FR2940918A3 - Air conditioning device for use in e.g. school, has cleaning filter with frame whose upper and lower walls comprise edge that expands outwardly at right-angle, where lower wall is fitted in retaining contact in support structure - Google Patents

Abstract

The device (1) has an electrostatic cleaning filter (2) with a parallel flat box shaped frame with two side walls, an upper wall and a lower wall. The frame extends from a front side of an inlet of air into the filter till to a rear side of an outlet (6) of air from the filter. An electrostatic deposition unit is accommodated in the air passage channel and electrically connected with a power supply unit. The upper and lower walls have an edge that expands outwardly at right-angle, where the lower wall is fitted in a retaining contact in guides of a support structure (3).

Description

The present invention relates to an apparatus for the treatment of air and an electrostatic purification filter for said apparatus, according to the preamble of the present invention. BACKGROUND OF THE INVENTION respective independent claims. The equipment for the air treatment and the electrostatic purification filter in question are located in the air treatment sector with installations, plants and equipment intended to purify or even modify the thermo-hygrometric characteristics of the air. The apparatus and the filter can therefore be advantageously used for filtering, purification, air purification in the air conditioning, heating and more generally air treatment sectors both in the civil field. , public and also industrial, to guarantee optimal air quality conditions for people who park or work in the ambient environments for which the air is intended. These ambient environments may be, for example, residential premises for civilian use or halls or also public premises such as shopping centers, airports, hospitals, schools, museums, libraries, buildings intended for sports activities, cinemas, theaters, etc. The term "air handling apparatus" is hereinafter referred to as any unit for filtering, or also conditioning and more generally treating, a flow of air for any premises. The apparatus may therefore be intended for premises for public use, private or offices and, in this case, may be constituted by a conditioner, an air conditioner, a purifier or other similar devices, or may be intended for a use in an industrial environment and, in this case, may be constituted by a suction, filtering or a separation and reduction installation for the treatment of air which, in this case, may include dust, fumes oil mists and / or vapors also containing harmful volatile substances. The apparatus for the treatment of the air subject of the present invention provides for the integrated use of a purification filter which is adapted to attract and capture the contamination particles contained in the air, eliminating them and forms the subject of an independent claim in this patent.

STATE OF THE ART As is known, the proliferation of microorganisms, as well as the concentration of dust or polluting substances, in the premises where people pass or stay must be strictly avoided in order to guarantee the necessary hygienic conditions and to prevent the spread of substances. harmful agents and pathogens that can cause damage to the health of these people. For this purpose, many different air-handling apparatuses and numerous different purification filters have spread to the market, all of which, although with different degrees of efficiency and different technical characteristics, are intended to fulfill the function of to purify the air, reducing the undesirable substances it contains. For example, it is known air handling units composed of various operational sections, generally arranged in functional and spatial successions, which each perform a control on the characteristics of the air. In particular, it may be provided for example an air treatment unit comprising a ventilation section, intended to circulate a flow of air in the ambient environment considered, a filtering section, intended to purify, by means of of a purification filter, the air passing by retaining the dust present in it and possibly reducing the microbial load, an air cooling section, a heating section, a control section of the humidity, for example with a resistance, and a humidifier to regulate the humidity of the air etc. In particular, the purification filters are intended to capture impurities and dusts which, as is known, rise in considerable quantities in heated or air-conditioned rooms. Given the very wide diffusion of equipment for air treatment, production standards have become established on the market for the above-mentioned purification filters, for the purpose, for example, of allowing the replacement of a filter for the treatment of air. purging exhausted by a new filter. These standards, however, combine the filters belonging, by their modality of operation, to the same typology, not allowing to replace between them filters of different typologies, since, beyond the characteristics of forms that can sometimes be standardized, There are also technical and functional characteristics which impose a different assembly in the processing unit and which, for this reason, do not allow a complete standardization. The air handling units of known type comprise, in the filtering section, specific housings of standardized dimensions, in which are arranged the filters of typologies provided. For example, mechanical type filters are known, available in different versions and classified according to their filtering efficiency and according to the dimensions of the particles they are able to capture. These filters are further usually divided into regenerable filters, whose optimal functionality can be restored by cleaning or washing, and non-regenerable filters, which must therefore be replaced when they are dirty or clogged. In general, regenerable filters, for example such as synthetic cell filters or metal cell filters, have a low efficiency and are used alone only in the case of low-level filtering, whereas they are usually used for more efficient filtering. pushed as protection filters for successive filters finer and higher efficiency, in order to avoid clogging them by retaining larger particles. As is known, the filters that are most used in traditional air treatment units are mechanical bag filters, which have a medium-high purification efficiency. These filters provide a considerable filtering surface that intercepts air by means of a plurality of pockets whose opening is oriented in the direction of air entry. These pockets may be flexible or rigid, depending on the material with which they are made, that is to say, synthetic fibers, glass fibers or glass microfibers or fiberglass-reinforced cellulose paper. Mechanical filters with rigid pockets generally have a better performance due to a better distribution of the air passing through them. However, according to the classification imposed by standard EN779, bag filters are still defined as intermediate filters, that is to say, belonging to the class F, not being able to intercept particles of dimensions less than 0.4 m. The various mechanical bag filters differ from each other, depending on the material with which they are made, simply on the basis of the filtering efficiency, the latter being able to vary between 40-60% (class F5) and a value greater than 95 % (class F9), but always with reference to particles larger than 0.4 m. Pocket filters, given their wide diffusion on the market and thanks to the fact that they all require similar technical conditions of operation (the mechanical filters do not require a power supply), are generally available on the market, produced by different companies, in standard dimensions that make it possible to replace them in a relatively simple way. The main disadvantage of mechanical bag filters in the air treatment units, and more generally in the air treatment apparatuses mentioned above, is the low efficiency. That is to say the impossibility of intercepting and eliminating dust and particles of very small dimensions. Another disadvantage of mechanical filters, and in particular mechanical bag filters, lies in the fact that they cause, especially when they are already partially obstructed, a load reduction in the air flows which force the fans to absorb a higher electrical power to maintain a constant flow through them, with a corresponding increase in the operating costs of the air handling unit. To solve this problem, air handling units have been developed which use electrostatic filters, which are more efficient and comparable to the category of filters which are called absolute and which, in accordance with EN1822, are These electrostatic filters, of a type known per se, act on the particles by capturing them by electrostatic action irrespective of their size. In this way, they succeed in attracting and retaining particles of dimensions up to 0.01 m, allowing to obtain an air completely free of impurities.

Electrostatic filters require, for operation in 2940918 an installation for air treatment and in particular in the air treatment units, technical specifications that can not be shared with the mechanical filters mentioned above, such as, for example, the power supply. they are therefore developed on the market with different production standards. In addition, the electrostatic purification filters comprise electrical and electronic components of considerable size which would not find their place in the housing for a mechanical purification filter of an air treatment unit. Among these particularly bulky components, it is necessary to mention, for example, the power supply unit, which comprises the necessary transformer and voltage booster, whose function is to generate the voltage levels required by the components of the electrostatic filter to carry out the process. filtering. Air handling units that use electrostatic filters of known type are made only for particular uses, to ensure a particularly high purity of the treated air. Consequently, these air treatment units and the electrostatic filters to be mounted on them are generally designed in the case in no case according to the specific use, by sizing them according to the volume of air to be treated and the required performance and predisposing accordingly the necessary electrical connections. As a result of the foregoing, the electrostatic purifying filters can not be inserted into the air handling units instead of the mechanical ones because they are distinguished by different production standards. that is, they require different installation technical characteristics. For this reason, it is not currently possible to provide interchangeability between filters of different typologies, but it is necessary to establish a priori the type of filter that one wishes to adopt, that is to say say mechanical or electrostatic type, and therefore the degree of filtering efficiency that can be achieved, a retrofit of the air treatment units to change the performance of the performance is not possible.

In addition, it should be taken into account that the air handling units require periodic cleaning operations, in particular to avoid the formation of bacterial colonies especially in the corners and areas where strong condensation occurs. humidity. But while cleaning with water and detergents is currently easily achievable where only mechanical filters are present, which require no power supply as already mentioned, it would not be possible in the presence of electrostatic filters that include components electric and electronic that certainly do not tolerate washing with water. For the reasons indicated above so far, the need to improve the efficiency of an air-treatment unit replacing the traditional mechanical-type, and in particular bag-type, purification filters by means of other electrostatic type filters of improved efficiency, has resulted in a reconstruction of a part of the processing unit with considerable costs and with a result of quality not constant, but dependent on the experience of the operator who realizes adaptation and replacement of filters.

PRESENTATION OF THE INVENTION In this situation, an essential object of the present invention is therefore to eliminate the disadvantages of the aforementioned solutions of the known type, by providing an apparatus for the treatment of air and an electrostatic purification filter. for said apparatus which are able to guarantee an optimal purification of the air with a high filtering efficiency.

Another object of the present invention is to provide apparatus for the treatment of air which is able to reversibly mount a mechanical type of purification filter and an electrostatic purification filter. Another object of the present invention is to provide an apparatus for the treatment of air whose filtering efficiency can be easily modified according to the performance requirements. Another object of the present invention is to provide an electrostatic purification filter which can be mounted, without special adaptations, in the housings provided for the mechanical purification filters of the air treatment units.

Yet another object of the present invention is to provide an easy-to-install electrostatic purification filter in an air handling apparatus which is both safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS The technical features of the invention, in accordance with the aforementioned objects, are clearly verifiable according to the content of the claims below and the advantages thereof will become even more evident in the detailed description which follows, with reference to the accompanying drawings, which represent a purely illustrative and non-limiting embodiment, in which: FIG. 1 is a perspective side view of an embodiment of an apparatus for the treatment of the air of the present invention with electrostatic purification filters mounted, also subject of the present invention, and with some cut parts to better highlight other parts; FIGs. 2A and 2B show a side view and an enlarged detail of the apparatus 25 for treating air shown in FIG. 1; FIG. 3 is a perspective front view of an electrostatic purification filter object of the present invention; FIG. 4 is a perspective top view of the electrostatic purification filter of FIG. 3 with electrical connection means indicated separately in evidence; FIG. 5 is an exploded view of an enlarged detail of the electrostatic purification filter object of the present invention, relating to the aforementioned electrical connection means; FIG. 6 shows a perspective view of two electrostatic purification filters 10 of the invention of different dimensions and with the electrical connection means indicated separately in evidence; FIGs. 7A and 7B show a side view and a front view of an electrostatic purification filter object of the present invention in a first possible format; FIGs. 8A and 8B show a side view and a front view of an electrostatic purification filter object of the present invention in a second possible format; FIG. 9 shows a block diagram of the electronic circuit included in the power supply means of an electrostatic purification filter object of the present invention. DETAILED DESCRIPTION OF AN EXAMPLE PREFERRED EMBODIMENT With reference to the accompanying drawings, it has been generally indicated by 1 an apparatus for the treatment of air according to the invention and by 2 an electrostatic purification filter integrated in this apparatus. this. The apparatus 1 for air treatment comprises a support structure, indicated generically by 3, which defines a channel 4 for the passage of air from an inlet section 5 to an outlet section 6 of the air outlet. 'air. Between the inlet section 5 and the outlet section 6 is arranged, to intercept the channel 4 of the air passage, a compartment 7, which can be accessed from the outside by means of a flap 8 .

The support structure 3 comprises, at the interior in correspondence of the compartment 7, at least one pair of horizontal guides 9 which are arranged transversely with respect to the extension of the channel 4 for the passage of air, spaced and aligned vertically. one above the other. These horizontal guides 9 are intended to each receive a projecting edge of a mechanical purification filter, which is thus mounted inside the channel 4 for the passage of air and, during the operation of the apparatus 1, receives the flow of air from the inlet section 5, filtering it before it reaches the outlet section 6. The apparatus 1 further comprises one or more electrostatic purification filters 2 each provided with a substantially parallelepiped box-shaped frame 11 formed of four opposing walls in pairs, the side walls 12 and 12 'of which are opposite one another and an upper wall 13 opposite to a lower wall 14. The frame 11 delimits with the walls an air duct 15 extending from a front face 16 of air inlet into the filter to a rear face 17 of the air outlet of the filter.

The electrostatic purification filter 2 further comprises electrostatic sensing means 18, housed in the duct 15 for passing air through the chassis 11 and electrically connected to electrical supply means 19. The electrostatic purification filter is provided with an ionization section and a sensing section. The ionization section is made with electrodes in the form of wire, generally tungsten, put at a positive potential, alternating with metal blades at the ground potential, while the sensing section is made with collector metal blades having a positive potential. potential lower than the potential of the electrodes, alternating with blades at ground potential. The dust and the particles contained in the incoming air flow, when they pass through the electrostatic field of the ionization section, are electrically charged thanks to the corona effect. The particles thus charged are attracted by potential difference and adhere to the collector metal blades of the sensing section. According to the present invention, the upper wall 13 and the lower wall 14 of the frame 11 of the electrostatic filter 2 are provided with an edge 10 which extends orthogonally projecting outwardly therefrom and which is adapted for mating with a retaining relationship in the horizontal guides 9 of the support structure 3. The edge 10 allows the electrostatic filter 2 to be installed in the standard-sized housings provided for the mechanical type filters in the apparatus for the air treatment, ensuring perfect interchangeability between mechanical filters and electrostatic filters 2 according to the present invention. Advantageously, the presence of the upper wall 13 of the frame 11, as a closure of the duct 15 for the passage of air in its upper part, makes it possible to obtain a better efficiency in filtering the apparatus 1.

Preferably, the horizontal guides 9 are arranged one in correspondence of a bottom wall 24 of the channel 4 and the other in correspondence of a top wall 25 of the channel 4. In accordance with the example shown in the figures appended, these guides 9 on the top 25 and bottom walls 24 are each coupled to a respective intermediate guide for producing the pair of guides in which the edges 10 of the electrostatic filter 2 are to be inserted. In addition, according to a preferred embodiment, on each of the side walls 12 and 12 'of the frame 11 is fixed at least one handle 32 which facilitates the introduction and extraction operations of the electrostatic filter 2 relative to the compartment 7. The power supply means 19 comprise an electronic circuit 5 hermetically sealed in an impervious housing 20, from which electrical connection means exit to a source of electrical energy 100. Advantageously, the electronic circuit contained in the housing 20 comprises the electronics high voltage, that is to say in particular the transformer and the voltage booster which function to generate the voltage levels (from 2 to 10 kV) required for the components of the electrostatic filter to achieve the process filtering. The electrical circuit is powered by the electrical energy source 100 external to the filter, advantageously constituted by the AC low-voltage power supply network, for example at 230 V and 50/60 Hz. The operating voltage of the electronic circuit is easily adaptable to the various power supply standards of the different countries up to a maximum of 600 V at 50/60 Hz. There is provided a filtering and rectifying unit 101 connected to the electrical network 100, which filters the noise emitted and received By the electronic circuit and transmitting the AC voltage of the DC voltage network, the DC voltage output 102 of the filtering and rectifying unit 101 is subdivided into a line 103 which connects a power module 104 containing a cross-converter. in a line 1 05 which connects an oscillator module 106, the oscillator module 1 06 is supplied with low DC voltage and sends a signal of on: mma: ide 107, from iype PWM (slug pulse modulation), to the power module 104. Cu last, by means of a pilot circuit, control of the active components (power MOSFETs) which enable in turn to open and close the contact at the terminals of the high voltage step-up transformer. It occurs thus on the secondary of the. elevator transformer a square wave signal at the frequency of. PWIVI signal, but with high voltage values and low currents. The signal. 108 output of the secondary of the step-up transformer, that is to say in. output of the power module 104, is transmitted to the multiplier module 109 which subsequently increases the value of the voltage. and transforms the square wave signal into direct current on two levels, one for the ionization wires and one for the sensing blades. The generated voltages are brought by means of electrical connection means 110, such as cables and / or spring contacts, to the. Ionization wires and aux. electrostatic filter pick-up plates 2. By means of a current measuring circuit incorporated in the power module 104, the current flowing through the active components is constantly monitored and a corresponding signal is transmitted to the oscillator module 106 by intermediate of a signal control link 111. From the functional point of view, if. If the signal exceeds the limit value expected during the design phase for • con.som_rnations or short circuits on the electrostatic filter, the electronic circuit will limit the control signal by saving the electronic components and. activating an alarm signal 112 on a corresponding alarm module 113. By means of a voltage measurement circuit incorporated in the multiplier module 109, the generated voltage is constantly monitored and the corresponding signal is transmitted to the oscillator module 106 via a signal control link 114.

In the case where the signal is lower than the limit value provided in the project phase, the electronic circuit activates the alarm signal 112 on the alarm module 113. Via a specific external command to be brought on a line 115 for transmitting a validation command, it is possible to activate or put the electronic circuit in STANDBY without interrupting the power supply, the electrical connection means 110 may advantageously be constituted by a cable or also by a spring-loaded contact or other similar solutions Advantageously, the above-mentioned impervious casing 20, containing the electronic circuit, is obtained by sealing its walls or by re-enclosing the components that it contains in accordance with the embodiment illustrated in the figures. attached, the electrical connection means 110 comprise a pad 21, constituted by a spring plate made of elastic material ue and conductor, preferably metal. This shoe 21 is fixed outside the housing 20, projecting below it, so as to make an electrical sliding contact with the metal blades to be loaded, located in the sensing section of the electrostatic filter 2. The that the power supply means 19 comprise the impervious housing 20 makes it possible to perform the cleaning and washing operations of the electrostatic filter 2, without requiring the prior removal of these power supply means 19. According to another characteristic of the In the present invention, the upper wall 13 of the frame 11 of the electrostatic filter 2 is shaped with a step 22 which extends longitudinally between the side walls 12 and 12 'and has a step surface 23 facing the rear face 17, on which the power supply means 19 are located. Advantageously, the power supply means 19, which are precisely arranged in the m arch 22 formed on the frame 11 of the electrostatic filter 2, are provided on the upper wall 13 and not on the side walls 12 or 12 'where they would have generated interference with the air flow to be treated due to the presence of portions of the chassis 11.

In more detail, according to a preferred embodiment of the present invention, the power supply means 19 are mounted in a box-shaped housing body 26, which has an elongated shape and is housed longitudinally on the step 22, to which it can be fixed by means of fixing means 27. The supply means 19 are fixed rigidly, via the box-shaped body 26, to the frame 11 of the electrostatic filter 2 and thus feed the sensing means electrostatic 18 without requiring the realization of electrical connections between mutually removable parts. This allows, in particular, to advantageously always keep in electrical contact the power supply means 19 and the electrostatic sensing means 18, even in the case where the electrostatic filter 2 would be subjected to vibrations or repeated shaking. For this reason, the electrostatic filter 2 object of the present invention is ideal for use on vehicles, such as for example buses, trains, taxis, etc. The box-shaped body 26 supports an electrical connection connector 29, mounted on at least one end wall 28 or 28 'of its longitudinal extension in correspondence of a side wall 12 or 12' of the frame 11. In accordance with the figures appended, the electrical connection connector 29 is a self-centering plug. The electrical connection connector 29 of a first electrostatic filter 2 is adapted to electrically and mechanically couple to the connector 29 of a second electrostatic filter 2 'disposed next to the first, with two side walls 12' juxtaposed and with the front 16 and rear 17 faces respectively aligned with each other. In particular, the coupling between the electrical connection connectors 29 of two electrostatic filters 2 and 2 'is achieved with the interposition of a connection connector 30.

In this way, it is possible to feed several electrostatic filters juxtaposed by means of a single external connector for the power supply 31, connected to the first filter, and making an electrical connection in parallel between the different filters. From the functional point of view, the replacement of a mechanical filter by an electrostatic filter 2 in an apparatus 1 for the treatment of air is obtained in an extremely simple manner by extracting the mechanical filter from the guides 9 and by inserting the electrostatic filter 2 formed with the edges 10 according to the present invention. The electrostatic filter 2 is then connected to the power supply and the apparatus 1 is ready to operate without making further adaptations or modifications.

The invention thus conceived thus achieves the goals set. Of course, it may also have in its practical embodiment forms and configurations different from that illustrated above without departing from the present framework of protection. Furthermore, all the details may be replaced by technically equivalent elements and the dimensions, shapes and materials used may be any depending on the requirements.

Claims (26)

REVENDICATIONS1. Apparatus for the treatment of air comprising: - a support structure (3) which defines: - at least one channel (4) for the passage of air from an inlet section (5) of the air to an outlet section (6) of the air; - at least one compartment (7), accessible from the outside through at least one flap (8), arranged to intercept said channel (4) for the passage of air between said inlet section (5) air and said outlet section (6) of the air; said support structure (3) comprising at least a pair of horizontal guides (9) adapted to receive at least one projecting edge of a mechanical purification filter, which guides (9) are arranged transversely with respect to the extension said air channel (4) spaced apart and vertically aligned one above the other; at least one electrostatic purification filter (2) comprising: a substantially parallelepiped box-shaped frame (11) formed by four opposing walls, two of which have two opposite side walls (12, 12 '); and an upper wall (13) opposite to a bottom wall (14), said frame (11) defining with said walls an air duct (15) extending from an inlet front face (16) air in the filters at a rear face (17) of the air outlet of the filter; - Electrostatic sensing means (18) housed in the air passage duct (15) of said frame (11) and electrically connected to power supply means (19); characterized in that the upper wall (13) and the lower wall (14) of said frame (11) are provided with an edge (10) which extends orthogonally projecting outwardly therefrom, and is adapted to mate with a retaining relationship in the guides (9) of said support structure (3). 2. Apparatus according to claim 1, characterized in that said power supply means (19) comprises an electronic circuit hermetically sealed in an impervious housing (20) which out of the means of electrical connection to a source of electrical energy (100). ). 3. Apparatus according to claim 1, characterized in that said power supply means (19) are connected to said electrostatic sensing means (18) via electrical connection means (110), which comprise a pad (21). ), constituted by a spring plate made of elastic and conductive material. 4. Apparatus according to claim 2, characterized in that said impermeable housing (20) is obtained by sealing of its walls or by re-housing components it contains. 5. Apparatus according to any one of claims 1 to 4, characterized in that the upper wall (13) of the frame (11) of said electrostatic filter (2) is shaped with a step (22) which extends longitudinally between the side walls (12, 12 ') and has a walking surface (23), facing the rear face 17, on which are housed said power supply means (19). 6. Apparatus according to any one of claims 1 to 5, characterized in that the guides (9) of said pair of guides are arranged one in correspondence of a bottom wall (24) of said channel (4) and the other in correspondence of a top wall (25) of said channel (4). Apparatus according to claim 5, characterized in that said power supply means (19) are mounted in a box-shaped housing body (26), which has an elongated shape and is housed longitudinally on said step ( 22), to which it can be fixed by means of fixing means (27). 8. Apparatus according to claims 7 and 3, characterized in that said supply means (19) are fixed rigidly, through said box-shaped body (26), to the frame (11) of said electrostatic filter (2), with said pad (21) resiliently pressed against said electrostatic sensing means (18). 9. Apparatus according to claim 7, characterized in that said box-shaped body (26) supports an electrical connection connector (29) mounted on at least one end wall (28 or 28 ') of its longitudinal extension, in correspondence of a side wall (12 or 12 ') of the frame (11). Apparatus according to Claim 9, characterized in that the electrical connection connector (29) of a first electrostatic filter (2) is adapted to electrically and mechanically couple to the connector (29) of a second electrostatic filter ( 2), arranged next to the first, with two lateral walls (12, 12 ') juxtaposed and the front faces (16) and rear (17) respectively aligned with each other. 11. Apparatus according to claim 10, characterized in that the coupling between the electrical connection connectors (29) of said two electrostatic filters (2) is formed by interposition of a connector (30). 12. Electrostatic purification filter intended in particular to be mounted on an apparatus (1) according to any one of the preceding claims, which comprises: - a box-like frame (11), substantially parallelepiped, formed by four opposite walls; in pairs, two side walls (12, 12 ') opposite one another and an upper wall (13) opposite a lower wall (14), said frame (11) delimiting with said walls an air duct (15) extending from an inlet front face (16) of air in the filters to a rear air outlet face (17) of the filter; - Electrostatic sensing means (18) housed in the air passage duct (15) of said frame (11) and electrically connected to power supply means (19); characterized in that said upper wall (13) and said lower wall (14) are provided with an edge (10) which extends orthogonally outwardly therefrom and which is adapted for coupling with a holding relation in horizontal guides (9) of an apparatus (1) for the treatment of air, arranged transversely relative to the extension of its channel (4) of air passage. 13. Screening filter according to claim 12, characterized in that said power supply means (19) comprise an electronic circuit hermetically sealed in an impermeable casing (20), from which electrical connection means spring to a source of power. electrical energy (100). The purification filter according to claim 12, characterized in that said power supply means (19) are connected to said electrostatic sensing means (18) via electrical connection means (110), which comprise a shoe (21) constituted by a spring plate made of elastic and conductive material. 15. Screening filter according to claim 13, characterized in that said impermeable casing (20) is obtained by sealing its walls or by re-housing the components it contains. 16. Screening filter according to any one of claims 12 to 15, characterized in that the upper wall (13) of the frame (11) of said electrostatic filter (2) is shaped with a step (22) which extends longitudinally between the side walls (12, 12 ') and has a walking surface (23), facing the rear face (17), on which are housed said power supply means (19). A purifying filter according to claim 16, characterized in that said power supply means (19) are mounted in a box-shaped housing body (26), which has an elongated shape and is housed longitudinally on said step (22), to which it can be fixed by means of fixing means (27). 18. A purification filter according to claim 17 and 14, characterized in that said supply means (19) are fixed rigidly, through said box-shaped body (26), to the frame (11) of said electrostatic filter ( 2), with said pad (21) elastically pressed against said electrostatic sensing means (18). 19. A purification filter according to claim 17, characterized in that said box-shaped body (26) supports an electrical connection connector (29) mounted on at least one end wall (28 or 28 ') of its longitudinal extension, in correspondence of a side wall (12 or 12 ') of the frame (11). 20. A purification filter according to claim 19, characterized in that the electrical connection connector (29) of a first electrostatic filter (2) is adapted to electrically and mechanically couple to the connector (29) of a second electrostatic filter (2), arranged next to the first, with two side walls (12, 12 ') juxtaposed and the front faces (16) and rear (17) respectively aligned with each other. 21. A purification filter according to claim 20, characterized in that the coupling between the electrical connection connectors (29) of said two electrostatic filters (2) is formed by interposition of a connection connector (30). 22. Sewage filter according to claim 13, characterized in that said electronic circuit comprises a filtering and rectifying unit (101) connected to said power supply source, in particular constituted by the network. electrical, said filtering and rectifying unit (101) transforming the AC mains voltage into DC voltage. Filter for purification according to claim 22, characterized in that the DC voltage output (102) of the filtering and rectifying unit (101) is subdivided into a one (10.33) which connects a power module. (104) containing a transformer and a line (1059) which connects an oscillator module (106) supplied with low DC voltage, adapted to transmit a control signal (107) to said power module (104). 24. A purification filter according to claim 23, characterized in that said power module (104) controls by means of active components the opening and closing of the contact at the terminals of the high voltage step-up transformer to produce at the secondary of the transformer. elevator a square wave signal at the signal frequency of the oscillator unit, but with high voltage values and low currents. Filtering filter according to Claim 24, characterized in that the signal (108) output from the secondary of the step-up transformer of the power module (104) is transmitted to a multiplier module (109) which subsequently increases the value of the voltage and t.ransfon e the two-level direct current DC wave signal, one for the ionization wires and one for the electrostatic filter pick-up wires (2). Filter filter according to claim 23, characterized in that, by means of a capacitor circuit (9) incorporated in the power module (104), the current flowing through the active components is constantly monitored and monitored. a corresponding signal is transmitted to the oscillator module (106) via a signal control link (111). A purification filter according to claim 25, characterized in that, by means of a measuring circuit incorporated in the multiplier module (109), the generated voltage is constantly monitored and the corresponding signal is transmitted to the oscillator module 0106) via a signal control link (114).