Self-Timing Cam and Cable Configuration for Archery Devices
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Solution Overview
Problem
Existing archery and crossbow systems face issues with cam lean, assembly complexity, and energy inefficiency due to cable misalignment and interference, leading to unwanted rotational movement and timing problems.
Innovation Solution
A self-timing cam and cable configuration where both ends of each cable are anchored to the same cam, with a mid-portion sliding on a pulley, allowing the cams to rotate 200-360 degrees without crossing the centerline, and utilizing strategically placed stops to prevent counter-rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cables are connected to opposing cams with crossing arrangement, then binary cam system efficiency is improved, but cam lean and unwanted rotational movement occur
Solution Approach 1:
Instead of connecting cable ends to opposing cams (conventional approach), both ends of each cable are anchored to the same cam. This inverted configuration eliminates cam lean and unwanted rotational movement while maintaining timing synchronization through the self-timing mechanism where cables slide on pulleys during cam rotation.
Solution Approach 2:
The cable crossing arrangement that causes interference and cam lean is removed. Cables are reconfigured to run parallel to the line drawn from first cam axle to second cam axle, extracting the harmful crossing geometry while preserving the functional relationship between cams and cables.
2Object-affected harmful factors
If cables are kept off-angle to avoid interfering with arrow flight, then cable interference is reduced, but twisting and torque in cam axle increases
Solution Approach 1:
The patent converts the potential harm of cable positioning into a benefit by establishing that cables should be parallel to the line drawn from first cam axle to second cam axle. This configuration simultaneously prevents cable interference with arrow flight and eliminates twisting and torque in the cam axle, transforming the design constraint into an optimal solution.
3Productivity
If cams rotate more than 180 degrees, then projectile launching capability is improved, but cable stacking and interference occur
Solution Approach 1:
The patent resolves the cable stacking problem by changing the spatial arrangement from a two-dimensional planar configuration to a three-dimensional configuration where cables pass through portals in the cams. This dimensional change allows cams to rotate 200-360 degrees without cable interference, enabling full rotation capability while maintaining cable organization.
4Manufacturing precision
If cable length variations occur, then timing synchronization between cables becomes difficult, but manual adjustment time increases
Solution Approach 1:
The patent implements a self-timing mechanism where cables with varying lengths automatically synchronize through sliding engagement on pulleys during cam rotation. The system self-adjusts timing without manual intervention, converting a precision-critical manual adjustment task into an automatic self-regulating process.
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 minimizes parasitic energy loss, reduces cam lean, and ensures precise timing, enhancing the efficiency and reliability of the projectile launching device by maintaining cable alignment and preventing unwanted cam rotation.
Implementation Method 1
a mid-portion of first and second cables partially wrap a first and second cable pulley, respectively... allows the device to have self-timing
Implementation Method 2
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 preferably includes a rail, a riser, two 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-segment of the first and second cables are slidably engaged with the first and second cable pulleys, respectively. The two cams are preferably built as mirror images of each other at a centerline of the rail. The two cams include a launch string track, having identical, but mirrored, upper and lower cable tracks. A stop is formed on each cam to prevent the cam from being able to rotate in a direction opposite the direction of drawing, when the bow is at rest.