US20070257064A1 - Stepped cylinder piston pump - Google Patents

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.

Description

SCOPE OF THE INVENTION
• This invention relates to piston pumps and, more particularly, to a stepped piston pump with a stepped cylinder to accommodate piston shrinkage or setting.
BACKGROUND OF THE INVENTION
• Piston pumps are well known in which a piston reciprocally slides within a chamber. For many piston pumps, the piston includes an annular disc with an inherent resiliency biasing a periphery of the disc into engagement with an inner wall of the chamber to form a seal therewith. Frequently such discs may permit fluid flow in one direction therepast by a pressure differential across the disc urging the disc against its bias away from sealed engagement with the inner wall of the chamber and with the inherent bias of the disc causing the disc to assume a sealed position.
• The present inventor has appreciated that under various conditions, the inherent resiliency of the disc may become impaired such that the disc will not adequately perform its function and the pump may have its performance reduced or fail. For example, the present inventor has appreciated that with pistons incorporating resilient discs which are made of plastic material, that the disc can be subject to setting and shrinkage. Setting arises, for example, when a disc is received in a chamber which disc has an initial inherent bias to assume a diameter larger than the diameter of the inner wall of the chamber such that the disc's inherent bias urges the disc into engagement with the inner wall of the chamber. That is, the disc is compressed inside the chamber. If, however, such disc may be left in such compressed condition in the chamber for an extended period of time, then the disc may loose its inherent resiliency as, for example, tending to set and retain the shape in which it is held for an extended period of time and losing its bias to expand further outwardly. The extent to which setting or set may arise will determine the extent to which the disc member forms a functional seal with the inner wall of the chamber. Set is increased with the time during which the disc is retained in one position. Set with most plastic materials increases with increased temperature. For example, with many relatively inexpensive plastic materials as may preferably be used to form pistons for pumps, leaving a disc of a piston in a fixed condition within a cylinder for a number of days at temperatures in excess of 35° C. and higher can significantly increase the extent to which a set is developed. Nevertheless, where the assembled pumps are left, for example, in storage in many climatic conditions, it may not be unrealistic for the pumps to be subjected for temperatures in the range of 35° C. to 60° C. for hours if not days as in transit, storage and the like.
• The present inventor has also appreciated that set and the reduced inherent resiliency of a disc may arise when the disc may be subjected to certain fluids to be dispensed by the pump including chemicals which negatively affect the properties of the plastic with the time that they are left in a particular position.
• The present inventor has also appreciated that there are plastic materials which may be preferred for use with pistons in pumps which can be subject to shrinkage when exposed to increased temperatures for periods of time. Thus, many plastic discs in piston pumps will also be subject to shrinkage when exposed to temperatures above, say, 35° C. for an extended period of time which shrinkage can be enhanced and rendered more permanent as when a disc is retained in a compressed condition within the cylinder during the time that it is subjected to the elevated temperatures.
SUMMARY OF THE INVENTION
• To at least partially overcome these disadvantages of previously known devices, the present invention provides 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.
• An object of the present invention is to provide an improved piston pump assembly to overcome difficulties which may arise due to setting, the loss of resiliency or shrinkage of a piston-forming member.
• Another object is to provide a piston pump which provides for useful operation of the pump even after a piston sealing member may have shrunk or become set to adopt an effectively smaller diameter.
• A pump in accordance with the present invention has a piston reciprocally axially slidable within a chamber, with the piston assuming an axial set position within the chamber when the piston is not in use or when it is stored as after initial assembly. While the piston is in such set position, the piston is received within a set portion of the chamber having a larger circumference than other portions of the chamber into which the piston will slide when moved for pumping. The piston may, due to engagement in the larger diameter set portion of the chamber, become set to assume the diameter of the larger diameter set portion of the chamber or may shrink as to assume the diameter of the larger diameter set portion of the chamber which may impair the engagement of the piston in the larger diameter set portion. However, on movement of the piston in use into the other portions of the chamber having smaller diameters, the effects of set or shrinkage of the piston on engagement with the chamber will be reduced. Preferably, when the piston is in the set portion of the chamber, even after reasonably expected setting or shrinkage, the piston will continue to engage the wall of the chamber. It is within the scope of the invention, however, that when the piston is in the set position that the disc not engage the wall of the chamber. Pumps in accordance with the present invention provide a stepped chamber with a larger diameter set portion of the chamber to be a portion or portions in which the piston is received when not operative and/or is being in storage preferably with the set position or positions being a fully retracted position or a fully withdrawn position. Preferably, the difference between the diameter of the larger diameter set portion and the other portion of the chamber is selected to be as small as possible to reasonably accommodate expected set or shrinkage.
• Piston pumps may have pistons with more than one disc to engage the inner walls of a piston chamber and a separate stepped arrangement may be provided for each disc although this may not be necessary and merely to provide a stepped configuration for one of the discs may be adequate to ensure reasonable operation of the pump.
• The present invention provides by use of a stepped chamber a mechanism for accommodating adequate function of the pump notwithstanding set or shrinkage and, as well, permits the piston for the pump to be made from more easily handled and less expensive materials as, for example, plastics having lower melting and increased likelihood of set and shrinkage.
• The invention is for use not only with pistons which have discs which extend radially outwardly to engage an inner wall of the chamber but also with arrangements in which a chamber may have a annular disc which extends radially inwardly as to engage a cylindrical surface on a piston. In the latter case, the diameter of the piston to be engaged by the radially outwardly extending disc should be reduced when the piston is in a set position it assumes when not in use.
• In one aspect, the present invention provides 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,
• 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.
• In another aspect, the present invention provides 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 forming element 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 positions,
• 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 position, the inner disc is in the intermediate chamber and the outer disc is in the outer chamber,
• when the inner disc is in 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.
• In another aspect, the present invention provides 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,
• 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.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further aspects and advantages of the present invention will become apparent from the following description taken together with the accompanying drawings in which:
• FIG. 1 is a schematic cross-sectional side view of a piston pump in accordance with a first embodiment of the present invention in an extended position;
• FIG. 2 is a view the same as inFIG. 1, however, with the piston in an intermediate position;
• FIG. 3 is a view the same as inFIG. 1, however, with the piston in a retracted position;
• FIG. 4 is a schematic cross-sectional side view of a piston pump in accordance with a second embodiment of the present invention in an extended position;
• FIG. 5 is a view the same as inFIG. 4, however, with the piston in an intermediate position;
• FIG. 6 is a view the same as inFIG. 4, however, with the piston in a retracted position;
• FIG. 7 is a schematic cross-sectional side view of a piston pump in accordance with a third embodiment of the present invention in a retracted position;
• FIG. 8 is a schematic cross-sectional side view of a piston pump in accordance with a fourth embodiment of the present invention in a retracted position;
• FIG. 9 is a schematic cross-sectional side view of a piston pump in accordance with a fifth embodiment of the present invention in a retracted position;
• FIG. 10 is a schematic cross-sectional side view of a piston pump in accordance with a sixth embodiment of the present invention in an retracted position;
• FIG. 11 is a view the same as inFIG. 10, however, with the piston in an inner intermediate position;
• FIG. 12 is a view the same as inFIG. 10, however, with the piston in an outer intermediate position; and
• FIG. 13 is a view the same as inFIG. 10, however, with the piston in an extended position.
DETAILED DESCRIPTION OF THE DRAWINGS
• Reference is made to FIGS.1 to3 which show aliquid dispenser10 having apump assembly12 attached to areservoir13 in accordance with the present invention.
• Thereservoir13 is a container with a threadedneck14. Thepump assembly12 has a piston chamber-formingbody16 defining achamber18 therein in which a piston forming element orpiston20 is slidably disposed for reciprocal movement to dispense fluid from the reservoir. Thechamber18 is defined inside side walls42 of aninner tube26. Thechamber18 is closed at aninner end wall23 and open at anouter end24.Openings22 in theend wall23 of thechamber18 are in communication with the fluid in thereservoir13. A one-way valve25 across the opening22 permits fluid flow outwardly from thereservoir13 into thechamber18 but prevents fluid flow inwardly.
• The piston chamber-formingbody16 has the cylindricalinner tube26 defining thechamber18 therein. An outertubular member28 is provided radially outwardly of theinner tube26 joined by aradially extending shoulder27 to theinner tube26. The outertubular member28 carriesthreads29 thereon which engages the threadedneck14 of thereservoir13 to form a fluid impermeable seal therewith.
• Fluid from thereservoir13 is in communication with thepiston chamber18 via theopening22.
• The one-way valve25 has a shoulderedbutton30 which is secured in a snap-fit inside a central opening in theend wall23 of thechamber18. A flexibleannular rim31 is carried by thebutton30 and extends radially outwardly to the side wall42 of theinner tube26. When the pressure in thechamber18 is less than that inreservoir13, therim31 is deflected away from the walls of theinner tube26 and fluid may flow from thereservoir13 throughexit openings22 and past therim31 into thechamber18. Fluid flow in the opposite direction is blocked byrim31, which is biased radially outwardly into the side wall42 of theinner tube26.
• The piston-forming element orpiston20 is preferably a unitary element formed of plastic. Thepiston20 has ahollow stem32.
• Two circular inner andouter discs33 and34 are located on thestem32 spaced from each other. Theinner disc33 resiliently engages the side wall of thechamber18 to permit fluid flow outwardly therepast by resilient deflection away from the side wall when the pressure in thechamber18 inward of thedisc33 is greater than the pressure outward of thedisc33.Inner disc33 prevents fluid flow inwardly therepast. Thus, theinner disc33 functions as a second one-way valve. Theouter disc34 engages the side wall of thechamber18 to prevent fluid flow outwardly therepast.
• The piston stem32 has ahollow passageway35 extending along theaxis40 of thepiston20 from a blindinner end38 to anoutlet36 at an outer end.Inlets37 to thepassageway35 are provided on thestem32 between theinner disc33 andouter disc34. By reciprocal movement of thepiston20 in thechamber18, fluid is drawn fromreservoir13 throughexit openings22 past theinner disc33 and via theinlets37 into thepassageway35 and along thepassageway35 to exit theoutlet36.
• The piston chamber-formingbody16 is preferably injection moulded as a unitary element. The one-way valve24 and thepiston forming element20 are separate elements.
• In FIGS.1 to3, thepiston20 is reciprocally movable in a single stroke of operation from an extended position as shown inFIG. 1 to the retracted position shown inFIG. 3 and then back to the extended position ofFIG. 1. In moving between the extended position ofFIG. 1 and the retracted position ofFIG. 3, the piston moves through the intermediate position shown inFIG. 2.
• In accordance with the first embodiment illustrated in FIGS.1 to3, thepiston20 is, after each stroke of operation, to be retained in the extended position until next activated. In this regard, in accordance with the first embodiment, a spring member (not shown) biases thepiston20 to the extended position with a stop mechanism (not shown) preventing further outward movement of the piston than the extended position ofFIG. 1. Such spring biased soap dispensers are well known in which a user will move the piston from the extended position to the retracted position against the bias of a spring and the spring will return the piston to a fixed extended position in which position the piston will remain until next activation by a user.
• As seen in FIGS.1 to3, the side wall42 of the chamber has three portions, aninner chamber portion44 of a constant diameter, anouter chamber portion48 of a constant diameter greater than the diameter of the inner portion and atransition portion46 which decreases in diameter outwardly from theinner portion44 to theouter portion48. As seen, a first transition line45 is disposed between theinner chamber portion44 and atransition portion46. Anothertransition line47 is disposed between thetransition chamber portion46 and theouter chamber portion48.
• In the extended position as shown inFIG. 1, theouter disc34 is received in theouter chamber portion48 and theinner disc33 is in theinner chamber portion44. In moving the piston inwardly from the extended position shown inFIG. 1, the outer disc passes through the transition portion into the intermediate position illustrated inFIG. 2 in which theouter disc34 is first received within theinner chamber portion44. In moving between the intermediate position shown inFIG. 2 and the retracted position inFIG. 3, theouter disc34 is maintained within theinner chamber portion44. A pump may be left in the extended position shown inFIG. 1 for long periods of time and under elevated temperature conditions. In the extended position as seen inFIG. 1, theouter disc34 preferably, at least when initially constructed, has an inherent bias such that the peripheral edges of thedisc34 are, due to the inherent bias of the disc, urged outwardly into the inner wall of theouter chamber portion48. With the passage of time, theouter disc34 may become subject to set or shrinkage such that it loses its resiliency and is biased outwardly with reduced force. Notwithstanding any setting or shrinkage of theouter disc34, on movement of theouter disc34 to the intermediate position ofFIG. 2, theouter disc34 becomes received within theinner chamber portion44 having a reduced diameter increasing the extent to which theouter disc34 engages the inner wall of the chamber, thus providing for improved pumping as contrasted with a pump in which the entirety of the chamber had the diameter of theouter chamber portion48.
• Reference is made to FIGS.4 to6 which illustrate a pump assembly similar to that in FIGS.1 to3 and which the same reference numerals are used to refer to the same elements. One difference in the second embodiment in FIGS.4 to6 is that the inner wall42 of thechamber18 has five portions, aninner chamber portion50, an innertransition chamber portion52, anintermediate chamber portion54, an outertransition chamber portion56 and anouter chamber portion58. Each of theinner chamber portion50,intermediate chamber portion54 andouter chamber portion58 have a constant diameter, however, with the diameter of theinner chamber portion50 being less than the diameter of theintermediate chamber portion54 and the diameter of theintermediate chamber portion54 being less than the diameter of theouter chamber portion58. In the embodiment of FIGS.4 to5, the pump is to remain in the extended position ofFIG. 4 when not in use and is to be moved in a cycle of operation from the extended position ofFIG. 4 through the intermediate position ofFIG. 5 to the retracted position ofFIG. 6 then back through the intermediate position ofFIG. 5 to the extended position ofFIG. 4. In the extended position, theouter disc34 is in theouter chamber portion58 and theinner disc33 is in theintermediate chamber portion54. From this position, the piston is initially moved inwardly to the intermediate position ofFIG. 5 in which theouter piston34 is in theintermediate chamber portion54 and theinner disc33 is in theinner chamber portion50. In sliding between the intermediate position ofFIG. 5 and the retracted position ofFIG. 6, theouter disc34 continues to remain in the constant diameterintermediate chamber portion54 and theinner disc33 remains in the constant diameterinner chamber portion50.
• With the embodiments of FIGS.4 to6, both theouter disc34 and theinner disc33, are in the extended position, in which they may remain when not in use in a larger diameter portion of the chamber than in a portion immediately inwardly therefrom in which they are substantially constantly retained during use of the pump in pumping. Thus, shrinkage or set by either of theouter disc34 or theinner disc33 is, to some extent, accommodated without performance reduction.
• FIG. 7 illustrates a third embodiment of a piston pump in accordance with the present invention in which the same reference numerals are used to refer to the same elements as inFIG. 1. In the embodiment ofFIG. 7, however, the pump is intended to be maintained in the retracted position, shown inFIG. 7, when not in use. In use, thepiston20 is to be moved from the retracted position to an extended position. In the retracted position, theouter disc34 is received in an enlarged diameterinner chamber portion44. With outward movement of the piston, theouter disc34 moves over atransition chamber portion46 to an intermediate position in which theouter disc34 first enters theouter chamber portion48 of reduced diameter. In reciprocal use of the pump, advantageous pumping occurs in sliding between an intermediate position and a fully extended position or in between such positions during which theouter disc34 is maintained in the outer chamber portion and theinner disc33 is maintained in the constant diameterinner chamber portion44.
• Reference is now made toFIG. 8 which illustrates a fourth embodiment in which in a manner analogous to that described with reference to FIGS.4 to6, but as in the embodiment inFIG. 7, the piston is to be retained in a retracted position when not in use. InFIG. 8, there are five portions in the chamber, namely, aninner chamber portion50, an innertransition chamber portion52, anintermediate chamber portion54, an outertransition chamber portion56 and anouter chamber portion58 of the chamber with theinner chamber portion50,intermediate chamber portion54,outer chamber portion58 having substantially constant but different diameters and with the diameter of theinner chamber portion50 being greater than the diameter of theintermediate chamber portion54 which is greater than the diameter of theouter chamber portion58. In a fully retracted position as seen inFIG. 8 in which the piston pump assumes at rest, each of theouter disc34 and theinner disc33 are received in an enlarged diameter chamber portions compared to the diameter of the chamber portions in which the discs are to slide in operation of the pump from an intermediate position to an extended position.
• The pump assembly in each of FIGS.1 to8 includes the one-way valve25 and apiston20 with twodiscs33 and34.FIG. 9 illustrates a pump assembly which avoids use of a separate one-way valve and thepiston20 carries three discs to provide, in effect, two one-way valves.
• Referring toFIG. 9, the piston has three discs, namely, anouter disc34, anintermediate disc33 and aninner disc70. The pump shown is intended to be maintained in the extended position shown inFIG. 9 when not in use. Theouter disc34 in the extended position is received in an enlarged diameteroutermost chamber portion58 such that on movement of the piston inwardly for pumping, theouter disc34 comes to be engaged within the smaller diameterintermediate chamber portion54. Theintermediate disc33 is always received in the constant diameterintermediate chamber portion54. Theinner disc70 is always received in the constant diameterinner chamber portion50. Astep shoulder52 is betweeninner chamber portion50 andintermediate chamber portion54. Atransition chamber portion56 is betweenintermediate chamber portion54 andouter chamber portion58.
• Reference is made toFIG. 10 which illustrates a sixth embodiment in accordance with the present invention. As seen inFIG. 10, theinner tube26 is shown to have aninner chamber portion50 of a first constant diameter, an innertransition chamber portion52, anintermediate chamber portion54 of a constant diameter, an outertransition chamber portion56 and an outerchamber wall portion58 of constant diameter. The innertransition chamber portion52 bridges between theinner chamber portion50 and theintermediate chamber portion54, and has a diameter less than the diameter of theintermediate chamber portion54. Theouter chamber portion58 has a diameter less than theintermediate chamber portion54. The pump is shown in four positions, a fully retracted position as illustrated inFIG. 10, an inner intermediate position as shown inFIG. 11, an outer intermediate position as shown inFIG. 12 and a fully extended position as shown inFIG. 13. The pump of FIGS.10 to13 is intended to be stored and shipped in the fully retracted position as illustrated inFIG. 10, for example, as (a) merely assembled and not coupled to a bottle reservoir or (b) assembled and coupled to a bottle but not engaged on a dispenser. In the fully retracted position, theouter disc34 is received within the reduced diameter innertransition chamber portion52. U.S. Pat. No. 5,975,360 issued Nov. 2, 1999 to Ophardt discloses inFIG. 8 a piston pump which is assembled and coupled to a bottle in a retracted position but which, when coupled to a dispenser as shown inFIG. 8 of that patent, is at rest in an extended position.
• The pump, after being stored in the retracted position ofFIG. 10, may then be coupled to a dispenser which dispenser firstly holds the pump in a rest position between strokes in the extended position ofFIG. 13 and in use moves the piston inwardly and outwardly between the fully extended position ofFIG. 13 and the inner intermediate position ofFIG. 11. Thus, the operation of the pump is preferably selected such that after being placed in a dispenser, thepiston20 is not moved inwardly past the inner intermediate position ofFIG. 11 and, hence, is not again moved to the storage, retracted position ofFIG. 10. In the operative stroking of the pump in use, thepiston20 is moved between the extended position ofFIG. 13 and the inner intermediate position ofFIG. 11. The pump is intended to be held when not in use in the extended position ofFIG. 13 in which theouter disc34 is engaged in the enlarged diameterouter chamber portion58. In operation, theinner disc34 substantially only engages and moves along the constant diameterinner chamber portion50 in all movement between the retracted position and the extended position. Theinner chamber portion50 is shown to have a diameter the same as theintermediate chamber portion54, however, it may have a diameter which is greater or lesser than theintermediate chamber portion54 with the innertransition chamber portion52 suitably modified.
• This embodiment ofFIG. 10 has the advantage that when the pump may be stored prior to use as, for example, in the stored retracted position ofFIG. 10, theouter piston34 is in the enlarged diameterinner chamber portion50 of the chamber and, as well, when incorporated into a dispenser for use, when not in use, theouter disc34 is in another enlarged diameterouter chamber portion58 of the chamber.
• In accordance with the present invention, pump arrangements are preferred wherein the position of the piston when stored or assembled, whether or not coupled to a bottle reservoir and whether or not coupled to a dispenser, is the same as the position of the piston when at rest in between cycles of operation. Storage of the piston can include storage as when a piston pump is assembled but before it may be coupled to a bottle reservoir and after the pump assembly may be coupled to a bottle reservoir before the pump and reservoir as a sub assembly may become coupled to a dispenser. Storage can also include a condition of being coupled to a dispenser ready for use.
• While not necessary, it is preferred in accordance with the present invention that the piston disc when in a larger diameter portion of a chamber continues to provide some seal and engagement between the outer disc and the inner wall of the chamber. In this regard, it is preferred that the difference in diameter, for example, in the context ofFIG. 1, between theinner chamber portion44 and theouter chamber portion48 is selected to be not greater than a difference required to accommodate for expected set and/or shrinkage. Minimizing this difference in diameter can be advantageous at least in reducing the extent to which thetransitional chamber portion46 may be required and providing for smooth sliding of the piston when subjected to relatively constant axial forces. Preferably, this difference in diameter is not greater than an amount selected from the group consisting of: 5% of the diameter of the inner chamber portion; 2% of the diameter of the inner chamber portion; 1% of the diameter of the inner chamber portion and 0.5% of the diameter of the inner chamber portion and 0.2% of the diameter of the inner chamber portion.
• The inner andouter discs33 and34 illustrated in the preferred embodiments preferably have resiliently deformable edge portions with elastic properties biasing the edge portion radially outwardly into engagement with the chamber wall. Such deformable edge portion may be formed from plastic material which is subject to reduction of its elastic properties biasing the edge portion radially outwardly when the edge portion is held in a set position for a period of time or when the edge portion is held in the set position for a period of time at temperatures above 35° C. or 40° C. or 50° C. or 60° C. In accordance with preferred embodiments of the present invention, the piston element is made from a plastic material preferably injection moulded as an unitary element from plastic material and, thus, the deformable edge portion is preferably formed from a plastic material.
• In accordance with the present invention, the deformable edge portion may be formed from relatively inexpensive plastics including polyethylene, low density polyethylene and polypropylene so as to advantageously reduce the costs of materials.
• Having regard to typical such plastics which may be used for construction of the piston, when the discs on the piston may have a diameter in the range of 5 to 40 mm, it is preferred that the difference in diameter between the inner chamber portion and the outer chamber portion be in the range of about 0.25% and 2%, more preferably, about 0.5% to about 1% with the disc having an inherent unbiased diameter of about 0.5% to 4% greater than the diameter of the inner chamber portion, more preferably, about 1% to 2% greater than the diameter of the inner chamber portion. In the embodiment ofFIG. 1, each of theinner disc33 andouter disc34 most preferably has an inherent diameter when unbiased or compressed of about 1.5% greater than the diameter of theinner chamber portion44; and theouter chamber portion48 preferably has a diameter of about one half the sum of the inherent diameter of thedisc34 and the diameter of theinner chamber portion44. In one preferred embodiment utilizing a low density polyethylene plastic material, the diameter of theinner chamber portion44 is about 12.15 mm, the diameter of theouter chamber portion46 is about 12.25 mm and the inherent diameter of theouter disc34 is about 12.33 mm.
• Embodiments as illustrated inFIGS. 7, 8 and10 have at least one chamber portion of a smaller diameter inward of a chamber portion of larger diameter. However, preferably, the piston-chamber forming member16 is formed by injection moulding as a unitary element. Due to the inherent resiliency of the plastic of the piston-chamber forming member16 during injection moulding, a centrally extending core may be provided with an enlarged portion to form the undercut, smaller diameter inward chamber portion. The relative difference between the diameter of the inner chamber portion and outer chamber portion is preferably limited to be no more than about 2%, more preferably, 1% or 0.5% to assist in permitting manufacture with such a removable core.
• While the invention has been described with reference to the preferred embodiments many variations and modifications will now occur to persons skilled in the art. For a definition of the invention reference is made to the following claims.

Claims (20)

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 inclaim 1 wherein the set position is the extended position.

3. A pump as claimed inclaim 1 wherein the set position is the retracted position.

4. A pump as claimed inclaim 1 wherein

the diameter of the inner chamber being lesser than the diameter of the outer chamber.

5. A pump as claimed inclaim 1 wherein

the diameter of the inner chamber being greater than the diameter of the outer chamber.

6. A pump as claimed inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 11 wherein

the deformable edge portion is formed from plastic material.

13. A pump as claimed inclaim 12 wherein

the deformable edge portion is formed from plastic material selected from polyethylene and polypropylene.

14. A pump as claimed inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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.

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