US Patent 10890353 Centrifugal pump flow modifier

There is provided a centrifugal pump comprising a pumping chamber (106). The pumping chamber (106) has an inner surface (108) defining a pump cavity (110); a pump inlet (112) defined in a first side of the pumping chamber (106); a shaft opening (116) defined substantially centrally in a second side of the pumping chamber (106), the second side substantially opposing the first side and arranged to be above the first side, in use; and a pump outlet (114). The centrifugal pump further comprises an impeller (120) retained within the pump cavity (110); and a shaft member (140) mechanically connected to the impeller (120) through the shaft opening (116), whereby rotation of the shaft member (140) causes rotation of the impeller (120) about a shaft axis (157) passing through the shaft opening (116) and movement of a pumping liquid from the pump inlet (112) towards the pump outlet (114). The centrifugal pump further comprises a flow modifier (150) provided adjacent to an outer surface (107) of the pumping chamber (106) at the shaft opening (116) to substantially prevent ingress of air into the pump cavity (110) through the shaft opening (116) during operation of the pump even when a water level in a liquid tank (104) surrounding the pumping chamber (106) drops below a level of the shaft opening (116). The flow modifier (150) comprises an annular portion (152) having defined therein a further shaft opening (156) spaced from the shaft opening (116) and having the shaft member (140) passing therethrough. The centrifugal pump comprises a spacing member (154) spacing the annular portion (152) from the outer surface (107). The flow modifier (150) defines a liquid overflow outlet (164) for liquid flow from the shaft opening (116) in a direction substantially transverse to the shaft axis (157). In one example, the liquid overflow outlet (164) is sized to substantially prevent the ingress of air into the pump cavity (110) through the shaft opening (116) during operation of the pump, even when the water level in the liquid tank (104) surrounding the pumping chamber (106) drops below the level of the shaft opening (116). In the same or an alternative example, the annular portion (152) comprises a first portion (158) having defined therein the further shaft opening (156) and a second portion (160) extending towards the outer surface (107) from the first portion (158) and defining the liquid overflow outlet (164). Also in the same or the alternative example, the annular portion (152) defines a stabiliser cavity (166) extending between the shaft opening (116) and the further shaft opening (156) and configured to remain filled with liquid during operation of the pump, even when the water level in the liquid tank (104) surrounding the pumping chamber (106) drops below the level of the shaft opening (116).