| 摘要 |
1394130 Threaded fasteners ILLINOIS TOOL WORKS Inc 31 Aug 1972 [1 Sept 1971] 40467/72 Heading F2H To prevent electrolytic corrosion between the head of a metal fastener, e.g. a steel selftapping screw 11, and a metal sheet 23 engaged by the fastener, the head, which has a non- circular portion 13 and a flange 14, is encapsulated by a complementary shaped cap member 17 which prevents direct contact between the fastener and the sheet, and which is made of metal, e.g. aluminium or an alloy of aluminium or magnesium, having a different contact potential from that of the head 13, 14. The member 7 is preferably of the same material as the sheet 23 to minimize corrosion between it and the sheet, and the head 13, 14 may be plated with a metal such as zinc or cadmium. An elastomeric sealing washer (25) may be fitted between an inturned skirt portion 20 of the member 17 and the sheet 23, (Figs. 4 and 5, not shown), part of the washer being received in an annular recess 15 in the flange 14 when the fastener is tightened.
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