Crossbow Cocking Mechanism with Dual-Recess Spool for Dynamic Force Control
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Solution Overview
Problem
Existing projectile launchers face design constraints due to heightened dynamic forces during operation, limiting the achievable projectile speed and force without adversely affecting accuracy or dimensions.
Innovation Solution
A crossbow design featuring a cocking mechanism with a spool that rotates in two directions to manage the trigger box movement, utilizing a one-way bearing and brake to control rotation, and a brake-engaged spool diameter variation to reduce dynamic forces, allowing increased projectile speed and force without compromising accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the degree of rotation of the cam is increased to store more potential energy in the limbs, then the projectile speed and force are improved, but the dynamic forces experienced by various components during operation are heightened
Solution Approach 1:
The patent employs a dynamic cam profile that varies its rotation degree during the firing cycle. The cam rotates through a greater angle during the power stroke to maximize energy transfer to the projectile, then returns through a controlled path that minimizes dynamic forces on components. This dynamic adjustment of the cam rotation profile allows the system to achieve high projectile speed while managing the dynamic loads on mechanical components.
Solution Approach 2:
The invention changes the operational parameters of the cam mechanism by implementing a non-uniform rotation profile. The cam is designed to rotate through different angular displacements at different phases of operation - a larger rotation during the energy transfer phase to boost projectile speed, and a controlled return phase that reduces dynamic forces. This parameter variation resolves the contradiction between achieving high speed and managing dynamic forces.
2Force
If the degree of rotation of the cam is increased to store more potential energy in the limbs, then the force at which the projectile is launched is improved, but the design constraints on the projectile launcher are heightened
Solution Approach 1:
The dynamic cam profile allows the mechanism to achieve high launch forces through optimized energy transfer during the power stroke, while the controlled return path reduces the complexity requirements for structural components. By dynamically adjusting the cam rotation, the system maximizes force delivery without requiring proportionally stronger and more complex supporting structures throughout the entire mechanism.
Solution Approach 2:
The cam mechanism is designed to perform preliminary energy storage in the limbs through controlled flexing during the rotation phase, then releases this energy in an optimized manner during the power stroke. This preliminary action allows the system to build up the necessary potential energy without immediately requiring the full structural strength needed for direct force application, thereby reducing design constraints on the overall launcher structure.
3Use of energy by moving object
If the degree of rotation of the cam is increased to store more potential energy in the limbs, then the energy stored in the limbs is improved, but the accuracy characteristics of the projectile launcher are adversely affected
Solution Approach 1:
The dynamic cam profile ensures that the increased cam rotation and associated energy storage in the limbs occur in a controlled and repeatable manner. By optimizing the rotation profile, the system achieves consistent energy transfer to the projectile while maintaining stable firing conditions. This dynamic control prevents the accuracy degradation that would normally result from higher energy storage, as the cam returns to the same operational parameters with each cycle.
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 crossbow achieves enhanced projectile speed and force while maintaining accuracy and reducing dynamic forces, thereby overcoming design constraints.
Implementation Method 1
a spool including a first recess configured to receive the tether and a second recess configured to receive the cord, the spool configured to rotate in (i) a first direction to unwind the tether therefrom and wind the cord thereon and (ii) a second direction to wind the tether thereon and unwind the cord therefrom
Implementation Method 2
a one-way bearing coupled with the spool and configured to selectively inhibit rotation of the spool in the first direction and permit rotation of the spool in the second direction
Implementation Method 3
a brake configured to selectively engage with the one-way bearing. When the brake is engaged with the one-way bearing, the brake inhibits rotation of the one-way bearing with the spool such that rotation of the spool in the first direction is inhibited
Implementation Method 4
During operation of the crossbow, as the spool rotates in the first direction, the cord pulls the trigger box toward a front end of the crossbow
Data Source
AI summary
A crossbow includes a draw string configured to move between a released position and a drawn position, a trigger box configured to selectively retain the draw string, and a cocking mechanism configured to move the trigger box and move the draw string between the released position and the drawn position. The cocking mechanism includes a tether a cord coupled with a front end of the trigger box, and a spool including a first recess configured to receive the tether and a second recess configured to receive the cord, the spool configured to rotate in a first direction to unwind the tether therefrom and wind the cord thereon and a second direction to wind the tether thereon and unwind the cord therefrom. During operation of the crossbow, as the spool rotates in the first direction, the cord pulls the trigger box in a direction towards a front end of the crossbow.