Expandable Broadhead Spring Blade Retention
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Solution Overview
Problem
Conventional blade-opening arrowheads often experience blade misalignment during launch due to high forces generated by compound archery bows, leading to decreased aerodynamic performance, as they fail to maintain blades in the closed position during flight.
Innovation Solution
Incorporating a spring element to hold blades in a retracted position until impact, allowing them to pivot and translate into an expanded position upon encountering a target, thereby maintaining aerodynamic efficiency during flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional blade-opening arrowheads are designed to launch and fly in a closed position, then aerodynamic performance should be maintained, but blades undesirably move out of the closed position during launch due to high forces generated by compound archery bows
Solution Approach 1:
The spring element is pre-loaded during assembly to exert a biasing force that holds the blade in the closed position before launch. This preliminary action ensures the blade remains stable during the high-force launch phase without requiring additional active control mechanisms during flight.
Solution Approach 2:
The spring element applies a counteracting force (biasing force) that opposes the disruptive forces generated during launch. This preliminary anti-action prevents the blade from moving out of the closed position by balancing the high forces generated by the compound archery bow.
2Reliability
If elastic bands or O-rings are used to hold blades in the closed position, then blade retention is achieved, but the elastic band breaks, severs or moves away upon impact with the target
Solution Approach 1:
The spring element is pre-loaded to provide continuous blade retention during flight, and the same pre-loaded spring is designed to function as an impact mechanism upon target contact, eliminating the need for separate retention and impact components.
Solution Approach 2:
The spring element serves dual functions: it acts as a retention mechanism during flight by maintaining blade closure, and simultaneously serves as an impact mechanism upon target contact where the compressed spring propels the blade forward to enhance penetration. This multi-functionality replaces the single-use elastic band with a reusable, multi-purpose component.
3Reliability
If blades are held firmly in the closed position during launch, then aerodynamic performance is maintained, but the mechanism must withstand tremendous forces from compound archery bows
Solution Approach 1:
The spring element applies a counteracting biasing force that balances the tremendous forces generated during launch, preventing blade displacement while maintaining aerodynamic stability. The spring's elastic properties allow it to absorb and dissipate the high launch forces.
Solution Approach 2:
The spring element's physical parameters (spring constant, coil density, material properties) are optimized to provide sufficient stiffness to resist launch forces while maintaining the ability to compress and expand during operation. This parameter optimization allows the mechanism to withstand extreme forces without permanent deformation.
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 spring element effectively keeps blades closed during launch and flight, enhancing aerodynamic performance by ensuring blades remain in the retracted position until impact, improving the arrow's overall flight dynamics.
Implementation Method 1
a spring element to hold each blade in the retracted position, particularly while encountering the relatively high forces generated at and through an arrow
Implementation Method 2
Each blade is designed to move from the retracted position to the expanded position when the impact force traveling through the blade overcomes a resistance bias force exerted by the spring element on the blade
Data Source
AI summary
An expandable arrowhead having a blade-carrying body with a slot that houses at least one movably mounted blade. Each blade can be pivotally mounted about a shaft. In some embodiments, the shaft is fixed with respect to the body. In other embodiments, the shaft is movably mounted with respect to the body, for example by mounting a shaft within the slot so that the shaft moves within the slot with respect to the blade-carrying body. In some embodiments of this invention, a spring element positively holds one or more blades in a closed position or a retracted position, particularly during extreme forces encountered when launching an arrow from an archery bow, such as a compound archery bow. The spring element of this invention can be used to improve blade opening capabilities of conventional blade-opening arrowheads or broadheads.