Tolerance Ring with Variable Curvature for Hard Disk Drive Assembly

Solution Overview

Problem

Conventional tolerance rings for hard disc devices are prone to contamination and difficult to press-fit due to their elliptical shape during assembly, which causes damage to the carriage and pivot shaft surfaces.

Innovation Solution

A tolerance ring with a ring shape featuring projections along the circling direction, where the curvature radius of the end portions matches the carriage opening and continuously reduces towards the ends, allowing for a press-fit without damaging the carriage or pivot shaft, and a manufacturing method involving shaping, projection formation, and curving to achieve this design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the curvature radius of the tolerance ring is designed larger than the curvature radius of the carriage opening for assembly operation, then the tolerance ring can be held inside the carriage, but the tolerance ring forms an elliptical shape during insertion that damages the carriage side surface and causes contamination

Engineering Contradiction:

Improveassembly operationVSAvoidcontamination and surface damage

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The tolerance ring applies local quality by having different curvature radii at different locations: the end portions have a first curvature radius that matches the carriage opening curvature, while the intermediate portions have a larger second curvature radius. This allows the end portions to fit smoothly into the carriage opening without damage, while the intermediate portions maintain adequate clearance for assembly operation.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the curvature radiuses of end portions are larger than the carriage opening curvature radius, then the end portion side is opened for manufacturing, but the minor axis of the ellipse is too small to provide sufficient press-fit amount for the pivot shaft

Engineering Contradiction:

Improvemanufacturing processVSAvoidpress-fit amount

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The tolerance ring applies local quality by having different curvature radii at different locations: the end portions have a first curvature radius that matches the carriage opening curvature, while the intermediate portions have a larger second curvature radius. This allows the end portions to fit smoothly into the carriage opening without damage, while the intermediate portions maintain adequate clearance for assembly operation.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the tolerance ring has a uniform curvature radius larger than the carriage opening, then the tolerance ring can be manufactured and assembled, but it cannot be inserted into the carriage opening without rubbing and damaging the side surface

Engineering Contradiction:

Improvemanufacturing and assemblyVSAvoidsurface integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The tolerance ring applies local quality by having different curvature radii at different locations: the end portions have a first curvature radius that matches the carriage opening curvature, while the intermediate portions have a larger second curvature radius. This allows the end portions to fit smoothly into the carriage opening without damage, while the intermediate portions maintain adequate clearance for assembly operation.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9429190B2Tolerance ring and method of manufacturing tolerance ring

Publication Date: 2016.08.30 NHK SPRING CO LTD

AI summary

A tolerance ring that has a ring shape approximately circling along a predetermined direction includes a plurality of projections, wherein the curvature radiuses of end portions in a circling direction are smaller than the curvature radius of a portion other than the end portions in the circling direction.