PURPOSE: To adjust the discharge of a pump in a simple method without using a complicated electric control system and an expensive discharge valve opening control mechanism or an expensive complicated-structure movable blade pump.
CONSTITUTION: Water discharged from a pump 1, which is communicated with a suction pipe 6 on the upstream side of an impeller chamber 4 and a discharge pipe 7 on the downstream side of the impeller chamber 4, to the outlet of the impeller chamber 4 is partially taken into a bypass 13 and recirculated to the outlet of an impeller 3. When the water level of a suction well 9 is lowered to a preset water level LWL by the draining operation of the pump 1 and water or the inlet 15B of an air suction pipe 15 is open to the atmosphere, air is intaken to the bypass 13 with suction arising in the low pressure section 13E of the bypass 13 and guided to the outlet of the impeller 3 to realize a smaller discharge amount of the pump.
MIYAUCHI SUNAO
KONISHI MASAHIDE
TSUGAWA TAKUJI
