Lifting tip seal pump

Claim 1

A pump having an inlet and an outlet comprising in combination: a housing having a pumping cavity therein, the cavity having an inlet and an outlet; a pair of intermeshing gears mounted for rotation within the cavity; a sealing block having a discharge chamber movably mounted within the cavity, the sealing block having two arcuate sealing surfaces for contacting the respective peripheries of the gears, the sealing block being adapted to be urged by a fluid pressure into firm contact with peripheries of the gears; a first conduit fluidly interconnecting the pump inlet with the cavity inlet; a hydrodynamic pump mounted within the first conduit in series flow relationship with the gears for increasing the pressure of fluid flowing thereto; a second conduit fluidly interconnecting the cavity outlet with the pump outlet; a positionable valve operatively connected to the housing for varying the fluid pressure urging the sealing block toward the gears; means at least partially located in the cavity and subjected to the fluid pressure to urge the sealing block into engagement with the gears and to allow fluid pressure forces acting directly on the sealing block to move the sealing block away from the gears; and a third conduit fluidly interconnecting the valve to the urging means to vent the fluid pressure to which the urging means is subjected and thereby allow the fluid pressure forces acting directly on the sealing block to move the sealing block away from the gears.