Controllable Hydraulic Turnbuckle

The invention relates to a controllable hydraulic turnbuckle for a power transmission member having a first mode of operation with increased forces and a second mode of operation with less forces, comprising: first (10) and second (11) lower and upper assembly elements, respectively, arranged at axially opposite ends; a tube (7) rigidly connected to the first assembly element (10) inside which a piston (5) slides, said piston being rigidly connected to the second assembly element (11); a resilient sleeve (3) surrounding the tube (7) and the piston (5), defining a low-pressure chamber (21); a prestressed spring (12) between the first (10) and second (11) assembly elements; a first channel (62, 63) provided inside the first (10) assembly element for placing the low-pressure chamber (21) and the inside of the tube (7) in communication, said first channel being provided with a first plugging device (8); a second channel (51, 52) provided in said piston (5), the end of which leads into the tube (7), said second channel being suitable for connecting a high-pressure chamber (20), located between the through-ends of the first (62, 63) and second (51, 52) channels, to the low-pressure chamber (21); and a second plugging