Retractable Broadhead Arrowhead Shear Pin Deployment

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Solution Overview

Problem

Existing retractable blade arrowheads face issues with aerodynamic drag and safety due to partially exposed blades, and existing solutions either suffer from inertia problems or require careful handling to prevent accidental injury.

Innovation Solution

The design features a cylindrical ferrule with retractable blades secured by a shear pin or detent projections, which fully deploy upon impact, minimizing aerodynamic drag and ensuring safe handling by using an elastomer shear pin that shears upon collision, allowing blades to swing out on a hinge pin for maximum hemorrhaging effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If retractable blade broadheads are used, then aerodynamic drag is reduced during flight, but blades may not fully retract causing safety problems and drag issues

Engineering Contradiction:

Improveaerodynamic dragVSAvoidblade retraction reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

A spring mechanism acts as an intermediary force to actively push the blades into the retracted position within the ferrule during flight. This spring force ensures reliable retraction without depending solely on the aerodynamic pressure, thereby solving the inconsistency in blade retraction while maintaining low drag.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The blades are pre-positioned in a retracted state within the ferrule before flight, and the spring mechanism is pre-loaded to maintain this position. This preliminary action ensures that the blades remain retracted during flight, reducing aerodynamic drag, and are only deployed when needed upon impact.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If fixed blade broadheads are used, then mechanical simplicity is achieved, but aerodynamic drag increases and safety handling becomes problematic

Engineering Contradiction:

Improvemechanical simplicityVSAvoidaerodynamic drag

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The broadhead transitions from a static fixed-blade design to a dynamic retractable-blade design. The blades can change position between retracted (low drag) and deployed (cutting) states, allowing the device to adapt its configuration based on flight or impact conditions, thereby reducing aerodynamic drag while maintaining cutting effectiveness.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If blades are kept slightly open for safety, then handling safety improves, but aerodynamic drag increases

Engineering Contradiction:

Improvehandling safetyVSAvoidaerodynamic drag

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The spring mechanism serves as an intermediary that actively maintains the blades in a fully retracted position during flight, overcoming any tendency for the blades to remain slightly open. This ensures minimal aerodynamic drag while safety is maintained through proper design of the release mechanism that only deploys blades upon impact.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If frictional engagement is used to hold blades, then blade retention is achieved, but control over engagement becomes difficult

Engineering Contradiction:

Improveblade retentionVSAvoidengagement control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The spring mechanism acts as an intermediary that provides a controlled and consistent force to maintain blade engagement with the ferrule walls during flight. This spring force is predictable and can be precisely calibrated, replacing the uncontrollable frictional engagement and providing reliable blade retention without the complexity of adjusting friction coefficients.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This design enhances the aerodynamic performance and safety of arrowheads by ensuring blades remain retracted during flight and fully deploy upon impact, reducing drag and the risk of injury during handling.

Implementation Method 1

the shank of the tip pushes the hinge pin and blades to move in a direction along the longitudinal axis of the ferrule away from the tip to shear the shear pin

Methodology Applied

Scientific EffectShear stress: Shear Stress

Implementation Method 2

using an elastomer shear pin that shears upon collision

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS9683819B2Arrowhead

Publication Date: 2017.06.20 CENTCROSSARCHERY LLC

AI summary

A broadhead arrowhead having fully retractable blades wherein a plunger of the tip of the arrowhead causes the blades to shear a shear pin and deploy when the arrowhead strikes a target. In an alternative embodiment, the blades are retained in the arrowhead by a friction fit that is overcome to deploy the blades when the arrowhead strikes a target.