What is the purpose of dead coils in the middle of a compression

What purpose do dead coils in the middle of a spring serve? For example, this spring from a ballpoint pen has two dead coils at each end and two in the center of the spring. Why add dead coils in the

Compression Springs: Calculation Formulas

Compression Springs - Learn About

Applied Sciences, Free Full-Text

Non-standard spring calculation

What is the purpose of dead coils in the middle of a compression spring? - Engineering Stack Exchange

Solved: Spring With Dead Coils & Active coils - Autodesk Community - Inventor

How do wave springs eliminate problems associated with coil springs

Why do springs get harder to compress? - Engineering Stack Exchange

Common Replacement Springs Repair & Replacement Hardware

Compression Springs: Materials, Types, Applications, and Advantages

applied mechanics - Spring - Piston with different extension and

Compression Springs: Materials, Types, Applications, and Advantages