Interrupted Semi-Automatic Firearm Action With Integrated Bolt Release

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Solution Overview

Problem

Existing interrupted-type semi-automatic actions for firearms are often cumbersome, not compact, and have complex mechanisms, which can affect the appearance and handling of the firearm.

Innovation Solution

The introduction of a dual acting safety feature in the form of a trigger interlock, combined with a bolt release mechanism that includes a spring-loaded disconnect lever and a user-operated release button, allows for a compact and aesthetically pleasing design while preventing unintentional firing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex actuator mechanism is used to hold the hammer rearward and manually release the bolt, then the bolt can be reliably held in the rearward position, but the device becomes cumbersome and affects handling

Engineering Contradiction:
Improvebolt retention reliabilityVSAvoidhandling convenience
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent extracts the essential function of bolt retention from a complex actuator mechanism and implements it through a simple spring-loaded disconnect lever that engages with the hammer. This lever is actuated by a minimalistic release button, eliminating the need for complex mechanisms while maintaining reliable bolt retention in the rearward position.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using a complex mechanism to actively hold the bolt rearward, the invention uses a spring-loaded lever that passively engages the hammer to prevent forward movement. The retention is achieved through the hammer's own weight and the spring force, inverted from active holding to passive constraint.

Inventive Principle:
Principle #13The other way round (Inversion)

2Volume of moving object

If a compact bolt release mechanism is used, then the firearm appearance and handling are improved, but safety features may be compromised

Engineering Contradiction:
Improvemechanism compactnessVSAvoidsafety reliability
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The patent merges the bolt release function and trigger interlock safety feature into a single integrated mechanism. The disconnect lever serves dual purposes: releasing the bolt when actuated and providing safety interlock with the trigger. This consolidation achieves compactness while maintaining safety through the combined functionality of the lever and trigger interaction.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The disconnect lever is designed to perform multiple functions: it releases the bolt by disengaging the hammer, provides trigger interlock safety by preventing trigger actuation when the bolt is held rearward, and returns to its neutral position automatically. This multi-functionality achieves compact design without compromising safety.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Productivity

If the bolt is released automatically after cartridge loading, then the action cycles quickly, but unintentional firing may occur

Engineering Contradiction:
Improveaction cycling speedVSAvoidunintentional firing risk
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary action through the trigger interlock safety feature that prevents the trigger from being actuated until the bolt release mechanism is returned to its unactuated position. This ensures that the bolt can only be released intentionally after the trigger is fully released, preventing unintentional firing while maintaining rapid cycling through the automatic return of the disconnect lever.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system uses feedback through the trigger interlock mechanism that senses the position of the disconnect lever and prevents trigger actuation accordingly. When the bolt is held rearward, the interlock prevents trigger pull; when the bolt is released, the interlock allows trigger actuation. This feedback loop ensures safe operation while maintaining fast cycling.

Inventive Principle:
Principle #23Feedback

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 safe and efficient interrupted semi-automatic action that prevents accidental firing and allows for rapid cycling, while maintaining a compact and user-friendly design.

Implementation Method 1

a spring-loaded disconnect lever selectively engageable with the hammer when in the rearward cocked position

Methodology Applied
Scientific EffectSpring force: Spring

Data Source

PatentEP3894777B1Interrupted semi-automatic action for firearms
Publication Date: 2025.04.02 STURM RUGER & CO INC
  • EP3894777B1 patent drawingFigure 1
  • EP3894777B1 patent drawingFigure 2
  • EP3894777B1 patent drawingFigure 3

AI summary

A firearm with interrupted action includes a barrel, receiver carrying a bolt movable between a forward closed breech position in battery with the barrel and rearward open breech position, a cockable hammer controlled by a trigger, and a bolt release mechanism operably interacting with the bolt. The mechanism may comprise a user-actuated release button and spring-biased disconnect lever coupled thereto and selectively engageable with the hammer. Upon firing, the bolt travels rearward under recoil contacting and partially rotating the disconnect lever to engage the hammer, while simultaneously engaging the hammer which holds the bolt rearward. Actuating the release button fully rotates the disconnect lever to disengage the hammer from the bolt which returns to its forward position via a recoil spring to reclose the breech. A dual interlock safety in one position provided by the release mechanism prevents pulling the trigger and in another position prevents actuating the release button.