Azimuth damper

Details Azimuth damper Azimuth damper

1984-02-06

1986-02-25

Reger, Duane A.

Brakes

Internal-resistance motion retarder

Using yieldable or fluent solid or semisolid

74574, F16F 930

Patent

active

045723370

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a fluid damper for damping aiming movements, for instance when tracking a target. The damper comprises a substantially disc-shaped cylindrical damper housing in which a drum wheel is supported for rotation so that an inner gap spacing is provided between the drum wheel and the damper housing which gap is filled with a highly viscous damping fluid.
For following a target or other object with high aiming accuracy it is necessary to introduce some sort of damping means for damping the aiming movements. Specifically in military applications some weapon systems require an accurate optical tracking of a target. For example in a portable missile launcher optical tracking of a target is provided for throughout the entire flight of the missile by the operator keeping the line of sight on the target. An accurate tracking is not required, however, only in military applications; also in civilian applications, such as optical sighting devices, television and cinematographic cameras, an accurate tracking is often required.
Waver, overshoot and other undesirable effects of a human operator should be eliminated by the damper. Even a very small deviation of the guidance control signals in response to waver is capable of causing a deviation in the missile trajectory so that the missile passes at the side of the target. Prior dampers which have been used for limiting such undesired deviations have usually been of the fluid damper type. In this case the necessary damping is provided by means of a highly viscous fluid which fills one or more gaps between a rotatable disc and some part of the damper housing. Such a damper generally provides for a linearly increasing damping torque to the angular aiming velocity. This means an increasing resistance to rapid aiming velocities which is usually no problem during the target tracking phase at which only low angular velocities are required. During target acquisition, however, when rapid slewing about the azimuth or elevation axes often is required, the torque of a conventional damper is often too high. It is therefore previously known to provide the damper with disengaging or overriding means to limit the increasing torque required at higher angular velocities specifically slipping couplings such as a maximum torque coupling.
In Swedish Pat. No. 74.13625-0 a fluid damper with a nonlinear damping is described which provides for an optimal and critical damping for low angular velocities but in which the damping torque has been limited for higher annular velocities so that rapid slewing for instance during target acquisition is facilitated. A highly viscous damping fluid as used in said patent gives a substantial damping of high-frequency vibrations such as trembling, jitter or the like caused by the human operator. The viscosity of the damping fluid has been decreased at higher shear rates by means of a specific design of the fluid gap of the damper.
It is evident that a nonlinear damping torque is required in such a way that the damping torque is linearly increasing up to a certain angular velocity, for instance 30 to 40 mrad/s, which corresponds to normal target tracking. For higher velocities, however, the increase of damping torque is limited and a low, constant damping torque is desired for angular velocities above said level. It has been difficult, however, to provide for such an ideal damping characteristic and it is also evident from FIG. 3 of said patent that no constant damping torque is obtained for higher angular velocities corresponding to the target acquisition phase. Especially at low temperatures the damping torque will be too high. This is unsatisfactory especially in portable weapon systems of the light-weight type in which a too high torque very easily brings the weapon out of position during target acquisition.
Accordingly, it is an object of the present invention to provide a fluid damper with high aiming accuracy for low aiming velocities i.e. velocities up to approximately 30 mrad/s, but in which the linear increase of the damping

REFERENCES:
patent: 1001065 (1911-08-01), Mursch
patent: 2514137 (1950-07-01), O'Connor
patent: 2614896 (1952-10-01), Pierce
patent: 2775317 (1956-12-01), Sinesteara
patent: 3517946 (1970-06-01), Rumsey et al.
patent: 3907079 (1975-09-01), Chapman

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