Patent attributes
A check valve for an injection string, comprises a cylindrical house with a central bore. A piston has a piston area exposed to the central bore, a protective sleeve at one end and a contact point affixed to the piston. A return spring is arranged between the house and the contact point so as to oppose a pressure force exerted on the piston area. A flapper valve—comprises a blade rotatable about a hinge between a closed position where the blade blocks a reverse flow through the central bore and an open position where the blade is received in a recess in a wall of the central bore. The piston is axially movable within the house between a first position where the protective sleeve is displaced from the recess and a second position where the protective sleeve covers the recess.
