Description

Grease filter and extractor hood comprising the grease filter

Technical field

The present invention relates to a grease filter and an extractor hood comprising the grease filter. The grease filters in the specific technical field trap and retain particles of liquid and/or solid grease suspended in fumes sucked in by the hoods. These particles are, for example, minute liquid and/or solid particles of oily, greasy substances, etc. An important function of the grease filter is to prevent particles from soiling and/or damaging extractor hood components fitted downstream of the filter.

Background art

Filters are known comprising one or more layers of fine-mesh netting. When the netting is struck by fumes they are permeable to the fumes, but not to the transported liquids or solids, which are therefore trapped and retained. The filters may be removed and washed in a dishwasher and then refitted in the extractor hood.

A problem with these filters is the high head losses and the high level of noise, which increase over time as the quantity of particles trapped by the filter increases. Another problem is linked to the fact that, due to the small dimensions of the mesh normally used, grease residue remains trapped even after washing in a dishwasher.

Labyrinth filters are also known in which the fluid stream to be filtered is guided along a labyrinth path with numerous changes in direction. The path is easily followed by the fumes, but not by the heavier particles which, due to their inertia, remain trapped along the labyrinth path and are separated from the air stream passing through the filter. These filters are periodically washed in a dishwasher to remove the particles deposited during use, and then refitted in the extractor hood.

These filters are not without problems, either. In particular, they are very costly. Also, the operation for removal

of the particles in a dishwasher is not always satisfactory as, due to the winding path, the deposits accumulated in some areas are not adequately removed.

Filters are also known in which the operation for trapping and separation of the particles from the fumes is performed directly by the hood extractor fan. In that case, the extractor is normally a traditional centrifugal electric fan with a squirrel cage rotor fitted in a scroll which acts as the stator element. The particles are drawn by the fluid stream sucked by the rotor inside the fan. The particles striking the rotor acquire a considerable centrifugal force and are projected in a radial manner against the scroll. The grease particles are sticky and tend to remain stuck to the walls of the scroll, thereby separating from the fluid stream which is evacuated through the delivery side.

After separating from the fluid stream, the majority of these particles tend to concentrate, by the effect of gravity, in a particular zone of the scroll, which is usually the lowest part. This area of the scroll is connected, by a duct, to a removable storage vessel outside the scroll in a position which is easily accessible to the user for the periodic removal of the grease accumulated therein.

This solution is not without problems, either.

The main problem is that the oily, greasy and dirty particles are separated from the fluid stream only inside the rotor scroll.

Consequently, the electric motor on which the rotor is fitted must be a completely insulated electric motor to avoid undesired infiltrations which could adversely affect the operation. The use of these motors is also required by the regulations. But these motors are more expensive than standard electric motors.

This solution also presents cleaning problems since, for obvious reasons, it is not possible to place the centrifugal fan with the relative electric motor in a dishwasher. Over time, increasingly large quantities of residue accumulate on the walls of the scroll, with adverse affects on health and hygiene (which

is a fundamental aspect, considering that these extractor hoods are normally fitted in kitchens above hobs) .

Disclosure of the invention The aim of this invention is to overcome the above-mentioned shortcomings by making available a grease filter and a hood comprising the grease filter that permits high levels of hygiene and cleanliness.

Another aim of this invention is to make available a grease filter and a hood comprising the filter which reduces the frequency of the filter cleaning operations.

A further aim of this invention is to make available a grease filter and a hood comprising the filter and thereby reduce costs . Yet another aim of this invention is to make available a grease filter and a hood comprising the filter which permits very quiet operation.

These and other aims, which are described in detail below, are achieved, with this invention, by a grease filter and a hood comprising the grease filter having structural and operational characteristics as described in the accompanying independent claims; other preferred embodiments of the grease filter and a hood being identified in the accompanying and corresponding dependent claims.

Description of the drawings

The invention is clearly described below, with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which:

- Figure 1 is a perspective view of a first preferred embodiment of a filter according to the invention.

- Figure 2 is a cross-section of the first preferred embodiment of the filter according to the invention. - Figure 3 is a cross-section according to section A-A shown in Figure 2 of the first preferred embodiment of the filter according to the invention.

- Figure 4 is the interrupted perspective view of a detail of a component shown in Figure 3.

- Figure 5 is a detail of Figure 4.

- Figure 6 is a partially exploded perspective view of the first preferred embodiment of the filter according to the invention.

- Figure 7 is a cross-section of a particular installation of the first preferred embodiment of the filter according to the invention. - Figure 8 is a partially interrupted perspective view (and with some parts removed to better highlight other parts) of the installation in Figure 7.

- Figure 9 is a cross-section of a second preferred embodiment of the filter according to the invention. - Figure 10 is a partially interrupted perspective view (and with some parts removed to better highlight other parts) of the second preferred embodiment of the filter according to the invention.

Detailed description of the preferred embodiments of the invention In the accompanying drawings, the numeral 1 denotes a grease filter to collect liquid and/or solid grease particles suspended in a fluid stream.

The filter 1 is applicable for kitchen hoods, in particular for hoods for domestic kitchens. The grease filter 1 in general enables the grease component of cooking vapours to be trapped. The grease particles include, for example, solid or liquid particles of oily, greasy and dirty substances.

The filter 1 includes: - a rotor 2 which: traps the particles. It is immersed in the fluid stream and is free to rotate around its axis of rotation 20; a casing 3 in which the rotor 2 is at least partially fitted and comprising at least one inlet 31 for the fluid stream to be filtered and at least one outlet 32 for the filtered fluid stream. In particular, the casing 30 comprises only one inlet 31 and only one outlet 32.

The casing 3 comprises a device 33 for collecting particles trapped by the rotor 2 and projected by the centrifugal force induced by rotation of the rotor 2. The particles trapped by the rotor 2 are projected at least with radial component of motion 203 with respect to the axis of rotation 20. In Figure 2, the casing 3 comprises various parts assembled together. Characteristically, the rotor 2 is rotated by the passage of the fluid stream inside the casing 3. The fluid stream is generated by devices outside the filter 1 such as, for example, an exhaust fan 6 fitted downstream of the filter 1.

The rotor 2 comprises blades 4 which, when struck by the fluid stream, rotate around axis of rotation 20 rotating the remaining parts of the rotor 2. In particular, the rotor 2 is not connected to a motor, but it is moved exclusively by the fluid dynamic force of the fluid stream on the blades 4. During use, the rotor 2 has a relative motion with respect to the casing 3, which remains still with respect to a fixed reference point in space. Each blade 4 runs at least in part along a transversal plane, but not at right angles to the axis of rotation 20.

The blades 4 preferably form a solid body with the remaining parts of the rotor 2.

As shown in Figure 3 merely by way of example without restricting the scope of the inventive concept, the rotor 2 comprises a disc 23. Advantageously, the blades 4 are distributed, preferably in a uniform manner, along the perimeter portion 230 of the disc 23. The axis of rotation 20 of the rotor 2 passes through the centre of the disc 23. Advantageously, the disc 23 runs in an orthogonal direction to the axis of rotation 20.

Advantageously, the rotor 2 runs in a transversal direction to the ideal flow paths 21 which the stream would assume at the position in which the rotor 2 is fitted, if the latter were absent . The axis of rotation 20 of the rotor 2 is substantially parallel to the ideal flow paths 21 which the stream would assume at the position in which the rotor 2 is fitted, if the latter were

absent .

In the first preferred embodiment illustrated in Figures 1 to 8, the inlet 31 of the casing 3 is advantageously coaxial with the rotor 2. During use, the rotor 2 is free to rotate in idle mode around its axis of rotation 20.

The filter 1 comprises means 200 for fixing the rotor 2 which, during use, only enables rotation of the rotor 2 around its axis of rotation 20. The rotor 2 is fitted to its own rotation shaft 202 supported by at least one bearing 201 with friction bodies. At least one bearing 201 is supported by a part of the filter 1 fixed to the casing 3. Opportunely, the rotor 2 extends in cantilever fashion at least in part inside the casing 3. The filter 1 comprises an annular hollow space 8 which, with respect to the axis of rotation 20 of the rotor 2 is placed radially between the disc 23 and the casing 3. The fluid stream which has been filtered of grease particles passes in the hollow space 8. The blades 4 are normally manufactured from suitably shaped plates .

In a preferred embodiment the disc 23 of the rotor 2 is also manufactured from plates and the thickness is usually between 1 mm and 3 mm with a diameter of between 150 mm and 300 mm (greater thicknesses are associated with greater diameters) . The use of a plate with a limited thickness and the choice of materials with a low volumetric weight, such as, for example, aluminium or plastic, enable the inertia of the rotor 2 to be kept low.

This has many advantages: - a first advantage is linked to the fact that, if for any reason the user comes into contact with the rotor 2 whilst it is rotating, the rotor 2 could easily stop and, consequently, the risk of injuries to the user would be limited; - a second advantage is linked to the fact that the rotor 2 is also rotated by fluid streams with a low flow rate, which could correspond to particular operational

conditions of the hood 10;

- a third advantage is linked to the reduced time delay with which the rotor 2 stops after the fluid stream no longer passes through the casing 3. The rotor 2 comprises a first surface 24 which is struck on the front by the fluid stream to be filtered. The first surface 24 preferably runs at least in part in an orthogonal direction to the axis of rotation 20 of the rotor 2. The filter 1 may be installed with the axis of rotation 20 of the rotor 2 substantially parallel to the physical vertical line (see, for example, figures 1 to 3 , and 9 and 10) . The physical vertical line is the direction identified by the vector of gravitational acceleration at the position considered. Alternatively, the filter 1 may be installed so that the axis of rotation 20 of the rotor is inclined with respect to the physical vertical line by an angle of between 0° and 60°, preferably between 0° and 30° (see, for example, figures 7 and 8) . In both cases, the inlet 31 of casing 3 is at least in part facing downwards in order to better trap the vapours from the hob which is usually positioned beneath the filter 1. Advantageously, every straight line passing through the inlet 31 and parallel to the axis of rotation 20 of the rotor 2 is intercepted by the first surface 24. However, at least a part of the rotor 2 faces the inlet 31 of the casing 3. The part of the rotor 2 which faces the inlet 31 is impermeable to the fluid stream and the grease particles. In this case, the blades 4 are outside the projection on the rotor 2 of the inlet 31 of the casing 3, as this projection is carried parallel to the direction of the axis 20 of rotation of the rotor 2.

The collection device 33 comprises an annular portion 330 which, with respect to the axis of rotation 20 radially surrounds the first surface 24 and is suitable to stop the particles projected in accordance with at least one radial component of motion 203 by the rotation of the rotor 2. The radial component of motion 203 is evaluated with respect to the axis 20 of rotation 20. In order to highlight the presence of the rotor 2, the annular portion 330 is shown in Figure 6 moved away from the rotor 2 (along the direction of the axis of rotation 20) with respect to

the configuration taken during normal use.

The annular portion 330 is impermeable to the fluid stream and to the grease particles. The annular portion 330 is not therefore crossed by the fluid stream and the grease particles. The collection device 33 comprises an annular cavity 331. The particles projected by the rotor 2 flow into the annular cavity 331 by gravity.

In particular, at least part of the particles stopped by the annular portion 330 flow into the annular cavity 331 by gravity. If the annular portion 330 is very far from the rotor 2 and/or the speed of rotation of the rotor 2 is low, a high number of particles projected by the rotor 2 could fall directly into the annular cavity 331 without first being intercepted by the annular portion 330. The reference plane 30 is orthogonal to the axis of rotation 20 and passes through at a least one point of a first surface 24 and ideally separates the space inside the filter 1 into two zones, 34 and 35. A first zone 34 comprising the inlet 31 of the casing 3 and a second zone 35 comprising the outlet 32 of the casing 3. The reference plane 30 is illustrated in Figures 2, 7 and 9 with a dashed line, with dashes of uniform length. Advantageously, the annular cavity 331 is comprised in the first zone 34 of the filter 1.

The filter 1 is designed to eliminate or at least minimise the quantity of grease particles collected downstream of the rotor 2.

The annular cavity 331 surrounds the inlet 31 of the casing 3. In particular, the annular cavity 331 comprises a retaining edge 338 which obstructs the release of particles present in the annular cavity 331. The edge 338 surrounds the inlet 31 of the casing 3. The presence of edge 338 permits accumulation of grease particles without adversely affecting the operation of the filter 1 and it reduces the frequency of filter cleaning operations.

Advantageously, the filter 1 comprises a nozzle 339 for access of the fluid stream into the filter 1. The nozzle 339 comprises at least a section in which the cross-section of the passage for the fluid stream is progressively reduced. In this

way, the fluid stream is guided and both the head losses and noise are reduced. Advantageously, the edge 338 defines a nozzle 339.

The annular cavity 331 defines a closed channel 332. In the preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept shown in Figures 7 to 10 (the rotor 2 is not shown in Figures 8 and 10 in order to better highlight the parts behind) the channel 332 comprises: an upper section 333; - a lower section 334;

- two intermediate sloping sections 335 connecting upper section 333 and lower section 334.

The intermediate sections 335 enable collection of particles by gravity at the lower section 334. The two intermediate sections 335 run along two branches of the closed channel 332. The two branches together circumscribe the inlet 31 of the casing 3.

The filter 1 comprises an evacuation channel 336 connecting the collection device 33 to a removable storage vessel 337 outside the casing 3 to facilitate disposal of the collected particles. In particular, the evacuation channel 336 connects the lower section 334 of the channel 332 to the removable storage vessel 337 (embodiment shown schematically in Figures 9 and 10) .

A grille 5 is fitted at the inlet 31 of the casing 3 for accident protection. This prevents accidental contact between the user and the rotor 2. The mesh size of the grille 5 prevents entry of the user's fingers. In a preferred embodiment, the mesh size must not be too small in order to prevent a large quantity of grease particles from being retained on the grille 5. It should be noted that the grille 5 is usually placed vertically above the hob and if it retains too many grease particles there is the risk that the particles may drip down onto the hob, soiling it and spoiling the food on the hob. As explained more clearly below, filter 1 advantageously comprises removable means of attachment 7 to a support, for example, to a part of hood 10. The scope of this invention is also a hood 10 comprising:

- a suction fan 6 for extraction of fluid stream;

- a filter 1 according to this invention.

With respect to the flow of the fluid stream inside the hood 10, the suction fan 6 is placed downstream of the filter 1. In this way, the fluid stream inside the suction fan 6 is essentially- free of grease particles. The filter 1 is connected in a removable manner to the remaining parts of the hood 10. This may be achieved by removable means of attachment 7 such as, for example, screws and quick coupling devices for elastic deformation. The filter 1 may therefore be removed from the hood 10 for cleaning (advantageously carried out in a dishwasher) and subsequently refitted. Advantageously, the hood 10 comprises a flue 11, fitted downstream from the filter 1, which carries the fluid stream. The filter 1 is fixed to the flue 11 by removable means of attachment 7. Advantageously, the casing 3 has a cylindrical symmetry with respect to the axis of rotation 20 of the rotor 2 (see Figures 1 to 8) . The flue 11 runs along a predominantly longitudinal direction 110 which is normally oriented along the physical vertical line. The filter 1 is connected to the flue 11 so that the angle formed by the axis of rotation 20 of the rotor 2 and the predominantly longitudinal direction 110 of flue 11 is between 0° and 60°, preferably between 0° and 30°.

In general, during use, the fluid stream drawn by the suction fan 6 of the hood 10 enters inside the casing 3 fitted with the rotor 2 (Figure 2 indicates the planned paths of the fluid stream into the filter 1 with numeral 100) . Due to their inertia, the solid or liquid particles are not able to follow the path of the fluid stream and strike the rotor 2. The particles adhering to the rotor 2 are subjected to centrifugal force since the rotor 2 is rotated around its axis of rotation 20. The rotation of the rotor 2 is determined by the pulling action imparted by the blades 4 struck by the fluid stream.

The particles are projected with a radial component of motion 203 until they strike the annular portion 330 of the collection device 33. These particles adhere to casing 3, but at least a part of the particles are drawn by gravity, with a greater or lesser speed, towards the annular cavity 331 of the casing 3. Here the particles are trapped until the filter 1 is cleaned or

until the particles are carried to the removable storage vessel 337 which may be easily emptied by the user.

The grease filter 1 in this invention has important advantages . Firstly, it may be installed on hoods fitted with an extractor fan with a standard electric motor, as the motor does not come into contact with grease particles.

Secondly, it improves the safety as an electric motor is not installed in a potentially explosive atmosphere, as could be the case in an atmosphere rich in greasy and oily residues.

Another important advantage is the lower operating noise.

An equally important advantage is the ease of cleaning and the chance of reducing the frequency of cleaning operations.

It is understood that the invention described may be modified and adapted in several ways without thereby departing from the scope of the inventive concept.

Moreover, all the details of the inventions may be substituted by technically equivalent elements.

All the materials used, as well as the dimensions, may be changed to meet specific needs.