Expandable Broadhead Cam Mechanism for Retention
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Solution Overview
Problem
Existing expandable broadheads face issues with premature blade extension due to increased launch speeds and impact forces from modern crossbows, and reliance on O-rings or external structures for maintaining retracted blade positions, which can be lost or broken.
Innovation Solution
A broadhead design featuring a ferrule with pivotally mounted blades and a cam device that resists blade extension until impact, eliminating the need for O-rings or external structures, allowing for controlled blade movement and easy retraction without external manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If O-rings or external attachment structures are used to maintain retracted blade positions, then blade retention during flight is improved, but device complexity increases and reliability decreases due to parts that can be lost or broken
Solution Approach 1:
The patent removes O-rings and external attachment structures from the broadhead design, replacing them with an internal cam mechanism integrated into the ferrule. This extraction of external components eliminates parts that can be lost or broken while reducing overall device complexity.
Solution Approach 2:
The cam mechanism is integrated directly into the ferrule structure, merging the blade retention function with the existing ferrule component. This consolidation eliminates separate attachment structures and reduces the total number of parts in the system.
2Strength
If blades are made thicker to withstand modern crossbow impact forces, then strength is improved, but aerodynamic drag increases when blades are extended
Solution Approach 1:
The broadhead uses a dynamic blade configuration that transitions from retracted to extended position based on impact conditions. During flight, thin aerodynamic blades remain retracted to minimize drag. Upon impact, the cam mechanism allows blades to extend to their full thickness for maximum strength and cutting performance.
Solution Approach 2:
The effective blade parameters (thickness, surface area) change based on operational state. During flight, blades maintain a streamlined profile with minimal exposed surface area. Upon impact, the same blades extend to provide increased thickness and strength, effectively changing their physical parameters to match operational requirements.
3Ease of operation
If blades extend immediately after launch, then cutting edge exposure is improved, but range and accuracy deteriorate due to increased drag
Solution Approach 1:
The broadhead is designed with blades in a preliminary retracted state during launch and flight, optimizing aerodynamic performance. The cutting edges are prepared and positioned but not yet exposed. Upon impact, the cam mechanism triggers blade extension, transitioning from the preliminary flight configuration to the operational cutting configuration.
Solution Approach 2:
The blade extension occurs as a periodic event triggered by impact rather than continuous extension. Blades remain retracted during the flight period, then extend during the impact period, creating distinct operational phases that optimize performance for each condition.
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 design ensures blades extend only upon sufficient impact, maintaining accuracy and range, and allows for thicker, stronger blades to withstand modern crossbow forces, with reliable operation and maintenance through the cam mechanism.
Implementation Method 1
a cam device that resists pivoting of the blades away from their retracted positions until impact of the blades with a target
Implementation Method 2
two blades pivotally mounted to the ferrule for angular pivotal displacement between retracted and extended positions
Implementation Method 3
The ferrule has a sharpened tip portion at the tip of the ferrule
Data Source
AI summary
An expandable broadhead includes blades pivotally mounted on a ferrule for movement between retracted and extended positions, and a cam device that resists initial movement of the blades from their retracted positions towards their extended positions. The cam device can prevent the blades from extending prematurely by contact with leaves, light brush, or the like prior to impacting an intended target.