Pallet fork
Encyclopedia
Lever escapement
The lever escapement is a key component of the typical movement found in most mechanical wristwatches, pocket watches and many small mechanical non-pendulum clocks....
of a typical mechanical watch
Mechanical watch
A mechanical watch is a watch that uses a mechanical mechanism to measure the passage of time, as opposed to modern quartz watches which function electronically. It is driven by a spring which must be wound periodically...
. Its purpose is to release the escape wheel one tooth at a time, at each swing of the balance wheel
Balance wheel
The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...
, and also give the balance wheel small pushes to keep it going.
The lever is shaped like a 'T', and is pivoted in the center; in operation it rocks back and forth. On the arms of the 'T' are angled surfaces called pallets which alternately engage the teeth of the escapement's escape wheel. The central shaft of the lever ends in a fork, which gives pushes to the balance wheel
Balance wheel
The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...
's impulse pin, which is set off center in a disk on the balance wheel's shaft. To reduce friction, the pallets are made of precisely shaped pieces of ruby jewel. The pallet which the teeth first contact is called the entry pallet, while the other one is called the exit pallet.
Under the fork there is a projecting guard pin which passes through a notch in a separate safety roller disk on the balance shaft. In normal operation it doesn't have a function. Its purpose is to make sure the fork is in the right position to receive the impulse pin if a jar to the watch prematurely 'unlocks' the lever from the escape wheel.
Mechanical alarm clock
Alarm clock
An alarm clock is a clock that is designed to make a loud sound at a specific time. The primary use of these clocks is to awaken people from their night's sleep or short naps; they are sometimes used for other reminders as well. To stop the sound, a button or handle on the clock is pressed; but...
s and kitchen timer
Timer
A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...
s use a less accurate form of the lever in which vertical metal pins are substituted for the pallet jewels. This is called a Roskopf
Georges Frederic Roskopf
Georges F. Roskopf , the inventor of the pin-pallet escapement, was born in Germany and became a naturalized Swiss citizen.- Early life and introduction :...
or pin-pallet escapement, and was previously used in cheap pin-lever watches.