CA2215992A1 - Pleated filter and a method for making the same - Google Patents

Pleated filter and a method for making the same Download PDF

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Publication number
CA2215992A1
CA2215992A1 CA002215992A CA2215992A CA2215992A1 CA 2215992 A1 CA2215992 A1 CA 2215992A1 CA 002215992 A CA002215992 A CA 002215992A CA 2215992 A CA2215992 A CA 2215992A CA 2215992 A1 CA2215992 A1 CA 2215992A1
Authority
CA
Canada
Prior art keywords
sheet
filter
filter element
pleat tips
boundary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002215992A
Other languages
French (fr)
Inventor
Wayne M. Wagner
Francis A. Friedmann
Daniel T. Risch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Donaldson Co Inc
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of CA2215992A1 publication Critical patent/CA2215992A1/en
Abandoned legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D46/00Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/52Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material
    • B01D46/521Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material using folded, pleated material
    • B01D46/523Particle separators, e.g. dust precipitators, using filters embodying folded corrugated or wound sheet material using folded, pleated material with means for maintaining spacing between the pleats or folds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D27/00Cartridge filters of the throw-away type
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D29/00Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/111Making filtering elements
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D29/00Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/13Supported filter elements
    • B01D29/15Supported filter elements arranged for inward flow filtration
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D29/00Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/13Supported filter elements
    • B01D29/15Supported filter elements arranged for inward flow filtration
    • B01D29/21Supported filter elements arranged for inward flow filtration with corrugated, folded or wound sheets
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D29/00Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/50Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition
    • B01D29/56Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in series connection
    • B01D29/58Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in series connection arranged concentrically or coaxially
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D46/00Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/0001Making filtering elements
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D46/00Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2411Filter cartridges
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2201/00Details relating to filtering apparatus
    • B01D2201/04Supports for the filtering elements
    • B01D2201/0407Perforated supports on both sides of the filtering element
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/4805Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the type of adhesives
    • B29C65/481Non-reactive adhesives, e.g. physically hardening adhesives
    • B29C65/4815Hot melt adhesives, e.g. thermoplastic adhesives
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/50Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like
    • B29C65/5057Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like positioned between the surfaces to be joined
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/05Particular design of joint configurations
    • B29C66/10Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/112Single lapped joints
    • B29C66/1122Single lap to lap joints, i.e. overlap joints
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/05Particular design of joint configurations
    • B29C66/20Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines
    • B29C66/23Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being multiple and parallel or being in the form of tessellations
    • B29C66/232Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being multiple and parallel or being in the form of tessellations said joint lines being multiple and parallel, i.e. the joint being formed by several parallel joint lines
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/40General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/41Joining substantially flat articles ; Making flat seams in tubular or hollow articles
    • B29C66/43Joining a relatively small portion of the surface of said articles
    • B29C66/432Joining a relatively small portion of the surface of said articles for making tubular articles or closed loops, e.g. by joining several sheets ; for making hollow articles or hollow preforms
    • B29C66/4322Joining a relatively small portion of the surface of said articles for making tubular articles or closed loops, e.g. by joining several sheets ; for making hollow articles or hollow preforms by joining a single sheet to itself
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/40General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/41Joining substantially flat articles ; Making flat seams in tubular or hollow articles
    • B29C66/43Joining a relatively small portion of the surface of said articles
    • B29C66/438Joining sheets for making hollow-walled, channelled structures or multi-tubular articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/737General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the state of the material of the parts to be joined
    • B29C66/7371General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the state of the material of the parts to be joined oriented or heat-shrinkable
    • B29C66/73715General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the state of the material of the parts to be joined oriented or heat-shrinkable heat-shrinkable
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29LINDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2016/00Articles with corrugations or pleats
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29LINDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00Other particular articles
    • B29L2031/14Filters

Abstract

The present invention relates to a filter including a filter element having a succession of inner connected pleats. The pleats have successive pleat tips which define an outer boundary of the filter element. Covering the entire outer boundary of the filter element is a permeable generally inelastic sheet which extends across successive pleat tips. The sheet is adhesively affixed to the pleat tips for maintaining spacing of the pleats. The sheet comprises a plurality of randomly arranged plastic filaments which are bonded to each other junction between the filaments and define a plurality of randomly spaced and shaped openings for allowing substantially unrestricted flow of a fluid through the sheet.

Description

CA 0221~992 1997-10-09 WO 96/33001 PCT/~JS96/05236 pr~Tt ATED FTT~TER AND A ]h~ ~Ql~ FQR MART~G THE ,~

Field o~ the Invention The present invention relates generally to pleated ~ilters. Speci~ically, the present invention relates to pleated ~ilters having means for maintaining pleat spacing and methods ~or making the same.

Backaround o~ the Invention The desirability of maintaining equal pleat spacing in a pleated ~ilter is well known in the art. By maintaining equal pleat spacing, the sur~ace area o~ the ~ilter is maximized which maximizes the capacity and li~e o~ the ~ilter and minimizes pressure drop across the ~ilter.
A variety of techniques have been developed ~or maintaining pleat spacing in a pleated ~ilter. For example, U.S. Patent Nos. 3,397,793 and 4,046,697 each disclose cylindrical pleated filters employing textile netting wraps a~ixed to the pleats for maintaining pleat spacing. The textile netting o~ such prior art ~ilters has a regular pattern of relatively large openings ~or allowing ~luid passage through the netting.
Additionally, the netting employed by such prior art ~ilters is elastic. Due to the elasticity o~ the textile netting, the pleats are not secured rigidly in place because the netting stretches when the ~ilter is in use to allow circum~erential ~lexing and ganging of the pleats under increased operating pressures. There~ore, during the periods o~ increased pressure, the existing ~ilters undergo periods o~ decreased capacity and high pressure drop as the pleats are ganged together.
Other prior art ~ilters, such as the pleated ~ilter disclosed in U.S. Patent No. 5,252,207, employ spiral outer wraps a~ixed to pleat tips ~or maintaining pleat spacing. However, these prior art ~ilters require regularly spaced relatively large openings in the outer CA 0221~992 1997-10-09 W O96/33001 PCTrUS96/05236 wraps. The regular openings in the wraps reduce the surface area of the pleat tips which can be bonded to the wraps thereby reducing support provided to the pleats by the wraps. Additionally, the spiral wraps of the prior art filters are difficult to uniformly apply and not practically well suited for automation. Furthermore, the spiral wraps also cause unwanted flow patterns to the filters thereby affecting the capacity of the filters.
Another feature of prior art filters is that they typically employ rigid metal and plastic frames, cores or liners for providing the filters with sufficient rigidity to withstand operating pressures.
What is needed is a pleated filter including an improved means for maintaining pleat spacing. Also what is needed is a pleated filter having pleats which are substantially held rigidly in place. Also what is needed is a filter which is inherently rigid and employs minimal additional frame work for support. What is additionally needed is a filter that is ideally suited for automated manufacturing processes.

Summary of the Invention The present invention relates to a filter including a filter element having a succession of interconnected pleats. The pleats have successive pleat tips which define a cylindrical boundary of the filter element. Covering the boundary of the filter element is a permeable generally inelastic sheet which extends across successive pleat tips. The sheet is wrapped about the filter element and preferably shrink-fitted against the pleat tips of the filter element by application of heat to the sheet. The sheet advantageously increases the rigidity of the filter and maintains pleat spacing without substantially interfering with the flow of a fluid through the filter.
The present invention also relates to a filter having a pleated filter element includlng successive CA 0221~992 1997-10-Os WO96/33001 PCT~S96/05236 pleat tips which define a planar boundary of the filter element. The filter includes a permeable generally inelastic sheet affixed to the pleat tips for maintaining pleat spacing and covering the planar boundary.
Another aspect of the present invention relates to a method for making a cylindrical filter. The method involves providing a pleated filter element having a succession of interconnected pleats. The pleats of the filter element have successive pleat tips which define a generally planar boundary of the filter element. A
permeable sheet is affixed to the pleat tips such that the sheet extends across the successive pleat tips along the planar boundary of the filter element. The permeable sheet provides sufficient structure to the filter element to allow the filter element to be easily rolled up into a cylinder shape such that the pleat tips define a generally cylindrical boundary of the filter element which is covered by the permeable sheet.
An additional aspect of the present invention relates to constructing a filter by placing a permeable plastic sheet around a cylindrical pleated filter element and post-tensioning the plastic sheet.
A variety of advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

Brief Descript;on of the Draw,ngs The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the CA 0221~992 1997-10-09 WO96/33001 PCT~S96/05236 invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows.
FIG. l is a perspective view of a cylindrical pleated filter that is an embodiment of the present invention.
FIG. 2 is a sectional view of the cylindrical pleated filter of FIG. l taken along section line 2-2 of FIG. l.
FIGS. 3A-3B illustrate two constructions of sheets used to retain pleat tips of a pleated filter.
FIGS. 4A-4E illustrate a method for making the cylindrical pleated filter which is embodied in FIG. l.
FIG. 5 is a perspective view of a flat pleated filter which is an embodiment of the present invention.

Detailed Descr,pt'on of the Invention Reference will now be made in detail to exemplary embodiments of the present invention which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring to FIGS. l and 2, there is illustrated a cylindrical filter 20 in accordance with the principles of the present invention. The filter 20 preferably includes a first end cap 22 that opposes and is generally parallel to a second end cap 24. The first and second end caps 22, 24 are preferably circular plates constructed of metal or plastic. The first end cap 22 is solid throughout while the second end cap 24 is annular and defines a circular hole 25 that is concentric with the center of the second end cap 24. The first and second end caps 22, 24 each include a raised lip 26 that extends around the entire circumference of each end cap 22, 24.

CA 022l~992 lss7-lo-Os WO96/33001 PCT/U~ 5236 The cylindrical filter 20 also includes a filter element 28 which is oriented between the first end cap 22 and the second end cap 24. The filter element 28 has a first end 30 inserted within the raised lip 26 of the ~irst end cap 22 and adhesively affixed to the first end cap 22. Similarly, the filter element 28 has a second end 32 inserted within the raised lip 26 of the second end cap 24 and adhesively affixed to the second end cap 24.
The filter element 28 is preferably composed of corrugated filter paper or a like material which is folded to form a succession of interconnected pleats 34.
The pleats 34 have successive outer pleat tips 36 which define a generally cylindrical outermost boundary of the filter element 28. Each of the outer pleat tips 36 has an outermost edge 37 which extends longitudinally between the first end cap 22 and the second end cap 24.
Similarly, the pleats 34 also have inner pleat tips 38 which define an innermost boundary of the filter element 28. The innermost boundary of the filter element 28 is generally cylindrical and is in general axial alignment with the circular hole 25 in the second end cap 24. Each of the inner pleat tips 38 also has an innermost edge 39 that extends longitudinally between the first end cap 22 and the second end cap 24.
An additional component of the cylindrical filter 20 is a permeable generally inelastic first sheet 40 comprising a liner which tightly covers the entire outermost boundary of the filter element 28. The first sheet 40 is preferably wrapped once about the filter element 28 such that the first sheet 40 extends across successive outer pleat tips 36 and is preferably adhesively affixed to the outer pleat tips 36. It is desireable for the first sheet 40 to have end portions overlapping at a first seam 42 which extends longitudinally from the first end cap 22 to the second end cap 24. However, it will be appreciated that the end CA 0221~992 1997-10-Os wos6l33ool PCT~396/05236 portions of the first sheet 40 may be flush with each other and reinforced by a thin strip of sheet material (not shown) or a layer of adhesive thereby forming an abutted longitudinal seam.
It is preferred for the wrapped first sheet 40 to be post-tensioned by shrink-fitting the first sheet 40 tightly against the outer pleat tips 36 through the application of heat to the first sheet 40. Furthermore, it i5 also preferred for the first sheet 40 to be adhesively affixed to essentially the entire outermost edge 37 of each o~ the outer pleat tips 36.
It has been determined by the inventors that because the first sheet 40 has a single longitudinal seam 42 and is post-tensioned tightly against the outer pleat tips 36, the ~irst sheet 40 extends tautly across the successive outer pleat tips 36 without having any substantial slack or wrinkles. Additionally, the tensioned first sheet 40 exerts uniformly distributed centripetal forces against the outer pleat tips 36 which are balanced against a perforated structural inner liner 41 of the filter 20 preferably constructed of metal or plastic. The balanced centripetal forces increase the rigidity of the filter 20 and assist in maintaining equal spacing of the pleats 34.
It will be appreciated that the first sheet 40 also may serve the purpose of protecting the filter element 28 during assembly and use of the filter 20 thereby eliminating the need for an additional protective covering such as a conventional outer liner constructed of perforated metal or plastic.
The cylindrical filter 20 further includes a permeable generally inelastic second sheet 44 comprising a liner which preferably covers the entire innermost boundary of the filter element 28. The second sheet 44 extends across successive inner pleat tips 38 and is adhesively affixed the inner pleat tips 38 in order to maintain spacing of the pleats 34 and to provide -CA 0221~992 1997-lo-09 WO96/33001 PCT~S96/05236 additional rigidity to the filter element 28. For some filtering applications, the second sheet 44 provides suf~icient support to the ~ilter element 28 to eliminate the need for the additional structural support provided 0 5 the structural inner liner 41 o~ the filter 20.
Referring to FIGS. 3A and 3B, the first and second sheets 40, 44 each preferably comprise a plurality of randomly arranged filaments 46 made of a plastic material such as polyester, polyamide or polypropylene.
10 The filaments 46 are bonded to each other at junctions 48 between the filaments 46. It will be appreciated that the filaments may be straight, as shown ln FIG. 3A, or =~
crimped as shown in FIG. 3B.
The plurality of randomly arranged filaments 46 15 define a plurality of randomly spaced and shaped openings 50 within the first and second sheets 40, 44. Due to their random arrangement, the filaments 46 provide equal strength in all directions. Additionally, the filaments 46 are relatively inelastic as compared to the typical 20 forces exerted on the sheets 40, 44 during use of the ~ilter 20. In this regard, it has been determined by the inventors that the relative inelasticity of the filaments 46 minimizes stretching o~ the sheets 40, 44 thereby allowing the sheets 40, 44 to firmly maintain the spacing 25 o~ the pleats 34.
It has also been determined by the inventors that important physical characteristics o~ the first and second sheets 40, 44 relate to their permeability and thickness. In this regard, it is desirable ~or the first 30 and second sheets 40, 44 to each have a Frazier air permeability greater than 500 and a thickness less than 0.009 inch. It has further been determined that under most filtering conditions, first and second sheets 40, 44 designed within the above established parameters perform 35 substantially no filtering function and experience substantially no cont~m;n~nt loading. Additionally, pressure drops caused by the first and second sheets 40, CA 0221~992 1997-lo-og WO96/33001 PCT~S96/05236 44 are substantially undetectable as compared to the pressure drop caused by the filter element 28 and the contaminants collected thereon.
It will be appreciated that in certain 5 conditions it may be desirable to employ ~irst and second r sheets 40, 44 having a Frazier air permeability less than 500 and a thickness greater than 0.009 inch. It will further be appreciated that for certain other conditions, it may be desireable ~or the ~irst and second 10 sheets 40, 44 to per~orm a filtering and/or agglomeration function.
It will be further be appreciated that Reemay Corporation manu~actures a polyester fabric sold under the trade name Reemay which can e~ectively be used as 15 the ~irst and second sheet 40, 44. Reemay Corporation also manufactures a polypropylene ~abric under the trade name Typar which can also be e~ectively used as the ~irst and second sheets 40, 44. Furthermore, the Fiberweb North America Inc. manufactures a fabric under 20 the trade name Cerex which is also suitable ~or use as the ~irst and second sheets 40, 44.
In operation, the cylindrical filter 20 is used to ~ilter contaminates ~rom a ~1uid. The contaminated fluid pre~erably passes through the openings 50 in the 25 first sheet 40 without experiencing any measurable pressure drop and without undergoing any substantial ~iltering effect by the first sheet 40. The contaminated ~luid then passes through the filter element 28 thereby having contaminates removed from the ~luid. Asymmetry in 30 the spacing o~ the pleats 34 and uneven cont~m;n~nt loading of the filter element 28 create paths of lesser resistance through which the ~luid has a tendency to flow. The non-uniform flow of fluid through the ~ilter element 28 generates lateral forces on the ~ilter element 35 28 which urge the pleats 34 to bunch, gang or collapse.
However, because the ~irst and second sheets 40, 44 are relatively inelastic as compared to the lateral ~orces CA 0221~992 1997-10-09 WO96/33001 PCT~s96/05236 and adhesively a~ixed to essentially the entire edges 37,39 of their respective pleat tips pleat tips 36, 38, and because the ~irst sheet 40 is tautly tensioned across the outer pleat tips 38, the ~irst and second sheets 40, 5 44 resist and balance the lateral forces generated by the non-uni~orm ~luid ~low thereby maintaining pleat 34 spacing and preventing bunching, ganging and collapsing o~ the pleats 34.
Once the ~luid passes through the ~ilter element 28, it next passes through the second sheet 44 pre~erably without experiencing any measurable pressure drop. Similar to the first sheet 40, the second sheet 44 pre~erably provides essentially no ~iltering e~ect on the ~luid and there~ore does not experience any 15 appreciable cont~mln~nt loading. As a ~inal step in the ~iltering process, the ~iltered ~luid exits the cylindrical ~ilter 20 through the circular hole 25 in the second end cap 24.
It will be appreciated that the cylindrical 20 ~ilter 20 works well as a liquid ~ilter or an air ~ilter.
The cylindrical filter 20 has been tested in oil to a pressure drop across the ~ilter element 28 o~ 150 psi without experiencing the usual pleat bunching which occurs at minimal pressure drops in conventional ~luid 25 ~ilters not having pleat tip retaining means.
It will be apparent to those skilled in the art that various modi~ications and variations can be made in the use and construction of the present invention without departing ~rom the scope or spirit o~ the invention. In this regard, it will be appreciated that the cylindrical ~ilter 20 is merely an example o~ a cylindrical ~ilter utilizing the pleat tip retention means o~ this invention ~or maintaining the spacing o~ the pleat tips. A variety o~ cylindrical ~ilter designs presently exist and the 35 particular embodiment o~ this invention illustrated by the cylindrical ~ilter 20 is not to be construed as being a limitation upon the invention.
-CA 022l~992 l997-lO-09 WO96/33001 PCT~S96/0~236 As an example o~ a typical modi~ication, a urethane potting compound may be used instead o~ metal end caps 22, 24 to secure the ends 30, 32 of the ~ilter 20. Furthermore, certain embodiments o~ the present invention may employ only the first sheet 40 to maintain the pleat 34 spacing o~ the ~ilter element 28 For many applications, the first sheet 40 surrounding the outermost boundary of the ~ilter element 28 and situated on the upside stream of the ~low will provide su~ficient support to the outer pleat tips 36 to prevent movement o~
the pleats 34 and to maintain adequate spacing o~ the pleats 34.
Re~erring to FIGS. 4A-4E, the cylindrical filter 20 is illustrated as it would appear at various stages o~ the manu~acturing process. At the ~irst step o~ the manu~acturing process, the filte~ element 28 of the cylindrical ~ilter 20 comprises a generally flat piece o~ ~ilter paper as shown in FIG. 4A which is generally uncoiled ~rom a roll.
The second step in the manu~acturing process is to ~orm the pleats 34 o~ the filter element 28 by folding the ~ilter element 28 through conventional folding techniques as shown in FIG. 4B. As folded, the successive inner pleat tips 38 de~ine a generally planar ~irst boundary o~ the ~ilter element 28 and the successive outer pleat tips 36 de~ine a generally planar second boundary o~ the ~ilter element 28. The ~irst boundary of the ~ilter element 28 opposes and is generally parallel to the second boundary o~ the ~ilter element 28. The ~olded ~ilter element 28 also has a ~irst end portion 55 and a second end portion 57.
The third step in the manu~acturing process relates to the application o~ the second sheet 44 to the inner pleat tips 38 o~ the ~ilter element 28. In this regard, the pleats 34 o~ the ~ilter element 28 are bunched or reefed together and the second sheet 44 is a~ixed to the inner pleat tips 38 while the ~ilter CA 0221~992 1997-lo-Os WO96/33001 PCT~S96/05236 element 28 is in the ~lat as shown in FIG. 4C. As af~ixed, the second sheet 44 has dimensions corresponding to the dimensions o~ the cylindrical inner boundary de~ined by the inner pleat tips 38 of the ~ilter element 5 28 when the ~ilter element 28 is incorporated within the cylindrical ~ilter 20.
It is pre~erred that the second sheet 44 be a~ixed to the inner pleat tips 38 by placing a sheet o~
heat sensitive adhesive, such as a non-woven web hot melt adhesive manufactured by Bostik Corporation, between the inner pleat tips 38 and the second sheet 44 and applying heat to the second sheet 44 to activate the sheet o~ heat sensitive adhesive. When the sheet o~ heat sensitive adhesive is heated, it melts into the inner pleat tips 38 15 and the second sheet 44 e~fectively bonding the second sheet 44 to the inner pleat tips 38 upon hardening. It will be appreciated that the second sheet 44 may also be bonded to the inner pleat tips 38 by alternative a~fixing techniques such as spray adhesives or heat ~usion.
The ~ourth step in the manufacturing process relates to rolling up the filter element 28, typically around the structural inner liner 41 o~ the ~ilter 20, such that the inner pleat tips 38 de~ine the generally cylindrical inner boundary which is covered by the second 25 sheet 44 and the outer pleat tips 36 de~ine the generally cylindrical outer boundary. It has been determined by the inventors that because the second sheet 44 is a~ixed to the inner pleat tips 38, the ~ilter element 28 has su~icient containment to be easily handled and rolled up 30 into the cylindrical shape. While the ~ilter element 28 is supported on the structural inner liner 41, the ~ilter element 28 is rolled up into the cylindrical shape and the ~irst and second end portions 55, 57 of the ~ilter element 28 are permanently a~ixed to each other as shown 35 in FIG. 4D.
The ~i~th step in the manu~acturing process o~
the cylindrical ~ilter 20 involves applying the ~irst CA 0221~992 1997-lo-os WO96/33001 PCT~S96105236 sheet 40 to the outer cylindrical boundary o~ the ~ilter element 28 as shown in FIG. 4E. It is pre~erred that the first sheet 40 be a~ixed to the outer pleat tips 36 by wrapping a sheet o~ heat sensitive adhesive, such as non-woven web hot melt adhesive, around the entire outercylindrical boundary o~ the ~ilter element 28. The ~irst sheet 40 is wrapped around the entire outer cylindrical boundary o~ the ~ilter element 28 such that the sheet of heat sensitive adhesive is positioned between the ~irst sheet 40 and the outer pleat tips 36.
When the ~irst sheet 40 is wrapped about the ~ilter element 28, the end portions o~ the ~irst sheet 40 overlap each other and are bonded to each other by conventional a~ixing techniques such as adhesives or hot melting to create the longitudinal seam 42. In the alternative, the end portions o~ the ~irst sheet 40 may be ~lush and the longitudinal seam 42 may be secured by a strip o~ material a~fixed over the end portions or a layer o~ resin covering the end portions.
Once the ~irst sheet 40 is seamed, heat is applied to the ~irst sheet 40. The heat causes the ~irst sheet 40 to shrink-fit tightly against the outer pleat tips 36 and concurrently activates the sheet o~ heat sensitive adhesive causing the adhesive to melt into the outer pleat tips 36 and the ~irst sheet 40 e~ectively bonding the ~irst sheet 40 to the entire edges 37 o~ the outer pleat tips 36. It will be appreciated that other adhesives such as spray adhesives may also be used to bond the ~irst sheet 40 to the outer pleat tips 36. It will also be appreciated that the first sheet 40 may be post-tensioned by other means such as ~orcibly inserting within the center o~ the ~ilter element 28 an inner liner having an outer diameter slightly larger than the inner diameter o~ the ~ilter element 28.
The final step in manu~acturing the cylindrical ~ilter 20 involves af~ixing the ~irst and second end caps 22, 24 to the ~ilter element 28. In this regard, potting CA 0221~992 1997-10-Os WO96/33001 PCT~S96/05236 compound is preferably applied to the first and second end caps 22, 24. The first and second end caps 22, 24 are then adhesively bonded by the potting compound to the first and second ends 30, 32 of the ~ilter element 28 as _ 5 shown in FIG. l.
It will be apparent to those skilled in the art that the present invention also includes modified methods for manufacturing cylindrical filters in which the sequence of the steps may be altered or certain steps eliminated from the process. For example, in may be desired to eliminate the above-described third step from the manufacturing process in order to manufacture a cylindrical filter which does not include the second sheet 44 covering the generally cylindrical interior 15 boundary of the filter element 28. Additionally, it may be desireable for the first sheet 40 to be affixed to the outer pleat tips 36 of the filter element 28 while the filter element 28 is in the flat and defines the generally planar second boundary. The filter element 28 20 may then be rolled up in the shape of a cylinder with the first and second end portions 55, 57 of the filter element 28 permanently affixed together such that the first sheet 40 is wrapped around the generally cylindrical outer boundary of the filter element 28. The 25 end portions of the first sheet 40 would preferably be reinforced by resin or a strip of material to secure the longitudinal seam 42. This modified process would preferably be used to manufacture a cylindrical filter including only the first sheet 40 for maintaining pleat 30 34 spacing.
It will also be appreciated that for some uses, the structural inner liner 41 may be eliminated form the filter 20.
Referring now to FIG. 5, there is illustrated 35 an alternate filter 120 in accordance with the present invention. The filter 120 includes a filter element 128 preferably made of conventional filter paper. The ~ilter , CA 022l~992 l997-lO-og W096/33001 PCT~S96/OS236 element 128 is ~olded to form a succession o~
interconnected pleats 134. The pleats 134 include successive inlet pleat tips 136 having first outermost edges 137 which de~ine a generally planar inlet boundary o~ the ~ilter element 128. Similarly, the pleats also include successive outlet pleat tips 138 having second outermost edges 139 which define a generally planar outlet boundary of the ~ilter element 128.
The filter 120 also includes a ~irst sheet 140 comprising a liner which covers the entire inlet boundary o~ the ~ilter element 128. The ~irst sheet 140 extends across and is adhesively bonded to the inlet pleat tips 136 o~ the ~ilter element 128. Similarly, the filter 120 ~urther includes a second sheet 144 comprising a liner which covers the entire outlet boundary of the ~ilter element 128. The second sheet 144 extends across and is adhesively bonded to the outlet pleat tips 138 of the ~ilter element 128.
It will be appreciated that the rirst and second sheets 140, 144 are made o~ the same material described previously with respect to the first and second sheets 40, 44 o~ the cylindrical filter 20.
Additionally, it is preferred for the first and second sheets 140, 144 to be a~ixed to the entire lengths o~
their respective pleat tips 136, 138 by heat sensitive adhesive. However, it will be appreciated that any conventional adhesive may be employed.
Because the first and second sheets 140, 144 are preferably affixed to the entire lengths of their respective pleat tips 136, 138, the first and second sheets 140, 144 prevent the pleats 134 from moving and increase the rigidity o~ the filter 120. The rigidity of the ~ilter 120 is ~urther increased by adhesively affixing rectangular end caps 131 made o~ cardboard or a like material to ~irst and second ends 130, 132 of the filter element 128. It will be appreciated that the first and second ends 130, 132 may also be capped by CA 022l~992 l997-lO-Os WO96/33001 PCT~S96/05236 alternate materials such as resin or potting compound, either of which may provide a surface to attach gasketing 133 around the filter 120 Due to the rigidity provided to the filter 120 by the first and second sheets 140, 144, it will be appreciated that for many uses the filter 120 does not require an exterior frame as is conventionally used by existing filters. Additionally, it will also be appreciated that the filter 120 may be manufactured in large scale by affixing large sheets to large pleated filter elements and then cutting the large filter element into filters having the desired dimensions. This type of manufacturing process is ideally suited for automation.
It will also be appreciated for certain uses, a filter may be constructed having only one sheet for maintaining pleat spacing. For this type of filter, it is desireable to have a sheet covering the inlet boundary of the filter for maintaining pleat spacing.
With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of shape, size and arrangement of the parts without departing from the scope of the present invention. It is intended that the specification and depicted embodiment be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the following claims.

Claims (24)

We claim:
1. A filter comprising:
a filter element (28) having a succession of interconnected pleats (34), the pleats (34) including successive spaced pleat tips (36) which define a generally cylindrical boundary of the filter element (28); and a permeable fibrous first sheet (40) extending around the cylindrical boundary of the filter element (28) for maintaining spacing of the pleats (34), the first sheet (40) including a plurality of heat shrunk fibers constructed of a plastic material, the plastic fibers being heat shrunk after the first sheet has been placed around the filter element such that the first sheet is tightened about the filter element.
2. The filter of claim 1, wherein the fibrous first sheet (40) is wrapped in substantially a single turn about the filter element (28) and covers substantially the entire generally cylindrical outer boundary of the filter element (28).
3. The filter of claim 1, wherein the first sheet has end portions that overlap one another to form a seam (42) that extends longitudinally along the filter element (28).
4. The filter of claim 1, wherein the plastic fibers are randomly arranged and bonded to each other at junctions between the fibers..
5. The filter of claim 1, wherein the first sheet (40) has a Frazier air permeability greater than 500.
6. The filter of claim 1, wherein each of the pleat tips (36) defines an edge (37) extending lengthwise along the filter element, and the first sheet (40) is adhesively affixed to essentially the entire edge (37) of each pleat tip (36).
7. The filter of claim 1, wherein the first sheet (40) has a thickness less than .009 inch.
8. The filter of any one of claims 1-7, wherein the first sheet (40) is affixed to the pleat tips by heat sensitive adhesive.
9. The filter of any one of claims 1-7, further comprising end caps (22, 24) affixed to opposite ends of the filter element (28).
10. The filter of claim 9, further comprising an inner liner (41) positioned within the filter element (28) and extending between the end caps (22, 24).
11. A method for making the filter of claim 1, comprising the steps of:
placing the first sheet (40) about the outer boundary of the filter element (26); and heat shrinking the first sheet (40) upon the filter element (26).
12. The method of claim 11, further comprising the step of applying heat sensitive adhesive to the pleat tips (36) before heat shrinking the permeable first sheet (40).
13. The method of claim 12, wherein the heat sensitive adhesive comprises a sheet of hot melt adhesive that is wrapped around the cylindrical boundary of the filter element (28) and is positioned between the pleat tips (36) and the permeable fibrous first sheet (40).
14. A method for making a filter comprising the steps of:
providing a filter element (28) having a succession of interconnected pleats (34), the pleats (34) including successive spaced pleat tips (36) which define a generally cylindrical boundary of the filter element (28);
securing a permeable fibrous plastic first sheet (40) around the cylindrical boundary of the filter element (28); and post-tensioning the first sheet (40) against the pleat tips (36) of the filter element (28) after the first sheet has been secured around the filter element.
15. The method of claim 14, wherein the first sheet (40) is post-tensioned by shrink-fitting the first sheet through the application of heat to the first sheet (40).
16. A method for making the filter comprising the steps of:

providing a pleated filter element (28) including a plurality of pleat tips (36);
adhesively affixing a first permeable fibrous sheet (40) to the outer pleat tips (36) such that the first sheet (40) extends across the pleat tips (36) along a generally planar boundary; and rolling the filter element (28) such that the pleat tips (36) define the generally cylindrical boundary of the filter element (28) which is covered by the first sheet (40) that is affixed to the pleat tips (36) .
17. The method of claim 16, wherein the cylindrical boundary is an outer boundary.
18. The method of claim 16, wherein the cylindrical boundary is an inner boundary.
19. A filter comprising:
a filter element (128) having a succession of interconnected pleats (134), the pleats (134) having successive first pleat tips (136) which define a first generally planar boundary of the filter element (128);
and a permeable fibrous first sheet (140) covering the first boundary of the filter element (128), the first sheet (140) extending across successive first pleat tips (136) and being adhesively affixed to the first pleat tips (136) for maintaining spacing of the pleats (134), the sheet (140) having a Frazier air permeability greater than 500.
20. The filter of claim 19, wherein each of the first pleat tips (136) defines an edge extending longitudinally along the filter element, and the first sheet (140) is adhesively affixed to essentially the entire edge of each first pleat tip (136).
21. The filter of claim 19, wherein the first sheet (140) is affixed to the first pleat tips (136) by heat sensitive adhesive.
22. The filter of claim 19, wherein the first sheet (140) has a thickness less than .009 inch.
23. The filter of claim 19, wherein the first sheet (140) includes a plurality of randomly spaced plastic fibers.
24. The filter of claim 19, wherein the filter element (128) includes a plurality of second pleat tips (138) defining a second generally planar boundary, and the filter further includes a second fibrous permeable sheet (144) covering the second boundary and being adhesively affixed to the second pleat tips (138).
CA002215992A 1995-04-21 1996-04-16 Pleated filter and a method for making the same Abandoned CA2215992A1 (en)

Applications Claiming Priority (2)

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US42622295A 1995-04-21 1995-04-21
US08/426,222 1995-04-21

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EP (1) EP0821613A1 (en)
JP (1) JPH11503963A (en)
KR (1) KR19990007949A (en)
CN (1) CN1068795C (en)
AU (1) AU715109B2 (en)
BR (1) BR9608151A (en)
CA (1) CA2215992A1 (en)
MX (1) MX9708020A (en)
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CN1181714A (en) 1998-05-13
AU5485996A (en) 1996-11-07
ZA963076B (en) 1997-11-18
EP0821613A1 (en) 1998-02-04
KR19990007949A (en) 1999-01-25
WO1996033001A1 (en) 1996-10-24
AU715109B2 (en) 2000-01-20
US5814219A (en) 1998-09-29
JPH11503963A (en) 1999-04-06
BR9608151A (en) 1999-02-09
CN1068795C (en) 2001-07-25
MX9708020A (en) 1997-11-29

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