Eccentric Power Cable Let-Out Mechanism for Compound Archery Bows
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Solution Overview
Problem
In compound archery bows, the direct connection of power cables to bow limbs can lead to interference and inefficient energy transfer, potentially resulting in a 'cocked' bow scenario where the draw force is completely let off, making it difficult to shoot the arrow without mechanical assistance.
Innovation Solution
The implementation of an eccentric let-out mechanism for the power cable, where one end is taken up and the other end is let out, using paired let-out members on opposite sides of the bow limb, either in a split cable or yoke arrangement, to manage the tension and prevent 100% let-off by controlling the lever arm ratios and rotation limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If power cable is directly connected to bow limb, then结构简单性 (structural simplicity) is improved, but 能量传递效率 (energy transfer efficiency) deteriorates and 可靠性 (reliability) worsens due to interference and potential 100% let-off
Solution Approach 1:
An eccentric let-out mechanism is introduced as an intermediary component between the power cable and the bow limb. This mechanism includes an eccentric wheel that rotates on the bow limb, with the power cable wrapped around it. The eccentric design allows the cable to be let out in a controlled manner, preventing direct interference with the bow limb while maintaining energy transfer efficiency and avoiding 100% let-off conditions.
2Ease of manufacture
If power cable is directly connected to bow limb, then制造成本 (manufacturing cost) is reduced, but 可靠性 (reliability) deteriorates due to potential cocked bow scenario requiring mechanical assistance
Solution Approach 1:
The eccentric let-out mechanism serves as a reliable intermediary that prevents the cocked bow scenario. By controlling the cable release through the eccentric wheel's rotation, the system ensures that the bow never reaches a 100% let-off state, thereby maintaining reliability without significantly increasing manufacturing complexity or cost.
3Loss of energy
If eccentric let-out mechanism is implemented, then 能量传递效率 (energy transfer efficiency) is improved, but 装置复杂性 (device complexity) increases
Solution Approach 1:
The eccentric wheel is designed with an asymmetric geometry where the cable attachment point is offset from the rotation center. This asymmetric design allows the mechanism to achieve controlled cable release and improved energy transfer efficiency through the varying lever arm during rotation, while maintaining a relatively simple overall structure that does not significantly increase device complexity.
4Reliability
If eccentric let-out mechanism is implemented, then 可靠性 (reliability) is improved by preventing cocked bow, but 装置复杂性 (device complexity) increases
Solution Approach 1:
The asymmetric eccentric wheel design provides inherent mechanical control over the cable release process. The varying radius from the rotation center to the cable attachment point creates a natural mechanical advantage that prevents the bow from reaching a cocked state, thereby improving reliability through a simple geometric modification rather than a complex control system.
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 solution ensures efficient energy transfer and prevents the bow from becoming 'cocked,' allowing for proper arrow shooting by maintaining draw force throughout the drawing process, avoiding the need for mechanical assistance to reset the bow.
Implementation Method 1
The power cable let-out mechanism comprises an eccentric wheel (357b) rotatably connected to the second bow limb (311b) and having a cable attachment point (357b) spaced radially from a rotation center of the eccentric wheel (357b)
Implementation Method 2
Tension developed as the bow is drawn and the power cable is taken up causes deformation of the bow limbs and storage of potential energy therein. A portion of that potential energy is transformed into the kinetic energy of the arrow shot by the bow.
Data Source
AI summary
A compound archery bow comprises a riser and two limbs extending therefrom; first and second pulley members on the corresponding limbs; a draw cable, and a power cable. The pulley members include corresponding draw cable journals, and the draw cable is engaged to be let out from them and to rotate the pulley members as the bow is drawn. The first and second pulley members further include power cable take-up and let-out mechanisms, respectively. The power cable is engaged to be taken up by the power cable take-up mechanism and to be let out by the power cable let-out mechanism as the bow is drawn and the pulley members rotate. The power cable let-out mechanism comprises paired let-out members disposed on opposite sides of the second bow limb, and the power cable is engaged with the let-out members in a split cable arrangement or a yoke arrangement.