Crossbow Trigger Arm Asymmetry for Torsion Reduction

Solution Overview

Problem

Crossbows with traditional trigger assemblies experience hard and rough trigger pulls due to high bowstring tension, leading to torsion issues that can result in unanticipated early or late release of the string, compromising safety and accuracy.

Innovation Solution

An adjustable trigger assembly with a trigger arm coupled to a sear, where the trigger arm is not parallel to the projectile path, allowing for adjustable trigger draw length and pull weight, reducing torsion and providing a comfortable, smooth trigger pull.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional trigger assembly with solid sear engagement is used, then mechanical advantage and stability are provided, but trigger pull becomes hard and rough

Engineering Contradiction:

Improvemechanical advantageVSAvoidtrigger pull smoothness

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The trigger assembly is divided into separate functional components: a trigger bar, a trigger arm, and a sear. The trigger arm is coupled to the trigger bar at a first location while the sear is coupled at a second location, creating segmented engagement points that distribute the bowstring tension forces and reduce the harshness of the trigger pull while maintaining mechanical advantage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The trigger arm serves as an intermediary element between the trigger bar and the sear. This intermediate component allows for controlled movement and force distribution, mediating between the user's pull on the trigger and the release of the sear, thereby smoothing the trigger pull while maintaining the necessary mechanical advantage for reliable engagement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If firm engagement between sear and trigger assembly is used, then high bowstring tension is retained, but torsion of trigger assembly occurs causing unanticipated release

Engineering Contradiction:

Improveengagement firmnessVSAvoidrelease predictability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The trigger arm is positioned asymmetrically relative to the trigger bar, with the connection point offset from the centerline. This asymmetric geometry creates a moment arm that counteracts torsional forces during trigger pull, allowing firm engagement of the sear while preventing unwanted rotation or twisting of the trigger assembly that could lead to unanticipated release.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The trigger arm is oriented at an angle non-perpendicular to the projectile path, introducing a dimensional component that addresses torsion. This angular orientation creates a force distribution pattern that maintains firm sear engagement while eliminating the torsional stress that causes unpredictable release timing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If trigger arm is positioned perpendicular to projectile path, then simple geometry is achieved, but torsion forces cause unanticipated early or late release

Engineering Contradiction:

Improvetrigger geometry simplicityVSAvoidrelease timing accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The trigger arm is positioned asymmetrically relative to the trigger bar, with the connection point offset from the centerline. This asymmetric geometry creates a moment arm that counteracts torsional forces during trigger pull, allowing firm engagement of the sear while preventing unwanted rotation or twisting of the trigger assembly that could lead to unanticipated release.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The trigger arm is oriented at an angle non-perpendicular to the projectile path, introducing a dimensional component that addresses torsion. This angular orientation creates a force distribution pattern that maintains firm sear engagement while eliminating the torsional stress that causes unpredictable release timing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 adjustable trigger assembly enhances safety by reducing inadvertent actuation, improving dry fire characteristics, and providing a comfortable, predictable trigger pull, while maintaining mechanical advantage and stability, thus preventing unintentional projectile launch.

Implementation Method 1

An adjustable trigger assembly with a trigger arm coupled to a sear, where the trigger arm is not parallel to the projectile path, allowing for adjustable trigger draw length and pull weight, reducing torsion and providing a comfortable, smooth trigger pull

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS8770178B2Shooting bow

Publication Date: 2014.07.08 KEMPF JAMES J

AI summary

A trigger assembly for a crossbow or other weapon system. The trigger assembly includes a trigger arm coupled between a trigger and a sear. The trigger arm is not parallel to the line of fire, thereby allowing for increased mechanical advantage and a smoother, safer trigger pull. The trigger assembly incorporates various safety measures, including a dry fire mechanism which prevents the unintentional damaging and potentially dangerous release of the bowstring before an arrow is positioned on the rail of the crossbow. The trigger assembly allows for various adjustments to vary the trigger length and pull, while maintaining smoothness and preventing the unintentional or inadvertent release of the bowstring.