Device forming a hydraulic jack and usable in a hydropneumatic suspension for automotive vehicles

Device forming a hydraulic jack comprising a cylinder housing a sliding piston-equipped structure configured so as to delimit in the cylinder first, second, and third self-contained chambers, wherein the first and second chambers are annular and enclose a sliding cylindrical element including a first piston delimiting the first and second annular chambers, and a second piston delimiting the third chamber which is a substantially cylindrical chamber contiguous to one of the first and second annular chambers, the sliding cylindrical element including two coaxial tubular sections having the same diameter, whose opposite ends are open, and which are separated from each other by a transverse inner partition, the first piston having an overall ring shape and being mounted on, and coaxially to, one of the tubular sections in proximity to the transverse partition, and the other of the two tubular sections forming said second piston.