Electrostatic filter

Abstract

 An electrostatic filter for air-purification equipment, comprising a prismatic box-shaped body (5), made of metallized thermoplastic material, substantially in the form of a tray, subdivided in a longitudinal sense by a multiplicity of equispaced walls perpendicular to the base (5a, 5c, 5e, 5g) alternating with dividing baffles (5b, 5d, 5f) of short length in relation to that of such walls, so as to form a multiplicity of parallel electrostatic cells within each of which is contained a fixed polarizing electrode (11; 111) located parallel to such walls and baffles and passing around the rear end of such baffles (5b, 5d, 5f) stretched between supports (12, 12a) integral with the air-purification device, such combination making it possible to ensure both the stable setting of such continuous polarizing electrode (11, 111) between each pair of walls and the removal of an individual cell (5), each of such electrostatic cells being furthermore subdivided in a longitudinal sense by at least one fin (9) of lower height than that of such walls and baffles.

Description

[0001] This invention refers to a removable single-purpose single-stage electrostatic filter, particularly for equipment for air purification in enclosed spaces.

[0002] As is known, the electrostatic filters currently used for air purification in inhabited spaces are based on the principle of separation from the air and precipitation of particulate matter, such as dust, mist, smoke and the like, by the passage of the air through an electric field of unidirectional potential created by ionizing electrodes facing one another and of large area. In particular, the air or gas passing through the strong electric field is ionized and its molecules release or acquire electrons which, on coming into contact with other molecules in the air, convert the latter into negative or positive ions which are irradiated around the polarizing electrode. During their journey, such ions bombard the solid particles or the droplets of mist, charging them negatively or positively and forcing them to gather on the surface of the opposite

[0003] electrode having an opposing charge, to which they are attracted. Electrostatic filters based on this principle are provided in practice with two operating sections or stages, for which reason they are commonly classified as two-stage electrostatic filters.

[0004] In practice they consist of the following:

a) A chamber for ionizing the airborne particles, comprised of a polarizing electrode - usually one or more wires of high positive potential - which generates an electric field within a chamber or section formed by pairs of metallic armatures (counter-electrodes) equispaced from the relevant electrodes, and

b) A second section for precipitation and collection, normally termed collector, which is formed by a multiplicity of metal plates parallel to one another and polarized alternatively with like sign respectively opposed to that of the corresponding ionizing electrode.

[0005] The particles suspended in the air flow passing through the two sections are ionized in the first ionizing chamber and, on arriving between the plates of the collector, are repelled by the plates of like sign, thus facilitating their adherence to the plates of opposite sign. The widespread use attained by two-stage electrostatic filters for ambient air purification is to a large extent due to their high efficiency in separating and disposing of the particulate matter present in the air, with the required low power consumption and with controlled operating costs.

[0006] On the other hand, a more widespread use of these two-stage electric filters is undoubtedly hampered by their low versatility, their complex construction which translates into high purchase costs and also by the fact that it is necessary to remove the ionizing cell and the relevant collector to allow regular cleaning by washing with suitable detergents.

[0007] Such removal and washing operations can, however, pose serious disadvantages, including in particular breakage of the wires forming the ionizing electrodes, as well as rapid deterioration of the entire structure as a result of the oxidizing action caused by the detergents which, in particular, corrode the discharging electrodes with consequent shortcircuiting and deactivation of the filter.

[0008] To overcome these disadvantages there have already been proposed solutions which provide for the removal and replacement of the single collector, but such solutions have proved acceptable only for those types of filters with a low air-purification capacity and a limited degree of separating efficiency, and furthermore cleaning of the ionizing stage must also be performed in this case by specialized personal using special, and often hazardous, detergents.

[0009] There is therefore posed the technical problem of providing an electrostatic filter designed in such a way as to obviate the disadvantages displayed by conventional two-stage electrostatic filters without in practice having an adverse effect on efficiency and on loss of charge, but with the considerable advantage of bringing about a substantially lower cost.

[0010] Within the scope of this problem, one aim is to provide an electrostatic filter for air purification in general environments capable of being manufactured in a manner and with materials such as to simplify both the ionizing section and the collecting section so as to allow ease of maintenance without danger of failure or breakage of the polarizing electrodes, that is, such as to allow the use of the collecting section once only.

[0011] Another aim of the invention is to provide an electrostatic filter designed in such a way as to enable it to be manufactured largely using pressable material of low cost, high reliability and capable of being dimensioned to cater for any use, that is, for private, public and industrial premises alike.

[0012] These and yet other aims, which may become more clearly apparent from the following description, are achieved by an electrostatic filter for air-purification equipment consisting of a prismatic box-shaped body made of metallized thermoplastic material, substantially in the form of a tray, subdivided in a longitudinal sense by a multiplicity of equispaced walls perpendicular to the base alternating with dividing baffles of short length in relation to that of the walls, so as to form a multiplicity of parallel electrostatic cells within each of which is contained a fixed polarizing electrode consisting of a continuous wire, pointed band or the like of high potential, located parallel to such walls and dividing baffles and passing around the rear end of such baffles, stretched between supports integral with the air-purification device so as to make possible both the stable setting of such continuous polarizing electrodes between each pair of armatures and the removal of an individual cell for replacement when it is spent.

[0013] Each of such electrostatic cells is furthermore subdivided in a longitudinal sense by at least one fin of lower height than that of such walls and baffles.

[0014] According to the invention, the electrostatic filter has a flat bottom provided with a multiplicity of through holes or apertures, capable of constituting further routes for the passage of purified air for suction thereof by means of a fan or the like.

[0015] In a preferred form the electrostatic filter has supports for holding and tensioning the continuous wire which can be adjusted with respect to the plane of the supporting cover to allow the positioning of the wire at variable distances from the armatures and at variable heights inside the electrostatic cells.

[0016] Provision is also made for such multi-section electrostatic cell to be secured to the internal walls of a body containing the air-purification device by means of flexible spring-action or like components for removal in a direction at right angles to the plane of containment of the fixed continuous wire or by means of dovetail or like parallel guides for removal in a direction parallel to such plane.

[0017] Further features and advantages of the invention may become more clearly apparent from the following detailed description, given with reference to the attached set of drawings, provided solely as a guide, which show:

In figure 1 :

an electrostatic filter made according to the invention, fitted to an air-recirculating unit, illustrated schematically partly in elevation and partly in section;

In figure 2 :

the electrostatic cell with multiple adjoining sections, illustrated in an axonometric view;

In figure 3 :

a plan or overhead view of the electrostatic cell complete with electrode, and

In figure 4 :

a generic cross-section of the cell in fig. 3, shown according to plotting plane IV-IV of the said figure 3;

In figure 5a:

an example of construction of the filter with a different formation of the walls defining the electrostatic cells and electrode, and

In figure 5b:

a section according to plotting plane Vb-Vb of fig. 5a.

[0018] With reference to the above-mentioned figures, the filtering device consists of a container body, generally marked 1, which is formed by two half-shells 1a and 1b facing one another and hinged to 2 and 2a at the opposite ends.

[0019] Half-shell 1a constitutes the container body proper, while half-shell 1b forms the cover capable of being opened on such hinges. In cover 1b are provided grille-type aperture 3 in a substantially central position, intended for the passage (according to arrow A) of the flow of air to be purified, and a series of apertures 4 at one end for the outflow (according to arrow B) of the purified air, as will become more clearly apparent later.

[0020] Within half-shell 1a is positioned in a removable manner a box-shaped body substantially in the form of a tray, generally marked 5 in the figures, intended to constitute the single-stage electrostatic cell, that is, a single cell capable of performing both ionization and collection of the particulate matter present in the incoming air flow and separation thereof within the said cell.

[0021] Such electrostatic cell 5 is dimensioned, relative to the outer container, in such a way as to create around the latter a free space 6 necessary for enabling the purified air flowing out from cell 5 to be sucked in (according to arrow C) (fig. 1) by a fan 7 and to be returned to the room via apertures 4.

[0022] More particularly, as clearly shown by figures 3 and 4, such electrostatic cell 5 is comprised of a prismatic container body (fig. 2) of rectangular shape substantially in the form of a multi-compartment tray, made of plastic material as a single body by pressforming according to known techniques.

[0023] Such cell 5 is internally divided into a multiplicity of ionizing-collecting spaces by means of equispaced vertical walls, parallel to one another and arranged according to the length of the box-shaped body. More specifically, between the two outer walls 5a, 5g are arranged intermediate walls, marked 5b, 5c, 5d, 5e and 5f in fig. 2; of these, outermost walls 5a and 5g and inner walls 5c and 5e are of equal height and of length such as to be integral with rear wall 5h, while intermediate walls 5b-5d-5f are also equal in height to the previous walls, but shorter in length so as to determine a free space 8 between their ends and rear wall 5h.

[0024] Between each pair of facing walls are provided two walls placed together and parallel to one another, marked 9, all of them having a lower height than that of the walls between which they are contained. All the above-mentioned walls are metallized to make them conductive. Each pair of facing walls 5a-5b, 5c-5d, etc. define the space within which the electric field is to be generated by means of a metal-wire polarizing electrode of known type, as will be more clearly explained later. Also, the lower pair of facing walls 9 constitute armatures the function of which is to increase the area of collection of particles within the said cell to ensure greater durability of the filter.

[0025] In this cell of multiple adjoining sections is inserted a continuous-wire polarizing electrode 11 of high potential (figs. 3 and 4) which is wound as a flat coil parallel to the bottom of the cell. Such single continuous wire is inserted between the higher armatures (fig. 4), starting from a more external pair, and is then wound around the shorter adjoining armature and so on until it emerges from the last section, as shown in fig. 4. Such free spaces 8 between the shorter armatures and rear wall 5h of the cell allow the return of the wire at the end of each section.

[0026] Wire 11 is supplied, as is known, with direct current of high potential and its stable position in the various sections is achieved by stretching the wire between two main supports 12-12a, integral with cover 1b (fig. 1), there being interposed at both ends tensioning or like springs and intermediate insulating supports (not shown), likewise integral with the cover, which support the wire on its route around the vertical walls of the sections.

[0027] With cover 1b closed, as in figure 1, anodic wire 11 is therefore positioned between each pair of higher armatures (fig. 4) and is furthermore adjustable for distance from lower armatures 9 so as to regulate the efficiency of separation of the particulate matter present in the air drawn in by the fan via front grille 3.

[0028] Cell 5 thus structured makes it possible, with a single continuous-wire polarizing electrode 11, to achieve ionization and collection of the particulate matter from all the sections of the cell whose armatures are polarized with opposite sign to that of electrode 11.

[0029] Still according to the invention, to improve the flow of purified air to the outlet, the bottom of cell 5 is provided with holes 13 and all the walls making up the vertical armatures have arched cuts 14 at the end turned toward fan 7. Furthermore, such single cell 5 is removably secured to outer box-shaped body 1 by means of spring-action fasteners, sliding guides or the like capable of allowing, with the cover open, that is, with the wire removed from the ionizing section, the removal of the particulate-matter collecting cell and its replacement with another, thus doing away with any cleaning or washing operating and above all avoiding any risk of damage to or irreparable failure of the wire electrode.

[0030] The removal of the cell may be carried out, always with the cover open, in a direction frontal to body 1 of the filter, or alternatively in an axial direction, from the part opposite the clean air outlet, even with cover 1b closed.

[0031] The equipment described above is further completed by a prefilter 15 made of fabric or the like, capable of handling the larger particles which may be contained in the air to be purified.

[0032] From the foregoing description it seems clear that the filter according to the invention achieves the predetermined aims, that is, considerable constructional simplicity, satisfactory separating efficiency with reduced loss of charge and well-controlled operating costs, plus the advantage of allowing the use of a single collecting cell which can be used only once then disposed of when fully covered and no longer able to attract particles.

[0033] In addition to the foregoing, the filter in question makes it possible to use any plastics press-forming techniques for producing the multi-section cell as a single body and to mould the individual walls constituting the armatures in the form of pyramids of elongated rectangular base which, in addition to facilitating the removal of the press-formed body, also make it possible to adjust the position of wire 11 with respect to the armatures and thus reduce electric power consumption where there is equality of section of the said wire.

[0034] In practice, there may be applied variants and modifications to the dimensions of the various constructions parts, to the materials used and to various other structural details, without departing from the scope of protection of the said invention, for example as illustrated in fig. 5a and 5b in which is shown a collecting arrangement in which the form of vertical walls 5 is of a downward slope toward the rear part of the collector and fins 9 are of substantially parallelepipedal form contained within the perimetral edge; in the same figure there is also illustrated a different polarizing electrode 111 in the form of a band with upper points 111a.

Claims

1. An electrostatic filter for air-purification equipment, characterized in that it consists of a prismatic box-shaped body (5), made of metallized thermoplastic material, substantially in the form of a tray, subdivided in a longitudinal sense by a multiplicity of equispaced walls perpendicular to the base (5a, 5c, 5e, 5g) alternating with dividing baffles (5b, 5d, 5f) of short length in relation to that of such walls, so as to form a multiplicity of parallel electrostatic cells within each of which is contained a fixed polarizing electrode (11; 111) located parallel to such walls and baffles and passing around the rear end of such baffles (5b, 5d, 5f) stretched between supports (12, 12a) integral with the air-purification device, such combination making it possible to ensure both the stable setting of such continuous polarizing electrode (11, 111) between each pair of walls and the removal of an individual cell (5), each of such electrostatic cells being furthermore subdivided in a longitudinal sense by at least one fin (9) of lower height than that of such walls and baffles.

2. An electrostatic filter according to claim 1, characterized in that such fins (9) are of equal height.

3. An electrostatic filter according to claim 1, characterized in that such fins (9) are of different heights arranged in symmetrical pairs between which is located a further fin of lower height.

4. An electrostatic filter according to one or more of the previous claims, characterized in that the flat bottom of such sections is provided with a multiplicity of through holes or apertures (13), capable of constituting further routes for the passage of the purified air for suction thereof by means of a fan or the like (7).

5. An electrostatic filter according to the previous claims, characterized in that such supports (12, 12a) for holding and tensioning continuous wire (11) can be adjusted with respect to the plane of supporting cover (1b) to allow the positioning of wire (11) at variable distances from armatures (5a, 5c, 5e, 5g) and at variable heights inside the electrostatic cells.

6. An electrostatic filter according to the previous claims, characterized in that such multi-section electrostatic cell (5) is secured to the internal walls of a body (1a) containing the air-purification device by means of flexible spring-action or like components for removal in a direction at right angles to the plane of containment of fixed electrode (11, 111) or by means of dovetail or like parallel guides for removal in a direction parallel to such plane.

7. An electrostatic filter according to claim 1, characterized in that such polarized electrode is of the type with a continuous wire, pointed band or the like, subjected to high potential.

Drawing