ADJUSTABLE SEAT HAVING A HYDRO-PNEUMATIC SPRING MECHANISM

An adjustable seat having a hydro-pneumatic spring mechanism which includes a cylinder connected to a seat back, a piston axially slidable in the cylinder, a piston rod projecting forwardly from the piston and connected to a seat structure and a valve connected to the piston rod to operatively engage with the piston. The cylinder has formed in its cylinder bore a gas compartment filled with a gas under pressure and a liquid compartment in which the piston and the valve are located. The cylinder together with the piston is rotatable relative to the piston rod through threads formed on the connecting portions of the piston and the piston rod, causing the cylinder to axially move relative to the seat so that the seat back is angularly moved between upright and reclining positions. Arrangements may be made to prevent the piston from being over-screwed and consequently sticking to the piston rod due to application of excess torque to the cylinder. Such arrangements include means to limit the angle of rotation of the cylinder or means to cause the valve to be deformed elastically when depressed by the piston.