Crossbow Cocking System Power Stroke Extension
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Solution Overview
Problem
Conventional crossbows have limited power stroke due to the design of string guides and power cables, which restrict the rotation of cams to about 270 degrees, limiting the kinetic energy that can be generated without increasing the size of pulleys, resulting in a larger and less usable bow.
Innovation Solution
A cocking system for a crossbow that includes a string carrier with a catch and a cocking rope mechanism, allowing the draw string to be retracted to a drawn configuration, with a retaining mechanism to maintain the string in this position, enabling a longer power stroke and increased kinetic energy generation without enlarging the bow components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power cables are used to synchronize rotation of the cams, then the mechanical advantage is increased, but the rotation of the cams is limited to about 270 degrees, reducing the power stroke length
Solution Approach 1:
The patent removes the power cable synchronization mechanism from the system. Instead of using power cables to connect and synchronize the cams, the invention allows the cams to rotate independently, eliminating the 270-degree rotation limitation imposed by the power cable arrangement.
Solution Approach 2:
The invention transitions from a static cable-based synchronization system to a dynamic independent rotation system. The cams are free to rotate through greater than 270 degrees without cable constraints, allowing the power stroke to extend further while maintaining mechanical advantage through the cam profile design.
2Length of moving object
If the diameter of the pulleys is increased to increase the length of the power stroke, then the power stroke length is increased, but the bow becomes larger and less usable
Solution Approach 1:
The invention uses dynamic cam rotation through greater than 270 degrees to achieve a longer power stroke without increasing pulley diameter. The cams are designed with specific profiles that provide the necessary mechanical advantage throughout the extended rotation range, allowing increased power stroke length while maintaining a compact bow size.
3Length of moving object
If the draw string is positioned on the down-range side of the string guides, then the power stroke is increased, but the cam rotation is limited by power cables
Solution Approach 1:
The invention extracts the power cable synchronization mechanism that limits cam rotation. By removing this constraint, the draw string can be positioned on the down-range side of the string guides to achieve a longer power stroke, with the cams rotating independently through greater than 270 degrees without cable interference.
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 system extends the power stroke by at least 25% and generates kinetic energy of over 125 ft.-lbs. with a power stroke of 10 to 15 inches, allowing for more efficient energy storage and accuracy in crossbow operations.
Implementation Method 1
A cocking system for a crossbow that includes a string carrier with a catch and a cocking rope mechanism, allowing the draw string to be retracted to a drawn configuration
Implementation Method 2
A retaining mechanism retains the string carrier in the retracted position and the draw string in the drawn configuration independent of the cocking ropes
Implementation Method 3
The system extends the power stroke by at least 25% and generates kinetic energy of over 125 ft.-lbs. with a power stroke of 10 to 15 inches
Data Source
AI summary
A cocking system for a crossbow. A string carrier slides along the center rail during movement with the draw string in the released configuration to a retracted position that locates the draw string in the drawn configuration. A trigger is positioned to move the catch from the closed position and the open position to fire the crossbow when the string carrier is in the retracted position. At least one cocking rope is configured to engage with the string carrier to retract the string carrier and the draw string to the drawn configuration. A retaining mechanism retains the string carrier in the retracted position and the draw string in the drawn configuration independent of the cocking ropes.