Backaround Art Known systems for the surface treatment of pieces such as metal pieces comprise a series of tanks containing baths, for example, electrolytic or chemical baths, arranged in succession in a manner such that the pieces coming out of one bath are immersed in the next bath. For processes for cleaning pieces, baths, for example, degreasing baths, washing baths, pickling baths, etc., are arranged in succession.

For electroplating processes, nickel-plating baths, galvanizing baths, or baths for similar processes for the surface application of metallic coatings are provided in addition to cleaning baths.

In order to immerse the pieces to be treated in the series of baths provided for the treatment, the pieces are first placed in containers which are then moved from one tank to another by means of overhead transfer devices which immerse the containers in the various baths and remove them therefrom according to the predetermined cycles of the process.

However, known transfer devices have the disadvantage of requiring a large amount of space since the containers can be moved by the overhead devices from one tank to another only if the tanks are arranged adjacent one another, generally at a single level or in a single working plane. Moreover, the insertion of the pieces to be treated in the containers and their removal therefrom

upon completion of the treatment take place manually so that operators are required for these operations.

The success of the treatment on these pieces may be compromised by vigorous rolling of the pieces to be treated by the structure of the containers.

Disclosure of the Invention In order to overcome these problems, the subject of the invention is a plant of the type indicated above formed in accordance with the following claims.

By virtue of this concept, it is possible to produce plants for the surface treatment of pieces in which the pieces can be supplied to the plant and discharged therefrom completely automatically. Moreover, the tanks of the plant can be arranged at different levels so as to take up less space and to facilitate the extraction of gases and vapours liberated during the treatment processes. Moreover, the pieces treated advantageously undergo relative movements during their transfer by conveyor means so that the treatment process can be performed more effectively and over the entire surfaces of all of the pieces treated.

According to a preferred characteristic of the invention, the conveyor means are constituted by a belt or plate conveyor which has a series of translating elements extending transverse the direction of advance of the conveyor and driven relative to a surface for supporting the pieces in order to transfer the pieces into the corresponding tank and from one tank of the plant to another.

It is thus possible to ensure the correct transfer of the pieces even along considerably inclined ramps of the conveyor.

According to a particularly advantageous

characteristic of the invention, a sheet-like element such as a cloth, a flexible sheet or a net is arranged bearing on the active pass of the conveyor so as to engage for sliding on the tops of the translating elements and to form a respective loop between each pair of adjacent translating elements, each of these loops being intended to house at least one piece to be treated ; the sheet-like element is restrained relative to the tanks so that the pieces are rolled and moved forwards on top of the sheet- like element as a result of the advance of the translating elements beneath the flexible sheet-like element.

This ensures that the pieces roll continuously during their treatment in the various baths, which considerably improves the overall reliability of the treatment performed and reduces the time spent by the pieces in the baths.

Brief description of the Drawinas Further characteristics and advantages of the invention will become clearer from the following detailed description given with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a schematic side elevational view of part of a plant for the surface treatment of pieces, formed in accordance with the invention, Figure 2 is a schematic side elevational view of a plant similar to that of Figure 1, having a device according to a variant of the invention, Figure 3 is a schematic side elevational view of a plant similar to that of the preceding figures, formed in a manner such as to extend at several levels one above another, Figures 4 and 5 are schematic views of two further embodiments of the plant of the invention, similar to that

of Figures 1 and 2, Figure 6 is a partial plan view of a detail of the plant of the preceding drawings, Figure 7 is a section taken on the line VII-VII of Figure 6, Figure 8 is a schematic view of a variant of the plant of Figure 1, Figure 9 is a schematic perspective view of a detail of the plant of Figure 8.

Best mode of carrying out the Invention With reference to the appended drawings, a plant for the surface treatment of pieces is generally indicated 1.

The plant 1 comprises a plurality of tanks 3 each of which contains a respective liquid or bath B suitable for treatments of a chemical or electrolytic nature for treating the pieces P, for example, a degreasing bath, a washing bath, a pickling bath, or a bath for the surface application of a metallic or non-metallic coating. In the case of electrolytic-treatment baths B, cathodes and anodes are arranged in the tanks, enabling the electrolytic process to be performed.

The tanks 3 may be distributed at a single working level, but it is advantageous to arrange them so as to occupy a plurality of levels one above another so that the plant 1 can take up a smaller space in plan. This facilitates the provision of extraction systems for the gases and vapours which are evolved in a more localized manner during the treatment process because the tanks 3 are grouped together.

With particular reference to Figure 1, a continuous conveyor device 5 for the pieces P is associated with at least a plurality of tanks 3, but preferably with all of the tanks 3 of the plant 1. This device may be formed by

a conveyor having an active pass with one or more consecutive portions immersed in the baths B of the tanks 3 with which it is associated. Each immersed portion of the conveyor 5 advantageously has a first inclined portion descending into the respective bath B and a final portion, which is also inclined and which ascends out of the bath B. Moreover, the various immersed portions of the conveyor 5 are connected to one another by portions disposed above the level of the liquid in the baths B to allow the conveyor 5 to pass over the side walls of the tanks 3.

Guide means associated with the conveyor 5 guide it along its portions above the liquid level, and along its emergent, descending, immersed and ascending portions.

These guide means, which are generally of known type, may include transmission rollers or rails for guiding the sides of the conveyor 5.

To favour the transfer of the pieces P by the conveyor 5, it has a series of translating elements arranged at regular intervals and formed, for example, by perpendicular walls which extend transverse the direction of advance of the conveyor 5 and which are joined together at their opposite ends by respective belts, chains or other similar means. With reference to Figures 6 and 7, the translating elements 7 are constituted by a plurality of L-shaped sections having opposite ends fixed to corresponding drive belts 8a, b of the conveyor 5. A plate-like body 9 mounted beneath the belts 8a, b has a surface 9a constituting a bearing surface for the pieces P moved by the translating elements 7 when the conveyor 5 is in motion. The plate-like body 9 is preferably perforated with a plurality of through-holes, all indicated 10, for ensuring an improved flow of current

between the anode and the cathode and more rapid run-off of the liquid of the bath B from the surface 9a, particularly in the portions of the conveyor disposed above the liquid level.

Figure 2 shows a variant of the plant of Figure 1 in which each tank 3 has a single endless conveyor 5 having an initial portion descending into the bath B and a portion, which is also inclined and which ascends out of the bath B. Between these portions, the conveyor 5 has a portion which is immersed in the tank 3. The arrangement of the conveyors 5 between adjacent tanks is such that the pieces transferred to the output portion of one conveyor are discharged onto the initial portion of the adjacent conveyor 5. Alternatively, auxiliary belt conveyors are interposed between the adjacent conveyors 5 for the transfer of the pieces between tanks 3 arranged in succession.

According to the nature of the baths used, devices 11 may be provided for washing the pieces in the regions of the portions disposed above the liquid level at the output from one tank and at the input to the next tank; these devices are shown schematically in Figure 1.

For electrolytic electroplating baths, there is provision for an electric current to be passed through the pieces P by a series of electrodes 12 immersed in the bath B by means of flexible wires 12a of which the opposite ends to the electrodes are fixed to a support element 13 arranged above the tank 3 (Figure 1). Each electrode 12 is thus kept in contact with the pieces P for a portion of the advance of the conveyor 5 and the electrodes are arranged along the tank 3 at intervals such as to ensure that each piece or group of pieces P in contact with one another is continuously in contact with a corresponding

electrode 12 so as to ensure that current passes from the electrode to the pieces P throughout the period for which they remain in the bath B.

Figure 3 shows part of a plant 1 of which the tanks, indicated 3a, 3b respectively, are arranged at several levels or in several planes one above another. In particular, in this case, each level of the plant 1 has at least one respective conveyor 5a, 5b.

Auxiliary means 14 are provided between one level of the plant 1 and another for delivering the pieces P to another level of the plant 1, for example, to a lower level. The auxiliary means 14 may be formed, for example, by a belt conveyor which is wound around a pair of spaced- apart return pulleys and is arranged with its axis generally inclined. A chute 14a is provided for transferring the pieces discharged from the conveyor 5a to the belt 14.

According to a preferred embodiment of the invention and with particular reference to Figure 4, each conveyor 5 of the plant 1 has a sheet or other flexible sheet-like element 15 such as a cloth or a net of non-conductive material arranged bearing on the conveyor so as to engage for sliding on the tops of the walls 7. The sheet 15 may advantageously be formed by a fabric made of polypropylene fibres, for example, of the type known by the registered name Meraklon.

The sheet 15 is arranged loosely over the walls 7 so as to form a respective loop 16 for housing pieces P between each pair of successive walls 7. Moreover, the sheet 15 is restrained relative to the tanks 3 of the same level so as not to be pulled along by the movement of the conveyor 5. It is therefore necessary for the sheet 15 to be connected to a fixed portion of the plant 1 at least at

an upstream end 16a thereof, generally transverse the direction of advance of the conveyor 5. Alternatively, and with specific reference to the embodiment of Figures 8 and 9, each wall 7 may bear, at its end which is in contact with the cloth 15, a respective roller 20 supported so as to be freely rotatable between shoulders 21 or, preferably, driven so as to rotate with the rolling motion of the contact with the cloth 15, or at a speed slightly greater than the rolling speed. The rollers 20 are driven by respective pinions 22 keyed to respective axial ends thereof and meshed with a rack 23 mounted so as to be stationary relative to the tank. The cylindrical surfaces of the rollers 20 are covered with rubber or other material with a high coefficient of friction; the cylindrical surfaces are protected on the upstream side, with reference to the direction of advance, by the corresponding wall which acts as a wiper. By virtue of the sheet 15 and of the movement of the conveyor 5 beneath it, each loop 16 advances relative to the tanks 3 in a wave-like manner with a translatory motion having a speed equal to the speed of advance of the conveyor 5, whilst the sheet 15 as a whole remains stationary. The pieces P housed in a loop 16 of the sheet 15 are therefore moved forwards relative to the tanks 3 of the respective level of the plant 1 as a result of the advance of the conveyor 5 and are rolled by the movement of the loops 16 along the sheet 15. The entire surface of each piece P is thus exposed to the bath B of each of the tanks 3 so as to be affected in an optimal manner by the respective treatment performed.

According to a further embodiment of the invention, shown in Figure 5, the tanks 3 have respective independent conveyors 5 and each conveyor has a respective flexible

sheet 15 fixed in the regions of the ends of each tank 3 or restrained as indicated above with reference to the embodiment of Figure 8. The flexible sheet 15 is arranged on the corresponding conveyor 5 in exactly the same way as in the previous embodiment.

The plant 1 preferably also comprises means for controlling the speed of advance of the conveyor 5 so that these means can be adjusted in order to regulate the time spent by the pieces P in each of the baths B of the tanks 3.

Naturally, the conveyor device 5 according to the invention may also be formed in a manner other than that described, for example, with the use of another conveyor device, for example, of the screw type, or a plurality of such devices arranged in succession along the series of tanks 3 of the plant 1.