S-Shaped Plane Torsion Spring for Precise Series-Elastic Actuation
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Solution Overview
Problem
Existing plane torsion springs for series-elastic actuators face challenges in achieving improved strength, reproducible deflection, and cost-effectiveness, while also dealing with mechanical stress distribution and hysteresis issues.
Innovation Solution
The design features S-shaped spring arms with a symmetrical, point-symmetric arrangement around the inner fastening point, optimizing spring properties and distributing mechanical stresses evenly. This design is manufactured using injection molding, potentially with amorphous metal, to reduce costs and enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional flat bending springs are used in series-elastic actuators, then the actuator can generate large forces and torques, but the stiffness makes it difficult to control the forces precisely
Solution Approach 1:
The patent changes the geometric parameters of the spring arms by introducing an S-shaped profile with specific curvature radii (R1, R2, R3, R4) and segment divisions. This modifies the spring's mechanical properties to achieve both high force generation and precise force control through optimized elasticity characteristics.
2Measurement precision
If an elastic element is connected in series with the actuator to improve force control, then force control accuracy improves, but the installation space requirements increase
Solution Approach 1:
The patent transitions from conventional linear spring designs to a planar S-shaped spring arm configuration that utilizes two-dimensional space more efficiently. The S-shaped profile compactly packs the elastic element within the actuator's installation space while maintaining the required force control accuracy.
Solution Approach 2:
The spring arm is divided into multiple nested segments (first, second, third, and fourth spring segments) that are arranged in a compact S-shaped configuration, allowing the elastic element to fit within limited installation space while preserving its force control functionality.
3Manufacturing precision
If subtractive manufacturing methods are used for plane torsion springs, then manufacturing precision can be achieved, but the costs become very high particularly for materials with high rigidity
Solution Approach 1:
The patent replaces expensive subtractive manufacturing processes with additive manufacturing (3D printing) technology. This substitution reduces manufacturing costs significantly while maintaining the required geometric precision for the S-shaped spring arm profile, especially for high-rigidity materials.
4Ease of manufacture
If additive manufacturing is used for plane torsion springs, then manufacturing costs are reduced, but problems occur at the connection point for force transmission due to twisting of pins or seizure of the mount
Solution Approach 1:
The patent optimizes the geometric parameters of the connection points and spring arm interfaces through precise S-shaped profile design. This includes optimizing curvature radii and segment dimensions to minimize stress concentrations and prevent pin twisting or mount seizure, thereby improving reliability while maintaining additive manufacturing cost advantages.
5Ease of manufacture
If the spring arms have a simple design, then manufacturing is easier and costs are lower, but the strength and reproducible deflection are insufficient
Solution Approach 1:
The spring arm is segmented into four distinct sections (first, second, third, and fourth spring segments) with different geometric characteristics. This segmentation allows each section to be optimized for its specific function while maintaining overall manufacturing simplicity through the standardized S-shaped profile and additive manufacturing process.
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 S-shaped profile of the spring arms provides enhanced strength and reproducible deflection, minimizing stress peaks and hysteresis. The injection molding process allows for cost-effective production with improved surface quality and reduced post-processing needs.
Implementation Method 1
the spring arms having a similar contour and extending symmetrically, preferably point-symmetrically, with respect to the inner fastening point
Implementation Method 2
The S-shaped profile of the spring arms provides enhanced strength and reproducible deflection, minimizing stress peaks and hysteresis
Data Source
AI summary
The plane torsion spring has an inner fastening point, at least two outer fastening points, and at least two spring arms. Each of the at least two spring arms connects the inner fastening point to one of the outer fastening points in a spring-elastic manner. The spring arms have a similar contour and extend symmetrically, preferably point-symmetrically, with respect to the inner fastening point. The spring arms of the plane torsion spring have an S-shaped profile.