WO2007096731A1

WO2007096731A1 - Composite greaseproof filter for kitchen hoods

Info

Publication number: WO2007096731A1
Application number: PCT/IB2007/000373
Authority: WO
Inventors: Alvaro Galassi; Gianfranco Pierantonietti
Original assignee: Faber S.P.A.
Priority date: 2006-02-22
Filing date: 2007-02-02
Publication date: 2007-08-30
Also published as: ITAN20060011A1

Abstract

This invention relates to a composite greaseproof filter (1) for extractor or filter hoods, comprising two arrays of intermediate baffles (2) and a microstretched filter (4) interposed between said arrays of intermediate baffles (2). Said baffles (T) are obtained from sections of profiles cut to measure, and can be equipped with spacers (2.3) to ensure correct positioning. Said composite greaseproof filter (1) is easily disassembled by the user for regular cleaning operations.

Description

COMPOSITE GREASEPROOF FILTER FOR KITCHEN HOODS.

DESCRIPTION

The present invention relates to a composite and modular greaseproof filter for kitchen hoods as well as a corresponding method for hood production and maintenance. Kitchen hoods, and in particular, those for household kitchens, positioned above cooking hobs for the elimination of smoke, smells and cooking vapours (hereafter referred to collectively as "cooking vapours") are commonly known and belong to two main categories: extractor hoods, that expel said cooking vapours to the exterior, and filter hoods, that recirculate said vapours into the kitchen environment after having cleaned them by means of so-called active carbon filters. Both types of filter are always equipped with a so-called greaseproof filter; this is positioned at the entry to the hood itself and is conceived to collect all greasy substances (mainly liquids) in suspension in the cooking vapours in aerosol form, to prevent their return into the room or their exit where they can soil external building walls, or their clogging the active carbon filter and, above all, the internal structural and functional parts of the hood itself. The presence of the greaseproof filter is necessary therefore, not only for hygienic reasons but also in order to prevent corrosion damage to operating hood parts caused over a period of time by chemicals, as well as to prevent fire hazard. Over recent years there has been a wide development in greaseproof hoods making them more efficient and long lasting. The simplest version is composed of a type of felted synthetic fibre held in position inside the support frame by two metal mesh grids. The main drawback is the fact that it is not washable, or rather, when it is washed it deteriorates rapidly, and therefore needs regular replacement, an operation that is a little unpleasant and which is often not performed regularly enough.

Certain progress has been made with the adoption of "microstretched" filters. These are composed of several overlaid layers of metal mesh made from very fine sheets, generally aluminium; it is commonly known that microstretched sheets are obtained from plain smooth sheeting incised with an infinite number of cut slits arranged in very closely packed lines, where each slit is staggered in relation to the position of the adjacent slit; when the sheet is micro-stretched, these slits open slightly to produce a type of grid with very tiny closely packed holes (commonly called "mesh"). When the cooking vapours pass through this filter composed of several mesh layers, the suspended greasy substances which are very sticky, are deposited directly on the sides of these holes. As well as being very efficient (collecting approximately 90% of suspended substances) this type of filter is durable since it is washable and is not corroded by greasy substances. This makes regular hood maintenance far easier to perform, hi addition, this type of filter has a relatively low resistance to air flow, at least, while it is clean. One drawback, however, is that the greasy substances that do not come into direct contact with the mesh are not retained very efficiently; moreover, little by little as the mesh becomes soiled, gradual clogging builds up preventing cooking vapour passage, and with the consequential reduction of aspiration power, and therefore, hood efficiency, hi the Italian patent application MI 99 U 000590, to be referred to for a more detailed description of prior state of the art, the patent describes the adoption of so-called "baffle" filters for household kitchen hoods, as being more durable and more easy to wash than mesh filters. In reality this does not strictly refer to filters as such since the routes imposed on the cooking vapours are relatively spacious, hi baffle filters cooking vapours are forced to follow a route that imposes sudden direction changes that the gaseous substances are able to follow, but each time they change direction the suspended liquid substances are projected by force of inertia against the walls along the route, where they are retained through adhesion. The result is that in baffle filters, the fine drops of greasy liquids in suspension are also eliminated by that part of the vapour flow that does not coine into direct contact with the walls along the route; this provides efficient vapour cleaning even though the passage is much wider than the holes in the microstretched filters. Load losses are generally higher than with microstretched filters but obviously much depends on the twists and turns in the air flow route and this does not increase when the filter is dirty. Vapour cleaning capacity with baffle filters is slightly less than of that obtainable with clean microstretched filters, but the same levels are maintained even when the baffles are dirty, and therefore, when comparing the same number of operating hours, baffle efficiency can be greater than that of microstretched filters and the regular washing frequency can be reduced considerably, and limited to hygiene requirements rather than those of efficiency.

However the most apparent behaviour difference between microstretched and baffle filters is that stated previously: a droplet in suspension tends not to deviate from its trajectory because of the force of inertia in proportion to its own mass, that is, its own volume V, while it does tend to be carried along by the flow or to adhere to the walls with which it is in contact through the viscous force in proportion to its own surface S; since, with the reduction of the diameter D of the droplets, the S/V ratio in proportion to the 1/D increases, it is well known that the effect of the viscous force will increase in relation to the force of inertia. Therefore the microstretched filters retain the smaller droplets more efficiently, while certain other droplets could escape due to force of inertia; the opposite effect occurs with the baffle filters where, due to viscosity, the smaller droplets tend to remain in suspension, carried along by the cooking vapour flow. Other differences, advantages and drawbacks of baffle filters in relation to microstretched filters will be illustrated during this treatise. The solution described in the aforesaid document MI 99 U 000590 is not free of drawbacks, above all, but not only, due to production costs. In particular, each baffle size requires specific pressing equipment, hi fact, it is obvious that although the device seems apparently simple because it is basically composed of three pieces, in reality it requires that all the baffles (shown as ribbing 24 and 25) be obtained from two shells 11 and 12 which are not only different for each size, but are also different from each other within the same model, since they must be closed for joint into one another. This report describes "composite" filters, in that they foresee the simultaneous presence of baffle and microstretched filters.

The document EP 0 856 347 shows a composite filter, where modular baffle elements also act as containers for a possible microstretched filter folded over to form a packet of several layers wherein the air is forced to cross through in a direction parallel to the layers in question. Said baffles can also possibly act as a seat for the insertion of active carbon filters. The device described has rather a complex construction and seems difficult for the normal user to disassemble and re-assemble for regular cleaning, and has a tendency to clog rapidly when the microstretched filter, where present, is soiled; Besides it seems that the baffle can not efficaciously operate in the spaces where the microstretched filter is placed; precisely, sudden changes in the air flow direction seem to be hindered by the presence of the microstretched filter.

The document WO 0 137 972 shows a modular filter exclusively of baffle type, having an air route with a large number of twists and bends that seems to provoke rather heavy load losses.

A less tortuous route, and therefore less likely to provoke strong resistance to air flow, is proposed in patent GB 1 409 195 relating to two layers of baffles set opposite each other and staggered so that the air flow is forced to make a double direction change; however doubts have arisen on the efficacy of this filter compared to microstretched filters because the distance between the baffles opposite one another is quite large and does not provoke sufficiently sudden direction changes. As far as construction is concerned, because of the filter design, the baffles need to be fixed one by one to the frame that retains them since there are no other means of support. In certain countries the use of greaseproof hoods is not common. As a result cooking vapours release a large part of the greasy liquids they contain inside the hood, including the ventilation fan scroll. The hoods and the internal components are designed so that these liquids, which run down the internal walls, are channelled into a small collector container from where they can be drained by opening a tap. In these countries, even if hoods were equipped with greaseproof filters, it would not be common for them to be washed regularly simply because out of habit, the large majority of users would not be aware it was necessary. The aforesaid document GB 1 409 195 and document US 4 944 782 illustrate baffle filters suitably sloped so that the grease collected by the baffles which also act as drain channels, is conducted towards a drainable pan, in this manner furnishing a solution for the needs of these countries. A composite filter such as that described in EP 0 856 347, equipped with microstretched filters, would have great difficulty in performing this function since the greasy liquids would be retained by the microstretched filter through capillarity and adhesion.

A first aim of the present invention is to create a composite greaseproof filter able to use to best advantage the particular qualities of microstretched filters as well as those of baffle filters, but separating the zones in which each type of filter operates.

Another aim of the present invention is to simplify the assembly of composite type greaseproof filter.

A further aim of the present invention is to provide a production method for composite type greaseproof filter substantially of any size without the need for specific equipment for each individual size.

Yet another aim of the present invention is to make the disassembly and re-assembly of composite type greaseproof filter easier for the user for cleaning purposes. Yet another further aim of the present invention, useful for certain types of hood, is to provide composite filters with a collector tub for the greasy liquids intercepted. These and other aims are achieved with a composite filter according to the invention, realised as described below and in the appended claims which compose an integrated part of the description, and also according to the examples in the appended drawings. Figure 1 shows a cross section according to plane A-A illustrated in figure 3, of a composite filter according to the invention. Figure 2 shows the same composite filter in perspective during the assembly stage. Figure 3 shows the same composite filter in perspective when completely assembled. Figure 4 shows a detail in perspective of one end of a general intermediate baffle composing part of composite filter. Figure 5 shows a detail in perspective of one end of a general terminal baffle composing part of composite filter. In reference to figure 1 in particular, the numeral 1 refers to a composite filter according to the invention; this comprises two layers of intermediate baffles 2 mounted with side walls 2.1 and a back surface 2.2; two terminal baffles 3 mounted with side walls 3.1, which can be identical to 2.1 on baffles 2, a first part of a section 3.2 and a second part of a section 3.3; a microstretched filter 4 interposed between said layers of intermediate baffles 2 ; a support frame 5.

The two terminal baffles 3 have a height H that is substantially equal to the total height H of the two intermediate baffles 2 plus the thickness of the microstretched filter 4. The frame 5, whose four sides are substantially profiled with a C channel, is provided with a stop side 5.1 and with an opposite closing side 5.2; Figures 2 and 3 illustrating this frame also show the other two sides that form lateral guides 5.3. The frame 5 encloses and supports the previous components since the internal cavity of its said C channel possesses the height H necessary to contain the two layers of intermediate baffles 2 and the edge of the microstretched filter 4 as well as the terminal baffles 3 with a minimum clearance that permits easy element insertion into the frame.

Again in reference to figure 1, the said baffles 2, having a width L, are arranged in an array with a suitable distance P between each other and the array positioned on top of the microstretched filter 4 is staggered by a suitable fraction S of said distance P in relation to the array set under the said microstretched filter 4; the entity of said suitable staggered distance will be provided in more detail later.

The terminal baffles 3 can be configured in a manner so that they maintain the same distance P and the same staggered distance S between their side walls 3.1 and the side walls 2.1, that exists between adjacent intermediate baffles 2 at least on one side of the microstretched filter 4, to ensure functional and appearance continuity between the intermediate baffles 2 and terminal baffles 3.

Said baffles 2 and 3 preferably have a flaring section; meaning that the corresponding side walls 2.1 and 3.1, are sloped at an established angle α greater than 90 ° (for example 120 °) compared to the back surface 2.2. Preferably, the materials used for the components described above will be those already commonly used for hood filters, in other words, suitable aluminium alloy or stainless steel for the microstretched filter 4 and stainless steel or aluminium for the frame 5 and for the baffles 2 and 3. Again, in Figure 1, F indicates the cooking vapour flow that crosses the composite filter 1 taken in by the fan in the hood. The aforesaid width L of the baffles 2 is greater than the distance between each intermediate baffle or terminal baffles 2 and 3; the aforesaid suitably staggered distance S is conceived to force the flow F deflected from a baffle 2 on top of the microstretched filter 4 to enter a baffle 2 set under the same microstretched filter 4.

Therefore thanks to the specific conformation of the composite filter, it can be seen how the flow F is forced to cross the microstretched filter 4 three times thus being subject to two sudden direction changes (of almost 180°), meeting the walls of the intermediate baffles or terminal baffles 2 and 3. In this manner, in composite filter 1 according to the invention, the droplets in suspension are separated from the cooking vapours because of adhesion to the microstretched filter 4 and also because they are projected against the walls of baffles 2 and 3 through the force of inertia that is generated. Consequently, according to the invention, this provides the typical and specific advantages described previously, in relation to both microstretched filters and baffle filters. It should be noted that the fact that the two layers of intermediate baffles 2 above and below the microstretched filter 4 are set very close to one another, separated only by a distance of a few millimetres from said microstretched filter 4, guarantees said sudden direction changes which are impossible to achieve in patent GB 1 409 195 which also catered for two sets of baffles conformed and staggered in a similar manner.

Furthermore said interposed microstretched filter 4 forms a means of support that helps to maintain baffles 2 and 3 in the established position inside the lateral guides 5.3. A general version of a composite filter 1 is shown in fig. 3. This can be obtained by means of the simple assembly illustrated in fig. 2. Above all, the figure shows how said intermediate baffles 2 and terminal baffles 3 are individual components and that can therefore be obtained through taking profile sections of any length and cutting them to the required length for each composite filter 1 model for example, then possibly completed at the ends as will be explained further on. The assembly process illustrated as an example involves the following steps: - Preparation of a part of the frame 5, substantially composed of a C channel comprising one stop side 5.1 and the lateral guides 5.3;

- The insertion into the guides of a first terminal baffle 3 and all the intermediate baffles necessary for the lower part of the composite filter 1 in this order and arranged according to the distance P;

- The insertion of the microstretched filter 4 on top of said baffles;

- The insertion of all the intermediate baffles necessary for the upper part of the composite filter 1 on top of said microstretched filter 4 in order and arranged according to the distance P; - The insertion of the second terminal baffle 3;

- Completion of the frame 5 and assembly with the application of the closing side 5.2 of frame 5.

Positioning according to the distance P can be performed using many well-known methods; for example, by maintaining the components assembled step by step with the required spacing using a positioning template, and then fixing the lateral guides 5.3 to the ends of the intermediate and terminal baffles 2 and 3 in position by riveting or welding, and in a similar manner welding the closing side 5.2 to the lateral guides 5.3 and/or placing between the ends of the two terminal baffles 2 or 3 adjacent spacers composed of suitably conformed pieces of C channel. A preferred solution however, shown in figures 4 and 5, is to provide at the ends of said baffles 2 and 3, with cut and bent stop element wings 2.3, with the configuration shown in the aforesaid figures conceived to act as spacers between each of the same intermediate baffles 2 or terminal baffles 3. As well as simplifying the assembly process, this solution also provides good appearance results because said stop element wings 2.3 can remain completely hidden inside the C channel from which the lateral guides 5.3 are made. Then, if the closing side 5.2 is attached by insertion into the lateral guides 5.3, according to any well known method which does not require illustration, a composite filter according to the invention can be achieved that is perfectly easy to disassemble, and just as easy to re-assemble for better cleaning, even by the user. However, it should be noted that a water spray can easily reach any area inside the intermediate 2 and terminal baffles 3, passing through the microstretched filter 4, without the need for disassembly.

The composite filter 1 is fixed in its seat inside the hood using any well-known method currently in practice such as block pins and small spring chains, and even preferably, said composite filter 1 has the same measurements and the same coupling means as those currently used on hoods in state of the art, so that they can be perfectly interchangeable. Lastly it should be noted how the microstretched filter 4 does not create an obstacle for the flowing of the greasy liquids collected inside the intermediate 2 and terminal baffles 3 so that, if the composite filter according to the invention is installed substantially as in common practice, for example, as described in the aforesaid GB 1 409 195, in other words with the intermediate baffles 2 and 3 set on a downward slant in the rear part of the hood, said greasy liquids can be collected at least as described in said GB 1 409 195. It is obvious that numerous variants can be applied to the aforesaid composite filter by those skilled in the art, while remaining within the context of the innovative concept of the invention, hi particular, it is possible to foresee a simplified version for applications where the use of baffles only is sufficient, wherein a plain perforated metal separation sheet is interposed between said baffle layers, to replace the microstretched filter 4 described above. It is also possible that said perforated metal separation sheet, or said microstretched filter 4 are not necessarily flat.

It is obvious that the aims described are achieved with a composite filter according to the invention. The aspects of the baffle filters are put to advantage as well as those of microstretched filters; the components can be obtained using cutting and bending equipment that are not limited by the size of the filter; assembly is very simple, as its disassembly by the user for maintenance purposes.

Claims

Claim 1 Composite greaseproof filter (1) for extractor or filter hoods, comprising

- two arrays of intermediate baffles (2) wherein each of said intermediate baffles (2) - has a substantially C channel profile,

- has an established width (L),

- is arranged in relation to the adjacent baffles at a determined distance

(P),

- comprises a back surface (2.2) and two side walls (2.1) wherein, in particular, said side walls (2.1) can form an angle greater than 90° with said back surface (2.2), and further comprising

- a perforated metal separation sheet (4),

- a support frame (5), said two arrays of intermediate baffles (2) being

- arranged in opposite positions,

- and staggered in relation to each other by a suitable staggered step (S) conceived to force the flow (F) of the cooking vapours deflected by a baffle (2) of the overlaid array to enter a baffle (2) of the array underneath, characterised in that

- said perforated metal sheet (4) is interposed between said arrays of intermediate baffles (2),

- said arrays of intermediate baffles (2) are separated only by the thickness of said perforated metal sheet (4).

Claim 2 Composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim, characterised in that said perforated metal sheet (4) is flat. Claim 3 Composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim, characterised in that said perforated metal separation sheet is a microstretched filter (4). Claim 4 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that said support frame (5) comprises two sides consisting of lateral guides (5.3) substantially formed by a C channel inside which the ends of said intermediate baffles (2) of the two said arrays are set, as well as the edge of said microstretched filter (4) interposed between said arrays.

Claim 5 Composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim, characterised in that the internal cavity of said lateral guides (5.3) of a substantially C channel has a height (H) necessary to contain the ends of said intermediate baffles (2) of the two said arrays as well as the edge of said microstretched filter (4) with just sufficient clearance to permit easy insertion of said intermediate baffles

(2) and of said microstretched filter (4).

Claim 6 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that said support frame (5) further comprises a stop element side (5.1) and an opposite closing side (5.2).

Claim 7 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that said intermediate baffles (2) are separated from the adjacent baffles by means of suitable spacers (2.3).

Claim 8 Composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim, characterised in that said suitable spacers (2.3) comprise stop element wings (2.3) obtained by cutting and bending the ends of said baffles (2).

Claim 9 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that each of said intermediate baffles (2) can be obtained by cutting a precise section of a profile of an unspecified length.

Claim 10 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that two terminal baffles (3) are also foreseen having lateral walls (3.1) which can also be identical to the walls (2.1) of said baffles (2).

Claim 11 Composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim, characterised in that said terminal baffles (3) have a height (H) substantially equal to the total height (H) of two of the said intermediate baffles (2) plus the thickness of said microstretched filter (4). Claim 12 Composite greaseproof filter (1) for extractor or filter hoods, according to at least claim 10, characterised in that said terminal baffles (3) are equipped with stop element wings (2.3) obtained by cutting and bending the ends of said baffles (3). Claim 13 Composite greaseproof filter (1) for extractor or filter hoods, according to at least claim 10, characterised in that said terminal baffles (3) can be obtained by cutting a precise section of profile of an unspecified length. Claim 14 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that the cooking vapour flow (F) is forced to perform two sudden inversions in direction. Claim 15 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that the cooking vapour flow (F) is forced to cross said microstretched filter (4) three times. Claim 16 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims from claim 6 onwards, characterised in that the closing side (5.2) of said frame (5) is fixed using means easily removable by the user. Claim 17 Composite greaseproof filter (1) for extractor or filter hoods, according to any of the previous claims, characterised in that if mounted in such a position that the intermediate baffles (2) are placed on a slant, the intercepted greasy liquids can be drained using commonly known means.

Claim 18 Assembly method for a composite greaseproof filter (1) for extractor or filter hoods, characterised in that it comprises the following stages

— the previous arrangement of a part of the frame (5), substantially composed of a C channel comprising a stop element side (5.1) and lateral guides (5.3),

- the insertion into said frame (5), in correct order and positioned at said distance (P), of a first terminal baffle (3), and all the necessary intermediate baffles (2) in the lower part of the composite filter (1), - the insertion, on top of said baffles (2, 3), of the microstretched filter (4), - the insertion on top of the microstretched filter (4), in correct order and positioned at said distance (P), of all the necessary intermediate baffles (2) in the upper part of the composite filter (1),

— the insertion of a second terminal baffle (3), - completion of the frame (5) and assembly by the application of the closing side (5.2) of the frame (5).

Claim 19 Assembly method of a composite greaseproof filter (1) for extractor or filter hoods, according to the previous claim characterised in that the spacing of said distance (P) between two consecutive intermediate baffles

(2) or terminal baffles (3) is ensured by placing said intermediate baffles (2) and terminal baffles (3) in position using suitable templates, and then fixing them permanently in position by riveting or welding the lateral guides (5.3) to the ends of the intermediate and terminal baffles (2, 3). Claim 20 Assembly method of a composite greaseproof filter (1) for extractor or filter hoods, according to Claim 17 characterised in that the spacing of said distance (P) between two consecutive intermediate baffles (2) or terminal baffles (3) is ensured by placing suitable spacers (2.3) as described according to claims 5 or 6.

Claim 21 Extractor or filter hood characterised in that it provides for a composite greaseproof filter (1) according to one or more of the previous claims.