Cold-Coiled Steel Spring Core With Low Relaxation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing steel wire spring cores for mattresses and seating face challenges in reducing local permanent deformation and relaxation, particularly due to the need for heat treatments which are not reliable at high coiling speeds, and the limitations of textile cloth in resisting thermal treatments.
Innovation Solution
A method involving cold coiling of steel wire springs with a specific steel alloy composition and microstructure, which provides a high yield strength to tensile strength ratio, allowing for high-speed manufacturing without heat treatments and minimizing relaxation, using a carrier like a bobbin to maintain mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatments are applied to reduce permanent deformation, then relaxation is reduced, but the manufacturing process becomes more complex and unreliable at high speeds
Solution Approach 1:
The patent extracts the heat treatment step from the manufacturing process by using cold coiling technology. The steel wire is coiled at ambient temperature without any heating, thereby eliminating the complexity and reliability issues associated with heat treatment equipment and processes while still achieving the desired reduction in permanent deformation through optimized wire properties and coiling technique.
Solution Approach 2:
Instead of using heat treatment to reduce permanent deformation, the patent inverts the approach by using cold coiling with specifically optimized steel wire properties (high Rp0.2/Rm ratio above 85%) and controlled coiling parameters to achieve the same effect without thermal processing. This reverse approach simplifies the manufacturing process while maintaining or improving relaxation resistance.
2Productivity
If cold coiling is used for high-speed manufacturing, then productivity increases, but permanent deformation and relaxation increase
Solution Approach 1:
The patent changes the material parameters of the steel wire by selecting or designing wire with a specific composition and microstructure that achieves a high yield strength to tensile strength ratio (Rp0.2/Rm > 85%). This parameter optimization allows the wire to withstand the stresses of high-speed cold coiling while minimizing permanent deformation and relaxation, thereby enabling both high productivity and high reliability.
3Duration of action of stationary object
If special heat treatments are applied to minimize relaxation, then spring core durability improves, but manufacturing time and energy consumption increase
Solution Approach 1:
The patent removes the heat treatment step entirely from the manufacturing process by employing cold coiling technology. The durability of the spring core is achieved not through thermal processing but through the inherent properties of the optimized steel wire and the precision of the cold coiling process, thereby eliminating the time and energy losses associated with heating and cooling cycles while maintaining long-term durability.
Solution Approach 2:
The patent performs preliminary optimization of the steel wire properties (composition, microstructure, mechanical properties) before coiling to ensure the wire can withstand service loads without relaxation. This preliminary preparation of the material eliminates the need for subsequent heat treatments, saving manufacturing time and energy while ensuring the spring core achieves its full service life potential from the outset.
Data Source
AI summary
A method to manufacture a steel wire spring core for a mattress or for seating is described, which comprises the steps of providing a carrier comprising steel wire; repeatedly cold coiling a steel wire spring from steel wire taken from the carrier; and connecting a series of the coiled steel wire springs to each other. The steel wire has a diameter d between 0.8 and 4.5 mm; and has a drawn pearlitic microstructure. The steel wire comprises a steel alloy having a carbon content between 0.35 wt % and 0.85 wt %. The steel wire on the carrier has a ratio—expressed as a percentage—of the yield strength Rpo 2 (in MPa) over the tensile strength Rm (in MPa) higher than 85%.