TORSION RESISTANT FILTER STRUCTURE

Abstract: A filter cartridge (10) for separation of aqueous colloidal suspensions utilizing a shell (12) which forms a chamber having a colloidal suspension inlet and outlets for permeate and concentrate streams. A core (50) is placed within the shell and includes a plurality of filter elements (52) which are located in overlying relationship with one another. Each filter element possesses a relative rigid backing member (88) and a filter membrane (90). The core is fastened to the shell by connecting a plurality of the backing members to the body of the core.

Description: TORSION RESISTANT FILTER STRUCTURE BACKGROUND OF THE INVENTION The present invention relates to a novel and useful filter cartridge which is employed with a source of torsional force. Filtration systems have been devised to separate solid matter from liquids and are used in many technologies. However, the separation of the liquid portion from the solid portion of a colloidal suspension has been problematic and considered in many industries difficult to achieve. United States patents 4,952,317 and 5,014,564 describe systems which are employed to separate colloidal suspensions. In those systems, a tangential force is applied to a filtration pack into which the colloidal suspension is directed. Permeate and concentrate streams result from the systems shown in the above patents and have been proven to be extremely useful in many fields. Although successful, the application of torsional force of a relatively high frequency tends to tear apart or destroy conventional filter packs or cartridges that are placed atop the torsional drive mechanism. Again, referencing United States patent 5,014,564, the drive mechanism used for this purpose is illustrated, therein. Constructing a filter cartridge which is capable of resisting torsional force breakdown would be a notable advance in the field of colloidal suspension separations. SUMMARY OF THE INVENTION In accordance with the present invention, a novel and useful filter pack for separating colloidal suspensions is herein provided. The filter pack of the present invention exhibits high strength, low density, and a low damping modulus. In this regard, the cartridge of the present invention includes as one of its elements a shell which is constructed of high strength, lightweight material such as a fiber reinforced resin. The shell may be formed such that the fibrous material angles upwardly in a spiral, criss-cross fashion for reinforcement purposes. In addition, the shell includes thickened end flanges to strengthened those portions where attachment takes place to the source of torsion force and to the inlet and outlet conduits communicating with the filter cartridge. Moreover, the shell may also be formed with end plates of relatively rigid construction such as metallic or composite materials. A core is located within the shell and includes a plurality of filter elements placed in overlying relationship to one another. Each filter element includes a relatively rigid backing member which may be of metallic construction and is capable of spanning the chamber within the shell. In addition, a membrane filter material is placed over the backing member and is separated from the backing member by a spacer to produce a channel for the permeate stream. The permeate stream from each filter element is passed to a central permeate opening and conducted from the filter element by a conduit. Successive, overlying, filter elements are separated from one another by an elastomeric gasket which lies at the periphery of the backing member of each filter element. The gasket seals the edge portion of each filter element and also provides spacing for the courses, which the concentrate stream follows along the membrane surfaces of each filter element. In certain cases, diverter trays may be employed to reverse the flow of the colloidal suspension passing through the filter cartridge. In this way, sediment build-up and clogging is greatly reduced. In certain embodiments, the membrane in backing member may take a corrugated form. Rigid spacer material may also be placed beneath the membrane and above the backing member to permit the membrane to flex and, again, prevent build-up of material within the filter core. Fastening means is also included for connecting the core to the shell and to restore the shell from expanding to the point of a hoop stress failure. Such fastening means includes connecting the plurality of filter element backing members directly to the shell. Such fastening may take the form of a resinous potting compound being placed at the periphery of the backing members to bond the backing members directly to the shell material which may also be a resinous material. In this regard, the edges of the backing members may be bead blasted or roughened to help the bonding process. The core filter elements each including a membrane and backing member are formed with at least three openings. The openings of the membrane and backing member are alignable and provide for passage of the entering colloidal suspension stream, the exiting concentrate stream, and the exiting permeate stream. Plugging prevention may also be further provided for in the present invention by the use of a dam within the channel of the permeate stream found between the membrane and the backing member. The dam is used in conjunction with an impermeable film or element to force permeate flow toward the periphery of the core. In this way, solid cake build-up is avoided and also directs the colloidal suspension to the periphery of the core, where the amplitude of vibration is the largest. Thus, separation of the colloidal suspension into the permeate and concentrate streams is also greatly aided by this structure. It is believed that a novel and useful filter cartridge for use in separation of aqueous colloidal suspension has been hereinabove described. It is therefore an object of the present invention to provide a filter cartridge used for separation of aqueous colloidal suspensions which exhibits sufficient strength to resist damage upon the application of torsional forces on the filter cartridge. Another object of the present invention is to provide a filter cartridge which provides excellent separation of aqueous colloidal suspensions into permeate and concentrate streams in an efficient manner. A further object of the present invention is to provide a filter cartridge for use in separating aqueous colloidal suspensions which may be scaled up into relatively high flow rate applications. A further object of the present invention is to provide a filter cartridge useable for separating aqueous colloidal suspensions which permits the use of composite material having high strength to weight characteristics. Yet another object of the present invention is to provide a filter cartridge useable for separating of aqueous colloidal suspensions which includes a filter core that possesses a structure to greatly eliminate clogging and solid cake build-up. Another object of the present invention is to provide a filter cartridge used in separating an aqueous colloidal suspension which may be operated under high torsional forces and relatively high pressure to force separation of the colloidal suspension into permeate and concentrate streams. Another object of the present invention is to provide a filter cartridge used for separation of aqueous colloidal suspensions which successfully resist tangential forces which tends to separate a stack of filter elements within a filter core. The invention possess other objects and advantages especially as concerns particular characteristics and features thereof which will become apparent as the specification continues. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the filter cartridge of the present invention with a broken away portion schematically illustrating the orientation of fibrous material in the shell and a portion of the stacked filter elements in the core therewithin. FIG. 2 is a bottom plan view of Fig. 1. FIG. 3 is a sectional view take along line 3-3 of Fig. l. FIG. 4 is a top plan view of a typical filter element. FIG. 5 is a sectional view taken along line 5-5 of Fig. FIG. 6 is a sectional view taken along line 6-6 of Fig. 4. FIG. 7 is an enlarged view of the elastomeric gasket member in place within a typical tray taken along line 7-7 of Fig. 6. FIG. 8 is an enlarged view of the relationship between the filter element and the gasket member taken along line 8-8 of Fig. 7. FIG. 9 is a sectional view illustrating the damming element in the permeate channel. FIG. 10 is a sectional view showing a corrugated membrane embodiment of the present invention. FIG. 11 is a sectional view showing a corrugated membrane and backing member embodiment of the present invention. FIG. 11A is a sectional view showing a ridged backing member embodiment of the present invention. FIG. 12 is a sectional view schematically depicting another embodiment of the present invention in which the spacer in the permeate channel is a porous rigid body. FIG. 13 is a sectional view depicting the roughening of the periphery of the backing member for connection to the shell. FIG. 14 is a sectional schematic view indicating the flow of concentrate with the use of a diverter tray. For a better understanding of the invention reference is made to the following detailed description of the preferred embodiments thereof which should be referenced to the hereinabove described drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various aspects of the present invention will evolve from the following detailed description of the preferred embodiments thereof which should be taken in conjunction with the hereinabove described drawings. The invention as a whole is depicted in the drawings by reference character 10. Filter cartridge 10 includes as one of its elements a shell 12 forming an inner chamber 13, Fig. 1. Shell 12 may be constructed of a resinous material such as epoxy and be reinforced by a plurality or multiplicity of fibers such as glass fibers 14. Shell 12 is generally depicted in Fig. 1 as being a cylindrical body. Plurality of fibers 14 extend around shell 12 in a spiral fashion as is indicated by criss¬ crossing lines 16. That is to say, general parallel fibers spiral around shell 12 in one direction, crossing generally parallel fibers spiraling around the shell 12 in the opposite direction. The pitch of these spiral paths is represented in Fig. 1 is about 45 degrees, however the invention herein is deemed not to be limited to this angle. Plurality of fibers 14 may also take the form of carbon fibers, Kevlar fibers, and the like. Flanges 18 and 20 extend outwardly or bulge at the end portions of shell 12 for the purpose of strength. Exemplary metallic insert 22, Fig. 3, represents one of a number of inserts placed in flanges 18 and 20. Metallic insert 22 includes a threaded surface 24 which accepts threaded bolts. Plurality of threaded bolts 26 and 28, associated with flanges 18 and 20, respectively, are intended to engage threaded surfaces such as threaded surface 24 in each of the threaded inserts employed about the periphery of flanges 18 and 20. End plates 30 and 32 are held to shell 12 by plurality of bolts 26 and 28, respectively. Although only a quartet of bolts are depicted on Fig. 2, plurality of bolts 28 extend completely around the periphery of end plate 32 and end plate 30 of Fig. 1. Conduits 34 and 36 extend through plate 30 and into chamber 13 for the purpose of carrying a colloidal suspension to filter cartridge 10. Permeate conduit 38 extends from the central torsion of cartridge 10 upwardly from end plate 30. End plate 32 serves as a support for concentrate conduit 40 and includes a boss 42 to support shaft 44 which connects to a source of torsional force such as that depicted in United States Patent 5,014,564 which is incorporated herewith in its entirety. Directional arrows 46 and 48 on Figs. 1 and 2, respectively, show the torsional motion imparted to shell 12 by the source of torsional force. Filter cartridge 10 also possesses a core 50, Fig. 1, including a plurality of filter elements 52 which are placed in overlying relationship with respect to one another. Filter elements 52 are depicted schematically in Figs. 1 and 6. With reference to Fig. 4, a typical filter element 54 is depicted in plan view. Central opening 56 is intended to carry permeate through conduit 38, Fig. 1, while recesses 58 and 60 carry the unseparated colloidal suspension, and the eventual concentrate which exits shell 12 through conduit 40. Elastomeric gasket 62 extends about the periphery of filter element 54 on side 64 thereof. It should be noted that a similar gasket would appear on the underside of filter element 54 between the top of the next succeeding filter element of the plurality of filter elements 52. Straight gasket sections 66 and 68 include a plurality of apertures 70, Fig. 5, which permit concentrate to pass along a course from side 64 of filter element 54 to recesses 58 and 60, which will be explained in greater detail hereafter. With reference to Fig. 6 it may be observed that plurality of filter elements 52 are shown typically stacked or in overlying configuration with respect to one another. Filter elements 54, 72, and 74 are shown in generally parallel configuration separated by gaskets at their periphery, identical to gasket 62. Streams 76, 78, and 80 represent permeate flow through filter elements 54, 72, and 74. The streams 82, 84, and 86 represent concentrate flow where flow penetration or filtering takes place with respect to filter elements 54, 72, and 80. Turning to Fig. 7, it may observed that filter element 54 is shown in detail having a steel backing member 88 which extends into the periphery of shell 12. Membrane layer 90 is placed atop a membrane support 92 which itself overlies a drain cloth 94. The permeate channel 96 is formed between membrane 90 and backing member 88. It should be noted that the proportions of these elements in Fig. 7 have been enlarged for the sake of emphasis in certain cases. For example, membrane layer 90 is generally quite thin. Membrane layer 90 may be formed of certain materials such as Teflon, polysulfone, nylon, polypropylene, and the like. Membrane support 92 may be formed of Kynar, non-woven glass, and the like. Also, drain cloth 94 may be formed of Typar, fiber glass in non-woven form, and the like. It is important that the drain cloth be porous such that permeate, shown by directional arrows 98, passes to permeate recess or opening 56 and through, eventually, permeate conduit 38, Fig. 1. Membrane unit 100 may also be found on the opposite side of backing member 88 from that of membrane 90. Thus, permeate may pass into a channel 102 within the drain cloth element similar to channel 94. Again, permeate will travel to permeate opening 56, per directional arrows 104. Fig. 8 shows even greater detail where sealing takes place at the periphery of tray 54. Drain cloth 94 does not extend beneath elastomeric gasket 62, in the embodiment of Fig. 8. However, membrane 90 and membrane support are pressed into contact between elastomeric gasket 62 and steel backing member 88. In addition, adhesive layers 106 and 108 are employed to aid in such sealing at the periphery of filter element 54. Adhesive 106 may take the form of an epoxy, a vinylester, melt-blown adhesive, and the like. Adhesive 108 may be constructed of the same materials, as well as a polysulfone material. With reference to Fig. 9, another embodiment of the present invention is shown in which a dam 106 of impenetrable material is placed within permeate channel 108 formed between backing membrane 110 and stainless steel plate 112. Impenetrable film 114 splits permeate channel 108 into two parts such that permeate entering permeate channel 108 must follows the route shown by directional arrows 116, 118, and 120 to central opening 56. Directional arrow 122 represents the minimum flux in this case, while directional arrows 124 represents the maximum flux. O-ring 126 and stainless steel gasket 128 seal central opening 56 against passage of material. Thus, the maximum transmembrane pressure is found at the outside diameter of filter core 50 and the minimum transmembrane pressure at the inner diameter of core 50. It has been found that the addition of dam 106 and impenetrable film 114 prevents the build-up of solid cake material within cartridge 10. It has also been discovered that the torsional source vibration may enhance flow if membrane 130, Fig. 10, is formed with a corrugation. A square wave mesh 132 may be placed within the recessed formed by corrugated membrane 130 and supported by drain cloth 134. Of course, stainless steel support or backing member 136 would also be used to form the permeate channel 138 as in the prior instances. With reference to Fig. 11, backing member 140 of corrugated construction is employed with corrugated membrane 132 to produce the same effect. Fig. 11A represents another embodiment of steel backing member 140 in which the corrugations appear as a series of bumps 142 rather than regular undulations. It has been found that provision of bumps 142 improves the flow through core 50. The present invention also includes fastening means 144 for connecting core 50 to shell 12. With reference to Figs. 6 and 13, it may be observed that fastening means 144 includes the provision of an epoxy material 146 which adheres to shell 12 and to the periphery of steel backing members such as those associated with filter elements 54, 72, and 74. Turning to Fig. 9, it may be observed that steel backing member 112 includes a roughened or bead blasted edge 148 which aids in the use of epoxy material 146 such that backing member 112 is securely fastened to shell 12. Fig. 13 also illustrates steel backing member 150 having roughened edge 152 in conjunction with sandwiching backed membranes 154 and 156. Elastomeric gaskets 158 and 160 are also shown on either side of steel backing member 150. Turning to Fig. 12, another embodiment of the present invention is depicted in which a relatively rigid spongy material 162 is found in permeate channel 164 between backed membrane 166 and steel backing member 168. For example, material 164 may be steel wool. Backed membrane 166 is normally fastened to the reciprocating steel support under the influence of the operating pressure within shell 12. The spongy material, in contrast, remains in a static state. The result is that scrubbing action occurs between membrane 166 and pad 162. Such scrubbing action eliminates fouling within permeate channel 164. Turning to Fig. 14, a schematic representation of shell 12 is depicted in which core 50 is shown within chamber 13. Colloidal suspension streams 170 and 172 pass around and across plurality of filter elements 52 through courses such as course 172 between filter elements 174 and 176. Diverter tray 178 allows the concentrate stream 180 to only pass in one direction through core 50. Diverter tray 178 tends to maintain a cross-flow of velocity according to a specific Reynold's number. The concentrate is thus distributed relatively evenly, although the fluid viscosity on each tray may vary. Diverter trays, such as diverter tray 178, may be placed at multiple levels within core 50 to maintain an even distribution of liquid therewithin. In operation, filter cartridge 10 is placed atop a source of torsional force such as that shown in United States Patent 5,014,564. Such unit is commercially available from New Logic International, Inc. of Emeryville, California under the designation V-SEP, Series I. Cartridge filter 10 is then vibrated torsionally according to directional arrows 46 and 48, Figs. 1 and 2. Colloidal suspension streams are then passed into conduits 34 and 36 to enter core 50 which consists of a plurality of filter elements 52. Each filter element, such as filter element 54, permits permeate to pass through a central opening or recess 56 and out from core 50 via conduit 38. Concentrate, which flows across plurality of filter elements 52 through concentrate courses, exits cartridge 10 through conduit 40. The extreme torsional forces exerted on cartridge 10 are absorbed by fastening means 144 which employs the stainless steel backing members to restore such forces to prevent the break-up of core 50 when filtering takes place. While in the foregoing, embodiments of the present invention have been set forth in considerable detail for the purposes of making a complete disclosure of the invention, it may be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and principles of the invention.

Claims: WHAT IS CLAIMED IS 1. A filter cartridge used for separation of an aqueous colloidal suspension into a permeate stream and a concentrate stream in conjunction with a source of torsional force comprising: a. a shell forming a chamber, said chamber including an inlet and a first outlet for the permeate stream and a second outlet for concentrate stream; b. a core located within said shell, said core including a plurality of filter elements placed in overlying relationship to one another, each of said filter elements including a backing member of spanning said chamber of said shell; and c. fastening means for connecting said core to said shell, said fastening means including fastening means for connecting said plurality of filter element backing members to said shell. 2. The cartridge of claim 1 in which each of said filter plates further possesses a permeable membrane of a pre-determined pore size, said backing member and said membrane each including first and second opening for passage of the concentrate stream and a third opening for passage of the permeate stream, said first, second, and third openings of said membrane being alignable with the correspondence first, second, and third openings of the backing member. 3. The cartridge of claim 1 which additionally includes a diverter element placed in overlying relationship to any one of said plurality of filter elements. 4. The cartridge of claim 1 in which said shell is constructed of resinous material. 5. The cartridge of claim 4 in which said shell is further constructed of a plurality of fibers, said plurality of fibers at least partially surrounding said chamber, said fibers being embedded in said resinous material . 6. The cartridge of claim 5 in which said plurality of fibers form a spiral path in said shell. 7. The cartridge of claim 1 in which said shell includes a first and second end portions each possessing flanges extending outwardly from said chamber. 8. The cartridge of claim 7 in which said cartridge further comprises first and second end plates fastened to said shell and connecting means for holding said cartridge to the source of torsional force. 9. The cartridge of claim 1 in which each of said filter elements includes a membrane and a porous spacer element for separating said membrane from the backing member to form a channel for the permeate stream, said channel communicating with the permeate stream opening through said membrane. 10. The cartridge of claim 9 which additionally comprises an elastomeric gasket, the periphery of said membrane being sandwiched between said elastomeric gasket and said backing member, said elastomeric gasket forming a concentrate stream flow course between said membrane and the backing member of an overlying filter element. 11. The cartridge of claim 10 in which said elastomeric gasket also engages said backing member of an overlying filter element. 12. The cartridge of claim 11 in which said filter element includes a membrane support engaging said membrane. 13. The cartridge of claim 12 in which the periphery of said membrane support is sandwiched between said membrane and said backing member. 14. The cartridge of claim 14 which further includes a first adhesive layer interposed said elastomeric gasket and said periphery of said membrane, and a second adhesive layer interposed said periphery of said membrane support and said backing member. 15. The cartridge of claim 10 in which said elastomeric gasket includes a plurality of openings therethrough to permit flow of the concentrate stream between said concentrate stream flow course and the first and second openings through said membrane and said backing member. 16. The cartridge of claim 4 in which said fastening means for connecting said plurality of filter element backing members to said shell includes a resinous material bondable with said resinous material of said shell. 17. The cartridge of claim 16 in which said plurality of backing member of said plurality of filter elements each include a peripheral roughened surface embedded in said resinous material of said fastening means. 18. The cartridge of claim 9 in which further comprises a dam placed adjacent said membrane in said channel for the permeate stream, said dam capable of preventing passage of particles of said permeate stream from said channel to said third permeate stream opening through said membrane, and an impermeable element placed in engagement with said plugable element causing a change of direction of said permeate stream within said channel toward the shell of said filter cartridge. 19. The cartridge of claim 2 in which said membrane is corrugated. 20. The cartridge of claim 19 which additionally comprises a mesh of material lying adjacent said corrugated membrane. 21. The cartridge of claim 19 which additionally comprises a corrugated membrane support and a porous spacer element lying between said corrugated membrane and said corrugated membrane support. 22. The cartridge of claim 21 in which said backing member is a corrugated member. 23. The cartridge of claim 9 in which said porous spacer element is a rigid element and said membrane is a flexible membrane.

Inventors: CULKIN JOSEPH BRADLEY, CULKIN, JOSEPH, BRADLEY
Applicants: CULKIN JOSEPH B, CULKIN, JOSEPH, BRADLEY
Application year: 1997
Main classification: B01D63
IPC codes: B01D25, B01D63, B01D65