Provisional Application 60/548,490, filed February 25,2004 and U. S. Provisional Patent Application 60/, filed January 14,2005.. The disclosure of U. S. Provisional Application 60/548, 490 and U. S. Provisional Application 60/are incorporated herein by reference, to the extent that is consistent with the present disclosure.

Field of the Invention The present disclosure concerns media arrangements for liquid filters.

It particularly concerns arrangements in which the media is pleated, and is supported by a support screen arrangement. The techniques can be used in preparation of filter cartridges, for liquid filtering. Examples are in filters for: lubricating fluid (oil); hydraulic fluid; or, fuel.

Background Many mechanical systems require the use of filter arrangements, for liquid flow therein. For example, filter arrangements are known for filtering lubricating fluid (oil); hydraulic fluids; and/or fuel. In general, such arrangements involve use of media through which the liquid to be filtered is passed, in use.

The media of such filter arrangements have generally been designed and constructed from: (a) cellulose and/or other natural fibers alone; (b) blends of natural fibers and synthetic fibers; or (c) 100% synthetic fibers. Examples of synthetic fibers include: organic polymeric fibers; glass fibers; quartz fibers ; and, ceramic fibers.

Typically the media is formed, from the various fibers, into a non- woven, sheet form. A variety of processes are used for preparation of the fibrous sheets, including, for example, wet laid techniques and dry laid techniques.

Within such media, various types of adhesives are typically applied to hold the fibers together. The adhesives are generally applied in either liquid, solid or gaseous form. The choice of adhesive is dependant on the structural characteristics appropriate for the end use. In many filters, the sheet of media is impregnated or saturated with a low viscosity liquid adhesive or binder. The binder content usually ranges from less than 5% (based on the overall weight of the impregnated web or sheet) to about 30%, for typical filtration media.

The resin content of filtered media is rarely applied over 30% by weight, because porosity of the media reduces as the resin content increases, due to filming caused by the adhesive. Also, sometimes the resulting media can become relatively brittle, with high resin contents, making it difficult to form the media into desirable shapes.

In some instances, the resin impregnated sheets are cut into discs or other patterns and are stacked to form cylindrical objects, which are then assembled into filter elements. In other instances, the media is pleated and assembled into the form of a filter element. This disclosure particularly concerns pleated media.

In general, pleating media provides for a relatively large surface area of filter media, within a given size of element. Pleated media is sometimes used in the planar (except for the pleats) form of a filter panel; or sometimes it is wrapped or coiled into a tubular configuration, for example a cylindrical configuration.

With many liquid filtering systems, as discussed below, support is needed for the media, in order to ensure media integrity during use. A variety of support structures are known, including woven wire mesh or extruded plastic screens.

In general, it is a desirable to provide spacing between adjacent pleats, to keep the area between the adjoining pleats open for passage of liquid therethrough, for efficient use of the media. With some screen systems this can be a problem. Also, where the media engages the support, especially at pleat tips, undesirable levels of abrasion of the media can occur with some screens.

Improvements in arrangements involving pleated media and support structures, to address the two identified concerns, have been sought. Efforts are ongoing.

Summary of the Invention According to the present disclosure, a preferred screen or screen arrangement for use in a pleated filter media/screen arrangement is provided. The preferred screens are configured to be positioned along the media, and to be pleated with the media. In general, the screens comprise: a plurality of major strands extending in a direction of at least 30°, and typically perpendicular, to the direction of extension of the pleat tips of the pleated media; and a minor strand network comprising a plurality of minor strands extending between the major strands. In general, the preferred screen has a smooth side and a rough or ribbed side. On the rough or ribbed side, the major strands project outwardly in relief from the minor strand network at least a preferred amount. Preferably the projection of relief, on the rough side, outwardly from the minor strand network is 0.24 mm or more.

Typically, it is in the range of 0.3-0. 4 mm. Preferably this relief difference is not more than 0.5 mm, although in some instances it could be.

On the smooth side, it would be useful if the major strand network is co-planar with the minor strand network. However, typically the minor strand network will project outwardly from the major strand network an amount of no more than 0.25 mm, typically 0.2 mm or less, and in some instances 0.1 mm or less.

Typically the minor strand network projects outwardly from the major strand network, on the smooth side, no more than 85% of the major strand network thickness. Preferably this projection is no more than 65% of this thickness ; and, typically no more than 60% of this thickness. If the major strands project outwardly from the minor strands, on the smooth side, it is no more than 0.25 mm preferably no more than 0.2 mm and in some instances 0.1 mm or less. The relative thicknesses (major and minor) would still be as previously defined. Most preferably, the major strands do not project outwardly from the minor strand network on the smooth side.

For the above, it will be understood that in some instances the issue relates not only to the specific amount of projection, but also to relative amount of

projection. Thus the smallest preferred projection relief on the rough side, 0.24 mm, is about the same as the largest acceptable projection on the smooth side (0.25 mm).

However, it is also preferred that the actual projection on the smooth side not be more than 85%, typically not more than 65% (and preferably not more than 60%) of the major strand thickness. The condition that the two projections be the same, is to be avoided. As a result, the screens are non-symmetric (asymmetric) with respect to surface roughness characteristics on opposite sides.

The thickness of the preferred screens, in some instances corresponding approximately to the thickness of the major strands plus the minor strands, is typically at least 0.3 mm, often within the range of 0.3-1. 4 mm inclusive.

The pleated screens are preferably used at least on the downstream side of the pleated media, and can be used on both sides of the pleated media, to advantage. Preferably the screens are co-pleated with the media, to form preferred pleated filter media/screen arrangements, according to the present disclosure. These pleated filter media/screen arrangements can be used in a variety of filter configurations, including cylindrical ones in which the pleated media/screen arrangements are configured in a cylinder, positioned to extend between first and second opposite end caps. Other useful arrangements include panel arrangements.

In general, methods of assembly and use are provided, as well as preferred dimensions and configurations for the screens.

Brief Description of the Drawings Fig. 1 is a fragmentary perspective view of a sheet of pleated media.

Fig. 2 is a plan view of a first support screen, for use with pleated media.

Fig. 3 is a cross-sectional view taken along lines 3-3, Fig. 2.

Fig. 4 is a plan view of a second support screen for use with pleated media.

Fig. 5 is a plan view of a third screen support for use in supporting media.

Fig. 6 is a cross-sectional view taken along line 6-6, Fig. 5.

Fig. 7 is a schematic plan view of a first preferred screen pattern for use in supporting media according to the present disclosure.

Fig. 8 is a schematic, fragmentary, enlarged view of a portion of Fig.

7.

Fig. 9 is an enlarged, fragmentary, schematic, cross-sectional view of the screen pattern depicted in Fig. 8, taken alone line 9-9 thereof.

Fig. 9'is an alternate enlarged fragmentary schematic cross-sectional view of the screen pattern depicted in Fig. 8, taken along line 9-9 thereof.

Fig. 10 is a schematic, fragmentary perspective view of two extensions of the screen depicted in Fig. 7, positioned on opposite sides of an extension of media, to form a media/screen arrangement.

Fig. 11 is an enlarged schematic, fragmentary view of a portion of the media/screen arrangement depicted in Fig. 10.

Fig. 12 is a schematic plan view of a second improved screen according to the present disclosure.

Fig. 13 is a schematic fragmentary, enlarged view of a portion of Fig.

12.

Fig. 14 is an enlarged, schematic, cross-sectional view of the screen pattern depicted in Fig. 13, taken along line 14-14 thereof.

Fig. 14'is an alternate enlarged schematic cross-sectional view of the screen pattern depicted in Fig. 3, taken along line 14-14 thereof.

Fig. 15 is a schematic, fragmentary perspective view of a media/screen arrangement including two extensions of the screen depicted in Fig. 12 on opposite sides of an extension of media.

Fig. 16 is an enlarged, schematic, fragmentary view of a portion of the media/screen arrangement depicted in Fig. 16.

Fig. 17 is a schematic plan view of third preferred screen pattern for use in supporting media according to the present disclosure.

Fig. 18 is an enlarged, schematic, fragmentary view of a portion of Fig. 17.

Fig. 19 is an enlarged schematic, cross-sectional view taken along line 19-19, Fig. 18.

Fig. 19'is an alternate enlarged schematic cross-sectional view taken along line 19-19, Fig. 18.

Fig. 20 is a schematic, fragmentary perspective view of a media/screen arrangement including two extensions of the screen depicted in Fig.

17, on opposite sides of an extension of media.

Fig. 21 is an enlarged, schematic, fragmentary view of the media/screen arrangement depicted in Fig. 20.

Fig. 22 is a schematic view of a filter element having pleated media.

Fig. 23 is an enlarged, schematic, view of a pleated media/screen arrangement useable in the element of Fig. 22.

Fig. 24 is an enlarged view of a portion of Fig. 23.

Fig. 25 is an efficiency curve plot, for certain comparative examples.

Fig. 26 is a loading curve plot, for certain comparative examples.

Fig. 27 is a schematic, fragmentary view of pleated media having a first media/screen arrangement.

Fig. 28 is a schematic, fragmentary view of pleated media having a second media/screen arrangement.

Fig. 29 is a schematic, plan, view of an alternate screen arrangement.

Fig. 30 is a schematic, fragmentary, cross-sectional view of a portion of Fig. 29, taken along line 30-30 thereof.

Fig. 30'is an alternate schematic fragmentary enlarged cross- sectional view of a portion of Fig. 29, taken along line 30-30 thereof.

Fig. 31 is a plot of pressure drop versus flow rate, for a variety of screen arrangements according to a experiment described herein.

Detailed Description I. The Issue of Supporting Pleated Media, Generally.

The reference numeral 1, Fig. 1, generally indicates a section of pleated filter media. The media would typically be used for filtering liquids, such as lubricating fluids, fuel or hydraulic fluids. That is, the figure depicts filter media 2 which has been pleated into a plurality of parallel pleats 3. In typical use, the pleated media 1 would be either used in a panel filter, or it would be coiled, for example into a cylindrical pattern, for use as a cylindrical filter element. While a variety of alternate shapes are also possible, these are the most common. In Fig. 1,

only a short, schematic, extension of media 2 is shown. Typical filter elements would use more pleats and with closer pleat spacing.

Individual pleats 3 are generally formed by folding, creasing or scoring the media along various parallel lines, to create two sets of opposite or alternating pleat tips 3a, 3b, each pleat tip 3a or 3b being separated from a next adjacent, opposite, pleat tip, 3b or 3a, by a pleat face or panel 3c.

Especially when used to filter liquid having a viscosity of greater than 35 cP (centipoise) typically the filter media surface 3c needs to be provided at least with some downstream support, or it is likely to be damaged and possibly fail.

Further, as the space between the pleats becomes very close, in a media having very large number of pleats per volume, the pleats tend to collapse against one another, especially under liquid flow. This type of collapse tends to reduce filter capacity or increase restriction.

Herein the term"pleat direction"and the term"machine direction" will sometimes be used to refer to media constructions. In this context, the term "pleat direction"is meant to refer to the direction of longitudinal extension of the edges and troughs of the various pleats. Typically the pleats extend parallel to one another, although being flexible they sometimes bend; and, for any given pleat the general direction of longitudinal extension is considered the pleat direction.

Referring to Fig. 1, the pleat direction is generally indicated by the double headed arrow designated at reference numeral 5.

The machine direction is orthogonal or perpendicular to the pleat direction, along the extension of the media. In Fig. 1, the machine direction is generally indicated by double headed arrow 6. The term"machine direction"when used to refer to a direction of extension of the media orthogonal or perpendicular to the pleat direction, is an artifact from the typical method of operation of equipment to form the pleated media. Typically the media is pleated in a direction orthogonal or perpendicular to the direction the media moves through the pleating equipment.

In this disclosure, the term"machine direction"is sometimes applied without specific regard to the particular method or operation to form the pleats; and, it is used simply to indicate the direction of extension of the media generally perpendicular to the pleats. If the media construction is coiled, for example in a tubular construction with the media forming a star shape in cross-section (i. e. , with pleats extending longitudinally along the length of the tube), the machine direction

for the media will generally be the direction circumferential to the tube and perpendicular to a central longitudinal axis of the tube. The term"machine direction"herein, is used interchangeably with the term"media direction orthogonal to pleat direction." In typical operation, liquid to be filtered is passed through the pleated media. The liquid deposits contaminant on an upstream surface of the media, or in the media by entrance into the upstream side. The deposited contaminant causes an increase in restriction to flow across the media. In time, the media becomes sufficiently occluded that the restriction is increased to a point for recommended servicing, typically by shutting down equipment and replacing structure containing the filter media.

Collapse of the media pleats, can cause premature increase in restriction and loss of preferred filter operation. Damage to the media can cause loss of efficiency.

A. The issue of media support.

In general, the media can be supported open (i. e. , against collapse), by utilization of a screen positioned to extend along a surface of the media, at least on the downstream side of the media. Typically the media is positioned with a support screen on both the upstream and the downstream side, sometimes referenced herein as a two-screen application. In typical two-screen applications, the screens are co-pleated with the media; i. e., the media (flat, non-pleated) is placed between two sheets of screen, and then the resulting structure is pleated, with the pleating process simultaneously pleating both the media and the screens. Herein, pleated media having a pleated screen on at least one side thereof, will sometimes be referenced as a pleated filter"media/screen construction or arrangement, "or by similar terms.

In this context, support screens, which are positioned against the media surfaces, should not be confused with pleat tip liners, not shown, which are typically non-pleated cylindrical constructions adjacent pleat tips (for example in cylindrical filters).

Attention is now directed to Fig. 27 in which a pleated media/screen arrangement 10 is shown, made using a specific type of screen similar to that of Fig.

2, discussed below. Such a screen can provide for some support to the media.

Unfortunately, the shape of such a screen does not operate well to provide for spacing and maintenance of spacing, in use. This concept will be understood, from a more close review of Fig. 27.

Referring to Fig. 27, again depicted at 10 is the pleated media/screen (or media/liner) construction. The pleated media/screen construction 10 generally comprises media 11 positioned between opposite screens 12 and 13. Screen 12, for example, may be a downstream screen and screen 13 an upstream screen. By this, it is meant that in normal use liquid would be directed through media/screen arrangement 10 in the direction of arrow 15. For the example of Fig. 27, screens 12, 13 are the same.

Referring to Fig. 27, for convenience the pleat direction is shown by double headed arrow 16 and the orthogonal, machine, direction is shown by double headed arrow 17.

In typical use, the pleated media/liner construction 10 would be positioned as part of either a panel filter or a filter having the media in a tubular form, for example a cylindrical form. For the following description it is assumed that it would be operated in one or the other of these forms. When positioned in such forms, the individual pleats may be distorted in shape from the particular depiction of Fig. 27.

Still referring to Fig. 27, the upstream pleat tips are indicated at 18, and the downstream pleat tips are indicated at 20. In this context, the term "upstream"is meant to refer to those pleats that are directed toward the direction of liquid flow entry into the media/liner construction 10, during normal filtering use in a filter apparatus. The term"downstream"is meant to refer to those pleats that point in the downstream direction, during normal filtering flow of liquid through the media/screen construction 10. Of course in a typical filter media/screen construction 10, each upstream pleat tip 18 is positioned between two, adjacent, downstream pleat tips 20; and, each downstream pleat tip 20 is positioned between two, adjacent, upstream pleat tips 18; except for end pleats in the instance of a panel construction.

The extension of media between any two adjacent pleat tips, is sometimes referred to as a pleat media surface (having opposite upstream and downstream surfaces).

As mentioned above, in typical use, the media/screen construction 10 is configured in a filter arrangement. In one type of arrangement, the filter

arrangement would be a frame or panel filter, in which media/liner construction 10 would be positioned with upstream pleat tips 18 generally in a first plane, and the downstream pleat tips 20 generally in a second plane, the media being secured in this configuration by a frame or other arrangement.

There are still other types of media constructions, sometimes referred to herein as tubular or coiled media arrangements, in which the media/screen construction 10 is curled or coiled into a tubular configuration, defining an open central area. Typical such tubular configurations are cylindrical, although alternative shapes are possible. Generally with such arrangements, opposite ends of the tubular construction are potted or embedded in end caps, although alternatives are possible. An example of such an arrangement is described below.

Typically, during formation into a panel construction or tubular construction, the media/liner combination 10 is configured to provide for a desirable (sometimes optimal or maximal) number of pleats within the volume provided. This is because longevity of the filter construction, before it needs to be refurbished or replaced, is generally a function, at least in part, of the amount of media surface area available for filtering.

As the pleated media/liner combination 10 is configured and packed into a defined media volume, pleat tips 18, 20 will be moved very close to one another, for example pleat tip populations on the order of about 8 to 12 pleat tips per inch, (about 3.1-4. 7 pleat tips per cm), along the inside (typically the downstream side) are common for coiled or tubular arrangements, especially when configured for out-to-in filtering flow. When compressed in this manner, adjacent flat surfaces (faces) of the pleats, on either side of the media, may tend to press toward one another, collapsing the pleats somewhat against filtering flow entering between the pleats. This can undesirably increase restriction to liquid flow, during use.

This type of restriction problem, is sometimes observed when screens of the type depicted in Figure 2 are used, for example on the downstream side of the media. Referring to Fig. 27, this collapse at the downstream side will be understood by reference to the following description. In connection with this, attention is directed to one specific pleat 24 having pleat faces or sides 25,26 separated by upstream pleat tip or edge 24a. Under pressure in the direction of arrow 15, sides 25,26 will generally tend to be biased or compressed toward one another and adjacent pleats may also compress. This type of pleat collapse, will generally reduce

capacity, increase restriction or reduce free flow of liquid in the general direction of arrow 15, through the construction. As will be understood from the discussion herein below, a screen such as that depicted in Fig. 2, is not well configured to resist this type of pleat distortion or collapse.

Herein, when the term"thickness"is used with respect to the screen or a portion of a screen, reference is meant to the dimension through the screen, as opposed to in a direction of the extension of the screen along the surface of the media.

The screen type of Fig. 2 would typically either be a woven wire mesh, or an extruded plastic mesh. Wire screens are typically about 0.014-0. 02 inches (0.35-0. 51 mm) thick in cross-section, i. e. , 2x a typical strand thickness of 0.007-0. 010 inch (0.17-0. 254 mm). Bi-planar extruded plastic screens like Figs.

2-4, discussed below, are also typically 0.014-0. 02 inches (0.35-0. 51 mm) thick; i. e. , 2x strand thickness of 0.007-0. 01 inch (0.35-0. 254 mm).

In Fig. 2, the weave or mesh pattern of screen 12 is such that, when used, both sets of the individual strands extend at an angle relative to the outside perimeter 27 of the screen, and thus eventually, when used to support the media in a pleated media/screen arrangement, the strands will extend at an acute angle to: the machine direction of the pleats, indicated at arrow 28, Fig. 2; and also to the direction which will eventually be the pleat direction of the pleats, indicated at arrow 29, Fig. 2.

As indicated above, in some instances the screens 12,13 would each be a wire mesh. When a wire mesh is used, generally the wires are either woven or secured in a pattern involving two sets of wires, each set comprising wires parallel to with one another; the two sets being oriented to extend generally perpendicular to one another. With an extruded screen of the type used in Fig. 2, in some instances a similar construction, but using an extruded material such as plastic, results.

However in this instance, each set of parallel strands is in a plane, and not a weave.

Such constructions are sometimes referenced as bi-planar. Screen 30, Fig. 2, could be made of a bi-planar extruded screen. In Fig. 3, the two planes, 31,32, formed by strands 33,34 respectively, can be seen.

In general, the types of screens represented by screen 30, Fig. 2, have similar surface characteristics on each side. That is, the surface profile of each side is the same.

The term"relative relief'when used herein in the context of screen side, is not meant to reference the thickness through the screen. Rather it is meant to indicate the relative peaks and valleys in the screen encountered, in movement across a surface. Alternatively stated, for a bi-planar extruded structure, such as in Figs. 2-3, looking at a surface, each (first) strand in that surface defines a peak, and each underneath (second) strand at locations between the (first) strands defines a valley in that surface.

Relatively smooth, thin, surfaces for the mesh or screen, are generally good with respect to contact with the media, since they do not provide rough features that rub against the media, abrading it undesirably, during use.

Typically screens for use with media are constructed to be at least about 60% open, typically at least 65-70% open, i. e. , to be occupied by aperture over at least 60% of the area defined by the outside perimeter of the screen, for good flow and loading characteristics. Screen 30, Fig. 2, has such a characteristic.

Screen 35 depicted in Fig. 4 is similar to the screen 30 depicted in Fig. 2, except in screen 35 the individual strands of the woven mesh or extrusion that extend generally with one strand set 37 parallel to the eventual machine direction 38 and one strand set 39 parallel to the eventual pleat direction 40.

As indicated previously, screens of the type characterized in Figs. 2 and 4, have identical opposite sides, with respect to relative relief. The opposite sides of the screens are thus generally of equal smoothness, since they are either identical, are mirror images of one another or are the same except for one being rotated 90° from the other, with respect to surface texture, pattern or relief.

B. A modified screen pattern.

In order to generate better pleat spacing or resistance to pleat collapse, screens can be used which have configurations such as that shown in Figs.

5 and 6.

In Fig. 5, a molded plastic screen 41 is shown. The screen 41 includes parallel major strands 42 which extend generally parallel to one another and to opposite sides 43a, 43b of an outer perimeter edge 43 of the screen 41. In use, the screen 41 is positioned so that the major strands 42 extend in the eventual machine direction 44a of the media pleats (i. e. , perpendicular to the pleat direction 44b).

Herein, the term"major strands"is used to indicate thicker strands (relative to other strands), in a screen.

The major strands 42 are interconnected by a network 45 of minor strands 46, which in this instance include at least some strands 46a that extend between (and in the examples shown in Fig. 5 generally perpendicular to) the major strands 42. As such in use they would extend generally in the pleat direction 44b.

Within the particular arrangement shown in Fig. 2, optional, additional minor strands 46b, parallel with the major strands 42, are included in the minor strand network 45. Herein, the term"minor strands"is meant to indicate thinner strands (in thickness relative to major strands) in a screen.

In Fig. 6, a cross-sectional view of the screen arrangement 41 of Fig.

5 is depicted. Referring to Fig. 6, the screen 41 has opposite sides 50, 51. The major strands 42 provide for relief outwardly from the minor strand network 45, in opposite directions.

Referring to Fig. 6, the thickness of the major strands 42, is typically about 1.7-2. 5 mm. The thickness of the minor strands is typically about 1.4-2. 1 mm.

Typically for a screen 41 such as that depicted in Figs. 5 and 6, the extent of relief afforded by the major strands 42 in each opposite direction, outwardly from the minor strand network 45, is at least 0.1 mm, and typically at least 0.12 mm, usually 0.15-0. 20 mm. Typically the amount of extension or relief is the same, for each direction; that is, the minor strand network 45 is positioned centrally, in cross-section, of the major strands 42. The relief at side 50 is shown at dimension A; and, the relief at side 51, at dimension B. The screen 41 depicted is symmetrical in roughness characteristics, thus A=B. Again, for typical such arrangements A and B are at least 0.1 mm, typically at least 0.12, for example about 0.15 to 0.20 mm.

When the screen 41 is used to support media, with the major strands 42 in the machine direction, i. e. , perpendicular to the pleat direction, pleating will cause the major strands 42 to fold back on themselves. This will help keep adjacent pleat faces spaced from one another, due to the presence of the major strands 42 acting as spacers, in relief, therebetween.

C. A problem with some screen arrangements, undesirable levels of pleat damage.

When a screen such as that depicted in Figs. 5 and 6 is used, a problem of media damage is sometimes observed. In particular, the uneven surface represented by the relative relief (A, B) between the major strands 42 and the minor strand network 45 (on whichever side (50, 51, Fig. 6) engages the media) tends to be abrasive to filtration media, and can create microfractures in the media. This can lead to a loss of efficiency in the media.

With the screens of Figs. 2-4, a combination of problems can occur.

Sometimes the issue is media damage from abrasion, sometimes the problem is pleat collapse.

II. Some Advantageous Media/Screen Arrangements.

A. Advantageous Screen Arrangements.

In Figs. 7-21, some advantageous screen arrangements are presented.

The media to be used with them may be generally as characterized above in the "Background"section.

Attention is first directed to Figs. 7-11. Referring to Fig. 7, screen arrangement 60 is depicted. Screen arrangement 60 would typically be a plastic arrangement, although similar geometries can be obtained with other materials including, for example, wires. With respect to typical use of the screen 60 with pleated media, the machine direction is generally indicated by double headed arrow 61, and the pleat direction by double headed arrow 62, although some alternatives are possible.

Still referring to Fig. 7, the screen 60 includes major strands 61 extending in the machine direction, interconnected by a minor strand network 64.

For the preferred embodiment shown, the major strands 61 extend perpendicular to the pleat direction. In general terms, to obtain some preferred advantage, the major strands 61 should extend at an angle of at least 30° to the pleat direction, most preferably perpendicular. Herein when it is said that the major strands"extend at least 30° to the pleat direction, "it is meant that the smallest angle (in projection) where the major strands cross the pleat direction, is at least 30°.

In the instance of screen 60, the minor strand network 64 is shown comprising strands 65 and 66. Strands 65 extend between the major strands 61. In this instance, although alternatives are possible, the direction of extension of the minor strands 65 is such that the strands 65 are parallel to one another and generally perpendicular to the major strands 61; i. e. , in this example the strands 65 extend in the eventual pleat direction 62. Minor strands 66, on the other hand, extend in the machine direction, i. e. , parallel to the major strands 61. In this instance, although alternatives are possible, each strand 66 is located spaced equally from an adjacent pair of major strands (except possibly for strands along the cut or extruded edges, depending on where the cut or extrusion terminates).

The screen arrangement 60 of Fig. 7, even though it includes major strands 61 and a minor strand network 64, has a very different cross section than the screen arrangement 41 of Fig. 5. In particular, the cross section of screen arrangement 60 is depicted schematically in Fig. 9. Screen arrangement 60 has first and second opposite sides 67, 68. The major strands 61 project away from the minor strand network 64 a distance Xi greater from one side (side 68) than any distance of extension X2 (of strands 61 from network 64 or network 64 from strands 61) from the other side (side 67). Indeed for the schematic shown in Fig. 9, neither the minor strands network 64 nor the major strands 61 project at all outwardly from side 67, and X2 is 0. 0.

In Fig. 9', an alternate schematic view of screen 60 is shown. Here the minor strand network 64 is shown generally in one plane, the major strand network 61 generally in another. The amount of projection Xl of the major strand network 61 from the minor strand network 64 on the rough side, is approximately the thickness of the major strand network 61 (in this instance a slightly less than such thickness due to some pressing of the major strand network into the minor strand network). In Fig. 9'X2, the amount of projection of the minor strand network for the major strand network on the smooth side, is shown as approximately the thickness of the minor strand network 64, in this instance a little less due to the two being pressed into one another. It will be understood that the example of Fig. 9' within the general teachings of the example of Fig. 9.

It is noted that the cross-sections of Figs. 9 and 9'are schematic.

Typically, with extruded or molded screen patterns, the strands will neck somewhat,

and thus thin down in thickness and distort, at intersections. This observations applies to the screen shown in other figures discussed below.

Typically and preferably the thickness of the major strand network is at least 0.24 mm. Often it is at least 0.3 mm and often within the range of 0.3-0. 5 mm, although alternatives are possible. Typically the thickness of the minor strand network is no more than 0.25 mm, often 0.2 mm or less, for example 0.1-0. 25 mm, although even smaller values are possible. Typically the overall thickness of the minor strand network is not greater than 85% of the thickness of the major strand network. Preferably thickness of the minor strand network is no more than 65% of the thickness of the major strand network. In some instances the thickness of the minor strand network will not be no more than 60% of the thickness of the major strand network. The term"thickness"when used in this context is meant to refer to a larger dimension taken in a direction through the screen.

Typically the overall thickness of the screen will correspond to no more than the thickness of the minor strand network plus the thickness of the major strand network. Typically that overall thickness will not be greater than 1.8 mm.

Often it will be within the range of 0.5-1. 4 mm.

Thus, the screen 60 has a relatively smooth side 67 and a relatively rough or ribbed side 68, Fig. 9.

Attention is directed to Fig. 8, which is an enlarged, fragmentary view of a portion of Fig. 7. In Fig. 8 the major strands 61 and the minor strand network 64 comprising strands 65 and 66, can be viewed.

The spacing of the major strands from one another is a matter of choice, for any given system. Generally the spacing of the strands will be chosen to provide a desirable level of flow, for the system of concern. That is, screen strands interrupt flow to the media surface, and it is desirable to provide a spacing choice for a given system, that provides for high flow to media surface.

A useable (although alternatives are possible) spacing in the major strands, on center, is within the range of 2-5 mm, typically about 2.5-4. 5 mm., inclusive; for example 3.0-3. 8 mm. The spacing between the minor strands that extend in the pleat direction, on center, would be on the order of about 0.5-2. 0 mm. , inclusive; typically 1.5-2. 0 mm, inclusive. However, again, strand spacing is a matter of choice, and alternatives can be used.

For the particular embodiment depicted in Fig. 7, a minor strand extends parallel to the major strands, positioned centrally therebetween, although alternatives are possible. For such an arrangement typically the spacing, on center, of the major strands to the parallel minor strands is on the order of 1.0-2. 5 mm, inclusive, for example 1.5-1. 9 mm.

It is noted that the cross-sectional configuration of the strands is shown as circular. This is meant to be an example only. The major strands of these screens, and the others presented herein, can be made with a variety of cross- sectional shapes including, for example: circular; semi-circular; oval; rectangular; square; or, triangular, as well as in some instances, irregular shapes in cross-section.

Screens of the type characterized herein with respect to Figs. 7-21 can be specified and obtained from a variety of commercial screen suppliers such as: Internet, Inc. , Minneapolis, Minnesota 55428; DelStar, Inc. , Austin, Texas 78745 ; and Netlon, Blackburn, Lancashire, BB2 4PJ, UK.

As indicated previously, the screens can be formed from a variety of materials, although plastic will be typically be used. Wire arrangements, for example, could also be configured to provide for the relative rough and relative smooth sides as characterized. Plastic screens can be constructed from a variety of extrudable materials, with an issue of choice in part depending on the environment of use. Materials such as polyamides, polyesters, polysulfones, polypropylenes and polyethylene can be used. It is anticipated that polyamides will be preferred, for caustic environments.

Referring to Fig. 9, in the schematic cross-section shown, the minor strand network 64 is depicted to be"flush"with a side of the major strands 61, as indicated at 61a, Thus, again, X2 is zero. When such is the case, generally dimension Xi equals the difference between the thickness of the minor strand network 64, i. e. , the thicknesses of the fibers therein; and, the thickness of the major strands 61.

In Fig. 9', on the other hand, the minor strand network 64 is depicted to project outwardly from the major strand network 61. An arrangement according to Fig. 9'is generally bi-planar, with the minor strand network 64 provided in one plane, and the major strand network 61 provided in another plane. Generally the planes either sit flush with one another, or, as shown, when extruded the major strand network 61 can be pressed into the minor strand network 64 somewhat.

In Fig. 10, the screen of Fig. 7 is shown in perspective view. Fig. 11 is an enlarged, fragmentary view of a portion of Fig. 10, allowing for the perspective view of side 68. In particular, in Fig. 10 a media/screen arrangement 69 is depicted comprising two extensions of screen 60, i. e. , extension 70 and extension 71 positioned on opposite sides of a media 72. Typically the media will be about 0.6- 1. 8 mm thick. It is noted that although screen extensions 70,71 may be the same, this is not required in all applications. Each screen 70,71 is oriented with its relatively smooth side against the media 72.

As a result of the configuration shown, Figs. 7 and 8, screen 60 can be said to have a non-symmetrical construction of different opposite sides or surfaces (67,68) in which: one side (67) is substantially flat or smooth in relative relief, X2 (Fig. 9') and the other side can be said to comprise a plurality of raised, parallel, bumps or ribs, typically the bumps or ribs resulting from a relative relief Xi (Fig. 9').

Referring to Fig. 10, a screen such as screen 60, will be particularly advantageous in use, at least on a downstream side (relative to fluid flow direction in use) of the media 72, with the smooth side 67 pressed against the media 72 and the relief side 68 directed away. This is because during pleating, the major strands, positioned to extend at least 30° to, and preferably perpendicular to, the pleat direction and projecting outwardly from the relief side 68, will form pleat spacers.

The smooth side 67, on the other hand, will be against the media, and will offer relatively little abrasion or microfracture damage to the media.

Of course, screen 60 can be used on both sides of the media.

However some benefit will result even if screen 60 is used on only one side, preferably the downstream side, of the media, and an alternate screen, for example according to the ones shown or described in connection with Figs. 2-6, is used on the opposite, typically upstream, side. In Fig. 10, the pleat direction is shown at 73, and the machine direction at 73 a.

Two additional screen constructions each having a smooth side for use against media, and a greater (relative) relief side, preferably comprising parallel ribs side, for use in providing pleat spacing, are shown in Figures 12-21. In each instance, preferably the screen includes major strands which extend at an angle of at least 30° to the pleat direction, preferably perpendicular to the pleat direction. A first of these is shown in Figures 12-16.

Referring to Fig. 12, screen 74 is depicted. Screen 74 comprises major strands 75 which are generally parallel to one another and to the two opposite sides 76 of the screen 74, in use, resulting in the major strands 75 being generally parallel to, or at least extending in, the machine direction 77. Thus, preferably the major strands 75 extend at an angle of at least 30° to the pleat direction, more preferably they are perpendicular to the pleat direction.

The major strands 75 are interconnected by a minor strand network 78. The minor strand network 78 comprises strands 79, which extend between the major strands 75, in this instance generally parallel to one another and to the pleat direction 80. Thus, in use, for the specific example shown, the minor strands 79 extend perpendicular to the machine direction 77; i. e. , parallel to the pleat tips.

Unlike the screen 60 of Figs. 7-11, screen 74 does not include any minor strands extending parallel to the major strands 71. Otherwise, screen 74 is similar to screen 60.

A schematic cross-sectional view of screen 74 is depicted in Fig. 14.

As with the arrangement of screen 60, screen 74 is constructed to have a smooth side 81 and an opposite rough or relief side 82. This results from the major strands 75 being positioned, relative to the minor strand network 78, to project outwardly more in one direction from side 82 than outwardly (if at all) in the opposite direction from side 81. Typically, the amount of relief Yl, of the major strands 75 from the minor strand network 78 along rough side 82, will be at least 0.24 mm, sometimes at least 0.3 mm and usually within the range of 0.3-0. 4 mm. Typically the relief difference is not more than 0.5 mm, although in some instance it could be. The amount of relief Y2, of the minor strands network 78 with respect to the major strands 75 (or the major strands 75 with respect to the minor strand network 78) on the smooth side 81, is typically no more than 0.25 mm, preferably 0.2 mm or less and in some instances no more than 0.1 mm.

Preferably the minor strand network projects outwardly from the major strands, on the smooth side, no more than 85% of the major strand network thickness, typically no more than 65% of this thickness; and, more preferably, no more than 60% of this thickness. In the schematic of Fig. 14, Ya is shown as 0.

In Fig. 14', a similar schematic is shown. In this instance the major strand 75 are shown in a plane adjacent to a plane of the minor strand network 78.

Here Yl is approximately the thickness of the major strand network 75, and Y2 is

approximately the thickness of the minor strand network 78, except, when plastic, for some pressing of the two planes together. The schematic of Fig. 14'is generally within the teachings of the schematic of Fig. 14.

Preferred thicknesses for the major strand network 75 and the minor strand network 78, and preferred dimensions resulting in Yl and Y2, are generally as described above for analogous features in the example of Fig. 7-9'.

In Fig. 13, an enlarged, fragmentary view of a portion of screen 74 is depicted. The spacing of the major strands would be about one-half as much as Fig.

7, and the minor strand spacing would be about the same.

In Fig. 15, screen 74 is depicted in perspective view, and in Fig. 16 an enlarged, fragmentary view of Fig. 15 is shown, enabling side 82 to be viewed in perspective.

In particular, in Fig. 15, a perspective view of a media/screen arrangement 84 is provided, comprising two extensions of screen 74, on opposite sides of a media extension 86. Each screen 74 is depicted with the smooth side positioned against the media 86. The pleat direction of the media is indicated at double headed arrow 87. The machine direction of the media 86 is depicted by double headed arrow 88. In Fig. 16, an enlarged fragmentary view of Fig. 15 is shown.

Referring to Fig. 17, screen 90 comprises major strands 91 which are generally parallel to one another and to two opposites side edges 92 of the screen 90, which, in use, results in the major strands 91 being generally parallel to, or extending in, the machine direction 93, and generally perpendicular or orthogonal to the pleat direction 94. In more general terms, preferably the major strands extend to an angle of at least 30° to the pleat direction, most preferably perpendicular as shown.

The major strands 91 are interconnected by minor strand network 95.

The minor strand network 95 comprises strands 96, which (except where cut at edges) extend between the major strands 91, in this instance generally parallel to one another and at an acute angle C non-perpendicular to the major strands 91. In this instance the acute angle of extension C between the major strands 91 and the minor strands 96 is meant to be about 38°. Typically constructions with an acute angle C of, for example, about 25° to 75° will be useable. Of course the previous

embodiments show minor strands perpendicular to the major strands, i. e. , with an angle of 90°.

A schematic cross-sectional view of screen 90 is depicted in Fig. 19.

As with the arrangements of screen 60 and screen 74, screen 90 is constructed to have a smooth side 98 and an opposite rough or relief side 99. This results from the major strands 91 being positioned, relative to the minor strand network 95, to project more outwardly in one direction (i. e. , from side 99) from the minor strand network 95 than outwardly (if at all) in opposite direction (i. e. , from side 98) from the minor strand network 95. Typically the amount of relief Z1 of the major strands 71 from the rough side 99 will be at least 0.24 mm (for example 0.3-0. 4 mm) and typically not more than 0.5 mm, although a greater relief is possible. The amount of relief Z2 of the minor strand network 95 from the major strands 91 (or the major strands 91 from the minor strand network 95) i. e. , at the smooth side, is typically no more than 0.25 mm, usually 0.2 mm or less, and in some instances 0.1 mm or less. The thickness of the minor strand network 95 is no more than 85%, typically no more than 65% and preferably no more than 60% of the thickness of the major strands 91.

Fig. 20 is a perspective view of the screen shown in Fig. 17. Fig. 21 is an enlarged fragmentary view of a portion of Fig. 20, enabling a perspective view of the rough side 99. In particular, Fig. 20 is a perspective view of a media/screen arrangement 100 comprising media 101 with extensions of screen 90 on opposite sides thereof. In Fig. 24, the machine direction is indicated double headed arrow 103, and the pleat direction by double headed arrow 104.

As with the embodiments of Figs. 7-11, the embodiments of Figs. 12- 21 can also be applied, to advantage, with use of the preferred screen on one side of the media, typically and preferably the downstream side; and, in use with a variety of alternate screens, including for example the screens of Figs. 2-4, on the opposite, typically upstream, side.

B. Some Preferred Filter Arrangements.

(i) A tubular arrangement.

Attention is now directed to Figs. 22-24. In Fig. 22, a schematic, perspective view of a filter element 150 is depicted. The filter element 150

comprises a media/screen arrangement 151, configured in a tubular form, in this instance a pleated, cylindrical form. Potted at opposite ends of the media/screen arrangement 151, are end caps 153 and 154.

A variety of arrangements can be used for the end caps 153/154, depending on the particular liquid filter system, in which the filter element 150 is to be used. The particular filter element 150 depicted, includes one closed end cap 154 and one open end cap 153. By"closed"in this context, it is meant that end cap 154 has no open central aperture therethrough. By"open"in this context, it is meant that end cap 153 has a open central aperture, Fig. 22, through which liquid can flow in use. Arrangements in which both end caps are open, are possible.

It will be assumed that the configuration of filter element 150 is provided for operation of liquid flow, during filtering, in an out-to-in flow pattern.

As a result, the side 156 viewable in Fig. 22, is an upstream side 156a. The downstream side 157, would be a side facing interior open area 157a. (The opposite, for in-to-out flow, is possible) The direction of pleat extension filter element 150 is in a direction between end caps 153,154. The perpendicular or orthogonal direction, with respect to preferred major strand extension, would be in a direction following the contour of the pleats, extending around the element in the general direction of double headed arrow 158.

Preferably, filter element 150 includes a screen along at least one side, for example a downstream side 157a of media 159 to form a support in the media/screen arrangement 151, configured to provide, as two opposite sides: a relatively smooth side against which the media is pressed; and, an opposite greater relief or relatively rough, ribbed, side. Preferably the screen along the downstream surface of the media, is a screen according to the above preferred descriptions for Figs. 7-21, for example having (parallel) major strands interconnected by a minor strand network, such that one side has a relief, for the major strands, of at least 0.24 mm, and the opposite side has a relief, between the major strands and the minor strand network, if any, of no greater than 0.25 mm, with the minor strand thickness no more than 85% of the major strand thickness, preferably no more than 65% and more preferably no more than 60% of this thickness. Preferably the downstream side screen is positioned with the major strands extending at an angle of at least 30° to, and more preferably generally perpendicular to, the pleat direction, i. e. , parallel

with arrow 158 as they follow the pleat contours. Preferably the screen on the downstream side 157, is in accord with one of screens 60,74 or 90, described.

A similar screen could be utilized for the opposite (in this instance upstream) side screen, viewable in Fig. 23 at 160. However such a screen at this location, typically is not needed (for an out-to-in flow system) to obtain some advantage. This will be apparent from certain test information provided below.

In Fig. 23 and 24, only the upstream side screen 160 is depicted. It should be understood that the downstream side screen, not shown, would be similarly constructed.

It is noted that a typical filter 150 would be provided with a seal arrangement, for sealing to a portion of a housing or other structure in which it is used. Element 150 is shown with seal ring 162 thereon, for this.

End caps 103,104 may be either molded, or may comprise metal pieces, to which the media/screen assembly 151 is secured by bonding. The particular arrangement 150 depicted, comprises metal end caps 165,166, with the media/screen arrangement 151 secured thereto by potting.

As indicated above, a tubular configuration depicted in Fig. 22, for the media/screen arrangement 151, is cylindrical. Alternate arrangements are possible, but typically will not be as easy to configure.

It is noted that the principles described herein, could readily be applied in a panel filter arrangement. A panel arrangement generally comprises a pleated media/screen arrangement, not coiled, positioned within an outer frame. The outer frame would typically have a seal arrangement attached thereto, either as a radial seal or as an axial pinch seal. The media/screen arrangement may be analogous to media/screen arrangement 151, Fig. 22, except for not being coiled into a tubular form.

III. An Alternate Embodiment, Figs. 29,30 and 30'.

Fig. 29, an alternate screen embodiment is depicted. In Fig. 29, a screen arrangement 300 is depicted with a pleat direction generally shown at double headed arrow 301 ; the machine direction or direction perpendicular to the pleat direction being shown at double headed arrow 302. The screen 300 comprises major strands 305 and a minor strand network 306 of minor strands 307. For the screen

300 depicted, the major strands extend at an angle non-perpendicular to the pleat direction 301.

Typically and preferably, the major strands for arrangements according to the present disclosure extend at an angle of at least 30° to the pleat direction, mostly preferably perpendicular. Herein when reference is made to"an angle of at least 30° to the pleat direction, "reference is meant to the smallest angle between the extension of the major strands and the extension of the pleats.

In general, the dimensions and relative dimensions for screen 300 may be similar to the dimensions for screen 90, Fig. 17, except for the direction of the major strand extension and the specific cross-section strand shape.

In Fig. 30, a schematic cross-sectional view of a portion of Fig. 29 is depicted, for clarity. Fig. 30', a schematic in accord with Fig. 30, in which the major strand network is in one plane and the minor strand network is in another, is shown.

IV. Some Comparative Examples To evaluate efficiency of the invention, some pleated arrangements were identically prepared, except for the screen used, and were compared with respect to efficiency (1/penetration). Thus, the media for the comparative arrangements was the same, as well as the test conditions. The plot presented in Fig.

25 provides an example of the results.

With respect to the comparative evaluation, example 26A was generally in accord with Fig. 28, with the upstream screen being according to Fig. 2 and the downstream screen being generally according to Fig. 17. Example 26B uses the screen of Fig. 2 on both sides. Example 26C was generally in accord with Fig.

27, using a screen according to Fig. 4 on both sides.

It can be seen from the example of Fig. 25, that in general the sample of 26A performed best with respect to efficiency, i. e. , absence of penetration. The performance of sample 26C, shows the result of microfracture damage due to the screen configuration.

Fig. 26 shows loading curves, i. e. , the relative ability of the samples 26A, 26B and 26C with respect to contaminant holding capacity. These curves further demonstrate that the screen design does affect filter element performance.

An additional evaluation is shown with respect to Fig. 31. The data is presented in a graph showing pressure drop versus flow rate for several different filter elements with different screen types. The tests were performed using a heavy weight gear oil with temperature controlled to provide a liquid viscosity of 450 cST.

Epoxy coated steel was the baseline and this is represented by the line AA. Lines BB, CC, DD and EE represent elements built with symmetric plastic nets. Lines FF, GG, JJ and KK represent elements using non-symmetrical plastic nets. Within each grouping, different approaches to pleat tip bonding involving roving versus hot melt beads were used.

The screen descriptions in Fig. 31 are as follows: Element Descriptions Epoxy Coated Symmetric Nonsymmetric Steel Screen Nylon Screen Nylon Screen Elements Elements Elements Upstream side MD strand strand density (strands/cm) 7.1 5 3.1 screen angle from machine (degrees) 0 30 0 direction diameter (mm) 0. 18 0. 26 0. 43 CMD strand density (strands/cm) 5.5 5 6.6 strand angle from machine (degrees) 90-30 44 direction diameter (mm) 0. 18 0. 26 0. 34 Total (mm) 0. 36 0.5 0.64 Thickness Downstream MD strand strand density (strands/cm) 3. 9 5 3. 1 3.9 5 3.1 screen angle from machine (degrees) 0 30 0 direction diameter (mm) 0.25 0.26 0.43 CMD strand density (strands/cm) 4.7 5 6.6 strand angle from machine (degrees) 90-30 44 direction diameter (mm) 0. 25 0. 26 0. 34 Total (mm) 0. 5 0. 5 0. 64 Thickness

In Fig. 31 1. Example AA = Epoxy coated woven steel screen on both sides.

2. Example BB = Symmetric nylon screen on both sides, beads for pleat tips.

3. Example CC = Symmetric nylon screen on both sides, roving used to bond pleat tips.

4. Example DD = Symmetric nylon screen on both sides, no beads or roving for pleat tips.

5. Example EE = Symmetric nylon screen on both sides, bead tips.

6. Example FF = non-symmetric screen on both sides, no beads or roving.

7. Example GG = non-symmetric screen on both sides, beads 8. Example JJ = non-symmetric screen on both sides, roving.

9. Example KK = non-symmetric screen on both sides, roving.

With respect to the experiment of Fig. 31, the epoxy coated steel screen operated better than any of the plastic screens, with respect to a low increase in pressure drop with flow rate increase. This is because metal will retain its shape well, even under substantial liquid pressures. However it is generally preferred to avoid metal screens, in some instances, for a variety of reasons including: the general avoidance of metal, i. e. , the provision of an element or filter cartridge which includes either no metal at all or a very small amount of metal. Also, metal screens may be less desirable with respect to efficiency, than certain plastic screens; efficiency not being shown in the experiment of Fig. 31.

Still referring to Fig. 31, it is noted that all of the non-symmetric plastic screens in accord with the present disclosure, items FF, GG, JJ and KK, performed better than the symmetric plastic screens BB, CC, DD and EE, with respect to a low pressure drop increase with flow rate increase.