Pleated media for a conical shaped filter element

Abstract

A frusto-conical filter includes at least one layer of a filtering material, wherein one or more layers of the at least one layer of a filtering material comprises a plurality of pleats. Each of the pleats has a center axis which essentially maintains a constant distance from the center axis of its adjoining pleats. The media filter has a first end and a second end, the second end being spaced apart from the first end, and one of the first and second ends is larger than the other of the first and second ends. A method of making this media involves cutting out a frusto-conical section from a generically shaped media and aligning it in such a way as to maintain the constant distance of the pleats from the adjacent pleats.

Claims

1. A frusto-conical filter comprising: a filter media comprising at least one layer of a filtering material; one or more layers of the at least one layer of the filtering material comprising a plurality of pleats, wherein each pleat has a center axis and an axial length, the center axis of each pleat essentially equidistant from the center axis of its adjacent pleat along its axial length; and the frusto-conical filter having a first end and a second end, the second end being spaced apart from the first end by the height of the cone, and one of the first and second ends is larger than the other of the first and second ends, wherein the filter has a seam and wherein one of the plurality of pleats adjacent to the seam runs substantially parallel to the seam, and at least one other of the plurality of the pleats has an end that intersects the seam.

2. A frusto-conical filter comprising: a filter media comprising at least one layer of a filtering material; one or more layers of the at least one layer of the filtering material comprising a plurality of pleats, wherein each pleat has a center axis and an axial length, the center axis of each pleat essentially equidistant from the center axis of its adjacent pleat along its axial length; and the frusto-conical filter having a first end and a second end, the second end being spaced apart from the first end by the height of the cone, and one of the first and second ends is larger than the other of the first and second ends, wherein the pleats are of varying axial lengths.

3. A frusto-conical filter comprising: a filter media comprising at least one layer of a filtering material; one or more layers of the at least one layer of the filtering material comprising a plurality of pleats, wherein each pleat has a center axis and an axial length, the center axis of each pleat essentially equidistant from the center axis of its adjacent pleat along its axial length; and the frusto-conical filter having a first end and a second end, the second end being spaced apart from the first end by the height of the cone, and one of the first and second ends is larger than the other of the first and second ends, wherein a portion of the pleats extend the slant height of the cone and, wherein a second portion of the pleats are shorter than the slant height of the cone.

4. A frusto-conical filter comprising: a filter media comprising at least one layer of a filtering material; one or more layers of the at least one layer of the filtering material comprising a plurality of pleats, wherein each pleat has a center axis and an axial length, the center axis of each pleat essentially equidistant from the center axis of its adjacent pleat along its axial length; and the frusto-conical filter having a first end and a second end, the second end being spaced apart from the first end by the height of the cone, and one of the first and second ends is larger than the other of the first and second ends, wherein the at least one layer of a filtering material comprises multiple layers of a filtering material and wherein a portion of the multiple layers of the filtering material comprise fewer pleats than the one or more layers of the at least one layer of a filtering material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view of a prior art pleated filter media formed in a cylindrical tube.

(2) FIG. 2 is an end view of FIG. 1.

(3) FIG. 3 is a view of a cylindrical tube of pleated filter media formed into conical shape.

(4) FIG. 4 is a cross-sectional view along line 1-1 of FIG. 3.

(5) FIG. 5 is a cross sectional view along line 2-2 of FIG. 3.

(6) FIG. 6 is shows a view of a filter for use in the present invention.

(7) FIG. 7 is a view of a cut portion of FIG. 6 according to the present invention.

(8) FIG. 8 is a view of another embodiment of a filter for use in the present invention.

(9) FIG. 9 is a view of the cut portion of FIG. 8 according to the present invention.

(10) FIG. 10 is a view of a pleated filter media according to the present invention.

(11) FIG. 11 is a cross-sectional view along line 3-3 of FIG. 10.

(12) FIG. 12 is a cross-sectional view along line 4-4 of FIG. 10.

(13) FIG. 13 is a view of another embodiment of a pleated filter media according to the present invention.

(14) FIG. 14 is a cross-sectional view along line 3-3 of FIG. 13.

(15) FIG. 15 is a cross-sectional view along line 4-4 of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

(16) FIGS. 1 and 2 show a known filter media configuration, wherein the filter is in the form of a tube 10. The filter has 2 ends 12 and, as is more clearly seen in FIG. 2, has a series of pleats 14 running the length of the tube.

(17) FIGS. 3, 4 and 5 show an alternative known filter configuration. This filter is in the form of a cone 20, and has a first end, 22 and a second, larger end 24. As can be seen in FIGS. 4 and 5, this known configuration results in having pleats 26, which have a wider spacing from each other at the larger end 24 than at the smaller end 22. As discussed herein, this can result in undesirable affects when the filter is used.

(18) FIG. 6 shows a square filter 100, from which a filter according to the present invention can be derived. A cut frustrum of a cone 110, is shown against the square filter of FIG. 6, and is then depicted in its cut shape in FIG. 7. It can be seen on FIG. 7 that there are differing numbers of pleats at ends 112 and 114. It can also be seen that in an embodiment of the invention, that on one side of the filter, the cut follows substantially parallel to the outside pleat 116, but on the other side of the media the cut cuts off the pleats at varying lengths along that side.

(19) FIGS. 8 and 9 show an alternative embodiment of the present invention. FIG. 8 shows a square filter 200, from which a filter according to the present invention can be derived. A cut frustrum of a cone 210, is shown against the square filter of FIG. 8, and is then depicted in its cut shape in FIG. 9. It can be seen on FIG. 9 that there are differing numbers of pleats at ends 212 and 214, with more pleats occurring at the larger end. It can also be seen that in this embodiment of the invention, that on both sides of the filter, the cut is configured so that it cuts off the pleats at varying lengths along that side.

(20) FIG. 10 shows the filter of FIG. 6 when it is formed into a cone. In this embodiment, a portion of the pleats 116 terminate at the end 112, and others terminate along the side 118 of the unrolled media. In the particular embodiment shown, end 112, as shown in FIG. 11 has 21 pleats 116, and end 114 as shown in FIG. 12 has 48 pleats. The exact number of pleats at each end can be calculated to maximize effectiveness based on the formula described hereinbelow.

(21) FIG. 13 shows the filter of FIG. 8 when it is formed into a cone. In this embodiment, a portion of the pleats 216 terminate at the end 212, and others terminate along the side 218 of the unrolled media. In the particular embodiment shown, end 212, as shown in FIG. 14 has 21 pleats 216, and end 214, as shown in FIG. 15, has 48 pleats 216. The exact number of pleats at each end can be calculated, again, to maximize effectiveness based on the formula described hereinbelow. In this embodiment, the peats 216 that terminate at edge 218 can, but are not required to, terminate against a corresponding pleat.

(22) The present invention provides a means of packing more surface area in a given volume, based upon the principal that a conical filter with a base inner radius (Ri) and height (h) as a cylindrical filter has a lower pleat packing capacity. As can be seen from the table below, the surface area advantage of the present filter (denoted as Pinnacle) over a conventional conical filter of the same pleat height increases as the ratio of the inner radii decreases. The loss of pleated filter media surface area of a pinnacle filter over a conical filter as compared to a cylinder with the same base is only 50%.

(23) TABLE-US-00001 TABLE 1 Table 1 - Surface Area comparison - All filters having the same base diameter, pleat count (at top of the element) and pleat height. (SAc (SAp (SAp (SAc SAcyl)/ SAp/ SAc)/ SAp/ SAcyl)/ SAc/ SAcyl)/ (SAp ri/Ri SAc SAc SAcyl SAcyl SAcyl SAcyl SAcyl) 0.1 5.5 450% 0.6 45% 0.1 90% 0.2 3.0 200% 0.6 40% 0.2 80% 0.3 2.2 117% 0.7 35% 0.3 70% 0.4 1.8 75% 0.7 30% 0.4 60% 0.5 1.5 50% 0.8 25% 0.5 50% 50.0% 0.6 1.3 33% 0.8 20% 0.6 40% 0.7 1.2 21% 0.9 15% 0.7 30% 0.8 1.1 13% 0.9 10% 0.8 20% 0.9 1.1 6% 1.0 5% 0.9 10%
The data in the table is based upon the following assumptions:

(24) PPI.sub.c=PPI.sub.p, hp=h.sub.c, (R.sub.0r.sub.0)<<h, SA maximized, PH.sub.c=PH.sub.p=r.sub.i, R.sub.cyl=(r+R)/2

(25) The following abbreviates are also used in the table:

(26) H=Filter height (subscript p, c designate conical and Pinnacle filters)

(27) PH.sub.c=Pleat Height of conventional conical filter

(28) PH.sub.p=Pleat Height of Present Invention (Pinnacle Filter)

(29) PPI.sub.c=Pleats per unit length at the small base of the conical filter.

(30) PPI.sub.p=Pleats per unit Length for the present invention (Pinnacle Filter with constant PPI throughout the element)

(31) r.sub.i=Inner radius of Frustum Cone (top)

(32) R.sub.i=Inner radius of Frustum Cone (bottom; base)

(33) SA=Filtration Surface Area

(34) SA.sub.c=Surface Area of Conventional Filter

(35) SA.sub.p=Surface Area of Pinnacle Filter

(36) SA.sub.cyl=Surface Area of conventional Cylindrical Filter

(37) SA.sub.p/SA.sub.c=(1+R.sub.i/r.sub.i)/2

(38) (SA.sub.pSA.sub.c)/SA.sub.c=(R.sub.i/r.sub.i1)/2

(39) SA.sub.p/SA.sub.cyl=(1+r.sub.i/R.sub.i)/2

(40) As the pleat count along the axis of the filter may change along the axis of the present invention, the surface area of the present invention may be optimized with deeper pleats than the prior art. The Filtration Surface area ratio of the present invention over the prior art conical filter element with the same filter height with optimum pleat depth for each filter type (PH.sub.c=r.sub.i/2, PH.sub.p=(r.sub.i+R.sub.i)/2, PPI.sub.p=constant) leads to the following equation:

(41) $\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}=\frac{1}{4}{\left(1+\frac{R_0}{r_0}\right)}^2\sqrt{1+{\left(\frac{R_0-r_0}{h}\right)}^2}\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}$

(42) Therefore, the surface ratio advantage of the present invention may be calculated for various scenarios. In cases where the filters are slender (R.sub.0r.sub.0)/h<<1, the above equation reduces to:

(43) $\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}=\frac{1}{4}{\left(1+\frac{R_0}{r_0}\right)}^2\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}$

(44) The surface advantage of the present invention is highlighted in the summary table below with PPI.sub.p=PPI.sub.c:

(45) TABLE-US-00002 TABLE 2 Surface Area Advantage of the Present Invention r.sub.i/R.sub.i r.sub.i/R.sub.i (SA.sub.p SA.sub.c)/ r.sub.o/R.sub.o (Prior art) (Invention) SA.sub.p/SA.sub.c SA.sub.c/SA.sub.p SA.sub.c 0.33 0.2 0.00 4.00 0.250 300% 0.46 0.3 0.15 2.51 0.399 151% 0.57 0.4 0.29 1.89 0.529 89% 0.62 0.45 0.36 1.71 0.584 71% 0.67 0.5 0.43 1.56 0.640 56% 0.75 0.6 0.56 1.36 0.735 36% 0.82 0.7 0.68 1.23 0.816 23% 0.89 0.8 0.79 1.13 0.886 13% 0.95 0.9 0.90 1.06 0.947 6% 0.97 0.95 0.95 1.03 0.974 3% 1.00 1 1.00 1.00 1.000 0%

(46) The PPI for a filter of the present invention where the filtration surface area is the same as the prior art filter may be calculated from the formula below:

(47) ${\mathrm{PPI}}_p=\frac{{\mathrm{SA}}_c}{{\mathrm{SA}}_p}{\mathrm{PPI}}_c=4{\left(1+\frac{R_0}{r_0}\right)}^{-2}{\mathrm{PPI}}_c$

(48) As the pleats of the present invention are uniformly spaced full utilization of the pleats along the axis of the filters is achieved. The filter may be designed with optimum pleat spacing for the application throughout the filter element. And in cases where the permeability of the filter pack is low and filter element is slender and long, the pleat spacing may be adjusted such that permeability through the pleat pack decreases along the axis of the filter to promote flow through the entire element.

(49) The maximum filtration area packing of the conical filters of the prior are is dictated by the small diameter of the cone. The maximum filtration packing is obtained where the pleat height is about of the outer diameter. Therefore, the maximum packing and pleat height is limited by the top endcap. The optimum pleat height may be different than this value once other considerations are made for other pressure loss such as fluid flow expansion/contraction through the element.

(50) In the conical filter of the present invention as the number of pleats may be varied along the longitudinal axis of the filter, the maximum filtration packing is dictated by the combination of the top and bottom endcaps (diameters of the cone). In the present invention, the maximum filtration packing is achieved at about of the average of the two outer pleat pack diameters. And as such provides a mean for additional packing than the prior art.

(51) Although the above comparison depicts clear advantages of filter media packing of the present invention, in most applications, the filter is confined in a vessel and thereby the annular space between the vessel wall and the filter also needs to be considered. In such cases, the appropriate comparison would be to compare a conical filter which its base would substantially expands the vessel will be appropriate, In cases that multiple elements are designed within a vessel, the filter base diameter would be substantially equal to the center-to-center distance between the elements with consideration to manufacturing tolerances and assuring no interference between the filter elements. The expansion at the base of the element where annular velocities would be negligible provides a means of packing more filtration media within the vessel.

(52) As shown above, the present invention provides a means of increase packing of filtration media within a conical filter. In coalescing applications, increase filter media provides a means of increase flow through the filter while maintain performance parameters. Therefore, the flow may be increased through the filter by the increased surface area or more importantly useable surface area. In order to negate the possibility of re-entrainment of coalesced droplet downstream it is preferred to maintain the annular velocity low and potentially same as before if annular space was at the limit of re-entrainment.

(53) Table 2 demonstrates filter media packing potential of the present invention for a similar size conical filters (based on outer dimensions, neglecting inner differences). Based on media packing potential of the present invention, there is a potential to increase fluid flow as long as re-entrainment of coalesced liquid droplets is not reached by excessive annular velocities. If the at a given r.sub.o/R.sub.o, the prior art conical filter is at the limit of re-entrainment, the present invention facilitates construction of a conical filter element which takes into consideration the increased filter packing and thereby the present invention filter will have a smaller r.sub.o/R.sub.o ratio as provided in the table 3 based on the noted assumptions:

(54) TABLE-US-00003 TABLE 3 Surface Area Advantage of the Present Invention (Sizing Guideline based on assumptions) Conical Filter r.sub.o/R.sub.o r.sub.i/R.sub.i Present Present Conventional Invention SA.sub.p/SA.sub.c Conventional invention 0.618 0.333 1.250 0.447 0.000 0.667 0.455 1.306 0.500 0.143 0.710 0.553 1.330 0.550 0.269 0.732 0.600 1.333 0.577 0.333 0.750 0.636 1.331 0.600 0.385 0.788 0.708 1.315 0.650 0.491 0.824 0.770 1.285 0.700 0.587 0.857 0.823 1.246 0.750 0.674 0.889 0.869 1.201 0.800 0.753 0.919 0.908 1.152 0.850 0.825 0.947 0.943 1.102 0.900 0.889 0.974 0.973 1.051 0.950 0.947 1.0000 1.000 1.000 1.000 1.000
The following assumptions were made in deriving this table:
PPI.sub.c=PPI.sub.p, hp=h.sub.c, (R.sub.0r.sub.0)<<h, SA maximize (PH.sub.c=r.sub.i, PH.sub.p=(r.sub.i+R.sub.i)/2);
and the following abbreviations are used:

(55) R.sub.o=Outer filter Radius is equal to vessel radius or center to center distance between elements in multi element vessel)

ABBREVIATIONS

(56) H=Filter height (subscript p, c designate conical and Pinnacle filters)

(57) PH.sub.c=Pleat Height of conventional conical filter=r.sub.ic

(58) PH.sub.p=Pleat Height of Present Invention (Pinnacle Filter)=(r.sub.ip+R.sub.i)/2

(59) PPI.sub.c=Pleats per unit length at the small base of the conical filter.

(60) PPI.sub.p=Pleats per unit Length for the present invention (Pinnacle Filter with constant PPI throughout the element)

(61) r.sub.ic=Inner radius of Frustum Cone (Conical Filter)

(62) r.sub.ic=Inner radius of Frustum Cone (Pinnacle Filter)

(63) R.sub.i=Inner radius of Frustum Cone (bottom; base; assumed to be the same for Conical and Pinnacle filters)

(64) SA=Filtration Surface Area

(65) SA.sub.c=Surface Area of Conventional Filter

(66) SA.sub.p=Surface Area of Pinnacle Filter

(67) Derived Formulas:

(68) $\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}=\left(\frac{1}{4}\right){\left(1+\frac{r_{\mathrm{ip}}}{r_i}\right)}^2\left(\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}\right){\left(\frac{R_i}{R_{\mathrm{ic}}}\right)}^2\frac{\mathrm{Annular}\mathrm{Space}\mathrm{of}\mathrm{Pinncle}}{\mathrm{Annular}\mathrm{Space}\mathrm{of}\mathrm{conical}}=\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}.fwdarw.\left(\frac{1-{\left(\frac{r_{\mathrm{ip}}}{R_i}\right)}^2}{1-{\left(\frac{r_{\mathrm{ic}}}{R_i}\right)}^2}\right)=\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}.fwdarw.\frac{R_{\mathrm{ip}}}{R_i}=\frac{1-\frac{1}{4}\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}\left({\left(\frac{R_i}{r_{\mathrm{ic}}}\right)}^2-1\right)}{1+\frac{1}{4}\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}\left({\left(\frac{R_i}{r_{\mathrm{ic}}}\right)}^2-1\right)}\frac{\left({\mathrm{SA}}_p/{\mathrm{SA}}_c\right)}{d\left(R_{\mathrm{ic}}/R_i\right)}=0.fwdarw.-32\left(\frac{r_{\mathrm{ic}}}{R_i}\right)\left(\left(\frac{{\mathrm{PPI}}_p}{{\mathrm{PPI}}_c}\right)\left({\left(\frac{r_{\mathrm{ic}}}{R_i}\right)}^2+1\right)-4\left(\frac{{\mathrm{PPI}}_c}{{\mathrm{PPI}}_p}\right){\left(\frac{r_{\mathrm{ic}}}{R_i}\right)}^2\right)=0\mathrm{If}{\mathrm{PPI}}_p={\mathrm{PPI}}_c.fwdarw.{\left(\frac{{\mathrm{SA}}_p}{{\mathrm{SA}}_c}\right)}_{\max }=\frac{4}{3}\mathrm{where}\frac{r_{\mathrm{ic}}}{R_i}=\sqrt{\frac{1}{3}}\&\frac{r_{\mathrm{ip}}}{R_i}=\frac{1}{3}$

(69) As may be seen in the above table, under the assumed conditions and in the case where the prior art is at optimum surface rare and annular velocity, the present invention provides a means of providing a conical filter with improved flow capacity. This is in addition to the fact that the present invention provides a means to maintain open pleat spacing throughout the element which is highly desired for optimum performance.

(70) As may be seen in the table there is an optimum r.sub.o/R.sub.o ratio at which the benefits of the present invention is maximized under the given assumptions. As the r.sub.o/R.sub.o ratio decreases and the benefits of the present invention in terms of surface area increase there is less annular space to be provided to take into account the added area. For the given example, the maximum improvement of 33% is achieved at r.sub.o/R.sub.o of 0.6 for the present invention under the presumed assumption.

(71) With the means provided here and known in the art, the present invention provides a substantial improvement in fluid flow through a conical filter element and better utilization of the available filter media. The present invention also provides flexibility in design where fluid flow may be directed to preferred parts of the element by varying the pleat spacing along the longitudinal axis.

(72) The variability of pleat count along the longitudinal axis is not limited to a conical filter in the present invention. The same principle may be applied to cylindrical filter, especially if there is a desire to promote flow within certain sections of the filter versus others. Varying pleat counts along a cylindrical filter may be generated according to the present invention.