Patent Publication Number: US-2012037494-A1

Title: Installation for the surface treatment of parts

Description:
The present invention belongs to the field of the treatment of surfaces of parts by immerging these parts in successive liquids contained in several treatment tanks and by transfer of the parts between these tanks, for example the electrochemical treatments of aluminum parts. As examples of such electrochemical treatments, the barrier anodizing or anodic passivation, the porous anodizing in acidic medium, the anodic dissolution, the hard or self-coloring anodizing, the electrolytic polishing and also electroplating such as nickel plating may be cited. The treating liquids may not only comprise electrolytes but also pre-treating liquids such as degreasing liquids, coloration liquids and rinsing liquids. 
     More particularly, the present invention provides an installation for the continuous surface treatment by immerging said parts in at least one treating liquid contained in a treatment tank, said installation including a plurality of tanks disposed in series, and a device for transferring the parts between the tanks, said tanks each comprising a rotary structure mounted on a rotation axle and able to receive said parts, the parts being immerged in said treatment liquid by a rotary movement of the rotary structure of the treatment tank selected in such a manner that air bubbles that may be formed during the immersion of said parts, are chased away from the surfaces of said parts. 
     The widest used installations for the treatment of the surface of aluminum parts are operated batchwise, i.e. by charges of a great volume. The document DE 2 119 401 describes the example of such an installation that comprises motorized carriages which move above several treatment tanks. The carriages are equipped with mobile arms for effecting vertical movements with large strokes for immerging important charges of objects to be treated and hanging from the mobile carriage, into successive tanks and to withdraw them therefrom. This kind of installation has several drawbacks:
         when the parts to be treated are hollow, air bubbles or pockets may appear at certain regions of their surface during the immersion step into the is treatment liquid; this will produce treatment irregularities and thus quality defects of the parts;   the volume of the tanks is important which leads to important volumes of polluting liquid effluents to be reprocessed before disposal;   the vertical movements of the charges above the tanks as well as the important open surfaces of these tanks generate the appearance of vapors and of droplets of active products, especially acidic vapors, in the atmosphere of the treatment unit, and this requires the installation of powerful and expensive aeration and filtration systems for the treatment of these gaseous effluents.       

     As a result, such treatment units can only be installed within a chemical plant that is specialized in surface treatments and processing and can therefore respect severe environmental security standards. The parts must thus be transported from the metallurgical factory where they were machined, to the factory where the surface treatment is effected, and then to the end user; high costs for packaging and transportation will have to be incurred. 
     In the international patent application No. WO 2006/084973 whose disclosure is incorporated into the present document by reference, the Applicant has already described an installation for the continuous surface treatment of parts, formed by a plurality of treatment tanks which each are equipped with a motorized rotary drum and whose axle of rotation is disposed horizontally in such a manner that the major portion of the drum is immerged in a treatment liquid contained in the corresponding tank. The parts to be treated, in particular when they are small, can before be put in place as small batches on supports that have the shape of boxes, for example those described in the patent application No. EP-A1-1 433 537 in the name of the Applicant, and these boxes are then transported by a conveyor system destined to feed each tank with parts to be treated and to transport the already treated parts downstream. The conveyor system has two parallel conveyor chains disposed on both sides of the upper portion of the tanks, the drum axes being disposed perpendicularly with respect to the two conveyor chains. Each tank is equipped with a device that transfers the boxes, one after the other, by means of a hydraulic cylinder by a horizontal push perpendicularly with respect to the axes of the conveyor chains, alternatively from one conveyor chain to the other, after the passage through the tank where they are temporarily fastened on slide rails disposed at the periphery of the rotary drum and where they undergo one or more rotations in the treatment liquid. Each rotary drum is driven via a cogwheel on the shaft of its motor which meshes with the periphery of a toothed disk or with a succession of pins disposed between two disks, these disks constituting a terminal face of the drum. The gear point is situated above the level of the liquid contained in the tank. The drums are supplied with electric current through these disks by means of sliding contact shoes which bear against these disks and are disposed in the tank above the level of the treatment liquid, in the manner described in the patent application No. WO 2007/122471 in the name of the Applicant. The current is then transmitted by the drum to the supports of the parts and then to the parts to be treated. 
     The rotations of the parts within the treating liquids eliminate the air bubbles or pockets from the surface of the parts and allow to obtain an excellent surface quality. The elimination of vertical displacements of the parts in an appreciable extent above the tanks reduces the overall space requirement of the installation and the formation of droplets and vapors and allows therefore to reduce the power of the air filtration systems in the treatment unit. However, since each tank constitutes an autonomous treatment sub-unit with its motorized drum and its transfer device, that installation uses a conveyor system and a transfer system that are relatively complicated, requiring an excellent synchronization of all these components. The installation also requires a driving device for each conveyor chain and several devices for the transfer between the chains and the tanks, and the costs of these devices is not negligible. 
     According to patent application No. WO 2008/035199 whose contents are incorporated into the present document by reference, the Applicant has described an installation for the continuous surface treatment of parts of the above depicted kind and composed of tanks containing motorized rotary drums that are similar to those described in the document No. WO 2006/084973, and regarding the tanks effecting an electrochemical treatment step as such, it comprises an electric supply system similar to that which is described in the document No. WO 2007/122471. Each tank, with its motorized drum, constitutes therefore only an autonomous sub-unit of the installation and mechanically independent from the other tanks. However, this installation uses a unique conveyor chain destined to supply each tank with parts to be treated, to collect the already treated parts and to transfer them into the next treatment station. The conveying of the parts is effected horizontally and parallel to the drum axes. The conveyor chain comprises horizontal transfer slide rails disposed between the tanks to which the slide rails of the rotary drums become to be aligned when the latter come to their uppermost position which emerges from the treatment liquid. Motorized carriages disposed above these slide rails make reciprocating movements on one guide rail that is parallel to the axes. Each carriage is equipped with an articulated rocker bar system comprising vertical arms allowing to push the boxes that are in their upper position and to drive them at each reciprocating cycle lengthwise on the slide rails of the drums and on the transfer slide rails. In this installation, it is intended to realize a rinsing of the parts by jets when they are positioned on a transfer slide rail between two tanks and/or after the last tank. 
     This installation has the same advantages as that which is described in the document No. WO 2006/084973 and simplifies the construction of the conveyor system. However, it uses as many driving motors as drums and at least as many articulated carriages as tanks, and the costs of these devices is not negligible. The installation also requires an excellent synchronization of the components since all displacements must be operated in a clocked manner. 
     It can be observed that, in the two installations mentioned above, the electric contact plots which are of graphite are wearing parts which are situated in the very interior of the electrolytic treatment tank, and that the contact zones of a drum disk with electric supply and with mechanical drives are exposed to treatment liquids, some of them being corrosive. It may also be noted that each driving motor of a drum is situated near the latter and adjacent to the upper opening of the tank and thus to the surface of the liquid which is contained therein. The cabinet of the motor is therefore exposed to vapors, in particular to corrosive vapors emerging from this tank. Maintenance costs must thus be incurred, in particular the replacement of contact parts and motor parts, and these costs are not negligible. 
     In the two installations for a continuous treatment described above, the conveyor chain transports the treated parts after the last rinsing step into a drying tunnel disposed downstream in these installations. The air coming from the drying tunnel is conducted into the air filtering system of the surface treating plant. 
     A first object of the present invention is to provide an installation of the kind defined above wherein the synchronization of the displacement of the parts can easier be realized. 
     Another object of the present invention is to provide an installation wherein the maintenance costs of the devices for realizing the supply with electric power to the parts to be treated as well as of the devices for rotating the part in the tanks are minimized. 
     A third object of the present invention is to provide an installation, especially an installation for anodizing aluminum parts, which can be run within a plant for the manufacture and machining of metal parts that is not yet equipped with devices for the treatment of effluents corresponding to standards required by a plant for electrochemical treatments. 
     A first object of the invention is a machine for the surface treatment of metallic parts by the immersion of said parts into at least one treatment liquid contained in a treatment tank, said machine including a plurality of tanks arranged in series, and a transfer device for the transfer of the parts between said tanks, said tanks each comprising a rotary structure mounted on a rotation axle and capable of receiving said parts, said parts being immerged in said treatment liquid by a rotational movement of the rotary structure of the treatment tank, selected in such a manner that air bubbles that may be formed during the immersion of said parts, are chased away from the surfaces of said parts, wherein said rotation axles of said rotary structures in the series of tanks of this machine are in rotary interlock condition and are driven by a common driving device. 
     The rotary coupling of the axles of the rotary structures and their drive by a unique device eliminates the difficulties of a synchronization of the movements of the rotary structures. 
     The invention has also as another object an installation for the surface treatment of metallic parts, comprising the machine having the above indicated characteristics, lodged in a container containing confinement a and retreating means for the fluids flowing out of said machine. Consequently, the container is a treatment unit that can be installed and operated within a plant that is not specialized for surface treatments. 
     In the machine according to the invention, the tanks in series may be contiguous. The rotation axles of said rotary structures of the tanks may be aligned and assembled in a manner to form a common rotation shaft or axle that traverses the whole machine. 
     In the machine according to the invention, the common driving device may be realized by means of an electric motor that drives directly the common rotary shaft or its segments that are put together with rotary interlocking by coupling. This driving motor may be disposed at a first extremity of the tanks series, especially at the downstream end. 
     Preferably, the rotary structure of the treatment tank which is intended to realize an electrochemical treatment step is connected to an electric generator via the rotation axle of the treatment tank, and said rotation axle of said treatment tank is electrically insulated from other segments of the machine axle. According to a mode of realization, the connection is implemented by means of a rotary connector which is mounted on said rotation axle of the treatment tank. According to a particular realization mode, the rotary connector is placed at a second extremity of the tank series. 
     In an installation according to the invention, where the common driving device, in particular the electric motor driving the axle of the rotary structures and/or the electric connector mounted on this axle, are disposed at the end portions of this axle, the lengths of these terminal portions may be selected such that they traverse the walls of the container in such a manner that the driving device or devices and/or the electric connection device will be placed outside the container. In such a configuration, these devices are not in contact with corrosive vapors, the frequency of replacement of parts is reduced and the maintenance of the devices is rendered easier. 
     If the machine according to the invention uses supports for holding the parts to be treated, for example supports in the form of boxes, said rotary structures are equipped with retaining devices capable of temporarily retaining these supports during the rotation movements of said rotary structures and capable of allowing a transfer movement of the supports between two rotation movements, the dimensions of said supports being adapted to said retaining device. Said supports have in turn fastening means adapted for holding and fixing said parts on said supports during said whole surface treatment. 
     According to a preferred realization mode, said retaining devices comprise slide rails which are parallel to the axles of said rotary structures, and each rotary structure of a tank is aligned with a rotary structure situated respectively immediately upstream and/or downstream, so as to allow the transfer of said supports over a tank and from one tank to the next one by sliding along said slide rails, under the action of transfer means. 
     The machine according to the invention comprises a transfer device disposed above the tanks and synchronized with the driving device of the machine axle, equipped with grasping elements for the supports which are in their upper position on said rotary structures, said transfer device effecting a simultaneous transfer movement of said supports in high position, each support in high position taking, under the influence of the transfer movement, the emplacement that was occupied before said transfer movement by the support in its high position immediately downstream. 
     According to a realization mode, said grasping elements comprise a pivoting shaft which extends over the series of tanks, and a group of arms mounted on said shaft, each arm bearing at its free end two pins distant and perpendicular with respect to the arm, the distance between these two pins of the same arm corresponding to the distance that separates two successive supports in upper position, the distance between two arms corresponding to the length of one said support. Preferably, the length of the arms is adjustable, and the height of the pins is also adjustable. 
     Preferably, the transfer device includes means for an alternating displacement between upstream and downstream of said grasping elements, and a particular realization mode comprises a group constituted by a driving pinion and a toothed rack, said pinion being fastened to a frame and a slide rail and meshing with said toothed rack that is fastened to a slider block, the stroke of said means for an alternating displacement being equal to the distance between two successive emplacements of the supports in high position. 
     The transfer device comprises also means for releasing said grasping elements which, according to a realization mode, include a motorized unit formed by a connecting rod and a crank for acting on said pivoting shaft in order to simultaneously activate and simultaneously release said grasping elements of all supports in upper position. 
     A particular object of the invention is a machine that is defined as described above and is destined for anodizing aluminum parts, comprising from upstream to downstream:
         an oxidation tank for containing an electrolytic treatment liquid, for example sulfuric acid, said oxidation tank comprising one or more electrodes serving as cathode(s), especially two cathodes disposed on both sides of the rotary structure of the treatment tank, said rotary structure serving as an anode,   a rinsing tank for containing a rinsing liquid, for example water, and   a warming and drying tank for being fed with hot air.       

     Another, particular object of this invention is a machine that is defined as described above and is destined for the electrolytic nickel plating of steel parts, including from upstream to downstream:
         a pickling tank for containing a pickling liquid;   a first rinsing tank for containing water;   a degreasing tank for containing an aqueous degreasing solution;   a second rinsing tank for containing water;   a depassivation tank for containing a sulfuric depassivation liquid;   a third rinsing tank for containing water;   a nickel plating tank for the actual electroplating and destined for containing a nickel sulfate solution and equipped with electrode forming nickel plates, especially two anodes disposed at both sides of the rotary structure of said nickel plating tank;   a fourth rinsing tank for containing water; and   a warming and drying tank fed with hot air.       

     In these machines, the rinsing tank may have compartments between its upstream and downstream portion, realized by one or more transverse separating walls, traversed by the rotation axle of said rinsing tank, said rotation axle bearing a rotary structure in each compartment. The downstream compartment has an entry opening for its supply with fresh rinsing liquid, and the upstream compartment has an exit opening for the used rinsing liquid, and the separation walls have a passage for the rinsing liquid. These passages may take the form of overflow openings installed in the upper portions of these transverse separations. 
     In the installation according to this invention, the bottom of the container forms a storage basin for liquids. The capacity of the storage basin may be selected such as to be able to receive the totality of the volume of the liquids contained in the machine. 
     Preferably, the container contains a reservoir for the treatment liquid, a reservoir for the used treatment liquid, and a reservoir for used rinsing liquid. 
     Preferably, a device for retreating the used treatment and rinsing liquids is lodged within the container. According to a realization mode, the device for the retreatment of used liquids is an evaporator which retreats these used liquids by distillation and condensation. 
     Preferably, the container includes a gas scrubbing station. Especially a station for washing gases, connected to a water circuit and disposed in the space above the tanks. 
     Other characteristics and advantages of the invention will become evident to the one skilled in the art from the following description of a realization mode that is only given by way of non limiting example, and with reference to the attached drawings wherein: 
    
    
     
         FIG. 1  is an external perspective view of the entire installation according to the invention; 
         FIG. 2  is a perspective view of the installation shown in  FIG. 1  but without conveyor chains and without the exterior walls of this installation; 
         FIG. 3  is a perspective view of the series of tanks of a machine according to the invention and showing their rotary structures; 
         FIG. 4  is a perspective view of the rotary structure of the electrolytic treatment tank; 
         FIG. 5  is a perspective view of the transfer device of the machine according to  FIG. 2 ; 
         FIG. 6  is an enlarged perspective view that shows the upstream extremity of the rotary structure of the treatment tank according to  FIG. 3 , and its electrical connector; and 
         FIG. 7  is an enlarged perspective view that shows the downstream extremity of the rotary structure of the drying tank and the motor that drives the axle. 
     
    
    
     To  FIGS. 1 and 2  illustrate an installation for the surface treatment of metallic parts according to this invention, in the present case for anodizing aluminum parts; the process requires the successive use of an electrolytic solution and a rinsing liquid. 
       FIG. 1  is a perspective view showing the exterior of the installation  700 . All portions using fluids are disposed within a container  701  which is placed on a storage basin  702 . A door  703  shown at the right in  FIG. 1  gives access to the interior of the container  701 . An air inlet  704  of a turbine is disposed on the front side of the container  701 . A rectifier block  705  for the supply of the machine within the container  701  with direct current is arranged outside the container and shown at the left in  FIG. 1 . The raw parts that are to be anodized have been fastened before on supporting boxes (a process step that is not shown in the Figures) and are placed onto the left conveyor band  706  and are transported to the inlet of the container through an opening  707  whose dimensions are reduced as far as possible in order to reduce emanations from the container. The supporting boxes containing the anodized parts are taken up through a similar opening  708  at the outlet of the container by the conveyor band  709  shown at the right in  FIG. 1 , and then unloaded for being transported to a downstream use. This kind of conveyor band is known as such to the one skilled in the art. The supporting boxes  850 ,  851  that are loaded with parts are illustrated in all Figures by simple rectangular parallelepipeds only which are to show their external space requirement. Some examples of such supporting boxes are described in detail in patent No. EP-1 433 537 in the name of the Applicant and whose disclosure is incorporated into the present document by reference. 
       FIG. 2  is a perspective view of the interior of the container  701  shown in  FIG. 1 , showing an access catwalk  710  and the storage basin  702 , on which are disposed the liquid tanks  500 ,  600 , a group of devices  300 ,  400  for the treatment of the fluids and which will be described later, and a machine  1  for the surface treatment according to the invention. 
     The treatment machine  1  comprises a group  100  of tanks, a group of rotary structures  800 , and a transfer device  200 . As can be seen in  FIGS. 2 and 3 , the tanks  100  are disposed in series and are contiguous. A transfer device  200  which will be described later, is arranged above the group  100  formed by the tanks. The transfer device is suspended on three traverses  711  fastened at an armature (not shown in  FIG. 2  for sake of clarity) of the container  701 . 
       FIG. 3  is a perspective view of the three tanks  101 ,  102 ,  103  that constitute the series of tanks  100  in  FIG. 2 , and shows the disposition of the rotary structures loaded with supporting boxes in the tanks. The unit formed by the three tanks includes from upstream to downstream and from the left to the right in  FIGS. 2 and 3 :
         an electrolytic treatment tank  101  in which are arranged laterally on both sides two metal plates  104 ,  105  that form two electrodes which constitute in this case the cathode;   a rinsing tank  102  with compartments between its upstream portion and its downstream portion, formed by two transverse separating walls  106  and  107 , the downstream compartment  108  having an entry for the supply with fresh rinsing liquid, the upstream compartment  110  having an exit for used rinsing liquid, and the separating walls having in their upper portions overflow openings;   a warming and drying tank  103  supplied with hot air by a turbine  111  via a conduct  112 .       

       FIG. 4  is an enlarged view of the rotary structure  801  of the electrolytic treatment tank  101 . The rotary structure comprises an axle  810  which is mounted horizontally for rotation and is suspended between bearings disposed in the upstream wall and the downstream wall of the corresponding tank. The axles  810 ,  820  and  830  of the three tanks  101 ,  102  and  103  are aligned with each other and fastened at their ends so that a unique common axle  840  is formed together that traverses the entire machine and is composed of the three axle segments  810 ,  820  and  830 , An electric motor  805  is fastened to the terminal downstream wall of the drying tank  103 , that drives by a direct drive the combined axle  840  and thus the rotary structures of the tanks  101 ,  102  and  103 . 
     The axle segment  810  of the electrolytic treatment tank  101  is connected to the axle segment  820  of the rinsing tank  102  through an element made of an electrically insulating material. This axle segment  810  bears at its other extremity that goes beyond the upstream wall of the electrolytic treatment tank, this axle segment  810  bearing a rotary connector  804  comprising three rolls which rotate in the interior and are in contact with a contact cylinder  806  which is connected to the rectifier block  705  that constitutes the device for supply with direct current. 
     As can be seen in  FIGS. 3 ,  4 ,  6  and  7 , each rotary structure comprises several transverse plates  807 ,  808 ,  812  having an essential polygonal contour, that are mounted perpendicularly on the corresponding axle segments  810 ,  820  and  830  and are interlocked for rotation of the combined axle  840 , see, for example, the reference  819 . Pairs of longitudinal slide rails  809 ,  811  are mounted on the periphery of these transverse plates parallel to the rotation axle; their dimensions and distances are adapted to receiving the supporting boxes  850 ,  851  such as those already mentioned above. In the realization mode illustrated in  FIGS. 3 ,  4 ,  6  and  7 , the transverse plates  807 ,  808  and  812  support four pairs of slide rails  809 ,  811  disposed at 90° with respect to each other. The transverse plates  807 ,  808  and  812  may comprise cut-outs  817  and  818  in order to reduce the weight of the unit composed of a rotary structure and, in the case of plate  812  in the drying tank  103 , for rendering easier the passage of the air flow. As can be seen in  FIG. 3 , each slide rail of the electrolytic treatment tank  101  is aligned with a slide rail of the tanks situated downstream so that the transfer of the supporting boxes from one tank to the next one by sliding along said slide rails is allowed. The alignment of the position of the slide rails is effected during the assembly of the machine and during the connection of the axle segments, and this procedure eliminates from the beginning later synchronization problems. 
     In the electrolytic treatment tank  101  as shown in  FIG. 3 , the slide rails  809 ,  811  are continuous from upstream to downstream of the tank. In contrast, the slide rails in the rinsing tank  102  are subdivided into three sections  814 ,  815  and  816  at short distances and aligned, each section of the slide rails being fastened on a pair of transverse plates  821 ,  822 , the three rotary substructures created in such a manner being separated from each other by the two separating walls  106 ,  107  of the rinsing tank  102 . 
     In the warming tank shown in  FIG. 3 , the slide rails  823 ,  824  are also segmented into two sections, each of these sections being fastened on a pair of transverse plates  812 ,  825 , but the two rotary substructures thus created in this tank are not separated from each other by any compartment means. 
     The slide rails bear resilient contact plots  813  whose positions and distances correspond to the length of the supporting boxes  850 ,  851  and to the compartments  108 ,  109 ,  110  of the rinsing tank  102 , thus allowing to withhold said supporting boxes at a predetermined longitudinal position on the slide rails during the rotation movements, and the sliding of the supporting boxes is allowed under the action of the transfer device between two rotation movements only. 
     The machine according to the invention comprises a transfer device  200  whose mounting position above the series of tanks  100  is shown in  FIG. 2 . Its constituting elements are shown in  FIG. 5 . It is synchronized with the driving device  805  of the machine axle. It includes a group of grasping elements of the supporting boxes that are temporarily situated in their upper position on said rotary structures. The transfer device effects a simultaneous transfer movement of all supporting boxes  850 ,  851  which are in their upper position, each support  850  in high position taking, under the effect of the said transfer movement, the place that has been occupied by the supporting box  851  immediately downstream in its high position before that transfer movement. 
     As it is shown in  FIG. 5 , the grasping elements for the supporting boxes include a horizontal shaft  201  that extends lengthwise above the series of tanks  100 , and a group of arms  202 ,  205  mounted perpendicularly on said shaft  201 , each arm bearing at its free extremity two pins  203 ,  204  that are oriented perpendicularly to the arm, the distance between two pins  203 ,  204  of the same arm  202  corresponding to the distance that separates two successive supporting boxes in their upper position, and the distance between two adjacent arms  202 ,  205  corresponding to the length of a supporting box. The length of the arms  202 ,  205  and their emplacement on the shaft  201  can be adjusted, and the height of the pins  203 ,  204  is also adjustable. Thus, the transfer device can be positioned and adjusted in such a manner that it can take up each supporting box  850 ,  851  simultaneously from the front and from behind, possible defects of the geometry of the rotary structures being compensated, and the reliability of the whole system is improved. 
     As it is shown in  FIG. 5 , the transfer device  200  comprises means for an alternating horizontal displacement between upstream and downstream positions of the shaft  201  and thus of the group of said grasping elements, and takes the form of a driven pinion and a toothed rack. The pinion  206  is fastened to a frame and a slide rail  208  that is fastened by traverses  711  to the armature bearing the device, and meshes with said rack mounted on a slider block  207 ; this slider block  207  being in turn fastened to the shaft  201 , the stroke of said alternating displacing means being equal to the distance between two successive emplacements of supporting boxes at their high position. 
     The transfer device  200  comprises also a system for the release of said grasping elements, including a driving motor  210  driving a unique group  209  composed of a connecting rod and a crank, this latter driving the alternating pivoting of the shaft  201  and thus of the arms  202 ,  205 , and this swinging motion engages and disengages simultaneously the pins  203 ,  204  of all supporting boxes that are in high position and allows the rotary structure  800  to rotate. The arms  202  will pivot between a lowered position near to the horizontal plane and a heightened position. The shaft  201 , the slider block  207  and the slide rail  208  are thus parallel with the supporting boxes but laterally offset with respect to the slide rail pairs in high position. When the grasping system is in its heightened position, the transfer device makes a translation of the shaft  201  in upstream direction thanks to the system of pinion and rack, and it will take the former position for the following transfer movement. 
     In a method for anodizing in using the treatment machine  1  that has been described above, the electrolytic treatment tank  101  is filled for example with a sulfuric acid solution and allows to realize the anodizing of aluminum parts attached to supporting boxes. For this kind of treatment, the tank  101  comprises two metal plates that form the cathode and are disposed on both sides of the rotary structure  801  near the lateral walls of the tank, the rotary structure being supplied with an electric current having the opposed polarity with respect to the electrodes, said electric current being transmitted to the parts to be treated via, successively, the axle  810 , the transverse plates  807 ,  808 , the slide rails  809 ,  811  and the supporting boxes  850 . During the implementation of the method in the treatment installation according to the invention, each part is immerged in the tank  101  by having it undergo, according to the realization mode shown in the Figures, four complete revolutions in such a manner that air bubbles and air pouches which may be formed in the interior of the tank in contact with the parts, are eliminated, thus allowing the treatment liquid to integrally treat the surface of the parts and rendering the treatment perfectly homogeneous. 
     Thus, the supporting boxes which hold the parts not yet treated, brought about by the conveyor chain  706 , are engaged by horizontal displacement at the upstream extremity of the pair of slide rails not immerged and situated momentarily at the summit of the rotary structure  801 , each supporting box being positioned lengthwise on the upper pair of slide rails thanks to the transfer device  200  which cooperates with the resilient contact devices  813  of the pair of slide rails. The totality of the treatment machine shown in  FIGS. 2 through 5  operates by sequenced, clocked and synchronized movements. According to the illustrated realization mode, the rotary structure  801  comprises on its periphery four pairs of slide rails  809 ,  811  oriented at 90° with respect to each other and provided for receiving the supporting boxes  850 ,  851  which hold the parts to be treated. After each rotation by 90° , all supporting boxes  850 ,  851  momentarily disposed at their emerged, high position, undergo a longitudinal translation whose length corresponds to the distance between two adjacent supporting boxes whereas the other supporting boxes which are immerged, are not displaced on the slide rails. As shown in  FIGS. 3 and 4 , each supporting box is rotated between two translations by a complete revolution of 360° subdivided into four rotations by 90° each. Each supporting box is thus immerged during nearly four complete rotations within the liquid contained in the electrolytic treatment tank  101  with the exception of the upper portion during each rotation where the supporting box is situated momentarily out of the liquid for allowing the emplacement, the advance, the transfer and the recovery of the parts. 
     At each sequence, namely after every rotation by 90° , one supporting box containing parts that have been treated by electrolysis, is transferred from the electrolytic treatment tank  101  onto the rotary structure  802  of the first compartment  110  of the rinsing tank  102  and is then immerged into the rinsing liquid during the next rotation, in order to make a complete revolution. Then, it is transported into the second compartment  109 , makes a rotation of 360° therein, and then passes into the third compartment  108  where it makes a final rotation of 360° before being transported into the warming tank  103 . The rinsing tank is continuously supplied with rinsing liquid. This rinsing liquid enters first into the third compartment  103  of the rinsing tank, then flows into the second compartment  109  through the opening in the separation wall  107  between these two compartments, and then into the first compartment  110  before being evacuated into a storing tank for used liquid. The one skilled in the art will have understood that, thanks to this arrangement, the rinsing operation is executed as a kind of “countercurrent washing” according to the terminology of the field of chemical separations. 
     In the third tank  103  which contains a rotary structure  803  whose length is equivalent to two positions of the supporting boxes, these latter make two complete revolutions before being engaged by the transfer device  200  against the conveyor chain  709  downstream the installation. This warming tank does not contain any liquid but is traversed by a hot air flow supplied by the turbine  111 ,  112 . Thanks to the rotation of the parts in the tank  103  with respect to the direction of the air flow, the droplets of the rinsing liquid are efficiently eliminated from the walls of the parts, even if the parts have cavities and hollow portions. Such a rotation is not provided in conventional drying tunnels. 
     The air that is charged with humidity and exits the drying tank  103 , is collected and mixed with the air charged with vapors sucked off by the hood  401  disposed above the oxidation tank  101  and above the rinsing tank  102  and then treated in a block  402  containing a fan and a gas scrubber, installed within the container  701 . The hourly aspiration capacity of the hood  401  and the fan and scrubber block  402  may be selected to be 2 to 8 times, typically 4 times, the inner volume of the container. This kind of apparatus is as such well known to the one skilled in the art of surface treatment. The air that exits from this gas collecting and scrubbing station  400  may be blown without any restriction into the surrounding atmosphere. 
     The water which exits from the gas scrubber is collected in an intermediate storage tank. This water is mixed with used rinsing liquids and retreated in the evaporator  300  which forms a small distillation-condensation unit. The distillate is recycled as a rinsing liquid. The residue that is composed of an acidic electrolyte solution is transferred to an intermediate storage tank and then mixed with fresh electrolyte. 
     The used electrolyte is also stored in an intermediate storage tank and then retreated in the evaporator; the distillate being combined with fresh electrolyte, and the distillation residue whose volume is small is stored for an external retreatment. Seen as a whole, the installation according to the invention only produces a small volume of rejections that cannot be treated in situ, and the installation can thus be used in a factory which does not have facilities of a plant for the electrochemical surface treatments. 
     Each supporting box that traverses the machine according to the invention makes a path that may globally be qualified as helical although it is in fact composed of a succession of rotations and translations. Furthermore, the path of each supporting box is composed of clocked sequences of these movements but the overall processing by treating a great number of supporting boxes should be considered as a continuous process. It is therefore possible to adjust the flow rate of the supplies of fluids, treatment liquids, rinsing liquids and air so as to operate an established continuous processing, the volumes and concentrations of the fluids in all tanks  100  of the series remaining constant. Therefore, the quality of the treated parts remains perfectly constant. 
     Furthermore, the quality of the air rejected by the gas scrubber installation remains also perfectly constant. The retreatment of the liquid effluents within the container can be executed as a continuous or a batchwise process thanks to the tanks  500 ,  600  that allow an intermediate storage. 
     EXAMPLES 
     1. Examples of Anodic Treatment of Aluminum Parts 
     The installation described above and whose group of tanks is illustrated in  FIGS. 2 and 3 , has especially been used to treat:
         caps for cosmetic product bottles;   nuts for pressure indicators;   brake pistons;   gearbox casings;   derailleurs for bicycle hubs;   buckles for handbags;   supports for rain detectors on motorcars;   couplers for automatic gear boxes.       

     The container of this installation, shown in  FIG. 1 , had a length of about 5 meters whereas an installation according to the document WO 2008/035199 for executing the same treatment has a length of about 12 meters, the drying tunnel included. 
     2. Examples of Electroplating Treatments 
     An installation according to the invention has been used for electrolytic nickel plating, namely an electroplating method but not a conversion method, of steel parts for motor car manufacture. The parts had been degreased before in a solvent. 
     In order to carry out this process, the installation uses 9 tanks comprising a total of 14 compartments:
         the first tank is a tank for sulfophosphoric pickling;   the second tank is a tank for double rinsing with demineralized water;   the third tank is a tank for electro-anodic degreasing with the use of sodium hydroxide;   the fourth tank is a tank for double rinsing containing demineralized water;   the fifth tank is a tank for sulfuric depassivation;   the sixth tank is a tank for double rinsing containing demineralized water;   the seventh tank is a tank for nickel plating using nickel sulfamate where the actual electroplating takes place; the tank contains a nickel sulfate solution heated to 60° C. The tank is equipped with two nickel plates forming the electrodes and disposed on both sides of the rotary structure of this tank. The section of the axle of the rotary structure of this tank is electrically insulated from the sections of this axle situated upstream and downstream;   the eighth tank is a tank for triple rinsing comprising a rinsing called “dead rinsing”, the three compartments containing demineralized water; and   the ninth tank is a warming and drying tank supplied with hot air.       

     The intensity of the electric current that is applied to the electrodes and the parts in the nickel plating tank is about 0.5 A/square decimeter. The nickel deposition formed on the surface of the parts presents an essentially constant thickness of 3 to 5 micrometers. The rate of rejection of defective parts is lower than 0.1%. 
     It will be noted that all rinsing tanks comprise two or three compartments for washing and rinsing the parts by countercurrent with the purpose of eliminating as completely as possible the residues of the active solutions in the treatment tank situated upstream and for avoiding a pollution of active solutions in the downstream treating tank. 
     3. Examples of Treatments That Can be Executed in the Machine and the Installation According to the Invention 
     a) Electrolytic treatments 
     Cathodic electrolytic coatings of:
         nickel Watts and nickel sulfamates   zinc and zinc-nickel   tin   copper   noble metals (silver, gold, rhodium, platinum metals family . . . )       

     Anodic transformations:
         aluminum oxidation   titanium oxidation . . .       

     Paints:
         chemical   anaphoresis   cataphoresis       

     Electrolytic polishing of stainless steels 
     b) Electroplating of plastics
         copper plating on plastics   nickel plating on plastics   chromium plating on plastics       

     c) Various chemical treatments such as:
         transformation by chemical deburing and/or mirror finishing of aluminum alloy and other substrates   chemical transformations such as steel and aluminum passivation   chemical stripping of titanium alloys (with nitro hydrofluoric mixtures)   chemical nickeling of current steels.       

     Of course, the above listing of treatments is not exhaustive and is given as non-limiting examples only. The one skilled in the art will know how to adapt, for every concrete application, the number of tanks and of compartments of the machine as well as the equipment provided for the treatment of the effluents. 
     Of course, the invention is not limited to the realization modes that have been described above, but it comprises numerous technical variants and their combinations:
         Thus,  FIG. 4  shows a rotary structure comprising 4 fastening positions for the boxes. This number may be a different one. With only 2 fixation positions for example, each transverse plate may be replaced by two arms.   The supporting boxes mentioned above are particularly well adapted to the treatment of series of parts having small dimensions. In the case of a unit for the treatment of parts having large but invariable dimensions, these parts may directly be fastened on the rotary structures and through the intermediate of other fastening means than sliders.   The axles of the rotary structures of two successive tanks may be connected through gears which put them into rotary interlocking condition without compulsory alignment.   The tank entity  100  may comprise several tanks separately constructed and then installed in series. It may also be realized by means of a tank having a great length and divided by parting walls to form a plurality of compartments providing different functions.