Gas or fluid driven mechanical stepper motor

A stepper motor for use in a MRI scanner, comprising:

• the stepper motor including a housing, in which a cylindrical rotor fixed on a central shaft can rotate but not translate along an axial direction, characterized in that there are cylindrical translators on both sides of the rotor, where the translators are sealed fit in a cylindrical space within the housing and around the central shaft and where the translators can only translate in an axial direction, where in one axial position of each of the translators, a respective set of triangular asymmetric teeth located on the respective translator can interact and fit into a respective set of triangular asymmetric teeth on the rotor, and where either the set of teeth of one of the translators relative to the set of teeth of another of the translators are tangentially shifted over a length equal to half the width of a tooth and the respective set of teeth at one side of the rotor is symmetric to the respective set of teeth on another side of the rotor, or one of the sets of teeth of the rotor relative to and another of the sets of teeth of the rotor are tangentially shifted over a length equal to half the width of a tooth and where each of the translators is moved by a pressure difference between a part of the cylindrical space between the housing and the respective translator and a part of the cylindrical space between the respective translator and the rotor, where the motor is made from a non-ferromagnetic material.

A method to rotate an axis of a stepper motor in surgical instruments or chemical plants, the stepper motor including a housing, in which a cylindrical rotor fixed on a central shaft can rotate but not translate along an axial direction, characterized in that there are cylindrical translators on both sides of the rotor, where the translators are sealed fit in a cylindrical space within the housing and around the central shaft and where the translators can only translate in an axial direction, where in one axial position of each of the translators, a respective set of triangular asymmetric teeth located on the respective translator can interact and fit into a respective set of triangular asymmetric teeth on the rotor, and where either the set of teeth of one of the translators relative to the set of teeth of another of the translators are tangentially shifted over a length equal to half the width of a tooth and the respective set of teeth at one side of the rotor is symmetric to the respective set of teeth on another side of the rotor, or one of the sets of teeth of the rotor relative to another of the sets of teeth of the rotor are tangentially shifted over a length equal to half the width of a tooth and where each of the translators is moved by a pressure difference between a part of the cylindrical space between the housing and the respective translator and a part of the cylindrical space between the respective translator and the rotor, comprising:

• alternately applying high and low pressure gas to the first space of the one translator and low and high pressure gas to the first space of the other translator, while keeping the the second spaces permanently at an intermediate pressure.