Patent Abstract:
According to one exemplary embodiment, a compact fluid purification device includes a housing having an inlet for receiving unfiltered liquid and an open end and a first valve disposed within the inlet and being configured to only permit unfiltered liquid to flow into a hollow interior of the housing. The device has a plunger received within the open end such that it slides within the interior of the housing. The plunger is movable between a fully extended position and a fully retracted position, wherein the plunger has an elongated housing that includes a filter element, such as, a plurality of hollow filter elements that are open at a distal end of the plunger housing and are in communication with an outlet that is associated with the plunger. Movement of the plunger toward the fully extended position causes unfiltered liquid to be drawn into the interior of the housing and the device includes a second valve disposed within the outlet and being configured to only permit filtered liquid to be discharged from the plunger housing. The unfiltered liquid is filtered when the plunger is moved toward the fully retracted position causing the unfiltered liquid in the interior to flow into the inside of the filter elements and then across the filter elements and into the outlet.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. patent application Ser. No. 60/890,251, filed Feb. 16, 2007, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to filtration devices, and more particularly, to a compact fluid purification device in which the filtering means is integrated as part of the pump mechanism. 
     BACKGROUND 
     When traveling on foot in remote locations such as during hiking, camping, military operations, or other, the size and weight of the equipment one is carrying is a very important issue. Devices used to purify water in these remote locations (where no electricity may be available) primarily fall into three categories: chemical disinfection (e.g., chlorine, iodine), adsorption (e.g., activated carbon, adsorptive resins), and filtration (e.g., membrane filters, ceramic or carbon filter blocks). A drawback of filtration devices used for this purpose is their relatively large size. The larger size is generally due to the fact that a pump mechanism is somehow attached to the filter so that one can generate sufficient pressure to force water across the filter as part of the purification process. A typical arrangement is one whereby a volume displacement type pump is in series with a filter device. The volume displacement pump is generally a piston type pump which includes a stationary barrel component and a moveable plunger component. Examples of these include First Need Delux, from General Ecology, Inc (Exton, Pa.), and SweetWater Purifier, from Mountain Safety Research, Inc. (Seattle, Wash.) Though the filter and pump mechanism can be semi-rigidly attached to one another, a problem with these designs is their large size is basically caused by having the filter and pump as two discrete elements. For example, the overall size (i.e. the volume the whole device occupies) is the sum of each component (i.e. it&#39;s the pump volume plus the filter volume). Upon examining the pump volume, one must use the whole barrel volume, regardless if the if the plunger component is fully inserted inside the barrel. This is because the area behind the plunger still takes up what would be considered storage space. 
     Thus, there is a perceived need for a compact fluid purification device with a manual pumping mechanism and which overcomes the above deficiencies. 
     SUMMARY 
     The objective of this patent is to overcome this problem by integrating the filter as part of the pump mechanism so as to make the filter device small and compact in size. 
     According to one exemplary embodiment, a compact fluid purification device includes a housing having an inlet for receiving unfiltered liquid and an open end and a first valve disposed within the inlet and being configured to only permit unfiltered liquid to flow into a hollow interior of the housing. The device has a plunger received within the open end such that it slides within the interior of the housing. The plunger is movable between a fully extended position and a fully retracted position, wherein the plunger has an elongated housing that includes a plurality of hollow fiber filter elements that are open at a distal end of the plunger housing and are in communication with an outlet that is associated with the plunger. Movement of the plunger toward the fully extended position causes unfiltered liquid to be drawn into the interior of the housing and the device includes a second valve disposed within the outlet and being configured to only permit filtered liquid to be discharged from the plunger housing. The unfiltered liquid is filtered when the plunger is moved toward the fully retracted position causing the unfiltered liquid in the interior to flow into the inside of the filter elements and then across the filter elements and into the outlet. 
     According to another embodiment, a compact fluid purification device that has redundant filtration includes a housing having a first compartment and a second compartment. The first compartment has an inlet at a first end for receiving unfiltered liquid and the second compartment has an outlet at a first end for discharging filtered liquid, with each of the first and second compartments having an open end. The device includes a first valve disposed within the inlet and being configured to only permit unfiltered liquid to flow into the first compartment and a second valve disposed within the outlet and being configured to only permit filtered liquid to be discharged from the second compartment. The device includes a plunger received within the open ends of the first and second compartments such that it slides within the first and second compartments. The plunger is movable between a fully extended position and a fully retracted position, wherein the plunger has a first elongated housing that includes a first set of hollow fiber filter elements and a second elongated housing that includes a second set of hollow fiber filter elements. Each of the first and second set of filter elements is open at distal ends thereof. The first set of hollow filter elements are in fluid communication with the inlet and the second set of hollow filter elements are in fluid communication with the outlet; and a connector conduit is provided that fluidly connects the first compartment to the second compartment. 
     Movement of the plunger toward the fully extended position causes unfiltered liquid to be drawn into the first compartment and wherein the unfiltered liquid is filtered when the plunger is moved toward the fully retracted position causing the unfiltered liquid in the interior to flow into the inside of the first set of filter elements and then across the first set of filter elements to produce once filtered liquid that flows through the connecting conduit filter to the second elongated housing where it is filtered across the second set of the filter elements and is then discharged through the outlet. 
     In another embodiment, a compact fluid purification device includes a housing having an inlet for receiving unfiltered liquid and an open end and a first valve disposed within the inlet and being configured to only permit unfiltered liquid to flow into a hollow interior of the housing. A plunger is received within the open end such that it slides within the interior of the housing. The plunger is movable between a fully extended position and a fully retracted position, wherein the plunger has a first housing that includes a first set of hollow fiber filter elements that are open at a distal end of the plunger housing and are sealed at an opposite end. The plunger housing has a through hole proximate the sealed ends of the first set of hollow fiber filter elements for discharging once filtered liquid after it has been filtered across the first set of hollow fiber filter elements. The plunger includes a second housing that has an open end that is sealingly attached to the first plunger housing such that the through hole in the first plunger housing is in fluid communication with an interior of the second plunger housing. The second plunger housing has a second set of hollow filter elements disposed therein and having open ends that are in fluid communication with an outlet through which twice filtered liquid is discharged after being filtered across the second set of filter elements. A second valve is disposed within the outlet and being configured to only permit twice filtered liquid to be discharged through the outlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         FIG. 1  is a perspective view of a compact fluid purification device with a manual pumping mechanism according to one exemplary embodiment; 
         FIG. 2  is a cross-sectional view of the device of  FIG. 1 ; 
         FIG. 3  is a close-up, localized cross-sectional view of an inlet end of the device of  FIG. 1 ; 
         FIG. 4  is a close-up, localized cross-sectional view of an outlet end of the device of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of the device of  FIG. 1  showing the filter/plunger in a fully inserted position; 
         FIG. 6  is a cross-sectional view of a conventional filtering device in which the filter and pump mechanism device are separate components; 
         FIG. 7  is a perspective view of a double barrel compact filter/pump device with redundant filter stages according to another embodiment; 
         FIG. 8  is a cross-sectional view of the device of  FIG. 7  with the plunger in a partially withdrawn state; 
         FIG. 9  is a cross-sectional view of the device of  FIG. 7  with the plunger at a fully extended position; 
         FIG. 10  is a cross-sectional view of the device of  FIG. 7  with the plunger in a close position with the plunger fully inserted inside the barrel; 
         FIG. 11A  is a cross-sectional view of a compact filter/pump device with redundant filter stages according to another embodiment; 
         FIG. 11B  is an enlarged cross-sectional view of a pre-filter screen of the device of  FIG. 11A ; 
         FIG. 11C  is an enlarged cross-sectional view of a coupling between first and second plunger housings of the device of  FIG. 11A ; 
         FIG. 12  is a partial cross-sectional view of the coupling between first and second plunger housings of the device of  FIG. 11A  with a one-way valve therebetween; and 
         FIG. 13  is a schematic showing a filter/pump device as part of a hydration backpack system. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A compact (size-efficient) filter device with integral manual hand pump mechanism for purification of water or other fluids is provided in accordance with several embodiments of the present invention. 
     A first embodiment is shown in  FIG. 1  which provides a perspective view of a compact filter/pump device  10  that resembles a syringe and/or a syringe type pump composed of a barrel  12  and a plunger  14 . The inlet  16  of the filter/pump device is positioned at the distal end of the barrel  12  and the outlet  18  of the filter/pump device is positioned near the end of the plunger  14 . Further description of the first embodiment is illustrated in cross-sectional views shown in  FIGS. 2 ,  3 ,  4 , and  5 . 
     It will be appreciated that the filter/pump devices disclosed herein are suitable for use with a number of different liquids for the purification of these liquids. One exemplary liquid is water and accordingly, the devices disclosed herein are suited for purifying unfiltered water; however, it will be appreciated that the present invention is not limited to being used with water. 
       FIG. 2  shows the filter/pump device with the plunger component  14  partially withdrawn from the barrel  12 . At the inlet  16  of the filter/pump device, a one-way check valve  20  is used to allow a source of unfiltered fluid  30  to enter the internal barrel compartment  40  when the plunger  14  is being withdrawn from the barrel  12  and to prevent unfiltered fluid filling barrel compartment  40  from leaking back out the inlet  16  when the plunger  14  is being pushed into the barrel  12 . In addition, a second one-way check-valve  22  is positioned at outlet  18  of the device such that filtered fluid  32  does not leak back into the barrel compartment  40  when the plunger  14  is being withdrawn from the barrel  12  and to allow filtered fluid  32  to exit the filter/pump device when the plunger  14  is being pushed into the barrel. The one-way check valves  20  and  22  can be a spring loaded ball/seat type as shown, or may another type such as a duck-bill, flexible disk, etc. as is known in the art. 
     The plunger  14  is in itself a filter device that is constructed with a plunger housing  42  that encases a filter element (or elements)  44  inside said plunger housing. As shown, the filter element may consist of a bundle of semi-permeable hollow fibers that are longitudinally placed along the axis of said plunger housing. The hollow fibers may be potted at each end  46  and  48  of the plunger housing  42  with a polyurethane, epoxy, or other such material as is known in the art. At a first end of the plunger housing, a plunger seal  50  may be attached. The plunger seal  50  creates a fluid type seal between the plunger  14  and the barrel  12  thereby preventing fluid from leaking in-between the plunger and barrel during operation of the filter/pump device. 
     Reference is now made to  FIG. 3  which shows a close-up cross-sectional view of said first end of the plunger housing  42 . At this end, the potted hollow fibers  46  have been opened, such as by a cutting or trimming operation, to form a tubesheet surface  60 . This allows unfiltered fluid contained in the barrel compartment  40  to flow into the lumen space of the hollow fibers when the plunger  14  is being pushed into the barrel  12 . The plunger seal  50  is configured with an opening such that it does not interfere with flow of fluid into the hollow fibers at the tubesheet  60 . 
     Reference is now made to  FIG. 4  which shows a close-up cross-sectional view of said second end of the plunger housing  42 . At this end, the potted hollow fibers  48  have not been opened by a secondary trimming operation. Here, the potting material forms a plug  62  that essentially seals the inside and outside of each of the hollow fibers and seals the end of the plunger housing  42 . As such, upon pushing the plunger  14  into the barrel  12 , fluid is forced across the semi-permeable hollow fiber membrane  44  since it cannot escape through the plugged ends  62 . The filtered fluid  70  is directed out of the plunger through the outlet check-valve  22 . A plunger cap  52  may be attached to said second end of plunger housing  42  as an aid to better grip and operate the filter/pump device. 
     It should be understood to those skilled in the art that operation of the filter/pump device is composed as two discrete pump phases as follows: 
     Fluid Suction Phase: The action of pulling the plunger  14  out of the barrel  12  creates a negative pressure inside the barrel compartment  40  that draws unfiltered fluid  30  into the inlet  16  of the device, through the inlet check-valve  20  and into the expanding barrel compartment  40 . The outlet check valve  22  further prevents fluid leaking back into the filter/pump device during this phase of the pump operation. 
     Fluid Expelling Phase: The action of pushing the plunger  14  into the barrel  12  creates a positive pressure in the contracting barrel compartment  40  that forces unfiltered fluid within compartment  40  across the filter elements  44  thereby removing fluid impurities such as bacteria, other microorganisms, and the like. The filtered fluid (or permeate)  70  collects downstream filter element and passes through the outlet check-valve  22  and out through the device outlet  18 . The inlet check valve  20  further prevents unfiltered fluid from leaking back out of the inlet  16  of the device during this phase of the pump operation. 
     It should also be understood to those skilled in the art that the design of the filter/pump device achieves the objective of having a very compact size. This is best illustrated in  FIGS. 5 and 6  showing cross-sectional views filter/pump devices.  FIG. 5  shows the first embodiment of the invention with the filter/plunger fully inserted inside the barrel  12 . This configuration, for example, would be used when carrying, transporting, and storing the device and as such represents its smallest size. As illustrated, the filter element of this device is an integral part of the plunger component  14 .  FIG. 6  illustrates current state of the art devices whereby a filter component  90  is coupled alongside a pump mechanism  92  to create a single filter/pump unit  100 . The pump mechanism shown is a similar piston type volume displacement pump with inlet and outlet one way check valves  80  and  82  respectively that allow for fluid to fill the barrel of piston when the plunger  96  is pulled out and to direct fluid toward the filter  90  when pushing the plunger into the piston barrel. It should be observed however, that in these designs, the filter and the pump mechanism are generally two discrete components of the device. The problem with these designs can be seen by examining the space that the device occupies in its smallest most compact configuration which is when the plunger is fully inserted into the barrel. In this case, there is an obvious dead-space  94  that resides within the piston barrel but behind the plunger seal  98 . This dead-space or volume must be considered when carrying, transporting, and storing the device. It should be apparent to those skilled in the art that there is no dead-space with the embodiment shown in  FIG. 5  since this space is occupied by the filter component. 
     It should be understood to those skilled in the art that the filter component of the preferred embodiment can be constructed of any suitable type filter material as known in the art which can include but not limited to hollow fiber membranes, flat or pleated sheet membranes, glass fiber or ceramic filter media, and/or carbon filter blocks. It should also be understood to those skilled in the art that the plunger housing  42  can include multiple filtration stages in series for safety reasons, should one filter stage fail during use. Examples of these multistage filter designs include but are not limited to those filed in U.S. patent applications Nos. 60/714,058, and 60/734,006, each of which is hereby incorporated by reference in its entirety. 
     A second embodiment of the invention is shown in  FIG. 7  as a double barrel filter pump device  200  consisting of a double barrel casing  212  and a double barrel plunger assembly  214  having redundant filter stages  201  and  202 , respectively. The redundant filter/plunger stages fit within a double barrel casing  212 . An inlet port  216  allows unfiltered fluid to feed into a first side of the double barrel casing  212  while an outlet port  218  allows filtered fluid to exit a second side of the double barrel casing  212 . Similar to the first embodiment, a tubesheets  260  and  261  can be formed at the end of each plunger/filter stage to allow fluid to enter and leave the filtration elements positioned inside the plunger housing. 
     Reference is now made to  FIG. 8  showing a cross-sectional view of the double barrel filter/pump device. The double plunger assembly  214  may be constructed by connecting two plunger housings  242  and  243  together with a connecting conduit  247 . The connecting conduit  247  fluidly connects the once filtered fluid exiting plunger housing  242  to the second plunger housing  243 . Similar to the first embodiment, each plunger housing  242  and  243  contains filter elements  244  and  245  respectively, which may be hollow fiber membranes as shown or may be another filter media type which may include flat or pleated sheet membrane, glass fiber or ceramic filter media, and/or carbon filter blocks. Also similar to the first embodiment, plunger seals  250  and  251  may be attached to each plunger housing end to create a leak-tight seal between the plunger housings and the double barrel casing  212 . In addition, one-way check valves  220  and  222  may be located near the inlet and outlet ports  216  and  218  respectively. A plunger cap  252  may be attached to said second end of plunger housings  242  and  243  as an aid to better grip and operate the double barrel filter/pump device. 
     It should be understood to those skilled in the art that operation of the double barrel filter/pump device is composed as two discrete pump phases as follows: 
     Fluid Suction Phase: The action of pulling the plunger assembly  214  out of the double barrel casing  212  creates a negative pressure inside the barrel compartments  240  and  241  that draws unfiltered fluid  230  into the inlet  216  of the device, through the inlet check-valve  220  and into the expanding barrel compartment  240 . Likewise, an even more negative pressure is created in the expanding barrel compartment  241  relative to barrel compartment  240  since fluid can only enter into this compartment by filtration through filter element  245 . The outlet check valve  222  further prevents fluid leaking back into the filter/pump device during this phase of the pump operation. As such, the fluid suction phase is characterized as both a filling of unfiltered fluid  230  into barrel compartment  240  and a simultaneous filtering process whereby twice filtered fluid passing through the plunger/filter assembly  214  collects in the expanding barrel compartment  241 . 
     Fluid Expelling Phase: The action of pushing the plunger assembly  214  into the double barrel casing  212  creates a positive pressure in the contracting barrel compartment  240  that forces unfiltered fluid within compartment  240  across the filter elements  244  and  245  thereby removing fluid impurities such as bacteria, other microorganisms, and the like. Because of its proximity to the fluid outlet port  218 , a less positive pressure is created inside the contracting barrel compartment  241  relative to barrel compartment  240 . As a result, fluid in barrel compartment  240  is forced into plunger/filter assembly  214  which in turn displaces the filtered fluid in barrel compartment  241  and pushes the twice-filtered fluid out through the outlet check-valve  222  and out through the device outlet  218 . The inlet check valve  220  further prevents unfiltered fluid  230  from leaking back out of the inlet  216  of the device during this phase of the pump operation. As such, the fluid expelling phase is characterized as both a filtering process whereby unfiltered fluid  230  inside barrel compartment  240  passes through the plunger/filter assembly  214  and simultaneously displaces and expels the twice-filtered fluid out of the contracting barrel compartment  241 . 
     An optional feature of this device may be the inclusion of a spring  271  that is positioned between the barrel casing  212  and the filter plunger assembly  214 . This could enable a one-handed operation of the filter/pump device whereby an individual could position their finger and thumb through the finger hole  281  and around the plunger cap  252 , respectively. The expelling phase of the filter/pump operation could then be accomplished by squeezing (or clenching) the finger and thumb together which compresses the spring  271  while the suction phase could be accomplished by relaxing the hand and allowing the spring  271  to recoil to its normal length. As shown in  FIG. 9 , one may securely attach only one end of the spring  271 , such as to the filter/filter assembly  214 . This would allow a two-handed operation of the device whereby one could achieve a faster pumping rate using a longer pump stroke length. 
     Reference is now made to  FIG. 10  where the double barrel filter/pump device  200  is shown with the filter/plunger assembly  214  fully inserted inside the barrel  214 . This configuration, for example, would be used when carrying, transporting, and storing the device and as such represents its smallest size. As in the first embodiment, the filter elements of this filter/pump device are both an integral part of the plunger assembly  214 . Therefore, it should be apparent to those skilled in the art that there is no dead-space associated with the pump mechanism with this second embodiment as the barrel space is again occupied by the filter component of the device. 
     Reference is now made to  FIGS. 11A-C  showing an alternate design of a two-stage filter/pump device  300  that consists of a single barrel  312  and a plunger assembly  314  that consists of two filtration stages. The right side of the device shows a sectional view to better visualize the internal construction of the device. In the same manner as the first embodiment, an inlet port  316  receives the fluid to be filtered and passes through an inlet one-way check valve  320 . The incoming fluid fills the expanding internal barrel compartment  340  as the plunger assembly  314  is being withdrawn. A one-way check valve  322  near the outlet port  318  of the plunger assembly  314  keep fluid from entering the filter pump device at this end as indicated in previous embodiments. 
     Construction of the first filter stage of the plunger assembly is similar to previous embodiments in that a filter housing  342  encloses a filter element  344 , such as hollow fibers as shown here. A first end of the plunger casing is potted with a potting compound  346  and is trimmed to form a tubesheet  360 . A plunger seal  350  is also attached at this end of the casing to form seal between the barrel  312  and the plunger housing  342 . An added feature may be the inclusion of a pre-filter screen  380  that keeps large particulate from reaching the tubesheet  360 . The may be beneficial since a large particle could block flow into one or more of the hollow fibers which could drastically reduce its efficiency. At the second end of the first filter stage, the filter elements  344  are sealed in potting compound  348 . An opening  376  in the filter housing  342  allows filtered fluid to exit the first filter housing. 
     Attached to the second end of the plunger housing  342  is a second filter housing  343  that encloses a second filter element  345 , such as hollow fibers as shown here. At a first end of the said second filter housing  343 , the housing  343  is joined to the plunger housing  342  to form a leak-tight joint  354 . This joint may be formed by ultrasonically welding the two parts together or may be cemented or solvent bonded together as is known in the art. The second end of said second filter housing is potted with a potting compound  370  and trimmed to form a tubesheet  371 . As shown, the filter elements may be hollow fibers and may be formed in a “U” shaped configuration. In this configuration, fluid being filter must traverse the membrane from the outside to the inside, whereby filtered fluid exits the lumens of the fibers at the tubesheet  371 . An external header cap  372  is also attached to said second end to direct the filtered fluid to the outlet one-way check valve  322  and outlet port  318 . The second filter housing  343  may preferentially be made with an optically clear material to aid in viewing the upstream side of the filter membrane. As described in U.S. patent application 60/809,648, which is hereby incorporated by reference in its entirety, there is an advantage of this design in that one can indirectly verify the integrity of the first filter stage by inspection of the upstream side of the filter membrane. If the first filter stage has failed, a build up of sediment on the second filter may be noticeable as a change in appearance whereby it looks “dirty” in color. 
     The operation of the filter/pump device  300  is as follows. 
     Fluid Suction Phase: The action of pulling the plunger  314  out of the barrel  312  creates a negative pressure inside the barrel compartment  340  that draws unfiltered fluid into the inlet  316  of the device, through the inlet check-valve  320  and into the expanding barrel compartment  340 . The outlet check valve  322  further prevents fluid leaking back into the filter/pump device during this phase of the pump operation. 
     Fluid Expelling Phase: The action of pushing the plunger  314  into the barrel  312  creates a positive pressure in the contracting barrel compartment  340  that forces unfiltered fluid within compartment  340  across the filter elements  344  thereby removing fluid impurities such as bacteria, other microorganisms, and the like. The once filtered fluid (or permeate)  377  collects downstream of the first filter element  344  and passes through an opening  376  of a first filter housing  342  and into an interstage compartment  352 . The once-filtered fluid  377  is then filtered a second time as it is forced across a second set of filter elements  345  whereby it is directed toward an outlet check-valve  322  and out through the device outlet  318 . The inlet check valve  320  further prevents unfiltered fluid from leaking back out of the inlet  316  of the device during this phase of the pump operation. 
     Reference is now made to  FIG. 12  which shows an alternative placement of the outlet one-way check valve  322  which is at the opening  376  between the two filter stages. It should be appreciated by those skilled in the art that placement in this position does not alter the function of the device, but reduces the complexity and number of components by taking advantage of the geometry of the opening and the relative configuration of the two filter housings  342  and  343  respectively. 
     Reference is now made to  FIG. 13  which shows a filter/pump device as part of a hydration backpack system  400  and in particular, the filter/pump device can be any of the previously discussed embodiments, including the device  300  of  FIGS. 11A-C  as shown in  FIG. 13 . As shown, the filter/pump device is physically attached to one of the shoulder straps  410  of the backpack. The shoulder strap has been modified to include an elastic element  404 , at least two securing straps  401  and  402 , and a pull handle  408 . The elastic element  404  can be an elastic band material as is known in the art. The inlet end of the filter/pump device is fluidly connected to a fluid reservoir  420  via a connecting tube  422 , while the outlet end of the filter/pump device may be attached to an outlet tube  424  and a mouthpiece fitting  426 . In the configuration shown, the barrel portion  412  of the filter/pump device is secured to the shoulder strap with securing strap  401  in a position above the elastic element  404  and the plunger portion  414  is secured to the shoulder strap with securing strap  402  in a position below the elastic element. It should be understood that the filter/pump device can include additional attachment points with additional slots and/or tabs constructed as part of the barrel and plunger components provided these do not interfere with the operation of the device. 
     Operation of the device may be performed with one-hand whereby the wearer of the backpack grasps and pulls down on the pull handle  408  which is attached to the shoulder strap at a position below the elastic element  404 . Because the top of the shoulder strap is supported by the wearer&#39;s shoulder, the action of pulling down on the pull handle results in a lengthening or stretching of the elastic element  404  of the shoulder strap while at the same time withdrawing the plunger component  414  out of the barrel  412  of the filter/pump device. This action thus accomplishes the “fluid suction” phase of the pump operation as described previously as well as serves to store a potential energy in the elastic element of the shoulder strap. Upon letting go of the pull handle  408 , the energy stored in the elastic element  404  serves to push the plunger  414  back into barrel  412  as it recoils back from its stretched position. This, therefore, accomplishes the “fluid expelling” phase of the pump operation as described previously. 
     It also should be understood that the filter/pump device may be a replaceable component of the hydration backpack system and as such may fit into a compartment (not shown) that includes a flap that can be opened for replacement of the filter/pump device. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to the embodiments described thus far with reference to the accompanying drawings; rather the present invention is limited only by the following claims.

Technology Classification (CPC): 1