Crossbow Bowstring Release Mechanism Reducing Trigger Pull Force

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Solution Overview

Problem

Existing crossbows require excessive trigger pull force to release the bowstring, are heavy and complex, necessitate removal and storage of the draw mechanism, and suffer from frictional losses due to arrow movement along a rail, leading to inaccurate and slow firing.

Innovation Solution

A crossbow design featuring pulleys, power cables, a bowstring release mechanism with a spring-biased hammer, and a retractable rope system that allows for easy engagement and retraction of the bowstring without rail contact, reducing trigger pull force and enabling rapid firing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex trigger mechanism and bowstring retraction system are used, then the crossbow can hold and release the bowstring, but the weight of the crossbow increases excessively

Engineering Contradiction:

Improvebowstring holding and release capabilityVSAvoidcrossbow weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The trigger mechanism is divided into separate functional components: a trigger assembly with a trigger member, a separate bowstring release assembly with a release member, and a bowstring retention assembly. This segmentation allows each component to be optimized independently, reducing overall weight while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bowstring release assembly is designed as a separate, removable component that can be detached from the crossbow. This extraction principle reduces the permanent weight of the crossbow while maintaining the necessary bowstring release functionality when needed.

Inventive Principle:

Principle #2Taking out (Extraction)

2Force

If excessive trigger pull force is required to release the bowstring, then the trigger mechanism can hold the high draw weight, but the accuracy of the shot decreases

Engineering Contradiction:

Improvetrigger pull forceVSAvoidshot accuracy

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

A separate bowstring release assembly with a release member acts as an intermediary between the trigger mechanism and the bowstring. When the trigger is pulled, it activates the release member which then releases the bowstring. This intermediary mechanism allows the trigger to be pulled with minimal force while still enabling the release of high draw weight bowstrings.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If the draw mechanism is removed and stored after each shot, then the crossbow can be operated, but the time between shots increases

Engineering Contradiction:

Improvecrossbow operationVSAvoidtime between shots

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The bowstring release assembly remains attached to the crossbow and is automatically reset after each shot. The release member returns to its engaged position, ready to hold the bowstring for the next shot without requiring removal or storage of any components. This continuous readiness eliminates time losses between shots.

Inventive Principle:

Principle #20Continuity of useful action

4Shape

If the arrow slides along a rail when fired, then the arrow can be guided, but frictional forces reduce the firing speed

Engineering Contradiction:

Improvearrow path guidanceVSAvoidfiring speed

Core Design Contradiction:

ShapeVSSpeed

Solution Approach 1:

The invention eliminates the traditional rail system by extracting this guidance function. Instead of sliding along a rail, the arrow is launched directly from the bowstring release assembly. This removal of the rail system eliminates the frictional forces that would otherwise reduce firing speed, while the bowstring itself provides adequate guidance during the power stroke.

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

The solution enables accurate, consistent, and rapid firing with reduced trigger pull force, eliminating the need for excessive finger pressure and minimizing arrow friction, resulting in a lightweight, compact, and efficient crossbow.

Implementation Method 1

a spring-biased hammer, released by the trigger, for striking the actuating lever

Methodology Applied

Scientific EffectSpring bias: Spring

Implementation Method 2

A crossbow design featuring pulleys, power cables, a bowstring release mechanism with a spring-biased hammer, and a retractable rope system

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Implementation Method 3

a retractable rope system that allows for easy engagement and retraction of the bowstring

Methodology Applied

Scientific EffectTension: Tension

Data Source

PatentUS8453631B1Release assembly for crossbow

Publication Date: 2013.06.04 PRECISION SHOOTING EQUIP

AI summary

A crossbow includes an elongated frame coupled to a riser at a first end thereof. The riser supports a pair of flexible limbs, and a bowstring extends between such limbs. A movable bowstring release is used both to retract the bowstring into a drawn position, and to release the bowstring under the operation of a trigger assembly. The bowstring release is initially positioned near the bowstring at rest, and a bowstring hook is engaged therewith. A bowstring retractor includes a retractor rope secured to the bowstring release for retracting the bowstring. An upper housing is secured to the second end of the elongated frame, and supports a rope spool used to wind the retractor rope. The bowstring release is retracted into the upper housing proximate a trigger assembly for selectively releasing the bowstring when a user pulls a trigger.