave gearing mechanism include a fixed circular spline, a flex spline attached to an output shaft, and a wave generator attached to an input shaft, the flex spline driven by the wave generator with respect to the circular spline. 
     A further embodiment of the present disclosure may include wherein the harmonic drive provides between a 30:1-320:1 gear ratio. 
     A further embodiment of the present disclosure may include wherein the actuator gear is a gear segment. 
     A further embodiment of the present disclosure may include wherein the actuator gear is operable to rotate through about 90 degrees. 
     A further embodiment of the present disclosure may include wherein the actuator gear is operable to rotate through about 0-40 degrees. 
     A further embodiment of the present disclosure may include wherein the actuator gear is mounted to a trunion of a variable vane. 
     A further embodiment of the present disclosure may include wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion. 
     A gas turbine engine, according to one disclosed non-limiting embodiment of the present disclosure can include an actuator; a harmonic drive driven by the actuator; a drive gear driven by the harmonic drive; a first variable vane stage with a multiple of first actuator gears, each of the multiple of first actuator gears mounted to a respective variable vane of the first variable vane stage; a second variable vane stage with a multiple of second stage actuator gears, each of the multiple of second stage actuator gears mounted to a respective variable vane of the second variable vane stage; and an extended geared unison ring driven by the drive gear, wherein the extended geared unison ring spans at least a first variable vane stage and a second variable vane stage, each of the multiple of first and second stage actuator gears driven by the extended geared unison ring. 
     A further embodiment of the present disclosure may include wherein the extended geared unison ring spans at least the first variable vane stage and the second variable vane stage. 
     A further embodiment of the present disclosure may include wherein the actuator is an electric motor. 
     A further embodiment of the present disclosure may include wherein the harmonic drive provides between a 30:1-320:1 gear ratio. 
     A further embodiment of the present disclosure may include wherein the extended geared unison ring includes a gear rack segment engaged with the drive gear. 
     A further embodiment of the present disclosure may include wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be appreciated; however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a schematic cross-section of an example gas turbine engine architecture; 
         FIG. 2  is a perspective view of a variable vane system for a gas turbine engine; 
         FIG. 3  is a partial perspective view of one stage of a variable vane system for a gas turbine engine; 
         FIG. 4  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 5  is a perspective view of a variable vane system for a gas turbine engine; 
         FIG. 6  is a schematic view of harmonic drive system; 
         FIG. 7  is an expanded perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 8  is a side view of the variable vane system of  FIG. 7 ; 
         FIG. 9  is a side view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 10  is an expanded perspective view of the variable vane system of  FIG. 9 ; 
         FIG. 11A  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 11B  is an expanded sectional view of the unison ring of  FIG. 11A ; 
         FIG. 12  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 13  is a expanded partial sectional view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 14  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 15  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 16  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 17  is a schematic view of the variable vane system of  FIG. 16  in a first position; 
         FIG. 18  is a schematic view of the variable vane system of  FIG. 16  in a second position; 
         FIG. 19  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 20  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 21  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 22  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 23  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 24  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 25  is a plan view of a link for use in the system of  FIG. 24 ; 
         FIG. 26  is a schematic view of the variable vane system of  FIG. 24  in a first position; 
         FIG. 27  is a schematic view of the variable vane system of  FIG. 24  in a second position; 
         FIG. 28  is a sectional view of the link of  FIG. 25 ; 
         FIG. 29  is a sectional view of a unison ring for a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 30  is a schematic view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 31  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 32  is a sectional view of the variable vane system of  FIG. 31 ; 
         FIG. 33  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 34  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 35  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 36  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 37  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
         FIG. 38  is a sectional view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; and 
         FIG. 39  is a perspective view of a variable vane system for a gas turbine engine according to one disclosed non-limiting embodiment; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool GTF (geared turbofan) that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engine architectures might include an augmentor section and exhaust duct section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section  26  then expansion thru the turbine section  28 . Although depicted as a GTF in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with GTF as the teachings may be applied to other types of turbine engines such as a Direct-Drive-Turbofan with high, or low bypass augmented turbofan, turbojets, turboshafts, and three-spool (plus fan) turbofans wherein an intermediate spool includes an intermediate pressure compressor (“IPC”) between a Low Pressure Compressor (“LPC”) and a High Pressure Compressor (“HPC”), and an intermediate pressure turbine (“IPT”) between the high pressure turbine (“HPT”) and the Low pressure Turbine (“LPT”). 
     The engine  20  generally includes a low spool  30  and a high spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing compartments  38 . The low spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  (“LPC”) and a low pressure turbine  46  (“LPT”). The inner shaft  40  drives the fan  42  directly or thru a geared architecture  48  to drive the fan  42  at a lower speed than the low spool  30 . An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. 
     The high spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  (“HPC”) and high pressure turbine  54  (“HPT”). A combustor  56  is arranged between the HPC  52  and the HPT  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
     Core airflow is compressed by the LPC  44  then the HPC  52 , mixed with fuel and burned in the combustor  56 , then expanded over the HPT  54  and the LPT  46 . The turbines  54 ,  46  rotationally drive the respective low spool  30  and high spool  32  in response to the expansion. The main engine shafts  40 ,  50  are supported at a plurality of points by the bearing compartments  38 . It should be understood that various bearing compartments  38  at various locations may alternatively or additionally be provided. 
     In one example, the gas turbine engine  20  is a high-bypass geared aircraft engine with a bypass ratio greater than about six (6:1). The geared architecture  48  can include an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3:1, and in another example is greater than about 3.0:1. The geared turbofan enables operation of the low spool  30  at higher speeds which can increase the operational efficiency of the LPC  44  and LPT  46  to render increased pressure in a relatively few number of stages. 
     A pressure ratio associated with the LPT  46  is pressure measured prior to the inlet of the LPT  46  as related to the pressure at the outlet of the LPT  46  prior to an exhaust nozzle of the gas turbine engine  20 . In one non-limiting embodiment, the bypass ratio of the gas turbine engine  20  is greater than about ten (10:1), the fan diameter is significantly larger than that of the LPC  44 , and the LPT  46  has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans, where the rotational speed of the fan  42  is the same (1:1) of the LPC  44 . 
     In one example, a significant amount of thrust is provided by the bypass flow path due to the high bypass ratio. The fan section  22  of the gas turbine engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10668 meters). This flight condition, with the gas turbine engine  20  at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust. 
     Fan Pressure Ratio is the pressure ratio across a blade of the fan section  22  without the use of a Fan Exit Guide Vane system. The relatively low Fan Pressure Ratio according to one example gas turbine engine  20  is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of (“T”/518.7) 0.5  in which “T” represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one example gas turbine engine  20  is less than about 1150 fps (351 m/s). 
     With reference to  FIG. 2 , one or more stages of the LPC  44  and/or the HPC  52  include a variable vane system  100  that can be rotated to change an operational performance characteristic of the gas turbine engine  20  for different operating conditions. The variable vane system  100  may include one or more variable vane stages. 
     The variable vane system  100  may include a plurality of variable vanes  102  circumferentially arranged around the engine central axis A. The variable vanes  102  each include a variable vane body that has an airfoil portion that provides a lift force via Bernoulli&#39;s principle such that one side of the airfoil portion generally operates as a suction side and the opposing side of the airfoil portion generally operates as a pressure side. Each of the variable vanes  102  generally spans between an inner diameter and an outer diameter relative to the engine central axis A. 
     With reference to  FIG. 3 , each of the variable vanes  102  includes an inner pivot pin  104  that is receivable into a corresponding socket (not shown) and an outer trunion  106  mounted through an outer case  108  such that each of the variable vanes  102  can pivot about a vane axis V. The outer trunion  106  is defined along the vane axis V ( FIG. 3 ). 
     With reference to  FIG. 4 , the variable vane system  100  further includes a unison ring  110  to which, in one disclosed non-limiting embodiment, each of the outer trunions  106  are attached through a drive arm  112  along a respective axis D. It should be appreciated that although a particular drive arm  112  is disclosed in this embodiment, various linkages of various geometries may be utilized. 
     The variable vane system  100  is driven by an actuator system  118  with an actuator  120 , a harmonic drive  122  and an actuator arm  124 . Although particular components are separately described, it should be appreciated that alternative or additional components may be provided. Although a single actuator system  118  may be utilized for each stage ( FIG. 5 ), multiple actuator systems  118  may be provided on a single stage ( FIG. 5 ) to facilitate additional stability for each singe unison ring  110 . 
     The actuator  120  may include an electric motor or other electric powered device. The actuator  120  is defined along an axis B. 
     The harmonic drive  122  includes a strain wave gearing mechanism  130  that, in one example, may provide a 30:1-320:1 gear ratio in a compact package that significantly reduces the rotation and increases the torque provided by the actuator  120 . The strain wave gearing mechanism  130  generally includes a fixed circular spline  132 , a flex spline  134  attached to an output shaft  136  along an axis B, and a wave generator  138  attached to an input shaft  141  which is connected to the actuator  120  along axis B ( FIG. 6 ). 
     The harmonic drive  122  essentially provides no backlash, compactness and light weight, high gear ratios, reconfigurable ratios within a standard housing, good resolution and excellent repeatability when repositioning inertial loads, high torque capability, and coaxial input and output shafts. The harmonic drive  122  thereby prevents back driving by the relatively high aerodynamic forces experienced by the variable vanes  102 . 
     The harmonic drive  122  need only rotate the drive arm  124  through about 90 degrees and, in a more specific embodiment, only about 0-40 degrees to drive rotation of the unison ring  110 , thence the individual variable vanes  102  through the respective drive arms  112 . That is, the actuator arm  124  rotates the unison ring  110  that, in turn, rotates the drive arms  112  along their respective axis B to rotate the trunions  106 , and thus the variable vanes  102  about axis V. 
     With reference to  FIG. 7 , in another disclosed embodiment, the actuator system  118 A includes a geared connection  140  between the harmonic drive  122  and a drive gear  142  that is meshed with an actuator gear  144  mounted to a trunion  106  of a variable vane  102 . The actuator gear  144  may be a gear segment of about ninety degrees. 
     The other variable vanes  102  are attached to the unison ring  110  though respective links  146 . The geared connection  140  provides for an offset to accommodate insufficient space for a direct connection attached concentric to the axis of a variable vane, such as the first LPC variable vane stage that is typically adjacent to a structural wall  148  such as a firewall ( FIG. 8 ). 
     With reference to  FIG. 9 , in another disclosed embodiment, the actuator system  118 C includes an axial geared connection  150  such that the actuator system  118 C is generally axial with the engine axis A for installations with limited vertical packaging space. In this embodiment, the geared connection  150  includes a drive gear  152  that is meshed with an actuator gear  154  mounted to a trunion  106  in a generally perpendicular arrangement ( FIG. 10 ). Alternatively, the geared connection  150  can be angled relative to the vane actuator via a bevel gear. 
     With reference to  FIG. 11A , in another disclosed embodiment, the actuator system  118 D includes an extended geared unison ring  160  that spans at least a first variable vane stage  162  with a vane gear  164  for each first stage variable vane trunion  106  and a second variable vane stage  166  with a vane gear  168  for each second stage variable vane trunion  106 . The extended geared unison ring  160  includes an associated first gear rack  170  and a second gear rack  172  that interface with the respective vane gears  164 ,  168 . This minimizes or eliminates axial motion of the extended geared unison ring  160 . In this embodiment, the geared connection  180  includes a drive gear  182  that is meshed with an actuator gear  184  on the extended geared unison ring  160 . The actuator gear  184  need be only a relatively short gear rack segment. 
     With reference to  FIG. 11B , the extended geared unison ring  160  includes an interface  174  with the outer case  108 . The outer case  108  may include a flange  176  to restrain axial movement of the extended geared unison ring  160 . Low friction devices  178  such as bumpers of low friction material, rollers, or other devices may be alternatively, or additionally, provided. 
     With reference to  FIG. 12 , in another disclosed embodiment, the actuator system  118 D may utilize a geared unison ring  190  to drive a first variable vane stage  192  with a vane gear  194  mounted to each first stage variable vane trunion  106 . A flange  176 , or flange segments, may axially restrain the geared unison ring  160  on the outer case  108  to stabilize the geared unison ring  160  and avoid hysteresis ( FIG. 13 ). 
     With reference to  FIG. 14 , in another disclosed embodiment, the actuator system  118 E may utilize a multi-planar gear  200 . The multi-planar gear  200  includes a first set of gear teeth  202  in a first plane  204  and a second set of gear teeth  206  in a second plane  208 . 
     The first plane  204  and the second plane  208  are offset such that the first set of gear teeth  202  are in mesh with a first drive gear  210  for a drive variable vane  102  in a first stage  212  and the second set of gear teeth  206  in mesh with a second drive gear  214  for a drive variable vane  102  in a second stage  216 . The first drive gear  210  and the second drive gear  214  may be arranged at different heights to interface with the multi-planar gear  200 . Since actuation requires only partial rotation, symmetry of the multi-planar gear  200  is not necessary. The gear ratio can be adjusted to provide different vane rotations per stage. 
     The first drive gear  210  and the second drive gear  214  also include a drive arm  218 ,  220  to rotate a respective unison ring  222 ,  224 . The driven variable vanes  102  are connected their respective unison ring  222 ,  224  by a respective linkage  226 ,  228  for each variable vane  102 . 
     With reference to  FIG. 15 , in another disclosed embodiment, the actuator system  118 E may include a multiple of idler gears  230 ,  231  that interconnect drive gears  232 ,  234 ,  236  of each of a multiple of stages  238 ,  240 ,  242 . Each of the multiple of idler gears  230  may be mounted to static structure (not shown) through a shaft  241 ,  243 ,  245  such that the multiple of idler gears  230  may be positioned above the variable vane structure. Alternatively, the idler gears  230  may be mounted directly to a variable vane to direct drive a driving vane. 
     In this embodiment, a multi-planar gear  232  may be driven by a drive shaft  241  driven by a remote actuator. 
     With reference to  FIG. 16 , in another disclosed embodiment, the actuator system  118 F may utilize a geared unison ring  260 . The geared unison ring  260  locates a gear  262  on an outer diameter of the geared unison ring  260 . 
     Rotation of the geared unison ring  260  by the actuator system  118 F drives the individual variable vanes  102  through the respective drive arms  205 . The actuator system  118 F is generally axial with the engine axis A for installations with limited vertical packaging space. The actuator system  118 F drives a drive gear  264  that is wider than the gear  262  as the rotation of the unison ring  260  results in a relatively small amount of axial motion ( FIGS. 17 and 18 ). This will require a small amount of sliding between gear teeth of the gears  262 ,  264 , but the rotation required to actuate the variable vanes is relatively small, typically, only a few degrees, and the actuation is slow, so a small amount of sliding may be acceptable. 
     With reference to  FIG. 19 , in another disclosed embodiment, the drive gear  264  may be an extended shaft with a multiple of gear segments  268 ,  270  to drive a respective multiple of unison rings  272 ,  274 . 
     With reference to  FIG. 20 , in another disclosed embodiment, the actuator system  118 G may utilize a cable drive system  280 . The cable drive system  280  includes a drum  282 , or alternatively, a drum segment  282 A ( FIG. 21 ) with a groove  284  within which a cable  286  is at least partially received. 
     The groove  284  defines a contoured path to guide the cable  286  ( FIG. 22, 23 ). The cable  286  defines a path that is contoured to avoid slack in the cable  286 . Alternatively, a tension-loading device may be used. The cable  286  is connected to the unison ring  288  such that cable  286  will always remain tangential to the unison ring  288 . 
     With reference to  FIG. 24 , in another disclosed embodiment, the actuator system  118 H may utilize a multiple of drive arms  300  which actuate the individual variable vanes  102 . Each of the multiple of drive arms  300  includes a slot  302  that permits single point actuation ( FIG. 25 ). Each slot  302  for each drive arm  300  receives a respective pin  304  that extends from the unison ring  306 . The axial motion is absorbed ( FIGS. 26 and 27 ) in the slots  302  of the individual links, so that the unison ring  306  is effectively stabilized, even with single point actuation. Each respective pin  304  that extends from the unison ring  306  and/or slot  302  may be tapered to permit rotation of the unison ring  306  with minimal play ( FIG. 28 ). 
     With reference to  FIG. 29 , the unison ring  306  has a “U” shaped cross section that provides significant stiffness while being light in weight. The unison ring  306  is supported on the engine case by a multiple of supports  308  that are arranged around the engine case. The support  308  may be generally cross-shaped to support a multiple of rollers  310 . In this example, each roller  310  interacts with an upper surface  312 , a forward surface  314 , and an aft surface  316  of the unison ring  306 . 
     With reference to  FIG. 30 , a single drive shaft  320  may include multiple drive gears  322 ,  324 ,  326  meshed with respective gear racks  328 ,  330 ,  332  of the associated unison rings  334 ,  336 ,  338  of each variable vane stage. The gear racks  328 ,  330 ,  332  are axially offset on the unison ring  334 ,  336 ,  338  to provide an extremely low profile. 
     With reference to  FIG. 31 , in another disclosed embodiment, the actuator  120  and the harmonic drive  122  are remotely located on one side of a firewall  350  with a drive shaft  352  from the harmonic drive  122  that extends therethrough to drive a HPC variable vane system  361  which is in a higher temperate environment. The extended drive shaft  352  permits the actuator  120  and the harmonic drive  122  to be located in a desirable environment. The extended drive shaft  352  may mesh with the single drive shaft  320  to drive a multiple of variable vane stages ( FIG. 32 ). 
     With reference to  FIG. 33 , in another disclosed embodiment, an actuator system  1181  includes a drive shaft  360  operable to control multiple stages of variable vanes (four shown). 
     With reference to  FIG. 34 , in another disclosed embodiment, if an axis V of the variable vane is aligned planer with the drive shaft  360 , a vane drive bevel gear  370  may drive a unison ring  372 , and thus all the variable vanes  102  ( FIG. 3 ) in a direct manner. 
     Alternatively, an additional actuation arm  380  may extend from the vane drive bevel gear  382  to provide the same linkage motion to the unison ring  384  as the actuation arms on the variable vanes, but is aligned to the bevel gear  382 . The unison ring  384  may include a bridge  386  which bridges a subset of a multiple of variable vane drive arms  388 . That is, the bridge  386  is mounted to the unison ring  384  to which the multiple of variable vane drive arms  388  are attached. The actuation arm  380 , since not tied directly to a variable vane, is mounted to static structure  390 . 
     With reference to  FIG. 35 , in another disclosed embodiment, a drive shaft  400  and gears  402  may be enclosed in a gear box  404  that is mounted to an engine case  406 . The drive shaft  400  has a single input  408  and a multiple of outputs  410 ,  412 ,  414 ,  416 . 
     The gearbox  404  may house all the necessary supports and bearings and may be mounted directly to the engine case  406  such as a HPC case. The gearbox  404  also provides a static structure from which to rotationally mount the variable vane actuation arms  420 ,  422  that are not tied directly to a variable vane  418 ,  424 . The variable vane actuation arms  420 ,  422  may be mounted to a bridge  424 ,  426  that is mounted to the respective unison ring  428 ,  430 . 
     With reference to  FIG. 36 , in another disclosed embodiment, a drive shaft  440  drives a multiple of links  442  (four shown) which drive a bridge  450 - 456  to respective unison ring. Although the links  442 - 448  are shown as linear, the links may alternatively be curved to conform the curvature of the case to provide a more compact package. Alternatively still, if there is sufficient space between stages, the bridge  450 - 456  may be mounted to a side of the respective unison ring to provide a more compact mechanism. 
     With reference to  FIG. 37 , in another disclosed embodiment, a drive shaft  460  drives a multiple of links  462  (four shown) which drive a bridge  464  to respective unison ring  466 . The links  462  are driven to provide a linear relationship between the vane rotation angles across all the stages. That is, as the first stage vane angle changes, each of the other stages will change based on a fixed ratio off the first. Alternatively, a non-linear relationship may be provided for optimal performance. The non-linear relationship may be optimized as, for each stage, there are 5 variables available: 2 initial angles (D, E) and three lengths (F, G, H). These variables may be specifically tailored to provide a resultant output from the drive shaft  460  that differs for each stage (four shown). 
     With reference to  FIG. 38 , in another disclosed embodiment, an actuator system  118 J may include a first actuator  480 , a first harmonic drive  482 , a first drive shaft  484 , a second actuator  486 , a second harmonic drive  488 , and a second drive shaft  490 . The actuators  480 ,  486  and the harmonic drives  482 ,  488  may be located on a side of firewall  500 , that provides a thermally controlled environment. In one example, the thermally controlled environment is about 160 F. The first drive shaft  484  and the second drive shaft  490  are coaxial and pass through the firewall  500  into a higher temperature environment of, for example, 200 F-600 F. 
     With reference to  FIG. 39 , the first drive shaft  484  and the second drive shaft  490  are independently actuated to respectively control a variable vane stage  502 ,  504 . The first drive shaft  484  and the second drive shaft  490  are operable to drive respective gears  506 ,  508  in a siding gear arrangement as described above to drive respective unison rings  510 ,  512  ( FIGS. 17, 18 ). The respective distal end  520 ,  522  of the first drive shaft  484  and the second drive shaft  490  may be supported by a support bracket  530  mounted to the engine case. 
     The actuator system  118 J permits variable vane stages to be actuated independently from a remote distance to provide thermal isolation behind a firewall, or because the motors must be relocated due to limited packaging space. 
     Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     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. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     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 disclosure. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.