A self-deploying airfoil mounted on the body of a device such as an artillery shell projectile and folded down and forward with respect to the relative airstream. The airfoil is attached to a yoke by a pivot pin. The yoke shaft is pivoted in the body in a manner to allow it to pivot 90 degrees tangentially with respect to the body. The airfoil assembly may be retained by a cover which is removable to deploy the airfoil. The shaft of the yoke is mounted at a small angle to the axis of the body so that the airfoil has an angle of attack relative to the airstream when it pivots tangentially outward. When the cover is removed, a spring starts the airfoil rotating out into the airstream where drag drives it to the 90 degree position. The yoke is locked in the 90 degree position by a yoke lock pin. The airfoil, which is rigidly attached by pins to the pivot pin, cannot begin to rotate about the pivot pin until the yoke has rotated 90 degrees. A flat on the head of the pivot pin rides on the surface of the body preventing rotation in a vertical direction until the 90 degrees of tangential rotation has been completed. Aerodynamic lift acting on the airfoil then rotates it upward to a position about normal to the body axis where it is locked by an airfoil lock pin.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates in general to deployable airfoil structures and 
particularly pertains to a self-deploying airfoil structure suitable for 
use on an artillery projectile or tube launched missile. 
2. Prior Art 
Improved ballistic performance and maneuverability is achieved through the 
use of airfoils on a projectile or missile and the like. However, in many 
devices employing aerodynamic forces for stability, lift or drag, it is 
necessary that airfoils such as wings, fins and the like be stowed within 
the body before deployment. The conventional method for doing so is to 
pivot an airfoil at one end and deploy it radially outward. This requires 
that a long axial slot must be cut in the skin of the projectile and the 
airfoil permitted to extend its full width into the body of the device. 
Such slots reduce the structural integrity of the skin and may seriously 
interfere with packaging of components. The present invention provides an 
airfoil which does not project into the skin its full width, thereby 
enhancing packaging efficiency and structural integrity. The present 
invention is instead designed to be self deployed from a stowed position 
in which the airfoil is folded down and forward with respect to the 
relative airstream and in a position which is substantially contiguous 
with the radial skin of the projectile. 
The most relevant prior art known to the applicant is U.S. Pat. No. 
4,664,339 to Crossfield issued May 12, 1987 and relating to a missle 
appendage deployment mechanism in which a radially contiguous stowed 
airfoil such as a wing or fin, when deployed rotates upwardly from a 
stowed into a feathered vertical position into the airstream of the missle 
or projectile. While this upward rotation from the stowed position is 
efficient from the standpoint of motion, it unfortunately requires that 
the attached end of the airfoil have a very complex shape in order to be 
compatible with a clevis with which is cooperates in order to achieve 
simultaneous rotation in two planes. The present invention overcomes the 
need for this complex prior art structure in the airfoil and cooperating 
elements by utilizing a novel combination of sequential motions the first 
of which is a tangential rotation in a plane tangential to the radial wall 
of the projectile and the second of which is a vertical rotation in a 
plane perpendicular to the axis of the projectile. While both the present 
invention and the Crossfield device exploit inherent aerodynamic forces to 
complete deployment of the airfoil, the unique sequential motion of the 
present invention permits the use of more conventional and thus less 
expensive structures both in the airfoil and in the attendant pivoting 
member or yoke thereby reducing the cost and complexity of the invention 
as compared to the prior art. 
Other relevant prior art includes the following: 
U.S. Pat. No. 4,323,208 to Ball is directed to a folding fin assembly for 
some type of flight vehicle which may be a guided/unguided missile. This 
disclosure relates to a two axis rotation and the fin is rotated about the 
axis Z--Z. The structure is mounted on a turntable which is rotatable with 
reference to the base about the axis W--W. 
U.S. Pat. No. 3,098,445 to Jackson is directed to an aerodynamically 
supported rocket system. It uses a double rotation. When the blades are 
pivoted about the pivotal mounting of sleeves from the folded state of 
FIG. 1 to the radially extended state of FIG. 2, the cam arms engage the 
bottoms of the cam slots to rotate the blades to predetermined angular 
positions. Alternatively as the blades are pivoted to the folded state of 
FIG. 1, the cam arms engage the tops of the cam slots to rotate the blades 
to the fin position. 
U.S. Pat. No. 4,667,899 to Wedertz is directed to a double swing wing 
self-erecting missible wing structure. This reference provides for a 
recess in the air frame in which the wing is stored in a retracted 
position. Each wing has a corresponding recess and there is a double 
rotation. 
U.S. Pat. No. 3,063,375 to Hawley et al is directed to still another type 
of folding wing or folding fin. There is disclosed a rotation about an 
axis normal to the longitudinal axis of the missle and then a rotation 
about this axis to put it into the position shown in FIG. 6 for flight. 
SUMMARY OF THE INVENTION 
The present invention overcomes the aforementioned disadvantages of the 
prior art by providing a self-deploying airfoil mounted on the body of a 
device such as an artillery shell projectile and folded down and forward 
with respect to the relative airstream. The airfoil is attached to a yoke 
by a pivot pin. The yoke shaft is pivoted in the body in a manner to allow 
it to pivot 90 degrees tangentially with respect to the body. The airfoil 
assembly may be retained by a cover which is removable to deploy the 
airfoil. The shaft of the yoke is mounted at a small angle to the axis of 
the body so that the airfoil has an angle of attack relative to the 
airstream when it pivots tangentially outward. When the cover is removed, 
a spring starts the airfoil rotation out into the airstream where drag 
drives it to the 90 degree position. The yoke is locked in the 90 degree 
position by a yoke lock pin. The airfoil, which is rigidly attached by 
pins to the pivot pin, cannot begin to rotate about the pivot pin until 
the yoke has rotated 90 degrees. A flat on the head of the pivot pin rides 
on the surface of the body preventing rotation in a vertical direction 
until the 90 degrees of tangential rotation has been completed. 
Aerodynamic lift acting on the airfoil then rotates it upward to a 
position about normal to the body axis where it is locked by an airfoil 
lock pin. Because of the unique combination of sequential, tangential and 
vertical rotation, the airfoil structure of the present invention may be 
relatively simple and easy to fabricate at relatively low cost. 
Additionally, the yoke and yoke pin of the present invention may be of 
relatively conventional configuration thereby obviating any requirement 
for special tooling or unique shapes that require costly manufacturing 
processes. 
OBJECTS OF THE INVENTION 
It is therefore principal object of the present invention to provide a 
self-deployable airfoil for use on a projectile such as an artillery shell 
for aerodynamic stabilization thereof, the airfoil being deployed by the 
pressure of the airstream due to the motion of the projectile, the airfoil 
comprising relatively conventional geometric shapes for ease of production 
and low cost. 
It is an additional object of the present invention to provide a 
self-deployable airfoil of the type used in projectiles such as artillery 
shells for stabilizing such projectiles during flight, the airfoil being 
deployable in response to the pressure of the airstream in two discrete 
sequential motions including a first such motion which constitutes a 
tangential rotation in the plane of a tangent to the projectile and a 
second such motion which constitutes a vertical rotation in a plane 
perpendicular to the axis of the projectile. 
It is still an additional object of the present invention to provide an 
airstream instigated deployable airfoil for stabilizing the aerodynamic 
characteristics of a projectile such as an artillery shell wherein the 
airfoil and the structure used for rotating the airfoil into proper 
position during deployment are of relatively conventional shape and 
geometry for minimizing the cost and manufacturing complexity thereof and 
wherein airfoil deployment is accomplished in two discrete steps, the 
first being a tangential rotation of the airfoil in a plane tangential to 
the projectile and the second being a vertical rotation of the airfoil in 
a plane perpendicular to the axis of the projectile.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring first to FIGS. 1 and 2 it will be seen that a projectile 10 would 
typically have a plurality of airfoil assemblies 12 of the present 
invention distributed radially around its exterior skin in the manner 
shown in FIG. 1. Each such assembly is provided, at least initially, with 
an outer cover 22 to protect the assemblies 12 and to provide a smooth, 
continuous surface in the projectile 10 such as to permit the firing of 
the projectile from a gun tube. As seen best in FIG. 2 beneath the outer 
cover 22 there is provided a recess 13 in which there is positioned an 
airfoil 14 lying in its stowed position initially parallel to the 
projectile 10. Airfoil 14 is free at its forward end and is connected at 
its aft end to a pivot pin 16 which forms part of a rotatable yoke 18 and 
has at one end thereof a head 19. As seen further in FIG. 2, the yoke 18 
is of a circular configuration and is adapted to be rotatable in a 
clockwise direction as seen in FIG. 2 whereby airfoil 14 may rotate 90 
degrees along a plane tangential to the projectile 10. A flat area 15 is 
provided to permit the airfoil to rotate in this manner. The airfoil 14 is 
secured to pivot pin 16 by a pair of rivets 21. 
A leaf spring 20 is provided along the top edge of airfoil 14 as seen in 
FIG. 2 in order to initiate the 90 degree tangential rotation of the 
airfoil along the flat 15. It will be understood that the force necessary 
to fully rotate the airfoil 14 through 90 degrees of tangential rotation 
along flat 15, is provided by the pressure of the airstream into which the 
airfoil is positioned initially by the spring 20. After the airfoil 14 has 
rotated through 90 degrees along plane 15, the same airstream pressure 
which produced that complete rotation then forces the airfoil into a 
vertical mode of rotation whereby pivot pin 16 rotates along its axis 
until the airfoil is fully deployed and locked into that position in the 
manner to be described hereinafter. More specifically, referring now to 
FIG. 3 it will be seen that pivot pin 16 is provided with a well 34. It 
will also be seen in FIG. 3 that along the axis of rotatable yoke 18, 
there is provided a lock pin 30 which rests on a compressed spring 32 
within a cylindrical jacket 33. It will be understood that when the 
airfoil 4 is rotated into its fully deployed position wherein it has 
completed the vertical rotation, pivot pin 16 is rotated 90 degrees until 
well 34 is aligned with lock pin 30 which enters the well and secures the 
airfoil in that position. 
It will also be seen in FIGS. 2, 3 and 4 that pivot pin 16 is provided with 
a head 19 which has a flattened edge 17. Flat surface 17 normally rests in 
close proximity to the underlying surface 35 of projectile 10 which 
prevents the head and therefore the pivot pin from rotating until the head 
is aligned with a slot 24 which is seen best in FIGS. 2 and 4 but it will 
be understood that such alignment does not occur until the yoke 18 has 
been rotated 90 degrees by rotation of the airfoil through its 90 degree 
tangential rotation into the configuration shown in FIGS. 5 and 6. 
As seen in FIG. 2 and FIG. 4, the bottom surface of yoke 18 is provided 
with a recess 25 while a portion of the adjacent structure of the 
projectile 10 offset from the center of the yoke is provided with a well 
27 in which there is positioned a lock pin 26 resting on a compressed 
spring 28. Lock pin 26 is designed to rest against the underlying surface 
of yoke 18 compressing spring 28 until it is aligned with well 27 at which 
point the spring forces the lock pin into the well thereby locking the 
yoke in its rotated configuration shown in FIG. 5 and 6. Thus after the 
airfoil 14 has rotated tangentially in a clockwise direction (as seen in 
FIG. 2) a full 90 degrees, the yoke 18 is locked by the lock pin 26 and 
the flat surface 17 of head 19 of the pivot pin 16 is aligned with the 
slots 24 permitting a pivot pin 16 to rotate. The airfoil 14 can then 
rotate through its vertical motion into its fully deployed configuration 
as shown in FIG. 7. As seen in FIGS. 4 and 5, the yoke axis is angled 
slightly relative to the normal to the projectile axis to further 
facilitate deployment. 
It will now be understood that what has been disclosed herein comprises a 
self-deploying airfoil mounted on the body of a device such as an 
artillery projectile and initially folded down and forward with respect to 
the relative airstream. The airfoil is attached to a yoke by a pivot pin. 
The yoke shaft is pivoted in the body in a manner to allow it to pivot 90 
degrees tangentially. The airfoil assembly is retained by a cover which is 
removed to deploy the airfoil. The shaft of the yoke is mounted at a small 
angle to the normal to the axis of the body so that the airfoil has an 
angle of attack relative to the airstream when it pivots tangentially 
outward. 
When the cover is removed, a spring starts the airfoil with a yoke rotating 
out into the airstream where drag drives it to the 90 degree position 
until the yoke is secured by a yoke lock pin. The airfoil, which is 
rigidly attached by pins to a pivot pin, cannot begin to rotate about the 
pivot pin until the yoke has rotated 90 degrees. A flat on the head of the 
pivot pin rides on the surface of the body preventing rotation until 90 
degrees of rotation of the yoke has been completed. Such rotation uncovers 
a slot in the body, releasing the head of the pivot pin. Aerodynamic lift 
acting on the airfoil then rotates it upward to a position substantially 
normal to the body axis where it is locked by an airfoil lock pin. 
The airfoil uses aerodynamic forces to complete deployment requiring only a 
small leaf spring to begin the tangential rotation of the airfoil. The air 
drag on the airfoil completes the tangential rotation. Because the axis of 
the yoke is tilted a few degrees backward from normal, the airfoil has an 
angle of attack relative to the airstream. This creates an aerodynamic 
lift on the airfoil in a direction to rotate the airfoil 90 degrees upward 
to a fully deployed position. The aerodynamic lift falls to zero in the 
fully deployed position of the airfoil. Unlike the prior art most relevant 
to the present invention, the airfoil herein disclosed exhibits two 
discrete sequential rotational motions the first of which is tangential to 
the projectile skin and the second of which is in a plane perpendicular to 
the axis of the projectile. Such simple sequential steps of rotation 
permit the airfoil and attendant yoke structure to be of a relatively 
simple configurations which are less complex and thus less costly to 
manufacture. 
Those having skill in the art to which the present invention pertains will 
now, as a result of the applicant's teaching herein perceive various 
modifications and additions which may be made to the invention. By way of 
example, shapes other than the particular shape and configuration of the 
airfoil and yoke herein disclosed may be used to produce the desired 
combination of tangential and vertical rotation relative to a projectile 
to produce the deployed configuration of an airfoil of relatively simple 
and producible structure. Accordingly, all such modifications and 
additions are deemed to be within the scope of the invention which is to 
be limited only by the claims appended hereto.