Captive Screw Sleeve and Press-Fit Nut for Lower-Cost Retention

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Solution Overview

Problem

The high cost of captive screws in computing devices due to the use of various metal parts, springs, and custom components increases the overall cost of manufacturing, particularly in servers where numerous screws are required.

Innovation Solution

A captive screw design utilizing a standard or custom screw with a sleeve that snaps onto a press fit nut, reducing the number of components and materials by ensuring the screw sits flush and preventing cross-threading, thereby lowering production costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional captive screw design with spring and multiple metal parts is used, then the screw can be ejected when loosened, but the manufacturing cost increases significantly

Engineering Contradiction:

Improvescrew ejection functionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent removes the spring component from the traditional captive screw design. Instead of using a spring-loaded mechanism, the screw is designed to be directly retained by the aperture structure itself, eliminating the need for separate spring components and reducing manufacturing complexity while maintaining the ejection function when loosened

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent integrates the retention function directly into the aperture structure of the first component. The aperture is designed with specific geometric features that inherently retain the screw when tightened and allow ejection when loosened, merging the retention mechanism with the existing structural element rather than requiring separate components

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If custom components and various metal parts are used in captive screw design, then the screw can be retained and ejected, but the overall cost of the computing device increases

Engineering Contradiction:

Improvescrew retention functionVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The aperture structure is designed to perform multiple functions: it provides the opening for screw access, retains the screw when tightened through its geometric configuration, and enables screw ejection when loosened. This multi-functional design eliminates the need for separate retention and ejection mechanisms, reducing component count while maintaining reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Instead of using active components (springs, retainers) to force the screw out, the design allows the screw to be passively ejected by the natural action of loosening. The aperture geometry is configured so that screw removal automatically results in ejection, inverting the traditional approach where active force is required for ejection

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11629747B2Captive screw

Publication Date: 2023.04.18 HEWLETT PACKARD ENTERPRISE DEV LP

AI summary

A captive screw, comprising: a screw; a press fit nut, to connect to an opening on a device and to accept a screw, including: a bottom portion, to extend through the opening; a top portion; and a middle portion, wherein the middle portion is smaller in circumference than the top portion and the bottom portion; and a sleeve including a protrusion, wherein the sleeve fits over the screw and attaches to the press fit nut via the protrusion.