Abstract:
An actuator synchronization system comprising a control valve in fluid communication with a plurality of actuators; each of the actuators comprising an input member moveable by the control valve, a main valve moveable from a null to an off-null position, an output member moveable from a first to a second output position, and a feedback linkage and a drive link configured such that selective movement of the input member causes movement of the valve from the null to the off-null position and movement of the output member to the second output position causes movement of the valve member from the off-null to the null position; and a mechanical connector between each of the input members or drive links of the actuators configured such that rotational motion of each of the respective drive links is synchronized.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to the field of engine nozzles, and more particularly to a nozzle synchronization system. 
       BACKGROUND ART 
       [0002]      FIGS. 1-4  show a conventional nozzle synchronization system. As shown in  FIG. 1 , such prior art systems comprise a plurality of spaced apart actuators that are flow summed to a single two stage electrohydraulic servo valve. As a result, each actuator has its own friction, flow force, rate and force characteristics. As shown in  FIGS. 1-4 , the output of each actuator is linked via piston motion to an acme screw and worm gear and a flexible synchronization cable. Nozzle position is fed back to the system to control the electrohydraulic servo valve command. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiments, merely for purposes of illustration and not by way of limitation, an actuator synchronization system ( 15 ) is provided comprising a control valve ( 18 ) in fluid communication with a plurality of actuators ( 16   a - 16   d ), each of the actuators comprising an input stage element in fluid communication with the control valve and having an input member ( 21 ) movably mounted along an input axis ( 61 ), and configured to be moved from a first input position ( FIG. 7 ) to a second input position ( FIG. 9 ) along the input axis by the control valve, a main valve ( 20 ) having a valve member ( 29 ) movably mounted in a valve chamber ( 28 ) along a main valve axis ( 62 ), and configured to be moved from a null position ( FIG. 7 ) to an off-null position ( FIG. 10 ) along the main valve axis to selectively meter fluid flow from at least one port (P 1 ) defined between the valve member and the valve chamber, an output stage element in fluid communication with the port of the main valve and having an output member ( 26 ) moveably mounted along an output axis ( 63 ), and configured to be moved from a first output position ( FIG. 7 ) to a second output position ( FIG. 13 ) along the output axis by a pressure differential applied on the output member by the main valve, the main valve and the output member configured such that the output member is at a pressure equilibrium and does not move when the valve member is in the null position, a feedback linkage ( 22 ) acting between the valve member and the output member, an eccentric drive link ( 40 ) acting between the input member and the feedback linkage and configured to rotate about a fixed drive axis ( 44 ), the drive link rotationally connected to the feedback linkage at a first pivot ( 47 ) that is off-set a distance ( 54 ) from the fixed drive axis and configured such that selective motion of the input member between the first input position and the second input position along the input axis causes the pivot of the feedback linkage to rotate about the drive axis, the feedback linkage and the drive link configured such that selective movement of the input member from the first position to the second position causes the drive link and the feedback linkage to move the valve member from the null position to the off-null position, the movement of the valve member from the null position to the off-null position causes the pressure differential on the output member and the output member to thereby move from the first output position to the second output position, and the movement of the output member to the second output position causes the feedback linkage to move the valve member from the off-null position back to the null position; and a mechanical connector ( 17 ) between each of the input stage elements and/or the drive links configured such that rotational motion of each of the respective drive links about the respective fixed drive axis is substantially the same and thereby synchronized. 
         [0004]    The control valve may comprise a servo valve. The respective fixed drive axes of the actuators may be aligned and the mechanical connector may comprise a shaft extending between the respective input stage elements and/or the respective drive links. The respective fixed drive axes of the actuators may not be aligned and the mechanical connector may comprise a cable or universal joint extending between the respective input stage elements and/or the respective drive links. 
         [0005]    The input member may comprise an input piston ( 21 ) moveably mounted in an input chamber ( 25 ) in fluid communication with the control valve. The input piston may comprise a portion having a slot ( 24 ) bounded by substantially-parallel walls and the drive link may comprise a rounded marginal end portion ( 41 ) engaging the slot walls. The output member may comprise an output piston ( 26 ) moveably mounted in an output chamber ( 35 ) in fluid communication with the port of the main valve. The feedback linkage may comprise a first link ( 45 ) engaging the valve member at a first connection and a second link ( 49 ) engaging the output piston at a second connection. The valve member may comprise a slot ( 30 ) bounded by substantially-parallel walls and the first link of the feedback linkage may comprise a rounded marginal end portion ( 42 ) contacting the slot walls to form the first connection. The output piston may comprise a contoured surface ( 27 ) and the second link of the feedback linkage may comprise a rolling marginal end portion ( 51 ) configured to contact the contoured surface of the output piston to form the second connection. The feedback linkage may comprise a third link ( 48 ) connected to the first link at a third connection ( 52 ) and connected to the second link at a fourth connection ( 53 ). The first link and the third link may be rotationally coupled at the third connection and the second link and the third link may be rotationally coupled at the fourth connection. The second link may be configured to rotate about a fixed feedback axis ( 50 ) and the fourth connection ( 53 ) may be off-set a distance from the fixed feedback axis such that selective motion of the output piston between the first output position and the second output position along the output axis causes the fourth connection of the feedback linkage to rotate about the feedback axis. The feedback linkage may be configured to move the valve member from the null position to the off-null position with selective rotation of the drive link about the drive axis. The feedback linkage may be configured to move the valve member from the off-null position back to the null position with selective rotation about the feedback axis. 
         [0006]    The main valve may comprise a second port (P 2 ); the output member may comprise an output piston ( 26 ) moveably mounted in an output chamber in fluid communication with the port of the main valve; the output chamber may comprise a first chamber ( 33 ) and a second chamber ( 34 ); the first port may be flow connected to the first chamber and the second port may be flow connected to the second chamber; and the output piston may be adapted to be moved from the first position to the second position along the output axis as a function of a hydraulic pressure differential between the first chamber and the second chamber. 
         [0007]    Each of the respective actuators may further comprise a bias mechanism ( 60 ) configured to bias one or more of the valve member, the drive link and the feedback linkage. The second link may be configured to rotate about a fixed feedback axis ( 50 ) and the bias mechanism may comprise a first bias element ( 60   a ) configured to bias the valve member along the main valve axis, a second bias element ( 60   b ) configured to bias the output member about the feedback axis and a third bias element ( 60   c ) configured to bias the drive link about the drive axis. The first bias element may comprise a compression spring and the third bias element may comprise a torsional spring. 
         [0008]    The valve member may comprise a valve spool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic view of a prior art nozzle synchronization system. 
           [0010]      FIG. 2  is a perspective view of the prior art nozzle synchronized system shown in  FIG. 1  installed on a conventional nozzle. 
           [0011]      FIG. 3  is a cross-sectional view of the prior art nozzle synchronized system shown in  FIG. 2 . 
           [0012]      FIG. 4  is a cross-sectional view of the prior art nozzle actuator shown in  FIG. 3 . 
           [0013]      FIG. 5  is a schematic view of an embodiment of an improved nozzle actuator synchronization system. 
           [0014]      FIG. 6  is an enlarged cross-sectional view of one of the actuators shown in  FIG. 5 . 
           [0015]      FIG. 7  is a cross-sectional view of the actuator shown in  FIG. 6  at the null position. 
           [0016]      FIG. 8  is a cross-sectional view of the actuator shown in  FIG. 6  upon a down command. 
           [0017]      FIG. 9  is a cross-sectional view of the actuator shown in  FIG. 6  as it continues to move down. 
           [0018]      FIG. 10  is a cross-sectional view of the actuator shown in  FIG. 6  with the output piston responding to the valve opening. 
           [0019]      FIG. 11  is a cross-sectional view of the actuator shown in  FIG. 6  with the feedback linkage providing a cancelling return. 
           [0020]      FIG. 12  is a cross-sectional view of the actuator shown in  FIG. 6  as the piston moves and the hydro-mechanical valve closes. 
           [0021]      FIG. 13  is a cross-sectional view of the actuator shown in  FIG. 6  with the piston no longer moving. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., crosshatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate. 
         [0023]    Referring now to  FIG. 5 , an improved nozzle synchronization system is provided, an embodiment of which is generally indicated at  15 . System  15  is shown as broadly including four actuators  16   a,    16   b,    16   c,  and  16   d,  a servo valve control  18 , and a synchronization cable  17  mechanically connecting actuators  16   a - 16   d  at connections  43   a,    43   b ,  43   c  and  43   d,  respectively. 
         [0024]    As shown, servo valve  18  has operative connections Ps, Pr, C 1  and C 2  with actuators  16   a - 16   d  to supply pressure Ps and fluid return Pr and provide controls C 1  and C 2 , respectively. While valve  18  in this embodiment is a four-way servo valve, it should be clearly understood that the embodiments are not limited to four-way valves, but could be readily adapted to some other form, as desired. 
         [0025]    As shown in  FIG. 6 , each of actuators  16   a - 16   d  generally comprises pilot input piston  21  connected to input crank  40 , hydro-mechanical servo valve  20 , output piston  26 , closed loop feedback linkage  22  and synchronization connection  43 . As shown in  FIG. 5 , each of the four pilot pistons of actuators  16   a - 16   d  are flow summed to servo valve  18  and are also synchronized via connection  43  with flexible cable  17 . As a result, a smaller servo valve  18  may be used that has less leakage. Supply and return pressure is individually connected to hydro-mechanical servo valve  20  of each actuator  16   a - 16   d.  As shown, cable  17  provides a mechanical connection  43   a - 43   d  between each respective input crank  40  of actuators  16   a - 16   d  and is configured such that rotational motion of each respective input crank  40  about its respective axis  44  is substantially the same and thereby synchronized. While synchronization connections  43   a - 43   d  are shown as being made directly between respective input cranks  40  of actuators  16   a - 16   d,  alternatively the mechanical connections could be made directly between respective pilot pistons  21  of actuators  16   a - 16   d.  While in this embodiment a cable provides the mechanical connector, it is contemplated that other mechanical connectors may be used to synchronize the input to valves  20  of actuators  16   a - 16   d.  For example, a universal joint may be employed as an alternative. Also, if respective axes  44  of actuators  16   a - 16   d  are aligned or coincide, a shaft or other rigid mechanical connector may be used, for example, as an alternative. 
         [0026]    As shown in  FIGS. 5-13 , pilot piston  21  is adapted to be selectively and controllably shifted either upward or downward, as desired, within cylinder  25  with servo valve  18  lines C 1  and C 2 . Pilot piston  21  includes curled or notched end  24 . 
         [0027]    Spool  29  of servo valve  20  has a plurality of lands and grooves along its longitudinal extent in the usual manner, and is adapted to be selectively and controllably shifted either leftwardly or rightwardly, as desired, within cylinder  28  from the null position shown in  FIG. 7 . In the null position, respective lands  31   a  and  31   b  on valve spool  29  cover the appropriate ports P 1  and P 2  communicating with the left and right chambers  33  and  34 , respectively, of output piston cylinder  35  to prevent flow through valve  20 . Ps and Pr ports are provided on the left and right sides, respectively, of land  31   a  of spool  29 . 
         [0028]    Closed loop feedback linkage  22  generally comprises input crank  40 , input link  45 , feedback link  48  and elbow link  49 . As shown, input crank  40  is configured to rotate about fixed axis  44  and includes quill  41  and cable attachment  43 . Quill  41  has a rounded distal end portion received in notched end  24  of pilot piston  21 . Flexible cable  17  is attached at cable attachment  43  and synchronizes the low force/low friction input cranks  40  of each of actuators  16   a - 16   d.  Crank  40  is rotationally connected at pivot joint  47  to input link  45 . 
         [0029]    The top end of input link  45  includes quill  42 , which has a rounded distal end portion received in notched end  30  of spool  29 . The other end of input link  45  is rotationally connected at pivot joint  52  to the left end of feedback link  48 . The right end of feedback link  48  is in turn rotationally connected at pivot joint  53  to the bottom left end of elbow link  49 . 
         [0030]    Elbow link  49  is configured to rotate about fixed axis  50 . Output piston  26  includes an inwardly and leftwardly-facing frusto-conical inner tapered bore  27 , as shown. The right upper end of elbow link  49  includes cam roller  51 , which bears against and rolls along the inner tapered surface  27  of piston  26 . Pivot joints  47 ,  52  and  53  are said to be floating pivot joints since their axis of rotation is not fixed relative to the actuator body. Axes  44  and  50  are not floating. 
         [0031]    As shown in  FIG. 6 , spring force preloads  60  are provided to bias spool  29  to the left, to bias elbow link  49  to rotate in a counter-clockwise direction about fixed axis  50 , and to bias input crank  40  to rotate in a counterclockwise direction about fixed axis  44 . As shown in  FIG. 7 , in the null position, center line  46  (in this embodiment extending through axes  47  and  52 ) of input link  45  is offset rightwardly a distance  54  from input crank axis  44 , and rotational or pivot axis  47  of input link  45  is below and to the right an eccentric distance relative to fixed axis  44  of input crank  40 . 
         [0032]      FIG. 7  shows actuator  16  in a first null position or configuration. As shown, in the null configuration of  FIG. 7  hydraulic flow between hydraulic control port P 1  and cylinder chamber  33  is blocked by land  31   a.  Similarly, hydraulic flow between control port P 2  and cylinder chamber  34  is blocked by land  31   b.  Thus, hydraulic fluid in chambers  33  and  34  is prevented from flowing out by spool lands  31   a  and  31   b,  respectively. Thus, piston  26  is constrained from moving. 
         [0033]      FIG. 8  shows actuator  16  immediately upon a command from servo valve  18  to move pilot piston  21  down on axis  61 . With this command, pilot piston  21  is configured and arranged to slide downward in cylinder  25 . As piston  21  moves down, end  24  causes quill  41  and input crank  40  to rotate counter-clockwise about axis  44 . Because at this point piston  26  is constrained from movement as described above, pivot joint  52  momentarily acts as a fixed axis. Because of this and the eccentric offset described above, counter-clockwise rotation of input crank  40  about axis  44  causes quill  42  of input link  45  to move to the right. The movement of quill  42  to the right causes notched end  30  and valve spool  29  to move to the right within cylinder  28  on axis  62 . As shown in  FIGS. 9-11 , as valve spool  29  is moved right, spool lands  31   a  and  31   b  are no longer aligned on control ports P 1  and P 2 , respectively, which allows fluid to flow to or from control ports Ps and Pr, respectively, and in turn to and from ports P 1  and P 2  and output piston chambers  33  and  34 , respectively. 
         [0034]    This controlled flow and hydraulic pressure in turn causes output piston  26  to move to the right on axis  63 . As shown in  FIGS. 10-11 , with such movement and the spring bias or preload described above, the relative movement of piston bore  27  past roller end  51  allows elbow link  49  to rotate incrementally counter-clockwise about fixed axis  50 . This causes pivot joint  53  to move counter-clockwise about axis  50  and to the right, which in turn pulls pivot joint  52  and the bottom end of input link  45  to the right. With piston  21  stationary, and input crank  40  also stationary, this causes input link  45  to rotate about axis  47  in a counterclockwise direction. At this point, counter-clockwise rotation of input link  45  about axis  47  in turn causes quill  42  of input link  45  to move to the left. The movement of quill  42  to the left causes valve  20  to close. In particular, movement of quill  42  to the left causes notched end  30  and valve spool  29  to move to the left within cylinder  28 . As shown in  FIGS. 12-13 , as valve spool  29  is moved left, spool lands  31   a  and  31   b  realign along control ports P 1  and P 2 , respectively, which stops fluid flow to and from control ports P 1  and P 2  and output piston chambers  33  and  34 , respectively. Piston  26  stops moving with the closing of the ports. The output piston  26  position is proportional to the input piston  21  position. 
         [0035]    The nozzle position is fed back to the system to control the electro-hydraulic servo valve  18  command to the input pilot piston  21  of each actuator  16 . As a result, the system will operate with higher loop gain and provide more accuracy. Each actuator is closed loop position servo to input. 
         [0036]    While the presently preferred form of the system has been shown and described, and several modifications thereof discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the scope of the invention, as defined and differentiated by the following claims.