Variable-Diameter Twisted String Transmission for Longer Service Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Twisted string transmissions in robotics experience wear and failure due to stress concentrations and abrasion at attachment points and splits, 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 along its length, with larger diameters at high-abrasion areas such as the motor and load connections or splits, using multiple threads or varying thread thickness to distribute wear more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the string diameter is increased to reduce wear and extend lifetime, then the string lifetime is improved, but more torque is required which increases motor size or requires gear reduction, increasing cost and device complexity
Solution Approach 1:
The string is designed with variable diameter along its length, having larger diameter at high-wear areas (attachment points and splits) and smaller diameter in middle sections. This local differentiation allows the string to withstand higher stress and abrasion at critical points without requiring a uniformly large diameter throughout, thus extending lifetime without proportionally increasing torque requirements or motor size.
2Duration of action of stationary object
If the string diameter is increased to reduce wear, then the string lifetime is improved, but the cost increases due to larger motors or gear reductions
Solution Approach 1:
By concentrating the larger diameter only at critical high-wear locations rather than throughout the entire string length, the amount of material required is reduced compared to a uniformly thick string. This localized approach extends string lifetime where it matters most while minimizing material costs and avoiding the need for larger motors or gear reductions.
3Device complexity
If a uniform diameter string is used, then the device complexity is low, but stress concentrations at attachment points and splits cause premature failure
Solution Approach 1:
The string features a non-uniform diameter profile with enlarged sections at attachment points and splits where stress concentrations occur. This local reinforcement at critical locations distributes stress more effectively and reduces wear at these vulnerable points, significantly improving string reliability and preventing premature failure while maintaining relatively simple overall structure.
Data Source
Figure 1a~2f
Figure 3a~3b
Figure 4a~4b
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.