Coil-Based Bending Structural Body for Stable Cord Guidance

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Solution Overview

Problem

The conventional bending structural bodies for robots and manipulators have a complicated structure due to the connection of multiple disk elements and the insertion of actuation cables through each element.

Innovation Solution

A bending structural body composed of an inner cylinder with first inner and outer coil parts and an outer cylinder with second inner and outer coil parts, where cord-like members are inserted and guided through the space between these cylinders, simplifying the structure and stabilizing the posture by preventing compression and guiding the members effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple disk elements are connected and actuation cables are inserted through each element, then bending motion is achieved, but the structure becomes complicated

Engineering Contradiction:
Improvebending motion capabilityVSAvoidstructural complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges multiple disk elements into a single integrated bending structural body with inner and outer cylindrical portions. The cord-like members pass through the space between these cylindrical portions instead of through multiple separate disk elements, combining the functions of multiple components into one unified structure, thereby reducing overall complexity while maintaining bending capability

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent employs a nested configuration where the inner cylindrical portion is positioned within the outer cylindrical portion, creating a concentric structure. The cord-like members are inserted through the annular space between these nested cylinders, allowing the bending mechanism to achieve complex motion through a simplified nested arrangement rather than multiple separate elements

Inventive Principle:
Principle #7Nested doll (Nesting)

2Device complexity

If the inner cylinder and outer cylinder are arranged with space between them, then the structure is simplified, but compression resistance may be compromised

Engineering Contradiction:
Improvestructural simplicityVSAvoidcompression resistance
Core Design Contradiction:
Device complexityVSStrength

Solution Approach 1:

The patent applies the anti-weight principle by having the inner cylindrical portion and outer cylindrical portion work in opposition to each other during compression. When compressive force is applied, the inner cylinder compresses while the outer cylinder expands, and vice versa. This counteracting behavior distributes and balances the compressive loads, preventing localized buckling and enhancing overall compression resistance despite the space between the cylinders

Inventive Principle:
Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The patent creates a composite structural system by combining the inner cylindrical portion, outer cylindrical portion, and cord-like members into an integrated load-bearing assembly. The interaction between these different components creates a composite structure where the space between cylinders becomes part of the load distribution mechanism, maintaining strength while enabling simplification

Inventive Principle:
Principle #40Composite materials

3Ease of operation

If cord-like members are inserted through the space between cylinders, then guidance is improved, but the risk of member compression increases

Engineering Contradiction:
Improvecord-like member guidanceVSAvoidmember compression prevention
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent uses the space between the inner and outer cylindrical portions as an intermediary passage for the cord-like members. This annular space acts as a protected channel that guides the members through the bending structural body, providing smooth guidance while the surrounding cylindrical structures protect the members from lateral compression and misalignment during bending operations

Inventive Principle:
Principle #24Intermediary (Mediator)

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 simplified structure allows for stable bending and restoration with high compression and torsion resistance, ensuring reliable guidance of the cord-like members and maintaining a stable posture during operations.

Implementation Method 1

an inner cylinder (3) which includes a first inner coil part (15) and a first outer coil part (13), and in which wound parts (15a) corresponding to the first inner coil part (15) are fitted to the pitches (13b) between adjacent wound parts (13a) of the first outer coil part (13)

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a plurality of cord-like members (9a, 9b) in a circumferential direction which are inserted into and guided by the space (21) between the inner cylinder (3) and the outer cylinder (5) in an axial direction

Methodology Applied
Scientific EffectTension: Tension

Data Source

PatentEP4238723B1Bending structural body
Publication Date: 2025.08.13 NHK SPRING CO LTD
  • EP4238723B1 patent drawingFigure 1
  • EP4238723B1 patent drawingFigure 2
  • EP4238723B1 patent drawingFigure 3

AI summary

The present invention provides a bending structural body with which a simplified structure can be achieved. The bending structural body comprises: an inner cylinder 3 that is formed from a first inner coil part 15 and a first outer coil part 13, and in which wound parts 15a corresponding to the first inner coil part 15 are respectively fitted to pitches 13b between adjacent wound parts 13a of the first outer coil part 13; an outer cylinder 5 that covers at least some of the outer circumference of the inner cylinder 3 with a space 21 therebetween, that is formed from a second inner coil part 19 and a second outer coil part 17, and in which wound parts 19a corresponding to the second inner coil part 19 are respectively fitted to pitches 17b between adjacent wound parts 17a of the second outer coil part 17; and drive wires 9a and guide wires 9b that are guided and axially inserted into the space 21 between the inner cylinder 3 and the outer cylinder 5.