Abstract:
An improved fin retention and release mechanism ( 15 ) comprising an elongated body ( 16 ), at least one fin ( 18   a ) mounted to the body and capable of moving from a stowed position ( 30 ) to a deployed position ( 32 ), an actuator ( 20   a ) connected to the fin and arranged to rotate the fin about a first axis ( 33 ), a fin retention member ( 19   a ) connected to the body and configured and arranged to rotate about a second axis ( 34 ) from a locked position ( 36 ) to a release position ( 38 ), the fin and the fin retention member configured and arranged such that the fm is held in the stowed position by the fin retention member when being in the locked position and the fin is not held in the stowed position by the fm retention member when being in the release position, and wherein actuation of the fin about the first axis by the actuator rotates the fm about the first axis in a first direction ( 39 ) and correspondingly rotates the fin retention member about the second axis in a second direction ( 40 ) opposite to the first direction and from the locked position to the release position.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to the field of projectile fin retention devices, and more particularly to an improved fin retention and release mechanism. 
       BACKGROUND ART 
       [0002]    Conventional projectiles, such as missiles, have actuated fins that help steer the projectile towards an intended target. Such projectiles often include a locking mechanism that retains the fins in a stowed position, such as prior to launch or during transportation. After launch, the fins are deployed and thereafter actuated to control the angle of attack of the fins and the control flight of the projectile. A control actuation system adjusts the position of the fins during operation in response to steering commands received from the controller. U.S. Pat. No. 6,726,147, entitled “Multi-Functional Actuator, and Method of Operating Same,” the disclosure of which is incorporated herein in its entirety, discloses an actuator system for a projectile fin. 
         [0003]    Conventional locking mechanisms for transitioning from a stowed position to a deployed position have included pyrotechnic or explosive release mechanisms, such as an explosive squib, and solenoids and fin lock release motors configured to hold the fins in a retracted or stowed position and to allow them to move into a deployed position by command. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    With parenthetical reference to corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides an improved fin retention and release mechanism ( 15 ) comprising an elongated body ( 16 ), at least one fin ( 18   a ) mounted to the body and capable of moving from a stowed position ( 30 ) to a deployed position ( 32 ), an actuator ( 20   a ) connected to the fin and arranged to rotate the fin about a first axis ( 33 ), a fin retention member ( 19   a ) connected to the body and configured and arranged to rotate about a second axis ( 34 ) from a locked position ( 36 ) to a release position ( 38 ), the fin and the fin retention member configured and arranged such that the fin is held in the stowed position by the fin retention member when the fin retention member is in the locked position and the fin is not held in the stowed position by the fin retention member when the fin retention member is in the release position, and wherein selective actuation of the fin about the first axis by the actuator rotates the fin about the first axis in a first direction ( 39 ) and correspondingly rotates the fin retention member about the second axis in a second direct ( 40 ) opposite to the first direction and from the locked position to the release position. 
         [0005]    The fin may be pivotally mounted to the body and rotatable around a third axis ( 35 ) from the stowed position to the deployed position. The fin retention and release mechanism may further comprise a spring element ( 23 ) arranged between the fin retention member and the body and configured to bias the fin retention member toward the locked position. The fin retention member may comprise a retaining end portion ( 24 ) and a shaft portion ( 25 ) and the spring element may comprise a torsion spring orientated about the shaft portion. The fin retention member may comprise a reset groove ( 26 ) configured and arranged to receive a reset tool, wherein the fin retention member may be manually rotated from the locked position to the release position. The fin may comprise a retaining pocket ( 21 ), the fin retention member may comprise a retaining end portion ( 24 ), and the fin retaining pocket may be configured and arranged to receive the end portion of the retention member when the fin is in the stowed position. The fin retention member may comprise a generally cam-shaped retaining end portion ( 24 ) and a shaft portion ( 25 ). The fin retention member may be connected to the body with a retaining ring ( 28 ). The body may comprise a fin stop ( 29 ). The first axis and the second axis may be parallel. 
         [0006]    The projectile may comprise a second fin ( 18   c ) mounted to the body and capable of moving from a stowed position to a deployed position, a second actuator ( 20   c ) connected to the second fin and arranged to rotate the second fin about a first axis, a second fin retention member ( 19   c ) connected to the body and configured and arranged to rotate about a second axis from a locked position to a release position, the second fin and the second fin retention member configured and arranged such that the second fin is held in the stowed position by the second fin retention member when the second fin retention member is in the locked position and the second fin is not held in the stowed position by the second fin retention member when the second fin retention member is in the release position, and wherein selective actuation of the second fin about the first axis by the second actuator rotates the second fin about the first axis in a first direction and correspondingly rotates the second fin retention member about the second axis in a second direct opposite to the first direction and from the locked position to the release position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a front plan view of a projectile with an embodiment of an improved fin retention and release mechanism. 
           [0008]      FIG. 2 a    is a top outer perspective view of the projectile shown in  FIG. 1 . 
           [0009]      FIG. 2 b    is a top interior view of the projectile shown in  FIG. 1 . 
           [0010]      FIG. 3  is a side perspective view of the projectile shown in  FIG. 1 . 
           [0011]      FIG. 4  is an enlarged perspective view of the fin retention and release mechanism shown in  FIG. 3 . 
           [0012]      FIG. 5  is a partial exploded and enlarged view of one fin retention and release mechanism shown in  FIG. 4 . 
           [0013]      FIG. 6  is a partial vertical cross-sectional view of the fin retention and release mechanism shown in  FIG. 2 b   , taken generally in line  6 - 6  of  FIG. 2   b.    
           [0014]      FIG. 7  is a partial horizontal cross-sectional view of the fin retention and release mechanism shown in  FIG. 6 . 
           [0015]      FIG. 8  is an exploded cross-sectional view of the fin retention and release mechanism shown in  FIG. 7 . 
           [0016]      FIGS. 9 a -9 f    are front plan views of the fin retention and release mechanism of  FIG. 3  showing a fin deployment sequence. 
           [0017]      FIGS. 10  is an enlarged view of the fin retention and release mechanism shown in  FIG. 4 . 
           [0018]      FIG. 11  is a further enlarged partial view of the fin retention and release mechanism shown in  FIG. 10 . 
           [0019]      FIGS. 12 and 13  are views of the fin retention and release mechanism shown in  FIG. 11  with alternate engagement depths. 
           [0020]      FIG. 14  is a front plan view of a projectile having switch-blade style fins. 
           [0021]      FIG. 15  is a top perspective view of the projectile shown in  FIG. 14 . 
           [0022]      FIGS. 16 a -16 c    are front plan views of the fin retention and release mechanism of  FIG. 14  showing a fin deployment sequence. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    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., cross-hatching, 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. 
         [0024]    Referring now to the drawings, and more particularly to  FIG. 1  thereof, a fin retention and release mechanism is provided, an embodiment of which is generally indicated at  15 . As shown in  FIG. 1 , projectile  17  generally comprises a body  16  and four deployable fins  18   a - 18   d  for controlling the flight of the projectile. Prior to deployment, fins  18   a - 18   d  are folded up in stowed position  30 , a position shown in  FIGS. 1-4 and 9   a . Anchored to hinge pins at their base, fins  18  pivot or rotate about axis  35  to deployed position  32 , shown in  FIGS. 9 e  and 9 f   , following missile launch. Torsional springs serve to urge fins  18  toward deployed position  32 . Fins  18  are retained in stowed position  30 , against the biasing force of the torsional springs urging them to pivot outward, by latching mechanism  15   
         [0025]    Each of fins  18   a - 18   d  is rotatably connected at its base to actuators  20   a - 20   d , respectively. Actuators  20  thereby control rotation of fins  18  about axis  33 . Actuators  20  are in electrical communication with a controller, such as a processor, which receives position signals from a flight control center. Based upon signals received by the controller, the controller commands the actuators to adjust the position of fins  18  as desired to steer projectile  17  towards a target or to release fins  18 . 
         [0026]    As shown, fin retention mechanism  15  generally comprises lock-pin  19 , torsional spring  23 , retaining ring  28 , and stop  29 . As shown in  FIGS. 5-8 , lock-pin  19  generally comprises shaft portion  25  and cam-shaped end portion  24  having a minimum outside diameter greater than the outside diameter of shaft  25 . As shown in  FIG. 8 , lock-pin  19  is generally bounded by rightwardly-facing vertical surface  50 , outwardly-facing horizontal cylindrical surface  51 , leftwardly-facing vertical annular surface  52 , outwardly-facing horizontal cylindrical surface  53 , rightwardly-facing vertical annular surface  54 , outwardly-facing horizontal cylindrical surface  55 , rightwardly-facing vertical annular surface  56 , outwardly-facing horizontal cam surface  57 , and leftwardly-facing vertical surface  58 . 
         [0027]    As shown, surfaces  52 ,  53  and  54  define shaft retention groove  41 , which is configured to engage retaining ring  28  fixed to body  19  such that lock-pin  19  is permitted to rotate about axis  34  but is secured from movement longitudinally or axially along axis  34 . Thus, lock-pin  19  is rotatably connected to body  19  such that end portion  24  can rotate at least partially about axis  34 . 
         [0028]    As shown, a specially configured pin recess  22  is formed in body  16  to receive shaft  25 . Recess  22  provides a housing to support rotating lock-pin  19  and anti-rotate torsion spring  23 . The inner portion of recess  22  is generally cylindrical and includes retaining ring  28  near the base of the cylindrical recess so as to receive shaft  25  in rotational engagement. Recess  22  is also includes a slot for receiving spring end  42 . 
         [0029]    Spring end  42  bears against the walls of recess  22 . The end of spring  23  on the other side of the coil from end  42  is captured in a hole in surface  56  of end portion  24  of pin-lock  19 . Thus, torsional spring  23  is installed on shaft  25  of lock-pin  19  such that it is anti-rotated in recess  22  and preloads lock-pin  19  against pocket  21  in the top end of fin  18 . Lock-pin  19  is biased toward locked position  36  and, absent a countering force, will move to locked position  36 . One side of surface  57  of end portion  24  bears against one side of pocket  21  in fin  18  such that fin  18  is loaded against stationary dowel pin  29  as a result of the torsional load of spring  23  on lock pin  19 . With shaft  25  axially secured to body  16  by retaining ring  28  in shaft retention groove  41 , part of surface  56  of end portion  24  of pin  19  bears against the outside surface of fin  18  to hold it in stowed position  30 . 
         [0030]    As shown in  FIGS. 9 a -9 f   , lock-pin  19  is configured to rotate about axis  34  from locked position  36 , in which tip  43  of end portion  24  engages pocket  21  in fin  18 , to release position  38 , in which tip  43  of end portion  24  of lock-pin  19  does not extend into pocket  21  of fin  18 . Thus, in a released position, lock-pin  19  does not restrain fin  18  from rotating about axis  35  from stowed position  30  to deployed position  32 . 
         [0031]    As shown in  FIGS. 9 a -9 f   , to release fin  18 , actuator  20  is programmed to rotate about fin axis  33  in counter-clockwise direction  39  relative to body  19  a set distance. The rotational force of actuator  20  is enough to overcome the countering spring force of spring  23  in the clockwise direction about pin axis  34 . Thus, the edge of pocket  21  bears against the side surface  57  of end portion  24  of pin  19 , causing pin  19  to rotate in clockwise direction  40  about pin axis  34 . As this rotation continues, as shown in  FIG. 9 c   , tip  43  of end portion  24  of pin  19  clears pocket  21  in fin  18 , thereby releasing fin  18  such that fin  18  can rotate about axis  35  from stowed position  30 , shown in  FIGS. 9 a -9 c   , to deployed position  32 , shown in  FIGS. 9 e  and 9 f   . This deployment from stowed position  30  to deployed position  32  is shown in  FIG. 9 d   . Once in deployed position  32 , as shown in  FIGS. 9 e  and 9 f   , fin  18  can be rotated back clockwise and actuated to the desired position about fin axis  33 . Thus, actuator  20  controls both the operational rotation of fins  18  as well as the rotation of lock-pin  19  from locked position  36  to release position  38  to release fin  18  for deployment. No separate motor, actuator, solenoid or pyrotechnic release mechanism is required. Thus, mechanism  15  employs passive mechanical retention, coupled with control surface actuator motion, to stow and then release fin  18 . 
         [0032]    Release mechanism  15  is also resectable. Once fin  18  moves out of stowed position  30 , spring  23  returns lock-pin  19  to the null or stowed position  30 , which prevents rattling in assembly. As shown, lock-pin  19  includes outer slot  26 , which is configured to receive the end of a flat-headed screwdriver, for example. By manually rotating lock-pin  19  using a torqueing device, lock-pin  19  may be moved to release position  38  and out of the way of fin  18  such that fin  18  can be placed back in stowed position  30 , and then re-locked in the stowed position by releasing lock-pin  19  and allowing tip  43  of end portion  24  of lock-pin  19  to engage pocket  21  in fin  18 . For resetting purposes, actuator  20  is of a back-drivable design that employs position feedback if it is to be manually reset. Alternatively, it can be reset using position commands to drive the fin back to the null or stowed-angle position about axis  33 . Actuator  20  may then be commanded to the given output position to release fin  18  from release mechanism  15 . 
         [0033]    As shown, release mechanism  15  as described above may be used to retain and release each of the fins  18   a - 18   d  on projectile  17  from a stowed position to a deployed position. 
         [0034]    Some designs may require more of a retention margin. Lock-pin mechanism  15  may be sized to keep fin  18  stowed with adequate margin when the assembly is subjected to external environment loads, including random vibration and shock events. A number of design alternatives may be used for altering the retention torque holding fin  18  in place. 
         [0035]    First, a torsion spring may be selected that allows for adequate preload force development, and sufficient travel for release of fin  18 . Depending on the amount of preload desired, and where the anti-rotating features of recess  22  in the housing are located, a torsion spring of 90-360 degrees can be used. Changing to a larger degree torsion spring allows for more preload in the same package, but also requires more driving torque from actuator  20  to release fin  18 . A larger or smaller wire torsion spring may be used to alter preload force with minimal impact on design and a larger or smaller outside diameter torsion spring and mating lock-pin shaft  25  may also be used to vary the force margin. 
         [0036]    Second, the depth of tip  43  of end portion  24  of lock-pin  19  in pocket  21  of fin  18  may be varied, as shown in  FIGS. 12 and 13 . By changing the depth of the engagement of end portion  24  of lock-pin  19  in pocket  21  of fin  18 , the amount of actuator  20  rotation required to release fin  18  can be modified and more or less margin can be added to retention of fin  18 . 
         [0037]    Third, the geometry of end portion  24  and “cam” surfaces  57 ,  58  of pin  19  may be varied together with pocket or slot interface  21 . Modifications to the interface geometry between lock-pin  19  and fin  18  can be performed to fine tune the load properties of retention mechanism  15 . For example, the applicable ramp angle of outer surface  57  of end portion  24  of lock-pin  19  may be varied, as can the length of the locking section of pin  19  and the tip design of end portion  24  of pin  19 . 
         [0038]    Fourth, depending on the type and orientation of the mechanism/spring for deploying fin  18  about axis  35 , lock-pin  19  may be moved to a different location on the fin to alter the effective moment arm and retention load on the fin. An example of this would be to lower the lock-pin location relative to the stowed fin so that it is closer to the base of fin  18 . This may be desired if the actuator has limited travel to release fin  18 . 
         [0039]      FIGS. 14, 15 and 16   a - 16   c  shown an alternative embodiment in which retention mechanism  15  is employed on a projectile having switch-blade release style fins. As shown in  FIGS. 16 a   - 16   c,  the pocket in the end of the fin is orientated perpendicular to the orientation of pocket  21  in flap-style release fins  18 . As with flap-style release fins  18  in the embodiment shown in  FIGS. 1-13 , actuation of switch-blade style fins  118  about axis  133  in a counter-clockwise direction causes rotation of pin  119  in a clockwise direction until tip  143  of end portion  124  of pin  119  clears pocket  121  in fin  118 , thereby releasing fin  118  from its stowed position and allowing it to move into a deployed position. 
         [0040]    The present invention contemplates that many changes and modifications may be made. Therefore, while an embodiment of the improved fin retention and release mechanism has been shown and described, and a number of alternatives discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.