Threaded Insert Receptacle With Undercut Locking for Plastic Parts

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Solution Overview

Problem

Existing methods for attaching threaded inserts to plastic components, such as those produced by injection molding or 3D printing, are labor-intensive, costly, and prone to assembly errors, requiring skilled workers and additional steps like melting or bonding, which prolong production times.

Innovation Solution

A device with a component featuring an integral receptacle for a threaded insert, incorporating an undercut and lateral contact surfaces, allows for a positive locking mechanism using a spring tongue or locking element carrier, enabling quick and secure attachment without machining, adhesives, or heating, and allowing for visual inspection and easy replacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If threaded inserts are bonded in place to ensure secure attachment, then reliability is improved, but manufacturing complexity and time increase

Engineering Contradiction:
Improvesecure attachmentVSAvoidmanufacturing process
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces chemical bonding methods with a purely mechanical locking system. The receptacle includes an undercut geometry that creates a mechanical interference fit with the threaded insert, eliminating the need for adhesives or thermal bonding processes while maintaining secure attachment.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The undercut structure is pre-formed in the receptacle during component manufacturing (injection molding or additive manufacturing). This preliminary preparation allows the threaded insert to be simply inserted and automatically locked in place without requiring subsequent bonding operations or skilled manual assembly.

Inventive Principle:
Principle #10Preliminary action

2Ease of manufacture

If threaded inserts are melted in to attach to thermoplastic components, then ease of manufacture is improved, but reliability and load-bearing capacity worsen

Engineering Contradiction:
Improveattachment processVSAvoidload-bearing capacity
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces thermal melting processes with a mechanical interference fit system. The undercut geometry creates a positive locking mechanism that physically prevents the threaded insert from being pulled out, providing superior load-bearing capacity compared to melted-in inserts while maintaining manufacturing simplicity through direct insertion.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If threads are cut directly into plastic components, then device complexity is reduced, but strength and stiffness are insufficient to withstand higher loads

Engineering Contradiction:
Improvethreading processVSAvoidload-bearing capacity
Core Design Contradiction:
Device complexityVSStrength

Solution Approach 1:

The patent separates the threading function from the component body by using a distinct threaded insert component. This allows the main component to remain simple (injection-molded or additively manufactured with an undercut receptacle) while the threading capability is provided by a separate, stronger insert that can withstand higher loads.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The solution creates a composite structure combining the plastic component with a threaded insert (typically metal or reinforced plastic). This composite assembly leverages the advantages of both materials: the plastic component provides design flexibility and manufacturing ease, while the insert provides high strength and load-bearing capacity for threading applications.

Inventive Principle:
Principle #40Composite materials

4Ease of operation

If threaded inserts are inserted using melting or bonding methods, then ease of operation is improved, but production time and costs increase due to skilled worker requirements

Engineering Contradiction:
Improveinsertion processVSAvoidproduction time
Core Design Contradiction:
Ease of operationVSProductivity

Solution Approach 1:

The patent replaces complex thermal or chemical bonding operations with a simple mechanical insertion process. The threaded insert is designed to be directly inserted into the undercut receptacle, creating an automatic mechanical lock that requires no specialized equipment, heating, cooling, or skilled manual operation, thereby dramatically reducing production time and costs.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 provides a cost-effective, rapid, and reliable method for attaching threaded inserts, capable of withstanding higher loads and preventing rotation, with assembly and disassembly possible without specialized tools, reducing production time and costs.

Implementation Method 1

The threaded insert can, for example, be inserted into the receptacle by elastically deforming the integral spring tongue and locked into place by the integral spring tongue

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

The undercut, into which a collar section of the threaded insert can preferably be inserted, allows the inserted threaded insert to be secured to the component by positive locking in the direction of the thread axis

Methodology Applied
Scientific EffectPositive locking: Mechanical Fastener

Implementation Method 3

The torques introduced into the threaded insert during tightening can be transferred via the edge surfaces of the threaded insert, in particular the edge surfaces of the spring tongue of the threaded insert, into the lateral contact surfaces, preferably via the webs, and into the component

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4653713A1Device with a receptacle for a threaded insert and method
Publication Date: 2025.11.26 LUFTHANSA TECHNIK AG
  • EP4653713A1 patent drawingFigure 1~2
  • EP4653713A1 patent drawingFigure 3~6
  • EP4653713A1 patent drawingFigure 7~8

AI summary

The invention relates to a device (40) with at least one component (30) having at least one integral receptacle (31) for a threaded insert (10), wherein the receptacle (31) comprises a through-hole (32) through the component (30). The receptacle (31) has an undercut (35) on at least one side for holding a section (19) of a threaded insert (10), wherein the receptacle (31) has two lateral contact surfaces (34), each of which is configured for lateral contact with lateral edge surfaces (20) of a threaded insert (10). The receptacle (31) has an integral spring tongue (39) for locking a threaded insert (10) in the receptacle (31) or an integral locking element carrier (36) with a locking element (37), wherein a spring tongue (15) of a threaded insert (10) can be inserted and locked under the locking element carrier (36).