Firearm Receiver Sliding Connection Wear Reduction
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Solution Overview
Problem
The connection between the upper and lower receivers in AR-style firearms can erode over time due to repetitive use, leading to increased clearances and movement, which allows gases to escape and dirt to enter, impacting the firearm's reliable operation.
Innovation Solution
The design incorporates axial grooves and rails on both the upper and lower receivers, allowing for a sliding connection that reduces wear and includes tapered ends for precise engagement, along with a locking pin to secure the receivers together, enhancing the assembly and disassembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pivot pins and takedown pins are used to connect upper and lower receivers, then assembly and disassembly is facilitated, but repetitive use erodes the pin surfaces leading to increased clearance and movement
Solution Approach 1:
The connection system is divided into multiple functional elements: a recess in the upper receiver, a protrusion on the lower receiver, and a retaining pin. This segmentation allows each element to perform its specific function while distributing the connection load, preventing erosion issues at single connection points.
Solution Approach 2:
The protrusion on the lower receiver is received within the recess of the upper receiver, creating a nested connection structure. This nesting provides inherent alignment and positioning while the retaining pin secures the assembly, eliminating the need for external pins that can erode.
2Ease of operation
If pins are used to connect receivers, then ease of assembly is improved, but excessive movement and slop occur over time due to erosion
Solution Approach 1:
The recess and protrusion are pre-formed during manufacturing to provide precise alignment and positioning before the retaining pin is installed. This preliminary action ensures that the receivers are correctly aligned during assembly, eliminating the need for post-assembly adjustments and preventing misalignment issues.
Solution Approach 2:
The retaining pin acts as an intermediary element that secures the recess-protrusion connection without requiring the pins themselves to bear the full connection load. This intermediary approach allows the primary connection to be maintained through the recess-protrusion interface while the pin provides additional securing.
3Ease of manufacture
If traditional pin connections are used, then manufacturing is simplified, but gas escape and dirt entry occur due to increased clearance
Solution Approach 1:
The recess and protrusion are designed with specific local geometries that create a precise fit at the connection interface. This local quality improvement ensures that gas tightness is achieved at the critical connection points without requiring complex overall structural modifications.
Solution Approach 2:
The traditional pin-based mechanical connection is replaced with a recess-protrusion interface that provides inherent gas tightness through precise geometric fit. This substitution eliminates the need for additional sealing mechanisms while preventing gas escape and dirt entry.
Data Source
AI summary
A firearm includes a barrel having a breech end. An upper receiver is engaged with the breech end of the barrel such that a majority of the barrel is outside of the upper receiver. A lower receiver is releasably connected to the upper receiver, and the firearm includes structure for slidingly connecting the upper receiver to the lower receiver.