Suction pump

A pump comprising:

• a cylinder conical body defining a metering chamber, said chamber having a bottom, an inlet at the bottom, and an inlet valve controlling flow through the inlet;
• a reciprocally movable piston in a top portion of the chamber and slidable in said chamber in peripheral ceiling engagement with an inner wall of the chamber between a top end-of-stroke position and a bottom end-of-stroke position, said end-of-stroke positions defined by respective top and bottom abutments;
• said bottom abutment defined by at least one radially projecting rib extending inwardly of the inner wall of the chamber;
• the sliding coefficient of friction between the piston and the tube being less than the sliding coefficient of friction between the tube and the inside wall of the chamber;
• a nozzle tube having a top end extending out of the chamber and a lower end including at least one delivery orifice, said piston carried by said nozzle tube and slidable relative to the nozzle tube along an outer length of the nozzle tube;
• said piston closing said delivery orifice when located at a first longitudinal position on said nozzle tube and exposing said delivery orifice when located at a second longitudinal position on said nozzle tube;
• said nozzle tube including a radially extending projection and said piston including an annular recess at its top end area adjacent said nozzle tube, said recess closed by an annular shoulder at its bottom area, said profile extendible into said recess up to said shoulder, so that longitudinal movement of the nozzle tube causes the nozzle tube to slide longitudinally relative to the piston until the profile of the tube engages the annular shoulder of the piston and thereafter continued longitudinal movement of the tube causes the piston to be moved with the nozzle tube in the chamber until said piston reaches its bottom end-of-stroke position defined by said bottom abutment;
• said piston being disposed in a delivery orifice opening position after initial downward longitudinal sliding of the nozzle tube relative to said piston in said chamber and up to the piston reaching its bottom end-of-stroke position;
• a resilient return element arranged to bias the nozzle tube towards a top discharge orifice closed position within the piston and to urge the tube and piston together towards the piston top end-of-stroke abutment.