Self-Timing Cam and Cable Configuration for Archery Bows
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Solution Overview
Problem
Existing archery bows and crossbows face issues with cam lean and inefficient cable timing due to cable interference, leading to twisting and torque in the cam axle, which limits the potential for low limb tip movement and arrow speed.
Innovation Solution
A self-timing cam and cable configuration where both ends of each cable are anchored to the same cam, allowing the cables to slide relative to pulleys and rotate 360 degrees, eliminating cam lean and enabling efficient energy storage and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cables are connected to opposing cams and cross the centerline to achieve binary cam system efficiency, then energy transfer efficiency is improved, but cam lean and twisting torque in the cam axle increase
Solution Approach 1:
The patent extracts the cables from the centerline area by routing them along the limb extensions, removing the source of interference and torque while preserving the binary cam system's energy transfer efficiency
Solution Approach 2:
The cable arrangement moves from a two-dimensional plane crossing the centerline to a three-dimensional configuration that follows the limb extensions, eliminating interference with the string flight path and reducing cam axle torque
2Object-generated harmful factors
If cables are routed to avoid crossing the centerline to reduce cam lean, then cam lean and torque are reduced, but cable timing precision and energy transfer efficiency deteriorate
Solution Approach 1:
The cable arrangement serves itself by using the limb extensions as natural routing paths, achieving proper timing and tensioning without requiring complex adjustment mechanisms or precise manual alignment
Solution Approach 2:
The limb extensions serve dual functions: structural support for the cams and guides for the cables, simplifying the overall system while maintaining timing precision
3Speed
If cable take-up track perimeter is reduced to achieve lower limb tip movement, then arrow speed is improved, but cam rotation angle and cable wrapping capability are limited
Solution Approach 1:
The cam system transitions from static cable routing to dynamic cable wrapping around the limb extensions, allowing the cable take-up track perimeter to be effectively extended without increasing the physical cam size
Solution Approach 2:
The cable wraps around the limb extensions which are themselves extensions of the cam structure, creating a nested configuration that increases the effective cable path length while maintaining compact overall 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
This configuration ensures precise timing and reduced cam lean, allowing for faster cam rotation and increased arrow speed without the limitations of traditional cable arrangements, achieving lower limb tip movement and improved performance.
Implementation Method 1
allows a portion of first and/or second cables to be slide-ably engaged to a first and second pulley
Implementation Method 2
both ends of each cable are anchored to the same cam
Implementation Method 3
The present invention may alternately use components other than flexible limbs for storing energy prior to launching the projectile
Data Source
AI summary
A projectile launching device includes self-timing without cam lean. The projectile launching device may include a frame, energy storing components, (such as two limbs), two cams, a launch string, and at least two cables. The ends of the launch string are attached to the two cams. Opposing ends of first and second cables are coupled to the first and second cams. A mid-portion of the first and second cables are slide-ably engaged with the first and second cable pulleys, respectively. The two cams are built as mirror images of each other, each cam having a cable payout track, a bowstring track, and a cable take-up track.