Core sampler

Core sampler associated with a coring bit (3), for grasping a core sample (C) to be brought to the surface:

• a deformable moving ring (5) having a cylindrical internal surface (6) designed to clamp the core sample (C) and a frustoconical external surface,
• a cavity (8) which has a wall (12) with an internal cone frustum-shaped bearing surface (12) corresponding in terms of its shape and size to the external frustoconical surface (7) of the moving ring (5), which is fixed to the core sampler (1) at least in the longitudinal direction thereof and in which the moving ring (5) can be housed in such a way that it can occupy, in the longitudinal direction, two extreme positions, one being a clamping position in which the moving ring (5) pressed into the internal cone frustum (12) is deformed inward so as to reduce its internal cross-section and thereby clamp the core sample (C) in order to immobilize it at this point in the core sampler(1), characterized in that
• in the other extreme position, known as the starting position, the moving ring (5) is exposed to zero or minimal strain from the bearing surface (12) and has an inside diameter not smaller than the outside diameter of the core sample (C) to be grasped, and the core sampler (1) comprises control means intended to move the moving ring (5) in the longitudinal direction from the extreme starting position as far as the extreme clamping position.