The present invention provides a check valve comprising a valve housing (1,2), a substantially circular flapper (3), a valve seat (16) for the flapper (3), an expandable chamber (11) in fluid contact with a connecting port (8) for hydraulics fluid, and a piston (4) having a first and a second end, the flapper comprises a first (19) and a second (18) connection point and is pivotably connected at the first connection point (19), said flapper is capable of pivoting between a closed position in close contact with the valve seat (16) and an open position which allows fluid to flow through the valve, the piston (4) is in contact with the expandable chamber (11) and a pre-stressed compressible device (15), said piston (4) pivotably connected at the first end to the flapper (3) via the second connection point (18), wherein the compressible device (15) can move the piston (4) in a direction towards the valve seat ( 16), and that hydraulics fluid can move the piston (4) in a direction away from the valve seat when sufficient hydraulics fluid is supplied through the connection port (8) to expand the chamber (11), and that the second connection point (18) is situated closer to the center of the circular part of the flapper than the first connection point (19), such that the flapper (3) comes into close contact with the valve seat (16) when the piston (4) is moved in a direction towards said valve seat and the flapper will pivot around the first connection point (19) in a direction towards the piston (4) when the piston is moved in a direction away from the valve seat (16).La présente invention concerne un clapet anti-retour comportant un corps (1,2) de clapet, un battant (3) sensiblement circulaire, un siège (16) de clapet destiné au battant (3), une chambre expansible (11) en contact fluide avec un orifice (8) de raccordement destiné à un fluide hydraulique, et un piston (4) présentant une première et une deuxième extrémité, le battant comportant un premier (19) et un deuxièm
