Stepped cylinder piston pump

Abstract

A piston pump in which, when the piston is stored or when the pump is not operative, the piston is received inside a portion of the chamber with the piston in a position having a larger diameter than portions of the chamber in which the piston is received when the piston is operative for pumping.

1 . A pump for dispensing fluid from a reservoir comprising: 
 a piston-chamber forming member having an inner cylindrical chamber and an outer cylindrical chamber, the inner 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 different than the diameter of the outer chamber,    the inner chamber and outer chamber being coaxial with the outer end of the inner chamber opening into the inner end of the outer chamber,    the inner chamber in fluid communication with the reservoir,    a piston forming element received in the piston-chamber forming member axially slidable inwardly and outwardly therein,    a disc on the piston forming element extending radially outwardly,    the piston forming element slidably received in the piston-chamber forming member for reciprocal axial inward and outward movement therein in a cycle of operation between an extended position and a retracted position to pump fluid from the reservoir out a pump outlet,    intermediate positions between the extended position and the retracted position,    one of the extended position and the retracted position being a set position,    in the set position and between the set position and the intermediate positions the disc is in the one of the inner chamber and outer chamber having the larger diameter,    in the intermediate positions, the disc is in the one of the inner chamber and outer chamber having the smaller diameter,    when the disc is in the one of the inner chamber and outer chamber having the smaller diameter, the disc engaging the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in that chamber past the disc in at least one of an inward direction and an outward direction,    the pump, after assembly of the piston-chamber forming member and the piston forming element, being in the set position or between the set position and the intermediate positions: (a) when the pump is stored prior to initial use, (b) when the pump is, after initial use, between cycles of operation, or, (c) when the pump is stored prior to initial use and when the pump is, after initial use, between cycles of operation.    
   
   
       2 . A pump as claimed in  claim 1  wherein the set position is the extended position.  
   
   
       3 . A pump as claimed in  claim 1  wherein the set position is the retracted position.  
   
   
       4 . A pump as claimed in  claim 1  wherein 
 the diameter of the inner chamber being lesser than the diameter of the outer chamber.    
   
   
       5 . A pump as claimed in  claim 1  wherein 
 the diameter of the inner chamber being greater than the diameter of the outer chamber.    
   
   
       6 . A pump as claimed in  claim 1  wherein the outer disc has an inherent diameter when unbiased in a range of 0.1% to 2% greater than the diameter of the inner chamber and the outer chamber having the lesser diameter.  
   
   
       7 . A pump as claimed in  claim 6  wherein the difference in diameters between the inner chamber and the outer chamber is in the range of about 0.5% to 1%.  
   
   
       8 . A pump as claimed in  claim 1  wherein the difference in diameters between the inner chamber and the outer chamber is not greater than an amount selected from the group consisting of: 5% of the diameter of the inner chamber, 2% of the diameter of the inner chamber, 1% of the diameter of the inner chamber, 0.5% of the diameter of the inner chamber, 1 mm, 0.1 mm, and 0.05 mm.  
   
   
       9 . A pump as claimed in  claim 8  wherein 
 when the disc is in the one of the inner chamber and outer chamber having the larger diameter, the disc engages the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in that chamber past the disc in at least one of an inward direction and an outward direction.    
   
   
       10 . A pump as claimed in  claim 1  wherein the disc having resiliently deformable edge portion with elastic properties biasing the edge portion radially outwardly into engagement with the chamber wall of the one of the inner chamber and outer chamber having the smaller diameter.  
   
   
       11 . A pump as claimed in  claim 10  wherein the deformable edge portion is formed from material which is subject to a reduction of its elastic properties biasing the edge portion radially outwardly when: (a) the edge portion is held in the set position for a period of time or (b) the edge portion is held in the set position for a period of time at temperatures above 30 degrees Celsius.  
   
   
       12 . A pump as claimed in  claim 11  wherein 
 the deformable edge portion is formed from plastic material.    
   
   
       13 . A pump as claimed in  claim 12  wherein 
 the deformable edge portion is formed from plastic material selected from polyethylene and polypropylene.    
   
   
       14 . A pump as claimed in  claim 1  wherein said piston forming element having an axially extending hollow stem having a central passageway having an outlet proximate an outer end and an inlet located on the stem between the inner disc and the outer disc, 
 the disc comprising an outer disc on the stem substantially preventing fluid flow in the inner chamber past the outer disc in an outward direction,    an inner disc on the stem spaced axially inwardly from the outer disc extending radially outwardly from the stem to proximate the chamber wall of the inner chamber circumferentially thereabout,    the inner disc substantially preventing fluid flow in the inner chamber past the inner disc in an inward direction,    the inner disc elastically deforming 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.    
   
   
       15 . A pump as claimed in  claim 14  wherein the outer disc substantially preventing fluid flow in the inner chamber past the outer disc in an inward direction.  
   
   
       16 . A pump as claimed in  claim 1  wherein said piston forming element having an axially extending hollow stem having a central passageway having an outlet proximate an outer end and an inlet located on the stem between the inner disc and the outer disc, 
 the disc comprising an inner disc on the stem,    an outer disc on the stem spaced axially outwardly from the inner disc extending radially outwardly from the stem to proximate the chamber wall of the outer chamber circumferentially thereabout,    the outer disc substantially preventing fluid flow in the outer chamber past the inner disc in an inward direction,    the outer disc elastically deforming away from the chamber wall of the outer chamber to permit fluid flow in the outer chamber past the outer disc in an outward direction.    
   
   
       17 . A pump for dispensing fluid from a reservoir comprising: 
 a piston-chamber forming member having an inner cylindrical chamber, an intermediate 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 less than the diameter of the intermediate chamber,    the diameter of the intermediate chamber being less than the diameter of the outer 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 with the outer end of the intermediate chamber opening into the inner end of the outer chamber,    the inner chamber in fluid communication with the reservoir,    a piston forming element received in the piston-chamber forming member axially slidable inwardly and outwardly therein,    an inner disc on the piston forming element extending radially outwardly,    an outer disc on the piston forming element extending radially outwardly,    the outer disc located on the piston axially outwardly from the inner disc,    the piston forming element slidably received in the piston-chamber forming member for reciprocal axial inward and outward movement therein in a cycle of operation between an extended position and a retracted position to pump fluid from the reservoir out a pump outlet,    intermediate positions between the extended position and the retracted position, in the retracted position and between the retracted position and the intermediate positions the inner disc is in the inner chamber and the outer disc is in the intermediate chamber,    in the extended position and between the extended position and the intermediate positions the inner disc is in the intermediate chamber and the outer disc is in the outer chamber,    when the inner disc is in the inner chamber, the inner disc engaging the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in the inner chamber past the inner disc in at least one of an inward direction and an outward direction,    when the outer disc is in intermediate chamber, the outer disc engaging the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in the intermediate chamber past the outer disc in at least one of an inward direction and an outward direction,    the pump, after assembly of the piston-chamber forming member and the piston forming element, being in the extended position or between the extended position and the intermediate positions: (a) when the pump is stored prior to initial use, (b) when the pump is, after initial use, between cycles of operation, or, (c) when the pump is stored prior to initial use and when the pump is, after initial use, between cycles of operation.    
   
   
       18 . A pump as claimed in  claim 17  wherein 
 said piston forming element having an axially extending hollow stem having a central passageway having an outlet proximate an outer end and an inlet located on the stem between the inner disc and the outer disc,    the inner disc provided on the stem extending radially outwardly from the stem,    the outer disc on the stem spaced axially outwardly from the inner disc and extending radially outwardly from the stem,    the inner disc when in the inner chamber substantially preventing fluid flow in the inner chamber past the inner disc in an inward direction,    the outer disc when in the intermediate chamber substantially preventing fluid flow in the intermediate chamber past the outer disc in an outward direction.    
   
   
       19 . A pump as claimed in  claim 18  including a one-way valve between the reservoir and the inner chamber preventing fluid flow inwardly from the inner chamber to the reservoir.  
   
   
       20 . A pump for dispensing fluid from a reservoir comprising: 
 a piston-chamber forming member having an inner cylindrical chamber, an intermediate 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 intermediate chamber being greater than the diameter of the inner chamber,    the diameter of the intermediate chamber being greater than the diameter of the outer 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 with the outer end of the intermediate chamber opening into the inner end of the outer chamber,    the inner chamber in fluid communication with the reservoir,    a piston forming element received in the piston-chamber forming member axially slidable inwardly and outwardly therein,    a disc on the piston forming element extending radially outwardly,    the piston forming element slidably received in the piston-chamber forming member for reciprocal axial inward and outward movement therein in a cycle of operation between an extended position and a retracted position to pump fluid from the reservoir out a pump outlet,    when the disc is in the intermediate chamber, the disc engaging the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in the intermediate chamber past the disc in at least one of an inward direction and an outward direction,    in the retracted position, the disc is in the inner chamber,    in the extended position, the disc is in the outer chamber,    the pump, after assembly of the piston-chamber forming member and the piston forming element, being in a position that the disc is in the inner chamber or in the outer chamber: (a) when the pump is stored prior to initial use, (b) when the pump is, after initial use, between cycles of operation, or (c) when the pump is stored prior to initial use and when the pump is, after initial use, between cycles of operation,    when the disc is in the one of the inner chamber or outer chamber, the disc engages the chamber wall thereof circumferentially thereabout to substantially prevent fluid flow in that chamber past the disc in at least one of an inward direction and an outward direction.