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 subjected to filtration may consist, by way of explanation, of hydraulic oils, lubricating oils, combustible fluids, glycol waters, emulsions and synthetic fluids. Among the filtering cartridges of the aforesaid type there are, by way of explanation, the so-called "spin-on" cartridg- es, i.e., filtering cartridges which may be reversibly screwed to a fluid-dynamic system. Incidentally, the adverb "reversibly" means that the filtering cartridges may be screwed to a plant and unscrewed therefrom an indefinite number of times.

Known filtering cartridges generally comprise a tubular filtering unit accommo- dated in an almost cylindrical container, closed, at one end, by a substantially discoidal flange. Said flange, which may be defined as a "fastening", is preferably made of aluminum or steel and is the component of the cartridge at which the latter may be connected to a fluid-dynamic system. More precisely, the flange comprises a central hole with a circular shape from which a tubular shank extending inside 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 the circular edge thereof.

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 coated by a pleated cylindrical element obtained by folding a composite filtering septum, with a single layer or multilayer, on itself, including cellulose fibers, inorganic microfibers 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 pleated element, at an end opposite the aforesaid base of the tubular core, is connected to a flange, which may be defined as "coupling", preferably made of aluminum or steel and substantially shaped as a circular crown. The (central) hole of the coupling flange is at the inlet mouth of the tubular core.

The filtering unit is accommodated inside the container, so that the coupling flange, at the hole thereof, is partially fitted on the shank of the fastening flange with the interposition of an annular gasket, such as, for example, an o-ring. A spring preferably presses the filtering unit against the fastening 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, external to the filtering unit, communicating with the aforementioned peripheral holes of the fastening flange, and a second compartment, inside the filtering unit, communicating with the abovementioned central hole of the fastening flange. A further annular gasket is clamped between the container and the flange, and a third annular gasket is accommodated on the flange, externally with respect to the latter, so as to ensure a tight coupling between the flange and the nipple to which the cartridge is possibly screwed. In case the container and the flange are made of relatively thin sheet metal, the seal therebetween, instead of being made by interposing an annular gasket, may be obtained by means of a bracketing including sealing material. 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 fastening 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 fastening flange.

The present invention relates to a coupling flange of a filtering unit and to a filtering unit comprising the coupling flange which is the object of the invention. Overview of the background art

Current coupling flanges of the filtering units comprise a first and a second plate preferably made of aluminum or steel, each of which is substantially shaped as a circular crown. The first plate has an outer diameter greater than that of the second plate. The inner diameters of the two plates are, conversely, almost equal to each other. The two plates partially and coaxially overlap each other. Furthermore, they are mutually welded at the surface portions where the two plates overlap.

The first plate, at the outer edge thereof, is orthogonally connected to a cylindrical wall of reduced height. The second plate, at the inner edge thereof, has an almost stepped pattern, so as to produce, together with the inner edge of the first plate, a seat for accommodating an annular gasket. The latter, as previously mentioned, is intended to ensure a seal between the coupling flange of the filtering unit and the fastening flange of the filtering cartridge including said unit. Since the two plates are made of metal and are obtained by dying, the surfaces thereof, instead of being perfectly flat, have irregularities. The portions of said surfaces at which the two plates mutually overlap do not, therefore, perfectly match with each other. Thereby, acid leaks may occur between the two plates following galvanic treatments (with consequent corrosion of the plates) or adhesive leaks may occur during the step of gluing the coupling flange to the pleated element of the filtering unit. Incidentally, in the present context, the coupling flanges are commonly referred to as "rings".

Objects of the Invention

It is the object of the present invention to overcome the aforesaid drawbacks by indicating a coupling flange (of a filtering unit) not subjected to the aforesaid leakages.

Summary of the Invention

It is the object of the present invention a coupling flange which may be comprised in a filtering unit, in turn part of a filtering cartridge including a fastening flange for the connection of said filtering cartridge to a fluid-dynamic system, said coupling flange being suitable for coupling said filtering unit to said fastening flange, said coupling flange consisting of a single portion of metal sheet folded on itself so as to comprise at least:

- a plate substantially shaped as a circular crown;

- a first wall cylindrical wall, delimited by two coaxial circular edges, said first wall being connected orthogonally, at a circular edge thereof, by means of at least one folding, to the outer circular edge of said plate;

- a second wall substantially shaped as a surface obtained by rotating a concave arc (i.e. a section of a curved line between two ends) about a straight line:

- having no common points with said arc,

- not orthogonal to a segment joining the two ends of said arc and

- arranged so that said arc faces said straight line from the side of the concavity thereof, so as to delimit a seat where an annular gasket may be at least partially accommodated, said second wall being delimited by two coaxial circular edges, said second wall being connected, at a circular edge thereof, by means of at least one folding, directly or with the interposition of one or more other walls, to the inner circular edge of said plate. Advantageously, the flange of the invention consists of a single metal body. Thereby, no joints or weldings are present in said flange and consequently the aforementioned leakage phenomena may not occur.

In addition to what has been said, in the known coupling flanges, the fact that the first and the second plates are welded to each other causes some geometric tolerances to be difficult to be respected, especially concentricity ones. Conversely, in the flange of the invention, the absence of joints and weldings ensures the coaxiality and the concentricity of the seat for accommodating the annular gasket.

It is another object of the invention a filtering unit, comprising the aforesaid coupling flange, which may be comprised in a filtering cartridge including a fastening flange for connecting said filtering cartridge to a fluid-dynamic system, More precisely, the filtering unit of the invention includes:

- a tubular support element comprising a substantially cylindrical wall:

- including a plurality of through holes,

- delimiting, at a first end, an opening for accessing a portion of space inside said cylindrical wall and

- hermetically occluded by a base at a second end opposite to said first end;

- a cylindrical filtering element, preferably pleated (for example, obtained by folding a filtering septum on itself), laterally, and at least partially, covering said cylindrical wall;

- a coupling flange according to the present invention, connected to said tubular element or to said filtering element so that:

- the inner circular edge of said plate (of the flange) is at said opening, delimited by the cylindrical wall of said tubular element, coaxially to the cylindrical wall of said tubular element and

- said first wall (of the flange) partially covers, externally and laterally, said filtering element;

- an annular gasket at least partially accommodated in said seat (of the flange). Further innovative features of the present invention are shown in the following description and are referred to in the dependent claims.

Brief description of the Figures

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

- Figure 1 shows an exploded view of a coupling flange of a filtering unit, ac cording to the background art;

- Figure 2 shows a diagrammatic cross section of the flange of Figure 1 ;

- Figure 3 shows a diagrammatic cross section of a coupling flange of a filtering unit, according to the present invention;

- Figure 4 shows a plan top view of the flange of Figure 3;

- Figure 5 shows a perspective bottom view of the flange of Figure 3;

- Figure 6 shows an exploded view of a filtering unit according to the present invention comprising the flange of Figure 3.

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.

Figures 1 and 2 show a coupling flange 1, according to the background art, which may be comprised in a filtering unit in turn part of a filtering cartridge including a fastening flange for the connection of said filtering cartridge to a fluid- dynamic system. The flange 1 is suitable for coupling said filtering unit to said fastening flange.

As previously mentioned, the flange 1 comprises a first plate 2 and a second plate 3 preferably made of aluminum or steel. Each of the plates 2 and 3 is substantially shaped as a circular crown. The plate 2 has an outer diameter greater than that of the plate 3. The inner diameters of the plates 2 and 3 are, conversely, almost equal to each other. Plates 2 and 3 partially and coaxially overlap each other. Furthermore, they are mutually welded at the surface portions where the two plates 2 and 3 overlap.

The plate 2, at the outer edge 4 thereof, is orthogonally connected to a cylindrical wall 5 of reduced height. The plate 3, at the inner edge 6 thereof, has an almost stepped pattern, so as to produce, together with the inner edge 7 of the plate 2, a seat 8 where an annular gasket may be accommodated. The latter is intended to ensure a seal between the flange 1 and the fastening flange of the filtering cartridge including the filtering unit which the flange 1 is intended to be part of.

Figures 3 and 5 show a coupling flange 10 of the invention, which, like the flange 1 , may be comprised in a filtering unit in turn part of a filtering cartridge including a fastening flange for the connection of said filtering cartridge to a fluid-dynamic system. The flange 10 is suitable for coupling said filtering unit to said fastening flange.

Unlike the flange 1 , the flange 10 is free of weldings and consists of a single metal body, preferably made of steel. More precisely, the flange 1 consists of a single portion of metal sheet (preferably a portion of sheet metal) folded on itself so as to comprise a plate 11 substantially shaped as a circular crown. The plate 11 , at the outer circular edge 12 thereof, is orthogonally connected (by means of at least one folding) to a first rim 13 shaped as a cylindrical wall. The rim 13 is delimited by two coaxial circular edges and is connected to the edge 12 of the plate 11 at the edge thereof arranged below in Figure 3.

The plate 11 , at the inner circular edge 14 thereof, is connected (by means of at least one folding) to a second rim 15 comprising a wall substantially shaped as a surface obtained by rotating a concave arc about a straight line having no common points with said arc. Furthermore, said straight line is arranged not orthogonally to a segment joining the two ends of the aforesaid arc and so that said arc faces said straight line from the side of the concavity thereof. The rim 15, like the rim 13, is delimited by two coaxial circular edges and is connected to the edge 14 of the plate 11 , by means of at least one fold, directly or with the interposition of one or more other walls, preferably at the edge thereof arranged below in Figure 3.

The arc, from the rotation of which a surface is obtained, like which the rim 15 is shaped, is preferably an arc of circumference and more preferably a semicircle. The straight line about which said arc is rotated to obtain a surface like which the rim 15 is shaped is preferably parallel to a segment joining the two ends of said arc. Incidentally, the aforesaid arc being preferably a semicircle and the straight line, about which said arc is rotated to obtain a surface like which the rim 15 is shaped, being preferably parallel to a string joining the two ends of the aforesaid semicircle, the rim 15 is preferably semi-toroidal, i.e., it is preferably shaped as a toroidal surface free from a central portion enclosed in a straight cylindrical surface coaxial to the toroidal surface and passing through the centers of the circumferences of the cross sections thereof. The aforesaid semicircle, from the rotation of which a surface is obtained like which the rim 15 is shaped, is therefore preferably substantially tangent to the plate 11 (at the edge 14 of the latter and at the end thereof arranged below in Figure 3).

The rim 15 delimits a seat 16 where an annular gasket may be at least partially accommodated. The latter is intended to ensure a seal between the flange 10 and the fastening flange of the filtering cartridge including the filtering unit which the flange 10 may be part of.

As it may be noted in Figure 3, the rims 13 and 15 preferably lie on the same side with respect to the plate 11.

The flange 10 may be made, by way of explanation, by sliding sheet metal into a press equipped with a progressive die. The first steps of the dying involve the drawing of the sheet metal and the perforation thereof so as to make the central hole of the plate 11 with a substantially cylindrical inner rim. By means of repeatedly folding said cylindrical rim the final, preferably semi-toroidal shape, is conferred. The last steps of the dying include the making of the outer cylindrical rim and the shearing of the sheet metal to obtain the flange 10.

Figure 6 shows a filtering unit 20 which may be comprised in a filtering cartridge including a fastening flange for connecting said filtering cartridge to a flu- id-dynamic system.

The unit 20, also a subject of the invention, differs from the known filtering units of the same type in that it comprises, as coupling flange, the flange 10. More precisely, the unit 20 comprises a tubular core 21 including a substantially cy- lindrical wall 22 preferably made of steel or plastic material and comprising a plurality of through holes. The wall 22, at a first end 23 (on the right in Figure 6), delimits an opening 24 for accessing a portion of space inside the wall 22. The latter, at a second end 25 (on the left in Figure 6) opposed to the end 23, is hermetically occluded by a preferably substantially discoidal base 26. The core 21 is laterally and externally coated by a cylindrical element 27, preferably pleated and more preferably obtained by folding a composite filtering septum, with a single layer or multilayer, on itself, including cellulose fibers, inorganic microfibers and/or plastic or metal meshes. The element 27 is supported by the core 21 and is the "proper" filtering component. The element 27 and the core 21 are fitted one on top of the other so as to be coaxial.

The element 27 (and/or the core 21) is connected to the flange 10, preferably so that the edge 14 of the plate 11 is at the opening 24, coaxially to the wall 22. The wall 13 further partially covers, externally and laterally, the element 27. The connection between the flange 10 and the element 27 is preferably made by gluing and more preferably by interposing therebetween a centrally perforated disk 28 (i.e., shaped as a circular crown) and comprising epoxy resin.

An annular gasket 31 (such as, for example, an o-ring) is at least partially accommodated in the seat 16.

The unit 20 preferably comprises a closing bottom 29 shaped as a circular crown and connected to the element 27 (and/or to the core 21 ), at the end of the latter, opposite to the one at which it is glued to the flange 10. Like the latter, the bottom 29 is connected to the element 27 preferably by gluing and more preferably by interposing therebetween a centrally perforated disk 30 (i.e., shaped as a circular crown) and comprising epoxy resin.

The bottom 29, as well as the other components of the unit 20, except for the flange 10, are known. Therefore, further details thereof are not provided herein. The unit 20 may be accommodated inside a filtering cartridge so that the flange 10, at the hole thereof, is partially fitted on the shank of the fastening flange of said cartridge with the interposition of the annular gasket 31. When the unit 20 is accommodated inside a filtering cartridge, a spring preferably presses the unit 20 against the fastening flange so as to ensure a tight coupling between the two by means of the gasket 31.

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.