Vehicular mounted tow missile system

A base of a TOW missile system is mounted on a rotatable turret of a vehicle and is also rotatably mounted relative to the rotation of the turret so that the orientation of the base about its own rotational axis remains stationary. The positioning of the TOW base on the turret allows the turret to rotate generally about an axis which can be aligned with the person operating the sight. Thus the diameter of the opening in the vehicle is reduced. One embodiment uses a planetary gear system for holding the orientation of the base. A second embodiment uses a flexible link.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention pertains to sighting devices which are secured to a turret 
or other heavy piece of equipment which rotates in response to changes in 
direction of the sight. More particularly, the invention pertains to a 
vehicular mounted TOW missile system which holds the base of the sighting 
unit relatively stationary about its axis of rotation to simulate the 
operation of a ground-mounted TOW missile system. 
2. Description of the Prior Art 
It is well established that the TOW (tube launched optically tracked, wire 
command, link guided) missile system of the type described in United 
States Army Technical Manual TM 9-1425-470-12, January, 1974, is a proven 
and perhaps unequalled system for tracking accuracy. The system uses a 
manually operated, viscous damped, position control, weapon pointing 
system. The system is generally mounted on a tripod which is stationary on 
the ground or on a vehicle with a post that is fixed to the vehicle and 
with the vehicle stationary on the ground. The operator then in sighting 
walks around the tripod or post with the missile launch tube being 
connected to the sight and thus movable directly therewith. The sighting 
mechanism has a day sight which is spaced vertically from a night sight 
and is also provided with an infrared sensing sight aligned with the day 
sight. Basically the operation of the missile system requires that the 
operator locate the cross hairs of one of the optical sights on the moving 
target and fires the missile. The operator then maintains the cross hairs 
on the target by moving the sight either elevationally or rotationally in 
traverse with the infrared sensing sight locating the missile and sending 
control signals to the missile to direct the missile from its initially 
fired direction to a corrected direction corresponding to the direction 
indicated by the cross hairs of the optical sight. 
It is desirable to mount a missile weapon system on a vehicle in a manner 
in which the operator is completely protected by heavy armor plate. That 
is, it is desirable to mount such a TOW missile system in a personnel 
carrier or a tank and preferably to mount it within the conventional 
rotatable turret in the vehicle. Most modern vehicular-mounted gun 
controls, such as presently in tanks, however are "rate" control systems 
as compared to the TOW weapon "position" control system. In a rate system 
the operator displaces his controls by an amount required to generate a 
turret turning velocity equivalent to the apparent velocity of the target. 
Thus, when tracking a constant speed target, the controls would be held 
displaced but stationary. As the target accelerated the control would also 
be moved to achieve a more rapid turning rate of the turret and if the 
target decelerated while traveling still in the same direction, the 
control would have to be retracted back by movement in a direction 
opposite to the direction of movement of the target. Unfortunately, rate 
control systems have been shown to be less accurate for the TOW type 
missile launcher then position control systems for the TOW type; missile 
launcher. Additionally, it requires extensive training to convert an 
experienced TOW operator from a position control operator to a rate 
control operator. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a position control system for a 
vehicle turret mounted TOW type missile system in which the control 
closely simulates the position control of a ground-mounted TOW system. 
It is another object of this invention to provide a vehicular-mounted 
position control system whose orientation remains generally stationary 
with respect to the ground. 
It is still another object of this invention to provide a vehicular-mounted 
TOW missile system in which the hull opening is of a minimum size. 
Basically, these objects are obtained by modifying the standard TOW missile 
system components and securing them to the turret in a vehicle but 
providing a counter rotation to parts of the components so that with 
rotational movement of the turret, the base component of the control will 
remain generally stationary about its own rotational axis relative to a 
point on the hull of the vehicle. In the preferred embodiment of the 
invention, the axis of rotation of the base component of the control is 
also offset laterally from the rotational axis of the turret so that the 
operator can be located generally along the axis of rotation of the turret 
thus reducing the diameter of the hull opening and thus the size of the 
turret to a minimum diameter necessary only to allow for the rotational 
movement of the sighting system about the rotational axis of the turret. 
One embodiment for providing this simulated ground-mounted position 
control with an offset sighting axis is provided with a planetary drive 
transmission which provides a counter rotation to the base of the control 
component as the turret upon which the base is mounted rotates in the 
other direction. Various other types of spur gear drive transmissions to 
achieve this function are also possible. Still another embodiment is to 
use a flexible, universal type linkage which prevents rotation of the base 
about its own axis while the base is being moved about the rotational axis 
of the turret during movement of the turret. 
As is readily apparent, the advantages of these systems are that the 
accuracy obtained is essentially identical to that of the ground-mounted 
TOW missile system. Secondly, the operation is identical to the 
ground-mounted TOW missile system so that training requirements are 
minimized. Still further, the operator can be positioned centrally in the 
turret with the diameter of the turret being small enough to merely allow 
rotation of the sight around the operator rather than rotation of the 
operator around the sight.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As best shown in FIGS. 1 and 7, the vehicle 10 is provided with a hull 11 
having a turret opening 12. In the preferred embodiment of the invention 
the hull is also provided with a vertically variable platform 13 for 
supporting the gunner or operator 14. The platform can be elevated by any 
suitable means and is designed to provide the operator, at eye level, with 
one of the two vertically spaced sights to be described. The hull is 
provided with a conventional turret 16, conventional turret servo 
controls, and an M 27 turret bearing ring such as for use in a M 114 scout 
vehicle. As is well understood, this turret is heavily armor plated and is 
rotatable around 360.degree. of rotation so that sighting and use of the 
weapon may travel through a complete 360.degree. traverse without moving 
the vehicle. 
The TOW missile system, as mentioned earlier, is provided with a traversing 
unit 18 which is mounted for pivotal movement about a vertical axis SA, 
called "traverse" movement, on a base 19. Generally the TOW traverse unit 
is able to be broken down and is mounted onto the base by a conventional 
band clamp 20. The traverse unit is provided with a bearing 22 for 
allowing the traverse pivotal movement which bearing is provided with a 
viscous dampening so that it requires up to forty pounds force to rotate 
the traversing unit depending on the velocity. It is this viscous 
dampening which enables the operator to track a target smoothly and 
accurately. The traverse unit is provided with a sighting mechanism 24 
which, as well known, includes a night sight 25 (FIG. 3), a lower day 
sight 26 and an infrared sensing sight or tracker 27. The sighting 
mechanism 24 is removable from the traversing unit as a separate unit and 
is pivotally mounted about a horizontal axis EA for elevation movement 
about an axis 28. The axis is coincident with an elevational axis EA (FIG. 
5) which is the pivotal axis for a bearing 29 that carries a rotor 30 to 
which the two missile tubes 32 are rigidly attached. Thus as the sights 
are elevationally rotated to maintain a fix on the target, the missile 
tubes through the servo control mechanism will also be rotated and the 
axes of rotation of the sight and the missile tubes will be identical. 
Since the sight and tracker are mounted on the traverse unit they 
therefore will follow exactly operator input to the controls. The launch 
tubes than are slaved by a conventional low performance (2 mills accuracy) 
servo system. 
Because of coincidence between the sight and rotor elevational axes, it can 
be seen that in a modified form of the invention (not shown), the sight 
and tracker can, rather than be mounted on the traversing unit, be mounted 
rigidly directly to the rotor. With this embodiment, the sight and tracker 
and the missile launch tubes will always be in exact alignment with each 
other independent of servo controls whereas in the former embodiment, the 
alignment between the elevation of the sights and elevation of the missile 
launch tubes in dependent upon the servo control correlation. In other 
words, in the modified embodiment, the sight and tracker being mounted on 
launcher rotor, therefore their relationship is fixed, however, now the 
sight and tracker are also positioned by the servo system, which must be 
of high performance (2/10 mill accuracy). 
The turret, as is well known, is provided with a traverse drive assembly 
having a hydraulic motor 34 (FIG. 6) which drives, through a reduction 
gear 36, a pinion 37. The pinion is in meshing engagement with an internal 
ring gear 38 fixed to the hull 11. Thus, rotation of the reversible, 
hydraulic motor 34 drives the turret 16 on the ring gear about a turret 
axis TA. Elevational movement of the rotor and thus the launch tubes 32 is 
through a hydraulic cylinder 40 (FIG. 5) in a well known manner. 
The preferred embodiment of the unique counter rotation mechanism for the 
base of the TOW traverse unit is best illustrated in FIGS. 2, 7 and 8A. 
The turret is provided with an annular adapter plate 42 which is bolted to 
the turret by bolts 43. The adapter plate is provided with a bearing 44 
with the inner race attached to the base 19 of the traversing unit 18. A 
set of three equidistantly spaced, split anti-backlash planet gears 46 are 
rotationally secured to the base 19 by spindles 47. These planet gears 
mesh with a ring gear 48 formed on the plate 42. The planet gears also 
mesh with a split, anti-backlash sun gear 49 which also meshes with the 
ring gear 38 on the hull. The sun gear is provided with anti-backlash 
springs 49a in a conventional manner to reduce backlash throughout the 
planetary system. The plate 42 is also provided with a bottom cover 42a 
which supports the input gears through suitable bearings. The plate 42 is 
provided with a central opening 42b through which the power cables and the 
like are carried. 
Referring to FIGS. 8A-8C it can be seen that in an initial starting 
position (FIG. 8A), the base 19 is pointed in the direction of the dotted 
arrow 1, the sights are pointed in the direction of the solid arrow 2. A 
circle 3 represents a point on the turret and is aligned with the arrows 
and a square 4 represents a point on the hull also aligned with the 
arrows. 
In FIG. 8B the sight has been moved so that arrow 2 is now turned slightly 
clockwise. The sight is moved into this position by the manual rotation of 
the upper traverse unit by the operator. The servo control then moves the 
turret to maintain its alignment with the arrow 2 and this is indicated by 
the position of the circle 3. The square 4 on the hull, of course, remains 
stationary. As the turret has moved to the position indicated by the 
circle 3, the axis of rotation SA of the base 19 has shifted in a 
clockwise direction but the base 19 has been counter rotated in the 
opposite direction so that the arrow 1 remains pointing in the same 
direction as it had in FIG. 8A. Thus, although it has shifted somewhat 
from its original starting position, the base has not rotated relative to 
a fixed point on the hull, but rather has retained its same directional 
orientation. 
An extreme position is shown in FIG. 8C where the arrow 2 on the sights has 
been shown as being manually rotated 180.degree.. The servo control, of 
course, also brings the turret to 180.degree. of rotation as shown by the 
circle 3 but the square on the hull 4 remains stationary as before. 
Likewise, while the base 19 has now been shifted about axis TA 180.degree. 
from its original position shown in FIG. 8A, the base still is pointing 
(arrow 1) in exactly the same direction relative to its initial direction 
and thus has remained rotationally stationary relative to a pivot point 
about the turret axis. 
Counter rotation of the base 19 can be provided by a number of additional 
techniques, such as using spur gearing rather than planetary gearing, a 
universal joint shaft, a flexible non-rotatable shaft connected to the 
hull floor at the center line of turret rotation, or with a servo system. 
FIG. 9 illustrates one of these embodiments, that of using a universal 
joint shaft. In this embodiment all of the components remain the same with 
the exception that the operator is provided with a seat 60 which is 
mounted on a bearing 62 concentric with the axis of rotation TA of the 
turret. A first universal connection 64 is coupled in a fixed relationship 
with the hull and is swivelly connected to a universal link 66. The 
universal link 66 is then coupled by universal coupling 68 to the base 19 
of the traverse unit which again is mounted on an adapter plate 42 that is 
secured to the turret 16. In this embodiment also as the turret is rotated 
the initial direction of the base remains stationary as illustrated in 
FIGS. 8A-8C. 
As an additional embodiment, a servo system arrangement would simply 
replace the mechanical gear drives between the base 19 and the hull and be 
controlled by relative rotation between the hull and the turret or, if the 
turret is stabilized for firing on the move, the servo system can be 
controlled by the stabilization system gyros which will maintain the 
control base 19 stationary in azimuth in inertial space. 
The servo controls described above are all well known in the art. One 
operational servo control system for the mounting system of this invention 
is shown in FIG. 10. The traverse and elevational movements of the sights 
are sensed and position azimuth or elevation slave valves 70 and 72 which 
in turn power the hydraulic motor 34 to rotate the turret with the 
feedback loop 34a establishing the position of the turret or the slave 
valve 72 controls operation of the cylinder 40 which in turn signals its 
position by a feedback loop 40a. 
While the functional diagram illustrates an hydraulic servo system, it can 
also be accomplished by conventional electrical servo controls. 
While the preferred embodiments of this invention have been illustrated and 
described it should be understood that variations will be apparent to one 
skilled in the art without departing from the principles herein. 
Accordingly, the invention is not to be limited to the specific embodiment 
illustrated in the drawing. In particular it should be understood that the 
sighting and tracking concepts also are applicable to other vehicular 
mounted weapon systems controlled from within a rotatable armored turret.