Electric lifting apparatus and roll press machine

A roll press machine comprising:

• (a) an electric lifting apparatus comprising:
• a ball screw including a threaded shaft having an axis,
• a pair of bearings configured to support the threaded shaft in such a manner that the threaded shaft is rotatable around the axis,
• a nut threadedly engaged with the threaded shaft via a plurality of rolling elements in such a manner that the nut moves linearly in a direction of the axis when the threaded shaft rotates,
• a frame configured to support the pair of bearings,
• an electric servo motor supported by the frame and having an output shaft being rotatable, wherein the output shaft of the electric servo motor and the axis of the threaded shaft are parallel to each other,
• a rotational force transferring mechanism configured to transfer a rotational force of the output shaft to a rotational force of the threaded shaft, wherein the rotational force transferring mechanism has a belt which is laid over the output shaft and the threaded shaft,
• a first moving body fixed to the nut and providing a first sliding surface inclined at a predetermined angle with respect to a plane including the direction of the axis, and
• a second moving body arranged to be movable linearly in a vertical direction perpendicular to the direction of the axis with respect to the frame, the second moving body having a second sliding surface configured to be slidably movable with respect to the first sliding surface,
• wherein the second moving body is caused to move linearly in the vertical direction by a sliding movement between the first sliding surface and the second sliding surface when the nut and the first moving body move linearly in a horizontal direction parallel to the axis,
• the threaded shaft extends through the first moving body in the direction of the axis, and
• the pair of bearings is arranged, respectively, on both sides of the first moving body;
• (b) first and second side rolls arranged in parallel to each other, wherein the first side roll is arranged stational, and the second side roll is arranged movable toward the first side roll to press itself against the first side roll by operation of the electric lifting apparatus;
• (c) a link member arranged between the second side roll and the second moving body of the electric lifting apparatus to transmit the vertical movement of the second moving body to the second side roll, wherein the link member includes a load cell for measuring a load applied by the second side roll against the first side roll;
• (d) a roll frame configured to support the first and second side rolls for rotation, wherein the roll frame extends downward below the first and second side rolls to surround at least part of the electric lifting apparatus, and
• (e) a controlling device connected to the electric servomotor and the load cell, the controlling device being configured to carry out a feedback control of the electric servo motor based on an applied load measured by the load cell and one of a target load value or a target load range,
• wherein two pairs of the first sliding surface and the second sliding surface are provided, wherein the first sliding surface and the second sliding surface are slidably movable to each other in each pair, and
• the two pairs of the first sliding surface and the second sliding surface are arranged on both sides with respect to the threaded shaft and at predetermined distances from the threaded shaft in a direction perpendicular to both the direction of the axis and the direction in which the second moving body is linearly movable.