Springs in Our World: Tape Measures
Flat springs were some of the first springs ever invented. Hundreds of years ago, ancient clock akers realized that if they coiled a flat piece of metal, it could wind and unwind over and over, creating an endless spring that was hard to break. Today, the flat springs are used in a variety of industries. Most flat springs are cut from sheet metal strips. These sheet metal springs are sturdy and have uses in a variety of industries. One place that you might not expect to see a flat spring used is in a tape measure. However, the winding mechanism provided by a flat sheet metal spring is the main control mechanism of a retractable tape measure. The construction process of a tape measure is actually simple, and it is amazing that it works so well time after time!
The factory cuts sheet metal strips from a long piece of thin sheet metal. Usually, the metal used is steel or aluminum. Then they wind the strips into a flat coil like a lollipop.
Next, the manufacturer either makes the casing or purchases it from another factory. A machine or a worker slips the wound metal strip into the casing and snaps all of the other pieces in place. Elsewhere, the factory prints a plastic strip with measuring information onto another strip of steel or aluminum. A machine or a worker attaches the end of the measuring tape strip to the end of the steel spring.
The measuring tape retracts inside the measuring tape due to the pressure applied by the internal spring. The user can now pull the measuring tape out and release it and the tape will automatically retract back inside the casing.
This innovative use of flat steel springs has continued to help construction workers, household DIY enthusiasts, and even manufacturing companies keep measurements accurate for many years.