Power spring or constant force spring: which one fits?

Power springs and constant force springs are both made from flat spring strip, but they produce different outputs and suit different mechanisms.

Power springs produce rotary torque

A power spring is wound between an inner shaft and an outer housing or connected mechanism. As the spring winds and unwinds, it stores and releases energy as rotary torque. Typical applications include vacuum-cleaner cord reels, garden hose reels, cable retractors and other rewind or return mechanisms.

Constant force springs produce a linear pull

A constant force spring has a formed natural curvature. As its strip is pulled from the coil, it can provide an approximately steady force over much of its working travel. It may be used in displacement sensors, counterbalance mechanisms and other systems that need a long, controlled linear pull.

Choose by output and installation

Start with the motion required at the load: rotation and torque, or linear travel and pull force. Then compare available space, shaft or drum geometry, working range, speed, duty cycle, environment and target life. End connections and assembly details also matter.

These spring types are not interchangeable based on appearance alone. Share a drawing, sample or application description so the spring and mechanism can be assessed together.