Hydraulic Elevators

One impact, the downward motion of the plunger assembly displaces oil through the metering tube holes. thereby decelerating the impacting mass. The buffers's performance characteristics are dependent upon the size and distribition of these holes.
The re-extension of the plunger after impact is effected by a unique gas spring. This gas spring contains nitrogen at a pressure of 20 to 30 bar. The area differential between the top and bottom of the piston results in a net force which re-extends the plunger after the compressive load is removed;(the gas in not compressed).
Thus the buffer performance on impact relies solely on oil displacement; the gas spring serves only to re-extend the plunger. Moreover, frictional forces of the plunger remains re-extended.