Locking device for columns of presses with at least one stationary platen and at least one movable platen, comprising: • a containment body connected to said column, and equipped on both ends with a bottom plate, a front plate, suitable to be firmly fastened to said moveable platen, and a rear plate; • one or more locking elements or wedges housed in the interior of said containment body and acting on the surface of said column, said wedges having a substantially conical or tapered outer surface; • at least one piston suitable to tighten said wedges on said column, said piston having a substantially conical or tapered inner surface corresponding to said outer surface of the wedges, to couple exactly with said wedges themselves; • a locking chamber located between said front plate and said piston, in which, through a junction, the operating fluid is injected in order to drive said piston in an axial direction and moving away from said moveable platen; • an unlocking chamber located between said rear plate and said piston, in which, through a junction, the operating fluid is injected in order to drive said piston in an axial direction and toward said moveable platen; and where applying a positive pressure in said locking chamber and maintaining controlled value of pressure in said unlocking chamber, said piston is pushed to compress said wedges that tighten on the column, while applying positive pressure in said unlocking chamber, maintaining zero pressure in said locking chamber, said piston is pushed in the axial direction but in the opposite direction, that is, toward said moveable platen, allowing the wedges to flex radially outward, releasing the column, characterized in that it comprises, in said containment body at least one wedge flange firmly fastened to the back of said wedges, able to translate axially wherein the wedge flange includes at least one stop surface which faces the inside of said unlocking chamber, which is substantially transversely oriented in respect to said axial direction and on which the pressure applied in said unlocking chamber operates, such that said wedge flange returns to said resting position, and where after the tightening of said wedges on said column by applying positive pressure in said locking chamber and maintaining zero or controlled pressure in said unlocking chamber, the group formed by said piston, said wedge flange, said wedges and said column translates with a maximum stroke (m) limited by a starting or resting position of the wedge flange to an end stop position, identified by the pressing of said wedge flange on said rear plate. • a containment body connected to said column, and equipped on both ends with a bottom plate, a front plate, suitable to be firmly fastened to said moveable platen, and a rear plate; • one or more locking elements or wedges housed in the interior of said containment body and acting on the surface of said column, said wedges having a substantially conical or tapered outer surface; • at least one piston suitable to tighten said wedges on said column, said piston having a substantially conical or tapered inner surface corresponding to said outer surface of the wedges, to couple exactly with said wedges themselves; • a locking chamber located between said front plate and said piston, in which, through a junction, the operating fluid is injected in order to drive said piston in an axial direction and moving away from said moveable platen; • an unlocking chamber located between said rear plate and said piston, in which, through a junction, the operating fluid is injected in order to drive said piston in an axial direction and toward said moveable platen;