1. Field of the Invention
This invention relates to fin control actuators for missiles carried on aircraft, and more particularly to a system for locking the fin shaft against aerodynamic loads and preventing the transmission of these loads through the drive train.
2. Description of the Prior Art
Missiles carried on aircraft have various control devices to control the flight and operation of the missile after launch. In certain missiles, the control of the missile is accomplished through control and position of the fins on the missile. The fin shaft is connected to an output shaft that is rotated by connection to a control motor. The output shaft is connected to the control motor through a drive train.
During flight before launch, the fin shaft is subjected to high aerodynamics loading. This loading causes the fin shaft to tend to move in the direction of the load and causes the output shaft to tend to rotate. The motor which is connected to the output shaft is provided with a brake that stops rotation of the output shaft. The aerodynamic load applied to the fins is, however, still transmitted to the motor brake through the drive train that connects the motor to the output shaft, causing flutter and fatigue failures.
To prevent the transmission of this aerodynamic loading through the drive train, a "one shot" pyrotechnical device is sometimes provided to lock the fin shaft. However, this device cannot be re-used and is subject to possible failure. In addition, the use of pyrotechnics in the control system of weapons devices, such as missiles, is always subject certain inherent dangers and presents other disadvantages. While a mechanical locking device would be desirable, none are known.