Leaf Spring Interlock Structure for Anti-Rotation Durability

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Solution Overview

Problem

Conventional leaf spring devices face space constraints and durability issues due to protruding holding plates, which can cause line contact and reduce the durability when adjacent leaf springs rotate relative to each other around a central axis.

Innovation Solution

A leaf spring device design featuring a restricting protrusion on one leaf spring and a recessed part on the adjacent leaf spring, both aligned in the longitudinal direction, with inclined surfaces to prevent relative rotation and distribute stress evenly, thereby preventing bulkiness and ensuring durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If holding plates are provided to prevent relative rotation between adjacent leaf springs, then the durability is improved, but the device becomes bulky and causes space constraints

Engineering Contradiction:
ImprovedurabilityVSAvoidbulkiness
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The restricting protrusion is inserted into the recessed part formed on the adjacent leaf spring, creating a nested configuration where one structural element fits within another. This eliminates the need for external holding plates that protrude outward, thereby preventing bulkiness while maintaining the anti-rotation function.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

Instead of adding external protruding structures (holding plates) to prevent rotation, the invention inverts the approach by creating a recessed part in one leaf spring and inserting a restricting protrusion from the adjacent leaf spring. This internal nesting approach achieves the same rotational restriction without external bulk.

Inventive Principle:
Principle #13The other way round (Inversion)

2Stability of the object's composition

If holding plates are provided to prevent relative rotation, then the structural stability is improved, but line contact occurs reducing durability

Engineering Contradiction:
Improvestructural stabilityVSAvoiddurability
Core Design Contradiction:
Stability of the object's compositionVSReliability

Solution Approach 1:

The restricting protrusion and recessed part are designed with curved surfaces that facilitate smooth surface contact during rotation. The arc-shaped configuration allows the protrusion to roll or glide within the recessed part, distributing contact stress across a curved surface area rather than concentrating it at a single line contact point, thereby improving durability while maintaining rotational stability.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Data Source

PatentEP4067688B1Leaf spring device
Publication Date: 2024.09.25 NHK SPRING CO LTD
  • EP4067688B1 patent drawingFigure 1
  • EP4067688B1 patent drawingFigure 2
  • EP4067688B1 patent drawingFigure 3

AI summary

A leaf spring device includes a plurality of leaf springs (11, 12), in which a restricting protrusion (14) is provided on one leaf spring (12), a recessed part (13) is formed on the other leaf spring (11), and the restricting protrusion is inserted into the recessed part, a first side surface (21) of the restricting protrusion and a third side surface (23) of the recessed part face each other in a plate width direction, a second side surface (22) of the restricting protrusion and a fourth side surface (24) of the recessed part face each other in the plate width direction, a first inclined surface (16) is formed on one of the first and third side surfaces to be further away from the other thereof from a central portion toward a first direction (X) in a longitudinal direction, and a second inclined surface (17) is formed on one of the second and fourth side surfaces to be further away from the other thereof from the central portion toward a second direction (Y) in the longitudinal direction.