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(11) | EP 1 332 802 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Spray painting booth |
| (57) Spray painting booth provided with a chamber (6) for receiving the products to be
treated by means of paint spraying operations liable to generate the conventional
discharge fumes containing air and suspended particles of paint. Washing means (7)
for purifying the fumes by separating the air from the particles of paint are envisaged,
said means being equipped with a plant (8) for distributing a flushing liquid and
a tank (9) for collecting the liquid, which is arranged substantially at the bottom
of the support structure (2) of the booth (1). The fumes are channelled into an air
conveying duct (11), which extends from a first opening (12) communicating with the
chamber (6) to a second opening (13) for expulsion from the booth (1), by means of
suction means (14) mounted on the support structure (2) and operationally associated
with the washing means (7). The duct (11) has a front wall (15) with a first top edge
(18) and first bottom edge (19), which is arranged so as to delimit the spray painting
booth (6) at the rear and is covered by a first layer of liquid (16) produced by means
of overspill from a small tank (17) arranged opposite the first top edge (18) and
fed by the distribution plant (8). The abovementioned first bottom edge (19) delimits
the first opening (12) together with the free surface of the liquid contained in the
collection tank (9) at the bottom of the booth (1). |
[0001] The present invention relates to a spray painting booth intended to be advantageously used for spraying paints or pigments onto the surface of any type of product to be sprayed, such as for example furniture, plastic objects, car bodywork, leather articles or other objects.
[0002] The booth in question is particularly suitable for limiting the dispersion, in the external environment, of the particles of paint contained in the fumes produced by the painting operations.
[0003] At present, as is known, the booths of the abovementioned type are generally provided with a hermetically closed or substantially open painting chamber inside which the products to be painted are placed. From a work station situated in front of the chamber, special guns spray the paint onto the products which are usually supported on movable carriages or belt or roller conveyors.
[0004] The chamber has a front wall which faces the guns and which is preferably covered by a layer of water (or other solvent solution) which, flowing from the top downwards, conveys with it most of the particles of paint which are propelled into the air by the guns and which do not reach the object to be painted.
[0005] Normally, the booths are also provided with suction means for conveying outside the chamber all the fumes produced by the painting operation.
[0006] During its travel path, the sucked-in air is forced to pass through several washing chambers with jets of water and/or cascades of water in which it is further purified of the particles of paint which are still suspended. All the washing water is then made to flow into a single collection tank arranged at the bottom of the booth, from where the waste paint is then removed. The washing plant usually forms a closed cycle in which it is therefore required to restore only the evaporated water.
[0007] Obviously the air expelled from the booth and introduced into the atmosphere must not pollute the environment and therefore must contain a quantity of paint particles able to satisfy all the existing regulations governing purification. For example, some regulations may stipulate that the abovementioned quantity of particles introduced into the atmosphere must be less than 0.3 mg/m3.
[0008] It is known, in fact, that excessive quantities of paint particles introduced into the atmosphere may be highly polluting, toxic and inflammable and therefore, in short, extremely dangerous for the population and the environment.
[0009] As well as the booths with an internal purification system of the washing water type mentioned above, other spray painting booths are also known where purification of the fumes is performed by means of special external filtration devices able to remove the polluted air from the inside of the painting chambers and purify it of the suspended particles of paint before re-introducing it into the atmosphere.
[0010] This latter solution, although it is operationally effective, has proved to be not entirely convenient from a cost point of view, in particular if considered in relation to the usually sole requirement for booths to purify the air only of the suspended particles in order to comply with the existing regulations governing harmful emissions.
[0011] Therefore, hitherto spray painting booths provided with internal purification systems of the washing water type have been developed more extensively. At present, in accordance with the art known hitherto, numerous different constructional forms of booths able to purify the painting fumes using washing water have been developed.
[0012] Frequently, these booths of the known type force the air with the paint particles to pass through series of drawers containing a plurality of spheres which are wetted by a stream of water and which, vibrating very rapidly upon coming into contact with the air, break up the flow thereof and therefore produce turbulence which is able to release the suspended particles into the water.
[0013] US patent No. 2,385,077 describes a spray painting booth provided with a first front wall which is wetted with a layer of water and conveys the air sucked by a ventilator inside a duct through an opening formed at the top of the booth.
[0014] This opening has, arranged above it, a first water distribution element with several nozzles which performs initial washing of the air. The same water emitted by this distribution element feeds the layer of water on the first wall by means of a first cascade which crosses the opening, purifying the air which is forced to pass through it.
[0015] The air then continues inside the duct delimited by the rear surface of the same front wall and by a second substantially vertical wall on which a second layer of water produced by the same first distribution element is provided. The second wall terminates at the bottom above the collection tank with a second opening where a second cascade is produced, said cascade again being passed through by the air.
[0016] Thereafter the air reaches a section of the duct delimited by the second wall and by the rear wall of the booth, where it encounters the water jets which are generated by a second distribution element and capture the remaining particles of paint still suspended in the air flow.
[0017] The air at this point, before being expelled from the booth, is then made to pass through droplet screening barriers in order to prevent the water being expelled outside together with the air.
[0018] The spray painting booth of the known type described briefly hereinabove has proved in practice to have certain drawbacks.
[0019] First of all, the opening of the duct arranged in a high position does not allow optimum suction of the painting fumes which, as is well known, being weighed down by the presence of paint particles inside them, tend to move downwards and not upwards.
[0020] Secondly, the layer of water which is formed on the front wall of the booth as a result of the water sprayed by the first distribution element does not have an optimum distribution.
[0021] Moreover, it has been found that the air leaving the booth still has an excessively large quantity of paint particles such that it does not satisfy entirely the more stringent regulations which govern the emission of paint fumes.
[0022] A further disadvantage of the constructional form described in US patent No. 2,385,077 consists in the fact that it requires droplet screening means to prevent expulsion of water outside.
[0023] As is known, the constructional form described and claimed in US patent No. 4,096,066, although improving the distribution of water on the front wall of the booth and although improving the suction of the fumes, removing them via an opening arranged especially at the bottom of the booth, does not allow the quantity of paint particles present in the fumes to be reduced in a sufficiently effective manner.
[0024] The main object of the present invention, therefore, is that of eliminating the drawbacks of the booths of the known type mentioned above, by providing a spray painting booth which is able to achieve, by means of suitable washing means, a drastic reduction in the quantity of paint particles present in the painting fumes before they are expelled into the external environment.
[0025] Another object of the present invention is that of providing a spray painting booth which allows the harmful emissions introduced into the environment to be controlled in such a way as to satisfy the existing regulations in this area.
[0026] A further object of the present invention is that of providing a spray painting booth which allows the expulsion of fumes containing a low concentration of water vapour or residual moisture.
[0027] A further object of the present invention is that of providing a spray painting booth which is constructionally simple and low-cost and operationally entirely reliable.
[0028] These and other objects are all achieved by the spray painting booth in question which comprises a support structure resting on the ground, a painting chamber delimited by the support structure and intended to receive products to be treated by means of paint spraying operations liable to generate discharge fumes containing air and suspended particles of paint, and washing means for purifying the fumes produced inside the chamber by separating the air from the paint particles, the abovementioned washing means being provided with a plant for distributing a flushing liquid, a tank for collecting the liquid, arranged substantially at the bottom of the support structure, an air conveying duct delimited by walls and extending from a first opening communicating with the chamber to a second opening for expulsion from the booth, and suction means mounted on the support structure, operationally associated with the washing means and able to remove the fumes from the painting chamber and convey them through the duct outside of the booth.
[0029] According to the invention, the booth is characterized in that the duct has a front wall with a first top edge and first bottom edge, which is arranged so as to delimit the painting chamber at the rear and is covered by a first layer of liquid produced by means of overspill from a small tank which is arranged opposite the first top edge and which is fed by the distribution plant, the first bottom edge delimiting the first opening together with the free surface of the liquid contained in the collection tank.
[0030] The technical features of the invention in accordance with the abovementioned objects may be clearly determined from the contents of the claims provided below and the advantages thereof will emerge more clearly from the detailed description which follows, with reference to the accompanying drawings which shows a purely exemplary and non-limiting embodiment thereof, in which:
FIG. 1 shows a schematic front view of the booth according to the present invention;
FIG. 2 shows a first schematic side view of the booth according to Fig. 1;
FIG. 3 shows a second schematic side view of the booth according to Fig. 1 with some parts removed so that other parts may be seen more clearly;
FIG. 4 shows an enlarged detail of the booth, relating to the plant for distribution of a flushing liquid;
FIG. 5 shows a detail of the distribution plant according to Fig. 4.
[0031] With reference to the attached drawings, 1 denotes in its entirety the spray painting booth according to the present invention.
[0032] In accordance with the example of embodiment shown in the accompanying figures, a spray painting booth of the open type has been described below, but, without departing from the scope of the present patent, said booth may also be of a different known type, such as, for example, a booth of the closed or sealed type.
[0033] With reference in particular to Figs. 2 and 3, the booth 1 has a support structure 2 resting on the ground with side walls 3, bottom wall 4 and awning 5.
[0034] The support structure 2 delimits, in a usually central position, a painting chamber 6 which is able to receive the products (not shown in the figures) to be treated with paint spraying operations, or similar products, from an adjacent work station.
[0035] These products, consisting for example of furniture, car body parts, plastic objects or the like, are transported into the chamber 6 in an entirely conventional manner by means of special conveyor belts, supported on rotating rollers, carriages or other systems.
[0036] The abovementioned painting operations are conventionally performed by means of automatic spraying devices or by means of an operator equipped with a special gun for spraying paint.
[0037] As is known, in any case, only a part of the paint which has been sprayed reaches the surface of the product to be treated, while the remaining part is inevitably dispersed into the air inside the chamber 6. Below we shall indicate by the term "discharge fumes" the mixture of air and suspended particle of paint, produced by these painting operations.
[0038] In order to cleanse the fumes of the paint particles before re-introducing them into the atmosphere, the booth 1 comprises suitable washing means which have been generally denoted by 7 in the accompanying figures.
[0039] In greater detail, these means comprise a plant 8 for distributing a flushing liquid generally consisting simply of water, a tank 9 for collecting this liquid, arranged in the bottom 10 of the support structure 2 and an air conveying duct 11 formed by various sections, as will be better explained below.
[0040] The duct 11 extends essentially from a first opening 12, able to allow communication with the chamber 6, to a second opening 13, able to allow expulsion of the fumes from the booth 1.
[0041] As will be described more clearly below, it is envisaged that the duct 11 is provided with at least one wall over which a layer of liquid passes and that it is intercepted by several cascades of liquid in order to wash the air of the particles of paint.
[0042] The booth 1 is also provided with suction means 14-per se are entirely conventional - which consist for example of a ventilator mounted on the support structure 2 above the awning 5 and which are operationally associated with the washing means 7 so as to wash the fumes. More clearly the ventilator 14 sucks the fumes from the painting chamber 6, forcing them to pass through the duct 11 so that they undergo cleaning with the flushing liquid, performed by the washing means 7.
[0043] According to the novel idea, the invention envisages that the duct 11 is provided with a front wall 15 delimiting the painting chamber 6 at the rear and covered on the side directed towards the said chamber 6 by a first layer 16 of liquid. The latter is obtained by means of overspill from a small tank 17 fed by the distribution plant 8 and arranged opposite a first top edge 18 of the front wall 15.
[0044] The front wall 15 also has a first bottom edge 19 which is positioned substantially at the bottom of the booth 1 so as to delimit and define with the free surface of the liquid contained in the collection tank the first opening 12.
[0045] Therefore, the fumes sucked in by the ventilator 14 are forced to pass initially through the first opening 12 via which they enter into the conveying duct 11.
[0046] The first layer of liquid 16 which passes over the front wall 15, descending from the small tank 17, produces, across the first opening 12, a first cascade 20 which intercepts the flow of fumes, resulting in initial washing thereof.
[0047] The product to be treated is arranged in between the spraying station and the front wall 15 and therefore most of the sprayed paint which does not reach the product directly continues its path, falling onto the first layer of liquid 16 which flows over the said front wall 15.
[0048] The remaining part of paint contained in the fumes which does not reach the product is sucked in by the ventilator 14 through the first opening 12, therefore undergoing, as mentioned, initial washing by means of the first cascade 20.
[0049] In accordance with the example of embodiment shown in the accompanying figures, the conveying duct 8 is composed of a first section 21 for conveying the fumes upwards, which is connected in succession to a second section 22 for conveying the fumes downwards, which is connected in turn and in succession to a third section 23 for conveying the fumes upwards. All of the abovementioned sections are arranged preferably in the vertical direction.
[0050] An intermediate wall 24 with a second top edge 25 and second bottom edge 26, and a rear wall 27 with a third top edge 28 and third bottom edge 29, also define the abovementioned sections.
[0051] In greater detail, the intermediate wall 24 separates the first section 21 for conveying the fumes upwards, from the second section 22 for conveying the fumes downwards, and for this purpose the second bottom edge 26 of the abovementioned wall 24 is immersed with a first portion 60 inside the collection tank 9. The rear wall 27 separates the second section 22 for conveying the fumes downwards from the third section 23 for conveying the fumes upwards and is arranged so that its bottom edge 29 delimits, together with the free surface of the liquid contained in the collection tank 9, a communication port 50 between the abovementioned two sections 22 and 23 of the duct 11.
[0052] Advantageously, the liquid distribution plant 8 is connected to a plurality of nozzles 30 which are distributed in an equidistant manner along a pipe 31 arranged opposite the top edge 25 of the intermediate wall 24.
[0053] As can be seen in the attached Fig. 5, the jets of the nozzles 30 intersect each other so as to create a barrier capable of intercepting in an uninterrupted manner the fumes passing into the duct 11 so as to purify them of the suspended particles of paint.
[0054] Advantageously, an additional pipe 131 provided with nozzles 130 for further purifying the fumes may also be arranged inside the first section 21 of the conveying duct 8 (see illustration in broken lines in Figure 3).
[0055] This helps reduce or prevent in particular the accumulation of paint on the walls of the duct 8 and in particular on the duct 24.
[0056] In accordance with a further constructional feature of the present invention, the first section 21 and the second section 22 of the duct 11 are connected together by means of a profiled part 32 having a substantially U-shaped form which is symmetrical with respect to the plane defined by the location of the intermediate wall 24 and is centred around the abovementioned pipe 31 and has its concavity directed downwards. As can be seen in the attached Figs. 1 and 2, the abovementioned profiled part 32 is intended to contain the fluid jets emitted by the nozzles 30.
[0057] The sprayed fluid which strikes the abovementioned shaped section 32 is divided into two streams which then flow down the two inner sides 33 until they reach the first and the second section of the duct 11, producing across the ends 34 of the latter a second cascade 35 and a third cascade 36, respectively. These cascades therefore intercept the flow of the fumes in another two sections of the duct 11, resulting in a further reduction in the quantity of particles suspended in the air.
[0058] The two streams of fluid produced by the jets of the nozzles 30 which are channelled into the two abovementioned sections of the duct 11 form respectively a second layer of liquid 37 on the intermediate wall 24 inside the second section 22, a third layer of liquid 38 on the intermediate wall 24 inside the second section 22, and a fourth layer of liquid 39 on the rear wall 27 again inside the second section 22.
[0059] This latter layer of liquid 39, once it reaches the communication port 50, produces a fourth cascade 40 for final washing of the fumes.
[0060] An opening 51 is provided above the awning (see Fig. 2) so as to allow the through-flow of a stream of compensating air (indicated by the arrow) in order to prevent pressure drops occurring inside the booth 1.
[0061] Finally, it should be noted that, in order to allow easier inspection of the duct 11, the front wall 15 is provided with a movable bottom section 41 which can be operated, by means of a special actuator 43, so as to be displaced between a raised position 44, where it is possible to perform inspection and maintenance operations, and a lowered position 45, where the booth 1 is in the operative condition.
[0062] In Fig. 4 the plant for distributing the flushing fluid is denoted in its entirety by 8. Said plant comprises essentially two delivery pipes 46 and 46' which are fed by two corresponding pumps 47, 47' which draw the liquid from the collection tank 9 via special mechanical filters 48, 48' and convey it respectively to the small tank 17 and to the pipe 31. In order to prevent any risk of blockage of the nozzles 30, suitable filtering means 49 are arranged upstream of the pipe 31.
[0063] From an operational point of view, all the remnants of the particles removed from the fumes converge into the collection tank 9 and form a sludge which remains confined, in a floating condition, inside a lateral partition of the said tank 9.
[0064] Advantageously, the fume washing system described hitherto allows, on the hand, the expulsion into the atmosphere of a very small quantity of particles of paint and, on the other hand, the emission of air with a very low moisture content or very few suspended droplets of water. This results, among other things, in the possibility of savings as regards the moisture recovery systems which are frequently used in the spray painting booths of the known type and are designed to expel water which otherwise would have to be frequently compensated for.
1. Spray painting booth comprising:
- a support structure (2) resting on the ground;
- a painting chamber (6) delimited by said support structure (2) and intended to receive products to be treated by means of paint-spraying operations liable to generate discharge fumes containing air and suspended particles of paint;
- washing means (7) for purifying said fumes produced inside said chamber (6) by separating the air from the paint particles, said washing means (7) being provided with a plant (8) for distributing a flushing liquid, at least one tank (9) for collecting said liquid, arranged substantially at the bottom of said support structure (2), and at least one air conveying duct (11) delimited by walls and extending from a first opening (12) communicating with said chamber (6) to a second opening (13) for expulsion from said booth (1) ;
- suction means (14) mounted on said support structure (2), operationally associated with said washing means (7) and able to remove said fumes from said painting chamber (6) and convey them by means of said duct (11) outside of said booth (1);
- characterized in that said duct (11) has a front wall (15) with a first top edge (18) and first bottom edge (19), which is arranged so as to delimit said painting chamber (6) at the rear and is covered by a first layer of liquid (16) produced by means of overspill from a small tank (17) which is arranged opposite said first top edge and which is fed by said distribution plant (8), said first bottom edge (19) delimiting said first opening (12) together with the free surface of the liquid contained in said collection tank (9).
2. Booth according to Claim 1, characterized in that said conveying duct (11) is respectively composed, in succession, of at least one
first section (21) for conveying the fumes upwards, at least one second section (22)
for conveying the fumes downwards and at least one third section (23) for conveying
the fumes upwards.
3. Booth according to Claim 2, characterized in that said conveying duct (11) has an intermediate wall (24) with a second top edge (25)
and second bottom edge (26), which is able to separate said first section (21) for
conveying the fumes upwards from said second section (22) for conveying the fumes
downwards, said second bottom edge (26) being immersed with a portion (60) inside
said collection tank (9) underneath the free surface of the liquid.
4. Booth according to Claim 2, characterized in that said conveying duct (11) has a rear wall (27) with a third top edge (28) and third
bottom edge (29), which is able to separate said second section (22) for conveying
the fumes downwards from said third section (23) for conveying the fumes upwards,
said third bottom edge (23) delimiting together with the free surface of the liquid
contained in said collection tank (9) a communication port (50) between said second
section and said third section (22, 23) of the duct (11).
5. Booth according to Claim 1, characterized in that said first layer of liquid (16) produces, across said first opening (12), a first
cascade (20) capable of intercepting the flow of said fumes.
6. Booth according to Claim 3, characterized in that it comprises a plurality of nozzles (30) which are arranged opposite the top edge
(25) of said intermediate wall (24) and are able to emit jets of fluid inside said
duct (11), capable of purifying the fumes of the suspended particles of paint.
7. Booth according to Claim 6, characterized in that said first section (21) for conveying the fumes upwards and said second section (22)
for conveying the fumes downwards are connected together by means of a profiled part
(32) with the concavity directed substantially downwards, intended to receive the
jets of fluids emitted by said plurality of nozzles (30) and divide the consequent
flow of liquid produced by them into two separate streams, channelling them into said
first and second sections (21, 22) respectively.
8. Booth according to Claim 7, characterized in that the two streams of the fluid flow produced by the nozzles (30) generate, as a result
of the shape of the profiled part (32), at least one second cascade (35) and at least
one third cascade (36) able to intercept the flow of fumes at the terminal end of
said first section (21) for conveying the fumes upwards and the leading end of said
section (22) for conveying the fumes downwards.
9. Booth according to Claim 6, characterized in that said jets of fluid generate at least one second layer of liquid (37) over said intermediate
wall (24) inside said first section (21) for conveying the fumes upwards and at least
one third layer of liquid (38) and one fourth layer of liquid (39) over said intermediate
wall (24) and over said rear wall (27) inside said second section (22) for conveying
the fumes downwards, respectively.
10. Booth according to Claim 7, characterized in that said profiled part (32) has a substantially symmetrical shape with respect to the
plane defined by the location of said intermediate wall (24).
11. Booth according to Claim 9, characterized in that said fourth layer of liquid generates a fourth cascade (40) across said communication
port (50).