Plastic Water Meter Metal Thread Insert

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Solution Overview

Problem

Plastic water meters often experience issues with threaded connections, such as stripping or cross-threading, when interfacing with metal-threaded water systems, due to the mismatch in materials and thread types.

Innovation Solution

The design incorporates a plastic spud insert with a collar and annular lip portion, paired with a metal ring having complementary threads, which discourages relative movement and secures the connection using a key-fit arrangement, ensuring reliable connectivity without direct metal-to-water contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If plastic threads are used in plastic water meters, then zero lead content requirement is satisfied, but thread stripping and cross-threading occur during installation

Engineering Contradiction:

Improvelead contentVSAvoidthread connection reliability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The connector assembly combines plastic and metal materials to create a hybrid structure. The body is made of plastic (satisfying zero lead content) while the insert is made of metal (providing reliable threading). This composite approach allows the plastic water meter to meet health requirements while the metal insert prevents thread stripping and cross-threading issues.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The threaded insert acts as an intermediary component between the plastic body and the metal piping system. Instead of directly threading metal into plastic (which causes stripping), the metal insert serves as a mediator that provides stable threading while the plastic body maintains zero lead content compliance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If metal threads are used for connection, then thread strength is improved, but lead content requirement is violated

Engineering Contradiction:

Improvethread strengthVSAvoidlead content

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The connector assembly is segmented into distinct components: a plastic body portion and a separate metal threaded insert. This segmentation allows each component to be optimized for its specific function - the plastic body for lead-free compliance and the metal insert for strong threading - while working together as an integrated assembly.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If plastic threads are used, then manufacturing simplicity is maintained, but installation reliability deteriorates

Engineering Contradiction:

Improvethread manufacturing simplicityVSAvoidinstallation reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The metal threaded insert is pre-formed with precise threading before being installed into the plastic body. This preliminary action ensures that the threading is already optimized for strength and reliability, eliminating the need to create weak threads directly in the plastic during the main manufacturing process.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8613220B2Non-metallic enclosure with metal threads

Publication Date: 2013.12.24 MUELLER INT LLC

AI summary

A water meter enclosure includes a non-metallic cover defining an interior cavity shaped to accept a metering device; a metal ring including threads for connection to a piping system; and an annular lip contacting a distal end of the metal ring to retain the metal ring in spatial relationship between the non-metallic cover and the annular lip.