Captured Spring Assembly for Firearm Noise Reduction
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Solution Overview
Problem
Conventional recoil spring systems in firearms, particularly in AR-15 rifles, produce a loud buzzing noise due to the bolt return spring, and existing solutions like pneumatic piston systems are not suitable for rifles with collapsible stocks or perform poorly in extreme temperatures.
Innovation Solution
A captured spring assembly that includes a guide rod with a buffer and shock absorber, where the bolt return spring is encircled and constrained, using O-rings and weights for shock absorption and a radiused ridge to reduce noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a standard coil spring is used for bolt return, then the rifle can be made lightweight and simple, but it produces loud buzzing noise during operation
Solution Approach 1:
The coil spring is nested around the guide rod, with the spring ends constrained by shoulder features on the guide rod and buffer. This nesting configuration captures the spring in a compact arrangement that prevents lateral movement and rubbing against the extension tube walls, eliminating the buzzing noise while maintaining a simple lightweight structure.
Solution Approach 2:
The guide rod serves as an intermediary element between the spring and the buffer assembly. By providing a central rod around which the spring is captured, the system eliminates direct contact between the spring and the extension tube walls, thereby reducing noise without requiring complex constraint mechanisms.
2Object-generated harmful factors
If a pneumatic piston system is used to reduce noise, then noise is reduced, but it cannot be accommodated in rifles with collapsible stocks and has limited reliability in extreme temperatures
Solution Approach 1:
The patent uses a simple mechanical spring-based system instead of a complex pneumatic system with seals and chambers. The spring is a robust, temperature-resistant component that can be easily accommodated in both full-length and collapsible stock configurations, providing versatility without the reliability issues of pneumatic systems in extreme environments.
3Object-generated harmful factors
If the spring is allowed to move freely in the extension tube, then the structure remains simple, but the spring rubs against the walls producing noise
Solution Approach 1:
The spring is nested around the guide rod with its ends captured by shoulder features, creating a constrained yet simple structure. This nesting prevents the spring from contacting the extension tube walls while maintaining structural simplicity and avoiding complex constraint mechanisms.
Solution Approach 2:
Instead of constraining the spring in the radial direction through complex mechanisms, the invention constrains it axially using the guide rod and buffer shoulders. This dimensional shift in constraint approach eliminates noise-causing contact while keeping the structure simple.
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 effectively reduces the noise and vibration associated with the bolt return spring operation, improving the operational quietness and reliability across various environmental conditions and stock configurations.
Implementation Method 1
a coil spring that encompasses the rod
Implementation Method 2
a movable buffer that defines an aperture that receives the forward end of the rod and is operable to reciprocate between a forward battery position and a rearward retracted position
Data Source
AI summary
A captured spring assembly for a firearm has a rod having a forward and rearward ends, a movable buffer that defines an aperture that receives the forward end of the rod and is operable to reciprocate between a forward battery position and a rearward retracted position, a coil spring that encompasses the rod, wherein the forward end of the rod has a limit element having a head that is larger in diameter than the rod, wherein the buffer has an internal limit element that is larger in diameter than the rod, and wherein the internal limit element has at least one portion that is smaller in diameter than the limit element head, but also larger in diameter than the rod. There may be a spring stop attached to the rearward end of the rod that is large enough for the spring to bear against and the buffer to strike against.