Rain-Tight EMT Fitting with Sleeve and Fastener

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Solution Overview

Problem

Existing electrical fittings fail to provide a rain-tight connection between electrical metal tubing (EMT) and electrical boxes, particularly in outdoor applications where moisture protection is critical.

Innovation Solution

A rain-tight fitting with a fitting body that includes a leading end for connection to the electrical box and a trailing end with a sleeve and fastener system, which creates a grounding path and ensures a rain-tight fit by tightening against the EMT, using a necked-down wall portion and a fastener for secure contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If EMT is used instead of RMC, then cost and weight are reduced, but rain-tight connection capability is lost

Engineering Contradiction:

Improveweight of electrical conduitVSAvoidrain-tight connection

Core Design Contradiction:

Weight of stationary objectVSReliability

Solution Approach 1:

The fitting is divided into distinct functional components: a body portion for structural support and connection, a sleeve portion for sealing and grounding contact, and a fastener for securing. This segmentation allows each component to optimize its specific function while maintaining overall rain-tight performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sleeve acts as an intermediary element between the EMT and the fitting body. It provides the critical interface that enables both grounding contact and rain-tight sealing, mediating the connection between the non-threaded EMT and the fitting structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If EMT with thinner wall is used, then cost is reduced, but threading capability is lost

Engineering Contradiction:

Improvecost of electrical conduitVSAvoidthreading capability

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

Instead of threading the EMT (which would require thick walls), the invention inverts the approach by having the fitting accommodate the EMT's outer periphery through a sleeve that contacts and secures to the tubing's exterior surface.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The mechanical threading system is replaced with a friction-based securing system where the fastener tightens the sleeve against the EMT's outer periphery, eliminating the need for threads while maintaining secure connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If standard electrical fitting is used, then installation is simple, but grounding path is not established

Engineering Contradiction:

Improveinstallation simplicityVSAvoidgrounding path

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The grounding function is merged with the sealing and securing functions in the sleeve component. The same sleeve that provides rain-tight sealing also establishes the grounding path by contacting the EMT's outer periphery and connecting to the fitting body.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sleeve serves multiple functions simultaneously: it provides rain-tight sealing, establishes the grounding path, and secures the EMT to the fitting. This multi-functionality eliminates the need for separate grounding components while maintaining installation simplicity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively secures a rain-tight and grounded connection between the EMT and the electrical box, preventing moisture ingress and ensuring reliable protection in outdoor conditions.

Implementation Method 1

the fastener is tightened to drive the fastener against the outer periphery of the EMT, thereby providing a grounding path between the fitting, the electrical box, and the EMT

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9831649B1Rain tight fitting for electrical metal tubing

Publication Date: 2017.11.28 ARLINGTON IND INC

AI summary

A rain-tight fitting for connecting electrical metal tubing to an electrical box in a rain-tight fit. The rain-tight fitting includes a fitting body having a leading end adapted to connect to the knockout of an electrical box and a trailing end adapted to create a rain-tight fit with an end of electrical metal tubing (EMT). One or more sleeves are seated within a trailing bore of the fitting body and are held in place by a fastener. A necked-down wall portion on the sleeve contacts the outer periphery of the EMT as it is inserted into the trailing end of the fitting. After the EMT is fully inserted within the trailing end of the fitting, the fastener is tightened to drive the fastener against the outer periphery of the EMT, thereby providing a grounding path between the fitting, the electrical box, and the EMT.