Self-Timing Cam and Cable Configuration for Crossbow Launching
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Solution Overview
Problem
Existing archery bows face issues with cam lean and timing due to cable interference, leading to inefficiencies and complex adjustment processes, particularly in binary cam systems where cables often cross and create torque.
Innovation Solution
A self-timing cam and cable configuration where neither end of the cable is anchored to the cam, with cables slidably engaged to transitional portals, allowing them to self-center and eliminate cam lean, using a harness system with first and second cams, and a launch string that winds into upper and lower cable tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If cables are anchored to cams in traditional binary cam systems, then cable control and power transmission are achieved, but cam lean and torque are created due to cable crossing and off-angle positioning
Solution Approach 1:
The patent removes the traditional cable anchoring to cam axles and replaces it with cable posts positioned away from the cam rotation axis. This extraction of the cable attachment point from the cam structure eliminates the off-angle cable configuration that causes cam lean and torque, while still allowing the cables to function in the binary cam system.
Solution Approach 2:
The patent introduces cable posts as intermediary elements between the cables and the cam system. These posts serve as new attachment points that are not part of the cam structure itself, allowing cables to be anchored at optimal positions that eliminate harmful cam lean while maintaining power transmission efficiency.
2Object-affected harmful factors
If cables are kept from interfering with arrow flight by being off-angle, then cable clearance is achieved, but twisting and torque are created in cam axles
Solution Approach 1:
The patent extracts cable attachment from the cam axle area by using separate cable posts. This allows cables to be positioned at angles that clear the arrow flight path without creating off-angle tension on the cam axles, thereby eliminating both cable interference and cam axle twisting simultaneously.
3Reliability
If traditional cable anchoring methods are used, then cable timing can be maintained, but complex adjustment processes are required when cables are not of exact length or stretch differently
Solution Approach 1:
The patent implements self-timing functionality where the cable posts and cam configuration automatically maintain proper cable timing during operation. The system self-adjusts to accommodate cable length variations and differential stretching without requiring user intervention, making the device easier to operate while maintaining reliable timing.
Data Source
AI summary
A projectile launching device includes self-timing without cam lean. The projectile launching device may include a rail, a riser, two energy storing components, (such as two limbs), two cams, a launch string, and at least one cable. The ends of the launch string are attached to the two cams. Opposing ends of first and second cables may be coupled to the rail or riser. A mid-portion of the first and second cables are slideably engaged with the first and second cams, respectively. Alternatively, a single cable may replace the first and second cables. 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.