WO2009095346A1

WO2009095346A1 - A filter for liquids

Info

Publication number: WO2009095346A1
Application number: PCT/EP2009/050659
Authority: WO
Inventors: Giorgio Girondi
Original assignee: Ufi Filters S.P.A.
Priority date: 2008-01-29
Filing date: 2009-01-21
Publication date: 2009-08-06
Also published as: ITRE20080010A1

Abstract

A filter for liquids, comprising an external casing (2) made of a non-electrically conductive material, an internal volume of which is sub-divided by a filter element (32) into a first chamber (4) communicating with an inlet (25) of a liquid to be filtered, and a second chamber (5) communicating with an outlet (26) of the filtered liquid; the internal surface of the external casing (2) being at least partially covered by a conductive cladding (6), which is made of a composite material comprising a polymer matrix in which particles of an electrically-conductive material are dispersed, and being connected to at least an electrically-conductive terminal (60) which is exposed to an outside of the casing (2).

Description

A FILTER FOR LIQUIDS

Technical Field

The invention relates to a filter for liquids destined to be associated to an internal combustion engine, in particular a filter for fuels.

Background Art

As is known, a filter for liquids normally comprises an external casing, an internal volume of which is sub-divided by a filtering element into two distinct chambers, of which a first chamber communicates with an inlet of the liquid to be filtered, and a second chamber communicates with an outlet for the filtered liquid.

To limit the production costs of the filter, the external casing is generally made of a plastic material, for example using a moulding process.

The plastic materials normally used are characterised in that they are electrically non-conductive.

During the crossing of the filtering element however, it happens that some liquids, among which for example diesel destined for supplying Diesel engines for motor vehicle, generate electrostatic charges internally of the chamber of the liquid to be filtered.

These electrostatic charges accumulate in proximity of the non-conductive walls of the external casing, causing rapid formation of small cracks which irreparably compromise the seal of the casing itself. In order to overcome this drawback, numerous solutions are known which, in a general sense, have the aim of creating an electrical connection between the inside and the outside of the filter casing, such as to discharge the accumulated electrostatic loads to earth.

One of these solutions comprises realising the filter casing with an electrically-conductive composite material comprising a polymer matrix in which particles of conductor material are dispersed randomly, such as for example filaments or particles of metal. This composite material has the double advantage of enabling migration of the electrostatic charges from the inside towards the outside of the filter, and of being usable in normal moulding processes of moulding for plastic materials, enabling a simple and economic production of the casing. Owing to the inclusion of conductor particles, the ease with which this material can undergo a moulding process is smaller than that with plastics normally used, so only filter casings having a generally simpler shape can be made. Further, the composite material is more expensive than traditional plastics, so that the choice of using the material for entirely realising the filter casing leads to a not insignificant rise in production costs.

An aim of the present invention is to make available a filter for liquids which enables migration of the electrostatic charges from inside to outside the casing, and which at the same time is constructionally more economical with respect to known filters. A further aim of the invention is to attain the above-cited objective with a solution that is simple and rational.

These aims are attained by the characteristics of the invention reported in the independent claims. The dependent claims delineate preferred and/or especially advantageous aspects of the invention. Disclosure of Invention

In particular, the invention provides a filter for liquids comprising an external casing made of an electrically non-conductive material, an internal volume of which is sub-divided by a filter element in a first chamber communicating with an inlet of the liquid to be filtered, and a second chamber communicating with an outlet of the filtered liquid. The internal surface of the casing is at least partially covered by an electrically-conductive cladding, which is made of a composite material comprising a polymer matrix in which particles of conductive material are dispersed, and in contact with at least an electrically- conductive terminal which is displayed externally of the casing. Thanks to this solution, the external casing of the filter can be made of a traditional plastic material in a usual moulding process, with consequent advantages in terms of complexity of the shapes obtainable and manufacturing costs, while the composite conductor material is used only for internal cladding, which can be kept small and simple, while enabling effective migration of the electrostatic charges towards the outside.

In a preferred aspect of the invention, the conductor casing is destined to cover at least a complete perimeter strip of the internal surface of the casing, and possibly at least a portion of a bottom surface thereof.

In this way, the cladding exhibits a large contact surface with the liquid, which enables the majority of the electrostatic charges which form internally of the filter to be discharged. In a further preferred aspect of the invention, the conductive cladding can be defined by a single continuous wall, or by a plurality of separate ribs which give it a cage shape.

The invention also provides a manufacturing process of the filter.

The method comprises first modelling the conductive material, preferably with a moulding process for plastic materials, and then modelling the external filter casing directly on the cladding obtained.

For example, the external casing can be realised via a process of moulding for plastic materials, in which the conductive material is first inserted internally of the mould, as a forming core. Brief description of the Drawings

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 accompanying tables of drawings.

Figure 1 is a filter of the invention sectioned in an axial plane. Figure 2 is a simplified perspective view of the lower portion of the filter of figure 1.

Figure 3 is the same view as in figure 2, relating to a variant of the filter of the invention.

Best Mode for Carrying Out the Invention The figures illustrate a filter 1 for filtering diesel fuel destined to supply a diesel engine mounted on board a motor vehicle. The filter 1 comprises an external casing, denoted in its entirety by 2, which is made of an electrically non-conductive plastic material. The non-conductive material can be made up, for example, of a nylon 6.6 polymer-matrix material, reinforced with glass fibre at 30% of the overall weight of the material.

The external casing 2 comprises a lower portion 20 having a substantially beaker-shaped conformation, and an upper cover 21 which is destined to closed the beaker 20 by interposition of a perimeter seal ring 22. The lower beaker 20 and the cover 21 are reciprocally fixed by means of a coaxial collar 23, which is rotatably coupled to the upper cover 21 , and is screwed to the outside of the beaker 20.

The beaker 20 is provided with a fastening flange 24, by which the filter 1 can be mounted on the vehicle, while the cover 21 is provided with an inlet conduit 25 for the diesel to be filtered, and an outlet conduit 26 for the filtered diesel.

The outlet conduit 26 exhibits a part which projects internally of the casing 2, and functions as a sleeve to which a filter cartridge 3 is coupled. The filter cartridge 3 comprises two opposite plates, respectively an upper plate 30 and a lower plate 31 , between which a filter element 32 is retained, the filter element 32 being generally toroidal in shape, for example a wall of pleated cellulose having a star-shaped geometry.

The upper plate 30 exhibits a central hole, internally of which a projecting tract of the outlet conduit 26 is inserted, with interposition of a seal ring 27. In this way, the filter cartridge 3 sub-divides the internal volume of the casing 2 into a chamber for the diesel to be filtered 4, which is defined between the external wall of the casing 2 and the filter element 32, and a chamber for the filtered diesel 5, which is defined internally of the filter element 32. The chamber 4 for the diesel to be filtered 4 communicates with the inlet conduit 25, while the chamber of the filtered diesel 5 communicates with the outlet conduit 26.

The internal surface of the casing 2 is partially covered by an electrically- conductive cladding 6, destined to be in direct contact with the diesel to be filtered in the chamber 4, which cladding 6 is made of a composite material comprising a solid polymer matrix, in which particles of an electrically- conductive material are sunk, for example filaments or particles of carbon and/or of other metals. The composite material can be formed, for example, by a polymer matrix of nylon 6.6, reinforced with glass fibre for 20% of its overall weight, and made conductive by particles of carbon of up to 10% of its overall weight. The internal cladding 6 is in contact with two electric terminals 60 made of an electrically-conductive material, which are rigid and substantially bar-shaped, and are located at the fixing flange 24 such as to be earthed.

With this solution, owing to the passage of the diesel through the filter element 32, the electrostatic charges which are generated in the chamber 4 of the diesel to be filtered can migrate into the cladding 6 and run along the electric terminals 60 up until they exit from the casing 2 and run to earth. The electric terminals 60 are sunk into the material of the external casing 2 such as not to compromise the hermetic seal, and can be made of the same composite material of the conductive cladding 6, and are preferable made in a single piece there-with. In the illustrated examples, the conductive cladding 6 is present only at the lower beaker 20, and dads a complete perimeter strip of the lateral surface as well as partially cladding the bottom surface.

The conductive cladding 6 is in reality made as a second beaker body which is coaxially inserted internally of the lower beaker 20 of the external casing 2, and which imitates a shape of the internal cavity thereof. As illustrated in figure 2, the conductive cladding 2 can be realised in a continual wall having a substantially constant thickness. In the alternative embodiment of figure 3, the conductive cladding 6 can be made from a plurality of reciprocally-separate distinct longitudinal ribs 61 , for example arranged in spoke-fashion about a common axis of symmetry, which substantially give it a cage-structure.

In this way, conductive composite material is saved, though enabling effective migration of the electrostatic loads towards the outside. From the constructional point of view, the cladding 6 can be modelled separately, preferably by means of a moulding process for plastic materials. The lower beaker 20 of the external casing 2 is thus obtained on the cladding 6. For example, the lower beaker 20 can be modelled by means of a moulding process for plastic materials, in which the conductive cladding 6 is first inserted into the mould such as to be sunk into the plastic material of the beaker 20. The cover 21 and the collar 23 are modelled separately, these too preferably by means of a moulding process, and finally they are coupled to the filter cartridge 3 and to the lower beaker 20 in which the cladding 6 is sunk. It is specified that the shape of the external casing 2, as well as the number of the components and means to which the components are coupled, can be significantly different with respect to what is described and illustrated in the figures, according for example to the filter model and/or the specific application to which the filter is destined.

Obviously a technical expert in the sector might make numerous modifications of a technical-application nature to the filter 1 as described herein above, without its forsaking the ambit of the invention as claimed herein below.

Claims

1 ). A filter for liquids, comprising an external casing (2) made of a non- electhcally conductive material, an internal volume of which is sub-divided by a filter element (32) into a first chamber (4) communicating with an inlet (25) of a liquid to be filtered, and a second chamber (5) communicating with an outlet (26) of the filtered liquid, characterised in that the internal surface of the external casing (2) is at least partially covered by a conductive cladding (6), which is made of a composite material comprising a polymer matrix in which particles of an electrically-conductive material are dispersed, and is connected to at least an electrically-conductive terminal (60) which is exposed to an outside of the casing (2).

2). The filter of claim 1 , characterised in that the cladding (6) covers at least a perimeter strip of the internal surface of the casing (2). 3). The filter of claim 2, characterised in that the cladding (6) at least partially covers an internal bottom surface of the casing (2). 4). The filter of claim 2 or 3, characterised in that the cladding (6) is made as a continuous wall.

5). The filter of claim 2 or 3, characterised in that the cladding (6) comprises a plurality of separate ribs (61 ) which give the cladding (6) a cage-structure. 6). The filter of claim 1 , characterised in that the electrically-conductive terminal (60) is at least partially sunk into the external casing (2).

7). A process for manufacturing a filter (1 ) as in claim 1 , comprising stages of first modelling the conductive cladding (6), and thus directly modelling at least a portion (20) of the external casing (2) on the conductive cladding (6). 8). The process of claim 7, wherein the portion (20) of the external casing (2) is modelled by means of a moulding process, wherein the conductive cladding (6) is first inserted into the mould.