Abstract:
The subject matter of this specification can be embodied in, among other things, a seal assembly that includes a compressible seal slidably mounted on a central longitudinal shaft of a rotor assembly, the seal having a first lateral surface adapted for contacting a first end surface of a first stator and a first end surface of the second stator and a first end surface of a first longitudinal vane and a first end surface of a second longitudinal vane, a compression member slidably mounted on the shaft, and a locking piston slidably mounted on the shaft, the locking piston including an opening sized to receive the shaft, an end surface adapted to contact the compression member, a circumferential surface sized to be received in the bore of the housing, and a lateral surface adapted to receive actuation fluid.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to an actuator device and more particularly to a rotary vane type actuator device wherein the vanes of the rotor are moved by fluid under pressure. 
       BACKGROUND 
       [0002]    Rotary hydraulic actuators of various forms are currently used in industrial mechanical power conversion applications. This industrial usage is commonly for applications where continuous inertial loading is desired without the need for load holding for long durations, e.g. hours, without the use of an external fluid power supply. Aircraft flight control applications generally implement loaded positional holding, for example, in a failure mitigation mode, using substantially only the blocked fluid column to hold position. 
         [0003]    In certain applications, such as primary flight controls used for aircraft operation, positional accuracy in load holding by rotary actuators is desired. Positional accuracy can be improved by minimizing internal leakage characteristics inherent to the design of rotary actuators. However, it can be difficult to provide leak-free performance in typical rotary hydraulic actuators, e.g., rotary “vane” or rotary “piston” type configurations. 
       SUMMARY 
       [0004]    In general, this document relates to rotary vane actuators. 
         [0005]    In a first aspect, a seal assembly for a rotary vane actuator includes a compressible seal slidably mounted on a central longitudinal shaft of a rotor assembly, the seal having an outer circumferential surface sized to be received in a bore of a stator housing and a central opening sized to receive the central longitudinal shaft, a first lateral surface adapted for contacting a first end surface of a first stator and a first end surface of the second stator and a first end surface of a first longitudinal vane and a first end surface of a second longitudinal vane, a compression member slidably mounted on the central longitudinal shaft, and a locking piston slidably mounted on the central longitudinal shaft, the locking piston including an opening sized to receive the central longitudinal shaft, an end surface adapted to contact the compression member, a circumferential surface sized to be received in the bore of the housing, and a lateral surface adapted to receive actuation fluid. 
         [0006]    In a second aspect, a sealing mechanism for a rotary vane actuator includes a stator housing having a bore disposed axially therethrough and a rotor assembly including a central longitudinal shaft having a central axis and at least a first longitudinal vane disposed radially on the central longitudinal shaft, and a second longitudinal vane disposed radially on the central longitudinal shaft. The sealing mechanism also includes a stator assembly including a first stator element disposed in the bore of the stator housing and a second stator element disposed in the stator housing, wherein the first longitudinal vane and the first stator define a first pressure chamber inside the bore of the stator housing, the second longitudinal vane and the first stator define a second pressure chamber inside the bore of the stator housing, the second longitudinal vane and the second stator define a third pressure chamber inside the bore of the stator housing, and the second longitudinal vane and the first stator define a fourth pressure chamber inside the bore of the stator housing. The sealing mechanism also includes a seal assembly including a compressible seal slidably mounted on the central longitudinal shaft of the rotor assembly, the seal having an outer circumferential surface received in the bore of the stator housing, a compression member slidably mounted on the central longitudinal shaft, the member, and a locking piston slidably mounted on the central longitudinal shaft, the locking piston including an opening sized to receive the central longitudinal shaft, an end surface adapted to contact the compression member, a circumferential surface sized to be received in the bore of the housing, and a lateral surface adapted to receive actuation fluid. 
         [0007]    Various embodiments can include some, all, or none of the following features. The sealing mechanism can include a port and passageways in the housing adapted to provide actuation fluid to the second lateral surface of the locking piston. The sealing mechanism can have a biasing member disposed around the central longitudinal shaft in the central bore of the housing having a first end contacting the compression plate and a second end adapted to contact the locking piston. The sealing mechanism can also include a first seal groove disposed in the first end surface of the first longitudinal vane and in the first end surface of the second longitudinal vane and a seal disposed in said first seal groove, and a second seal groove disposed in the first end surface of the first stator element and the first end surface of the second stator element, and a seal disposed in said second seal groove and wherein a portion of the first surface of the compression seal of the seal assembly contacts the seal disposed in the seal groove of each of the first and second longitudinal vanes and the first and second stators. 
         [0008]    In a third aspect, a sealing mechanism for a rotary vane actuator includes a stator housing having a bore disposed axially therethrough, and a rotor assembly including a central longitudinal shaft having a central axis, and at least a first longitudinal vane disposed radially on and rigidly connected to the central longitudinal shaft, said first longitudinal vane having a first end surface disposed perpendicular to the central axis and a second end surface disposed perpendicular to the central axis, and a second longitudinal vane disposed radially on and rigidly connected to the central longitudinal shaft, said first longitudinal vane having a first end surface disposed perpendicular to the central axis, and a second end surface disposed perpendicular to the central axis, said second vane disposed substantially opposite from the first vane. The sealing mechanism also includes a stator assembly including a first stator element having a concave interior surface adapted to contact a cylindrical surface on the central longitudinal shaft and a convex outer surface adapted to be secured to the bore of the stator housing, a first end surface disposed perpendicular to the central axis, and a second end surface disposed perpendicular to the central axis, and a second stator element having a concave interior surface adapted to contact a second cylindrical surface on the central longitudinal and a convex outer surface adapted to be secured to the bore of the stator housing, a first end surface disposed perpendicular to the central axis, and a second end surface disposed perpendicular to the central axis. The sealing assembly also includes a seal assembly including a compressible seal slidably mounted on the central longitudinal shaft of the rotor assembly, the seal having an outer circumferential surface sized to be received in the bore of the stator housing and a central opening sized to receive the central longitudinal shaft, a first lateral surface adapted for contacting the first end surface of the first stator and the first end surface of the second stator and the first end surface of the first longitudinal vane and the first end surface of the second longitudinal vane, a compression member slidably mounted on the central longitudinal shaft, the plate having a first surface adapted to contact a second lateral surface of the compression seal, a locking piston slidably mounted on the central longitudinal shaft, the locking piston including an opening sized to receive the central longitudinal shaft, an end surface adapted to contact the compression plate, a circumferential surface sized to be received in the bore of the housing, and a lateral surface adapted to receive actuation fluid. 
         [0009]    Various embodiments can include some, all, or none of the following features. The sealing mechanism can also include a port and passageways in the housing adapted to provide actuation fluid to the second lateral surface of the locking piston. The sealing mechanism can have a biasing member disposed around the central longitudinal shaft in the central bore of the housing having a first end contacting the compression plate and a second end adapted to contact the locking piston. The sealing mechanism can also include a first seal groove disposed in the first end surface of the first longitudinal vane and in the first end surface of the second longitudinal vane and a seal disposed in said first seal groove, and a second seal groove disposed in the first end surface of the first stator element and the first end surface of the second stator element, and a seal disposed in said second seal groove and wherein a portion of the first surface of the compression seal of the seal assembly contacts the seal disposed in the seal groove of each of the first and second longitudinal vanes and the first and second stators. The first longitudinal vane and the first stator can define a first pressure chamber inside the bore of the stator housing, the second longitudinal vane and the first stator can define a second pressure chamber inside the bore of the stator housing, the second longitudinal vane and the second stator can define a third pressure chamber inside the bore of the stator housing, and the second longitudinal vane and the first stator can define a fourth pressure chamber inside the bore of the stator housing. 
         [0010]    In a fourth aspect, a method of actuation of a seal assembly includes providing a rotary vane actuator including a stator housing having a bore disposed axially therethrough and a rotor assembly including a central longitudinal shaft having a central axis, and at least a first longitudinal vane disposed radially on the central longitudinal shaft. The actuator also includes at least a second longitudinal vane disposed radially on the central longitudinal shaft and a stator assembly including a first stator element disposed in the bore of the stator housing, and a second stator element disposed in the stator housing, wherein the first longitudinal vane and the first stator define a first pressure chamber inside the bore of the stator housing, the second longitudinal vane and the first stator define a second pressure chamber inside the bore of the stator housing, the second longitudinal vane and the second stator define a third pressure chamber inside the bore of the stator housing, and the second longitudinal vane and the first stator define a fourth pressure chamber inside the bore of the stator housing. The actuator includes a seal assembly having a compressible seal slidably mounted on the central longitudinal shaft of the rotor assembly, the seal having an outer circumferential surface received in the bore of the stator housing, a lateral surface and an end surface, a compression member slidably mounted on the central longitudinal shaft, the member having a first surface and second surface, a locking piston slidably mounted on the central longitudinal shaft, the locking piston including an end surface, a circumferential surface received in the bore of the housing, a lateral surface and a biasing member disposed between the compression member and the locking piston. The method also includes providing pressurized fluid to the end surface of the locking piston, slidably displacing the locking piston and contacting the first surface of the compression plate, slidably displacing the compression plate and thereby partially compressing the biasing member, and contacting the first surface of the compressible seal with the biasing member and slidably displacing the compressible seal into sealing contact with a first end surface of the first longitudinal vane and a first end surface of the second longitudinal vane and a first end surface of the first stator element and a first end surface of the second stator element. 
         [0011]    Various embodiments can include some, all, or none of the following features. The rotary actuator can also include a first seal groove disposed in the first end surface of the first longitudinal vane and in the first end surface of the second longitudinal vane and a seal disposed in said first seal groove, and a second seal groove disposed in the first end surface of the first stator element and the first end surface of the second stator element, and a seal disposed in said second seal groove, and the method further includes contacting with a portion of the first surface of the compression seal of the seal assembly with the seal disposed in the seal groove of each of the first and second longitudinal vanes and the first and second stators. 
         [0012]    The systems and techniques described here may provide one or more of the following advantages. First, a system can provide improved position-holding capability. Second, the system can provide a fail-safe mechanism that can provide position-holding capability in event of loss of actuation fluid pressure. 
         [0013]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view of an example rotary vane actuator with a fluid actuated mechanical lock. 
           [0015]      FIG. 2  is an exploded view of an example rotary vane actuator with a fluid actuated mechanical lock. 
           [0016]      FIGS. 3A and 3B  are cross-sectional side views of an example rotary vane actuator with a fluid actuated mechanical lock. 
           [0017]      FIG. 4  is a cross-sectional end view of an example rotary vane actuator with a fluid actuated mechanical lock. 
           [0018]      FIGS. 5A-5D  are cross-sectional end views of an example rotary vane actuator with a fluid actuated mechanical lock in example rotational configurations. 
           [0019]      FIGS. 6A and 6B  are cross-sectional side views of an example rotary vane actuator with a fluid actuated mechanical lock in a failure mode. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  is a perspective view of an example rotary vane actuator with a fluid actuated mechanical lock  100 . In general, the actuator  100  integrates one or more rotors and rotor vanes with compressible seals at the ends of the rotor shaft. A fluid actuated locking mechanism provides a dual-mode operation to impart different sealing conditions during “normal” and “failure” operation cases. During “normal” mode operation, the actuator  100  sealing functions like a typical rotary vane actuator (RVA) allowing some fluid leakage through rotor vane seal to stator seal interfaces. During “failure” mode operation, a fluid pressure activated spring load mechanically squeezes the rotor/stator vane seal interface to counteract the force of fluid pressure trapped in the actuator  100 , thereby substantially locking the fluid within the pressure chamber. Internal fluid leakage across the sealing interfaces can be significantly reduced as fluid column pressure is contained. 
         [0021]    The use of such fluid actuated locking mechanisms increases the ability of the actuator  100  to maintain a selected rotational position in the event of a malfunction, e.g., hydraulic failure. In general, by providing this mechanical lock, the position holding ability of an RVA such as the example rotary vane actuator with a fluid actuated mechanical lock  100  is enhanced. 
         [0022]      FIG. 2  is an exploded view of the example rotary vane actuator with a fluid actuated mechanical lock  100   
         [0023]    A rotor  210  includes a central shaft  212 . Two integral rotor vanes  216  are formed axially along the central shaft  212 . The rotor vanes  216  include a seal groove  218 . The seal groove  218  is formed axially along an outward peripheral edge of each of the rotor vanes  216 . The seal groove  218  is formed to accommodate a rotor seal  201  and bring the rotor seal  201  into sealing contact with an inner surface  232  of a central bore  234  of a housing  230 . 
         [0024]    The example rotary vane actuator with a fluid actuated mechanical lock  100  includes a pair of stator sections  220 . Each of the stator sections  220  is a generally semicircular plate having an axial length substantially equal to the lengths of the rotor vanes  216 , a thickness substantially equal to the difference between the radius of the central shaft  212  and the radius of the central bore  234  (less tolerance for movement between the elements), a radially inner surface  222  formed with a curvature substantially equal to that of the central shaft  212 , and a radially outward surface  224  formed with a curvature substantially equal to that of the inner surface  232  of the central bore  234 . 
         [0025]    A seal groove  226  is formed axially along a central portion of the surfaces  222  and  224 , and about the ends of each stator section  220 . A pair of stator seals  227  is formed to be accommodated within the seal grooves  226 . In some implementations the stator seal is a single continuous seal inserted into the seal grooves  226  and is positioned on both surfaces  222  and  224  and around the longitudinal ends of the stator  226 . The seal grooves  226  are formed to bring the stator seals  227  into sealing contact with the rotor shaft  212 , an upper corner seal  286 , a lower corner seal  288 , and the inner surface  232  of the central bore  234  when the actuator  100  is assembled. As used herein, when referring to a “seal disposed in a seal groove,” it is understood that at least a portion of the seal is positioned in the seal groove but a portion of the seal may extend outside the groove to make sealing contact with other elements of the actuator. In some implementations, each of the stator sections  220  can include two or more of the seal grooves  226  and the stator seals  227  arranged along the length of the stator section  220 . 
         [0026]    The rotor shaft  212  is supported by a bearing  240 . When assembled, the bearing  240  provides support between the rotor shaft  212  and a central bore  235  of the bearing housing  236  and end cap  260 . 
         [0027]    A compression plate  284 , a spring  282 , and a lock piston  280  are placed about the rotor shaft  212 . The spring  282  provides a compliant force separating the compression plate  284  and the lock piston  280 . The compression plate  284 , the spring  282 , and the lock piston  280  will be discussed further in the descriptions of  FIGS. 3A and 6A . 
         [0028]    During assembly the two stator sections  220  are inserted into the bore  234  of the housing  230 . A collection of fasteners  250 , e.g., bolts, are passed through a collection of holes  252  formed through the bore  234  of the housing  230 . The fasteners  250  are threaded into corresponding threaded holes  254  formed in the stator sections  220  to removably secure the stator sections  220  to the housing  230 . An end cap  260  is placed about a bearing housing  236  to at least partially retain the rotor  210 , the bearing  240 , the upper corner seal  286 , the lower corner seal  288 , the compression plate  284 , the spring  282 , the lock piston  280 , and the bearing housing  236  axially within the central bore  234 . A spline section  262  extends radially outward from an end portion of the rotor shaft  212 . When assembled the spline section  262  will extend from the central bore  235  of the bearing housing  236  and a central bore  262  of the end cap  260  and thereby be positioned outside of the housing  230 . The spline section  262  can be attached to an item to be moved (actuated) by the actuator  100 . 
         [0029]    A pair of fluid ports  270 ,  272  are in fluidic communication with fluid chambers defined by an assemblage of the housing  230 , the rotor  210 , the stator seals  227 , and the rotor seal  201 . A pair of fluid ports  274 ,  276  is in fluidic communication with a lock valve assembly (not shown). The fluid ports  270 ,  272  will be discussed further in the descriptions of FIGS.  4  and  5 A- 5 D. The fluid ports  274 ,  276  and the lock valve assembly will be discussed further in the descriptions of  FIGS. 3A ,  3 B,  4 A, and  4 B. 
         [0030]      FIG. 3A  is a cross-sectional side view of the example rotary vane actuator with a fluid actuated mechanical lock  100  in an assembled form. As discussed in the description of  FIG. 2 , the actuator  100  includes the rotor  210 , which is positioned within the central bore  234  of the housing  230 . The rotor  210  is rotatably supported at a distal end by the lower corner seal  288  and the housing  230 . The rotor  210  is rotatably supported at a proximal end by the bearing  240  and the bearing housing  236 . The bearing housing  236  is removably secured in place by the end cap  260 . The stator sections  220  are positioned to hold the stator seals  227  in substantially sealing contact with the inner surface  232 , the rotor shaft  212 , the upper corner seal  286 , the lower corner seal  288 , and the rotor seal  201 . 
         [0031]    The pair of fluid ports  270 ,  272  are in fluidic communication with fluid chambers formed by the housing  230 , the rotor  210 , the stator seals  227 , the upper corner seal  286 , the lower corner seal  288 , and the rotor seal  201 . A collection of axial seals  320  substantially prevent the intrusion of dust, water, and/or other external contaminants into the interior of the example rotary vane actuator with a fluid actuated mechanical lock  100 . 
         [0032]    The compression plate  284 , the spring  282 , and the lock piston  280  are assembled about the rotor shaft  212 . The spring  282  provides a compliant force separating the compression plate  284  and the lock piston  280 . The lock piston  280  is a fluid piston formed to slide axially along the central bore  234  about the rotor shaft  212 . When actuated, the lock piston  280  is urged into compressive contact with the spring  282 , which in turn compliantly compresses the compression plate and the upper corner seal  286  against the stator seals  227 , the rotor seals  210 , and the rotor vanes  216 . This compression mechanically squeezes the seal-to-seal interfaces tightly to counteract fluid pressure trapped in the actuator  100 , thereby locking the fluid within the pressure chambers. Internal leakage across the sealing interfaces is substantially reduced as fluid column pressure is contained. 
         [0033]    The example rotary vane actuator with a fluid actuated mechanical lock  100  includes a lock valve assembly  350 , shown in additional detail in  FIG. 3B . 
         [0034]      FIG. 3B  is an enlarged partial cross-sectional side view of the lock valve assembly  350  of the example rotary vane actuator with a fluid actuated mechanical lock  100 . The assembly  350  includes a fluid duct  352  in fluid communication with a first pair of fluid chambers within the actuator  100 . A fluid duct  354  is in fluid communication with a second pair of fluid chambers within the actuator  100 . The aforementioned fluid chambers will be discussed in the descriptions of  FIGS. 5A-5D . 
         [0035]    The lock valve assembly  350  also includes a plunger  360   a  and a plunger  360   b . A fluid chamber  362  is provided between the plungers  360   a ,  360   b . The plungers  360   a ,  360   b  are partly biased apart from each other by a bias spring  364  located between the plungers  360   a ,  360   b  within the fluid chamber  362 . The plungers  360   a ,  360   b  are also partly biased apart from each other by a pressurized fluid provided to the fluid chamber  364  by a fluid duct  356 . The fluid duct  356  is in fluid communication with the fluid port  274  and/or  276 , shown in  FIG. 2  to receive a supply fluid pressure. 
         [0036]    Under normal operating conditions, the plungers  360   a ,  360   b  are biased apart by the bias spring  364  and fluid pressure provided into the fluid chamber  364  by the fluid duct  356 . The plungers  360   a  and  360   b  are biased apart with sufficient force to seal the fluid duct  352  and the fluid duct  354  from fluidic communication with a fluid duct  370 . In some embodiments, fluid pressure in the pressure chambers and within the fluid ducts  352  and  354  can be substantially maintained by fluidically blocking the fluid ports  270  and  272 , e.g., to maintain the rotor  210  in a substantially fixed rotational position. Operations of the example rotary vane actuator with a fluid actuated mechanical lock  100  under “normal” operating conditions is discussed in the descriptions of  FIGS. 5A-5D , and use of the fluid duct  370  and operations under “abnormal” (e.g., failure mode) conditions are discussed in the descriptions of  FIGS. 6A and 6B . 
         [0037]      FIG. 4  is a cross-sectional end view of the example rotary vane actuator with a fluid actuated mechanical lock  100  which includes a one-piece rotor seal  201 . The cross-section shown in  FIG. 4  is taken along a section generally shown by line AA of  FIG. 1 . During assembly, the stator sections  220  are inserted into bore  234  of the housing  230  and the fasteners  250  are inserted through the holes  252  and are threaded into the threaded holes  254  to removably secure the stator sections  220  to the housing  230 . The stator sections  220  maintain the stator seals  227  in sealing contact with the inner surface  232  and the rotor shaft  212  (not shown in this view). In some embodiments, the stator sections  220  may be fastened to the housing in arrangements other than the one illustrated in the example  FIG. 4 , which depicts two rows of fasteners arranged axially on each side of the stator seals  227 . For example, one or both of the stator sections  220  may be formed with two or more of the stator seal grooves  226 , and the fasteners  250 , the holes  252 , and the threaded holes  254  may be arranged between pairs of the seal grooves  226  formed in a single one of stator sections  220 . 
         [0038]      FIGS. 5A-5D  are cross-sectional end views of the example rotary vane actuator with a fluid actuated mechanical lock  100  in four example rotational configurations  500   a - 500   d . In some embodiments, the transitions of the configurations shown in  FIGS. 5A-5D  may be considered as “normal” operations of the actuator  100 . 
         [0039]    The cross-sectional views of  FIGS. 5A-5D  show the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  with the rotor  210 . The rotor  210 , the stator sections  220 , and the housing  230  form a pair of pressure chambers  510   a ,  510   b  and a pair of pressure chambers  512   a ,  512   b . The pressure chambers  510   a ,  510   b  are located substantially opposite each other on opposing radial sides of the rotor  210 , and are in fluidic communication through a fluid channel  514 . A fluid, e.g., hydraulic fluid, air or gas, is applied at the fluid port  270  and flows into the pressure chamber  510   a , through the fluid channel  514 , and into the pressure chamber  510   b , thereby substantially balancing the pressures in the pressure chambers  510   a  and  510   b . In reverse flow, the fluid may escape the pressure chamber  510   b  through the fluid channel  514  into the pressure chamber  510   a  and out the fluid port  270 . The pressure chambers  512   a ,  512   b  are located substantially opposite each other on opposing radial sides of the rotor  210  opposite the pressure chambers  510   a ,  510   b , and are in fluidic communication through a fluid channel  516 . A fluid, e.g., hydraulic fluid, air, applied at the fluid port  272  can flow into the pressure chamber  512   a , through the fluid channel  516 , and into the pressure chamber  512   b  thereby substantially balancing the pressures in the pressure chambers  512   a  and  512   b . In reverse flow, the fluid may escape the pressure chamber  512   b  through the fluid channel  516  into the pressure chamber  512   a  and out the fluid port  272 . 
         [0040]      FIG. 5A  depicts the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  with the pressure chambers  512   a ,  512   b  pressurized at a mid-stroke rotational configuration of the rotor  210 . When fluid is applied to the fluid port  272 , the pressure chambers  512   a ,  512   b  become pressurized and urge rotation of the rotor  210  in a clockwise rotational direction. In some implementations, the rotor  210  can be held in a substantially fixed rotational position by holding the pressures of the fluid ports  270  and/or  272  steady, e.g., by fluidically blocking one or both of the fluid ports  270 ,  272 . The configuration of the rotor seals  201  and the stator seals  227  substantially eliminates the use of corner seals used in prior designs and reduces the potential for cross-chamber fluid leakage that occurs across the corner seals of prior designs, and thereby improves the ability of the example rotary vane actuator with a fluid actuated mechanical lock  100  to maintain a rotational position when the fluid ports  270 ,  272  are held at a steady pressure, e.g., are fluidically blocked. 
         [0041]      FIG. 5B  depicts the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  with the pressure chambers  512   a ,  512   b  pressurized at a clockwise hard-stopped rotational configuration of the rotor  210 . When fluid is applied to the fluid port  272 , the pressure chambers  512   a ,  512   b  become pressurized and urge rotation of the rotor  210  in a clockwise rotational direction. In the illustrated example, the clockwise rotation of the rotor  210  can stop when the clockwise faces of one or both rotor vanes  216  contacts one or both of the counterclockwise end faces of the stator sections  220 . 
         [0042]      FIG. 5C  depicts the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  with the pressure chambers  512   a ,  512   b  pressurized at another mid-stroke rotational configuration of the rotor  210 . For example, the configuration depicted by  FIG. 5C  may be achieved when the rotor  210  is rotated away from the rotation configuration shown in  FIG. 5B . When fluid is applied to the fluid port  270 , the pressure chambers  510   a ,  510   b  become pressurized and urge rotation of the rotor  210  in a counterclockwise rotational direction. In some implementations, the rotor  210  can be held in a substantially fixed rotational position by holding the pressures of the fluid ports  270  and/or  272  steady, e.g., by fluidically blocking one or both of the fluid ports  270 ,  272 . 
         [0043]      FIG. 5D  depicts the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  with the pressure chambers  510   a ,  510   b  pressurized at a counterclockwise hard-stopped rotational configuration of the rotor  210 . When fluid is applied to the fluid port  270 , the pressure chambers  510   a ,  510   b  become pressurized and urge rotation of the rotor  210  in a counterclockwise rotational direction. In the illustrated example, the counterclockwise rotation of the rotor  210  can stop when the counterclockwise faces of one or both rotor vanes  216  contacts one or both of the clockwise end faces of the stator sections  220 . 
         [0044]      FIGS. 6A and 6B  are cross-sectional side views of the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  in a failure mode. In some embodiments, the configuration of the actuator  100  as shown in  FIGS. 6A and 6B  may depict the actuator  100  in an “abnormal” or “failure” operating configuration. Under abnormal operating conditions, such as a fluid supply failure, stator seal  227  failure, or rotor seal  201  failure within the example rotary vane actuator with a fluid actuated mechanical lock  100 , the rotor  210  may be urged out of a selected locked position by external forces, e.g., wind resistance or G-forces acting on an aircraft control surface actuated by the rotor  210 . The actuator  100  can resist such external action when the pressure in the fluid chamber  364  is lowered. With the pressure in the fluid chamber  364  sufficiently lowered, pressure from the pressure chambers through the fluid ducts  352  and/or  354  can urge one or both of the plungers  360   a ,  360   b  to compress the bias spring  362  and unseal the fluid ducts  352  and/or  354 . When one or both of the fluid ducts  352 ,  354  is unsealed, a fluidic circuit is established between the fluid ducts  352  and/or  354  and a fluid duct  370 . 
         [0045]    Referring now to  FIG. 6B , which is an enlarged partial cross-sectional side view of the lock valve assembly  350  of the example rotary vane actuator with a fluid actuated mechanical lock  100  under “abnormal” operating conditions. As discussed previously, under “normal” operating conditions the plungers  360   a ,  360   b  are biased apart by the bias spring  362  and fluid pressure provided into the fluid chamber  364  by the fluid duct  356 . The plungers  360   a  and  360   b  are biased apart with sufficient force to seal the fluid duct  352  and the fluid duct  354  from fluidic communication with a fluid duct  370 . 
         [0046]    However, during the “abnormal” or “failure” operating mode depicted in  FIGS. 6A and 6B , there is insufficient pressure present in the fluid chamber  364  to cause the plungers  360   a ,  360   b  to seal the fluid ducts  352 ,  354 . In some embodiments, pressure in the fluid chamber  364  may drop due to a malfunction, e.g., failure of a fluid pump or a break in a fluid supply line feeding the fluid ports  274  or  276 . In some embodiments, pressure in the fluid chamber  364  may be purposely dropped, e.g., as a fluidic control signal to the actuator  100 . When pressure builds either of the fluid ducts  352  or  354 , the pressure may become sufficient to overcome the bias force of the spring  362  and any remaining fluid pressure in the fluid chamber  364 , and urge a corresponding one of the plungers  360   a ,  360   b  to become unsealed and create a fluidic circuit between the corresponding fluid duct  352  or  354  and the fluid duct  370 . 
         [0047]    In the illustrated example, the plunger  360   a  has been unsealed by pressure from the fluid duct  352 , creating a fluidic circuit between the fluid duct  352  and the fluid duct  370 . In some implementations, pressure in the fluid ducts  352  and/or  354  can be developed when the rotor  210  is urged to rotate by external forces acting upon a mechanism connected to the rotor  210 , e.g., wind resistance or G-forces acting on an aircraft control surface actuated by the actuator  100 . 
         [0048]    Referring now to  FIG. 6A , fluid pressure is provided through the fluid duct  370  of the example rotary vane actuator with a fluid actuated mechanical lock  100  of  FIG. 1  to a junction  610  located at the interface of the lock piston  280  and the bearing housing  236 . As fluid enters the junction  610 , the lock piston  280  is urged toward the spring  282 . The spring  282 , in turn, is urged into compliant compression against the compression plate  284 , which compresses the upper corner seal  286 , the rotor  210 , and/or the lower corner seal  288 . This action creates a tightly compressed sealing interface at the sides of the rotor vanes  216  and the stator sections  220 , and the increased seal friction imparted on the rotor  210  by the spring  282  normal force substantially holds position of the rotor shaft  212  and any appropriate actuated load. In some implementations, fluid pressures in the fluid chambers may be increased as the rotor shaft  212  is loaded, and may further energize the upper corner seal  286  and/or the lower corner seal  288 , thereby increasing sealing force and/or friction, and substantially lock the rotor  210  from turning. 
         [0049]    Although a few implementations have been described in detail above, other modifications are possible. For example, various combinations of single piece rotor seals, multiple piece rotor seals, single piece stator seals, and multiple piece stator seals may be combined to achieve desirable results. In addition, other components may be added to, or removed from, the described actuators. Accordingly, other embodiments are within the scope of the following claims.