Segmented Bow Cam With Flat Cable Journals for Reduced Cable Wear
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Solution Overview
Problem
Existing archery bows suffer from issues such as cam lean, excessive cable wear, and inefficient mechanical draw-force characteristics due to the use of helical cable journals, which cause premature cable failure and difficult timing adjustments.
Innovation Solution
A self-timing cam configuration with five stacked journals sharing a common axis, featuring flat power cable journals and smooth transition zones, allowing cables to slideably engage with cams without radial extensions, reducing wear and enabling desirable mechanical draw-force characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If helical cable journals are used, then cable wrapping capability is improved, but cable wear increases and cable longevity decreases
Solution Approach 1:
The cable journal is divided into multiple flat segments stacked along the cam axis, each segment providing a flat surface for cable contact. This segmentation eliminates the continuous helical groove that causes angular pressures and friction, while still providing sufficient wrapping surface area through the stacked segments.
Solution Approach 2:
Instead of using a traditional helical groove that forces the cable to climb at an angle, the patent inverts the approach by using flat journal surfaces that allow the cable to wrap parallel to the cam axis. This reversal of the wrapping geometry eliminates angular pressures and significantly reduces cable wear.
2Stability of the object's composition
If cables are routed off-angle to avoid interfering with arrow flight, then cable-cam contact is improved, but cam lean increases due to twisting and torque
Solution Approach 1:
The patent moves the cable wrapping action from a radial dimension (helical groove around the cam circumference) to an axial dimension (flat surfaces stacked along the cam axis). This dimensional change allows cables to wrap without creating torque on the cam axle, eliminating cam lean while maintaining proper cable-cam contact.
3Ease of operation
If separate cables are confined to helical tracks above and below the string track, then cable routing control is improved, but timing adjustment difficulty increases
Solution Approach 1:
The flat cable journals serve multiple functions: they provide cable wrapping surfaces, enable smooth cable transition between segments, and allow for self-timing through the natural interaction of cables with the flat surfaces. This multi-functionality simplifies the overall system compared to complex helical track arrangements requiring precise timing adjustments.
4Reliability
If helical cable journals with radial extensions are used, then cable retention is improved, but friction and wear on cables increase
Solution Approach 1:
The patent applies different surface qualities to different parts of the cable journal: the top and bottom surfaces of each flat segment provide high-friction cable contact surfaces for retention, while the sides of the segments provide smooth transition surfaces with low friction. This local differentiation of surface properties optimizes both cable retention and reduced wear.
Data Source
AI summary
A cam for an archery bow having flat segmented power cable tracks or journals. The cam preferably includes five stacked journals sharing a common axis. The middle journal receivable for a bowstring with opposing mirrored and segmented cable journals above and below the bowstring journal plane. Alternately, the cam having three stacked journals; a bowstring journal and two segmented cable journals. A bowstring and cable(s) interact with the cam(s) and other components to fire a projectile, such as an arrow.