A lubricator (1) includes a coaxial compartment (3) with a shaped seat (4) upon which a sliding shutter (5) consisting of a front shaped plug (6) and an intermediate stem (7) with a back beat (8) associated with a first stop pin (9), operates; in the rear threaded end (10) of the compartment (3) a security dowel (11) with a front beat (12) associated with a second stop pin (13), screws on. A counter spring (15) engages itself between pins (9) and (13). The stem (7) of the shutter and the dowel (11) present peripheral helical grooves (14, 14′) with a spiral developing in the opposite direction as to the threading (10) of the compartment (3) and the threading of the dowel (11) itself.