Power Springs

            A power spring, commonly known as a clock spring, consists of a strip of spring-tempered material wound on an arbor and housed within a circular case (keeper). The inner end engages the arbor and the outer end engages the restraining case. The spring stores rotational energy by being stressed in bending when wound around the arbor. When the arbor is allowed to rotate, the spring delivers rotational energy to the arbor by expanding to the maximum curvature allowed by the keeper.

            The torque-deflection characteristic of a power spring is non-linear. This condition is caused by the constantly changing amount of active material, the normal hysteresis effect throughout the working deflection, and inter-coil friction.

            Most spring motors operate through a maximum of about fifteen useful revolutions. It is possible to prestress the strip by forming, and then backwinding it into the retainer. This causes higher stresses; however, it also increases the number of useful turns to as high as thirty-five. A more constant torque load through the entire spring deflection will result. John Evans' capabilities range from very thin (.002”) to heavy (.080”) material, and widths from fractions of an inch to multiple inches.

 

            Our Sales Department and Engineering Department are available to help you optimize your power spring design.