Hammer-Mounted Blocking Pin for Drop-Impact Discharge Prevention

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Solution Overview

Problem

Hammer-operated firearms, such as revolvers, are prone to accidental discharge when dropped or impacted, particularly in certain orientations, necessitating an improved safety mechanism to prevent unintended firing.

Innovation Solution

A spring-biased blocking pin is mounted to the hammer, which engages a fixed pivot pin notch to arrest the hammer's motion upon impact, preventing discharge by aligning with the notch when the hammer is cocked.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a traditional trigger mechanism is used to hold the hammer in a cocked position, then the firearm can be easily operated, but the hammer may accidentally release when the firearm is dropped or impacted

Engineering Contradiction:
Improvetrigger operationVSAvoidhammer retention
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

A blocking pin is introduced as an intermediary component between the hammer and the trigger mechanism. This blocking pin engages with a blocking feature on the hammer to prevent accidental release, while still allowing controlled release through proper trigger operation. The blocking pin acts as a mediator that adds a layer of safety without completely restricting the trigger mechanism's functionality.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The blocking pin is positioned in advance in a retracted state, ready to engage with the blocking feature on the hammer if an abnormal force is applied. This preliminary positioning ensures that the safety mechanism is already in place to prevent accidental discharge before any harmful event occurs, maintaining readiness while preventing unintended firing.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If a safety mechanism is added to prevent accidental hammer release, then reliability is improved, but the device complexity increases

Engineering Contradiction:
Improvefirearm safetyVSAvoidmechanism structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The safety mechanism is segmented into distinct functional components: a blocking pin with a specific geometry, a blocking feature on the hammer, and a spring mechanism. This segmentation allows each component to perform its specific function independently, making the overall system easier to manufacture, assemble, and maintain while providing reliable safety functionality.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The spring mechanism automatically actuates the blocking pin when abnormal force is applied, eliminating the need for manual intervention or complex control systems. The mechanism self-regulates based on the forces applied to the firearm, deploying the blocking pin only when necessary and returning to its normal state when the abnormal force is removed, thereby reducing overall system complexity.

Inventive Principle:
Principle #25Self-service

3Reliability

If the blocking pin is always engaged with the blocking feature, then the hammer cannot rotate, but the firearm cannot be fired properly

Engineering Contradiction:
Improvehammer blockingVSAvoidfiring function
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The blocking pin's engagement state is made dynamic rather than static. Under normal operating conditions, the blocking pin remains disengaged from the blocking feature, allowing free hammer rotation and firing. When abnormal force is applied, the spring mechanism dynamically shifts the blocking pin into engagement with the blocking feature to prevent accidental discharge. This dynamic behavior ensures the safety mechanism only interferes with normal operation when necessary.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The blocking pin is pre-positioned in a retracted state that does not interfere with normal hammer rotation or firing operations. The spring mechanism is pre-loaded to automatically deploy the blocking pin only when abnormal force is detected, ensuring that the safety feature is activated at the appropriate moment without hindering legitimate firing sequences.

Inventive Principle:
Principle #10Preliminary action

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 mechanism automatically deploys without user intervention to prevent accidental firing, ensuring safety by arresting the hammer's rotation and preventing the transfer of energy to the cartridge.

Implementation Method 1

a spring-biased blocking pin mounted to the hammer

Methodology Applied
Scientific EffectSpring: Spring

Data Source

PatentEP4004480B1Safety mechanism for hammer-operated firearms
Publication Date: 2025.08.27 STURM RUGER & CO INC
  • EP4004480B1 patent drawingFigure 1
  • EP4004480B1 patent drawingFigure 2
  • EP4004480B1 patent drawingFigure 3

AI summary

A firearm with safety mechanism in one embodiment includes a barrel supported by a housing, at least one cartridge-receiving chamber in communication with a bore of the barrel, and a rotatable hammer. The safety mechanism includes a biased safety component, which may be a blocking pin in one embodiment, mounted to and rotatable with the hammer. When the firearm is exposed to an abnormal impact force caused by bumping or dropping the firearm, the safety component changes position and interacts with a blocking feature on the hammer pivot pin to stop or delay the motion of the hammer in a manner which prevents discharging the firearm. The blocking feature may be a notch in one embodiment. Rotating the hammer between rearward cocked and forward firing positions alternatingly aligns or misaligns the blocking pin with the notch, respectively.