| 摘要 |
1,259,528. Centrifugal pumps. J. OPLANDER Nov.11, 1969 [Nov. 12, 1968], No.55169/69. Heading F1C. A pump assembly, e. g. for central heating systems, comprises two separately-driven pumps 4, 5, Fig. 1, mounted in a common casing 1 having an inlet 2 and an outlet 3. The pumps may be operated independently or simultaneously and each is associated with means at its outlet 8 or 9 for preventing backflow in the main flow duct 1a when the respective pump is operative. In the embodiment shown, the means comprises a flap valve 10 or 11 movable into one of two positions by the discharge flow from the associated pump or by the flow through the adjacent portion of the duct 1a when the pump is inoperative. In an alternative embodiment, Fig. 2 (not shown), the backflowpreventing means comprises an ejector-type pump (16, 18 or 17, 19). Operation of the pumps 4, 5 may be controlled manually or automatically, e. g. by a timer device and/or in accordance with the quantity of flow through the assembly or with the pressure differential across the inlet and outlet of the assembly. |
