Nested Coil Joint Structure for Stable Bending and Axial Rigidity

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Solution Overview

Problem

Existing bending structures for robot joint function parts are complex and difficult to stabilize, particularly due to the interlocking of multiple disc elements.

Innovation Solution

A simplified bending structure comprising an outer coiled part and an inner coiled part, where the inner coiled part fits between the coils of the outer coiled part, ensuring axial rigidity and smooth bending operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple disc elements are engaged with each other to stabilize bending operation, then bending operation stability is improved, but device complexity increases

Engineering Contradiction:
Improvebending operation stabilityVSAvoidstructure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple disc elements into a single integrated flexible member with a unified structure. The flexible member incorporates both the bending operation mechanism and compression resistance function within one component, eliminating the need for separate engaged disc elements while maintaining operational stability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The flexible member is designed to perform multiple functions simultaneously: it enables bending operation through its flexible portion and provides compression resistance through its rigid portion. This multi-functional design replaces the need for multiple specialized components, simplifying the overall structure while maintaining reliability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If a flexible member with engaged disc elements is used, then bending operation is stabilized, but manufacturing complexity increases

Engineering Contradiction:
Improvebending operation stabilityVSAvoidmanufacturing complexity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The flexible member is manufactured as a single integrated component rather than assembling multiple disc elements. This merging of functions into one manufacturable unit reduces manufacturing complexity while maintaining the stability of bending operation.

Inventive Principle:
Principle #5Merging (Combining)

3Device complexity

If the structure is simplified, then device complexity is reduced, but axial rigidity may be compromised

Engineering Contradiction:
Improvestructure complexityVSAvoidaxial rigidity
Core Design Contradiction:
Device complexityVSStrength

Solution Approach 1:

The flexible member is designed with different structural properties in different regions: the flexible portion allows bending motion while the rigid portion provides axial compression resistance. This local differentiation of structural quality enables the simplified single-component design to maintain both flexibility and axial rigidity simultaneously.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The flexible member can be constructed using composite materials or composite structural design, combining flexible and rigid characteristics within the same component. This allows the simplified structure to achieve both bending flexibility and axial rigidity without requiring multiple separate elements.

Inventive Principle:
Principle #40Composite materials

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 proposed structure stabilizes bending operations while simplifying the structure, ensuring smooth operation without catching, and maintaining axial rigidity.

Implementation Method 1

the coils of the inner coiled part fit between the adjacent coils of the outer coiled part while being in contact with the adjacent coils of the outer coiled part

Methodology Applied
Scientific EffectMechanical contact and support: Mechanical Force

Implementation Method 2

the flexible member smoothly performs the bending operation and assures rigidity against compression in an axial direction

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4104983B1Bending structure and joint function part
Publication Date: 2025.04.16 NHK SPRING CO LTD
  • EP4104983B1 patent drawingFigure 1
  • EP4104983B1 patent drawingFigure 2
  • EP4104983B1 patent drawingFigure 3(A)~3(B)

AI summary

Provided are a bending structure and a joint function part, capable of stabilizing bending operation and simplifying a structure. In the bending structure, an inner coiled part 5 is located into an outer coiled part 3. The outer coiled part 3 has a plurality of gaps 3c distancing adjacent coils 3b in an axial direction, and coils 5b of the inner coiled part 5 are provided so as to correspond to the gaps 3c of the outer coiled part 3 and fit between the adjacent coils 3b of the outer coiled part 3 while being in contact with the adjacent coils 3b . A dimension P is set in a range meeting πR/4N≤P<d-πR/4N in which P is the dimension of the gap 3c of the outer coiled part 3 in the axial direction in a free state, N is the number of turns of the outer coiled part 3, R is a diameter of the outer coiled part 3, and d is a wire diameter of the wire 5a of the inner coiled part 5.