Abstract: A sealing device includes a tubular central core (1, 40, 61) of generally U-shaped cross section. The central core has a degree of elasticity to deformation of its shape in a plane perpendicular to its longitudinal direction (2). A membrane (5, 41, 65) is disposed around said central core. The membrane is made of a flexible and elastic material having a much higher coefficient of elasticity than the central core. The membrane is sealed with edges of side walls (15) of the central core and at the longitudinal end of the membrane to the core to form a closed deformable chamber (8, 42, 68) of substantially crescent-shaped cross section. A fluid under pressure is admitted to the inside of the chamber (8, 42, 68).