WO2015092681A1

WO2015092681A1 - Multi-layered filter element and method for making the same

Info

Publication number: WO2015092681A1
Application number: PCT/IB2014/066970
Authority: WO
Inventors: Giorgio Rocca; Paolo Vitagliani; Umberto Cornaglia
Original assignee: Officine Metallurgiche G. Cornaglia S.P.A.
Priority date: 2013-12-18
Filing date: 2014-12-16
Publication date: 2015-06-25
Also published as: ITTO20131038A1

Abstract

Multi-layered filter element (11) comprising at least two layers (13,15) of filtering material made of paper pleated in an accordion-like way along parallel bending lines, so as to define, along said bending lines, a series of ridges (13a, 15a) alternated with grooves (13b, 15b), the at least two layers (13,15) being undetachably held together in the filter element, except when the filter element itself becomes destroyed, by sealing gaskets (23,25) made of plastic material in which the paper of the layers (13,15) is partially incorporated, adjacent layers (13,15) of filtering material being arranged close to each other and the ridges (13a, 15a) of different layers being mutually parallel, wherein between adjacent layers (13,15) there are provided spacers (17) arranged on the paper ridges (13a, 15a) perpendicularly thereto, said spacers preventing the ridges (13a, 15a) of a layer (13,15) from penetrating into the grooves (13b, 15b) of the adjacent layer (13,15) and vice versa; the invention further relates to a method for making the filter element.

Description

Multi-layered filter element and method for making the same

DESCRIPTION

Technical Field

The present invention relates to a multi-layered filter element and to a method for making the same.

More particularly, the invention relates to a multi- layered filter element for air filters of IC engines.

Background Art

As is known, IC engines are usually equipped with a suction circuit for combustion air provided with a filter for purifying air. The air filter is necessary for purifying the air that is sent to the combustion chambers of the engine, thus preventing dust and dirt particles from entering the engine and damaging its inner parts.

Air filters for suction circuits of IC engines usually comprise an air-tight housing in which a cartridge-like filter element is received. The filter housing is provided with an air inlet opening and an air outlet opening and is formed at its inside in such a way that the impure air entering through the inlet opening is forced to pass through the filtering material of the cartridge and exits clean through the outlet opening.

A filter element widespread in the field of air filters for IC engines consists of a sheet of pleated filtering material that is glued so as to be kept in its desired shape. A material typically used for making this kind of filters is cellulose paper. A pleating machine forms, starting from a flat sheet unwound from a roll, a series of pleats in the sheet so as to obtain a substantially accordion-like configuration, which is maintained by depositing glue between the pleats. The material is cut to the desired length and usually arranged either in a flat orientation, so as to obtain an accordion-like pack, for instance having a parallelepipedal shape, or wound around a central axis so as to obtain a pack having a cylindrical or conical shape. More recently, with the widespreading of techniques of computer- controlled cutting, filter elements have been developed having irregular shapes, which are chosen for following the irregular shape of the housing, which in turn must fit in the available space, for instance in the engine compartment of a land vehicle.

The accordion-like pack of paper is then usually provided with end gaskets which will contact in a tight manner the walls of the housing or of a cover thereof, so as to prevent part of the impure air from bypassing the filter element and exiting the filter without having been purified.

One of the problems that are encountered in the making of air filters for IC engines derives from the need to obtain a good purification of air on one part and to avoid an excessive pressure drop (ΔΡ) along the suction circuit.

For this reason, the properties of the filtering material are usually chosen depending on the environment in which the engine is to be used, for instance more or less dusty environment, and according to the characteristics of the engine and its requirements as to air purification quality and air volume to be sucked per unit of time.

A solution applied in the past provides that impure air is passed through a plurality of filter elements arranged in series and having increasingly higher filtering capacities. According to this technique the highly impure air is passed through a first gross filter having the purpose of removing bigger particles from the airflow and then through a finer filter having the purpose of removing smaller particles. This kind of configuration allows on one hand to obtain an exiting airflow that is highly purified and on the other hand to prevent the material of the finer filter from becoming rapidly clogged because of the bigger particles. On the basis of this principle filters have been developed that are provided with two or more filter elements having different filtering capacities and arranged in series as well as filters provided with a single filter element obtained by mutually superposing two layers of material with different filtering capacities.

EP 2 119 901 (Al) shows an example of the first kind of filter, i.e. the one provided with two independent filter elements arranged in series that are mounted separately into the filter and can therefore also be replaced separately, thus obtaining also an economic saving when it is desired to replace only one of the two filter elements.

CN202398236 (U) shows instead an example of the second kind of filter, i.e. the one provided with a multi-layered filtering material defining a single composite filter element .

This second kind of arrangement provides that the layers of filtering material have mutually different structures in order to ensure different filtering capacities. For this reason the layers are made of different materials deriving from different manufacturing processes and this brings about an increase in production costs. Moreover, where either of the layers is made of pleated paper, the second layer is made of a material with structural properties suitable for maintaining the shape of the paper layer, even when the opposite faces thereof are subjected to remarkable pressure differences during operation of the engine.

A first object of the invention is therefore to provide a solution to the problem of how to obtain a filter element that has the advantages of the multi-layered elements but is more cost-effective to manufacture than the current ones.

A second object of the invention is to provide a multi- layered filter element having improved performance and being therefore suitable for being used also in particularly dusty environments .

A third object of the invention is to provide a multi- layered filter element that, conveniently sized, can be used on a wide range of engines with very different engine cylinder capacities.

It is a further object of the invention to provide a method for the making of a multi-layered filter element that is suitable for large-scale industrial use for the making of filter elements intended for several applications.

Disclosure of the Invention

These and other objects are achieved with a filter element and with a method for making the same as claimed in the appended claims.

Advantageously, according to the invention, the filtering part of the whole filter element can be made entirely of paper, for instance of cellulose paper. This feature makes the filter element thus obtained particularly cost-effective thanks to the simplification of the process which uses machines conventionally employed for the making of filters from single-layer pleated paper and is based on the same kind of material and on the same technology for each layer .

According to a main aspect of the invention, a first layer of the filter element, i.e. the one intended to be first to be passed through by the impure air entering the filter when the filter is in use in the suction circuit of the engine, is advantageously made of a pleated paper which is very permeable, i.e. which filters bigger dust particles. The last layer of the filter element intended to be the last to be passed through by the air is instead made of a less permeable pleated paper, which filters smaller particles, and the intermediate layers have a filtering capacity that becomes increasingly finer from the first layer to the last layer .

Moreover, advantageously, still according to the invention, the filter element attains a high accumulation of dust with the same quantity of paper and a reduced pressure drop .

According to the invention, whatever the geometric shape of the filter element may be, the layers of filtering material making up the filter element are undetachably held together in the filter material, except when the filter element itself becomes destroyed, by sealing gaskets of plastic material in which the paper of the layers is partially incorporated. These gaskets perform both the function of preventing air that enters the grooves of the layers from exiting laterally parallel to the ridges and grooves and the function of obtaining a tight seal between the filter element and the walls of the housing receiving the filter element.

Said gaskets will therefore be advantageously arranged on the faces of the filter element body that are perpendicular to the bending lines of the paper. Thus, for instance in the case of filter elements obtained from solids of revolution, the gaskets will be arranged on the opposite circular bases, whereas in the case of filter elements with prismatic shapes the gaskets will be arranged on the opposite flanks perpendicular to the bending lines of the paper.

Brief Description of the Drawings

Some preferred embodiments of the invention will be given by way of non-limiting examples with reference to the annexed figures, wherein:

Fig.l is a perspective view of a filter element according to the invention in a cylindrical configuration;

Fig.2 is a perspective view in partial section of a part of the element of Fig.l; Fig.3 is a plan view of a layer of the filter element during a manufacturing step;

Fig.4 is a perspective view in partial section of a filter element according to the invention in a prismatic configuration;

Fig.5A is a perspective view in partial section of a filter element according to Fig.4 deprived of one of the layers in order to make visible the support element;

Fig.5B is an enlarged view of a detail of Fig.5A.

Description of a Preferred Embodiment

With reference to Figs.l and 2 there is illustrated an embodiment of the invention in which the filter element, indicated as a whole with reference numeral 11, has a cylindrical shape.

The filter element 11 is obtained by combining two layers 13,15 of filtering material made of paper pleated in an accordion-like way. The pleats of the paper of each layer 13,15 are made along parallel bending lines so as to define, along said bending lines, a series of ridges 13a, 15a alternated with grooves 13b, 15b. The pleating of the paper can be effected for instance by means of a knife pleating machine, which is of a known type and therefore is not further described here, and which acts onto a flat filter paper sheet typically unwound from a roll.

According to the invention and as it will become clearer from the following description, the two layers 13,15 of filtering material are undetachably held together in the filter element 11, except when the filter element itself becomes destroyed, by sealing gaskets of plastic material in which the paper of the layers 13,15 is partially incorporated .

Still according to the invention, adjacent layers 13,15 of filtering material are arranged close to each other and are oriented so that the ridges 13a, 15a of the paper of one layer are parallel to those of the other layer. According to the invention, this very same arrangement is maintained also in the case where the filter element comprises more than two layers and therefore all the layers of the element 11 will have mutually parallel ridges and grooves. In the case of an element 11 made as a solid of revolution, for example with a cylindrical of frusto-conical shape, the ridges and grooves will further be arranged parallel to the longitudinal axis of the cylinder.

Still according to the invention, spacers 17 arranged on the ridges 13a, 15a of the paper and perpendicularly thereto are advantageously provided between adjacent layers 13,15. These spacers 17 have the purpose of preventing the ridges 13a, 15a of a layer 13,15 from penetrating into the grooves 13b, 15b of the adjacent layer 13,15 and vice versa and so reducing the performances of the filter element.

These spacers 17 are visible with reference to Fig.3 showing a manufacturing step of the method for obtaining one of the layers 13,15. According to the invention, the spacers 17 are preferably constituted by corresponding strings of hardened thermofusible material, for instance a thermofusible glue. The material of the spacers 17 is deposited on the ridges 13a, 15a of the face of at least one of the layers 13,15 facing the adjacent layer when the layers 13,15 are arranged close to each other, face to face, in order to define the filter element 11. Thermofusible glues suitable for making the spacers 17 are for example polyurethane glues. Still according to the invention, these strings 17 are arranged on the ridges 13a, 15a of the layers 13,15, perpendicularly to the direction of the bending lines and, consequently, perpendicularly to the ridges 13a, 15a and to the grooves 13b, 15b.

According to a preferred embodiment of the invention, the strings 17 extend along said face of at least one of the adjacent layers 13,15, over the whole length thereof, without discontinuity so as to define a continuous rib that forms a corresponding spacer which, extending continuously among all the ridges, prevents the ridges of the adjacent layer from penetrating into the grooves of the first layer.

According to a preferred embodiment of the invention, the strings 17 of thermofusible material are laid down in their melted state at the exit of the pleating machine that forms the pleats in the paper and are hardened before the paper can stretch flat again thus annulling the effect of the pleating machine. In this way, the strings 17 perform both the function of preventing the ridges of a layer from penetrating into those of the adjacent layer when two layers are arranged close to each other for making the filter element and the function of maintaining optimal the width of the grooves 13b, 15b defined between said ridges.

The height of the spacers 17, i.e. their extension in a direction perpendicular to the plane of the face of the filter element to which the spacers are attached, will be chosen depending on the applications, but it can be approximately comprised between about 1 mm and 10 mm and will preferably be about 2-3 mm.

Owing to the presence of the spacers 17, between the adjacent layers 13,15 there is further defined a gap 19 having a width essentially equal to the height of the spacers 17. Dust particles that have passed through a first grosser layer but not through the adjacent second finer layer, will therefore accumulate in the gap 19, thus reducing the risk of clogging of the filtering layer arranged downstream the gap.

Referring again to Figs.l and 2, the filter element 11 is provided with an inner support element 21, for instance made of plastics or of metal, in the form of a grid with very large meshes, essentially having the sole function of preventing radial squeezing of the cylindrical filter element .

The cylindrical filter element 11 is further provided with a first gasket 23 closing a first base of the filter element 11 (lower base in the arrangement of Figs.l and 2) and with a second gasket 25 having a central opening 27 and closing the opposite base (upper base in the arrangement of Figs.l and 2) . Both gaskets 23, 25 can be made of plastic material, such as polyurethane foams, applied in their melted state and successively hardened. The gasket 23 and the gasket 25 partially incorporate the paper of the layers 13,15 in the plastic material of which they are made and prevent said layers forming the element 11 from being mutually separated, except when the filter element itself becomes destroyed. The axial opening 27 provided in the gasket 25 allows the passage of air, usually the exit of clean air, after this has radially crossed the layers 13,15 and has reached the center of the filter element, within the volume enclosed by the innermost filtering layer.

The invention has been described so far with reference to an embodiment comprising two layers of filtering material. However, the invention may advantageously be applied for the making of filter elements with three or more layers of filtering material of pleated paper. According to the invention, in the case where the element 11 is made by two or more layers, the paper of the layer that is intended to be the first to be passed through by the air when the element 11 is installed in the suction circuit of an engine, will preferably have a gross filtering capacity and the layer that is intended to be the last to be passed through by the air has a fine filtering capacity, whereas the intermediate layers will have a filtering capacity that becomes increasingly finer from the first layer to the last layer. Furthermore, other geometric shapes of the filter element are possible, such as for instance a parallelepipedal flat shape, a conical shape, or irregular geometric shapes.

Referring now to Fig.4, there is illustrated an embodiment of the filter element according to the invention having the prismatic shape of a parallelepiped. The filter element has been indicated as a whole with reference numeral 411 and comprises two layers 413,415 of filtering material made of paper pleated in an accordion-like way. The pleats of the paper of each layer 413,415 are made along parallel bending lines, so as to define, along said bending lines, a series of ridges 413a, 415a alternated with grooves 413b, 415b.

Similarly to the cylindrical configuration previously described, according to the invention, the two layers 413,415 of filtering material are undetachably held together in the filter element 411, except when the filter element 411 itself becomes destroyed, by a sealing gasket 423 of plastic material in which the paper of the layers 413,415 is partially incorporated.

Adjacent layers 413,415 of filtering material are arranged close to each other and are oriented so that the ridges 413a, 415a of the paper of a layer are parallel to those of the other layer.

Between adjacent layers 413,415 there are provided spacers 417 arranged on the ridges 413a, 415a of the paper and perpendicular thereto. These spacers 417 have the purpose of preventing the ridges 413a, 415a of a layer 413,415 from penetrating into the grooves 413b, 415b of the adjacent layer 413,415 and vice versa and so reducing the performances of the filter element. The sealing gasket 423 surrounds the prismatic pack defining the filter element and seals the gap 519 formed between the two layers 413,415. The gasket 423 is preferably made of polyurethane foam. Referring to Figs.5A and 5B, there can be seen a filter element 511 having a prismatic shape and provided with a stiffening element 521. In the embodiment shown the element 521 consists of a net with rhomboidal meshes. The net can advantageously be made of metal or plastics. The element 521 is located between two ad acent layers 513,515 and advantageously stiffens the structure of the filter element 511. In other embodiments it is possible to provide said element 521 adjacent to one of the opposite faces of the filter element 11, similarly to the example shown in Fig.2.

Still with reference to Figs.5A and 5B, there can be seen the sealing gasket 523, preferably made of polyurethane foam. The gasket 523 surrounds the pack of paper comprising the two layers 513,515 and laterally seals the gap 519 provided between the two layers 513,515. As better visible in Fig.5B, the spacers 517 are preferably provided on both adjacent layers 513,515, whereby the element 521 is arranged in a sandwich-like manner between said spacers 517.

The filter element and the method for making the same as described and illustrated are capable of several variations and modifications falling within the same inventive principle .

Claims

1. Multi-layered filter element ( 11 ; 411 ; 511 ) comprising at least two layers ( 13, 15; 413, 415; 513, 515) of filtering material made of paper pleated in an accordion-like way along parallel bending lines, so as to define, along said bending lines, a series of ridges ( 13a, 15a; 413a, 415a; 513a, 515a) alternated with grooves ( 13b, 15b; 413b, 415b; 513b, 515b) , the at least two layers ( 13, 15; 413, 415; 513, 515) of filtering material being undetachably held together in the filter element by sealing gaskets (23, 25; 423; 523) made of plastic material in which the paper of the layers

( 13, 15; 413, 415; 513, 515) is partially incorporated, adjacent layers ( 13, 15; 413, 415; 513, 515) of filtering material being arranged close to each other and the ridges (13a, 15a) of the paper of different layers being mutually parallel, wherein between adjacent layers ( 13, 15; 413, 415; 513, 515) there are provided spacers (17) arranged on the paper ridges

( 13a, 15a; 413a, 415a; 513a, 515a) perpendicularly thereto, said spacers preventing the ridges ( 13a, 15a; 413a, 415a; 513a, 515a) of a layer ( 13, 15; 413, 415; 513, 515) from penetrating into the grooves ( 13b, 15b; 413b, 415b; 513b, 515b) of the adjacent layer

( 13, 15; 413, 415; 513, 515) and vice versa.

2. Filter element according to claim 1, wherein said spacers (17; 417; 517) are constituted by corresponding strings made of hardened thermofusible material deposited on the ridges (13a, 15a) of at least one of the faces of the layers

( 13, 15; 413, 415; 513, 515) that are mutually facing when the layers ( 13, 15; 413, 415; 513, 515) are arranged close to each other, face to face, in order to define the filter element

(11;411;511) .

3. Filter element according to claim 2, wherein said hardened thermofusible material is a glue, for instance a polyurethane glue.

4. Filter element according to claim 2 or 3, wherein the strings (17; 417; 517) extend along the face of at least one of the adjacent layers ( 13, 15; 413, 415; 513, 515) over the whole length thereof without discontinuity so as to define a continuous rib that forms a corresponding spacer which, extending continuously among all the ridges ( 13a, 15a; 413a, 415a; 513a, 515a) of a first layer, prevents the ridges of the adjacent layer from penetrating into the grooves ( 13b, 15b; 413b, 415b; 513b, 515b) of said first layer.

5. Filter element according to any of the preceding claims, wherein the height of the spacers (17; 417; 517) in a direction perpendicular to the plane of the face of the filter element (13, 15; 413, 415; 513, 515) to which the spacers (17;417;517) are attached is comprised between about 1 mm and 10 mm.

6. Filter element according to claim 5, wherein said height of the spacers is comprised between about 2 mm and 3 mm.

7. Filter element according to any of the preceding claims, wherein between the adjacent layers ( 13, 15; 413, 415; 513, 515) there is defined a gap (19; 419; 519) having a width essentially equal to the height of the spacers (17; 417; 517) .

8. Filter element according to any of the preceding claims, wherein the paper of the layer that is intended to be the first to be passed through by the air has a gross filtering capacity and the layer that is intended to be the last to be passed through by the air has a fine filtering capacity, the possible intermediate layers having a filtering capacity that becomes increasingly finer from the first layer to the last layer .

9. Method for the making of a multi-layered filter element according to any of the claims 1 to 8, wherein the spacers (17; 417; 517) are laid down onto the ridges at the exit of the pleating machine that forms the pleats in a paper sheet unwound from a roll.

10. Method according to claim 9, wherein said spacers (17; 417; 517) comprise strings of thermofusible material that are laid down in their melted state at the exit of the pleating machine that forms the pleats in the paper and are hardened before the paper can stretch flat again thus annulling the effect of the pleating machine.