Fixed-Anchor Crossbow Draw String for Lower Dynamic Forces
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Solution Overview
Problem
Existing projectile launchers face design constraints due to heightened dynamic forces during operation, limiting the maximum force and speed of projectile launch without adversely affecting accuracy or dimensions.
Innovation Solution
A crossbow design featuring a frame with flexible limbs, pulley assemblies, and a draw string configuration that reduces dynamic forces by utilizing pulleys and columns to manage limb flexion and energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
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:
A draw string guide is introduced as an intermediary component between the draw string and the cam. This guide redirects the draw string to contact the cam at an optimized location, allowing the system to achieve high projectile launch forces while reducing the dynamic forces transmitted to other components during operation
Solution Approach 2:
The patent changes the geometric parameters of the cam and draw string routing to optimize the location where the draw string contacts the cam. By adjusting these parameters, the system achieves more favorable force distribution that reduces peak dynamic forces on components while maintaining high potential energy storage in the limbs
2Speed
If the degree of rotation of the cam is increased to store more potential energy in the limbs, then the projectile speed is improved, but the accuracy characteristics of the projectile launcher are adversely affected
Solution Approach 1:
The draw string guide acts as a mediator that ensures consistent and accurate draw string routing during the cocking process. This intermediary component maintains precise geometric relationships between moving parts, allowing increased cam rotation for higher projectile speed while preserving accuracy characteristics
3Power
If the degree of rotation of the cam is increased to store more potential energy in the limbs, then the projectile launch force is improved, but the dimensions of the projectile launcher are adversely affected
Solution Approach 1:
The draw string guide enables more efficient force transmission through optimized routing, allowing the system to achieve high projectile launch forces with reduced cam rotation. This intermediary component effectively decouples the relationship between cam rotation angle and launch force, enabling compact launcher dimensions
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 achieves increased projectile speed and force while maintaining accuracy and reducing dynamic forces, enhancing overall performance.
Implementation Method 1
The crossbow includes a first pulley assembly and a second pulley assembly. The first pulley assembly is coupled to the second end of the first flexible limb and includes a first pulley. The second pulley assembly is coupled to the second end of the second flexible limb and includes a second pulley.
Implementation Method 2
a first flexible limb including a first end and a second end, where the first end is coupled to the frame, and a second flexible limb including a first end and a second end, where the first end is coupled to the frame
Data Source
AI summary
A crossbow includes a frame, a first flexible limb, and a second flexible limb. The first flexible limb includes a first end and a second end, the first end coupled to the frame. The second flexible limb includes a first end and a second end, the first end coupled to the frame. A first pulley assembly is coupled to the second end of the first flexible limb and includes a first pulley. A second pulley assembly is coupled to the second end of the second flexible limb and includes a second pulley. A draw string is engaged with the first pulley and the second pulley, the draw string configured to move between a released position and a drawn position. The draw string includes a first loop coupled to a first attachment point on the frame; and a second loop coupled to a second attachment point on the frame.