WO1994013954A1 - Compact water filtration and purification pump - Google Patents

Abstract

A portable, manually-operated water filtration pump (10) for purifying water. The pump includes an inexpensive, disposable filter cartridge which can be easily changed when the filter elements are no longer effective. The pump (10) uses a lever (22) to actuate a double-acting piston. The lever (22) is collapsible to one side of the pump (10) for compact storage. The filter cartridge is a tubular cylinder having an inner bore forming the pump cylinder. A cylindrical mechanical filter is concentric with and adjacent to the inner bore to filter out particulates larger than .3 microns. A fluidized granular activated charcoal filter surrounds the mechanical filter to absorb chlorine and chlorine-related compounds such as herbicides and pesticides. The pump (10) pumps filtered water into a bottle adaptor (62) which will fit most standard water containers. A prefilter (70) is provided to screen out large particulates from the pump (10) to enhance the life of the filter elements. The prefilter (70) is shaped such that it will sink in water sources and to keep the prefilter inlet upright in still water or downstream in moving water.

Description

COMPACT WATER FILTRATION AND PURIFICATION PUMP

FIELD OF THE INVENTION

This invention relates to the field of water purification units, and particularly to the field of portable water filtration pumps for back-country or travel use and other applications where manual water purification is required.

STATEMENT OF THE PROBLEM Water purification is a critical problem in today's world. There presently are a large number of systems for home and industrial water purification. However, these units are relatively large and designed to be affixed to a pressurized water source. A strong need exists for a portable system of water purification, particularly for a lightweight, compact water filtration unit. Such a unit is necessary for purifying water sources for travelers, campers, backpackers, fishermen, hunters, rafters, in emergency situations, and the like.

Water sources, even those that appear to be clear, are often contaminated. Water contaminants include particulate matter, chemicals, insects, nematodes, fungi, algae, yeasts, microorganisms, discoloration and radioactive contamination. The microorganisms often found in water sources include pathogenic microbes such as protozoa (which includes Giardia Lamblia) , bacteria, and viruses. Chemicals often found in water sources include halogens and other halogen related compounds such as herbicides and pesticides.

Present portable systems for water purification are of three types: boiling, chemical treatment, and mechanical filtration. Boiling water is time consuming and requires the need for fire. Also, boiling water will only kill microorganisms. It does not remove the contaminants. Chemical treatments, such as iodine tablets, leave an aftertaste, and may produce an allergic reaction with some people. Also, chemical treatments will only kill microorganisms and do not remove contaminants.

The only filtration systems that actually remove contaminants from the water are mechanical filtration units. Typically, mechanical filtration units are of two types, passive filtration units and pump filtration units.

Passive filtration systems typically use a water bag having a filtration system in the bottom of the bag. Water is poured into the bag which is then hung onto a tree or elevated structure. Water flows downward under the force of gravity through the filters in the bag and into a reservoir. This type of system is cumbersome to transport, operates slowly and requires frequent replacement of the filters due to bacteria growth in the filters.

There are presently several pump-type water purifiers available on the market. One such device is the FIRST NEED WATER PURIFIER, available from General Ecology, Inc. 151 Sherree Blvd, Lionville, Pennsylvania. This purifier uses a handle to move a pump piston vertically in a cylinder. A canister containing a charcoal filter is mounted parallel to the cylinder and is connected by plastic tubing to the cylinder. The bottom of the cylinder has another piece of tubing which is placed in the water source. The bottom of the canister has a short piece of tubing which is placed in the water container. Operation of the handle pumps water through the canister to filter the water. This system weighs approximately sixteen ounces and requires frequent sterilization of the filter by halogen to prevent bacteria growth. The canister requires replacement at periodic intervals. The replacement canisters are relatively expensive. This system, under normal usage, purifies water at the rate of one quart per ninety seconds. A prefilter is recommended for use with this system.

Another popular portable water purification filter is manufactured by Katadyn. This system uses a ceramic filter. This pump system again uses a handle type pump to move water through the system. This system is expensive compared with other devices.

A third commercially available water filter pump is the MSR WATERWORKS FILTER, manufactured by Mountain Safety Research, Seattle, Washington. This system uses a small, horizontally-mounted pump with a lever to pump water through a series of filters. These filters include an articulated urethane foam prefilter, a fine mesh stainless steel screen, a cylinder of activated carbon and a micro-porous membrane cartridge having a pore size ratio of .1 micron absolute. This system screws on to a water container. This system is relatively expensive with expensive replacement filters. The approximate weight of this system is 20 ounces. Other devices are known, typically using a separate pump and filter mechanism. These devices are cumbersome to operate and are relatively slow to filter water.

The prior filtration systems are relatively cumbersome to store and to use. None of these units has the capacity to fold for compact storage. Also, these units require two hands to operate. This creates an opportunity for spillage of the filtered water. An additional problem with the prior filtration units is the turbulent fluid flow through the pumps. Non-laminar (turbulent) fluid flow creates problems in the pumping process. These problems include uneven fluid flow through the pump, pressure drops in the filters, erosion of the pump components and filters, and increased workload. Pressure drops are created in the prior pumps pump due to higher flow in one direction of the pump piston than the other direction of the pump piston. This pressure drop requires increased work in pumping water through the filters. Also, the pressure drop can decrease the life and efficiency of the filtering process.

There presently exists a need for a lightweight, compact, inexpensive water purification pump that operates with uniform flows at high rates without extensive exertion.

SOLUTION TO THE PROBLEM

The present invention provides a solution to these and other problems. The present invention provides a lightweight pump capable of compact storage and filtering fluid at high rates with minimal exertion.

The present invention provides a portable, manually-operated, water filtration pump for filtering water of harmful contamination. The pump uses a lever actuating a piston at a mechanical advantage. This lever is collapsible to one side of the pump for compact storage. The lever is easily secured to the piston for actuation of the pump. In one preferred embodiment, the pump is secured onto the piston by a "captured pin" which engages a detent to fasten the handle to the piston.

The pump includes an inexpensive, disposable filter cartridge which can be easily changed when the filter elements are no longer effective. The filter cartridge is a tubular cylinder having an inner bore through which the piston is movable.

An inlet having a screen mesh is located at the bottom of the inner bore of the filter cartridge. A check valve is provided adjacent the inlet to allow water to enter during the upstroke of the piston but prevents water from leaving during the downstroke of the piston. A flexible seal is provided on the piston which prevents water from flowing around the piston during the upstroke but allows water to flow around the piston during the downstroke. This provides a double-acting piston for uniform fluid flow and uniform pressure during the pumping process. Water is pumped from the inner bore through a baffle into an inner plenum. The baffle prevents high velocity jet flow to assure a laminar flow into the inner plenum. The inner plenum has an annular width chosen to minimize pressure drops and to provide uniform flow through the filter. This laminar flow and minimal pressure drops reduce the work of the pumping process as well as minimizing erosion of the pump and filters.

A cylindrical mechanical filter is concentric with the inner bore adjacent the inner plenum to filter out particulates larger than .1 micron. A fluidized granular activated charcoal filter surrounds the mechanical filter to absorb halogens and halogen-related compounds such as herbicides and pesticides. A screen prevents the granular activated charcoal from moving through the system. An outer plenum is^' provided for the filtered water to exit the charcoal filter in a uniform flow. The outer plenum is connected through an outlet to a bottle adaptor which will fit most standard water containers. The adaptor will prevent spillage of the treated water in the container during the pumping process or contamination of the treated water.

A prefilter is provided to screen out large particulates from the pump to enhance the life of the filter elements. The prefilter is connected by an offset inlet opening so the prefilter will sink in water sources with the inlet staying upright in still water or downstream in moving water.

The pump of the present invention is designed to be relatively inexpensive, with recyclable inexpensive filters. The pump is lightweight, approximately .25 to .32 pounds, capable of pumping greater than 1.5 liters per minute in normal use and is compact, about eight inches long with a diameter of about 2 inches. The pump is formed of lightweight durable components to withstand rugged use and can be easily used by one person. These and other features will become evident from the detailed description of a preferred embodiment taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a side view of one possible preferred exemplary embodiment of the invention; Figure 2 is a cutaway view of the pump of Figure 1 disassembled from the disposable filter cartridge;

Figure 3 is a cutaway view of the pump of Figure 1 with the handle in the storage position; Figure 4 is a cutaway view of the pump of Figure 1 with the handle in the operating position and the piston in an upstroke;

Figure 5 is a cutaway view of the pump of Figure 1 with the piston in a downstroke;

Figure 6 is a cutaway view of the prefilter of the preferred embodiment;

Figure 7 is a view of a pump of the preferred embodiment with a pre-conditioning unit attached;

Figure 8 is a cutaway view of a second preferred embodiment of the present invention; Figure 9 is a cutaway view of the embodiment of Figure 8 assembled;

Figure 10 is a side cutaway view of the prefilter in moving water;

Figure 11 is a side view showing a second embodiment of the collapsible pump handle;

Figure 12 is a top view of the collapsible pump handle of Figure 11;

Figure 13 is a side view of the collapsible pump handle of Figure 11 secured on the piston; Figure 14 is a top view of the pump handle of Figure 11 in a first stage of mounting;

Figure 15 is a side view of the pump handle of Figure 11 in a second stage of mounting;

Figure 16 is a top view of the apparatus of Figure 15; Figure 17 is a perspective view of a second embodiment of the bottle adaptor of the present invention;

Figure 18 is a side cutaway view along lines 2-2 of Figure 17 mounted on a water container; and

Figure 19 is a bottom view of the bottle adaptor of Figure 17.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention comprises a portable compact lightweight water filtration pump which effectively filters particles down to .1 microns (a micron equals one-millionth of a meter) . The pump of the present invention provides uniform flow at rates greater than 1.0 liters per minute with normal usage. The pump is easily usable by one person with minimal exertion. This device is relatively inexpensive and uses inexpensive, disposable filters which purify up to 100 gallons of water. The disposable filters are recyclable and easy to change.

One possible preferred embodiment is illustrated in Figures 1-6. This description of a preferred embodiment is for explanatory purposes and is not meant to limit the scope of the claimed inventive concept. Other variations and embodiments are considered to be within the scope of the claimed inventive concept.

The water filtration pump of the present invention includes a pump housing, a filter cartridge, and a double-acting piston, all of which are discussed in detail below.

um Housing

Water filtration pump 10 of the present invention is shown in Figure 1. Pump 10 may also include prefilter 70 and container adapter 62, both of which are discussed fully below. Pump 10 includes pump housing 12, as shown in Figure 2, having a cylindrical shape and an inner bore in . which piston rod 14 is slidable therein. Piston 16 is formed or mounted on one end of piston rod 14. Seal groove 18 is formed around the circumference of piston 16 as described below. O-ring or U-cup seal 20 or any well-known type of seal is mounted in housing 12 allowing piston rod 14 to pass through housing 12 while preventing water from the force of piston 16, as described below, from passing upward through housing 12 or contaminates from passing down through housing 12. Cross head 9 is affixed to the upper end of piston rod 14.

Slot 26 of lever 22 engages pin 28 on cross head 9. Lever 22 is also attached to housing 12 by pivot link 24. This allows lever 22 to move piston 16 up and down in cartridge 30 as described below with a mechanical advantage. In the embodiment described, the mechanical advantage is three to five times, meaning that the lever provides three to five times the force as would the same effort moving piston 16 up and down without the lever advantage.

Lever 22 is designed to be moved to a storage position when pump 10 is not in use. Lever 22 is unhooked from pin 28 and collapsed to one side of pump 10 as shown in Figure 3. This provides a compact unit for storage and transportation. This can be an important concern for travelers and backpackers who have limited space available.

Filter Cartridge Filter cartridge 30 is designed to be quickly and easily attached to housing 12. In the described preferred embodiment, this is accomplished by a screw mounting attachment. Filter cartridge 30 is screwed into the lower portion of housing 12 and rotated until the mounting is secure. Seal 32 is provided between housing 12 and filter cartridge 30 to prevent leakage at the connection between the housing 12 and filter cartridge 30. The present invention is not meant to be limited to this descriptive embodiment but encompasses other variations. For instance, the filter cartridge may use a bayonet attachment, or a snap-on attachment, or other well- known attachment devices.

Filter cartridge 30 includes tubular plastic cylinder 34. Inner bore 36 is formed in filter cartridge 30 having an inner diameter for piston 16 to closely fit within along with a flexible seal as discussed below. At the lower end of inner bore 36 is an inlet 38 for unfiltered water to enter into filter cartridge 30. In the preferred embodiment, inlet 38 includes an extended outer barb 40 on which a section of tubing is attached. Inlet check valve 42 is mounted in inner bore 36 adjacent inlet 38. Inlet check valve 42 is a cantilevered reed valve which allows water to enter filter cartridge 30 but prevents water from exiting through inlet 38. The operation of inlet check valve 42 is discussed in detail below.

Double-actinσ Piston Flexible seal 60 is mounted within groove 18 of piston 16 as illustrated in Figures 2, 4 and 5. Seal 60 is formed from an elastomer or an elastomer-like thermoplastic. Seal 60 mounted within groove 18 of piston 16 allows piston 16 to be double acting to provide uniform flow and pressure during both the upstroke and downstroke of piston 16. Seal 60 has an accordion-like, flexible lip that moves toward the wall of inner bore 36 during the piston upstroke so water above piston 16 is forced through baffle 48 and into inner plenum 46. At the same time, water is being drawn upward through inlet 38 and through the open inlet check valve 42 as shown in Figure 4. The outer lip of seal 60 moves away from the wall of inner bore 36 during the downstroke of piston 16 by the force of the water as shown in Figure 5. The water below piston 16 is forced downward, thus closing cantilevered reed check valve 42 or similar valve to force the water upward around piston 16 and by seal 60 as shown in Figure 5.

Filters

Inlet 44, shown in Figures 4 and 5, is formed at the upper end of inner bore 36 leading into inner plenum 46. Inner plenum 46 surrounds inner bore 36 and is critically sized as discussed below. Baffle 48 is formed in inlet 44 to prevent high jet velocity flow into inner plenum 46 and to provide laminar flow from inner bore 36 into inner plenum 46. As discussed in the background section, non- laminar flow results in uneven flow, high pressure drops and increased work. Also the life of the pump and filter is reduced due to erosion. Baffle 48 is formed of a non-erodible material such as structural plastic. Flow from inner bore 36 is forced through inlet 44 against baffle 48 which directs the fluid flow parallel to the surface of filter 50. This parallel flow encourages laminar flow. Also, the water is allowed to enter filter 50 more easily without increased pressure necessary. Adjacent inner plenum 46 is mechanical filter 50. Mechanical filter 50 is a borasilicate cylinder, or a plastic membrane cylinder, or a porous plastic tubular cylinder having pores filtering out particles having a size greater than .1 to 1.0 microns from exiting the pump. In the preferred embodiment, .3 microns is used as the filter size. This size effectively filters most particle contaminates that may feasibly be filtered. Trapped particle contaminates can be backwashed to eliminate the buildup of particles in the pump. Mechanical filter 50 is sealed at the top and bottom by mechanical interference with the filter cartridge cylinder 32 ( Figure 5) .

Granular activated carbon bed 52 surrounds mechanical filter 50. Granular activated carbon bed 52 is a tubular cylinder formed from fluidized granular activated charcoal with a particle size to maximize adsorption of halogens, halogen-related products and other chemicals, such as herbicides and pesticides. The fluidized granular activated charcoal provides an efficient adsorption rate with a low pressure drop.

The lower end of fluidized granular activated charcoal bed 52 is sealed by mechanical interference with filter cartridge cylinder 32. Outer plenum 54 is formed at the upper end of filter 52. Outer plenum 54 is in the shape of an annular ring formed around the top of fluidized granular activated charcoal bed 52. The dimensions of outer plenum 54 are critically selected to provide uniform flow rates through the bed 52 and filter 54. Outlet 56 is connected to outer plenum 54 and includes a hose barb 58 for attachment to a section of tubing as discussed below.

Uniform Fluid Flow Through the Pump The pressure drop across the filter 54 may be characterized as ΔP = C^" where ΔP = pressured drop across filter where C, = filter resistance which is a function of filter-design and the amount of particles the filter has retained where N = 1 for laminar flow;

2 for fully turbulent flow; and between 1 and 2 for transition flow ( l a m i n a r t o turbulent) The minimum work to pump a given amount of water through the filter occurs at a uniform flow rate. In a double acting piston pump, the minimum work occurs when the flow rate is the same in the "up" and "down" strokes.

The use of a double-acting piston with the same flow rate in the "up" and the "down" stroke provides a uniform flow rate, and thus the minimum pressure drop in the pump and filters. This reduces the force necessary to operate pump and reduces the potential of damage to the filter elements and to the pump. The equal volume in both directions of the double-acting piston, the critical dimensions of the inner and outer plenums and the use of laminar flow into the inner plenum minimize pressure drops and uneven turbulent flow to reduce the "work" in operating the pump of the present invention.

The internal volume of inner bore 36 and the dimensions of piston rod 14 are selected under the teachings of the present invention so the volume of water displaced during the upstroke of the piston is equal to the volume of water displaced during the downstroke of the piston to further assure uniform flow and minimal pressure drop. The water displaced in the downstroke is equal to the volume of the inner bore 36 minus the volume of piston rod 14. The water displaced in the upstroke is equal to the volume of piston rod 14. Therefore, the volume of piston rod 14 must equal the volume of inner bore 36 minus the volume of piston rod 14. The dimensions of piston rod 14 and inner bore 36 can thus be varied to achieve the desired dimensions. The dimensions of inner plenum 46 are also selected under the teachings of the present invention to minimize pressure drops and to provide uniform flow through pump 10. Inner plenum 46 is designed as an annulus around inner bore 36 with a width between the range of .02 to .05 of the diameter of the entire filter. A width smaller than this range creates a high pressure drop in inner plenum 46. A width greater than this range causes non-uniform flow through the filter creating high pressure drops in the filter. In the preferred embodiment, shown in Figure 5, width t (distance between outside of inner bore 36 and inner surface of the filter) of inner plenum 46 is critical. This dimension is a function of the geometry of the filter system and of the flow rate. This function can be expressed in dimension-less numbers as follows:

VD

R - tmmmllK wherein:

V

D -

A

In the preferred embodiment, inner plenum 46 has a width t between the range of .02 to .05 of the diameter of the entire filter. A width smaller than this range creates a high pressure drop in inner plenum 46. A width greater than this range causes non-uniform flow through the filter creating high pressure drops in the filter. The dimensions of outer plenum are selected as well to provide uniform flow out of the filter. Outer plenum 54 is connected to outlet 56. Operation of the First Preferred Embodiment

In the first preferred embodiment, pump 10 is designed for lightweight, compact storage for use in travel or backpacking. Pump 10 has an overall length with lever 22 in storage position of about eight inches with filter cartridge 30 having a two inch diameter and a five inch length. The overall weight is .5 pounds. Pump 10 filters water under normal usage at a rate greater than 1.0 liters per minute. Filter cartridge 30 will last for approximately 100 hundred gallons under normal usage. Filter cartridge 30 is inexpensive and easily replaced after filters 50 and 52 are no longer effective. Also, filter cartridges 30 may be replaced after periods of non-use in order to prevent the effects of bacteria growth if the filters were not sterilized after use. The used filter cartridges are designed to be recyclable. These design parameters are for descriptive purposes. Other sizes and designs are considered to be encompassed by the claimed invention.

Pump 10 and the housing of filter cartridge 30 are formed from polycarbonate or another appropriate structural plastic with lever 22 formed from glass-filled or graphite fibre filled polycarbonate or another appropriate structural plastic to be lightweight yet durable. Mechanical filter 50 is formed from borasilicate, or porous plastic to be durable. Previous devices using silver impregnated ceramic tended to be fragile, with some fear of the effect of silver impregnation on drinking water. The use of fluidized granular activated charcoal provides a more efficient adsorption with a lower pressure drop than many charcoal filters. The above description is for explanatory purposes and is not meant to limit the invention as claimed. Other materials, pump designs and filter designs are considered to be within the claimed inventive concept.

Pump 10 is transported with lever 22 in the storage position as shown in Figure 3. When it is desired to purify water from a water source, lever 22 is unfolded so that it engages pin 28 of cross head 9. Water container adaptor 620, discussed below, is inserted into the opening of a water container. Prefilter 70, discussed below, is dropped into the water source. Lever 22 is operated up and down to pump water from the water source through prefilter 70 and into pump 10. The water is moved in a uniform, laminar flow by double-acting piston through mechanical filter 50 to remove particulate contamination, then through carbon-bed 52 to remove chemical contamination. The water is then pumped through outlet 56 and into the water container.

After approximately 100 gallons has been pumped or after extended periods of non-use of the pump, filter cartridge 30 can be quickly and easily replaced by a new filter cartridge. The old filter cartridge is then able to be recycled.

BaeoTif. Pump Embodiment A second possible preferred embodiment is illustrated in Figures 8 and 9. This embodiment operates similar to the above-described embodiment. As illustrated in Figure 8, an inner pump cylinder 100 is formed on pump housing 12. Inner pump cylinder 100 includes threaded attachment 102 which mates with threaded attachment 104 on filter cartridge 30. Filter cartridge 30 has an inner mechanical filter 50' , identical to filter 50 described above, carbon bed 52*, identical to carbon bed 52 described above, and outlet plenum 54• attached to outlet 56• , both similar to 54 and 56 described above.

Inner pump cylinder 100 includes an inlet opening 38' which opens through inlet valve 42 into inner pump cylinder 100. U-cup or O-ring 106 is mounted near the bottom of inner pump cylinder 100 adjacent inlet opening 38'. Inner pump cylinder 100 has a thin-walled casing 108 in which piston 16 is movable. Seal 60 interacts inlet valve 42 to provide the double-acting performance described above.

Pressure relief valve 110 is also illustrated in Figures 8 and 9. Pressure relief valve 10 includes radial hole 112 formed in piston rod 14 above piston 16. Longitudinal passage 118 is formed in piston rod 14 communicating with radial hole 112 and an opening formed in piston rod 14. Spring 114 is inserted in radial hole 112 biasing ball 116. The bias is selected so that when pressure builds up in pump cylinder, from clogging of the mechanical filter 50 or other causes, ball 116 is forced inward against spring 114 to allow water to flow up through passage 118 and out of the pump to relieve the pressure build up. Inner pump cylinder 100 is easily assembled onto pump housing 32 by screwing the threaded attachments 102 and 104 together. U-cup 106 seals the lower portion of inner pump cylinder against lower portion 120 of the filter cartridge housing. This forms an inner plenum spaced as described above. The baffle 44 works similar as above to create uniform, laminar flow into the filters. The pump works as did the earlier described embodiment to provide uniform pressure and flow through the pump. The second embodiment allows a more inexpensive filter cartridge to be used, since the inner pump cylinder remains with the pump housing. Second Lever Embodiment

A second preferred embodiment of the attachment of lever 22 to a cross head 8 and piston 12 is shown in Figures 11 - 13. Lever 220 is similar to lever 22 in function. Lever 220 includes a textured gripping portion 222 for ease in grasping lever 220. Lever 220 also includes rectangular reduced portion 224 (Figure 11) with reduced width portions 226, 228 (Figure 11) to reduce the overall weight of the pump. Attachment means 230 of lever 220, shown in Figure 11 includes a circular hole portion 232 having hole or keyway portions 234 superimposed on the circumference of hole portion 232. Pivot link 240 (Figure 11) having reduced width portion 242 is pivotally secured to handle 220 by pin 244. The opposing lower end of pivot link 240 is pivotally secured onto collar 250 by pin 246. Lever 220 is thus able to be pivoted against pump 30, as shown in Figure 11, for compact storage.

Piston assembly 8 (Figure 11) includes a cross head 260 (comparable to cross head 9 of Figure 1) and a piston rod 12 (not shown) and a piston 16 (not shown) since they are comparable to elements 12 and 16 of the embodiment of Figures 1-5. Cross head 260 is affixed to the top of piston rod 12 (not shown) to move piston 16 with a mechanical advantage. Cross head 260, as shown in Figure 12, includes rectangularly shaped slot 262 in the top of cross head 260 and a substantially circular hole 264 in the lower wall 270 of slot 262 and extending perpendicular to slot 262. Slot 266 extends along one side of hole 264, as discussed in detail below, and terminates in upper end wall 268. Lower wall portion 270 is formed on cross head 260 opposite top end wall 268. Cam surface 272 is formed on outside of lower wall portion 270 beginning at the terminus of slot 266 and forming an outwardly sloping ramp surface on the outer surface of wall portion 270. Cam surface 272 starts in slot 266 and terminates after a 270 degree rotation in detent slot 276.

Captured pin assembly 280 (Figure 12) includes handle 282 and backing flange 284 affixed to the top end of pin portion 286 which is formed of a low friction material and has a diameter to closely fit within hole 264. Pin 288 extends perpendicularly out of one side of the lower end of pin 286. Pin assembly 280 (Figure 12) is assembled onto cross head 260 by inserting pin 286 through hole 264 so that its lower end extends out of lower wall portion 270. Pin 288 is then inserted into the lower end of pin 286 to "capture" pin 286 onto cross head 260. Upper end wall 268 of hole 264 prevents pin 280 from exiting cross head 260. Lever 220 is moved from the storage position, shown in Figure 11 to the operating position, as indicated by arrows 300, 302 shown in Figure 13, when pump 30 is to be operated. Mid portion 230 of lever 220 (Figure 12) is inserted into slot 262 of cross head 260 so that hole 232 (Figure 11) of handle portion 230 is aligned with hole 264 in cross head 260. In this position, key slot 234 (Figure 11) will also be aligned with slot 266. Pin assembly 280, as shown in Figure 14, is then pushed, as indicated by arrows 304 and 306 (Figure 14) through hole 264 of cross head 260 and hole 232 of lever 220. Once pin 288 clears hole 264, handle 282, as shown in Figure 15, is rotated counterclockwise, as indicated by arrow 308. This causes pin 288 to move against sloping cam surface 272 as indicated by arrow 310 (Figure 15) . Pin 286 and cross head 260 are resiliently compressed by the action of pin 288 against sloping cam surface 272 so that as pin 288 enters detent slot 276, pin 288 (Figure 16) , is resiliently biased into detent slot 276. Thus, lever 220 is securely affixed to cross head 260. Lever 220 can then be moved up and down to move piston 12 within the pump cylinder to force fluid through the filter.

To prepare pump 30 for storage, the procedure is reversed. Pin 288 is rotated clockwise until pin 288 is aligned in slot 266. Handle 282 is withdrawn until pin 286 abuts against end wall 268. Lever 220 is then pivoted upward and against the wall of pump 30. Pump 30 is then in the compact storage position.

Adaptor

Outlet 56 is connected to a section of tubing 58, illustrated in Figure 1, leading to water container adaptor 62. Adaptor 62 is designed to closely fit within the openings of most standard water containers. In one preferred embodiment, shown in Figure 1, adaptor 62 has a first section 64 to fit smaller openings and a second section 66 to fit larger openings. This allows hands free operation of the device without having to hold the water container being filled. The fit of adaptor within the water container opening is such that should the water container tip or fall over, filtered water will not spill out and contaminates will not enter the water container. Adaptor 62 can also be designed to screw into the openings of the water containers. Tubing 58 can be clamped or bonded onto hose barb 56 and onto adaptor 62 if desired. Second Bottle Adaptor

A second preferred embodiment of bottle adaptor 62 is shown in Figures 17 - 19. Bottle adaptor 620 (Figure 17) , includes a cylindrical portion 622. Cylindrical hose connector 624 extends upwardly from the center of the upper surface of cylindrical portion 622 for connection to outlet hose 58. Opening 626 (Figure 18), extends through the center of hose connector 624 so that filtered fluid can be pumped through hose 58 and through adaptor 622. Air vent 647 is located adjacent the inlet 626 to allow the compressed air in the water bottle to leave the water bottle as the water bottle is filled. A series of concentrically spaced rings 630, 636, 642 (Figures 18 and 19) extend perpendicularly downward from the lower surface of cylindrical portion 622. Rings 630, 636, 642 have outer diameters sized to respectively fit snugly within the openings of standard sized water containers. The lower edges 632, 638, 644 of each ring 630, 636, 642 are tapered to provide ease of insertion into the appropriate water container. Also, each ring 630, 636, 642 includes an upper sealing portion 634, 640, 646 to seal the water container from spillage. The adaptor is formed of a resilient material to allow the adaptor to snugly conform to the desired water container opening. Thus, different sizes of water containers can be easily filled with filtered fluid by hands-free operation and without danger of spillage or contamination.

Prefilter

Filter cartridge inlet 38, as illustrated in Figure 2 is connected to prefilter 70 by tubing 72.

If desired, tubing 72 can be securely attached by clamps or bonding to inlet 38 over hose barb 40 and to prefilter 70 over hose barb 74 shown in Figure 6. Typically, a .25 to .38 inch internal diameter elastomer or plastic tubing is used at a length up to 5 feet. Prefilter 70 is dropped into a water source to filter out large particle contaminates down to 70 to 120 microns in size. Pump 10, under normal usage, is able to "pull" water easily at least through an elevation of 5 feet. This allows the user to comfortably operate the pump without kneeling or actually getting into the water source.

As illustrated in Figure 6, prefilter 70 has a semi-spherical-shaped lower portion 76. Upper portion 78 is attached to lower portion 76 by living hinge 80 and snap-lock 82 so that upper portion 78 can be easily opened to clean prefilter 72. Inlet opening 84 having a molded or woven or metal mesh screen with .01 to .02 millimeter pore size, is formed in upper portion 78. Filter screen 88 is mounted in the interior 90 of lower portion 76 formed of either metal or plastic and filtering particles larger than 100 microns.

The geometry and weight of prefilter 70 are critically determined to insure that inlet opening 84 is under water in both still and moving water. The geometry also insures that inlet opening 84 is away from the bottom of a still water source and is downstream in moving water. This minimizes the intake of particles into the prefilter. The weight of prefilter 70 provides an effective specific gravity (weight of prefilter/volume of prefilter) to have the prefilter below the surface in still water and moving water. Moving water is defined as flow velocity greater than 2 feet per second. In the preferred embodiment, prefilter 70 has a specific gravity greater than .1 pounds per cubic inch. Prefilter 70 has a semi-spherical shape to maintain the inlet screen facing away from the bottom of the water source in still water and downstream in moving water. The prefilter housing is chosen to have a radius R with an included angle between ninety and one-hundred-forty degrees.

The geometry of the prefilter 70 causes the prefilter 70 to locate in moving water tilted so that the inlet screen of the prefilter is facing downstream to reduce the amount of particles borne by the moving water from impinging on the inlet screen as shown in Figure 10. This tilt is caused by the combination of the hydraulic forces on the spherical surface of the prefilter 94 and the moment caused by the distance between the inlet tube connection 74 and the center of gravity of the prefilter 91. This distance 7 must be .5 to .5 of the radius R of the sphere as shown in Figure 6.

Operation of Prefilter 70 (Figure 6 and 10) Water is drawn by pump 10 through inlet screen 84 down through filter screen 88 into the interior 90. The water then is drawn through outlet 92 up through tubing 72 into inlet 38 of filter cartridge 30 of pump 10. Prefilter 70 screens large particle contaminates from pump 10 to increase the life of disposable filter cartridges 30. Upper portion 78 can be unsnapped to clean each of the filters 86 and 88 as necessary. If desired upper portion 80 can be rolled over and permanently affixed to upper portion 78 if it is not desired to open prefilter 70 for cleaning.

The majority of contaminates typically on the surface of the water source. Prefilter 70, by sinking below the surface in moving and still water, misses the surface contaminates. Additionally, in still water, prefilter 72 is held with inlet opening 84 in an up position to prevent bottom dirt from being pulled into prefilter 70. Also, the offset location of the hose barb causes a moment between the inlet tube and the center of gravity of the prefilter 70. In moving water, this will cause the lower portion to move downstream first, thus tilting upper portion 78 and inlet opening 84 in the downstream position. This prevents waterborne large particles from flowing into inlet opening 84 and reducing clogging of prefilter 70.

Prefilter 70 is designed to be small, lightweight, inexpensive and to create an insignificant pressure drop to allow uniform flow through pump 10. In the descriptive preferred embodiment, prefilter 70 has an outer diameter of less than 1.75 inches and a pressure drop of less than .25 psi at a flow rate of 1.0 liters per minute. Prefilter 70 and water container adaptor 60 allows pump 10 to be used by a single person without the need for additional assistance or contortions in filtering from a stream or other water source.

Additional Conditioning Units

Filter cartridge 30 is adapted to be fitted with additional pre-conditioning or post- conditioning units for further purification of water. For instance, as illustrated in Figure 7, pre-conditioning unit 96 is attached to the lower end of filter cartridge 30 by a screw-on attachment 98. Pre-conditioning unit 96 contains an iodine- coated resin bed to kill viruses, bacteria, and the like which are too small to be filtered out. Fluidized granular activated charcoal bed 52 then absorbs any iodine ions in the water. The present invention provides a lightweight, compact, inexpensive filtration unit that is easily used. The claimed invention is not meant to be limited by this description. Other embodiments and variations are considered to be within the inventive scope of the claimed invention.

Claims

CLAIMS We Claim:

1. A pump for fluid filtration and purification, said pump comprising: a housing having an inlet and an outlet; filtering means within said housing operatively connected to said inlet and to said outlet for filtering fluid; a cylinder in the interior of said housing operatively connected to said inlet; a piston assembly comprising a piston cross head and a piston rod and a piston; said piston being slidably positioned within said cylinder for pumping fluid from said inlet through said cylinder and said filtering means and out of said outlet; a lever; means for engaging said lever and said piston cross head to slidably move said piston with mechanical advantage within said cylinder and for disengaging said lever and said piston to allow said lever to be moved to a storage position; wherein said engaging means includes: detent means formed on an outer surface of said piston cross head; a pin insertable through said lever and said piston cross head; and means connected to said pin for resiliently engaging said detent means for preventing said lever from accidental disengagement from said piston.

2. The pump of claim 1 wherein said lever engaging means further includes: a cam surface formed on an outer surface of said piston cross head; and said resilient engaging means on said pin includes cam follower means for engaging said cam surface to provide a resilient bias as said cam follower means engage said detent means.

3. The pump of claim 2 wherein said cam follower means include a member extending perpendicularly from the longitudinal axis of said pin; and said detent means include a first slot formed in said cam surface.

4. The pump of claim 1 wherein said pin is captured on said piston cross head by said cam follower means to prevent loss of said pin.

5. The pump of claim 1 wherein said pump further comprises adapter means connectable to said pump outlet for engagement into an opening of a container; said container opening engaging means include means for sealing the engagement of said adapter means into a plurality of differing sizes of container openings.

6. The pump of claim 5 wherein said adapter means includes: a cylindrical member having a connector adapted to be connected via a hose with said pump outlet; a vent hole adjacent to said connector to allow air to leave the water bottle as it is filled with fluid; a plurality of concentric ring-shaped members of differing diameters formed on a surface of said cylindrical member wherein each of said plurality of concentric ring-shaped members has a diameter to snugly engage in a different size opening of a container.

7. A pump for filtration and purification of fluids, said pump comprising: a housing having an inlet and an outlet; filtering means within said housing and operatively connecting with said inlet and said outlet for filtering fluid; a cylinder in the interior of said housing and operatively connected to said inlet; a piston assembly comprising a piston cross head and a piston rod and a piston; a lever for moving said piston within said cylinder at a mechanical advantage; said piston being slidably positioned by said lever within said cylinder for pumping fluid from said inlet through said cylinder through said filtering means and out of said outlet; a pin inser able through said lever and said piston cross head to engage said lever to said piston cross head; an inclined cam surface formed on an outer surface of said piston cross head; a first detent slot formed in said cam surface; and a cam follower connected to said pin for engagement with said cam surface to resiliently bias said cam follower into said first detent slot to prevent accidental disengagement of said lever from said piston cross head.

8. The pump of claim 7 wherein said pin is secured from removal from said piston cross head.

9. The pump of claim 7 wherein said pump further comprises: a container adaptor for connection by a hose to said pump outlet; said container adaptor including a plurality of surfaces having differing diameters; and each of said plurality of differing diameter surfaces snugly engageable in a differing size opening of containers to seal said containers.

10. The pump of claim 9 wherein said differing diameter of surfaces includes: a plurality of concentrically spaced rings.

11. A method of filtering fluid through a pump, said method comprising the steps of: moving a piston within said pump for pumping fluid through said pump; engaging a lever of said pump with a piston cross head connected said piston for moving said piston at a mechanical advantage; inserting a pin through said lever and a piston cross head to secure said lever on said piston cross head by means of a cam follower on an end of said pin; and resiliently biasing said cam follower into engagement with a detent slot formed on a surface of said piston cross head.

12. The method of claim 11 wherein said step of resiliently biasing said cam follower further includes the steps of: providing a sloping cam surface on said surface on said piston cross head; and rotating said pin so that said cam follower engages said sloping cam surface with increasing force as said pin is rotated until said cam follower engages said detent slot.

13. The method of claim 11 wherein said method further comprises the steps of: providing a container adaptor having a plurality of concentric surfaces sized to engage differing sizes of openings in various sizes of containers; connecting said container adaptor to the outlet of said pump; and inserting one of said concentric surfaces into the opening of a container.

14. The method of claim 13 wherein said container adaptor includes steps of: a plurality of concentric ring members extending from a flat surface of said container adaptor for engagement within various sizes of openings of containers.

15. An adaptor for filling containers, said adaptor comprising: an inlet for connection to a source of fluid; an outlet for filling a container with fluid from said source; and means on said adaptor for engaging in and sealing various sizes of openings to prevent spillage of fluid from said container.

16. The adaptor of claim 15 wherein said engaging means include a plurality of concentric surfaces formed on said adaptor; and each of said concentric surfaces having a diameter to engage in and seal an opening of one of a plurality of differing sizes of openings.

17. The adaptor of claim 15 wherein said adaptor further includes means for allowing air to escape the container as said container is filled through said adaptor. \

18. The adaptor of claim 15 wherein said adaptor includes means for connection to a filtration unit.

19. A pump for fluid filtration and purification, said pump comprising: a housing, a piston rod mounted on said housing to be slidable relative to said housing along a first axis of said housing; a piston affixed to an end of said piston rod; means for slidably moving said piston rod relative to said housing; a cartridge filter removably affixed to said housing, said cartridge filter including: an inner bore within said cartridge filter forming a pump cylinder for said piston to slide therein when said cartridge filter is affixed to said housing; inlet means on said cartridge filter for fluid to enter into said inner bore when said piston moves away from said inlet means; means concentric with and surrounding said inner bore for filtering fluid; means formed between said inner bore and said filtering means for enabling unfiltered fluid to be pumped from said inner bore into said filtering means when said piston moves away from said inlet means; and outlet means on said cartridge filter adjacent said filtering means for enabling said filtered fluid to exit said cartridge when said piston moves away from said inlet means.

20. The pump of claim 19 wherein said pump further comprises: sealing means on said piston for providing a double-acting piston to provide uniform flow through said pump when said piston slides within said inner bore; and said inner bore formed having an inner volume equal to twice the volume of said piston rod of said pump so that the volume of fluid displaced when said piston moves away from said inlet means in said inner bore is equal to the volume of fluid displaced when said piston moves toward said inlet means in said inner bore to further provide uniform flow through said pump.

21. The pump of claim 20 wherein said cartridge filter further includes: an inner plenum formed between said inner bore and said filtering means having predetermined dimensions providing minimum pressure drop through said pump; and said outlet means include an outer plenum formed adjacent the exit area of said filtering means for providing minimum pressured drop through said pump and uniform flow out of said pump.

22. The pump of claim 21 wherein said means between said inner bore and said filtering means further include: baffle means formed at the entrance of said inner plenum for preventing high velocity jet flow into said inner plenum and for providing laminar flow into said inner plenum.

23. The pump of claim 19 wherein said sealing means on said piston prevents fluid flow past said sealing means during the movement of said piston away from said inlet means and enables fluid to flow past said sealing means during the movement of said piston toward said inlet means; and said inlet means includes inlet valve means for enabling fluid to enter said inner bore during the movement of said piston away from said inlet means and preventing fluid from exiting said inlet means during the movement said piston toward said inlet means.

24. The pump of claim 23 wherein said sealing means include a seal having a flexible outer lip shaped to move toward the wall of said inner bore during the movement of said piston away from said inlet means to prevent fluid flow past said piston during the movement of said piston away from said inlet means, and to move away from said wall of said inner bore during the movement of said piston towards said inlet means to allow fluid flow past said piston during the movement of said piston towards said inlet means.

25. The pump of claim 23 wherein said inlet valve means includes a cantilevered flap mounted in said inner bore adjacent said inlet means to move into said inlet bore to allow fluid flow into said inner bore during said movement of said piston away from said inlet means and to move against said inlet means to seal said inlet means under the force of fluid in said inner bore under pressure from said piston during said movement of said piston towards said inlet means to close said inlet means.

26. The pump of claim 19 wherein said piston moving means include a lever handle providing a mechanical advantage to increase the flow rate of said pump with low force, said lever handle movable between a first position to move said piston and a second position on one side of said pump for compact storage.

27. The pump of claim 19 wherein said pump further comprises prefilter means connected to said inlet means for removing large contaminates from the fluid before the fluid enters said inner bore, said prefilter means include: inlet means for water to enter said prefilter means; means for maintaining said prefilter inlet means in an upright position in still water and maintaining said prefilter inlet means in a downstream position in running water; and means for sinking said prefilter in still or running water.

28. The pump of claim 27 wherein said means for maintaining said prefilter inlet means in an upright position in still water and maintaining said prefilter inlet means in a downstream position in running water includes: an upside-down semi-spherical lower portion with an upper portion including said inlet means and an outlet means; and a weighted portion attached to said semi-spherical lower portion to force said semi-spherical portion down and upright in still water and to tilt said inlet means downstream in running water.

29. The pump of claim 19 wherein said outlet means include: an adaptor connected to said outlet means, said adaptor shaped to closely fit the opening of water containers.

30. The pump of claim 19 wherein said cartridge filter inlet means further comprise: iodine filtration means for purifying said water of bacteria.

31. The pump of claim 19 wherein said filtering means include: a rigid, cylindrical, tubular mechanical filter means concentric with and surrounding said inner bore for removing particulate contamination; and a cylindrical fluidized granular activated charcoal filter means concentric with and surrounding said mechanical filter means for absorbing chlorine and chlorine compounds.

32. The pump of claim 31 wherein said mechanical filter means filters particulate having a size not less than .1 micron.

33. A pump for fluid filtration, said pump comprising: an upper housing structure; a piston rod slidably mounted on said housing structure for linear movement relative to said housing structure; a piston mounted on the lower end of said piston rod; lever means mounted on said housing structure for pivoting movement relative to said housing structure, said lever means are also attached to the upper end of said piston rod to slidably move said piston rod and said piston relative to said housing; a cartridge filter removably affixed to said housing structure, said cartridge filter including: an inner bore formed along the longitudinal axis of said cartridge filter to create a pump cylinder for slidably receiving said piston; inlet means formed on a first end of said inner bore for enabling fluid to enter said inner bore when said piston moves away from said inlet means in said inner bore; filtering means surrounding said inner bore and concentric therewith for filtering contaminates from said fluid; means formed at a second end of said inner bore for providing uniform flow of fluid pumped from said inner bore into said filtering means during the entire pumping process; and means adjacent an outer end of said filtering means for enabling said filtered fluid to exit said cartridge filter.

34. The pump of claim 33 wherein said inner bore has a volume equal to twice the volume of said piston rod to provide said uniform flow during the pumping process.

35. The pump of claim 33 wherein said pump further comprises a flexible seal on said piston, said seal having an outer edge portion which moves outward toward the wall of said inner bore during the movement of said piston away from said inlet means in said inner bore to prevent fluid flow past said piston, and which moves inward away from said wall of said inner bore during the movement of said piston towards said inlet means in said inner bore to allow fluid flow past said piston during said movement of said piston towards said inlet means.

36. The pump of claim 35 wherein said inlet means include a cantilevered flap mounted to move into said inner bore during said movement of said piston away from said inlet means to enable the flow of fluid into said inner bore and to move against said inlet means to close during said movement of said piston towards said inlet means to prevent the flow fluid out of said inner bore during said movement of said piston towards said inlet means.

37. The pump of claim 33 wherein said cartridge filter includes an inner plenum formed between said inner bore and said filtering means and an outer plenum formed in said outlet means, said inner plenum and said outer plenum have predetermined dimensions to provide uniform flow through said pump with minimum pressure drop.

38. The pump of claim 33 wherein said pump further comprises prefilter means connected to said inlet means for removing large contaminates from the fluid before the fluid enters said inner bore, said prefilter means include: inlet means for water to enter said prefilter means; an upside-down semi-spherical lower portion with an upper portion including said inlet means and an outlet means; and a weighted portion attached to said semi-spherical lower portion to force said semi-spherical portion down and upright in still water to maintain said pre-filter inlet means upright and to tilt said inlet means downstream in running water.

39. The pump of claim 33 wherein said cartridge filter outlet means include an adaptor connected to said cartridge filter outlet means having means to closely fit the opening of water containers.

40. The pump of claim 33 wherein said filtering means include: a mechanical filter for removing particulate contaminates; and a fluidized granular activated carbon bed filter for absorbing chlorine and chlorine compounds.

41. A filter cartridge adapted to be affixed to a piston-operated fluid filtration pump; said filter cartridge comprising: a first filter means for filtering particulate contaminates; a second filter surrounding said first filter means for filtering chlorine and chlorine compounds; an inner bore within said first filter means forming a pump cylinder to slidably receive said pump piston; inlet means for enabling water to enter said inner bore; outlet means for enabling water to exit said filter cartridge after passing through said first filter means and said second filter means; and means for removably affixing said filter cartridge to the housing of said pump.

42. The filter cartridge of claim 41 wherein said first filter means includes a tubular mechanical filter concentric with and surrounding said inner bore.

43. The filter cartridge of claim 41 wherein said second filter means includes a fluidized granular activated carbon bed concentric with and surrounding said first filter means.

44. The filter cartridge of claim 41 wherein said filter cartridge further comprises an inner plenum between said first filter means and said inner bore with predetermined dimensions for minimizing pressure drop of said water being pumped through said pump; baffle means between said inner bore and said inner plenum for preventing a high velocity jet flow of said water into said plenum and for providing laminar flow of said water into said inner plenum; and an outer plenum between said second filter means and an outer surface of said cartridge for providing uniform flow of said water and pressure out of said pump.

45. The filter cartridge of claim 41 wherein said piston includes sealing means for preventing flow between said inner bore and said piston during the movement of said piston away from said inlet means in said inner bore and allowing flow between said inner bore and said piston during the movement of said piston towards said inlet means in said inner bore.

46. The filter cartridge of claim 45 wherein said filter cartridge further comprises a cantilevered flap adjacent said inlet means moving into said inner bore during the movement of said piston away from said inlet means to enable fluid to enter into said inner bore and moving against said inlet means to close said inlet means under the force of fluid pressured downward during the movement of said piston towards said inlet means.

47. The filter cartridge of claim 41 wherein said inner bore includes an inner volume equal to twice the volume of the piston rod of said piston so that the volume of water displaced during the movement of said piston away from said inlet means is equal to the volume of water displaced during the movement of said piston towards said inlet means to provide uniform flow and uniform pressure throughout said pump.

48. The filter cartridge of claim 41 wherein said filter cartridge further comprises iodine filtration means mounted near said inlet means.

49. The filter cartridge of claim 41 wherein said filter cartridge further comprises prefilter means for filtering large contaminates from said cartridge inlet means, said prefilter means include: a lower semi-spherical portion having an upper planar inlet portion; an outlet portion formed on said upper portion; and a weighted portion attached to a lower section of said semi-spherical portion to sink said prefilter means and maintain said inlet means upright in still water and downstream in moving water.

50. A pump for fluid filtration, said pump comprising: a housing; a piston rod slidably mounted on said housing for movement along a first axis of said housing; a piston affixed to one end of said piston rod; lever means attached to said housing and to said piston rod for slidably moving said piston said first axis of said housing; a pump cylinder mounted to said housing for enabling said pump piston to slide within said cylinder, said cylinder having inlet means for enabling water to enter into said inner bore when said piston moves away from said inlet means; a replaceable cartridge removably affixed to said housing, said cartridge including: means concentric with and surrounding said inner pump cylinder for filtering fluid when said fluid is pumped through said filtering means; entry means between said inner pump cylinder and said filtering means for enabling a uniform, laminar flow of unfiltered fluid to be pumped from said inner pump cylinder into said filtering means when said piston moves away from said inlet means; and outlet means for said filtered water to exit said cartridge when said water is pumped through said filtering means.

51. The pump of claim 50 wherein said pump further includes means sealing said inner pump cylinder within said cartridge.

52. The pump of claim 50 wherein said pump includes sealing means on said piston for enabling fluid to flow past said piston in one direction of stroke of said piston and preventing flow past said piston on the opposing direction of stroke of said piston.

53. The pump of claim 50 wherein said filtering means comprise filter means concentric with said pump cylinder, said filter means including: a first mechanical filter means for filtering particulate contaminates; and a second filter means for filtering chlorine and chlorine compounds.

54. The pump of claim 50 wherein said pump further comprises a prefilter means connected to said inlet means for removing relatively large contaminates from the water, said prefilter means include: a lower semi-spherical portion having an upper planar inlet portion; an outlet portion formed on said upper portion; and a weighted portion attached to a lower section of said semi-spherical portion to sink said prefilter means and maintain said inlet means upright in still water and downstream in moving water.

55. A pump for fluid filtration, said pump comprising: a housing, inlet means for enabling fluid to enter said housing and preventing fluid from exiting said housing through said inlet means; means for filtering fluid affixed to said housing; a piston slidably mounted within said pump; means between said piston and said filtering means for conducting fluid pumped from said inlet means through said filtering means; outlet means for enabling fluid to exit said housing after the fluid has been pumped through said filtering means; means for slidably moving said piston relative to said housing to pump fluid through said inlet means and through said filtering means and said outlet means; and means for providing substantially uniform flow through said filtering means during the pumping process.

56. The pump of claim 41 wherein said means for providing substantially uniform flow includes: an inner bore in said housing for said piston to slide within; sealing means on said piston for providing a double-acting piston; and said inner bore has an inner volume equal to twice the volume of the piston rod of said double-acting piston.

57. The pump of claim 41 wherein said means for providing substantially uniform flow includes: a piston cylinder formed in said housing for said piston to slide within; said filtering means include filtering means concentric with and surrounding said piston cylinder; said inlet means formed at one end of said piston cylinder; and said means for conducting fluid flow between said piston and said filtering means include: a plenum formed between the outer wall of said piston cylinder and said filtering means; and baffle means formed near the end of said piston cylinder opposing said inlet means to direct fluid flow into said plenum and into said filtering means at a laminar rate; wherein said plenum has dimensions sized to provide fluid velocity adequate to allow uniform flow through said filtering means with negligible pressure drop in said plenum.

58. The pump of claim 57 wherein the width of said plenum is proportional to the flow rate of the fluid through said plenum and to the effective length of said plenum and to the total wetted perimeter of said plenum.

59. The pump of claim 57 wherein the dimensions of said plenum are chosen for laminar flow through said plenum such according to the following ratio:

K Q L₀ *' -p ^rβ—ff D ^UF- wherein:

R,_j = a dimension-less number ranging between

500 and 1500;

K = a constant depending upon fluid viscosity; Q = volumetric flow rate through said plenum;

L = effective length of said plenum;

P_eff = effective wetted perimeter of said plenum; and D_f = inner diameter of said filtering means adjacent said plenum.

60. A pump for fluid filtration, said pump comprising: a housing; inlet means for enabling fluid to enter said housing and preventing fluid from exiting said housing through said inlet means; means for filtering fluid affixed to said housing; a piston slidably mounted within said pump; means between said piston and said filtering means for conducting fluid pumped from said inlet means through said filtering means; said means between said piston and said filtering means including baffle means for directing the fluid flow from said piston parallel to said filtering means at a laminar flow rate; outlet means for enabling fluid to exit said housing after the fluid has been pumped through said filtering means; means for slidably moving said piston relative to said housing to pump fluid through said inlet means and through said filtering means and said outlet means.

61. The pump of claim 60 wherein said baffle means include a non-erodible surface formed in said baffle means to direct the fluid flow from said piston parallel to said filtering means.

62. The pump of claim 60 wherein said pump includes: a piston cylinder for said piston to slide within; said filtering means surrounding and concentric with said cylinder; means near one end of said pump cylinder for directing said fluid flow from said cylinder into said filtering means; and said baffle means formed adjacent said directing means for deflecting said fluid flow into said filtering means at a laminar flow rate.

63. The pump of claim 62 wherein said filtering means are removably affixed to said housing; and said piston cylinder is formed within the inner bore of said filtering means.

64. A pump for fluid filtration, said pump comprising: a housing; filtering means affixed to said housing for filtering fluid; inlet means in said housing for fluid to enter said filtering means; outlet means in said housing for filtered fluid to exit said filtering means; a piston slidably mounted within said pump for pumping fluid from said inlet means through said filtering means out of said outlet means; and lever handle means pivotally attached to said housing, said lever handle means being movable from a compact storage position folded against said housing and disengaged from said piston to a pumping position engaging said piston to move said piston within said housing at a mechanical advantage.

65. The pump of claim 64 wherein said filtering means including: a cartridge filter removably affixed to said housing; an inner bore formed within said cartridge housing forming a pump cylinder for said piston to slide therein; said inlet means allowing fluid to enter said inner bore as said piston moves away from said inlet means and preventing fluid from exiting said inlet means as said piston moves toward said inlet means; said filtering means surrounding and concentric with said inner bore.

66. A prefilter for filtering particulates from the inlet of filtration mechanism, said prefilter comprising: a housing; a filter screen affixed to an upper surface of said housing and sized to prevent particles greater than about 100 microns from entering said housing; outlet means for the pre-filtered fluid to exit said prefilter; and means for maintaining said prefilter below the surface of a body of fluid.

67. The prefilter of claim 66 wherein said prefilter further comprises: means for maintaining said prefilter in a position so that said filter screen is oriented downstream when said body of fluid is moving.

68. The prefilter of claim 66 wherein said means for maintaining said prefilter below the surface includes: said prefilter having a specific gravity greater than about .07 pounds per cubic inch.

69. The prefilter of claim 67 wherein said means for maintaining said prefilter in moving fluid includes: locating said outlet means a predetermined distance from the center of gravity of said prefilter to create a moment on said prefilter in moving fluid to tilt said prefilter so that said filter screen is angled downstream.

70. The prefilter of claim 69 wherein said housing includes a semi-spherical shape with said filter screen formed on a substantially flat upper surface and said outlet means formed on said upper surface.

71. The prefilter of claim 70 wherein said predetermined distance is within the range of about one-half the radius of said semi-spherical shaped housing and about eight-tenths of said radius.

72. The filter cartridge of claim 45 wherein the dimensions of said plenum are chosen for uniform flow through said plenum according to the following ratio:

wherein:

R^ = a dimension-less number ranging between

500 and 1500 ;

K = a constant depending upon fluid viscosity; Q = volumetric flow rate through said plenum;

L = effective length of said plenum;

P_eff = effective wetted perimeter of said plenum; and D_f = inner diameter of said filtering means adjacent said plenum.