Patent ID: 7303099
Filing Date: 2007-12-04
Classification: A47K,B05B

Abstract:
1. A pump for dispensing liquid from a reservoir comprising: piston-chamber forming member having an inner cylindrical chamber, an intermediate cylindrical chamber and an outer cylindrical chamber, the inner chamber, intermediate chamber and outer chamber each having a diameter, a chamber wall, an inner end and an outer end, the diameter of the inner chamber being greater than the diameter of the intermediate chamber, the diameter of the outer chamber being greater than the diameter of the intermediate chamber, the inner chamber, intermediate chamber and outer chamber being coaxial with the outer end of the inner chamber opening into the inner end of the intermediate chamber, and the outer end of the intermediate chamber opening into the inner end of the outer chamber, the inner end of the inner chamber in fluid communication with the reservoir, a piston forming element received in the piston-chamber forming means axially slidable inwardly and outwardly therein between an inward retracted position and an outward extended position, said piston forming element having a central axially extending hollow stem having a central passageway closed at an inner end and having an outlet proximate an outer end, an inner disc extending radially outwardly from the stem, the inner disc adapted to engage the chamber wall of the inner chamber, an intermediate disc extending radially outwardly from the stem spaced axially outwardly from the inner disc, the intermediate disc adapted to engage the chamber wall of the outer chamber, an outer disc extending radially outwardly from the stem spaced axially outwardly from the intermediate disc, the outer disc engaging the chamber wall of the outer chamber, an inlet located on the stem between the intermediate disc and the outer disc in communication with the passageway, the piston forming element slidably received in the piston-chamber forming means for reciprocal axial inward and outward movement therein with the inner disc in the inner chamber, the intermediate disc in the intermediate chamber and the outer disc in the outer chamber, the inner disc substantially preventing fluid flow in the inner chamber past the inner disc in an inward direction, the intermediate disc substantially preventing fluid flow in the intermediate chamber past the intermediate disc in an inward direction, the outer disc substantially preventing fluid flow in the outer chamber past the outer sealing disc in an outward direction, the inner disc elastically deformable away from the chamber wall of the inner chamber to permit fluid flow in the inner chamber past the inner disc in an outward direction, the intermediate disc elastically deformable away from the chamber wall of the intermediate chamber to permit fluid flow in the intermediate chamber past the intermediate disc in an outward direction, wherein: (a) in the piston forming element moving from the extended position to the retracted position, a volume of liquid from the reservoir equal in volume to a first volume is displaced in an outward direction past the inner disc to between the inner disc and the intermediate disc, and a volume equal in volume to a second volume which is greater than the first volume and comprises both liquid and air is displaced from between the intermediate disc and the outer disc through the inlet and passageway and out the outlet; (b) in the piston forming element moving from the retracted position to the extended position, a volume equal to the first volume comprising liquid is displaced in an outward direction past the intermediate disc to between the intermediate disc and the outer disc, and a volume equal to the second volume and comprising both liquid and air is drawn into between the intermediate disc and the outer disc, in the piston forming element moving from the retracted position to the extended position, the volume equal to the second volume which is drawn into between the intermediate disc and the outer disc comprises the volume equal to the first volume comprising liquid displaced in the outward direction past the intermediate disc and a third volume comprising air from the atmosphere.