Screw jack for lifting water, has radial dimensions of screw blade at bottom end of screw designed to reduce injury to migrating fish

摘要

The radial dimensions of the screw blade (8) at the bottom end (14) of the conveyor screw (17) decrease evenly in the opposing direction to the top end (15) of the screw. The conveyor screw comprises a screw beam (7) with at least one screw blade extending around it, as well as a trough (18) in which the screw is rotatably mounted in a tight fit manner. The screw has a slanting central axis and its rotation direction is chosen so that water is transported from its bottom end to its top end. An independent claim is also included for a water lift apparatus, comprising a casing (2) which extends between a lower body of water (3) and a higher body of water (5), containing this screw jack (1).