Provided is a nut that resists being loosened and is easy to be tightened. A nut 600 includes a nut main body 10 having a tapped hole 30 formed therein; an annular member 41 formed on the side of a top surface of the nut main body 10; and an outer frame member 45 formed on the side of an outer edge of the annular member 41. The annular member 41 includes a second end portion 42b in contact with a top surface 11 of the nut main body 10 and a first end portion 42a located opposite to the second end portion 42b. A top surface of the first end portion 42a is located above a top surface of the second end portion 42b. A first gap 40 is formed between the first end portion 42a and the top surface 11 of the nut main body 10. A second gap 49 is formed between a side surface of the annular member 41 and an inner wall 47 of the outer frame member 45. The top surface of the first end portion 42a of the annular member 41 is located above a top surface 46 of the outer frame member 45. The inner wall 47 of the outer frame member 45 is inclining while tapering in an upward direction.

Provided is a nut that resists being loosened and is easy to be tightened. A nut 600 includes a nut main body 10 having a tapped hole 30 formed therein; an annular member 41 formed on the side of a top surface of the nut main body 10; and an outer frame member 45 formed on the side of an outer edge of the annular member 41. The annular member 41 includes a second end portion 42b in contact with a top surface 11 of the nut main body 10 and a first end portion 42a located opposite to the second end portion 42b. A top surface of the first end portion 42a is located above a top surface of the second end portion 42b. A first gap 40 is formed between the first end portion 42a and the top surface 11 of the nut main body 10. A second gap 49 is formed between a side surface of the annular member 41 and an inner wall 47 of the outer frame member 45. The top surface of the first end portion 42a of the annular member 41 is located above a top surface 46 of the outer frame member 45. The inner wall 47 of the outer frame member 45 is inclining while tapering in an upward direction.

According to a first aspect of the invention we provide a three-piece self-reacting fastener, or lock nut, for connecting a joint having a threaded connector including: a first nut member engageable with the threaded connector and axially displaceable; a second nut member engageable with the first nut member and rotatable about an axis; a third nut member non-rotatably but axially displaceably connected with the first nut member, which during rotation about the axis, applies a load to the threaded connector and to tighten the lock nut; and a locking means which substantially non-rotatably connects the second nut member and the threaded connector with one another after tightening the lock nut.

An object of the present invention is to provide an anti-loosening device that exhibits its anti-loosening effect by means of an eccentric fit between a protrusion 12 of a nut 10 and a recess 22 in a nut 20, wherein the inclination of the nut 20 relative to the nut 10 when they have been tightened is minimized. The outer peripheral surface of the protrusion 12 and the inner peripheral surface of the recess 22 are constructed in such a manner that, with the nuts screwed to a threaded shaft S and an eccentric fit established between the protrusion 12 of the nut 10 and the recess 22 in the nut 20, the tapered outer peripheral surface portion 12a of the protrusion 12 interferes with the tapered inner peripheral surface portion 22a of the recess 22 along part of the circumference while a gap is formed between the distal-end outer peripheral surface portion 12b of the protrusion 12 and the closer-to-bottom inner peripheral surface portion 22b of the recess 22 along the entire circumference.

An object of the present invention is to provide an anti-loosening device that exhibits its anti-loosening effect by means of an eccentric fit between a protrusion 12 of a nut 10 and a recess 22 in a nut 20, wherein the inclination of the nut 20 relative to the nut 10 when they have been tightened is minimized. The outer peripheral surface of the protrusion 12 and the inner peripheral surface of the recess 22 are constructed in such a manner that, with the nuts screwed to a threaded shaft S and an eccentric fit established between the protrusion 12 of the nut 10 and the recess 22 in the nut 20, the tapered outer peripheral surface portion 12a of the protrusion 12 interferes with the tapered inner peripheral surface portion 22a of the recess 22 along part of the circumference while a gap is formed between the distal-end outer peripheral surface portion 12b of the protrusion 12 and the closer-to-bottom inner peripheral surface portion 22b of the recess 22 along the entire circumference.

Disclosed is a ring type locknut, where a frustum-shaped internal thread concave cavity is arranged on a nut, inside which an annular member with frustum-shaped internal and external threads matching the concave cavity nut is provided, an eccentric value based on a specification thread fit clearance is set between internal threads and external threads of the annular member, so that when the annular member is screwed into a bolt together with the nut for locking, the expected objective that the nut will not loosen by only locking a single structure is achieved thanks to a comprehensive effect of the formed original nut structure, the eccentricity of the annular member and the structure of multiple properties of the tapered thread; the single-structure nut is used in a superposed mode, or the annular member is arranged on another nut, so that the overall anti-loosening effect is improved by the double-nut structure.