Stepper motor with a housing 1,2,4,6,16, in which a cylindrical rotor 11,15 fixed on a central shaft 12 can rotate but not translate along an axial direction. There are cylindrical translators 9, 14 on both sides of the rotors 11, 15, where the translators 9, 14 are sealed fit in a cylindrical space within the housing 6 and around the central shaft 12 and where the translators 9, 14 can only translate in an axial direction, where in one axial position of a translator 9, 14 a set of triangular asymmetric teeth 20 located on the translator 9, 14 can interact and fit into a set of triangular asymmetric teeth 21 on the rotor 11, 15, where the shape of the teeth 21 on both sides of the rotor 11, 15 is symmetric and where one of the sets of teeth 20, 21 between one translator 9 (14) and the rotor 11 (15) and a set of teeth 20, 21 between the other translator 9 (14) and the rotor 11 (15) are tangentially shifted, i.e. offset over a length equal to half the width of a tooth 20, 21 and where the translators 9, 14 can be moved by a pressure difference between the part of the cylindrical space between the housing 6 and a translator 9, 14 and the part of the cylindrical space between the translator 9, 14 and the rotor 11, 15.La présente invention porte sur un moteur pas à pas ayant un boîtier (1, 2, 4, 6, 16), dans lequel un rotor cylindrique (11, 15) fixé sur un arbre central (12) peut tourner mais ne peut pas se déplacer en translation le long d'une direction axiale. Il y a des dispositifs de translation cylindriques (9, 14) des deux côtés des rotors (11, 15), les dispositifs de translation (9, 14) étant scellés dans un espace cylindrique à l'intérieur du boîtier (6) et autour de l'arbre central (12) et les dispositifs de translation (9, 14) pouvant seulement se déplacer en translation dans une direction axiale, dans une position axiale d'un dispositif de translation (9, 14), un ensemble de dents asymétriques triangulaires (20) situées sur le dispositif de translation (9, 14)
