Projectile Safe-and-Arm Device Unbalanced Rotor Mechanism
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Solution Overview
Problem
Existing safe-and-arm devices for projectiles with second-stage propulsion lack an effective mechanism to ensure the projectile is safely armed only after it has reached a sufficient distance from the launcher, adhering to safety standards like MIL-STD-1316E.
Innovation Solution
A safe-and-arm device utilizing an unbalanced rotor controlled by a pinion and verge assembly, with a lockpin mechanism that prevents the rotor from turning until the projectile has experienced a second acceleration force and spin forces, ensuring safe arming only after reaching a safe distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a safe-and-arm device is designed for traditional single-stage projectiles, then it can ensure basic safety arming, but it cannot effectively sense and respond to the two unique environments (launcher barrel exit and second-stage ignition) required by MIL-STD-1316E for second-stage propulsion projectiles
Solution Approach 1:
The safe-and-arm device employs dynamic components including an unbalanced rotor that rotates in response to acceleration forces, a lockpin that moves between extended and retracted positions based on sensed conditions, and a setback pin that responds to launch acceleration. These dynamic elements allow the device to automatically adapt its state based on the projectile's flight conditions and second-stage ignition events.
Solution Approach 2:
The unbalanced rotor acts as an intermediary mechanism that translates acceleration forces from the second-stage ignition into rotational motion, which then triggers the arming sequence. The lockpin serves as another intermediary by mechanically linking the rotor's rotation to the arming/disarming state of the device, ensuring that arming only occurs after proper sensing of flight conditions.
2Productivity
If the projectile is armed immediately after launch, then it can be ready for detonation, but it violates safety requirements by not ensuring minimum safe distance from the launcher
Solution Approach 1:
The device performs preliminary sensing actions during the flight phase before arming occurs. The unbalanced rotor accumulates rotational motion in response to acceleration forces, and the lockpin remains in a position that prevents arming until the projectile has traveled a sufficient distance from the launcher. This preliminary action ensures that arming only occurs after safety conditions are met.
Solution Approach 2:
The safe-and-arm device incorporates feedback mechanisms where the unbalanced rotor's rotation, driven by acceleration forces from second-stage ignition, provides continuous information about the projectile's flight state. This feedback controls the lockpin position and ultimately determines when arming can occur, ensuring that arming readiness is contingent upon verified safe flight conditions.
3Reliability
If a complex sensing mechanism is added to detect second-stage ignition, then safety compliance improves, but the device complexity increases
Solution Approach 1:
The unbalanced rotor utilizes the projectile's own acceleration forces from second-stage ignition to drive its rotation and trigger the arming sequence. The system serves itself by using the flight conditions it needs to sense as the direct driving force for its operation, eliminating the need for separate sensors or power sources to detect these conditions.
Solution Approach 2:
The invention replaces electronic or complex sensor-based detection systems with a purely mechanical sensing mechanism. The unbalanced rotor and lockpin assembly uses mechanical forces and motion to detect and respond to acceleration events, substituting complex electronic sensing with elegant mechanical force-based detection that is inherently reliable and simple.
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 solution effectively ensures that the projectile is safely armed only after it has traveled a sufficient distance, enhancing safety and compliance with military standards by utilizing a mechanical mechanism that responds to propulsion stages.
Implementation Method 1
the lockpin, in response to both the second acceleration and spin forces, retracts and releases the unbalanced rotor to turn
Implementation Method 2
an unbalanced rotor that is configured to rotate inside the safe-and-arm device or mechanism, with a rate of rotation of the unbalanced rotor being controlled by a pinion and verge assembly
Implementation Method 3
the lockpin is being urged by a spring to extend
Implementation Method 4
a rate of rotation of the unbalanced rotor being controlled by a pinion and verge assembly
Implementation Method 5
after the projectile is propelled out of a launcher barrel and the projectile is a safe distance away from the launcher barrel, a second propellant is ignited
Implementation Method 6
the projectile experiences a second acceleration force or impulse together with spin forces
Data Source
AI summary
The present invention describes a safe-and-arm device, mechanism or assembly (160) for a projectile (100,102) equipped with a second-stage propellant (124). The second-stage propellant (124) is ignited after the projectile has been ejected out from a launcher barrel. A lockpin (190), being urged by a spring (194), is responsive to ignition of the second-stage propellant; after the lockpin (190) and spring (194) sense and respond to the second propulsion, an unbalanced rotor (164) forming part of the safe-and-arm device or assembly (160), is released to rotate from a “safe” state to an “armed” state, as the projectile continues traveling along its trajectory to a target. In one embodiment, the projectile is configured with a 40 mm cartridge containing a first propellant (122). An impact sensor may trigger an electric detonator or a point detonator may trigger a stab detonator to set off explosives disposed in the projectile.