Multi-piece Tolerance Ring with Opposing Gaps for Concentricity
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Solution Overview
Problem
Tolerance rings used in robot joints exhibit performance variability due to uneven stiffness, particularly with waves nearest to the gap being the weakest, leading to resonance and alignment issues, which can be exacerbated by optimizing one performance parameter at the expense of others, compromising overall performance.
Innovation Solution
A multi-piece tolerance ring design with gaps extending along its length, balancing force differentials by locating opposing gaps to achieve balanced stiffness, thereby reducing load imbalances and enhancing concentricity between the drive shaft and the bore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-gap tolerance ring design is used, then manufacturing and assembly are simplified, but stiffness is uneven causing resonance and alignment issues
Solution Approach 1:
The tolerance ring is divided into multiple segments separated by gaps positioned at specific locations. This segmentation creates multiple independent regions that can flex independently, balancing the stiffness distribution around the ring circumference while maintaining manufacturing simplicity through standardized segment construction.
2Reliability
If gaps are positioned to optimize one performance parameter, then that parameter improves, but other parameters deteriorate
Solution Approach 1:
The gaps are positioned asymmetrically at specific angular intervals rather than uniformly distributed. This asymmetric positioning optimizes concentricity by compensating for stiffness variations in critical regions while maintaining manageable complexity through a limited number of strategically placed gaps rather than continuous adjustment.
3Strength
If the tolerance ring uses a continuous structure, then structural integrity is high, but it cannot compensate for dimensional variations and thermal expansion
Solution Approach 1:
The tolerance ring employs a thin-walled flexible structure with strategic gaps that allow controlled deformation. The thin walls provide sufficient structural integrity while enabling the ring to flex and adapt to dimensional variations, thermal expansion, and assembly tolerances through elastic deformation of the segments between gaps.
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
The multi-piece tolerance ring provides improved concentricity and reduced load imbalances, increasing the lifespan of servomotors and maintaining precise rotation, as demonstrated by significant reductions in concentricity measurements and improved performance across multiple tests.
Implementation Method 1
A tolerance ring, generally comprises a strip of resilient material, for example a metal such as spring steel
Implementation Method 2
the protrusions can be compressed. Each protrusion can act as a spring and to exert a radial force against the shaft and the surface of the bore
Data Source
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AI summary
A tolerance ring can include a generally cylindrical body having a first partial-cylindrical sidewall and a second partial-cylindrical sidewall opposite the first partial-cylindrical sidewall. Each partial-cylindrical sidewall defines a first end and a second end. Further, a first gap can be established between the first end of the first partial-cylindrical sidewall and the first end of the second partial- cylindrical sidewall after installation around a post. The first gap can extend along the entire length of the tolerance ring such that a split is formed in the tolerance ring. The tolerance ring can also include a second gap between the second end of the first partial-cylindrical sidewall and the second end of the second partial-cylindrical sidewall. The second gap can extend along the entire length of the tolerance ring such that a split is formed in the tolerance ring. The tolerance ring can provide an installed concentricity, C, ? 50 ?m.