Abstract: A fluted piston for a volume-compensated pressurized adjustable length positioner. The cylinder is charged through the charging/discharging valve so that the opposed fluid chambers defined inside the cylinder bore by the slidably movable piston are filled with compressible fluid at elevated pressure. An actuating rod in the piston operates a valve in the piston to open communication between the opposed chambers and allow selective extension and retraction of the piston rod. The large-diameter piston rod has an elongated head configuration formed by flute ribs. These ribs provide bearing support for the extended piston rod and create a volume compensating space in the piston head to account for the large ratio of extended-rod cylinder volume to retracted rod cylinder volume.

Abstract: A gas cylinder for applications requiring height adjustments such as found in chairs, stools, or like structures supported by columns. The cylinder has an elongated rechargeable unit of double-wall construction provided with a springless check valve inside a fluid port thereof preferably all of molded plastic. A single-piece sealed plunger assembly includes a single actuating rod with velocity controls incorporated therein which permit vertical extension from collapsed to fully-extended positions. Depression of the actuating rod allows circulation of the pressurized fluid between the chambers, with pressure force acting to extend the plunger when the unit is unloaded. When the unit is loaded, the plunger can be retracted.