BACKGROUND OF THE INVENTION
Field of Invention:
This invention relates to fin lock systems for missiles,
in accordance with the preamble of claim 1. Such a system is described in JP 10-253300.
Description of the Related Art:
Typically, the fins of a missile must be locked during
transportation on an aircraft or other launch vehicle. However, at launch time,
they must be quickly unlocked to be ready for missile flight. For example, a missile
carried on an F-16 aircraft has its fins locked prior to launch. When the pilot
is ready to fire the missile, a signal is sent from the cockpit which starts the
missile's battery. When the cockpit has confirmation that the missile is powered,
it signals the missile's fins to unlock and wiggle to verify function. When fin
release and function is confirmed, the cockpit signals the missile launcher to unlock
and launch the missile.
In a combat situation, where time is critical, it is essential
that the fins unlock as quickly as possible. However, the small diameter (typically
5 inches) of many missiles has been an impediment to designing a fin lock system
for quick release.
Prior approaches include a complicated system employing
a gas generator. To effect fin release, this prior system collects gas and distributes
it through a manifold to each fin piston, which compresses to release the fin. This
system has many parts and is slow taking on the order of 70 milliseconds to unlock
the fins. Also, it is difficult to maintain the pressure in the one large reservoir
because of gas leaks. Accidental firings are a problem with this system, and it
cannot be reused because of contamination.
Another prior approach utilizes a shear pin which fractures
to unlock the fins. This system requires a high energy input from an electric motor.
It is also prone to failure and debris contamination. Exploding bolts have also
been used, but these suffer from contamination problems as well.
JP 10-253300 discloses a steering fin for a flying object.
A fixed part of a rear edge of the fin is fixed by a pawl and at the time of launching
the object the pawl is removed from the fixed part of the fin.
JP 04-158198 discloses a steering blade locking device
for a missile. A restricting member is pressed fixedly to the outer periphery of
an airframe by a spring. The restricting member engages with the steering blade
to prevent rotation of the blade. Upon launch of the missile, the spring is collapsed
by generated thrust force or discharge heat and the restricting member is separated
from the airframe.
GB 2 240 954 A discloses a lock means for missile control
fins which comprise a protruding lock pin for engagement in a mating aperture in
a control fin. The fin is moveable by fluid pressure actuating means including a
control piston in a cylinder and a balance piston in a cylinder. The lock means
protrude from the external surface of the missile.
Thus, a need remains in the art for a less complex, more
reliable system which can lock the fins of a small diameter missile yet quickly
unlock them for launch.
SUMMARY OF THE INVENTION
The need in the art is addressed by the present invention
which provides a fin lock device for a missile comprising:
- a mechanism for locking a missile fin by grasping an edge of said fin, and
- a mechanism for retracting said mechanism for locking to release said fin,
characterised in that:
- said mechanism for locking comprises a piston for extending from an airframe
of said missile, said piston having a notch therein for receiving said fin edge,
- said piston being located in a housing which lies within the airframe, and said
mechanism for retracting is for causing said piston to retract into said airframe.
In a specific embodiment, the piston is retracted to release
the fin by burning a pyrotechnic powder in a cavity adjacent to the piston to fill
the cavity with gas and create a pressure differential to force the piston away
from the fin.
BRIEF DESCRIPTION OF THE DRAWINGS
DESCRIPTION OF THE INVENTION
- Fig. 1 is a perspective view of a missile quadrant employing the fin lock system
of the present invention.
- Figs. 2a and 2b depict side and end views, respectively, of the missile quadrant
with the fin lock system of the present invention in the locked position.
- Figs. 3a and 3b depict side and end views, respectively, of the missile quadrant
with the fin lock system of the present invention in the unlocked position.
- Fig. 4 is an end view of the fin lock system of the present invention.
- Fig. 5 is a cutaway end view of the fin lock system of the present invention.
An illustrative embodiment will now be described with reference
to the accompanying drawings to disclose the advantageous teachings of the present
The invention is a single fin locking device for a single
fin release. The piston in the device protrudes from the airframe and holds the
fin securely in place until the device receives a firing pulse and the piston releases
the fin. The design has only one moving part, the piston, and operates reliably
to release the fin much faster than any known device.
Fig. 1 shows a quadrant 10 of a small-diameter missile
(not shown). The missile has plural fins of which only one fin 14 is shown in Fig.
1. Each fin is attached to the airframe 16 of the missile. In accordance with the
present teachings, the fin 14 is secured against movement by an inventive fin lock
device 12. The fin lock device 12 protrudes through the airframe 16 as depicted
in Fig. 1.
Figs. 2a and 2b depict side and end views, respectively,
of the missile quadrant 10 with the fin 14 in a locked position. The piston 18 of
the fin lock device 12 is extended through the airframe 16, holding the outer surface
of the fin 14 in a locked position at its inboard aft end. In this configuration,
the fin 14 is secured for transportation on its launcher.
Figs. 3a and 3b depict side and end views, respectively,
of the missile quadrant 10 with the fin 14 in an unlocked position. The piston 18
is not visible, having been retracted through the airframe 16 to release the fin
14. In this configuration, the missile is ready for fin function check and subsequent
Fig. 4 shows an end view of the fin lock device 12 of the
present invention. The piston 18 is extended in the locked position. On a typical
small-diameter missile having four fins, a device 12 would be disposed to lock each
fin, for a total of four independent fin lock devices. The devices are readily installed,
requiring only a 4 screw mechanical connection (not shown) and a 2-pin electrical
connection (not shown).
Fig. 5 is a cutaway end view of an exemplary embodiment
of the fin lock device 12 of the present invention. In the illustrative embodiment,
the piston 18 is made of steel or other suitable material. The piston 20 has a notch
20 at the upper end thereof adapted to engage the fin 14 of Fig. 1. The piston 18
is shown in Fig. 5 in the fin locked position and sits in a housing 36 made of steel
or other suitable material.
To unlock the fin, a release signal is sent through the
2-pin connector 30 in a conventional manner. The signal causes initiator 32 to ignite
a fast-burning pyrotechnic powder, such as gunpowder, in the initiation chamber
42. As the powder burns, the initiation chamber 42 fills with gas, and the expansion
of the gas forces the piston 18 to move down into deployment chamber 40 due to a
pressure differential. When the piston 18 has moved to the bottom of deployment
chamber 40, it no longer protrudes through the airframe. The fin is thus rapidly
unlocked and ready to function.
A further advantage of the inventive system is that the
device is completely sealed by O-rings 34, which hold the piston down and prevent
any contaminants from exiting the device. The sealed system also has a longer shelf
life as rust and corrosive elements cannot enter during storage. In addition, a
steel shear pin 38 (rated to forty pounds in the preferred embodiment) holds the
piston in the locked position prior to firing, preventing accidental fin release,
but is readily sheared through when the device is actuated.
The present invention thus has many advantages over the
known art. It is more reliable and much less complex, having only one moving part.
Because it employs a smaller chamber that fills more quickly, the device operates
much faster than prior systems. The sealed system prevents contamination and allows