| 摘要 |
Fastener assemblies for mounting a workpiece such as a hub centered wheel rim include a threaded fastener and a clamp washer. The fastener includes a body having a thread structure and a structure engageable by a tool for tightening of a threaded joint to urge the fastener assembly against the workpiece. The clamp washer includes a central aperture surrounding the thread structure and interposed between the fastener body and the workpiece. A pair of cooperating bearing surfaces are formed on the inner end of the workpiece and the outer side of the clamp washer, and a clamp surface is defined on the inner side of the clamp washer. When the fastener assembly is tightened against the workpiece, the bearing surfaces comprise continuous annular spherical zones having common centers and radii of curvature to the end that the bearing surfaces are in intimate wide area face-to-face contact and the clamp surface is in flat area contact with the workpiece regardless of the squareness condition of the threaded joint. The clamp washer may be resiliently deformable during tightening and the clamp surface may initially be of a truncated cone shape in initial circular line contact at its outer periphery with the workpiece. The clamp washer bearing surface may initially be in circular line contact only with the fastener body bearing surface to prevent rotation of the clamp washer against the workpiece. A body of low friction plastic material may be interposed between the bearing surfaces to prevent large frictional forces at the bearing surfaces, and the clamp surface may be scored or roughened to prevent low friction forces at the workpiece. |
