WO2010014713A1

WO2010014713A1 - Filter with molded-in-place filter material

Info

Publication number: WO2010014713A1
Application number: PCT/US2009/052109
Authority: WO
Inventors: Edward Kandel
Original assignee: Illinois Tool Works Inc.
Priority date: 2008-08-01
Filing date: 2009-07-29
Publication date: 2010-02-04

Abstract

A fluid filter provides pleated sheet filter material with margins directly in-molded to the supporting housing. Pleat supports extending across the lumen of the housing may support the pleats at their fold edges.

Description

FILTER WITH MOLDED-IN-PLACE FILTER MATERIAL

CROSS REFERENCE TO RELATED APPLICATION

[0001] This Non-Provisional Application claims benefit to United States Provisional Application Serial No. 61/085,737 filed August 1, 2008 and hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to filter elements for filtering fluids and, more particularly, to an improved filter and method of fabricating the same.

BACKGROUND OF THE INVENTION

[0003] Fluid filters are used in a variety of applications including automobile fuel lines, washing machine water lines, medical IV or blood lines and the like, where they serve to filter foreign material from a flowing fluid including gases or liquids. Such filters may use a filter material in the form of a sheet, such as a porous nonwoven fabric, supported in a housing that defines a passageway through which the fluid must flow. The filter material is positioned in the passageway to intercept the flow, and may be pleated or corrugated to increase its surface area within the area of the passageway.

[0004] Desirably, the housing of a filter element provides walls that protect the filter material and that resist the pressure of flowing fluid. The housing may include end caps providing for connection points to other fluid conduits such as hoses, tubes or the like.

[0005] The design and construction of filter elements is complicated by the need to provide an appropriate seal between the walls of the housing and the filter material itself. For unpleated filter materials, this sealing may be accomplished by simply clamping the filter material between opposed planar surfaces forming a rim of the passageway. For pleated filters, the seal may be an adhesive applied to the edges of the pleated material attaching the edges to a rigid mounting frame that can be inserted into the housing. Leak-free adhesive seals of this type can be difficult to fabricate, particularly in small filter elements with small area passageways. SUMMARY OF THE INVENTION

[0006] The present invention provides a filter in which the margins of the filter material are molded directly into the housing during an injection molding process. Specially designed mold core pins provide the ability to pleat and support the filter material during the molding process. At the time of the molding, supporting ribs can be fabricated to support the pleats at the pleat edges thereby allowing thinner filter material and larger amplitude pleating for increased surface area in small passageways.

[0007] Specifically, the present invention provides a method of manufacturing a filter in which a sheet filter medium having margins is folded into pleats. A molding tool is used to support the pleats of the sheet filter medium and, while the pleats are so supported, to mold a rigid thermoplastic housing around the pleats to embed the margins within the thermoplastic, the thermoplastic housing defining a lumen through which fluid may pass by passage through the filter medium as retained and supported by the housing.

[0008] It is thus a feature of at least one embodiment of the invention to eliminate the need for a separate gasketing material or adhesive between the filter medium and the housing, simplifying construction and increasing the effective filter area by eliminating the area occupied by the gasketing or adhesive.

[0009] The lumen may curve at regions of the housing in which the margins of the pleats are embedded.

[0010] It is thus a feature of at least one embodiment of the invention to provide a fabrication technique that permits great flexibility in housing designs including housings that are cylindrical tubes.

[0011] The pleats may be substantially rectilinear to have fold edges where the sheet filter material is folded and a mold core of the molding tool may provide a passage at the fold edges allowing admission of thermoplastic to provide a supporting rib of thermoplastic passing along the fold edge and crossing the lumen.

[0012] It is thus a feature of at least one embodiment of the invention to provide pleat support structure, permitting the use of filter materials that are not self-supporting in the particular pleat configuration, for example, pleats of thin material or large amplitude pleats such as maximize filter surface area.

[0013] The rib may be adhered to a convex side of the fold edge.

[0014] It is thus a feature of at least one embodiment of the invention to provide a rib design that can be readily molded using simple injection molding tools.

[0015] The mold core of the molding tool may provide inwardly extending ledges from opposite inner walls of the lumen to support fold edges of the pleats adjacent to the walls of the housing orienting the sheet material to pass into the walls of the housing along a plane substantially perpendicular to an axis of the lumen.

[0016] It is thus a feature of at least one embodiment of the invention to permit molding tools to part along a single plane while clamping ends of the filter medium for stability.

[0017] The molding tool may include at least one core components moving to define the lumen, the core component having pleat formers for forming the sheet filter medium into the pleats as the core component moves.

[0018] It is thus a feature of at least one embodiment of the invention to provide a molding tool that both pleats the filter material and molds the same into the housing.

[0019] The pleat formers may include a truncated triangular prism element, a truncated apex of the prism providing passage for a supporting rib attached to a pleat fold.

[0020] It is thus a feature of at least one embodiment of the invention to provide a method of both forming pleats and molding ribs using the same mold cores.

[0021] The present invention also includes the resulting filter having a thermoplastic housing providing a rigid housing defining a lumen through which fluid may pass along an axis between an entrance aperture and an exit aperture. A sheet filter medium is formed in substantially rectilinear pleats having fold edges and unfolded margins and supported within the lumen between the entrance aperture and exit aperture so that the fold edges are substantially perpendicular to the axis. The unfolded margins are embedded in the thermoplastic housing so that fluid may pass through the lumen only by passing through the sheet filter medium. [0022] It is thus a feature of at least one embodiment of the invention to provide an improved filter eliminating adhesive or gasket material that may interfere with fluid flow or provide a source of contamination or leakage.

[0023] Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.

BRIEF DESCRIPTION OF THE FIGURES

[0024] Fig. 1 is a perspective view of an embodiment of a filter of the present invention having a housing (in phantom) holding a pleated filter material;

[0025] Fig. 2 is a cross-sectional view through the filter of Fig. 1 showing the position of ribs supporting the pleated filter material;

[0026] Fig. 3 is perspective view of a molding system, in an open state, suitable for producing the filter of Figs. 1 and 2;

[0027] Fig. 4 is a cross-section taken along lines 4-4 of the molding system of Fig. 3 in a closed state;

[0028] Fig. 5 is a figure similar to that of Fig. 4 showing the molding system in a closed state immediately prior to the injection of thermoplastic;

[0029] Fig. 6 is a cross-sectional view similar to that of Fig. 2 of an alternative embodiment of the filter of the present invention showing multiple pleats and end caps providing for connections to second fluid conduits;

[0030] Fig. 7 is a plan view of the filter of Fig. 2 showing portions of filter material outside of the housing that are removed during the manufacturing process; and

[0031] Fig. 8 is a view of the precut filter blank that may be used in the present invention;

[0032] Fig. 9 is a perspective view of a transparent housing having flexible double walls for priming operation; and

[0033] Fig. 10 is a front elevation overview of the housing of Fig. 9 showing compression of the outer walls without distortion of the inner filter supporting walls. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] Referring now to Figs. 1 and 2, the present invention provides a filter element 10 having an outer housing 12 defining a lumen 14 through which a fluid (not shown) may pass between an entrance aperture 16 and an exit aperture 18. In one embodiment, as depicted, the housing 12 may be a substantially cylindrical tube extending along an axis 20.

[0035] Positioned within the lumen 14, is a sheet filter material 22 being, for example, a porous nonwoven or woven fabric, screen or mesh, having pore sizes selected to filter foreign material from the fluid passing through the lumen 14. The sheet filter material 22 may be formed in a pleat to increase its surface area within the cross- section of the lumen 14.

[0036] In this embodiment, a single triangular pleat is formed having an apex 24 centered within the lumen 14 and base edges 26 attached to an inner wall of the housing 12. The apex 24 follows a fold edge 30 of the sheet filter material 22 along an axis perpendicular to axis 20 providing equal acute angles between the axis 20 bisecting the pleat and two downwardly extending portions of the sheet filter material 22 as pass from the apex 24 to the base edges 26. The base edges 26 follow fold edges 34 of the sheet filter material 22 directing the downwardly extending portions outward along cross-sectional plane 38 normal to axis 20 into the walls of the housing 12.

[0037] In one embodiment, a thermoplastic rib 32 spans the cross-section of the lumen 14 perpendicular to the axis 20 and along the fold edge 30 to support an outside or convex face of the fold edge 30 at the apex 24. The rib 32 is adhered to the sheet filter material 22 during the molding process in which molten thermoplastic of the rib 32 fuses to or infuses into the sheet filter material 22.

[0038] Similarly, thermoplastic ledges 36 extend inwardly from the walls of the housing 12 near the base edges 26 to support an underside or convex face of fold edges 34 at the base edges 26 as similarly adhered to the sheet filter material 22. Margins 40 of the periphery of the sheet filter material 22 at the base edges 26 and all along the pleat near the outer edge of the lumen are embedded in the walls of the housing 12. In this way all fluid passing between the entrance aperture 16 and the exit aperture 18 must pass through sheet filter material 22.

[0039] Referring now to Fig. 3, the filter of Figs. 1 and 2 may be fabricated in an injection molding process employing a molding tool 41 providing first and second opposed mold halves 42 and 44 and corresponding opposed first and second mold cores 46 and 48 each independently movable along axis 50 generally corresponding to axis 20 of the molded filter element 10. In one embodiment as depicted, each mold half 42 and 44 may provide for concentric first cylindrical bores 52 and 54 and second cylindrical bores 56 and 58, respectively, aligned with axis 50. The first bores 52 and 54 are of greater diameter than the second bores 56 and 58 and define by their diameter the outer diameter of the housing 12. The second bores 56 and 58 are equal to the diameter of the inner wall of the housing 12 and match the diameter of the shafts of the mold cores 46 and 48, respectively, passing therethrough. The larger bores 56 and 58 are positioned adjacent to opposed faces 60 of the mold halves 42 and 44, such faces 60 that abut during molding, and the bores 52 and 54 are displaced to the outer edges of the mold halves 42 and 44.

[0040] As noted, the shafts of the mold cores 46 and 48 are cylindrical and aligned with axis 50 and with axes of the bores 52 and 54 to slide through the bores 52 and 54 in a manner that provides sealing against passage of molten thermoplastic. Opposed faces 62 of the mold cores 46 and 48 that abut during the molding process provide pleat formers 64 and 66 being approximately complementary shapes so as to interfit when the mold cores 46 and 48 are brought together. The pleat former 64 for a single pleat, per the filter element 10 of Fig. 1, is a triangular prism having a cross-section that is nearly an isosceles triangle conforming generally to the pleated surface of the sheet filter material 22 shown in Figs. 1 and 2. The apex of the prism of pleat former 64 nearest mold core 46 is truncated or flattened to provide a passageway for the rib 32 described above. Conversely, the pleat former 66 is a triangular notch whose walls describe a triangular prism complementing that of the pleat former 64 except for the truncation of the apex of pleat former 64.

[0041] As depicted, and in one embodiment, a spool 68 of sheet filter material 22 positioned outside the molding tool 41 may feed sheet filter material 22 between the faces 60 of the mold halves 42 and 44 along the cross-sectional plane 38 normal to the axis 50 where the mold halves 42 and 44 abut when the molding tool 41 is closed. The sheet filter material 22, as so positioned, may advance between molding operations as will be described.

[0042] Referring now to Fig. 4, during a first stage of the molding operation, sheet filter material 22 may be advanced between the mold halves 42 and 44, and the open mold cores 46 and 48 may be brought together along axis 50 while mold halves 42 and 44 remain separated. This process of drawing together mold cores 46 and 48 gathers a portion of the sheet filter material 22 between the pleat formers 64 and 66 beginning the formation of a single pleat as shown. During this time, a slight tension 67 may be maintained on opposite ends of the sheet filter material 22 to pull the sheet filter material 22 tightly over the pleat former 64.

[0043] Referring now to Fig. 5, once the mold cores 46 and 48 are abutting, completing the formation of the pleat, the mold halves 42 and 44 may be brought together around the mold cores 46, clamping the sheet filter material 22 therebetween in a manner to prevent the egress of thermoplastic material. The early stages of this clamping may be used, in part, to provide the tension 67 on the sheet filter material 22 described above.

[0044] At this time, the sheet filter material 22 will be pulled tightly against the apex of pleat former 64 leaving a channel 70 between the apex of the pleat former 64 and the corresponding mating pleat former 66. This channel 70 may be filled by thermoplastic material through an injection port (not shown) providing thermoplastic for the housing 12 and for the supporting rib 32 for the sheet filter material 22. Similarly, the sheet filter material 22 near the base edges 26 may be pulled tightly against the pleat former 66 leaving a channel 72 between corresponding portions of the pleat former 64 and 66 such as forms the ledges 36 extending inwardly from bores 58 and 56 of the mold halves 42 and 44. The inner walls of the bores 56 and 58 and outer walls of the shafts of mold cores 46 and 48 also provide channel 80 that forms the wall of the housing. When these channels 72, 80, and 70 are filled with thermoplastic material per conventional molding techniques, the sheet filter material 22 will be fully supported and sealed with in housing 12. [0045] Referring now to Fig. 7, per the above molding process, the margins 90 of the sheet filter material 22 will be wholly embedded within the housing 12 of the filter and in one embodiment, depicted in Fig. 7, the sheet filter material 22 may be trimmed by a die cutting operation during molding by cutting edges incorporated into the mold halves 42 and 44 or elsewhere to remove excess material. Alternatively as shown in Fig. 8, the sheet filter material 22 may be pre-trimmed to provide a first tapering curvilinear sections 82 on either side of a line of the fold edge 30 and second arcuate sections 84 conforming generally to the cuts that would be made as described in Fig. 7. Preferably the trimming of the sheet filter material 22 is such that it does not extend through the walls of the housing.

[0046] Referring now to Fig. 6, the present invention contemplates at the housing 12 may be joined to end caps 86 (only one shown) either separately attached or integrally molded to the housing 12 and that may provide junctions communicating with tubing or hoses 88 or the like. Similarly, multiple pleats may be formed from the sheet filter material 22 with multiple supporting ribs 32 using the technique described above. It will be understood that the housing 12 need not be cylindrical but maybe of arbitrary shape.

[0047] The thermoplastic material used in the molding may be a conventional polymer or may be other materials including electrically conductive materials. The sheet filter material 22 may also be material such as metal screens or other filter media.

[0048] Referring now to Fig. 9, in yet a further embodiment, the housing 12 may be rectangular in outline to provide a generally rectangular cross-sectional lumen 14 with integrally molded end caps 86 to define an internal filter volume. In this design, the margins 40 of the filter material may be embedded in first opposed housing walls 92a and 92b respectively, the latter extending the full height of the filter volume along axis 50 but only a portion of the width of the filter volume to allow fluid flow there about. The housing walls 92a and 92b are contained inside of outer housing walls 94a and 94b parallel to and flanking housing walls 92a and 92b and within housing walls 96a and 96b perpendicular to housing walls 94a and 94b and attached thereto and perpendicular to housing walls 92a and 92b but not attached thereto. These walls of the housing 12 may be molded of the transparent flexible material such as vinyl. [0049] As shown in Fig. 10, a user may grasp the outer surface of the housing 12 with their fingers and thumb 100 pressing on the walls 94a and 94b to compress the walls 94a and 94b inward to reduce the internal filter volume to provide a priming or slight pumping action thereby. This distortion of walls 94a and 94b is isolated from the inner walls 92a and 92b preventing undesired tension or distortion of the filter material 22 held thereby.

[0050] Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.

[0051] Various features of the invention are set forth in the following claims.

Claims

CLAIMSWe claim:

1. A method of manufacturing a filter comprising:

(a) forming a sheet filter medium having margins into pleats;

(b) using a molding tool to:

(i) support the pleats of the sheet filter medium;

(ii) while the pleats are so supported, mold a rigid thermoplastic housing around the pleats to embed the margins within the thermoplastic, the thermoplastic housing defining a lumen through which fluid may pass by passage through the filter medium as retained and supported by the housing.

2. The method of claim 1 wherein the lumen provides a curved wall at regions of the housing in which the margins of the pleats are embedded.

3. The method of claim 1 wherein the pleats are substantially rectilinear to have fold edges where the sheet filter material is folded and wherein a mold core of the molding tool provides a passage at the fold edges allowing admission of thermoplastic to provide a supporting rib of thermoplastic passing along the fold edge and crossing the lumen.

4. The method of claim 3 wherein the rib is adhered to a convex side of the fold edge.

5. The method of claim 1 wherein the pleats are substantially rectilinear to have fold edges where the sheet filter material is folded and wherein a mold core of the molding tool provides inwardly extending ledges from opposite inner walls of the lumen to support fold edges adjacent to the walls of the housing orienting the sheet material to pass into the walls of the housing along a plane substantially perpendicular to an axis of the lumen.

6. The method of claim 1 wherein the sheet filter medium is initially a substantially continuous strip and including the step of cutting the sheet filter medium during molding of the housing.

7. The method of claim 1 wherein the sheet filter medium is initially a substantially continuous strip and including the step of pre-cutting the sheet filter medium to remove portions that would extend outside of the housing before molding of the housing.

8. The method of claim 1 wherein the molding tool includes at least one components to define the lumen, the component having pleat formers for forming the sheet filter medium into the pleats with movement of the mold tool component.

9. The method of claim 8 wherein the pleat formers include a truncated triangular prism element, a truncated apex of the prism element providing passage for a supporting rib attached to a pleat fold.

10. The method of claim 8 wherein the molding tool provides mold halves defining an outer surface of the housing wherein the mold halves clamp a portion of the sheet filter medium before injection of a thermoplastic material.

11. The method of claim 8 wherein the mold halves close and separate along an axis parallel to the axis of the lumen.

12. A filter comprising: a thermoplastic housing providing a rigid housing defining a lumen through which fluid may pass along an axis between an entrance aperture and an exit aperture; a sheet filter medium formed in substantially rectilinear pleats having fold edges and unfolded margins and supported within the lumen between the entrance aperture and exit aperture so that the fold edges are substantially perpendicular to the axis and the unfolded margins are embedded in the thermoplastic housing so that fluid may pass through the lumen only by passing through the sheet filter medium.

13. The filter of claim 12 wherein the lumen provides a curved wall at regions of the housing in which the unfolded margins of the pleats are embedded.

14. The filter of claim 12 further including thermoplastic supports supporting the fold edges along lengths of the fold edges extending perpendicular to the axis.

15. The filter of claim 14 wherein the supports are adhered to a convex side of the fold edges.