A self-locking nut assembly includes a nut, and a washer connected with the nut. The nut has a screw bore and a protruding conical ring. The washer has a central portion provided with a conical hole which includes a limit section and an annular tapered section. The conical ring is extended through the conical hole. The conical ring of the nut has a distal portion provided with an annular opening which is enlarged and expanded outward to form a protruding flange. The protruding flange is limited by the limit section of the conical hole. Thus, a determined clearance is defined between the conical ring of the nut and the conical hole of the washer, so that the nut and the washer have determined axial and radial gaps, and the washer can be rotated freely.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 3 and 4, a self-locking nut assembly in accordance with the preferred embodiment of the present invention comprises a nut20, and a washer30connected with the nut20.

The nut20has a hexagonal shape and has a central portion provided with a screw bore21. The nut20has a bottom provided with a first wedge-shaped portion22. The first wedge-shaped portion22of the nut20includes at least one oneway wedge-shaped tooth23. The oneway wedge-shaped tooth23of the first wedge-shaped portion22includes a ramp231and a vertical catch face232. The ramp231of the oneway wedge-shaped tooth23has an outer edge and an inner edge. The outer edge and the inner edge of the ramp231have the same height at the same central angle. The nut20has a periphery provided with a protruding conical ring24located between the first wedge-shaped portion22and the screw bore21. The conical ring24of the nut20has a cross-sectional profile with the same outer diameter. The conical ring24of the nut20has a distal portion provided with an annular opening241. The conical ring24of the nut20has an inner conical shape and has a root portion whose thickness is greater than that of the annular opening241. The annular opening241of the conical ring24has a periphery provided with a protruding flange242.

The washer30has a top provided with a second wedge-shaped portion32having a shape matching that of the first wedge-shaped portion22of the nut20. The washer30has a bottom provided with a plurality of protruding bars33which are arranged in a radiating manner. Each of the protruding bars33of the washer30includes an oblique wall331and a vertical wall332. The oblique wall331of each of the protruding bars33is arranged in a screwing direction of the nut20. The washer30has a central portion provided with a conical hole31. The conical hole31of the washer30includes a limit section311and an annular tapered section312. The limit section311of the conical hole31has a diameter slightly greater than an outer diameter of the conical ring24of the nut20as shown inFIG. 4. The second wedge-shaped portion32of the washer30has at least one oneway wedge-shaped tooth. The limit section311of the conical hole31extends from a bottom of the oneway wedge-shaped tooth of the second wedge-shaped portion32toward the bottom of the washer30, and has a determined thickness “A”. The annular tapered section312of the conical hole31is inclined relative to and extended outward from the limit section311and has a tapered angle “B” relative to an axis of center of the conical hole31. Preferably, the thickness “A” of the limit section311has an optimum value ranged between 0.1 mm and 0.3 mm, and the tapered angle “B” of the annular tapered section312has an optimum value ranged between 25° and 35°, so that the nut20and the washer30are connected in an optimum manner. The washer30has a circular shape and has an outer periphery provided with at least one slot34to allow insertion of a special tool. Alternatively, the washer30has a hexagonal shape for operation of a normal hand tool.

In fabrication, the conical ring24of the nut20is extended through the conical hole31of the washer30. Then, a plunger40of a stamping die is inserted into the annular opening241of the conical ring24to enlarge the annular opening241of the conical ring24so as to form the protruding flange242. At this time, the annular opening241of the conical ring24has a determined thickness smaller than that of the root of the conical ring24, so that the annular opening241of the conical ring24is easily expanded outward to form the protruding flange242. In such a manner, the protruding flange242of the conical ring24has a size greater than a diameter of the conical hole31of the washer30, so that the protruding flange242of the conical ring24is limited by the limit section311of the conical hole31. Thus, the nut20and the washer30are combined together and will not be detached from each other.

Especially, the annular opening241of the conical ring24has a determined thickness smaller than that of the root of the conical ring24, so that the angle of the outer diameter of the protruding flange242can be contracted inward, and the outer diameter of the protruding flange242is disposed at a vertical state. In addition, the outer diameter of the conical ring24will not be expanded outward and enlarged so that the conical ring24has an upright and flat outer portion under the protruding flange242. Thus, a determined clearance is defined between the conical ring24of the nut20, and the limit section311and the annular tapered section312of the washer30, so that after the nut20and the washer30are combined together, the nut20and the washer30have determined axial and radial gaps, and the washer30can be rotated freely.

Accordingly, a determined clearance is defined between the conical ring24of the nut20and the conical hole31of the washer30, so that the nut20and the washer30have determined axial and radial gaps, and the washer30can be rotated freely.