Projectile Arming Device Friction Elimination
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Solution Overview
Problem
Conventional micro-machined safety and arming devices for pyrotechnic chains in projectiles face challenges due to their complex structure and size limitations, particularly in medium-caliber ammunition, where the centrifugal flyweight generates friction that disturbs the movement and delays arming, making them unsuitable for compact applications.
Innovation Solution
A micro-machined safety and arming device with an axial rotational movement mechanism, featuring a pyrotechnic chain interrupter shutter immobilized by two locks: a breakable axial acceleration lock and a centrifugal lock with tilting locking fingers, where the flyweight contacts an extension to release the lock, ensuring smooth movement without frictional interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional micro-machined safety and arming device uses a centrifugal flyweight to maintain a lock engaged in a shutter indentation, then the device can ensure safety during storage and firing, but the friction generated by maintaining the lock disturbs the movement of the flyweight and delays the centrifugal arming
Solution Approach 1:
The locking mechanism is segmented into two independent locks: a first lock (axial acceleration lock) that breaks under firing acceleration to release the shutter, and a second lock (centrifugal lock) that releases only under centrifugal force during rotation. This segmentation allows each lock to be optimized for its specific function, with the centrifugal lock using tilting fingers that engage only when needed, minimizing friction during storage while ensuring reliable release during arming.
Solution Approach 2:
The second lock uses dynamic tilting fingers that can pivot between engaged and disengaged positions. The fingers are held in a neutral position during storage but tilt to engage the shutter indentation when centrifugal force is applied, and return to neutral when the force is removed. This dynamic behavior eliminates continuous friction while maintaining safety during rotation.
2Reliability
If the second lock uses a flyweight to maintain engagement throughout the stroke, then safety is ensured, but friction disturbs the flyweight movement and affects centrifugal arming delay
Solution Approach 1:
The tilting fingers transition from a static engaged position to a dynamic position that engages only when centrifugal force is applied. During storage, the fingers remain in a neutral position without contacting the shutter, eliminating friction. During rotation, the fingers tilt to engage the shutter indentation, providing safety only when needed, and return to neutral when the rotation stops.
Solution Approach 2:
The tilting fingers act as intermediaries between the flyweight and the shutter. Instead of the flyweight directly maintaining engagement throughout the stroke, the fingers transmit the centrifugal force from the flyweight to the shutter only when engaged, allowing the flyweight to move freely during storage without frictional interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device ensures reliable arming without frictional disturbances, is compact, and suitable for medium-caliber projectiles, providing a sufficient arming delay and improved reliability by eliminating the need for return springs and complex locking mechanisms.
Implementation Method 1
a flyweight arranged in a housing of the shutter and sliding under the effect of the centrifugal acceleration
Implementation Method 2
A first lock (or axial acceleration lock) which is released following the application of the acceleration imparted to the projectile during firing
Data Source
Figure 1
Figure 2a~2b
Figure 2c~4
AI summary
The invention relates to a micro-machined or micro-engraved safety and arming device (12) for a pyrotechnic chain of a projectile that is animated by an axial rotational movement during firing. This device comprises a pyrotechnic chain interruption flap (14) held immobilized by at least two latches: a first latch (17) that is released following the application of the firing acceleration, and a second latch (18) that is a centrifugal latch. This device is characterized in that the second latch comprises at least one pivoting locking finger (18a) against which the flap (14) is pressed in the locked position. The finger has an extension (18d) against which, at the end of its travel, a weight (21) disposed in a recess of the flap (14) makes contact. The flap slides under the effect of the centrifugal acceleration.