Patent Publication Number: US-6989176-B2

Title: Device and method for supplying atomizers, and spraying installation equipped with such a device

Description:
FIELD OF THE INVENTION 
   The present invention relates to a device and a method for supplying with coating products the atomizers of an installation for spraying coating products. 
   BACKGROUND OF THE INVENTION 
   It is known to supply the atomizers of an installation for spraying coating products via product circulation conduits, also known as “circulatings”, from large-capacity tanks of products, whose capacity may attain several thousands of liters. Such tanks are generally located in storage premises at a distance from the spraying installations. Taking into account the usual distance between the store and the spraying installation, the products present in the circulatings during operation are of the order of several hundreds of liters, which renders it economically impossible to change products in such circulatings, as the quantities of products lost thereby are inacceptable. It is therefore necessary to provide one circulating per shade of colour used. 
   Now, the number of shades used in an installation for spraying coating products is tending to increase, which induces an increase in the number of circulating lines and increases the cost of the installation accordingly, while problems of space requirement are raised, particularly at the level of the passages through partitions. 
   The use of tanks borne on the arm of a multi-axis robot does not necessarily enable this problem to be solved. In effect, in the system known from EP-A-0 274 322, coating product circulatings are provided up to the zone of activity of the robot. In other systems, such as disclosed for example in EP-A-0 796 665, a carrousel is provided for filling cartridges with coating products but circulatings for supplying coating products are provided up to the vicinity of this carrousel for filling the cartridges. 
   In all cases, the permanent stirring of the coating products in the circulatings leads to a degradation of their physico-chemical properties due to the mechanical stresses to which they are subjected, in particular the shear undergone at the level of the changes in direction, the pumps or the pressure regulators. 
   Another solution known from DE-A-197 04 573 consists in using prefilled cartridges, which are for example disposable, but this leads to complex manipulations of a large number of cartridges, which is not economically satisfactory and renders the system of management of such an installation considerably complex. 
   It is a particular object of the present invention to overcome these problems by proposing a novel atomizer supply device which does not necessitate the construction of a circulating up to the vicinity of an installation and avoids the manipulation of too large a number of cartridges. 
   SUMMARY OF THE INVENTION 
   To that end, the invention relates to a device for supplying coating products to the atomizers of an installation spraying such products onto objects displaced by a conveyor, this device comprising at least one principal tank adapted to supply secondary tanks each intended for an atomizer, and means for displacing this principal tank up to the vicinity of the afore-mentioned secondary tanks. 
   The principal tank or tanks make it possible to supply different secondary tanks of the installation by being displaced up to said tanks. The principal tanks may be packaged outside the factory in which the installation is employed and, in particular, in the premises of the coating product manufacturer, the principal tanks in that case corresponding to a particular packaging of the product. It then suffices to transport different principal tanks up to the vicinity of the installation then, as a function of the coating product to be sprayed, to displace a principal tank as far as the different secondary tanks in order to supply them with coating products. No degradation of the coating product by shear occurs in the principal tank or tanks. The secondary tanks remain in the installation and it is unnecessary to manage a large number of disposable or refillable cartridges. 
   According to advantageous aspects of the invention, the device incorporates one or more of the following characteristics: 
   The or each principal tank is adapted to contain a quantity of coating product sufficient to supply the secondary tanks intended for the sprays of the installation for completely coating an object or one side of an object. In this way, a principal tank may for example enable all the sprays located on one side of the installation to be supplied with an adequate quantity of paint, without waste. In a variant, the quantity of products present in the principal tank corresponds to the complete coating of an object. 
   The afore-mentioned displacement means comprise at least one conveyor adapted to displace the principal tanks parallel to the direction of advance of a conveyor for displacing the objects. 
   The means for displacing the principal tanks are constituted by the conveyor displacing the objects to be coated. 
   According to a first advantageous embodiment of the invention, the principal tanks may be connected to at least one secondary tank borne by a robot and associated with an atomizer. 
   According to another embodiment of the invention, the device comprises at least one station for temporary storage of at least one secondary tank and means for temporary connection of a principal tank with at least one secondary tank in place in this station. In that case, the secondary tanks may be filled in masked time in the temporary storage station. 
   The invention also relates to a method which may be carried out with the device described hereinabove, and more specifically to a method which comprises the steps consisting in:
         conducting at least one principal tank containing a coating product up to the vicinity of at least one secondary tank intended for an atomizer;   transferring coating product from the principal tank towards the secondary tank, and supplying the atomizer with coating products from the secondary tank.   According to a first advantageous embodiment of the invention, the method comprises more particularly the steps consisting in:   conducting the principal tank up to in the zone of activity of a robot for positioning the atomizer and a secondary tank intended for that atomizer;   displacing the secondary tank by means of the robot up to the immediate vicinity of the principal tank before transferring the product from the principal tank towards the secondary tank, and   after the transfer, displacing the secondary tank towards a position in which the atomizer is able to coat the afore-mentioned objects.       

   According to another advantageous embodiment of the invention, the method comprises the steps consisting in:
         conducting the principal tank up to the vicinity of a station for temporary storage of at least one secondary tank;   transferring product from the principal tank towards at least one secondary tank in place in the station, and   mounting at least one secondary tank filled from said principal tank on a paint-applying robot.       

   In that case, each secondary tank may be provided to form a sub-assembly with an atomizer for which it is intended and such a sub-assembly is provided to be mounted on the robot after filling of the secondary tank in the temporary storage unit. 
   Whatever the embodiment envisaged, the method advantageously consists in filling the principal tank with a sufficient quantity to coat the same object or one side of the same object by different atomizers and in supplying the atomizers by means of secondary tanks filled by transfer from this principal tank. 
   Finally, the invention relates to an installation for spraying coating products, comprising a device as described hereinabove, possibly employed with the method as described hereinbefore. The cost price of such an installation is substantially less than the known installations having to be supplied with circulatings and it is much simpler to use than an installation supplied solely with cartridges each intended for an atomizer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description of two embodiments of an installation in accordance with its principle, given solely by way of example and made with reference to the accompanying drawings, in which: 
       FIG. 1  schematically shows a plan view of an installation according to a first embodiment of the invention, the atomizers all being in the course of application. 
       FIG. 2  is a partial section, on a larger scale and along line II—II of  FIG. 1 , of part of the installation of  FIG. 1  in the course of cleaning/filling of a tank of a robot thereof. 
       FIG. 3  is a view similar to  FIG. 1  for an installation according to a second embodiment of the invention, and 
       FIG. 4  is a section along line IV—IV of  FIG. 3 . 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring now to the drawings, the installation shown in  FIG. 1  is provided for coating automobile vehicle bodies  1  with liquid paint, said bodies being displaced by a conveyor  2  in a substantially rectilinear direction X–X′. The bodies  1  are each supported by a carriage or toboggan  3  driven by the conveyor  2 . 
   Multi-axis robots  10  to  17  are distributed on either side of the conveyor  2  and toboggans  3 , and are each equipped with an atomizer  20  to  27  and a tank  30  to  37  associated therewith. The tanks  30  to  37  are permanently mounted in the vicinity of the wrist of each robot. The capacity of each tank  30  to  37  is sufficient to allow the desired application of coating products on a body  1 . 
   The robots  10  to  13  may be provided to be intended for the application of a first coating layer inside a body, while the robots  14  to  17  are intended for the application of a second layer inside the bodies. According to a variant of the invention (not shown), the installation may also comprise other robots intended respectively for the application of a first layer and a second layer outside the body, a station for manual retouching possibly being provided in the downstream part of the booth of the installation. 
   After a body has been coated, each tank  30  to  37  must be cleaned and filled with a fresh coating product, most often different from that used previously, as the automobile vehicles are painted as a function of the customers&#39; orders. 
   To that end, stations  40  to  47  for cleaning the tanks are provided in the vicinity of each robot  10  to  17 . Station  40  is supplied with air via a conduit  40 A and with solvent via a conduit  40 S, while a drain conduit  40 P allows the paint and solvent residues resulting from a cleaning operation to be collected. The other stations are connected in the same manner to their environment. 
   After the product contained in the tank  30  has been used, the robot  10  approaches the tank  30  and the atomizer  20  towards the station  40 , as represented by arrow F 1  in  FIG. 2 . A plate  40   f  of station  40  is then applied on the atomizer  20 , this plate being provided with connection means  40   e  adapted to cooperate with corresponding connection means  20   e  provided on the atomizer  20 . Inside the robot  10  there are provided conduits (not shown) connecting the atomizer  20  to the tank  30  and making it possible, via means  20   e , to supply the tank  30  with air and solvent and to collect the residue thereof. 
   In this way, the station  40  makes it possible to clean the atomizer  20  and the tank  30  before they are used again. 
   The same applies for stations  41  to  47  and the other atomizers and tanks. 
   For filling the tanks  30 ,  32 ,  34  and  36 , it is provided that principal tanks  50  circulate on a conveyor  52  leaving a loading zone  53  and arriving at an unloading zone  54 . The conveyor  52  comprises a branch  52   a  and a branch  52   b  substantially parallel to direction X–X′, the circulation taking place in the direction of advance of the conveyor on branch  52   a  and in the opposite direction on branch  52   b.    
   Each principal tank  50  has a capacity equal to the sum of the capacities of tanks  30 ,  32 ,  34  and  36  and is provided with connection means  50   a  provided to cooperate with connection means  30   a  arranged on or in the vicinity of the tank  30 . 
   Tanks  32 ,  34  and  36  are likewise provided with such connection means  32   a ,  34   a  and  36   a.    
   Functioning is as follows: Depending on the shade provided for a body entering the installation, a tank  50  is selected and disposed, by a manipulator robot (not shown), on the loading zone from which it is conducted by the conveyor  52  up to the robot  10 . After the preceding body has been coated, the robot  10  pivots and docks on the cleaning station  40  as indicated hereinabove. The position of the tank  50  is in that case such that the movement F 1  of the robot induces a coupling of the means  30   a  and  50   a , which makes it possible to take from the tank  50  the quantity provided to be stored in the tank  30  and applied by the atomizer  20  on said body. 
   With the foregoing in mind, cleaning of the atomizer  20  and of the tank  30  and filling of the tank  30  take place thanks to a single movement of the robot  10 . In other words, the position of cleaning of the atomizer and of the tank is the same as the position of filling of the tank. 
   As the robot  10  is docked on the station  40  during filling of the tank  30  from the tank  50 , it is possible to supply the tank  50  with air for pressurization from the station  40  and through the robot  10 . In this way, the transfer of products from the tank  50  towards the tank  30  may take place under pressure, thus reducing the cycle time. 
   The air supply  40 A of station  40  may also be used for actuating stirring means provided in the tank  50 , in order to homogenize the product before it is transferred towards the tank  30 . 
   During this cleaning and filling, the body  1  in question progresses in the direction of the robot  10  and, at the end of the operation of filling of the tank  30 , the application with the atomizer  20  may begin. 
   The conveyor  52  then displaces the principal tank  50  in the direction of the robot  12  at whose level the tank  32  is cleaned and filled like the tank  30  with a view to applying the same product on the same body. 
   The tank  50  then continues its advance in the direction of robots  14  and  16  with a view to successive cleaning and filling of tanks  34  and  36 . 
   After the last robot, the tank  50  is conducted towards the unloading zone  54  by a return along branch  52   b  of the conveyor  52 . 
   The same applies to the opposite side of the bodies  1  where a conveyor  52 ′ is provided, between a loading zone  53 ′ and an unloading zone  54 ′, for conducting principal tanks  50 ′ up to robots  11 ,  13 ,  15  and  17  with a view to filling tanks  31 ,  33 ,  35  and  37 . 
   If other robots are provided downstream of robots  16  and  17 , the capacity of tanks  50  and  50 ′ is increased. In any case, the tanks  50  and  50 ′ transport a sufficient quantity of paint to completely coat one side of a body  1 . In practice, it may be envisaged to fill the tanks  50  and  50 ′ with a quantity slightly greater than that which is theoretically needed, in order to have a reserve available, for example for a manual application. 
   Where a manual application station is provided, the tanks  50  and  50 ′ are conducted up to this station. The painters&#39; guns are equipped with incorporated tanks which may be filled from the principal tanks. According to an advantageous variant, the hand guns are not equipped with tanks incorporated therein, the guns being directly supplied by the principal tanks  50  and  50 ′ via flexible pipes. In that case, a means for pressurizing the interior volume of the principal tanks may be provided. 
   Racks  55  and  55 ′ are arranged in the vicinity of the loading zones  53  and  53 ′ for supplying the conveyors  52  and  52 ′ with principal tanks  50  and  50 ′, as a function of the shades selected for the bodies  1 . These racks may be prepared outside the paint spray workshop, the distribution of the shades in the different tanks  50  and  50 ′ being predetermined as a function of the envisaged use of the installation. 
   In the case of coating products composed of two components, the base of the products may be provided to be transported in the principal tanks  50  and  50 ′, while the catalyst, which is identical whatever the base considered, is conducted via a conduit  40 K, shown solely in  FIG. 2 , at the level of station  40 . In this way, when the tank  30  is being filled with base from tank  50 , a filling of catalyst may take place from station  40 . 
   In a variant, the conduit  40 K supplying catalyst may be disposed in the arm of each robot, as represented in dashed-and-dotted lines for the robot  10  in  FIG. 2 . 
   In any case, the base and the catalyst are mixed just before the product contained in the tank  30  is used. 
   In the second embodiment of the invention shown in  FIGS. 3 and 4 , the elements similar to those of the first embodiment bear identical references, increased by  100 . In this embodiment, bodies  101  are conveyed by toboggans  103  displaced by a conveyor  102 . Robots  110  to  117  are disposed on either side of this conveyor and are equipped with sub-assemblies  160  to  167  each comprising an atomizer  120  to  127  and a tank  130  to  137 , each sub-assembly being removably mounted at the end of the arm of a robot. As previously, the principal tanks  150  and  150 ′ are conducted by conveyors  152  and  152 ′ along the conveyor  102 . 
   Between the robots  110  and  112 , there is installed a station  140  for temporarily storing sub-assemblies  160  and equivalent, this station  140  being intended for the preparation of sub-assemblies provided to be mounted on the robots  110  and  112 . 
   As is more particularly visible in  FIG. 4 , the station  140  defines four housings  140   a ,  140   b ,  140   c  and  140   d  for receiving sub-assemblies  160  and  162 . More precisely, housings  140   a  and  140   b  are intended for receiving the sub-assemblies to be mounted on the robot  110 , while housings  140   c  and  140   d  are intended for the sub-assemblies to be mounted on the robot  112 . The housing  140   a  effectively contains a sub-assembly  160 ′, while housing  140   b  is ready to receive the sub-assembly  160  mounted at the end of the robot  110 . In the same way, housing  140   c  contains a sub-assembly  162 ′ intended to be mounted on the robot  112 , while housing  140   d  is empty and ready to receive the sub-assembly  162  mounted on the robot  112 . The sub-assemblies  160 ′ and  162 ′ respectively comprise atomizers  120 ′ and  122 ′ and tanks  130 ′ and  132 ′ similar to those of sub-assemblies  160  and  162 . 
   The station  140  is equipped with an air supply conduit  140 A, a solvent supply conduit  140 S and a drain conduit  140   p.    
   With the foregoing in mind, it will be understood that the robots  110  and  112  alternately take one of the sub-assemblies  160  or  162  available in the station  140 , one sub-assembly being able to be filled while the other subassembly is being used on one of the robots. 
   Such filling takes place thanks to the tank  150  which is conducted by the conveyor  152  up to the level of the station  140 , the tank  150  being provided with a means  150   a  for quick connection with connection means  140   e  borne by a plate  140   f  capable of movements of translation, represented by arrow F 2  in  FIG. 4 , being controlled by a jack  140   g  which may be hydraulic, pneumatic or electric. 
   The connection means  140   e  are connected by flexible pipes (not shown) to the sub-assemblies  160  and  162  present in the housings  140   a  to  140   d.    
   It is possible to fill the tanks  130  and  132  of the sub-assemblies  160  and  162  when they are in place in the station  140  and before the robots  110  and  112  take over these sub-assemblies with a view to spraying the coating products on the bodies  101 . 
   The tank  150  may be supplied with air for pressurization or with air for actuating a stirrer from the conduit  140 A of the station  140  when the plate  140   f  is in contact with the tanks  150 , in which case appropriate connecting means are provided. 
   Another station  141 , similar to station  140 , is provided between the robots  114  and  116  for preparing the sub-assemblies  164  and  166 , and particularly for cleaning the atomizers  124  and  126  and cleaning/filling the tanks  134  and  136 . Tank  150  is conducted towards station  141  after its connection to station  140 . 
   On the opposite side of the conveyor  102  there are provided two stations  140 ′ and  141 ′ for temporary storage and cleaning/filling of the sub-assemblies  161 ,  163 ,  165  and  167 . Principal tanks  150 ′ are conducted by a conveyor  152 ′ up to the vicinity of the stations  140 ′ and  141 ′ for filling the tanks  131 ,  133 ,  135  and  137 . 
   As previously, loading zones  153  and  153 ′ and zones  154  and  154 ′ for unloading the conveyors  152  and  152 ′ are provided, racks  155  and  155 ′ allowing temporary storage of the tanks  150  and  150 ′, full or empty, in the vicinity of zones  153 ,  153 ′,  154  and  154 ′. 
   Manipulation of the principal tanks  50 ,  50 ′,  150  and  150 ′ between the racks and the loading/unloading zones may be effected by a manipulator robot or by an operator. 
   The second embodiment of the invention presents the particular advantage that the secondary tanks  130  to  137  are filled in masked time with respect to the spraying, this consequently allowing the cycle time to be reduced. 
   According to an advantageous aspect of the invention, the stations  140 ,  140 ′,  141  and  141 ′ are provided inside a spraying booth, while conveyors  152  and  152 ′ are arranged outside this booth, for example at a different level. In that case, the tanks  130  to  137  are filled via a passage through the partition of this booth. According to a variant, the stations  140 ,  140 ′,  141  and  141 ′ may be arranged outside the booth where they are supplied with coating products, these stations being at least partly mobile in order to conduct the sub-assemblies  120  to  127  inside the booth by traversing a partition thereof, in order that the robots  110  to  117  can access the housings  140   a  to  140   d  and equivalent. 
   According to a variant of the invention (not shown), a station for temporary tank storage may be associated with each robot  110  to  117 , each station comprising two housings for receiving two sub-assemblies mounted alternately on each robot. The embodiment represents the grouping of the stations for two robots, with four locations for receiving sub-assemblies, allowing a saving of space and a more attractive cost price. Whatever the embodiment considered, means for monitoring the temperature of the product in the principal tanks may be provided, such means being able to be activated permanently or just before the transfer towards the secondary tanks. Similarly, stirring means may be activated permanently or just before transfer. 
   According to a variant of the invention (not shown), applicable to the two embodiments described, the conveyors for displacing the principal tanks may be constituted by the conveyor  2  or  102 , insofar as the principal tanks may be supported by the toboggans  3  or  103 , the movement of connection of the robots or the parts of the temporary storage stations being adapted accordingly. 
   The invention has been described with an installation for spraying liquid coating products. It is applicable to the spraying of all types of liquid products containing solvents, hydrosoluble or composed of two components, and to the spraying of pulverulent coating products. 
   The invention has been represented in the case of an installation for coating automobile vehicle bodies. However, it is applicable to the coating of all types of objects, particularly spare parts, by means of atomizers of all types, electrostatic or not, rotary or pneumatic. 
   The invention has been represented with multi-axis robots. It is applicable with any type of robot adapted to displace at least one atomizer opposite objects to be coated, in particular with machines of “reciprocator” type or of the type known from EP 0 720 515. The invention might also be carried out in an installation comprising a succession of manual coating stations. 
   In the case of an existing installation already comprising circulatings or in the case of an installation provided for the spraying of so-called “current” products and so-called “rare” products used less often, circulatings may be employed for supplying the atomizers with the products most often employed, while the device with principal tanks is used for the products used least often. 
   Whatever the variant considered, one or more atomizers mounted on a robot or a machine may be supplied from the same secondary tank. 
   According to a variant of the invention (not shown), the zones  53  and  54  for loading/unloading the principal tanks may be provided at two opposite ends of the booth, which avoids having to resort to a loop conveyor  52 . This is also applicable to the second embodiment.