WO2013150398A1

WO2013150398A1 - Apparatus and method for eliminating electrostatic charges from a body

Info

Publication number: WO2013150398A1
Application number: PCT/IB2013/051806
Authority: WO
Inventors: Barbieri Girolamo
Original assignee: Barbieri Girolamo
Priority date: 2012-03-27
Filing date: 2013-03-07
Publication date: 2013-10-10
Also published as: EP2832189A1; EP2832189B1; ITMI20120492A1

Abstract

Described is an apparatus for eliminating electrostatic charges from a body comprising a disperser (6) of electrostatic charges designed to generate a flow of an electrostatic charge receiver fluid and in turn comprising : a core (10), connected to a body (3) through a connection wire (5) for receiving electrostatic charges from the body (3), the core (10) being immersed in the flow of the electrostatic charge receiver fluid for releasing the electrostatic charges to the fluid, - a plurality of tips (14) arranged around the core (10) and facing thereto in a manner such that the tips (14) are immersed in the flow of electrostatic charge receiver fluid; and a magnetic circuit (19) for generating a potential difference between the tips (14) and a ground wire (18).

Description

APPARATUS AND METHOD FOR ELIMINATING ELECTROSTATIC CHARGES FROM A BODY

This invention relates to an apparatus for eliminating electrostatic charges from a body, and is designed particularly for use in painting systems so as to obtain an efficient dissipation of the electrostatic charges which tend to accumulate in the products being processed or in any other apparatus or system subject to disturbance of electrostatic currents.

It is known that, in painting systems and in particular in electrostatic painting systems, it is of fundamental importance to provide a good connection to earth of the product being processed, so that the latter can efficiently attract the powdered paint particles which are dispensed towards the product after crossing an ionized electric field. If it is not connected to earth, the product would tend to accumulate on itself the electrostatic charges reaching it by means of the charges present on the particles of paint applied to it and due to the effect of the ionization filed produced by the electrodes associated with the paint dispensing gun. The greater the accumulation of electrostatic charge on the product the more the further adhesion of paint particles will be compromised. In effect, in these conditions, an effect of "saturation" of the product is triggered caused by the fact that the electrostatic charges accumulated in large quantities on the product prevent the reception of further charges and, therefore, obstruct the adhesion of the paint particles dispensed by the paint guns . Italian patent No. 1276106 in the name of the Applicant discloses a device for eliminating the electrostatic charge from a product undergoing painting. This device comprises a charge absorber which is interposed between the painting system (and in particular the products to be painted) and an electrostatic charge disperser and connected to it by means of special connection wires. The electrostatic charge disperser comprises a layer of non-woven fabric made of electrically insulating synthetic fibre and folded back on it itself to define a plurality of overlapping layers.

On the two surfaces of the above-mentioned layer of non- woven fabric metallic filaments are arranged in the form of short fibres or continuous wires mutually linked and air or another charge receiver fluid is made to flow across this layer; during the crossing of the folded layer the fluid being ionized and picking up the electrostatic charges from the layer.

In this technical field, and starting from the prior art solution, the Applicant found that it is possible to further improve the efficiency of removing the electrostatic charge, both in terms of capacity of removing the electrostatic charge in general, and in terms of adaptability of the apparatus to operate in conditions of use which differ on each occasion, depending on the specific use planned.

The aim of this invention is substantially to provide an apparatus for eliminating electrostatic charges from a body which has a greater efficiency of removing the electrostatic charge. The aim of this invention is also to provide an apparatus for eliminating electrostatic charges from a body which is able to optimise and concentrate the effect of removing the electrostatic charge depending on the specific use planned on each occasion. In other words, this aim results in an architecture of the apparatus which is easily adaptable to different contexts of use.

This aim and others, which shall become more apparent in the description which follows, are substantially achieved by an apparatus for eliminating electrostatic charges characterised in that it comprises a central core connected by a connection wire to a body from which electrostatic charges are picked up and immersed in a flow of electrostatic charge receiver fluid, a plurality of tips arranged around the core and facing thereto in a manner such that the tips are immersed in the flow of electrostatic charge receiver fluid, and devices for generating a potential electrical difference between the tips and a ground wire. This configuration optimises the efficiency of dissipating the electrostatic charges, increasing the efficiency relative to prior art systems. Preferably, the core comprises a laminated pack defined by metal plates fitted in parallel next to each other in a mutual contact relationship.

More specifically, there can be storage plates alternated with drainage plates according to a predetermined sequence. This predetermined sequence can be defined in advance as a function of the material constituting the body from which the electrostatic charges must be removed and/or other morphological features of the painting system. In this way it is possible to provide in a simple and fast manner a suitable architecture of the apparatus depending on the various conditions of use.

The storage plates are preferably made of lead or other ferrous material having specific weight greater than that of the drainage plates. The drainage plates are preferably made of ferrous material or other metallic material having electrical conductivity greater than that of the storage plates.

A metal net, preferably made of copper, can be wrapped around the core. The metal net preferably has a plurality of sharpened terminations arranged on a main surface of extension of the metal net, so as to favour the dissipation of the electrostatic charge in the receiver fluid.

The tips are preferably supported and electrically connected to each other by at least one conductor bar made of electrically conductive material, preferably aluminium.

The tips can be made of titanium or another preferably metal material having greater resistivity than that of the conductor bar.

Preferably, the disperser comprises a load-bearing structure having a tubular wall defining a duct therein within which the core is positioned. Between the core and the tubular wall a substantially annular volume is preferably defined. The tips are preferably supported by the tubular wall.

There can also be a fan or other device suitable for generating in the annular volume and along the tubular wall a flow of the receiver fluid, for example air.

The devices for generating a potential difference between the tips and the ground wire can comprise a magnetic circuit having an inductor winding connectable to a power network and/or an induced winding. The induced winding preferably has a first terminal electrically connected to the tips and a second terminal electrically connected to the ground wire.

Preferably, the wires which make up one or both the windings of the magnetic circuit are made of aluminium coated with electrically insulating material.

There can also be an absorber of electrostatic charges, operating along the connection wire. For example, the connection wire has a first segment connected with a first connection terminal of the absorber and connectable with a body from which electrostatic charges are to be removed, and a second segment that connects a second connection terminal of the absorber with the core .

According to a further aspect, the invention relates to a process for eliminating electrostatic charges from a body which contemplates the setting up of an apparatus made as described above.

According to an aspect of this process, an end of the connection wire is connected to a body from which electrostatic charges are to be removed or to a support structure of the body.

A difference of potential is generated between the tips and the ground wire, alongside a flow of the electrostatic charge receiver fluid, in a manner such that said flow hits the core and the tips. Other features and advantages will become more apparent from the detailed description of a preferred non- limiting embodiment of an apparatus and a process for eliminating electrostatic charges from a body according to this invention. The description is set out below with reference to the accompanying drawings which are provided solely for purposes of illustration without restricting the scope of the invention and in which:

Figure 1 shows an apparatus for eliminating electrostatic charges according to this invention applied to a painting systems;

- Figure 2 shows a disperser according to this invention and used in the apparatus of Figure 1, with some parts in cross-section to illustrate the inside;

- Figure 3 shows an enlarged view of a detail of the disperser of Figure 2;

Figure 4 shows a top portion of the core of the disperser of Figure 2;

- Figure 5 is a side view of a portion of the core of the disperser of Figure 2;

- Figure 6 shows an electrostatic charge absorber used in the apparatus of Figure 1.

With reference to the accompanying drawings, the numeral

1 denotes in its entirety an apparatus for eliminating electrostatic charges according to this invention.

In the embodiment described and as illustrated in Figure 1, the apparatus 1 is associated with a painting system

2 which is not described nor illustrated in detail because it is of a per se known type and conventional, in which one or more products 3, constituting the body from which the electrostatic charges are to be removed, are subjected to an electrostatic painting process. In a per se known manner the products 3 being processed are engaged with a metallic support structure 4, which can be usually equipped with a belt or other type of movement means for suitably translating the products along the painting system.

The support structure 4 is connected with at least one connection wire 5 which, through the metallic parts constituting the support structure 4, is connected electrically to the products 3 being processed. As described below, the connection wire 5 makes an electrical guide through which the electrostatic charges are removed and moved away from the products 3 to an area for dispersion of the charges.

More specifically, according to the quantity of electrostatic charge to be removed, a plurality of connection wires 5 can be used, arranged electrically in parallel with each other to increase the cross-section for passage of the electrostatic charge.

The connection wire 5 is connected, on the side opposite the metallic support structure 4, to at least one electrostatic charge disperser 6 illustrated in detail in Figure 2.

The disperser 6 is designed in such a way as to generate a flow of an electrostatic charge receiver fluid to which the electrostatic charges received from the products 3 are transferred through the connection wire 5.

Preferably, the electrostatic charge receiver fluid is air . The disperser 6 comprises a load-bearing structure 7 having a tubular wall 8 of substantially cylindrical shape defining a duct 9 therein which, in the accompanying drawings, extends vertically but could adopt any spatial orientation.

The duct 9 extends between an inlet section 9a to an outlet section 9b.

At least the above-mentioned tubular wall is made of electrically insulating material, for example polypropylene .

The disperser 6 also comprises a core 10 arranged inside the duct 9 in such a way that between the core 10 and the tubular wall 9 a substantially annular volume 11 is defined. The core 10 is electrically connected to the connection wire 5 for receiving electrostatic charges from the latter.

The above-mentioned annular volume 11 contains the flow of electrostatic charge receiver fluid, which flows along the duct 9, such that the core 10 is immersed in the fluid.

More specifically, the apparatus 1 comprises special devices 12 for generating the flow of the electrostatic charge receiver fluid. In the embodiment illustrated, the devices for generating the flow comprise a fan or ventilator 12, preferably facing the inlet section 9a of the duct 9 for generating an axial flow of air along the duct 9.

Preferably, a grille 13 or other support element is interposed between the fan 12 and the duct 9 allowing passage of the air delivered from the fan 13 and at the same time defining a stable support surface for the core 10. In this situation, there can be a suitable electrical insulation between the grille 13 and the core 10 applied on it.

The dispenser 6 also comprises a plurality of tips 14 arranged around the core 10 and facing thereto in a manner such that the tips 14 extend into the annular volume 11 and are therefore immersed in the flow of electrostatic charge receiver fluid flowing through the duct 9.

Each tip 14 has at least one respective connection wire end facing the core 10 and immersed in the flow in the duct 9.

Preferably, moreover, all the tips 14 are oriented radially relative to an axis of symmetry of the duct 9, and distributed parallel to the axis of symmetry.

In the embodiment illustrated in Figure 2, the tips 14 are arranged on parallel rows coinciding with generatrices of the tubular wall 8 and each row comprises a plurality of tips 14 preferably equidistant from each other.

Preferably, the tips 14 are connected with each other by at least one conductor bar 15, preferably made of aluminium or other suitable conductive material.

In the embodiment illustrated, there is a plurality of the conductor bars 15 each arranged along a respective row of tips 14 (arranged, therefore, parallel to a generatrix of the tubular wall 8) and each connected to all the tips 14 of the same row. The conductor bars 15 are fixed inside the tubular wall 9 in positions angularly spaced from one another, about the axis of extension of the duct 9. Figure 3 shows a detail of the tips 14 and of the conductor bars 15.

According to that figure, the tips 14 are defined by ends of pieces 16 of C-shaped metallic filament having a central portion 16a arranged along the conductor bar 15 and a pair of end portions 16b extending from the central portion 16a and substantially perpendicular to it.

In a preferred embodiment, each conductor bar 15 is defined by an aluminium sheet folded back on itself in such a way that the longitudinal parallel flaps 15a, 15b of the sheet are brought close to one another and can firmly grasp the central portions 16b of the pieces 16. The central portion 16a of each piece 16 is retained by the respective conductor bar 15 whilst the free ends of the end portions 16b define the above-mentioned tips 14 and extend away from the conductor bar 15 perpendicularly to it.

Preferably, the pieces 16 and therefore the tips are made of titanium or another preferably metal material having greater resistivity than that of the conductor bar 15.

The apparatus 1 also comprises devices 17 for generating a potential electrical difference between the tips 14 and a ground wire 18, electrically connected to earth. Preferably, the above-mentioned devices 17 for generating a potential difference between the tips 14 and the ground wire 18 comprise a magnetic circuit 19 having an inductor winding 19a connectable to a power network and an induced winding 19b. Preferably, the inductor winding 19a and the induced winding 19b are arranged about a same metal core 19c, in positions axially spaced from one another.

The induced winding 19b has a first terminal electrically connected to the tips 14 and a second terminal electrically connected to the ground wire 18. The induced winding 19b therefore determines a potential difference between the tips 14 and the ground wire 18. Preferably, the wires which make up one or both the windings 19a, 19b of the magnetic circuit are not made of copper but of aluminium coated with electrically insulating material. It has in effect been found that the use of aluminium considerably reduces the transmission of electrostatic charges to the other parts of the apparatus 1 compared with the copper.

Figures 4 and 5 show in detail the structure of the core 10.

The core 10 comprises a laminated pack defined by a succession of metal plates 20, 21 fitted in parallel next to each other in a mutual contact relationship. The plates 20, 21 lie respectively in main planes and are next to each other along planes of mutual contact extending along an advancement direction of the flow in the duct 9, parallel to the above-mentioned main planes. In other words, the plates 20, 21 are arranged in a vertical position in the embodiment illustrated in the accompanying drawings .

In accordance with a preferred embodiment of the invention, the plates 20, 21 are made of two different materials. More specifically, there are drainage plates 20 and storage plates 21. The drainage plates 20 are made of ferrous material or other metallic material having electrical conductivity greater than that of the storage plates 21. The storage plates 21 are made of lead or other metallic material having specific weight greater than that of the drainage plates 20.

According to the invention, there is a different number of the two types of plates 20, 21 in the pack constituting the core.

In an embodiment illustrated in detail in Figure 4, the iron plates 20 are grouped together in groups "G" of seven plates each and the groups "G" are arranged in succession and separated from each other by a respective lead plate 21. In more detail, in this embodiment there are eight groups "G" of seven iron plates 20 each and seven lead plates 21 alternated with the above-mentioned groups "G".

In an embodiment of the core 10 shown in Figure 4, each iron plate 20 has thickness "si" equal to approximately 0.5 millimetres whilst each lead plate 21 has thickness "s2" equal to approximately 1 millimetre.

The pack of plates 20, 21 is wrapped externally by a metal net 22, preferably made of copper, which has a plurality of sharpened terminations 23 arranged on the main surface of extension of the net 22.

The sharpened terminations 23, like the tips 14, are immersed in the flow of electrostatic charge receiver fluid and their sharpened terminations promote the transmission of the electrostatic charges with the fluid .

Preferably, the apparatus 1 also comprises an absorber 24 of electrostatic charges, operatively interposed between the products 3 and the disperser 6. In this embodiment, the connection wire 5 has a first segment 5a which connects a first connection terminal 24a of the absorber 24 to the products 3 (and in particular to the above-mentioned metallic support structure 4), and a second segment 5b which connects a second connection terminal 24b of the absorber 24 with the core 10.

The absorber 24, shown more in detail in Figure 3, is designed to favour the removal of electrostatic charges from the products 3 being processed. The absorber 24 basically comprises a storage mass 25 made of lead or other material having specific weight greater than that of the product 3 and the support structure 4, and a drainage element 26 made of copper or other material having electrical conductivity greater than that of the storage mass 25. The drainage element 26 has, at the respective opposite ends, the two connection terminals 24a, 24b respectively engaged with the terminals of the first and second segments 5a, 5b of the connection wire 5. More specifically, the storage mass 25 and the drainage element 26, each made in the form of a continuous belt, are mutually coupled at respective exchange sides and are wound in the form of a cylindrical reel 27 according to a plurality of consecutive turns 27a. On opposite sides of the exchange sides, the storage mass 25 and the drainage element 26 have respective separation sides each spaced from the respectively adjacent turn 27a, if necessary with the interposing of a layer of insulation made of paper 28 or other dielectric material.

This invention is designed particularly for use in painting systems according to what is described above, so as to obtain an efficient dissipation of the electrostatic charges which tend to accumulate in the products being processed.

This does not exclude, obviously, the possibility of applying the innovative concepts proposed by the invention in any other circumstance where the elimination of electrostatic charges from an object is desired .

The invention achieves the preset aims.

In effect, it has been found that the architecture of the apparatus according to the invention, and in particular the structure with central core, tips subjected to a potential difference relative to earth and flow of air between core and tips improves the dissipation of the electrostatic charges relative to the existing solutions.

Moreover, the special embodiment of the core in a succession of packed plates makes the apparatus 1 easily adaptable to the use for removing electrostatic charges from various materials. In effect, it has been found that by varying the number and the reciprocal proportion of the iron and lead sheets an architecture is obtained which is able to optimise the ability of removing the electrostatic charges from diverse materials, such as for example, iron or wood.

In more detail, the specific configuration described is optimised for the dissipation of electrostatic charges in the painting of iron products whilst an increase in the number of iron plates for each group tends to optimise the dissipation of electrostatic charges in the painting of wooden products.

Claims

1. Apparatus for eliminating electrostatic charges from a body, comprising:

a disperser (6) of electrostatic charges set to generate a flow of an electrostatic charge receiver fluid;

at least one connection wire (5), operatively connected to said disperser (6) and connectable to a body (3) from which electrostatic charges are to be removed;

characterized in that said disperser (6) comprises:

- a core (10), connected to said connection wire (5) for receiving electrostatic charges from said body (3), and immersed in said flow of the electrostatic charge receiver fluid for releasing said electrostatic charges to said fluid,

- a plurality of tips (14) arranged around the core (10) and facing thereto in a manner such that said tips (14) are immersed in said flow of electrostatic charge receiver fluid; and

devices (17) for generating a potential difference between said tips (14) and a ground wire (18) .

2. Apparatus according to claim 1, wherein said core (10) comprises parallel metal plates (20, 21) fit next to each other in a mutual contact relationship.

3. Apparatus according to claim 2, wherein said metal plates (20, 21) are fit next to each other along planes of mutual contact which are extended along an advancement direction for said flow in the disperser (6) .

4. Apparatus according to claim 2 or 3, wherein the core comprises storage plates (21) sequentially alternated with drainage plates (20), wherein the storage plates (21) are made of metal material having specific weight greater than that of the drainage plates (20), and the drainage plates are made of metal material having electrical conductivity greater than that of the storage plates .

5. Apparatus according to any one of the preceding claims from 2 to 4, also comprising a metal net (22), preferably made of copper, wound around the core (10) and having a plurality of sharpened terminations (23) arranged on a predominant extension surface of said metal net ( 22 ) .

6. Apparatus according to any one of the preceding claims, wherein said tips (14) are connected with each other by at least one conductor bar (15) made of electrically conductive material, preferably aluminum.

7. Apparatus according to claim 6, wherein said tips (14) are made of titanium or another preferably metal material having greater resistivity than that of the conductor bar (15) .

8. Apparatus according to any one of the preceding claims, wherein said disperser (6) comprises:

- a load-bearing structure (7) having a tubular wall (8) defining a duct (9) therein, in which said core (10) is arranged, in a manner such that between the core (10) and the tubular wall (8) a substantially annular volume (11) is defined, said tips (14) being supported by said tubular wall (8), and

devices (12) for generating a flow of said electrostatic charge receiver fluid, set for generating an axial flow of said fluid in said annular volume (11) and along said tubular wall (8) .

9. Apparatus according to any one of the preceding claims, wherein said devices (17) for generating a potential difference between the tips (14) and the ground wire (18) comprise a magnetic circuit (19) having an inductor winding (19a) connectable to a power network and an induced winding (19b) having a first terminal electrically connected to the tips (14) and a second terminal electrically connected to the ground wire (18) .

10. Apparatus according to any one of the preceding claims, also comprising an electrostatic charge absorber (24), wherein said connection wire (5) has a first segment (5a), connected with a first connection terminal (24a) of the absorber (24) and connectable with a body (3) from which electrostatic charges are to be removed, and a second segment (5b) that connects a second connection terminal (24b) of the absorber (24) with said core (10) .

11. Process for eliminating electrostatic charges from a body, characterized in that it comprises the steps of:

- arranging an apparatus (1) according to any one of the preceding claims;

electrically connecting one end of said connection wire (5) to a body (3) from which electrostatic charges are to be removed or to a support structure (4) of said body ( 3 ) ;

generating a potential difference between the tips (14) and the ground wire (18);

- generating a flow of the electrostatic charge receiver fluid in a manner such that said flow hits the core (10) and the tips (14)