Heat-Activated Triggering Device with Safety Valve and Linkage
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Solution Overview
Problem
Existing triggering devices for munitions fail to prevent unintended activation due to thermal runaway or aero-thermal heating, leading to potential safety hazards such as premature ignition or propulsive events during slow cook-off or flight.
Innovation Solution
A heat-activated triggering device with a firing pin mechanically coupled to a linkage that includes a cylindrical valve element and a shape memory alloy sleeve, which aligns a through hole with an output channel only when the firing pin has moved sufficiently, preventing premature operation and incorporating an inertial lock-out to prevent movement post-launch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a firing pin is used to trigger the primer, then the shaped charge can be detonated, but unintended activation may occur due to thermal runaway or aero-thermal heating
Solution Approach 1:
The valve element is pre-positioned to block the output channel before the firing pin reaches the primer. This preliminary blocking action prevents thermal runaway effects from causing unintended activation, as the channel remains sealed until the precise moment of intended firing when the firing pin's movement mechanically opens the valve
Solution Approach 2:
The valve element acts as an intermediary between the firing pin and the output channel. It mediates the flow path by being mechanically coupled to the firing pin, ensuring that the channel remains blocked during thermal events unless the firing pin's movement actively opens the valve, thus preventing harmful thermal effects from causing premature detonation
2Productivity
If the output channel is always open, then detonation products can exit freely, but premature ignition or propulsive events may occur during slow cook-off
Solution Approach 1:
The valve element is pre-positioned in a closed state that blocks the output channel before the firing pin reaches the primer. This preliminary blocking prevents premature ignition during slow cook-off, while allowing immediate product egress once the firing pin's movement opens the valve at the intended firing moment
Solution Approach 2:
The valve element transitions from a static blocked state to a dynamic state where its position changes in response to the firing pin's movement. This dynamic opening ensures the channel remains closed during thermal events but opens freely when needed, balancing productivity and reliability
3Ease of operation
If the firing pin is allowed to move freely, then the primer can be initiated, but movement cannot be prevented post-launch
Solution Approach 1:
The lockout mechanism applies preliminary anti-action by preventing the firing pin from moving in the opposite direction after launch. The lockout member is positioned to block reverse movement, ensuring the firing pin cannot accidentally re-engage the primer after the initial firing event, thus maintaining reliability without affecting the ease of initial operation
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
Effectively prevents undesired triggering of shaped charges by ensuring the firing pin can only initiate detonation after reaching a predetermined temperature and being mechanically locked post-launch, thereby preventing safety hazards like premature ignition or explosion.
Implementation Method 1
a shape memory alloy sleeve, which aligns a through hole with an output channel
Implementation Method 2
incorporating an inertial lock-out to prevent movement post-launch
Data Source
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AI summary
A heat-activated triggering device, such as for a missile or munition, includes a firing pin that is driven into a primer, to initiate a detonation and/or combustion reaction. The firing pin may be mechanically coupled to a linkage that prevents egress of output from the primer if the firing pin has not been moved. The linkage may include, for example, a cylindrical valve element with a through hole, the through hole being alignable with an output channel from the primer when the firing pin has been moved sufficiently. The movement of the firing pin slides a dowel pin that is attached to the firing pin. This in turn translates a cam element that turns the cylindrical element. Partial movement of the firing pin still may leave the valve closed. Preventing the primer from prematurely operating to trigger explosion, for example preventing full operation due to a primer being heated.