TWO-STAGE FILTER CARTRIDGE FOR FLUID SEPARATION, CARTRIDGE ASSEMBLY AND USE METHOD

Abstract

To simplify the assembly of a filter cartridge (1) which contains the filter element (EF) in a crimped housing (2) having a mechanical fixing face and fluidic connection, while integrating two separate filtration means, the framework of the element results from the interconnection of two parts (11, 12) each serving to carry at least one winding of filter media (M1, M1', M2), by integrating in the first part a first perforated tube (7) and a closed flange (5a) which is inserted into the bottom of a filtration chamber delimited by the housing (2), while the second part includes an open flange with a second tube (8), central and delimiting a central hollow (6) of the element (EF) which communicates with the outlet of the cartridge via the opening of the flange (5b) which is engaged against a cover element (20) forming all or part of the fixing face and fluidic connection. Figure for the abridged version: Figure 1

Description

Title of the invention: TWO-STAGE FILTRATION CARTRIDGE FOR FLUID SEPARATION, ASSEMBLY METHOD AND CARTRIDGE USE technical field

[0001] The invention relates to fluid circuit equipment that allows the separation of a particular liquid or fluid from a main flow such as a gaseous flow (in particular air). A two-stage air filtration cartridge for separating oil or fluid carried in the flow, a method for assembling the cartridge, and a method for using the cartridge are proposed. Technological background

[0002] A filtration operation can be provided in a compact manner by using a cartridge, with the advantage of being replaceable. Purification, with several media to improve separation, is often made possible by such a cartridge for a fluid flow, typically gaseous as in the case of air in circuits becoming saturated with oil: this type of configuration is found in pneumatic braking systems or compressed air supply systems, for example. To allow the circulation of purified air in circuits supplying airflow to areas of interest, for example, to enable friction during braking, it is known to use separation elements to remove oil from the air in compressors, particularly oil-lubricated and oil-cooled screw compressors. In screw compressors, it is common for air to come into contact with oil. The oil is used for sealing, cooling, and lubricating the compressor screw. Separation is achieved in the filter chamber of an oil-separation unit, which is mounted on a support that includes a pipe receiving the separated oil (for recirculation into the oil circuit). Filters with this type of housing for air oil separation can be designed as a screw-on filter cartridge (commonly called a "spin-on" cartridge).

[0003] An oil removal device may include several separation stages. US document 8080080B2 (or its equivalent EP 1 844 840) describes a separator equipped with a pre-separator, an annular oil coalescing filtration element and a post-separator, formed as modules. The design and assembly of the filter element, which must be housed in a cartridge casing, poses difficulties when several filter elements are required.

[0004] To avoid these problems, some high-separation filter media are evolving towards increased efficiency, but at the cost of greater complexity (and therefore higher production costs) and / or a higher pressure drop. This is undesirable, especially since the cartridge is generally a part that is discarded after a certain period of use, thanks to a removable attachment that allows the connection head to be reused.

[0005] More broadly, there is therefore a need for cartridges that are less restrictive for the assembly of the separation parts, while guaranteeing a high level of efficiency and robustness of the assembly. Summary

[0006] To improve the situation, a removable filter cartridge with a rotating mounting fitting is proposed for mounting on a support along a rotating mounting axis, the cartridge allowing the separation of a fluid portion or oil from an admitted flow and comprising: - a filter element having a central axis and provided with a (structural) framework including a first closed flange and a second flange with a central opening which define opposite axial ends of the filter element; - a first piece or structural element, belonging to the framework, including the first flange and a first perforated tube which extends longitudinally from the first flange, around the central axis to an annular end rigidly connected to the second flange; - an external casing delimiting an internal volume containing the filtering element which separates said internal volume into an upstream zone and a downstream zone; - a cover element, belonging to the housing, which includes the fixing fitting and delimits at least one inlet passage communicating with the upstream area where the admitted flow circulates and an outlet passage of a purified flow communicating with the downstream area, the outlet passage formed in the fixing fitting being crossed by the central axis; - a first filtration stage and a second filtration stage which is radially spaced from the first filtration stage to be closer to a hollow interior space in the downstream area; with the particularity that: - the hollow interior space is delimited by a second perforated tube, called the central tube, which is designed and formed with the second flange in a second piece of the framework, which is separate from the first piece; and the frame is made of only these parts (which can allow the frame to be reduced to two parts), each made of plastic material, with the first tube which: - allows the insertion, into the first part or structural element, of the central tube via the annular end of the first tube; - extends around the central tube supporting the second filtration stage; and - supports the first filtration stage.

[0007] The first tube can preferably completely enclose the second (central) tube with the first filtration stage (which can be any type of filtration, for example, with at least one wound filter medium or several combined media). It is understood that the first tube allows the first filtration stage to be positioned along a peripheral space within the internal volume that forms part of the upstream zone, which typically allows this peripheral (annular) space to be delimited from the upstream zone along with the housing. An inlet / access face is thus defined through which the admitted flow (airflow to be filtered or other fluid) arriving through the base or lid element of the cartridge and then circulating around the filter element can pass in a centripetal direction (centripetal filtration direction).

[0008] With these arrangements, it is possible to simplify the assembly of the filter element and the cartridge. The second flange may include a projecting annular axial projection opposite the second tube, extending from the central opening (formed in a radial portion of the flange), to form an axial outlet conduit. The flange with the opening (central opening) is engaged, typically by this type of projection, against the cover element that forms all or part of the mounting and fluid connection face of the cartridge. Advantageously, the second part combines several functions: - by supporting the second filtration stage (from the downstream side following the direction of filtration) on an inner face / turned towards the central axis of a medium of this second stage; - by forming a rigid guide for delimiting the hollow interior space, compatible with guiding a male fixing fitting or similar insert to achieve rotational fixing (screwing or bayonet connection for example); - by also axially supporting the stages, via a common internal flange face coupled / connected to the corresponding ends of the two filtration stages, with the possibility of radially separating the filtration media / means of these two stages, creating a radially intermediate partitioning effect between the peripheral space of the upstream zone and the central tube; and - by defining a fixing / support seat to prevent the lid element from sinking / axially blocking when closing the case, possibly by crimping. The cartridge can present a simple interface for mechanical and fluidic connection to a support base in the form of a connection head incorporating several flow channels.

[0009] In practice, the cover element may form all or part of the fluid connection and fixing face (base side) that allows the housing to be fixed with a rotational lock onto a connection fitting, such as a male threaded fitting or a bayonet fitting with lugs / grooves, for example. The cartridge may be of the crimped housing type, which is entirely metallic or metallic at least in the cover element and the crimped fixing part. It is understood that the filtration stages can be designed as rolls or a winding with one or more media having an annular cross-section around the central axis, while the cover element extends perpendicularly to the central axis. The frame of the filter element results from the interconnection of only two parts, each serving to support at least one winding of filter media.

[0010] The cartridge can be adapted for oil-gas separation. More broadly, the upstream zone can be a flow zone containing a product to be separated, for example, a gaseous flow containing oil / lubricant, which constitutes the inlet flow. The cartridge separates the oil from the gaseous flow by means of the first and second filtration stages, preferably by coalescing with the formation / recovery of oil droplets, all or part of which are separated from the gaseous flow in the hollow internal space.

[0011] In embodiments, the second filtration means or stage includes or consists of a filter medium that has a higher filtration fineness than each filter medium of the first filtration stage. Alternatively, the second filtration stage may include or consist of a filter medium that has a lower filtration fineness than at least one filter medium of the first filtration stage.

[0012] According to one particular feature, the second part is a molded part, preferably made from a thermoplastic material, reinforced or not. The second part may be metal-free. The second part (second flange and central tube) is designed independently of the rest of the filter element in a single molding step. The second part, designed separately from the first part, may have at least the following features: - an annular edge formed by a free end of the central tube; - a thickening to reduce the passage cross-section, the thickening being carried out at a distance from the free end of the central tube and / or from an opposite annular end formed by the axial projection formed on the second flange.

[0013] According to one particular feature, the first part is a molded part, preferably made from a thermoplastic material, reinforced or not. The first tube may be molded with a constant circular cross-section and / or by forming a cylindrical lateral outer face without any discontinuity in material / composition between this first tube and the first flange. The first part may be metal-free. The first part (first flange and first tube) is designed independently of the rest of the filter element in a single molding step, possibly followed by a surface treatment.

[0014] The first part, designed separately from the second part, may have at least the following features: - an annular edge formed by a free end of the first tube; - a thickness exceeding 1 or 2 mm in the first tube, the thickness of the first tube being able to be constant. In addition to, or independently of, the above, the outer diameter of the second tube, which remains substantially constant, can be more than half the (substantially constant) outer diameter of the first tube, but with a ratio between these diameters not exceeding 7:10 (the outer diameter of the central tube, or second tube, thus not exceeding approximately 70% of the outer diameter of the first tube). With this arrangement, the available volume between the two flanges can be advantageously optimized by the filtration system (and thus allow for multiple layers of media), without resorting to complex filtration methods and / or by maintaining a radial spacing between two of the filtration elements / stages, which is beneficial for avoiding pressure drop effects.

[0015] Optionally, in the first part, a radial sealing portion provided in the first flange closes, on the side of a cartridge bottom axially opposite the outlet conduit, the hollow internal space. In addition or alternatively, the annular edge can be snapped onto the first flange and / or embedded in a bonding layer with the first flange, to form a first annular junction between the first part and the second part, which is a junction: - adjacent to the radial obturation part; and - adjacent and radially more inward than an annular axial fixation zone, against the first flange, of a filtering medium of the second filtration stage.

[0016] In embodiments of the cartridge, one or more of the following features may be provided: - the first tube forms a T-shaped section with the first flange in a longitudinal cross-sectional view passing through the central axis. - the first tube is provided with orifices (radial passage) having at least one portion of a straight edge, - the first tube has two parallel, typically straight edges for each of the radial passage orifices. - the second tube is provided with orifices (radial passage) having at least one portion of a straight edge, - the second tube has two parallel, typically straight edges for each of the radial passage orifices. - the radial passage ports for one and / or the other of the tubes of the two parts have a rectangular or square format. - the filtering element has rotational symmetry. - the cartridge is a crimped cartridge, in particular with a peripheral crimp around a lid which includes the lid element. - the cover may include an annular sheet metal part which serves (as a part / means of fastening) for crimping and covers the outside of the cover element, for example by being welded onto the cover element. In some options, the cartridge features a removable cover allowing for selective replacement of the filter element.

[0017] In embodiments of the filtering element, at least one of the following provisions is provided: - the first stage of filtration includes a first filter medium, preferably arranged in the form of a single-layer or multi-layer winding. - the second stage of filtration includes a second filter medium, preferably arranged in the form of a single-layer or multi-layer winding. - the first medium includes glass fibers and / or constitutes a first filter / filtration medium coalescing (oil coalescing), preferably able to form the outermost radially part / inlet face of the first filtration stage. - one of the media is fibrous and / or contains glass fibers, for example with the constituent fibers holding together, without possibility of release. - in the first filtration stage, a filter medium with an oil coalescing effect is provided which includes several layers of the same filter material (layers wound around the central axis, on the outside and possibly arranged adjacent to or against the first tube), - in a multilayer arrangement with an oil coalescing effect in the first and / or second filtration stage, an individual layer of the filter material has an air permeability greater than 150 or 180 L / m2s without exceeding a threshold which is, for example, approximately 1400 or 1600 L / m²s (maximum). This air permeability, which can be measured according to the DIN 53887 standard, makes the cartridge particularly effective for treating oil-laden compressed air. - a coalescing filter material constituting at least one of the first filtration medium / stage and the second filtration medium / stage has an individual layer thickness that is submillimeter. - a coalescing filter material constituting at least one of the first filtration medium / stage and the second filtration medium / stage may optionally have a density which is between 65 and 190 kg / m3, for example without exceeding 70 kg / m3. - the second filter medium comprises or consists of a non-woven material, preferably with the first medium including individual layers wound in a multi-layer arrangement, each individual layer being thinner than an individual filtration layer constituted by the second filter medium.

[0018] In some embodiments, the filter element keeps the filtration means (of the respective filtration stages) spaced apart, for example, by a radial distance greater than 3 or 4 mm. It is understood that: - the first piece and the second piece define between them an intermediate region where a filter medium carried by the second piece can be placed (this medium can be the filter medium of the second stage of filtration, for example with a higher filtration fineness by presenting a non-woven structure whose thickness is greater than 1 or 2 mm). - the first perforated tube and the first flange allow the first part to carry the first filter medium by placing the latter radially further out than the intermediate region. - the first filter medium is adapted to be permeable or semi-permeable to oil, having a coalescing effect. - the second medium is adapted to be permeable to oil, having a coalescing effect.

[0019] According to one particular feature, where the first and second parts define an intermediate region containing at least one filter medium, the first tube is radially spaced from an outer (radially outermost) lateral face of the second filtration stage and / or the filter element allows droplets that have passed through the first filtration stage to fall / begin to fall by gravity towards the second flange, upstream of the second filtration stage. The filter medium placed in the intermediate region may be: - carried by the second piece; and - designed to allow oil droplets to coalesce by joining the hollow interior space.

[0020] In examples of cartridge embodiments, one and / or the other of the following arrangements may be provided: - the only metallic parts of the cartridge belong to the housing and / or are external to the filter element. - the cover element is metallic and connected, via a conductive connecting part, to the second tube and to at least one of the media of the first filtration stage and / or the second filtration stage. - the frame is axially in contact with the lid element. - the contact, preferably annular, of the frame on the cover element is achieved by the axial projection which forms a barrier element between the upstream area and the axial outlet conduit. - the cover element forming a cartridge connector to allow removable rotating mounting. - the cover element is part of a cartridge end located opposite the first flange, this cartridge end forming a fluidic fixing and connection face, preferably by integrating an annular seal arranged on the periphery / around the gas inlet passages or openings. - the lid element is a part of the housing which extends parallel to the bottom of a main component or bowl of the housing, axially opposite this bottom in the cartridge whose mounting axis can be confused with the central axis of the filter element. - the cartridge includes a single sealing element, formed by the annular seal mounted on the fixing and fluidic connection face (outer side / opposite the inner volume), the second piece not carrying any sealing element separate from the frame. - the filter cartridge is mounted removably by its connection face, for example by having internal fixing means in a central recess of a plate (made in one piece, preferably metallic) constituting the cover element. - the lid element has a central recess forming a female screwing element. - the filter element is pre-assembled by a connection step between the first part and the second part. - The connection step typically includes or is performed simultaneously with: a connection step of an axial end of each filter media of the first stage with the second flange (on its inside); and a step of connection of an axial end of each filter media of the second stage with the first flange (on the inside of it).

[0021] The interior space and the intermediate space can be spaces with rotational symmetry. In some options, the first part has a shell shape made of a single plastic material, possibly delimiting a central hollow by a cylindrical inner face. The first piece can define: - an external diameter of the filter element, by an external annular edge of the first flange; and - an internal volume of the shell (which is for example an empty space of the cartridge made up of the central hollow, preferably of circular cross-section), accessible by an axial opening having a diameter. Typically, the first tube has a total length, measured from a plane of the first flange, equal to a length of the central tube, so that the central tube is entirely located within the volume.

[0022] Depending on the options, the filter element has a second flange with annular edges projecting towards the first flange. A radial (annular) portion of the second flange supports or provides a means of connection, for example by bonding, with the annular end of the second part. The two annular edges (annular projections) can each define a receiving area on an inner face of the second flange, allowing for the application of an adhesive layer whose outer circumference is delimited, respectively, by one of these annular edges. Regardless of any specific reliefs or projections on the inner side of the second flange (around the periphery of the central tube), the second flange has, externally / on the side of the cover element, an axial projection that forms one end of the filter element opposite (axially) to the other end of the filter element formed by the first flange. Optionally, the axial projection may define an internal diameter larger than the diameter of the hollow internal space defined by a cylindrical face of the second tube.

[0023] The filter element can be elongated along the central axis so that the frame is longer than it is wide. Typically, the second piece is the longer part of the filter element, which consists of only two rigid parts: the first and second pieces. The central tube of the second part can: - present a constriction zone, preferably by presenting an annular bulge radially projecting inwards, to define a minimum passage section for access to the hollow interior space, opposite the second flange; - and / or be thicker than the second flask.

[0024] Optionally, the filter element has: - a hollow annular end, proximal to or in contact with the lid element, formed by the axial projection of a circular section (or more generally with an annular geometry), preferably made without discontinuity (without a slit or opening). - a second flange which has a single central opening for the selective passage of a fitting (hollow tubular insert) inserted beyond a screwing area (typically threaded area) or connection with rotation locking. - in both flanges, the same external diameter.

[0025] Depending on one or more specific features, the first part has: - in the first flange an average thickness which is less than or equal to an average thickness of the first tube. - on the side of an outer face (forming an external face of the filter element), a guide to center an elastic return element (helical spring for example) interposed between a bottom of the housing and the filter element. - a protruding annular relief forming the guide for the elastic return element. - a rim, preferably annular, for retaining the outermost filter media (radially) in the filter element, the rim forming a (short) projection parallel to the first tube extending from the same plane of the first flange, which is defined by the radial sealing part of the flange.

[0026] After securing the filtration means to the corresponding support tubes, the assembly operation can be rapid, without the need for an additional frame component (flange or other part designed separately from the flanges). When overmolding of a filter medium is planned onto a corresponding tube, this can be done on the outside of that tube (on an external face of the shell / tube), typically with a frame uncovered / without filter media on the internal face of the central tube. Throughout this text, the gas stream to be purified is referred to as air or airflow. Naturally, the cartridge can separate oily liquid from any type of gas stream whose main component is air.

[0027] In embodiments of the filtering element, one or more of the following features may be provided: - a frame tube includes a bead, ribs or projections, for example radially projecting opposite an annular / tubular filtration layer carried by that tube. - the thickness of one medium and / or each medium is between 3 and 20 mm, preferably between 4 and 10 mm. - the framework has, on both flanges, two edges projecting axially towards each other, so that the first filtering medium is held between a perforated lateral face of the first tube and the two edges. - the frame is entirely made of plastic material, without any metal parts in either piece and / or possibly with the integration of an electrically conductive plastic part, for example in the second flange.

[0028] According to another aspect, a method for assembling a filter cartridge, preferably an oil-gas filter (to separate liquid oil), is proposed, which has an external housing containing a filter element and including a fixing fitting (fixing with rotational movement for locking, for example a screw) allowing this cartridge to be mounted removably on a support along an axis (axis of the rotating mounting), the method comprising the following steps: - forming two perforated tubes in two separate parts, a first part / structural element including a first tube and a first flange, and the other is a second part which includes a second flange and a second tube called the central tube, which is narrower than the first tube, the second flange being perpendicular to the central tube and having a central opening to allow axial access to a hollow internal space delimited by the central tube; - to secure a first stage of filtration to the first part in order to allow a first filtration around the first tube; - attach a second filtration stage to the second part in order to allow a second filtration around the central tube; - assemble the filter element by interconnecting the first piece which supports the first filtration stage and the second piece which supports the second filtration stage, by inserting the central tube into the first tube (which can join the first flange in a final insertion state), so that the filter element has a framework made up of these two pieces, with the second filtration stage radially spaced from the first filtration stage to be further away from a central axis of the filter element which is an axis of symmetry for each of the tubes; - insert the filter element into a hollow component or bowl of the external housing and then enclose the filter element in the external housing, by fixing on the hollow component a cover element provided with the fixing fitting with a purified flow outlet passage which communicates with the hollow interior space, said cover element also delimiting at least one inlet passage of admitted / filtered flow.

[0029] The method can limit the number of structural parts of the filter element to maintain the different filtration means / stages and thus the number of fasteners between these different parts. Assembly is easy and compatible with the use of a housing (with its cover element) compatible with existing operations and / or machines for attachment to a connection head. The fixing allowed by the fitting provided in the (rigid) cover element can be of the screw type or bayonet connection type. Once both shells / parts are supplied, the process can proceed with the following successive steps or operations: - the filtration media are joined on the two pieces, leaving one axial face of the media uncovered for each of these media; - the two shells or parts are joined together to obtain the filter element as a single unit; - the filter element is inserted inside the hollow component of the housing; - the opening of the hollow component is sealed to close the filtration chamber, by axially interposing the cover element between the frame and an annular fixing / connecting element which seals the housing, preferably with a crimping operation of a cover including the cover element. Optionally, a rigid tube (fitting for fixing to the connection head) with an insertable part is added, which fits into the hollow internal space of the filter element, possibly by establishing internal contact against an annular bead provided on the central tube.

[0030] The various connections on the inside of the flanges of the filter element and the media attachments to the respective tubes can thus be achieved in a minimum number of steps. This is advantageous for a two-stage assembly, each stage having one or more wound layers consisting of at least one filter medium. The first flange seals one end of the first tube, thus forming a closed flange, which allows an axial access point in the first tube opposite the purified gas outlet of the filter element to be sealed, with the flange arrangement perpendicular to a longitudinal axis of the first tube.

[0031] According to one particular feature, the interconnection, preferably achieved without rotational indexing, is carried out until the central tube is inserted to the point where the axial support of the second filtration stage is aligned with a radial portion of the second flange. This flange supports, on the same inner side, the respective annular axial ends of the first and second filtration stages. In another variant, rotational indexing is provided for assembling the filter element. The internal volume (filtration chamber) of the cartridge can be divided into two zones (upstream and downstream) by the filter element without the need for an elastomeric or similar annular seal attached to the filter element. Preferably, to achieve the final inserted state of the filter element, the cover element is directly engaged, by axial contact, against the frame by pushing An axial projection of the second protruding piece, opposite the central tube, from the radial portion of the second flange. The axial support of the axial ends of the stages occurs, for example, simultaneously, the radial portion potentially forming a flat internal surface opposite the filtration stages. Optionally, the axial ends of the filtration stages may be coplanar.

[0032] According to one aspect, it is proposed to use the filter cartridge as defined above to filter a compressed air stream. Typically, the cartridge that enables this type of filtration is screwed, via the mounting fitting, onto a connection head belonging to the lubrication system of a mechanism. After this screwing or similar connection, the cartridge can provide a stream of compressed air purified by oil removal. A coalescence effect is provided in at least one of the filtration means / stages. In this configuration / use, the cartridge is configured such that: - a male fitting (forming a sub-part of the mounting base or connection head) is inserted into the central tube by making radial contact against an internal face of the central tube; - at least one inlet passage receives compressed air coming out of a lubrication zone of the mechanism.

[0033] The cartridge's filtration means, distributed around the central axis at various positions, are suitable for being arranged in a small / compact volume (the internal volume of the housing can be less than 4 or 5 L) and for allowing filtration of a high gas flow rate (optionally an air or similar gas flow rate), with, for example, a filtration capacity greater than 150 or 300 m³ / h permitted for the cartridge, possibly reaching or exceeding 500 m³ / h, for operation compatible with working pressures exceeding ten or fifteen bar. Optionally, the cartridge constitutes a submicron oil separator for removing oil mist and any fine particles. Furthermore, the absence of structural metal parts in contact with the media of the filtration stages avoids corrosion / alteration problems of metal parts. Brief description of the drawings

[0034] Other features, details and advantages will become apparent from reading the detailed description below, and from analyzing the accompanying drawings, on which: [Fig.1] is a longitudinal sectional view of a cartridge provided with two tubes which are part of the frame of the insert or filter element, with one of the tubes engaged on a male fitting of a cartridge support, according to one embodiment. Fig. 2 is a perspective view illustrating, here omitting the filter media, a pair of parts forming the framework of the filter element fitting a screw-on cartridge such as the one visible in Fig. 1. Figure 3 is a flowchart showing an example of the sequence of steps in a cartridge assembly process, according to an embodiment that separates the attachment of the outermost filter element to a first frame component from the attachment of subsequent filter elements to a second frame component. Figure 4A shows, in detail, an example of attachment means used to connect at least one of the tubes, via an annular end, to the flange belonging to the other frame component. Fig. 4B represents, with a longitudinal section, an example of an implementation obtained by bonding, here in areas distributed on the inside of the flanges in a way compatible with the partitioning allowed by the first tube interposed between the two means / stages of filtration, so that the two parts of the framework are made inseparable. Figure 5 represents a longitudinal section of a cartridge, in an embodiment option with a metal cover and a conductive element to prevent an electrostatic discharge phenomenon at the level of the filtration means. Figure 6 schematically represents the use of the cartridge to purify an oil-laden gas from a compressed gas flow circuit. Description of implementation methods

[0035] With reference to Figures 1 and 2, an assembled arrangement of a filter cartridge 1 on a mounting insert forming a hollow tube-type RC fitting is shown, with a peripheral mounting area provided on this RC fitting. The cartridge 1 comprises an outer housing 2, a filter element EF housed inside a hollow component or bowl of this housing 2, and a positioning interface for the filter element EF allowing its mounting along a mounting axis. The filter element EF may have a central axis X, for example, such that the filter element EF has rotational symmetry about this central axis X. The hollow component of the housing 2 may be made in one piece.The housing 2 is closed by sealing the single opening of the hollow component with a cover, after having previously installed the filter element, possibly by compressing or energizing an elastic return element RI (for example in the form of a spring) engaged against an axial end of the filter element EF located opposite the single opening of the hollow component.

[0036] The housing 2 may include a domed apex 2a (forming a bottom of the hollow component) and a side wall extending around the filter element EF from the domed apex 2a to a connection end of the housing 2. The side wall is of preferably substantially cylindrical and without opening, the inlet for the airflow (with typically an inlet passage distribution O) and the outlet of purified air 20s being arranged in the lower end located opposite the bottom of the cartridge 1. The connection end makes it possible to make a connection face FC of the cartridge 1 (as seen in [Fig.6]) and can here be constituted by a wall which extends transversely, for example substantially perpendicularly, to the central axis X of the filter element EF.

[0037] As clearly shown in Figures 1 and 6, the cartridge 1 forms a filter for purifying a liquid portion of an admitted flow, which may be a gaseous flow, by defining a filtration chamber corresponding to the internal volume of the housing 2. A gas-liquid filtration cartridge can be obtained. The installation with such a filter includes a reusable connection head S and the replaceable filter cartridge 1. Two separate filtration means or stages 3, 4 (typically spaced apart) are provided in the filter element EF. In the non-limiting example of [Fig. 1], the filter element EF comprises two flanges 5a, 5b, between which the respective filtration media constituting the filtration stages extend (in a coiled or annular fashion). Each filter medium extends parallel to the central X axis, forming a tubular wall through which the gas / fluid to be filtered can pass, for example allowing this flow to be de-oiled.More broadly, a fluid part of an (undesirable) component which is transported in the admitted flow can be separated by the combination of media provided in these filtration stages 3, 4. The filter element EF includes a frame 15 comprising two flanges, which are respectively: a first closed flange 5a positioned opposite the connection face FC, and therefore opposite the cover element 20 which includes the inlet passages O; and a second flange 5b with a central opening 05 allowing axial circulation of the purified flow (airflow in the case of [Fig. 6]) which can exit the cartridge 1 through its central outlet, via the cover element 20 and the connection face FC. The cartridge 1 may include an external seal, relative to the housing 2, which is a sealing element / ring seal arranged around the periphery / around the inlet passages or openings O.

[0038] With reference to [Fig. 2], the frame 15 is designed in only two parts 11, 12, the first part 11 including the first closed flange 5a, and the second part 12 including the second flange 5b with its opening 05. These two flanges 5a, 5b define opposing axial ends E1, E of the filter element EF. The central tube 8 may include an end forming an end 12a or free annular edge of the second part. The frame 15 further has a two-tube arrangement 7, 8, which may be concentric around the central axis X. The first flange 5a is integrally formed with the first flange 5a in the first part 11, while the second tube 8 which is a central tube is integrally formed with the second flange 5b in the second piece 12. As can be clearly seen for example in [Fig. 1], each of the two tubes 7, 8 is perforated (with respective radial openings 7a and 8a), which allows the filter element EF to perform centripetal filtration, the airflow or admitted flow being able to circulate first in the first filtration stage 3 carried by the first part 11 by extending around the first tube 7, before then passing through the second filtration stage 4 carried by the second part by extending around / against the central tube 8.

[0039] The outer face of the first tube 7 allows to support a layer of filter media of the first filtration stage 3.The outer face of the second tube / central tube 8 can support a layer of filter media of the second filtration stage 4 which is a layer which covers the entire tube (or at least all the radial openings 8a of this tube 8), up to the end 12a, while the inner face of this central tube 8 allows to delimit an internal space 6 hollow of the filter element EF. . In the first part 11, which includes a first tube 7 wider than the central tube 8, it is intended that the dimensions of the first flange 5a with an external diameter D15 are similar or identical to those of the second flange 5b. Figure 2 illustrates the non-limiting case in which the filter element EF has an external diameter D15 which corresponds to an external dimension common to both flanges 5a and 5b.

[0040] The first part 11 extends longitudinally from the first flange 5a, around the central axis X, to an annular end E2 which is rigidly connected to the second flange 5b, during the single step of interconnecting parts 11 and 12 allowing to obtain the framework 15, while finalizing the assembly of the filter element EF. The filter element EF separates the internal volume of the housing 2 into an upstream zone ZI and a downstream zone Z2. The filter element EF is substantially tubular and separated from the side wall of the housing by a peripheral space that forms part of the upstream zone ZI. The upstream zone ZI corresponds to an inlet space for the flow (laden with liquid / oil) admitted into the cartridge 2, before filtration, at the bottom of the filter 1 in the case illustrated in [Fig. 1] and on the periphery. The upstream zone ZI is thus connected to the inlet of the cartridge 1. The downstream zone Z2 corresponds to the internal space 6 through which the oil-free air or similar purified flow circulates, and may include an additional sub-zone delimited by an axial, annular projection 8c of the second flange 5b which joins the cover element 20. This zone Z2 communicates with the outlet passage for the purified flow (gas / purified air, for example).

[0041] The cover element 20, belonging to the housing 2, includes an RF fastening region or means which forms part of the cartridge fitting 1 to allow its mounting with rotational fixing / locking along a rotating mounting Z-axis. The RF fixing region or means allows rotational engagement with the complementary ZF fixing zone. It is understood that the axial outlet conduit formed by the projection 8c and the outlet passage 20s can be aligned. Preferably, the cover element 20 can define a passage section slightly narrower than the inner diameter of the projection 8c, with a threaded area delimiting this passage section, the threaded area forming the RF fixing region. Option(s) for manufacturing the structural parts of the filter element

[0042] More broadly, the first part 11 can be a rigid, molded plastic part, preferably molded from a thermoplastic material. The radial openings 7a of the tube 7 can result from this molding, with an opening shape that may have straight edges, including two longitudinal edges. The second part 12 can be a rigid molded plastic part, preferably made from a thermoplastic material. The radial openings 8a of the tube 8 can result from this molding, with an opening format having straight edges, including two longitudinal edges.

[0043] In the second part 12, the axial projection 8c can extend outwards so as to be located, in the assembled cartridge, opposite a guide 7c, for example a hollow one, formed on an outer face of the first flange 5a (forming an outer face of the filter element EF). As can be seen in the example in [Fig. 1], the guide 7c, annular or formed of annularly distributed reliefs, can allow the elastic return element RI (helical spring, for example) interposed between a bottom / top of the housing 2 and the filter element EF to be centered. This guide 7c is formed, in the first part 11, opposite the tube 7, and the first flange 7c forms a disk between these two elements.

[0044] The second flange 5b has an annular inner face which can be adapted to allow the insertion of the annular end E2 of the first part 11 into an intermediate region (radially) between an external rim 102, typically annular, of the flange 5b and a short, ring-shaped projection 5c, projecting on the inside and adapted to retain an axial end of a filter medium M2 of the second filtration stage 4. The axial projection 8c can delimit a slightly enlarged passage section, compared to a more interior section of the tube 8, typically by delimiting an internal diameter D8' ([Fig.5]) larger than a diameter D8 ([Fig.1]) of the hollow interior space 6 delimited by the cylindrical (interior) face of the tube 8.

[0045] With reference to [Fig. 1], it is understood that the second part 12 can constitute the most elongated part of the filter element EF, which comprises only two rigid / structural parts consisting of the first and second parts 11, 12. In [Fig. 2], We can see that the two pieces are hollow in the manner of a shell, with a longitudinal passage with a single outlet formed in tube 7 and a longitudinal passage with two opposing outlets in tube 8. The first piece 11 can have a shell shape by being made of a single plastic material.

[0046] This first part 11 defines, on the one hand, an external diameter D15 of the filter element EF, by an external annular edge of the first flange 5a, and on the other hand, an internal volume V7 of the shell, accessible by an axial opening having a diameter D7 sufficiently large for the complete insertion of the tube 8 of the volume V7. It can be noted that, on the side of the first flange 5a, several openings 8a which open radially into the downstream zone Z2 delimited by the radial portion PR are very close to the flange 5a and, optionally, less distant axially from the first end El than are the radial openings 7a closest to this end El.

[0047]

[0048] The frame 15 can accommodate at least two filter media of different design / structure, for example, with two filter media M1, M1' assembled in the first filtration stage 3 and positioned further out (radially) than the first tube 7, and at least one filter media M2 positioned radially further inward than the first stage 3, preferably between the central tube 8 and the short projection 5r (possibly smaller than 10 or 13 mm). The filter media M2, positioned away from the first tube 7, can constitute all or part of the second filtration stage 4. The outermost of the media Ml can define the peripheral inlet face 3a of the filter element which extends parallel to the central axis along the upstream zone ZI. Filtration means constituting the filtration stages

[0049] With reference to [Fig.5], showing in more detail the connection face FC, it is understood that the frame 15 can integrate an intermediate region 14, between the two tubes 7 and 8 which is not entirely filled by the second filtration stage 4. The first part 11 and the second part 12 thus define, between them, the intermediate region 14 where at least one filter medium M2 carried by the second part 12 is disposed, in such a way that an inlet face F4 of this second stage 4 is uncovered, with the possibility for oil droplets emerging (by coalescence, typically) from the first stage 3 to fall or shift axially, before passing through the second filtration stage 4. Before the frame 15 is rigidly fixed, the filter media M2 can be supported by the second part 12, by being assembled onto the central tube 8 from the outside, while the filter media Ml, Ml' can be carried by the first part 11, by being assembled on the central tube 7 from the outside.

[0050] At least in a media Ml, Ml' constituting the first filtration stage 3, it can be provided that each individual layer of the corresponding filter material has an air permeability greater than 150 or 180 L / m2s, as measured according to a DIN 53887 standard. More broadly, it can be provided for the first filtration stage 3 a filter medium Ml, Ml' which has an oil coalescing and / or oil-removing effect and which limits the effects of pressure drop.

[0051] Figure 4A shows that, after installing the filtration stages 3 and 4, a snap-fit ​​connection, using clips, can be made so that one end of a tube of part 11 or 12 (here, tube 7) is fixedly connected to the flange of the other part 11 or 12. A groove G7 can be provided on the end of one of the tubes 7 or 8 for the engagement of a snap-fit ​​connector edge or clips 5C provided on the inside of the flange. More generally, the areas for making the connection can be close to the flanges 5a and 5b so as not to interfere with the centripetal filtration. An embossing method of bonding can also be implemented, where appropriate with compression of the media at its end in axial contact with a flange. Figure 4B shows, as an alternative or additional method, the possibility of gluing the inside of flanges 5a and 5b to allow for the fixing of the annular axial ends of the filtration stages 3 and 4. Example(s) of assembling a filter cartridge with two stages

[0052] A method for assembling a filter cartridge 1, such as that shown in [Fig. 1], may involve a reduced number of fastening steps. With reference to [Fig. 3], a step 50 of supplying the frame parts 15 is carried out, with the formation of: - at molding step 50a, of the first part 11 in a single structurally homogeneous block (mono-material for example); and - at molding step 50b, of the second part 12 in a single structurally homogeneous block (mono-material for example). The molding can be of the injection type (without blow molding). More broadly, it is understood that shaping the plastic material of these two parts 11, 12 allows the two perforated tubes 7, 8 to be formed in two separate parts, each including a suitable end flange.

[0053] A fixing phase 51 is then carried out to mount and secure each of the filtration stages 3, 4 to a corresponding tube. This fixing phase 51 involves: - securing 51a the first filtration stage 3, typically by winding one or more layers of at least one filter medium M1, M1' around it of the first tube 7, the winding can for example be obtained prior to fixing on the first tube 7; - secure 51b the second stage of filtration 4, typically by mounting a winding, in the form of one or more layers, of at least one filter medium M2 around the central tube 8. This involves distributed fastening operations, which allow for the creation of two modules before a connection operation between these two modules. This connection is achieved by inserting the second stage / filtration medium, structured by the central tube 8, into the hollow or volume V7 of the first tube 7 and securing it with flanges 5a and 5b at the end of this insertion. This connection operation corresponds to step 52 of the assembly of the filter element EF. The media M1, M1', and M2 can be selected to enable oil-gas filtration of the cartridge 1.

[0054] The bondings 51a, 51b thus correspond to preliminary steps (for example two separate steps) of fixing media M1, M1', M2. During these preliminary media fixing steps, at least one layer of adhesive L7, L7', L8 or a fixing material may already be pre-deposited on the inside of one and / or the other of the flanges 5a, 5b, on an annular holding area. As in the example of [Fig.4B], it is understood that the first flange 5a allows two continuous but separate connection zones to be defined, with the possibility of receiving a first layer of adhesive L7 used for the axial fixing of the first filtration stage 3 and a second layer of adhesive L7' used for the axial fixing of the second filtration stage 4, which can be separated from each other by an annular section of the tube 7 at which the latter joins the flange 5a in a T-profile section. The first part 11 includes a radial sealing portion PR provided in the first flange 5a to close the hollow internal space 6, on the side of a cartridge bottom axially opposite to the axial outlet conduit of the connection face FC. Whether the annular end or edge 12a is snapped onto the first flange 5a and / or embedded in the bonding or adhesive layer L7' (layer deposited on the radial portion of the first flange 5a), it is understood that it is permissible to create a first annular junction between the first part 11 and the second part 12 which is a junction: - adjacent to the radial sealing portion PR; and - formed on the end or edge 12a, being located radially more inward than an annular zone F2 for the axial fixation of the filter media M2 against the first flange 5a.

[0055] More broadly, after structuring the filtration stages by the two joinings 51a, 51b, it is understood that the assembly process provides for finalizing the obtaining of a filter element (here with two filtration stages), at step 52 by an effective assembly so that the filter element EF has its two ends. Opposite flanges El and E (one of which is closed) enclose the respective media Ml, Ml', and M2. The internal space of the central tube 8 is then sealed by the radial portion PR of the first flange 5a and becomes the hollow internal space 6 of the filter element EF. More generally, it is understood that this hollow internal space 6 is delimited only (laterally and axially) by metal-free plastic parts. Step 52 includes the interconnection of the first part 11 which supports the first filtration stage 3 and the second part 12 which supports the second filtration stage 4, so that the filter element EF has a double tube frame 15 made up of the two parts 11, 12, with the second filtration stage 4 radially spaced from the first filtration stage 3 (to be further away from the central axis X).

[0056] In certain options, such as the one shown in [Fig. 5], the filter element EF may further incorporate a conductive line 17 for connecting all or part of the media M1, M1', M2 of the filtration stages to ground via the cover, in particular via the cover element 20, which is metallic and has a thread / fixing area ZF. In the case illustrated here, a conductive element forms the connection or conductive line 17, which extends around the periphery of the second flange 5b in its portion connecting to the cover element 20. Another portion of this conductive line 17 may run radially inward along the second flange 5b to at least one of the media of the first filtration stage 3 and / or the second filtration stage 4.It is understood that the conductive element can also be integrated, for example in the form of a charged or conductive layer forming part of the second flange 5b extending to the cover element 20. More broadly, an electrical charge dissipation effect can be provided by any conductive part or line 17, a portion of which is carried by the filter element EF.

[0057] Again with reference to [Fig. 3], after obtaining the filter element EF with or without the integration of an electrical charge dissipation function, the process includes a step 53 of placing the filter element EF into a hollow component or bowl of the housing 2, by inserting the filter element from the side of its first flange 5a towards the apex 2a at the bottom of the hollow component. The flanges 5a, 5b, with respective rims 101, 102 (made of plastic material which may be the constituent material of parts 11, 12), protect the first media M1 during this insertion. The guide 7c, an example of whose design is clearly visible in [Fig. 2], surrounds or is arranged annularly around the elastic return element RI at the end of this insertion, before carrying out step 53 of closing the outer housing 2.The closing position of the cover element 20 is locked by use of a retaining element 20', arranged in an annular manner without covering the outlet passage 20s or the opening(s) O provided around / at a distance from the central axis X in this cover element 20. This retaining element 20' covers a portion of the margin of the cover element 20 and can define a receiving groove for the annular seal 5. The element 20' can be in the form of sheet metal or metal foil, previously attached (for example by being welded), before the closing step 53, to the cover element 20. A crimping is for example carried out on an external edge of the element 20 and on an annular end of the hollow component, around the housing opening which allowed the insertion of the filter element EF.

[0058] In the non-limiting case of [Fig.5], the cover element 20 is directly engaged, by axial contact, against the frame 15 by pushing the axial projection 8c of the second part 12. A centering projection may be provided, internally and in a position adjacent to the fixing region RF, in order to engage, with a guiding effect, in the axial projection 8c. The RC fitting, in contact with the cover element, can be a fixed part which remains permanently with the connection head, for example having the RCb part, external to the cartridge 1, which remains attached to the rest of the connection head S, while the RCa insertion part retains the cartridge 1 in its mounting position by fixing zone ZF. Example(s) of support - Applications

[0059] In the non-limiting example of [Fig. 1], the cartridge 1 is shown screwed onto the rigid RC fitting, which is, for example, in the form of a metal sleeve. It is understood that the fitting is part of a mounting base or connection head S intended to be connected to an air circuit passing through a lubrication zone. The connection head S may have an inlet, for example in the form of a channel C4, for raw air laden with oil / oil mist, and an outlet—possibly with a lower extension corresponding to a diverging path—for purified air. The RC fitting with its central insert or insert part RCa has, in Figures 1 and 6, an axial sleeve permanently attached to an interface of the connection head S.This type of connection interface with the RC fitting allows for quick and easy attachment of the filter cartridge 1, and is suitable for use with conventional filter cartridges (screw-on / spin-on type) whose housing 2 is formed from a thin layer of metal.

[0060] It can be noted that the lower end of the part forming the RC connection can allow air to be released in a lower area of ​​the connection head, once the cartridge has been mounted / assembled and locked along its mounting axis Z. In some options, all or part of the connection head can be made of a plastic material, for example by being molded, in order to reduce the weight of the circuit.

[0061] More broadly, the filter cartridge can form a filter in an air or gas flow circuit, access to and return from which are permitted by the connection head S. The A filter cartridge can be used to filter a compressed air flow by equipping a machine or device with a lubrication system of a mechanism by affecting / charging a gas flow, in such a way that oil will be transported to the connection head S. To ensure a good seal at the outlet of the cartridge and / or to minimize the risk of oil re-entrainment, the RC fitting can be provided to form a male fitting which is inserted into the central tube 8, at least more than one-third of the length of the hollow internal space 6, making radial contact against an internal face of the central tube 8, for example at the level of the internal bead 8b which is for example adjacent to the second flange 5b.

[0062] The filter cartridge can, more specifically, purify a compressed air stream originating from this machine or device and conveyed to the upstream zone ZI via the inlet passage(s) O. This compressed air passes through and exits the lubrication zone of the mechanism, a non-limiting example of which is illustrated in [Fig. 6]. More generally, the cartridge 1 can be used for any application in which a gas must be purified by separating it from a liquid, such as oil / lubricant. [Fig. 6] shows that the raw gas can typically arrive from one side, through a channel C4 from a machine or piece of equipment which may, for example, include an oil collection sump 200 and an oil-lubricated mechanism. The channel C4 then forms part of a support base / connection head S and communicates with the inlet passages O. Such a base is generally metallic and can constitute a fixed S connection head, while the filter cartridge 1 is mounted removably by its FC connection face.

[0063] In the non-limiting case of [Fig. 6], a filter cartridge 1 equipped with its two filtration means / stages 3, 4 can be fitted to a screw compressor 100 (for example, a twin-screw compressor 16, 18) or similar machine in which a gas stream becomes contaminated as it passes through a lubrication zone. The filter cartridge 1 can be mounted on a support or connection head S in fluidic connection with the compressed air circuit. Such a support / connection head S is, for example, located away from or opposite a mounting flange 120 for the mechanical connection of the screw compressor 10 to an electric motor. This type of machine has a casing 200, filled with oil 22 at least on the side of a bottom of the card, in which the main components (components of the screw compressor 10) are housed / mounted.

[0064] An inlet connector 24 is provided for the outside air intake, to allow the air supply to the screw compressor 10. An air filter 26 (separate from the cartridge 1) can be arranged on this inlet connector 24. Typically, an air inlet 28 is provided (here radially) on the air inlet connector 24. On the outlet side of the two screws 16, 18, there is an air outlet pipe 34 with a riser pipe. 36. More broadly, it is understood that the machine equipped with cartridge 1 can have such an air outlet 34 to evacuate air laden with oil. In the illustrated example, a temperature sensor 38 is optionally provided near the end of the upstream line 36 to monitor the oil temperature. It should be noted that this type of circuit has already been described in document US2019 / 338777.

[0065] It is understood that the oil-separating cartridge 1 can be fitted to the connection head S located in an air outlet zone of such a machine. In the assembled state, the connection head S or support for the cartridge 1 can include the RC fitting (entirely traversed by an axial channel, along the direction of the Z-axis), mounted in the passage 20s, with the CC conduit allowing the purified gas to exit. This RC fitting, separated from the connection head S in the schematic illustration of [Fig. 6], can in practice be welded onto the connection head S. The purified gas flow can then pass through an exhaust pipe equipped with a non-return valve (not shown). Of course, by mounting a cartridge on another type of device / circuit, it is possible to achieve a different filtration, for example to separate a non-oily liquid carried by the admitted flow. Example of liquid drainage parallel to the air outlet passage

[0066] With reference to [Fig. 6], the support may incorporate a channel C5 for draining liquid droplets that may have been separated in the hollow internal space 6. The male insertion fitting RC, as seen in [Fig. 1], may, for example, include a passage radially further outward than the central conduit CC, for the liquid flow of this oil. More generally, when the cartridge 1 is fitted to a machine equipped with an oil sump, the liquid corresponding to the droplets collected in the hollow internal space 6 may return to the channel C5 for the oil return to the sump 200 (a downward channel, for example, to discharge this separated liquid from the bottom side of the sump for oil collection), optionally an oil return line 58 that directs this oil to the area to be lubricated. In certain designs, such as in [Fig. 5], one or more locally machined reliefs r8 can allow liquid to flow along the RC fitting, through the contact area with the bead 8b, for example. More broadly, one or more discontinuities in this contact can allow oil droplets to flow towards the C5 channel. The cartridge 1 then has a female connection portion whose RF mounting area extends peripherally around this flow path, isolated and separated from the upstream area ZI by the projection 8c connected to the cover element 20.

[0067] It should be obvious to persons versed in the art that the present invention permits embodiments in many other specific forms without departing from the field of application of the invention as claimed. For example, although tubes 7 and 8 have been illustrated as cylinders, it is permissible to obtain slightly different geometries, for example with an oval rather than a circular cross-section, or by including flat areas for one or both of tubes 7 and 8. Furthermore, the first tube 7 may possibly result from an assembly of two shells or halves connected by a longitudinal hinge, for example a hinge formed from the material with the remainder of the first part 11. Optionally, in a complementary or alternative manner, the second tube 8 may also result from an assembly of two shells or halves connected by a longitudinal hinge, for example a hinge formed from the material with the remainder of the second part 12.

Claims

1. Demands Removable filter cartridge (1) with rotating mounting fitting for mounting on a support along a rotating mounting axis, the cartridge (1) allowing separation of a fluid portion or oil from an admitted flow and comprising: - a filter element (EF) having a central axis (X) and provided with a frame (15) including a first closed flange (5a) and a second flange (5b) with a central opening which define opposite axial ends of the filter element (EF); - a first piece (11) or structural element, belonging to the framework (15), including the first flange (5a) and a first perforated tube (7) which extends longitudinally from the first flange (5a), around the central axis to an annular end (E2) rigidly connected to the second flange (5b); - an external casing (2) delimiting an internal volume containing the filter element (EF) which separates said internal volume into an upstream zone (Z1) and a downstream zone (Z2); - a cover element (20), belonging to the housing, which includes the fixing fitting and delimits at least one inlet passage (O) communicating with the upstream zone (Z1) where the admitted flow circulates and an outlet passage (20s) of a purified flow communicating with the downstream zone (Z2), the outlet passage formed in the fixing fitting being crossed by the central axis (X); - a first filtration stage (3) and a second filtration stage (4) which is radially spaced from the first filtration stage (3) to be closer to a hollow interior space (6) of the downstream zone (Z2); characterized in that the hollow interior space (6) is delimited by a second perforated tube (8) called central tube which is designed and formed with the second flange (5b) in a second piece (12) of the framework, which is distinct from the first piece or structural element, the second flange (5b) including a projecting annular axial projection (8c) opposite the second tube (8), from the central opening, to form an axial outlet conduit; and in that said framework (15) is made up of only said parts (11, 12), each formed of plastic material, with the first tube (7) which: - allows the insertion, into the first part (11) or structural element, of the central tube (8) via the annular end of the first tube (7); - extends around the central tube (8) supporting the second filtration stage (4); and - supports and allows the first filtration stage (3) to be positioned along a peripheral space of the internal volume which is part of the upstream zone (Zl).

2. Cartridge according to claim 1, wherein the upstream zone (Zl) is a circulation zone of an oil-laden gas stream which constitutes the admitted stream, the cartridge (1) allowing the oil to be separated from the gas stream by means of the first filtration stage (3) and the second filtration stage (4), preferably by achieving a coalescence with recovery of oil droplets, all or part of which is separated from the gas stream in the hollow internal space (6).

3. Cartridge according to claim 1 or 2, wherein the second part (12) has an annular edge (12a) formed by a free end of the central tube (8), and wherein a radial sealing part (PR) provided in the first flange (5a) closes the hollow internal space (6), on the side of a bottom of the cartridge axially opposite to the axial outlet conduit, the annular edge (12a) being snapped onto the first flange (5a) and / or embedded in a bonding layer (L7') with the first flange (5a), to form a first annular junction between the first part (11) and the second part (12) which is a junction: - adjacent to the radial sealing part (PR); and - adjacent and radially more interior than an annular zone (F2) of axial attachment, against the first flange (5a), of a filter medium (M2) of the second filtration stage (4).

4. Cartridge according to claim 1, 2 or 3, wherein the first part (11) and the second part (12) define between them an intermediate region (14) where a filter medium (M2) carried by the second part (12) is disposed, which is said filter medium (M2) of the second filtration stage (4), while the first perforated tube (7) and the first flange (5a) allow the first part (11) to carry the first filter medium (M1) by disposing of the latter radially further out than the intermediate region (14).

5. Cartridge according to claim 2, alone or combined with claim 3, wherein the first part (11) and the second part (12) define between them an intermediate region (14) where is disposed at least one filter medium (M2) which is: - carried by the second part (12); and - allows oil droplets to coalesce by joining the hollow interior space (6), knowing that the first tube (7) is radially spaced from a radially outermost lateral face of the second filtration stage (4).

6. Cartridge according to any one of the preceding claims, wherein the frame (15) is axially in contact with the cover element (20), by said axial projection (8c) which forms a barrier element between the upstream zone (Zl) and the axial outlet conduit, the cover element (20) forming a connector of the cartridge (1) to allow removable rotary mounting.

7. Cartridge according to any one of the preceding claims, wherein the first part (11) has a shell shape made of a single plastic material, the first part (11) defining: - an external diameter (D) of the filter element (EF), by an external annular edge of the first flange (5a); and - an internal volume (V7) of the shell, accessible through an axial opening having a diameter (D7); the first tube (7) having a total length, measured from a plane of the first flange (5a), equal to a length of the central tube (8), so that the central tube (8) is entirely located inside the volume (V7).

8. Cartridge according to any one of the preceding claims, wherein the cover element (20) is metallic and connected, via a conductive connecting part (17), to the second tube (8) and to at least one of the media of the first filtration stage (3) and / or the second filtration stage (4).

9. Cartridge according to any one of the preceding claims, wherein the central tube (8) belonging to the second part (12) has a constriction zone, preferably by having an annular ridge (8b) radially projecting inwards, for

10. define a minimum passage section for access to the hollow interior space (6), opposite the second flange (5b). Method for assembling a filter cartridge (1), preferably for oil-gas filtration, which has an external housing (2) containing a filter element (FE) and including a rotating mounting fitting for removable mounting on a support along a rotating mounting axis, the method comprising the following steps: - form (50) two openwork tubes (7, 8) in two separate pieces, the first piece (11) including a first tube (7) and a first closed flange (5a), which closes an axial access of the first tube by being arranged perpendicular to a longitudinal axis of the first tube (7), and the other is a second piece (12) which includes a second flange (5b) and a second tube called central tube (8) less wide than the first tube (7), the second flange (5b) perpendicular to the central tube (8) having a central opening to allow axial access to a hollow interior space (6) delimited by the central tube (8); - to secure (51a) a first filtration stage (3), which has one or more rolled layers of at least one filter medium (Ml, Ml'), to the first part (11) in order to allow a first filtration around the first tube (7); - to secure (51b) a second filtration stage (4), which has one or more rolled layers of at least one filter medium (M2), to the second part (12) in order to allow a second filtration around the central tube (8); - assemble (52) the filter element (EF) by interconnecting the first part (11) which supports the first filtration stage (3) and the second part (12) which supports the second filtration stage (4), by inserting the central tube (8) into the first tube (7) which joins the first flange (5a) in a final insertion state, so that the filter element (EF) has a framework (15) made up of said two parts (11, 12), with the second filtration stage (4) radially spaced from the first filtration stage (3) to be further away from a central axis (X) of the filter element (EF) which is an axis of symmetry for each of the tubes (7, 8); - insert (52) the filter element (EF) into a hollow component or bowl of the external housing (2) and then enclose (53) the filter element in the external housing (2), by fixing on the hollow component a cover element (20) provided with the fixing fitting with a purified flow outlet passage which communicates with the hollow interior space (6), said cover element (20) further defining at least one flow inlet passage (O) to be filtered.

11. Assembly method according to claim 10, wherein the interconnection, preferably carried out without rotational indexing, is made until an end of insertion of the central tube (8) which coincides with an axial support of the second filtration stage (4) on a radial portion of the second flange (8) serving as a support, by the same inner side, of the respective annular axial ends of the first filtration stage (3) and the second filtration stage (4), and wherein, to reach the final inserted state of the filter element (EF), the cover element (20) is directly engaged, by an axial contact, against the frame by pushing an axial projection (8c) of the second piece (12) which protrudes, opposite the central tube (8), from the radial portion of the second flange (5b).

12. Use of the filter cartridge (1) according to any one of claims 1 to 9 for filtering a compressed air stream, wherein the cartridge (1) is screwed, by the fixing fitting, onto a connection head (S) belonging to a lubrication system of a mechanism, such that: - a male fitting (RC) is inserted into the central tube (8) making radial contact against an internal face of the central tube (8); - at least one inlet passage (O) receives compressed air exiting from a lubrication zone of the mechanism.