Semiautomatic Rifle Trigger Cam Mechanism
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Solution Overview
Problem
Bullpup style semi-automatic rifles face challenges in achieving a smooth and consistent trigger pull mechanism that is resistant to accidental release due to impact or vibration, while maintaining a low trigger pull force.
Innovation Solution
The trigger assembly incorporates a two-piece hammer linkage and a trigger cam system with a sealed ball bearing, which ensures a smooth trigger pull and prevents accidental hammer release, utilizing a cam return spring to maintain contact with the receiver housing and a sear return spring to lock the hammer in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional trigger mechanism is used in bullpup rifles, then the structure is simple, but the trigger pull is inconsistent and prone to accidental release
Solution Approach 1:
The trigger assembly is divided into multiple functional components: trigger cam (54), pull rod (45), hammer linkage (72), sear (73), and return springs (58, 79). Each component performs a specific function in the trigger pull sequence, allowing for precise control and consistency while maintaining manageable complexity through modular design
Solution Approach 2:
The trigger cam (54) acts as an intermediary mechanism between the trigger pull and hammer release. It converts the linear trigger pull into rotational motion that smoothly releases the hammer, ensuring consistent trigger pull characteristics and preventing accidental discharge through controlled engagement and disengagement
2Ease of operation
If the trigger pull force is reduced for ease of operation, then the trigger is easier to pull, but accidental release due to impact or vibration increases
Solution Approach 1:
The sear return spring (79) and hammer linkage (72) are designed to maintain pre-load and engagement pressure before trigger pull, creating a secure locked state that resists accidental release from external impacts or vibrations. The sear (73) engages deeply with the hammer notch, providing preliminary anti-action against harmful factors
Solution Approach 2:
The trigger cam (54) utilizes curved cam surfaces that provide progressive release of the hammer linkage. The curvature allows for smooth, controlled motion that reduces the required pull force while maintaining secure engagement through the cam's geometric profile, preventing accidental release
3Reliability
If a cam mechanism is added to smooth the trigger pull, then the trigger pull becomes consistent, but the device complexity increases
Solution Approach 1:
The trigger cam (54) is integrated with the pull rod (45) and hammer linkage (72) in a unified assembly. The cam's rotational axis is shared with the pull rod, and the hammer linkage is directly actuated by the cam's cam surface, merging multiple functions into a single compact mechanism that provides smooth trigger pull without excessive complexity
Solution Approach 2:
The trigger cam (54) transforms the static trigger pull into a dynamic rotational motion that smoothly varies the release force. The cam's rotating profile creates a progressive, controlled disengagement of the hammer linkage, providing consistent and smooth trigger pull characteristics throughout the firing sequence
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 provides a substantially smooth and consistent trigger pull with a low force requirement, preventing accidental hammer release even under impact or vibration, ensuring reliable operation.
Implementation Method 1
a cam return spring to maintain contact with the receiver housing
Implementation Method 2
a sear return spring to lock the hammer in place
Implementation Method 3
a trigger cam system with a sealed ball bearing, which ensures a smooth trigger pull
Data Source
AI summary
Methods and apparatus are provided for a semiautomatic rifle with a trigger in a receiver portion of the rifle positioned substantially forward of a back end of the rifle barrel, and a hammer assembly that includes a pivotally mounted sear, a disconnector, and a hammer mounted in the receiver behind the back end of the barrel. A hammer linkage proximate the hammer assembly has a first end connected to the trigger by a pull rod, and a second end configured to push a back end of the sear in an upward direction.