Bow Cam System for Cable Replacement and Draw Load
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Solution Overview
Problem
Conventional bows, such as those with compound designs, face challenges in reducing the burden on archers due to the need to bend limbs or high cable pulling loads, making it difficult to replace cables and maintain efficiency in energy conversion.
Innovation Solution
A bow design featuring rotatable string cams and cams with differing diameters to elastically deform separate cables, reducing the force required for drawing and allowing easy cable replacement by decoupling the cables from the string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the small diameter pulley and large diameter pulley are arranged in sequence in the axial direction, then the cable can be wound to achieve elastic deformation, but the cable replacement becomes difficult due to crossing between pulleys
Solution Approach 1:
The bow is divided into two independent sides (left and right), with each side having its own set of pulleys (small diameter pulley and large diameter pulley). This segmentation allows the cable on one side to be replaced independently without affecting the other side, solving the cable replacement difficulty caused by the crossing arrangement.
2Ease of operation
If cylindrical or disc-like cams are used, then the cable can be wound effectively, but the pulling load increases with drawing distance
Solution Approach 1:
The pulley system is designed to dynamically change the mechanical advantage during the drawing process. As the archer draws the string, the pulleys rotate and the cable gradually unwinds from the large diameter pulley and winds onto the small diameter pulley, continuously adjusting the leverage ratio to maintain more consistent pulling load throughout the drawing distance.
Solution Approach 2:
The system changes the effective radius parameter during operation by transitioning cable contact between pulleys of different diameters. This parameter change allows the mechanical advantage to be optimized at different stages of the draw, reducing the peak load the archer must exert while maintaining effective energy transfer.
3Reliability
If the cable is wound between large and small diameter pulleys, then elastic deformation is achieved for arrow propulsion, but the cable crossing complicates maintenance
Solution Approach 1:
The cable system is segmented into independent loops on each side of the bow. Each side's cable can be accessed, removed, and replaced independently without disturbing the other side's cable routing or pulley arrangement, significantly simplifying maintenance despite the complex-sounding pulley configuration.
Solution Approach 2:
The cable can be extracted from the pulley system by reversing the winding process. By pulling the cable end and rotating the pulleys in reverse, the cable is gradually unwound from both pulleys and can be removed for replacement, making maintenance feasible despite the crossed arrangement.
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 design reduces the archer's burden by efficiently converting string pulling force into cable deformation energy, maintaining high power conversion efficiency while enabling easy cable replacement, thus improving maintainability.
Implementation Method 1
the cable is pulled and elastically deformed at a portion tensed between the small diameter pulley of one end and the large diameter pulley of the other end and at a portion tensed between the large diameter pulley of one end and the small diameter pulley of the other end. As a result, the arrow is shot by the elastomeric force caused by the elastomeric deformation of the cable.
Data Source
AI summary
A bow includes: a bow body; a first string cam provided on one end of the bow body to be rotatable, one end of a string being fixed to the first string cam; a first small diameter cam rotated with the first string cam, one end of a cable being wound on the first small diameter cam; a first large diameter cam rotated with the first string cam, one end of a cable being wound on the first large diameter cam; a second string cam provided on the other end of the bow body to be rotatable, the other end of the string being fixed to the second string cam; a second small diameter cam rotated with the second string cam, the other end of the cable being wound on the second small diameter cam; and a second large diameter cam rotated with the second string cam, the other end of the cable being wound on the second large diameter cam.