MULTIPLE-DISC FILTER

Abstract: A multiple-disc filter body (10) for separating solid particles from a fluid flowing through the filter body from its inlet side to its outlet side, comprises a stack of filter discs (14) in which the side faces (14a,14b) of each pair of adjacent discs (14) are formed with ribs (42a,b,c) of at least two different heights such as to define filtering passageways of a larger size on the inlet side of the filter stack and filtering passageways of a smaller size on the outlet side of the filter stack in series with the larger-size filtering passageways, whereby coarse particles are first separated by the fluid in the larger size fil­ tering passageways, and then finer particles are se­ parated from the fluid in the smaller size filtering passageways.

Description: The present invention relates to multiple-disc filters, and particularly to the construction of the discs used in such filters. Multiple-disc filters are gaining wide spread use in a large number of applications, for example in water irrigation systems for removing foreign particles which may clog the water irrigation devices. Such filters include a stack of filter discs in which the side faces of each pair of adjacent discs are formed with ribs defining filtering passageways between them. A multiple-disc filter of this construction according to the precharacterizing portion of independent claim 1 is illustrated in EP-A-0 177 434, in which the ribs of one face of each pair of adjacent discs are of a first configuration, and the ribs on the other face of each pair of adjacent discs are of a second configuration and contact the first configuration ribs of the next adjacent disc such that the filter passageways between each pair of adjacent discs are of a size determined by the height of the second configuration ribs. In the preferred embodiment described in the above-cited EP-A-0 177 434, the first configuration ribs are of sinuous shape, and the second configuration ribs are of annular shape. It has been found that filters of such a construction have a low sensitivity to clogging by dirt particles, may be more effectively cleaned in a quick and simple manner, and have an increased dirt-removing and dirt-holding capacity, as compared to conventional multiple-disc filters. Reference is also made to CH-A-139 793 which discloses a multiple-disc filter body. The filtering passages between the filter discs are provided with inlet portions converging in the fluid flow direction. The object of the invention is to provide a multiple-disc filter body of the recited type which provides even further advantages regarding dirt-removing and dirt holding capacity. According to the present invention, to achieve this, there is provided a multiple-disc filter body for separating solid particles from a fluid flowing through the filter body from its inlet side to its outlet side, comprising a stack of filter discs in which the adjacent side faces of each pair of adjacent discs are formed with ribs defining filtering passageways therebetween, the ribs of one face of each pair of adjacent discs being of a first configuration, and the ribs of the other face of each pair of adjacent discs being of a second configuration and contacting the ribs of said one face such that the filtering passageways between the pair of adjacent discs are of a size determined by the height of said ribs of said other face of said pair of adjacent discs, characterized in that the first configuration ribs on said one face are formed to define with said second configuration ribs at least two groups of filtering passages arranged in series flow relationship between the adjacent side faces of each pair of adjacent discs, and that the second configuration ribs on said other face are arranged in at least two groups of ribs, the height of the ribs in one of said groups being different from the height of the ribs in a second of said groups, with the higher height group of ribs being on the inlet side of the filter stack so as to define larger size filtering passages of a first of said groups of filtering passages on the inlet side of the filter stack and the smaller height group of ribs being on the outlet side of the filter stack so as to define smaller size filtering passages of a second of said groups of filtering passages on the outlet side of the filter stack. Such a construction provides a number of advantages which are quite important when the filter is used for removing dirt particles from liquids, but are particularly important when the filter is used for removing dirt particles from air or other gases. Thus, by providing filtering passageways of different sizes in series, such that the coarse particles are first removed and then the finer particles, a more efficient filtering action is produced with a smaller pressure drop across the filter; this is because the coarse particles are separated from the fluid before they can clog the fine passageways for the fine particles, which fine passageways determine the particle size removed by the filter. Moreover, the dirt-holding capacity of the filter is substantially increased since the dirt particles are separated and held in depth within the filter, rather than being concentrated along the inlet surface of the filter body as the case in most conventional filters of this type. Still further, a filter constructed in accordance with the foregoing features may be more effectively cleaned by back-flushing. Advantageous embodiments of the filter body are defined in the dependent claims. The multiple-disc filter body is herein described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a longitudinal sectional view illustrating one form of multiple-disc filter constructed in accordance with the present invention; Fig. 2 illustrates the construction of one face of each filter disc in the filter of Fig. 1; Fig. 3 illustrates the opposite face of each of the filter discs; Fig. 4 is a fragmentary view more particularly illustrating the construction of the two faces of the disc of Figs. 2 and 3; Fig. 5 is a fragmentary view illustrating a variation in the rib configuration of the disc face illustrated in Fig. 2; Fig. 6 is a fragmentary view illustrating another variation in the rib construction of the face illustrated in Fig. 2; Fig. 7 is a sectional view along lines VII--VII of Fig. 6; Fig. 8 illustrates a plurality of discs of the construction of Figs. 6 and 7 arranged in a stack; Fig. 9 is a fragmentary view illustrating a modification in the rib construction of Fig. 6; and Fig. 10 illustrates a filter body constituted of two types of filter discs, one being formed with ribs of one configuration on both faces, and the other being formed with ribs of the other configuration on both faces. The filter illustrated in Fig. 1 comprises a housing 2 having an inlet 4 connectable to the upstream fluid supply pipe, and an outlet 6 connectable to the downstream fluid supply pipe. Housing 2 further includes an intermediate cylindrical section 8 in which is disposed a filter body 10 which removes the solid particles from the fluid (e.g., air or other gas, or water or other liquid) as the fluid passes from the inlet 4 to the outlet 6. Cylindrical housing section 8 is closed at its bottom by a threaded cap 12. Filter body 10 is constituted of a plurality of filter discs 14 secured between a pair of ends discs 16 and 18. End disc 16 is integrally formed with a central tubular section 16a tapered at its outer tip to facilitate its reception within a sleeve 20 integrally formed in an apertured wall 21 in housing 2. End disc 18 is also integrally formed with a central tubular section 18a tapered at its outer tip to facilitate its reception within a cylindrical sleeve 22 integrally formed in end cap 12. Each of the end discs 16, 18 further includes a tubular sleeve 16c, 18c supported centrally of the respective disc by plurality of radial arms 16e, 18e. A reinforcement rod 24 extends axially through central sleeves 16c, 18c and the filter discs 14, and firmly secures the discs in a stack. The fluid to be filtered is introduced via inlet 4 into an annular passageway 30, and flows through the spaces between the filter discs 14 of the filter body 10 into an inner passageway 28 and out through the spaces between the radial ribs 16e of the end disc 16 to the outlet 6. It will thus be seen that the outer edges of the filter discs 14 constitute the upstream side of the filter body receiving the unfiltered fluid, and the inner edges of the filter disc constitute the downstream side of the filter body through which the filtered fluid exits. In the embodiment illustrated in Fig. 1, all the filter discs 14 are of identical construction, being of circular shape formed with a central opening defining the inner passageway 28. Fig. 2 illustrates one face 14a of each filter disc 14, and Fig. 4 illustrates the opposite face 14b of each filter disc. Thus, as shown in Fig. 2, face 14a of each filter disc 14 is formed with three ribs 40 of sinuous configuration, each rib extending the complete circumference of the disc and radially spaced from the next adjacent rib and also 180° out of phase with the next adjacent rib. Thus, ribs 40 on face 14a of each filter disc includes a sinuous rib 40a adjacent to the outer edge 30a of the disc, an intermediate sinuous rib 40b, and an inner sinuous rib 40c adjacent to the inner edge 28a of the disc. It will also be seen that the intermediate rib 40b is 180° out of phase with respect to both end ribs 40a and 40c; thus, the valleys of rib 40b are aligned with the crests of ribs 40a, 40c, and the crests of rib 40b are aligned with the valleys of ribs 40a, 40c. As shown in Fig. 3, the opposite face 14b of each filter disc 14 is formed with a plurality of coaxial annular ribs 42 radially spaced from each other. These ribs are divided into three groups, namely group 42a adjacent to the outer edge 30a of the disc, group 42b located inwardly of group 42a, and group 42c located adjacent to the inner edge 28a of the disc. As shown in Fig. 4, the three sinuous ribs 40a, 40b, 40c on face 14a are all of the same height. However, the annular ribs 42 on face 14b are not of the same height. Rather group 42a adjacent to edge 30a is of the largest height; the intermediate group 42b is of smaller height; and the inner most group 42c adjacent to edge 28a is of the smallest height. The overall thickness of each disc, defined by the outermost edge of the sinuous ribs 40a-40c and the outermost edge of the annular ribs 42a-42c is uniform from the outer edge 30a to the inner edge 28a of the disc. It will thus be seen that when a plurality of discs 14 are placed in a stack, the outermost edges of the annular ribs 42a-42c will contact the outermost edges of the radially-extending portions 44 of the sinuous ribs 40a-40c at substantially right angles to those ribs, to define groups of different filtering passageways in series flow relationship between the respective faces of each pair of adjacent discs. The size of the filtering passageways in each group will be determined by the height of the respective annular rib; the length of each filtering passageway will be determined by the spacing between the annular ribs; and the width of each filtering passageway will be determined by the thickness of the respective sinuous rib, particularly the radially-extending section thereof contacted by an annular rib 42a-42c. Since the three groups of annular ribs 42a, 42b, 42c are of decreasing height from the outer (upstream) edge 30a of the filter disc to the inner (downstream) edge 28a, the filtering passageways will be of decreasing size from the outer edge to the inner edge of the discs. The path of the fluid flowing from the outer edge 30a to the inner edge 28a of the stack of filter discs 14 is shown by the arrows 44 in Fig. 2. It will be seen that the fluid first enters the space 44a between the crests of the outermost sinuous rib 40a; then flows through the group of filtering passageways defined by the sinuous rib 40a and annular ribs 42a into the space 44b between sinuous rib 40a and the next sinuous rib 40b; then through the group of filtering passageways defined by sinuous rib 40b and annular ribs 42b into the space 44c defined by sinuous rib 40b and sinuous rib 40c; then through the group of filtering passageways defined by sinuous rib 40c and annular ribs 42c, and finally into the inner chamber 28 communicating with the filter outlet 6. It will also be seen that since the annular ribs 42a, 42b, 42c are of decreasing height, from the outer upstream edge 30a to the inner downstream edge 28a, the filtering passageways, which are connected in series in the above-described flow of the fluid, decrease in size from the upstream side 30a of the filter body to the downstream side 28a. Thus, the coarser particles are first separated from the fluid in the large size passageways defined by the largest, outermost annular ribs 42a, then finer particles are separated in the filtering passageways defined by the intermediate annular ribs 42b, and finally the finest particles are separated by the innermost annular ribs 42c. Such a construction provides a number of important advantages as briefly indicated above. Thus, by first separating the coarser particles and lastly the finest particles, a more efficient separation of the particles is effected with a minimum pressure drop across the filter body. In addition, the described arrangement separates and holds the particles in depth within the filter body, thereby substantially increasing the dirt-removing and dirt-holding capacity of the filter body, as compared to more conventional filters where the particles are separated mostly at the upstream surface of the filter body. Further, the described arrangement permits more efficient cleaning of the filter by back-flushing since there is little tendency of particles becoming wedged within the filtering passageways. Fig. 5 illustrates a variation in the construction of the face of the filtering disc including the sinuous ribs. Thus, as shown in Fig. 5, the ribs 140 formed on face 114a of each filter disc 114 are constituted by only two sinuous ribs 140a, 140b; the opposite face (not shown) of each disc 114 would therefore be formed with only two groups of annular ribs (corresponding to ribs 42a-42c on face 14b in Figs. 2-4), so that adjacent contacting discs would define only two groups of different size passageways in series with each other in the flow of the fluid from the outer edge to the inner edge of the discs, as shown by the arrows in Fig. 5. Figs. 6-8 illustrate another construction of filter discs which may be used in order to produce filtering passageways of decreasing sizes in series with the flow of the fluid from the upstream side to the downstream side of the filter body. In this construction, the ribs 240 formed on face 214a of the filter disc 214 are constituted by a first plurality of essentially radially and circumferentially extending ribs 240a, and a second plurality of essentially circumferentially extending ribs 240b. The first plurality of ribs 240a are arranged to define a first plurality of circumferentially spaced generally rectangular areas extending radially of the disc 214 and having radially inner and outer area sections bounded by the first plurality of ribs 240a. The second plurality of ribs 240b interconnect the radially extending ribs of the first plurality of ribs 240a and define with the first plurality of ribs 240a a second plurality of generally rectangular radially extending areas bounded by the first and second plurality of ribs 240a, 240b. The second plurality of areas being located circumferentially between the first plurality of areas and alternating therewith in radially staggered relationship with the inner and outer area sections of the first plurality of areas. In addition, there are defined by the first and the second plurality of ribs 240a, 240b radially outwardly open inlet areas unbounded by a rib adjacent the outer edge 230a of the disc 214 and located circumferentially between the first plurality of areas and radially outwardly of the second plurality of areas, and radially inwardly open outlet areas unbounded by a rib adjacent the inner edge of the disc 214 and located circumferentially between the first plurality of areas and radially inwardly of the second plurality of areas. The fluid flows radially in the spaces between the adjacent discs 214 from the open inlet areas and the open outlet areas passing through the first and second bounded areas, as shown by the arrows in Fig. 6. In the construction illustrated in Figs. 6-8, the annular ribs 242 formed on the opposite face 214b of the filter discs 214 are divided into four (4) groups 242a, 242b, 242c, 242d, so as to define four groups rather than three groups of different size filtering passageways in series with each other in the flow path of the fluid, as shown by the arrows in Fig. 6. This is more clearly illustrated in Fig. 8 showing a plurality of (three) discs 214 arranged in a stack, wherein it will be seen that the flow passageways defined by annular ribs 242a adjacent to the outer edges 230a of the stack are of largest dimensions and therefore separate the coarsest particles, and annular ribs 242d define the smallest filtering passageways and therefore separate the finest particles. Fig. 9 illustrates a variation in the rib construction of Figs. 6-8. In this embodiment, the ribs 340 formed on the face 314a of each filter disc 314 comprises a first plurality of essentially radially and circumferentially extending ribs 340a, and a second plurality of substantially circumferentially extending ribs 340b. The first plurality of ribs 340a are arranged to define a plurality of circumferentially spaced generally rectangular areas extending radially of the disc 314 and bounded by the first plurality of ribs 340a. The second plurality of ribs 340b interconnect the radially extending ribs of the first plurality of ribs 340a between the inner and outer extremities thereof and define therewith a plurality of radially outwardly open inlet areas and a plurality of radially inwardly open outlet areas unbounded by a rib adjacent the outer edge and the inner edge, respectively, of the disc 314. The fluid flows radially in the spaces between the adjacent discs 314 from the open inlet areas, to the open outlet areas passing through the areas bounded by the first plurality of ribs 340a, as shown by the arrows in Fig. 9. Such a construction is most similar to the sinuous rib construction illustrated in Fig. 5, but in which the peak of the innermost sinuous rib joins the crest of the outermost sinuous rib. The construction in Fig. 9, like that in Fig. 5, requires only two groups of annular ribs on the opposite sides of the filter disc to define passageways of only two groups of different size in series in the path of the fluid flow through the stack of filter discs, as illustrated by the arrows in Fig. 9. In all the above described embodiments, the filter discs are all of the same construction, namely each including the sinuous or area-defining ribs (e.g., 40a-40c or 240a,240b) on one face and the annular ribs (e.g., 42a-42c) on the opposite face. Fig. 10 illustrates another arrangement wherein the stack is constituted of a plurality of discs 414a of one type including the ribs 440 of sinuous configuration on both its faces, alternating with a plurality of discs 414b of a second type including the annular ribs 442 on both its faces. Such an arrangement defines the same type of filtering passageways, and separates the solid particles from the fluid flowing through these passageways in the same manner as described above with respect to the other embodiments of the invention. An advantage of the arrangement of Fig. 10 is that the filter discs of the first type 414a may be the same for all size filters, the size of the filtering passageways in the filter being determined by the dimensions of the annular ribs in discs 414b. This arrangement thereby saves initial tooling and inventory costs in those cases where the filter discs are to be used with filters of many different sizes. A further advantage in all the disclosed embodiments is that the spaces between the sinuous ribs or the rectangular areas may be filled with various materials (e.g., purifiers, deodorisers, filters, etc.) in the form of particles having larger sizes than the filtering passageways defined by the ribs.

Claims: Multiple-disc filter body for separating solid particles from a fluid flowing through the filter body from its inlet side (4) to its outlet side (6), comprising a stack of filter discs (14;114;214;314;414a,414b) in which the adjacent side faces (14a,14b;114a;214a,214b;314a) of each pair of adjacent discs are formed with ribs (40,42;140;240,242;340;440,442) defining filtering passageways therebetween, the ribs (40;140;240;340;440) of one face (14a;114a;214a;314a) of each pair of adjacent discs being of a first configuration, and the ribs (42;242; 442) of the other face (14b;214b) of each pair of adjacent discs being of a second configuration and contacting the ribs of said one face such that the filtering passageways between the pair of adjacent discs are of a size determined by the height of said ribs of said other face of said pair of adjacent discs, characterized in that the first configuration ribs (40;140;240;340;440) on said one face (14a;114a;214a;314a) are formed to define with said second configuration ribs (42;242;442) at least two groups of filtering passages arranged in series flow relationship between the adjacent side faces of each pair of adjacent discs, and that the second configuration ribs (42;242;442) on said other face (14b;214b) are arranged in at least two groups of ribs, the height of the ribs in one of said groups being different from the height of the ribs in a second of said groups, with the higher height group of ribs being on the inlet side of the filter stack so as to define larger size filtering passages of a first of said groups of filtering passages on the inlet side of the filter stack and the smaller height group of ribs being on the outlet side of the filter stack so as to define smaller size filtering passages of a second of said groups of filtering passages on the outlet side of the filter stack. Filter body according to claim 1, characterized in that the first configuration ribs (40;240) and the second configuration ribs (42;242) are formed to define three or more groups of different height filtering passageways in series flow relationship, said filtering passageways decreasing in size from group to group from the inlet side (4) to the outlet side (6) of each pair of adjacent discs (14;214). Filter body according to claims 1 or 2, characterized in that the second configuration ribs (42;242;442) on said other face (14b;214b) of each pair of adjacent discs (14;114;214;414a;414b) are disposed to contact the first configuration ribs (40;140;240;340;440) on said one face (14a;114a;214a;314a) of the pair of adjacent discs substantially at right angles. Filter body according to claim 3, characterized in that said discs (14;114;214, 314;414a,414b) are of circular shape and are formed with a central opening; the first configuration ribs (40;140;240;340;440) on said one face (14a;114a;214a;314a) of each pair of adjacent discs (14;114;214;414a;414b) including portions extending radially of the discs; the groups of ribs of the second configuration on said other face (14b;214b) of the pair of adjacent discs comprising each a plurality of annular, coaxial ribs (42a,42b,42c;242a,242b,242c,242d;442) contacting the radial portions of said first configuration ribs. Filter body according to claim 4, characterized in that said first configuration ribs (40;140) on said one face (14a;114a) of adjacent discs (14;114) include a sinuous rib (40a,40b,40c;140a,140b) for each group of different-height annular ribs (42a,42b,42c) on said other face (14b) of each pair of adjacent discs (14;114). Filter body according to claim 5, characterized in that said one face (14a;114a) of each pair of adjacent discs (14;114) includes at least two sinuous ribs (40a,40b,40c;140a,140b), one extending circumferentially adjacent to the outer edge (30a) of the disc face, and the other extending circumferentially adjacent to the inner edge (28a) of the disc face; and that said other face (14b) of each pair of adjacent discs (14;114) is formed with a number of groups of annular ribs (42a,42b,42c) corresponding to the number of sinuous ribs (40a,40b,40c;140a,140b), including at least one of said groups of annular ribs (42a) extending adjacent to the outer edge (30a) of the disc face, and another of said groups of annular ribs (42c) extending adjacent to the inner edge (28a) of the disc face. Filter body according to claim 4, characterized in that the first configuration ribs (240;340) on said one face (214a;314a) of each pair of adjacent discs (214;314) include a first plurality of ribs (240a;340a) arranged to define a plurality of circumferentially spaced, radially extending and generally rectangular first areas bounded by said first plurality of ribs (240a;340a), and a second plurality of ribs (240b;340b) interconnecting said first plurality of ribs (240a;340a) and defining therewith a plurality of inlet and outlet areas unbounded by a rib on the inlet and outlet side of the filter stack, respectively, said inlet and outlet areas being located circumferentially between the bounded areas and alternating therewith. Filter body according to claim 7, characterized in that each of said first areas comprises a radially inner and a radially outer area section, and that said second plurality of ribs (340b) are arranged to define radially between each inlet and outlet area a second generally rectangular area bounded by said first and second plurality of ribs (340a,340b) and being in radially staggered relationship with the inner and outer area sections of pairs of adjacent first areas. Filter body according to claim 7 or 8, characterized in that the first plurality of ribs (240a;340a) comprise generally radially and circumferentially extending ribs defining said first bounded areas, and said second plurality of ribs (240b;340b) comprise generally circumferentially extending ribs extending between and interconnecting the radially extending ribs of the first plurality of ribs (240a,340a) between the inner and outer extremities thereof. Filter body according to any one of claims 1-9, characterized in that all said filter discs (14;114;214;314) in the stack are of the same construction, each including ribs of said first configuration (40;140;240;340) on one face (14a;114a;214a;314a), and ribs (42;242) of said second configuration on said other face (14b,214b). Filter body according to any one of claims 1-9, characterized in that said stack of discs (414a,414b) includes a first plurality of discs (414a) of one type including ribs (440) of said first configuration on both its faces, alternating with a plurality of discs (414b) of a second type including ribs (442) of said second configuration on both its faces.

Inventors: ROSENBERG, PERETZ
Applicants: ROSENBERG, PERETZ
Application year: 1987
Main classification: B01D29
IPC codes: B01D29