F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
F04B15/00—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts
F04B15/02—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts the fluids being viscous or non-homogeneous
F04B15/023—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts the fluids being viscous or non-homogeneous supply of fluid to the pump by gravity through a hopper, e.g. without intake valve