Device for cleaning a conveyor belt

Abstract: The vessel or vessels (7, 7', 7") in contact with the solvent used for cleaning the conveyor (T) are designed and arranged in such a way that they are enclosed, and the portion of conveyor belt which is wetted with solvent is also isolated by suitable means from contact with the external environment containing the ventilation air of the painting chamber. In a preferred solution, where rotating scraping cylinders (1, 5) are used, the solvent vessel (7, 7', 7") is placed in such a way that it is enclosed by the two successive cleaning cylinders, by the portion of conveyor belt which runs between these cylinders, and by its lateral walls which are as close as possible to the said cylinders and to the said portion of the conveyor belt. At the end of each painting cycle, clean solvent is made to flow into the solvent vessel and the cleaning cylinders and the conveyor belt of the painting machine are temporarily kept active so that they clean themselves.

Description: The present invention relates to a device for removing a fluid substance from a conveyor belt closed on itself to form a loop and running around at least two end rollers, at least one of which is powered. In particular, the invention relates to conveyor belts of machines and installations for painting, colouring or impregnation processes, described more simply as "painting" in the following text, which make the articles to be treated pass through a chamber for spraying the fluid treatment substance, for example the paint. The conveyor belt has two branches: an upper, outgoing branch, on which are placed the articles to be treated and which is struck by the sprays of paint, and a lower return branch, which is splashed with paint and which has to be cleaned before it returns to the upper level, to enable the conveyor to receive new articles to be painted and to enable the removed paint to be recovered. The devices in use at the present time for cleaning the belt comprise, in the first place, means for wetting the surface to be cleaned with solvent and subsequent means for removing the paint fluidized by the solvent, by a scraping or shaving operation, for example by means of fixed scraper blades or by means of rotating cylinders. Figure 1 of the attached drawing shows an example of a cleaning device with double reverse cylinders, of the type described in European patent EP 425969 held by the applicant. In this figure, the letter T indicates the final part of the conveyor of the painting machine, with its upper branch T1 and lower branch T2 running around the roller R. The cleaning device comprises a first preliminary cleaning cylinder 1, opposite and parallel to the roller R, which operates in contact with the branch T2 of T, and is made to rotate by suitable means in such a way that its periphery moves in the opposite direction to that of the branch T2, to carry out an effective action of scraping this branch and to remove from it the recovered paint which is then readily removed from the cylinder 1, by the scraping edge 102 of a trough 2 in which the recovered paint is collected and then removed and recycled by suitable means. The cylinder 1 is partially immersed in a vessel 3 containing solvent, so that the cylinder cleans itself and carries a film of the solvent into the area of contact with the lower branch T2 of T, to wet the area from which the paint is removed, and to cause the said branch T2 to leave the cylinder 1 with a small amount of solvent which has the function of softening any residual traces of paint. Downstream from the preliminary cleaning cylinder 1 there is a finishing cylinder 5, parallel to the cylinder 1 and rotating in the same direction, which operates in contact with the branch T2 of T to remove any residual traces of paint and the film of solvent initially transferred on to T2. The paint and solvent recovered by the cylinder 5 are removed from it by the scraping edge 106 of a trough 6, in which the recovered fluid material is collected, and is then recycled together with that collected by the trough 2. The number 4 indicates idle counter-rollers which can if necessary be provided in the various positions in which the cleaning means exert a thrust against the branch T2 of T, in order to oppose this thrust and make the action of the cleaning means more efficient. In a system for cleaning the belt T of the type illustrated in Figure 1, or in other known systems which comprise a succession of belt scraping units and open-topped vessels for wetting the belt with solvent and for collecting the recovered paint, the following drawbacks are encountered: a) high evaporation of solvent from the said open-topped vessels and from the surface of the conveyor to which the solvent is applied. In this respect it should be pointed out that the whole of the cleaning equipment is located in a lower extension of the painting chamber, subject to the action of ventilation means which draw air from this chamber and discharge into the atmosphere through means of suppressing polluting products. The large surfaces affected by the solvent and by the ventilation air flow therefore cause a considerable evaporation of the solvent, which consequently becomes even less effective in its specified function; b) it is necessary to empty and clean or replace periodically the vessel 3 of solvent under the cylinder 1 and the solvent recovery trough 6, since the recovered paint or the residue of the paint-contaminated solvent tend to accumulate on their walls; c) whenever a painting cycle ends, the cylinders 1 and 5 have to be cleaned manually by the operators, at the cost of considerable inconvenience for them. The quality of cleaning also depends on the ability and frequently on the scrupulousness of the operators, which are not always constant factors. Document US 5 649 616 A discloses a device for cleaning a conveyor belt, which conveyor belt runs around a roller and includes an upper active branch and a lower return branch, said device being used to remove substances, such as paint, deposited on the conveyor belt and comprising at least one vessel containing a solvent for the substances and distributing means to distribute the solvent onto at least one portion of the return branch of the conveyor to soften the substances deposited on the conveyor, a first scraping unit and a second scraping unit in succession along the return branch for scraping and cleaning the return branch to remove the substances with the solvent for subsequent recovery and removal and enclosing means for enclosing in a closed environment which is isolated from the external environment the portion of the return branch of the conveyor and associated parts of said first and second scraping units in contact with the solvent, in order to prevent or limit the evaporation and dispersion of the solvent in the external environment. According to the invention, there is provided a device of the type disclosed above, further comprising the characterizing features of claim 1. Further characteristics of the invention, and the advantages derived therefrom, will be made clear by the following description of some preferred embodiments of the invention, illustrated purely by way of example and without restrictive intent in the figures of the attached sheets of drawings, in which: Fig. 1 shows schematically and in lateral elevation the known composite cleaning device described in the introductory part of the present description; Figs 2, 3 and 4 show schematically and in lateral elevation the different embodiments of a device according to the invention, which carries out the cleaning in successive preliminary cleaning and finishing stages; Figs. 5 and 6 show schematically and in lateral elevation some possible composite solutions for the device according to the invention. It is preliminarily to be noted that the embodiment of Figure 2 does not make part of the present invention. In Figure 2, the letter T indicates the conveyor to be cleaned, running around the downstream roller R which, in the example in question, again rotates in a clockwise direction, in the same way as the preliminary cleaning cylinder 1, which operates in contact with the return branch T2 of T, parallel and in opposition to R, to remove the paint from T2 and to discharge it into the recovery and removal trough 2, as in the known art. The lower part of the trough 2 is provided with a hole 202 connected to the known means of removing the recovered paint. According to the invention, the trough 2 can advantageously be provided with a top cover 302 which limits the exposure of the recovered paint to the air. The cover 302 can touch the cylinder 1 with its side walls, but does not touch this cylinder with its front transverse edge. Immediately downstream from the preliminary cleaning cylinder 1, there is a vessel 7 provided with a U-shaped front edge 107, which is made from such material and shaped in such a way that it interacts in a sealed way with the lateral surface of the cylinder 1, and which is kept in contact with this cylinder by suitable means, the said vessel 7 being provided with lateral and transverse containing walls 207, 307 which are integral with each other and with the said sealing edge 107 and having a height such that they are as close as possible to the branch T2 of T, so that the vessel 7 in question is essentially closed by the conveyor T. A scraper blade 8 of suitable material is provided on the upper edge of the transverse wall 307 of the vessel 7, and is pressed by suitable means against the branch T2 to be cleaned, which is controlled if necessary by opposing rollers 4 of a known type. Solvent 9 is made to flow into the vessel 7 and is kept at a predetermined level, the said vessel being provided for this purpose, in its opposite lateral walls 207, with corresponding holes 10, one of which is connected to solvent delivery means, while the opposite hole is connected to a discharge channel. By rotating in contact with the solvent in the vessel 7, the cylinder 1 transfers a film of this solvent to the branch T2, to soften any residues of paint which are then removed by the scraper blade 8 and fall into the flow of solvent 9 by which they are removed. Clearly, the described solution resolves one of the problems of the known art, since the solvent vessel 7, the cylinder 1 and the portion of belt T2 in contact with the solvent are form an enclosure for each other to limit the evaporation of the said solvent. To prevent the dispersion of any leaks of product from the sealing edge 107 of the vessel 7, and therefore to enable the device to be made without highly precise tolerances, an auxiliary trough 11 can be arranged under the vessel 7 so that the edges of its walls can interact in contact with the vessel 7 and close to or in contact with the cylinder 1, but without touching this cylinder at least with its front transverse edge 111, to limit the amount of exposure of its internal parts to the air. The trough 11 can usefully be utilized as a channel for the return of the solvent discharged from the vessel 7, replacing the channel which makes the return available on the same side of the device as that on which the solvent delivery means operate. Should any traces of paint tend to pass beyond the scraper blade 102 of the trough 2, they would be recovered by the scraping carried out by the edge 107 on the cylinder 1 and would fall into the auxiliary trough 11. In the solution in Figure 3, the preliminary cleaning cylinder 1 is used, with the corresponding sufficiently enclosed trough 2, and a finishing cylinder 5 similar to that in Figure 1 is used in place of the preceding vessel 7, with the difference that the two cylinders are now placed in contact with each other, in such a way that, when the upwardly diverging space between the cylinders is enclosed with suitable lateral walls 207', and the walls 207' are designed in such a way that they essentially come into contact with the branch T2 of T, this space can be sealed from the ventilation air and it is possible to form a vessel 7' sealed with respect to the external environment, a correct quantity of solvent 9 being made to flow into this vessel to wet both cylinders 1 and 5 and the branch T2 of T running above, as is required for proper cleaning of the return branch of the conveyor T. The walls 207' of the vessel 7' are provided with holes 10 for the delivery and discharge of the solvent, which can return to the side of the device on which the delivery means operate, through a return channel parallel to the cylinders, or through an auxiliary trough 11' which is located in the downwardly diverging space between the cylinders 1, 5, and which preferably scrapes the cylinder 5 with its edge 111', but which does not touch the cylinder 1 with its edge 111. The trough 11' can operate with its lateral walls 211' in contact with the cylinders 1 and 5, so that it is essentially enclosed with respect to the external air flow. In the solution in Figure 3, as in that of Figure 2, the auxiliary trough 11' can recover any leaks of product from the upper vessel 7', or residues of paint which pass beyond the trough 2. The cylinders 1 and 5 can rotate at equal or different speeds. The solution of Figure 4 differs from that of Figure 3 in that the cylinders 1 and 5 are placed apart from each other and that a driven cylinder 12 is placed between them and touches both of the said cylinders with a seal. Thus the solvent vessel 7" is completely closed at the bottom. To recover any residues of paint from the cylinders 5 and 12 and any leaks of product from the vessel 7", the auxiliary trough 11" can be placed under the cylinders 5 and 12, with both of its edges 111" scraping the cylinders, and can also be used as a channel for the return of the solvent which is made to flow into the said vessel 7". To achieve thorough cleaning of the return branch T2 of the conveyor T, it is possible to use of the described devices, followed by one or more of the known cleaning devices described, for example, in the patent EP 448080 held by the applicant; or two devices of the type in question can be used, in series with each other. It is possible to use cleaning cylinders or scraper blades in the second device which have different characteristics of roughness from those of the cylinders or scraper blades of the first device, to improve cleaning in the case of products which are particularly difficult to recover. Figure 5 shows, by way of example, how the device of Figure 3 can be provided with a multiple cleaning function, by placing in contact with the branch T2 of the conveyor and with the cylinder 5 a similar parallel cylinder 5', rotating in the same direction. A solvent vessel 7' can be placed between the upper parts of the cylinders 5, 5' and an auxiliary trough 11' can be placed between the lower parts, these devices being identical, respectively, to the devices 7' and 11' described above. Figure 6 shows how a multiple cleaning device can be formed by combining the solutions of Figure 3 and Figure 2. A vessel 7, with an auxiliary trough 11 if necessary, identical to those described with reference to Figure 2, are placed adjacent to the cylinder 5 of a device such as that of Figure 3. It is to be understood that these considerations are also applicable to the device of Figure 4, which can be made into a multiple cleaning device by the addition of parts 12, 5, 7", 11" of the said device of Figure 4 and/or of parts 7, 11 or 5, 7' respectively of the device of Figure 2 or the device of Figure 3. The cylinders of the described devices can be made from hard material, for example chromium-plated steel, or from relatively elastic material, for example rubber, and the selection of the material may depend on the acceptable friction between the cylinders and the branch T2 of the conveyor, or may depend on the seal required between the cylinders, or on specific requirements. In addition to the advantages of containing the evaporation of the solvent used, it should be pointed out that, when the painting machine or installation is stopped, it is possible with this invention to start a stage of self-cleaning of the described devices, by keeping them temporarily active, together with the conveyor T, and pumping clean solvent into the vessels 7, 7', 7". At the end of the cleaning cycle, the vessel 7 in the device of Figure 2 can be replaced if necessary, together with any auxiliary troughs 11, 11', 11" if these are not used for the return of the solvent. Clearly, the self-cleaning of most of the components of the described devices also simplifies the necessary maintenance of the machine or installation at the end of each operating cycle.

Claims: Device for cleaning a conveyor belt (T), which conveyor belt runs around a roller (R) and includes an upper active branch (T1) and a lower return branch (T2), said device being used to remove substances, such as paint, deposited on the conveyor belt and comprising at least one vessel containing a solvent for the substances and distributing means to distribute the solvent onto at least one portion of the return branch of the conveyor to soften the substances deposited on the conveyor, a first scraping unit (1) and a second scraping unit (5) in succession along the return branch (T2) for scraping and cleaning the return branch to remove the substances with the solvent for subsequent recovery and removal and enclosing means for enclosing in a closed environment which is isolated from the external environment the portion of the return branch of the conveyor and associated parts of said first and second scraping units in contact with the solvent, in order to prevent or limit the evaporation and dispersion of the solvent in the external environment, characterised by the fact that a) the first and the second scraping units of the return branch of the conveyor comprise respective first (1) and second (5) cylinders which are parallel to each other and to the roller (R) of the conveyor, b) the first cylinder (1) is opposite to the roller (R), c) the peripheries of the first and second cylinders (1, 5) rotate in the opposite direction to that of the return branch (T2) of the conveyor and touch the said return branch to remove substances therefrom, d) a scraper blade (102) is provided to scrape removed substances from the first cleaning cylinder (1) and to transfer then by gravity into a recovery and removal trough (2), e) the peripheries of said first and second cylinders (1, 5) are positioned close to each other, and f) the space between the first and second cylinders is closed upwardly by the return branch (T2) of the conveyor, is closed downwardly either by means of said cylinders (1, 5) in contact with each other or by means of a third cylinder (12) placed between them and in contact with them, and is closed laterally by walls (207', 207") which form a seal with the said first and second cylinders (1, 5) and which walls are arranged so that they form an enclosure with the said return branch (T2) of the conveyor such that said space forms a vessel (7', 7") which is isolated from the external environment and into which the solvent (9) required for the process of cleaning the conveyor is made to flow. Device according to claim 1, characterised in that the peripheries of said cylinders (1, 5) are in contact with each other to close the space downwardly, said contact being such as to allow the said cylinders to counter rotate the one with respect to the other. Device according to Claim 2, characterized in that it further comprises, under the solvent vessel (7'), an auxiliary trough (11') having its transverse rear edge (111') in contact with the second cylinder (5) and its transverse front edge (111) close to the first cylinder (1), to collect any leaks of solvent from the upper vessel (7') and any residues of paint remaining on the said cylinders. Device according to Claim 1, characterized in that the said cylinders (1, 5) are positioned close to but spaced from each other and a third cylinder (12) is placed between them and in contact with them and is rotated by the said first and second cylinders, the space between the three cylinders being closed downwardly by the said third cylinder (12). Device according to Claim 4, characterized in that it further comprises, under the area of contact between the second scraping cylinder (5) and the intermediate cylinder (12), an auxiliary trough (11") whose transverse edges (111") come into contact with the cylinders, to collect any leaks of solvent from the upper vessel (7") and any residues of paint remaining on the cylinders. Device according to Claim 3 or 5, characterized in that the said auxiliary troughs (11', ', 11 ") can be used as channels for the return of the solvent made to flow into the upper vessels (7', 7").

Inventors: DOVADOLA MASSIMO, FRANZONI LUIGI, DOVADOLA, MASSIMO, FRANZONI, LUIGI
Applicants: CEFLA COOP, CEFLA SOC. COOP. A R.L.
Application year: 2001
Main classification: B65G45
IPC codes: B65G45, B05B15