Patent Description:
As is well known, flue ducts are hollow containers that convey away the combustion fumes produced by a combustion chamber arranged upstream thereof.

Inevitably, combustion fumes carry combustion residues in the form of particulates, dust, soot, ash and the like which, in order to limit polluting emissions, must be filtered out of said fumes before they are emitted into the atmosphere.

Such particulate matter may be captured by means of the use of electrostatic filters comprising a charged high-voltage electrode that ionizes the air and consequently the fumes crossing the duct.

The particulate suspended in the fumes is in turn electrostatically charged, with a generally negative but also positive charge, and attracted towards the inner metallic walls of the duct which are grounded, thus attracting the electrostatic charges of the fumes by means of a potential difference. The inner walls of the flue therefore become surfaces for the deposition of particulate which may accumulate, also in large quantities, within a few hours of combustion chamber operation.

The accumulated particulate matter must obviously be removed, since the accumulation thereof may lead to numerous problems, such as for example:.

The phenomenon of "reentering" emits coarse particulate matter into the atmosphere which presents fewer problems for human health than ultrafine particulate matter. Notwithstanding this, reentering is a problem during product emission sampling tests. Emission tests are in fact performed using a gravimetric sample, which involves drawing in combustion fumes and passing them through a filter. Reentering therefore significantly increases the weight of the filter.

To solve those problems relating to the presence of the particulate deposited in the flue, known in the art are manifolds with an automatic cleaning system for the removal of the collected particulate.

Such known solutions include, for example, an auger with an integrated brush that removes, by abrasion, the particulate that accumulates along the inner walls of the flue.

The known solutions have some drawbacks and disadvantages.

In fact, these known solutions do not ensure complete cleaning of the inner surface of the flue and are also cumbersome. Furthermore, also the auger itself accumulates particulate upon the surface thereof that cannot be cleaned.

Furthermore, the cleaning, i.e. the removal of the particulate matter, is not thorough, since known brushes with metal bristles cannot remove all of the encrustation that accumulates on the walls, not even at those points that are reached by the same. This is also due to the fact that the geometry of the flue ducts is not particularly precise, and therefore known brushes cannot exert a constant mechanical action upon all portions of the inner surface of the flue duct.

Finally, the known solutions, during cleaning, are quite noisy: this aspect is by no means negligible and constitutes a considerable drawback since users do not appreciate the noises of the cleaning phase (especially for combustion plants that are installed within domestic environments). Known solutions according to the preamble of claim <NUM> are disclosed, for example, by <CIT>.

The need to solve the drawbacks and limitations mentioned with reference to the prior art is therefore felt.

This requirement is met by an electrostatic filter for a flue duct outlet from a combustion chamber, provided with a cleaning system, perfected in accordance with claim <NUM>.

Further features and advantages of this invention will become more apparent from the following detailed description of preferred, non-limiting embodiments thereof, wherein:.

Elements or parts of elements common to the embodiments described hereinafter will be indicated with the same numerical references.

With reference to the above figures, reference sign <NUM> has been used to indicate an overall view of an electrostatic filter for flue duct outlets from a combustion chamber. For the purpose of the present invention, the type of combustion chamber whereto the electrostatic filter <NUM> is applied is not relevant. In general, the present invention applies, in a broad sense, to any type of combustion chamber, including for example also wood-burning fireplaces, wood-burning ovens or in general biomass combustion equipment. The size or power of said combustion chambers does not matter either.

The electrostatic filter <NUM> comprises a hollow manifold <NUM> having an inner side wall <NUM> delimiting a volume <NUM> for the passage and conveying of fumes, from an inlet end <NUM> of the fumes to an outlet end <NUM> of the fumes.

Said inlet end <NUM> and outlet end <NUM> are offset with respect to a vertical rising direction Y-Y of the fumes. With the term offset it is meant that said inlet end <NUM> and outlet end <NUM> are at different heights with respect to the vertical direction Y-Y. In one specific embodiment, the inlet end <NUM> and outlet end <NUM> are coaxial with respect to the vertical direction Y-Y. The inner side wall <NUM> is lapped by said fumes.

In general, the definition of inner side wall <NUM> is to be understood in a broad sense: in other words, not only the wall that delimits the volume laterally, but also the opposing lower and upper faces which enclose said side wall. In other words, the term inner side wall <NUM> refers to any surface facing or inserted into said volume <NUM> and lapped by the fumes produced by the combustion chamber, introduced therein by means of the inlet end <NUM>.

The hollow manifold <NUM> may have any type of geometry; preferably, but not necessarily, the hollow manifold <NUM> is cylindrical and axially symmetrical with respect to an axis of vertical symmetry X-X, parallel to said vertical direction Y-Y.

Usually, but not necessarily, the inlet end <NUM> and the outlet end <NUM> are aligned with each other, with respect to said vertical direction Y-Y.

Said inlet end <NUM> and outlet end <NUM> may have any geometry, for example a circular or elliptical geometry, typically counter-shaped with respect to the geometry of the pipe or flue whereto they are fluidly connected.

The electrostatic filter <NUM> comprises at least one electrode <NUM>, housed at least partially in said volume <NUM> and/or in a side duct <NUM>, fluidly connected with said volume <NUM>, and configured so as to ionize the fumes crossing said volume <NUM> so as to adhere the particulate transported by the fumes to said inner side wall <NUM>. The at least one electrode <NUM> is therefore essential in order to allow the particulate to cling onto the inner side wall <NUM> of the hollow manifold <NUM>; this particulate must then be removed using suitable removal means that are better described below.

In accordance with one possible embodiment, the electrostatic filter <NUM> comprises two electrodes <NUM> at least partially superimposed along the vertical direction Y-Y.

The use of multiple electrodes <NUM> allows for more effective ionization of the fumes, and therefore efficient filtration of the particulate that adheres to the inner side wall <NUM> of the hollow manifold <NUM> and/or the elements contained therein and that will not be expelled from the outlet end <NUM> together with the fumes.

Preferably, in the embodiment comprising two electrodes <NUM>, said electrodes <NUM> have different cantilevered sections <NUM> within said volume <NUM>. Said cantilevered sections <NUM> are preferably oriented parallel to a plane perpendicular to said vertical direction Y-Y.

For example, said electrodes <NUM> each comprise a coating sleeve <NUM> made of insulating material, typically a ceramic material, which electrostatically insulates them near said inner side wall <NUM> of the manifold <NUM>.

The electrostatic filter <NUM> further comprises a cleaning device <NUM> configured so as to at least partially abrade said inner side wall <NUM> so as to remove the particulate attached thereto.

Said cleaning device <NUM> comprises at least one movable frame <NUM> within the volume <NUM>, which frame is operatively connected to motor means <NUM>. Preferably, said motor means <NUM> comprise electric motors with relative motion transmission elements.

The movable frame <NUM> may provide various movement trajectories. According to one possible embodiment, said movable frame <NUM> is a frame which is rotatable around said axis of vertical symmetry X-X. It is also possible for the movable frame <NUM> to have a translation movement or even a rotation-translation movement, within said volume <NUM>, so as to reach those portions of the inner side wall <NUM> that are to be cleaned.

Advantageously, the frame <NUM> is provided with a plurality of brushes <NUM> configured so as to flap and clean said inner side wall <NUM>.

In accordance with one possible embodiment, said brushes <NUM> comprise silica fiber and/or basalt fiber and/or ceramic fiber.

Preferably, said movable frame <NUM> comprises vertical sections <NUM>, parallel to the vertical direction Y-Y, provided with said brushes <NUM>.

The movable frame <NUM> comprises a plurality of cantilevered portions <NUM> that are discrete and separated from each other, provided with said vertical sections <NUM>.

According to one possible embodiment, said cantilevered portions <NUM> are radial elements, provided with a main extension along a radial direction R-R, perpendicular to the vertical direction Y-Y. Said cantilevered portions may be parallel or angled with each other and may also be arranged in diametrically opposite positions to each other with respect to an axis of rotation of the frame <NUM>, parallel to said vertical direction Y-Y.

According to one embodiment, said cantilevered portions <NUM> have a height <NUM>, measured parallel to the vertical direction Y-Y, less than a width <NUM>, measured perpendicular to the vertical direction Y-Y.

In accordance with one possible embodiment, said inlet end <NUM> and outlet end <NUM> are coaxial with respect to said vertical rising direction Y-Y of the fumes.

For example, said brushes <NUM> have a cantilevered height with respect to the movable frame <NUM> of between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

The manifold <NUM> comprises a bottom plate <NUM> having a plurality of discharge holes <NUM> for the particulate that are connected to an underlying collection compartment <NUM> for the particulate. In other words, the particulate, once removed from the brushes <NUM>, is pushed by the latter to the discharge holes <NUM>, arranged at the bottom plate <NUM>, wherethrough the particulate may precipitate, thus being collected within the collection compartment <NUM>.

In accordance with one possible embodiment, said discharge holes <NUM> are on the side opposite the inlet end <NUM> of the fumes, with respect to a vertical centerline plane M-M of the hollow manifold <NUM>.

In accordance with one possible embodiment, said discharge holes <NUM> have an arched elongated configuration that prevents the fibers of the brushes <NUM> from being damaged and/or detaching from the frame <NUM>. In other words, such a configuration prevents the brushes from becoming caught, even partially, in the discharge <NUM> holes during the handling of the movable frame <NUM> and thus being damaged by, for example, tearing, ripping, or breaking.

Preferably, said discharge holes <NUM> have tapered ends <NUM> with respect to an enlarged central body <NUM>.

According to one possible embodiment, said discharge holes <NUM> have a predominantly circumferential orientation with respect to an axis of vertical symmetry X-X of the hollow manifold <NUM> having a cylindrical shape.

Preferably, said at least one movable frame <NUM> comprises a plurality of brushes <NUM> configured so as to flap and clean said bottom plate <NUM> during the movement of the frame <NUM> itself.

Preferably, the hollow manifold <NUM> comprises at least one separation plate <NUM>, arranged perpendicular to said vertical direction Y-Y within the volume <NUM>, so as to create a forced path for said fumes along a horizontal direction O-O perpendicular to said vertical direction Y-Y.

Said separation plate <NUM> is provided with at least one discharge hole <NUM> for the particulate. Preferably, the discharge holes <NUM> of the separation plate <NUM> have the same configuration as the discharge holes <NUM> of the bottom plate <NUM>.

Preferably, said movable frame <NUM> is counter-shaped so as not to interfere with the separation plate <NUM> during the movement thereof within the volume <NUM>. In other words, the movable frame <NUM> itself must not collide with the separation plate <NUM> during the movement thereof.

Preferably, the movable frame <NUM> comprises a plurality of brushes <NUM> configured so as to flap and clean said separation plate <NUM> during the movement of the frame <NUM>. The brushes <NUM> are therefore designed to be interfaced for sliding against the separation plate <NUM>.

According to one possible embodiment, said at least one electrode <NUM>, housed at least partially in said volume <NUM>, is positioned at least partially cantilevered within the volume <NUM> of the hollow manifold <NUM> and said movable frame <NUM> is counter-shaped with respect to the electrode <NUM> so as not to interfere with the electrode <NUM> during the movement thereof within the volume <NUM>. In other words, the movable frame <NUM> must not strike the electrode <NUM> during the movement thereof within the volume <NUM>.

In accordance with one possible embodiment, the movable frame <NUM> comprises a plurality of brushes <NUM> configured so as to flap and clean the at least one electrode <NUM> during the movement of the frame <NUM> within the volume <NUM>.

According to a possible embodiment, said frame <NUM> comprises at least one elastic element <NUM> configured so as to elastically influence the brushes <NUM> in abutment against said inner side wall <NUM> of the hollow manifold <NUM>.

In other words, it is possible to envisage an embodiment wherein elastic elements <NUM> are provided between the movable frame <NUM> and the brushes <NUM>. In this case, only the elastic elements <NUM> elastically press the brushes <NUM> in abutment against the inner side wall <NUM>.

For example, said at least one elastic element <NUM> elastically influences the brushes <NUM> in a radial direction R-R, perpendicular and incident to a vertical axis of rotation of the frame <NUM> and/or in said vertical direction Y-Y. The elastic forces exerted by said elastic elements <NUM> are schematically shown with the references 'F' in <FIG>.

Furthermore, said movable frame <NUM> is counter-shaped so as not to interfere with said electrodes <NUM> during the movement thereof.

The operation of an electrostatic filter according to this invention will now be described.

In particular, the combustion fumes produced within the combustion chamber enter the electrostatic filter <NUM>, through the inlet end <NUM>, and follow a path that is preferably serpentine due to the presence of shelves, i.e., of the at least one separation plate <NUM>, within the hollow manifold <NUM>. On each shelf or separation plate <NUM> there are frames, which are for example integral with a central shaft <NUM>, which allows for the synchronous rotation of the movable frames <NUM> themselves. Brushes <NUM> comprising a temperature-resistant ceramic fiber are applied to the external part of the frames <NUM>, which makes it possible to clean the surfaces of the inner side wall <NUM> of the manifold <NUM> when the cleaning system is set in motion.

When the cleaning device <NUM> is activated, the frames <NUM> turn within the manifold <NUM> and the brushes <NUM> make it possible to clean the surfaces of the inner side wall <NUM> of the same.

The agglomerated particulate falls between the various surfaces or plates via the appropriate discharge holes <NUM>, which are preferably slotted or tapered, until terminating within a tank or collection compartment <NUM> which is positioned at the base or bottom plate <NUM> of the hollow manifold <NUM> and easily accessible for seasonal cleaning of the collected soot.

The frames are equipped with ceramic and/or silicon and/or basalt fiber brushes <NUM>, which resist temperatures above <NUM> (the temperatures of the fumes within the manifold may reach <NUM>).

As may be appreciated from that which has been described, the present invention overcomes the drawbacks of the prior art.

In particular, the present invention makes it possible to thoroughly clean those surfaces that are reached by the brushes. In fact, the brushes, by virtue of the envisaged geometry and material, adapt perfectly to the not completely regular geometry of the inner walls of the hollow manifold <NUM> (due to the inevitable machining tolerances that are significant within the sector).

Furthermore, the present invention, unlike the known solutions, makes it possible to increase the deposition surfaces of the particulate and to clean up to <NUM>% of these surfaces lapped by the fumes of the manifold <NUM>, where, due to the electrostatic effect and serpentine passageways, most of the particulate is deposited.

In this way, the phenomenon of reentering is avoided, or else the periods of filter operating time are significantly lengthened before having to perform special maintenance.

The solution of the present invention also has reduced dimensions.

The noise level of the solution according to the present invention is particularly low with respect to the known solutions, whereby there are no problems or inconveniences as regards locating the boiler and flue within enclosed spaces.

Advantageously, by virtue of the particular geometry of the slots <NUM> themselves, the brushes do not fit into the slots that are provided for the evacuation of the removed particulate.

The present invention, as seen, applies broadly and generally to any boiler, wood-burning fireplace, wood-burning oven or biomass combustion equipment.

A person skilled in the art, for the purpose of satisfying contingent and specific needs, may make numerous modifications and variations to the solutions described above.

Claim 1:
Electrostatic filter (<NUM>) for flue duct outlets from a combustion chamber comprising
- a hollow manifold (<NUM>) having an inner side wall (<NUM>) delimiting a volume (<NUM>) for the passage and conveying of fumes, from an inlet end (<NUM>) of the fumes to an outlet end (<NUM>) of the fumes, said inlet end (<NUM>) and outlet end (<NUM>) a being offset with respect to a vertical rising direction (Y-Y) of the fumes,
- at least one electrode (<NUM>), housed at least partially in said volume (<NUM>) and/or in a side duct (<NUM>) fluidly connected with said volume (<NUM>), and configured so as to ionize the fumes crossing said volume (<NUM>) so as to adhere the particulate transported by the fumes to said inner side wall (<NUM>),
- a cleaning device (<NUM>) configured to at least partially abrade said inner side wall (<NUM>) so as to remove the particulate attached thereto,
- wherein the cleaning device (<NUM>) comprises at least one movable frame (<NUM>) within the volume (<NUM>), operatively connected to motor means (<NUM>), the frame (<NUM>) being provided with a plurality of brushes (<NUM>) configured to flap and clean said inner side wall (<NUM>),
characterized in that said movable frame (<NUM>) comprises vertical sections (<NUM>), parallel to the vertical direction (Y-Y), wherein the movable frame (<NUM>) comprises a plurality of cantilevered portions (<NUM>), discrete and separated from each other, provided with said vertical sections (<NUM>).