Capped Nut Retention Using Recess-and-Prominence Locking

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Solution Overview

Problem

Existing methods for securing a cap to a nut body, such as in wheel nuts, often damage the decorative surface, are unreliable, or complicate production, especially when a thrust washer is not used or when the cap design is restricted.

Innovation Solution

The cap is secured to the nut body through encircling recesses on the nut body's outer surface and corresponding prominences on the cap's inner surface, allowing a secure and reliable connection without interfering with the nut body's design or requiring additional production steps, and enabling surface treatments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electric ring welding is used to connect the cap to the nut body, then a reliable connection is achieved, but the decorative outer surface of the cap may be impaired

Engineering Contradiction:

Improveconnection reliabilityVSAvoidsurface damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the welding process (thermal/mechanical system) with a mechanical interference fit system consisting of recesses and protrusions. This mechanical coupling achieves reliable connection without thermal damage to the decorative surface, resolving the contradiction between connection reliability and surface integrity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces intermediate geometric features (recesses in the cap and corresponding protrusions on the nut body) that act as mediators for connection. These features enable mechanical coupling without direct contact between the welding tool and the decorative surface, preventing surface impairment while maintaining connection reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a thrust washer is used with the locking means, then the cap can be held securely, but the design freedom of the nut body is restricted

Engineering Contradiction:

Improvecap retentionVSAvoidnut body design freedom

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent merges the function of the thrust washer and locking means into an integrated system of recesses and protrusions. This combination eliminates the need for separate components, providing secure cap retention while maintaining full design freedom for the nut body geometry.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The recess-protrusion system serves multiple functions simultaneously: it provides mechanical locking, distributes contact pressure, and accommodates various nut body designs. This multi-functionality replaces the specialized thrust washer component while enhancing design versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If an interference fit is used to hold the cap on the nut body, then the cap can be secured, but fitting is difficult and the decorative surface may be impaired

Engineering Contradiction:

Improvecap retentionVSAvoidfitting complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent segments the interference fit into discrete recesses and protrusions with defined geometric parameters. This segmentation reduces fitting complexity by providing clear assembly features while maintaining reliable retention, and prevents surface impairment by controlling the deformation zones.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by concentrating the interference fit effect in specific regions (recess and protrusion zones) rather than uniform interference throughout. This localized approach simplifies fitting operations and protects the decorative surface from unnecessary deformation.

Inventive Principle:

Principle #3Local quality

4Reliability

If the bottom free end of the cap is drawn into the nut body, then secure connection is achieved, but production becomes very complicated

Engineering Contradiction:

Improveconnection strengthVSAvoidproduction complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of drawing the cap end into the nut body (complex deformation process), the patent inverts the approach by creating recesses in the cap that receive protrusions from the nut body. This reversal simplifies production while achieving equivalent or superior connection strength.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8109707B2Nut having a nut body and a cap held on the nut body

Publication Date: 2012.02.07 METALLWARENFAB HERMANN WINKER

AI summary

The present invention relates to a nut (10, 110, 210) having a nut body (11, 111, 211) and a cap (20, 120, 220, 320) held on the nut body (11, 111, 211), wherein there is/are provided on the outer surface of the nut body (11, 111, 211) an encircling recess (16, 216) or recesses (116) encircling in sections, in which an encircling prominence (23) provided on the inner surface of the cap (20, 120, 220 320) or respectively prominences (123, 330) encircling in sections engage.