| 摘要 |
A fastener includes a threaded shank (10) with a driving head (11) on one end and a cylindrical washer (16) of resiliently yieldable material encircling the shank and disposed beneath the head to be compressed between the latter and a workpiece (17, 18) as the shank is driven into the workpiece. The head includes a skirt (15) engaging the washer and the underside of the skirt is concave and formed with an annular rib (21). As the washer is compressed, the rib (21) exerts a downward force and produces a sealing circle between the washer (16) and the workpiece (17, 18). At the same time, the inner side of the rib (21) forces the washer downwardly and inwardly to form a seal around the shank (10). A flange (22) on the periphery of the skirt (15) traps and retains the washer (16) in the cavity on the underside of the skirt (15). <IMAGE> |
