Patent Publication Number: US-7708166-B2

Title: Bellows dispenser

Description:
RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 11/145,221 filed Jun. 6, 2005 now U.S. Pat. No. 7,303,099. 

   SCOPE OF THE INVENTION 
   This invention relates to liquid dispensers and, more particularly, liquid dispensers to dispensing liquid preferably as a foam. 
   BACKGROUND OF THE INVENTION 
   Liquid dispensers for dispensing soaps and other similar fluids in liquid form are known. For various reasons in some applications, it is preferable to dispense soaps and other similar fluids in the form of a foam. Generally, in the form of a foam, less soap liquid is required to be used as contrasted with the soap in the liquid form. As well, soap as foam is less likely to run off a user&#39;s hands or other surfaces to be cleaned. 
   SUMMARY OF THE INVENTION 
   The present invention provides improved and simplified apparatuses for dispensing a fluid preferably with air as a foam. 
   The present invention provides a pump mechanism utilizing a resilient flexible bellows member to function as a displacement pump and/or a spring. The bellows member preferably is integrally formed from plastic as a component of a piston for the pump. 
   The present invention also provides a pump assembly with a first pump to displace a first volume and a second pump to displace a second volume greater than the first volume. The first pump draws liquid from a reservoir and dispenses it to the second pump. The second pump draws in the discharge from the first pump and an additional volume of air such that the second pump discharges both liquid and air. The first pump preferably has a piston movable in a first inner chamber and the second pump has the same piston movable in a second outer chamber. The first and second chambers communicate together. In one version, a one-way valve provides flow outwardly only from the first chamber to the second chamber and the first pump discharges while the second pump draws in, and vice versa. In a second version, the one-way valve is provided between the first chamber and the reservoir to provide flow outwardly only from the reservoir to the first chamber and the first pump and the second pump discharge at the same time and draw in at the same time. In accordance with the first version, the present invention may be characterized as a pump for dispensing air and fluid comprising an air compartment having an inlet and an outlet, a fluid compartment having a fluid inlet and a fluid outlet, the fluid inlet being in flow communication with a fluid containing reservoir, a mixing member to mix air and fluid passing therethrough, the mixing member positioned downstream from the air compartment outlet and the fluid outlet to receive fluid which has been discharged through the fluid outlet and air which has been discharged through the air compartment outlet, a discharge outlet downstream from the mixing member open to the atmosphere for discharge of any air and fluid discharged outwardly through the mixing member, the pump comprising a first member and a second member cooperating to define the air compartment and the fluid compartment, the second member being movable with respect to the first member, whereby moving the second member in a first direction relative the first member pressurizes the air compartment thereby forcing liquid and air through the mixing member and simultaneously drawing fluid from the reservoir through the fluid inlet into the fluid compartment, and whereby moving the second member in a second direction opposite to the first direction relative the first member pressurizes the fluid compartment thereby discharging fluid from the fluid compartment out the fluid outlet and simultaneously drawing air into the air compartment. 
   Preferably, simultaneously, discharged air and liquid may preferably produce foam by passing through a foam generator, such as a porous member, or be atomized as by passing through a nozzle. 
   An object of the present invention is to provide an improved pump for dispensing a liquid. 
   Another object is to provide an improved pump for dispensing a liquid in the form of a foam. 
   Another object is to provide an improved pump with a bellows member to function as one or more of a displacement pump and a spring. 
   In one aspect, the present invention provides a pump for dispensing liquid from a reservoir comprising: 
   a piston-chamber forming member, 
   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 with an inner end and having an outlet proximate an outer end extending out of the piston-chamber forming member and from which liquid is dispensed, 
   at least one annular chamber formed annularly about the stem between the piston forming element and the piston-chamber forming member providing for controlled movement of liquid from the reservoir into the annular chamber and for dispensing of liquid in the annular chamber to the outlet with reciprocal sliding of the piston forming element between the retracted position and the extended position, 
   said piston forming element having a bellows member extending inwardly from the stem to form with the piston-chamber forming member a bellows chamber open to the inner end of the passageway, 
   the bellows member being collapsible to increase and decrease volume of the bellows chamber with reciprocal sliding of the piston forming element between the retracted position and the extended position to draw fluid through the outlet via the passageway into the bellows chamber and to expel fluid in the bellows chamber via the passageway out the outlet. 

   
     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 partially cut-away side view of a first preferred embodiment of a liquid dispenser with a reservoir and pump assembly in accordance with the present invention; 
       FIG. 2  is a partially exploded perspective view of the pump assembly shown in  FIG. 1 ; 
       FIG. 3  is a cross-sectional side view of an assembled pump assembly of  FIG. 2  showing the piston in a fully retracted position; 
       FIG. 4  is the same side view as in  FIG. 3  but showing the pump in a fully extended position; 
       FIG. 5  is a cross-sectional side view of a pump assembly in accordance with a second embodiment of the present invention showing the piston in a fully retracted position; 
       FIG. 6  is the same side view as in  FIG. 5  but showing the pump in an extended position; 
       FIG. 7  is a cross-sectional side view of a pump assembly in accordance with a third embodiment of the present invention showing the piston in a fully extended position in solid lines and in a fully retracted position in dashed lines; 
       FIG. 8  is the same side view as in  FIG. 7  but showing the pump with the inner chamber axially reduced in length axially; 
       FIG. 9  is a cross-sectional side view of a pump assembly in accordance with a fourth embodiment of the present invention showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 10  is the same side view as in  FIG. 9  but showing the pump with the piston chamber forming body axially displaced outwardly compared to  FIG. 9 ; 
       FIG. 11  is a cross-sectional side view of a pump assembly in accordance with a fifth embodiment of the present invention showing the piston in a fully extended position in solid lines and a retracted position in dashed lines; 
       FIG. 12  is a cross-sectional side view of a pump assembly in accordance with a sixth embodiment of the present invention showing the piston in a fully extended position in solid lines and a retracted position in dashed lines; 
       FIG. 13  is a seventh embodiment of the pump in accordance with the present invention showing a piston in an extended position in solid lines and in a retracted position in dashed lines; 
       FIG. 14  is a eighth embodiment of the pump in accordance with the present invention having similarities to  FIG. 13  and showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 15  is an ninth embodiment of the pump in accordance with the present invention having similarities to the pump of  FIG. 14  showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 16  is the same as  FIG. 15 , however, with the body axially displaced compared to that shown in  FIG. 15  showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 17  is a tenth embodiment of the invention having similarities to that illustrated in  FIG. 14  showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 18  is an eleventh embodiment of the invention and showing the piston in a fully extended position in solid lines and a fully retracted position in dashed lines; 
       FIG. 19  is a cross-sectional side view of the first alternate piston for use in the embodiment of  FIGS. 2 to 4 ; 
       FIG. 20  is a cross-sectional side view of a second alternate embodiment of a piston for use with the embodiment of  FIGS. 2 to 4 ; 
       FIG. 21  illustrates a twelfth embodiment of the invention having similarities to the pump of  FIGS. 2 to 4  with the piston shown in a retracted position; 
       FIG. 22  is of the same side view as in  FIG. 21  but showing the pump in an intermediate position and an extended position; 
       FIG. 23  illustrates a thirteenth embodiment of the invention; 
       FIG. 24  is a fourteenth embodiment of the present invention representing modification of the embodiment of  FIG. 6  to adopt a bellows member; 
       FIG. 25  is a fifteenth embodiment of the invention representing a further modification of the embodiment of  FIG. 24  to adopt a second bellows member; 
       FIG. 26  illustrates a sixteenth embodiment of the invention showing a gravity feed positive displacement pump with a bellows; 
       FIG. 27  is a seventeenth embodiment of the invention illustrating a foam pump arrangement with a single bellows member; and 
       FIG. 28  is an eighteenth embodiment of the present invention showing a liquid pump having one bellows member merely as a spring. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
   Reference is made first to  FIGS. 2 ,  3  and  4  which show a first embodiment of a pump assembly generally indicated  10 . Pump assembly  10  is best shown in  FIG. 2  as comprising two principal elements, a piston chamber-forming body  12  and a piston  14 . 
   The piston chamber-forming body  12  has three cylindrical portions illustrated to be of different radii, forming three chambers, an inner chamber  20 , an intermediate chamber  22 , and an outer chamber  24 , all coaxially disposed about an axis  26 . The intermediate cylindrical chamber  22  is of the smallest radii. The outer cylindrical chamber  24  is of a radius which is larger than that of the intermediate cylindrical chamber  22 . The inner cylindrical chamber  20  is of a radius greater than that of the intermediate cylindrical chamber  22  and, as well, is shown to be of a radius which is less than the radius of the outer cylindrical chamber  24 . 
   The inner chamber  20  has an inlet opening  28  and an outlet opening  29 . The inner chamber has a cylindrical chamber side wall  30 . The outlet opening  29  opens into an inlet end of the intermediate chamber  22  from an opening in a shoulder  31  forming an outer end of the inner chamber  20 . The intermediate chamber  22  has an inlet opening, an outlet opening  32 , and a cylindrical chamber side wall  33 . The outlet opening  32  of the intermediate chamber  22  opens into an inlet end of the outer chamber  24  from an opening in a shoulder  34  forming the inner end of the outer chamber  24 . The outer chamber  24  has an inlet opening, outlet opening  35  and a cylindrical chamber side wall  36 . 
   Piston  14  is axially slidably received in the body  12 . The piston  14  has an elongate stem  38  upon which four discs are provided at axially spaced locations. An inner flexing disc  40  is provided at an innermost end spaced axially from an intermediate flexing disc  42  which, in turn, is spaced axially from an outer sealing disc  44 . The inner disc  40  is adapted to be axially slidable within the inner chamber  20 . The intermediate disc  42  is adapted to be axially slidable within the intermediate chamber  22 . 
   The intermediate disc  42  has a resilient peripheral edge which is directed outwardly and adapted to prevent fluid flow inwardly yet to deflect to permit fluid flow outwardly therepast. Similarly, the inner disc  40  has a resilient outer peripheral edge which is directed outwardly and is adapted to prevent fluid flow inwardly yet to deflect to permit fluid flow outwardly therepast. 
   The outer sealing disc  44  is adapted to be axially slidable within the outer cylindrical chamber  24 . The outer sealing disc  44  extends radially outwardly from the stem  38  to sealably engage the side wall  36  of the outer chamber  24 , and prevent flow therepast either inwardly or outwardly. 
   The piston  14  essentially forms, as defined between the inner disc  40  and the intermediate disc  42 , an annular inner compartment  64  which opens radially outwardly as an annular opening between the discs  42  and  44 . Similarly, the piston  14  effectively forms between the intermediate sealing disc  42  and the outer sealing disc  44  an annular outer compartment  66  which opens radially outwardly as an annular opening between the discs  42  and  44 . As seen in  FIGS. 3 and 4  the annular inner compartment  64  comprises a fluid compartment between the body  12  and the piston  14  in between the inner disc  40  and the intermediate disc  42  in the inner chamber  20  and the intermediate chamber  22 . The inner disc  40  serves as a fluid inlet valve movable between an open position to allow fluid from the reservoir to enter the inner compartment  64  and a closed position preventing fluid flow from the reservoir to enter the inner compartment  64 . The intermediate disc  42  serves as a fluid outlet valve movable between an open position to allow fluid in the inner compartment  64  to exit the inner compartment  64  and closed position preventing fluid to enter the inner compartment  64 . As seen in  FIGS. 3 and 4  the annular outer compartment  66  comprises an air compartment between the body  12  and the piston  14  in between the intermediate disc  42  and the outer disc  44  in the intermediate chamber  42  and the outer chamber  22 . 
   An outermost portion of the stem  38  is hollow with a central passageway  46  extending from an outlet  48  at the outermost end  50  of the stem  38  centrally through the stem  38  to a closed inner end  52 . A radially extending inlet  54  extends radially through the stem into the passageway  46 , with the inlet  54  being provided on the stem in between the outer disc  44  and the intermediate disc  42 . A foam inducing screen  56  is provided in the passageway  46  intermediate between the inlet  54  and the outlet  48 . The screen  56  may be fabricated of plastic, wire or cloth material. It may comprise a porous ceramic measure. The screen  56  provides small apertures through which an air and liquid mixture may be passed to aid foam production as by production of turbulent flow through small pores or apertures of the screen thereof in a known manner. 
   The piston  14  also carries an engagement flange or disc  62  on the stem  38  outward from the outer sealing disc  44 . Engagement disc  62  is provided for engagement by an activating device in order to move the piston  14  in and out of the body  12 . 
   In a withdrawal stroke with movement from the retracted position of  FIG. 3  to the extended position of  FIG. 4 , the volume between the inner disc  40  and the intermediate disc  42  decreases such that fluid is displaced outwardly past the intermediate disc  42  to between the intermediate disc  42  and the outer disc  44 . At the same time, the volume between the intermediate disc  42  and the outer disc  44  increases, with such increase being greater than the volume decrease between the inner disc  40  and the intermediate disc  42  such that in addition to the fluid displaced outwardly past intermediate disc  42 , air is drawn inwardly via the outlet  48 , passageway  46 , and the inlet  54  in between the intermediate disc  42  and the outer disc  44 . 
   In a retraction stroke from the position of  FIG. 4  to the position of  FIG. 3 , the volume between the intermediate disc  42  and the outer disc  44  decreases such that air and liquid therebetween and in the passageway  46  above the screen  56  is forced under pressure out through the screen  56  commingling and producing foam. At the same time, in the retraction stroke, the volume between the inner disc  40  and the intermediate disc  42  increases drawing liquid from inside a container past the inner disc  40 . Reciprocal movement of the piston  14  between the retracted and extended positions will successively draw and pump precise amounts of fluid from a container and mix such fluid with air from the atmosphere and dispense the fluid commingled with the air as a foam. 
   Operation of the pump assembly illustrated in  FIGS. 2 to 4  will draw liquid out of a container creating a vacuum therein. The pump assembly is preferably adapted for use with a collapsible container. Alternatively, a suitable vent mechanism may be provided if desired as, for example, for use in a non-collapsible container to permit atmospheric air to enter the container and prevent a vacuum being built up therein which prevents further dispensing. 
   It is to be appreciated that the inner disc  40  and the intermediate disc  42  form a first stepped pump and, similarly the intermediate disc  42  and the outer disc  44  form a second stepped pump. The first pump and second pump are out of phase in the sense that in any one retraction or extension stroke while one pump is drawing fluid in, the other is discharging fluid out. 
   Both the piston  14  and the body  12  may be formed as unitary elements from plastic as by injection molding. 
   Reference is now made to  FIG. 1  which shows a liquid soap dispenser generally indicated  70  utilizing the pump assembly  10  of  FIGS. 2 to 4  secured in the neck  58  of a sealed, collapsible container or reservoir  60  containing liquid hand soap  68  to be dispensed. Dispenser  70  has a housing generally indicated  78  to receive and support the pump assembly  10  and the reservoir  60 . Housing  78  is shown with a back plate  80  for mounting the housing, for example, to a building wall  82 . A bottom support plate  84  extends forwardly from the back plate to support and receive the reservoir  60  and pump assembly  10 . As shown, bottom support plate  84  has a circular opening  86  therethrough. The reservoir  60  sits supported on shoulder  79  of the support plate  84  with the neck  58  of the reservoir  60  extending through opening  86  and secured in the opening as by a friction fit, clamping and the like. A cover member  85  is hinged to an upper forward extension  87  of the back plate  80  so as to permit replacement of reservoir  60  and its pump assembly  10 . 
   Support plate  84  carries at a forward portion thereof an actuating lever  88  journalled for pivoting about a horizontal axis at  90 . An upper end of the lever  88  carries a hook  94  to engage engagement disc  62  and couple lever  88  to piston  14 , such that movement of the lower handle end  96  of lever  88  from the dashed line position to the solid line position, in the direction indicated by arrow  98  slides piston  14  inwardly in a retraction pumping stroke as indicated by arrow  100 . On release of the lower handle end  96 , spring  102  biases the upper portion of lever  88  downwardly so that the lever draws piston  14  outwardly to a fully withdrawn position as seen in dashed lines in  FIG. 1 . Lever  88  and its inner hook  94  are adapted to permit manual coupling and uncoupling of the hook  94  as is necessary to remove and replace reservoir  60  and pump assembly  10 . Other mechanisms for moving the piston can be provided including mechanised and motorized mechanisms. 
   In use of the dispenser  70 , once exhausted, the empty, collapsed reservoir  60  together with the attached pump  10  are removed and a new reservoir  60  and attached pump  10  may be inserted into the housing. Preferably, the removed reservoir  60  with its attached pump  10  are both made entirely out of recyclable plastic material which can easily be recycled without the need for disassembly prior to cutting and shredding. 
   Reference is now made to  FIGS. 5 and 6  which illustrate a second embodiment of a pump assembly in accordance with the present invention. Throughout the drawings, the same reference numerals are used to refer to like elements. 
     FIG. 5  also shows a pump assembly  10  having a piston chamber-forming body  12  and a piston  14 . The piston chamber-forming body  12  is adapted to be threadably secured to the neck of a bottle or reservoir not shown. 
   The body  12  is formed with a cylindrical outer tubular portion  108  connected at an inner end via a radially extending flange portion  110  to a cylindrical inner tubular portion  112 . The inner tubular portion  112  extends axially radially inside the outer tubular portion  108 . The body  12  also carries on its flange portion  110  an inward axially extending generally cylindrical support tube  170  adapted to support an air chamber-forming member  172 . Member  172  has a cylindrical side wall  174  and is closed at its inner end by end wall  176 . Openings  178  are provided aligned through the wall  174  to provide communication from the interior of the reservoir into the interior of the member  170  and hence into the inner chamber  20  as indicated by arrow  179 . 
   The outer chamber  24  is formed radially inwardly of the outer tubular portion  108  having a side wall  36  thereabout and open at its outlet opening  34 . As shown, the side wall  36  tapers outwardly at chamfers proximate the outlet opening  35  to facilitate entry of the piston  14 . 
   The intermediate chamber  22  is formed radially inwardly of the inner tubular portion  112 . The inner tubular portion  112  defines an outlet opening  32  of the intermediate chamber  22  and a side wall  33  thereof. The intermediate chamber  22  has its side wall  33  taper outwardly as a chamfer proximate the outlet opening  32  to facilitate entry of the piston  14  into the intermediate chamber  22 . 
   The inner chamber  20  is formed radially inwardly of the cylindrical support tube  170 . The cylindrical support tube  170 , inner tubular portion  112 , outer tubular portion  108 , inner chamber  20 , intermediate chamber  22  and outer chamber  24  are each coaxial about axis  26 . 
   The piston  14  is formed from five elements which are secured together as a unit. These elements include elements, namely, an outer casing  120 , an inner core  122 , a foam producing element, an engagement disc  62  and an air pump disc  180 . 
   The foam producing element is a combination of two screens  56  and  57  and a three-dimensional basket-like screen  188  having generally frustoconical walls with small openings therethrough as in the manner of known filter members. 
   The piston  14  carries at its inner end the air pump disc  180  fixedly supported by a hollow neck tube  182  being fixedly secured within a hollow support tube  118  of the inner core  122 . The neck tube  182  defines a passageway  46  therethrough open at both ends. 
   The air pump disc  180  includes a locating flange  184  to locatably engage the cylindrical side wall  174  and a resilient flexible circular sealing disc  185  which sealably engages the side wall  174  and prevents flow of fluids axially outwardly therepast. An air chamber  186  is defined between the air chamber-forming member  172  and the air pump disc  180  which will increase and decrease in volume as the piston  14  is moved axially in the body  12  between the extended and retracted positions. The air chamber  186  is in communication with the passageway  46  via the neck tube  182 . 
   The outer casing  120  is of enlarged diameter at its axially inner end where the outer disc  44  is provided. The outer disc  44  is shown as including a locating flange  128  to locatably engage the cylindrical side wall  36  of the outer chamber  24  and a resilient flexible circular sealing flange  130  which sealably engages the side wall  36  and prevents flow of fluids axially outwardly therepast. 
   The outer casing  120  is shown with the outer disc  44  carried as a radially outwardly extending flange on a cylindrical large tube portion  132  which extends axially outwardly to a radially inwardly extending shoulder  134  supporting a small tube portion  136  extending axially outwardly from the shoulder  134  to the outlet  48 . Screens  56 ,  57  and  88  are located on the shoulder  134  sandwiched between the shoulder and the outer end of the inner core  122 . 
   The inner core  122  carries the inner disc  40  and the intermediate disc  42 . Each of the inner disc  40  and intermediate disc  42  comprise circular resilient flexible discs each of which extends radially outwardly and toward the outlet  48 . The inner disc  40 , when engaged with the inner chamber  20 , that is, with the cylindrical side wall of the cylindrical support tube  170 , prevent fluid flow axially inwardly therepast through the inner chamber  20 , however, is adapted to have its resilient outer edge deflect radially inwardly to permit fluid flow, under pressure differentials above a predetermined pressure, axially outwardly therepast. The intermediate flexible disc  42 , when engaged with the intermediate chamber  22 , that is, with the interior wall of the inner tubular portion  112 , prevents fluid flow axially inwardly therepast through the intermediate chamber  22 , however, is adapted to have its resilient outer edge deflect radially inwardly to permit fluid flow, under pressure differentials above a predetermined pressure, axially outwardly therepast. 
   The inner disc  40  has its outer periphery extending outwardly so as to engage the cylindrical inner wall of the support tube  170  so as to prevent fluid flow inwardly therepast. The other periphery of the inner sealing disc  40  is, however, sufficiently resilient that it can deflect radially inwardly away from the support tube  170  to permit fluid flow therepast outwardly. Similarly, the intermediate disc  42  has its resilient periphery extend outwardly and engage the cylindrical interior wall of the inner tubular portion  112  so as to prevent fluid flow inwardly therepast yet is sufficiently resiliently deflectable so as to permit fluid flow outwardly therepast. 
   The inner core  122  has the passageway  46  which is open at both an axial inner end and open at an axial outer end. The inner core  122  includes a cylindrical lower portion  123  which has a plurality of flutes at circumferentially spaced locations thereabout which effectively form with the outer casing  120  peripheral passageways  152  which extend axially. Passageways  152  are open to the outer compartment  66  between discs  42  and  44  at the inner ends of the passageways. At the outer ends, the passageways  152  join radial inlets  54  in the lower portion  123  which provide communication into the central passageway  46 . 
   The piston  14  provides a central flow path for flow of fluids in the passageway  46 , through the screens  56 ,  57  and  88  and, hence, through the smaller tube portion  136  to the outlet  48 . The piston  14  provides another flow path for flow of fluid from the outer compartment  66  via openings  152 , peripheral passageways  150  and inlets  54  into the passageway  46 . This pathway permits fluid flow both inwardly and outwardly and is particularly adapted to receive any liquid which under gravity flows down to the lower and axially outermost portion of the outer compartment  66  where the openings  150  to the peripheral passageways  150  are provided. 
   Operation of the second embodiment of  FIGS. 5 and 6 , other than in respect of the air pump disc  180 , is similar to that with the first embodiment of  FIGS. 2 to 4 . 
   In movement of the piston  14  in a withdrawal stroke from a retracted position as illustrated in  FIG. 5  to the extended position illustrated in  FIG. 6 , of course, with the cover  107  shown in  FIG. 5  having been removed, fluid between the inner disc  40  and the intermediate disc  42  is forced outwardly past the intermediate disc  42  because the volume between the discs  40  and  42  decreases with outward movement of the piston  14 . 
   In the withdrawal stroke of the piston, atmospheric air is drawn inwardly via the outlet  48  and passageway  46  into the air chamber  186  and, at the same time, in between the intermediate disc  42  and the outer disc  44  via inlets  54  and passageways  152 . 
   Air is drawn into the area between the larger diameter outer disc  44  and the smaller diameter intermediate disc  42  since the volume between the discs  42  and  44  increases as the piston  14  is drawn outwardly. 
   In a retraction stroke, the volume between the inner disc  40  and the intermediate disc  42  increases and since intermediate disc  42  prevents fluid flow outwardly therepast, a vacuum is created which deflects the inner disc  40  so as to draw fluid from the container as indicated by arrow  179  through inlet  178  and hence outwardly past the deflecting inner disc  40 . In the retraction stroke, the volume between the outer disc  44  and the intermediate disc  42  decreases and, thus, any air or liquid therebetween is forced out passageway  152  and inlet  54  to pass outwardly through the passageway  46 , through the screens to the outlet  48 . At the same time in the retraction stroke, air from the air chamber  186  is forced outwardly via the passageway  46  to also pass outwardly through the screen  188 . 
   Operation of the pump illustrated in  FIGS. 5 and 6  will draw liquid out of a container creating a vacuum therein. 
   As shown in  FIG. 5 , the outer disc  44  includes a resilient sealing flange  130  which is formed as a thin resilient flange having an elastically deformable edge portion near the side wall  36  of the outer chamber  24 . This edge portion of the sealing flange  130  is deflectable radially inwardly so as to permit, under a sufficiently high vacuum differential, air to flow axially inwardly therepast. Preferably, the piston  14  may be configured such that substantially all air to be drawn inwardly is drawn inwardly via the outlet  48 , however, a device could be arranged such that the restriction to flow through the screens  56 ,  57  and  188  is such that some proportion or substantially all the air is drawn past the sealing flange  130 . The locating flange  128  on the outer disc  44  is preferably provided to permit fluid flow therepast but could be configured to prevent fluid flow inwardly and/or outwardly. Other embodiments are possible in which a one-way valve mechanism is provided in outlet tube  136  which prevents flow back through the outlet  48 . 
   In sliding of the piston  14  in an extension stroke from the retracted position shown in  FIG. 5  towards an extended position, fluid, notably air from the outlet  48  but also possibly liquid and/or foam in the outlet tube  136  and passageway  46 , is drawn upwardly into the air chamber  186  at the same time as liquid, foam and/or air is drawn into the lower compartment  66 . In sliding of the piston  14  from in a retraction stroke to the extended position to the retracted position, air and/or other foam or fluid in the air chamber  186  is pressurized and forced outwardly through the passageway  46  through the screens. The air pump disc  180  provides for inhalation and expulsion of fluids, notably air, in addition to the quantities of fluid inhaled and expulsed by the remainder of the pump assembly and, thus, the air pump disc  180  increases the volume of air which is available to be forced through the screens to produce foam. The configuration shown has an air pump  179  comprising the air chamber-forming member  172  and the air pump disc  180  inward from the remainder of the pump assembly  10  and of a diameter not exceeding that of the outer tubular portion  108 . This is an advantageous configuration to provide additional air pumping capacity with the same piston stroke in a device which can be inserted into the mouth of a reservoir. 
   The inner disc  40  and intermediate disc  42  form a first stepped pump. The intermediate disc  42  and the outer disc  44  form a second stepped pump, out of phase with the first pump. The air pump  179  is in phase with the second pump and out phase with the first pump. 
     FIG. 5  shows, in addition to the two screens  56  and  57  to produce foam, a three-dimensional basket-like screen  188  having generally frustoconical walls with small openings therethrough as in the manner of known filter members. Only one of the three screens needs to be provided. Other porous members to produce foam may be used. 
   In  FIGS. 5 and 6 , only one passageway  152  and inlet  54  is shown to provide communication from the outer compartment  66  to the passageway. Other passageways may be provided to provide communication from the outer compartment  66  to the passageway  46 . 
   It is to be appreciated that the nature of the liquid to be dispensed including its viscosity and flow characteristics will be important in order for a person skilled in the art to make suitable selection of the relative sizes and dimensions and resistance to flow provided by the various passageways, inlets, outlets and screens and/or past the various discs. As well, the quantity of liquid desired to be dispensed in each stroke will have a bearing on the relative proportion and sizing of the components including particularly the inner compartment  64 , outer compartment  66  and the axial length of a stroke of the piston. 
   In the preferred embodiments, the engagement disc  62  is provided on the piston  14  for engagement to move the piston inwardly and outwardly. It is to be appreciated that various other mechanisms can be provided for engagement and movement of the piston relative the body  12 . 
   The preferred embodiments show dispensers for passing liquid and air through screens  56 ,  57  and  188  to dispense the liquid as a foam. The screens  56 ,  57  and  188  can be eliminated in which case the dispenser illustrated could serve to dispense liquid with air. The foaming screens could be replaced by another orifice device such as an atomizing nozzle to produce a mist or spray. 
   The preferred embodiments of the invention show passages for dispensing of the air and/or liquid as being provided internally within a piston. Such an arrangement is believed preferred from the point of view of ease of construction of the pump assembly  10 . However, it is to be appreciated that passageways for dispensing the liquid and/or foam may be provided, at least partially, as part of the body  12  or removably mounted to the body  12 . 
   In accordance with the preferred embodiment illustrated, the relative buoyancy of air within the liquid and, hence, the separation of air and liquid due to gravity are utilized as, for example, to permit air in the compartment  64  to flow upwardly into the reservoir  60  and liquid in the reservoir  60  to flow downwardly into the inner compartment  64  as, for example, when the inner compartment  64  is open to the reservoir. It is to be appreciated, therefore, that the pump assembly in accordance with the presence invention should typically be disposed with what has been referred to as the inner end of the pump assembly at a height above the height of the outer outlet end. 
   Reference is made to  FIGS. 7 and 8  which show a third embodiment of a pump assembly in accordance with the present invention. The pump assembly of the embodiment of  FIGS. 7 and 8  is identical to the embodiment of  FIGS. 2 to 4 , however, the piston chamber forming body  12  is formed of two separate members, an outer body member  13  and an inner body member  11  which are adapted to move axially relative to each other. In this regard, the outer body member  11  is an annular ring which is circular in cross-section and has a radially inwardly extending flange  90  at its inner end which defines the cylindrical chamber side wall  30  of the inner chamber  20 . The flange  90  ends at a shoulder  91  with the outer body member  13  extending axially therefrom as a ring-like portion  92  whose radially inwardly directed surface carries threads  93 . The inner body member  11  is an annular member which is circular in cross-section and defines internally thereof the intermediate chamber  22  and the outer chamber  24 . As well, the inner body member  11  carries and defines the shoulder  31  which forms an outer end of the inner chamber  20 . The inner body member  11  has a lower portion  95  carrying a cylindrical outer surface which is threaded with threads which match with and engage the threads on the outer body member  13  such that relative rotation of the body members  11  and  13  will axially move the body members  11  and  13  relative to each other. The inner body member  11  has a shoulder  96  on its outside surface in opposed relation to the shoulder  91  on the outer body member  11 . Inward of the shoulder  96 , the inner body member  11  has a circumferential outer wall  97  which is adapted to sealably engage with a radially inwardly directed cylindrical wall  30  of the flange  90  of the outer body member  13  so as to form a seal therebetween. As to be seen in the comparison between  FIGS. 7 and 8 , with relative axial movement of the inner body member  11  and outer body member  13 , the axial extent of the outer chamber  20  may be varied, however, the intermediate chamber  22  and the outer chamber  24  are not changed. The embodiment of  FIG. 7  shows an arrangement in which the piston  14  moves through the stroke indicated being an axial distance represented by the letter S. In the fully retracted position as illustrated in dotted lines in  FIG. 7 , the inner disc  40  is intended to be maintained in a sealed condition with the side walls of the inner chamber  20  thus preventing fluid flow outwardly therepast. The volume of fluid which will be drawn from the reservoir in each cycle of the piston will be determined by the length of the stroke times the difference in the cross-sectional area between the inner chamber  20  and the intermediate chamber  22 . Referring now to  FIG. 8 , the axial extent of the inner chamber  20  has been reduced. The stroke of the piston in  FIG. 8  is the same as in  FIG. 7  and is also indicated by S. However, in each complete cycle of the piston, the volume of fluid to be drawn from the reservoir is represented merely by the axial extent of the inner chamber  20  that the inner disc  40  is in sealed engagement therewith which is merely a fraction of the axial extent that the inner disc is in sealed engagement with the inner chamber in  FIG. 7 . Thus, it is to be appreciated, that by axial movement of the inner chamber member  11  relative to the outer chamber member  13 , the amount of fluid dispensed in each complete stroke can be varied, however, since the displacement of the pump between the intermediate disc  42  and outer disc  44  has not changed, effectively, the relative volume of liquid dispensed to air dispensed in each stroke can be varied for a constant length stroke of the piston. 
   Referring to  FIG. 8 , it is to be appreciated that when the inner disc  20  is inwardly of the inner chamber  20  such that the inner disc  40  is no longer in engagement with the inner chamber  40 , then the inner disc  20  does not prevent fluid flow from the reservoir into or out of the inner chamber  20 . 
   Reference is made to  FIGS. 9 and 10  which illustrate a fourth embodiment of the present invention. The piston  14  and body  12  in  FIGS. 9 and 10  have identical features to those illustrated in the first embodiment of  FIGS. 2 to 4 , however, with different proportions in the axial direction and with the cylindrical outer surface of the body  12  threaded so as to threadably engage with an annular support ring  15  which carries mating threads on its cylindrical interior surface. The support ring  15  is to be located in a fixed position relative to the support plate  84  of the dispenser as shown in  FIG. 1  such that the support ring  15  will be in a fixed position relative to the lever  88 . By rotating the body  12  about its axis, the axial, that is, vertical location as seen in  FIG. 1 , of the body  12  can be varied. However, with the lever  88  fixed in position relative to the support ring, it follows that the piston  14  which is held by the lever  88  is held in a fixed position relative to the support ring  15 . 
   Referring to  FIG. 9 , the position of the piston  14  is illustrated in an extended position in solid lines and in a retracted position in dotted lines. The movement of the piston axially from the extended position to the retracted position is the axial length of a single stroke of constant fixed length indicated as S. In  FIG. 9 , during the entire stroke, the inner disc  40  is retained within the inner chamber  20 . 
   Referring to  FIG. 10 ,  FIG. 10  illustrates a position in which the body  12  has been moved axially outwardly relative to the support ring  15 . As shown, in comparing  FIGS. 9 and 10 , in  FIG. 9 , the body  12  extends from the support ring  15  a distance X whereas in  FIG. 10 , the body  12  extends from the support ring a distance equal to X plus Y. In each of the embodiments, the axial distance of the engagement flange  62  from the ring support  15  is a constant distance represented as Z. In the embodiment of  FIG. 10 , in the retracted position, the inner disc  40  is axially inwardly of the inner chamber  20  and thus does not prevent flow of liquid from the reservoir inwardly or outwardly of the inner chamber  40 . In a cycle of the piston  14  in  FIG. 10  through a constant stroke indicated as S, there is effectively pumping for an axial distance that the inner disc  20  passes from first coming to seal the inlet end of the inner chamber  40  to the position of the inner disc  20  in the extended position of the stroke indicated in solid lines in  FIG. 10 . 
   In describing  FIGS. 9 and 10 , the position of the piston  14  in a retracted position is defined as an indexing position. From this indexing position, the piston  14  is moved in each stroke relative to the body  12  to the extended position and then back to the indexing (retracted) position. In the pump of  FIGS. 9 and 10 ,  FIG. 9  illustrates the pump  10  in a first indexing condition with the piston  14  having a first indexing position relative to the body  12 . In a cycle of operation involving one retraction stroke and one extension stroke, for a fixed length of stroke indicated as S, a first fixed volume of fluid is drawn from the reservoir and displaced past the intermediate disc  22 . The pump is capable of assuming other indexing configurations such as the one indicated in  FIG. 10  in which the piston is in a different indexing position than the indexing position of  FIG. 9 . For the same fixed length stroke of the piston, the volume of liquid discharged past the intermediate disc  22  is equal to a different amount having regard to the relative proportion of the stroke that the inner disc  40  engages the inner chamber  20  to prevent fluid flow inwardly therepast. The axial movement of the body  12  relative to the support ring  15  provides an indexing adjustment mechanism to change the indexing position of the piston  14  so as to change the volume dispensed. 
   Reference is now made to  FIG. 11  which shows a fifth embodiment of the present invention with the piston  14  in a fully extended position in solid lines in a fully retracted position in dashed lines. The piston  14  is identical to the piston of the embodiment of  FIGS. 2 to 4 . The body  12  is similar, however, the axial length of the inner chamber  20  and the intermediate chamber  22  have been reduced. As seen in the extended position in solid lines, the intermediate disc  42  extends outwardly beyond the intermediate chamber  22  and the inner disc  40  is engaged in the inner chamber  20 . In the extended position, air from outer chamber  24  may flow inwardly past the intermediate disc  42  to between the intermediate disc  42  and the inner disc  40  and fluid may flow outwardly past the intermediate disc  42 . When in the retracted position as illustrated in dashed lines, the inner disc  40  is inwardly beyond the inner chamber  20  and the intermediate disc  42  is engaged in the intermediate chamber  22 . Air which may be between the intermediate disc  42  and the inner disc  40  may, under gravity, move upwardly so as to enter a bottle or other reservoir disposed above the pump  10 , and fluid from the reservoir may flow downwardly to fill the inner chamber  40 . This configuration can have the advantage of being capable of being used with a non-collapsible, rigid container so as to provide an allotment of air into a reservoir in each stroke which can assist in preventing a vacuum from being developed inside the reservoir. The pump of  FIG. 11 , in fact, can positively pump air into the reservoir. The extent to which either the inner disc  40  extends inwardly past the inner chamber  20  and the extent the intermediate disc  42  extends outwardly past the intermediate chamber  22  can assist in determining the amount of air that may pass upwardly into the reservoir. 
   Reference is made to  FIG. 12  which shows a sixth embodiment of the present invention with the piston  14  in a fully extended position in solid lines and in a retracted position in dashed lines. The pump assembly  10  of  FIG. 12  is the same as that of  FIGS. 2 to 4  but modified to remove the intermediate disc  42  from the piston  14  and to provide an equivalent flexible annular intermediate disc or flange  142  to extend inwardly from the body  12  within the intermediate chamber  22 . In this regard, the piston  14  has its stem  38  to be of a constant diameter between the inner disc  40  and the outer disc  44 . The piston  14  is also shown to be constructed of two parts, an inner portion  43  carrying the inner disc  42  and an outer portion  45  carrying the outer disc  44 . 
   The intermediate flange  142  extends radially outwardly and downwardly and has a flexible outer periphery which engages the stem  38  between the inner disc  40  and the outer disc  44  to prevent fluid flow inwardly therepast yet which is resiliently deflectable radially outwardly to permit fluid flow outwardly therepast. In each of the embodiments of  FIGS. 1 to 11 , the intermediate disc  42  may be replaced by an intermediate flange  142  as in  FIG. 12 . Similarly, in each of the embodiments of  FIGS. 13 to 17 , the inner disc  40  may be replaced by a similar intermediate flange to extend inwardly from the inner chamber  20 . 
     FIGS. 1 to 12  illustrate a first version of the invention in which the inner chamber  20  is of a greater diameter than the intermediate chamber  22  and the intermediate chamber  22  is of a greater diameter than the outer chamber  24 . 
   Reference is now made to  FIGS. 13 to 17  which illustrate a second version of the pump assembly of the invention in which the inner chamber  20  is of a smaller diameter than the intermediate chamber  22  and the intermediate chamber  22  is of a smaller diameter than the outer chamber  24 . The piston illustrated in each of  FIGS. 13 to 17  has components identical to the components illustrated in  FIGS. 2 to 4 , however, with a notable difference that the inner disc  40  is smaller than the intermediate disc  42 .  FIG. 13  illustrates a seventh embodiment of the invention in which the inner disc  40  and the intermediate disc  42  form a first stepped pump and the intermediate disc  42  an the outer disc  44  form a second stepped pump. The two stepped pumps are in phase in a sense that both operate to discharge fluid outwardly on a retraction stroke and to draw fluid in between their respective discs on an extension stroke. In an extension stroke, the inner pump effectively serves to draw liquid from the reservoir and between the inner disc  40  and the intermediate disc  42  and to discharge it past the intermediate disc  42  between the intermediate disc  42  and the outer disc  44 . The second pump serves to draw air inwardly into between the intermediate disc  42  and the outer disc  44  in a withdrawal stroke and to discharge liquid and air outwardly through the outlet  48  in a retraction stroke. 
   Reference is made to  FIG. 14  which illustrates an eighth embodiment of the invention which is identical to the embodiment shown in  FIG. 13  with the exception that the axial length of the inner chamber  20  is reduced to an extent that in the retracted position illustrated in dashed lines in  FIG. 14 , the inner disc  40  extends inwardly beyond the inner chamber  20 . In the embodiment of  FIG. 14 , compared to that of  FIG. 13 , the fluid drawn from the reservoir in each cycle of the piston, will be reduced having regard to the axial extent in each stroke that the inner disc  40  is in engagement with the inner chamber  20 . 
     FIGS. 16 and 17  illustrate a ninth embodiment of the second version of the pump having an arrangement similar to that illustrated in  FIGS. 9 and 10  of the first version with the body  12  being elongated and threadably received within a locating ring  15  such that relative axial displacement of the body  12  relative to the ring  15  will vary the volume of liquid that is drawn into the pump from the reservoir in each cycle of the pump. In comparison of  FIG. 15  to  FIG. 16 , with the ring support member  15  fixed relative to the dispenser support member  84  and the pivot point of the lever  88 , the body  12  is moved inwardly from the position of  FIG. 15  to the position of  FIG. 16  by an axial distance equal to Y. Each of  FIGS. 15 and 16  show movement of an identical piston through an identical equal stroke distance indicated S. 
   Reference is made to  FIG. 17  which illustrates a tenth embodiment similar to  FIG. 14 , however, in this embodiment not only in the retraction position is the inner disc  40  inward of the inner chamber  20  but, in addition, in the withdrawal position, the intermediate disc  42  is outward of the intermediate chamber  22 . The embodiment of  FIG. 17  can be used with a non-collapsible bottle in that in each stroke, some quantity of air can be permitted to pass firstly when the pump is in the extended position from between the outer disc  44  and the intermediate disc  42  inwardly past the intermediate disc  42  and, subsequently, when the piston is in the retracted position to pass from between the intermediate disc  42  and the inner disc  40  to past the inner disc  40  and into the reservoir. Relative selection of when each of the discs  40  and  42  come to disengage from their respective chamber and their relative sizes of the different chambers can be used to determine the amount of air which may be permitted to be passed back into a reservoir in any stroke. Preferably, as shown, at all times, at least one of the inner disc and the intermediate disc  44  are in engagement with their respective chamber to prevent fluid flow outwardly. 
   Reference is made to  FIG. 18  which shows a third version of the pump assembly of the invention in which, while similar to the first and second versions, the outer chamber  24  is larger than chamber  42  intermediately inwardly therefrom. Rather than providing a one-way valve mechanism for one way flow inwardly from the reservoir to the chamber  42 , such as the inner disc  40  in an inner chamber in the case of  FIGS. 1 to 17 , a one-way valve  150  is provided in an inlet port  152  to the chamber  42 . Valve  150  has a stem  154  which carries an inner valve disc  156  which extends radially outwardly from the stem  154  to engage the side wall of the chamber  42 . The valve disc  156  has a resilient outer perimeter which is directed outwardly and engages the chamber  42  to prevent fluid flow therepast inwardly yet deflects radially inwardly to prevent fluid flow outwardly therepast. Similar such one-way valves could be used in replacement of the inner disc  40  in the embodiments of  FIGS. 13 to 17 . 
   Reference is made to  FIG. 19  which illustrates a first alternate form of a piston  14  adapted for substitution of the piston  14  in the embodiment of  FIGS. 2 to 4 . Piston  14  as shown in  FIG. 19  is identical to that shown in  FIGS. 2 to 4 , however, includes a one-way valve  160  provided on the outer disc  44  and adapted to provide for fluid flow inwardly through the outer disc  44  and to prevent fluid flow outwardly. In this regard, the disc  44  is provided with a center opening  162  therethrough and a pair of openings  164  on either side of the center opening. A valve member  165  has a stem with an arrow-like head  166  which is adapted to pass through the center opening and secure the valve member therein against removal. The valve member includes an inner flexible disc member  168  which inherently assumes a flat condition to overlie and close the openings  162  and  164 , however, which is resiliently deflectable so as to deflect to the positions illustrated in dashed lines in  FIG. 19  so as to permit air flow inwardly through the opening as when, in an extension stroke, a pressure differential is created as a result of creating a vacuum inside the outer chamber  44 . Thus, on an extension stroke, atmospheric air may flow into the outer chamber  24  through the one-way valve  165  provided in the outer disc  44 . However, on a retraction stroke on moving of the piston  14  inwardly, the one-way valve  165  prevents fluid flow outwardly through the one-way valve. 
   Reference is made to  FIG. 20  which shows a second alternate form of a piston  14  for use in the embodiment of the piston assembly shown in  FIGS. 2 to 4 . The second alternative shown in  FIG. 20  is identical to that shown in  FIGS. 3 and 4  with the exception that the outer disc  44  is provided with an inwardly directed resilient inner periphery  41  which is adapted to engage the wall  36  of the outer chamber  24  so as to prevent fluid flow outwardly therepast yet which is adapted to deflect radially inwardly so as to permit atmospheric air to flow past the outer disc  44  on the piston  14  moving outwardly. The second alternative piston  14  of  FIG. 20  also includes a one-way valve  170  provided internally within the passageway  46  between the inlet  54  and the screen  56 . This valve  170  has an inner securing disc  172  frictionally received in the passageway  46  against movement. A stem  173  extends axially from the disc  172  and carries a resilient outwardly directed flexible disc  174 . The securing disc has openings  176  therethrough permitting passage. The flexible sealing disc  174  has a resilient outer periphery which is adapted to engage the inner surface of the passageway  46  to prevent fluid flow inwardly therepast yet is adapted to deflect radially inwardly so as to permit fluid flow outwardly through the passageway  46 . In use of a piston as illustrated in  FIG. 20 , the one-way valve  170  inside the stem  38  substantially prevents any fluid flow back into the outer chamber  24  in an extension stroke such that effectively all air to be drawn into the outer chamber  24  in the extension stroke must be drawn past the deflecting outer periphery of the outer disc  44 . As a further embodiment, the interior one-way valve  170  is not provided and, thus, in the extension stroke, there may be draw back of air and foam through the screen  56  as well as drawing of air into the chamber  24  by reason of deflection of the resilient periphery  41  of the outer disc  44 . 
   Reference is now made to  FIG. 21  which shows an eleventh embodiment of a pump assembly in accordance with the present invention. The pump assembly  10  in  FIG. 21  is identical to the pump assembly of  FIGS. 2 to 4  with the exception that the piston  14  has been modified so as to provide the outer disc  44  with an annular resilient peripheral flange indicated  180 . The resilient flange includes not only an inwardly and outwardly directed outer arm  41  but also a resilient radially inwardly and inwardly directed inner arm  39 . The body  12  in  FIG. 21  is identical to that in  FIGS. 2 to 4  with the exception that an annular channel  182  extends inwardly into the shoulder  34  of the outer chamber  24  which annular chamber  182  has a common outer wall  36  with the remainder of the chamber  24  and provides a new outwardly directed inner wall  184 . 
   The outer arm  41  is adapted to engage the cylindrical wall  36  of the outer chamber  44  to prevent fluid flow outwardly therepast. 
   While the inner arm  39  engages on the cylindrical inner wall  184 , the inner arm prevents flow of fluid, notably atmospheric air, past the outer disc  44  inwardly to between the outer disc  44  and the intermediate disc  42 . Thus, in a withdrawal stroke, on the piston  14  moving from the retracted position illustrated in  FIG. 21  to an intermediate position in which the inner arm  39  is axially outward from the shoulder  34  such that the inner arm  39  does not engage the inner wall  184  or the shoulder  34 , then the flow of air inwardly past the outer disc  44  is prevented. However, in an extraction stroke, once the inner arm  39  is outwardly of the shoulder  34  and thus out of the annular channel  182 , atmospheric air may be drawn inwardly past the outer disc  44  by deflection of arm  41 . It is to be appreciated, therefore, that from a retracted position illustrated in  FIG. 21  moving the piston outwardly initially while the inner arm  39  is within the annular channel  182 , there is drawback of fluid including air and liquid from the passageway  46  as can be advantageous as to prevent dripping of liquid and foam out the outlet  48 . However, on further outward movement of the piston  14  with the inner arm  39  outwardly of the annular channel  182 , the suction produced between the outer disc  44  and the intermediate disc  42  may also draw air inwardly past the outer arm  41  and, as a result, atmospheric air may flow between the outer disc  44  and the intermediate disc  42  either outwardly past the outer disc  44  or through the passageway  46  with the relative proportion of the flow having regard to the relative resistance of flow through each of the two pathways. It is to be appreciated, that while the inner arm  39  is within the annular channel  182  that there is drawback only through the passageway  46  and that once the inner arm  39  clears the annular channel  182  that there may be effectively only flow inwardly past the outer periphery of the outer disc  44 . A bifocated inner disc as illustrated in  FIG. 21  may be adapted for use in other of the embodiments illustrated. 
   Reference is made to  FIG. 23  which shows a fourth version of a pump assembly in accordance with the present invention. The pump assembly illustrated in  FIG. 23  can be considered to be similar to that in  FIG. 4 , however, with the intermediate disc  42  removed, the stem  38  provided with a cylindrical constant cross-sectional area between the inner disc  40  and the outer disc  44  and the intermediate chamber  42  reduced in diameter to a diameter close to that of the stem  38  between the inner disc  40  and the outer disc  44  so as to effectively prevent any substantial fluid flow therebetween. A one-way valve  180  is provided between the inner and outer chambers. Two channels  184  and a center opening  182  are provided between the inner chamber  20  and the outer chamber  24  having inlets in the outer shoulder  31  of the inner chamber  20  and an outlet in the inner shoulder  34  of the outer chamber  24 . A one-way valve member  185  is provided which prevents fluid flow inwardly through the channels  184  and opening  182  yet permits fluid flow outwardly through the channels  184 . The one-way valve member  185  has a central stem passing through the central opening  182  carrying a flexible disc outwardly of the channels  184  and an arrowhead retained inwardly. The channels  184  and the one-way valve member  185  therefore provide a similar function to the intermediate disc  42  of the embodiment of  FIGS. 2 to 4  or the intermediate flange  142  of the embodiment of  FIG. 12 .  FIG. 23  is also modified to show replacement of the screen  56  by a nozzle member  156  disposed proximate the outlet  48  to at least partially atomize liquid when liquid and air pass therethrough simultaneously. 
   In  FIG. 21 , the piston  14  is slightly modified over that illustrated in  FIGS. 2 to 4  in respect of the inner disc  40  which has had its outer periphery reduced in thickness so as to show a configuration in which the inner disc  40  is sufficiently resilient that the inner disc  40  may pass inwardly through the intermediate chamber  22  such that the piston may be formed as a unitary element from plastic as by injection moulded and inserted through the outer chamber  24 . This, for example, avoids the need of the piston to be made into portions as illustrated, for example, in the embodiment of  FIG. 12 . 
   In operation of the pump illustrated in  FIGS. 2 to 4 , in the piston  14  moving from the retracted position to the extended position, a volume of liquid equal to a first volume is displaced in an inward direction past the intermediate disc  42  to between the intermediate disc  42  and the outer disc  44  and a volume equal to a second volume which is greater than the first volume and comprises both liquid and air is drawn in between the intermediate disc  42  and the outer disc  44 . In the piston  14  moving from the extended position to the retracted position, a volume of liquid from the reservoir equal in volume to the first volume is displaced in an outward direction past the inner disc  40  to between the inner disc  40  and the intermediate disc  42  and a volume equal in volume to the second volume and comprising both liquid and air is displaced from between the intermediate disc  42  and the outer disc  44  out of the outlet  48 . In the piston  14  moving from the retracted position to the extended position, the volume equal to the second volume which was drawn in between the intermediate disc  42  and the outer disc  44  comprises the first volume displaced in the outward direction past the intermediate disc plus a third volume comprising air from atmosphere and may include as a fourth volume liquid drawn back via the outlet from the passageway. 
   In respect of an embodiment using a piston  14  as illustrated in  FIG. 20  in a body as illustrated in  FIGS. 2 to 4  and including the interior one-way valve  170  within the passageway  46 , then on the piston  14  moving from the retracted position to the extended position, the volume equal to the second volume which was drawn into between the intermediate disc  42  and the outer disc  44  comprises the first volume consisting of fluid displaced in the outward direction past the intermediate disc  42  and a third volume comprising air from the atmosphere drawn inwardly past the outer disc  44 . Insofar as the piston as illustrated in  FIG. 20  is used in a body as in  FIGS. 2 to 4  but without one-way valve  170 , then the second volume would comprise the first volume displaced in the outward direction past the intermediate disc  42  and a third volume comprising air from the atmosphere which may be drawn through the passageway  46  and/or outwardly past the outer disc  44 . The same would be true in respect of the embodiment illustrated in  FIG. 21 . Insofar as there is drawback of liquid through the outlet  48 , then the second volume would also include as a fourth volume liquid drawn back through the passageway  46 . 
   The embodiment of  FIGS. 7 and 8  as well as  FIGS. 9 and 10  and  FIGS. 15 and 16  illustrate configurations in which the relative amounts of liquid and air may be dispensed can be varied. The embodiment of  FIGS. 7 and 8  effectively illustrate modification by varying the axial extent of the inner chamber  20 . In accordance with the present invention, the body  20  may be manufactured by injection moulding with the mould cavity forming the body  12  to provide for variable axial extent of the inner chamber  20 . In this manner, by using substantially the same mould, bodies and therefore pumps, may be provided which provide for dispensing of different volumes of liquid merely by varying the axial length of the inner chamber  20 . 
   A principal operation of pumps in accordance with many of the embodiments of the invention is that the volume dispensed past the outer disc is greater than the volume dispensed past the intermediate disc. Thus, for example, in the embodiment such as in  FIGS. 2 to 4 , with the volume dispensed past the outer disc  44  being greater than the volume dispensed past the intermediate disc  42 , this allows for air to be drawn into the pump assembly and, subsequently, dispensed. Where the inner, intermediate and outer discs all remain in engagement with their respective chambers throughout the retraction and extension strokes, then it is preferred that the difference in area between the outer chamber and the intermediate chamber is greater than the difference in area between the inner chamber and the intermediate chamber. This relation may be seen, for example, in the embodiment of  FIGS. 2 to 4 . 
   Reference is made to  FIG. 22  which shows a thirteenth embodiment of a pump assembly in accordance with the present invention. The pump assembly illustrated in  FIG. 22  can be considered to be similar to that in  FIG. 4 , however, with the intermediate disc  42  removed, the stem having a cylindrical constant cross-sectional area between the inner disc  40  and the outer disc  44 , the intermediate chamber is effectively reduced in diameter to a diameter which will engage the stem between the inner disc  40  and the outer disc  44  and effectively prevent a substantial fluid flow therebetween. A channel is, however, provided between the inner chamber  20  and the outer chamber  24  having an inlet in the outer shoulder of the inner chamber and an outlet in the inner shoulder of the outer chamber. A one-way valve is provided in this channel which prevents fluid flow inwardly through the channel yet permits fluid flow outwardly through the channel. The channel and the one-way valve therefore provide a similar function to the intermediate disc  42  of the embodiment of  FIGS. 2 to 4  or the intermediate flange of the embodiment of  FIG. 22 .  FIG. 23  is also modified to show a replacement of the screen  56  by a nozzle member  156  disposed proximate the outlet  48  to at least partially atomize liquid when liquid and air pass therethrough simultaneously. 
     FIG. 24  is a modification of the embodiment illustrated in  FIG. 6  so as to provide at the inner end of the piston  14  rather than the air pump disc  180  which slides within the air chamber-forming member  172 , a flexible inner bellows/spring member  200  which extends rearwardly as an integral portion of the piston  14  to engage the rear wall  176  of the element  172 . The inner bellow member  200  as illustrated in  FIG. 24  is compressed such that the inner bellows member  200  always urges the disc  40  forwardly towards engagement with the shoulder  110 . With inward movement of the piston  14  in use, the inner bellows member  200  further resiliently deflects and, in this regard, acts as a spring to bias the piston  14  outwardly. In addition, as the piston  14  is moved rearwardly, the internal volume in the air chamber  186  inside the inner bellows member  200  decreases such that the inner bellows member  200  draws air in and expels air out during use. 
   The inner bellows member  200  has the advantage of serving both as a pump and an internal spring to bias the piston  14 , however, it may in other embodiments serve merely one or the other or both of these functions and, as well, may be adapted for pumping air, or fluid or a mixture of air and fluid. 
     FIG. 25  illustrates a further modification of  FIG. 6  over that of  FIG. 24  such that the piston outer disc  130  of  FIG. 6  is also replaced by a second bellows member  202  which will not only draw in and dispense air/liquid but also acts as a spring to bias the piston  14  outwardly. 
   Reference is made to  FIG. 26  which illustrates a further embodiment of a pump in accordance with the present invention and which an inner bellows member  200  is provided at the inner end of an inner core  122  of a pump in a similar manner to that shown in  FIG. 24 . However, in FIG. 29, the pump mechanism is a gravity feed metering pump for movement and dispensing of fluid from a reservoir past disc  42  as in a manner disclosed in U.S. Pat. No. 6,601,736 to Ophardt et al, issued Aug. 5, 2003. It is to be appreciated that the inner bellows  200  in FIG. 29 has replaced a piston pump similar to that illustrated in  FIG. 6 . As well, it is to be appreciated than an outer bellows  202  could be provided in replacement of the sealing flange  130  in  FIG. 28 . 
     FIG. 27  is a further embodiment in which an outer bellows  202  is provided which forms the sole air chamber for drawing air in via outlet  48  and dispensing it outwardly through outlet  48 . The bellows chamber  66  receives liquid from the reservoir from a stepped cylinder liquid pump including discs  40  and  42 . Both air and liquid are dispensed via port  54  to passageway  46  and out through the foam generators  56 ,  188  and  57 . 
     FIG. 28  illustrates a modified form of the embodiment of  FIG. 26  including an outer bellows  202  which is adapted to serve merely as a spring since the bellows  202  has an air vent opening  204  to relatively, freely permit passage of air inwardly and outwardly therefrom. While an accordion-like outer bellows member  202  is shown in  FIG. 28 , a bellows member such as in  FIG. 27  could also be used with an air vent. 
   Disc  42  is modified over that of  FIG. 27  so as to prevent fluid flow outwardly therepast. An inlet  256  is provided through the side wall of the stem  38  of the piston between the discs  40  and  42  directing fluid between discs  40  and  42  outwardly into passageway  46 . The dispenser of  FIG. 28  merely dispenses liquid. 
   In each of the embodiments illustrated in  FIGS. 24 to 28 , each of the inner bellows  200  and outer bellows  202  provide a bellows chamber inside a flexible and collapsible side wall which bellows chamber increases in volume with movement of the piston  14  towards the extended position and reduces with volume with movement of the piston  14  towards a retracted position. Each of the bellows is provided to act as a resiliently collapsible and expandable pump so as to draw fluid inwardly into the bellows chamber and dispense fluid outwardly from the bellows chamber. 
   In the preferred embodiments illustrated, the resilient bellows member is formed integrally with a component of the piston having a central axially extending hollow stem with a bellows formed as an extension of the hollow stem and open to the hollow stem. 
   Each of the bellows members  200  and  202  illustrated are formed as the end of a tubular member. In each of the embodiments in  FIGS. 25 to 28 , the piston  14  is formed from a number of elements secured together as a unit and including as two principal elements an outer casing  120  and an inner core  122 . The inner core  122  carries a hollow support tube  118  from whose inner end the inner bellows  200  extends inwardly to its inner end  206  which engages in a sealed manner the end wall  176  of the air chamber-forming member  172 . The outer casing  120  includes a small tube portion  136  at its outer end and a large tube portion  132  open at an inner end from which the outer bellows  202  extends inwardly to its inner end  208  which engages in a sealed manner an outer side of the flange portion  110 . 
   In both the embodiments of  FIGS. 24 and 25 , the inner bellows member  200  is formed as an inner extension of a portion of the piston  14  open to the central internal passageway  46  through the hollow stem  38 . 
   In each of the embodiments of  FIGS. 24 to 28 , at least one annular chamber is formed annularly about the stem  38  between the piston  14  and the piston-chamber forming member  12  such that with reciprocal sliding of the piston  14  between the retracted and the extended position, there is controlled movement of liquid from the reservoir into the annular chamber and for dispensing of liquid in the annular chamber to the outlet with or without the simultaneous dispensing of air. 
   Each of the bellows  200  and  202  is formed from a resilient material which will have an inherent tendency to assume an expanded configuration. Plastic material such as polyethylene and polypropylene and copolymers provide for adequate resiliency. The bellows effectively forms an axially compressible, resilient tube section, the outer wall of which forms the plurality of stepped annular portions. The resiliency of the wall provides an inherent bias like a compression spring to return the wall to an extended configuration. The side wall effectively is pleated and adapted to collapse the side wall longitudinally. The side wall illustrated in  FIG. 25  is roughly conical increasing in diameter stepwise inwardly. In  FIG. 28 , the bellows member  202  is shown as having an accordion-like side wall of relatively constant diameter. Alternatively, the side wall may be formed with spiral grooves and spiral lands therebetween rather than merely annular lands. 
   While this invention has been described with reference to preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference is made to the appended claims.