| 摘要 |
928,416. Centrifugal pumps. ETA-CORPORATION G.m.b.H. June 30, 1959 [April 3, 1959], No. 22392/59. Class 110 (1). A centrifugal pump for mixed media, particularly a centrifugal pump of the kind employed for conveying liquid or gaseous media, or both, which entrain solids or slurries, comprises a casing having a central inlet and an open-sided bladed impeller mounted within the casing with its open side facing the inlet, the impeller having a plurality of stages with the delivery surface of the first stage extending substantially radially towards an annular outlet nozzle, the direct flow path to the outlet nozzle for material delivered from the surface being unobstructed by blades. In the two-stage pump shown, the front wall 2 of the casing and the edges 7 of the impeller blades are formed with respective radii of curvature 6, 8 about a common centre. The front wall 2 and the back wall 3 of the casing merge into the throat of an annular outlet nozzle 4 in such manner that the mean flow line 5 merges into the median axis of the nozzle. The widening angle a of the nozzle, which may be greater than 12 degrees, may be such as to cause breakaway of flow at at least one of the side walls of the nozzle, thereby forming cavities in which vacuum pressures arise, for the purpose of facilitating the pumping of liquids with gaseous occlusions. The delivery surface 11 of the first stage may project into the flow path as shown in dotted lines, in which case the front wall 2 may be similarly shaped with a projection at 12 to form a throat or nozzle-like constriction. The blades of at least one stage may be wholly or partly of rubber or the like; and the pitch, shape, obliquity and number of the blades may vary from stage to stage. The front and back walls of the easing may be generated by arcs of circles of the same radii so as to form a symmetrical annular outlet nozzle having an axial width at its entry which is greater than the inlet diameter of the casing and a throat width approximately equal to the inlet diameter so that large lumps of material entering the pump are not intercepted by obstructions. Specification 928,415 is referred to. |
