| 摘要 |
A screw is adapted to cooperate with a casing and at least one pinion-wheel for compressing or expanding a fluid within the space located between two screw threads, the casing and a tooth of the pinion-wheel. The casing and the crests of the threads carry two cooperating surfaces, and at least part of one of the surfaces comprises lands defining continuity of the surface but being discontinued along any circle centered on the axis of the screw. The lands separate cells which trap formative seizure particles and, thus, reduce the clearance needed between the screw and the casing.
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