Safety Clutch

a coupling that disconnects two shafts or a shaft and a component fitted to it when there is an excessive increase in the torque transmitted (an overload) or in the speed of rotation; that is, it protects a machine from breakage when the normal operating conditions are exceeded.

Safety clutches are classified as torque-limiting, which have breakable elements, usually shear pins, that can be replaced after the clutch disengages; dog, ball, and other clutches that are kept engaged by springs until the torque increases to the point of overcoming the spring forces; and friction clutches, in which pressure is created between frictional surfaces by springs adjusted to transmit the maximum permissible torque. The function of protecting machines from overloads is often performed by other types of clutches, such as hydrodynamic clutches. Safety clutches that limit the speed of rotation are usually of the centrifugal type.