Clock Escapement
In a mechanical clock, the regulator is called an 'escapement'; it controls the 'escape' of power from the spring or weight.
The first common escapement was the 'verge'. This consists of a crown wheel (a wheel with inclined teeth) and a wheel-topped piece (the verge). Pegs ('palletts') on the verge are pushed by the teeth of the crown, oscillating the balance wheel. It remained in use until about 1800. A variation of this was the foliot; a bar with adjustable weights replaced the balance wheel.
Clocks using this type of escapement have to be exactly level otherwise the balance wheel or foliot will rotate unevenly.
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anchor escapement
The anchor escapement of 1670 is controlled by the swing of the pendulum. The anchor is a C-shaped piece of metal on the ends of which are the teeth which perform the same function as the palletts on the verge. These control the movement of the escape wheel which is like a flattened crown wheel. Many verge clocks were converted to use the anchor escapement.
A third type of escapement is the 'dead beat' escapement; this is much more rare and used mainly on regulators and other precision clocks.
In a longcase clock, the escapement is usually of one of two types - anchor and dead beat. Anchor escapements are typical from the late 17th century to the middle of the 19th.
In a bracket clock, the escapement was usually a verge in the 17th and 18th centuries, but some in the late 18th century used a short pendulum with an anchor escapement.
In the 18th century, the fusee was introduced in spring movements; this uses a conical spool and a wire to even out the pull of the spring.