Molded Wire Thread Insert for Vibration-Resistant Thermoplastic Joints
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Solution Overview
Problem
Current methods for securing screws in plastic components, especially in the aerospace industry, face challenges with self-loosening and require complex manufacturing processes due to dynamic loads and high vibrations, necessitating overmolded metal inserts or separate insertion of wire thread inserts.
Innovation Solution
A thermoplastic component with a wire thread insert molded internally, featuring a narrowed turn with a reduced inner diameter that elastically engages with screws, eliminating the need for separate insertion and providing enhanced pull-out strength and retightening capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wire thread insert is separately inserted into a component opening after manufacturing, then the screw connection can be secured against self-loosening, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent combines the wire thread insert integration with the component manufacturing process itself. The injection mold includes a core element with threading that directly forms the wire thread insert within the thermoplastic material during molding, eliminating the need for separate insertion steps and reducing manufacturing complexity while maintaining screw connection reliability
Solution Approach 2:
The wire thread insert is pre-formed within the component during the molding process using a threaded core element. This preliminary integration ensures the insert is properly positioned and secured before the component is completed, avoiding the need for subsequent assembly operations
2Reliability
If overmolded metal inserts with thread reinforcement are used for aerospace applications, then high pull-out strength and reliability are achieved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the material parameter from metal to thermoplastic for the wire thread insert, while maintaining the necessary mechanical properties through proper molding techniques. The thermoplastic material is molded around a threaded core element to create an integrated insert that provides sufficient pull-out strength for aerospace applications without requiring metal construction
Solution Approach 2:
The patent creates a composite structure by molding thermoplastic material around a threaded core element. This composite construction combines the structural integrity of the core element with the bonding properties of the thermoplastic, achieving reliable screw connections under dynamic loads without the complexity of overmolded metal inserts
3Productivity
If the wire thread insert is completely molded into the component in the axial direction, then manufacturing is simplified and repeatability is improved, but the insert must accommodate material shrinkage during cooling
Solution Approach 1:
The patent incorporates a threaded core element within the injection mold that anticipates and compensates for material shrinkage during cooling. The core element is positioned and dimensioned to account for the thermoplastic material's contraction, ensuring that the final thread pitch and geometry meet precision requirements despite the shrinkage that occurs during the molding process
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 offers a reliable screw locking mechanism with improved repeatability and simplified manufacturing by integrating the wire thread insert, suitable for aerospace applications with high thermal stability and reduced manufacturing complexity.
Implementation Method 1
During the molding process, the wire thread insert is axially compressed due to material shrinkage as the material cools, resulting in the desired thread pitch
Implementation Method 2
comprises at least one narrowed turn between the first and the second axial end with a third inner diameter that is reduced compared to the first and second inner diameters and is movable radially outwards to an inner wall of the component
Data Source
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AI summary
The invention relates to a component (1) consisting of a thermoplastic material with a continuous working temperature of at least 130°C and comprising a wire thread insert (10) moulded therein. The wire thread insert comprises a first axial end (12) with a first inner diameter and a second axial end (14) with a second inner diameter, is completely moulded into the component in the axial direction, and comprises, between the first and the second axial ends, at least one narrowed winding (16) with a third inner diameter that is shorter than the first and second inner diameters, which can be radially outwardly moved up to a component inner wall.