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999,493. Centrifugal pumps. H. KRAEMER. Jan. 13, 1964 [Jan. 12, 1963], No. 1364/64. . Heading F1C. [Also in Divisions F2 and H2] In a multi-stage rotary pump driven by a gap tube electric motor, the impellers and the armature are arranged at opposed ends of a shaft, and that part of the shaft extending therebetween is supported by a single bearing. A shaft 3, carrying in overhung fashion the pump impellers 5 and the motor armature 6, is mounted at its centre in a bearing 4. The bearing 4 is lubricated and, if necessary, cooled by liquid by-passed from an intermediate or, as shown, the final pump stage, through a screen 13, openings 12, a bore 8 in the shaft 3, and a gap 26 between the motor gap tube 7 and the armature 6 to the motor end of the bearing clearance 17 which extends to the pump inlet chamber. The liquid entering the clearance 17 is clean since any solid particles are centrifugally separated at the outlet end of the gap 26. The liquid not entering the clearance 17 passes through openings 28 to the inlet chamber 18. Alternatively, the by-passed liquid may be returned to an intermediate pump stage. The by-passed liquid cools the motor 2 and, in the gap 26, creates a floating bearing for the shaft 3. The pressure drop in the liquid passing through the gap 26 enables the armature 6 to act as a pressure compensating piston for the pump 1. A case hardened ball 23 contacting a thrust face 21 supports the shaft 3 axially when the pump is stationary or during starting thereof. A hollow screw 15 at the pump end of the shaft 3 may be replaced by one having a different size aperture 16 to adjust the quantity and pressure of the liquid passing to the gap tube 7. The pump may be used as an underwater massage pump, the heat removed from the motor being supplied to the circuit of the massage bath to maintain the liquid temperature therein. Alternatively, the pump may be used in a steam plant to pump and partially heat the condensate.
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