ESCAPEMENT is part of the clock that controls speed and regularity by converting continuous rotational energy into discrete motions. This is accomplished through the use of gears and a lever attached to a pendulum. the most common form in use today powered by key wound springs.
When the pendulum swings the lever locks in the tooth of the gear, this is the tick. The back swing of the pendulum the lever releases the gear, this is the tock. The process is repeated over an over until the clock needs winding. Thus, the familiar tick tock of a clock. The speed and accuracy of the clock is achieved by adjusting the pendulum bob up or down. Adjusting the bob up speeds the clock, adjusting the bob down slows the clock.
The earliest escapement can be traced back to a Buddhist monk Yi Xing in china around 725A.D. He was also a Chinese astronomer, mathematician, and mechanical engineer of the Tang Dynasty (618-907). His contribution was designing and operating a water-powered armillary sphere.
Many escapements have been designed and developed over the years. One that predates the pendulum around 1275A.D. is the Verge escapement, also known as the crown-wheel-and-verge escapement. This escapement design and function is similar to a teeter- totter on a playground. The problem was this system had no natural frequency of oscillation, it is simply force pushing inertia around.
The next development was attaching the verge escapement to a pendulum. Galileo had the idea for a pendulum clock in 1637. This increased the accuracy of clocks enormously, from about 15 minutes per day to 15 seconds per day, leading to their rapid spread as existing clocks were retrofitted with pendulums. In order for this to work the axis of the verge became horizontal. This design was good at keeping time, but the swing of the pendulum was very wide up to 100 degrees.
Anchor escapement also known as recoil escapement was the next big development in 1670. The swing of the pendulum was greatly reduced to 4-6 degrees. The teeth of an anchor escape wheel project radially from the edge of the wheel, much like an up side down anchor. The second pendulum clock was built by Christian Huygens, in 1673. Development of this escapement allowed the introduction of the long clock better know as a grandfather clock, made by William Clement around 1680. The increased accuracy resulting from these developments caused the minute hand, previously rare, to be added to clock faces beginning around 1690.
Improvements in designs lead to the Dead beat escapement introduced around 1715 by George Graham. This design lead to the lever escapement. The up side down anchor was given a rounded edge so as not to lock the gear. This allowed the pendulum to operate the clock on both back and forth swings. Wear on the escapement was greatly reduced. In most wall clocks that use a pendulum, the pendulum swings once per second. In small cuckoo clocks the pendulum might swing twice a second. In large grandfather clocks, the pendulum swings once every two seconds,
The lever escapement is widely used and very accurate. Clocks today have a very long and rich history. Depending on which clock suits your need or desire you can have confidence in there accuracy and dependability.
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