The open screw pump:
Fig. 2-16. This pump is discussed as an indication to the reader that there are numbers of pump configurations that do not conform to the more or less classical forms, as we have discussed.The forerunners of this device are to be found in antiquity.The occasional designation of Archimedes’ screw takes the design back to the early Greeks.The pump consists of a U-shaped channel, into which a rotating screw fits closely. The channel, angled at inclinations up to forty-five degrees, takes water from a lower level and literally “screws” the water from the lower to a higher level.The screw, of course, does not develop any pressure, as it is merely a conveyer.Modern forms of this pump are quite large.Used extensively in wasterwater plants for moving contaminated water, ther are excellent for this purpose, as there is very little to go wrong.The large sizes, with a closely-fitted screw, are quite efficient.One version surrounds the screw within a large tube, and the whole assembly is then rotated. All bearings are thus outside of the liquid and there is no leakage.