Patent Application
20130306547
The present disclosure generally relates to filter media, and more particularly to, pleated filter media for use in cartridges having continually varying intermediate pleat heights.
Cartridge filter devices generally include top and bottom plates, an annular core, a cage spaced apart from the core, and a cylindrically shaped pleated filtration media intermediate the core and the cage. It is well known in the art that pleated filter media for cartridge filter devices and the like are generally limited with respect to filtration area due to geometric constraints of the cartridge itself For example, the outside diameter of the cartridge core limits the number of pleats that can be wrapped about the circumference of the core. Likewise, if a cage is present, the inside diameter of the cage limits the pleat height. Still further, the length of the cartridge provides additional limitations to the filtration area. For example, in a standard radially pleated filter cartridge such as disclosed in U.S. Pat. No. 3,692,184, the amount of filter media that may be packed into the cartridge is limited by the number of pleats that can be packed about the cartridge core. Consequently, there is substantial amount of empty space between adjacent pleats at the outer periphery of the filter element.
Prior art
Performance of the filter element of this kind is mainly determined by total area of the filtering surface. The filtering surface area can be increased or enlarged either by increasing the dimension of each pleat 1 or by increasing the number of the pleats. The enlarged dimension of the pleat is obtained by increasing the diameter D1 and/or decreasing the diameter D2, but the filtering devices usually limit the size of filter element. On the other hand, by increasing arrangement density the number of the pleats per unit of volume can be increased to the extent that the two adjacent pleats can be separated from each other sufficiently to permit the fluid to flow therebetween and to minimize the loss of capacity due to the accumulation of dust, sludge and the like.
In the conventional element as illustrated in
Efforts to increase the filter area while minimizing filtration unit size have led to a variety of filter arrangements. For example, U.S. Pat. No. 3,799,354 describes W pleating, which is similar to and sometimes referred to as M pleating depending on the point of reference. W and M pleating configurations provide alternating intermediate pleats. The intermediate pleats extend partway from the cage wall towards the core and are typically of the same height. So called laid over pleats are disclosed in U.S. Pat. Nos. 5,543,047 and 5,690,765. The laid over pleat configuration generally includes a pleat height that is larger than the perpendicular height between the core and cage, which results in bending of the pleats so as to fit within the cartridge. As a result, the opposing surfaces of adjacent pleats are in intimate contact with one another over a substantial portion of the length of the filter element. U.S. Pat. No. 6,315,130 discloses pleated media having an intermediate pleat at every third pleat. U.S. Pat. No. 6,598,749 discloses having 2 different pleat heights within the cartridge.
While these prior art pleated filter cartridges are suitable for its intended use, it would be desirable to further improve filtration area while minimizing unit size.
Disclosed herein are filtration media and filtration devices. In one embodiment, pleated filtration media for a filter cartridge comprises a plurality of circumferentially disposed linear pleats extending from a constant inner core diameter (d) to a constant height (h) defined by an outer diameter; and one or more intermediate pleats circumferentially disposed between a plurality of adjoining linear pleats, wherein each one of the intermediate pleats has a height less than the constant height, and wherein the height of the intermediate pleats progressively decreases in a clockwise or a counter clockwise direction.
In another embodiment, a pleated filtration media comprises a plurality of circumferentially disposed linear pleats extending from a constant inner core diameter (d) to a constant height (h) defined by an outer diameter; and one or more intermediate pleats circumferentially disposed between a plurality of adjoining linear pleats, wherein each one of the intermediate pleats has a different height relative to another intermediate pleat.
A filtration cartridge comprises an annular perforated inner core having a constant diameter; a filter media radially disposed about the annular perforated inner core, the filter media comprising a plurality of circumferentially disposed linear pleats extending from the inner core to a constant height (h) defined by an outer diameter; and one or more intermediate pleats circumferentially disposed between a plurality of adjoining linear pleats, wherein each one of the intermediate pleats has a height less than the constant height, and wherein the height of the intermediate pleats progressively decreases in a clockwise or a counter clockwise direction; and end caps disposed at each end, wherein at least one of the end caps includes an inlet in fluid communication with the annular perforated inner core.
A method for maximizing surface area for a pleated filtration media for a cartridge filter comprises forming a plurality of circumferentially disposed linear pleats extending from the inner core to a constant height (h) defined by an outer diameter; and forming one or more intermediate pleats between a plurality of adjoining linear pleats, wherein each one of the intermediate pleats has a height less than the constant height, and wherein the height of each one of the intermediate pleats is different.
The disclosure may be understood more readily by reference to the following detailed description of the various features of the disclosure and the examples included therein.
Referring now to the figures wherein the like elements are numbered alike:
The present disclosure is generally directed to a pleated filtration media, i.e., a filtration element, suitable for use in filtration cartridges. The pleated filtration element generally includes a plurality of circumferentially disposed pleats and a plurality of intermediate pleats, wherein the intermediate pleats have varying heights. In one embodiment, the intermediate pleat heights progressively vary about the circumference of filtration element. The pleated filtration element in accordance with the present disclosure maximizes filtration area, thereby overcoming many of the problems noted with the prior art. Hold-up volume is significantly minimized and a higher pleat density is obtained leading to increased stiffness, among other advantages. The filtration element can be employed to filter a variety of fluids including gases and liquids.
The particular filtration element is not intended to be limited to any particular material and may include materials such as felt, paper, wet laid paper, glass fiber, microporous membranes, multilayered composite, and combinations thereof, so long as the material can be pleated. Likewise, the filtration element can be utilized in any radially constructed filtration device such as a cartridge filter.
For ease of understanding,
The circumferentially disposed pleats 112 have outer ridges 116 that define the outermost diameter of the filter material 100 and inner ridges 118 radially disposed about the outer diameter (d) of the core. The outermost diameter is constant. In some embodiments, the outer ridges abut a cage wall.
The intermediate pleats 114 also have outer ridges 120 and inner ridges 122. The inner ridges 122 of the circumferentially disposed pleats 114 have a progressively increasing diameter (d1, d2, d3, . . . dn), wherein d1>d; d2>d1; d3>d2, and so on. The outer ridges 120 are at the same diameter as outer ridges 116 of pleats 112. Consequently, the intermediate pleats 114 have a height that progressively decreases, e.g., h>h1; h1>h2; h2>h3; and so on. By increasing arrangement density in this manner, the number of the pleats per unit of volume can be increased to the extent that the two adjacent pleats can be separated from each other sufficiently to permit the fluid to flow therebetween and to minimize the loss of capacity due to the accumulation of dust, sludge and the like.
Since the number of conventional radial pleats is limited by the circumference of the core diameter d, the first intermediate pleat cannot be introduced at any diameter less than what can fit both the conventional radial pleat count plus one intermediate pleat. For conventional radial pleating, the number of pleats “N” is determined by the circumference of “d” and can be mathematically represented by formula (1):
N=πd/2t, (1)
wherein “d” is the core diameter, i.e., the core outside diameter, and “t” is the thickness of the filter media with its optional support materials. Rearranging formula (1), the core outside diameter “d” can then be expressed by mathematical formula (2):
d=2tN/π. (2)
Thus, the first intermediate pleat can occur at an inside diameter “d1” with height “h1”.
d1=d+2t/π (3)
h1=(D−d1)/2, (4)
wherein D is the outermost diameter of the pleated filter material as defined by outer ridge 116 of pleats 112, e.g., inside diameter of the cage, if present. Additional intermediate pleats can be added in the same manner such as is mathematically defined in formulas (5) and (6).
d2=d1+2t/π (5)
h
2=(D−d2)/2 (6)
As this practice is continued, the pleat heights, e.g., h3, h4, h5, etc., will become successively smaller and can be accomplished with a computer controlled pleater. At some point, the increase in area (Area=2(h)(N)(L)) provided by progressively increased diameter intermediate pleats will be minimal Likewise, the filter material properties, e.g., composition, thickness, and the like, may limit the number of intermediate pleats that can be formed.
The pleated filter material of the present disclosure can be manufactured by a variety of techniques. In general, however, the filtration material and support media, if any, to be pleated may be stored on separate rolls and simultaneously fed to a pleating machine and pleated.
Referring now to
The operation of the filtration cartridge will generally depend on the configuration and end application for the filter device. In one embodiment, fluid flows through inlet 220 of the device 200 and through the filter element 204 as indicated by arrows 222 to effect filtration of the fluid. The filter fluid then flows through the perforations of the perforated outer cage 216, wherein the filtered fluid may be used or further processed depending on the particular application. Alternatively, the fluid flow can be in an opposite direction. That is, fluid flows through the outer cage, through the pleated filter element, and then is discharged thought an outlet disposed in an end cap.
The following examples are presented for illustrative purposes only, and are not intended to limit the scope of the invention.
In this example, total filtration area was measured as a function of increasing the number of intermediate pleats from 0 to 11 in a conventional radial filter material (e.g., similar to the radial pleat configuration shown in
As demonstrated, the pleated filter material without any intermediate pleats had a total filtration area of 201.5 in2. Each intermediate pleat that was added to the filter element configuration was at a progressively increasing diameter and decreasing height. Moreover, the contribution to total filtration area generally decreased as a function of increasing number of intermediate pleats. The total area provided by the addition of 11 intermediate pleats in this manner was 298.5 in2.
In this example, total filtration area was measured as a function of increasing the number of intermediate pleats from 0 to 118 in a conventional radial filter material (e.g., similar to the radial pleat configuration shown in
The total area is calculated as follows. A=2(h)(N)(L). When the number of radial pleats (N) is equal to 97 having a height (h) of 0.775 (h=(2.75−1.2)/2) and a length (L), the total area is 1503.5 square inches (Atotal=2(0.775)(97)(10). The area for each successive intermediate pleat is calculated in the following manner: d1=d+2t/π=1.200+2(0.20)/π=1.213; h1=(D−d1)/2=(2.75−1.213)/2=0.769 inches; A1=2(h1)(N)(L)=2(0.769)(1)(10)=15.4 square inches. As such, including one intermediate pleat increases the total area to 1518.9 square inches (Atotal=1503.5+15.4). Adding a second pleat would be calculated in a similar manner. For example, the areas attributed to a second pleat is calculated as follows: d2=1.2+2(2)(0.020)=1.225; h2=(2.75−1.225)/2=0.762; A2=2(0.762)(1)(10)=15.2 square inches. Thus the total area provided by a pleated filter media having 97 radial pleats and two intermediate pleats is 1503.5+15.4+15.2=1534.1 square inches. As would be expected, since each additional intermediate pleat is at a progressively smaller height, the contribution to total surface area decreases as evidenced by the results are shown in Table 2.
As demonstrated in Table 2, total filtration area was increased to 2438.6 in2 for the pleated filtration material with 118 intermediate pleats of successively increasing diameter and corresponding decrease in height compared to the pleated filtration material having a conventional radial configuration similar to that shown in
In this example, the filtration area of a pleated filter cartridge of Example 2 was compared to various prior art pleated filter materials at the same material thicknesses. The various prior art pleated filter materials included a radial pleating type; a laid over pleating type such as is disclosed in U.S. Pat. No. 5,543,047; an “M” pleating type; a “W” pleating type; and an intermediate third pleating type as disclosed in U.S. Pat. No. 6,315,130. The basis for each pleat type was the same as in Example 2 and included 97 radial pleats, a core diameter of 1.200 inches, a height of 0.775 inches, a material thickness of about 0.020 inches, and length of 10 inches.
In the “M” pleat type, the filtration area calculations assumed every fourth pleat to be an “M” pleat. It was determined that if the “M” pleat number were every second pleat, i.e., equal number of pleats as the radial pleat type without intermediate pleats, that the calculated pleat height (hm) would be 0.005 inches, which would be impractical from a design aspect. Making every 4th pleat an “M” pleat, the following calculations were used to determine total filtration area.
N
m=1/3N=1/3*97=32 intermediate pleats
N
total=97+32=129
d
m=(2)(t)(Ntotal)/π=2*0.020 in.*129/π=1.642 in.
h
m=(D−dm)/2=(2.75 in.−1.2 in)/2=0.554 in.
A
m=2hmNmL=2*0.554 in*32*10 in=354.6 in2
A
total=1503.5 in2+354.6=1858.1 in2
In the “W′ pleat type, the filtration area calculations assumed every second pleat of the radial pleat type was modified with a “W” pleat. As noted in Example 2 the total number of radial pleats without any intermediate pleats was 97 (see Table 2). The filtration area was calculated in the following manner
N
total=97+97=194
d
w=(2)(t)(Ntotal)/π=2*0.020 in*194/π=2.470 in.
h
w=(D−dw/2=(2.75 in.−2.470 in.)/2=0.140 in.
A
2=2hwNwL=2*0.140 in*97*10 in=271.6 in2
A
total=1503.5 in2+271.6 in2=1775.1 in2
In the “intermediate third pleat” type, the filtration area calculations assumed every third pleat to be an intermediate pleat. Thus, for every 2 radial pleats, there is 1 intermediate pleat. The total filtration area was calculated in a similar manner as provided for in Table 2 with the exception that Ntotal=97+48=145. As shown in Table 2 above, the total area provided from the addition of 48 pleats (N=145) is 2097.8.
The results are summarized in Table 3 below.
As demonstrated in Table 3, filtration area was maximized by with the filter media having the continually varying intermediate pleats as described herein.
Advantageously, the pleated cartridge filter media in accordance with the present disclosure uses conventional pleated cartridge methods and adds intermediate pleats to the pleat pack to maximize filtration area. The filter cartridge including the filter media as described herein provides a decreased pressure drop when in use, and increases useful operating lifetimes. Because of the increased density from the intermediate pleats as described, the media of the pleated filter media has an increased stiffness, which can further aid manufacturability especially when it comes to attaching end caps to the cartridge assembly. The increased density of the pleat pack may also have the effect of giving the pleated filter cartridge a higher strength with regards to crushing under pressure.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
