Timer - Mechanical Timers

Mechanical Timers

Mechanical timers use mechanical clockwork to measure time. Manual timers are typically set by turning a dial to the time interval desired; turning the dial stores energy in a mainspring to run the mechanism. They function similarly to a mechanical alarm clock; the energy in the mainspring causes a balance wheel to rotate back and forth. Each swing of the wheel releases the gear train to move forward by a small fixed amount, causing the dial to move steadily backward until it reaches zero, when a lever arm strikes a bell. The mechanical kitchen timer was invented in 1926 by Thomas Norman Hicks. More inaccurate, cheap mechanisms use a flat paddle called a fan fly that spins against air resistance; mechanical egg-timers are sometimes of this type.

The simplest and oldest type of mechanical timer is the hourglass, in which a fixed amount of sand drains through a narrow opening from one chamber to another to measure a time interval.