EP0524866A1 - Electrolytic installation more particularly to paint a car body by cataphorese - Google Patents

Abstract

The invention relates to an electrolysis plant especially for painting a motor vehicle body shell by cataphoresis. This plant comprises a sled (2) on which a vehicle body shell is carried, at least one hanger (1) from which the sled (2) can be suspended with articulation, the said sled (2) being connected to a source of current by the establishment of an electrical contact between two contact elements (7, 9) connected to the sled (2) and to the hanger (1), at least one of the elements (7) comprising an elastic means for continuously returning the said elements (7, 9) one against the other, and the abovementioned two elements being joined together in rotation during the pivoting of the sled (2). This invention applies especially to plants for painting motor vehicle body shells by cataphoresis. <IMAGE>

Description

The present invention relates to an electrolytic installation in particular for painting a motor vehicle body by cataphoresis.

The known methods of obtaining a coating of paint by electrophoresis (electrodeposition) on a bodywork of a motor vehicle consist in immersing the body of a vehicle in a tank containing a bath of an electrically conductive paint, having introduced in this same bath two electrodes (respectively anode and cathode) of a direct current generator, the cathode being connected to the vehicle body in the case where the paint used is of the cationic type.

The paint coating is obtained by displacement of the paint particles towards the vehicle body, under the effect of the electric field produced by said generator. This process has a certain number of known advantages due to the fact in particular on the one hand, that it lends itself to automation, on the other hand that the paint can access the interior parts of the bodywork and that it is constantly renewed by an equivalent quantity as and when it is applied.

The implementation of this method is carried out in a manner known per se, by means of an installation comprising a conveyor driving one or more hangers moving on rails, and intended to transport a sledge supporting the body of the vehicle towards the tank containing the paint bath. The deposition of a layer of paint on a vehicle by this process requires the body of said vehicle to be connected to the negative pole of the current generator and generally to ground; what is done, in order to avoid unwanted traces left on the bodywork, rather by bringing the sledge to earth via a mechanism fixed to the base of the hanger and comprising two contact elements connected respectively to the sledge and to one or more hangers.

Now it turns out on the one hand, that the path of the hangers on the rails is not continuously rectilinear and has curves corresponding to the descent and ascent of the boxes in the paint bath, on the other hand, that the aforementioned mechanism will be immersed during the passage in the bath. From these two considerations it follows that the aforementioned contact must fulfill certain conditions. It will be necessary that the two aforementioned contact elements are clean and fixed with respect to each other, and particularly during the descents and ascent of vehicles in order to avoid the appearance of electric arcs which can go so far as to cause unwanted welds. It will therefore be desirable for a minimum of mobile connections between the parts to be made, but nevertheless for a clearance to remain between these elements to allow the paint to be removed in order to prevent the risks of blockage of the current flow.

Several systems have been implemented to date to meet these requirements. It has indeed been proposed to establish direct contact between each hanger and the sledge. However, this type of contact by support at four points clearly generates poor contact between one of the hangers and the sledge, and consequently results in the formation of electric arcs. In addition, the two facing metal faces being covered with paint, an accumulation of uncooked cataphoresis is formed in the contact zone producing an air gap also capable of generating electric arcs.

It has also been proposed to establish contact by means of a magnet supported by the hanger and connected to the mass routing cable, and a contact plate secured to the sledge. However, this solution requires two automatic cleaning stations, one for the magnet and the other for the plate, which must have a very clean surface as regards the magnet, and a rectified surface also very clean as regards concerns the plaque. In addition, it is observed that the attraction force of the magnet diminishes over time.

The present invention aims to solve these problems and provides an electrolytic installation, in particular for painting a motor vehicle body by cataphoresis, of easy design, and allowing transmission of the current between the hanger (s) and the sledge in particular. reliable, avoiding the use of devices for cleaning the electrical contact elements conventionally required in such installations.

To this end, the subject of the present invention is an electrolytic installation, in particular for painting a motor vehicle body by cataphoresis, of the type comprising a sledge on which a motor vehicle body is transported in electrical contact with said sledge, at least one hanger to which said luge can be suspended in an articulated manner, said hanger being moved by a conveyor to transport said luge to a station at which it enters at a certain inclination into a cataphoresis bath by pivoting around the hanger, said luge being electrically connected to one of the poles of a current source by establishing an electrical contact between two electrical contact elements connected respectively to the sledge and the hanger, in the loaded position of the sledge on the hangers, one of the two the aforementioned elements retracting to allow the loading of the sledge on the hanger, this installation being characterized in that at least one of the two aforementioned contact elements comprises an elastic means permanently applying the two contact elements one pressing against the other in the loaded position of the sledge by pushing back at least one of said elements during loading, and in that the sledge and the hanger cooperate with a means of securing the two aforementioned contact elements during the pivoting of the sledge relative to the hanger so as to maintain a fixed contact between these two elements when the body is lowered into the bath, at least one of the two contact elements being returned to the initial service position, facing the other contact element of so that the two aforementioned elements can establish electrical contact during a subsequent charge.

According to a particular embodiment of the invention, one of the aforementioned contact elements is mounted to rotate relative to the axis around which the sledge pivots relative to the hanger and the aforementioned securing means is a means for securing the two in rotation aforementioned items.

The contact element supported by the hanger is integral with a sleeve rotatably mounted around the pivot axis of the sledge relative to the hanger, said sleeve comprising two fingers capable of coming into contact with part of the sledge to secure in rotation the two contact elements. Advantageously, the aforementioned part of said sledge is the electrical contact element integral with the sledge itself.

According to another characteristic of the invention, at least one of the abovementioned contact elements comprises at least one strip made of an elastic and conductive material.

According to an alternative embodiment, the two aforementioned contact elements are formed for the first of several parts, and for the second of a part, said parts each comprising at least one edge, the two contact elements being applied one against the other. the other by means of a spring, the respective edges of the parts of the first and of the second contact element being pickled by friction against one another when the sledge is loaded on the hanger. Advantageously, the edges of the two aforementioned contact elements having different inclinations.

It will be noted that the parts of the first contact element comprise a chamfered part cooperating with a corresponding chamfered part of the other part of the second contact element favoring the retraction of one of the contact elements during the positioning of the sledge on the hanger.

According to another characteristic of the invention, one of the aforementioned contact elements is connected to the current source by means of a flexible element allowing a current transmission during the rotation of the sledge relative to the hanger. Advantageously, this flexible element is a braid or a cable.

According to another characteristic of the invention, the return spring of at least one of the contact elements after each operation is secured by one of its ends to the upper part of the hanger and by its other end to an intermediate piece support on which is fixed the contact element supported by the hanger and recalls one of the contact elements in the engagement position with the other contact element before loading a sledge.

According to another characteristic, said installation comprises means for checking the presence of the spring. These means comprise a pendulum presence sensor and a spring presence sensor, and means for verifying the synchronization of the signals emitted by said sensors, activated at the start of the return circuit of the pendants.

According to another characteristic of the invention, the installation further comprises a means for controlling the continuity of the flow of current between two hangers. This means comprises an additional rail on which engages one of the rear hangers when one of the front hangers is in guided contact with a front rail connected to said current source, a device for subjecting the additional rail to a direct voltage. and a device for checking the passage of current in the circuit thus created.

However, other characteristics and advantages of the invention will appear better in the detailed description which follows and which refers to the appended drawings given solely by way of example and in which:

Figure 1 is a partial front view in section, illustrating an electrolytic installation according to an embodiment of the invention, for the painting of a motor vehicle body.

Figure 2 is a sectional view along II-II of the previous figure, illustrating the hanger without the sledge.

Figure 3 is a view similar to Figure 1, but illustrating a second embodiment of the means of transmission of electric current between hanger and sledge.

Figure 4 is a sectional view along IV-IV of Figure 3, similar to Figure 2, but illustrating a second embodiment of the current transmission device between hanger and sledge.

Figures 5 and 6 are side views of the electrical contact elements according to the embodiment illustrated in Figures 3 and 4, while Figures 7 and 8 are respectively front views.

FIG. 9 is a partial schematic view of a hanger of an electrolytic installation equipped with a device for checking the presence of the return spring of the contact element in the initial position,

Figure 10 is a schematic representation illustrating two hangers moved along the guide rails, and a system for monitoring the continuity of the flow of current.

In FIGS. 1 and 2, we see a part of the electrolytic installation I of the invention for the transport of a vehicle body in a tank (not shown in this figure) for painting said body by plating. This installation I comprises for each operation on the one hand, four hangers 1 (of which only one is shown in this figure) moving by their upper ends on guide rails when driven by a conveyor (not shown), and a sledge 2 suspended from the above-mentioned hangers (the hanger is moved perpendicular to the plane of the figure). Each aforementioned hanger 1 comprises a vertical element 10 and a horizontal element 11 forming an axis of articulation on which axis 11 said sledge 2 is pivotally mounted. At the upper part of the hanger 10 is fixed a support piece 12 to which is connected perpendicularly, by means of a screw 120 and nut 121 assembly, one of the ends 30 of a braid 3 of which the other end 31 is secured, also by means of a screw 43 and nut 42 system, to a bracket 4 for connecting said braid 3 to an intermediate support piece 5 of a contact element 7, said intermediate piece 5 being integral with a sleeve 8 rotatably mounted on another sleeve 111 integral with the axis forming part 11 of the hanger 1. Instead of a braid, it is advantageous to use a flexible cable with metal lugs. As for parts 5 and 8, they must be made of insulating material. The aforementioned contact element 7, supported by the hanger 1, is constituted according to this particular embodiment by four spring blades 70 fixed to a metal part 5b by bolts 79 or screws placed from the outside, the part 5b being itself fixed on part 5 by screws 5a, the upper part of the intermediate part 5 being further connected by means of a second bracket 40 to a return spring 41 whose function will be explained later and one end 411 of which is engaged in an orifice provided in said bracket 40 while the other end 412 is suspended from the support piece 12 fixed to the upper part of the hanger 1. The spring can also be held by pins on the parts 5 and 12. The sleeve 111 fixed on and surrounding the part of the hanger 1 forming a hinge pin 11 is formed from three parts of different diameters 111a, 111b, 111c; the sleeve 8 is pivotally mounted around the middle part 111b having the smallest diameter and has on its face oriented towards the sledge 2 two fingers 80 incorporated and arranged on either side of the aforementioned sleeve 111. Thus, in the position of use of the assembly, the intermediate support part 5, the electrical contact element 7 and the rotary sleeve 8 and its incorporated fingers 80 are integral in rotation around the fixed sleeve 111 and the axis 11 of the hanger 1.

The axis forming part 11 of the hanger I is intended, as already mentioned, to support the sledge 2 on which the vehicle body will be placed.

This sledge 2 consists of a pallet which can pivot around the axes of the hanger 1, and which comprises on one of its sides two electrical contact plates 9 intended to cooperate with the aforementioned strips 70 of two hangers 1 opposite this side of the sledge 2.

According to a second embodiment of the invention, illustrated in Figures 3, 4, 5, the electrical contact element 7 supported by the hanger 1 (see also Figures 5, 6, 7 and 8) consists of four parts 71 , 72, 73, 74 of substantially trapezoidal section in contact with an intermediate support part by their side of greater length, and mounted against a spring (not shown) applying them to the other contact element 94 integral with the sledge 2. These four parts comprise, on the side opposite to the intermediate support, projecting elements forming ridges 75 parallel to one another, inclined relative to the base of said parts. The contact element (FIG. 6 and FIG. 8) intended to be supported by the sledge 2, for its part, consists of a part 94 of substantially rectangular shape fixed to the sled 2 and also comprising on its face opposite to the sled 2 projecting elements forming edges 91.

In addition, the upper part of the part forming the first contact element 7 mentioned above is chamfered (a) to cooperate with another chamfer (b) provided at the bottom of the other contact element 94 in the manner which will be described further on in the description.

There will indeed be carried out through the following a description of the operation of the installation I first of all in its first embodiment.

The sledge 2, on which the vehicle body is placed, is transported firstly above the parts forming the axis 11 of the four hangers 1; then a table (not shown) ensuring the transport of said luge 2, lowers the luge on the hangers with the effect of suspending said luge from said hanger. During this lowering of the sledge 2, the electrical contact plate 9 of the sledge 2 compresses the elastic strips 7 thus establishing electrical contact with the mass conveyed from a cable running along the upper part of the hangers 1 and passing respectively through the screws and nuts 120, 121, 43, 42, the braid 3, the bracket 4, the screws 5a and the part 5b. At this stage, the hangers 1 are moved by a conveyor along guide rails 50 (see FIG. 10) which bend at the level of the tank containing the paint bath, in order to allow the introduction of the box into said bath according to a slope of 45 °. However, when the first two hangers 1 move along the curved part 51 of the guide rails 50, the sledge 2 is made to pivot around the axes 11 formed by the lower parts of the hangers 1; this rotation of the electrical contact plate 9 of the sledge 2 causes the rotation of the two fingers 80 and consequently of the sleeve 8 in which they are incorporated and which is integral with the contact strips 7, which strips are in this way coupled to the movement of sledge 2.

This results in the establishment of a fixed electrical contact between the aforementioned lamellae 70 and the contact plate 90, which advantageously avoids the electric arcs produced when the parts slide relative to each other, which is all the more necessary as the mechanism is immersed in the paint; the realization of an elastic electrical contact also contributing to the elimination of electric arcs, and making it possible to maintain over time a good electrical contact independently of the variations in the size of the sleds for example, the dimensional dispersions of the equipment in general, and wear of the mechanism over time. The stripping of the electrical contact elements is carried out when the sledge 2 is lowered, the paint being removed by rubbing the strips 70 against the plate 90. As for the unloading of the sledge 2 from the hangers 1, it is obtained by raising the sledge 2 by means of the lifting table, which produces the decompression of the strips 70 with the plate 90, the sleeve assembly 8, intermediate piece 5, strips 70, braid 3, being returned to the vertical position by the spring 41 in the perspective of a new loading. It should be noted that in this embodiment the pickling is carried out automatically, only on the strips 70 during loading, the plate 9 secured to the sledge 2 requiring pickling by shot blasting. The strips 70 are preferably made of treated stainless steel to have a low elasticity and therefore easy automatic pickling.

The means of transmitting the mass to the sledge 2 according to the second embodiment operates in the same manner as previously described. Loading the sledge 2 on the hanger 1 produces the engagement of the two chamfers (a) (b) provided respectively at the upper parts of the contact parts 71, 72, 73 and 74 and at the lower part of the other part 94 , this resulting in the displacement of the aforementioned parts 71, 72, 73, 74 against the aforementioned spring, which makes it possible to press parts 71, 72, 73, 74 against part 94.

It should be noted that in the latter case, the contact parts 71, 72, 73, 74 are made of tungsten carbide to withstand the scraping of the cooked cataphoresis and the high intensity of the electrodeposition current (750 A max. ).

The control of the continuous flow of current between the hanger and the sledge is carried out as follows. When the hanger 1 reaches the curvature of the rails allowing the sledge to enter the tank, it engages on a grounding rail 52 while the rear hangers 13 engage on a control rail 53 which is measured the voltage (figure 10). This control is carried out via a stabilized supply U, for example 24 VDC and a threshold voltage relay R. The state of relay R is scanned throughout the duration of the control by an automaton A. Any fault detected triggers the memorization M of the image of the number of the rear hanger incriminated 13; this number is then displayed (E) in the cockpit where it triggers an alarm which alerts a maintenance team.

Before the cataphoresis operation and before loading the sledge 2 on the hanger 1, the presence of the spring 41 is checked, essential for the slinging to be accomplished satisfactorily. This control is implemented by means of two vane sensors 16, 15 in the start of the return circuit of the hangers 1, which hangers are equipped with earthing systems and can move in the vertical position. The pivoting of the pallets 15, 16 when the spring 41 and the upper part of the hanger pass respectively generates a signal, any desynchronization between the state of the two sensors 16, 15 triggering an alarm memorized in the flight hall intended to warn a support team.

It will also be noted on the one hand that the parts 8, 111, 12 will advantageously be made of a plastic material in order to prevent the hanger from being grounded, on the other hand that the contact elements will preferably be arranged on one side of the sleds to facilitate installation, and that the conductive surfaces in contact with the bath will be protected by a deposit of cooked cataphoresis.

Thanks to the invention, an electrolytic installation has therefore been produced, in particular for painting a motor vehicle body by cataphoresis, eliminating the risks of production of electric arcs between the respective contact elements of the hanger and the sledge, thanks to a contact permanent throughout the duration of the electrodeposition Due to the elastic connection and the rotational attachment, not requiring a particular quality of surface condition as is the case with the magnet, while compensating for dimensional variations sleds, and not requiring the establishment of chemical pickling stations requiring maintenance, use and treatment of mandatory and expensive chemicals.

Of course, the invention is in no way limited to the embodiments described and illustrated which have been given only by way of examples.

On the contrary, the invention includes all the technical equivalents of the means described and their combinations if these are carried out according to his mind. In addition, it does not only apply to cases of motor vehicles, but can be used for the treatment of a basket of spare parts for example.

Claims (14)

Electrolytic installation, in particular for painting a motor vehicle body by cataphoresis, of the type comprising a sledge on which a motor vehicle body is transported in electrical contact with said sledge, at least one hanger to which said sled can be suspended in an articulated manner, said hanger being moved by a conveyor to transport said sled to a station at which it enters at a certain inclination into a cataphoresis bath by pivoting around the hanger, said sled being connected to one of the poles of a current source by establishing an electrical contact between two electrical contact elements respectively connected to the sledge and supported by the hanger in the loaded position of the sledge on the hanger, one of the two aforementioned elements retracting to allow loading of the sledge on the hanger, characterized in that at least one of the two abovementioned contact elements és (7, 9) comprises an elastic means permanently applying the two contact elements (7, 9) one pressing against the other in the loaded position of the sledge (2) by pushing back at least one of said elements contact (7, 9) during loading, and in that one of the aforementioned contact elements (7, 9) is mounted rotatably relative to the axis (11) about which the sledge (2) pivots relative to the hanger (1), the sled (2) and the hanger (1) cooperating with a means for securing in rotation the two aforementioned contact elements (7, 9) during the pivoting of the sled (2) relative to the hanger (1 ) so as to maintain a fixed contact between these two elements when the body is lowered into the bath, at least one of the two contact elements (7, 9) being returned to the initial service position facing live with each other contact element after each operation. Installation according to claim 1, characterized in that the contact element (7) supported by the hanger (1) is integral with a sleeve (8) rotatably mounted around the pivot axis (11) of the sledge ( 2) relative to the hanger (1), said sleeve (8) comprising two fingers (80) capable of coming into contact with a part of the sledge (2) to secure in rotation the two contact elements (7, 9) during pivoting of the sledge. Installation according to claim 2, characterized in that the aforementioned part of said sledge is the electrical contact element (9) integral with the sledge (2) itself. Installation according to any one of the preceding claims, characterized in that at least one of the abovementioned contact elements (7, 9) comprises at least one strip (70) made of an elastic and conductive material. Installation according to any one of claims 1 to 3, characterized in that the two aforementioned contact elements (7, 9) consist for the first, of several parts (71, 72, 73, 74) and for the second of a piece (94), said pieces each comprising at least one edge (75, 91), the two contact elements (7, 9) being brought back against each other by means of a spring, and the respective edges (75, 91) of the parts of the first contact element (7) and of the part of the second contact element (9) being scoured against each other when loading the sledge (2) on the hanger (1). Installation according to claim 5, characterized in that the edges (75, 91) of the two aforementioned contact elements (7, 9) have different inclinations. Installation according to claim 5 or 6, characterized in that the parts (71, 72, 73, 74) of the first contact element (7) comprise a chamfered part (a) cooperating with a corresponding chamfered part (b) of the another part (90) constituting the second contact element (90), favoring the retraction of one of the contact elements (7, 9) during the positioning of the sledge (2) on the hanger (1) . Installation according to any one of the preceding claims, characterized in that one of the abovementioned contact elements (7, 9) is connected to the current source by means of a flexible element (3) allowing the transmission of the current when the sledge (2) rotates relative to the hanger (1). Installation according to claim 8, characterized in that the aforesaid flexible element is a braid (3) or a cable. Installation according to any one of the preceding claims, characterized in that a spring (41) for returning at least one of the contact elements after each operation is secured by one of its ends (412) to the upper part of the hanger (1), and by its other end (411), of an intermediate support piece (5) on which is fixed the contact element (7) supported by the hanger (1). Installation according to claim 10, characterized in that it comprises means for checking the presence of the spring (41). Installation according to claim 11, characterized in that these means comprise a presence sensor (16) of the hanger (1) and a sensor (15) of the presence of the spring (41), and means for checking the synchronization of the signals transmitted. by the two sensors (15, 16), put into action at the start of the return circuit of the hanger (1). Installation according to any one of the preceding claims, characterized in that it further comprises means for controlling the continuity of the flow of current between two hangers (1). Installation according to claim 13, characterized in that this means comprises an additional rail (53) on which engages one of the rear hangers (13), when one of the front hangers (14) is in guided contact with a front rail (52) connected to the current source, a device for subjecting the additional rail (53) to a DC voltage, and a device allowing the verification of the passage of current in the circuit thus created.

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