Screw union for pipe closure - has threads divided circumferentially into equal numbers of thread-free and threaded strip zones

摘要

The screw union is between outer and inner threaded parts, one of which is drawn against a stop. The outer and inner threads are divided circumferentially into thread-free areas (9,11) and further areas parallel to the thread lengthways axis which are threaded (8a,10a). The number of thread-free areas (9,11) is equal to that of the strips (8,10) of threaded zones. The breadth (b) of the strips (8,10) measured in a circumferential direction is slightly less than that (B) of the thread-free areas (9,11). The union is esp. for use in the closure of a cover in or over a pipe or shaft inlet, where the cover can be drawn against a stop.