Aeronautics and astronautics – Missile stabilization or trajectory control – Externally mounted stabilizing appendage
Reexamination Certificate
2000-03-02
2001-11-13
Carone, Michael J. (Department: 3641)
Aeronautics and astronautics
Missile stabilization or trajectory control
Externally mounted stabilizing appendage
C244S003240, C244S003290
Reexamination Certificate
active
06315240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved tail fin assembly and method of attachment as employed in a high performance tactical missile assembly
2. Description of the Related Art
High performance tactical missiles employ a plurality of tail fins to control performance of the missile during flight to the target. Known missile assemblies mount each tail fin on a fin platform which is itself attached to the missile by special screws mounted on opposite sides of platform. In order to initiate movement of the tail fins, each platform is attached to a control shaft that mates to the bottom surface of the tail fin assembly. As the control shaft is made to rotate, the attached tail fin also rotates in a pre-determined direction, thereby controlling movement of the tactical missile assembly. A primary drawback to such an attachment assembly is the need for special tools to attach the fin platform to the control shaft. Such tools must be maintained in the inventory of all stations that could possibly have a need to replace a damaged tail fin.
To assure that the tail fin can withstand the forces incurred during high performance flight, known missile assemblies such as the AMRAAM missile employ a tail fin mounted on a fin platform and formed of a complex internal honeycomb/spar design with brazed facesheets: a design that has proven expensive to manufacture. Such a design is also missile specific, preventing the same tail fin construction design from being adapted for a variety of tactical missiles.
It has also been found that maintaining the required tolerances between conventional tail fin assemblies and their missile attachment members can be difficult at best. If the fastening screws attaching the tail fins to the missile are improperly torqued, the tail fin may become misaligned, damaging the aerodynamic integrity of tail fin assembly, which may lead to failure of the missile assembly during flight.
It is clear that there exists a need in the art for an improved tail fin assembly and method of attachment to the missile frame. Such an assembly should be able to be assembled within proper tolerances without the need for any special tools. Preferably, the tail fins should be constructed from a simple, homogenous design which can be manufactured at the lowest possible costs.
SUMMARY OF THE INVENTION
The need in the art is addressed by the unique, controllable fin assembly as well as the unique method of attaching the controllable fin to a control shaft on the missile assembly. The present invention provides a controllable fin, preferably of homogenous design, requiring no special attachment tools and yet capable of being easily assembled within required tolerances.
The controllable fin assembly of the present invention is adaptable for use in a high performance missile capable of unprecedented maneuverability. The fin is of aerodynamic configuration and includes a pair of outer side walls extending between a relatively thin outer edge and a widened inner fin platform. The fin platform has at least one cavity having a mouth and a pair of inclined side walls extending toward one another in a direction away from the mouth. The output control shaft has a pair of inclined side walls extending parallel to the walls of the cavity, such that the side portions make surface contact as the fin cavity is lowered over the output shaft.
The mating surfaces of the fin cavity and control shaft are selectively tightened into firm attachment with each other by fasteners extending through the fin and into control shaft end portion. The inner wall of the fin cavity and the outer walls of the control shaft end portion are inclined relative to the rotational axis of the control shaft. This configuration results in the walls of the cavity being pressed into flat contact with the outer surfaces of the control shaft along the entire surface. In effect, as the tail fin is increasingly forced onto the control shaft by torquing of the fasteners, a high degree of press fit is achieved between the confronting surfaces, while maintaining acceptable static margins of safety against material failure. The tolerances are such that the possible conditions of contact between the fin cavity and output shaft range from flat contact across the entire surface, to predominant contact at the entrance of the cavity in the fin. These tolerances are designed to avoid the condition where contact occurs solely at the deepest part of the fin cavity. This would result in an undesirable instability in the mounting configuration whereby the fin would be allowed to rock back and forth creating an insecure attachment and a danger for material fatigue in the attachment screws. Because the fin is pre-loaded, there is minimum clearance between the fin and the outer surface of the missile, producing a clean aerodynamic profile.
REFERENCES:
patent: 3093075 (1963-06-01), Garrett et al.
patent: 3117520 (1964-01-01), Kerr et al.
patent: 3228335 (1966-01-01), Thompson
patent: 3276377 (1966-10-01), Bell
patent: 3360216 (1967-12-01), Schwesig
patent: 3648953 (1972-03-01), Polk, Jr.
patent: 3650496 (1972-03-01), Svensson
patent: 4693435 (1987-09-01), Percival et al.
patent: 1-1990664 (1965-08-01), None
Brogmus Eric
Rasmussen Perry
Stubbs Scott
Benman William J.
Carone Michael J.
Lenzen, Jr. Glenn H.
Raytheon Company
Semunegus Lulit
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