Re-adjustable Chairs

Chairs nowadays are re-adjustable to add to the comfort of the users. There is a gas cylinder that has an internal piston that compresses a gas to a higher pressure when weight is put on it. A friction clamp is present to hold the piston's rod in a set position. This clamp acts like the height selector. A soft spring gives a bit of cushion when a person sits on the chair. If the chair is too low, a lever releases the friction clamp, letting the piston come up, raising the chair against the chair's weight. If a person is sitting in the chair at that time, the gas pressure against the piston is not enough, and the chair goes down.