Fin retention and release mechanism

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

TECHNICAL FIELD

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

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.

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

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 (18a) mounted to the body and capable of moving from a stowed position (30) to a deployed position (32), an actuator (20a) connected to the fin and arranged to rotate the fin about a first axis (33), a fin retention member (19a) 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.

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.

The projectile may comprise a second fin (18c) mounted to the body and capable of moving from a stowed position to a deployed position, a second actuator (20c) connected to the second fin and arranged to rotate the second fin about a first axis, a second fin retention member (19c) 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and more particularly toFIG. 1thereof, a fin retention and release mechanism is provided, an embodiment of which is generally indicated at15. As shown inFIG. 1, projectile17generally comprises a body16and four deployable fins18a-18dfor controlling the flight of the projectile. Prior to deployment, fins18a-18dare folded up in stowed position30, a position shown inFIGS. 1-4 and 9a. Anchored to hinge pins at their base, fins18pivot or rotate about axis35to deployed position32, shown inFIGS. 9eand 9f, following missile launch. Torsional springs serve to urge fins18toward deployed position32. Fins18are retained in stowed position30, against the biasing force of the torsional springs urging them to pivot outward, by latching mechanism15

Each of fins18a-18dis rotatably connected at its base to actuators20a-20d, respectively. Actuators20thereby control rotation of fins18about axis33. Actuators20are 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 fins18as desired to steer projectile17towards a target or to release fins18.

As shown, surfaces52,53and54define shaft retention groove41, which is configured to engage retaining ring28fixed to body19such that lock-pin19is permitted to rotate about axis34but is secured from movement longitudinally or axially along axis34. Thus, lock-pin19is rotatably connected to body19such that end portion24can rotate at least partially about axis34.

As shown, a specially configured pin recess22is formed in body16to receive shaft25. Recess22provides a housing to support rotating lock-pin19and anti-rotate torsion spring23. The inner portion of recess22is generally cylindrical and includes retaining ring28near the base of the cylindrical recess so as to receive shaft25in rotational engagement. Recess22is also includes a slot for receiving spring end42.

Spring end42bears against the walls of recess22. The end of spring23on the other side of the coil from end42is captured in a hole in surface56of end portion24of pin-lock19. Thus, torsional spring23is installed on shaft25of lock-pin19such that it is anti-rotated in recess22and preloads lock-pin19against pocket21in the top end of fin18. Lock-pin19is biased toward locked position36and, absent a countering force, will move to locked position36. One side of surface57of end portion24bears against one side of pocket21in fin18such that fin18is loaded against stationary dowel pin29as a result of the torsional load of spring23on lock pin19. With shaft25axially secured to body16by retaining ring28in shaft retention groove41, part of surface56of end portion24of pin19bears against the outside surface of fin18to hold it in stowed position30.

As shown inFIGS. 9a-9f, lock-pin19is configured to rotate about axis34from locked position36, in which tip43of end portion24engages pocket21in fin18, to release position38, in which tip43of end portion24of lock-pin19does not extend into pocket21of fin18. Thus, in a released position, lock-pin19does not restrain fin18from rotating about axis35from stowed position30to deployed position32.

As shown inFIGS. 9a-9f, to release fin18, actuator20is programmed to rotate about fin axis33in counter-clockwise direction39relative to body19a set distance. The rotational force of actuator20is enough to overcome the countering spring force of spring23in the clockwise direction about pin axis34. Thus, the edge of pocket21bears against the side surface57of end portion24of pin19, causing pin19to rotate in clockwise direction40about pin axis34. As this rotation continues, as shown inFIG. 9c, tip43of end portion24of pin19clears pocket21in fin18, thereby releasing fin18such that fin18can rotate about axis35from stowed position30, shown inFIGS. 9a-9c, to deployed position32, shown inFIGS. 9eand 9f. This deployment from stowed position30to deployed position32is shown inFIG. 9d. Once in deployed position32, as shown inFIGS. 9eand 9f, fin18can be rotated back clockwise and actuated to the desired position about fin axis33. Thus, actuator20controls both the operational rotation of fins18as well as the rotation of lock-pin19from locked position36to release position38to release fin18for deployment. No separate motor, actuator, solenoid or pyrotechnic release mechanism is required. Thus, mechanism15employs passive mechanical retention, coupled with control surface actuator motion, to stow and then release fin18.

Release mechanism15is also resectable. Once fin18moves out of stowed position30, spring23returns lock-pin19to the null or stowed position30, which prevents rattling in assembly. As shown, lock-pin19includes outer slot26, which is configured to receive the end of a flat-headed screwdriver, for example. By manually rotating lock-pin19using a torquing device, lock-pin19may be moved to release position38and out of the way of fin18such that fin18can be placed back in stowed position30, and then re-locked in the stowed position by releasing lock-pin19and allowing tip43of end portion24of lock-pin19to engage pocket21in fin18. For resetting purposes, actuator20is 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 axis33. Actuator20may then be commanded to the given output position to release fin18from release mechanism15.

As shown, release mechanism15as described above may be used to retain and release each of the fins18a-18don projectile17from a stowed position to a deployed position.

Some designs may require more of a retention margin. Lock-pin mechanism15may be sized to keep fin18stowed 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 fin18in place.

First, a torsion spring may be selected that allows for adequate preload force development, and sufficient travel for release of fin18. Depending on the amount of preload desired, and where the anti-rotating features of recess22in 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 actuator20to release fin18. 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 shaft25may also be used to vary the force margin.

Second, the depth of tip43of end portion24of lock-pin19in pocket21of fin18may be varied, as shown inFIGS. 12 and 13. By changing the depth of the engagement of end portion24of lock-pin19in pocket21of fin18, the amount of actuator20rotation required to release fin18can be modified and more or less margin can be added to retention of fin18.

Third, the geometry of end portion24and “cam” surfaces57,58of pin19may be varied together with pocket or slot interface21. Modifications to the interface geometry between lock-pin19and fin18can be performed to fine tune the load properties of retention mechanism15. For example, the applicable ramp angle of outer surface57of end portion24of lock-pin19may be varied, as can the length of the locking section of pin19and the tip design of end portion24of pin19.

Fourth, depending on the type and orientation of the mechanism/spring for deploying fin18about axis35, lock-pin19may 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 fin18. This may be desired if the actuator has limited travel to release fin18.

FIGS. 14, 15 and 16a-16cshown an alternative embodiment in which retention mechanism15is employed on a projectile having switch-blade release style fins. As shown inFIGS. 16a-16c, the pocket in the end of the fin is orientated perpendicular to the orientation of pocket21in flap-style release fins18. As with flap-style release fins18in the embodiment shown inFIGS. 1-13, actuation of switch-blade style fins118about axis133in a counter-clockwise direction causes rotation of pin119in a clockwise direction until tip143of end portion124of pin119clears pocket121in fin118, thereby releasing fin118from its stowed position and allowing it to move into a deployed position.

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.