Spiral spring:

A spiral flat spring (also known as a clock spring, power spring, or flat spiral spring) is a type of spring made from a flat strip of material wound into a spiral shape. Unlike helical springs, which are coiled vertically, spiral flat springs store and release energy through rotational motion.
Key Features of Spiral Flat Springs:
Material:Usually made of high-carbon steel, stainless steel, or phosphor bronzefor flexibility and fatigue resistance.
Sometimes coated for corrosion resistance.
Design:Flat strip wound in an Archimedean spiral(constant gap between coils) or involute spiral (variable gap).
One end is fixed to a central arbor (shaft), and the other is anchored to a housing.
Energy Storage:Works on torsional (rotational) energy—unwinds when released.
Self-Retracting Mechanism:Often used in applications where the spring must rewind automatically(e.g., tape measures, retractable cords).
Types of Spiral Flat Springs:

Common Uses:
Power Spring
Stores high energy in tight spaces
Toy cars, wind-up mechanisms

Constant-Force Spring
Delivers near-constant torque
Retractable badge reels, seatbelts
Hairspring (Balance Spring)
Precision micro-spring
Mechanical watch regulation

Motor Spring
Used for mechanical drives
Clockwork mechanisms, gramophones

Applications:
Retractable Devices: Tape measures, dog leashes, vacuum cord reels.
Timekeeping: Mainspring in clocks/watches.
Automotive: Seatbelt retractors, starter motors.
Toys & Gadgets: Wind-up toys, self-winding mechanisms.