TECHNICAL FIELD

The present invention relates to a filter cartridge destined to be installed in a filter group. In greater detail, the present invention relates to a filter cartridge installed in a filter group that can be used in the automotive field or generally in the motor vehicle field, for example for filtering fuel, in particular diesel oil, oil or blow-by gas, of an internal combustion engine.

PRIOR ART

As is known, the filter groups used in the motor-vehicle field normally comprise an external casing provided with an inlet for the fluid to be filtered and an outlet of the filtered fluid, and a filter cartridge located internally of the casing, which is able to subdivide the internal volume into a first communicating chamber with the inlet and a second chamber communicating with the outlet.

In many applications the filter cartridge comprises a filter element that is generally tubular, which is interposed and fixed between two support plates. The filter element can be, for example, a pleated filter membrane having a thin wall and a star-shaped geometry, or a depth filter membrane realised as a cylindrical body of non-woven textile made of polymer fibres, obtained for example by a melt-blown process.

The filter cartridge generally also comprises a support core, conformed as a cylindrical cage, which has the function of supporting the filter element in opposition to the pressure of the fluid to be filtered which acts on it.

The filter groups destined, for example, for filtering the diesel oil generally also comprise a cylindrical heating device which is inserted internally of the filter cartridge and has the function of heating the diesel when the ambient temperature falls below a level at which paraffins form which occlude the surface of the filter membrane, preventing passage of the diesel.

Filter groups of known type, while performing the function they are built for, need a certain amount of time in order to melt the paraffins as they are positioned relatively distant from the surface of the filter membrane on which the paraffins have formed. In practice the dissolving of the paraffins occurs only after the diesel internal of the cartridge has reached a determined temperature.

Further, the above-mentioned filter groups are relatively unwieldy and expensive to realise. In fact the presence of the heater internally of the cartridge reduces the quantity of fuel contained in the side of the filter inlet, forcing manufacturers to realise large-dimension filters.

An aim of the present invention is therefore to obviate the above-mentioned drawbacks in the prior art, with a solution that is simple, rational and relatively inexpensive.

These aims are attained by the characteristics of the invention recited in the independent claims. The dependent claims delineate preferred and/or particularly advantageous aspects of the invention.

SUMMARY OF THE INVENTION

In particular, an embodiment of the present invention relates to a filter cartridge comprising two support plates between which a tubular filter membrane is interposed, which filter membrane is provided with at least a conductive portion provided with two ends, characterised in that an electrical connection element is connected to each end of the conductive portion, which electrical connection element comprises an annular body.

This solution enables realising a smaller cartridge as a part of the heater is directly integrated in a conductive portion of the filter membrane. Further, the annular body of the electrical connection element is simple and economical to realise, as well as making a wide contact surface available.

In an aspect of the invention, the annular body is positioned in proximity of a central opening of the two support plates.

This aspect of the invention has the advantages of providing a rather simple and ergonomic solution for positioning the annular body.

In a different aspect of the invention, the annular body comprises at least a flexible tab, which branches from the annular body, and which projects at least partially internally of a central opening of the support plates.

The providing of a flexible tab always guarantees, owing to the flexibility of the tab, an excellent electrical contact independently of the working tolerances.

In fact, the flexible tab guarantees stability of the electrical contact against any eventual vibrations generated by the functioning of the motor and at the same time a reduction of the axial dimension occupied by the electrical connection element, increasing the space available for the filter medium. In a further aspect of the invention, the annular body comprises at least a plurality of flexible tabs, angularly distanced from one another, which project internally of the filter membrane.

This solution enables a better distribution of the electrical current in the annular body and at the same time provides the same advantages as the preceding aspect of the invention.

In a particular aspect of the invention, the electrical connection element comprises at least a tooth inserted in the conductive portion of the filter membrane.

The inclusion of the tooth inserted in the conductive position is a practical and economical solution for realising an electrical contact.

In a further aspect of the invention the connection element is entirely realised in the support plates.

This solution enables simple realisation of the electrical connection element simply by making the plates in a conductive material.

The electrical connecting element can advantageously be realised as a conductive element integrated in the plate made of insulating material, for example nylon and/or nylon loaded with glass fibre, by injection moulding. In a further aspect of the invention the electrical connection element is entirely realised in a support core interposed between the two support plates. This solution further enables simple realisation of the electrical connection element simply by making a support core in a conductive material.

Each electrical connecting element can advantageously be realised as a conductive element integrated at the axial ends of the reinforcing core made of insulating material, for example nylon and/or nylon loaded with glass fibre, by injection moulding.

In a further aspect of the invention, the filter membrane comprises a first conductive portion, located on the inlet side of the diesel, in series with a second non-conductive portion.

This solution reduces the production costs of the cartridge as the materials constituting the conductive portion of the filter membrane are much more expensive than those which realise the non-conductive portion thereof.

A further embodiment of the invention discloses a filter group, comprising an external casing provided with an inlet conduit for a fuel to be filtered, with an outlet conduit for the filtered fuel, and internally of which a filter cartridge is housed, made according to the present embodiment, the filter group being provided with a pin inserted axially internally of the filter cartridge, and provided with two electrodes, each of which is placed in contact with a respective electrical connection element of the cartridge.

The presence of the electrodes on the pin and the fact of realising a filter membrane with a conductive portion enable integrating the heater internally of the cartridge, reducing dimensions and simplifying, at the same time, the configuration of the filter cartridge from the constructional point of view.

The pin with the electrodes can be fixed to the cover of the filter group, facilitating the replacement operations of the filter cartridge.

The pin can advantageously be realised in a single piece with the cover of the filter group by injection moulding.

In a further aspect of the invention each electrode comprises an annular collar.

This aspect of the invention enables a simple realisation of an electrical contact which guarantees the electrical contact independently of the relative orientation between the electrode and the connection element.

In a further aspect of the invention the annular collar and the electrical connection element have a complementary shape, respectively concave and convex, configured for realising an axial hooking means of the pin to the filter cartridge.

This aspect of the invention provides the advantage of contemporaneously realising a hooking means and an electrical contact for passage of the electrical current which enables heating the conductive portion of the filter membrane.

In a variant of the invention the annular collar comprises a flexible tab that projects externally of the pin, and at least partially internally of the filter membrane.

As the flexible tab can flex so as to radially distance from the central axis of the pin during insertion thereof internally of the filter membrane, electrical contact between the electrode and the electrical connection element is ensured.

Further, the providing of the flexible tab guarantees stability of the electrical contact against any eventual vibrations generated by the functioning of the motor and at the same time a reduction of the axial dimension occupied by the electrical connection element, increasing, given same dimensions, the space available for the filter medium.

Additionally, integrating the heating function on the filter element provides for many advantages even in case of filtering devices intended for treating motor oil, wherein the conductive portion is used for heating the oil and having its viscosity taking values such as to ensure the best lubrication properties, or intended for treating blow-by gases wherein during the first heating steps of the engine it could be necessary to remove any condensate crystals, which have been formed during the engine downtime, from the surface of the filter media.

Further characteristics and advantages of the invention will emerge from a reading of the following description, provided by way of non-limiting example with the aid of the figures illustrated in the appended tables of drawings.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a section view, along an axial plane, of a filter group according to the invention.

Figure 2 is a perspective view of a filter cartridge fastened to the pin according to an embodiment of the present invention.

Figure 3 is section Ill-Ill of figure 1 .

Figure 4 is a perspective view of a pin detached from the filter cartridge according to figure 1 . Figure 5 is section V-V of figure 4.

Figure 6 is a view along a longitudinal section of a filter membrane according to claim 1 .

Figure 7 is a larger-scale view of a portion of figure 3.

DETAILED DESCRIPTION OF THE INVENTION

The figures illustrate a filter group 1 , comprising an external casing 2 provided with an inlet conduit 3 for a fuel to be filtered, with an outlet conduit 4 for the filtered fuel, and internally of which a filter cartridge 10 is housed, able to divide the internal volume of the casing 2 in a first chamber 200 communicating with the inlet conduit 3, and a second chamber 201 , communicating with the outlet conduit 4.

In greater detail, the casing 2 is formed by a beaker body 5 superiorly closed by a cover 6 on which the inlet conduit 3 for the diesel to be filtered and the outlet conduit 4 for the filtered diesel are located.

In particular, the cover 6 comprises a central hole 7 in which a pin 40 is inserted, having a substantially cylindrical shape and internally hollow, which extends axially internally of the casing 2, and which is configured to receive an end of the inlet conduit 3.

On the other hand a threaded central hole 8 is present on the bottom of the beaker body 3, closed by a cap 9, which is removed in order to discharge the water which collects on the bottom of the beaker body 5 during use of the filter group 1 .

A filter cartridge is housed internally of the casing 2. With particular reference to figures from 2 to 6, the filter cartridge 10 comprises a filter membrane 15 that is substantially tubular, in the example cylindrical, having a central axis Y.

In the illustrated example, the filter membrane 15 is a depth filter membrane, i.e. a cylindrical body having a rather thick wall which comprises a first conductive portion 17, destined to be located at the inlet side of the diesel, and which is at least partially realised by a layer of conductive fibres.

According to the present embodiment of the invention, the filter membrane 15 also comprises a second portion 18, made by a filter layer of non-conductive fibres, which is coaxial to and in series with the first conductive portion 17.

The first conductive portion 17 can be constituted by a layer of non-woven fibre comprising metal fibres and non-conductive polymer fibres.

In the illustrated example the metal fibres are made of stainless steel, a material that guarantees good electrical conductivity, an excellent resistance to contact with chemical substances, good workability and good mechanical resistance.

Other embodiments of the invention include the use of other types of conductive fibres, such as for example conductive polymeric fibres, carbon or graphite fibre nanotubes, or a mixture of those substances.

The second portion 18, non-conductive, of the filter membrane is made of non-conductive fibres of known type, for example made of polyester, polyamide, poly butylene terephthalate (PBT), glass fibres, paper, viscose, regenerated viscose or a blend of viscose and synthetic fibres, for example viscose and polyester.

It is specified that according to other embodiments of the invention the filter membrane might be of the slim-walled type, such as for example a pleated membrane wound about a central axis, so as to assume a geometry known as star-shaped. In this case too the filter membrane might comprise a conductive layer and a non-conductive layer, laminated the subsequently pleated so as to assume a star-shaped geometry.

Additionally, according to another embodiment of the invention, the first conductive portion 17 of the filter membrane 15 can have a geometry different from the geometry of the second non-conductive portion 18. For example, the first portion 17 can have a cylindrical geometry whereas the second portion 18 can have a star-shaped geometry, which is coaxial to and in series with the first portion.

Lastly it is specified that the filter membrane, in other embodiments of the invention, might be made only with conductive fibres.

The filter cartridge 10 further comprises two support plates, respectively an upper support plate 20 and a lower support plate 25. These support plates 20, 25 have a substantially disc-shaped conformation and are made of a non- electrically conductive plastic material, for example by means of an injection- moulding process.

The support plates 20 and 25 are coaxially fixed respectively to the upper end and the lower end of the filter membrane 15, using a hermetically-sealed fixing system. In this way, the filter membrane 15 is coaxially interposed between the upper support plate 20 and the lower support plate 25. Both the support plates 20 and 25 are provided with a central through-hole, denoted respectively by reference numerals 30 and 35 (figure 6), which has a substantially circular shape, coaxial and communicating with the internal cavity 16 of the filter membrane 15.

In greater detail, an annular shank 26, provided with a bottom wall 27 branches inferiorly at an edge of the opening 35 of the lower plate 25.

Differently, an annular shank 28 branches superiorly at an edge of the opening 30 of the upper plate 20.

With reference to figures 3 and 4, the pin 40 which is conformed as an internally hollow tubular body, in the example cylindrical, has on the lateral wall thereof a plurality of through-holes 45, for example having a rectangular shape.

The pin 40 can be made of a plastic material, for example by means of an injection-moulding process. The pin 40 has an axial extension that is greater than the axial extension of the filter membrane 15, and has an external diameter that is smaller than the internal diameter of the central openings 30 and 35 of the support plates 20 and 25. By virtue of these dimensions, the pin 40 is coaxially inserted internally of the internal cavity (which coincides with the chamber 200) of the filter membrane 15, and retained in position thanks to the hooking means described in the following. It is specified that the central axis of the pin 40 coincides with the central axis Y of the filter membrane 15 and the central openings 30 and 35 made in the support plates 20 and 25.

The pin 40 comprises two electrodes 50 able to be placed in contact with the conductive portion of the filter membrane.

In particular, each electrode 50 comprises an annular collar 55 connected to a respective plate 60, a free end of which, opposite the annular collar 55, advances beyond the upper end of the pin 40 and is connected to an electronic board 100 for electrical supply of the electrodes 50, which is located externally of the filter group 1 .

It is specified that in other embodiments of the invention the position of the electronic board 100 can be different, for example the electronic board 100 can be associated directly to and externally of the cover 6, or it can be inserted internally of the filter group 1 in a special chamber fashioned, for example, at the cover 6.

The annular collar 55, made of an electrically conductive material, is housed in a complementary annular seating realised on the external surface of the pin 40 and exhibits an annular central portion 550 (figures 5, 7) that is concave towards an outside of the pin 40, at a lower end of which a second truncoconical portion 551 branches that is inclined towards the central axis Y of the pin.

The truncoconical portion 551 has the function of improving the fixing of the electrode on the pin 40.

When the pin is inserted internally of the filter membrane the annular collars 55 of the two electrodes 50 are respectively substantially at the central openings 30 and 35 of the support plates 20 and 25, i.e. the collars 55 of the electrodes 50 are located substantially in proximity of the upper and lower end of the pin 40.

In this position of the pin 40 the two collars 55 come into contact with a respective electrical connection element 70 connected to the end of the conductive portion 17 of the filter membrane 15.

Further, the electrical connection element comprises an annular body 71 made of an electrically conductive material, able to go into contact with the collar 55 of the electrode 50.

In an aspect of the invention, the annular collar 55 and the electrical connection element 70 preferably have a complementary shape, respectively concave and convex, configured for realising, apart from an electrical connection, also an axial hooking means of the pin 40 to the filter cartridge 40.

The annular body 71 comprises at least a flexible tab 80 which projects at least partially internally of the central openings 30 and 35 of the support plate 20 and 25 so as to go into contact with the respective collar 55 of the electrode 50.

The electrical connection element 70 preferably comprises a plurality of flexible tabs 80, angularly distanced from one another, and having a convex shape, in the direction of the central axis Y of the filter cartridge 10, complementary to the concave shape of the annular collar 55 of the electrode, so as to have the maximum contact surface between the tabs 80 and the collar 55 of the electrode 50.

Said annular body 71 preferably comprises a plurality of flexible tabs 80, angularly distanced from one another, and having a convex shape, in the direction of the central axis Y of the filter cartridge 10, complementary to the concave shape of the annular collar 55 of the electrode 50, so as to have the maximum contact surface between the tabs 80 and the collar 55 of the electrode 50.

In practice, each flexible tab 80 projects from the annular body 71 in a radial direction towards the inner part of the filter membrane 15, i.e. towards the centre of the annular body 71 (in the direction of the axis Y).

Each flexible tab 80 is provided with an end which is constrained, for example fastened, to the annular body 71 and to an opposite free end.

In the illustrated example, the flexible tabs 80 are made integral with the annular body 71 .

From what is described it can be observed that the tabs 80 and the annular collar of the electrode 50, respectively having a concave and a convex shape, complementary to one another, not only realise the electrical contact but also make a hooking means which prevents axial movements of the pin 40 with respect to the filter membrane 15.

In general the electrical connection element 70 comprises at least a tooth 75 insertable in the conductive portion 17 of the filter membrane 15.

According to the described and illustrated embodiment the lower edge of the connection element has a plurality of teeth 75 which are inserted internally of the conductive portion 17 of the filter membrane 15.

According to a variant of the invention that is not illustrated, the annular collar of the electrodes 50 can comprise a plurality of flexible tabs, entirely similar to the flexible tabs 80 described in the foregoing, angularly distanced from one another and having a convex shape towards the outside of the pin 40. In this case the electrical connection element of the conductive portion 17 of the filter membrane will have the shape of an annular body which has a concave surface in the direction of the central axis Y of the filter cartridge 10, but is without the flexible tabs. The concave surface of the annular body of the connecting element will be complementary to the convex shape of the annular collar of the electrode, so as to have the maximum contact surface between the tabs and the collar of the electrode.

Further, according to the invention, on the diesel outlet side a hydrophobic net for separation of the water contained in the diesel can be associated to the non-conductive portion 18 of the filter membrane 15.

In the invention various types of sensors can also be associated to the pin 40, such as for example a temperature sensor, and/or a thermal switch adapted to enable power supplying to the electrodes 50, and therefore to the conductive portion 17 of the filter membrane 15, based on the working fluid temperature. A sensor, detecting the level of water collected in a special chamber fashioned in the filter group in which the cartridge is housed, can be associated to the pin 40.

In other embodiments of the invention the electrical connection element 70 is made in the support plates which in this case will be made of a conductive material.

The connection element 70 comprises an annular body 71 with at least a flexible tab 80 projecting at least partially internally of the central openings 30 and 35, respectively, of the support plates 20 and 25 for contacting the respective collar 55 of the electrode 50.

Said electrical connection element 70 preferably comprises an annular body 71 comprising a plurality of flexible tabs 80, angularly distanced from one another for contacting the annular collar of the electrodes carried by the pin 40, as described above.

Alternatively the electrical connection element 70 might be made of a reinforcing core, not illustrated as it is of known type, interposed between the two support plates 20, 25 internally of the internal cavity of the filter membrane, i.e. on the inlet side of the diesel.

From what is described it can be understood that the technical characteristics of the invention enable obtaining the heating of the filter medium and of the working fluid. The technical characteristics of the invention, in case of a diesel oil filter, enable obtaining the dissolving of the paraffins which rapidly form on the diesel inlet side, while at the same time enabling a realising of the filter cartridge that is easy to install and relatively inexpensive.

In fact the replacement of the cartridge primarily comprises removing the cover 6 of the beaker body 2. This operation enables contemporaneously extracting the cartridge 10, which can be simply de-inserted from the pin 40, on which a new cartridge 10 is then inserted, and then replacing the cover and the cartridge internally of the beaker body 2.

In an embodiment that is not illustrated, the cartridge 10 is fixed to the removable collecting tray using special hooking devices arranged between the plate of the cartridge and the internal surface in the tray. The tray is then re-screwed to the main body of the casing 5, ensuring correct insertion of the pin 40 in the internal cavity of the cartridge 10 and ensuring adequate contact of the electrical connecting elements 70 with the electrodes 50 integrated on the pin 40.

Further it is stressed that the position of the electrical connection elements 70 of the cartridge 10 enable the electrical current supplied by the electronic board 100 to cross the whole conductive cylindrical portion 17, making heating thereof particularly rapid and effective.

Obviously a technical expert in the sector might make numerous modifications of a technical-applicational nature to the filter cartridge 10 without its forsaking the scope of the invention as claimed in the following.