Archery Bow Pulley Elastomeric Ring Friction
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Solution Overview
Problem
Compound archery bows with rotating cam assemblies experience slippage between the bowstring and pulley, leading to reduced arrow speed due to inadequate engagement, as traditional designs fail to maintain consistent contact during firing.
Innovation Solution
Enhancing the engagement between the bowstring and pulley by applying surface texturing, using high friction materials, and incorporating elastomeric elements such as rings or coatings to increase friction and maintain consistent contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional smooth pulley surfaces are used, then the device complexity is low, but the bowstring slips during firing resulting in reduced arrow speed
Solution Approach 1:
The patent applies surface texturing to specific localized areas of the pulley where the bowstring contacts, rather than modifying the entire pulley surface. This creates high-friction zones exactly where needed to prevent slippage, while maintaining the simplicity of the overall pulley design. The textured regions provide reliable engagement during the critical firing moment without requiring complex modifications throughout the entire component.
Solution Approach 2:
The patent changes the surface friction parameter of the pulley by applying elastomeric materials or surface texturing. This modifies the coefficient of friction between the pulley and bowstring, transforming the interaction from low-friction slippage to high-friction reliable engagement. The material or surface properties are altered to optimize the friction parameter specifically at the contact interface, enabling consistent energy transfer during firing.
2Reliability
If high friction materials or surface texturing are applied to the pulley, then the engagement between bowstring and pulley is improved, but the manufacturing complexity increases
Solution Approach 1:
Instead of treating the entire pulley surface with complex high-friction materials, the patent applies texturing or elastomeric coatings only to the specific regions where the bowstring contacts the pulley. This localized approach maintains manufacturing simplicity while achieving the reliability improvement, as only small portions of the pulley require modification rather than the entire component.
3Loss of energy
If smooth surfaces are used between bowstring and pulley, then the manufacturing is simple, but energy transfer efficiency is reduced due to slippage
Solution Approach 1:
The patent modifies the friction parameter at the bowstring-pulley interface by applying surface texturing or elastomeric materials. This changes the physical interaction from low-friction slippage (which causes energy loss) to high-friction reliable engagement (which improves energy transfer). The parameter change is achieved through material or surface modification rather than complex mechanical structures, maintaining simplicity while reducing energy loss.
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
Improves arrow speed by ensuring higher frictional engagement between the bowstring and pulley, resulting in more efficient energy transfer and consistent performance.
Implementation Method 1
A ring comprising an elastomeric material is positioned in the peripheral groove. The string segment contacts the ring.
Implementation Method 2
A second rotatable member, which comprises a pulley comprising a peripheral groove comprising surface texturing.
Data Source
AI summary
In some embodiments, an archery bow comprises a riser, a first limb and a second limb. The first limb supports a first rotatable member, which comprises a cam. The second limb supports a second rotatable member, which comprises a pulley comprising a peripheral groove. A ring comprising an elastomeric material is positioned in the peripheral groove. A power cable is arranged to be taken up on the cam as the bow is drawn. A string segment is arranged to wrap around the pulley. The string segment contacts the ring.