AR Trigger Switching Shaft for Readable Pull-Weight Adjustment

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Solution Overview

Problem

Existing AR-type firearm triggers lack a user-friendly mechanism for adjusting trigger pull weight without requiring additional tools or disassembly, and the set weight is not easily readable or verifiable.

Innovation Solution

A trigger mechanism with a switching shaft having varying depth steps and a Torx® drive allows for easy adjustment of trigger pull weight by rotating the shaft, with markings indicating the set weight, eliminating the need for disassembly and additional tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a stepless trigger pull adjustment is achieved by turning an adjustment screw on the trigger mechanism, then the trigger pull weight can be adjusted continuously, but the exact trigger pull weight is not visible or discernible and requires additional measuring devices

Engineering Contradiction:
Improvetrigger pull weight adjustmentVSAvoidtrigger pull weight information
Core Design Contradiction:
Adaptability or versatilityVSLoss of information

Solution Approach 1:

The patent applies color-coded markings on the adjustment screw to indicate different trigger pull weight settings. As the user rotates the adjustment screw, the markings change color or position, providing immediate visual feedback about the current trigger pull weight setting without requiring external measuring devices.

Inventive Principle:
Principle #32Color changes

Solution Approach 2:

The patent implements a feedback mechanism where the adjustment screw has visible markings that provide real-time information about the trigger pull weight setting. This allows the user to see the current setting immediately after adjustment, eliminating the need for separate measurement steps.

Inventive Principle:
Principle #23Feedback

2Ease of manufacture

If trigger pull weight adjustment requires removing the trigger from the receiver, then the adjustment can be made, but the process becomes time-consuming and complex

Engineering Contradiction:
Improvetrigger adjustment capabilityVSAvoidadjustment time
Core Design Contradiction:
Ease of manufactureVSLoss of time

Solution Approach 1:

The adjustment screw is designed to be accessible and functional while the trigger remains installed in the receiver. The screw is positioned such that it can be accessed through existing openings or gaps in the trigger housing, allowing users to adjust the trigger pull weight without disassembling the trigger from the receiver.

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

Solution Approach 2:

The trigger mechanism is designed to be self-adjustable by the user without requiring professional disassembly or special tools. The adjustment screw is positioned for easy access and the markings provide self-explanatory guidance, enabling users to perform the adjustment themselves quickly and easily.

Inventive Principle:
Principle #25Self-service

3Adaptability or versatility

If spring replacement is used to adjust trigger pull weight, then different trigger weights can be achieved, but the springs or retaining screws can be lost during replacement and the process is time-consuming

Engineering Contradiction:
Improvetrigger pull weight variationVSAvoidparts loss risk
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

Instead of replacing static springs to change trigger pull weight, the patent uses a dynamic adjustment mechanism where a single spring's tension can be varied continuously by rotating an adjustment screw. This eliminates the need to handle multiple springs and retaining screws, thereby eliminating the risk of losing parts during adjustment.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent extracts the need for multiple springs and retaining screws by implementing a single adjustable spring mechanism. The adjustment screw modifies the tension of one spring to achieve different trigger pull weights, removing the complexity and risk associated with replacing multiple spring components.

Inventive Principle:
Principle #2Taking out (Extraction)

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

Enables straightforward adjustment and clear visualization of trigger pull weight without tools or disassembly, reducing the risk of unintentional discharge and simplifying the adjustment process.

Implementation Method 1

a switching shaft (18), which has a first cylindrical section (34), at least one extension (35) and a second cylindrical section (36), is rotatably and axially displaceably guided in the opening (29, 31), and wherein the switching shaft (18) is pressed with its at least one contact shoulder (37) against the step (30) or into one of the at least two shoulders of different depths by the force of a trigger spring (21)

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4560249B1Trigger with incrementally adjustable trigger weight for ar-type weapons
Publication Date: 2025.12.31 RECKNAGEL GMBH & CO KG
  • EP4560249B1 patent drawingFigure 1
  • EP4560249B1 patent drawingFigure 2
  • EP4560249B1 patent drawingFigure 3

AI summary

A trigger with a stepwise adjustable trigger weight is described for weapons of the AR (3) type, which trigger is characterized in that the trigger blade (15) has at least one opening, wherein the at least one opening has a step (30), and wherein the step (30) has at least two shoulders (32) and (33) of different depths, and wherein a switching shaft (18), which has a first cylindrical section (34), at least one extension (35) and a second cylindrical section (36), is guided in the opening in a rotatable and axially displaceable manner, and wherein the switching shaft (18) is pressed with its at least one contact shoulder (37) against the step (30) or into one of the at least two shoulders (32) and (33) of different depths by the force of a trigger spring (21), which is supported on a bottom surface (23) in the trigger housing (14) or on the bottom of the housing lower part (5) of the weapon.