Abstract: A movable center-of-gravity tube comprising a tube body (41), a center-of-gravity body (42) accommodated inside the tube body and balls (43) held on the center-of-gravity body (42) is provided, in which the center-of-gravity body (42) has a slightly smaller diameter than the diameter of an inner surface of the tube body and comprises three or more rows of ball circulation grooves (44) on its outer surface in parallel with each other, in which the ball circulation grooves (44) accommodate the balls in a circulation manner, and each of which comprises two rows connected to each other, in such manner that the balls in one groove of the ball circulation grooves rotate and circulate in contact with the inner circumferential surface of the tube body, while the balls in another groove rotate and circulate in no contact with the inner circumferential surface of the tube body, when the center-of-gravity body moves.

Abstract: A linear-motion bearing is disclosed including: an outer cylinder member having a plurality of endless steel ball circulation paths each including an outer-peripheral-side steel ball circulation path and an inner-peripheral-side steel ball circulation path, and having planar spaces in regions that are opposed to the endless steel ball circulation paths, respectively; a plurality of steel balls accommodated and arrayed in the endless steel ball circulation paths: and a synthetic resin plate including a metal piece at which the synthetic resin plate is held in contact with a steel ball row, the metal piece having an elongated shape in a direction along the steel ball row in the inner-peripheral-side steel ball circulation path, in which the elongated metal piece is curved so as to protrude toward an inner peripheral side of the outer cylinder member in the direction along the steel ball row in the inner-peripheral-side steel ball circulation path.

Abstract: A control apparatus of an ultrasonic motor, comprises a driving wave number determining means for determining a driving wave number based on the targeted displacement of a driven object driven by the ultrasonic motor, a normative driving wave generating means for generating continuously normative driving waves in the number of times determined at the driving wave number determining means, inserted an interval determined based on the targeted velocity of the driven object, every at least one cycle of the normative driving waves, and a driving wave generating means for generating driving waves having the predetermined frequency and the predetermined amplitude based on the normative driving waves generated at the normative driving wave generating means.

Abstract: A ball slideway which is employed, for example, for slidably supporting a work table on the bed of a machine tool, and which is suitable for use with large loads and easy to manufacture. A ball slides are provided with two ball circulating paths, each holding therein a number of balls. A ball slide is disposed on either side of an elongated rectangular guide member between the guide member and the inner sides of a bracket which surrounds three sides of the guide member. The balls make angular contact with both sides of the guide member and the adjacent inner sides of the bracket.