filter

Abstract

A filter (100) is provided that comprises a casing (110) and a plurality of filtration elements (11) stacked between a first cover (50) and a second cover (60). The first cover (50) abuts against the casing (110) in a stacking direction of the filtration elements, and the filter further comprises a cover backing (40) coupled to the second cover (60) by a return system (44) configured to return the second cover (60) towards the first cover (50), the cover backing (40) abutting against the casing (110) in the stacking direction, and the second cover (60) separating a section (118a) of the casing intended to receive a filtered fluid from a section (114a) of the casing intended to receive a fluid to be filtered.

Description

[Technical Field]

[0001] The present disclosure relates to filters, optionally with automatic backwashing. More particularly, the present disclosure relates to improvements in the construction of such filters and methods of assembling such filters. [Background technology]

[0002] Patent Document 1 describes a filtration unit including at least two filter components, each of which has an inner surface, an outer surface, a filtering mesh, two concentric circular edges (an inner edge and an outer edge between which the filtering mesh extends), and radial ribs on at least the inner surface, which extend between the concentric edges and are distributed circumferentially to form separate sectors on the inner surface. The filter components are configured to be assembled with each other so that their respective inner surfaces face each other to define a space therebetween, and the radial ribs separating the sectors form circumferential compartments within the space. At least one of the inner and outer edges has a passage communicating with the corresponding sector. The filter components are stacked axially between a first cover and a second cover.

[0003] By stacking a selected number of filter component pairs, the desired filter area for the intended application is achieved. Typically, the fluid to be filtered penetrates into the stack through passages in the inner edge, passes through the filtering mesh, and, once purified, exits through other passages defined in the outer edge. Of course, the flow of fluid through the filtering mesh can be reversed or arranged in some other way.

[0004] Depending on the dirtiness of the fluid to be filtered, the pressure drop across the filtering mesh can push the facing internal surfaces apart. In exceptional circumstances, this force can even overcome the force of the return springs provided to maintain the filtering components in sealing contact with each other. Leaks can therefore occur. Therefore, there is a need for a filter with improved reliability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Application No. WO2012 / 028824 Summary of the Invention [Means for solving the problem]

[0006] In this regard, the present disclosure relates to a filter comprising a casing and a plurality of filtering elements stacked between a first cover and a second cover, the first cover abutting the casing in a stacking direction of the filtering elements, the filter further comprising a cover backing coupled to the second cover by a return system configured to return the second cover towards the first cover, the cover backing abutting the casing in the stacking direction, the second cover separating a section of the casing adapted to receive a filtered fluid from a section of the casing adapted to receive a fluid to be filtered.

[0007] A filtration element is an element configured to filter a fluid when the fluid flows across the filtration element. The filtration element may comprise two filtering components.

[0008] The first cover and the cover backing abut against the casing in the stacking direction. The first cover and the cover backing may abut against facing portions of the casing, so that the casing prevents the first cover and the cover backing from moving away from each other.

[0009] The second cover is coupled to the cover backing and is returned or biased toward the first cover by a return system that thus provides a force, e.g., a compressive or tensile force, to maintain the filtering element stacked between the first and second covers in sealing contact with each other.

[0010] In addition, because the second cover separates the section of the casing adapted to receive the filtered fluid (hereinafter, for simplicity, referred to as the "clean side") from the section of the casing adapted to receive the fluid to be filtered (hereinafter, for simplicity, referred to as the "dirty side"), the fluid pressure is not the same on both sides of the second cover due to the fluid pressure loss across the filtration element. Thus, the pressure drop across the second cover presses the second cover against the filtration element, thereby complementing the return system to ensure proper sealing contact of the filtration element. Because the pressure drop across the second cover increases with the pressure drop across the filtration element, the force due to the pressure loss across the filtration element does not exceed the force due to the pressure difference across the second cover and the return force of the return system. Thus, filter reliability is improved.

[0011] In some embodiments, the cover liner is openwork. That is, the cover liner may have one or more internal openings for fluid flow therethrough. This facilitates the flow of the fluid to be filtered toward the second cover, reducing pressure loss across the cover liner and thus increasing pressure on the dirty side of the second cover. This further improves filter reliability.

[0012] In some embodiments, at least one of the first cover and the second cover includes a gasket, which may be provided on the periphery of the cover, thereby providing a more reliable separation of the different regions.

[0013] In some embodiments, the return system includes at least one return assembly, each of which includes a spring and a stressing member for stressing the spring. The return system may include multiple return assemblies distributed between the cover backing and the second cover to apply a uniform return force. The springs may be any type of spring, such as helical springs, conical washers, Belleville washers, leaf springs, etc. Each assembly may include two or more springs. Additionally, the stressing member may be any member suitable for stressing a spring, including, for example, a nut, a lock nut, a pin, etc. The spring may be pre-stressed upon activation of the stressing member.

[0014] In other embodiments, each return assembly may comprise a return element other than the spring, for example a resilient element such as an elastomer or magnetic assembly. Without loss of generality, only the case of a spring will be described below.

[0015] In some embodiments, the spring is attached between the second cover and the cover backing. The spring may be a compression spring.

[0016] In some embodiments, the filter further comprises a sleeve extending from the first cover to the second cover. The sleeve may be concentric with the filtering element.

[0017] In some embodiments, the sleeve has a keyed connection with at least one of the first cover and the second cover, thus ensuring proper orientation of the first cover and / or the second cover, further helping to improve reliability.

[0018] In some embodiments, the sleeve has a circumferential groove on the side of the second cover facing the filtering element. That is, the groove may be on the dirty side of the second cover. The groove may be on the same side of the second cover as the cover backing. The groove may aid in assembly of the filter, as described in more detail below.

[0019] In some embodiments, at least one of the first and second covers includes a key for attaching one of a plurality of filtering elements at a predetermined position relative to the at least one of the first and second covers. The one of the filtering elements may be an element adjacent to the first or second cover. The key is an element that provides a keyed connection between the first and / or second cover and a filtering element. Thus, the key predetermines the relative position of the first and / or second cover, for example, angularly, relative to the filtering element. Thanks to the key, the predetermined position between the first and / or second cover can be easily taken into account when assembling the filter.

[0020] The present disclosure is further directed to a method for assembling a filter, the method comprising: - stacking a plurality of filter elements between a first cover and a second cover; - connecting the transmission to the first cover; - coupling the cover backing to the second cover via a return system, the return system configured to return the second cover toward the first cover; - pre-stressing the return system and clamping the cover backing to the transmission; - mounting a plurality of filter elements in a casing such that the first cover abuts the casing in a stacking direction of the filter elements; - at least partially removing the cover backing from the transmission part so that the cover backing abuts the casing in the stacking direction and the second cover separates the section of the casing adapted to receive the filtered fluid from the section of the casing adapted to receive the fluid to be filtered.

[0021] A transmission may be any part configured to withstand a load and transfer the load from the first cover to the cover backing, such load maintaining the filter element stacked between the first cover and the second cover. Thus, by connecting the transmission to the first cover and clamping the cover backing to the transmission, the connection (alternatively, clamping) causes the transmission to neutralize the load and hold the first cover and cover backing against forces applied by the stack of filter element, second cover, and return system.

[0022] By pre-stressing the return system before tightening the cover backing to the transmission, the cover backing may be closer to the first cover than it will be in the final configuration of the filter. Thus, multiple filtering elements can be installed with the first cover, the second cover, and the cover backing in the casing such that the first cover abuts the casing in the stacking direction of the filtering elements, and such that the cover backing abuts the casing in the stacking direction after the cover backing is removed from the transmission.

[0023] At least partially removing the cover backing means releasing at least one degree of freedom of the cover backing to allow it to abut against the casing. In this configuration, the load between the cover backing and the first cover is not transmitted through the transmission part (which may be removed or may be left in place if it has a functional role, for example, for a filter), but through the casing itself. In other words, after fastening, the mechanical load between the first cover and the cover backing is transmitted through the transmission part. After removal, the mechanical load between the first cover and the cover backing is transmitted through the casing. Therefore, the transmission part does not need to be excessively large, and the mechanical load may be temporary.

[0024] The filter resulting from the assembly method may be the filter described above and may have any of the properties described above.

[0025] In some embodiments, the transmission section is located near the filtering element. In this context, "near" means that the transmission section does not intersect with the functional surface of the filtering element, but if the filtering element is annular, the transmission section may be located radially inside or radially outside the filtering element. In these embodiments, the surface of the filtering element may be dedicated to filtering, which may result in increased filtering efficiency. In addition, the transmission section can be more easily removed if necessary.

[0026] In some embodiments, the transfer portion includes a filter sleeve mounted coaxially with the filtering element. The sleeve may be mounted coaxially inside the filtering element.

[0027] In some embodiments, fastening the cover backing to the transmission includes disposing a fastener between the cover backing and the transmission, and the fastener may be configured to stop the cover backing in a stacking direction, e.g., to prevent the cover backing from moving away from the first cover in the stacking direction.

[0028] In some embodiments, the fasteners are located on the side of the cover backing opposite the second cover, so that the fasteners are easily removable, either partially or completely, upon removal, thereby simplifying filter assembly.

[0029] In some embodiments, the load of the return system is transmitted through a first portion of the cover backing when the cover backing is secured to the transmission and through a second portion of the cover backing when the cover backing abuts the casing. The first and second portions of the cover backing may be separate from one another. The first portion may be a portion for fastening the cover backing to the transmission, and the second portion may be a portion configured to abut the casing. In these embodiments, the first and second portions may be operated separately, which facilitates assembly.

[0030] The present disclosure further relates to a filtering component for a filtration unit with backwash, the filtering component being annular and comprising an inner edge, an outer edge and a filtering medium extending between the inner and outer edges, the filtering component having an inner surface and an outer surface on either side of the filtering medium, on the inner surface, ribs extending between the inner and outer edges being circumferentially distributed to form sectors, the filtering component being adapted to be assembled to a first identical filtering component such that each facing inner surface defines a space circumferentially bounded by each contacting rib of said inner surface, the first of the inner and outer edges having passages communicating with each sector on the inner surface, the outer surface having a key for mating with the filtering component at a given position to a second identical filtering component, the key being arranged such that the passages of the second identical filtering component are offset relative to the passages of the filtering component.

[0031] The filtration media may extend over some or all of the distance between the inner edge and the outer edge. One side of the filtration media defines the interior surface of the filtration component, and the opposite side of the filtration media defines the exterior surface of the filtration component. The filtration component may be generally flat.

[0032] It should be understood that the first identical filtering component and the second identical filtering component are identical to the disclosed filtering component (also referred to as the "reference" filtering component to avoid ambiguity) with respect to at least the cited characteristics, and may differ with respect to other characteristics.

[0033] The internal surface of the reference filtering component is therefore configured to be assembled to the internal surface of a first identical filtering component. The external surface of the reference filtering component is therefore configured to be assembled to the external surface of a second identical filtering component. Thus, a stack of identical filtering components can be obtained, each filtering component being upside down relative to the adjacent filtering component. However, despite being assembled to identical filtering components, the internal and / or external surfaces of the reference filtering component may also be assembled to different filtering components.

[0034] The ribs defined on the interior surface allow for the isolation of the backwash sectors. The exterior surface need not be partitioned. At least one passage may be provided on the exterior surface, e.g., the second of the inner and outer edges, for the clarified fluid outlet and the backflush inlet. Conversely, on the interior surface, the second of the inner and outer edges may be devoid of passages, so that fluid entering one sector via a passage must cross the filtration media to exit that sector.

[0035] Because the passages communicating with each sector on the internal surface are all located on the first of the inner and outer edges, the direction of the filtered flow is the same for all sectors on the internal surface. Therefore, the external surface may be simplified. As a result of both considerations, the flow is more uniformly distributed, reducing pressure loss. Additionally, because the direction of the filtered flow is the same for all sectors on the internal surface, the material forming the internal surface is distributed regularly during the manufacturing of the filtering component, reducing the possibility of manufacturing defects.

[0036] A key is an element that provides a keyed connection between the respective exterior surfaces of a reference filtering component and a second identical filtering component. The key thus predetermines the relative position, e.g., angularly, of the second identical filtering component with respect to the reference filtering component. The key may include a physical element that provides the physical cooperation.

[0037] The key may be located between the inner and outer edges to reduce the bulk of the filtering component.

[0038] The offset may be a circumferential offset of the annular filtering component.

[0039] By arranging the keys so that the passages of a second identical filtering component are offset relative to the passages of the filtering component, the passages of adjacent filtering components can be isolated for backwashing sequentially rather than simultaneously. Therefore, the number of sectors backwashed simultaneously is reduced. As a result, the specific backflush flow, i.e., the backflush flow per unit surface of the filtering medium, is increased within the backwashed sectors without increasing the overall backflush flow, which would require the filter to be oversized as described above, or increasing the number of sectors, which would reduce the overall filtering surface due to the space occupied by the ribs. Therefore, backwash efficiency is improved.

[0040] In some embodiments, the key is configured to prevent assembly of the exterior surface with the interior surface of a second identical filtering component. For example, the key may be mechanically incompatible with the interior surface of the second identical filtering component. Thus, proper assembly of the filter, and therefore proper positioning of the passageway, is ensured.

[0041] In some embodiments, the interior surface comprises a first indicator and a second indicator for mating with a corresponding second indicator and a corresponding first indicator, respectively, on the interior surface of a first identical filtering component, and the key is offset relative to an axis of symmetry that transforms the first indicator into the second indicator.

[0042] As explained above, the internal surface of the reference filtering component is adapted to be assembled to the internal surface of the first identical filtering component. The relative positions of the reference filtering component and the first identical filtering component are determined by respective first indicators paired with respective second indicators. The first and second indicators may provide a keyed connection.

[0043] Since a first indicator of one of the filtering components is paired with a second indicator of the other filtering component, there is a symmetry that transforms the first indicator into a second indicator within the same filtering component. This symmetry has an axis, and the keys are offset relative to that axis. Thus, the key of the reference filtering component is shifted relative to the key of the first identical filtering component. This induces a progressive offset of the exterior surfaces of the filtering components relative to each other, and therefore the passages of the subsequent filtering components.

[0044] In some embodiments, the ribs extend beyond the filtration media to the exterior surface, and the thickness of the ribs on the exterior surface is less than the thickness of the ribs on the interior surface. That is, the exterior surface includes ribs that extend the ribs on the interior surface. However, the thickness of the ribs on the exterior surface is less than the thickness of the ribs on the interior surface. Thus, pressure drop across the exterior surface is reduced, but the mechanical durability of the filtration component is not reduced.

[0045] In some embodiments, the keys face at least one of the ribs across the filtration medium. While the keys are located on the exterior surface and the ribs are located on the interior surface, having the keys facing at least one of the ribs across the filtration medium maximizes the filtration medium surface available for filtering fluid flow. Filtration and backwash efficiency are therefore increased. Where applicable, the keys may be located on the ribs on the exterior surface.

[0046] In some embodiments, the filtration media comprises a mesh that slopes from one end of the inner edge to the opposite end of the outer edge, helping to increase the filtration surface area and reduce pressure drop.

[0047] The present disclosure is further directed to a filter element for a filtration unit with backwash, the filter element being annular and having an inner edge, an outer edge, and a filter medium extending between the inner edge and the outer edge to define a pre-filter chamber, at least the pre-filter chamber being circumferentially partitioned in sectors, at least one of the inner edge and the outer edge having a passage communicating with each sector, the filter element further having a key for mating with an identical filter element at a given position, the key being arranged such that the passages of the identical filter element are offset relative to the passages of the filter element.

[0048] The filtration element may comprise a pair of facing filtration components, such as a reference filtration component and a first identical filtration component, as described above. In this case, the pre-filter chamber may be defined between the interior surfaces of the facing filtration components. In addition, the identical filtration element may comprise a second identical filtration component. In other embodiments, the filtration element may not be divisible into two filtration components.

[0049] The filtering element may be used as a filtering element in the filters described above.

[0050] By arranging the keys so that the passages of the same filter element are offset relative to the passages of the filter element, backwash efficiency is improved for the same reasons as detailed above.

[0051] In some embodiments, the key is outside the pre-filter chamber.

[0052] In some embodiments, the keys are provided on two opposite sides of the filter element at different positions on the two opposite sides. Thus, the filter element assembled on one side of the reference filter element may have a different position than the filter element assembled on the other side of the reference filter element, and / or both may have a different position than the reference filter element itself. Thus, a better distribution of passages is obtained, making backwashing more efficient.

[0053] The present disclosure is further directed to a filtration section for a filtration unit with backwash, the filtration section being a filtration component as previously described or a filtration element as previously described.

[0054] In some embodiments, the key comprises a protrusion and a recess, the protrusion being configured to engage a recess in the same filtering portion, thus ensuring proper positioning.

[0055] Where applicable, the protrusions and / or recesses may be invisible to avoid creating channels in which filtered fluid mixes with unfiltered fluid.

[0056] In some embodiments, the offset is an offset by a non-integer multiple of a sector. A non-integer multiple is a multiple that is not an integer and is either less than or greater than 1, for example, 1 / 2, 1 / 3, 3 / 2, 2.4, etc. An offset of only 1 is an offset that transforms sectors into adjacent sectors, and in particular, aisles into adjacent aisles. Thus, by having the offset be an offset by a pitch that is a non-integer multiple of a sector, the offset of the aisles can be accurately and uniformly controlled.

[0057] In some embodiments, the key makes the filtering portion non-rotationally symmetric, i.e., there is no rotation greater than 0° and less than 360° through which the key is transformed onto itself, thus ensuring unique positioning of the continuous exterior surface of the filtering portion.

[0058] The present disclosure is further directed to a filtration assembly for a filtration unit with backwashing, comprising a sleeve and a plurality of filtration sections stacked on one another, each filtration section having a filtration medium and a plurality of passages for directing fluid to the filtration medium, the passages opening onto partitioned sectors, and the filtration sections keyed to the sleeve such that the passages of one filtration section are offset relative to the passages of an adjacent filtration section.

[0059] As previously described, the filtration section may be a filtering element or component and may have some or all of the properties described above.

[0060] The sleeve may be assembled around the stack of filtration sections, or inside the stack of filtration sections if the filtration sections are annular. The sleeve itself may be annular.

[0061] It should be noted that the filtration sections do not have to be keyed to each other, as long as they are keyed to a common element, here the sleeve. A hybrid solution is also conceivable, where some filtration sections are keyed to each other and some to the sleeve.

[0062] Because the filter section is keyed to the sleeve so that the passages in one filter section are offset relative to the passages in an adjacent one of the filter sections, backwash efficiency is improved for the same reasons detailed above.

[0063] In some embodiments, the sleeve has openings facing the passages, and the openings are circumferentially offset along the length of the sleeve, i.e., the openings at one longitudinal position are circumferentially offset from the openings at another longitudinal position. In addition to matching the passages of the filtering section, offsetting the passages circumferentially along the length mechanically strengthens the sleeve.

[0064] Alternatively or additionally, the openings may be elongated to match different locations in the filtering passageway.

[0065] The present disclosure is further directed to a filtration unit including a plurality of filtration components as described above, or a plurality of filtration elements as described above, or a plurality of filtration sections as described above, or a filtration assembly as described above, the filtration unit further including a rotary backwash distributor configured to selectively isolate passageways to enable backwashing within corresponding sectors.

[0066] The rotary backwash distributor may have an opening that is periodically and selectively in communication with the passageways, for example, at least one of the passageways aligned perpendicular to the direction of movement of the rotary backwash distributor.

[0067] The invention and its advantages will be better understood on reading the following detailed description of embodiments, given by way of non-limiting example, which description refers to the accompanying drawings, in which: [Brief explanation of the drawings]

[0068] [Figure 1] FIG. 1 is a perspective view of an interior surface of a filtering component according to one embodiment. [Figure 2] FIG. 2 is a perspective view of the exterior face of the filtering component of FIG. 1. [Figure 3] FIG. 1 is a perspective view of a stacked filtering component according to one embodiment. [Figure 4] 7 is a cross-sectional view of a filtration unit according to an embodiment taken along plane IV-IV of FIG. 6. [Figure 5] 7 is a cross-sectional view of a filtration unit according to an embodiment taken along plane VV of FIG. 6. [Figure 6] 1 is a longitudinal cross-sectional view of a filter according to one embodiment. [Figure 7] FIG. 7 is an exploded perspective view of some of the components of the filter of FIG. 6. [Figure 8] FIG. 7 is a detailed view of region VIII in FIG. 6. [Figure 9] 1A-1D illustrate steps of a method for assembling a filter according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0069] A filtering component 10 according to one embodiment is described with reference to Figures 1 through 3. To properly distinguish between different filtering components when described together, elements related to filtering component 10 (also known as the reference filtering component) receive a standard reference, elements related to a first identical filtering component 10' receive the same reference with the addition of a ' (prime), and elements related to a second identical filtering component 10" receive the same reference with the addition of a ' (double prime), but may not be shown or labeled in the figures themselves.

[0070] The filtering component 10 is annular about a central axis X and defines an axial direction (hereinafter "axial direction X"). A radial direction is a direction that is perpendicular to and intersects the central axis. An axial plane is a plane that contains the central axis. A radial plane is a plane that is perpendicular to the central axis. A circumferential plane is a circle that is contained within the radial plane and has its center on the central axis. A tangential or circumferential direction is a direction that is tangent to the circumferential surface and is perpendicular to the central axis but does not intersect it.

[0071] Unless otherwise stated or understood from context, "inner" and "outer" are used with reference to the radial direction, such that inner elements are closer to the central axis X than outer elements.

[0072] Here, the filtering component 10 includes an inner edge 24, an outer edge 26, and a filtering medium 22 extending between the inner edge 24 and the outer edge 26. The inner and outer edges 24, 26 may be annular and circular about a central axis X. For example, as shown, the inner and outer edges 24, 26 may be concentric. The inner edge 24 extends primarily in a radial plane. The outer edge 26 extends primarily in a radial plane.

[0073] In this embodiment, the diameter of the outer edge 26 ranges from about 100 mm to about 600 mm.

[0074] The filtration medium 22 may be a filtration mesh (hereinafter "mesh 22" without loss of generality) or any other filtration medium. The mesh 22 defines, on either side in the axial direction X, an inner surface 20, shown in FIG. 1, and an outer surface 21, shown in FIG. 2, of the filtration component 10. The characteristics of the mesh 22 may be adapted to the fluid to be filtered and the expected impurities to be removed from that fluid.

[0075] The filtering component 10 comprises ribs 28 provided at least on the inner surface 20. The ribs 28 extend from the inner edge 24 to the outer edge 26. The ribs 28 may extend radially. The ribs 28 may also be linear. The ribs 28 are, for example, regularly distributed circumferentially to form sectors on the inner surface 20, as shown in FIG. 1.

[0076] Thus, when the filtration component 10 is assembled to a first identical filtration component 10' (see FIG. 3, in which the filtration media 22 is omitted for clarity) so that the respective interior surfaces 20, 20' face each other, the respective ribs 28, 28' contact each other to circumferentially define a space between the interior surfaces, also known as a pre-filter chamber.

[0077] In the non-limiting example shown, each filtering component 10 is divided into 20 regularly spaced sectors in the circumferential direction. Depending in particular on its diameter size, a filter element may have fewer or more sectors, for example due to mechanical limitations.

[0078] The reinforcing ribs 29 may additionally extend between the inner edge 24 and the outer edge 26, and / or between the ribs 28 and each other, and / or between the ribs 28 and at least one of the inner edge 24 and the outer edge 26, as shown in Figure 1. In this embodiment, the reinforcing ribs 29 are provided between two consecutive ribs 28. The reinforcing ribs 29 may extend radially as shown for ease of manufacturing, however, other orientations (e.g., circumferential, angled, etc.) are contemplated.

[0079] On the inner surface, the reinforcing ribs 29 may not extend axially as far as the ribs 28, i.e. may be at least partially recessed compared to the ribs 28, so that the reinforcing ribs 29 do not create separations between the sectors. In other words, the distal surfaces of the reinforcing ribs 29 may be closer to the mesh 22 than the distal surfaces of the ribs 28. However, other configurations are possible to ensure that the reinforcing ribs 29 do not further separate the sectors.

[0080] When the filtering component 10 is assembled to a first identical filtering component 10′ (see FIG. 3) with the respective inner surfaces 20, 20′ facing each other, the respective reinforcing ribs 29, 29′ may face each other in a direction perpendicular to the filtering mesh (e.g., axially or substantially axially) to facilitate the flow of filtered fluid and thus reduce pressure loss.

[0081] As previously mentioned, the first of the inner edge 24 and outer edge 26, here inner edge 24, has passages 30 that each communicate with a corresponding one of the sectors on the interior surface 20. The passages 30 may be provided as notches or cutouts in the inner edge 24. The passages 30 may be provided between successive radial ribs 28.

[0082] On the other hand, the other edge, here outer edge 26, may have no passages on inner surface 20 such that, for example, when filtering component 10 is assembled to a first identical filtering component 10′ with their respective inner surfaces 20, 20′ facing each other (see FIG. 3), the respective outer edges 26, 26′ are in sealing contact with each other to prevent flow from the space defined between said inner surfaces (pre-filter chamber) through outer edge 26.

[0083] Figure 2 shows the exterior surface 21 of the filtering component 10 of Figure 1. As shown in Figure 2, on the exterior surface 21, the outer edge 26 has passages 32. The passages 32 may be provided as notches or cutouts in the outer edge 26. The passages 32 may be provided between successive radial ribs 28.

[0084] The radial ribs 28 on the inner surface 20 and the outer surface 21 face each other on opposite sides of the mesh 22. In other words, the ribs 28 on the inner surface 20 and the outer surface 21 correspond axially to each other. In other words, the ribs 28 extend from the inner surface 20, across the filtration media, to the outer surface 26.

[0085] On the exterior surface 21, at least some of the ribs 28 and reinforcing ribs 29 may have protrusions 31 that may protrude axially from said ribs. The protrusions 31 separate passages 32 on the exterior surface 26 from one another. The protrusions 31 may extend from the outer edge 26 and / or from the corresponding ribs 28 or reinforcing ribs 29. As a result of the protrusions 31, the ribs 28 may not separate sectors on the exterior surface 21. In addition, the thickness of the ribs 28 on the exterior surface 21 is less than the thickness of the ribs 28 on the interior surface 20 to reduce pressure loss on the exterior surface 21.

[0086] The filter component 10 may be manufactured by molding around the mesh 22. In other words, the filter component 10 may be manufactured by injection molding or the like, with the mesh 22 forming an insert in a mold. The molded part may be made of metal (e.g., aluminum alloy) or plastic material, in particular a polymer. The ribs 28, reinforcing ribs 29 and the inner and outer edges 24, 26 may be coated with an elastomer to prevent leakage between the filter components 10.

[0087] In operation, the fluid to be filtered, e.g., a liquid such as oil or water, enters through passages 30 in inner edge 24 of filter element 10 and can pass across filtering mesh 22 from interior surface 20 to exterior surface 21, whereupon the liquid is filtered and exits filter element 10 through passages 32 in outer edge 26. The opposite flow direction is also possible.

[0088] To increase the available filtering surface, multiple filter components 10 can be stacked. As previously described, filtering components 10 are assembled one to the other such that inner surface 20 faces inner surface 20′ of an adjacent filtering component (e.g., a first identical filtering component 10′) and outer surface 21 faces outer surface 21″ of an adjacent filtering component (e.g., a second identical filtering component 10″).

[0089] As shown in FIG. 1 , the interior surface 20 includes a first indicator 34 and a second indicator 35 for mating with a corresponding second indicator 35′ and a corresponding first indicator 34′, respectively, on the interior surface of the first identical filtering component 10′. In this embodiment, the first indicator 34 includes a protrusion, e.g., a male bushing or boss. In this embodiment, the second indicator 35 includes a recess, e.g., a female bushing. The shapes of the first indicator 34 and the second indicator 35 are complementary. The first indicator 34 and the second indicator 35 may be provided so that the filtering component 10 and the first identical filtering component 10′ can be assembled in a single relative position, as shown in FIG. 3 . The first indicator 34 and the second indicator 35 may be diametrically opposed.

[0090] Additionally, the exterior surface 21 has a key 36 for mating with a filtering component at a given (possibly unique) location relative to a second identical filtering component 10". The key 36 may include a protrusion 37 (e.g., a male bushing or boss) and a recess 38 (e.g., a female bushing). As shown in FIG. 2, there may be multiple protrusions 37 and / or recesses 38, with only one being shown for the sake of brevity. The protrusion 37 is configured to engage with a recess 38" of the second identical filtering component 10". Similarly, the recess 38 is configured to receive the protrusion 37" of the second identical filtering component 10", as shown in FIG. 3. The protrusion 37 and recess 38 may be diametrically opposed.

[0091] To prevent incorrect assembly of the filter components with one another, the key 36 may be configured to prevent assembly of the exterior surface 21 onto the interior surface 21" of a second identical filtering component 10". In this embodiment, for example, the first and second indicators 34, 35 on the interior surface 20 have a similar shape to the keys on the exterior surface 21, but are sized such that they cannot cooperate with one another. For example, the protrusion of the first indicator 34 may not fit into the recess 38 of the key 36.

[0092] As previously described, the key 36 is positioned such that the passage 30" of the second identical filtering component 10" is offset relative to the passage 30 of the filtering component 10. In particular, as shown in FIG. 2, the key 36 is offset relative to the axis of symmetry Y that transforms the first indicator 34 into the second indicator 35. Thus, when the second identical filtering component 10" is inverted and assembled to the exterior surface 21 of the reference filtering component 10, the second identical filtering component 10" must be rotated relative to the key 36 of the filtering component 10 to match the key 36" of the second identical filtering component 10".

[0093] Thus, the offset may be a circumferential angular offset. The offset may be an offset by a non-integer multiple of a sector. In the illustrated embodiment, the offset is an offset by a half sector. Thus, the passages 30 are circumferentially shifted by a half sector from one filtering component to another.

[0094] The key 36 makes the filtering component 10 rotationally non-symmetrical, as shown diagrammatically in FIG. 2, where axis Z is perpendicular to the central axis X and the symmetry axis Y. Thus, a given position for mating with a second identical filtering component 10" is unique.

[0095] To ensure an effective filtration surface, key 36 may face at least one of the ribs, including rib 28 or reinforcing rib 29, in a direction across filtration medium 22, here in axial direction X. Similarly, but independently, first indicator 34 and / or second indicator 35 may face at least one of ribs 28 or reinforcing rib 29 in a direction across filtration medium 22.

[0096] Optionally, and as shown (see FIG. 1), first indicator 34 and / or second indicator 35 may face key 36 in a direction across filtration media 22 .

[0097] The bushings forming part or all of the first indicator 34, the second indicator 35 or the key 36 may be obscured, for example as shown in Figure 1 relative to the key 36, to avoid leakage. In fact, the bushings may not face each other along the entire stack of filtering components 10 due to an offset, so that sealing cannot be ensured only by having adjacent bushings engage each other on the entire stack.

[0098] By assembling a filtering component 10 with a first identical filtering component 10', a filtering element 11 is created, where each filtering component 10 corresponds to a so-called half-filter element. Furthermore, in general, filtering elements 11 can be formed differently, for example as a unitary part or as an assembly of non-identical parts.

[0099] The above characteristics may also apply to a filter element for a filtration unit with backwashing, where the filter element is annular and has an inner edge (instead of the combination of respective inner edges 24, 24′), an outer edge (instead of the combination of respective outer edges 26, 26′), and a filter medium extending between the inner and outer edges to define a pre-filter chamber (instead of the space between facing interior surfaces 20, 20′), at least the pre-filter chamber being circumferentially partitioned in sectors (perhaps by separation other than by respective abutting ribs 28, 28′), at least one of the inner and outer edges having passages communicating with each sector, and the filter element further having a key (perhaps similar to key 36) for mating with an identical filter element at a given position, the key being arranged so that the passages of identical filter elements are offset relative to the passages of the filter elements.

[0100] The key may be external to the pre-filter chamber to facilitate assembly of the filtration element 11 with an adjacent (possibly identical) filtration element 11'. In the above embodiment, the exterior surface 21 is external to the pre-filter chamber defined between the facing interior surfaces 20, 20'.

[0101] Additionally, the keys are provided on two opposite sides of the filtering element at different positions on the two opposite sides. The different positions may be circumferentially offset relative to each other to induce a circumferential offset of another filtering element assembled to the filtering element. If the filtering element comprises, for example, two filtering components as described above, the different positions may be with their respective outer surfaces facing away from each other.

[0102] Everything stated in this disclosure with respect to a filtering component applies mutatis mutandis to a filtering element. The expression "filtering section" refers to a filtering component and / or a filtering element, as the case may be.

[0103] 4 and 5 illustrate the principle of backwashing a filtering component 10. For this purpose, FIG. 4 shows a filtering unit 90 with a sleeve 70 and multiple filtering sections stacked on top of one another, but only one filtering component 10 is visible in a cross-sectional view. The sleeve 70 is arranged concentrically with the filtering component 10, here beside (e.g., radially inside) the filtering component 10. The sleeve 70 is in sealing contact with the filtering component 10. The sleeve 70 has an opening 72 facing the passage 30 of the filtering component 10. The opening 72 is therefore circumferentially offset along the longitudinal direction of the sleeve, here along the axial direction X, as shown in FIG. 6.

[0104] To avoid pressure loss, openings 72 may have approximately the same size as passages 30 (e.g., within 10% or less), so that the sleeve is not mechanically weakened. In other embodiments, to facilitate manufacturing of the sleeve, openings 72 may be circular, e.g., the diameter of the circle is the largest dimension of the corresponding passage 30.

[0105] Filtration unit 90 further includes a rotary backwash distributor 80 configured to selectively isolate passageways 30 to enable backwashing within corresponding sectors. In this embodiment, distributor 80 is mounted within a central conduit 92 formed inside sleeve 70 and through which fluid to be filtered is supplied to passageways 30.

[0106] For example, in this embodiment, distributor 80 has a shutter 82 with a discharge opening 84 and is mounted to rotate, for example, about central axis X, so that discharge opening 84 is cyclically and selectively connected to each of passages 30.

[0107] 6, the discharge openings 84 may extend longitudinally, whether or not continuous, over multiple filter sections, so that all passages 30 radially corresponding to the discharge openings 84, e.g., all of the passages aligned, are simultaneously in communication with the discharge openings 84. For example, the openings 84 may be linear. The openings 84 may extend parallel to the central axis X.

[0108] 4 and 5 show that the shutter 82 is large enough to ensure that the passageway 30 is not in communication with the discharge opening 84 and the central conduit 92 simultaneously.

[0109] Although the illustrated embodiment has a unique discharge opening 84, multiple discharge openings 84 may be provided. The discharge openings may be circumferentially distributed so that the frequency of backwashing a given sector can be increased without increasing the speed of the backwash distributor 80. The multiple discharge openings 84 may be such that when one sector is fully backwashed through one of the discharge openings 84, the other discharge openings 84 do not face any passageway or the backwash-specific flow is reduced.

[0110] Due to the offset of the passages 30 in adjacent filtering sections, the number of passages 30 simultaneously in communication with the discharge openings 84 is reduced. The backflush flow is therefore divided among fewer sectors, increasing the specific backflush flow.

[0111] In fact, FIG. 5, a view similar to FIG. 4 but relating to another filtering component, here an adjacent filtering component, shows that the discharge openings 84 are not in contact with any of the passages 30 in the plane of FIG. 4, but are in communication with the passages 30 in the plane of FIG. 5. Upon rotation of the backwash distributor 80, the shutter closes the passages 30 in FIG. 5, and the discharge openings 84 are in contact with the passages 30 in FIG. 4. This configuration achieves a filter with continuous backwashing, i.e., at least one sector is backwashed for every position of the backwash distributor 80. Continuous backwashing may also be obtained in other ways, for example, with multiple discharge openings 84. Conversely, with an appropriate size of the discharge openings 84, the filter may achieve discontinuous backwashing, i.e., there are positions of the backwash distributor 80 in which no sectors are backwashed.

[0112] Additionally, other types of backwash distributors are included, such as backwash distributors having fixed columns in communication with each of the passages 30.

[0113] It should be noted that in addition to or instead of being keyed to one another, the filter sections may be keyed to the sleeve 70 such that the passages of one filter section are offset relative to the passages of an adjacent one of the filter sections. All types of keying are encompassed, including those described above.

[0114] In the '661 patent, the filter sections are held together by a rod that extends through the entire stack of filter sections. Then, given the progressive offset of the filter sections relative to each other, providing the necessary features to allow for the insertion of the rod through the entire stack of filter sections adds unnecessary complexity. Instead, an alternative assembly system has been proposed.

[0115] 6 shows a filter 100 comprising a casing 110 and a stack of filtering parts, such as the filtering elements described above, each filtering element comprising a pair of filtering components 10. The filtering elements are stacked axially between a first cover 50 and a second cover 60.

[0116] The first cover 50 abuts against the casing 110 in the stacking direction of the filtering elements, here in the direction of the central axis X. In particular, the first cover 50 may abut against a shoulder 112 of the casing 110, which shoulder 112 forms a stop for the first cover 50 against axial and optionally radial movement.

[0117] The first cover 50 may be generally annular. The first cover 50 may have a central opening for insertion of the sleeve 70, as shown in FIG. 6 . The first cover 50 may extend radially from the sleeve 70 and outwardly relative to at least the outer edge 26 of the filtering component 10. The first cover 50 and the sleeve 70 may be in sealing contact with one another, for example, with a tight gap therebetween. A gasket may be provided, if desired.

[0118] The first cover 50 may include a gasket 52. In this embodiment, the annular gasket 52 is received in a circumferential groove in the first cover 50, and the gasket 52 is then compressed between the casing 110 and the first cover 50.

[0119] Similarly, but independently, the second cover 60 may be generally annular. The second cover 60 may have a central opening for insertion of the sleeve 70, as shown in FIG. 6 . The second cover 60 may extend radially from the sleeve 70 and outwardly relative to at least the outer edge 26 of the filtering component 10. The second cover 60 and the sleeve 70 may be in sealing contact with each other, for example, with a tight gap therebetween. However, because the sleeve 70 and the second cover 60 are both within the dirty section, no sealing is necessary.

[0120] Thus, the sleeve 70 extends from at least the first cover 50 to the second cover 60 .

[0121] The second cover 60 may include a gasket 62. In this embodiment, the annular gasket 62 is received in a circumferential groove in the second cover 60, and the gasket 62 is then compressed between the casing 110 and the second cover 60.

[0122] To ensure proper alignment of the openings 72 in the sleeve 70 and the passages 30 in the filtering element, the sleeve 70 may have a keyed connection with at least one of the first cover 50 and the second cover 60. For example, as shown in FIG. 7 , the first cover 50 may have at least one flat surface 54 (here, two regularly spaced flat surfaces) configured to mate with a corresponding flat surface 74 on the sleeve 70 or on a circular surface. Although not provided in this embodiment, the same type of connection or another keyed connection may be provided between the sleeve 70 and the second cover 60. For example, instead of having a separate flat surface 74, the sleeve 70 may have a locally polygonal cross-section.

[0123] Additionally, at least one of the first cover 50 and the second cover 60 may include a key for mounting one of a plurality of filtering elements at a given position relative to the at least one of the first cover 50 and the second cover 60. In this embodiment, FIG. 7 shows that the second cover 60 includes a key 64. The key 64 may include a recess configured to engage with the key 36, particularly the protrusion 37, of the filtering element. FIG. 6 shows that the first cover 50 similarly, but independently, includes a key 56. The key 56 may include a recess configured to engage with the key 36, particularly the protrusion 37, of the filtering element. Thus, the filter 100 here illustrates a keyed connection between the sleeve 70 and the filtering element through at least one of the first cover 50 and the second cover 60, e.g., the first cover 50. For ease of manufacturing, the keys 56, 64 of the first and second covers may match the keys 36 of the filtering element without being identical.

[0124] As shown diagrammatically by the arrows in FIG. 6 , the fluid to be filtered enters the filter through an inlet 114 of the casing 110, passes through a strainer 116, and enters the central conduit 92 and the openings 72 of the sleeve 70 that are not isolated by the backwash distributor 80. After filtering through the filtration section, the filtered fluid is conveyed outside the filtration section and extracted at an outlet 118 of the casing 110. Simultaneously, the backwash distributor 80 is driven to rotate, for example, by the motor 104. The backwash fluid is discharged through the discharge opening 84 and directed to a discharge outlet 120 for backwash fluid. If desired, the backwash fluid itself may be purified through another similar filtration unit.

[0125] Thus, within the casing 110, the second cover 60 separates the section 118a of the casing 110 adapted to receive the filtered fluid from the section 114a of the casing adapted to receive the fluid to be filtered. A fluid pressure drop between the so-called dirty section 114a and the so-called clean section 118a therefore biases the second cover 60 towards the first cover 50, thus helping to maintain the filtering components 10 in sealing contact with one another.

[0126] Additionally, as previously described, the filter 110 further comprises a cover backing 40. The cover backing 40 is coupled to the second cover 60 by a return system configured to return the second cover 60 toward the first cover 50. As shown in FIG. 6 , the cover backing 40 abuts the casing 110 in the stacking direction. In particular, the cover backing 40 may abut a shoulder 122 of the casing 110, which forms a stop against axial and optionally radial movement of the cover backing 40. The shoulder 122 may have a continuous annular shape or may be provided as a plurality of separate supports.

[0127] The cover backing 40 may be generally annular. The cover backing 40 may have a central opening for insertion of the sleeve 70, as shown in FIG. 6. The cover backing 40 may extend radially from the sleeve 70 and outwardly relative to at least the outer edge 26 of the filtering component 10.

[0128] 7, the cover backing 40 is openwork, i.e., the cover backing 40 has through openings 42 that allow fluid to pass through, which helps maximize the pressure differential across the second cover 60. The openings 42 may be angularly distributed around the periphery of the cover backing 40.

[0129] A method for assembling filter 100 will now be described with reference to FIGS.

[0130] As described above, the method includes step S1 of stacking a plurality of filtering elements between a first cover 50 and a second cover 60. Each filtering element may include a pair of filtering components 10, and the connection between adjacent filtering elements and / or components may be keyed as described in detail above. Each of the first cover 50 and / or second cover 60 may face the exterior surface 21 of the filtering component 10 closest thereto.

[0131] Then, in step S2, the transmission part is connected to the first cover 50. In this embodiment, the transmission part is a sleeve 70. In this embodiment, the transmission part is provided beside the filtering element, here radially inside and coaxially. However, other arrangements are possible, for example, radially outside the filtering element.

[0132] The sleeve 70, or more generally the transmission portion, may cooperate with the first cover 50 such that relative displacement of the first cover 50 with respect to the sleeve 70 is at least partially prevented. In this embodiment, as shown in FIG. 6 , the shoulder 76 of the sleeve 70 acts as a fastener for the first cover 50. Additionally, as described in detail above, the flat surface 74 limits rotation of the first cover 50 with respect to the sleeve 70. Thus, the sleeve 70 is radially and axially connected to the first cover 50.

[0133] It should be noted that step S2 may also be performed before or simultaneously with step S1. Thus, a transfer part such as sleeve 70 may act as a guide for stacking the filtering element onto first cover 50.

[0134] Thereafter, in step S3, the cover backing 40 is coupled to the second cover 60 via the return system 44. The return system 44 includes at least one, and here a plurality of, return assemblies 45, one of which is shown in more detail in FIG. 8. The return system 44 is configured to return the second cover 60 toward the first cover 50. In this embodiment, the return assemblies 45 are each provided between two adjacent openings 42.

[0135] It should be noted that the openings 42 may extend over more than half the surface of the cover backing 40 between two consecutive return assemblies 45 (e.g., two consecutive holes 40a, see below and FIG. 7). Relatively large openings 42 make it possible to avoid the accumulation of contamination on the cover backing 40.

[0136] In this embodiment, the return assembly 45 includes a spring 46 (here, a helical compression spring, but other springs are also encompassed) and a stress-applying member 47, such as a lock nut (hereinafter referred to as "lock nut 47"). The return assembly 45 may further include a pin 48.

[0137] The pin 48 has a pin head 48a that cooperates with a corresponding engagement portion 66, e.g., a recess, in the second cover 60. Optionally, a flange 48b is provided below the pin head 48a so as to abut against the second cover 60, so that the load is distributed over a larger portion than the sole pin head 48a.

[0138] The pin 48 includes a pin body 48c extending from a flange 48b opposite the pin head 48a. The pin body 48c may be inserted into a hole 40a in the cover backing 40. The pin body 48c may have a non-circular cross-section in the hole 40a to prevent rotation of the pin 48 relative to the cover backing 40.

[0139] At the end of the pin body 48c opposite the flange 48b, the pin 48 may have a locking portion 48d configured to cooperate with the stressing member 47. Here, the locking portion 48d includes a threaded portion for cooperation with the locking nut 47. However, other embodiments are also encompassed, such as an auxiliary pin configured to be inserted into a transverse hole in the pin 48.

[0140] When coupling the cover backing 40 to the second cover 60, the pin head 48a may be inserted into the engagement portion 66 to prevent rotation between the cover backing 40 and the second cover 60. The spring 46 is attached around the pin 48, particularly around the pin body 48c, with one end of the spring 46 abutting the flange 48b. The cover backing 40 is attached to the other end of the spring 46, and the lock nut 47 is threaded onto the stop 48d. The lock nut 47 may be threaded until the spring 46 is as compressed as possible. As shown, the maximum level of compression may be determined by the enlarged portion of the pin body 48c against which the cover backing 40 abuts when the lock nut 47 cannot be further threaded.

[0141] Thus, the stressing member, lock nut 47, stresses the spring 46. In doing so, preferably for each return assembly, the return system 44 is pre-stressed (step S4).

[0142] It should be noted that the cover backing 40 and the return system 44 may be provided pre-assembled together as a subassembly. Similarly, the cover backing 40 may be pre-coupled to the second cover 60, and thus steps S3 and / or S4 may be performed before the other steps.

[0143] In step S5, the cover backing 40 is fastened to the transmission part, i.e., the sleeve 70. In particular, step S5 may include the step of disposing a fastener 130 between the cover backing 40 and the transmission part 70. The fastener 130 may be provided, for example, as a collar with two halves configured to be fastened together by bolts. The fastener 130 is configured to be disposed within a corresponding groove 78 in the sleeve, as shown in FIGS. 6 and 7 . The groove 78 may be disposed on the side of the second cover 60 opposite the filtering element. Furthermore, the groove 78 may be positioned on the sleeve beyond the cover backing 40 such that, when installed within the groove 78, the fastener 130 is disposed on the side of the cover backing 40 opposite the second cover 60.

[0144] The fasteners 130 are configured to limit the stroke of the cover backing 40 in the axial direction X, away from the first cover 50 and the second cover 60 .

[0145] In another embodiment, the fastener 130 may be provided as a resilient collar, perhaps a split collar. In yet another embodiment, the fastener 130 may be provided as one or more screws or pins inserted laterally into the sleeve 70 and cover backing 40. The screws or pins may be inserted from the inside of the sleeve 70 to facilitate removal of the filtration unit 90 when it is installed within the casing 110. In these embodiments, the groove 78 is not necessary. The cover backing 40 may have a thickened portion for insertion of the screws or pins. The thickened portion may be tapered toward the opening 42 to reduce pressure loss.

[0146] In step S6, optionally, lock nut 47 is loosened so that the resulting expansion of spring 46 biases cover backing 40 against fastener 130 and second cover 60 against the filtration element. In doing so, pin head 48 a is prevented from exiting engagement portion 66 when the stack of filtration elements is inverted or otherwise manipulated with a view to installing it within casing 110. Of course, if the clearance required for pin head 48 a to exit engagement portion is greater than the clearance between cover backing 40 and fastener 130, step S6 is not necessary.

[0147] As can be seen in FIG. 6, the lock nut 47 is located in the dirty section 114a so that even when separated from the pin 48 it does not interfere with the purified fluid.

[0148] In this state, the load holding the filtering element together is carried from the first cover 50 to the second cover 60 through the sleeve 70, fasteners 130, cover backing 40, and return system 44. Note that, as shown in FIG. 9, the load provided by return system 44 is transferred through a first portion of the cover backing 40, i.e., the radially inner portion of the cover backing 40.

[0149] In step S7, the plurality of filtering elements, together with the cover backing 40, the first cover 50, the second cover 60, the sleeve 70 and the fastener 130, are mounted within the casing 110 such that the first cover 50 abuts the casing 110 (e.g., the shoulder 112 as described above) in the stacking direction of the filtering elements, i.e., in the axial direction X.

[0150] Thereafter, in step S8, the cover backing 40 is at least partially removed from the transmission part, i.e., the sleeve 70. This may be done by removing the fasteners 130. In doing so, under the influence of the return system 44, the cover backing is further biased away from the second cover 60 until the cover backing 40 abuts the casing 110 in the stacking direction as described above.

[0151] In this configuration, as shown in FIG. 6, the second cover 60 separates the clean section 118a from the dirty section 114a.

[0152] Additionally, with the removal of fasteners 130, no more load is transferred to the transfer section. Instead, the load holding the filter element together is carried from first cover 50 to second cover 60 through casing 110, shoulder 122, cover backing 40, and return system 44. Note that, as shown in FIG. 6, the load provided by return system 44 is transferred through the second portion of cover backing 40, i.e., the radially outer portion of cover backing 40.

[0153] Although this disclosure refers to certain exemplary embodiments, modifications may be made to these examples without departing from the general scope of the invention as defined by the claims. For example, the steps of the above-described methods may be performed in any technically practical order. In addition, the cover backings as described may be used with other types of filtration units, e.g., conventional filtration units. Conversely, the filtration units described herein may be assembled with conventional means, e.g., stacked rod-shaped rods inserted into bushings disposed radially outside the outer periphery, instead of a cover backing. More generally, individual features of different illustrated / described embodiments may be combined in additional embodiments. Accordingly, the description and drawings should be considered in an illustrative rather than a restrictive sense. [Explanation of symbols]

[0154] 11 Filtration element 40 Cover backing 44 Return System 45 Return Assembly 46 Spring 47 Stress-applied members 50 First Cover 52 Gasket 54 Key Connection 56 keys 60 Second Cover 62 Gasket 64 keys 70 Sleeve, transmission part 74 Key Connection 78 Peripheral groove 100 filters 110 Casing Section 114a Section 118a 130 Fasteners

Claims

1. A filter (100) comprising a casing (110) and a plurality of filtering elements (11) stacked between a first cover (50) and a second cover (60), wherein the first cover (50) abuts against the casing (110) in a stacking direction of the filtering elements, and the filter further comprises a cover backing (40) coupled to the second cover (60) by a return system (44) configured to return the second cover (60) towards the first cover (50), the cover backing (40) abutting against the casing (110) in the stacking direction, and the second cover (60) separating a section (118a) of the casing adapted to receive a filtered fluid from a section (114a) of the casing adapted to receive a fluid to be filtered, The cover backing (40) has openings (42) that allow fluid to pass through such that the force due to pressure loss in the filtering element (11) does not exceed the force due to the pressure difference across the second cover (60).

2. The filter of claim 1, wherein at least one of the first cover (50) and the second cover (60) includes a gasket (52, 62).

3. 2. The filter of claim 1, wherein the return system (44) comprises at least one return assembly (45), each of the at least one return assembly (45) comprising a spring (46) and a stressing member (47) for stressing the spring (46).

4. The filter of claim 1, further comprising a sleeve (70) extending from said first cover (50) to said second cover (60).

5. 5. The filter of claim 4, wherein the sleeve (70) has a keyed connection (54, 74) with at least one of the first cover (50) and the second cover (60).

6. 6. A filter according to claim 4 or 5, wherein the sleeve (70) has a circumferential groove (78) on the side of the second cover (60) opposite the filtering element (11).

7. 2. The filter of claim 1, wherein at least one of the first cover (50) and the second cover (60) comprises a key (56, 64) for mounting one of the plurality of filtering elements (11) in a given position relative to the at least one of the first cover (50) and the second cover (60).

8. A step (S1) of stacking a plurality of filtering elements (11) between a first cover (50) and a second cover (60); a step (S2) of connecting a transmission unit (70) to the first cover; a step (S3) of coupling a cover backing (40) to the second cover (60) via a return system (44), the return system (44) being configured to return the second cover (60) towards the first cover (50); a step (S4) of pre-stressing the return system (44) and a step (S5) of fastening the cover backing (40) to the transmission part (70); a step (S7) of attaching the plurality of filter elements (11) in the casing (110) so that the first cover (50) abuts against the casing (110) in the stacking direction of the filter elements (11); a step (S8) of at least partially removing the cover backing (40) from the transmission part (70) so that the cover backing (40) abuts the casing (110) in the stacking direction and the second cover (60) separates the section (118a) of the casing intended to receive the filtered fluid from the section (114a) of the casing intended to receive the fluid to be filtered; A method for assembling a filter (100), comprising:

9. 9. The method according to claim 8, wherein the transfer section (70) is provided adjacent to the filtering element (11).

10. 10. The method according to claim 8 or 9, wherein the transfer part comprises a sleeve (70) of the filter mounted coaxially with the filtering element (11).

11. 10. The method according to claim 8 or 9, wherein the step (S5) of fastening the cover backing (40) to the transmission part (70) includes a step of placing a fastener (130) between the cover backing (40) and the transmission part (70).

12. The method of claim 11, wherein the fastener (130) is located on a side of the cover backing (40) opposite the second cover (60).

13. 10. The method according to claim 8 or 9, wherein the load of the return system (44) is transmitted through a first portion of the cover backing (40) when the cover backing (40) is fixed to the transmission part (70), and through a second portion of the cover backing (40) when the cover backing (40) abuts against the casing (110).

Images