Variable-Diameter Twisted String Transmission for Wear Reduction
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Solution Overview
Problem
Twisted string transmissions in robotics experience wear and failure at attachment points and splits due to stress concentrations and abrasion, leading to reduced lifespan, and increasing string diameter requires more torque or gear reduction, increasing costs.
Innovation Solution
A twisted string transmission with a variable diameter string, where specific portions, especially at the motor, load, or split, have a larger diameter to reduce abrasion, achieved by using different diameter threads united through knots, braiding, or integrated fibers, to prolong lifespan without increasing overall torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the string diameter is increased to reduce wear and extend lifespan, then the string lifetime is improved, but more torque is required which increases motor size or requires gear reduction, increasing cost
Solution Approach 1:
The string is designed with variable diameter along its length, featuring larger diameter sections at high-wear locations (attachment points and split areas) and smaller diameter in intermediate sections. This local quality variation allows the string to resist wear where needed most without requiring a uniformly large diameter throughout, thereby extending lifespan without proportionally increasing torque requirements across the entire string length.
2Reliability
If a larger diameter string is used to reduce abrasion, then the string lifetime is improved, but the device complexity increases due to larger motors or gear reductions
Solution Approach 1:
Instead of using a uniformly large diameter string that would require larger motors or gear reductions, the invention applies local quality by varying the string diameter along its length. The larger diameter is localized only to portions experiencing high abrasion (attachment points and split areas), while intermediate portions maintain smaller diameter. This reduces the overall torque requirement and eliminates the need for additional motor size or gear reduction mechanisms, thereby maintaining device simplicity while improving durability.
3Object-affected harmful factors
If the string diameter is increased to reduce wear, then the abrasion resistance is improved, but the weight of the string increases
Solution Approach 1:
The variable diameter string design applies local quality by concentrating larger diameter sections only at high-wear locations (attachment points and split areas) where abrasion resistance is most needed. Intermediate sections maintain smaller diameter, reducing unnecessary material usage. This localized approach provides enhanced abrasion resistance where required while minimizing overall string weight compared to a uniformly large diameter string.
Data Source
AI summary
A twisted string transmission for converting a rotational motion to a linear motion is provided, comprising a motor (1) and a string (2) to be connectable to a load (3). The string (2) has a variable diameter along its length.