EP3997324B1

EP3997324B1 - Air filter intended for i.c. engines and having replaceable cartridges

Info

Publication number: EP3997324B1
Application number: EP20737598.1A
Authority: EP
Inventors: Nazzareno BERTUCCI; Umberto Cornaglia; Mauro GOTELLI; Paolo Vitagliani
Original assignee: Officine Metallurgiche G Cornaglia SpA
Current assignee: Officine Metallurgiche G Cornaglia SpA
Priority date: 2019-07-08
Filing date: 2020-07-07
Publication date: 2023-11-15
Anticipated expiration: 2040-07-07
Also published as: EP3997324A1; TR201922275A2; WO2021005509A1; IT201900011190A1; BR112022000414A2; EP3997324C0

Description

Technical Field

The invention relates to an air filter intended for I.C. engines and having a replaceable cartridge. More particularly, the invention relates to an air filter having a replaceable cartridge, of the kind that is equipped with an additional, or secondary, or safety cartridge. The invention relates to an air filter intended for I.C. engines and designed in particular, though not exclusively, for heavy use, for example in air intake circuits of I.C. engines mounted on agricultural machines, earth-moving machines, industrial vehicles and the like.

Background Art

In the field of I.C. engines, for example for use in the automotive field, air filter are known equipped with a replaceable main filter element, which is received within a housing that can be closed by means of a removable lid. The housing and the corresponding lid comprise an inlet mouth for the entry of so-called "dirty" air, taken in from the outer environment, and an outlet mouth for the exit of so-called "clean" air towards the engine. The housing and lid of the filter ate configured in such a way as to define, within the filter, an obligatory air path, whereby substantially all the air taken in through the inlet mouth passes through the filter element and is discharged from the filter through the outlet mouth. As they pass through the filter element, the particles of dust and other foreign materials, which could damage the engine and the other parts involved, are separated from the flow of air in transit and the air coming out of the filter is therefore purified and suitable to be introduced into the combustion chambers of an I.C. engine.
The replaceable filter element typically includes a cartridge made of pleated paper, or other suitable materials known to the person skilled in the art. The cartridge is also typically provided with a sealing gasket, for example made of rubber, or polyurethane foam, which serves to ensure the necessary airtight seal inside the filter, preventing dirty air, especially from the outside, from being introduced into the intake circuit of the I.C. motor located downstream of the filter, thereby bypassing the filter element. In general, the sealing gasket of the filter cartridge is made in such a way that it rests against a seat devised for the purpose and provided in the lid and/or housing of the filter. The sealing gasket and the corresponding seats in the lid and/or housing are also configured in such a way that when the lid is closed, the sealing gasket is adequately compressed to obtain the desired airtight seal and to prevent the cartridge from moving inside the enclosure in which it is received, due to the vibrations to which the filter is subjected during use of the vehicle.
Imperfections in the construction of the seats and gasket, for example in the case of poorly made spare parts, or incorrect assembly of the cartridge, or the presence of impurities, or deformations of materials, can cause lack of airtight seal and instability of the cartridge inside the filter, resulting in the passage of dirty air and risk of damage to the engine. In addition, poor tightness tends to become more pronounced while the vehicle is in motion due to the vibrations of the cartridge inside the housing, which increases the risk of dirty air entering the casing and damaging the engine. These drawbacks are accentuated in the case of heavy-duty filters, due to the higher intensity and persistence of vibrations during use.
One of the problems encountered in the development of an air filter for endothermic engines equipped with an interchangeable cartridge is therefore how to obtain an optimal airtight seal and how to hold the cartridge permanently inside the filter, despite the vibrations generated during use of the vehicle.
In the past, some solutions have been proposed with the aim of resolving the above problem and ensuring an optimal positioning of the cartridge inside the filter. Some of these solutions involve the adoption of projections on the seal. BRMU8702523 (U) and DE102015112698 (A1 ) provide examples of the above solutions.
The solutions according to prior art, however, are poorly efficient, both because they do not completely solve the problem mentioned above, and because they determine an increase in production costs. The known solutions mentioned above also require, in general, the creation of a significantly modified housing and therefore do not lend themselves to be easily adopted in already designed filters.
A main object of the invention is therefore to provide an air filter for I.C. engines equipped with a replaceable cartridge, which is not affected by the drawbacks of the prior art, in particular those related to poor tightness and imperfect positioning of the cartridge in the housing of the filter.
In the field of heavy-duty I.C. engines, for example for use in fields of agriculture and earth-moving machinery, air filters are known having, besides the main filter element or main cartridge, a secondary filter element, or safety cartridge. The safety cartridge is provided downstream of the main cartridge, in the direction of air flow from the outer environment towards the engine. The function of the safety cartridge is mainly to prevent excessively dirty air from entering the part of the intake circuit located downstream of the filter, with the consequent risk of damage to the engine. This circumstance can occur, for example, as a result of the breakage of the filter material of the main cartridge, or during the replacement of the main cartridge, due to the unwanted entry of material into the filter, or even when, by mistake or forgetfulness, the main cartridge is not mounted. Both the main cartridge and the safety cartridge must be replaced when clogged.
WO03084641 (A2 ) US2013/327005 (A1 ) and US2017/291129 (Al ) describe examples of an air filter for I.C. engines that is provided with a safety cartridge.
An undesirable effect due to the presence of the safety cartridge is the need to design the filter in such a way that it can work correctly, also without the safety cartridge. In fact, it is not uncommon for users to need to operate the filter even without the safety cartridge, either for cost reasons, or because in the field of application of the filter, the risk associated with the absence of the safety cartridge is negligible. In addition, because the safety cartridge is difficult to remove and reposition due to its location inside the filter, downstream of the main cartridge, users tend to rarely replace the safety cartridge, or even remove it, without replacing it with a new one for ease of maintenance. Obviously, an air filter deprived of the safety cartridge is exposed to the above-mentioned risks of unwanted entry of material into the intake ducts of an I.C. engine associated with the filter.
The problem of how to guarantee the necessary airtight seal and correct centering of the main cartridge is generally more evident in filters equipped with a safety cartridge, in particular of the type that can be used even without the said safety cartridge. The absence of the safety cartridge can in fact determine, depending on the configurations, the absence of the necessary support or hold for the main cartridge, with consequent risk of movements of the latter inside the housing caused by vibrations and reduction of the sealing action of the gasket.
Another object of the invention is therefore to provide an air filter for I.C. engines that has a replaceable cartridge, is suitable for being employed in a filter designed for being equipped with a safety cartridge, and overcomes the prior art drawbacks mentioned above, both when said safety cartridge is present and when it is not present in the filter.
Another object of the invention is to provide an air filter for I.C. engines that has a replaceable cartridge, is easy to maintain and therefore allows quick and safe replacement of the cartridge.
Another object of the invention is to provide an air filter for I.C. engines that is compact and has high flow rate and high filtering capacity.
Not the least object of the invention is to provide an air filter of the aforementioned type that can be industrially manufactured in a cost-effective manner.
These and other objects are achieved by the invention as claimed in the appended claims.

Summary of Invention

The air filter for I.C. engines according to the invention mainly comprises a housing, a removable lid, a replaceable main filter element, i.e. a main filter element that can be replaced, if necessary, with a similar one. The main filter element is housed in a compartment defined within the housing and comprises a main cartridge.
The function of the main cartridge is to separate impurities from the flow of dirty air passing through the filter, during operation of the engine with which the filter is associated. The air that comes from the outside environment and has passed through the main cartridge is therefore essentially so-called clean air, i.e. air that can be introduced into the combustion chambers of an I.C. engine. The main cartridge, when its service life is exhausted, can be replaced with a new one by opening the lid of the filter and removing the exhausted cartridge from the housing compartment in which it is received.
According to the invention, the main cartridge is provided with a sealing gasket, which is configured to be arranged between the housing and the lid and comprises at least one centering seat or centering projection for receiving a corresponding centering projection or centering seat provided on the lid or on the housing, when the main filter element is within the housing and the housing is closed by the lid. Preferably, when the lid is closed on the housing, the sealing gasket is in contact with a perimeter edge surrounding the housing as well as with a corresponding perimeter edge surrounding the lid. Said gasket is also preferably compressed between said perimeter edges when the lid is closed with known means such as screws or hooks.
In a preferred embodiment of the invention, the main filter element comprises an open base intended for air entry and surrounded by said sealing gasket, and preferably said sealing gasket extends radially in a cantilevered manner outside the filter element, defining a pair of opposite abutment surfaces.
The seats or projections are preferably provided on the surface of said pair of surfaces facing the main filter element. Corresponding projections or seats are correspondingly provided on the edge of the housing defining the compartment that houses the main cartridge.
In a preferred embodiment of the invention, the seats extend through the thickness of the gasket for a depth between 30 and 60 % of the thickness of the gasket at said seats. Advantageously, in this way, it is possible to provide complementary projections provided in the lid or, preferably, in the housing of the filter, and having enough axial extension, without, however, weakening the structure of the gasket, but such as to ensure optimal centering of the main cartridge relative to the housing of the filter.
In a preferred embodiment of the invention, the perimeter of the gasket and, correspondingly, the perimeter of the opening of the housing that received the main cartridge have a substantially rectangular shape with rounded corners. Preferably, in addition, the seats and the projections are four in number , one for each side of the rectangle defined by the gasket. Preferably, in addition, the projections extend over the perimeter of the gasket for a length between about 20 mm and 50 mm.
According to a preferred embodiment of the invention, the housing comprises an opening that can be closed by said lid, for the introduction of the main cartridge, and said projections are provided on an abutment edge surrounding said opening of the housing intended for accessing the compartment in which the main cartridge is received.
Advantageously, according to a preferred embodiment of the invention, the sealing gasket of the main cartridge comprises a stiffening inner core made of a plastic material and having higher rigidity than the material, typically rubber of polyurethane foam, of which the gasket is made.
According to the invention, the filter further comprises a secondary filter element or safety cartridge. In addition, both the main and secondary filter elements can be replaced individually. According to the invention, the secondary filter element defines a corresponding pocket in which the main filter element is received. Both the main filter element and the secondary filter element further comprise a corresponding annular sealing gasket. According to the invention, said gaskets cooperate with each other to define a corresponding hermetic seal when said main and secondary filter elements are received in the housing of the filter and the lid is closed.
The housing of the filter according to the invention preferably comprises a side wall and a pair of opposite bases. A first one of said bases is open and closeable by the lid of the filter, and a second one of said bases, opposite to the first one, is provided with an outlet opening for clean air.
In addition, the lid of the filter preferably comprises a plurality of separators to separate larger impurities from the air flow passing through the lid.
According to a preferred embodiment of the invention, the main cartridge comprises a pair of packs of pleated paper, arranged in a "V"-like configuration, such as to define a central passage for the entry of air flowing out of the center of the main cartridge and towards the periphery through the pleats of the paper.
When the safety cartridge is present, within the housing and in direction of air flow through the filter, the main cartridge is functionally arranged upstream of the safety cartridge.
Preferably, according to the invention, the main cartridge has a filtering capacity higher than that of the safety cartridge. Even more preferably, the filtering capacity of the main filter element or main cartridge is by at least 50% higher than that of the secondary filter element or safety cartridge.
The function of the safety cartridge is to prevent impurities from penetrating into the intake circuit of the I.C. engine, especially during replacement of the main filter element, or in case of accidental breakage of the filter material of said main filter element.
Said cartridges are individually removable, i.e. they can be removed individually and replaced independently of each other when necessary.
According to the invention, the safety cartridge defines a corresponding pocket in which the main cartridge is received. According to the invention, therefore, the safety cartridge surrounds, preferably almost entirely, the main cartridge, leaving only one side of the main cartridge free in order to allow air entry.
In a preferred embodiment of the invention, the main cartridge and the safety cartridge have a substantially complementary shape and the inner pocket defined in the safety cartridge is preferably sized in such a way as to minimize the distance between the outer surface of the walls of the main cartridge and the inner surface of the walls of the pocket. Even more preferably, the inner pocket defined in the safety cartridge is sized so that the outer surface of the walls of the main cartridge is in contact with the inner surface of the walls of the pocket by at least 50% of the outer surface of the walls of said main cartridge. Even more preferably, said percentage is at least 70%. Advantageously, thanks to this measure, the main cartridge is housed in the pocket defined in the safety cartridge, without appreciable increase in the overall volume of the pair of filter elements. In the most preferred embodiment providing for contact between the walls of the two cartridges, this increase in volume is essentially determined by the thickness of the walls of the safety cartridge.
Preferably, according to the invention, the safety cartridge comprises a support structure, in which a side wall and a pair of opposite bases are provided. The side wall and a first one of the opposite bases are preferably both provided also with openings for air passage. The support structure is further coated, preferably inside, at least at said openings, with a layer of filter material, made of a synthetic material or a cellulose-based material.
Advantageously, according to the invention, the walls of the support structure are preferably made with a reduced thickness, comprised between 1.5 and 5.0 mm. Even more preferably, the thickness of the walls of the support structure is about 2.5 mm. In addition, the thickness of the walls of the safety cartridge is preferably approximately constant over the entire body of the cartridge. The thickness of the layer of filter material is preferably in the order of millimeters, and even more preferably, it is between 0.3 and 0.9 mm. The second opposite base of the safety cartridge is preferably open, for allowing easy passage of the main cartridge, which, during use of the filter, is housed within the secondary cartridge.
In a preferred embodiment of the invention, the main cartridge and the safety cartridge have a substantially prismatic shape, with opposite bases that are substantially rectangular and parallel to each other and have different areas, whereby the side walls are slightly tapered from the major base towards the minor base.
Advantageously, according to the invention, the provision of the safety cartridge within the filter according to the invention guarantees the presence of a safety filter layer, which retains any impurities and foreign bodies, preventing them from penetrating into the intake circuit of the engine. Advantageously, in addition, the safety cartridge does not lead to an appreciable increase in the size of the filter, since it is substantially configured as a pocket in which the main cartridge is received.
According to the invention, the support structure is preferably made of plastic, for example a plastic mesh, with large windows for air passage. The support structure therefore confers a certain rigidity to the safety cartridge, which can therefore be advantageously inserted into and removed from the housing with ease and without risk of breakage and consequent unwanted entry of material into the filter.
The support structure of the safety cartridge preferably includes a molded one-piece plastic grid extending along the side walls and one of the bases of the safety cartridge. This grid also defines, preferably, a perimeter portion, radially projecting towards the outside of the safety cartridge, around the open base, and defining a stiffening core for a corresponding sealing gasket of the safety cartridge, for example made of rubber or polyurethane foam. Preferably, in addition, the support structure and the gasket are co-molded, or the gasket can be attached, or applied, in a separate processing step, on the projecting portion of the support structure.
In addition, according to the invention, the gasket of the safety cartridge has a cross-section having substantially the shape of and overturned "U" and capable of cooperating with a first inner perimeter edge provided in the housing of the filter. This cooperation determines the correct centering of the safety cartridge inside the compartment of the housing of the filter and an adequate airtight seal between the gasket and said first edge of the housing, thus preventing unwanted entry of air from the outside environment directly into the compartment of the housing, by-passing the main and safety cartridges.
Still according to the invention, the safety cartridge preferably includes a pair of inner side guides cooperating with a pair of outer side projections provided in the main cartridge. The outer side projections are preferably defined at a bottom closing one of the basis of the main cartridge. The guides provided in the safety cartridge are preferably provided at the bottom of the cartridge and, by cooperating with the side projections of the main cartridge, they are advantageously adapted to guide the main cartridge inside the pocket defined in the safety cartridge, during replacement of the main cartridge. Advantageously, thanks to this measure, the centering of the main cartridge relative to the safety cartridge is optimal and the replacement of the main cartridge can be carried out easily and without removing the safety cartridge. In a preferred embodiment of the invention, the guides are defined by pairs of inclined planes converging towards the bottom of the safety cartridge and defining a frustoconical inlet surface for the projections of the main cartridge. Preferably, the angle of the inclined planes is such as to define an inlet surface with a conicity between 45° and 90°.
The filter according to the invention provides that, preferably, both the main cartridge and the safety cartridge each include a corresponding perimeter sealing gasket. In addition, according to a preferred embodiment of the invention, said gaskets cooperate with each other to define the corresponding hermetic seal when these cartridges are housed in the housing of the filter and the lid has been closed. According to a particular embodiment of the invention, the safety cartridge comprises a perimeter edge surrounding the open base and having a sealing gasket. Said sealing gasket advantageously defines an abutment surface distal relative to the safety cartridge, for a corresponding abutment surface provided on the sealing gasket of the main cartridge.
Advantageously, according to the invention, the sealing gasket of the main cartridge comprises at least on centering seat or centering projection, adapted to receive a corresponding centering projection or centering seat provide on the lid or on the housing of the filter, when the main filter element is within the housing and housing is closed by the lid. Preferably, said at least one centering seat or centering projection further cooperates with frustoconical inlet surfaces, by means of the projections provided on the bottom of the main cartridge, for advantageously retaining the main cartridge in the housing, preventing movements of said main cartridge and resulting loss of tightness.
The housing of the filter according to the invention preferably comprises a side wall and a pair of opposite bases. A first one of said bases is open and closeable by the lid of the filter, and a second one of said bases, opposite to the first one, is provided with an outlet opening for clean air.
In addition, the lid of the filter preferably comprises a plurality of separators to separate larger impurities from the air flow passing through the lid.
According to a preferred embodiment of the invention, the main cartridge comprises a pair of packs of pleated paper, arranged in a "V"-like configuration, such as to define a central passage for the entry of air flowing out of the center of the main cartridge and towards the periphery through the pleats of the paper.

Brief Description of Drawings

Some preferred embodiments of the invention will be described by way of nonlimiting examples with reference to the annexed drawings, in which:

Fig. 1
Fig.1 is an exploded view of the filter according to the invention;
Fig. 2
Fig.2 is a bottom plan view of the main cartridge of the filter of Fig.1;
Fig. 3
Fig.3 is a perspective view of the housing of the filter of Fig.1;
Fig. 4
Fig.4 is a longitudinal section of the main cartridge of the filter of Fig.1;
Fig. 5
Fig.5 is an enlarged view of a detail of Fig.4;
Fig. 6
Fig.6 is a perspective view of the safety cartridge of the filter of Fig.1;
Fig. 7
Fig.7 is a longitudinal section of the housing of the filter of Fig.1;
Fig. 8
Fig.8 is a longitudinal section of the filter of Fig.1;
Fig. 9
Fig.9 is a longitudinal section of the safety cartridge of the filter of Fig.1;
Fig. 10
Fig.10 is a perspective view of the main cartridge of the filter of Fig.1.

Description of Some Preferred Embodiments

Referring to Fig.1, an air filter 11 for I.C. engines made in accordance with the invention comprises a housing 13, a removable lid 15 and a main filter element or main cartridge 17. The filter 11 further comprises a secondary filter element or safety cartridge 19. The main cartridge 17 and the safety cartridge 19 are both housed within a compartment 21 defined within the housing 13.
The function of the main cartridge 17 is to separate impurities from the flow of dirty air passing through the filter 11, during operation of the engine with which the filter 11 is associated. The air that comes from the outside environment and has passed through the main cartridge 17 is therefore essentially so-called clean air, i.e. air that can be introduced into the combustion chambers of an I.C. engine. The main cartridge 17, when its service life is exhausted, can be replaced with a new one by opening the lid 15 of the filter 11 and removing the exhausted cartridge 17 from the compartment 21 of the housing 13 in which it is received.
According to the invention, the main cartridge 17 is provided with a sealing gasket 23, which is configured to be arranged between the housing 13 and the lid 15.
In the illustrated embodiment, when the lid 15 is closed on the housing 13, the sealing gasket 23 is in contact with a perimeter edge surrounding the housing 13 as well as with a corresponding perimeter edge surrounding the lid 15. Said gasket 23 is also preferably compressed between said perimeter edges when the lid 15 is closed with known means such as screws or hooks.
In the illustrated preferred embodiment of the invention, the main cartridge 17 comprises an open base 25, for air entry. Said base 25, in the illustrated embodiment, is surrounded by the sealing gasket 23 radially in a cantilevered manner outside the main cartridge 17. Still referring to the illustrated embodiment, the gasket 23 defines a pair of opposite abutment surfaces 27,29 facing the housing 13 and the lid 15, respectively.
Referring to Figs.2 and 3, the sealing gasket 23 comprises a plurality of centering seats 31. Said centering seats 31, in the illustrated embodiment, are adapted to receive each a corresponding axial centering projection 33 provided on the housing 13, when the main cartridge 17 is within the housing 13 and the housing 13 is closed by the lid 15.
Still referring to the illustrated embodiment, the centering seats are four in number and are provided on the surface 27 of the cantilevering 23 oriented towards the housing 13. Corresponding axial seats 33 are correspondingly provided on the edge 35 of the housing 13 defining the compartment 21 that houses the main cartridge 17, around the opening 37 intended for the introduction of the main cartridge 17 into the compartment 21 and closable by the removable lid 15.
In this embodiment of the invention, the seats 31 extend through the thickness of the gasket 23 for a depth corresponding to about 40% of the thickness of the gasket 23, at said seats 31. Advantageously, in this way, it is possible to provide complementary projections 33 provided in the housing 13 of the filter 11 and having enough axial extension, without, however, weakening the structure of the gasket 23, but such as to ensure optimal centering of the main cartridge 17 relative to the housing 13 of the filter 11.
In this embodiment of the invention, the perimeter of the gasket 23 and, correspondingly, the perimeter of the opening 37 of the housing 13 housing the main cartridge 17 have a substantially rectangular shape with rounded corners. Preferably, in addition, the seats 31 and the projections 333 are four in number, one for each side of the rectangle defined by the perimeter of the gasket 23. Preferably, in addition, the seats 31 and the projections 33 extend over a length between 20 mm and 50 mm along said perimeter.
According to a preferred embodiment of the invention, the housing 13 comprises an opening 37 closeable by said lid 15 for introduction of the main cartridge 17 into the compartment 21 and said projections 33 are advantageously provided on an abutment edge 35 surrounding said opening 37.
Referring to Fig.4 and still with reference to the illustrated embodiment, the main cartridge 17 comprises a pair of packs of pleated paper 39 arranged in a "V"-like configuration, such as to define a central passage 41 for the entry of air flowing out of the center of the main cartridge 17 and towards the periphery through the pleats of the paper (arrows F1).
The base 25 of the main cartridge 17 is open for air entry and is surrounded by a gasket 23 made of rubber or polyurethane foam. Preferably, the gasket 23 comprises a stiffening inner core 43 made of a plastic material and having higher rigidity than the material, typically rubber of polyurethane foam, of which the gasket 23 is made.
As can be better appreciated in Fig.5, said core 43 has a substantially "T"-like cross-section.
Referring again to Fig.1, the housing 13 of the filter 11 according to the invention preferably comprises a side wall 45 and a pair of opposite bases 47,49. A first one 47 of said bases is open and can be closed by the lid 15 of the filter, and a second one 49 of said bases, opposite to the first one, is provided with an outlet opening 51 for clean air.
In addition, the lid 15 of the filter 11 preferably comprises a plurality of separators 53 to separate larger impurities from the air flow passing through the lid 15.
According to the invention, the filter 11 further comprises a secondary filter element or safety cartridge 19. Both the main 17 and secondary 19 filter elements can be replaced individually. According to the invention, the secondary filter element 19 defines a corresponding pocket 61 in which the main filter element 17 is received. Both the main filter element 17 and the secondary filter element 19 further comprise a corresponding annular sealing gasket 23, 63, said sealing gaskets cooperating with each other to define a corresponding hermetic seal when said main 17 and secondary 19 filter elements are received in the housing 13 of the filter 11 and the lid 15 is closed.
When the pair of cartridges 17,19 are installed within the filter 11, the safety cartridge 19 therefore surrounds almost entirely the main cartridge 17, leaving substantially only the air inlet base 25 of said main cartridge 17 free in order to allow entry of the air coming from the lid 15.
Referring to Figs.6 and 7, in the illustrated embodiment, the safety cartridge 19 comprises a support structure 65, in which a side wall 67 and a pair of opposite bases 69,71 are defined. The side wall 67 and a first one 69 of the opposite bases 69,71 are preferably both provided also with openings 73 for air passage. The support structure 65 is further coated, preferably inside, at least at said openings, with a layer of filter material 75, for example made of a synthetic material or a cellulose-based material. In the illustrated embodiment, the side wall 67 of the support structure 65 has a substantially constant thickness of about 2.5 mm. In the illustrated embodiment, the thickness of the layer of filter material 75 is about 0.5 mm. in addition, the safety cartridge 19 is made such as to be substantially in contact with the outer surface of the main cartridge 17 and, overall, the presence of the safety cartridge 19 determines only a minimum increase in the volume of the main cartridge,
The second opposite base 71 of the safety cartridge 19 is preferably made completely open, to allow easy passage of the main cartridge 17, which, in use, is housed within the safety cartridge 19 within the pocket 61 defined therein.
In the illustrated embodiment, the support structure 65 is made of plastics and is provided with large openings 73 for air passage, on the base 69 and on the opposite, major faces 77a,77b of the support structure 65. The opposite side flanks 77c,77d of the support structure 65, instead, have no opening and comprise a rectilinear axial projection 79 cooperating with a corresponding guide 81 provided within the housing 13 of the filter, to correctly keep the safety cartridge 19 in place within the compartment 21 defined in the filter 11.
In the illustrated embodiment, the opening 83 provided at the base 71 of the safety cartridge 19 is surrounded by a sealing gasket 63, for example made of rubber or polyurethane foam and preferably co-molded with the support structure 65.
The support structure 65 confers a certain rigidity to the safety cartridge 19, which can therefore be advantageously inserted into and removed from the housing 13 with ease and without risk of breakage and consequent unwanted entry of material into the filter.
Referring to Fig.8 and still with reference to the illustrated embodiment, the support structure 65 comprises a perimeter portion 85 radially projecting towards the outside of the safety cartridge 19, around the opening 83 of the base 71, and defines a stiffening core for the corresponding sealing gasket 63 preferably co-molded with said support structure 65.
Still according to the invention, and referring to Figs.9 and 10, the safety cartridge 19 comprises a pair of inner side guides 87 arranged along the opposite side flanks 77c,77d and cooperating with a pair of outer side projections 89 provided in the main cartridge 17. Said side projections 89 are defined at a bottom 91 closing the base of the main cartridge 17 opposite to the opening of the base 25.
In the illustrated preferred embodiment of the invention, the inner side guides 87 are defined by pairs of inclined planes 93a,93b converging towards the bottom of the safety cartridge 19 and defining a frustoconical inlet surface 93c for the projections 89 of the main cartridge 17. In the shown example, the angle of the inclined planes 93a,93b is such as to define an inlet surface 93c with a conicity α of about 60°.
The guides 87 provided within the safety cartridge 19, by cooperating with said side projections 89, are advantageously adapted to guide the main cartridge 17 inside the pocket 61, defined by the safety cartridge 19, during replacement of the main cartridge 17. Advantageously, thanks to this measure, the centering of the main cartridge 17 relative to the safety cartridge 19 is optimal and the operations for replacing the main cartridge 17 can can be carried out easily and without removing the safety cartridge 19. The function of the main cartridge 17 is to separate impurities from the flow of dirty air passing through the filter, during operation of the engine with which the filter is associated. The air that comes from the outside environment and has passed through the main cartridge is therefore essentially so-called clean air, i.e. air that can be introduced into the combustion chambers of an I.C. engine. The main cartridge 17, when its service life is exhausted, can be replaced with a new one by opening the lid 15 of the filter and removing the exhausted cartridge 17 from the compartment in which it is received.
The function of the safety cartridge 19 is to prevent impurities from penetrating into the intake circuit of the I.C. engine, especially during replacement of the main filter element 17, or in case of accidental breakage of the filter material of said main filter element 17.
Said cartridges 17,19 are individually removable, i.e. they can be removed individually and replaced independently of each other when necessary.

Claims

An air filter (11) for I.C. engines, comprising a housing (13), provided with a removable lid (15), in which a compartment (21) is provided receiving a main filter element (17) which is replaceable and provided with a sealing gasket (23) adapted to be interposed between the housing (13) and the lid (15), wherein the sealing gasket (23) comprises at least one centering seat or projection (31) for receiving a corresponding centering projection or seat (33) provided on the lid (15) or on the housing (13) when the main filter element (17) is located within the housing (13) and the housing (13) is closed by the lid (15), wherein a secondary filter element (19) is provided, wherein said main (17) and secondary (19) filter elements are individually replaceable, characterized in that the secondary filtering element (17) defines a corresponding pocket in which the main filtering element is received, in that the secondary filter element (19) comprises a corresponding annular sealing gasket (63), which has a cross-section having substantially the shape of an overturned "U" and capable of cooperating with a first inner perimeter edge provided in the housing (13) of the filter (11), and in that said gaskets (23, 63) cooperate with each other in order to define a corresponding hermetic sealing when said main and secondary filter elements (17, 19) are received in the housing (13) and the lid (15) is closed.
The filter according to claim 1, wherein the main filter element (17) comprises an open base (25) intended for the entry of air and surrounded by said sealing gasket (23) of the main filter element, and wherein said sealing gasket (23) of the main filter element extends radially in a cantilevered manner outside the filter element (17) and defines a pair of opposite abutment surfaces (27,29).
The filter according to claim 2, wherein the at least one centering seat provided in the sealing gasket (23) of the main filter element is formed on the surface of said pair of opposite abutment surfaces (27,29) which faces the housing (13) when the main filter element (17) is received in said housing and the lid (15) is closed.
The filter according to claim 3, wherein said seats (31) extend in the thickness of the sealing gasket (23) of the main filter element by a depth comprised between 30 and 60% of the thickness of the gasket at said seats.
The filter according to any of the preceding claims, wherein the perimeter of the sealing gasket (23) of the main filter element is substantially rectangular, and wherein said seats (31) and said projections (33) are four in number, one for each side of the rectangle.
The filter according to any of the preceding claims, wherein said seats (31) and said projections (33) extend over a length comprised between 20 mm and 50 mm.
The filter according to any of the preceding claims, wherein the housing (13) comprises an opening (37) closeable by said lid (15) for the entry of the main filter element (17), and wherein said projections (33) are provided on an abutment edge (35) surrounding said opening of the housing.
The filter according to any of the preceding claims, wherein the sealing gasket (23) of the main filter element comprises a stiffening inner core (43) made of plastic material