Bolt Carrier Cam Path Geometry for 22.5° Rotation
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Solution Overview
Problem
Prior art bolt carriers in M16 family rifles, such as AR-15 type rifles, experience undesired contact between the cam pin head and the upper receiver sidewall due to a cam path that only rotates the bolt by less than 22.5°, leading to damage from the cam pin striking the sidewall.
Innovation Solution
A modified cam path that ensures a full 22.5° rotation of the bolt, preventing the cam pin from striking the upper receiver sidewall by altering the cutting path to accommodate a full rotation of the bolt lugs and cam pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the cam path is designed to rotate the bolt by less than 22.5°, then the bolt carrier structure is simpler, but the cam pin strikes the upper receiver sidewall causing damage
Solution Approach 1:
The patent modifies the cam path geometry parameters to achieve a specific 22.5° rotation angle. By changing the cam path shape and dimensions, the bolt rotation is precisely controlled to clear the upper receiver sidewall, preventing cam pin impact while maintaining reliable locking lug engagement.
Solution Approach 2:
The patent addresses the impact problem by adding a rotational dimension to the solution. Instead of merely reducing cam path complexity, it optimizes the rotational trajectory to achieve exactly 22.5° of bolt rotation, which provides the necessary clearance in the spatial dimension to prevent cam pin contact with the upper receiver sidewall.
2Reliability
If the cam path is modified to achieve full 22.5° rotation, then the cam pin clearance is improved, but the cam path geometry becomes more complex
Solution Approach 1:
The patent applies parameter changes by precisely defining the cam path geometry to achieve the optimal 22.5° rotation angle. This specific parameter value balances the competing requirements of ensuring sufficient cam pin clearance for reliable operation while maintaining a manufacturable cam path design.
Solution Approach 2:
The patent uses partial action by rotating the bolt exactly 22.5° - not more, not less. This precise partial rotation is sufficient to clear the upper receiver sidewall and prevent cam pin impact, while avoiding the excessive rotation that would require even more complex cam path geometry.
3Reliability
If the bolt rotation is increased to 22.5°, then the cam pin clearance is sufficient, but the manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific cam path parameters that achieve the 22.5° rotation target. These parameter values are chosen to provide adequate clearance margins, which helps accommodate normal manufacturing tolerances while ensuring reliable cam pin clearance in finished parts.
Solution Approach 2:
The patent performs preliminary design optimization of the cam path geometry before manufacturing. By pre-calculating and pre-defining the optimal 22.5° rotation path, the design incorporates built-in clearance margins that compensate for potential manufacturing variations, ensuring reliable operation without requiring extreme manufacturing precision.
Data Source
AI summary
The invention is a bolt carrier with a modified cam path that prevents undesired contact between a cam pin and the sidewall of an upper receiver.