Helical Spring End Contacts for Uniform Resistance Heat Treatment
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Solution Overview
Problem
Existing methods for heat treating helical springs via electric resistance heating often result in inadequate tempering at the extended end regions due to non-uniform cross-sectional current density, leading to inconsistent metallurgical treatment along the entire length of the spring.
Innovation Solution
The use of pair of end insert contacts with notches, spaced apart to accommodate the ends of the spring, and connected to an electric power source, ensures uniform current distribution by compressing the ends into the notches and using complementary contacts to enclose the ends, allowing for uniform electric resistance heating across the entire length of the spring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If plate-type electrical contacts are used to heat treat the spring, then the entire spring can be heated, but the current density becomes non-uniform in the extended end regions resulting in inadequate tempering
Solution Approach 1:
The patent applies local quality by using a moveable plate contact that can be positioned at different locations along the spring axis. This allows the contact area and current density distribution to be optimized for different regions of the spring, ensuring uniform tempering across both coiled and extended end regions rather than using a fixed contact configuration for the entire spring.
Solution Approach 2:
The patent employs dynamics by making one of the plate-type electrical contacts moveable rather than fixed. This moveable contact can be adjusted along the spring axis to optimize the current path and density distribution. The dynamic positioning capability allows the system to adapt to different spring geometries and achieve uniform current density and temperature distribution throughout the entire spring length.
2Strength
If connectors are placed remote from the free ends of the coil spring, then the coiled section can be hardened or tempered to a greater degree, but the extended end regions receive insufficient heat treatment
Solution Approach 1:
The moveable plate contact enables dynamic adjustment of the current path through the spring. By positioning the moveable contact at appropriate locations, the system can direct sufficient current through both the coiled section (for hardening) and the extended end regions (for adequate tempering), resolving the trade-off between prioritizing coiled section strength versus end region heat treatment.
Solution Approach 2:
The patent changes the parameter of contact position dynamically. By adjusting the position of the moveable plate contact along the spring axis, the current density distribution can be modified to ensure that both the coiled section receives sufficient current for hardening and the extended end regions receive adequate current for proper tempering, eliminating the insufficient heat treatment problem.
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
This approach ensures that the ends of the spring are heat-treated to the same degree as the coiled section, maintaining a uniform cross-sectional current density and preventing temperature gradients, thus achieving consistent metallurgical treatment throughout the spring.
Implementation Method 1
heat treating the entire length of a helical spring, or a similar article of manufacture, by electric resistance heating
Data Source
AI summary
Apparatus is provided for metallurgical heat treatment of coil springs, or similarly shaped workpieces and articles of manufacture, by electric resistance heating along the entire length of the workpiece so that the ends of the workpiece can be heat treated to the same degree and quality as the section of the workpiece between its two ends.