Actuators are devices that convert some type of stored energy into motion. The stored energy is usually in the form of compressed air (pneumatic pressure), electrical potential, or liquid (hydraulic) pressure.
Cams are mechanical devices used to convert the rotation of a shaft into simple or complex reciprocating linear motion. They can be sliding or rotational pieces in a mechanical linkage.
Gears are mechanisms that mesh together via teeth and are used to transmit rotary motion from one shaft to another. Gears are defined by two important items: radius and number of teeth.
Levers are mechanical devices used to scale the amount of force and/or travel in a mechanism.Levers are a versatile mechanism that can be used in a wide range of applications from small to large.
Ratchets are mechanisms that serve to limit either rotary or linear motion to only one direction. Ratchet designs vary but the basic composition of parts is fairly universal.
Springs are mechanisms that have the capacity to absorb, store and release energy through a change in shape. The most common use for a spring is to return a mechanism to its starting position and/or to add cushioning.