CORRESPONDING AIR FILTER"

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102018000009291 filed on 9/10/2018, the entire disclosure of which is incorporated herein by reference

FIELD OF THE INVENTION

The present invention relates to a vehicle provided, at the intake, with an air filter and to a corresponding air filter .

The present invention can advantageously be applied to an aircraft (i.e., a man-made machine that is able to fly by gaining support from the air to transport persons or objects within the Earth's atmosphere) and in particular to a helicopter, to which the following disclosure explicitly refers without any loss of generality.

PRIOR ART

Modern helicopters are usually provided with at least one turbine engine that drives a rotor blade system which allows said helicopter to take off and land vertically, to hover and to fly laterally, backwards and forwards. The turbine engine has an air intake at the front, through which the turbine engine takes in the external air needed for it to operate (i.e., the external air containing the oxygen needed for combustion) .

Generally speaking, the air intake may comprise a metal grid with a relatively large mesh size (in the region of one or two centimeters) the purpose of which is to prevent birds from getting in. Between the air intake and the turbine engine there may be an air filter with the function of filtering the air that is taken in, so as to hold back small impurities (dust and the like) which could, in the long term, lead to premature wear of the turbine engine.

Generally, the air filter comprises a peripheral frame 10 (made of aluminum, of plastic material or of a composite material) that supports a panel 11 of pleated filtering material (i.e. wave-shaped, that is folded on itself to form a succession of waves) . Furthermore, the air filter comprises a thin pleated outer reinforcement net and a thin pleated inner reinforcement net which rest against opposite surfaces of the filtering material panel (i.e., enclosing the filtering material panel between them) to give said filtering material panel a stable shape and strength.

The filtering material can be made up of an overlapped series (normally up to six) of layers of gauze (that is of a wide-mesh fabric) oiled (or oil soaked) ; this solution allows to obtain limited load losses but on the contrary implies a relatively high overall weight. In order to reduce the overall weight (a pressing requirement in aeronautical applications), it has been proposed to replace the layers of oiled gauze with several layers of non-woven fabric; this solution allows to reduce the total weight (above all thanks to the absence of the oil) but on the other hand presents higher pressure drops.

Patent application US2004083697A1 discloses an air filter provided with a wave-shaped filtering material panel made up of a plurality of filtering layers which are superimposed on each other and are enclosed in a sandwich between an external reinforcing net and an internal reinforcing net; some filtering layers can comprise meshes, mats or spun-bond polyester webs, which are prepared from drawn, randomly-laid, and thermally-, or ultrasonically- bonded continuous polyester filaments.

Patent application US2002182062A1 discloses an air filter for a helicopter provided with a wave-shaped filtering material panel made up of a plurality of filtering layers which are superimposed on each other and are enclosed in a sandwich between an external reinforcing net and an internal reinforcing net; preferably, the filter material which constitutes the filtering layers includes cotton or polyester or a felt.

Patent application US2008196369A1 discloses an air filter for a helicopter provided with a wave-shaped filtering material panel made up of a plurality of filtering layers which are superimposed on each other and are enclosed in a sandwich between an external reinforcing net and an internal reinforcing net; in particular, the panel of filtering material is composed of a fabric (for example of cotton or synthetic material or even of other material with fire- retardant characteristics), which is soaked in oil and is folded on itself to form for example four layers overlapping each other.

DESCRIPTION OF THE INVENTION

The purpose of the present invention is to propose a vehicle provided, at the intake, with an air filter and a corresponding air filter, said vehicle and air filter overcoming the drawbacks described above and, at the same time, being easy and inexpensive to produce.

According to the present invention there is provided a vehicle equipped, at the intake, with an air filter and a corresponding air filter, as claimed in the attached claims.

The claims disclose embodiments of the present invention forming an integral part of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting embodiment thereof, in which:

• Figure 1 is a perspective schematic view of a helicopter built according to the present invention;

• Figure 2 is a schematic cross-sectional view of an air box provided with an air filter and through which the air needed to operate a turbine engine of the helicopter shown in Figure 1 is taken in;

• Figure 3 is a plan view of the air filter shown in

Figure 2;

• Figure 4 is a cross-sectional view along the line IV- IV of the air filter shown in Figure 2;

• Figure 5 is an exploded cross-sectional view along the line IV- IV of the air filter shown in Figure 2; and

• Figure 6 is an enlarged scale view of a detail of

Figures 4 and 5.

PREFERRED EMBODIMENTS OF THE INVENTION

In Figure 1 denoted as a whole by reference numeral 1 is a helicopter comprising a turbine engine 2 that drives a rotor blade system which enables said helicopter to take off and land vertically, to hover and to fly laterally, backwards and forwards .

The turbine engine 2 comprises a tubular housing 3 having, at the front, an air intake 4 (through which the turbine engine 2 takes in the external air needed for it to operate, i.e., the external air containing the oxygen needed for combustion) and, at the back, an air outlet 5 (through which the turbine engine 2 expels the exhaust gas produced by the combustion process) . In the area of the air intake 4 there is a metal grid 6 with a relatively large mesh size (in the region of one or two centimeters) the function of which is to prevent birds from getting in.

As illustrated in Figure 2, in the tubular housing 3 there is an air box 7 which has, on the inside, a cavity with an inlet opening coupled to the air intake 4 of the tubular housing 3 and an outlet opening coupled to an intake system 8 of the turbine engine 2 (fresh air is conveyed through the intake system 8 towards the moving parts of the turbine engine 2 in which fuel combustion takes place using the air taken in as the comburent air i.e., towards the combustion chamber of the turbine engine 2) . Inside the cavity of the air box 7 there is an air filter 9 which is interposed between the inlet opening and the outlet opening and thus divides the cavity into an intake chamber, which is arranged upstream of the air filter 9 and communicates with the external environment, and an outlet chamber, which is arranged downstream of the air filter 9 and communicates with the intake system of the turbine engine 2. The air filter 9 is arranged downstream of the air intake 4 and has the function of filtering the intake air in order to withhold small impurities (dust and the like) which could, in the long term, lead to premature wear of the turbine engine 2.

The air filter 9 comprises a peripheral frame 10 (made of aluminum, of plastic material or of a composite material) that supports a panel 11 of filtering material. It is important to observe that the shape of the air filter 9 as seen in a plan view may vary (for example round, rectangular, elliptical, triangular, trapezoidal or a combination of these) depending on the shape of the tubular housing 2, i.e., depending on the shape of the air box 7 in which the air filter 9 is housed.

According to that illustrated in Figures 3-6, the air filter 9 comprises the peripheral frame 10 which supports the panel 11 of wave-shaped filtering material (i.e., with a wave-shaped configuration to increase the useful surface of filtering material without increasing the external dimensions) .

According to that illustrated in Figure 6, the air filter 9 comprises a thin pleated outer reinforcement net 12 and a thin pleated inner reinforcement net 13 which rest against opposite surfaces of the filtering material panel 11 (i.e., enclosing the filtering material panel 11 between them) to give said filtering material panel 11 a stable shape and strength. In other words, the filtering material panel 11 is covered on both sides by the reinforcement nets 12 and 13 (i.e., it is contained between the reinforcement nets 12 and 13) which give said filtering material panel 11 a stable shape. It is important to observe that the reinforcement nets 12 and 13 are dimensioned both to give the panel 11 the required shape stability in order to withstand the air pressure without becoming deformed, even when the helicopter 1 travels at high speed with a strong headwind, and so that it does not constitute too big an obstacle to the air flow (i.e., so as not to produce an excessive loss of load in the intake air flowing through the air filter 9) .

The outer reinforcement net 12 rests against an outer surface of the filtering material panel 11 through which the intake air enters to pass through said filtering material panel 11; the inner reinforcement net 13, instead, rests against an inner surface of the filtering material panel 11 which is opposite the outer surface. In other words, the outer reinforcement net 12 is arranged upstream of the filtering material panel 11 with respect to the intake air flow, whereas the inner reinforcement net 13 is arranged downstream of the filtering material panel 11 with respect to the intake air flow.

The filtering material panel 11 consists of a single layer (i.e. only one layer) of a fabric which is made up of a plurality of warp wires 14 (i.e. which make up the warp) and a plurality of weft wires 15 (i.e. which make up the weft) intertwined to form a plurality of meshes; in other words, the fabric constituting the filtering material panel

11 is a product with a flat, thin and flexible surface formed by a weaving of warp threads 14 and weft threads 15 perpendicular to each other (this interweaving determines the formation of a plurality of meshes) . The warp wires 14 extend in a linear direction, whereas the weft wires 15 are fed through the shed of the warp wires 14 by "winding" them around said warp wires 14. In other words, the weft wires 15 are interlaced with the warp wires 14 in such a way that the filtering material panel 11 is obtained by means of a weaving process (i.e., by interlacing the warp wires 14 with the weft wires 15) . The interweaving of the warp wires 14 with the weft wires 15 causes the formation of a plurality of meshes, which have a very small size and generally comprised between 15 and 75 microns (i.e. the sides of each mesh have a dimension comprised between 15 and 75 microns) ; preferably, the meshes of the polymeric fabric have a dimension comprised between 20 and 50 microns.

It is important to note that the micrometric mesh fabric that makes up the filtering material panel 11 is not soaked (wet) with any type of liquid (particularly oil) . In other words, the micrometric mesh polymer fabric that makes up the filtering material panel 11 blocks the largest particles present in the sucked air only by means of mechanical retention (i.e. it blocks the larger particles of the micrometric mesh by mechanical interference) without using any type of liquid that is absorbed by (wets) the micrometric mesh fabric.

The warp wires 14 and the weft wires 15 are made of a polymeric material; preferably the warp wires 14 and the weft wires 15 are made of PEEK (polyether ether ketone) which is completely hydrophobic, but other polymers such as polyethylene terephthalate or polyethylene terephthalate (PET) or polyamides (PA) may also be used. Preferably, the warp wires 14 and the weft wires 15 present: a specific weight comprised between 1.20 and 1.40 g/mm ³ , a textile resistance comprised between 33 and 75 daN/mm ² , a relative resistance in wet conditions comprised between 95% and 100%, a breaking elongation comprised between 20% and 40%, and a moisture absorption at 20°C and 65% relative humidity less than a 1%.

As mentioned previously, the filtering material panel 11 consists of a single layer of thick meshes (or micrometrically meshes) polymer fabric having a size between 15 and 75 microns (a micrometric mesh has a maximum mesh size of 100 microns); in other words, there are no more overlapped layers of fabric but there is a single layer of fabric, i.e. the warp wires 14 and the weft wires 15 constituting the single layer are not superposed other warp wires 14 and weft wires 15.

According to a possible embodiment shown in Figure 5, both reinforcement nets 12 and 13 are made of aluminum (lighter and less resistant material) and in this case it is generally also provided a steel (heavier and more resistant material) flat stiffening grid 16, which is internally disposed (i.e. it rests on the inner side of the filtering material panel 11) and has the function of helping the corrugated filtering material panel 11 to withstand pressure determined by the air in suction without deformations (the function of the reinforcing stiffening grid 16 is more important in the case of air filters having a high surface) . According to an alternative embodiment, only one of the reinforcing nets 12 and 13 is made of aluminum while the other of the reinforcing nets 12 and 13 is made of steel; in this embodiment the stiffening grid 16 is not present because its function is replaced by the reinforcing mesh 12 or 13 made of steel (i.e. the stiffening grid 16 is integrated / incorporated in one of the reinforcing nets 12 and 13) .

As shown in Figure 5, the peripheral frame 10 comprises a cup-shaped main body 17 having a perforated bottom wall (that is, centrally provided with a large through hole 18) and a flat cover 19 which is permanently connected to the main body 17 (for example glued or riveted) and is perforated (i.e. it is centrally provided with a large through hole 20) . The filtering material panel 11 is enclosed between the main body 17 and the cover 19, i.e. it is kept inside the main body 17 by the cover 19. To manufacture the air filter 9, the reinforcement nets

12 and 13 and the filtering material panel 11 are manufactured separately as flat pieces, then the reinforcement nets 12 and 13 are placed on opposite surfaces of the filtering material panel 11 to form a unit (i.e., a "sandwich") which is also flat and is then bent in a wave shape to give said unit its final shape; lastly, said wave shaped unit is coupled to the peripheral frame 10 (usually by means of glue and/or resin) which, in addition to giving the air filter 9 a stable shape, also has the function of holding together the unit formed by the reinforcement nets 12 and 13 and the filtering material panel 11.

In the embodiment illustrated in the accompanying Figures, the air filter 9 has a flat, practically rectangular shape (and as a consequence the filtering material panel 11 also has the same shape) , but the air filter 9 (and thus the filtering material panel 11) could clearly be of any other shape to adapt to the shape of the air intake; by way of example, the air filter 9 (and thus the filtering material panel 11) could have a flat circular or elliptical shape, a cylindrical shape, a cone shape, a truncated-cone shape, etc .

The embodiment illustrated by way of example in the accompanying Figures refers to a helicopter 1, but the present invention may also be advantageously used in any type of aircraft or other vehicle, including road or sea vehicles provided with an engine which must suck in air from the outside in order to operate.

The embodiments described herein can be combined without departing from the scope of protection of the present invention.

Numerous advantages are achieved with the helicopter 1 described above.

Firstly, the helicopter 1 described above comprises an air filter 9 which, at the same time, has a decidedly reduced overall weight (lower than the use of non-woven fabric) , and of low load losses (even better than the oil bath system) ; this result is obtained thanks to the fact that the filtering material panel 11; this result is obtained thanks to the fact that the panel filtering material panel llconsists of a single layer of a polymeric fabric (i.e. a web of warp threads 14 and weft threads 15) with micrometric meshes.

Also the integration of the stiffening grid 16 in the external reinforcement net 12 or in the internal reinforcement net 13 (i.e. the replacement of the stiffening grid 16 with one of the two reinforcement nets 12 and 13 made of steel) allows to further reduce the however the overall 9 air filter.

Moreover the polymeric fabric can be easily rendered hydrophobic (using for its realization hydrophobic polymers such as PEEK) also improving the use of the turbine engine 2 in case of rain or flight on the seas. Finally, the realization of the air filter 9 is relatively simple and of low cost since the polymeric fabric with micrometric meshes is commercially available.

LIST OF REFERENCE NUMBERS OF FIGURES

1 helicopter

2 turbine engine

3 tubular housing

4 air intake

5 air outlet

6 metal grid

7 air box

8 intake system

9 air filter

10 peripheral frame

11 filtering material panel

12 outer reinforcement net

13 inner reinforcement net

14 warp wires

15 weft wires

16 stiffening grid

17 main body

18 through hole

19 cover

20 through hole