Machine Gun Trigger Assembly for Open-Bolt Select Fire
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Solution Overview
Problem
Machine guns lack a select fire function, which is necessary for operators to choose between semiautomatic and fully automatic fire, especially for open-bolt systems like the M240 machine gun.
Innovation Solution
A trigger assembly with a selector that allows for safe, semiautomatic, and fully automatic fire positions, incorporating a sear block and disconnector catch to prevent inadvertent firing and reduce wear, and a rolling connection between the sear link and sear to ensure controlled operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a machine gun uses an open-bolt system without a selector, then the structure is simple and reliable, but it cannot provide selective firing modes (semiautomatic or fully automatic)
Solution Approach 1:
The trigger assembly is designed to perform multiple functions through a single integrated structure. The selector switch enables the same trigger assembly to provide safe, semiautomatic, and fully automatic firing modes, making the device universal and adaptable to different operational requirements without needing separate trigger mechanisms for each mode.
Solution Approach 2:
The trigger assembly is divided into functional segments: the trigger itself, the selector switch, the sear mechanism, and the disconnector. This segmentation allows each component to be optimized for its specific function while working together to provide selective firing modes, resolving the contradiction between versatility and complexity.
2Ease of operation
If the sear is allowed to move freely during charging, then the action can be charged properly, but inadvertent firing may occur if the firearm is dropped
Solution Approach 1:
The sear block is positioned in advance to potentially block the sear's movement path. During normal charging operation, the sear block moves out of the way to allow proper charging. However, if the firearm is dropped or subjected to abnormal forces, the sear block can engage to prevent the sear from moving and causing inadvertent firing, thus providing preliminary protection against accidental discharge.
Solution Approach 2:
The sear block acts as an intermediary component between the sear and the external environment. It mediates the sear's movement by allowing it during normal charging operations while blocking it during abnormal conditions such as drops, thereby preventing accidental discharge without interfering with proper function.
3Duration of action of stationary object
If traditional trigger mechanisms are used without wear reduction features, then the structure is simpler, but component wear increases over time
Solution Approach 1:
The rolling connection between the sear link and sear provides beforehand cushioning against wear. By introducing a rolling contact mechanism, the patent reduces friction and wear before they can cause significant damage to the components, thereby extending service life without requiring complex replacement or maintenance systems.
Data Source
AI summary
A trigger assembly includes a selector operable between a safe position, a semiautomatic fire position, and an automatic fire position. In one example, the assembly includes a trigger rotatable between a resting position and a pulled position, a disconnector pivotable between a first position where it is in the path of the operational rod, and a second position where it is out of the path of the operational rod. A sear is pivotable between an engaged position and a disengaged position and is biased to the engaged position where it is positioned in the path of the operational rod. A sear link is pivotably connected to the trigger, such that pulling the trigger moves the sear link into contact with the sear to pivot the sear towards the disengaged position. The sear link is spaced from the sear when the trigger is in the resting position.