Field of application of the invention The present invention finds application in the field of the industry concerning filtering cartridges which may be connected to a fluid-dynamic system (such as, for example, an oleodynamic, hydraulic or motor plant) for decontaminating one or more fluids circulating therein. The fluids subject to filtration may consist, by way of explanation, of hydraulic oils, lubricating oils, combustible fluids, glycol waters, emulsions and synthetic fluids.

Known filtering cartridges generally comprise a filtering unit accommodated in an almost cylindrical container, closed, at one end, by a substantially discoidal flange. Said flange is the component of the cartridge at which the latter may be connected to a fluid-dynamic system, possibly by means of other elements such as, for example, a "head".

The present invention relates, in particular, to a filtering cartridge, the flange thereof connecting to a fluid-dynamic system being in abutment against a radial rim of the container forming part of said cartridge.

Review of the background art As mentioned above, known filtering cartridges generally comprise a substantially tubular filtering unit accommodated in a near-cylindrical container. The latter, at a first end, is hermetically closed by a base usually called "spherical cap". At a second end, opposite to the first end, the container comprises an opening occluded by a substantially discoidal flange for connecting the cartridge to a flu- id-dynamic system. The flange comprises a central hole with a circular shape from which a short tubular shank extending towards the inside of the cartridge departs. The shank may be internally threaded so as to be screwable to an externally threaded nipple (of a fluid-dynamic system) at a cylindrical coupling surface. The flange further comprises a plurality of peripheral holes arranged circumferentially about the central hole. The fluid to be filtered enters the cartridge through the peripheral holes and, after having been filtered by the filtering unit, comes out of the cartridge through the central hole.

The container is usually made of drawn sheet metal and is connected to the flange at a circular edge thereof delimiting the aforementioned opening. The flange has an outer diameter smaller than the diameter of the aforesaid edge of the container. The connection between the container and the flange is therefore usually realized by means of a suitable interface ring. More precisely, the flange is bracketed or welded coaxially to the interface ring and the latter is coaxially curled to the container at the aforesaid circular edge with the interposition of a sealing material, such as, for example, mastic.

The filtering unit comprises a tubular core made of steel or plastic, closed by a base at one end and including a plurality of through holes at the side wall thereof. The tubular core is laterally and externally lined by a pleated cylindrical element obtained by folding a composite filtering septum, with a single layer or multilayer, on itself, including cellulose fibers, inorganic microfibres and/or plastic or metal meshes. Said pleated element is supported by the tubular core and is the "proper" filtering component. The pleated element and the tubular core are fitted one on top of the other so as to be coaxial.

The filtering unit is accommodated inside the container so that the mouth of the tubular core is partially fitted on the flange shank with the interposition of an annular gasket, such as, for example, an o-ring. A spring presses the filtering unit against the flange so as to ensure a tight coupling between the two by means of the aforesaid gasket. Thereby, the filtering unit divides the inner volume of the container into two compartments: a first compartment, outside the filtering unit, communicating with the aforementioned peripheral holes of the flange, and a second compartment, inside the filtering unit, communicating with the aforementioned central hole. A further annular gasket is accommodated in the interface ring so as to ensure a tight coupling between the container and the element to which the cartridge is connected.

During the operation of the system to which the cartridge is connected, the fluid to be filtered enters the latter through the peripheral holes of the flange and fills the aforesaid first compartment. As a result of a pressure difference between the inside and the outside of the filtering unit, the fluid tends to pass through the side wall of the latter, thus decontaminating itself and accumulating in the second compartment. From here, the fluid returns to the system coming out of the cartridge through the central hole of the flange.

In known filtering cartridges, the fact that the flange connecting to a fluid- dynamic system is fastened to the container by means of an interface ring curled at the circular edge thereof causes some geometric tolerances to be hardly respected, especially coaxiality ones. In addition to this, to avoid fluid leakages between the container and the ring, the curling must be carried out with extreme precision and only after having awaited the complete polymerization of the mastic applied to the ring.

Objects of the Invention

It is the object of the present invention to overcome the aforesaid drawbacks by indicating a filtering cartridge not subjected to fluid leakages between the container and the interface ring, and when manufacturing it, the geometric tolerances associated with the position of the flange and of the interface ring are more easily respected with reference to known cartridges.

Summary and advantages of the invention

The object of the present invention is a filtering cartridge which may be connected to a fluid-dynamic system for decontaminating one or more fluids circulating therein, said cartridge comprising:

• a substantially discoidal flange including:

- at least one first through hole, to allow the entry of a fluid to be filtered into said cartridge;

- at least one second through hole, to allow the exit of said fluid from said cartridge after having been filtered;

• a container including:

- at least one substantially cylindrical side wall;

- a base hermetically connected to said side wall at a first end thereof;

- a substantially circular opening at a second end of said side wall opposite to said first end, said opening being occluded by said flange, said opening and said flange being coaxial both to each other and to said side wall of the container;

• a filtering unit including:

- at least one substantially cylindrical filtering side wall;

- a base connected to said side wall of the filtering unit at a first end thereof;

- an opening at a second end of said side wall of the filtering unit opposite to said first end, said filtering unit being accommodated inside said container so that

- said bases (of the container and the filtering unit) are counterposed to each other and

- said opening of the filtering unit is counterposed to said flange and communicates with said second hole, said filtering unit dividing the space inside said container into:

- a first compartment, outside said filtering unit, accessible by means of said first hole;

- a second compartment, inside said side wall of the filtering unit, accessible by means of said second hole and said opening of the filtering unit;

• elastic means accommodated inside said container and compressed between said bases, so as to push said filtering unit towards said flange;

• sealing means between said flange and said filtering unit so that the passage of a fluid between said first and second compartments may occur only with a passage of said side wall of the filtering unit, in which, in accordance with the invention, said container comprises a substantially annular wall delimiting said opening of the container, said substantially annular wall being coaxial to said side wall of the container and radially extending, at least partially, from the latter towards a longitudinal axis of said side wall of the container, said side wall of the container and said substantially annular wall being connected to each other by a fold, said side wall of the container and said substantially annular wall consisting, as a whole, of a single portion of plastically deformed metal sheet (for example, sheet metal), the outer diameter of said flange being greater than the inner diameter of said substantially annular wall (i.e., the diameter of the opening of the container), said flange being at least partially accommodated inside said container and being pressed against said substantially annular wall by said filtering unit pushed by said elastic means, said filtering cartridge comprising means for guiding said flange with respect to said container, said guiding means constraining said flange to translate, with respect to said side wall of the container, along said longitudinal axis (i.e., keeping the same coaxial geometries) and, at the same time, preventing any rotation between said flange and said side wall of the container.

Advantageously, in the filtering cartridge object of the invention, the side wall and the substantially annular wall of the container consist of a single metal body. Thereby, as the substantially annular wall acts as an interface ring between the side wall of the container and the flange, between said lateral and substantially annular walls there are no joints nor weldings, and consequently fluid leakage phenomena may not occur therebetween.

In addition to what has been said, in the cartridge object of the invention the absence of joints and weldings ensures the respect of the coaxiality tolerances of the flange and of the substantially annular wall with respect to the side wall of the container.

Other innovative features of the present invention are shown in the following description and are referred to in the dependent claims.

According to an aspect of the invention, said flange, at an outer edge thereof, is in contact with said side wall of the container, inside the latter.

According to another aspect of the invention, said guiding means comprise:

• at least one tooth preferably radially protruding from said side wall of the container inside the latter, said tooth preferably longitudinally extending along said side wall of the container starting from said substantially annular wall;

• at least one recess preferably radially extending in said flange starting from said outer edge, said outer edge being in contact with said side wall of the container, at least partially matching the latter, at least outside said recess, said tooth and said recess being shaped and arranged so that

• said tooth is accommodated in said recess and is slidable in the latter with a translation of said flange with respect to said side wall of the container along said longitudinal axis (i.e., keeping the same coaxial geometries) and

• the accommodation of said tooth in said recess allows a translation between said flange and said side wall of the container along said longitudinal axis, while at the same time preventing a rotation therebetween about said longitudinal axis.

Advantageously, the fact that the outer edge of the flange at least partially matches the side wall of the container constitutes a further assurance with regard to respecting geometric coaxiality tolerances.

According to another aspect of the invention, said flange, at said outer edge, comprises a rim substantially shaped like a cylindrical wall interrupted at said recess and extending towards said base of the container, said flange and said side wall of the container being in contact with each other, matching, at least partially, at least at said rim.

Advantageously, said rim gives the flange a greater flexural stiffness.

According to another aspect of the invention, said rim is connected to a remaining portion of said flange by a fold, said flange consisting of a single portion of perforated and plastically deformed metal sheet.

According to another aspect of the invention, said flange, at the edge delimiting each of said first and second holes, comprises a rim substantially shaped like a cylindrical wall extending towards said base of the container.

According to another aspect of the invention, said rims of the first and second holes are connected to a remaining portion of said flange by respective folds made at the edges delimiting said first and second holes, said flange consisting of a single portion of perforated and plastically deformed metal sheet. More precisely, the holes of the flange are preferably made by cutting said sheet by means of a punch.

According to this aspect of the invention, the rims at the holes, besides giving the flange a greater resistance to flexion, deviate the cracks formed in the flange during the cutting exerted by the punch. This advantageously reduces the risk of rupture of the flange due to crack propagation (conversely, a relatively widespread problem in the flanges of the filtering cartridges of the background art).

According to another aspect of the invention, said flange is in contact with said substantially annular wall, partially matching the latter at a peripheral portion of said substantially annular wall consecutive to said side wall of the container. According to another aspect of the invention, said substantially annular wall, at a face thereof facing towards the outside of the container, comprises at least one seat where an annular gasket may be accommodated, said seat being shaped so that, when an annular gasket is accommodated in said seat, said annular gasket is coaxial to said side wall of the container. According to this aspect of the invention, the sheet portion from which the side wall and the substantially annular wall of the container are obtained is plastically deformed so as to also include a seat for accommodating an annular gasket which ensures a tight coupling between the container and the element to which the cartridge is connected.

Brief description of the Figures

Further objects and advantages of the present invention will become apparent from the following detailed description of an embodiment thereof and from the accompanying drawings, merely given by way of explanation and not by way of limitation, in which:

- Figure 1 shows a diagrammatic cross section of a filtering cartridge according to the present invention;

- Figure 2 shows a perspective view of a first component of the cartridge of Figure 1. Said first component is, more precisely, a flange connecting the cartridge of Figure 1 to a fluid-dynamic system;

- Figure 3 shows a diagrammatic cross section of the flange of Figure 2;

- Figure 4 shows a perspective view of a second component of the cartridge of Figure 1. Said second component is, more precisely, a container integrating an interface ring delimiting an opening which may be occluded from the flange of Figure 2;

- Figure 5 shows a perspective view of the container of Figure 4 with the aforesaid opening occluded by the flange of Figure 2.

Detailed description of some preferred embodiments of the invention In the following of the present description, a Figure may also be shown with reference to elements not expressly indicated in that Figure but in other Figures. The scale and the proportions of the various elements depicted do not necessarily correspond to the real ones.

Figure 1 shows a filtering cartridge 1 , object of the invention, which may be connected to a fluid-dynamic system for decontaminating of one or more fluids circulating therein. The cartridge 1 comprises a flange 2 accommodated, at least partially, in a container 3.

The flange 2, visible in Figures 2 and 3 isolated from the remaining components of the cartridge 1 , is substantially discoidal. It comprises a first central and preferably circular through hole 5 and one or more second peripheral holes 6, also through holes and preferably arranged circumferentially about the hole 5. The holes 6, shown by way of explanation in a number equal to eight, are preferably circular, circumferentially equidistant from one another and equal to one another.

As it may be noticed in Figure 3, the flange 2, for each of the holes 5 and 6, at the edge 7 or 8 delimiting the same, preferably includes a rim 9 or 10 substantially shaped like a cylindrical wall. The flange 2 is preferably made of sheet metal and the rims 9 and 10 are preferably connected to the remaining portion of flange 2 by respective folds obtained by plastically deforming the sheet metal at the aforesaid edges 7 and 8. More precisely, the holes 5 and 6 and the rims 9 and 10 are preferably made by cutting the sheet metal (i.e., the metal sheet) in which the flange 2 is obtained by means of a punch.

As it may be noticed in Figure 1 , the rim 9 originating from the edge 7 of the hole 5 appears as a short, substantially tubular shank extending towards th.e inside of the container 3. The shank 9 may be internally threaded so as to allow the flange 2 to be screwed to an externally threaded cylindrical surface of a nipple of a fluid-dynamic system. The flange 2 is in fact the component of the cartridge 1 by means of which the latter may be connected to a fluid-dynamic system for filtering a fluid circulating in said system. More precisely, the holes 6 (corresponding to the aforementioned "first hole") allow the entry of the fluid to be filtered into the cartridge 1. The hole 5 (corresponding to the aforementioned "second hole") allows the exit of the filtered fluid from the cartridge 1. Incidentally, although the holes 6 are shown by way of explanation in a number equal to eight, to allow the entry of the fluid to be filtered into the cartridge 1 it is sufficient that the latter includes a hole 6.

As it may be noticed in Figure 2, one or more recesses 11 preferably radially extend in the flange 2 starting from an outer edge 12 thereof. The recesses 11 (shown, by way of explanation, in a number equal to four) are preferably circumferentially equidistant from one another and are preferably equal to one another. As it will be described below in the present description, the recesses 11 contribute to immobilizing the flange 2 on the container 3.

The flange 2, at the edge 12, preferably comprises a rim 13 substantially shaped like a cylindrical wall interrupted at the recesses 11. Being the flange 2 preferably made of sheet metal, like the rims 9 and 10 of the holes 5 and 6, the rim 13 is preferably connected to the remaining portion of flange 2 by a fold obtained by plastically deforming the sheet metal at the aforesaid edge 12. In light of the foregoing, the flange 2 preferably consists of a single portion of a perfo- rated and plastically deformed metal sheet.

As it may be noticed in Figure 3, the rims 9, 10 and 13, originating from the edges 7, 8 and 12, extend from the same side with respect to the remaining portion of flange 2. In addition to this, the rims 9, 10 and 13 are respectively preferably connected substantially orthogonally to the remaining portion of flange 2. In other words, each of the rims 9, 10 and 13 is preferably substantially orthogonal to the portion of flange 2 surrounding the edge 7, 8 or 12 (i.e., to the portion of flange 2 from which the fold at said edge 7, 8 or 12 originates). Figure 4 shows a front perspective view slightly from above of the container 3. The container 3 comprises a substantially cylindrical side wall 15, hermetically closed by a base 16 at a first end, and terminating in an opening 17 at a second end of the wall 15 opposite to said first end. The opening 17 is substantially circular and coaxial to the wall 15. As shown in Figure 1 , when the cartridge 1 is completely assembled, the flange 2 is at least partially accommodated inside the container 3 to occlude the opening 17. More precisely, the flange 2 is at least partially accommodated in the container 3 coaxially to the wall 15, with the rims 9, 10 and 13 directed towards the base 16.

The opening 17 is delimited by a substantially annular wall 18 coaxial to the wall 15 and radially extending, at least partially, from the latter towards a longitudinal axis of the wall 15. The walls 15 and 18, as a whole, preferably consist of a single portion of plastically deformed sheet metal. I.e., said walls 15 and 18 consist of a single metal body and are connected to each other by a fold.

An annular gasket 19 (shown in Figure 1) may be accommodated at a seat 20, also annular, made at the wall 18. The seat 20 is preferably concentric to the opening 17 (i.e., coaxial to the wall 15) and is made at one face of the wall 18 facing towards the outside of the container 3. The gasket 19 is preferably an o- ring and, when accommodated in the seat 20, it is compressed axially (i.e., along the aforesaid longitudinal axis of the wall 15) to a connection to a fluid- dynamic system of the cartridge 1 , so as to ensure a tight coupling between said two elements. Incidentally, instead of being an o-ring, the gasket 19 may have a rectangular cross section or a cross section of another shape. Incidentally again, being the seat 20 preferably concentric to the opening 17, the seat 20 is preferably shaped so that the gasket 19, when accommodated in the seat 20, is coaxial to the wall 15.

One or more teeth 21 preferably protrude radially from the wall 15 inside the container 3. The teeth 21 (shown, by way of explanation, in a number equal to four) preferably extend longitudinally along the wall 15 starting from the wall 18, are preferably circumferentially equidistant from one another and are preferably equal to one another. As it will be described below in the present description, the teeth 21 , together with the recesses 11 , contribute to immobilizing the flange 2 on the container 3. To this end, the teeth 21 are equal in number to the recesses 11.

With reference to Figure 1 , it may be noticed that the cartridge 1 includes a filtering unit 25 accommodated inside the container 3. The unit 25 comprises a substantially cylindrical filtering side wall 26, closed by a base 27 at a first end, and delimiting an opening 28 at a second end of the wall 26 opposite to said first end. The unit 25 is arranged (inside the cartridge 1) so that the walls 15 and 26 are coaxial, the bases 16 and 27 are counterposed to each other, and the opening 28 is counterposed to the flange 2 and communicating with the hole 5. More precisely, the shank 9 of the flange 2 at least partially penetrates inside the unit 25 by means of the opening 28. In other words, the unit 25 is partially fitted on the shank 9 at the opening 28 (where the unit 25 is therefore connected to the flange 2).

The wall 26 comprises a tubular core 29 preferably made of plastic material, including a plurality of through holes and externally lined by a cylindrical element 30, preferably pleated, obtained by folding a composite filtering septum, with a single layer or multilayer, on itself, preferably including cellulose fibers, inorganic microfibres and/or plastic or metal meshes. The element 30 is supported by the core 29 and is the "proper" filtering component of the cartridge 1. The core 29 and the element 30 are substantially known. Therefore, further details thereof are not provided herein.

A spring 31 is accommodated inside the container 3 and longitudinally compressed between the bases 16 and 27. The spring 31 therefore acts as an elastic means suitable for pushing the unit 25 towards the shank 9 of the flange 2, exerting a longitudinally directed force.

As previously mentioned and as shown in Figure 5, the flange 2 is at least partially accommodated in the container 3, coaxially to the wall 15, so as to occlude the opening 17. More precisely, the flange 2 has an outer diameter greater than the inner diameter of the wall 18 and is in contact with the wall 15, inside the container 3, at the outer edge thereof. The flange 2 is pressed against the wall 18 by the unit 25, in turn pushed by the spring 31. Preferably, the flange 2 partially matches the wall 18 at a peripheral portion of the latter connected to the wall 15.

The immobilization of the flange 2 with respect to the container 3 preferably occurs by virtue of the presence of the recesses 11 and of the teeth 21. More precisely, the flange 2 is at least partially accommodated in the container 3 so as to at least partially match the wall 15 at least at the rim 13 (i.e., at the outer edge thereof, at least outside the recesses 11) and each of the teeth 21 accommodated in a respective recess 11. The teeth 21 and the recesses 11 are shaped and arranged so that:

• each tooth 21 is slidable in the recess 11 where it is accommodated with a translation of the flange 2 with respect to the wall 15 along the longitudinal axis of the latter (i.e., keeping the flange 2 and the wall 15 coaxial) and

• the accommodation of each tooth 21 in a respective recess 11 allows a translation between the flange 2 and the wall 15 along the longitudinal axis of the latter, while at the same time preventing a rotation therebetween about said longitudinal axis.

In light of the foregoing, the recesses 11 and the teeth 21 form part of guiding means (of the flange 2 with respect to the container 3) constraining the flange 2 to translate, with respect to the wall 15, along said longitudinal axis of the latter (i.e., keeping the same coaxial geometries) and preventing any rotation between the flange 2 and the wall 15.

Being the outer edge of the flange 2 in contact with the wall 15, inside the container 3, at least partially matching the latter at least outside the recesses 11 , and being the flange 2 pressed against the wall 18 by the unit 25, in turn pushed by the spring 31 , the recesses 11 and the teeth 21, preventing a rotation between the flange 2 and the wall 15 about the longitudinal axis of the latter, immobilize the flange 2 with respect to the container 3.

Incidentally, being the outer edge of the flange 2 in contact with the wall 15, in- side the container 3, at least partially matching the latter at least outside the recesses 11 (i.e., at least at the rim 13), although the recesses 11 and the teeth 21 are shown by way of explanation in a number equal to four, to obtain the immobilization between the flange 2 and the container 3 it is sufficient that the latter comprise, respectively, a single recess 11 and a single tooth 21. An annular gasket 32 is compressed (by virtue of the presence of the spring 31), between the flange 2 and the unit 25 so as to ensure a tight coupling between said two elements. The gasket 32, previously identified with the expression "sealing means", is preferably an o-ring and is preferably fitted on the shank 9 outside the latter. It is therefore compressed between the portion of flange 2 about the hole 5 (i.e., about the edge 7) and the portion of unit 25 about the opening 28.

By virtue of the presence of the gasket 32, the unit 25 divides the space inside the container 3 into two compartments: a first compartment, outside the unit 25, accessible by means of the holes 6, and a second compartment, inside the tub- ular core 29 of the unit 25, accessible by means of the hole 5 and of the opening 28. More precisely, by virtue of the presence of the gasket 32, the passage of a fluid between the aforesaid first and second compartments may occur only with a passage through the core 29 and through the element 30 of the unit 25. Incidentally, as shown in Figure 5, the wall 18 does not occlude, or only partially occludes, the holes 6 of the flange 2.

According to the description provided for a preferred embodiment, it is apparent that certain changes may be introduced by those skilled in the art without departing from the scope of the invention as defined by the following claims.