Glossary
Buffer
An energy-absorbing device located in the pit beneath the car and counterweight travel paths, designed to safely decelerate the car or counterweight in the event of an overtravel beyond the normal limits.
Buffers are the last line of defence in an elevator safety system. They are positioned in the pit directly below the paths of the car and counterweight. If the elevator overtravels past the lowest landing (or if the counterweight overtravels past its lowest point), the buffer absorbs the kinetic energy and brings the moving mass to a stop.
Two types are common. Spring buffers use heavy coil springs and are permitted for elevators with rated speeds up to 0.75 m/s (about 150 ft/min). Oil buffers use a piston-and-cylinder arrangement filled with oil that is forced through orifices during compression, providing a controlled deceleration profile suitable for higher-speed elevators. Oil buffers must be maintained to ensure proper oil level and free piston return.