Plastic Helical Spring Design for Corrosion Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional helical springs made of spring steel are not suitable for applications requiring resistance to chemical corrosion, non-magnetism, low thermal and electrical conductivity, and a high strength-to-weight ratio, and the use of plastic springs faces challenges in achieving sufficient load-bearing capability and strength due to material limitations and manufacturing difficulties such as kinks and knit lines.
Innovation Solution
A helical spring design featuring end coils with gradual transition coils and a trapezoidal cross-section, along with a specialized mold design allowing for injection molding with minimal stress points and kinks, utilizing high-performance thermoplastic materials like Ultem resin for enhanced strength and recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If spring steel is used to provide high load bearing capability, then strength is improved, but corrosion resistance and recyclability deteriorate
Solution Approach 1:
The invention changes the material parameter from metal to plastic, specifically using high-performance thermoplastics with glass fiber reinforcement. This material substitution maintains load bearing capability while achieving corrosion resistance and recyclability. The plastic material parameters (molecular structure, fiber reinforcement) are optimized to match the mechanical properties previously only available from spring steel.
2Object-affected harmful factors
If plastic material is used to achieve corrosion resistance and recyclability, then corrosion resistance is improved, but load bearing capability deteriorates
Solution Approach 1:
The invention uses composite plastic materials consisting of thermoplastic matrix combined with glass fiber reinforcement. This composite structure provides both the corrosion resistance of plastic and the enhanced strength needed for load bearing applications. The glass fibers act as reinforcement to compensate for the inherently lower strength of pure plastic materials.
Solution Approach 2:
The invention optimizes plastic material parameters by selecting high-performance thermoplastics and adjusting molecular weight, cross-linking density, and fiber reinforcement content. These parameter changes enable plastic materials to achieve load bearing capabilities previously only attainable with metal spring steel.
3Ease of manufacture
If conventional multi-section mold design is used for injection molding, then ease of manufacture is improved, but manufacturing precision deteriorates due to kinks and knit lines
Solution Approach 1:
The invention divides the mold into multiple sections (first mold section, second mold section, third mold section) with specific functional assignments. The first mold section forms the helical spring structure, while the second and third sections form the end coils. This segmentation allows each section to be optimized for its specific function, eliminating the kinks and knit lines that occur when all sections attempt to form the helix simultaneously.
Solution Approach 2:
The invention applies different mold section designs to different parts of the spring. The main body of the spring is formed by the first mold section with its specific helical cavity, while the end coils are formed by separate second and third mold sections. This local differentiation of mold quality and design ensures that each region of the spring receives the appropriate forming conditions for its specific geometric requirements.
4Device complexity
If conventional mold design with four similar sections is used, then device complexity is reduced, but manufacturing precision deteriorates due to undercuts impeding mold withdrawal
Solution Approach 1:
The invention segments the mold into distinct sections with specialized functions: the first mold section for the helical body, and separate second and third mold sections for the end coils. This segmentation eliminates the undercut problems that plague conventional four-section designs, as each section is designed to withdraw without interference from the helical geometry.
Solution Approach 2:
The invention resolves the withdrawal problem by separating the end coil formation into distinct dimensional steps. The second and third mold sections form the end coils at different positions and orientations, allowing them to be released from the helical spring body without the sections needing to withdraw through the tight helical undercuts that trap conventional multi-section molds.
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 design achieves a high strength-to-weight ratio, minimizes side thrust, and reduces stress points, enabling the production of lightweight, corrosion-resistant, and non-magnetic plastic helical springs with improved load-bearing capacity and fatigue life.
Implementation Method 1
it is difficult to create practical mold designs for the manufacture of helical springs from plastic material. Conventional mold tool designs have four relatively similar mold sections that come together to form the mold cavity equally for each circular quadrant of the spring. Molten plastic material is injected into the mold cavity formed by the mold sections through a center or core pin around which the four mold sections are situated. After cooling, the mold sections pull apart and the spring is released from the mold.
Implementation Method 2
Molten plastic material is injected into the mold cavity formed by the mold sections through a center or core pin around which the four mold sections are situated. After cooling, the mold sections pull apart and the spring is released from the mold.
Data Source
AI summary
This invention provides a helical spring formed of plastic material, comprising a pair of end coils situated at respective ends of said helical spring; at least one full pitch active coil between said pair of end coils; a pair of transition coils, each transition coil interconnecting an end of a respective end coil to an end of a respective proximate full pitch active coil, and having a varying pitch.