WO2002041964A2

WO2002041964A2 - Fluid filtration assemblies and core elements therefor

Info

Publication number: WO2002041964A2
Application number: PCT/US2001/042830
Authority: WO
Inventors: Charles C. Schuyler
Original assignee: Usf Filtration And Separations Group, Inc.
Priority date: 2000-11-22
Filing date: 2001-10-29
Publication date: 2002-05-30
Also published as: WO2002041964A3; AU2002214670A1

Abstract

Fluid filtration assemblies (10) include a generally cylindrical core element (20) which supports a filter membrane (36) (e.g., a microporous film preferably formed of polytetrafluoroethylene, PTFE) and is concentrically positioned in a rigid (e.g., stainless steel) tubular housing (12). The core element (20) is most preferably formed of a fluorocarbon polymer so as to be compatible with the PTFE microporous membrane film (36) wrapped around its cylindrical external periphery. The core element (20) itself includes annular spaced-apart support ribs (34) for the membrane film (36) and openings (40) through the core sidewall. Dual seal flanges (24, 26) are unitarily formed at one end of the core element. In use, the flanges (24, 26) will be press-fit into, and be permanently deformed by, the internal cylindrical surface of the rigid housing (12) thereby forming a tight fluid seal therebetween.

Description

FLUID FILTRATION ASSEMBLIES AND CORE ELEMENTS THEREFOR

FIELD OF THE INVENTION

The present invention relates generally to the field of fluid filtration (e.g., filtration of gas and/or liquid streams). In preferred forms, the present invention relates to fluid filtration assemblies having a core element which supports a membrane filter element.

BACKGROUND AND SUMMARY OF THE INVENTION

Semiconductor fabrication techniques typically employ filtration assemblies for the filtration of inert gases used in the fabrication processes. These conventional fluid filtration assemblies generally are comprised of a rigid tubular housing having axially opposed fluid inlet and outlet passageways and containing a core element adapted to support a membrane filter element are well known. Typically, fluid (e.g., an inert gas) enters the housing through the fluid inlet passageway and then passes through the membrane in a direction toward a central passageway of the core element, and then on to the fluid outlet passageway. A fluid seal must therefore exist near the fluid outlet to prevent fluid "by-pass" of the filter membrane.

Conventional core elements employed to support filtration membranes have typically been provided with one or more O-ring seals positioned near the outlet passageway of the filter housing. Such conventional O-ring seals can be problematic in use as they might be damaged during the assembly process when the core element is forcibly seated within the tubular housing. It would therefore be highly desirable if fluid filtration assemblies could be provided with enhanced fluid seals between the filter housing and the core element housed therein. It is towards providing such a need that the present invention is directed.

Broadly, the present invention is embodied in fluid filtration assemblies comprised of a generally cylindrical core element which supports a filter membrane (e.g., microporous film preferably formed of fluoropolymer, such as polytetrafluoroethylene (PTFE)) and is concentrically positioned in a rigid (e.g., stainless steel) tubular housing. The core element is most preferably formed of molded fluoropolymer so as to be compatible with the PTFE microporous membrane film wrapped around its cylindrical external periphery. The core element itself includes annular spaced-apart support ribs for the membrane film and openings through the core sidewall.

Important to the present invention, however, is the provision of dual seal flanges unitahly formed at one end of the core element. Most preferably, the seal flanges are in the form of relatively shallow-pitched (e.g., about 30°) substantially conical sections which are concentrically disposed relative to the elongate axis of the core element. In use, the flanges will be press-fit into, and be permanently deformed by, the internal cylindrical surface of the rigid housing thereby forming a tight fluid seal therebetween. In addition, this seal is enhanced by the fact that the seal flanges are sized and configured so that the downstream seal flange will be deformed in such a way that its trailing edge overlaps a plane of the leading edge of the adjacent upstream seal flange which is transverse to the elongate axis of the core element. In use, therefore, the fluid pressure in will tend to ensure that the seal flanges are maintained in fluid-tight sealing disposition with respect to the housing interior. The assemblies of the present invention are especially usefully employed in the filtration of gases, preferably inert gases, that may , for example, be used during semiconductor fabrication processes.

These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein;

FIGURE 1 is a perspective view, partly sectioned, of a fluid filtration assembly in accordance with the present invention;

FIGURE 2 is a cross-sectional view of the fluid filtration assembly depicted in FIGURE 1 ;

FIGURE 3 is an enlarged cross-sectional view of the permanently deformed seal flanges unitarily formed with the core element;

FIGURE 4 is a perspective view of the preferred core element employed in the fluid filtration assembly depicted in FIGURE 1 ;

FIGURE 5 is a cross-sectional view of the core element depicted in FIGURE 4;

FIGURE 6 is a discharge end view of the core element depicted in FIGURE 4; F1GURE 7 is a side elevational view of the core element depicted in FIGURE 4. and

FIGURE 8 is an inlet end view of the core element depicted in FIGURE 4.

DETAILED DESCRIPTION OF THE INVENTION

A fluid filtration assembly 10 in accordance with the present invention is depicted in accompanying FIGURES 1-3. As shown, the assembly 10 includes a housing 12 formed of rearward and forward housing sections 12a, 12b, respectively, rigidly joined to one another (e.g., by welding, soldering or like metal joining techniques). The rearward and forward housing sections 12a, 12b include coaxially opposed inlet and outlet nipples 14, 16 defining inlet and outlet passageways 14a, 16a, respectively. The inlet and outlet nipples 14, 16 may be provided with respective threaded regions 14a, 16a for threaded connection to process tubing supplying fluid to and discharging fluid from the housing 12.

The inlet and outlet passageways 14a, 16a communicate with the cylindrical interior 18 defined by the housing 1 . A generally cylindrical core element 20 is positioned within the cylindrical interior 18 of the housing 12 coaxially between the inlet and outlet passageways 14a, 16a, respectively. As is perhaps shown more clearly in accompanying

FIGURES 4-8, the core element 20 includes a pair of rearwardly projecting feet 22 disposed at the core element's proximal end 20a, and a pair of concentrically disposed seal flanges 24, 26 disposed at the core element's distal end 20b. A central passageway 28 extends between the proximal and distal ends 20a, 20b. The central passageway 28 is closed at the proximal end 20a by rear wall 30 and communicates with the outlet passageway 16a of the outlet nipple 16 via outlet opening 32.

A series of axially spaced-apart annular ribs (a representative few of which are identified in the drawing FIGURES by reference numeral 34) are disposed between the proximal and distal ends 20a, 20b of the core element 20. The annular ribs 34 support a filter membrane 36, for example, a PTFE microporous film (see FIGURES 2 and 3) and thereby define a plurality of channels (a representative few of which are identified in the drawing FIGURES by reference numeral 38) therebetween. Each of the channels 38 communicate with a respective one of a diametrically opposed pair of openings 40 which establish fluid communication between the channels 36 and the central passageway 28.

In use, fluid will flow into the housing interior 18 through the inlet passageway 14a. The rearwardly projecting feet 22 thereby serve as stand-off structures to ensure that the fluid entering the interior space 18 of the housing 12 flows into the concentric space established between the filter membrane 36 and the housing 12. The fluid will then be forcibly passed through the filter membrane 36 (i.e., due to fluid pressure difference between the higher pressure inlet passageway 14a and the lower pressure outlet passageway 16a) and thus filtered thereby. The now filtered fluid will therefore flow within respective annular channels 38 and into the central passageway through respective ones of the openings 40. The filtered fluid in the central passageway 40 may then flow on to the outlet passageway 16a.

As noted above, important to the present invention is the provision of the annular seal flanges 24, 26 at the distal end 20b of the core element 20. As shown, all structural elements associated with the core element 20 (including the feet 22, seal flanges 24, 26, rear wail 30 and the annular support ribs 34) are all formed as a unitarily as a one-piece structural unit. Most preferably, the core element and its structural elements are formed as a one-piece unit from a molded thermoplastic material. Preferably, the core element is formed from a thermoplastic fluorocarbon polymer, for example, a perfluoralkoxy fluorocarbon polymer (e.g., TEFLON^® PFA 440 HP and the like).

FIGURES 4-8 depict the core element 20 in a state prior to being seated within the interior space 18 of the housing 12. As shown, the seal flanges 24, 26 are most preferably in the form of relatively shallow-pitched

(e.g., about 30°) substantially conical sections which are concentrically disposed relative to the elongate axis of the core element 20. In use, as depicted in accompanying FIGURES 1-3, the seal flanges 24, 26 will be press-fit into, and be permanently deformed by, the internal cylindrical surface 18 of the rigid housing 12 thereby forming a tight fluid seal therebetween. During assembly, the distal end 20b of the core element 20 is forcible inserted within that portion of the interior 18 defined by the forward section 12b of housing 12. Thereafter, the rearward section 12a of housing 12 may be positioned in covering relationship to the core element 20 and abutted against the forward section 12b thereof. The juncture between the rearward and forward housing sections 12a, 12b, respectively, may then be rigidly joined to one another via welding, soldering or the like.

As is perhaps more clearly shown in accompanying FIGURE 3, when inserted forcibly into the interior space 18 of the housing 12, the seal flanges 24, 26 are each permanently deformed in such a way that the trailing edge of the downstream seal flange 24 overlaps a latitudinal plane 25 coincident with the leading edge of the adjacent upstream seal flange 26 (that is, a plane 25 which is transverse to the longitudinal (elongate) axis of the core element 20 and which is coincident with the annular leading edge of the seal flange 26 (see also FIGURES 5 and 7)). The seal formed by virtue of such permanently deformed seal flanges 24, 26 will therefore be quite reliable in use. Moreover, fluid pressure in use will tend to ensure that the seal flanges 24, 26 are maintained in fluid-tight sealing disposition with respect to the housing interior 18.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A fluid-filtration assembly comprising a rigid external housing defining fluid inlet and outlet passageways in fluid communication with a generally cylindrical interior cavity, and a core element having a coaxially separated pair of seal flanges in the form of generally conical segments, said generally conical segments being permanently deformed so as to establish a fluid-tight seal between said core element and said housing.

2. The fluid-filtration assembly as in claim 1 , wherein a trailing edge of a downstream one of said pair of permanently deformed seal flanges overlaps a latitudinal plane of a leading edge of an adjacent upstream one of said permanently deformed seal flanges.

3. The fluid-filtration assembly as in claim 2, wherein said pair of seal flanges are formed as one-piece structures with said core element.

4. The fluid-filtration assembly as in claim 1 , wherein said core element defines a central passageway having a proximal end blocked by a rear wall, and a forward end in fluid communication with said outlet passageway of said housing.

5. The fluid-filtration assembly as in claim 4, wherein said core element includes a series of longitudinally spaced-apart annular support ribs defining therebetween a series of longitudinally spaced-apart channels.

6. The fluid-filtration assembly as in claim 5, further comprising a filtration membrane supported by said annular support ribs between said proximal and distal ends of said core element.

7. The fluid-filtration assembly as in claim 5 or 6, wherein said core element includes a series of longitudinally spaced-apart apertures positioned so as to establish fluid-communication between respective ones of said annular channels and said central passageway.

8. The fluid-filtration assembly as in claim 4, wherein said core element includes at least one foot member extending rearwardly from said rear wall thereof.

9. The fluid-filtration assembly as in claim 6, wherein said filter membrane is a microporous polytetrafluoroethylene film.

10. A core element for a filtration assembly comprising a generally tubular body defining an interior passageway which is blocked at a proximal end by a rear wall, and is open at a distal end thereof so as to communicate with an outlet opening of a filtration housing in which the core is positioned, said core element having a coaxially separated pair of seal flanges in the form of generally conical segments, said generally conical segments being permanently deformable so as to establish a fluid- tight seal between said core element and the filtration housing, said seal flanges being sized and configured such that, when permanently deformed, a trailing edge of a downstream one of said pair of seal flanges overlaps a latitudinal plane of a leading edge of an adjacent upstream one of said seal flanges.

11. The core element as in claim 10, wherein said pair of seal flanges are formed as one-piece structures with said core element.

12. The core element as in claim 11 , which includes a series of longitudinally spaced-apart annular support ribs defining therebetween a series of longitudinally spaced-apart channels.

13. The core element as in claim 12, wherein said core element includes a series of longitudinally spaced-apart apertures positioned so as to establish fluid-communication between respective ones of said annular channels and said central passageway.

14. The core element as in claim 10, wherein said core element includes at least one foot member extending rearwardly from said rear wall thereof.

15. The core element as in any one of claims 10-14, molded as a one-piece unit consisting entirely of polytetrafluoroethylene.