REVERSE OSMOSIS APPARATUS

Abstract: The reverse osmosis membrane cartridge unit (10) includes a reverse osmosis membrane permeator (11) spirally wound on a central winding tube (12) and surrounded by an impermeable barrier layer (15) which is, in turn, surrounded by a spirally wound prefilter (16). A postfilter (30) is placed centrally within the winding tube (12). The cartridge unit (10) is designed for functional installation in a housing tube (44) fastened and sealed to a valve plate (45) at one end and closed by a removable end cap (46) at the other or outboard end. Feed water enters the cartridge unit through an inlet port (48) in the valve plate (45) at an outer radius to pass lengthwise in prefilter (16). Prefiltered water returns lengthwise through the reverse osmosis permeator (11) to a waste-water outlet port (43) in the valve plate (45) at an intermediate radius. Product water which has permeated through the membrane flows inwardly through holes (92) in the winding tube (12), into a clearance space (40) and then through the length of the postfilter (30) to a purified-water outlet port at an inner radius in the valve plate (45). The reverse osmosis membrane cartridge (10) is axially removable from the housing tube (44). lve plate (45). The reverse osmosis membrane cartridge (10) is axially removable from the housing tube (44).

Description: REVERSE OSMOSIS APPARATUS Field of the Invention This invention relates to a system for producing purified water from feed water, and more particularly to a cartridge reverse osmosis water— ilter unit for such a system. Description of the Prior Art Drinking-water purification systems have found increasing use in the home and the work place to improve the quality of tap water for drinking, cooking, ice—making and the like. "Reverse osmosis processes" are a known class of processes in general use in these systems. The processes employ "reverse osmosis membranes" which are selectively impermeable to dissolved salts in aqueous solution. Reverse osmosis membranes for this purpose must be efficient, compact and self—contained so that no extra outside additional filtering apparatus are required. Some typical prior—art purification systems include, in addition to the reverse osmosis membrane permeator, a prefilter for initial screening of the feed water, removing particulate matter to prevent clogging and to protect the membrane, and a postfilter for further purification, especially for the removal of organics such as dissolved hydrocarbons. In general, in these systems tap water or feed water is filtered and separated as purified product water and waste water. Reverse osmosis membrane permeators constitute a major restriction to the flow of water through these purification systems, and so the filtration process is relatively slow. Therefore, a system which is economically and aesthetically practical for the home s generally unable to generate product water on demand but must include a product water storage reservoir. Pressures within the system require control to optimize the system operation. Finally, waste water must be disposed of. While a water—purification system will include a control— alve subsystem, a reverse osmosis filter unit and a product water reservoir, this invention is directed at a cartridge reverse osmosis membrane cartridge and filter unit for such a system. The prior art includes US Patents 3,789,993, 3,792,135 and 3,824,299 to Brown and Ray. These patents disclose the specifics of composition and manufacture of reverse osmosis membrane per eators used in this invention. The prior art also includes US Patents 3,504,796 and 3,542,199 to Bray, which disclose a particular configuration and combination of prefilter, membrane permeator and postfilter in a water—purification system. These prior—art items are background to this invention and are incorporated by reference herein. Summary of the Invention In summary, this invention comprises a reverse osmosis membrane cartridge unit for use in a water—puri ication system. The reverse osmosis membrane cartridge unit includes a reverse osmosis membrane spirally wound on a central winding tube surrounded by an impermeable barrier layer which is, in turn, surrounded by a spirally wound prefilter. Preferably, a postfilter of granulated activated carbon or charcoal is placed within the winding tube of the cartridge. The cartridge unit includes the prefilter, reverse osmosis membrane permeator and postfilter installed in a housing tube mounted on a valve plate at one end and having a removable end cap at the other end. A suitable supply of water to be purified is connected to the cartridge unit, through a feed water port in the valve plate, for flow in an axial direction through the prefilter, and then in a return axial direction through the reverse osmosis membrane permeator which separates the feed water as product water and waste water. Waste water is that portion of feed water which does not permeate the membrane but flows axially to a waste-water port located at an intermediate radius in the valve plate and then to drain. Product water is that portion of feed water permeating the membrane radially and flowing spirally inward in a permeate—conducting layer to the outer surface of the winding tube. Product water passes through holes in the winding tube and travels to the outboard end of the cartridge unit to return through the length of the postfilter to a product—water outlet port in the valve plate at an inner radius, and then to a product—water storage reservoir. The cartridge unit is axially removable from the housing pipe for ease of replacement. No piping connections need be disturbed to make this replacement, and all three filter components are replaced with the cartridge unit. Brief Description of the Drawings Fig. 1 shows the cartridge unit mounted in a housing tube with the valve plate at one end and the end cap at the other end according to this invention. Fig. 2 shows in cross—section the reverse osmosis membrane cartridge unit in accordance with one preferred embodiment of this invention. Fig. 3 shows in cross—section the postfilter prior to inserting it into the cartridge unit according to this invention. Fig. 4 shows a horizontal cross—section of the cartridge unit of Fig. 2 taken along the line 4-4. Fig. 5 shows a cartridge unit mounted in a housing tube with the valve plate- at one end and the end cap at the other end according to another embodiment of this invention. Description of the Preferred Embodiment Referring particularly to Figs. 1 through 3, the apparatus comprises a reverse osmosis cartridge unit indicated generally at 10, comprising a spirally wound prefilter 16, a reverse osmosis membrane permeator having separating and spacer layers 11 and a postfilter member 30. Fig. 1 shows the reverse osmosis cartridge unit 10 installed in housing tube 44 which is adhesively sealed at the bottom to lower valve plate 45 and at the top closed by removable end cap 46. 0— ings 47 or any other suitable ring—sealing device are used to make the housing, comprising valve plate 45, housing tube 44 and removable end cap 46, a watertight unit when internal water pressure is applied. The removable end cap is preferably held in place by four tie rods and threaded nuts not shown in Fig. 1, but alternatively can be held together by screw threads on the end cap, bayonet or a snap—ring device. Housing tube 44 may be fabricated of any material which will withstand the water pressure under which it will operate. Suitable plastic materials such as polyvinyl chloride, polyethylene or polypropylene may be used. For higher pressures, a high—strength material may be required. Referring now particularly to Fig. 2, the reverse osmosis membrane unit 10, along with its separating and spacer layers, is spirally wound onto the central tube 12 to form wound membrane 11. A mounting spoked wheel 13 is cemented onto the bottom end of winding tube 12. The spoked wheel 13, by means of a cylindrical rim extension 14, provides a surface to be joined and sealed to the outside of the wound membrane 11 by a spirally wound, impermeable barrier layer 15. Outside of barrier layer 15 is then spirally wound a prefilter 16 comprising alternating layers of filter media sheet and open-weave spacer sheet. By adhesively bonding alternate pairs of filter media sheet and spacer sheet along one edge for one pair and along the other edge for the other pair 20, as shown in Fig. 2, an axial flow with considerable filtering surface area is created. This prefilter is then wrapped with an impermeable barrier layer 17, leaving both end surfaces of the prefilter open for inlet feed water 18 and subsequent water outlet flow 19 of prefilter 16. A top cartridge 21 and a plastic pull ring 22, integrally attached to the end cap and preferably molded from polypropylene material, are then cemented into the top end of the winding tube 12. A cartridge external seal ring 23 of resilient material, covered with pliable tape, is wound onto the top end of the wound filter near its top end. The cylindrical postfilter shown in Fig. 3 is inserted into the inside of the winding tube 12. The postfilter 30 is comprised of a carrier tube 31, made from a suitable impermeable plastic material, which is closed at its bottom end, as shown in Fig. 3, by lip seal cap 32 with a radial lip seal 33 and a postfilter pull handle 34. Lip seal cap 32 also carries a porous disc 35 which functions to keep the carbon granules within post filter 30. The top open end of the carrier tube 31 is filled with carbon granules 36 and closed with top spacer cap 37, having as one of its features a plurality of radial projections 38 and axial projections 39 to insure a free flow path from the clearance space 40 surrounding the postfilter to the upper end, as shown, 2 of the reverse osmosis membrane unit 10. Also incorporated in the spacer cap 37 is an umbrella-type valve 41 inserted in a retaining hole in the center of the spacer cap 37 so that the umbrella skirt lies outside a series of flow passage holes around the central retaining hole, and with the umbrella positioned on the inside of the cap to permit flow into the spacer cap from the top side as shown in Fig. 2. Also in the spacer cap 37 is positioned a porous disc 35 to retain the carbon granules 36. In operation, the reverse osmosis membrane cartridge unit is connected to a suitable supply of water to be purified under pressure by connection of feed water port 48 to a household feed—water supply and to a product— ater reservoir. The flow paths through the cartridge reverse osmosis cartridge unit are as follows, all described with reference to Figs. 2 and 3. Feed water from the water supply is brought to an outer radial position from the cartridge centerline, to enter the prefilter 16 at annular open end surface 18 to pass upward, as shown in Fig. 2, between impermeable layer 15 on the inside and impermeable layer 17 on the outside to exit the prefilter at open annular end surface 19. Because of the configuration of the pairs of filter media sheet and open—weave spacer sheet, with alternate edge sealing 20, inlet flow at the bottom can enter at an open edge of spacer sheet at one layer, but not at one layer above or below because these edges are filled with adhesive sealant. Flow cannot pass straight through in the same open—weave spacer sheet because the top end of this channel is filled with sealant along the other edge. The only flow path available is through the filter media sheet lying immediately above or below, and then to the open—weave spacer sheet just beyond. These two open—weave spacer sheets are open on the top edge because of the alternate edge sealing. Flow exiting the prefilter 16 at upper end 19 can then pass around the upper end of impermeable layer 15 to enter the upper end of reverse osmosis membrane 11 where it is conducted downward through the spacer layer and over the surface of the reverse osmosis membrane, where a major portion of the flow exits the reverse ' osmosis membrane 11 at the bottom end 43 as waste water at an intermediate radius from the cartridge centerline. A minor portion of the water entering the reverse osmosis membrane 11 is able to permeate through the membrane where it is conducted in an inwardly spiraling path in a conducting sheet to the outer surface of the winding tube 12. Said winding tube contains a plurality of holes 92 which permit the permeate to enter a collection space 40 inside the winding tube 12 and outside the postfilter carrier tube 31. The permeate in this collection space cannot flow downward because it is blocked by lip seal 33 on lip seal cap 32, shown in Fig. 3. The permeate therefore flows upward and through the space provided by radial protrusions 38 and axial projections 39 on spacer cap 37. Flow from above the spacer cap continues through openings 90 in spacer cap 37 to the upper side, as shown in Fig. 2, of umbrella valve 41 within the skirt of the umbrella. Pressure from the flow can deflect the skirt to allow flow to continue downward through postfilter 30. The purpose of the umbrella valve 41 is to isolate the water which may remain in the clearance space 40 and may deteriorate in quality during an extended period of shutdown. The volume of water in the clearance space 40 is small, and the umbrella valve 41 protects the larger volume of the postfilter from deterioration. As the permeate flows downward, as shown in Fig. ' 2, through the post filter 30, it first passes through upper porous disc 35, then through the carbon granules 36, filling the carrier tube 31, and out the bottom end through the lower porous disc 35. The permeate is then free to leave the reverse osmosis filter cartridge 10 at an inner radius 91 from the cartridge centerline. See Fig. 1. To provide the proper seals to separate feed water at an outer radius from waste water an intermediate radius, 0—ring 47 or other equivalent sealing ring is placed in the groove in spoked wheel 13. To separate the waste water at an intermediate radius from the product water at an inner radius, 0—ring 47 is placed in its groove in the spoked wheel 13. The reverse osmosis cartridge unit is now complete and ready for packaging as a replacement filter unit or for installation in a drinking—water system. Referring again to Fig. 1, which shows the reverse osmosis cartridge unit 10 installed in housing tube 44, as described above, a supply of water is supplied into the cartridge unit 10 through feed—water port 48 in valve plate 45 at an outer radius from the cartridge centerline. Feed water is prevented from bypassing the prefilter 16 by cartridge external seal ring 23 which compressibly fits a short distance into the inside of the housing tube 44 at its upper end, as shown in Figs. 2 and 3. Feed water enters the annular end surface 18 of prefilter 16 to flow upward to the outlet annular end surface 19. Flow which moves upward through the prefilter 16 is now redirected by the removable end cap 46 in a downward direction through the length of he reverse osmosis membrane filter 11, entering at annular surface area 49. After flowing through a spacer layer and over the surface of the reverse osmosis membrane, the major portion of this flow exits the lower annular surface at waste—water outlet port 43 at an intermediate radius from the cartridge centerline. A minor portion of the prefiltered water which has been able to permeate the membrane flows spirally inward to the holes 92 in the winding tube 12, upward in the clearance space 40 and then downward through the postfilter 30 to exit through valve plate 45 at permeate outlet port 91 at an inner radius from the cartridge centerline. To change the cartridge reverse osmosis filter 10 in a drinking—water system, it is necessary only to take off the removable end cap 46, raise the pull ring 22 and pull out the cartridge reverse osmosis fitter 10. A fresh cartridge reverse osmosis filter 10 can readily be removed from its packaging and pushed into place in the housing tube 44. The new cartirdge filter unit cannot be installed incorrectly. New O-ring seals 47 and external ring seal 23 are provided with each cartridge filter 10. The removable end cap 46 is now put back on the housing tube 44 and fastened in place. No piping or tubing connections need be disturbed or removed in order to install replacement reverse osmosis cartridge unit 10 of the present invention. Referring now to Fig. 5 which illustrates another embodiment of the invention, the reverse osmosis filter unit 50 includes a cylindrical outer housing tube 52, integrally mounted on and extending axially from a mounting end plate 51 on one end. Mounting end plate 51 is also the back plate of the associated control valve block to which this reverse osmosis filter unit is mounted, and may hereinafter in context be referred to as valve plate 51. Valve plate 51 includes a feed-water port 54, a waste-water port 56 and a product—water port 58. Valve plate 51 is configured to provide a pair of concentric cylindrical bearing surfaces 53. Housing pipe 52 is covered at its other end by a removable end cap 55 which is sealed to the pipe 52 by one or more O-rings 59. End cap 55 may be mounted on housing pipe 52 by several means such as tie rods, a threaded engagement or a bayonet fit, to name some examples. There are also other sealing devices to effect sealing of end cap 55 on housing pipe 52, which are well—known equivalents of O-rings 59. End cap 55 may optionally include an air—vent fitting, shown at 80. The valve plate 51, outer housing pipe 52 and removable end cap 55 are permanent parts of the reverse osmosis filter unit 50. A removable and disposable filter cartridge 60 is shown enclosed within the housing pipe 52. The filter cartridge includes an inner permeator mounting tube 62 with a mounting spoke wheel 61 sealed and fixed on one end of mounting tube 62 and a cartridge end cap 63 sealed and fixed on the other end of mounting tube 62. A suitable adhesive or other bonding means form the bond and seal 79 between tube 62 and wheel 61 and between tube 62 and cartridge end cap 63. Mounting wheel 61 includes an outer rim 65 adapted for sliding fit within the larger cylindrical—bearing surface 53, and an extended central hub 67 for sliding fit within the smaller cylindrical—bearing surface 53a. The outer rim 65 of the mounting wheel includes a cylindrical rim extension 69. The mounting wheel 61 further includes a plurality of waste—water passages 66, these being, for example, the spaces between radial spokes of the wheel or simply an array of holes through the wheel. The sliding fit of the mounting wheel 61 within the cylindrical—bearing surfaces 53a of valve plate 51 is sealed by V seals 59a. The cartridge end cap 63 includes an integral pull handle 63a by which the cartridge is grasped for insertion or removal with respect to housing pipe 52. Filtration media, including an inner annular reverse osmosis membrane permeator 70 and an outer annular prefilter 72, are spirally wound on the permeator mounting tube 62, with an impermeable barrier layer 71 positioned between them to confine their respective flow paths, i.e., to prevent a liquid "short circuit" within the filter media. The mounting spoke wheel 61, by means of its cylindrical rim extension 69, is joined and sealed to the barrier 71 and forms a continuation of it to define the several water-flow passages between the filter media and the valve plate 51. The rim extension 69 of mounting wheel 61 is only one convenient means to facilitate joining the mounting wheel to the impermeable barrier 71; it is not essential, however. The mounting wheel 61 might simply be abutted against the membrane permeator 70 and the impermeable barrier 71 wound around them both. At the juncture with valve plate 51, the sealed outer rim 65 of mounting wheel 61 and the housing pipe 52 form between them an annular feed—water passage 64 which communicates with feed—water port 54 in the valve plate 51. The mounting wheel itself includes a plurality of axial waste—water passages 66 leading directly to waste—water port 56 in the end plate and ultimately to drain. The central hub 67 of the spoke wheel forms a central product—water passage 68 leading directly to product—water port 58 in the valve plate and ultimately to a product—water reservoir. At the other end of the reverse osmosis filter unit, the cartridge end cap 63 and the ends of the membrane permeator 70 and prefilter 72 define an intermediate flow passage 74 for radial inward flow from the outlet (right) end of prefilter 72 to the inlet (right) end of membrane permeator 70. A suitable adhesive or other bonding means form a bond and seal 79 between cartridge end cap 63 and prefilter 72. The wall of the permeator mounting tube 62 includes a number of permeate flow apertures 73 spaced along its length and around its circumference for the inward flow of permeate water from the membrane permeator 70 into the mounting tube 62. A cylindrical postfilter, generally indicated at 75, is positioned within the mounting tube 62. Postfilter 75 includes a body of granulated filter material 76 within a carrier tube 77 and with porous end disks 78 at each end holding the filter body in place. The filter body 76 is preferably granulated activated carbon, or charcoal, although other similar materials might be used such as ground granular brass, ion—exchange resins or mixtures of granulated activated carbon or charcoal with either ground granular brass or ion—exchange resins. As mechanical support disks, end disks may be formed of sintered metal such as bronze, or porous plastic such as polyethylene, an example being porous polyethylene, 0.100—inch thick and of 20—micron porosity. For function as a bacteriological filter disk, end disks may be formed of fiber glass, an example being 0.100—inch thick, of 3—micron porosity, impregnated with quaternary ammonium functionality and positively charged. There may be one or more of each type of disk 78 at each end of the postfilter. In the example shown in Fig. 5, there is a single mechanical (porous plastic) disk at the inlet end of the postfilter adjacent the cartridge end cap 63, and one mechanical and one bacteriological disk at the outlet and adjacent the valve plate 51. Although this embodiment is to include a postfilter 75 and end disks 78, it may be excluded from a reverse osmosis filter unit which has been designed for a specific application. A lip seal cap 89, with axial projections 81, a radial seal 82 and a postfilter pull handle 83, fits over the end of the carrier tube 77 adjacent the product—water passage 68. Lip seal cap 89 serves to hold end disks 78 in place, to seal that end of the annular space 87 surrounding the carrier tube 77, and to insure an axial clearance space at the discharge end of the postfilter for discharge into the product—water passage 68. The postfilter pull handle 83 permits easy removal of the carrier tube 77 and postfilter 75 from within the mounting tube 62 after the same is removed from the housing pipe 52. A spacer cap 84, with axial projections 85 and a plurality of radial tabs 86, fits over the end of the carrier tube 77 adjacent the cartridge end cap 63. Spacer cap 84 serves to hold end disk(s) 78 in place, to center the carrier tube 77 within the mounting tube 62, and to insure an axial clearance space at the inlet end of the postfilter for intake from the end permeate passage 88. Note that spacer cap 84 is not a seal; permeate water is free to flow axially from the annular space 87 around the carrier tube, past the spacer cap 84 and into the end permeate passage 88. Prefilter Prefilter 72 is an axial-flow annulus of a filter medium or element. In its simplest form, some porous material such as cotton might be used. In its presently preferred embodiment, however, prefilter 72 is a spirally wound composite of a filter element, a spacer web, another filter element and another spacer web. Alternate spacer webs are sealed at one end, and successive alternate spacer webs are sealed at the other end. Thus, inflow channels at one end and outflow channels at the other end are not common channels; the water must traverse the interleaved filter elements to get from an inflow channel to an outflow channel. The filter elements are preferably of graded pore structure, 0.008—inch thick and of 5— icron porosity, including either spun—bonded and/or melt blown fibers such as polyester, polypropylene, polyethylene or nylon. The spacer webs are preferably of polyolefin netting of 0.018—inch strand thickness, 0.035—inch nodule thickness and 0.080—inch pitch diameter pattern, or of epoxy—impregnated polyester tricot, 0.012—inch thick, 34 wales per inch. The end sealant is preferably two—part polyurethane or a two—part epoxy or an electromagnetically actuated polypropylene adhesive sealer or similar suitable sealing composition, so that the prefilter sealed end is liquid—tight. Wound prefilter modules have also used resin separator webs with ridges and grooves in a corrugated shape which separates successive windings of the filter medium. The grooves between successive corrugated ridges create longitudinal channels to admit inflow at one end and outflow of filtered liquid from the other. Many different materials may be used for separator webs and filter medium. Different ridge and groove shapes of the spacer web are also possible, and these can be varied to adjust the ratio by which the inflow volume exceeds the outflow volume. The preferred filter medium must be sufficient to remove, from a fluid stream, minute particles as small as 25 microns and preferably smaller down to 0.1 micron. Preferably, removal of particles nominally sized from 3 to 5 microns is the best balance between particle removal and life expectancy. Commonly made filter layers can be inorganic, such as alumina, silica, fiber glass or glass, or made from organic polymers such as nylon, Dacron, polyethylene or polypropylene, or of resins such as phenolic, vinyl chlorides or melamine. Animal fibers or vegetable fibers such as cellulose or cotton may also be used. These materials may be blended, if desired, and formed into filter material by well—known methods such as winding, felting, needling, flocculating, etc., the elements usually being held together by application of appropriate binders which are applied during filter—material fabrication. In addition, it is known to impregnate carbon into the filter material during fabrication. The fluid—impermeable separator web may comprise any flexible material sufficiently strong to prevent fluid passage even at high pressures. It is desirable that this layer, as well as the filter layer, be relatively thin to maximize filter surface area for a given filter volume. The separator material must be sufficiently pliable to permit crimping into corrugated form and winding it around a core without fracturing to prevent fluid passage even at high pressures. Particularly suitable fluid-impermeable materials include polyesters such as polethylene terephthalate, polyvinyl materials such as polyvinyl chloride and polyvinyl acetate or polyolefins such as polyethylenes and polypropylene. Reverse Osmosis Membrane Permeator Reverse osmosis membrane permeator is a spiral winding of cellulosic reverse osmosis membrane. It can be fabricated with material known in the art to be useful as a semipermeable membrane. Such membranes typically are disclosed in the aforementioned US Patents 3,789,993, 3,792,135 and 3,824,299 to Brown and Ray. Other inorganic materials such as porous glass, sintered metals and ceramics may be used as the microporous substrate. Advantageously, microporous substrates prepared from organic materials in a known manner may be used. Examples of the organic materials include cellulose ester derivatives such as cellulose acetate, cellulose butyrate, cellulose propionate, cellulose acetate butyrate and cellulose triacetate; cellulose ether derivatives such as methyl cellulose, ethyl cellulose and ethyl methyl cellulose; polysul one derivatives such as polysulfone and sulfonated polysulfone and those described in US Patents 4,207,182, 4,026,977, 3,855,122 and 3,567,810; sulfonated polyphenylene oxide; phenolic resins and sulfonated phenolic resins; polyvinyl compounds such as polyacrylonitrile, polyvinyl butyral, halogenated vinyl polymers containing vinylidene fluoride such as those described in US Patent 4,203,848 and halogenated vinyl polymers containing vinyl chloride; polyamides such as nylon poly(meta—phenylene isophthalamide) , poly(para—phenylene terephthala ide) and those described in US Patent 4,277,344; polyamide hydrazides such as the one obtained from meta—aminobenzoic hydrazide and terephthaloyl chloride; polyesters such as polyethylene terephthalate, polybutylene terephthalate or sulfonated polyethylene terephthalate; and polystyrenes. Preferably, the substrate is used reinforced at its back with a woven or nonwoven cloth or the like. Examples of the woven or nonwoven cloth are those of polyethylene terephthalate, polystyrene, polypropylene, nylon and vinyl chloride resins. Operation The function of the prefilter 72 is the initial removal of macroscopic impurities from the feed water. The primary function of the membrane permeator 70 is to exclude dissolved salts from the permeate water. The primary function of the postfilter 75 is to remove organics, such as dissolved hydrocarbon gases, by adsorption from the product water. The filter media including prefilter 72, membrane permeator 70 and postfilter 75 are mounted on or in the mounting tube 62 which is, in turn, fastened to the cartridge end cap 63. Removal of the end cap 55 permits the removal of the cartridge end cap 63 by means of its pull handle 63a, and with it the winding tube 62 and all the filter media, from within the housing pipe for replacement from time to time as required. The postfilter pull handle 83 permits selective removal of the postfilter from the remainder of the filter cartridge should it be desirable to replace less than the entire filter cartridge 60. In operation, the principal water—flow paths through this system are as follows: Feed water is admitted through the feed-water port 54 of the valve plate 51 to the annular feed—water passage 64 of the reverse osmosis filter unit 50. Feed water flows axially from the annular feed—water passage 64 through the prefilter 72 to the intermediate flow passage 74 at the other end, and from there in a return axial direction through the reverse osmosis membrane permeator 70. In the membrane permeator 70, a portion of the water permeates the membrane radially and spirally inward to the mounting tube 62 and through the permeate apertures 73 of mounting tube 62 into the annular space 87 surrounding the postfilter carrier tube 77. The permeate water then moves axially along the annular space 87, past the spacer cap 84 into the end permeate passage 88, and axially through the postfilter 75 into product—water passage 68, at which point it is "product water". Product water flows from the product—water passage 68 into product—water port 58 in the valve plate 51 and from there through associated control valving to a product—water reservoir. In the membrane permeator 70, water not permeating the membrane flows axially along the membrane and through waste—water flow passages 66, at which point it is "waste water". Waste water flows from the waste—water flow passages 66 into waste—water port 56 in the valve plate 51 and from there through associated control valving and to drain. Advantages The reverse osmosis membrane cartridge unit herein described has several significant advantages. Replacement of all filter media can be accomplished by simple removal and replacement of a single cartridge unit. Optional removal and replacement of only the postfilter is possible, also by a simple procedure. Upon replacement, the new unit automatically replaces all cartridge seals. The removal of end cap from the housing tube 50 provides all necessary access to the interior of the unit without the ieed to disconnect piping. The nested "packaging" of the components minimizes the space required by the unit. The three components of the filter cartridge, namely, the prefilter, the reverse osmosis membrane and the postfilter, can be designed and sized for a particular useful life, depending upon the anticipated use of individual components.

Claims: We claim : 1. A reverse osmosis membrane cartridge 10 having means for introducing feed water under pressure to said membrane cartridge 10 and outlet means for product water produced by said membrane cartridge, comprising: (a) a spirally wound prefilter 16 comprising alternating layers of filter media sheet and open—weave spacer sheet surrounded by an impermeable barrier layer 17, and (b) a reverse osmosis membrane 11 spirally wound on a winding tube 12 through which liquid permeate is drawn through from said membrane, said membrane 11 being surrounded by an impermeable barrier layer 15, and (c) a postfilter 30 comprising a carrier tube 31 including granulated filter material 36 inserted within said winding tube 12, and (d) controlling means for said feed water to control flow of liquid axially through said prefilter 16 into said membrane 11 which separates said feed water as waste water directed axially along said membrane 11, and water permeating radially through said winding tube 12, said permeate flowing axially within an open channel 40 into said postfilter 30 and from said postfilter 30 as product water. 2. A reverse osmosis membrane cartridge according to Claim 1, wherein said means for controlling feed water comprises a spoked circular wheel 13 sealed to one end of said winding tube 12 including two ring seals 47 to define an outer radius inlet 18 of feed water to said prefilter and an inner radius outlet 43 to remove waste water, and said spoked circular wheel 13 further providing access 35 to remove product water from said cartridge at a radius inside the radius of the smaller seal. 3. A reverse osmosis membrane cartridge according to Claim 2, wherein said means for controlling liquid flow comprises a top end ca 21 sealed to the end of said winding tube 12 closing the end of said winding tube 12 and providing a chamber inside said end cap for permeate to flow into the adjacent end of said postfilter 30. 4. A reverse osmosis membrane cartridge according to Claim 3, wherein said top end cap 21 includes an umbrella valve 41 in the in— eed end of the postfilter 30. 5. A reverse osmosis membrane cartridge according to Claim 2, wherein said means for controlling liquid flow includes a lip seal cap 32 on the outlet end of the postfilter 30 sealed to the inside of said winding tube 12 to prevent permeate from bypassing said postfilter 30. 6. A reverse osmosis membrane cartridge according to Claim 1, wherein said cartridge 10 includes a resilient ring seal 23 exterior of the prefilter 16. 7. A reverse osmosis membrane cartridge according to Claim 3, wherein said top end cap 21 includes a flexible plastic pull ring 22 integrally attached to said cap 21. 8. A reverse osmosis membrane cartridge according to Claim 5, wherein said lip seal cap 32 on the outlet of said postfilter 30 includes a flexible plastic pull ring 34 integrally attached to said seal cap 32. 9. A reverse osmosis membrane cartridge according to Claim 1, ^ wherein said prefilter 16 comprises at least two pairs of sheet material including at least one sheet of filter media paired with an open—weave fluid—conducting material, adhesively bonded along alternative opposite edges and all sheets are spirally wound onto said reverse osmosis membrane barrier layer. 10. A reverse osmosis membrane cartridge according to Claim 1, wherein said prefilter 16 comprises filter media of grade pore structure, 0.008 inches thick and of 5—micron porosity, including spun-bonded or melt—blown fibers selected from the group consisting of polyester, polyolefins or polyamides. 11. A reverse osmosis membrane cartridge according to Claim 10, wherein said prefilter 16 comprises spacer materials of polyolefin netting of about 0.018-inch strand thickness, 0.035-inch nodule thickness and 0.080-inch pitch diameter pattern. 12. A reverse osmosis membrane cartridge according to Claim 10, wherein said prefilter 16 comprises spacer materials of epoxy—impregnated polyester tricot. 13. A reverse osmosis membrane cartridge according to Claim 1, wherein the postfilter 30 comprises granulated activated carbon or charcoal or mixtures thereof. 14. A reverse osmosis fiter cartridge comprising a reverse osmosis membrane spirally wound on a winding tube 12, including: - a spoked wheel adhesively sealed to said winding tube 12; and - an impervious barrier layer 15 over said reverse osmosis membrane 11 and overlapping the spoked wheel 13; and - a prefilter 16 spirally wound onto said reverse osmosis membrane 11 comprising at least two pairs of filter media sheet and open—weave fluid—conducting spacer sheet material, one pair adhesively sealed along one edge and alternately sealed along the opposite edge; and — an impervious barrier layer 17 over said prefilter 16; and — a circular ring seal 23 formed of a resilient material covered with an adhesive tape, said ring seal applied over the outer-barrier layer 17 near the end of the filter opposite the spoked wheel 13; and — a spacer cap 21 adhesively sealed to the flush end of said winding tube 12; and — a flexible plastic pull ring 22 attached to said spacer cap end 21; and — a seal ring 47 in a groove in the spoked wheel 13 to seal the feed water from the waste water at the connection between the cartridge 10 and a valve plate end 45; and — a seal ring 47 in a groove in the spoked wheel 13 to seal the waste water from the product water at the connection between the cartridge and the valve plate end 45; and — a postfilter 30 inserted into the winding tube 12 comprised of: a carrier tube 31 closed at the valve plate end 45 by a lip seal cap 32 having a lip seal 33 to prevent product water from bypassing the postfilter 30, the lip seal cap 32 including a porous disk 35 to hold the filter material 36, said lip seal cap 32 including a flexible plastic pull ring 34; and a top spacer cap 37 attached to the other end of the postfilter carrier tube 31, said top spacer cap 37 including radial 38 and axial projections 39 to maintain an open fluid channel to conduct permeate to the inlet end of the postfilter 30 through an umbrella valve 41, then through a porous disk 35, before passing through the length of the postfilter 30. 15. A water filtration apparatus for separating feed water as product water and waste water, and including a disposable reverse osmosis membrane cartridge 10 removably positioned within a filter housing 44, said disposable cartridge including: a membrane mounting tube 12 supported at one end by a cartridge end cap 21 and at the other end by a mounting wheel 13, said mounting tube 12 including a plurality of permeate flow apertures 92 through the wall thereof; a reverse osmosis membrane 11 mounted around said mounting tube 12; an axial flow prefilter 16 mounted around said membrane 11 and separated therefrom by an impermeable barrier 15; and control means to control flow of feed water to said filtration apparatus to flow axially through said prefilter 16 and into said membrane 11 which separates said feed water as waste water directed axially along said permeator, and permeate water permeating radially through said permeate flow apertures 92; said permeate flows axially into said mounting tube 12 as product water. 16. A water filtration apparatus for separating feed water as product water and waste water, and including a reverse osmosis membrane cartridge 10 removably positioned within a filter housing 44, said disposable cartridge including: a membrane mounting tube 12 supported at one end by a cartridge end cap 21 and at the other end by a mounting wheel 13, said mounting tube 12 including a plurality of permeate flow apertures 92 through the wall thereof; a reverse osmosis membrane mounted around said mounting tube 12; an axial flow prefilter 16 mounted around said membrane 11 and separated therefrom by an impermeable barrier 15; and a postfilter element disposed within said mounting tube 12; " and control means to control flow of feed water to said filtration apparatus to flow axially through said prefilter 16 and into said membrane 11 which separates said feed water as waste water directed axially along said membrane, and permeate w;ι i t τ: permeating radially through said permeate flow apertures 92; said permeate flows axially within said mounting tube 12 and into said postfilter 30 and from said postfilter as product water.

Inventors: BROWN BARRY M, EDWARDS EVAN A, HOLZER JOSEPH C, PAVEL AUGUSTINE, TONE FREDERICK, WEST HENRY L, BROWN, BARRY, M., EDWARDS, EVAN, A., HOLZER, JOSEPH, C., PAVEL, AUGUSTINE, TONE, FREDERICK, WEST, HENRY, L.
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1988
Main classification: B01D13
IPC codes: B01D61, B01D63, B01D65, C02F1