Device for separating films from a mass of waste moving in one direction, comprising: - a frame, - a moving part mounted on the frame and having an endless peripheral surface delimiting an inner space, - teeth mounted so as to be movable with the moving part, distributed along the endless peripheral surface and retractable in the inner space via openings provided in the endless peripheral surface, - means (14, 15, 16, 17) for circulating the moving part, and thus the teeth, along a closed circulation path comprising an area of engagement of the films by the teeth, in which, in use, the direction of movement of the teeth is opposed to the direction of movement of the mass of waste, and an area of disengagement of the films with respect to the teeth, - means for controlling the exit (24, 40) and the re-entry of the teeth such that, in the engagement area, the teeth are in the exited position, in which they protrude from the endless peripheral surface for the engagement of films, and such that, in the disengagement area, the teeth are in the re-entered position, in which they are retracted in the inner space, and - means (24, 41) for maintaining the teeth in the exited position in the engagement area, comprising, on one hand, support rigid means each of which are integral with one or more teeth and, on the other hand, at least one track defining a support path the position of which is fixed with respect to the closed circulation path followed by the moving part, the one or more tracks being connected to the frame, characterized in that the one or more tracks is/are in the inner space of the separation device and positioned such that, when the one or more teeth integral with a support rigid means are in the engagement area, said support rigid means is in contact with at least one track and thus prevents the one or more teeth from being brought in the re-entered position. - a frame, - a moving part mounted on the frame and having an endless peripheral surface delimiting an inner space, - teeth mounted so as to be movable with the moving part, distributed along the endless peripheral surface and retractable in the inner space via openings provided in the endless peripheral surface, - means (14, 15, 16, 17) for circulating the moving part, and thus the teeth, along a closed circulation path comprising an area of engagement of the films by the teeth, in which, in use, the direction of movement of the teeth is opposed to the direction of movement of the mass of waste, and an area of disengagement of the films with respect to the teeth, - means for controlling the exit (24, 40) and the re-entry of the teeth such that, in the engagement area, the teeth are in the exited position, in which they protrude from the endless peripheral surface for the engagement of films, and such that, in the disengagement area, the teeth are in the re-entered position, in which they are retracted in the inner space, and - means (24, 41) for maintaining the teeth in the exited position in the engagement area, comprising, on one hand, support rigid means each of which are integral with one or more teeth and, on the other hand, at least one track defining a support path the position of which is fixed with respect to the closed circulation path followed by the moving part, the one or more tracks being connected to the frame, characterized in that the one or more tracks is/are in the inner space of the separation device and positioned such that, when the one or more teeth integral with a support rigid means are in the engagement area, said support rigid means is in contact with at least one track and thus prevents the one or more teeth from being brought in the re-entered position.