Mortar Grenade Detonator Shear Bolt Safety Mechanism
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Solution Overview
Problem
Mortar shells fired from pin mortars lack an independent safety mechanism to prevent unintentional activation of the active charge during transport or before reaching the target, and existing solutions using air flow pressure are costly and complex when integrated with propellant charge igniters.
Innovation Solution
A second safety device is implemented using a shear collar bolt that directs propellant charge gases to separate a shear collar bolt, ensuring that only sufficient pressure can pivot the detonator carrier into ignition position, independent of launch acceleration, and a spring-loaded locking pin is used to secure the detonator carrier until ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second safety device is added to prevent unintentional activation during transport, then safety reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines the second safety device (shear collar bolt mechanism) with the existing detonator carrier and locking pin structure. The shear collar bolt integrates with the transverse bore and connecting bore system, merging multiple safety functions into a unified mechanical assembly that prevents unintentional activation while maintaining structural efficiency
Solution Approach 2:
The safety mechanism is segmented into distinct functional components: the shear collar bolt as a separate safety element, the locking pin for detonator carrier retention, and the transverse bore with connecting bore for gas channeling. This segmentation allows each component to perform its specific safety function independently while contributing to the overall reliability without requiring complete system redesign
2Reliability
If a shear collar bolt mechanism with transverse bore is used for the second safety device, then safety functionality is improved, but manufacturing complexity increases
Solution Approach 1:
The transverse bore serves multiple functions: it houses the shear collar bolt mechanism, channels propellant charge gases to the correct location, and provides structural integration with the detonator carrier assembly. This multi-functionality reduces the need for separate components and simplifies the manufacturing process by consolidating features into existing structural elements
Solution Approach 2:
The shear collar bolt is nested within the transverse bore, and the connecting bore is integrated into the breech head structure. This nesting approach allows complex safety mechanisms to be embedded within existing structural components, reducing the overall part count and simplifying assembly operations while maintaining robust safety functionality
3Adaptability or versatility
If propellant charge gases are used to actuate the shear collar bolt, then the safety mechanism becomes independent of launch acceleration, but the structure becomes more complex
Solution Approach 1:
Propellant charge gases serve as an intermediary medium to transmit the firing command to the shear collar bolt mechanism. Instead of relying on launch acceleration directly, the ignited propellant gases pressure-build up and actuate the safety release sequence, providing a more reliable and acceleration-independent triggering mechanism that works consistently across different firing conditions
Solution Approach 2:
The propellant charge serves a dual purpose: it provides the firing force for the mortar shell and simultaneously acts as the actuating medium for the second safety device. The same propellant gases that drive the projectile also pressure-build up to separate the shear collar bolt, eliminating the need for a separate actuating system and reducing overall structural complexity
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
This solution provides a minimally invasive, cost-effective safety mechanism that prevents irregular ignition and ensures the active charge is only activated upon intended firing, maintaining functional integrity and reducing the risk of accidental detonation.
Implementation Method 1
a spring-loaded locking pin, which is supported with its first end on a shear bolt
Implementation Method 2
cause an increase in pressure there that is sufficient to separate the part of the shear bolt provided with the guide contour from the remaining part of the shear bolt
Implementation Method 3
the detonator carrier is released so that it is pivoted into its ignition position (e.g., by a prestressed torsion spring)
Implementation Method 4
the safety bolt is pushed out of the second recess by the inertial forces against the pressure of the restoring element when a predetermined firing acceleration is reached
Data Source
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AI summary
The invention relates to a detonator (8) for an active part of a mortar grenade (1), in particular for a mortar grenade that can be fired from a spigot mortar and has a detonator (8) arranged at the base (action face). In order to obtain in a simple and low-cost way a first safety system (10), for avoiding unintentional activation of the detonator (8), the invention proposes providing a locking pin (12), which can be moved axially by means of a restricted guidance, in a secured position of a pivotable detonator carrier (9) of the detonator (8) engages in a first recess (18) of the detonator carrier (9) and, when the mortar grenade (1) is fired, is withdrawn from the first recess by the propellant gases (25) acting on the action face (2) of the mortar grenade (1), wherein the restricted guidance of the locking pin (12) takes place by means of a shear bolt or shear collar bolt (14), which is provided with a guiding contour (16) and is arranged in a transverse bore (15).