Bow String Guide System With Helical Take-Up Journal
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Solution Overview
Problem
Conventional bow designs are limited by the rotation of cams and pulleys, restricting the power stroke due to the size of power cables, which limits the rotation of string guides to about 270 degrees, thereby reducing the length of the power stroke.
Innovation Solution
A string guide system that allows for greater rotation of string guides by using power cables with wider take-up journals and helical journals, enabling the power cables to wrap around and translate away from the draw string journals, allowing for more than 360 degrees of rotation without increasing the diameter of the pulleys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the diameter of pulleys is increased to allow greater rotation, then the power stroke length is improved, but the bow size becomes larger and less usable
Solution Approach 1:
The power cable take-up journal is designed with a width (dimension along the axis of rotation) at least twice the width of the power cable, allowing the cable to wrap around and translate away from the draw string journal in a different spatial dimension. This enables greater than 360 degrees rotation without increasing pulley diameter, thus extending power stroke length without increasing bow size.
2Duration of action of moving object
If the power cables are made wider to increase rotation, then the power stroke is extended, but the bow becomes larger and less manageable
Solution Approach 1:
The helical journal configuration allows the power cable to translate along the axis of rotation rather than requiring a larger radial dimension. This enables extended power stroke duration through greater rotation while maintaining a compact bow size that remains easy to operate and manage.
3Volume of stationary object
If the rotation of string guides is limited to about 270 degrees by power cable constraints, then the bow remains compact, but the power stroke length is reduced
Solution Approach 1:
By designing the power cable take-up journal with sufficient width and implementing the helical journal configuration, the system allows the power cable to utilize the axial dimension for translation. This enables the string guides to rotate more than 360 degrees, extending the power stroke length while keeping the bow compact through efficient use of three-dimensional space.
Data Source
AI summary
A string guide for a bow having a reverse draw configuration with a draw string located adjacent a down-range side of the bow in a released configuration. First and second string guides rotate around first and second axes, respectively, as the draw string is displaced from the released configuration to the drawn configuration. A first power cable take-up journal on the first string guide rotates around the first axis to take up a power cable. The first power cable take-up journal includes a width measured along the first axis at least twice a width of the first power cable. The first power cable is biased away from at least the draw string. The first power cable is translated along the first power cable take-up journal as the bow is drawn from the released configuration to the drawn configuration.