The safety device (10) includes a tubular body (12) configured to receive a barrel (102), a head arrangement configured to abut against the flange (107) and to lock into a flange (107), at least two actuation arms (16,216) connecting the tubular body (12) and the head arrangement, said actuation arms (16,216) having a proximal link (39,239) connected to the head arrangement by a proximal hinge (42,242) and a distal link (40,240) connected to the tubular body (12,212) by a distal hinge (47,247), the proximal link (39,239) and the distal link (40,240) being connected by an intermediate hinge (49,249), the actuation arm (16,216) being movable between a collapsed position in which the tubular body (12,212) is maintained in a position proximally close to the flange (107) uncovering the needle (101) and an extended position in which the tubular body (12,212) is maintained in a position distally distant from the head arrangement shielding the needle (101); a locking means for maintaining the actuation arms (16,216) in a collapsed position and a locking means for maintaining the actuation arms (16,216) in an extended position.