Abstract:
Foam dispensers having a housing and an air compressor connected to the housing are disclosed herein. The air compressor releasably mates with a refill unit. The refill includes a container and liquid pump housing. The liquid pump housing includes: a liquid reservoir; an inlet valve; an outlet valve; an air inlet opening through the liquid pump housing; a foaming screen; and a foam dispensing nozzle secured to the liquid pump housing. The liquid pump housing is configured to releasably mate with an air compressor that is not part of the refill unit but is secured to a foam pump dispenser housing, and the refill unit is configured to be removed from the foam dispenser without removing the air compressor from the foam dispenser.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/069,214, titled Bifurcated Stem Foam Pump, which was filed on Feb. 8, 2008 and will issue as U.S. Pat. No. 8,047,403 on Nov. 2, 2011. This application is also a continuation-in-part of U.S. patent application Ser. No. 12/069,321, titled Bifurcated Foam Pump Assembly, which was filed on Feb. 8, 2008. This application is a continuation-in-part of U.S. patent application Ser. No. 12/069,320, titled Bifurcated Stem Foam Pump, which was also filed on Feb. 8, 2008 and will issue as U.S. Pat. No. 8,047,404 on Nov. 2, 2011. This application claims priority to and the benefits of these three applications which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention herein reside in the art of liquid dispensing mechanisms and, more particularly, to those mechanisms that are particularly adapted for dispensing a liquid in the form of a foam. Specifically, the embodiments relate to the foam pump generators for such dispensers, and particularly one that is bifurcated or separable between the liquid pump portion and the air pump portion. Specifically, the embodiments relate to foam pumps that allow the liquid pump portion to be fixed to and a part of the disposable refill cartridge containing the liquid, and in which the air pump or compressor portion is a non-disposable portion secured to the dispenser housing. 
     BACKGROUND OF THE INVENTION 
     For many years, it has been known to dispense liquids such as soaps, sanitizers, cleansers, disinfectants, and the like from a dispenser housing maintaining a removable and replaceable cartridge containing the liquid. The pump mechanism employed with such dispensers has typically been a liquid pump, simply emitting a predetermined quantity of the liquid upon movement of an actuator. Recently, for purposes of effectiveness and economy, it has become desirable to dispense the liquids in the form of foam, generated by the interjection of air into the liquid, generating the formation of bubbles thereby. Accordingly, the standard liquid pump has given way to a foam generating pump, which necessarily requires means for combining the air and liquid in such a manner as to generate the desired foam. However, foam generating pumps are more expensive than liquid dispensing pumps, necessarily increasing the cost of disposable cartridges that include the pump with each cartridge. 
     Typically, foam pumps include an air compressor portion and a fluid passing portion—the two requiring communication to ultimately create the foam. The portion required for compressing the air is not given to wear and degradation to the extent of the portion required for passing the liquid and generating the foam from the combination of liquid and air. Accordingly, it has been determined that there is no necessity for replacing the air compressor, but only the liquid pumping and foam generating portion of the pump when replacement of the cartridge is necessary. Accordingly, a bifurcation of the pump has been determined to be possible and desirable. 
     SUMMARY 
     Embodiments of foam dispensers including a housing, an air compressor connected to the housing and an actuator for actuating the air compressor are disclosed herein. The air compressor releasably mates with a refill unit. The dispenser has an “empty state” and a “refilled state.” The empty state occurs when there is not a refill unit positioned in the dispenser, and the refilled state occurs when the refill unit is positioned in the dispenser. The air compressor remains connected to the housing during the refilled state and remains connected to the housing during the empty state. In addition, embodiments of refill units for the foam dispenser are also disclosed herein. One refill unit for a foam pump dispenser includes a container for containing a foamable liquid and liquid pump housing connected to the container. The liquid pump housing includes: a liquid reservoir; an inlet valve; an outlet valve; an air inlet opening through the liquid pump housing; a foaming screen; and a foam dispensing nozzle secured to the liquid pump housing. The liquid pump housing is configured to releasably mate with an air compressor that is not part of the refill unit but is secured to a foam pump dispenser housing, and the refill unit is configured to be removed from the foam dispenser without removing the air compressor from the foam dispenser. The air inlet passage is in fluid communication with the atmosphere prior to being installed in a foam dispenser and the air inlet passage is in fluid communication with an air compressor when the refill unit is placed in the foam dispenser. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a complete understanding of the aspects, structures and techniques of the invention, reference should be made to the following detailed description and accompanying drawings wherein: 
         FIG. 1  is an illustrative functional view of a bifurcated stem foam pump made in accordance with embodiments of the present invention; 
         FIG. 2  is a cross sectional view of a bifurcated stem foam pump made in accordance with embodiments of the present invention; 
         FIG. 3  is an illustrative view of a dispenser and liquid cartridge employing a bifurcated foam pump assembly made in accordance with embodiments of the present invention; 
         FIG. 4  is a cross sectional view of a bifurcated foam pump assembly made in accordance with embodiments of the present invention; 
         FIG. 5  is an illustrative functional view of a bifurcated stem foam pump made in accordance with embodiments of the present invention; 
         FIG. 6  is a partial sectional view of the foam pump of  FIG. 5  in the “at rest” position; 
         FIG. 7  is a partial sectional view of the foam pump assembly of  FIG. 5 , showing the hollow stem in cross section; 
         FIG. 8  is a partial sectional view of the stem foam pump structure of  FIG. 5  showing the same in a position for foam generation; and 
         FIG. 9  is a partial sectional view of the stem foam pump of  FIG. 5  showing the same in the fully extended activated position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and more particularly  FIG. 1 , it can be seen that a foam solution dispenser employing the bifurcated foam pump assembly of the invention is designated generally by the numeral  10 . It will be appreciated that the foam solution dispenser may be of any of various types, adapted for dispensing soap, lotion, sanitizers, cleaners or the like in the form of a foam. The dispenser  10  includes a housing  12 , typically of molded plastic or the like. The housing  12  defines a cavity which is adapted to receive a bottle or cartridge  14  of liquid of the particular type required for generating the desired foam. The bottle or cartridge  14  is nestingly received by the housing  10  and, may be received and contained by supporting brackets, collars and the like within the housing  12 . 
     A liquid pump  16  is connected to and provided as a portion of the disposable refill cartridge or bottle  14 . In contradistinction, an air compressor unit  18  is provided as part and parcel of the dispenser housing  12 . In one embodiment of the invention, the air compressor  18  includes a dispensing nozzle  20 , through which the generated foam is dispensed onto the hand of the user, utensil or otherwise. However, preferably, any portion that contacts liquid or foam is part and parcel of the disposable refill unit or cartridge. 
     A suitable actuator  22  is operatively connected to the air compressor  18  to achieve actuation of the foam generator comprising the combination of the liquid pump  16  and air compressor  18 . Those skilled in the art will understand that foam is typically generated from a combination of air and liquid, with the two being forced together, agitated, stirred, forcefully blended or the like. The actuator  22  may be either manually actuated as in the case of a lever, push bar or the like, or it may be electronically or optically actuated as in the implementation of touch free dispensers. 
     It will be appreciated that a concept of the invention, and as particularly presented below, is the implementation and utilization of a bifurcated foam pump assembly, in which the liquid pump portion is attached to and made a portion of the disposable and replaceable cartridge  14  containing the liquid ingredient of the foam solution, while the air compressor  18  and associated nozzle  20  are not disposable, but remain a portion of the dispenser housing  12 . However, many concepts of the invention have the nozzle  20  connected to the disposable refill bottle or cartridge  14 . 
     With reference now to  FIG. 2 , an appreciation can be obtained regarding the specific structure and interrelationships of the liquid pump  16  and the air compressor  18  embodied in the bifurcated pump of one embodiment of the present invention. Specifically, with regard to the air compressor  18  and nozzle  20 , which constitute a fixed permanent part of the housing  12  of the dispenser  10 , it will be appreciated that a primary portion thereof is an annular collar  24 . The collar  24  consists of an outer ring  26  interconnected with an inner ring formed from a first inner wall  28  interconnected with a second inner wall  30 . As shown, an annular cavity  32  is defined between the outer ring  26  and the inner ring comprised of the first and second inner walls  28 ,  30 . The cavity  32  establishes the air chamber which is employed as a portion of the air compressor of the invention. A seal ring  34  extends from a bottom portion of the second inner wall  30  and defines an annulus that receives the stem of the liquid pump of the invention and serves as a seal as the piston thereof moves to effect dispensing, as will be discussed below. 
     An air piston  36  is received by the outer ring  26  and is reciprocatingly movable within the cavity  32  to effect operation of the air compressor. The air piston  36  includes a top annular disk  38  having a circumferential seal  40  extending thereabout. The seal  40  engages the inner wall surface of the outer ring  26 , as shown. A one-way check valve or button valve  42  is provided within an aperture of the top annular disk  38  to allow air to enter the cavity or air chamber  32  during operation, as will become apparent below. 
     It will be appreciated that a spring (not shown) may be maintained within the cavity  32  and interposed between the top annular disk  38  and the annular collar  24  to bias the two away from each other toward a position maximizing the volume of the cavity of the air chamber  32 . Embodiments of the invention contemplate either an interior spring, exterior spring or other type of biasing structure, readily perceivable by those skilled in the art, for implementation with the invention. 
     The annular collar  24  is received by a mounting ring  44  which is part and parcel of the dispenser housing  12 . Similarly, the mounting ring  44  provides a stop for the top annular disk  38  during operation. As presented above, the air compressor and nozzle  18 ,  20  are contemplated to be a fixed permanent portion of the dispenser housing and, to the extent there received and maintained by the mounting ring  44 , and comprise a portion of the dispenser housing. However, nozzle  20  may be part of the disposable refill unit. 
     Embodiments of the present invention contemplate that the liquid pump may be a conventional stem-type pump, frequently used in the dispensing of various fluids. The liquid pump  16  includes a reservoir collar  46  received by the annular collar  24  and connected to the disposable and replaceable cartridge  14  and forming therewith liquid reservoir  66 . The reservoir collar  46  receives a hollow valve stem  48  that extends from the reservoir collar  46  downwardly to the nozzle  20 , when the pump  16  is placed into the air compressor  18 . As with conventional liquid pumps, a one-way inlet valve may be included to allow liquid to enter valve stem  48 . A sealing flange  50  extends radially outwardly from the hollow valve stem  48  and makes sealing engagement with the inner surface of the second wall  30 , as shown. As illustrated, the interior of the second wall  30  defines an extension of the liquid reservoir cavity defined by the reservoir collar  46 . The sealing flange  50  moves axially within the liquid reservoir cavity with the valve stem  48  to reduce the volume of the cavity, thus forcing liquid within the cavity through the hollow valve stem in a customary manner. 
     The hollow valve stem  48  includes a check valve  52  in an aperture passing therethrough. Further, the valve stem  48  includes an inner extending annular ring forming a valve seat  54 , as shown. A ball valve  56  is in operative engagement with the valve seat  54  and biased there-against by means of a sponge, screen, mesh or the like  58 . The element  58  serves to assist in the generation of foam by receiving and passing liquid and air therethrough. In any event, it is preferred that the element  58  be resilient, serving as both a foam generating member and a valve biasing member, urging the ball valve  56  into sealing engagement with the valve seat  54 . As can be seen with respect to  FIG. 1  and  FIG. 2 , the opening in the hollow valve stem  48 , through which check valve  52  is placed is in fluid communication with the atmosphere ( FIG. 1 ) when the refill unit is not mated with the air compressor portion  18  and is in fluid communication with compressor  18  ( FIG. 2 ) when the refill unit and liquid pump  16  are mated together. 
     A final screen  60  extends across an outlet aperture  62  at the end of the hollow valve stem  48 , as shown. An outlet passage  64  extends axially from the nozzle  20 . As illustrated, an air aperture  68  passes through the second wall  30  of the inner ring defining the air chamber  32 . 
     It will be appreciated that the liquid pump  16 , comprising primarily the elements  46 - 66  just described, is part and parcel of the disposable cartridge  14 , filled with appropriate liquid or the like. The liquid pump assembly  16  is inserted into and received by the air compressor  18 , which is a fixed portion of the dispenser housing  12 . Of course, appropriate seals are provided on the pump  16  and/or compressor  18  to effect this mating engagement. 
     In operation, the air chamber or cavity  32  is filled with air and the hollow stem valve  48  and associated liquid reservoir  66 , in communication with the interior of the cartridge  14 , is filled with appropriate liquid. When the actuator  22  is engaged, the air piston  36  is driven upwardly into the air chamber  32 , compressing the air therein and urging it through the aperture  68  and into the area surrounding the valve stem  48  as it moves upwardly within the sealing ring  34 . With this upward movement, the liquid within the container  14  and reservoir  66  is driven through the hollow stem valve  48  downwardly against the ball valve  56 , unseating it from the seat  54 . The check valve  52  prevents the liquid from otherwise escaping from the hollow stem  48 . 
     When the check valve  52  travels beyond the seal ring  34 , the compressed air from the air chamber  32  passes through the check valve  52  and into the hollow valve stem  48 , further driving the ball valve  56  from the seat  54  and into the sponge, screen, mesh or the like  58 . Accordingly, with continued movement of the piston  36 , liquid and air are driven past the ball valve  56  and through the element  58  by which the air and liquid are sufficiently mixed to form a foam that is extruded through the screen  62  and out the passage  64  of the nozzle  20 . 
     At the end of the dispensing stroke, as determined by the actuator  22  or otherwise, an appropriate biasing member urges return of the air piston  36 . Upon such urging, the one-way check valve or button valve  42  opens, allowing air to return into the air chamber  32 . Similarly, the element  58  urges the ball valve  56  into engagement with the valve seat  54  to preclude any further passage of liquid to the element  58 . With the hollow valve stem  48  urged by a spring or other biasing member toward the air piston  36 , the hollow valve stem  48  is repositioned for the next dispensing cycle. 
     Thus, it can be appreciated that the aspects of the invention have been achieved by the structure presented above. The fluid pump of the invention can be a commonly available fluid pump requiring minimal if any modification. The fluid pump is fixedly attached to and remains a portion of the disposable liquid cartridge  14 . Since the liquid pump is primarily in gravity-effected nesting engagement with the air compressor  18 , removal and replacement of the cartridge  14  is easily achieved. Moreover, the liquid pump can be manufactured of inexpensive materials, with the only requirement that it perform satisfactorily for the number of dispensing cycles required to deplete the cartridge  14 . On the other hand, the air compressor portion of the invention is an integral and permanent portion of the dispenser housing, and is capable of repeated use through numerous refills and replacements of the cartridge  14 . 
     Referring now to  FIG. 3 , another bifurcated foam pump assembly of an embodiment of the present invention is designated generally by the numeral  110 . The dispenser may be of any of various types, adapted for dispensing soap, lotion, sanitizers, cleaners or the like in the form of a foam. The dispenser  110  includes a housing  112 , typically of molded plastic or the like. The housing  112  defines a cavity which is adapted to receive a bottle or cartridge  114  of a set volume of a liquid of the particular type required for generating the desired foam. The bottle or cartridge  114  is nestingly received by the housing  110  and may be received and contained by supporting brackets, collars and the like within the housing  112 . 
     A liquid pump  116  is connected to and provided as a portion of the disposable refill cartridge or bottle  114 . In contradistinction, an air compressor unit  118  is provided as part and parcel of the dispenser housing  112 . Alternatively, the air compressor  118  or the liquid pump  116  may include a dispensing nozzle  120 , through which the generated foam is dispensed onto the hand of the user, utensil or otherwise. 
     A suitable actuator  122  is operatively connected to the air compressor  118  to achieve actuation of the foam generator comprising the combination of the liquid pump  116  and air compressor  118 . Those skilled in the art will understand that foam is typically generated from a combination of air and liquid, with the two being forced together, agitated, stirred, forcefully blended or the like. The actuator  122  may be either manually actuated as in the case of a lever, push bar or the like, or it may be electronically or optically actuated as in the implementation of touch free dispensers. 
     It will be appreciated that a concept of the invention, as particularly presented below, is the implementation and utilization of a bifurcated foam pump assembly, in which the liquid pump portion is attached to and made a portion of the disposable and replaceable cartridge  114 , containing the liquid ingredient of the foam solution, while the air compressor  118  and associated nozzle  120  are not disposable, but remain a portion of the dispenser housing  112 . 
     Referring now to  FIG. 4 , an appreciation can be obtained of a bifurcated liquid pump and air compressor assembly, and wherein the two are shown in the operative engagement achieved when the replaceable cartridge  114  with liquid pump  116  attached thereto is matingly received by the air compressor  118  and attached nozzle  120  that are received by and maintained as a portion of the dispenser housing  112 . As can be seen in  FIG. 4 , the air compressor  118  includes an annular collar  124  that is formed from an outer ring  126  and an inner ring established by first and second stepped walls  128 ,  130 . A cavity  132  is defined between the outer ring  126  and the inner ring formed by the interconnected walls  128 ,  130 . A piston  134 , consisting of an outer piston sleeve  136  and an inner piston sleeve  138  is received within the cavity  132  of the annular collar  124  and is adapted to operate between the outer ring  126  and one of the stepped inner rings  130 . As will be readily appreciated by those skilled in the art, the piston assembly  134  is adapted for reciprocation within the cavity  132 . The extending motion of the piston  134  is limited by stops  140 ,  142  of the annular collar  124  and piston assembly  134 , as shown. It will also be appreciated that the inward compressive movement of the piston  134  may be limited in various similar ways, including a limitation on the movement of the actuator  122 . 
     A one-way inlet valve  144  is provided in a base portion of the piston  134 , to allow air to reenter the air chamber or cavity  132  during operation, as will become apparent herein. It will also be noted that an outlet aperture  146  is provided in the wall  130  of the annular collar  124 , to allow communication between the air chamber or cavity  132  and the liquid pump assembly, as will be discussed below. 
     With continued reference to  FIG. 4 , it can be seen that the liquid pump  116  includes a collar  150  which is appropriately received by the throat of the disposable cartridge or container  114 . The collar defines a cavity  152  and is characterized by an upwardly extending truncated conical valve seat  154  at a bottom portion thereof, as shown. The various ribs and rings illustrated as comprising a portion of the collar  150  are primarily interposed for purposes of strength and rigidity as will be readily appreciated by those skilled in the art. According to a preferred embodiment of the invention, the collar  150 , as with the majority of the components of the invention, are molded of an appropriate plastic. 
     An intermediate cap  156  is attached to and closes an end of the collar  150  to define a liquid dispensing cavity  158  therebetween. A ball valve  160  is received within the cavity  158  and is adapted to sealingly nest with the valve seat  154  during operation. Ball valves  160 ,  174  may be hollow to increase buoyancy and further urge ball valves  160 ,  174  against seats  154 ,  164 . A second valve seat  162 , again of a truncated conical nature, is formed as part and parcel of the intermediate cap  156 , as shown, and operates as the seat for an outlet valve, as will become apparent below. 
     An annular recess or cavity  164  is provided about the interior wall surface of the cap  156  to provide a ring-like passage between an aperture  166  provided through the wall of the cap  156  and the aperture  168  provided through the wall of the collar  150 . Accordingly, there is a passage for communication between the air chamber cavity  132  and the liquid chamber cavity  158  through the apertures  146 ,  166  and  168 , by means of the annular recess or passage  164 . As can be seen with respect to  FIG. 3  and  FIG. 4 , apertures  168  are in fluid communication with the atmosphere ( FIG. 3 ) when the refill unit is not mated with the air compressor portion  118  and are in fluid communication with compressor  118  ( FIG. 2 ) when the refill unit and liquid pump  116  are mated together. 
     A nozzle  120  is received by and closes the end of the intermediate cap  156 , as shown in  FIG. 4 . A cavity  170  is thus defined between the nozzle  120  and the intermediate cap  156 . This outlet chamber or cavity  170  receives an appropriate sponge, screen, mesh assembly or the like to assist in the generation of foam as a mixture of air from the air chamber or cavity  132  and liquid from the liquid chamber or cavity  158 . A ball valve  174  is received by the cavity  170  and is urged by the resilient nature of the sponge, screen, or mesh assembly  172  into nesting sealing engagement with the valve seat  162 , at rest. For this purpose, an appropriate recess  176  may be provided in the element  172 . 
     It will be appreciated that the elements comprising the liquid pump  116  are attached to and are a part of the refill cartridge  114  and are received by the annular collar  124  and the remainder of the air chamber or compressor  118  when replacement of the refill cartridge  114  is effected. To that end, appropriate O-ring seals  180  are received within the first and second walls  128 ,  130  of the inner ring of the collar  124 . This allows for and ensures that the passage of liquid from the container  114  only occurs after it is converted to foam for dispensing through the outlet  178  of the nozzle  122 . 
     In operation, the liquid of the cartridge  114  that is required for generating the desired foam passes from the container  114  through the cavity  152  of the collar  150  and, by gravity, passes the seat and ball valve arrangement  154 ,  160  and flows into the liquid cavity  158  to await a dispensing operation. The seat and ball valve  162 ,  174  is closed at this time due to the biasing nature of the element  172 . When a dispensing operation is initiated as by the actuator  122 , the piston  134  moves from engagement between the stops  140 ,  142  and begins to compress air within the air chamber or cavity  132 , forcefully passing that air through the apertures  146 ,  166 , annular recess or passage  164 , and through the aperture  168  and into the liquid chamber  158 . This compressed air forces the ball valve  160  into sealing engagement with the valve seat  154  and urges the ball valve  174  to disengage from the seat  162  against the biasing of the screen, sponge or mesh  172 . A mixture of air and liquid is then forced through the valve assembles  162 ,  174  and through the foam generating member  172  such that an appropriate foam is emitted through the outlet  178  and onto the hands of the user or a desired tool or implement. At the end of the dispensing cycle, appropriate springs or biasing devices in the actuator  122  cause the piston  134  to retract from the cavity  132  until contact is made between the stops  140 ,  142 . During this activity, air is drawn through the one-way valve  144  into the expanding cavity  132  to await the next cycle of operation. Liquid is replenished from the container  114  through the valve assembly  154 ,  160  by gravity, until the cavity  158  is replenished. The bifurcated foam pump assembly comprising the liquid pump  116  and the air compressor  118  then awaits the next dispensing cycle. 
     Only the liquid portion of the foam generator is required for replacement upon depletion of the cartridge  114 , rather than total replacement of the assembly as with prior art devices. Additionally, the bifurcated foam pump assembly is reliable and durable in use, the element  172  being of sufficient strength and durability to accommodate depletion of the cartridge  114  while generating a high quality foam. 
     Referring now  FIG. 5 , another embodiment of a bifurcated foam pump assembly of the invention is designated generally by the numeral  210 . It will be appreciated that the foam solution dispenser may be of any of various types, adapted for dispensing soap, lotion, sanitizers, cleaners or the like in the form of a foam. The dispenser  210  includes a housing  212 , typically of molded plastic or the like. The housing  212  defines a cavity which is adapted to receive a bottle or cartridge  214  of liquid of the particular type required for generating the desired foam. The bottle or cartridge  214  is nestingly received by the housing  212  and may be received and contained by supporting brackets, collars and the like within the housing  212 . 
     A liquid pump  216  is sealed to and provided as a portion of the disposable refill cartridge or bottle  214 . In contradistinction, an air compressor unit  218  is provided as part and parcel of the dispenser housing  212 . In a preferred embodiment of the invention, the liquid pump  216  includes a dispensing nozzle  220 , through which the generated foam is dispensed onto the hand of the user, utensil or otherwise. 
     A suitable actuator  222 , an integral part of the housing  212 , is operatively connected to the air compressor  218  to achieve actuation of the foam generator comprising the combination of the liquid pump  216  and air compressor  218 . Those skilled in the art will understand that foam is typically generated from a combination of air and liquid, with the two being forced together, agitated, stirred, forcefully blended or the like. The actuator  222  may be either manually actuated as in the case of a lever, push bar or the like, or it may be electronically or optically actuated as in the implementation of touch free dispensers. 
     It will be appreciated that a concept of the invention, and as particularly presented below, is the implementation and utilization of a bifurcated foam pump assembly, in which the liquid pump portion is sealingly attached to and made a portion of the disposable and replaceable cartridge  214  containing the liquid ingredient of the foam solution, while the air compressor  218  and associated nozzle  220  are not disposable, but remain a portion of the dispenser housing  212 . 
     Referring now to  FIG. 6 , the air compressor portion  218  of the invention includes a collar  224  receiving a piston  226  sealingly and reciprocatingly therein. The piston  226  is actuated by the actuator  222 . A sealing ring  228  extends about an upper edge of the piston  226  in engagement with an interior surface of the cup-shaped collar  218 , as best shown in  FIG. 7 . A one-way check valve  230  is provided in a bottom portion of the piston  226  for purposes of replenishing air within the air chamber defined between the piston  226  and collar  224 . Further comprising a portion of the air compressor  218 , a collar  232  extends centrally downwardly from the collar  224  and is adapted to receive the bottle or cartridge of liquid  214 , having the liquid pump portion  216  of the invention attached thereto. 
     With continued reference to  FIGS. 6 and 7 , it can be seen that the liquid pump  216  includes an upper pump housing  234  and a lower pump housing  236 , the two being reciprocatingly interengaged as will become apparent below. A collar  238  forms an upper portion of the upper pump housing  234  and is adapted to sealingly engage a neck of the cartridge  214 . An upper sleeve portion  240  of the upper pump housing  234  extends downwardly from the collar  238 , as shown. The collar  238 , in association with the neck of the container  214 , defines a first liquid reservoir in communication with the pump. 
     A second liquid reservoir  244  is defined by the lower pump housing  236  and includes a lower sleeve portion  246  that extends downwardly, ending at the nozzle  220 . A cavity  248  is defined within the lower sleeve  246  and is adapted to receive a mesh, screen, sponge or the like  250  for purposes of generating foam from a combination of liquid and air imparted thereto. The sleeve  246  includes a collar  252  adapted for interengagement with the actuator  222 . However, it will be appreciated that the actuator  222  may otherwise engage the pump, as will be readily understood by those skilled in the art. 
     A ring seal  254  extends about the lower end portion of the upper sleeve  240  of the upper pump housing  234 , as illustrated. The ring seal  254  engages the inner wall of the lower pump housing  236  defining the second liquid reservoir  244 . 
     A hollow stem  260  is received within and extends between the upper and lower pump housing sections  234 ,  236 . A lower end of the hollow stem  260  is secured to the lower pump housing  236 , as shown. The hollow stem  260  includes a central bore  262  that is closed at the top end thereof and that opens into the cavity  248  at the bottom thereof. Feeder passages  264  extend angularly upward to provide communication between the second liquid reservoir  244  and the central bore  262  of the hollow stem  260 . 
     An upper ring seal  266  extends about the top end of the hollow stem  260 , as shown. The upper ring seal  266  engages the inner wall surfaces of the first liquid reservoir  242  and serves as a wiper or seal between the hollow stem  260  and the walls of the cavity  242 . A guide collar  268  extends circumferentially around the hollow stem  260  slightly below the upper ring seal  266  to ensure axial alignment within the reservoir  242 . 
     A lower ring seal  270  extends about the hollow stem  260  and within the upper sleeve portion  240 , making wiping sealing contacting engagement with the inner wall thereof. As shown in  FIG. 6 , the second liquid reservoir  244  maintains, in the standby condition, a reservoir of liquid at the level  272 , just below the interconnection of the passageway  264  with the central bore  262  of the hollow stem  260 . As will be appreciated below, the liquid is moved from the cartridge  214  and first liquid reservoir  242 , through the sleeve  240 , past the one-way valve lower ring seal  270  and into the second liquid reservoir  244 . A liquid droplet  274  is shown in  FIG. 6  passes from the sleeve  240 , past the lower ring seal  270  and into the second liquid reservoir  244 . 
     As best seen in  FIGS. 8 and 9 , there is a clearance between the sleeve  240  of the upper pump housing  234  and the lower pump housing  236  defining the reservoir  244 . This allows for telescoping reciprocating movement between the upper and lower pump housing members  234 ,  236 , and further accommodates the passage of air through the clearance  276  from the air chamber defined between the collar  224  and piston  226  and the second liquid reservoir  244  upon actuation of the pump. 
     It will be appreciated that a liquid pump portion  216 , primarily comprising elements  234 ,  236  described above, is provided as part and parcel of the replaceable cartridge  214  and is adapted to be received by the air compressor  218 , comprising elements  224 - 232 , which are a fixed integral portion of the dispenser housing  212 . Of course, appropriate seals are provided on the pump and air compressor mating portions to ensure leak-free operation, as to both liquid and air. 
     With an appreciation of the structure of the invention, an understanding of its operation can be obtained.  FIGS. 6 and 7  illustrate the at-rest or standby position of the dispenser and foam pump assembly of the invention. At this point, a level of liquid  272  is maintained within the second liquid reservoir  244 . Upon actuation of the actuator  222 , the piston  226  compresses within the collar  224 , compressing the air chamber defined therebetween, sealing the one-way check valve  230 , and driving air through the clearance  276  between the upper and lower pump housing member  234 ,  236  and into the second liquid reservoir  244 . Accordingly, both liquid and air are driven through the feeder passages  264  and into the central bore  262  of the hollow stem  260 . The combination of air and liquid is then forced from the central bore  262  and into the cavity  248  maintaining an appropriate mesh,  250  screen, sponge or the like to extrude the combination of liquid and air into a foam that is emitted from the nozzle  220 . 
     The pump is shown at its maximum compression in  FIG. 9 . Thereafter, a spring or other appropriate return mechanism that may be either provided interiorly between the collar  224  and piston  226 , or as part and parcel of the actuator  222 , causes return of the pump to its standby position. At the maximum extension shown in  FIG. 9 , liquid from the cartridge  214  passes by the lifted upper ring seal  260  and into the first liquid reservoir  242 . As the return mechanism draws the hollow stem  260  downwardly between the pump housings  234 ,  236 , the liquid within the first liquid reservoir  242  is driven past the lower ring seal  270 , serving as a one-way valve. That liquid then replenishes the second liquid reservoir  244  to the level  272  shown in  FIG. 6 . During this operation, the one-way check valve  230  is opened by the vacuum created in the air chamber cavity between the collar  224  and piston  226 , allowing air to replenish the air chamber. The pump is then available for a subsequent dispensing operation. 
     Thus, it can be appreciated that the aspects of the invention have been achieved by the structure presented above. The fluid pump of the invention can be a commonly available fluid pump requiring minimal modification. The fluid pump is sealingly fixedly attached to and remains a portion of the disposable liquid cartridge  214 . Being a commonly known and readily available liquid pump, the cost of the disposable cartridge  214  is greatly reduced. Moreover, the air compressor portion of the foam generating assembly remains an integral part of the dispenser housing  212 , further reducing refill and replacement costs. 
     While, in accordance with the patent statutes, only the best mode and preferred embodiments of the invention have been presented and described in detail, the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.