A step actuator includes a housing, a stator in the housing, a rotor including a magnet provided radially inward of the stator and a nut member inserted into the magnet and protruding through one side of the housing, a bearing rotatably supporting the nut member, a screw member coupled with the nut member to linearly move as the rotor rotates, and a mounting member supported on one side of the housing to support the screw member in such a manner that the screw member is linearly movable. The nut member includes an end portion passing through the bearing and a coupling portion extending from the end portion to couple with the bearing.

A step actuator includes a housing, a stator in the housing, a rotor including a magnet provided radially inward of the stator and a nut member inserted into the magnet and protruding through one side of the housing, a bearing rotatably supporting the nut member, a screw member coupled with the nut member to linearly move as the rotor rotates, and a mounting member supported on one side of the housing to support the screw member in such a manner that the screw member is linearly movable. The nut member includes an end portion passing through the bearing and a coupling portion extending from the end portion to couple with the bearing.

Medical devices in accordance with various embodiments of the present invention employ one or more coaxial screw gear sleeve mechanisms. In various embodiments, coaxial screw gear sleeve mechanisms include a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to expand.

A method of manufacturing a ball screw device includes a nut unit preparation step, a screw shaft preparation step, and an assembly step. In the nut unit preparation step, a nut unit is prepared in which a circulation component, a ball, and a temporary shaft that prevents the ball from falling off are assembled to a nut provided with an inner peripheral track surface. In the screw shaft preparation step, a screw shaft provided with an outer peripheral track surface is prepared. In the assembly step, after the nut unit preparation step and the screw shaft preparation step, the temporary shaft of an arbitrary nut unit is replaced with an arbitrary screw shaft to manufacture the ball screw device.

The system comprises a roller screw mechanism 12 which is provided with a screw 16 which comprises at least a first outer threaded portion 18, a nut 20 and a plurality of rollers 24 which cooperate with the first outer portion 18 and an inner thread of the nut. The system further comprises a roller thrust bearing 14 which is mounted on a second outer portion 52 of the screw and which is provided with a bushing 50 and a plurality of rollers 56 which comprise flanks which cooperate with flanks of the second outer portion 52 of the screw and the bushing 50. The flanks of the screw, the bushing and the rollers are configured so that, during a rotation of the screw, the rollers 56 are fixed axially relative to the screw 16 and relative to the bushing 50.

Medical devices in accordance with various embodiments of the present invention employ one or more coaxial screw gear sleeve mechanisms. In various embodiments, coaxial screw gear sleeve mechanisms include a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to expand.

Medical devices in accordance with various embodiments of the present invention employ one or more coaxial screw gear sleeve mechanisms. In various embodiments, coaxial screw gear sleeve mechanisms include a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to expand.